Orthodontic Tooth Trajectory Segmentation for PDL Strain Reduction
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Solution Overview
Problem
Existing orthodontic treatment planning methods can cause damage to the periodontal ligament (PDL) due to excessive strain during tooth movement, particularly when teeth are mesially inclined within the gingiva.
Innovation Solution
The method involves determining the tooth trajectory based on reference points on the tooth axis corresponding to the vertical boundaries of the PDL, with a focus on the most distant point from the target position. This trajectory is then segmented to ensure each segment does not exceed a predetermined safety threshold, minimizing strain on the PDL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tooth trajectory is determined based on the center of resistance (CR) point, then the tooth movement can be planned from initial position to target position, but other points on the tooth axis within the crown and root portions may displace at a longer distance causing excessive strain to the PDL
Solution Approach 1:
The patent segments the tooth into multiple portions (crown portion, root portion) and determines separate reference points for each portion. Instead of using a single CR point, the system identifies a first reference point on the tooth axis within the crown portion and a second reference point within the root portion, allowing independent trajectory analysis for each segment to prevent excessive PDL strain.
Solution Approach 2:
The patent performs preliminary determination of multiple reference points and their respective trajectories before final treatment execution. By calculating the trajectories of both the first reference point (crown portion) and second reference point (root portion) in advance, the system can identify which trajectory is longer and use that as the basis for segmenting the overall tooth movement into safe increments.
2Manufacturing precision
If the tooth is mesially inclined within the gingiva, then the CR point moves towards the target position, but other points on the tooth axis displace at a longer distance exceeding the safety threshold
Solution Approach 1:
The patent applies local quality by treating different portions of the tooth (crown and root) with different reference points and trajectory analyses. Each portion is evaluated independently to determine its specific displacement characteristics, allowing the system to account for local variations in tooth geometry and inclination that affect PDL strain distribution.
Solution Approach 2:
The patent extends the analysis from a single-point (CR point) trajectory to multi-point trajectories along the tooth axis. By considering the third dimension of tooth inclination and the vertical distribution of reference points within the crown and root portions, the system can comprehensively evaluate displacement in multiple spatial dimensions to ensure PDL safety.
Data Source
AI summary
A method and a system for planning an orthodontic treatment are provided. The method comprises: acquiring an arch form 3D digital model including a representation of the given tooth in a current position thereof within a subject's gingiva; determining an initial crown reference point and an initial root reference point; obtaining a target position of the given tooth within the arch form 3D digital model; determining a number of steps for the given tooth to displace from the current position to the target position thereof in the course of the orthodontic treatment; and storing data indicative of the number of steps associated with the given tooth for use in the planning the orthodontic treatment.