Universal dentin bonding system: influence of handling conditions on the determination of adhesive properties on dentin

Resumo

Objective: Despite advances on dentin bonding systems (DBSs), their adhesive potential can still be significantly affected by storage conditions and handling. The present study aimed to evaluate the influence of DBS manipulation on the physical-mechanical properties of these materials. Material and Methods: Three DBSs were tested: Adper Scotchbond Multi-Purpose [MP] (3-step etch-and-rinse), Clearfil SE Bond [SE] (2-step self-etch), and Adper Single Bond Universal [SU] (universal adhesive). The experimental conditions were Control [CTRL] – recommended storage; Laboratory-aged [LAB] – artificially aged under controlled laboratory conditions; and Clinically used [CLIN] – exposed to a 2-week clinical routine. Degree of conversion (DC) was assessed using Fourier Transform Infrared Spectroscopy (FTIR) on 3 μL samples (n = 5), while the surface microhardness (SM) was tested on disc specimens (KHN 10kgf/5s/n=6). For microtensile bond strength (μTBS), 90 human molars were randomized according to the DBS, restored with a two 2 mm-increment of composite resin and sectioned into beams (0.64 mm2 cross-section) after 24 h and tested at 0.5 mm/min under a 500 N load (n = 10). Data were analyzed using two-way ANOVA and the Tukey`s tests (p = 0.05). Results: SE presented the highest DC values, while SU presented the lowest. MP reached the highest SM under clinical conditions, while SU exhibited consistently low values among all conditions. For the μTBS, SU decreased under LAB and CLIN, while MP remained stable throughout. Conclusion: SU was more affected by handling conditions than MP and SE. Proper storage and clinical use protocols are essential to preserve DBS performance.

KEYWORDS

Dentin; Dentin-bonding agents; Dental bonding; Mechanical tests; Surface properties.