Influence of time on bond strength after bleaching with 35% hydrogen peroxide.
OBJECTIVE
The aim of this in vitro study was to evaluate the influence of time after treatment with a 35% hydrogen peroxide bleaching agent on the shear bond strength between composite resin and sound enamel and dentin.


METHODS
Eighty dental slabs - 40 enamel (E) slabs and 40 dentin (D) slabs - were embedded, flatted, and divided into four groups (n=10). In G1 the E and D slabs were kept in artificial saliva for 14 days. For the G2, G3, and G4 groups the E and D slabs were submitted to bleaching treatment with a 35% hydrogen peroxide bleaching agent. At different times after bleaching treatments (G2=immediate; G3=seven days; G4= fourteen days), composite resin cylinders were made using an adhesive system. Tests were performed in a universal testing machine at a speed of 0.5 mm/min to obtain the values in MPa.


RESULTS
For enamel, the Kruskal-Wallis test and Dunn Method showed G1 differed significantly from G2 (G1=13.40 a; G2=6.64 b; G3=16.76 a; G4=11.64 ab). For dentin, the analysis of variance (ANOVA) and Tukey tests showed that G1 differed significantly from G2 and G3 (G1=12.11 a; G2=4.97 b; G3=8.67 c; G4=11.86 ac).


CONCLUSIONS
It is recommended adhesive restorative procedures in enamel be delayed for seven days post-bleaching treatment with 35% hydrogen peroxide, while restorations in dentin should be delayed for 14 days following bleaching treatment.
Barbosa
Cinthia Maria
CM
School of Dentistry and Dental Research Center, São Leopoldo Mandic, Campinas, SP, Brazil. dra_cinthia@hotmail.com
Sasaki
Robson Tetsuo
RT
Florio
Flavia Martao
FM
Basting
Roberta Tarkany
RT
D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding; D003743:Dental Enamel / Q000187:drug effects*; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects*; D016877:Oxidants / Q000009:adverse effects*; D019279:Resin Cements; D033081:Shear Strength; D018709:Statistics, Nonparametric; D013997:Time Factors; D014073:Tooth Bleaching / Q000009:adverse effects*
D003188:Composite Resins; C444701:Filtek Z250; D016877:Oxidants; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D006861:Hydrogen Peroxide