Correlation between cuspal inclination and tooth cracked syndrome: a three-dimensional reconstruction measurement and finite element analysis

Background/Aim This paper explored the correlation between cuspal inclination and tooth cracked syndrome by measuring and reconstructing the cuspal inclinations of cracked maxillary first molars through three-dimensional (3D) finite element analysis (FEA). Material and methods The cuspal inclinations of 11 maxillary left first molars with cracked tooth syndrome and 22 intact controls were measured by 3D reconstruction. The mean values of each group were used to construct two 3D finite element models of maxillary first molar for comparing stress distribution under the loads of 200N at 0 degrees, 45 degrees, and 90 degrees, respectively, to the tooth axis. Results There was statistically significant difference in the cuspal inclination between the incompletely fractured group and the intact control group ( P <0.001), which was 5.56.7 degrees steeper. The model from the mean cuspal inclinations of the incompletely fractured molars showed the maximum tensile stress of 5.83, 10.87, and 25.32MPa, respectively, in comparison with 5.40, 8.49, and 22.76MPa for the model of the control group. Besides, the tensile stress was mainly at the center groove and cervical region of the molar model. Conclusions Steeper cuspal inclinations resulted in an increment in tensile stress that was mainly at the center groove and cervical region of the molar model under equivalent loads. Higher unfavorable tensile stress was generated with the increasing horizontal component load on the cuspal incline. This indicates an effective reduction of cuspal inclination to the compromised teeth for dentists.