Effect of firing and fabrication technique on the marginal fit of heat-pressed lithium disilicate veneers

Statement of problem. Studies on the fit of heat-pressed anterior lithium disilicate veneers are sparse, and whether fit is affected by glaze firing or ceramic addition is unclear. Purpose. The purpose of this in vitro study was to evaluate and compare the marginal fit of heat pressed anterior lithium disilicate veneers (IPS e.max Press) fabricated with the staining or cutback technique by using 3-dimensional analysis. Material and methods. Two groups of heat-pressed maxillary left central incisor lithium disilicate veneers were fabricated (n=10) differing only in core thickness and the fabrication process. The tooth preparation was standardized at 0.6 mm cervical and middle third and 0.7 mm incisal third, with 1.5 mm of incisal reduction. Group S (staining) was an anatomic contour veneer with 1 glaze firing. Group CB (cutback) had a cutback core of 0.6 mm on the cervical and middle third and 0.5 mm on the incisal areas for ceramic application with 3 firings (wash, incisal, and glaze firing). The amount of ceramic application was standardized, and all veneers had identical final dimensions. Marginal fit was evaluated at 2 stages: after pressing the copings (control) and after glaze firing or ceramic addition using the virtual replica technique and 3-dimensional analysis. The wax copings were invested, eliminated, and pressed with IPS e.max lithium disilicate high translucency ingots, and the overall marginal fit and change in marginal fit after firing were measured in the cervical, mesial, distal, and incisal areas. The Shapiro-Wilk test was used to evaluate normality. Repeated-measures ANOVAs were used to explore differences between the 2 groups (S and CB) as per time (before and after firing) for each location (cervical, mesial, distal, and incisal) (a=.05). Results. A statistically significant change in marginal fit after firing was found for the mesial and distal areas of the CB group (P<.05). In all other areas of measurements, no statistically significant differences were found (P>.05). The mean +/- standard deviation marginal fit of group S was 63 +/- 13 mm and 62 +/- 9 mm for group CB. Conclusions. The results suggest that firing affects the marginal fit of heat-pressed anterior lithium disilicate veneers fabricated with the cutback technique but not for the staining technique.

Automated summary

The study evaluated and compared the marginal fit of anterior lithium disilicate veneers fabricated with different techniques, finding that firing affects the marginal fit of veneers made with the cutback technique but not for those made with the staining technique.