title: Thermal and mechanical load cycling on microleakage and shear bond strength to dentin.
abstract: This study evaluated the influence of mechanical and thermal cycling on microleakage at the cervical margins of proximal slot restorations and shear bond strength on flat dentin surfaces. Microleakage Evaluation: One hundred and twenty slot cavity restorations were performed on bovine incisors. The restorations were randomly divided into four groups (n = 30): control (no thermal and mechanical load cycling), thermal cycling (2,000 cycles, 5 degrees C-55 degrees C), mechanical load cycling (50,000-80N) and thermal and load cycling (2,000 5 degrees C-55 degrees C/50,000-80N). The specimens were sealed with acid resistant varnish, leaving a 1-mm window around the cervical margin interface. To detect marginal leakage, a 2% methylene blue buffered solution was used for four hours. The specimens were sectioned longitudinally and qualitatively evaluated by stereomicroscopy (45x) following a ranked score for the dentin cervical margin. The data were analyzed by Kruskal-Wallis test (alpha = 0.05). Shear Bond Strength Evaluation (SBS): Eighty bovine incisors were embedded and polished to obtain a flat standard surface on dentin. The surfaces were restored with Single Bond adhesive system and a resin composite subsequently inserted in a bipartite Teflon matrix. The specimens were randomly divided into the four groups (n = 20) described above for microleakage. Shear bond strengths were measured in a universal testing machine with a crosshead speed of 0.5 mm/minute. The data were analyzed by one way ANOVA test (alpha = 0.05). No statistically significant influence of thermocycling, mechanical load cycling or the combination was observed for both microleakage and shear bond strength.
authors.affiliation: University of North Carolina, School of Dentistry, Chapel Hill, NC, USA.
authors.forename: Ana Karina Barbieri
authors.initials: AK
authors.lastname: Bedran-de-Castro
authors.forename: Paulo Eduardo Capel
authors.initials: PE
authors.lastname: Cardoso
authors.forename: Glaucia Maria Boni
authors.initials: GM
authors.lastname: Ambrosano
authors.forename: Luiz André Freire
authors.initials: LA
authors.lastname: Pimenta
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D004396:Coloring Agents; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification; D003763:Dental Leakage / Q000145:classification*; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D008422:Materials Testing; D008751:Methylene Blue; D011897:Random Allocation; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013696:Temperature; D019237:Tooth Cervix / Q000648:ultrastructure; D016474:Weight-Bearing
chemical_list: D004396:Coloring Agents; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D008751:Methylene Blue