Biomechanical Effect of Osteotomy and Corticotomy on Orthodontic Molar Uprighting

Objectives: Uprighting mesially tilted molars are often necessary prior to dental implant placement. However, orthodontic treatment can be lengthy and discourage patients from choosing implant prosthesis. Periodontally accelerated osteogenic orthodontics are reported to facilitate molar movements. Thus, the study objective was to determine the biomechanical effects of various corticotomy and osteotomy approaches on uprighting of a mesially tilted mandibular second molar in a 3-dimensional finite element (FE) model.
Methods: Healthy male (46yrs) with a mesially tilted second molar underwent CBCT scanning to develop 3D solid models of the mandible and tilted molar. 3D solid models including the periodontal ligament (PDL) surrounding the tilted molar and orthodontic bracket were generated using design software. FE models simulating eight different surgical cuts were recreated. Three different mechanical loading conditions were applied including distal crown tipping, mesial root movement without restraint, and mesial root movement with restraint. Molar displacement and PDL strain calculated by the FE models were compared under the three loading configurations to determine the effect of corticotomy and osteotomy. FE models were validated by comparing predicted molar displacement with clinical observations of molar movement for the same subject.
Results: Molar displacement pattern predicted from FE models agreed well with corresponding clinical surgical treatment. FE analysis demonstrated osteotomy approaches resulted in increased molar displacement and PDL strain in all three loading configurations, while corticotomy approaches had increased molar movement but decreased PDL strain. The most extensive surgical approaches, combined mesial and distal osteotomy with horizontal corticotomy and circumferential corticotomy, resulted in the most tooth displacement for both approaches and the least PDL strain induced for circumferential corticotomy.
Conclusions: Osteotomy and corticotomy had significant biomechanical effects on orthodontic molar uprighting movement. Different surgical approaches had specific effects in tooth displacement and PDL strain, providing insights for clinicians to develop future surgical approaches for molar uprighting.