Comparative evaluation of marginal fit in conventional versus high-speed-sintered zirconia crowns: an in vitro study

High-speed sintering has emerged as a promising innovation for enhancing the efficiency of dental prosthesis fabrication. However, its impact on marginal adaptation remains a critical factor in ensuring the long-term clinical success of restorations. The aim of the study to evaluate the marginal fit of high-speed and regular-speed-sintered zirconia crowns.

A maxillary right second molar on a typodont was prepared for an all-ceramic crown. A PVS impression was taken and a Type V stone master cast was fabricated. This cast was scanned via a laboratory scanner to produce 20 milled zirconia crowns. The crowns were divided into two groups (n = 10). Group A was subjected to a fast-sintering program, whereas group B was sintered via a conventional-speed-sintering program. Marginal fit was assessed via a stereoscopic microscope at four well-defined points (mid-distal, mid-lingual, mid-mesial, and mid-buccal) on each crown. Three readings were taken at each point. The marginal gaps of both groups were compared via the Wilcoxon signed-rank test.

Statistically significant difference between groups A and B (p < 0.001) was revealed. Although the mean marginal gap in both groups was below the clinically acceptable limit (< 90 μm), the fast-sintering program produced restorations with a larger marginal gap than the restorations sintered via the conventional program.

Crowns produced via both sintering programs were clinically acceptable, although the regular-speed-sintering program yielded a significantly superior marginal fit.