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

Abstract

To investigate and analyze the impact of teeth preparation designs and sintering protocol on marginal fit and fracture resistance of monolithic translucent zirconia laminate veneers. A total of 40 extracted intact human maxillary central incisors were assigned into 4 groups (n=10/each group) to investigate 2 variables: (1) the design of tooth preparation (a 1.5 mm incisal reduction with or without palatal chamfer) and (2) the two different sintering programs used for translucent zirconia restoration (standard or speed sintering procedure). Marginal discrepancy was evaluated using a digital microscope. The specimens were loaded to failure in the compression mode, using a universal testing machine with a crosshead speed of 0.5 mm/min. Marginal adaptation of monolithic translucent zirconia laminates are affected by both tooth preparation design and sintering protocol. However, resistance to fracture of translucent zirconia laminates has affected mainly by sintering procedure regardless the teeth preparation design used.

Evaluation of Marginal and Internal Fit of a CAD/CAM Monolithic Zirconia‐Reinforced Lithium Silicate Porcelain Laminate Veneer System

“…8,22,28 The choice of marginal evaluation sites was based on earlier studies. 6,8,18 A total of 36 readings were recorded for each PLV specimen, for both MG and IG. The predetermined sagittal and transverse slice positions on each abutment-PLV sample served as references for isolation and relocation of the same evaluation sites for measurements on each sample, hence, maintaining standardization of the entire procedure.…”

“…There are a few possible limitations in this report, which bear discussion. Although the study design permitted marginal fit evaluation of all regions (cervical, middle, and incisal) at the abutment-PLV junction at 12 different locations, the statistical differences between different zones were not analyzed in this article, unlike few previous studies, 7,14,18 which demarcated and discussed the location-based differences. The present study might have also potentially found such measurement site-based differences in the MG and IG, had it investigated in this line, but as it is, it remains unknown.…”

“…The sample size for this study was based on earlier published studies, which were closely related to the current investigation. 6,7,14,16,18 Based on the assumed mean difference of 21 μm and standard deviation of 13 μm, 7 the total sample size was estimated at a minimum of eight for each material group (ZLS and LDS), at α = 0.05 and power of 85% (G* Power statistical power software v.3.1.9.7), to determine if there was a significant difference in the MG. Similarly, based on the assumed mean difference of 9 μm and SD of 5 μm, 18 the sample size was determined at 16 specimens (eight for each group of incisal preparation design [butt joint and chamfer]), at α = 0.05 and power of 90% (G* Power v.3.1.9.7), to elicit a significant difference in the MG. A sample size of 10 was thus chosen for this study.…”

“…Two of the commonly used PLV tooth-preparation designs, based on the differences in incisal edge preparation, include incisal shoulder or butt joint, and, chamfer. Past studies have shown significant differences between the two preparation designs, in terms of marginal gap (MG) and internal gap (IG), for both pressed 17 and machined monolithic translucent zirconia 14,18 PLVs, with butt joint design, generally performing better than the chamfer. However, there is paucity of data on the effect of preparation design on the marginal and internal adaptation of newer CAD/CAM glass ceramic materials, including ZLS, and this might require investigation.…”

Dentin Exposure after Tooth Preparation for Laminate Veneers: A Microscopical Analysis to Evaluate the Influence of Operators’ Expertise

“…An LV is defined as a superficial or attractive display in multiple layers that restores a tooth at the incisal, buccal, and/or part of palatal and interproximal surfaces [ 4 ]. It could be made of porcelain-based or porcelain-free materials, such as feldspar ceramics, lithium disilicate, zirconia, or zirconia-reinforced lithium silicate [ 5 , 6 , 7 ]. This type of restoration allows for the restoring of dental aesthetics, in cases of misalignment, wear, discoloration, fractures, and morphological alterations [ 8 , 9 ].…”