Objectives: To study the influence of dentin age and composition of a 2-bottle etch-&-rinse adhesive (with/without a polyalkenoic acid copolymer, VBCP), on dentin microtensile bond strengths (µTBS).
Methods: Thirty extracted caries-free human teeth (molars and pre-molars), were assigned to three group ages: (<21); (21-40), and (>40). For each group age, specimens were randomly assigned to one dentin adhesive: Adper Single Bond Plus with VBCP (SBP+VBCP, 3M ESPE, n=9); Adper Single Bond Plus without VBCP (SBP-VBCP, 3M ESPE, n=9); and Adper Scotchbond Multi-Purpose (MP, 3M ESPE, n=12) as the control group. Buildups were constructed with a hybrid composite resin (Filtek Z250, 3M ESPE) and cured in 3 increments of 2mm each. Specimens were sectioned with a slow-speed diamond saw under water to obtain bonded sticks with a cross-section of 0.8±0.2 mm2. The sticks were individually attached to a stainless steel jig and tested to failure in tension mode at a crosshead speed of 1mm/min. Statistical analysis: t-Test and 2-way-ANOVA/Tukey, at p<0.05 (SPSS 14.0, SPSS Inc). Results: (Mean±SD, MPa) SBP+VBCP/(<21): 41.9±23.6; SBP+VBCP/(21-40): 43.2±18.7; SBP+VBCP/(>40): 43.6±20.1; SBP-VBCP/(<21): 26.0±9.8; SBP-VBCP/(21-40): 37.2±15.1; SBP-VBCP/(>40): 32.0±16.4; MP/(<21): 71.5±21.0; MP/(21-40): 66.4±22.0; MP/(>40): 59.8±19.8. No pre-testing failures occurred. The highest mean µTBS were obtained in the control group (MP) for all age groups. SBP+VBCP resulted in statistically higher mean μTBS than SBP-VCP for all age groups: p<0.0001 for (<21); p<0.038 for (21-40); and p<0.002 for (>40). When means were pooled for the variable age group, SBP+VBCP resulted in significantly higher mean µTBS than SBP-VBCP at p<0.001. When means were pooled for the variable dentin adhesive, no significant differences were found between pairs of the variable age group. Conclusion: A correlation between dentin age and μTBS cannot be established. The presence of VBCP in the composition of SBP influenced its bonding ability, resulting in statistically higher mean µTBS.