Assessment of Porcelain Fused to Metal Crown Preparations by General Practitioners in Saudi Arabia

Background: Principles for fabricating prosthetic restorations include sufficient axial preparation and adequate occlusal clearance of the prepared teeth. This study measured the convergence angles in the prepared teeth for porcelain fused to metal (PFM) crowns done by general practitioners in different regions of Saudi Arabia. In addition, the presence of planar occlusal reductions, functional cusp bevels and rounded angles in prepared casts were evaluated.

Methods: Sixty dies were selected from the working casts of prepared PFM crowns by general dental practitioners. The dies were divided into four equal groups according to the region. All the measured dies were mounted with the occlusal plane of the prepared teeth parallel to the floor. Photographs of buccal and proximal aspects of the dies were taken and then transferred into a personal computer. An AutoCAD software program was used to measure the mesiodistal and buccolingual convergence angles. The planar occlusal reduction, functional cusp bevel and presence of rounded angles of each preparation were evaluated. The data were recorded, then analyzed using SPSS version 20.0.
Results: The mean convergence angles were high above the ideal range (4º-14º) in all of the selected regions. The mean mesiodistal convergence angle nearest to the ideal range was registered in teeth prepared in Dammam region, which was lower than tooth preparations from Jeddah, Abha and Jazan regions. Statistically significant differences with buccal, lingual taper and buccolingual convergence existed between the regions. Also significant differences were observed between the teeth preparation samples from four regions with distal taper and mesiodistal convergence angles.
Conclusion: The achieved convergence angles of tooth preparations for PFM crowns by different general practitioner were out of the recommended range mentioned in dental literature.