Effect of Minimal and Non-Preparation Techniques and Universal Adhesive Systems on the Fracture Resistance of Direct Composite Veneers

Background: Fracture resistance at the interface between the tooth substrate and adhesive systems is a key determinant of the clinical durability of direct composite veneer restorations. Evaluating the influence of different preparation strategies and universal adhesive systems on fracture resistance is essential for improving the predictability of clinical outcomes.Materials and Methods: Forty extracted maxillary incisors were randomly allocated into two groups according to the preparation technique: no preparation and minimal preparation. Each group was further subdivided based on the adhesive system used: Single Bond Universal or Prime & Bond Universal. Direct composite laminate veneers were fabricated for all specimens, which were subsequently embedded in acrylic resin blocks. Fracture resistance was measured. Failure patterns were classified as adhesive, cohesive, or mixed. Data were analyzed using one-way ANOVA followed by Tukey’s HSD post hoc test (α=0.05).Results: The lowest bond strength values were observed in the Single Bond Universal no-preparation (SBN) group, whereas the highest values were recorded in the Prime & Bond Universal minimal-preparation (PBM) group. There was no significant statistical difference identified among the groups (p>0.05).Conclusions: Both universal adhesive systems demonstrated clinically acceptable fracture resistance regardless of the preparation technique. Proper treatment planning may contribute to long-term functional and aesthetic success in direct composite veneer restorations.