Effects of the light tip position on the degree of conversion and dentin bond strength of a universal adhesive

Introduction/Objectives. To measure the degree of conversion (DC), immediate and long-term microshear bond strength (?SBS) to dentin a universal adhesive relative light tip position application protocol. Methods. Mid-coronal flat 48 human third molars was exposed split in halves. Single Bond Universal (SBU; 3M) applied each half following ?total-etch? (TE) or ?self-etch? (SE) approach. Depending on (Bluephase G2, Ivoclar Vivadent, Schaan, Liechtenstein) angle distance from surface, three groups were compared: ?1 mm_90?? (control); ?8 mm_60??. Cylindrical composite build-ups (o1.7mm, Filtek Z250, prepared half. DC measured using Raman spectroscopy. ?SBS after 24 hours six months storage distilled water at 37?C. Fracture types analyzed. Results. No significant difference detected between (89.1 ? 6.2%) (94.6 1.2%) (p > 0.05), both showing significantly higher < 0.05) than mm_60?? group (74.9 9.5%) 0.05). Initially, there no differences Group TE (12.8 4.3 MPa) (14.7 5.7 showed lower aging (8.4 MPa 9.2 2.6 MPa, respectively) Adhesive fractures predomintantly detected. Conclusion. protocols resulted similar suboptimal curing conditions. In long-term, SE greater resistance degradation resulting smaller decrease compared TE. Light angulation affected more tip-to-surface distance.