title: Microhardness evaluation of in situ vital bleaching on human dental enamel using a novel study design.
abstract: OBJECTIVE
  The aim of this 'in situ' study was to evaluate the microhardness of dental enamel following treatment with an in-office and an at-home vital bleaching agent through a novel approach using samples temporarily bonded 'in vivo'.
  
  
  METHODS
  Human dental enamel slabs (n=88) were subjected to sequential polishing and initial Knoop microhardness tests were performed. The slabs were fixed to the facial surfaces of the maxillary first molars of 44 human volunteers. They were divided into four groups (n=11) according to the treatment group: G1- in-office-CP37+ at-home-CP10; G2- in-office-CP37+ at-home-PLA; G3- in-office-PLA and at-home-CP10; G4- in-office and at-home-PLA. After 3 weeks of treatment, final microhardness measurements were performed.
  
  
  CONCLUSIONS
  ANOVA and Tukey's HSD hoc analysis (alpha=0.05) revealed no differences among initial or final microhardness values (p>0.05); however, significant differences occurred between initial and final values for each group (p<0.01), The evaluation of microhardness revealed a reduction of 6.8% for G1, 4.1% for G2, 3.4% for G3 and 3.5% for G4. In-office bleaching with 37% carbamide peroxide, an at-home bleaching with 10% carbamide peroxide, and a combination of both resulted in lower enamel microhardness when measured immediately post-treatment. However, long-term effects of these treatments are not known, and are believed to be clinically insignificant due to the relatively small reductions observed in enamel microhardness. Interestingly, the carrier, Cabopol 934P, also resulted in similar reduction in enamel microhardness even when administrated alone as a placebo.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry at Piracicaba, University of Campinas, Piracicaba, Brazil.
authors.forename: José A
authors.initials: JA
authors.lastname: Rodrigues
authors.forename: Giselle M
authors.initials: GM
authors.lastname: Marchi
authors.forename: Glaucia M B
authors.initials: GM
authors.lastname: Ambrosano
authors.forename: Harald O
authors.initials: HO
authors.lastname: Heymann
authors.forename: Luiz A
authors.initials: LA
authors.lastname: Pimenta
mesh_terms: D000179:Acrylates / Q000633:toxicity; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D003742:Dental Devices, Home Care; D003743:Dental Enamel / Q000187:drug effects*; D004338:Drug Combinations; D005260:Female; D006244:Hardness / Q000187:drug effects; D006801:Humans; D008297:Male; D016877:Oxidants / Q000633:toxicity*; D010545:Peroxides / Q000633:toxicity*; D014073:Tooth Bleaching / Q000009:adverse effects*; D017001:Tooth Demineralization / Q000139:chemically induced; D014508:Urea / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D000179:Acrylates; D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea; C453622:carbopol 934P