A method of 2D-3D registration constructs a three-dimensional open model and evaluates implant space stenosis

Abstract

This invention discloses a method for constructing a three-dimensional opening model using 2D-3D registration and evaluating implant spatial resistance, relating to the field of oral implant technology. The method includes: acquiring a patient's fully open-mouth photograph and correcting for distortion; acquiring a three-dimensional intraoral scanning model of the maxillary and mandibular dentition; performing 2D-3D registration based on the PnP algorithm; constructing a three-dimensional surgical area opening model; registering and overlapping the virtual implant site model with the opening model; importing a simulation instrument; establishing two collision detection methods: working stage detection and placement stage detection; performing dual detection on drilling and implantation steps respectively; and evaluating the feasibility of a relay implantation strategy for cases where implantation cannot be performed in one attempt. This invention requires only a single photograph and an intraoral scanning model to construct a three-dimensional opening model, eliminating the need for CBCT radiation exposure or expensive equipment. It elevates spatial resistance assessment from empirical qualitative to quantitative geometric analysis, accurately determining surgical accessibility under different instrument lengths and guidance methods, thereby improving the safety and predictability of implant surgery.

Description

Technical Field

[0001] This invention relates to the field of dental implant technology, specifically to a method for constructing a three-dimensional opening model using 2D-3D registration and evaluating implant space steric hindrance. Background Technology

[0002] In oral implant surgery, sufficient surgical area mouth opening (SO) is paramount to ensuring smooth instrument operation and avoiding three-dimensional spatial obstruction with the opposing jaw or surrounding anatomical structures. Insufficient SO may force the surgeon to alter the instrument's operating path or angle due to spatial obstruction, ultimately deviating from the target implantation site and affecting implant accuracy and restorative outcomes. Therefore, accurately assessing the patient's SO during the preoperative virtual design phase is crucial for instrument path planning, avoiding spatial obstruction, and ensuring surgical accessibility.

[0003] Current methods for obtaining patient SO have the following shortcomings: Traditional measuring rulers can only provide the opening distance in one dimension. However, spatial steric hindrance does not only occur in the implant axis, but may also exist in the steric hindrance of rigid structures such as adjacent teeth, dental arches, guide plates, and implant machine handles. One-dimensional SO is difficult to cover a comprehensive assessment of three-dimensional spatial steric hindrance.

[0004] Digital intraoral scanning with mouth opener requires patients to keep their mouths open for a long time, which is uncomfortable, and the excessively long scanning path may lead to image stitching errors.

[0005] Three-dimensional facial scanning or mandibular motion recording equipment is expensive and has a complex operating procedure, making it difficult to routinely perform in clinical practice.

[0006] Taking a CBCT scan with the mouth open increases radiation exposure and may produce motion artifacts, so it is generally not used as a routine examination method.

[0007] In recent years, monocular 6D pose estimation methods in computer vision technology can estimate the 6D pose (3D translation and 3D rotation) of an object from a single 2D photograph and register it with the object's 3D model to reconstruct the object's spatial state at the moment of capture. Applying this technology to the construction of 3D-SO (Simultaneous Oral Measurement), theoretically, only one open-mouth photograph containing the upper and lower jaws is needed. Combined with the patient's existing 3D intraoral scan model, the 3D positional relationship of the upper and lower jaws during mouth opening can be constructed through 2D-3D registration.

[0008] The published paper, "Clinical Decision-Making for Implant Guidance Methods Guided by a New Classification of Implant Area Opening Degree" by Haiyang Yu (West China Journal of Stomatology, 2023), proposes the concept of SO and makes decisions on implant guidance methods based on measured opening degree values. The published paper (CN202211374812.X) uses CBCT three-dimensional reconstruction and a 2D-3D pose estimation algorithm (PnP) to register the three-dimensional model of the jaw with the two-dimensional image for oral implant navigation. Summary of the Invention

[0009] The purpose of this invention is to provide a method for constructing a three-dimensional surgical site opening model based on 2D-3D registration technology. Based on this model, a systematic geometric analysis method and process are used to evaluate spatial obstruction during implant surgery, providing an objective arithmetic basis for instrument length selection and implant guidance method decisions, thereby improving the accessibility and safety of implant surgery. This method is applicable to the preoperative assessment of spatial obstruction in various implant procedures, including conventional intraosseous implantation, transzygomatic implantation, and transpterygoid implantation.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for constructing a three-dimensional opening model through 2D-3D registration and evaluating steric hindrance in planting spaces includes the following steps: S1: Acquire a single two-dimensional photograph of the patient with their mouth wide open, including both the upper and lower jaws; acquire the intrinsic parameter matrix and distortion coefficients of the camera; and perform camera distortion correction on the photograph. S2: Obtain a three-dimensional model of the patient's upper and lower jaw dentition through digital intraoral scanning; S3: Select at least 4 pairs of corresponding feature points on the photograph and the model, calculate the 6D pose of the model relative to the photograph based on the PnP algorithm, realize the 2D-3D registration of the model, and construct a three-dimensional surgical area opening model containing the three-dimensional positional relationship of the maxillary and mandibular dentition. S4: Perform three-dimensional registration and overlap between the dentition and jawbone model containing virtual implant sites and the three-dimensional surgical area opening model, and import the three-dimensional models of implant handpieces and simulation instruments to unify all models under the same coordinate system. S5: Establish a spatial steric hindrance collision detection method, the detection method including: Working phase detection: Align the simulated instrument to the final position of the operation, rotate it 360° with the implantation long axis as the rotation axis, and determine the usable handle rotation range where the instrument does not intersect with rigid structures such as the dental arch and guide plate through collision detection; Positioning stage inspection: The assembled simulation instrument is placed directly above the surgical site entrance along the implantation axis to check whether the top surface of the instrument head intersects with the opposing dentition. S6: Apply the aforementioned detection method to the drilling and implantation steps respectively to perform dual detection on the candidate instruments, and output the specifications of the instruments that pass the detection and their usable handle rotation range.

[0011] In this invention, the drilling step involves sequentially assembling candidate drill bits onto the implantation handpiece, first performing a working stage detection to retain those that pass and their available rotation range, then performing a placement stage detection on the passing drill bits, and outputting the drill bits that pass both detections. The implantation step involves sequentially assembling the candidate nail holders onto the implantation handpiece and connecting them to the implant. First, a working phase test is performed to retain those that pass and their available rotation range. Then, a placement phase test is performed on the nail holders that pass the test. Instruments that pass both tests are output as a feasible solution for single-instrument implantation.

[0012] In this invention, the implantation step includes a relay implantation strategy evaluation: When a disposable implantation device fails the placement test, the longest device that can pass the placement test is selected from the alternative staplers. This device is then retracted from the implant terminal site along the implantation direction to the position where the device head just collides with the rigid structure. This position is recorded as the deepest accessible implantation depth. At this connection point, a second placement test is performed on the long instrument that failed the placement test but passed the working test. If an instrument passes the second placement test, the relay implantation plan is deemed feasible.

[0013] In this invention, the detection method is used for conventional intra-alveolar bone implantation, transzygomatic implantation, and transpterygoid implantation procedures. In transzygomatic or transpterygoid implantation, the collision detection object is expanded from the dentition to a deep maxillofacial bony structure model including the maxilla, zygomatic bone, and pterygoid process of the sphenoid bone.

[0014] In this invention, the detection method includes soft tissue steric hindrance assessment: The usable handle rotation range obtained during the working phase is compared with the patient's tolerance range for soft tissue traction at the corner of the mouth. If the operator determines that the soft tissue resistance of all instruments is too great, the designed site is deemed unreachable for surgery.

[0015] In this invention, the detection method is used for three guidance methods: freehand planting, C-shaped tube guide plate guided planting, and column-shaped tube guide plate guided planting. Evaluations S5 and S6 are performed independently for each of the three guidance methods. The manual implantation and the C-shaped cannula guide implantation use the bone surface or soft tissue surface as the placement reference plane. The cylindrical tube guide plate uses the opening plane of the guide plate as the positioning reference plane and takes into account the increase in height of the guide plate.

[0016] In this invention, when all guiding methods fail to provide a feasible solution, the process returns to adjusting the implantation design, including variables such as implantation site, implantation axis, implant system, or implant specifications. If no feasible solution is found after multiple adjustments, the patient is deemed unsuitable for implant repair due to limited opening in the surgical area.

[0017] This invention provides a planting spatial steric hindrance assessment system, characterized in that it comprises: The acquisition module is used to acquire a single two-dimensional photograph of the patient with their mouth wide open, including both the upper and lower jaws, to acquire the intrinsic parameter matrix and distortion coefficients of the camera, and to perform camera distortion correction on the photograph. The digital modeling module is used to acquire a three-dimensional model of the patient's upper and lower jaw dentition through digital intraoral scanning; Registration module: used to register the 3D model and 2D photograph based on the PnP algorithm to construct a 3D surgical area opening model that includes the 3D positional relationship of the maxillary and mandibular dentitions; Fusion module: used to perform three-dimensional registration and overlap of the dentition and jawbone model containing virtual implant sites with the three-dimensional surgical area opening model, and import the three-dimensional models of implant handpieces and simulation instruments, so that all models are unified in the same coordinate system; Collision detection module: used to establish a general spatial steric collision detection method, perform working stage detection and positioning stage detection, and output the available handle rotation range and positioning judgment results of the instrument; Decision output module: Used to output the instrument specifications that have passed the test and the range of rotation of the available handle.

[0018] In this invention, the system further includes: a drilling module, used to sequentially assemble candidate drill bits onto the implantation handpiece, first perform a working stage detection, retain those that pass and their available rotation range, then perform a placement stage detection on the passed drill bits, and output the drill bits that pass the dual detection; The implantation module uses a device to sequentially assemble alternative staple holders onto the implantation handpiece and connect them to the implant. First, a working phase test is performed to retain those that pass and their available rotation range. Then, a placement phase test is performed on the staple holders that pass the test. Instruments that pass both tests are output as a feasible solution for single-instrument implantation.

[0019] In this invention, the system further includes an implantation strategy evaluation module, which is used to select the longest instrument that can pass the placement test from the alternative nail holders when the disposable implantation instrument fails the placement test, and retract it from the implantation terminal site along the implantation direction to the position where the head of the device just collides with the rigid structure. This position is recorded as the deepest accessible implantation depth. At this connection position, a second placement test is performed on the long instrument that failed the placement test but passed the working test. If there is an instrument that passes the second placement test, the relay implantation scheme is deemed feasible.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention can construct a three-dimensional surgical area opening model with only a single two-dimensional photograph and a three-dimensional intraoral scan model, without the need for additional CBCT radiation exposure or expensive mandibular motion recording equipment, making it low-cost and easy to operate.

[0021] This invention elevates the spatial steric hindrance problem in implantation from empirical qualitative judgment to quantitative geometric analysis, defines key geometric parameters and provides a systematic calculation process, making preoperative assessment more objective and repeatable.

[0022] This invention, through systematic geometric analysis, can accurately determine the surgical accessibility under different instrument lengths and implantation guidance methods before surgery, avoiding unexpected biological damage or inoperability caused by forced placement during surgery.

[0023] This invention provides a structured clinical decision-making pathway that covers the entire process from virtual implantation site design, spatial steric hindrance assessment, device length selection to implantation guidance method decision-making.

[0024] The scope of application of this invention is not limited to conventional intraosseous implantation, but can also be naturally extended to special procedures such as transzygomatic implantation and transpterygoid implantation. Since the spatial hazard collision detection method relies only on the spatial relationship between the "three-dimensional opening model + virtual implant site + simulation instrument", it is not limited by the specific type of implant or the implantation site. Therefore, no specific modifications to the system architecture or decision-making process are required to complete the preoperative spatial hazard assessment of the above-mentioned special procedures. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart illustrating the process of this embodiment; Figure 2 A schematic diagram is generated for the three-dimensional surgical area opening model; Figure 3 A schematic diagram of model registration; Figure 4 This is a schematic diagram of the testing process during the working phase. Figure 5 This is a schematic diagram of the in-place testing phase. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1 This embodiment constructs a three-dimensional surgical site opening model based on a implantation spatial steric hindrance assessment system. The system includes: The acquisition module is used to acquire a single two-dimensional photograph of the patient with their mouth wide open, including both the upper and lower jaws, to acquire the intrinsic parameter matrix and distortion coefficients of the camera, and to perform camera distortion correction on the photograph. The digital modeling module is used to acquire a three-dimensional model of the patient's upper and lower jaw dentition through digital intraoral scanning; Registration module: used to register the 3D model and 2D photograph based on the PnP algorithm to construct a 3D surgical area opening model that includes the 3D positional relationship of the maxillary and mandibular dentitions; Fusion module: used to perform three-dimensional registration and overlap of the dentition and jawbone model containing virtual implant sites with the three-dimensional surgical area opening model, and import the three-dimensional models of implant handpieces and simulation instruments, so that all models are unified in the same coordinate system; Collision detection module: used to establish a general spatial steric collision detection method, perform working stage detection and positioning stage detection, and output the available handle rotation range and positioning judgment results of the instrument; Decision output module: Used to output the instrument specifications that have passed the test and the range of rotation of the available handle.

[0028] The collision detection module also includes a drilling module, which is used to assemble the candidate drill bits into the implantation mobile phone in sequence, first perform the working stage detection, retain the ones that pass and their available rotation range, then perform the placement stage detection on the drill bits that pass, and output the drill bits that pass the dual detection. The implantation module uses a device to sequentially assemble alternative staple holders onto the implantation handpiece and connect them to the implant. First, a working phase test is performed to retain those that pass and their available rotation range. Then, a placement phase test is performed on the staple holders that pass the test. Instruments that pass both tests are output as a feasible solution for single-instrument implantation.

[0029] The implantation module also includes an implantation strategy evaluation module, which selects the longest instrument that can pass the placement test from the alternative staplers when the disposable implantation device fails the placement test. The longest instrument is then moved back from the implantation terminal point along the implantation direction to the position where the head of the device just collides with the rigid structure. This position is recorded as the deepest accessible implantation depth. At this connection position, a second placement test is performed on the long instrument that failed the placement test but passed the working test. If there is an instrument that passes the second placement test, the relay implantation plan is deemed feasible.

[0030] This embodiment uses the above system to construct a three-dimensional surgical area opening model, such as Figure 1 As shown, it includes the following steps: Step 1: Obtain a photograph of the patient with their mouth wide open, including both upper and lower dentition, and use Zhang Zhengyou's camera calibration method to obtain the intrinsic parameter matrix and distortion coefficients of the camera, and then perform distortion correction on the photograph.

[0031] This embodiment uses an ultra-wide-angle camera (lens focal length 2.16 mm, equivalent full-frame 14 mm, aperture f / 2.2, focusing distance set to the closest focusing distance). A checkerboard calibration board (11 columns, 8 rows, 6.0 mm square size) was used, and 17 images of the calibration board were captured from different angles, with an image resolution of 4080×3060 pixels. The checkerboard corner points were detected using the findChessboardCorners function in the OpenCV library, and sub-pixel precision corner points were extracted using the cornerSubPix function. Based on multiple sets of corresponding points, the calibrateCamera function was used to calculate the camera intrinsic parameter matrix K and distortion coefficient D, with a calibration reprojection error of 0.5843 pixels. The calibration results were stored in the camera parameter library for later use. The camera was used to take clinically photographs of the patient with their mouths wide open, simultaneously showing the upper and lower jaws. Distortion correction was performed using the undistort function based on the corresponding camera intrinsic parameters and distortion coefficients.

[0032] Step 2: Obtain the patient's maxillary and mandibular dentition models (PLY or STL format) using digital intraoral scanning, and import the models into a 3D visualization environment.

[0033] Digital intraoral scanners are used to acquire models of the patient's upper and lower jaw dentition, which are then imported into the system in PLY or STL format. A 3D rendering engine is used to construct a visual scene, supporting 3D translation and rotation of the model. A 2D photograph is overlaid as a semi-transparent mask in the 3D view; by adjusting the transparency of the photograph and the model, the operator can easily observe the correspondence between 2D feature points and 3D anatomical structures.

[0034] Step 3: Select 5 pairs of corresponding feature points on the photograph and model (e.g., cusp apex, pit and fissure, etc., clearly defined anatomical landmarks; for edentulous jaws, mucosal folds, etc., can be selected, or manually drawn / pasted markers). The coordinates are shown in the table below: Based on the above point pairs, the OpenCV solvePnP function was used to roughly calculate the initial values ​​using the SOLVEPNP_EPNP algorithm and iteratively refine them using the SOLVEPNP_ITERATIVE algorithm. The rotation matrix and translation vector of the upper and lower jaw models relative to the camera coordinate system were solved respectively. The results are shown in the table below: Based on the obtained rotation matrix and translation vector, the 3D model is transformed to a spatial pose that coincides with the corresponding dentition in the 2D photograph after coordinate system transformation. After registration of the upper and lower jaws separately, the operator can manually fine-tune the registration as needed. Finally, the upper and lower jaw dentition models are merged and exported to form the 3D surgical area opening model, such as... Figure 2 As shown.

[0035] Step 4: Use implant planning software to complete the virtual implant site design and export the dentition model and jawbone model containing the virtual implant positions. In the 3D visualization software, using the dentition model as a common reference medium, perform 3D registration and overlap (multi-point registration or best fit method) with the 3D surgical area opening model constructed in Step 3, so that the two are unified under the same coordinate system. In addition, import the simplified 3D models of the various implant system toolkits and instruments (such as drills, screw holders, implants, extension rods, etc.) and the 3D models of the implant handpieces into the same visualization scene (e.g., Figure 3 (As shown). For zygomatic or pterygoid implants, import extra-long drill bits and implant models of the appropriate length according to the specifications of the selected implant system.

[0036] In this embodiment, the DentsplyAstra implant system was selected, with the implant model Astra EV 4.2S– 9 mm (4.2 mm in diameter and 9 mm in length), and a flap surgery was employed (using the bone surface as the placement reference plane). The simplified 3D models of the system's accompanying instruments and the implant handpiece model were imported into the scene. The specifications of all alternative instruments are shown in the table below.

[0037] Step 5: Establish a general spatial steric collision detection method.

[0038] Spatial steric hindrance in the implantation procedure described in this embodiment mainly includes the following four situations: (1) Implant handpiece head obstruction with opposing tooth. This occurs during the instrument placement stage. When the total length of the instrument (the total length of the instrument after assembly with the implant handpiece) exceeds the vertical space allowed by the opening of the surgical area along the implant axis, the instrument cannot be placed into the mouth and reach directly above the surgical area. In this case, only a shorter instrument can be used.

[0039] (2) Obstruction between the implant handpiece head and adjacent teeth. This occurs during the instrument's working phase. When the distance between the long axis of the virtual implant site and the adjacent tooth is less than the radius of the handpiece head, if the instrument is not long enough, the handpiece head will be blocked by the adjacent tooth as the instrument penetrates deeper, preventing it from reaching the intended working depth. The way to avoid this obstruction is to use a longer instrument so that the handpiece head is in a higher position when the instrument reaches the working depth.

[0040] (3) Occlusal obstruction between the implant handpiece handle and the dentition / guide. This occurs during the instrument operation phase. As the instrument is gradually inserted, the handpiece handle may collide with rigid structures such as the dentition or guide in the anterior part of the edentulous area. The method to avoid this obstruction is to rotate the handpiece handle around the implant's long axis, usually deflecting it towards the edentulous side, so that the handle forms an angle with the dentition to avoid the obstruction.

[0041] (4) Implant handpiece obstruction by soft tissue at the corner of the mouth. This occurs in the situation described in (2) above. If the minimum rotation angle required for the handpiece to avoid the dentition exceeds the passive traction range of the patient's corner of the mouth, the handpiece will be restricted by the soft tissue at the corner of the mouth and cannot be rotated further. The soft tissue tension can be relieved by the patient appropriately reducing their mouth opening, or by using a longer instrument to reduce the required rotation angle.

[0042] For the rigid spatial steric hindrances (the first three types) among the four types of steric hindrances mentioned above, a unified collision detection method is established, including two types of detection: Working phase testing (such as) Figure 4 As shown): Align the simulation instrument to the final position of the operation (the working end of the drill bit during drilling, and the tip of the virtual implantation site during implantation; the working end of the drill bit is usually 1 mm deeper than the tip of the implantation site, depending on the drill bit compensation specified by the selected implantation system). Rotate the simulation instrument 360° around the implantation long axis as the rotation axis. Use collision detection to determine the usable handle rotation range where the instrument does not intersect with rigid structures such as the dentition and guide plates: if a usable range exists, the instrument passes the operation test, and the usable handle rotation range is recorded; if there is intersection throughout the entire circumference, the instrument fails.

[0043] In-place phase detection (e.g.) Figure 5 As shown): Place the assembled simulation instrument along the implantation axis directly above the surgical site entrance (i.e., the starting position of the surgery, such as the bone surface, soft tissue surface, or guide plate opening plane), and check whether the top surface of the instrument head intersects with the opposing dentition: if there is no intersection, the instrument can pass the placement test; if there is an intersection, the instrument is too long and cannot be placed into the mouth.

[0044] Step Six: Apply the general testing methods to both the drilling and implantation steps. Drilling procedure: The two alternative drill bits (31 mm and 36 mm in total length) from the freehand tool kit were sequentially assembled onto the implantation handpiece. A working stage test was then performed: the working ends of the drill bits were aligned with the final drilling position, and the simulation instrument was rotated around the implantation long axis. Results showed that both the 31 mm and 36 mm drill bits passed the working stage test, and each had a usable handle rotation range.

[0045] Next, a placement test was performed on the two drill bits: the assembled simulation instrument was placed directly above the bone surface of the edentulous area along the implantation axis, and the top surface of the drill head was checked to see if it intersected with the opposing dentition. The results showed that the 31 mm drill bit passed the placement test; the top surface of the 36 mm drill bit intersected with the opposing dentition and could not be placed. Therefore, the 31 mm drill bit was selected for the drilling procedure.

[0046] The implantation procedure utilizes a stapler-implant combination instrument. The stapler and implant are detachably connected, and the tool kit contains multiple support staplers, thus allowing for both single-stage and relay implantation strategies.

[0047] Single-stage implantation strategy: Two support staplers (27 mm and 37.5 mm in total length after implant assembly) from the manual tool kit were connected to the implant and assembled to the implant handpiece, and working and positioning tests were performed sequentially. Results showed that the 27 mm stapler combination passed both tests, indicating a feasible single-instrument implantation approach; the 37.5 mm stapler combination passed the working test, but during the positioning test, the cephalic surface intersected with the opposing dentition, preventing proper positioning. Therefore, the single-stage implantation strategy is feasible in this embodiment, and there is no need to proceed to the relay implantation strategy evaluation.

[0048] This embodiment visualizes the available handle rotation range of the combination of the 31 mm drill bit selected in the drilling step and the 27 mm stapler selected in the implantation step. The operator assessed that the above rotation range was within the tolerance range of the soft tissue traction at the corner of the mouth and could be achieved naturally during the operation. The final surgical plan was determined to be: Dentsply Astra EV 4.2S - 9 mm implant, using a flap technique and freehand guided implantation, with the selected instruments being: a 31 mm drill bit for drilling and a 27 mm stapler for implantation.

[0049] The evaluation process described in this embodiment applies to three methods: freehand planting, C-shaped tube guide plate guided planting, and column-shaped tube guide plate guided planting. The following differences should be noted during evaluation: Instrument source: The instruments used in the guide plate guided planting tool box may differ in length, specifications and connection interface from those of manual instruments. The system should match the corresponding instrument database according to the selected guidance method, and in principle, they should not be used interchangeably.

[0050] Positioning reference plane: The reference plane for collision detection during the instrument positioning phase varies depending on the selected surgical procedure and guidance method. When guided by hand or C-plate, the instruments are positioned on the bone / soft tissue surface directly above the implantation site (depending on whether a flap procedure is used). When guided by a cylindrical guide plate, the instrument is located at the opening plane of the guide plate; The placement reference plane of the cylindrical guide plate has an increase in height compared to the bone / soft tissue surface (i.e., the vertical distance from the upper edge of the guide plate opening to the bone / soft tissue surface). This increase raises the initial placement height of the instrument, directly compressing the effective working length margin of the instrument, and must be taken into account during the placement assessment. The system performed the above evaluation independently for each of the three guidance methods. In this embodiment, under the C-type guide plate and column guide plate guidance methods, the positioning tests of the three drill bits (35.5 mm, 38.5 mm, 42.5 mm) and one support nailer (36 mm) in the guide plate tool box all failed. Furthermore, the increase in guide plate height of the column guide plate further compressed the effective working length of the instrument. Therefore, neither of the two guide plate guidance methods is feasible in this case.

[0051] If no feasible option is found under all guided methods, the designed implant site is deemed surgically inaccessible given the current anatomical conditions. In this case, the implant design needs to be adjusted. Adjustable variables include, but are not limited to: changing the implant site (membranous / distal, buccal / lingual displacement), changing the implant axis (tilted implantation), changing the implant system (different systems have different tool and instrument specifications), or adjusting the implant specifications. If all adjustments fail to achieve the desired outcome, the patient is deemed unable to undergo implant restoration under the current conditions due to limited surgical opening.

[0052] Example 2 Based on Example 1, the general spatial hazard collision detection method is also applicable to zygomatic or pterygoid implant surgery. It is only necessary to expand the detection object from the dentition to an anatomical model containing deep maxillofacial bony structures such as the maxilla, zygomatic bone, and pterygoid process, according to the instrument usage procedure of the selected implant system and based on the three-dimensional surgical area opening model containing the jawbone and dentition constructed in steps one to four. Then, the simulated surgery is performed in sequence according to the actual drilling sequence and implantation steps of the system to evaluate whether the virtual implant site is surgically accessible under the existing anatomical conditions.

[0053] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space, characterized in that, Includes the following steps: S1: Acquire a single two-dimensional photograph of the patient with their mouth wide open, including both the upper and lower jaws; acquire the intrinsic parameter matrix and distortion coefficients of the camera; and perform camera distortion correction on the photograph. S2: Obtain a three-dimensional model of the patient's upper and lower jaw dentition through digital intraoral scanning; S3: Select at least 4 pairs of corresponding feature points on the photograph and the model, calculate the 6D pose of the model relative to the photograph based on the PnP algorithm, realize the 2D-3D registration of the model, and construct a three-dimensional surgical area opening model containing the three-dimensional positional relationship of the maxillary and mandibular dentition. S4: Perform three-dimensional registration and overlap between the dentition and jawbone model containing virtual implant sites and the three-dimensional surgical area opening model, and import the three-dimensional models of implant handpieces and simulation instruments to unify all models under the same coordinate system. S5: Establish a spatial steric hindrance collision detection method, the detection method including: Working phase detection: Align the simulated instrument to the final position of the operation, rotate it 360° with the implantation long axis as the rotation axis, and determine the usable handle rotation range where the instrument does not intersect with rigid structures such as the dental arch and guide plate through collision detection; Positioning stage inspection: The assembled simulation instrument is placed directly above the surgical site entrance along the implantation axis to check whether the top surface of the instrument head intersects with the opposing dentition. S6: Apply the aforementioned detection method to the drilling and implantation steps respectively to perform dual detection on the candidate instruments, and output the specifications of the instruments that pass the detection and their usable handle rotation range.

2. The method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space according to claim 1, characterized in that, include: In the drilling step, the candidate drill bits are sequentially assembled onto the implantation handpiece. First, a working stage test is performed to retain the ones that pass and their available rotation range. Then, a positioning stage test is performed on the drill bits that pass the test, and the drill bits that pass the double test are output. The implantation step involves sequentially assembling the candidate nail holders onto the implantation handpiece and connecting them to the implant. First, a working phase test is performed to retain those that pass and their available rotation range. Then, a placement phase test is performed on the nail holders that pass the test. Instruments that pass both tests are output as a feasible solution for single-instrument implantation.

3. The method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space according to claim 2, characterized in that, The implantation process includes an evaluation of a relay implantation strategy: When a disposable implantation device fails the placement test, the longest device that can pass the placement test is selected from the alternative staplers. This device is then retracted from the implant terminal site along the implantation direction to the position where the device head just collides with the rigid structure. This position is recorded as the deepest accessible implantation depth. At this connection point, a second placement test is performed on the long instrument that failed the placement test but passed the working test. If an instrument passes the second placement test, the relay implantation plan is deemed feasible.

4. The method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space according to claim 2, characterized in that, The detection method includes soft tissue steric hindrance assessment: The usable handle rotation range obtained during the working phase is compared with the patient's tolerance range for soft tissue traction at the corner of the mouth. If the operator determines that the soft tissue resistance of all instruments is too great, the designed site is deemed unreachable for surgery.

5. The method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space according to claim 1, characterized in that, The detection method is used for routine intra-alveolar bone implantation, transzygomatic implantation, and transpterygoid implantation procedures. In transzygomatic or transpterygoid implantation, the collision detection object is expanded from the dentition to a deep maxillofacial bony structure model including the maxilla, zygomatic bone, and pterygoid process of the sphenoid bone.

6. The method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space according to claim 1, characterized in that, The detection method is used for three guidance methods: freehand planting, C-shaped tube guide plate guided planting, and column-shaped tube guide plate guided planting. Evaluations S5 and S6 are performed independently for each of the three guidance methods. The manual implantation and the C-shaped cannula guide implantation use the bone surface or soft tissue surface as the placement reference plane. The cylindrical tube guide plate uses the opening plane of the guide plate as the positioning reference plane and takes into account the increase in height of the guide plate.

7. The method for constructing a three-dimensional opening model through 2D-3D registration and evaluating the steric hindrance of planting space according to claim 6, characterized in that, If all guidance methods fail to provide a feasible solution, then return to adjusting the implantation design, adjusting variables including implantation site, implantation axis, implant system, or implant size. If no feasible solution is found after multiple adjustments, the patient is deemed unsuitable for implant repair due to limited opening in the surgical area.

8. A planting spatial steric hindrance assessment system for implementing the method of any one of claims 1-7, characterized in that, include: The acquisition module is used to acquire a single two-dimensional photograph of the patient with their mouth wide open, including both the upper and lower jaws, to acquire the intrinsic parameter matrix and distortion coefficients of the camera, and to perform camera distortion correction on the photograph. The digital modeling module is used to acquire a three-dimensional model of the patient's upper and lower jaw dentition through digital intraoral scanning; Registration module: used to register the 3D model and 2D photograph based on the PnP algorithm to construct a 3D surgical area opening model that includes the 3D positional relationship of the maxillary and mandibular dentitions; Fusion module: used to perform three-dimensional registration and overlap of the dentition and jawbone model containing virtual implant sites with the three-dimensional surgical area opening model, and import the three-dimensional models of implant handpieces and simulation instruments, so that all models are unified in the same coordinate system; Collision detection module: used to establish a general spatial steric collision detection method, perform working stage detection and positioning stage detection, and output the available handle rotation range and positioning judgment results of the instrument; Decision output module: Used to output the instrument specifications that have passed the test and the range of rotation of the available handle.

9. The planting spatial steric hindrance assessment system according to claim 8, characterized in that, include: The drilling module is used to assemble the candidate drill bits into the implantation handpiece in sequence. First, it performs a working stage test to retain the ones that pass and their available rotation range. Then, it performs a positioning stage test on the drill bits that pass the test and outputs the drill bits that pass the double test. The implantation module is used to sequentially assemble alternative nail holders onto the implantation handpiece and connect them to the implant. First, it performs a working phase test, retaining those that pass and their available rotation range. Then, it performs a placement phase test on the nail holders that pass the test, and outputs the instruments that pass the dual tests as a feasible solution for single-instrument implantation.

10. The planting spatial steric hindrance assessment system according to claim 9, characterized in that, Includes an implantation strategy evaluation module, When a disposable implantable device fails the placement test, the longest device that can pass the placement test is selected from the alternative staplers. This device is then moved back from the implant terminal point along the implantation direction to the position where the head of the device just collides with the rigid structure. This position is recorded as the deepest accessible implantation depth. At this connection position, a second placement test is performed on the long device that failed the placement test but passed the working test. If there is a device that passes the second placement test, the relay implantation plan is deemed feasible.

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