title: Impact of refrigeration on the surface hardness of hybrid and microfilled composite resins.
abstract: This in vitro study evaluated the Knoop hardness of the composite resins Charisma (C) and Durafill VS (D) polymerized in 3 different conditions: at room temperature (A) (23 +/- 1 degrees C); refrigerated at 4 +/- 1 degrees C and immediately photo-activated after removal from the refrigerator (0); and, refrigerated at 4 +/- 1 degrees C and photo-activated after a bench time of 15 min at room temperature (15). One hundred and twenty specimens (4 mm diameter and 2 mm depth) were made using a stainless steel mold and following manufacturer's instructions. All specimens were tested immediately after polymerization (I) and after 7 days of water storage in the dark at room temperature (7d). The data were subjected to ANOVA and post-hoc Tukey's test (alpha=0.05). On the top surface, C(AI) was statistically similar to C(15I) and D(AI) to D(15I) (p>0.05). On the bottom surface, C(AI) presented higher hardness values when compared to COI and C(15I) (p<0.05). The D groups showed no significant differences (p>0.05) on the bottom surfaces for any tested polymerization condition. After 7 days of storage, the Knoop hardness decreased significantly (p<0.05) for groups C(7d) and D(7d) except for C(07d), which was not different from C(OI) at either surface (p>0.05). D(07d) showed higher Knoop hardness (p<0.05) values on the top surface when compared to the other groups.
authors.affiliation: Department of Restorative Dentistry, Pontifical Catholic University of Paraná, Curitiba 80215-901, PR, Brazil.
authors.forename: Fernando Henrique Ruppel
authors.initials: FH
authors.lastname: Osternack
authors.forename: Danilo Biazzetto de Menezes
authors.initials: DB
authors.lastname: Caldas
authors.forename: Rodrigo Nunes
authors.initials: RN
authors.lastname: Rached
authors.forename: Sérgio
authors.initials: S
authors.lastname: Vieira
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Platt
authors.forename: Janaina Bertoncelo de
authors.initials: JB
authors.lastname: Almeida
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D012034:Refrigeration
chemical_list: C084111:Charisma composite resin; D003188:Composite Resins; C039734:Durafill