Effect of surface treatment on the bond strength of chairside hard liners bonded to traditional and contemporary CAD-CAM denture base polymers

Abstract

Statement of problem: Research on the bonding between hard liners and contemporary computer-aided design and computer-aided manufacture (CAD-CAM) denture base polymers treated with different surface treatments is lacking.

Purpose: The purpose of this in vitro study was to evaluate the tensile bond strength of 2 extensively used hard liners on specimens fabricated with heat-polymerized polymethylmethacrylate (PMMA), milled PMMA, and a photopolymer for 3-dimensional (3D) printing denture bases and to assess the effect of the surface treatment on the bond strength.

Material and methods: Denture base specimens were fabricated with 3 different denture base polymers (Lucitone 199; Dentsply Sirona, IvoBase CAD; Ivoclar AG, and NextDent Denture 3D+; NextDent B.V). Using a balanced full-factorial experimental design, specimens of each group were treated with 1 of 2 surface treatments: the manufacturer's bonding agent or a light-polymerized methacrylate primer (Visio.Link; bredent UK Ltd) and subsequently relined with GC Reline (GC America Inc) or MucoHard (Parkell Inc). All specimens underwent a thermocycling regime simulating 5 years of intraoral service. Subsequently, for specimens that survived the thermocycling, the tensile bond strength was evaluated with a universal testing machine. Data were analyzed using 3-way analysis of variance (ANOVA) and post hoc Bonferroni-corrected pairwise comparisons (α=.05).

Results: A significant 3-way interaction was found (P<.001) between the 2 materials being bonded and the surface treatment, with the light-polymerized methacrylate primer providing greater bond strength when bonding MucoHard to the 3D printed denture base material (P<.001) but leading to a lower bond strength for some other bonding situations (P≤.005). Additionally, when bonding to heat-polymerized PMMA, a greater bond strength was found for MucoHard over GC Reline when using the manufacturer's bonding agent (P=.009).

Conclusions: The surface treatment affects the bond strength of hard liners bonded to CAD-CAM and traditional denture base materials. The light-polymerized methacrylate primer evaluated may be used to enhance the bonding of hard liners to denture base polymers with chemical formulations other than PMMA.