Improving retention of dental veneers fabricated from an experimental enamel-based biopolymer compared with CAD/CAM hybrid materials

Abstract

Objectives: CAD/CAM hybrid materials have become increasingly utilized in restorative dentistry. However, their low tensile bond strength (TBS) may lead to the detachment of minimally invasive restorations. When prepared, an experimental enamel-based biopolymer prosthesis provided a honeycomb-like interfacial layer with luting adhesives leading to a higher TBS than Ni-Cr-Be based alloy, lithium disilicate-based ceramic, and cured-resin-composite. This study aimed to compare TBSs of dental veneers fabricated from experimental biopolymer and commercial hybrid materials bonded to enamel using two different luting adhesives.

Methods: Laminate veneers (4 × 4 mm) 1 mm thick were prepared from commercial CAD/CAM blocks: VITA ENAMIC, SHOFU Block HC, KATANA AVENCIA, and an experimental biopolymer. The flat bonding surface of the veneers was ground to 600-grit, followed by 50-μm alumina air-abrading for standardization. Each veneer was fixed on flat ground bovine enamel using either Super-Bond C&B or RelyX™ U200 resin (n = 10). The surface treatment and bonding procedures were treated as recommended by the manufacturers. All bonded specimens were stored in water at 37 °C for 24 h before tensile testing with a universal testing machine at a cross-headed speed of 1.0 mm/min. The fractured surface was examined with a stereomicroscope and scanning electron microscope. TBS data were statistically analyzed using two-way ANOVA and Tukey's HSD test (α = 0.05).

Results: Experimental biopolymer veneers demonstrated the highest mean TBS with cohesive failure in the luting agents. Adhesive failure at the veneer side interface was found in other groups. There was no significant difference between the two luting agents.

Conclusion: The results indicate that the experimental biopolymer veneer bonded to enamel provided the best retention. The TBS at the enamel-resin interface is higher than at the veneer-resin interface for all commercial CAD/CAM hybrid materials.

Clinical significance: An experimental enamel-based biopolymer veneer can provide better retention than CAD/CAM hybrid materials in clinical treatment.

Keywords: CAD/CAM hybrid Ceramics; Dental veneer; Enamel-based biopolymer; Hybrid materials; Luting adhesives; Prosthesis retention; Tensile bond strength.

Fig. 1

A schematic workflow of experimental procedures.

Fig. 2

Stereomicroscope and SEM images of the fractured surface in experimental biopolymer specimens bonded with (a) Super-Bond C&B, (b) RelyX™ U200 demonstrating the cohesive failure in cured luting resin (C). (original × 40 and × 5000 for Stereomicroscope and SEM, respectively).

Fig. 3

SEM micrographs of fractured experimental biopolymer bonded with Super-Bond C&B demonstrating the consistent thickness of the hybrid layer (arrowed) at the veneer-luting resin interface in (a) polished and (b) after soaking in 6 mol/L HCl for 30s (original × 3500 and × 6000, respectively; E = experimental biopolymer, R = resin, ME = modified experimental biopolymer).

Fig. 4

Stereomicroscope and SEM images of the fractured surface in VITA ENAMIC specimens bonded with (a) Super-Bond C&B, (b) RelyX™ U200 demonstrating the adhesive failure at the veneer side interface (AV). (Original × 40 and × 5000 for Stereomicroscope and SEM, respectively).

Fig. 5

Stereomicroscope and SEM images of the fractured surface in KATANA AVENCIA specimens bonded with (a) Super-Bond C&B, (b) RelyX™ U200 demonstrating the adhesive failure at the veneer side interface (AV). (Original × 40 and × 5000 for Stereomicroscope and SEM, respectively).

Fig. 6

Stereomicroscope and SEM images of the fractured surface in SHOFU Block HC specimens bonded with (a) Super-Bond C&B, (b) RelyX™ U200 demonstrating the adhesive failure at the veneer side interface (AV) with the dislodgement of filler particles (original × 40 and × 5000 for Stereomicroscope and SEM, respectively).