Edge chipping and translucency comparison among lithium silicate-based ceramics

Lithium disilicate glass-ceramics have excellent esthetic characteristics, but lack the strength of zirconia. Some newer lithium silicates now contain zirconia and are marketed as "zirconia-reinforced" with the implication that they are improved in strength. The purpose of this study was to determine the edge chip resistance/toughness and translucency of lithium silicate-based glass-ceramics.

Four lithium silicate/disilicate glass-ceramic materials, IPS e.max CAD-HT/MT and GC Initial LiSi-HT/LT blocks, and two zirconia-lithium silicate glass-ceramic materials, VITA Suprinity PC and Celtra Duo, were tested (N = 20/group). Specimens (14 × 12 × 1.5 mm) were sectioned from commercially available chairside CAD-CAM blocks, fired (if indicated), ground, and polished. Translucency was assessed via a spectrophotometer. For edge chipping, specimens were adhered to a resin bed. Edge chips were produced using a 120-degree sharp, diamond indenter mounted in a universal testing machine with the specimen's edge positioned at distances ranging from approximately 0.4 to 1 mm horizontally from the indenter tip. Translucency was compared with one-way ANOVA and edge chipping was evaluated with regression and Kruskal-Wallis tests.

Significant differences in translucency parameter (TP₀₀) were found between the materials (p ≤ 0.001). The statistical ranking of the TP₀₀ was: GC Initial LiSi-HT > IPS e.max CAD-HT > Celtra Duo > GC Initial LiSi-LT > VITA Suprinity PC = IPS e.max CAD-MT. For edge chipping, VITA Suprinity PC and Celtra Duo had significantly (p <0.05) lower edge chip resistance (R_eA) than IPS e.max CAD HT, but all other comparisons were not significant.

The incorporation of zirconia in lithium silicate glass-ceramics did not result in superior edge chip resistance. Moreover, VITA Suprinity PC was more opaque than the other tested ceramics except IPS e.max CAD-MT.