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

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.