Efeito de movimentos ortodônticos no comportamento biomecânico de pré-molares com lesões cervicais não cariosas

Abstract

Non-carious cervical lesions (NCCL) are characterized by loss of hard tissue dental surfaces closest to the cement-enamel junction. These Lesions are caused by multifactorial etiology, and occlusal factors, orthodontic force could have influence on these. The objective of this research is evaluate the biomechanical behavior of premolars with NCCLS submited to differents orthodontic loads, by three-dimensional finite element method (MEF) and extensometry. 3D-FEA orthotropic, linear, and elastic models were generated with meshes of tetrahedral elements, which are: sound tooth (SO); unrestored NCCL; and NCCL restored composite resin (CR). Five static orthodontic loads were applied which were on a displacement constraint in the bone, with the following forces: 5N rotation (RO), 5N extrusion (EX), 1,5N intrusion (IN), 5N buccal tipping (BT) and 5N lingual tipping (LT). The analysis used in MEF was maximum tension. For the strain-gauge tests, 10 sound maxillary premolars were collected and a strain gauge was attached on the buccal surface between the cement-enamel junction and the bracket bottom. It was then held all orthodontic load in sound tooths. After the record tooth strains during all orthodontic loads, a NCCL was simulated and resubmitted to strain-gauge test. Following, the NCCL were restored with composite resin and the strains were measured. Two-way Repeated Measures ANOVA was used with 95% confidence level. FEA showed that NCCL result in greater stress concentration in cervical region, especially on EX and RO loads. CR presents the stress distribution closer to SO for all loads simulated. For strain gauge test, NCCL showed higher strain values and CR was statics similar to SO independently of orthodontic loads. EX (36.70 μS) and LT (42, 74 μS) showed greater strain for NCCL. This study allows to conclude that the presence of NCCLS promotes greater accumulation of strain and deformation in the cervical region when was applied orthodontic loads. Whereas etiologic factor NCCL progression involves biomechanical factors, it is suggested restoring the NCCL prior to orthodontic treatments.