Method and system for determining a position of a marker member

Abstract

A method for determining a position of a marker member for alignment of a surgical handpiece is provided. The surgical handpiece has an imaging unit releasably attached thereto and being configured to detect the marker member. The surgical handpiece further has a probe comprising a probe tip arranged at a defined position relative to the imaging unit. The method comprises providing the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient. The method comprises obtaining a data set indicative of a shape of a landmark and a position of the landmark relative to the marker member. The method comprises determining whether the data set meets one or more data collection criteria. The method comprises, upon the data set meeting the one or more data collection criteria, matching the data set to a digital model of the dental and / or cranio-maxillofacial structure. The method comprises mapping the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data set.

Description

[0001] METHOD AND SYSTEM FOR DETERMINING A POSITION OF A MARKER MEMBER

[0002] Technical Field

[0003] The present disclosure pertains to the field of restorative dentistry. The present disclosure relates to a method and a system for determining a position of a marker member for alignment of a surgical handpiece.

[0004] Background

[0005] Computer-assisted surgery (CAS) in the field of dental procedures relies on precise localization of surgical instruments relative to a patient's anatomy. To achieve this, a marker is used within the coordinate system of a computer-aided design (CAD) model of the patient's teeth. The marker must remain detectable by a camera system throughout the entire surgical procedure to ensure accurate tracking and navigation.

[0006] Currently, the optimal position of the marker is predetermined by the producer of dental implants rather than the operating dentist. In typical workflows, the dentist sends the preoperative planning files to the manufacturer, who fabricates a dental tray with the marker affixed in a fixed position. This pre-defined marker positioning may not always account for patient-specific anatomical variations, surgical conditions, or intraoperative constraints.

[0007] If the marker is not positioned optimally, challenges arise in accurately tracking the handpiece during the procedure. Additionally, in cases where surgery needs to be performed urgently, the fixed marker position may introduce difficulties, as adjustments cannot be made in real time. These issues can compromise surgical accuracy, efficiency, and overall outcomes. Therefore, there is a need for a more flexible and reliable system for determining and adjusting the marker’s position within the CAD model to ensure optimal tracking conditions during surgery.

[0008] Summary

[0009] Accordingly, there is a need for methods and systems for determining a position of a marker member for alignment of a surgical handpiece, which may mitigate, alleviate, or address the existing shortcomings, and provide a less time consuming andmore accurate method for determining a position of a marker member to allow accurate tracking and navigation during surgery.

[0010] According to a first aspect of the present disclosure, there is provided a method for determining a position of a marker member for alignment of a surgical handpiece. The surgical handpiece comprises an imaging unit releasably attached thereto and configured to detect the marker member and a probe comprising a probe tip arranged at a defined position relative to the imaging unit. The method comprises providing the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient. The method comprises obtaining a first data set indicative of a shape of a first landmark and a position of the first landmark relative to the marker member. The method comprises obtaining a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member. The method comprises obtaining a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member. The landmarks are associated with the dental and / or cranio-maxillofacial structure. The data sets are obtained by probing the respective landmark using the probe tip of the surgical handpiece while detecting the marker member with the imaging unit. The method comprises determining whether the first, second and / or third data set meets one or more data collection criteria. The method comprises upon the first, the second and the third data set meeting the one or more data collection criteria, matching the first data set, the second data set, and the third data set to a digital model of the dental and / or cranio-maxillofacial structure. The method comprises mapping the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the first data set, the second data set, and the third data set.

[0011] According to a second aspect of the current disclosure, there is provided a system for determining a position of a marker member for alignment of a surgical handpiece. The system comprises the marker member and the surgical handpiece, wherein the marker member is configured to be arranged to a dental and / or cranio-maxillofacial structure of a patient. The system further comprises an imaging unit, the imaging unit being releasably attached to the surgical handpiece at a first section of the surgical handpiece and configured to detect the marker member, and a probe comprising a probe tip, the probe being releasable attached to the surgical handpiece ata second section of the surgical handpiece. The system is configured to obtain a first data set indicative of a shape of a first landmark and a position of the first landmark relative to the marker member. The system is configured to obtain a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member. The system is configured to obtain a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member. The data sets may be obtained by registering one or more data point(s) and a detected distance and direction relative to the marker member for each of the one or more data point(s) upon the probe tip being moved along the respective landmark. The distance and direction may herein also be referred to as a vector indicative of the relative position of the landmark(s) to the marker member. The landmarks are associated with the dental and / or cranio-maxillofacial structure. The system is configured to determine whether the first, the second and / or the third data set meet one or more data collection criteria. The system is configured to, upon the first, second and third data sets meeting the one or more data collection criteria, match the first data set, the second data set, and the third set to a digital model of the dental and / or cranio-maxillofacial structure. The system is configured to map the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data points comprised in the first data set, the second data set, and the third data set.

[0012] By obtaining the relative position of three landmarks in relation to the marker member, its precise location can be determined — for example, using triangulation — directly by the operating dentist during the procedure, rather than being predefined by the dental implant manufacturer. This approach allows the marker member’s position within the digital model to be established based on its actual placement, eliminating the need for pre-positioning at a fixed, predetermined location, which could otherwise introduce positioning errors.

[0013] Since the dentist has the ability to determine the marker member's position in real time, last-minute adjustments can be made as needed, ensuring greater flexibility. The method for determining the marker member’s position can therefore be performed once the marker member has been definitively placed.By acquiring a dataset comprising multiple data points for each landmark, an exact mapping of the landmark’s shape to the digital model of the dental and / or craniofacial structure can be achieved, enhancing accuracy in determining the marker member’s position. This improved accuracy in marker localization leads to more precise tracking of the handpiece throughout the procedure.

[0014] As a result, surgical precision, procedural efficiency, and overall outcomes in computer-assisted surgery (CAS) are significantly enhanced.

[0015] Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

[0016] Brief Description of the Drawings

[0017] Fig. l is a diagram illustrating an example system for determining a position of a marker member for alignment of a surgical handpiece according to the current disclosure,

[0018] Fig. 2 is a diagram illustrating a triangulation procedure for determining a position of the marker member relative to a plurality of landmarks according to the current disclosure,

[0019] Fig. 3 is a flow chart showing an example method for determining position of the marker member relative to a plurality of landmarks according to the current disclosure,

[0020] Figs. 4A-4F illustrates a probing procedure according to the current disclosure. Figs. 5A-5B are diagrams illustrating optional landmarks to be used for probing in an edentulous scenario according to the current disclosure, and

[0021] Figs. 6A-6B are diagrams illustrating a method for determining a position of the marker member for an edentulous patient.

[0022] Detailed Description

[0023] The current disclosure provides a method for determining a position of a marker member for alignment of a surgical handpiece, for example for enabling a computer-assisted surgery. The surgical handpiece comprises an imaging unit releasably attached to the surgical handpiece. The marker member may comprise a pattern, such as a printedor engraved pattern, configured to be optically detected by the imaging unit. The imaging unit is configured to detect the marker member, such as the pattern on the marker member. The imaging unit may e.g. be an optical tracking system, or a photogrammetry system, or an intraoral scanner. The surgical handpiece further comprises a probe comprising a probe tip arranged at a defined position relative to the imaging unit. The probe can herein be seen as an attachment designed to interact with a tracking or navigation system, enabling precise localization of the handpiece within a computer-assisted surgical environment. The probe tip of the probe may serve as a reference point that can be detected by an optical or electromagnetic tracking system, such as the imaging unit, to accurately determine the position and orientation of the handpiece relative to the patient's anatomy.

[0024] The method may be a computer-implemented method. In other words, one or more processors may be configured to carry out the method as disclosed herein.

[0025] The method may comprise providing the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient. The marker member provides a detectable reference point within a tracking system, allowing for accurate positioning, orientation, and movement monitoring within the computer-aided surgical environment. In other words, the marker member may provide an interface between a coordinate system of the imaging unit and a coordinate system of the patient to correctly track a position, an orientation and / or a movement of the handpiece in relation to the patient. In one or more example methods, providing the marker comprises arranging the marker member outside of the patient at a structure being fixed relative to the dental and / or cranio-maxillofacial structure of the patient. In one or more example methods, providing the marker comprises arranging the marker member on or at the dental and / or cranio-maxillofacial structure of the patient. The marker member may be an optical tracker configured to be detectable by an imaging unit, such as a camera.

[0026] In one or more examples, the marker member is arranged on a support, such as a jaw mount structure, that provides a stable, reproducible platform for positioning the marker member e.g. a jaw mount structure configured to be mounted on the jaw bone of a patient in patients without sufficient dentition (“edentulous tray”) or a jaw mount structure configured to be attached to any remaining teeth (“dental tray”) . The supportmay be designed to engage a dental and / or craniomaxillofacial structure through a broad oral support surface that conforms to the underlying jawbone. A mounting interface, such as a rotationally asymmetric post, keyed connection, or other anti-rotation geometry, may project from an oral -facing side of the support and may be configured to receive the marker member in a plurality of predefined orientations. In one or more examples, the mounting interface may be a starshaped rotationally asymmetric interface providing a plurality of distinct rotational positions for receiving the marker member. The marker can thus be arranged to face in a plurality of directions while in a same location in the oral anatomy. The underside of the support may further comprise one or more stabilizing projections and / or apertures configured to receive securing elements, such as screws or pins, for fixation of the support to the jawbone. By combining bone anchorage, anti-rotation features, and an accurately referenced mounting interface for the marker member, the support may provide a reliable reference platform that enables accurate spatial alignment and marker positioning during the execution of the method for determining the position of the marker member, particularly in computer assisted dental or craniomaxillofacial procedures.

[0027] The method comprises obtaining a first data set indicative of a shape of a first landmark and a position of the first landmark relative to the marker member, a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member, and a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member. By determining the respective position of three landmarks relative to the marker member, a precise location of the marker member in the digital model can be determined, e.g. using triangulation. The relative position of the landmarks to the marker member may comprise a distance between the respective landmark and the marker member and a direction, such as an angle, of the respective landmark to the marker member.

[0028] In one or more example methods, a single data set may be obtained being indicative of one or more landmarks. The location of the marker member may be determined based on a plurality of data points comprised in the single data set, as long as the data points fulfil one or more data collection criterion / criteria. In other words, in some example methods subsets of the data points comprised within the single data set may be used as separate landmarks for determining the relative position of the markermember. In one or more examples, three subsets of data points of the single data set may be used to triangulate the relative position of the marker member.

[0029] The landmarks, such as the first landmark, the second landmark, and the third landmark, are associated with the dental and / or cranio-maxillofacial structure as dental and / or cranio-maxillofacial structures exhibit significant individual variability, making them useful for identification. For example, the size, shape, and wear of teeth are distinct for each person, contributing to unique dental patterns. Similarly, palatal rugae patterns, such as ridges on the roof of the mouth, are highly individualized and remain relatively unchanged throughout life. The mandible and maxilla also vary in shape and size due to genetic and environmental influences, making them distinguishable in medical imaging such as X-rays and CT scans. Additionally, features such as gum patterns, tongue size, and overall oral cavity shape further contribute to the uniqueness of each individual’s oral anatomy. A landmark can herein be seen as a fixed structure acting as a distinct anatomical or artificial reference point used for spatial alignment, registration, and tracking during surgical procedures. The landmark may serve as a key reference position that helps map the patient's actual anatomy to a preoperative computer-aided design (CAD) model or imaging data, enabling accurate guidance of surgical tools and implants relative to the patient throughout a procedure. Anatomical landmarks may include anatomic soft- or hard tissue or bone, natural dental structures such as teeth, alveolar ridges, a fibrous peripheral zone, a fibrous median zone, a glandular zone, a fat pad zone, or bony prominences that serve as fixed reference points during surgery. Artificial landmarks may be fiducial markers, screws, or other detectable elements added to the patient’s anatomy or surgical tools for enhanced tracking. A fixed structure herein can be seen as a structure that remains stable during the procedure to provide consistent and accurate reference point, such as a structure that is not subject to displacement due to surgical manipulation or movement of the patient. In one or more examples, the landmark is a solid part of the dental and / or cranio-facial structure, such as one or more of a tooth, a pre-set screw or pin, or a bone associated with the dental and / or cranio-facial structure. The term "associated with" in this context refers to a structure that is either physically attached to or integrated as part of the dental and / or cranio-facial structure.The data sets are obtained by probing the respective landmark using the probe tip of the surgical handpiece while detecting the marker member with the imaging unit. Probing the respective landmark may comprise moving the probe, such as the probe tip, across the landmark while recording a plurality of data points indicative of a shape of the landmark using the imaging system. By detecting the marker member with the imaging unit during probing, a relative position of the landmark, such as a relative position of each data point, in relation to the marker member may be captured in a coordinate system of the marker member. The relative position may comprise a distance and a direction of the landmark and / or each data point relative to the marker element. In one or more example methods, the probing may be performed until one or more data collection criteria, which will be described in further detail in the following, have been fulfilled. Probing can herein be seen as a systematic process of collecting spatial data points indicative of the shape and position of the landmark(s) by moving the probe tip of the probe along one or more surface(s) of the landmark. The probing can be used to determine a precise shape, position, and orientation of the landmark relative to a reference coordinate system, such as a digital model in (CAS).

[0030] In one or more example methods, such as when the landmark is an artificial landmark, such as a fiducial marker or a screw, a centre of the artificial landmark may be probed, and a single data point may be captured. To ensure consistency within the dataset, this data point may be upsampled, for instance, by recording it multiple times until the total number of data points for the respective dataset meets the minimum required threshold, such as a first threshold number or a predetermined number of data points.

[0031] The method comprises determining whether the first data set, the second data set and / or the third data set meets, such as respectively meet, one or more data collection criteria. Determining whether each data set meets one or more of the data collection criteria may be performed continuously during probing of the respective landmark.

[0032] A first criterion of the one or more data collection criteria is that the number of data points recorded in the set is equal to or above, such as greater than, a first threshold number. In one or more example methods, the first threshold number is 50 data points. This may for example be the case for fully automated probing procedures. In one or more example methods, such as when there is a need to compensate for humaninconsistencies during the probing procedure, the first threshold number may be 120 data points. If one or more additional data collection criteria remain unmet after the collection of the first threshold number of data points, an additional set of data points, such as 50 additional data points, may be recorded. If the criteria are still not satisfied following the recording of these additional data points, the current probing and data collection process may be discarded, and a new probing procedure may be initiated for the landmark.

[0033] A second criterion of the one or more data collection criteria is that the recorded data points are located on at least two different planes. Landmarks often have complex geometries. By collecting data points from two or more planes a three-dimensional (3D) structure the accuracy and reliability of spatial registration of the landmark in the coordinate system of the CAD model can be improved. By acquiring information from multiple orientations, the system can better define the landmark’s position and orientation within the coordinate system. The second criterion may not apply to an artificial landmark, such as a screw, a pin or a fiducial marker, having exactly one position and no topology constraints.

[0034] A third criterion of the one or more data collection criteria is that a ratio between the number of data points on each plane is equal to or higher than 1 :4.

[0035] A fourth criterion of the one or more data collection criteria is that the two data points defining the greatest pairwise distance in the data set are separated by a distance equal to or smaller than a first threshold distance. In other words, the two data points in the data set being farthest away from each other must not be closer to each other than the first threshold distance. In one or more examples, the first threshold distance is at least 3 mm, such as 5 mm.

[0036] A fifth criterion of the one or more data collection criteria is that the two data points defining the greatest pairwise distance in the data set have a pairwise distance, such as a distance in a vertical direction, being equal to or larger than a second threshold distance. In other words, the two data points in the data set being farthest away from each other must have a minimum height difference equal to or larger than the second threshold distance. In one or more example methods, the second threshold distance is 2 mm. However, a farther pairwise distance is beneficial.The first to fifth criteria may be criteria applying to each data set respectively. During probing of the plurality of landmarks, to capture the first, second and third data sets, additional correlation criteria may apply. To efficiently determine the exact location of the marker member, it is beneficial that the landmarks are sufficiently spaced apart to enable triangulation. Therefore, in one or more examples, the method comprises determining whether a distance between the respective landmarks is equal to or larger than a third threshold distance. In other words, during probing of the second landmark, the method comprises checking, such as determining, whether the second landmark is sufficiently spaced apart from the first landmark. In one or more examples, the third threshold distance may be in the range of 0.8-2.2 cm, such as 1-2 cm. Upon the second landmark being sufficiently spaced apart from the first landmark, the collected second data set may be used, such as stored. Upon the second landmark not being sufficiently spaced apart from the first landmark, the second data set may be discarded. Optionally, an indication may be output, the indication indicating to a user of the system that the current landmark does not meet the criteria and that a new landmark has to be found and probed. The indication may be a visual or an audible indication.

[0037] Correspondingly, when the third landmark is probed, the method may comprise determining whether the third landmark is sufficiently spaced apart from the first landmark and the second landmark respectively. Additionally, the method may comprise determining, such as checking, whether the landmarks, such as the first, second and third landmark, are arranged on a straight line. In case the landmarks are all arranged in a straight line, triangulation of the marker member is not possible. Therefore, the method may comprise checking to ensure that the landmarks are arranged in a triangular constellation, to enable the triangulation of the marker member. Upon determining that all three landmarks are arranged in a straight line, the third data set may be discarded. Upon determining that the landmarks are arranged in a triangular constellation, the third data set may be collected and used for further processing.

[0038] In one or more example methods, the method comprises aligning a number of data points comprised respectively in the first data set, the second data set, and the third data set to a predetermined number of data points. By aligning the number of data points in the respective data sets, each landmark can be awarded the same weight, thereby contributing equally to the determination of the position of the marker member. In oneor more examples, the number of data points may be aligned by downsampling the number of data points to the predetermined number of data points. The predetermined number of data points may be lower than the first threshold number. In one or more example methods, the predetermined number of data points is 100 data points. For example, in scenarios where the number of data points captured in the data set is equal to or above the first threshold number, the number of data points may be downsampled to the predetermined number of data points, such as from 120 to 100 data points. By downsampling the number of data points in the data sets, a computational efficiency of the method may be increased. In one or more examples, aligning the number of datapoints, such as downsampling the number of data points, comprises deleting one of the two data points defining the closest pairwise distance in each respective data set, until the predetermined number of data points has been reached.

[0039] In one or more examples, the downsampling may be performed by deleting a data point being located farther away than 5 mm from the next closest data point from the set of data points.

[0040] In one or more examples, the downsampling may be performed by deleting one of the data points in the closest pair of points in the data set iteratively until the predetermined number of data points is reached. The actual distance between the points is not relevant, instead one of the data points in the pair of data points arranged the closest to each other is removed to achieve a homogeneous distribution of data points in the data set by thinning out, such as reducing the density of, the data points.

[0041] As mentioned above, when the landmark is an artificial landmark, such as a fiducial marker or a screw, a single data point may be captured during probing and this data point may then be upsampled to the predetermined number of data points, in order to align the number of data points in the data sets.

[0042] Upon the first, the second and the third data set meeting the one or more data collection criteria, the method comprises matching the first data set, the second data set, and the third data set, such as the plurality of data points in each data set, to a digital model of the dental and / or cranio-maxillofacial structure. The digital model of the dental and / or cranio-maxillofacial structure may be a digital model obtained based on an intraoral scan of the oral cavity, such as an upper jaw or lower jaw of the patient. The digital model of the dental and / or cranio-maxillofacial structure may comprise apatient specific coordinate system. The intraoral scan may be performed prior to performing the method for determining the position of the marker member.

[0043] To determine the position of the marker relative to the digital model of the dental and / or cranio-maxillofacial structure, the method comprises mapping the position of the marker member to the digital model of the dental and / or cranio-facial structure based, at least in part, on the first data set, the second data set, and the third data sets. The mapping of the position of the marker member to the digital model of the dental and / or cranio-facial structure may be based on the data points comprised in the first data set, the second dataset and the third data set. In other words, the data points comprised in these datasets may be mapped to the digital model, such as to corresponding data points of the digital model, to ensure accurate spatial alignment. The shapes defined by the data points in the first, second, and third data sets may be compared and aligned with the corresponding shapes within the digital model. In this process, the obtained data sets are overlaid onto the digital model to facilitate the alignment, superimposition, and mapping of corresponding landmarks between the datasets and the digital model.

[0044] To achieve precise positioning, the data sets are iteratively adjusted until the corresponding data points, representing key landmarks in the first, second, and third data sets, are accurately aligned with their counterparts in the digital model. Proper alignment is considered achieved when the deviation in shape and orientation of the landmarks meets or exceeds a predefined deviation threshold.

[0045] Once the datasets have been successfully mapped to the digital model, the position of the marker member can be transformed from the marker coordinate system to the patient coordinate system of the digital model. This transformation enables the determination of the marker member’s position within the digital model, allowing the computer-assisted surgery (CAS) system to continuously track the position and orientation of the handpiece throughout the surgical procedure, provided that the marker member remains monitored by the imaging unit.

[0046] In one or more example methods, obtaining the data sets, such as the first, second and third data sets, may be initiated by placing the probe tip on the respective landmark and maintaining the position for a predetermined initiating period. Upon the position of the probe being maintained for the predetermined initiating period, such asa specified number of frames, the system may be configured to initiate the detection of a marker member and commence recording data points. Maintaining the position of the probe tip for a predetermined initiating period can herein be seen as refraining from moving the probe tip beyond a predetermined distance over the predetermined initiating period. The predetermined distance may for example be 1mm. In other words, the position of the probe tip is considered maintained as long as its movement does not exceed 1 mm during the predetermined initiating period. In one or more examples, the predetermined initiating period may correspond to 20 frames, with each frame having a duration of for example 124 ms. In other words, initiating obtaining the first data set may comprise placing the probe tip on the first landmark and maintaining the position of the probe tip on the first landmark for the predetermined initiating period. Initiating obtaining the second data set may comprise placing the probe tip on the second landmark and maintaining the position of the probe tip on the second landmark for the predetermined initiating period. Initiating obtaining the third data set comprises placing the probe tip on the third landmark and maintaining the position of the probe tip on the third landmark for the predetermined initiating period.

[0047] A challenge arises when the marker member’s position, such as a rotational position, on the support is changed during the procedure. Typically, this would require a repeated localization process even if the support remains fixed. To address this, the method may comprise obtaining information indicative of a new rotational position, such as a new orientation, of the marker member on the support. The method may further comprise determining an updated position of the marker member based at least in part on the obtained information and the geometry of the mounting interface. This enables a determination of the updated position of the marker member based on the initial localization and the geometry of the mounting interface of the support, without having to perform a new localization procedure. This solution saves time and improves the workflow, particularly when placing implants in different quadrants where marker rotation adjustments are needed for visibility.

[0048] In one or more examples, the geometry of the mounting interface is star-shaped and supports a plurality of distinct rotational positions, such as in the range of 8-12 rotational positions. The method may further comprise obtaining information indicativeof the geometry of the mounting interface, such as the number of distinct positions and / or an angular distance between the distinct rotational position.

[0049] The updated position of the marker member can be determined without rerunning a full localization procedure by exploiting the known geometry of the mounting interface, such as the star-shaped interface, that permits a fixed number of discrete rotational orientations of the marker member. Since both the base and the marker member have predetermined mating geometries, all orientations of the marker member permitted by the geometry of the mounting interface can be calculated in advance and stored in a library. When the marker member is rotated during the procedure, the imaging system, which has a known field of view and / or known set of orientations, captures the new appearance of the marker member, such as the pattern of the marker member, which can be compared to the pre-rotation view to identify the corresponding orientation of the marker member from the library. Alternatively, instead of relying on camera-based detection, a user of the system may input the number of distinct positions, such as index steps or star points, by which the marker was rotated into the system, thereby enabling the system to directly retrieve the correct orientation from the library. In both cases, the system can immediately compute the marker member’s new spatial orientation based on the original localization and the predefined geometry of the mounting interface. The current disclosure further provides a system for determining a position of the marker member for alignment of the surgical handpiece. The system comprises the marker member, the surgical handpiece, an imaging unit, and a probe comprising a probe tip. The marker member may be configured to be arranged to a dental and / or cranio-maxillofacial structure of a patient. The imaging unit may be configured to be releasably attached to the surgical handpiece at a first section of the surgical handpiece and configured to detect the marker member when in use. The probe is releasable attached to the surgical handpiece at a second section of the surgical handpiece, such as at a defined position relative to the imaging unit. The system may further comprise an interface, a memory, and one or more processors, wherein the one or more processors are configured to perform a method as described herein.

[0050] The system, such as the one or more processors, is configured to obtain, e.g. via the interface and the imaging unit, a data set, such as a plurality of data sets, such as a first data set indicative of a shape of a first landmark and a position of the first landmarkrelative to the marker member, a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member, and a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member.

[0051] The system, such as the one or more processors, may obtain a data set, such as the first, and / or the second and / or the third data set by registering one or more data point(s) and a detected distance and direction relative to the marker member for each of the one or more data point(s) upon the probe tip being moved along the respective landmark. The landmarks are associated with the dental and / or cranio-maxillofacial structure. The distance and the direction relative to the marker member may be detected by the imaging unit and sent to the one or more processors via the interface.

[0052] In one or more examples, the system, such as the one or more processors, is configured to initiate obtaining of the data seat, such as the first data set, the second data set, and / or the third data set, by detecting that the probe tip is maintained in the same position for the predetermined initiating period. In other words, the system, such as the one or more processors, may be configured to initiate an obtaining of the data set, such as the first data set by placing the probe tip on the first landmark and maintaining the position for the predetermined initiating period. Accordingly, the system may be configured to initiate an obtaining of the second data set by placing the probe tip on the second landmark and maintaining the position for a predetermined initiating period, and to initiate an obtaining of the third data set by placing the probe tip on the third landmark and maintaining the position for a predetermined initiating period.

[0053] The system, such as the one or more processors, may be configured to determine whether the data set, such as the first, second and / or third data set meet one or more data collection criteria. The system, such as the one or more processors, may be configured to match the data set, such as the first data set, the second data set, and the third set, to a digital model of the dental and / or cranio-maxillofacial structure, upon the first, and / or second, and / or third data sets meeting the one or more data collection criteria.

[0054] The system, such as the one or more processors, may be configured to map the position of the marker member to the digital model of the dental and / or cranio-facialstructure based at least in part on the data points(s) of the data set, such as the first data set, the second data set, and / or the third data set.

[0055] The system, such as the one or more processors, may be configured to determine that a first data collection criterion is met upon a number of data points recorded in the set being equal to or above the first threshold number, such as equal to or above 50 data points.

[0056] The system, such as the one or more processors, may be configured to determine that a second data collection criterion is met upon the recorded data points being located on at least two different planes. This criterion may not apply to an artificial landmark, such as a screw, a pin or a fiducial marker, having exactly one position and no topology constraints.

[0057] The system, such as the one or more processors, may be configured to determine that a third data collection criterion is met upon the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance, such as the first threshold distance mentioned herein in relation to the method.

[0058] The system, such as the one or more processors, may be configured to determine that a fourth data collection criterion is met upon the two data points defining the greatest pairwise distance in the data set have a pairwise distance being equal to or larger than a second threshold distance, such as the second threshold distance mentioned herein in relation to the method.

[0059] The system, such as the one or more processors, may be configured to determine that a fifth data collection criterion is met upon a ratio between the number of data points on each plane is equal to or higher than 1 :4.

[0060] In one or more examples, the system, such as the one or more processors, is configured to obtain the first data set, and / or second data set, and / or third data set by capturing one or more data point(s) while the probe tip is moved along the respective landmark.

[0061] In one or more examples, the system, such as the one or more processors, is configured to align a number of datapoints comprised in the data set, such as comprised respectively in the first data set, the second data set, and the third data set, to a predetermined number of data points. In one or more examples, the system, such as theone or more processors, is configured to align the number of data points by downsampling the number of data points to the predetermined number of data points.

[0062] In one or more examples, the system is configured to align the number of datapoints by deleting any data points defining a pairwise distance larger than the first threshold distance in each respective data set.

[0063] In one or more examples, the system, such as the one or more processors, is configured to match the data set, such as the first data set, and / or the second data set, and / or the third set to the digital model based on the shape of the respective landmark.

[0064] In one or more examples, the system, such as the one or more processors, is configured to, upon one or more of the first data set, the second data set, and the third data set not meeting the one or more data collection criteria, discard that data set. Discarding the data set may comprise initiating obtaining a new data set.

[0065] In one or more examples, the system, such as the one or more processor(s), is configured to obtain information indicative of a new rotational position, such as a new orientation, of the marker member on the support. The system, such as the one or more processors, may further be configured to determine an updated position of the marker member based at least in part on the obtained information and the geometry of the mounting interface. This enables the system to determine the updated position of the marker member based on the initial, such as the previous, localization and the geometry of the mounting interface of the support, without having to perform a new localization procedure. In one or more examples, the geometry of the mounting interface is starshaped and supports a plurality of distinct rotational positions, such as in the range of 8-12 rotational positions. The system, such as the one or more processor(s) may further be configured to obtain information indicative of the geometry of the mounting interface, such as the number of distinct positions and / or an angular distance between the distinct rotational position.

[0066] Fig. 1 illustrates an example system 1 for determining a position of a marker member for alignment of a surgical handpiece, such as for determining a position of a marker member in a digital model. The system 1 comprises a marker member 2, the surgical handpiece 3, an imaging unit 4, and a probe 5 comprising a probe tip 6. The system 1 may further comprise processing circuitry 10 for processing data obtained by the surgical handpiece 3 and / or the imaging unit 4. The processing circuitry 10comprises one or more processors / processor circuitry 11, imaging circuitry 12, memory / memory circuitry 13 and an interface 14. The marker member 2 may be configured to be arranged to a dental and / or cranio-maxillofacial structure of a patient. The imaging unit 4 is arranged on, such as releasably attached to, the surgical handpiece at a first section 31 of the surgical handpiece 3. The imaging unit 4 is configured to detect the marker member during the use of the surgical handpiece 3, such as while performing a procedure. The probe 5 is arranged on, such as releasable attached to, the surgical handpiece 3 at a second section 32 of the surgical handpiece 3, such as arranged at a defined position relative to the imaging unit 4. The first section 31 may be arranged at a first end of the handpiece 3 and the second section 32 may be arranged at a second end if the handpiece 3. The imaging unit 4 may be configured to communicate with the processing circuitry 10 via the interface 14. The interface 14 may be a wired or wireless interface.

[0067] The example system 1, such as the one or more processor(s) 11, is configured to perform a method as described herein. In other words, the system 1, such as the one or more processor(s) 11, is configured to obtain a plurality of data sets, such as a first data set indicative of a shape of a first landmark and a position of the first landmark relative to the marker member, a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member, and a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member. The imaging unit 4 is configured to monitor the marker member 2 during probing of the respective landmarks and detect a distance and / or a direction of the probed landmark relative to the marker member 2. The imaging unit 4 may provide data, such as a set of data points, indicative of the distance and / or a direction of the probed landmark relative to the marker member 2 to the one or more processor(s) 11 via the interface 14. This may be done upon the probe tip 6 being moved along the respective landmark. The one or more processor(s) 11 may obtain the first data set, the second data set and / or the third data set, by registering one or more data point(s) and the detected distance and / or direction relative to the marker member for each of the one or more data point(s), for example upon the probe tip being moved along the respective landmark.The one or more processor(s) 11 are configured to determine whether the first, second and / or third data set meet one or more data collection criteria.

[0068] The one or more processor(s) 11 and / or the imaging circuitry 12 are configured to, upon the first, second and third data sets meeting the one or more data collection criteria, match the first data set, the second data set, and the third set to a digital model of the dental and / or cranio-maxillofacial structure.

[0069] The one or more processor(s) 11 and / or the imaging circuitry 12 are configured to map the position of the marker member 2 to the digital model of the dental and / or cranio-facial structure based at least in part on the data points(s) of the first data set, the second data set, and the third data set.

[0070] The system 1, such as the one or more processors 11, may be configured to initiate obtaining of the first data set, the second data set, and / or the third data set by detecting, e.g. via the imaging unit 4, that the probe tip 6 is maintained in a same position for a predetermined initiating period.

[0071] Fig. 2 illustrate a scenario for determining a position of the marker member for alignment of the surgical handpiece, such as during computer assisted surgery.

[0072] Three reference landmarks may be established, such as a first landmark LM1, a second landmark LM2 and a third landmark LM3. The three landmarks may be known landmarks identified on a dental or craniofacial structure of a patient. These landmarks may be one or more of teeth (e.g., molars or incisors), pre-set screws or fiducial markers, and bone structures. Each landmark has a known, fixed position within a patient coordinate system, which may be obtained from a preoperative scan, such as an intraoral scan, or a digital model. The landmarks may be selected so that they are arranged in a triangular constellation, to allow a triangulation for determining the position of the marker member 2.

[0073] A marker member, such as the marker member 2, may be arranged to a dental and / or cranio-maxillofacial structure of the patient, such as placed near a surgical site. The marker member being arranged to can herein be seen as being fixedly arranged in relation to the dental and / or cranio-maxillofacial structure, but does not necessarily require the marker member to be arranged on the dental and / or cranio-maxillofacial structure. In order to track the surgical handpiece during a procedure, such as a CAS, the position of the marker member must be determined relative to the landmarks.Using the system disclosed herein, such as the surgical handpiece having the probe and the imaging unit (as shown in Fig. 1), the landmarks may be probed and the relative positions, such as the relative distances and directions, between the marker member and each of the three landmarks are measured.

[0074] To calculate the exact position of the marker member 2 within the coordinate system of the patient, triangulation of the marker member based on the relative positions of the landmarks. Triangulation involves using the measured distances and / or the directions between the marker member 2 and the three known landmarks LM1, LM2, LM3. Mathematically, the triangulation can be solved using one or more of a Three-sphere intersection (for distance-based triangulation), an angle-based triangulation (if angles between points are known), and a least squares optimization (to refine the marker member positioning). By solving these equations, the exact (x, y, z) position of the marker is determined relative to the landmarks.

[0075] Once the position of the marker member relative to the landmarks has been determined within the reference system of the marker member, the coordinates of the marker member may be transformed into the digital model of the of the dental and / or cranio-facial structure of the patient, allowing the surgical handpiece to be tracked relative to the marker within the digital model.

[0076] Fig. 3 is a flow chart illustrating a method 200 for determining a position of the marker member for alignment of a surgical handpiece according to the current disclosure. The method may be performed using the system 1 shown in Fig. 1.

[0077] In one or more examples, the method 200 comprises providing S202 the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient.

[0078] In one or more examples, the method comprises initiating S204 obtaining of a data set, such as the first data set, the second data set, and / or the third data set, by placing the probe tip on the respective landmark and maintaining the position for a predetermined initiating period. Maintaining the position of the probe tip for a predetermined initiating period comprises refraining from moving the probe tip beyond a predetermined distance over a predetermined initiating period. The predetermined distance may for example be 1mm. In one or more examples, the predetermined initiating period may correspond to 20 frames, with each frame having a duration of forexample 124 ms. In other words, initiating obtaining the first data set may comprise placing the probe tip on the first landmark and maintaining the position of the probe tip on the first landmark for the predetermined initiating period. Initiating obtaining the second data set may comprise placing the probe tip on the second landmark and maintaining the position of the probe tip on the second landmark for the predetermined initiating period. Initiating obtaining the third data set comprises placing the probe tip on the third landmark and maintaining the position of the probe tip on the third landmark for the predetermined initiating period.

[0079] The method 200 comprises obtaining S206 a data set, such as a first data set, indicative of a shape of a landmark, such as a first landmark, and a position of the landmark, such as the first landmark, relative to the marker member. The method 200 may further comprise obtaining S206 a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member, and a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member. The landmarks may be associated with the dental and / or cranio-maxillofacial structure. Obtaining the data sets comprises probing the respective landmark using the probe tip of the surgical handpiece while detecting the marker member with the imaging unit. A probing procedure according to the current disclosure is described in further detail with reference to Figs. 4A-G. The landmark(s) may be a solid part of the dental and / or cranio-facial structure, such as one or more of a tooth, a pre-set screw or pin, or a bone associated with the dental and / or cranio-facial structure. The relative position may comprise a distance and a direction, such as an angular direction, relative to the marker element.

[0080] The method 200 comprises determining S208 whether the data set, such as the first, and / or second and / or third data set meets one or more data collection criteria. The one or more data collection criteria comprise one or more of a number of data points recorded in the set being equal to or above a first threshold number, the recorded data points being located on at least two different planes, the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance, the two data points defining the greatest pairwise distance in the data set have a pairwise distance being equal to or larger than a secondthreshold distance, and a ratio between the number of data points on each plane is equal to or higher than 1:4.

[0081] In other words, a first data collection criteria of the one or more data collection criteria may specify that a number of data points recorded in the set is equal to or above a first threshold number. A second data collection criteria of the one or more data collection criteria may specify that the recorded data points are located on at least two different planes. A third data collection criteria of the one or more data collection criteria may specify that the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance. A fourth data collection criteria of the one or more data collection criteria may specify that the two data points defining the greatest pairwise distance in the data set have a pairwise distance equal to or larger, such as greater, than a second threshold distance. A fifth data collection criteria of the one or more data collection criteria may specify that a ratio between the number of data points on each plane is equal to or higher than 1:4.

[0082] In one or more examples, the method comprises aligning S210 a number of data points comprised respectively in the first data set, the second data set, and / or the third data set to a predetermined number of data points. Aligning S210 the number of datapoints may comprise deleting S210A any data points defining a pairwise distance larger than the first threshold distance in each respective data set. In one or more examples, the number of data points may be aligned by downsampling the number of data points to the predetermined number of data points.

[0083] In one or more example methods, such as when the landmark is an artificial landmark, such as a fiducial marker or a screw, a single data point may be captured during probing. In this case, aligning S210 may comprise upsampling S210B the single data point to the predetermined number of data points, in order to align the number of data points in the data sets.

[0084] The method 200 further comprises, upon the first, the second and the third data set meeting the one or more data collection criteria, matching S212 the data set, such as the first data set, the second data set, and the third data set, to a digital model of the dental and / or cranio-maxillofacial structure.The method 200 further comprises mapping S214 the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data set, such as the first data set, the second data set, and / or the third data set, such as based on one or more of the data points comprised in the respective data set(s). In other words, mapping the position of the marker member to the digital model of the dental and / or cranio-facial structure may be based on the data points comprised in the first data set, the second dataset and the third data set. Mapping of the position of the marker member to the digital model of the dental and / or cranio-facial structure may be based on the data points comprised in the first data set, the second dataset and the third data set. In other words, the data points comprised in these datasets may be mapped, such as overlayed, to the digital model, such as to corresponding data points of the digital model, to ensure accurate spatial alignment.

[0085] Figs. 4A-4F illustrate a probing procedure for determining one or more of a shape, a position, and an orientation of the landmark(s) relative to a reference coordinate system, such as to the coordinate system of the marker member. During the probing procedure the probe tip 6 of the probe 5 is moved along one or more surfaces of the landmark, in Figs. 4A-G represented by a tooth 20. As can be seen in Figs. 4A-4B, the probing may comprise moving the probe tip along a first surface of the landmark, such as a lingual surface or a palatal surface of the tooth 20, to trace the shape of the first side. Once the first side of the landmark has been probed, the probe tip may be moved to a second surface being substantially perpendicular to the first side, such as to an occlusal surface of the tooth 20, as shown in Figs. 4C-4D. Finally, a third surface, such as a facial surface (e.g. buccal or a labial surface) of the tooth 20 may be probed, as shown in Figs. 4E-4F. Moving the probe tip 6 along the respective surfaces may comprise moving it in between an anterior end and a posterior end, between a coronal end and an apical end, and / or between a facial and a lingual or palatal surface. While the probe tip 6 is moved along the one or more surfaces, the probe tip physically touches multiple points on the surface of the landmark. A data point indicative of the relative position of the data point to the marker member may be recorded by the one or more processor(s) and / or the imaging unit, thereby defining a spatial structure of the landmark. The spatial structure may be indicative of one or more of a shape, a position, and an orientation of the landmark in relation to the marker member. The collected datapoints may thus create a mapped outline of the landmark which can be used to align the landmark to its own representation in the digital model and thus enables an alignment of the actual position of the marker member relative to the landmarks within the digital model.

[0086] Figs. 5A-5B illustrate further example anatomical areas that may be used as landmarks in the method disclosed herein. Anatomical reference points serve as essential landmarks for accurately positioning a marker member in both the upper and lower jaw. In scenarios where the patient is edentulous, i.e. is missing all teeth, other reference points than teeth may be used as landmarks when positioning the marker member in the digital model. As shown in Fig. 5A, in the upper jaw, key anatomical reference points include the incisive papilla 50, which is located behind the central incisors and may serve as a stable landmark; the palatine rugae 51, a series of ridges on the anterior palate that provide orientation; and the palatine raphe 53, a midline structure running along the hard palate. Additionally, the midline of the alveolar ridge 52 and the maximum extension of the impression tray vestibularly 54, which determines the furthest extent of an impression tray in the vestibular area, may be suitable as landmarks. The maxillary tuberosity 55, a posterior bony prominence, and the Ah-line 56, which marks the transition between the hard and soft palate, are also reference points suitable as landmarks for determining the position of the marker member. In the lower jaw, any one of the midline 53, which may be transferred from the palatine raphe of the upper jaw, the midline of the alveolar ridge 52, the maximum extension of the impression tray vestibularly 54A and lingually 54B, and the retromolar triangle 57, a triangular area behind the last molar, may serve as anatomical landmarks for ensuring accurate of the marker member.

[0087] Fig. 5B shows additional anatomical areas in the upper jaw that may be used as landmarks according to this disclosure. These anatomical areas are the fibrous peripheral zone 61, the fibrous median zone 62, the glandular zone 63, and the fat pad zone 64.

[0088] Figs. 6A-6B illustrate example steps of the method disclosed herein for fully edentulous cases, where no natural landmarks, such as teeth, can be found. A plurality of artificial landmarks, such as screws, pins, or fiducial markers, may be inserted into a bone, such as a jaw bone, of the patient prior to performing an intraoral scan of the oralcavity is performed. In the example shown in Fig. 6A, three artificial landmarks LR1, LR2 and LR3, in this case screws, may be screwed into the bone of the patient. Once the artificial markers have been placed, an intraoral scan of the oral cavity with the artificial landmarks may be performed to generate the digital model of the dental and / or cranio-maxillofacial structure of the edentulous per son.

[0089] As shown in Fig. 6B, the marker member 2 may be positioned relative to the cranio-maxillofacial structure by attaching it to a support 70 secured to the bone, such as the jaw bone, of the patient via one or more securing elements 71, such as screws or pins. The support 70 may be designed to engage a dental and / or craniomaxillofacial structure through a broad oral support surface that conforms to the underlying jawbone. A mounting interface 72, such as a rotationally asymmetric post, keyed connection, or other anti-rotation geometry, may project from an oral-facing side of the support 70 and may be configured to receive the marker member 2 in a plurality of predefined orientations. In one or more examples, the mounting interface 72 may be a starshaped rotationally asymmetric interface providing a plurality of distinct rotational positions for receiving the marker member 2. The marker member 2 can thus be arranged to face in a plurality of directions while in a same location in the oral anatomy. The underside of the support 30 may further comprise one or more stabilizing projections and / or apertures configured to receive the securing elements for fixation of the support to the jawbone. Once the marker member has been positioned, the artificial landmarks LM1, LM2 and LM3 may probed using the probe tip of the surgical handpiece and a data point indicate of the artificial landmarks position relative to the marker member can be recorded. Due to the limited surface area of the artificial landmark, a data set indicative of the artificial landmark may only comprise one single data point. To ensure consistency within the datasets, this single data point may be upsampled, for instance by recording it multiple times until the total number of data points for the respective dataset meets the minimum required threshold, such as a first threshold number or a predetermined number of data points. This may be repeated for each of the artificial landmarks LM1, LM2 and LM3, until a data set indicative of the three landmarks, such as respective data set for each landmark, has been recorded. The data set(s) may then be used to determine the relative position of the marker member 2 and to map the position of the marker member to the digital model of the cranio-maxillofacial structure.Examples of methods and products (method and system for determining a position of a marker member) according to the disclosure are set out in the following items:

[0090] Item 1 A. A method for determining a position of a marker member for alignment of a surgical handpiece, the surgical handpiece having an imaging unit releasably attached thereto and configured to detect the marker member and a probe comprising a probe tip arranged at a defined position relative to the imaging unit, wherein the method comprises:

[0091] - providing (S202) the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient, obtaining (S206)

[0092] i. a first data set indicative of a shape of a first landmark and a position of the first landmark relative to the marker member, ii. a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member, and

[0093] iii. a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member, wherein the landmarks are associated with the dental and / or cranio-maxillofacial structure, wherein the data sets are obtained by probing the respective landmark using the probe tip of the surgical handpiece while detecting the marker member with the imaging unit,

[0094] determining (S208) whether the first, second and / or third data set meets one or more data collection criteria,

[0095] - upon the first, the second and the third data set meeting the one or more data collection criteria, matching (S212) the first data set, the second data set, and the third data set to a digital model of the dental and / or cranio-maxillofacial structure, andmapping (S214) the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the first data set, the second data set, and the third data set.

[0096] Item IB. A method for determining a position of a marker member for alignment of a surgical handpiece the surgical handpiece having an imaging unit releasably attached thereto and configured to detect the marker member and a probe comprising a probe tip arranged at a defined position relative to the imaging unit, wherein the method comprises:

[0097] - providing (S202) the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient, obtaining (S206) a data set indicative of a shape of a landmark and a position of the landmark relative to the marker member, determining (S208) whether the data set meets one or more data collection criteria,

[0098] - upon the data set meeting the one or more data collection criteria, matching (S212) the data set to a digital model of the dental and / or cranio-maxillofacial structure, and

[0099] - mapping (S214) the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data set.

[0100] Item 2. The method according to Item 1 A or IB, wherein the one or more data collection criteria comprise one or more of:

[0101] a number of data points recorded in the set being equal to or above a first threshold number,

[0102] - the recorded data points being located on at least two different planes, - the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance,

[0103] - the two data points defining the greatest pairwise distance in the data set have a pairwise distance being equal to or larger than a second threshold distance, anda ratio between the number of data points on each plane is equal to or higher than 1:4.

[0104] Item 3. The method according to any one of the previous Items, wherein the method comprises aligning (S210) a number of data points comprised respectively in the data set, such as the first data set, the second data set, and the third data set, to a predetermined number of data points.

[0105] Item 4. The method according to Item 3, wherein aligning (S210) the number of datapoints comprises:

[0106] deleting (S210A) any data points defining a pairwise distance larger than the first threshold distance in each respective data set.

[0107] Item 5. The method according to any one of the previous Items, wherein mapping the position of the marker member to the digital model of the dental and / or cranio-facial structure is based on the data points comprised in the data set, such as the first data set, the second dataset and the third data set.

[0108] Item 6. The method according to any one of the previous Items, wherein the method comprises:

[0109] - initiating (S204) obtaining of the first data set, the second data set, and / or the third data set by placing the probe tip on the respective landmark and maintaining the position for a predetermined initiating period.

[0110] Item 7. The method according to Item 6, wherein maintaining the position of the probe tip for a predetermined initiating period comprises refraining from moving the probe tip beyond a predetermined distance over the predetermined initiating period.

[0111] Item 8. The method according to any one of the previous Items, wherein the landmark is a solid part of the dental and / or cranio-facial structure.Item 9. The method according to any one of the previous Items, wherein the landmark is one or more of a tooth, a pre-set screw or pin, or a bone associated with the dental and / or cranio-facial structure.

[0112] Item 10. The method according to any one of the previous Items, wherein the relative position comprises a distance and a direction relative to the marker element.

[0113] Item 11. The method according to any one of the previous Items, further comprising obtaining information indicative of an updated rotational position of the marker member on a support.

[0114] Item 12. The method according to Item 11, wherein obtaining the information comprises detecting, via the imaging unit, a new orientation of the marker member based on a pattern captured by the imaging unit.

[0115] Item 13. The method according to Item 11, wherein obtaining the information comprises receiving a user input indicative of a number of distinct positions by which the marker member has been rotated on a support.

[0116] Item 14. The method of any one of Items 11 to 13, further comprising determining an updated position of the marker member based at least in part on the obtained information and a geometry of a mounting interface.

[0117] Item 15. The method of Item 14, wherein the geometry of the mounting interface is star-shaped and supports a plurality of distinct rotational positions.

[0118] Item 16. The method of any one of Items 14 to 15, further comprising obtaining information indicative of the geometry of the mounting interface, including a number of distinct rotational positions and / or an angular distance between adjacent rotational positions.Item 17. The method of any one of the previous Items, wherein all orientations of the marker member permitted by the geometry of the mounting interface are stored in a library.

[0119] Item 18. The method of any one of the Items 11 to 17, wherein determining the updated position of the marker member comprises comparing a captured appearance of the marker member with stored orientations in a library to identify a corresponding rotational orientation of the marker member.

[0120] Item 19A. A system for determining a position of a marker member for alignment of a surgical handpiece, the system comprising:

[0121] the marker member, wherein the marker member is configured to be arranged to a dental and / or cranio-maxillofacial structure of a patient, - the surgical handpiece,

[0122] an imaging unit, the imaging unit being releasably attached to the surgical handpiece at a first section of the surgical handpiece and configured to detect the marker member, and

[0123] a probe comprising a probe tip, wherein the probe is releasable attached to the surgical handpiece at a second section of the surgical handpiece, wherein the system is configured to:

[0124] obtain

[0125] i. a first data set indicative of a shape of a first landmark and a position of the first landmark relative to the marker member, ii. a second data set indicative of a shape of a second landmark and a position of the second landmark relative to the marker member, and

[0126] iii. a third data set indicative of a shape of a third landmark and a position of the third landmark relative to the marker member, by registering one or more data point(s) and a detected distance and direction relative to the marker member for each of the one or more data point(s) upon the probe tip being moved along therespective landmark, wherein the landmarks are associated with the dental and / or cranio-maxillofacial structure, determine whether the first, second and / or third data set meet one or more data collection criteria,

[0127] - upon the first, second and third data sets meeting the one or more data collection criteria, match the first data set, the second data set, and the third set to a digital model of the dental and / or cranio-maxillofacial structure, and

[0128] - map the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data points(s) of the first data set, the second data set, and the third data set.

[0129] Item 19B. A system for determining a position of a marker member for alignment of a surgical handpiece, the system comprising:

[0130] the marker member, wherein the marker member is configured to be arranged to a dental and / or cranio-maxillofacial structure of a patient, - the surgical handpiece,

[0131] an imaging unit, the imaging unit being releasably attached to the surgical handpiece at a first section of the surgical handpiece and configured to detect the marker member, and

[0132] a probe comprising a probe tip, wherein the probe is releasable attached to the surgical handpiece at a second section of the surgical handpiece, wherein the system is configured to:

[0133] obtain a data set indicative of a shape of a landmark and a position of the first landmark relative to the marker member by registering one or more data point(s) and a detected distance and direction relative to the marker member for each of the one or more data point(s) upon the probe tip being moved along the landmark, wherein the landmark is associated with the dental and / or cranio-maxillofacial structure,

[0134] determine whether the data set meets one or more data collection criteria,- upon the data set meeting the one or more data collection criteria, match the data set to a digital model of the dental and / or cranio-maxillofacial structure, and

[0135] - map the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data points(s) of the data set.

[0136] Item 20. The system according to Item 19A or 19B, wherein the one or more data collection criteria comprise one or more of:

[0137] a number of data points recorded in the set being equal to or above a first threshold number,

[0138] - the recorded data points being located on at least two different planes, - the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance,

[0139] - the two data points defining the greatest pairwise distance in the data set have a pairwise distance being equal to or larger than a second threshold distance, and

[0140] a ratio between the number of data points on each plane is equal to or higher than 1:4.

[0141] Item 21. The system according to any one of the Items 19 A, 19B, and 20, wherein the system is configured to obtain the data set, such as the first, second and / or third data set, by registering one or more data point(s) while the probe tip is moved along the respective landmark.

[0142] Item 22. The system according to any one of the Items 19A to 21, wherein the system is configured to align a number of datapoints comprised in the data set, such as comprised respectively in the first data set, the second data set, and the third data set, to a predetermined number of data points.Item 23. The system according to Item 22, wherein the system is configured to delete any data points defining a pairwise distance larger than the first threshold distance in the data set, such as in each respective data set.

[0143] Item 24. The system according to any one of Items 19A to 23, wherein the system is configured to match the first data set, the second data set, and the third set to the digital model based on the shape of the respective landmark.

[0144] Item 25. The system according to any one of the Items 19A to 24, wherein the system is configured to initiate obtaining of the data set, such as the first data set, the second data set, and / or the third data set, by detecting that the probe tip is maintained in a same position for a predetermined initiating period.

[0145] Item 26. The system according to any one of the Items 19A to 25, wherein the system is configured to, upon the data set, such as one or more of the first data set, the second data set, and the third data set, not meeting the one or more data collection criteria, discard the data set not meeting the data collection criteria.

[0146] Item 27. The system according to any one of the Items 19A to 26, wherein the system is configured to obtain information indicative of an updated rotational position of the marker member on a support.

[0147] Item 28. The system according to the Item 27, wherein the system is configured to detect, via the imaging unit, a new orientation of the marker member based on a captured pattern of the marker member.

[0148] Item 29. The system according to Item 27, wherein the system is configured to receive a user input indicative of a number of distinct rotational positions by which the marker member has been rotated.Item 30. The system according to any one of the Items 27 to 29, wherein the system is configured to determine the updated rotational position of the marker member based at least in part on the obtained information and a geometry of a mounting interface.

[0149] Item 31. The system according to Item 30, wherein the geometry of the mounting interface is star-shaped and supports a plurality of distinct rotational positions.

[0150] Item 32. The system according to Item 31, wherein the plurality of distinct rotational positions is in the range of 8 to 12.

[0151] Item 33. The system according to any one of the Items 30 to 32, wherein the system is configured to obtain information indicative of the geometry of the mounting interface, including a number of distinct rotational positions and / or an angular distance between adjacent rotational positions.

[0152] Item 34. The system according to any one of the Items 30 to 33, further comprising a library storing all orientations of the marker member permitted by the geometry of the mounting interface.

[0153] Item 35. The system according to Item 34, wherein the system is configured to compare a captured appearance of the marker member with orientations stored in the library to identify a corresponding rotational orientation.

[0154] The use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not denote any order or importance, but rather the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used to distinguish one element from another. Note that the words “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used here and elsewhere for labelling purposes only and are not intended to denote anyspecific spatial or temporal ordering. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0155] It may be appreciated that the figures comprise some circuitries or operations which are illustrated with a solid line and some circuitries or operations which are illustrated with a dashed line. Circuitries or operations which are comprised in a solid line are circuitries or operations which are comprised in a broad embodiment. Circuitries or operations which are comprised in a dashed line are example embodiments which may be comprised in, or a part of, or are further circuitries or operations which may be taken in addition to circuitries or operations of the solid line example embodiments. It should be appreciated that these operations need not be performed in order presented. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any order and in any combination.

[0156] It is to be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed.

[0157] It is to be noted that the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements.

[0158] It is to be noted that the term “indicative of’ may be seen as “associated with”, “related to”, “descriptive of’, “characterizing”, and / or “defining”. The terms “indicative of’, “associated with”, “related to”, “descriptive of’, “characterizing”, and “defining” can be used interchangeably. The term “indicative of’ can be seen as indicating a relation.

[0159] It is to be noted that the word "based on" may be seen as “as a function of’ and / or “derived from”. The terms “based on” and “as a function of’ can be used interchangeably. For example, a parameter or data determined “based on” a data set can be seen as a parameter or data determined “as a function of’ the data set. In other words, the parameter or data may be an output of one or more functions with the data set as an input.

[0160] A function may be characterizing a relation between an input and an output, such as mathematical relation, a database relation, a hardware relation, logical relation, and / or other suitable relations.It should further be noted that any reference signs do not limit the scope of the claims, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several “means”, “units” or “devices” may be represented by the same item of hardware.

[0161] The various example methods, devices, and systems described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program circuitries may include routines, programs, objects, components, data structures, etc, that perform specified tasks or implement specific abstract data types. Computer-executable instructions, associated data structures, and program circuitries represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

[0162] The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

CLAIMS1. A method for determining a position of a marker member for alignment of a surgical handpiece the surgical handpiece having an imaging unit releasably attached thereto and configured to detect the marker member and a probe comprising a probe tip arranged at a defined position relative to the imaging unit, wherein the method comprises:- providing (S202) the marker member at a fixed position relative to a dental and / or cranio-maxillofacial structure of a patient,obtaining (S206) a data set indicative of a shape of a landmark and a position of the landmark relative to the marker member, determining (S208) whether the data set meets one or more data collection criteria, wherein a first data collection criterion of the one or more data collection criteria specifies that a number of data points recorded in the data set is equal to or above a first threshold number, - upon the data set meeting the one or more data collection criteria, matching (S212) the data set to a digital model of the dental and / or cranio-maxillofacial structure, and- mapping (S214) the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data set.

2. The method according to claim 1, wherein the one or more data collection criteria further comprise one or more of:- the recorded data points being located on at least two different planes, - the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance,- the two data points defining the greatest pairwise distance in the data set have a pairwise distance being equal to or larger than a second threshold distance, anda ratio between the number of data points on each plane is equal to or higher than 1:4.

3. The method according to claim 1 or 2, wherein the method comprises aligning (S210) a number of data points comprised respectively in the first data set, the second data set, and the third data set to a predetermined number of data points.

4. The method according to claim 3, wherein aligning (S210) the number of datapoints comprises:deleting (S210A) any data points defining a pairwise distance larger than the first threshold distance in each respective data set.

5. The method according to any one of the previous claims, wherein mapping the position of the marker member to the digital model of the dental and / or cranio-facial structure is based on the data points comprised in the first data set, the second dataset and the third data set.

6. The method according to any one of the previous claims, wherein the relative position comprises a distance and a direction relative to the marker element.

7. The method according to any one of the previous claims, wherein the method further comprises:obtaining information indicative of an updated rotational position of the marker member on a support, anddetermining an updated position of the marker member based at least in part on the obtained information and a geometry of a mounting interface.

8. A system for determining a position of a marker member for alignment of a surgical handpiece, the system comprising:the marker member, wherein the marker member is configured to be arranged to a dental and / or cranio-maxillofacial structure of a patient,- the surgical handpiece,an imaging unit, the imaging unit being releasably attached to the surgical handpiece at a first section of the surgical handpiece and configured to detect the marker member, anda probe comprising a probe tip, wherein the probe is releasable attached to the surgical handpiece at a second section of the surgical handpiece, wherein the system is configured to:obtain a data set indicative of a shape of a landmark and a position of the first landmark relative to the marker member by registering one or more data point(s) and a detected distance and direction relative to the marker member for each of the one or more data point(s) upon the probe tip being moved along the landmark, wherein the landmark is associated with the dental and / or cranio-maxillofacial structure,determine whether the data set meets one or more data collection criteria, wherein a first data collection criterion of the one or more data collection criteria specifies that a number of data points recorded in the data set is equal to or above a first threshold number,- upon the data set meeting the one or more data collection criteria, match the data set to a digital model of the dental and / or cranio-maxillofacial structure, and- map the position of the marker member to the digital model of the dental and / or cranio-facial structure based at least in part on the data points(s) of the data set.

9. The system according to claim 8, wherein the one or more data collection criteria further comprise one or more of- the recorded data points being located on at least two different planes, - the two data points defining the greatest pairwise distance in the data set being separated by a distance equal to or smaller than a first threshold distance,- the two data points defining the greatest pairwise distance in the data set have a pairwise distance being equal to or larger than a second threshold distance, anda ratio between the number of data points on each plane is equal to or higher than 1:4.

10. The system according to any one of claims 8 to 9, wherein the system is configured to obtain the first, second and / or third data set by registering one or more data point(s) while the probe tip is moved along the respective landmark.

11. The system according to any one of claims 8 to 10, wherein the system is configured to align a number of datapoints comprised respectively in the first data set, the second data set, and the third data set to a predetermined number of data points.

12. The system according to claim 11, wherein the system is configured to delete any data points defining a pairwise distance larger than the first threshold distance in each respective data set.

13. The system according to any one of claims 8 to 12, wherein the system is configured to match the first data set, the second data set, and the third set to the digital model based on the shape of the respective landmark.

14. The system according to any one of claims 8 to 13, wherein the system is configured to initiate obtaining of the first data set, the second data set, and / or the third data set by detecting that the probe tip is maintained in a same position for a predetermined initiating period.

15. The system according to any one of claims 8 to 14, wherein the system is configured to, upon one or more of the first data set, the second data set, andthe third data set not meeting the one or more data collection criteria, discard that data set.

16. The system according to any one of claims 8 to 15, wherein the wherein the system is configured to:obtain information indicative of an updated rotational position of the marker member on a support, anddetermine an updated position of the marker member based at least in part on the obtained information and a geometry of a mounting interface.

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