The effect of cold-light-activated bleaching treatment on enamel surfaces in vitro

This in vitrostudy aims to evaluate the crystal and surface microstructure of dental enamel after cold-light bleaching treatment. Twelve sound human premolars were cross-split into four specimens, namely, mesio-buccal （Group LP）, disto-buccal （Group P）, mesio-lingual （Group NP） and disto-lingual （Group L） specimens. These four groups were treated using the standard cold-light bleaching procedure, a bleaching agent, a peroxide-free bleaching agent and cold-light, respectively. Before and after treatment, all specimens were analyzed by high-resolution, micro-area X-ray diffraction and scanning electron microscopy. Using a spectrometer, tooth color of all specimens was measured before and after treatment. The phase of the enamel crystals was identified as hydroxyapatite and carbonated hydroxyapatite. After treatment, specimens in Groups LP and P showed significantly weaker X-ray diffraction peaks, significant reduction in crystal size and crystallinity, significant increase in L~ but decrease in a＊ and b＊, and obvious alterations in the surface morphology. However, specimens in Groups NP and L did not show any significant changes. The cold-light bleaching treatment leads to demineralization in the enamel surface. The acidic peroxide-containing bleaching agent was the major cause of demineralization, whereas cold-light did not exhibit significant increase or decrease effect on this demineralization.

Minimally invasive approach for improving aesthetic in a patient with tetracycline-stained teeth by bleaching:A clinical evaluation

Objective:To compare 16% carbamide peroxide(CP)with a higher concentration of hydrogen peroxide(HP)for bleaching teeth in office or at-home to erase tetracycline stains on teeth.Materials and methods:In a randomized,self-controlled clinical trial,we assigned eligible subjects to group A with 40% HP compared with 16% CP or group B with 45% CP compared with 16% CP on the split maxillary arch and followed the manufacturers’instructions.Tooth color changes were measured with vita 3D-bleached guide and colorimeter at baseline and three-time assessment.Tooth sensitive intensity was evaluated using numeric rating scales,and oral soft and hard tissue examination was recorded.Patient satisfaction survey was conducted at the last tooth color evaluation.Results:There were 20 subjects enrolled.The color changes by the end of the study were A1(40% HP)=8.22,A2(16% CP)=8.20,B1(45% CP)=11.27,B2(16% CP)=8.26 respectively.All groups experienced significant shade reductions by bleaching,the 45% CP group had significantly greatest color changes compared with the other groups(p=0.03).For tooth sensitivity evaluation,significant differences were observed in 40% HP group(p=0.01),but with mild level.None patients suffered oral soft or hard tissue abnormalities before and after treatment.Patients were more in favor of using 45% CP according to the questionnaire results.Conclusion:The 3 whitening agents were effective and safe for the whitening of tetracycline-stained teeth,the 45% CP agent had quicker whitening efficacy with low tooth sensitivity and positive feedback.Clinical significance:45% of high-concentration CP whitener by at-home using,brought faster and superior efficacy to bleaching tetracycline-stained teeth while had the equal intensity of tooth sensitivity.

Effects of 45S5 bioglass on surface properties of dental enamel subjected to 35% hydrogen peroxide

Tooth bleaching agents may weaken the tooth structure. Therefore, it is important to minimize any risks of tooth hard tissue damage caused by bleaching agents. The aim of this study was to evaluate the effects of applying 45S5 bioglass （BG） before, after, and during 35% hydrogen peroxide （HP） bleaching on whitening efficacy, physicochemical properties and microstructures of bovine enamel. Seventy-two bovine enamel blocks were prepared and randomly divided into six groups： distilled deionized water （DDW）, BG, HP, BG before HP, BG after HP and BG during HP. Colorimetric and microhardness tests were performed before and after the treatment procedure. Representative specimens from each group were selected for morphology investigation after the final tests. A significant color change was observed in group HP, BG before HP, BG after HP and BG during HP. The microhardness loss was in the following order： group HP〉 BG before HP, BG after HP〉 BG during HP〉DDW, BG. The most obvious morphological alteration of was observed on enamel surfaces in group HP, and a slight morphological alteration was also detected in group BG before HP and BG after HP. Our findings suggest that the combination use of BG and HP could not impede the tooth whitening efficacy. Using BG during HP brought better protective effect than pre/post-bleaching use of BG, as it could more effectively reduce the mineral loss as well as retain the surface integrity of enamel. BG may serve as a promising biomimetic adjunct for bleaching therapy to prevent/restore the enamel damage induced by bleaching agents.