Bond strength and failure analysis of lining materials to denture resin

Objectives: This study was conducted to investigate the bonding properties of five lining materials to a denture base resin. Two hard (chemical-cured resin: Kooliner “Coe Labs, USA” and light-cured VLC resin: Triad “Dentsply, USA”) and three soft (chemical-cured resin: Express “Alcos,-USA”, heat-temperature vulcanized ‘HTV’ silicone material: Molloplast-B “Regneri GmbH, Germany” and room-temperature vulcanized ‘RTV’ silicone material:Ufi Gel-P “Voco,Germany”) liners were used. Methods: Paladent 20 “Heraeus Kulzer GmbH, Germany”, a conventional heat-cured polymethylmethacrylate (PMMA), was used as the denture base resin and as the control material. Bonding strength and adhesion properties of the liners to PMMA were compared by tensile test and scanning electron microscope (SEM) analysis. After curing, an aging process was applied and the samples were immersed and stored in distilled water at 37±1°C and taken out at certain aging intervals (at 0, 15, 30 and 90 days) for examination. Specimens (168) were processed for tensile tests and other specimens (24) for fracture tests. The mean and standard deviation values were calculated. Changes in the mechanical properties and the SEM findings of the adhered surfaces were evaluated. Results: Triad (a hard liner) has the closest tensile strength to the control, indicating the strongest bonding between the base and the liner. Also, during the aging process, formation of better adhesion was observed in SEM micrographs. From the SEM analysis it was found that, Molloplast-B (a soft liner) also has a very good filling capacity. Significance: Among the hard lining materials, VLC resin to chemical-cured resin; and among the soft lining materials, HTV resin to RTV and chemical-cured ones should be preferred for relining procedures. Molloplast-B and Express as resilient liners were found to have adequate adhesive values for clinical use.