High-concentrated carbamide peroxide bleaching agents effects on enamel surface

Concern has been expressed regarding the adverse effects of peroxide-containing tooth bleaching agents on enamel surface. This study examined enamel average surface roughness before (baseline) and after an in-office bleaching protocol and investigated the influence of high concentrations of carbamide peroxide gels on its surface staining and morphology. Flat enamel surfaces were submitted to 35 and 37% carbamide peroxide or to no bleaching treatment (n = 10) and evaluated with a profilometer. Eight specimens from each group were randomly selected and immersed in a 2% methylene blue solution. Afterwards, specimens were ground into powder and prepared for the spectrophotometric analysis. Two remained specimens of each group were examined using a scanning electron microscope. Data were subjected to analysis of variance and Tukey test (P > 0.05). Baseline roughness average was statistically similar for all groups, however, 35% carbamide peroxide produced the roughest enamel surfaces. Different concentrations of carbamide peroxide produced similar staining means and enamel surface morphological alterations.     

过氧化脲漂白剂对釉质显微硬度影响的实验研究

目的:评价不同载体和浓度的过氧化脲(carbam ide peroxide,CP)漂白剂对釉质表面显微硬度的影响。方法:在18个离体前磨牙的颊、舌面各制备2 mm×2 mm的平面,随机分为6组。分别用卡波姆(Car-bopol)、聚乙烯吡咯烷酮(PVP)或泊洛沙姆(poloxam er)为增稠载体的含11%、21%CP的漂白剂,在37℃100%湿度条件下每天漂白6~8 h,持续2周。漂白前、后测量釉质表面的显微硬度。21%CP治疗组在漂白治疗结束后继续浸入人工唾液2周,再次测量显微硬度。结果:11%CP漂白2周后,釉质的显微硬度与漂白前相比没有显著差异(P>0.05);21%CP漂白2周后,釉质的显微硬度明显低于漂白前(P<0.01),继续浸入人工唾液2周,显微硬度明显高于漂白后(P<0.05),但与漂白前相比仍有显著差异(P<0.05)。在相同CP浓度下,不同增稠载体组间的显微硬度没有显著差异(P>0.05)。结论:11%CP漂白剂对釉质的显微硬度没有影响,21%CP漂白剂可明显降低釉质的显微硬度,人工唾液可在一定程度上增加釉质的再矿化能力,不同的增稠载体对釉质的显微硬度没有明显影响。     

过氧化脲漂白剂的体外细胞毒性研究

目的:评价不同增稠载体过氧化脲漂白剂的细胞毒性,并与同类商品漂白剂进行比较.方法:采用琼脂覆盖法通过直径5咖的滤膜圆片,分别评价以Carbopol或PVP为增稠载体的100 g/L、200 g/L过氧化脲漂白剂及同种浓度Opalescence漂白凝胶对L929小鼠成纤维细胞的毒性作用.结果:以Carbopol或PVP为增稠载体的100g/L、200 g/L CP漂白剂和Opalescence 100 g/L、200 g/LCP漂白凝胶的细胞毒性均为2级,中度毒性.结论:不同增稠载体的过氧化脲漂白剂和Opalescence漂白凝胶的细胞毒性没有显著差别.     

过氧脲素漂白剂对牙釉质表面特性的影响

目的：观察１０％～３０％过氧脲素漂白剂对牙釉质表面特性的影响。方法：选用正畸拔除的健康前磨牙，经１０％、１５％、３０％过氧脲素漂白剂处理１５ｄ后，采用显微硬度测定仪、电子显微镜等手段检查。结果：１０％、１５％、３０％过氧脉素漂白剂对牙釉质表面硬度无降低作用，与对照组（ＨＶ：５８１．９±１１７．５）无明显差异；扫描电镜显示，牙釉质经漂白显现较光滑外观，无腐蚀、溶解现象。结论：１０％～３０％过氧脉素漂白剂对牙釉质表面结构无破坏作用。     

Effect of carbamide peroxide bleaching agents on tensile strength of human enamel.

OBJECTIVES: The aim of this study was to evaluate the effects of low concentrations of carbamide peroxide bleaching agents (CP) on the ultimate tensile strength of enamel (UTS). METHODS: Resin composite structure was built-up on the bonded occlusal surface of 12 sound third molars to facilitate specimen preparation for microtensile testing. The bonded teeth were sectioned in a bucco-lingual direction in slices approximately 0.7 mm thick. Each slice was trimmed with a fine diamond bur to reduce the buccal, internal slope enamel of the cusps to a dumb-bell shape with a cross-sectional area at the 'neck' of less than 1 mm2. The sample was randomly divided into six groups of 10 specimens each: Control (C-untreated); Opalescence 10% (O10), Opalescence 15% (O15), Opalescence 20% (O20), Whiteness 10% (W10) and Whiteness 16% (W16). Specimens in each group received the application of the CP for 6 h/day, at 37 degrees C, during 14 days and were stored in artificial saliva in between each application. After the bleaching regimen, specimens were tested with the microtensile method at 0.5 mm/min. Data were analyzed by ANOVA and Tukey test (5%). RESULTS: Mean tensile strengths were (MPa): C = 47.5 +/- 6.2a; O10 = 37.6 +/- 5.8b; O15 = 33.2 +/- 6.0b; O20 = 31.2 +/- 3.5b; W10 = 32.5 +/- 6.1b; W16 = 30.6 +/- 7.7b. Specimens subjected to the bleaching regimen presented significantly lower UTS than the control group. No differences were found among the type and concentration of the bleaching agents. SIGNIFICANCE: Results suggested that bleaching enamel with CP could significantly reduce its UTS within a 14 days treatment.     

The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time

Background: Different concentrations of carbamide peroxide (10 to 22 percent) have been used successfully as bleaching agents, but the adverse effects on enamel microhardness at different times are unknown. Methods: The authors analyzed seven bleaching agents and a placebo. The agents were applied on the surface of human dental fragments for eight hours per day for 42 days and stored in vials containing artificial saliva. Microhardness measurements were performed at baseline, eight hours and seven, 14, 21, 28, 35 and 42 days, as well as at seven and 14 days after treatment had ended. Results: Enamel treated with different bleaching agents or a placebo experienced a similar decrease in microhardness values over time, with the exception of fragments exposed to Opalescence PF 20 percent (Ultradent Products, South Jordan, Utah), or OPA20. Until the 49th day, the enamel exposed to OPA20 exhibited the lowest differences from baseline values. After 14 posttreatment days, enamel treated with placebo, Nite White 10 percent Excel (Discus Dental, Los Angeles), Nite White 16 percent Excel and Opalescence 10 percent exhibited the greatest differences from baseline values. An increase in enamel microhardness occurred at the end of the posttreatment period, although baseline values were not reached. Conclusions: Different concentrations of carbamide peroxide agents result in decreases in enamel microhardness. A post-bleaching period in artificial saliva resulted in recovery of baseline microhardness values (one agent) or an increase in values, although baseline values were not reached for these products. Clinical Implications. Higher concentrations of carbamide peroxide containing 0.11 percent ion fluoride can bleach teeth in a shorter period, with fewer hazardous effects on the enamel mineral content.     

不同增稠载体的过氧化脲漂白剂对釉质表面形态的影响

目的:研究不同载体和浓度的过氧化脲(carbamide peroxide,CP)漂白剂对釉质表面形态的影响。方法:分别以Carbopol、PVP、Poloxamer为凝胶增稠载体,配制含100g/L、150g/L和200g/LCP的CP漂白剂(pH6.5)和不含CP的凝胶制剂,利用近期拔除的离体前牙牙冠分组观察CP漂白剂对釉质表面形态的影响。结果:以Carbopol,PVP或Poloxamer作为增稠载体的漂白剂,随着CP浓度的增高,釉质表面从轻度溶解、脱矿,蜂窝状改变,直至正常釉质层消失,"鱼鳞状"的釉柱结构清晰可辨。其中以Poloxamer为增稠载体的漂白剂较之更甚。结论:以Carbopol,PVP或Poloxamer作为增稠载体的漂白剂,随着CP浓度的增高,釉质表面出现不同程度的形貌改变。     

3种过氧化脲漂白剂对釉质表面作用的SEM观察

目的：了解3种过氧化脲漂白剂在体情况下对釉质表面的影响。方法：选用临床正畸患者即将拔除的健康前磨牙，分为4组，每天分别给予3种过氧化脲漂白剂(300、160g／L CP—Rembrandt，150g／L CP—瑞康)漂白处理，空白对照组不作处理。2周后，拔除受试牙，即刻用扫描电镜对釉质表面进行观察。结果：300g／L过氧化脲漂白组釉质表面局部有轻度溶解、脱矿现象；160、150g／L组漂白后釉质表面较光滑，无明显脱矿。结论：临床情况下，以上受试产品中，300g／L过氧化脲对釉质局部表面有轻微脱矿作用，160、150g／L过氧化脲对釉质表面无明显脱矿作用。上述脱矿现象与釉质本身表面结构有关。     

In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time

Purpose: This study evaluated the effect of two home bleaching regimens (1 h/day versus 7 h/day for a total of 21 days) on the microhardness of superficial enamel treated with 10% carbamide peroxide gel.
Materials and Methods: Rectangular enamel specimens (2.5 × 2.5 × 1 mm) were obtained from human third molars and mounted on the palatal aspect of removable orthodontic retainers. Nine enamel specimens were mounted in each of 10 retainers, used by 10 volunteers during the active phase of the study. Modified 0.089 cm thick bleaching trays were fabricated for each participant. Each bleaching tray fit a participant's arch and the retainer containing the enamel specimens. Enamel specimens were treated with a 10% carbamide peroxide bleaching gel (Nite White® Excel 2Z, Discus Dental, Culver City, CA, USA) for either 1 h/day ( n = 30) or 7 h/day ( n = 30), both for 21 days. Three enamel specimens in each retainer were never treated and served as controls. The retainers were worn by the participants whether or not they underwent bleaching. This simulated the natural action of the saliva/oral fluids on the enamel specimens. Enamel specimens were subjected to pre- and post-treatment microhardness measurements. Post-treatment Knoop hardness numbers were compared with baseline values and analyzed statistically.
Results: Bleaching treatment resulted in a nonsignificant reduction in microhardness values when compared with values of the control nontreated specimens (1.7% and 2.5% reduction in hardness for 1 h/day and 7 h/day, respectively). There was no difference in microhardness between the different treatment regimens.
Conclusion: Home bleaching with 10% carbamide peroxide for up to 7 h/day for 21 days does not significantly affect enamel microhardness.
CLINICAL SIGNIFICANCE
Bleaching with 10% carbamide peroxide for 1 h/day or 7 h/day for a total of 21 days is safe for human enamel.     

过氧化脲漂白凝胶对牙釉质光学性质的影响

目的　探讨过氧化脲漂白凝胶对牙釉质光学性质的影响。方法　采用Opalesence10 %过氧化脲凝胶在 40颗离体前磨牙上作家庭漂白实验。漂白前测出各牙釉质的最大透光度及此时的可见光波长λ 。在漂白 2周、4周、再矿化 1周 ,分别测出可见光波长λ 时牙釉质的透光度。结果　漂白前λ =72 1nm时 ,牙釉质透光度最大 ,为 2 5 .7%。漂白前透光度 (2 5 .7% )与漂白 2周的透光度 (37.9% )及漂白 4周透光度 (39.2 % )与再矿化 1周的透光度 (4 8.4% )有极显著性差异 (P <0 .0 0 1) ,而漂白 2周与漂白 4周的透光度无显著性差异 (P >0 .0 5 )。结论过氧化脲漂白凝胶使牙釉质透光性增强 ,脱色与脱矿作用并存 ,再矿化处理能提高及稳定漂白效果。     

Effect of carbamide peroxide bleaching on enamel characteristics and susceptibility to further discoloration

Statement of problem

Whether tooth whitening alters the surface topography of enamel causing an increase in surface roughness that could increase susceptibility to restaining is unclear.

In vitro effects of hydrogen peroxide combined with different activators for the in-office bleaching technique on enamel

Abstract

Objective. The aim of this study was to evaluate the alteration of human enamel bleached with high concentrations of hydrogen peroxide associated with different activators. Materials and methods. Fifty enamel/dentin blocks (4 × 4 mm) were obtained from human third molars and randomized divided according to the bleaching procedure (n = 10): G1 = 35% hydrogen peroxide (HP – Whiteness HP Maxx); G2 = HP + Halogen lamp (HL); G3 = HP + 7% sodium bicarbonate (SB); G4 = HP + 20% sodium hydroxide (SH); and G5 = 38% hydrogen peroxide (OXB – Opalescence Xtra Boost). The bleaching treatments were performed in three sessions with a 7-day interval between them. The enamel content, before (baseline) and after bleaching, was determined using an FT-Raman spectrometer and was based on the concentration of phosphate, carbonate, and organic matrix. Statistical analysis was performed using two-way ANOVA for repeated measures and Tukey’s test. Results. The results showed no significant differences between time of analysis (p = 0.5175) for most treatments and peak areas analyzed; and among bleaching treatments (p = 0.4184). The comparisons during and after bleaching revealed a significant difference in the HP group for the peak areas of carbonate and organic matrix, and for the organic matrix in OXB and HP+SH groups. Tukey’s analysis determined that the difference, peak areas, and the interaction among treatment, time and peak was statistically significant (p < 0.05). Conclusion. The association of activators with hydrogen peroxide was effective in the alteration of enamel, mainly with regards to the organic matrix.     

Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness

This in vitro study evaluated the surface microhardness of human enamel submitted to bleaching with 10% carbamide peroxide (CP) containing calcium or fluoride. Ninety-eight dental blocks (5 x 5 mm2) with polished enamel surfaces were randomly assigned to 7 treatment groups (n=14), as follows: without bleaching and storage in artificial saliva (control); 10% CP; 10% CP + 0.05% calcium; 10% CP + 0.1% calcium; 10% CP + 0.2% calcium; 10% CP + 0.2% fluoride; and 10% CP + 0.5% fluoride. During 14 days, enamel surfaces were daily exposed to a 6-h bleaching regimen followed by storage in artificial saliva. Surface microhardness was measured before (baseline), during (7th day), immediately after bleaching (14th day) and 1 week post bleaching. Data were analyzed by two-way ANOVA and Tukey's test (p<0.05). All treatments reduced SM significantly during the bleaching cycle (7th day), immediately after bleaching (14th day) and 1 week post bleaching, compared to baseline and to the unbleached control group. In conclusion, in spite of the addition of calcium and fluoride, all bleaching treatments affected the enamel surface microhardness.     

In vitro evaluation of the effect of delaying toothbrushing with toothpaste on enamel microhardness subsequent to bleaching the teeth with 15% carbamide peroxide

Changes in enamel surface microhardness as a result of bleaching with carbamide peroxide in various in vitro conditions have been reported. The present study evaluated the effect of oral hygiene procedures on enamel microhardness at three time intervals following bleaching with 15% carbamide peroxide. Although this was an in vitro study, the purpose was to address whether or not a patient's toothbrushing following at-home bleaching might affect surface changes in tooth enamel. Eighty enamel slabs were prepared from impacted human third molars that had been extracted surgically. Subsequent to placing the specimens in acrylic resin, their surfaces were smoothed, and they were randomly divided into four equal groups. The specimens were initially evaluated for microhardness by Vickers test. The bleaching procedure was carried out for 21 days for 6 hours daily. In each group, the surfaces of specimens were brushed with toothpaste immediately, 1 hour, and 2 hours after bleaching except for the control group. The specimens were stored in artificial saliva. Enamel microhardness was again measured at the end of the bleaching period. Then the differences in enamel microhardness between the two periods were calculated. Data were analyzed with a nonparametric Kruskal-Wallis test at a significance level of p<0.05. The differences in the microhardness values before and after intervention between the groups were not significant (p=0.59). Daily oral hygiene procedures either immediately or 1 or 2 hours after daily bleaching procedures and exposing the specimens to artificial saliva during the study period produced no significant differences in enamel microhardness values.     

The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ.

This in situ study evaluated the microhardness of sound and demineralized enamel and dentin submitted to treatment with 10% carbamide peroxide for three weeks. A 10% carbamide peroxide bleaching agent--Opalescence/Ultradent (OPA)--was evaluated against a placebo agent (PLA). Two hundred and forty dental fragments--60 sound enamel fragments (SE), 60 demineralized enamel fragments (DE), 60 sound dentin fragments (SD) and 60 demineralized dentin fragments (DD)--were randomly fixed on the vestibular surface of the first superior molars and second superior premolars of 30 volunteers. The volunteers were divided into two groups that received bleaching or the placebo agent at different sequences and periods at a double blind 2 x 2 crossover study with a wash-out period of two weeks. Microhardness tests were performed on the enamel and dentin surface. The SE and DE submitted to treatment with OPA showed lower microhardness values than the SE and DE submitted to treatment with PLA. There were no statistical differences in microhardness values for SD and DD submitted to the treatment with OPA and PLA. The results suggest that treatment with 10% carbamide peroxide bleaching material for three weeks alters the enamel microhardness, although it does not seem to alter the dentin microhardness.     

Effect of carbamide peroxide and hydrogen peroxide on enamel surface: an in vitro study

The aim of the study was to investigate changes in the micromorphologyl and microhardness of the enamel surface after bleaching with two different concentrations of hydrogen peroxide (HP) and carbamide peroxide (CP). Bovine enamel samples were embedded in resin blocks, and polished. Specimens in the experimental groups (n = 10) were treated with bleaching gels containing 10% CP, 35% CP, 3.6% HP, and 10% HP, respectively, for 2 h every second day over a period of 2 weeks. The gels had the identical composition and pH and differed only in their HP or CP content. The roughness and morphology of the enamel surface were analyzed using laser profilometry and SEM. Microhardness was measured using a Knoop hardness tester. The data were evaluated statistically. Specimens in the 10% HP group showed significantly higher roughness after bleaching compared to the control group (ΔRa, p = 0.01). Bleaching with 35% CP showed only a tendency to increase roughness (ΔRa, p = 0.06). Application of 10% CP or 3.6% HP had no significant influence on Ra. Enamel microhardness was significantly higher after application of 10% HP compared to the control (ΔMic = 8 KHN, p = 0.0002) and 35% CP (ΔMic = 20KHN, p = 0.01) groups. In summary, application of CP and HP showed only small quantitative and qualitative differences. In addition, the influence of bleaching procedure on the morphology and hardness of the enamel surface depended on the concentration of the active ingredients.