title: Comparative evaluation of effects of bleaching on color stability and marginal adaptation of discolored direct and indirect composite laminate veneers under in vivo conditions.
abstract: BACKGROUND
  Change in color and loss of marginal adaptation of tooth colored restorative materials is not acceptable. Bleaching is commonly used for treating discolored teeth. However, the literature is scanty regarding its effect on color and marginal adaptation of direct and indirect composite laminate veneers (CLVs) under in vivo conditions.
  
  
  OBJECTIVE
  Purpose of the study was to determine the effect of bleaching on color change and marginal adaptation of direct and indirect CLVs over a period of time when exposed to the oral environment.
  
  
  METHODS
  For this purpose, a total of 14 subjects irrespective of age and sex indicated for CLV restorations on maxillary anterior teeth were selected following the inclusion and exclusion criteria. For each subject, indirect CLVs were fabricated and looted in the first quadrant (Group 1) and direct CLV's (Group 2), were given in the second quadrant. Color change was assessed clinically using intra-oral digital spectrophotometer and marginal adaptation was assessed on epoxy resin replica of the tooth-restoration interface under scanning electron microscope. After 6 months, the subjects underwent a home bleaching regimen for 14 days using 10% carbamide peroxide. The assessment of color change and marginal adaptation was done at 6 months after veneering (0-180 days), immediately after the bleaching regimen (0-194 days) and 3 months after the bleaching regimen (0-284 days).
  
  
  RESULTS
  The difference in median color change (ΔE) between the groups was tested using Wilcoxon rank sum test while the median color change with time within the groups was tested using Wilcoxon signed rank test. The difference in the rates of marginal adaptation was tested between the groups using Chi-square/Fisher's exact test. Bleaching led to statistically significant color change at cervical (CE), middle and incisal (IE) regions when direct and indirect composites were compared (P < 0.05). During intra-group comparison, direct CLV's showed significant color change at CE and IE regions when ΔE was compared at 180 days and 284 days (CE 10 vs. CE 30, P = 0.008, IE 10 vs. IE 30, P = 0.003). No significant differences were found when within group comparison was made for indirect laminates. Intergroup comparison between the groups showed significant difference in marginal adaptation at CE margin at all.time points (at baseline, P = 0.005; at 180 days, P = 0.007; 194 days, P = 0.025; at 284 days, P = 0.067).
  
  
  CONCLUSIONS
  After bleaching, indirect CLVs performed better in terms of color stability whereas direct CLVs performed better in terms of marginal adaptation.
  
  
  CONCLUSIONS
  Indirect composites should be preferred to direct composites as veneering materials as they have better color stability. Special attention should be given to their marginal adaptation especially in the CE region. Bleaching should be avoided in patients with composite restorations in the mouth.
authors.affiliation: Department of Prosthodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Veena
authors.initials: V
authors.lastname: Jain
authors.affiliation: Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Taposh K
authors.initials: TK
authors.lastname: Das
authors.affiliation: Department of Prosthodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Gunjan
authors.initials: G
authors.lastname: Pruthi
authors.affiliation: Department of Prosthodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Naseem
authors.initials: N
authors.lastname: Shah
authors.affiliation: Department of Prosthodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Suresh
authors.initials: S
authors.lastname: Rajendiran
keywords: CIELAB color system; color change; composites; discoloration; spectrophotometer; veneers