Bond strength of CAD-CAM resin composite blocks cemented with flowable or pre-heated resin composites using different adhesive strategies

Abstract

Objective: To evaluate the bond strength of CAD-CAM resin composite blocks cemented with flowable or pre-heated resin composites using different adhesive strategies. Material and Methods: Seventy Brava Block (FGM) CAD-CAM resin composite cylinders were milled, and one surface was treated by 50 μm alumina sandblasting, followed by ultrasonic cleaning and 70% alcohol cleaning. The cylinders were distributed into seven groups: one control group using a light-cured resin cement (Variolink Esthetic LC), three with flowable composite resin (FR), and three with preheated composite resin (PR), applying different adhesive strategies. The cementing agents were light-cured (VALO Grand, 1200 mW/cm2 ) and specimens were stored at 37 °C for 24 hours. Bond strength was evaluated using shear testing (OM150, 1 mm/min), calculating average values and classifying fracture types. Data were analyzed using ANOVA and Tukey’s post hoc test (p<0.05). Results: The protocol with Monobond N primer and flowable resin composite presented the highest mean bond strength values and was statistically similar to the protocols with Monobond N primer and preheated resin, and with Monobond N primer, adhesive, and flowable resin composite. However, only the later two protocols did not differ significantly from the light-cured resin cement control group. The protocol with Prosil primer and preheated resin exhibited the lowest bond strength. Mixed failures were predominant across most experimental groups. Conclusion: The use of Monobond N primer combined with flowable resin composite promotes favorable bond strength to CAD-CAM resin composite blocks, while pre-heated resin composites show lower performance, particularly when associated with conventional silane. The selection of the adhesive strategy plays a critical role in optimizing bonding effectiveness for these materials.

KEYWORDS

CAD-CAM systems; Composite resins; Dental adhesion; Dental materials; Silanes.