Technical Accuracy of Dental Laboratories in the Quality and Shade Matching of Porcelain Fused to Metal Crowns: An In Vitro Study

Abstract

Dental laboratories (LABs) are integral to the performance of a dentist in providing successful oral rehabilitation. The aim of this study was to compare the adaptation, contour, contacts, and shade matching of different government and commercial dental LABs in the fabrication of porcelain fused to metal (PFM) crowns. Thirty-two dental LABs were selected to fabricate PFM crowns (one PFM crown each). Marginal adaptation, contour, proximal contacts, and shade matching were evaluated. Evaluation of the crowns’ quality was performed following modified USPHS/FDI criteria. Visual and colorimeter assessments were employed to evaluate shade matching. Differences between groups were examined by Pearson’s Chi-square and Fisher’s exact test. The quality of marginal adaptation of crowns was good in 81.25%, however the quality of contours, contacts, and shade matching was compromised in 43.75%, 59.38%, and 39% of all LABs, respectively. Visual and colorimeter shade matching was acceptable in 62.5% and 80% of LABs in the cervical third and middle third regions of crowns, respectively, however in the incisal third the shade matching was unacceptable in nearly 60% of LABs. Commercial laboratories showed significantly better contours and shade matching, but not marginal adaptation. However, no significant differences were found in comparison of proximal contacts between the groups.

Comparison of Marginal Integrity and Surface Roughness of Selective Laser Melting, CAD-CAM and Digital Light Processing Manufactured Co-Cr Alloy Copings

“…It has been proposed that different fabrication techniques exhibit different Ra levels for cast indirect restorations. The casting with lost-wax technique (Cast-LWT) is commonly used to fabricate metal copings for PFM crowns [6,7]. The process involves the carving of inlay wax on a dye that mimics the anatomy and morphology of the lost tooth followed by spruing, investing, burnout, and casting with metal ingots [8].…”

Color Analysis of Metal Ceramic Restorations Fabricated from Different Dental Laboratories

“…Metal ceramic restorations are widely used because they provide composite of both strength and esthetic [2,3]. Multiple features of restorations such as shade, shape, and texture play an instrumental role in giving a natural appearance [4]. Duplicating the exact shade of that of surrounding teeth is more challenging in the case of metal ceramic restorations due to the dark-colored metal underlying the translucent porcelain [2,[5][6][7].…”

“…Duplicating the exact shade of that of surrounding teeth is more challenging in the case of metal ceramic restorations due to the dark-colored metal underlying the translucent porcelain [2,[5][6][7]. Factors other than the underlying metal that make the color matching more demanding include adequate tooth preparation, proper selection of appropriate shade in clinics, different brands of porcelain requiring variation in condensation techniques, translucency, fluorescence, opacity, thickness of porcelain layer, surface characteristics, time, and temperature of firing porcelain [2,4,5,7].…”

“…To attain best possible esthetics, the duplication of shades of porcelain is performed in two phases, shade selection followed by shade duplication [4]. The first step is performed in the clinic and the second is a challenge for the laboratory (lab) [4,5].…”

“…To attain best possible esthetics, the duplication of shades of porcelain is performed in two phases, shade selection followed by shade duplication [4]. The first step is performed in the clinic and the second is a challenge for the laboratory (lab) [4,5]. In dental clinics, the shade selection is dependent on multiple factors such as observer, light source, surroundings such as makeup, color of walls, gloves, cleanliness of teeth, duration and time of shade selection, distance from teeth, and level of eyes of observer when noting the shade [8].…”