Effect of preparation design on marginal and internal adaptation of translucent zirconia laminate veneers

Abstract

This study investigated the effect of preparation design on the marginal and internal adaptation of laminate veneers (LVs) fabricated from translucent zirconia. Thirty‐three resin teeth were prepared for LVs of three designs: window preparation (WP); incisal shoulder preparation (ISP); and incisal palatal chamfer preparation (IPP). Marginal adaptation was evaluated by measuring the vertical discrepancy between the LV margin and the finish line at 60 points. The internal adaptation was assessed by measuring the internal space width as the distance between the LV and the tooth at cervical, central, and incisal sites after sectioning. At the incisal, mesial, and distal sites, mean marginal discrepancies were significantly lower in the WP group than in the other two groups; the IPP group had the highest marginal discrepancies. At incisal sites, the median internal space was significantly higher in the IPP group than in the WP and ISP groups and higher in the ISP group than in the WP group. At the incisal site, marginal and internal adaptations were better for the non‐overlap translucent zirconia LV design (WP) than for the overlap designs (ISP and IPP). The characteristics of the translucent zirconia LVs used in the present study indicate acceptable clinical performance.

Marginal discrepancy and load to fracture of monolithic zirconia laminate veneers: The effect of preparation design and sintering protocol

“…Marginal gaps at cervical margin showed comparable values regardless the variables tested in the current study. This result was in accordance with the findings of Aboushelib et al 33) and Kusaba et al 36) . During the design stage of zirconia veneers using CAD-CAM design software, the cement gap thickness (50 µm) was adjusted 1 mm from the preparation margin, which leads to better adaptation of laminates at cervical margin.…”

“…In a comparative study where marginal fit of zirconia laminate veneers was assessed, the palatal shoulder preparation design showed a significantly higher marginal fit than those with palatal chamfer preparation 36) .…”

“…In addition, tooth preparation design, a size discrepancy of the cutting tools may cause misfit and contribute to inferior marginal adaptation of CAD/ CAM-generated restorations. Additionally, shrinkage of translucent zirconia during sintering procedure by approximately 20% could have affected marginal fit at the incisal areas of tooth preparation design 35,36) .…”

“…The load to fracture values were evaluated using a universal testing machine (AG-5 kNG, Shimadzu, Kyoto, Japan) equipped with a 1-kN load cell. The load was oriented at a 90-degree angle to the palatal aspect of the tooth using specially designed mounting jig [35][36][37] (Fig. 3).…”

Marginal Accuracy of Fully Contoured Zirconia Veneer With Two Preparation Designs

“…(42,43) The palatal over lab showed significant higher values compared to butt joint design which was in agrement with previous studies. (55) This was attributed to complixety of preparation of the palatal over lab in relation to the butt joint design with subsequent limitation of path of insertion in addition of high risk of fracture and chipping in addition to impression detail and finish line demarcation on the working model is more easier in butt joint preparation. (56,57) The null hypothesis that machined fully contoured zirconia veneer will not reveal high marginal adaptation as pressable lithium disilicate veneer was rejected.…”