Restoration effects of composite resin on different types of wedge-shaped defects:a three-dimensional finite element analysis

AIM:To examine the restoration effects of composite resin on four kinds of wedge-shaped defects in first mandibular premolars.METHODS:Three-dimensional finite element models of wedge-shaped defects,with a depth of 1 mm and angles of 30°,60°,90° and 120° were established in the first mandibular premolar.By given dentin and composite resin parameters,the simulate composite resin restoration models,the complete experimental teeth models and the unrepaired wedge-shaped defects teeth models were achieved.100 N axial loadings were loaded on these models and the stress distributions were investigated by using the three-dimensional finite element method.RESULTS:The stress distributed on the experimental complete teeth models was similar to that on the composite resin restoration models.Both showed that the stress on the mesial side was higher than that on the distal side.The Von Mises stress concentration points of different degrees of wedge-shaped defect teeth were similarly located on the outer surfaces' mesial edges of the restorations.The max Von Mises stress values on the filling parts of the composite restoration models were lower than those on the complete teeth models.At 30° wedge-shaped defect teeth cases,the scopes on the composite resin restoration models which bear relatively high stress on the plane O were larger than those on the complete teeth models.However at 60°,90° and 120° cases,those scopes on the composite resin restoration models were smaller than those on the complete teeth models.At 30°,60° wedge-shaped defect teeth cases,the Von Mises stress distributions on the line L were similar on composite resin models and complete teeth models.Both of them were obviously lower than those on the unrepaired wedge-shaped defect teeth models.At 90° and 120° cases,the Von Mises stress distributions on the line L were lower on the complete teeth models than those on the composite resin models while the Von Mises stress distributions were lower on the composite resin models compared to the values on the unrepaired models.CONCLUSION:The composite resin restorations had protective effects on all of the four kinds of wedge-shaped defects.Particularly in the cases of acute angle wedge-shaped defects,the stress distribution inside the teeth could be recovered thus the stress concentration was better blocked.