title: The influence of plastic light cure sheaths on the hardness of resin composite.
abstract: OBJECTIVE
  This study investigated the influence of a disposable light cure sheath on both the surface hardness and hardness at varying thicknesses of resin composite.
  
  
  METHODS
  A series of resin composite discs (Spectrum) were fabricated with varying depths up to 6 mm. The light curing units used were a standard halogen unit (Elipar Trilight) and an LED unit (Elipar Freelight 2). Recommended curing times from the manufacturer were followed. The disposable light-curing sheath (Cure Sleeve) was used with both light-curing units. Two additional groups without the sheath were employed as controls. Each specimen (n = 4) was subjected to hardness testing to evaluate hardness from 0 mm to 5 mm thick. A 200g load was applied for 10 seconds using a Vickers diamond indenter and six indentations were obtained from each specimen. Statistical analysis was performed using two-way ANOVA.
  
  
  RESULTS
  The LED without a sheath achieved the highest surface hardness value (47.2 VHN +/- 5.5). There was no significant difference between the groups regarding surface hardness (p > 0.05). As the thicknesses of the resin composite increased, the hardness values decreased in all groups. The LED light curing unit, in combination with a sheath, demonstrated the lowest hardness values at a 5 mm thickness of resin composite (p < 0.05).
  
  
  CONCLUSIONS
  All four different methods of light curing resulted in a significant reduction in hardness values with increasing resin composite thickness, which could compromise the mechanical properties of the resin composite. However, the use of the light cure sheaths still provided an acceptable depth of cure when used following the 2 mm increment rule. It was not until 3 mm that the use of the light cure sheaths compromised the hardness results. It is recommended that the curing depth should not exceed 2 mm, regardless of light curing method.
authors: University of Sheffield, Adult Dental Care, School of Clinical Dentistry, Claremont Crescent, Sheffield, United Kingdom. s.pollington@sheffield.ac.uk
authors: Sarah
authors: S
authors: Pollington
authors: Nuwanthi
authors: N
authors: Kahakachchi
authors: Richard
authors: R
authors: van Noort
mesh_terms: D003188:Composite Resins; D055117:Curing Lights, Dental; D003799:Dental Stress Analysis; D004209:Disposable Equipment; D006244:Hardness; D010969:Plastics
chemical_list: D003188:Composite Resins; D010969:Plastics; C420128:Spectrum composite resin