Biomechanical Effects of Clear Aligners with Different Palatal Edge Extension in Extraction Cases: A Three-dimensional Finite Element Study

doi:10.13701/j.cnki.kqyxyj.2024.11.004

Abstract

Abstract: Objective: To investigate the displacement of dentition during retraction of anterior teeth under different palatal edge extension of clear aligners in extraction cases. Methods: A finite element model was constructed to analyze the characteristics of tooth movement and periodontal membrane stresses of clear aligners. The model was based on different palatal edge extension and classified into four cases: working condition 1: supergingival 1 mm, working condition 2: flanking gingival, working condition 3: extended 1 mm, and working condition 4: extended 2 mm. Results: Clear aligners therapy caused lingual tipping and extrusion of incisors, distal tipping of canines, and mesial tipping of posterior teeth in each group. With increasing palatal edge length, the degree of sagittal inclination was gradually decreased in central incisors and the lateral incisors were minimized at work condition 2. The distal tipping of the canine increased gradually, lingual tipping gradually decreased, and extrusion displacement increased in working conditions 1 to 3 and decreased in working condition 4. The medial tipping and intrusion of the second premolar initially increased and tended to decrease in condition 4. The mesial tipping and intrusion of the first molar were gradually increased. The Mises stresses exhibited the highest peak stresses in the apical region of the cusps. Conclusion: Clear aligners can be a roller coaster when retracting upper anterior teeth in extraction cases, extending the palatal edge can facilitate the bodily movement of incisal, but the canine distal tipping displacement increased. If the edge length exceeds 1mm, it can effectively prevent the canine lingual inclination and extrusion, and the second premolar medial inclination. However, there is a need of greater anchorage to support the first molar.

Key words: finite element analysis, clear aligner, extraction orthodontics, orthodontic space closure

WANG Jiangting, CHEN Mei, ZHANG Ruijing, LIU Linyi, SHE Rui, WEN Xiujie. Biomechanical Effects of Clear Aligners with Different Palatal Edge Extension in Extraction Cases: A Three-dimensional Finite Element Study[J]. Journal of Oral Science Research, 2024, 40(11): 960-966.

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