title: Class I gap-formation in highly-viscous glass-ionomer restorations: delayed vs immediate polishing.
abstract: This in vitro study evaluated the effects of delayed versus immediate polishing to permit maturation of interfacial gap-formation around highly viscous conventional glass-ionomer cement (HV-GIC) in Class I restorations, together with determining the associated mechanical properties. Cavity preparations were made on the occlusal surfaces of premolars. Three HV-GICs (Fuji IX GP, GlasIonomer FX-II and Ketac Molar) and one conventional glass-ionomer cement (C-GIC, Fuji II, as a control) were studied, with specimen subgroups (n=10) for each property measured. After polishing, either immediately (six minutes) after setting or after 24 hours storage, the restored teeth were sectioned in a mesiodistal direction through the center of the model Class I restorations. The presence or absence of interfacial-gaps was measured at 1000x magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface (n=10; total points measured per group = 140). Marginal gaps were similarly measured in Teflon molds as swelling data, together with shear-bond-strength to enamel and dentin, flexural strength and moduli. For three HV-GICs and one C-GIC, significant differences (p<0.05) in gap-incidence were observed between polishing immediately and after one-day storage. In the former case, 80-100 gaps were found. In the latter case, only 9-21 gaps were observed. For all materials, their shear-bond-strengths, flexural strength and moduli increased significantly after 24-hour storage.
authors.affiliation: Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama, Japan. mirie@md.okayama-u.ac.jp
authors.forename: Masao
authors.initials: M
authors.lastname: Irie
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Maruo
authors.forename: Goro
authors.initials: G
authors.lastname: Nishigawa
authors.forename: Goro
authors.initials: G
authors.lastname: Nishgawa
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Suzuki
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D003737:Dental Cavity Preparation / Q000145:classification; D003743:Dental Enamel / Q000648:ultrastructure; D018772:Dental Marginal Adaptation; D003775:Dental Polishing / Q000379:methods*; D003793:Dental Restoration, Permanent / Q000145:classification*; D003804:Dentin / Q000648:ultrastructure; D004548:Elasticity; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D033081:Shear Strength; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: C439808:Fuji IX GP Fast; D005899:Glass Ionomer Cements; C424245:Ketac-Molar Aplicap; D014867:Water; C084541:Fuji glass-ionomer lining cement