Influence of porcelain firing on changes in the marginal fit of metal-ceramic fixed partial dental prostheses fabricated with laser sintering: An in vivo study.

Qusay Nassif,Fendi Alshaarani

doi:10.17219/dmp/114196

Abstract

Marginal fit is the most important criterion in the evaluation of the clinical acceptability of fixed restorations. Due to cement solubility and plaque retention, marginal gaps are potentially harmful to both the teeth and the periodontal tissues. The aim of the study was to investigate the accuracy of the fit of dental metal-ceramic bridges manufactured with the use of direct metal laser sintering (DMLS), and to explore the effects of porcelain firing on the marginal, axial and occlusal fit of metal-ceramic frameworks. The study involved 10 patients with 3-unit metal-ceramic restorations produced using the DMLS technique. Using the silicone replica technique, we examined the marginal, axial and occlusal fit of the dental bridges before and after ceramic firing. The Shapiro-Wilks normality test and Student's paired t‑test were implemented to analyze the mean differences in the marginal, axial and occlusal fit of the restorations before and after ceramic firing. A 95% confidence interval (CI) and discrepancy values at the level of 1% and 0.1% (p > 0.05) were applied. All the mean values of the measurements of marginal (156.08 μm), axial (95.75 μm) and occlusal (252.83 μm) gaps were lower before ceramic veneering than after ceramic veneering, when the mean value for the marginal gap was 178.17 μm, for the axial gap - 106.75 μm and for the occlusal gap - 266.00 μm. Porcelain firing caused no statistically significant differences in the discrepancy values of marginal, axial and occlusal fit. For clinical application, further improvement of the DMLS system is highly recommended. Marginal gaps in DLSM bridges significantly exceed the permissible inaccuracy values of 100-120 μm for prosthetic restorations.

Highlights

Dental porcelain fused to metal bridges is considered the best choice in prosthetic dentistry, especially in the posterior area of the jaws, due to a high tolerance of these materials to stress.[1,2] The clinical survival of these bridges is largely dependent on the distance between the internal surface of the restoration and the external surface of the abutment.[3,4] When the marginal gap is larger than the clinically acceptable limit, it eventually can cause cement dissolution, followed by secondary caries or periodontal inflammation.[4,5]The lost-wax technique is considered a conventional method to fabricate metal bridges.[6]
Objectives.The aim of the study was to investigate the accuracy of the fit of dental metal-ceramic bridges manufactured with the use of direct metal laser sintering (DMLS), and to explore the effects of porcelain firing on the marginal, axial and occlusal fit of metal-ceramic frameworks
Using the silicone replica technique, we examined the marginal, axial and occlusal fit of the dental bridges before and after ceramic firing

Summary

Introduction

Dental porcelain fused to metal bridges is considered the best choice in prosthetic dentistry, especially in the posterior area of the jaws, due to a high tolerance of these materials to stress.[1,2] The clinical survival of these bridges is largely dependent on the distance between the internal surface of the restoration and the external surface of the abutment.[3,4] When the marginal gap is larger than the clinically acceptable limit, it eventually can cause cement dissolution, followed by secondary caries or periodontal inflammation.[4,5]The lost-wax technique is considered a conventional method to fabricate metal bridges.[6]. When the marginal gap is larger than the clinically acceptable limit, it eventually can cause cement dissolution, followed by secondary caries or periodontal inflammation.[4,5]. The manual phases of the casting process may result in distortions in the metal framework.[4,7,8]. Some of these complications could be avoided by using the computer-aided design and computer-aided manufacturing (CAD-CAM) technologies,[9,10] or the laser sintering method (an additive manufacturing technique used in fixed prosthodontics)[11,12] or casting with 3D-printed patterns.[13]. The laser sintering technology uses a high-power laser beam transformed by galvano mirrors to aggregate metal powder layer by layer, making three-dimensional (3D) complex patterns. Marginal fit is the most important criterion in the evaluation of the clinical acceptability of fixed restorations. Due to cement solubility and plaque retention, marginal gaps are potentially harmful to both the teeth and the periodontal tissues

Objectives

Methods

Discussion

Conclusion