A Comparison of Microtensile Bond Strength, Film Thickness, and Microhardness of Photo-Polymerized Luting Composites

Abstract

The aim of this study was to evaluate the effect of CAD/CAM composite thickness on micro-tensile bond strength (µTBS), microhardness (HV), and film thickness (FT) of different luting composites. Composite blocks (6.8 mm × 6.8 mm) were divided into 12 groups according to: CAD/CAM thickness and luting composite. For each group, 21 rods (1 mm × 1 mm) were tested in tension at crosshead speed of 1 mm/min. Fracture modes were categorized as adhesive, mixed, and cohesive. Microhardness (n = 5/group) was assessed using microhardness tester. Film thickness (12-rods/group) was evaluated using a stereomicroscope (×40). Data were analyzed using the two-way ANOVA/Tukey’s HSD test (p = 0.05). Parameters “thickness”, “cement”, and “thickness x cement” showed significant difference on µTBS and HV (p < 0.05). At 2 mm, heated x-tra fil composite showed the highest µTBS (45.0 ± 8.5 MPa), while at 4 mm thickness, Grandio Flow revealed the lowest µTBS (33.3 ± 6.3 MPa). Adhesive, mixed, and cohesive failures were reported. The HV of all composites decreased when photo-polymerized through 4 mm thickness (p < 0.05). Regardless of CAD/CAM thickness, photo-polymerized composites can be successfully used for luting CAD/CAM composite.

Operator versus material influence on film thickness using adhesive resin cement or pre‐heated resin composite

“…As a result, the first null hypothesis of no difference between the film thickness of DC‐ARC and PH‐RC, independently of the operator's expertise, must be rejected. This is in agreement with results found in previous studies 41,45,56 …”

“…This is in agreement with results found in previous studies. 41,45,56 Some authors have described differences in the flowability of composites when pre-heated at 37 or 69 C 31 while others have not observed such differences at 23, 54 or 68 C. 55 In this study, the highest heating temperature dispensed by the ENA-heat heater (55 C) was used. An under 10 s delay between the removal of the pre-heated cartridge and its use was carefully observed by the two operators, as important temperature drops have been shown passed delay.…”

“…31 Moreover, multiple studies also showed the importance of preheating resin composites to improve their flowability. 11,28,31,56 However, a recent systematic review stated that reported PH-RC film thicknesses were higher than the DC-ARC one's. 8 The current study has demonstrated that the pre-heating of conventional composites to 55 C does not produce lower values of film thickness than those produced by the dual-cured resin cements at room temperature, even when handled by an expert.…”

“…Moreover, multiple studies also showed the importance of pre‐heating resin composites to improve their flowability 11,28,31,56 . However, a recent systematic review stated that reported PH‐RC film thicknesses were higher than the DC‐ARC one's 8 .…”

Is There a Correlation Between Physical Properties and Film Thickness of Dual- and Photo- polymerized Luting Resins and CAD/CAM-Dentin Micro-Tensile Bond Strength?

“…Recently, a thermo-viscous photo-polymerized bulk ll resin composite was introduced (VOCO GmbH Germany) in order to get the advantages being applied in bulk and reducing viscosity for improving adaptation. To the best of our knowledge, only in a recent in vitro study [12], thermos-viscous bulk-ll resin composite was used as luting resin for CAD/CAM composite bonding. In this study, the authors suggested the use of such bulk-ll material as an alternative approach to dual-polymerized resin cement.…”