title: Effect of interfacial bond quality on the direction of polymerization shrinkage flow in resin composite restorations.
abstract: Shrinkage in light curing resin composites is assumed to be directed toward the light source. However, the strong bond at the dentin-resin interface achieved by newer generation dentin bonding systems may affect the direction of polymerization shrinkage. In this study, various curing modes of adhesive resin simulating different bond qualities were applied to determine the extent of interfacial gap formation with a scanning electron microscope. We also measured the free surface depression with a profilometer. The direction of polymerization shrinkage was inferred from the ratio of the interfacial gap measurement at the floor to the free surface depression. Various curing modes used in this study include Group 1: light curing of resin composite without the bonding agent as the negative control; Group 2: simultaneous light curing of the bonding agent and resin composite; Group 3: start of the chemical cure of the dual-cured bonding agent before light curing the resin composite; Group 4: curing the light-initiated bonding agent before insertion and light curing of the resin composite. When the bonding agent was light cured prior to inserting the resin composite (Group 4), the free surface depression was the greatest and the interfacial gap smallest among those in all groups. Therefore, if a good bond between dentin and resin composite can be established, the shrinkage flow will be directed toward a center located near the bonded interface rather than toward the incident light, thus reducing detrimental shrinkage stress.
authors.affiliation: Seoul National University, College of Dentistry, Department of Conservative Dentistry and Dental Research Institute, Korea. chobh@plaza.snu.ac.kr
authors.forename: Byeong-Hoon
authors.initials: BH
authors.lastname: Cho
authors.forename: Sabine H
authors.initials: SH
authors.lastname: Dickens
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Bae
authors.forename: Chang-Gok
authors.initials: CG
authors.lastname: Chang
authors.forename: Ho-Hyun
authors.initials: HH
authors.lastname: Son
authors.forename: Chung-Moon
authors.initials: CM
authors.lastname: Um
mesh_terms: D000134:Acid Etching, Dental; D000704:Analysis of Variance; D017609:Barium Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008027:Light; D016555:Matched-Pair Analysis; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D011108:Polymers / Q000737:chemistry; D012212:Rheology; D012822:Silicon Dioxide / Q000737:chemistry; D013223:Statistics as Topic; D013499:Surface Properties; D015040:Zirconium
chemical_list: C121035:Aeliteflo; D017609:Barium Compounds; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D011108:Polymers; C083568:Z100 composite resin; C100742:All-Bond 2; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium