Apical film x-ray centerline positioning device and method

Abstract

This invention discloses a periapical radiograph centerline positioning device and method, comprising a personalized substrate, an angle positioning mechanism, and an optical indicator. The shape of the inner surface of the personalized substrate matches the anatomical morphology of the occlusal and buccal surfaces of the patient's target dentition. The angle positioning mechanism is fixedly disposed on the buccal side of the personalized substrate. The optical indicator is detachably mounted on the angle positioning mechanism. The angle positioning mechanism is configured to adjust and lock the angle of the optical indicator in both the horizontal and vertical directions. Using this device for positioning, this periapical radiograph centerline positioning device and method can materialize and visualize personalized digital angles, and guide the X-ray tube of the dental radiograph for precise and rapid alignment.

Description

Technical Field

[0001] This invention specifically relates to a device and method for positioning the centerline of X-rays in periapical radiographs. Background Technology

[0002] In the field of oral medicine, dental X-ray periapical radiographs are an indispensable imaging tool for diagnosing dental pulp diseases and assessing the quality of root canal treatment. A high-quality periapical radiograph requires a low image distortion rate (usually below 5%), and can clearly and non-overlappingly display the morphology of the root and root canal system of the target tooth, thereby providing accurate length measurements and morphological basis for treatment.

[0003] However, traditional periapical radiography techniques, especially when applied to the anatomically complex maxillary posterior teeth, face significant challenges. The widely used bisector projection technique heavily relies on the personal experience and intuition of the radiographer or dentist. The technician needs to estimate the optimal projection angles of the X-ray tube in the vertical (sagittal inclination) and horizontal (horizontal inclination) directions based on the target tooth's position in the dental arch. Since maxillary posterior teeth are often multi-rooted (such as molars), and the buccal and palatal roots have significant bifurcation and varying directions in three-dimensional space, using a uniform or empirically estimated angle can easily lead to problems such as overlap between the buccal and palatal roots, image stretching or compression distortion, and interference from adjacent teeth in two-dimensional images. As a result, a single imaging session often fails to obtain a high-quality image that meets diagnostic requirements, forcing clinicians to perform multiple repeated imaging sessions to try different angles. This not only significantly increases the radiation dose received by the patient and prolongs treatment time but also can mislead treatment due to image distortion, such as causing errors in root canal length measurement, leading to underfilling or overfilling, and affecting the long-term success rate of root canal treatment.

[0004] In recent years, with the widespread adoption of cone-beam computed tomography (CBCT), clinicians can accurately measure the theoretically optimal projection angle required to clearly visualize specific tooth roots (such as buccal or palatal roots) in three-dimensional space. This provides a digital foundation for solving the aforementioned problems. However, how to accurately convert and repeatedly apply the precise angle data calculated by CBCT in virtual space to actual two-dimensional X-ray imaging without distortion remains a technological gap. There is a lack of a bridging tool that can effectively connect digital planning with clinical physics operations. Existing attempts are mostly limited to theoretical or software simulation stages, or are overly complex and difficult to use stably and conveniently in routine clinical environments. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide an auxiliary positioning device and positioning method that can materialize and visualize personalized digital angles and guide the X-ray tube of dental X-ray machine to perform precise and rapid alignment.

[0006] To achieve the above objectives, the present invention provides a device for positioning the centerline of an X-ray in periapical radiograph, comprising: Personalized substrate, the shape of its inner surface is matched with the anatomical morphology of the occlusal and buccal surfaces of the patient's target dentition; A connecting rod is disposed on the personalized base plate, and when the personalized base plate is located at the target dentition position, the connecting rod extends to the outside of the oral cavity; An angle positioning mechanism is connected to the end of the connecting rod located outside the oral cavity; and An optical indicator is detachably mounted on the angle positioning mechanism; The angle positioning mechanism is configured to adjust and lock the angle of the optical indicator in the horizontal and vertical directions.

[0007] Furthermore, the angle positioning mechanism includes: A horizontal angle adjustment component, connected to the personalized substrate, is used to provide the optical indicator with rotational freedom in the horizontal plane; and A vertical angle adjustment component, disposed on the horizontal angle adjustment component, is used to provide the optical indicator with a degree of freedom of swing in the sagittal plane.

[0008] Furthermore, the horizontal angle adjustment component includes: A connecting shaft is fixed to the end of the connecting rod located outside the oral cavity; A turntable, rotatably mounted on the connecting shaft via a first rotating shaft; and A first locking element is used to lock the turntable relative to the connecting shaft; The turntable is provided with a horizontal angle scale around its perimeter.

[0009] Furthermore, the turntable is provided with a horizontal reference indicator line. When the horizontal reference indicator line is aligned with the zero mark engraved on the connecting shaft, the optical indicator points parallel to the patient's sagittal plane.

[0010] Furthermore, the vertical angle adjustment component includes: A cantilever, pivotally mounted on the turntable via a second pivot; and The second locking element is used to lock the cantilever relative to the turntable; The turntable is equipped with a vertical angle scale.

[0011] Furthermore, the optical indicator is a laser pointer, and the end of the cantilever is provided with a mounting channel for accommodating the laser pointer, the geometric center line of the mounting channel coinciding with the swing center line of the cantilever or ball joint.

[0012] Furthermore, the personalized substrate is also provided with an occlusal pad, which extends from the occlusal surface morphology of the personalized substrate toward the opposing teeth to form a plane or curved surface for patient occlusion to stabilize the guide plate.

[0013] Furthermore, the personalized substrate is made of photocurable resin material through 3D printing process, and the morphology of its inner surface is manufactured based on a three-dimensional digital model of the dental arch reconstructed from the patient's intraoral scan data or CBCT data.

[0014] Furthermore, the vertical angle adjustment component is a universal ball joint structure, comprising: A ball joint seat is fixed to the turntable; A ball joint link, wherein the ball joint portion is constrained within the ball joint seat and can rotate omnidirectionally within a certain angle; and The third locking element is used to lock the ball joint after it has been adjusted to the target angle.

[0015] A method for positioning the X-ray centerline in periapical radiographs, using the aforementioned X-ray centerline positioning device, the method comprising the following steps: Data acquisition and guide plate fabrication: Acquire three-dimensional oral cavity data of the patient's target dentition, and design and manufacture a personalized substrate with an inner surface morphology that matches the data. Device wearing and initial positioning: The personalized substrate is worn on the target dentition inside the patient's mouth, and the connecting rod extends out of the oral cavity; Horizontal angle setting: According to the target horizontal projection angle planned before the operation, operate the horizontal angle adjustment component of the angle positioning mechanism to adjust and lock the horizontal direction of the optical indicator to the corresponding angle; Vertical angle setting: According to the target vertical projection angle planned before the operation, operate the vertical angle adjustment component of the angle positioning mechanism to adjust and lock the vertical direction of the optical indicator to the corresponding angle; Optical pre-alignment: Turn on the optical indicator, and the beam emitted by it forms an indicator spot on the patient's face; move the X-ray tube of the dental X-ray machine so that the indicator spot on the X-ray tube coincides with the indicator spot formed by the optical indicator; Imaging procedure: After optical pre-alignment is completed, X-ray exposure is performed to acquire periapical radiographs of the target dentition.

[0016] The beneficial effects of this invention are: The above-mentioned X-ray centerline positioning device and method for periapical radiography have at least the following advantages: 1. This invention constructs a complete standardized operating procedure through a three-in-one system design of "personalized substrate - angle positioning mechanism - optical indicator". First, the personalized substrate, with its inner surface morphology perfectly matching the patient's dentition, establishes a unique, stable, and accurate initial spatial coordinate system in the mouth, eliminating the initial errors caused by inconsistent film handling or sensor positioning in traditional methods. Second, the angle positioning mechanism, as a core functional module, can mechanically and accurately reproduce and lock the horizontal and vertical projection angles planned by digital means such as CBCT, transforming the originally abstract angle values, which depend on the technician's subjective feeling, into objective, quantifiable mechanical positions. Finally, the optical indicator (such as a laser pointer) projects this locked spatial angle direction directly into the form of a visible beam. This system completely eliminates the reliance on the operator's personal experience, enabling each image to accurately reproduce the predetermined and optimized projection geometry.

[0017] 2. Because the projection angle is calculated and precisely set based on the patient's specific anatomy and the target tooth root, this guide plate can minimize image distortion, overlap, and deformation. In clinical applications, it can directly increase the success rate of Grade A films to the theoretical optimal level and significantly reduce the rates of Grade B, Grade C, and rejected films. This not only means obtaining more reliable images that are more conducive to accurate diagnosis and treatment, but more importantly, it greatly reduces the number of repeated imaging sessions required to obtain a qualified image. For patients, this directly reduces the ineffective X-ray radiation dose they receive, conforming to the principle of optimal radiation protection; for departments, it improves diagnostic and treatment efficiency and saves time and consumable costs.

[0018] 3. Due to the visible light beam generated by the optical indicator, a clear light spot is formed on the patient's facial skin. The operator only needs to move the X-ray tube of the dental X-ray machine so that its built-in indicator light spot coincides with the laser spot of the guide plate to confirm that the X-ray tube is in the correct spatial orientation. This "what you see is what you get" pre-alignment process is intuitive to operate and provides immediate feedback, greatly simplifying the alignment difficulty, shortening the alignment time, and giving the operator full confidence. It avoids the lag and uncertainty of the traditional method of "blindly shooting" and waiting for film development or interpretation to confirm the effect. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to scale.

[0020] Figure 1 This is a schematic diagram of a periapical radiograph X-ray centerline positioning device provided in an embodiment of the present invention; Figure 2 for Figure 1The diagram shown is a schematic of another angle of the X-ray centerline positioning device for periapical radiography. Figure 3 for Figure 2 A schematic diagram at point A in the middle; Figure 4 for Figure 1 The diagram shown is a schematic of another angle of the X-ray centerline positioning device for periapical radiography. Figure 5 for Figure 4 A schematic diagram at point B in the middle; Figure 6 For use Figure 1 The method of positioning using the X-ray centerline positioning device shown; Figure label: 1. Buccal side; 2. Occlusal surface; 100. Personalized base plate; 200. Angle positioning mechanism; 210. Horizontal angle adjustment component; 211. Connecting shaft; 212. Turntable; 213. First locking element; 214. Horizontal angle scale; 215. Horizontal reference indicator line; 220. Vertical angle adjustment component; 221. Cantilever; 222. Second locking element; 223. Vertical angle scale; 300. Optical indicator; 400. Connecting rod. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention; therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Please see Figures 1 to 5 The present invention provides a periapical radiograph X-ray centerline positioning device, including a personalized substrate 100, a connecting rod 400, an angle positioning mechanism 200, and an optical indicator 300.

[0023] Specifically, the personalized substrate 100 is the positioning cornerstone of the entire device. Its inner surface is manufactured to perfectly match the occlusal surface 2 and buccal surface 11 (closer to the cheek) of the patient's target dentition (e.g., the arch segment containing the maxillary first molars for which periapical radiographs are required). This highly customized shape ensures that the guide plate automatically and uniquely positions itself in the correct position when worn, providing a stable and accurate initial reference frame for subsequent angle positioning.

[0024] A connecting rod 400 is mounted on the personalized base plate 100 and extends outside the oral cavity when the personalized base plate 100 is in the target dentition position. The mechanism includes an optical indicator 300 for carrying and adjusting the direction of the X-ray centerline. An angle positioning mechanism 200 can make precise angle adjustments independently or jointly in two key dimensions—horizontal (rotation about an axis perpendicular to the occlusal plane) and vertical (pitch in the sagittal plane in the anteroposterior direction)—and can be securely locked in place after adjustment. The angle positioning mechanism 200 is detachably connected to the connecting rod 400 to accommodate different personalized base plates 100.

[0025] An optical indicator 300 is detachably mounted at the end of the angle positioning mechanism 200. The beam emitted by this indicator (typically a laser pointer) visually defines a straight line in space, which simulates the X-ray centerline at the target projection angle. Adjusting the direction of this beam through the angle positioning mechanism 200 is equivalent to pre-setting the exit path of the X-rays inside the X-ray tube externally.

[0026] This positioning guide plate materializes and visualizes the abstract projection angle. It avoids the traditional cycle of "technician experience estimation - test shooting - adjustment," establishing a standardized new process of "digital design - mechanical positioning - optical verification." By reproducing the digital angle through a mechanical structure and pre-aligning it with a visible light beam, it fundamentally eliminates the error variables introduced by human experience.

[0027] In this embodiment, the angle positioning mechanism 200 adopts the principle of "degree-of-freedom decoupling". It includes a horizontal angle adjustment component 210 and a vertical angle adjustment component 220.

[0028] The horizontal angle adjustment component 210 is directly connected to the personalized base plate 100. It provides a rotational degree of freedom, allowing the entire vertical assembly and optical indicator 300 mounted thereon to rotate horizontally about an axis approximately perpendicular to the patient's jaw plane. This rotational movement corresponds to the deflection angle of the X-ray centerline in the horizontal plane, which is crucial for avoiding adjacent tooth overlap and aligning with the target tooth root bifurcation.

[0029] The vertical angle adjustment component 220 is mounted above the horizontal angle adjustment component 210. It provides another degree of freedom of movement, allowing the optical indicator 300 to pitch within the sagittal plane of the human body (i.e., the front-to-back plane viewed from the side). This pitch corresponds to the vertical tilt angle of the X-ray centerline and is a key parameter determining whether the image is compressed or stretched.

[0030] This approach decomposes spatial angle adjustment into independent movements within two planes, greatly simplifying the operational logic. The operator can use a theodolite, setting one dimension first, then the other, avoiding the chaos and interference of simultaneously adjusting multiple angles. This design also allows for the setting of high-precision scales in each dimension, achieving quantification and repeatability of angles. Furthermore, the two components can be arranged in series or parallel, among other mechanical layouts, to adapt to different oral cavity spaces and operating habits.

[0031] In this embodiment, the horizontal angle adjustment assembly 210 includes a connecting shaft 211, a turntable 212, and a first locking member 213. The connecting shaft 211 is fixed to the end of the connecting rod 400 located outside the mouth by means of bonding, bolting, or integral molding. The connecting shaft 211 is the mounting platform for the entire horizontal adjustment assembly.

[0032] Turntable 212 is rotatably connected to connecting shaft 211. Turntable 212 can be understood as a "tray" that supports all subsequent components. On the circular periphery of turntable 212, a precise horizontal angle scale 214 is etched or printed, with scale values ​​typically in degrees and subdivided.

[0033] The first locking element 213 (e.g., a set screw with a knob, a friction brake knob, or a quick clamping handle) is used to fix the turntable 212 relative to the connecting shaft 211 after it has been rotated to the target angle, preventing accidental rotation during subsequent operations.

[0034] Operating principle: During operation, according to the preoperative planning data (such as "horizontal angle + 15°"), loosen the first locking element 213, rotate the turntable 212 by hand to align the corresponding scale on the scale with a fixed reference mark (such as a pointer or zero line) on the connecting shaft 211, and then tighten the locking element. At this time, the turntable 212 and all components above it are locked at that horizontal angle.

[0035] To ensure absolute accuracy in adjusting the horizontal angle, the present invention provides a horizontal reference indicator line 215 (which can be a scribed line or an arrow) on the turntable 212. Simultaneously, a zero-position scale is correspondingly engraved on the connecting shaft 211.

[0036] When the operator rotates the horizontal reference indicator line 215 on the turntable 212 until it is precisely aligned with the zero mark on the connecting shaft 211, the entire angle positioning mechanism 200 is in a defined "zero" state. In this state, the optical indicator 300 is pre-calibrated to be parallel to the patient's sagittal plane (the longitudinal plane that divides the human body into left and right halves). This definition is crucial because all preoperatively planned horizontal angle data are relative to the sagittal plane.

[0037] This design provides an absolute angular reference. It means that every "+X°" or "-X°" reading on the dial 212, starting from "zero," is a true, unbiased horizontal deflection angle relative to the patient's own anatomical coordinate system (sagittal plane). This solves the problem of coordinate system misalignment caused by slight tilting of the guide plate or initial installation deviations, ensuring the fidelity of the conversion from digital angles to mechanical angles.

[0038] In this embodiment, the vertical angle adjustment component 220 includes a support base, a cantilever 221, and a second locking member 222. The support base is fixedly mounted on the upper surface of the turntable 212, which has been pre-set at a horizontal angle. The support base is provided with a vertical angle scale 223, which is typically an arc-shaped ruler with angle graduations.

[0039] The cantilever 221 is hinged to the turntable 212 via a horizontal second pivot, allowing it to swing up and down in the sagittal plane in front of the turntable 212 (i.e., towards the patient's face) like a pendulum. The cantilever 221 is the direct mounting carrier for the optical indicator 300.

[0040] The function of the second locking member 222 is similar to that of the first locking member 213, which is to lock the cantilever 221 after it swings to the target vertical angle.

[0041] In use, when setting the vertical angle (e.g., "vertical angle -10°"), loosen the second locking element 222, move the cantilever 221 up and down to align a pointer fixed on the cantilever 221 with the corresponding mark on the scale of the turntable 212, and then lock it. This "separate adjustment" structure (i.e., horizontal and vertical adjustment are performed separately) has clear logic, step-by-step operation, good stability, and both dimensions of the scale can be made large, resulting in high reading accuracy. It is particularly suitable for clinical scenarios with extremely high precision requirements and a relatively relaxed operating rhythm.

[0042] As another preferred embodiment of the vertical angle adjustment component 220, it adopts a more compact and faster universal ball joint structure.

[0043] The structure mainly includes a ball joint seat, a ball joint connecting rod, and a third locking element. The ball joint seat is fixed on the turntable 212 and has a spherical cavity inside. The ball head of one end of the ball joint connecting rod is housed in this spherical cavity, with a precise clearance fit between them. This allows the ball joint connecting rod to rotate omnidirectionally within a certain conical angle range in the front-back and left-right directions. The third locking element (usually a locking collar fitted outside the ball joint seat) is used to lock the ball head after the angle adjustment is completed by pressing the elastic part of the ball joint seat or directly generating friction.

[0044] During operation, the third locking element is released, and the operator can hold the end of the ball joint (i.e., the end where the optical indicator 300 is installed) and continuously and simultaneously adjust its direction in three-dimensional space until the optimal projection direction is found, then lock it. This "omnidirectional" structure has extremely high adjustment efficiency, smooth movements, and is more intuitive, making it particularly suitable for scenarios requiring rapid positioning or simultaneous fine-tuning of two angles. It provides another flexible option for clinical operations.

[0045] In this invention, the optical indicator 300 is preferably a small, low-power laser pointer. To achieve precise integration with the angle positioning mechanism 200, a precision cylindrical mounting channel is machined at the end of the cantilever 221 (for split-type structures) or the ball joint (for universal structures).

[0046] The geometric centerline of the mounting channel must coincide with the swing centerline of the cantilever 221 (i.e., the axis of the second rotating shaft), or with the theoretical rotation centerline of the ball joint. Only when this condition is met can the direction of the laser beam emitted by the laser pointer fully represent the spatial vector direction set by the entire angle positioning mechanism 200 without introducing additional deviations.

[0047] This design ensures "what you see is what you get"—the direction of the laser beam in space is precisely the direction of the X-ray centerline to be taken. The spot formed by the laser beam on the patient's facial skin provides a clear and intuitive target for the X-ray tube of the dental X-ray machine to focus. Furthermore, the laser pointer features a detachable design for easy battery replacement and maintenance, and also allows for the use of different colors (such as green, which is more visible on skin) or types of indicator light sources.

[0048] In order to eliminate the need for patients or assistants to hold the guide plate for extended periods during the imaging process, the present invention adds an occlusal pad to the personalized substrate 100.

[0049] The occlusal pad extends from the occlusal surface 2 of the base plate (i.e., the part covering the occlusal surface of the teeth) towards the patient's opposing teeth (usually the mandibular teeth), forming a plane with a certain thickness and strength or a curved surface that matches the shape of the opposing dental arch. After the guide plate is worn, the patient only needs to gently bite down on this occlusal pad with their opposing teeth to use their own biting force to stably hold the entire guide plate in the correct position in the mouth.

[0050] This design completely frees the operator's hands, allowing them to focus on angle positioning and X-ray tube alignment. At the same time, the bite-locking mechanism is more stable and reliable than hand-held control, effectively preventing guide plate displacement due to slight patient movement or fatigue, ensuring a constant projection angle throughout the entire imaging process.

[0051] To further enhance the stability and anti-rotation capability of the personalized substrate 100 during initial intraoral wear, multiple elastic anti-slip protrusions are distributed on its inner surface (i.e., the side in contact with teeth and gums).

[0052] These bumps are typically made of soft, elastic materials such as medical-grade silicone. They can be attached to a resin substrate through secondary injection molding or directly printed as part of the substrate. When the guide plate is inserted, these bumps undergo slight elastic deformation, thereby increasing the friction with the tooth structure and mucosa.

[0053] The flexible, non-slip bumps serve a dual purpose: "microscopic positioning" and "non-slip padding." They not only prevent the guide plate from sliding in the buccal-lingual or mesiodistal direction, but also provide sufficient temporary fixation during brief procedures before the patient has engaged the occlusal pad. Furthermore, the soft bumps enhance patient comfort, avoiding the discomfort that may arise from hard materials.

[0054] In specific implementation, the personalized substrate 100 is preferably made of a photocurable resin material with good biocompatibility and is manufactured in one piece by a high-precision 3D printing process (such as digital light processing DLP or stereolithography SLA).

[0055] The manufacturing process begins with the patient's oral data. The morphology of the inner surface is entirely based on a 3D digital model of the dentition reconstructed from the patient's intraoral scan data (three-dimensional data of the teeth and soft tissue surfaces acquired through an intraoral scanner) or CBCT data. In computer-aided design software, a 3D model of the substrate that fits perfectly with the patient's dentition is precisely generated based on this data and then sent to a 3D printer for manufacturing.

[0056] Please see Figure 6 In addition, the present invention also provides a method for taking a periapical radiograph using the above-mentioned periapical radiograph X-ray centerline positioning device, comprising the following steps: S100: Data Acquisition and Guide Plate Fabrication Specifically, the first step is to obtain precise three-dimensional anatomical data of the patient's target dentition (e.g., the maxillary first molar for which root canal treatment is planned). This can be achieved through two mainstream digital technologies: one is to use an intraoral scanner to directly optically scan the patient's dental arch to obtain three-dimensional data of the tooth and gingival surfaces; the other is to use the patient's existing cone-beam computed tomography (CBCT) DICOM data to reconstruct a high-precision three-dimensional model of the dentition using specialized software.

[0057] After obtaining the digital model, a personalized substrate 100 is designed based on the model using computer-aided design (CAD) software. The inner surface of this substrate is designed as a "negative shape" to perfectly fit the occlusal surface 2 and buccal surface 1 of the target dentition. Simultaneously, a connecting rod 400 extending from the buccal surface 1 of the substrate is designed, its length ensuring that the end of the connecting rod 400 extends beyond the corner of the mouth when the substrate is in place, facilitating manipulation. The design data is then used in 3D printing (such as SLA or DLP) with a biocompatible photocurable resin material to integrally print the personalized substrate 100 and the connecting rod 400. This step transforms the patient's individual anatomical information into a unique, physical positioning reference.

[0058] S200: Device Wearing and Initial Positioning Specifically, the operator places the customized substrate 100 into the patient's mouth and guides them to align the substrate with the target dentition. Due to the highly customized morphology of the substrate's inner surface, it automatically and uniquely positions itself correctly. At this point, the connecting rod 400 naturally extends from the corner of the mouth to the outside. Subsequently, the patient is instructed to gently bite down, allowing the opposing teeth to stably bite onto the pre-set occlusal pads on the substrate. The occlusal pads are designed to ensure that the entire substrate is firmly fixed by the patient's own biting force, without the need for manual support. The elastic anti-slip protrusions on the inner surface of the substrate further enhance initial stability and prevent slight slippage. This step establishes a stable physical reference platform within the patient's mouth that is strictly aligned with the patient's own anatomical coordinate system. Finally, the pre-prepared, reusable angle positioning mechanism 200 is connected to the external end of the connecting rod 400 via its interface.

[0059] S300: Horizontal Angle Setting. Setting the horizontal angle is crucial for controlling the deflection of the X-ray centerline in the horizontal plane, used to avoid overlapping of adjacent teeth and align with the bifurcation of the target tooth root. The operator determines the target horizontal projection angle based on the preoperative CBCT data analysis (for example, to clearly show the mesobuccal root of the maxillary first molar, the centerline needs to be deflected distally by +10°).

[0060] In practice, the operator first observes and ensures that the horizontal reference indicator line 215 on the turntable 212 is aligned with the zero mark on the connecting shaft 211 (or base). This alignment indicates that the optical indicator 300 is parallel to the patient's sagittal plane, i.e., at a reference position with a horizontal angle of 0°. Then, the operator loosens the first locking element 213 (e.g., a thumb screw) and slowly rotates the turntable 212 by hand until the "+10°" mark on the horizontal angle scale 214 around the turntable 212 aligns with the fixed reference mark on the connecting shaft 211. Finally, the operator tightens the first locking element 213 to securely lock the turntable 212. At this point, the horizontal direction of the entire angle positioning mechanism 200 (including the subsequent vertical adjustment assembly and the optical indicator 300) has been precisely set to +10°.

[0061] S400: Vertical Angle Setting Specifically, the setting of the vertical angle determines the degree of stretching or compression of the image in the vertical direction, which is crucial for clearly displaying tooth roots at different depths. The operator obtains the target vertical projection angle according to the preoperative plan (for example, a vertical angle of -5° is required to make the ray perpendicular to the long axis of the target tooth root).

[0062] The operator operates the vertical angle adjustment component 220. Loosen the second locking member 222, and move the cantilever 221 up and down until the pointer on the cantilever 221 points to the "-5°" mark on the vertical angle scale 223 on the turntable 212 (or independent support base). Then, tighten the second locking member 222. If a universal ball joint structure is used, the operation is more intuitive: loosen the third locking member, directly adjust the direction of the ball joint end to a comfortable pitch angle by hand, and then tighten. Regardless of the structure, after this step, the vertical direction of the optical indicator 300 is precisely set.

[0063] S500: Optical Pre-alignment Steps Specifically, the mechanically set angles are visually verified and finally aligned. After setting the angles for S300 and S400, the operator installs the optical indicator 300 (such as a laser pointer) into the mounting channel at the end of the cantilever 221 or ball joint and turns it on. The laser pointer emits a visible laser beam whose direction perfectly represents the theoretical X-ray centerline path determined after the above two mechanical adjustments.

[0064] The laser beam projects a clear indicator spot onto the patient's facial skin. The operator then moves the X-ray tube of the dental X-ray machine, adjusting its position and orientation until the tube's built-in focus indicator spot (usually red light) perfectly aligns with the laser indicator spot on the patient's face. This "spot-to-spot" optical pre-alignment process provides immediate and intuitive visual feedback, ensuring a perfect match between the theoretical angle set by the intraoral guide and the actual physical spatial position of the X-ray tube, thus confirming the correctness of the projection geometry before exposure.

[0065] S600: Shooting Execution Specifically, once optical pre-alignment is confirmed, all positioning steps are complete. The operator places the digital X-ray sensor or traditional film on the lingual / palatal side of the target tooth and instructs the patient to maintain a stable bite. Subsequently, the exposure button is triggered to take an X-ray image. Because the projection angle has been individually calculated, mechanically precisely positioned, and optically verified in real time, the first image can very likely obtain a high-quality periapical image that meets the Class A film standard (e.g., distortion rate <5%, complete structural display).

[0066] This method, through a standardized process consisting of the above six steps, transforms the traditional trial-and-error model that relies on the technician's personal experience into a deterministic process based on digital design and precise physical positioning. It systematically solves the problem of inaccurate angle control in maxillary posterior tooth periapical radiographs, significantly improving the success rate and image quality of a single radiograph, while directly reducing the radiation dose and treatment time for patients.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A device for positioning the centerline of an X-ray in periapical radiograph, characterized in that, include: Personalized substrate, the shape of its inner surface is matched with the anatomical morphology of the occlusal and buccal surfaces of the patient's target dentition; A connecting rod is disposed on the personalized base plate, and when the personalized base plate is located at the target dentition position, the connecting rod extends to the outside of the oral cavity; An angle positioning mechanism is connected to the end of the connecting rod located outside the oral cavity; as well as An optical indicator is detachably mounted on the angle positioning mechanism; The angle positioning mechanism is configured to adjust and lock the angle of the optical indicator in the horizontal and vertical directions.

2. The positioning device according to claim 1, characterized in that, The angle positioning mechanism includes: A horizontal angle adjustment component, connected to the personalized substrate, is used to provide the optical indicator with rotational freedom in the horizontal plane; and A vertical angle adjustment component, disposed on the horizontal angle adjustment component, is used to provide the optical indicator with a degree of freedom of swing in the sagittal plane.

3. The positioning device according to claim 2, characterized in that, The horizontal angle adjustment component includes: A connecting shaft is fixed to the end of the connecting rod located outside the oral cavity; A turntable, rotatably mounted on the connecting shaft via a first rotating shaft; and A first locking element is used to lock the turntable relative to the connecting shaft; The turntable is provided with a horizontal angle scale around its perimeter.

4. The positioning device according to claim 3, characterized in that, The turntable is provided with a horizontal reference indicator line. When the horizontal reference indicator line is aligned with the zero mark engraved on the connecting shaft, the optical indicator points parallel to the patient's sagittal plane.

5. The positioning device according to claim 4, characterized in that, The vertical angle adjustment component includes: A cantilever, pivotally mounted on the turntable via a second pivot; and The second locking element is used to lock the cantilever relative to the turntable; The turntable is equipped with a vertical angle scale.

6. The positioning device according to claim 5, characterized in that, The optical indicator is a laser pointer, and the end of the cantilever is provided with a mounting channel for accommodating the laser pointer. The geometric center line of the mounting channel coincides with the swing center line of the cantilever.

7. The positioning device according to claim 1, characterized in that, The personalized substrate is also provided with an occlusal pad, which extends from the occlusal surface morphology of the personalized substrate toward the opposing teeth to form a plane or curved surface for patient occlusion to stabilize the guide plate.

8. The positioning device according to claim 1, characterized in that, The personalized substrate is made of photocurable resin material using a 3D printing process, and the morphology of its inner surface is manufactured based on a three-dimensional digital model of the dental arch reconstructed from the patient's intraoral scan data or CBCT data.

9. The positioning device according to claim 4, characterized in that, The vertical angle adjustment component is a universal ball joint structure, including: A ball joint seat is fixed to the turntable; A ball joint link, wherein the ball joint portion is constrained within the ball joint seat and can rotate omnidirectionally within a certain angle; and The third locking element is used to lock the ball joint after it has been adjusted to the target angle.

10. A method for locating the centerline of an X-ray in a periapical radiograph, characterized in that, The method, using the X-ray centerline positioning device as described in any one of claims 1-9, comprises the following steps: Data acquisition and guide plate fabrication: Acquire three-dimensional oral cavity data of the patient's target dentition, and design and manufacture a personalized substrate with an inner surface morphology that matches the data. Device wearing and initial positioning: The personalized substrate is worn on the target dentition inside the patient's mouth, and the connecting rod extends out of the oral cavity; Horizontal angle setting: According to the target horizontal projection angle planned before the operation, operate the horizontal angle adjustment component of the angle positioning mechanism to adjust and lock the horizontal direction of the optical indicator to the corresponding angle; Vertical angle setting: According to the target vertical projection angle planned before the operation, operate the vertical angle adjustment component of the angle positioning mechanism to adjust and lock the vertical direction of the optical indicator to the corresponding angle; Optical pre-alignment: Turn on the optical indicator, and the beam emitted by it forms an indicator spot on the patient's face; move the X-ray tube of the dental X-ray machine so that the indicator spot on the X-ray tube coincides with the indicator spot formed by the optical indicator; Imaging procedure: After optical pre-alignment is completed, X-ray exposure is performed to acquire periapical radiographs of the target dentition.

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