FEA evaluation of the resistance form of a premolar crown.

Purpose: The purpose of this study was to evaluate the influence of buccal and lingual wall convergence angles on the ability of the preparation to resist rotational displacement.

Materials And Methods: An intact premolar digitized by micro-CT yielded a 3D reproduction of a human tooth. Simulated crown preparations with known buccolingual axial wall convergence angles (4°, 8°, 12°, 16°, 20°, 24°, 28° 32°), sloped-shoulder marginal area, and occlusal reduction were created and restored with a ceramic crown. The tooth restoration was loaded with a 200 N force at 45° to the incline of the buccal cusp. The responses of the restored tooth with luting agents were analyzed using the 3D finite element method.

Results: This study demonstrated that a convergence angle of the preparation above 12° produced a decrease of the resistance of the crown to rotational effects. The study also showed that the use of luting agents that provide bonding between the restoration and dentine improved the rotational resistance of the crown on preparations with large convergence angles.

Conclusions: Use of buccolingual convergence angles greater than 12° reduced the resistance form of the preparation. Luting agents capable of delivering strong bonding between the crown and the preparation improved the resistance in highly tapered preparations.