title: The influence of a packable resin composite, conventional resin composite and amalgam on molar cuspal stiffness.
abstract: Packable resin composites may offer improved properties and clinical performance over conventional resin composites or dental amalgam. This in vitro study examined the cuspal stiffness of molars restored with a packable resin composite, a conventional posterior microfilled resin composite and amalgam. Forty-eight intact caries-free human third molars were distributed into four treatment groups (n=12) so that the mean cross-sectional areas of all groups were equal. Standardized MOD cavity preparations were made and specimens restored using one of four restorative materials: (1) a spherical particle amalgam (Tytin); (2) Tytin amalgam with a dentin adhesive liner (OptiBond Solo); (3) a conventional microfilled posterior resin composite (Heliomolar); (4) a packable posterior resin composite (Prodigy Posterior). Cuspal stiffness was measured using a Bionix 200 biomaterials testing machine (MTS). Specimens were loaded vertically to 300 N at a crosshead speed of 1.0 mm/minute. Stiffness was measured at 10 intervals: (1) prior to cavity preparation (intact); (2) following cavity preparation, but before restoration; (3) seven days after restoration; then (4) 1, 2, 3, 4, 5, 6 and 12 months after restoration. All specimens were stored at 37 degrees C in deionized water throughout the study and thermocycled (5 degrees/55 degrees C; 2000 cycles) monthly for 12 months. Repeated Measures ANOVA revealed significant differences among treatment groups over time (p<0.0001). Cavity preparation reduced cuspal stiffness by more than 60%. At 12 months, the cuspal stiffness of restored teeth was, on average, 58% that of intact specimens. Neither the packable nor the conventional resin composite increased cuspal stiffness over that of amalgam.
authors.affiliation: USN, Branch Dental Annex, Indian Head, MD 20640, USA. molinarojd@nnd10.med.navy.mil
authors.forename: J D
authors.initials: JD
authors.lastname: Molinaro
authors.forename: K E
authors.initials: KE
authors.lastname: Diefenderfer
authors.forename: J M
authors.initials: JM
authors.lastname: Strother
mesh_terms: D000180:Acrylic Resins; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D003722:Dental Alloys; D003723:Dental Amalgam; D003736:Dental Cavity Lining; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D004548:Elasticity; D006801:Humans; D008689:Methacrylates; D008963:Molar; D018583:Pliability; D011140:Polyurethanes; D019228:Tooth Crown / Q000502:physiology*; D014082:Tooth Fractures / Q000517:prevention & control
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D003722:Dental Alloys; C513708:Heliomolar; D008689:Methacrylates; C428805:OptiBond SOLO; D011140:Polyurethanes; C099128:Prodigy; D017438:Bisphenol A-Glycidyl Methacrylate; C036886:tytin; D003723:Dental Amalgam