title: Influence of curing tip distance on composite Knoop hardness values.
abstract: The purpose of this paper was to study the influence of curing tip distance on Knoop hardness values, at different depths, of two composites, Z100 and Silux Plus. Specimens (5 mm in diameter and 2.5 mm in height) were prepared in a copper mold, covered with mylar strip and polymerized for 40 s, at 3 tip-to-composite surface distances: 0 mm (surface contact), 6 and 12 mm, utilizing an XL 3000 curing unit, with 750 mW/cm2 power. The specimens were then stored at 37 degrees C for 24 h. Knoop hardness values were measured using a microhardness tester, with a load of 50 g for 30 s for each indentation. Four specimens were made for each distance and composite and eighteen indentations were made of each specimen. The results were submitted to analysis of variance and Tukey test at 5% significance level. The results indicated that 1) composite Z100: the larger the curing tip distance in relation to the composite, the lower the Knoop hardness values; 2) Silux Plus: increasing the curing tip distance did not produce a statistically significant difference in the Knoop hardness values; however, at 6 and 12 mm, the deeper layers showed lower Knoop hardness values in relation to the surface; 3) Z100: statistically superior in relation to Silux Plus at all three curing tip distances and at all depths (P < 0.05).
authors.affiliation: Area Materiais Dentários, Faculdade de Odontologia de Piracicaba, UNICAMP, Piracicaba, SP, Brasil. sobrinho@fop.unicamp.br
authors.forename: L C
authors.initials: LC
authors.lastname: Sobrinho
authors.forename: A A
authors.initials: AA
authors.lastname: de Lima
authors.forename: S
authors.initials: S
authors.lastname: Consani
authors.forename: M A
authors.initials: MA
authors.lastname: Sinhoreti
authors.forename: J C
authors.initials: JC
authors.lastname: Knowles
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000295:instrumentation*; D004867:Equipment Design; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry; D012822:Silicon Dioxide; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium
chemical_list: D003188:Composite Resins; D011108:Polymers; C083568:Z100 composite resin; C074741:Silux Plus; D012822:Silicon Dioxide; D015040:Zirconium