Influence of additive and subtractive zirconia and lithium disilicate manufacturing on tensile bond strength and surface topography.

STATEMENT OF PROBLEM

Although bonding is important for long-term clinical success, studies on the bonding of additively manufactured ceramics are sparse.

PURPOSE

The purpose of this in vitro study was to determine the influence of manufacturing methods, additive (LCM) versus subtractive (CAM). and ceramic materials, zirconia (ZrO) and lithium disilicate (LiSi), on the tensile bond strength (TBS), failure mode, and surface roughness of ceramics.

MATERIAL AND METHODS

A total of 240 ceramic specimens (n=60/group; 2×2×10 mm) were prepared. Two additively manufactured (LCM-printed) ceramics, LiSi and ZrO (Lithoz), subtractively manufactured LiSi (IPS e.max CAD), and subtractively manufactured ZrO (KATANA Zirconia HTML PLUS) were evaluated. From each material, 40 specimens were bonded together (n=20 ceramic-ceramic specimens/group), and 20 specimens were bonded to equally sized human dentin specimens (n=20 ceramic-dentin specimens/group). The ZrO specimens were airborne-particle abraded (AlO, 50 µm, 0.1 MPa), and the LiSi specimens were etched with hydrofluoric acid. Then, a universal primer (Monobond Plus) was applied. After the dentin was coated with an etch-and-rinse adhesive (Syntac Classic), the specimens were bonded with luting composite resin (Variolink Esthetic DC), light polymerized for 40 seconds, thermally aged (10 000 cycles between 5 °C and 55 °C), tested for TBS, and statistically analyzed (1- and 3-way ANOVA and Weibull analysis). The ceramic surface was examined with scanning electron microscopy, and surface roughness was measured with digital microscopy before and after surface pretreatment.

RESULTS

TBS varied between 5.88 ±2.22 MPa and 6.34 ±2.26 MPa in the ceramic-dentin groups and 12.40 ±1.56 MPa and 18.82 ±5.92 MPa in the ceramic-ceramic groups. No significant difference was observed regarding the manufacturing method and material for different bonding conditions (P>.05). Additive and subtractive LiSi showed the highest reliability with m=18.27. The ceramic-ceramic specimens failed cohesively in the luting composite resin, whereas the ceramic-dentin specimens failed adhesively.

CONCLUSIONS

The manufacturing method and material used had little effect on bond strength values or surface properties. The recently introduced printed materials performed similarly to conventionally milled materials.