title: Polymerization shrinkage influences microtensile bond strength.
abstract: Shrinkage results from a complex spatial strain network, producing movements within materials. The purpose of this study was to test whether microtensile bond strength (microTBS) of a light-curing resin composite to enamel depends on distance to the center of the curing mass. Labial surfaces of bovine incisors were ground flat, divided into 2 groups (n = 8), acid-etched, and coated with an unfilled resin bond. A resin-based composite was placed in one increment (group A) or separately at gingival, central, and incisal sites (group B), and light-cured. Teeth were sectioned, yielding stick-shaped specimens assigned to one of 9 groups according to distance to incisal edge of restoration (NDistanc). Microtensile bond strength was transformed to percentages of its maximum values within each tooth (PMPa). Comparisons within groups showed (group A) that mean PMPa decreased from central to gingival and from central to incisal (p < 0.01). Comparisons between groups showed that mean PMPa was significantly lower in group A compared with group B, only at gingival and incisal sites. Microtensile bond strength significantly decreased as the distance increased to the center of the curing mass.
authors.affiliation: Department of Restorative Dentistry, Faculty of Odontology, Complutense University of Madrid, Plaza Ramón y Cajal s/n, Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Cabrera
authors.forename: J C
authors.initials: JC
authors.lastname: de la Macorra
mesh_terms: D000179:Acrylates; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000528:radiation effects*; D001840:Dental Bonding; D003743:Dental Enamel; D003799:Dental Stress Analysis; D008027:Light; D044367:Phase Transition; D019279:Resin Cements; D018709:Statistics, Nonparametric; D013718:Tensile Strength
chemical_list: D000179:Acrylates; D003188:Composite Resins; C444701:Filtek Z250; D019279:Resin Cements; C040415:heliobond