Assessment of Convergence Angles of Tooth Preparation for Porcelain Fused to Metal Restorations by General Dentists

• Published in: Majallah-i Dānishgāh-i ʻUlūm-i Pizishkī̄-i Bābul Vol. 13; no. 2; pp. 51 - 56
• Main Authors: A Madani, A Ghahramanloo, M Shokati
• Format: Journal Article
• Language: Arabic; English
• Published: Babol University of Medical Sciences 01.03.2011
• Subjects: convergence angel; general dentists; porcelain fused to metal restoration; tooth preparation
• ISSN: 1561-4107; 2251-7170

BACKGROUND AND OBJECTIVE: One of the important factors in the longevity of fixed restorations is fundamental considerations of tooth preparation. One of these fundamentals is axial walls preparation with minimum tapering for retention and resistance form. The aim of this study was to assess convergence angles of tooth preparation for Porcelain Fused to Metal (PFM) restorations by general dentists. METHODS: Referring to Mashhad dental laboratories, 600 die patterns were collected, and divided into five groups including maxillary and mandibular anterior teeth, premolars, maxillary and mandibular molars (120 in each group). Photographic views of the samples were taken by a digital camera (EOS-450D model) to exactly examine the convergence of the tooth walls. One photograph was taken from the facial surface, and the other taken from the proximal. Angles related to the tapering of axial walls, in mesiodistal and faciolingual dimensions were measured by using engineering software (AutoCAD 2008) for each die. Also, the inclination of buccal and lingual walls of posterior teeth was measured separately and then assessed and compared with the standards.FINDINGS: Mean M-D and F-L convergence angle for maxillary and mandibular molars, premolar, maxillary and mandibular teeth were (31.02±10.72, 28.48±11.92), (32.06±9.98, 37.14±11.92), (21.83±7.46, 24.25±11.72), (28.66±13.18, 15.51±8.98) and (31.31±13.78, 18.11±7.95) degrees, respectively. M-D and F-L tapering in all groups have statistical significant difference with optimum degree of tooth preparation taper. Also there was a significant difference between M-D and F-L tapering in all groups (p<0.001). Inclination of preparation in posterior teeths also measured buccal inclination is bigger than of lingual walls in posterior teeth (p<0.001). CONCLUSION: According to results of this study, in all cases the tapering angles were more than normal. M-D and F-L tapering in mandibular molars were more than the others. Tendency of dentists was to more tapering in buccal than lingual surfaces in posterior teeth.