Effect of light curing tip distance and resin shade on microhardness of a hybrid resin composite.
Resin composite shades and resin composite polymerization performed with a distanced light tip are factors that can affect polymerization effectiveness. This in vitro study aimed to evaluate the influence of curing tip distance and resin shade on the microhardness of a hybrid resin composite (Z250-3M ESPE). Forty-five resin composite specimens were randomly prepared and divided into nine experimental groups (n = 5): three curing tip distances (2 mm, 4 mm, and 8 mm) and three resin shades (A1, A3.5, and C2). All samples were polymerized with a continuous output at 550 mW/cm(2). After 24 hours, Knoop microhardness measurements were obtained on the top and bottom surfaces of the sample, with a load of 25 grams for 10 seconds. Five indentations were performed on each surface of each sample. Results showed that bottom surface samples light-cured at 2 mm and 4 mm presented significantly higher hardness values than samples light-cured at 8 mm. The resin shade A1 presented higher hardness values and was statistically different from C2. The resin shade A3.5 did not present statistical differences from A1 and C2. For the top surface, there were no statistical differences among the curing tip distances. For all experimental conditions, the top surface showed higher hardness values than the bottom surface. It was concluded that light curing tip distance and resin shade are important factors to be considered for obtaining adequate polymerization.
Department of Restorative Dentistry, Piracicaba School of Dentistry, Campinas State University.
Flávio Henrique Baggio
FH
Aguiar
Carolina Rodrigues
CR
Lazzari
Débora Alves Nunes Leite
DA
Lima
Glaucia Maria Bovi
GM
Ambrosano
José Roberto
JR
Lovadino
D003116:Color; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003748:Dental Equipment; D003793:Dental Restoration, Permanent / Q000295:instrumentation* / Q000592:standards; D006244:Hardness / Q000528:radiation effects; D008027:Light; D008422:Materials Testing; D011108:Polymers; D013499:Surface Properties
D003188:Composite Resins; D011108:Polymers