Effect of Different Time Periods of Vital Bleaching on Flexural Strength of Bovine Enamel and Dentin Complex

Abstract

Aim 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 and Materials One hundred sound bovine teeth were selected for use. Blocks (2×3×8 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 (α=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. Conclusion 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. Citation Ghavamnasiri M, Abedini S, Tazangi AM. Effect of Different Time Periods of Vital Bleaching on Flexural Strength of Bovine Enamel and Dentin Complex. J Contemp Dent Pract 2007 March;(8)3:021-028.

Coronal resistance to fracture of endodontically treated teeth submitted to light-activated bleaching

“…These ultra-structural alterations increase dentin permeability 11 , reduce hardness and elasticity. 12,17,22 Chng et al 17 reported a significant decrease in the ultimate tensile and shear strengths of dentin after intracoronal bleaching with 30% hydrogen peroxide for 24 h. Recently, Ghavamnasiri et al 30 also showed that the flexural strength of bovine dentin decreased after the application of j o u r n a l o f d e n t i s t r y 3 6 ( 2 0 0 8 ) 9 3 5 -9 3 9…”

Effect of high-concentrated bleaching agents on the bond strength at dentin/resin interface and flexural strength of dentin

“…There are few studies that evaluated the mechanical properties of dentin submitted to tooth bleaching (15,16,20,21). Pobbe et al (16) found that the fracture strength of teeth was reduced after three sessions of internal bleaching with 38% hydrogen peroxide.…”

Effect of Bleaching Treatment on Fatigue Resistance and Flexural Strength of Bovine Dentin

“…21 The flexural strength of bovine dentin was significantly reduced by an application of 20% carbamide peroxide bleach for 2 weeks. 22 In another in vitro study, the fracture toughness of dentin was significantly reduced by the indirect (through intact enamel) application of peroxide bleaching agents (this represents a simulation of clinical bleaching of teeth with full enamel coverage), as well as by a direct bleach application method to dentin, and that it was reduced more for the longer application time period (8 versus 2 weeks) and for the higher (16% versus 10%) bleach concentration. 23 The clinical relevance of these in vitro studies is uncertain and in vivo studies are lacking.…”