title: Effect of oxygen inhibition on composite repair strength over time.
abstract: The study was aimed at examining whether an oxygen inhibition layer is required for bonding a repairing to a pre-existing composite, and to determine the time required for free radicals within a composite substrate to decay to the extent that the composite repair strength drops significantly. Ten slabs of Gradia Direct Anterior (GC Corp.) were divided into (1) control group: an interfacial oxygen inhibition layer was created by applying and light-curing two layers of bonding resin (D/E Resin, Bisco) to the slabs surface in atmospheric air; (2) experimental group: the absence of an interfacial oxygen inhibition layer was obtained by light-curing the second bonding resin layer in a nitrogen atmosphere. After 1 and 2 h, 1, 14, and 30 days of air storage, a composite repair was layered over the bonding resin. Microtensile bond strengths were measured and statistically analyzed. The curing atmosphere was not a significant factor for bond strength (p = 0.82), and time and curing atmosphere-time interaction were significant (p < 0.001). The 30 day-strengths were the lowest (p < 0.05). An oxygen-inhibited layer is not initially required for bonding to resin composite, and it takes more than 14 days before the bond strength between a pre-existing and a fresh composite drops.
authors.affiliation: Department of Dental Materials, University of Siena, Policlinico Le Scotte, Viale Bracci, Siena 53100, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Dall'Oca
authors.forename: Federica
authors.initials: F
authors.lastname: Papacchini
authors.forename: Cecilia
authors.initials: C
authors.lastname: Goracci
authors.forename: Alvaro H
authors.initials: AH
authors.lastname: Cury
authors.forename: Byoung I
authors.initials: BI
authors.lastname: Suh
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
authors.forename: Antonella
authors.initials: A
authors.lastname: Polimeni
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
mesh_terms: D001696:Biomechanical Phenomena; D003188:Composite Resins / Q000737:chemistry; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D009584:Nitrogen; D010100:Oxygen / Q000037:antagonists & inhibitors*; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C470230:Gradia; D009584:Nitrogen; D010100:Oxygen