Effect of metalloproteinase inhibitors and volatilization temperature on the bond strength, nanoleakage, and collagenolytic activity of adhesive restorations

Even with the advance of dental materials and techniques, adhesive restorations have long term limitations. The aim in this study was to evaluate the effect of dentin pretreatment with metalloproteinase inhibitors (chlorhexidine 2% - CHX and glutaraldehyde 5% - GD) and the volatilization temperature (23 and 40ºC) of the solvent of the adhesive system on bond strength (BS), nanoleakage (NL), and collagenolytic activity (CA) of adhesive restorations after 24 h and aging. Thirty-six sound human third molars (n = 6) were collected (CAAE 73605617.4.0000.5515), the teeth had coronary dentin of medium depth exposed, then the acid conditioning was performed, followed by dentin pretreatment with distilled water (control), CHX (Clorhexedina, Villevie) or GD (Gluma, Heraeus Kulzer). In the end, the adhesive system was applied by total acid etching technique, volatilized at 23 or 40ºC, and light cured to posterior confection of a composite resin block. The specimens were cut in 0.8 x 0.8 mm sticks, half of the sticks were evaluated after 24 h and the other half was evaluated after aging (10,000 thermal cycles and 4 weeks of storage in 0.2% collagenase). BS was obtained by the microtensile test using a universal test machine and NL will be analyzed by scanning electron microscopy after infiltration with silver nitrate (n = 6). CA was evaluated by in situ zymography using a confocal laser scanning microscopy. Data were analyzed by tree-way ANOVA for repeated measures and Bonferroni test (a = 0.05). Dentin pretreatment using GD showed higher BS (55.03 ± 7.19 MPa) compared to distilled water (49.18 ± 7.23 MPa), and CHX pretreatment showed intermediate BS value (51.89 ± 6.70 MPa). Volatilization of adhesive at 40ºC increased BS (53.32 ±7.23 MPa) compared to 23ºC (50.46 ± 7.27 MPa) and reduced the NI. After thermal cycling and collagenase storage the BS was reduced (50.23 ± 7.72 MPa) compared to 24 h (54.04 ± 6.62 MPa) and CA increased for all groups, especially for pretreatment with water and volatilized at 23ºC. Aging decreased the BS, but dentin pretreatment using GD and the use of warm air stream for solvent volatilization were effective for improvement of BS and to reduce NL and CA of dental adhesive restorations.