Session: 07-07-02: Computational Modeling in Biomedical Applications II

Paper Number: 166051

Finite Element Analysis of Non-Extraction Clear Aligner Treatment 

Background

Clear aligner therapy has become one of the most popular orthodontic treatment modalities. Tooth extraction is a widely accepted treatment prior to the clear aligner therapy for effective gap closure and teeth alignment correction. In contrast, the clinical study has demonstrated that the patients who undergo clear aligner therapy without the prior tooth extraction usually require secondary refinement plans and approximately twice the number of aligners compared with the initial prediction. This work aims to reveal the fundamental changes in tissue response and orthodontic force distribution of non-extraction therapy by comparing the biomechanical response between the clear aligner therapies with and without extraction using finite element analysis (FEA).

Material and Method

A patient-specific maxillary model was reconstructed, which contained alveolar bone, periodontal ligaments (PDL), and teeth. The clear aligner was generated with the aim of retracting the central incisors by 0.1 mm. The teeth, PDL and clear aligner were assumed as linear and homogeneous material properties, while bone is assumed as rigid. Two parallel finite element analysis (FEA) were conducted with the identical clear aligner configuration and patient model: one for the non-extraction (NE) case and another for the extraction (EX) case, where the first premolars were suppressed during simulation. The displacement patterns of all teeth were analyzed to evaluate morphological variations between the two cases. Additionally, root reaction forces were measured for both anterior (incisors and canines) and posterior teeth (premolars and molars) to assess differences in biomechanical responses.

Result

The distance of teeth retraction differed significantly between NE and EX cases. The EX case usually revealed greater retraction. Central incisors exhibited 0.062mm of crown retraction in EX cases compared to 0.052mm in NE cases; lateral incisors showed 0.024mm and 0.021mm of retraction in EX and NE cases, respectively. The movement pattern observed in EX case was more predictable, characterized by distal movement of anterior teeth and mesial movement of posterior teeth. In contrast, NE cases demonstrated more complex tooth movements. Specifically, canine and premolars in NE cases showed altered displacement patterns, transitioning from distal and medial movements to buccal displacement; posterior teeth in NE cases showed irregular movement patterns, combining axial rotation with intrusive forces.

This disorganized tooth movement observed in NE case, particularly in the anterior teeth, may be attributed to the interactions between the first premolar and its adjacent teeth (canine and second premolar). Additional forces acting on the canine and second premolar crowns (1.60 N and 1.24 N respectively) established a new equilibrium across all contact surfaces of adjacent teeth. The complexity of the interproximal area of teeth resulted in the fluctuations and redirections of root reaction forces. Notably, posterior teeth experienced an increment of forces in the buccal direction and a reduction in the mesial direction. Given that posterior teeth typically serve as anchorage points in clear aligner therapy, the change of the force pattern may lead to unpredictable tooth movement which potentially compromises the therapy outcomes and increases the likelihood of requiring mid-course refinements.

Conclusion

This investigation provided a quantitative analysis of tooth movement and orthodontic root forces for NE treatment prior to clear aligner treatment. Comparative analysis with the EX case using the identical aligner configuration revealed that the NE case requires more monitoring, regarding irregular buccal tooth movement and unpredictable root reaction force on anchorage teeth.

Presenting Author: Jianing Wang Florida Institute of Technology

Presenting Author Biography: Jianing Wang is a graduate student of Biomidical Engineering from Florida Institute of Technology. His research areas include finite element analysis (FEA), biomedical devices and experiments, and mechatronics.

Authors:

Jianing Wang Florida Institute of Technology
Thyagaseely Sheela Premaraj Nova Southeastern University
Sundaralingam Premaraj Nova Southeastern University
Bo Wang Medical College of Wisconsin
Linxia Gu Florida Institute of Technology
Pengfei Dong Florida Institute of Technology