TY - JOUR ID - TI - The Effect of in-office Tooth Whitening on the Microhardness of Esthetic Restoration (An invitro Study). AU - Ammer A Sultan AU - Omar S Rahawi AU - Ashraf S. Qasim PY - 2009 VL - 9 IS - 1 SP - 83 EP - 89 JO - Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان SN - 18121217 19980345 AB - Aims: To determine if the composite resin restoration need to be replaced after power bleaching at
different times.Materials and methods: Three composite resins (a flowable, a conventional and
ceramic composite) were used for this study. Transparent discs with 2mm thickness with a hole of
5mm diameter were used for the production of composite samples, six samples were made for each
type of composite with a total of 18 samples were used. The bleaching procedure was followed on the
top surface of each sample. For each sample a newly fresh material were mixed (lase peroxide sensy
gel) and applied over the prepared sample. Bleaching took place for 15, 30 and 45 minutes according to
the manufacturer instructions. For the microhardness measurements, a Vickers microhardness tester
(Wolpert, Germany) was used, with a 200g load. Five microhardness measurements were obtained on
the top surface of each sample on the following time periods: before bleaching, after 15 min., after 30
min. and after 45 min. of bleaching. Data were analyzed using T-test, a value of p≤0.05 was considered
significant followed by the analysis of variance (ANOVA). Results: The results showed a significant
increase in the microhardness of all the three types of composite resins after bleaching with a different
time when compared to the control.Conclusion The bleaching agent that was tested has a significant
increase of the microhardness of the composite resins and there is no sufficient reason to indicate the
replacement of restorations.

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