title: Effects of polymerization contraction on interface's microTBS of luting material and dentin.
abstract: Polymerization contraction of composite resin luting materials is known to produce high stresses in the interfaces being cemented that are described as perpendicular to them. This study describes the effect of shearing strains of curing luting materials on microtensile bond strength (microTBS) of interfaces. A flat surface of labial dentin of bovine incisors was exposed and teeth randomly assigned to A (n = 12) or B (n = 6) groups. Adoro rectangular (2 x 3 x 11 mm) restorative composite resin blocks were cemented (Excite DSC + Variolink II) completely (group A) or partially (group B, only on extremes and center) occupying luting space. After visible light curing, stick compound bars were sectioned perpendicular to interface and submitted to tension until detachment. microTBS decreased from the center to the extremes in group A (Spearman tests p < 0.0008) and not in group B, where microTBS was higher in extremes than in correspondent locations in group A and equivalent to that in group A in the central location. Weibull's analysis showed that m modulus and characteristic stresses also decreased from the center to periphery of restorations in group A. Mechanical resistance of bonded interface of a luting material and dentin decreases peripherally, and this reduction is caused by polymerization contraction.
authors.affiliation: Conservative Dentistry Department, Faculty of Odontology, Complutense University, Plaza Ramon y Cajal s/n, Ciudad Universitaria, Madrid, Spain. elenacabrerajeronimo@yahoo.es
authors.forename: Elena
authors.initials: E
authors.lastname: Cabrera
authors.forename: José C
authors.initials: JC
authors.lastname: de la Macorra
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D055119:Elastic Modulus; D006813:Humidity; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C420130:Excite cement; D008689:Methacrylates; D010756:Phosphoric Acids; D011108:Polymers; D019279:Resin Cements; C103502:Variolink; D012822:Silicon Dioxide; C030242:phosphoric acid