Tooth Whitening Procedures May Reduce Dentin Fracture Toughness
Tooth Whitening Procedures May Reduce Dentin Fracture Toughness
December 17th, 2007 by The MediNEWS Team
Dental bleaching techniques, commonly known as tooth whitening, are simple and conservative procedures for aesthetic restoration of discolored teeth. However, dental bleaching agents may cause enamel sensitivity as well as mild irritation to the soft tissues around the bleached tooth. Now, in a new research article published in the latest issue of the Journal of Dental Research, it has been reported that bleaching techniques reduce the fracture toughness of the dentin.
The invitro study, conducted by Canadian researchers, Tam LE and Noroozi A, at the University of Toronto, evaluated the response of the dentinal structures to peroxide tooth bleaching. On the compact test specimens consisting of human dentin, either bleach (16% or 10% carbamide peroxide or 3% hydrogen peroxide) or control material containing 0.1% sodium fluoride was applied. The bleach was applied directly to the dentin or indirectly via the enamel (6 hours/ day) for a period of 2 weeks and 8 weeks. Based on an Analysis Of Variance (ANOVA) and Fisher’s Least Significant Difference (LSD) test, the fracture toughness results were evaluated. A significant decrease in the mean fracture toughness was observed, with a more prominent decrease after direct bleaching techniques (19-34% after 2 weeks and 61-68% after 8 weeks) compared to the indirect technique (up to 17% after 2 weeks and 37% after 8 weeks). The decrease was also directly proportional to the application time and bleach concentration.
Earlier this year, the same team of researchers had conducted a similar study (Journal of Esthetic and Restorative Dentistry, 2007) to evaluate the effects of prolonged bleaching techniques. The study was done for 8 weeks on the dentin of recently extracted molars, which was directly or indirectly treated at-home (10% carbamide peroxide or 3% hydrogen peroxide, 6 hours/day, 5 days/week) or in-office (30% hydrogen peroxide, 1 hour/week). The control materials for this study were placebo gel and distilled water. The team observed that upon prolonged use, directly bleached specimens showed a prominent decrease in the dentin fracture toughness (P < 0.05).
Bleaching agents not only decrease the dentin fracture toughness but also have a dehydrating effect on the dentin (Operative Dentistry, 2006). Application of dental varnishes prior to bleaching can reduce or prevent the dehydration of dentin due to the peroxides.
Dental bleaching does not change the color of the crown, caps or fillings, and the whitening effect of the procedure is temporary. Also, care should be taken when using bleach for prolonged duration in cases with dentinal exposure in the form of occlusal attrition or in the case of gingival recession.
Over the past five years, the demand for tooth bleaching has increased by more than 300 percent. Recent studies show that about 80 percent of adults aged between 18 to 49 years would prefer to have whiter and brighter teeth. There are many bleaching techniques available such as nightguard (home) bleach, as well as in-office bleaches. For all these procedures, peroxide is used in varying concentrations and duration. With new evidence establishing that the dentin fracture toughness is dependent on the concentration and duration of the peroxides used during whitening, utmost care should be employed while perform these procedures.
December 17th, 2007 by The MediNEWS Team
Dental bleaching techniques, commonly known as tooth whitening, are simple and conservative procedures for aesthetic restoration of discolored teeth. However, dental bleaching agents may cause enamel sensitivity as well as mild irritation to the soft tissues around the bleached tooth. Now, in a new research article published in the latest issue of the Journal of Dental Research, it has been reported that bleaching techniques reduce the fracture toughness of the dentin.
The invitro study, conducted by Canadian researchers, Tam LE and Noroozi A, at the University of Toronto, evaluated the response of the dentinal structures to peroxide tooth bleaching. On the compact test specimens consisting of human dentin, either bleach (16% or 10% carbamide peroxide or 3% hydrogen peroxide) or control material containing 0.1% sodium fluoride was applied. The bleach was applied directly to the dentin or indirectly via the enamel (6 hours/ day) for a period of 2 weeks and 8 weeks. Based on an Analysis Of Variance (ANOVA) and Fisher’s Least Significant Difference (LSD) test, the fracture toughness results were evaluated. A significant decrease in the mean fracture toughness was observed, with a more prominent decrease after direct bleaching techniques (19-34% after 2 weeks and 61-68% after 8 weeks) compared to the indirect technique (up to 17% after 2 weeks and 37% after 8 weeks). The decrease was also directly proportional to the application time and bleach concentration.
Earlier this year, the same team of researchers had conducted a similar study (Journal of Esthetic and Restorative Dentistry, 2007) to evaluate the effects of prolonged bleaching techniques. The study was done for 8 weeks on the dentin of recently extracted molars, which was directly or indirectly treated at-home (10% carbamide peroxide or 3% hydrogen peroxide, 6 hours/day, 5 days/week) or in-office (30% hydrogen peroxide, 1 hour/week). The control materials for this study were placebo gel and distilled water. The team observed that upon prolonged use, directly bleached specimens showed a prominent decrease in the dentin fracture toughness (P < 0.05).
Bleaching agents not only decrease the dentin fracture toughness but also have a dehydrating effect on the dentin (Operative Dentistry, 2006). Application of dental varnishes prior to bleaching can reduce or prevent the dehydration of dentin due to the peroxides.
Dental bleaching does not change the color of the crown, caps or fillings, and the whitening effect of the procedure is temporary. Also, care should be taken when using bleach for prolonged duration in cases with dentinal exposure in the form of occlusal attrition or in the case of gingival recession.
Over the past five years, the demand for tooth bleaching has increased by more than 300 percent. Recent studies show that about 80 percent of adults aged between 18 to 49 years would prefer to have whiter and brighter teeth. There are many bleaching techniques available such as nightguard (home) bleach, as well as in-office bleaches. For all these procedures, peroxide is used in varying concentrations and duration. With new evidence establishing that the dentin fracture toughness is dependent on the concentration and duration of the peroxides used during whitening, utmost care should be employed while perform these procedures.
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