European Journal of Prosthodontics and Restorative Dentistry

Assessment of Posterior Teeth Preparations for Metal-Ceramic Crowns

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Cover Date

September 2015

Print ISSN

0965-7452

Vol

23

Issue

3

Abstract

Assessment of Posterior Teeth Preparations for Metal-Ceramic Crowns
Keywords
tooth Preparation tooth Reduction Metal-ceramics

AbstRAct
Objectives: To evaluate teeth preparation designs for metal-ceramic crowns in private dental practice in Jordan. Materials and methods: One-hundred and seventy two dies were included. Different aspects of tooth preparations were quantified, analyzed and compared with the recommended guidelines. Results: Almost 64% of preparations finish lines were positioned subgingivally. Shoulder finish lines were observed in 74.4% whereas 22.7% showed chamfer finish lines. Total occlusal convergence angles were 29.8° in BL plane, 24.7° in MD plane. Conclusions: Dental practitioners in private practice in Jordan did not fully adhere to the recommended guidelines for tooth preparations for MCRs.

Authors
Ziad n. AL-Dwairi *
(bDs, PhD, FIADFE) (bDs)

Mahmoud Mamdouh bashatwa # Edward Lynch Δ

(bDentsc, MA, FDs, PhD)

IntRoDuctIon
Metal-ceramic restorations (MCRs) have been considered the “gold standard” in modern prosthetic dentistry because of their excellent mechanical properties, acceptable degree of esthetic outcomes, satisfactory marginal fit and internal adaptation, in addition to long- term scientific evidence of clinical success.1-6 Several studies showed that MCRs are more resistant to fracture than all-ceramic ones.7-9 A 5-year survival rate of 94.4% was reported for all metal-ceramic bridges compared to a 5-year survival rate of 88.6% for allceramic bridges.5 A success rate of 71% was reported for metal-ceramic fixed partial dentures after 18 years of use,10 and a 5-year survival rate of 95.6% for metal-ceramic crowns.4 As the MCR is a combination of metal and ceramic, it is mandatory that adequate, anatomical reduction is essential to create enough space for both materials. Without this space for a sufficient thickness of the materials, the restoration would be poorly contoured with unacceptable esthetic results and could adversely affect the periodontium. However, over reduction can endanger the pulp and may lead to loss of pulp vitality.10 Recommendations and guidelines of the desirable values of different aspects of tooth preparations for different types of indirect restorations have been proposed aiming to develop restorations that are functionally durable, provide acceptable esthetic results, and to support a healthy periodontium.11-13 For MCRs with porcelain veneered margins and occlusal surfaces, the recommended reduction of the axial surface is from 1.0-1.7 mm and is 2.0 - 2.5 mm for the incisal/occlusal surface. A number of different types of finish lines have been advocated; these include: chamfer, beveled chamfer, shoulder and beveled shoulder. The recommended finish line depth is from 1.0 - 1.5 mm. Supragingival finish lines on sound dental tissue should

Address for correspondence
Ziad n. AL-Dwairi * Email: [email protected]
* Professor of Prosthodontics Department of Prosthodontics Faculty of Dentistry Jordan university of science and technology Po boX 3030 code 22110
#

Postgraduate student Department of Prosthodontics Faculty of Dentistry Jordan university of science and technology Head of Dentistry, Warwick Medical school university of Warwick cV7 4AL, uK

Δ

Received: 13.02.15 Accepted: 19.06.15 doi: 10.1922/EJPRD_1447AL-Dwairi09

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