Effect Of Pit And Groove Retention Form On Occlusal Veneers:Three-dimensional Finite Element And Weibull Analyses

Objective:A three-dimensional finite elements analysis（FEA）and Weibull analysis was used to study the influence of the pit-and-groove retention form（PGRF）on the biomechanics and failure probability of the mandibular first molar occlusal veneer restoration,exploring the feasibility of adding PGRF and the better designs of the PGRF to provide a feasible solution for the occlusal veneer restoration of worn mandibular first molars.Methods:Three-dimensional finite element models of mandibular first molars with two degrees of wear—0.5 mm and 1.0 mm—were established,each with 10 groups.Two different restoration designs—common occlusal veneer and PGRF occlusal veneer—were simulated;PGRF was set at four different depths（0.25 mm,0.5 mm,0.75 mm,and 1.0mm）,and two different CAD/CAM materials—IPS e.max CAD（LD）and Lava Ultimate（LU）were used.A load of 241 N was applied to the lingual plane of the buccal cusp of the mandibular first molar in three different directions（vertical,at a 45°angle and horizontal）.The maximum principal stress(σ_max)and maximum displacement of the occlusal veneer restoration models were calculated.Weibull analysis was used to evaluate the failure probability of the models.Results:Theσ_maxvalues of the PGRF occlusal veneer were slightly higher than those of the common occlusal veneer,while those of the dental tissue were lower.With the increase in the PGRF depth,the maximum displacement peak value of the occlusal veneer and cement layer decreased significantly.The overall failure probability of the model tended to decrease.Conclusion:This numerical study shows that the design of PGRF on the occlusal veneer may be a favorable restoration strategy that can significantly reduce the debonding tendency of occlusal veneer,and this can improve the clinical longevity of occlusal veneer prostheses.