Palatal Rugae in 3D Superimposition Technique

Abstract

Background: Superimposition of three-dimensional (3D) digital models on reportedly stable palatal rugae (PR) facilitates the assessment of tooth movement during growth and orthodontic treatment. Available techniques using manual annotation of features on dental casts and photographs are time-consuming and prone to errors.

Objectives: Develop a consistent stable reference frame using the PR and validate their stability and the consistency of an associated reference frame.

Methods: 3D textured intraoral scans of orthodontic patients were manually segmented (using MeshMixer software) to label individual teeth and PR. The segmented scans were colored and separated using MeshLab software. The rugae of same patients were superimposed to verify their stability over-time. Each single ruga, pair of rugae, and the whole PR surface were superimposed to identify the most stable region in different malocclusions and treatment modalities. Superimposition on the most stable area was performed before and after orthodontic treatment to evaluate amount and direction of tooth movement.

Results: Segmentation of the rugae proved efficient as a basis to compare the stability of the rugal components. Superimposition on individual rugae, the mesial part of the 3rd rugae, and 2nd rugae were the most stable references, respectively.

Conclusion: The results indicate the validity of the method. A new contribution is that a single ruga is sufficient as a reference. The findings on the 3rd rugae corroborate previous reports. The method will allow the use of the rugae superimposition to quantify tooth movement and perform more frequently needed evaluations and will minimize reliance on x-rays.