title: Comparative depth of cure among two light-cured core build-up composites by surface vickers hardness.
abstract: OBJECTIVE
  Depth of cure of composite material is restricted and it depends on many parameters such as thickness. The aim of this in-vitro study was to evaluate the depth of cure of two light-cured core build-up composites (Quixfil and Photocore) in different thicknesses, when cured for 60 seconds.
  
  
  METHODS
  The Vickers microhardness measurements were made for each side of the top irradiated surfaces of 1,2,3,4,5,6,7 and 8-mm-thick cylindrical blocks of two core build-up light-cured composites (Quixfil and Photocore) and a micro hybrid composite (Z250) as the control group. For each thickness a bottom to top Vickers Hardness Number (VHN) ratio was determined and a value of at least 80% was used to indicate the acceptable depth of curing. The results were analyzed with two way ANOVA and Tukey HSD test. P value<0.05 was considered significant.
  
  
  RESULTS
  A two way ANOVA indicated that both the depth of cure and VHN were significantly influenced by composite type (P< 0.001) and thickness (P< 0.001). The bottom to top VHN ratio reflecting the relative curing degree showed acceptable curing at a depth of 5 mm for Quixfil and Photocore; however, it was 3 mm for Z250. The surface micro hardness of Photocore was significantly higher than the other materials in all thicknesses.
  
  
  CONCLUSIONS
  Although both two composites can be bulk cured, their curing depths were lower than that was expected. Curing depth is a property which is material specific and decreases with thickness (P < 0.001).
authors.affiliation: Assistant Professor, Department of Operative Dentistry, Faculty of Dentistry, Shahed University, Tehran, Iran.
authors.forename: Mr
authors.initials: M
authors.lastname: Rouhollahi
authors.forename: M
authors.initials: M
authors.lastname: Mohammadibasir
authors.forename: Sh
authors.initials: Sh
authors.lastname: Talim
keywords: Core Build-Up Composite; Depth of Cure; Microhardness; Polymerization