title: Influence of thermal and mechanical load cycling on microtensile bond strengths of total and self-etching adhesive systems.
abstract: This study evaluated the influence of different thermal (TC) and mechanical (MC) cycling protocols on microtensile bond strength (muTBS) to cervical dentin margins of Class II restorations using two total-etch (TE) adhesives and one self-etching (SE) primer. Class II slot cavities were prepared on the mesial surfaces of 168 bovine incisors and were divided into three groups according to the bonding system used: Single Bond, OptiBond Solo Plus and Clearfil SE Bond. All cavities were restored with Filtek Z250 composite. Following restorative procedures, the restored teeth were allocated to seven subgroups (n = 8) according to the thermal/mechanical protocol performed: G1-control (no cycling), G2-100,000 MC, G3-200,000 MC, G4-500,000 MC, G5-100,000 MC+1,000 TC, G6-200,000 MC+1,000 TC, G7-500,000 MC+1,000 TC. TC was performed using 5 +/- 2 degrees C and 55 +/- 2 degrees C baths, with a dwell time of 60 seconds in each bath. MC was achieved with an axial force of 80 N at 2 cycles/second. The restorations were sectioned perpendicular to the cervical bonded interface into two 0.8-1-mm thick slabs. The slabs were trimmed at the interface to obtain a cross-sectional surface area of 0.8-1 mm2. All specimens were then subjected to muTBS (v = 0.5 mm/minute). Fracture mode analysis was performed using SEM. Bond strength mean values (MPa) were analyzed with ANOVA 3-way and Tukey's test (alpha = 5%). Dunnett's test was used to compare tested groups against Control groups of each adhesive system (alpha = 56%). SE primer presented lower mean bond strength values when compared to TE adhesives (p = 0.05). In addition, specimens restored with the SE primer did not resist to the 200,000 and 500,000 MC associated with TC. The application of 100,000 MC did not present a significant decrease in bond strength when compared to the control. Mixed failures were predominant for all groups. The higher the amount of thermal/mechanical cycles, the greater the number of mixed failures and the lower the percentage of adhesive failures.
authors.affiliation: Department of Restorative Dentistry, University of State of Amazon (UEA), Manaus, AM, Brazil. fabio_mitsui@yahoo.com.br
authors.forename: Fabio Hiroyuki Ogata
authors.initials: FH
authors.lastname: Mitsui
authors.forename: Alessandra Rezende
authors.initials: AR
authors.lastname: Peris
authors.forename: Andrea Nóbrega
authors.initials: AN
authors.lastname: Cavalcanti
authors.forename: Giselle Maria
authors.initials: GM
authors.lastname: Marchi
authors.forename: Luiz André Freire
authors.initials: LA
authors.lastname: Pimenta
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D002417:Cattle; D019232:Dental Restoration Failure; D006358:Hot Temperature / Q000009:adverse effects; D019279:Resin Cements / Q000737:chemistry*; D013718:Tensile Strength; D016474:Weight-Bearing
chemical_list: D000269:Adhesives; C438313:Clearfil SE Bond; C451600:OptiBond Solo Plus; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate