Effect of a modified laminate veneer preparation design on absolute margin discrepancy and marginal overhang

Abstract

Statement of problem: Veneer preparation designs impact veneer accuracy. However, whether a modified design could reduce absolute margin discrepancy and marginal overhangs is unclear. Purpose: The purpose of this in vitro study was to investigate whether a modified veneer preparation design enhances the absolute margin discrepancy and marginal overhang. Material and methods: The absolute margin discrepancy and the marginal overhang of 3 different veneer preparation designs on a typodont tooth (n=20): feather edge, shoulder, and shoulder with wings were measured. The feather edge design was prepared first and subsequently modified to create the shoulder and shoulder with wings preparations. Ceramic veneers were fabricated using computer-aided design and computer-aided manufacture with each veneer assessed for fit before cementation. Ten specimens were cut vertically, and 10 were cut horizontally in each group. The absolute margin discrepancy and marginal overhangs were measured for each cross-section with scanning electron microscopy. Descriptive data analysis and hypothesis testing were conducted using the nonparametric Kruskal Wallis test (α=.05). Results: On the vertical sections, the shoulder with wings preparation had the best absolute margin discrepancy and overhang. The design was also best for mesial overhang and mesial absolute margin discrepancy when measuring horizontally. Conclusions: The shoulder with wings preparation design produced the smallest cervical absolute margin discrepancy and overhang. This design also produced absolute margin discrepancy and overhangs comparable with those of the shoulder design in the proximal areas.