Effect of different time periods of vital bleaching on flexural strength of the bovine enamel and dentin complex.
OBJECTIVE
The aim of this in vitro study was to evaluate the effect of 20% carbamide peroxide (CP) on the flexural strength (FS) of bovine enamel and dentin complex.


METHODS
One hundred sound bovine teeth were selected for use. Blocks (2 x 3 x 8 mm) from the middle portion of the facial surfaces of each crown were sectioned from the teeth. The specimens were randomly divided into five groups (n=20) based on the time period of vital bleaching. Group 1 comprised the control group kept in artificial saliva. The experimental groups subjected to immersion in 20% CP, Opalescence, for four, six and eight weeks, respectively (eight hours daily). Mechanical testing was performed 24 hours after the last treatment using an Instron Universal Testing Machine with a crosshead speed of 0.5 mm/min. The results were analyzed by one-way analysis of variance (ANOVA) and Tukey's test (a=0.05).


RESULTS
Mean values for FS were 141.27, 103.06, 120.71, 130.23, and 117.90 (Mpa), respectively. Statistically significant differences in FS were noted among the groups. A statistically significant difference was observed between Group 2 (two week bleach) and the control.


CONCLUSIONS
Application of 20% CP bleach for two weeks provided significant decreases in FS of bovine enamel and dentin complex. Similar decreases were not observed among the other groups.
Ghavamnasiri
Marjaneh
M
Department of Operative Dentistry, School of Dentistry, Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. dr_marjaneh@yahoo.com
Abedini
Sara
S
Mehdizadeh Tazangi
Alireza
A
D000704:Analysis of Variance; D000818:Animals; D000077463:Carbamide Peroxide; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects; D004338:Drug Combinations; D016877:Oxidants / Q000008:administration & dosage / Q000633:toxicity*; D010545:Peroxides / Q000008:administration & dosage / Q000633:toxicity*; D018583:Pliability / Q000187:drug effects; D013997:Time Factors; D014073:Tooth Bleaching / Q000009:adverse effects*; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000633:toxicity
D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea