Influence of exposure time to saliva and antioxidant treatment on bond strength to enamel after tooth bleaching: an in situ study.
OBJECTIVE
This study evaluated the influence of different exposure times to saliva in situ in comparison with an antioxidant treatment on composite resin bond strength to human enamel restored after tooth bleaching.


METHODS
Forty human teeth specimens measuring 5x5 mm were prepared and randomly allocated into 5 groups with 8 specimens each: Gct (control group, restored on unbleached enamel); Gbl (restored immediately after bleaching); Gsa (bleached, treated with 10% sodium ascorbate gel for 60 min and restored); G7d (bleached, exposed to saliva in situ for 7 days and restored); and G14d (bleached, exposed to saliva in situ for 14 days and restored). Restored samples were cut into 0.8 mm2 sticks that were tested in microtensile. Specimens were microscopically analyzed and failure modes were classified as adhesive, cohesive, or mixed. Pretest and cohesive failures were not considered in the statistical analysis, which was performed with one-way ANOVA and Tukey's post-hoc test (α=0.05), with the dental specimen considered as the experimental unit.


RESULTS
Mean bond strength results found for Gbl in comparison with Gct indicated that bleaching significantly reduced enamel adhesiveness (P<0.01). However, no statistically significant differences were found between Gct, Gsa and G7d (P>0.05). Bond strength found for G14d was significantly higher than for Gsa (P<0.01). Fractures modes were predominantly of a mixed type.


CONCLUSIONS
Bonding strength to bleached enamel was immediately restored with the application of sodium ascorbate and exposure to human saliva in situ for at least 7 days. Best results were obtained with exposure to human saliva in situ for 14 days. Treatment with sodium ascorbate gel for 60 min may be recommended in cases patients cannot wait for at least 7 days for adhesive techniques to be performed.
State University of Maringá, Department of Dentistry, MaringáPR, Brazil.
Thais Aglaet Matos
TA
Miranda
University North of Paraná, Department of Dentistry, LondrinaPR, Brazil.
Sandra Kiss
SK
Moura
Private practice, MaringáPR, Brazil.
Vitor Hugo de Oliveira
VH
Amorim
State University of Maringá, Department of Dentistry, MaringáPR, Brazil.
Raquel Sano Suga
RS
Terada
State University of Maringá, Department of Dentistry, MaringáPR, Brazil.
Renata Corrêa
RC
Pascotto
D000704:Analysis of Variance; D000975:Antioxidants / Q000737:chemistry*; D057886:Bleaching Agents / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D003738:Dental Cements / Q000737:chemistry; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects*; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D012463:Saliva / Q000737:chemistry*; D013499:Surface Properties / Q000187:drug effects; D013718:Tensile Strength; D013997:Time Factors; D014073:Tooth Bleaching / Q000009:adverse effects / Q000379:methods*
D000975:Antioxidants; D057886:Bleaching Agents; D003188:Composite Resins; D003738:Dental Cements