ADHESIVE PERFORMANCE OF HYBRID CAD/CAM MATERIALS

Abstract

Objective: To establish a strong and durable bond, an appropriate treatment of the respective surfaces is crucial. Therefore, the aims of this study were: 1) To evaluate the influence of different surface treatments on the bonding strength between hybrid CAD/CAM materials and universal resin cement system using notched-edge shear bond strength (SBS) test. 2) To examine the microstructures of different hybrid materials and the surface changes after applying different surface treatments that contribute to the bonding performance of the restoration using scanning electron microscopy (SEM). Materials and Methods: CAD CAM blocks of three hybrid materials (LuxaCam Composite; LC, Lava Ultimate; LU, and Cerasmart; CS) were sectioned into 2 mm thick slices (N=630), polished with silicon carbide paper (1200 grit) and cleaned ultrasonically in ethanol for 5 min. Each material was sub-divided into seven groups (n=30) based on the applied surface treatment (NS: no surface treatment, SB: sandblasting only, SL: silane only, MP: Monobond Plus only, SS: sandblasting and silane, SM: sandblasting and Monobond Plus, CS: CoJet and silane). Composite cylinders (Filtek Z250 composite) were fabricated using a bonding mold inserts and cemented to the CAD CAM slices under standardized load of 1 kg. Universal bonding agent and universal resin cement (Universalbond and Universalzement) were used for bonding according to the manufacturer’s instructions and light cured for 20 sec/surface. Half of each group was tested for early SBS after 24h storage in distilled water at 37 °C, other half was tested for late SBS after artificial aging by thermo-cycling for 20K cycles at 5 °C-55 °C (dwell time: 30 sec, transfer time: 10 sec) and 6 months of water storage at 37 °C. Notched-edge SBS was measured using a universal testing machine (Instron 6596) by loading specimens until failure. Failure modes were assessed with a stereo microscope and reported. Statistical analysis was performed with 3-way-ANOVA model using Bonferroni post-hoc multiple comparisons with α = 0.05.Results: Shear bond strength (SBS) of hybrid CAD/CAM materials increased with micromechanical surface treatments (SB) compared to chemical treatments (SL and MP). Depending on the restorative material, chemical treatment increased early SBS but it deteriorated after artificial aging. Generally, combination surface treatments (SS, SM, and CS) performed similarly to SB alone. Conclusions: Adhesive performance of hybrid CAD/CAM materials is influenced by surface treatment and deteriorates over time.