Effect of non-vital tooth bleaching on microleakage of coronal access restorations

This study evaluated the effect of non-vital tooth bleaching on microleakage of composite resin/bovine tooth interface at different post-bleaching times. A total of 320 teeth were cleaned. A pulp chamber access cavity was made at the lingual surface of each tooth. The teeth were randomly divided into four groups: SPH - sodium perborate + 30% hydrogen peroxide; SPW - sodium perborate + distilled water; CP-37% carbamide peroxide; and CON-distilled water (control). The bleaching agents were replaced every 7 days, over 4 weeks. Following bleaching procedures, the groups were divided into four subgroups (n = 20), according to the post-bleaching times: 0 (baseline), 7, 14 and 21 days. After that, the cavities were restored with an adhesive system (Single Bond; 3M Co., St Paul, MN, USA) and a composite resin (Z100/3M). The specimens were thermocycled, stained with 2% methylene blue solution (pH 7), and sectioned longitudinally. The teeth were evaluated blind and independently by three previously calibrated examiners, to provide representative scores. The data were submitted to Kruskal-Wallis and multiple comparison tests (alpha=0.05). At baseline and 7 days, the SPH group showed a higher degree of dye penetration than the CON (P=0.04). At 14 and 21 days, there were no differences among groups. The association of sodium perborate with 30% hydrogen peroxide or with water may affect the sealing ability of composite resin restorations performed up to 7 days after bleaching procedures.     

漂白后牙本质颜色改变对牙齿体部与颈部颜色变化不同的影响研究

目的:探讨漂白后牙齿体部与颈部颜色变化不同的原因。方法:将36个新鲜拔除的人前磨牙沿唇(颊)舌方向中央剖开、去髓,随机分成3组,联合漂白组(A):380 mL/L过氧化氢(HP)45 min/d×1次+150 g/L过氧化脲(CP)8 h/d×4次;诊室漂白组(O):380 mL/L过氧化氢(HP)45 min/d×2次;家庭漂白组(H):150 g/L过氧化脲(CP)8 h/d×14次。3组分别于漂白前、后用Crystaleye电脑比色仪测量牙齿唇(颊)面靠近剖面中线区体部、颈部及相对应剖面靠近釉牙本质界牙本质漂白前后的ΔE值。结果:3种漂白方案疗程结束后,体部、颈部牙齿颜色及与其对应的剖面牙本质均出现了颜色变浅(P﹤0.05),但体部牙齿颜色改变程度超过颈部(P<0.05)。体部、颈部牙本质颜色改变无显著性差异(P>0.05);体部、颈部牙齿表面与其分别对应的剖面牙本质颜色改变无显著性差异(P>0.05)。结论:漂白剂对牙本质的颜色改变不受釉质厚度的影响。牙本质颜色变化和漂白后体部、颈部牙齿表面颜色变化不相关。牙齿体部颜色改变慢于颈部可能是体部釉质厚度大于颈部及半透明性改变产生的。     

Effect of internal bleaching agents on dentinal permeability of non-vital teeth: quantitative assessment

Abstract  – The aim of this in vitro study was to assess quantitatively dentin permeability of pulpless teeth after intracoronal bleaching therapy with three different agents. Twenty-four maxillary central incisors were randomly assigned to four groups according to the bleaching agent used: I – non-bleached control; II – 37% carbamide peroxide; III – sodium perborate/20% hydrogen peroxide paste; IV – 27% carbamide peroxide. After standard access and root-canal preparation the access opening, biomechanical preparation and root-canal filling, a cervical glass ionomer plug was prepared and intracoronal bleaching procedures were carried out in a standardized fashion. The access cavities were opened and the teeth were externally sealed and immersed in a 10% copper sulfate aqueous solution for 30 min, in vacuum for the first 5 min. Then, samples were removed, dried with absorbing paper and immersed in a 1% rubianic acid alcohol solution, for the same above-mentioned period in solution and in vacuum. Copper ion penetration was indicated by the rubianic acid staining. Mean values and SD for the experimental groups were: I – 7.88% (±1.33), II – 16.94% (±5.72); III – 11.45% (±3.90) and IV – 8.98% (±4.19). Data were submitted to one-way anova . The results showed that the 37% carbamide peroxide provided the highest increase in dentin permeability, followed by sodium perborate with 20% hydrogen peroxide. The 27% carbamide peroxide provided the lowest results and showed statistical similarity to the control group. On basis of these findings, it may be concluded that, among the tested intracoronal bleaching agents, 37% carbamide peroxide presented an optimized overall performance in increasing dentinal permeability.     

Microleakage effect on class V composite restorations with two adhesive systems using different bleaching methods

Abstract

Objective. The main objective of this study was to evaluate the effects of an at-home and two in-office (chemically activated and KTP laser-activated) bleaching methods on the microleakage of composite resin restorations bonded with etch-and-rinse and self-etch adhesive systems. Materials and methods. Class V cavity preparations were performed on 96 premolars and teeth were divided into two groups according to the two adhesive systems (etch-and-rinse and self-etch). After cavities were restored with an adhesive systems and composite resin, they were submitted to thermocycling procedures. Teeth were divided into four sub-groups according to the bleaching systems (control, at-home bleaching, chemically activated office bleaching and KTP laser-activated office bleaching). After the bleaching procedure, teeth were evaluated for marginal leakage. All data were analyzed using the Mann-Whitney U and Kruskal-Wallis tests (p < 0.05). Results. The results of the present study showed that the control group presented lower microleakage values compared with the groups treated with bleaching agents, except for the chemically activated in-office bleaching. When the scores of microleakage at the enamel and gingival margins of the four groups were compared, the differences among the groups were found to be statistically significant (p < 0.05). Comparing the gingival and enamel margins in each group, statistically significant differences were found in the at-home group (p < 0.05) and no significant differences were seen in the other groups (p > 0.05). No significant difference was found between the adhesive systems after treatment with the same bleaching techniques. Conclusion. Under the conditions of this study, microleakage of composite resin restorations differs according to the bleaching methods used and no difference was found between the adhesive systems.     

不同操作模式的加热恒温漂白对健康自然牙漂白效果的临床评价

目的对不同操作模式的加热恒温漂白效果进行临床评价。方法 12名受试者分2组接受2种不同操作模式的加热恒温漂白治疗,包括在一次就诊时连续漂白操作3次(A)以及分为3次就诊,间隔1天,每次就诊漂白操作1次(B)。以牙科色度计测定各次操作之后以及漂白术完成1周后受试者上中切牙的颜色参数值,并计算相应的白度值和色差值。结果不论何种操作模式,漂白术后牙色的L*值提高,b*值降低。操作模式A术后1周与B各次操作后及术后1周获得的色差值之间并无统计学差异。操作模式A术前与术后1周的白度值之间存在显著性差异。操作模式B术前与第1次、第2次、第3次及术后1周的白度值之间存在显著性差异。结论两种操作模式下加热恒温漂白均可导致健康上中切牙发生亮度增加以及蓝色转变的颜色变化。     

一种实用的牙齿漂白技术

将国际公认的牙齿漂白药物过氧化脲加入无毒高分子成膜剂配成胶状液 ,涂于干燥牙面1— 2分钟形成附着于牙面的薄膜 ,可维持 1小时以上。此期间过氧化脲分解释放新生氧而将牙齿漂白。临床研究表明 :牙齿增白涂膜是一种安全、有效、实用的漂白牙齿方法。本产品已获中国专利 (专利号 :96 1186 0 5.4 ,PCT/ CN97/ 0 0 0 0 4 )     

Effect of concentrated hydrogen peroxide solution on the surface morphology of cut human dentin

Abstract The effect of concentrated hydrogen peroxide solution, alone and in combination with acid-etching with 37% phosphoric acid for 60 s, on the surface morphology of cut human dentin was investigated by SEM and compared to controls in which saline solution rather than hydrogen peroxide solution was used. Examination of the specimens revealed that the smear layer on the surface of cut dentin was not removed by hydrogen peroxide alone, and that a dense amorphous precipitate was formed on the surface of the smear layer after extended exposure. The precipitate accumulation was first noted after 20 min of exposure. Examination of the dentin after hydrogen peroxide exposure followed by acid-etching revealed the presence of a fine granular deposit on an otherwise clean dentin surface. A modest amount of amorphous precipitate was seen over the entire dentin surface after 60 min of hydrogen peroxide exposure. Examination of specimens that were acid-etched before being exposed to hydrogen peroxide indicated that the smear layer was effectively removed and the orifices of the dentinal tubules were enlarged to permit more effective penetration of the peroxide solution. It also resulted in less accumulation of precipitate on the dentin surface than the other methods.     

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目的评价不同漂白方法对氟斑牙漂白的临床效果。方法轻中度氟斑牙患者30例随机分为3组,每组10例60颗牙。分别采用联合漂白、激光漂白、家庭漂白3种方法进行上前牙区漂白,在漂白前、漂白后即刻、漂白后1个月、漂白后1年记录其L＊a＊b＊值,比较3组漂白效果及颜色回复情况。应用统计学分析软件CS10.34对数据进行t’检验。结果 3组漂白后的L＊a＊b＊值与漂白前比较差异均有统计学意义（均P〈0.05）;漂白后1个月,联合组与激光组颜色有所回复（P〈0.05）;漂白后1年,联合组、激光组颜色与漂白后即刻相比有所回复（P〈0.05）,与漂白后1个月相比颜色回复差异无统计学意义（P〉0.05）;家庭组颜色回复差异无统计学意义,但1个月到1年期间颜色变化小于治疗后即刻到1个月的变化（P〈0.05）。结论 3种漂白方案治疗1个疗程都得到相似的美白效果,但短期内也出现漂白牙的颜色回复,家庭漂白颜色相对稳定,诊室漂白收效快,3种治疗方案各有其适应人群。     

Efficacy of different whitening modalities on bovine enamel and dentin

Previous studies have shown that bleaching treatment may be efficient in both enamel and dentin, but it is still unknown how much the subsurface dentin contributes to the color change of teeth. This in vitro study evaluated the whitening effect of different external bleaching agents on enamel-dentin slabs and subsurface dentin. Ninety bovine teeth were distributed among six groups (A, Opalescence 10%; B, Opalescence PF 15%; C, Opalescence Quick; D, Opalescence Extra Boost; E, Rapid White; F, Whitestrips). Two enamel-dentin specimens were prepared from the labial surface of each teeth. In one of the specimens enamel was removed, resulting in a dentin (CD) disc of 1 mm high. The labial and the pulpal sides of the second specimen were ground until the remaining enamel and dentin layers of the enamel-dentin sample (ED) were 1 mm each. Whitening treatment of the ED specimens was performed according to manufacturers instructions. Pre- and posttreatment Lab values of ED samples were analyzed using CIE-Lab. Baseline Lab values of dentin were analyzed by evaluation of the CD specimen. Finally, enamel of the ED specimens was removed and color change of the exposed dentin (D) was recorded. For all treatment agents significant color changes (E) were observed for enamel-dentin samples and subsurface dentin specimens compared to controls. In groups A–D E was significantly higher in dentin than enamel-dentin. Furthermore, L and b values of bleached enamel-dentin and subsurface dentin samples differed significantly from baseline. Treatment with the tested external whitening bleaching agents resulted in color change of both enamel-dentin and subsurface dentin samples. The results indicate that color change of treated teeth might be highly influenced by color change of the subsurface dentin.     

冷光美白技术与夜间活髓牙脱色技术协同漂白四环素牙的临床研究

目的评价冷光美白技术与夜间活髓牙脱色技术（NGVB）协同治疗四环素牙的临床效果。方法将90名四环素牙患者根据四环素牙着色的轻、中、重度随机分入治疗组、对照1组、对照2组,其中治疗组30名患者472颗四环素牙,采用冷光美白技术与NGVB对四环素牙进行漂白;对照1组30名患者466颗四环素牙,采用冷光美白技术对四环素牙进行漂白;对照2组30名患者469颗四环素牙,采用NGVB对四环素牙进行漂白。在治疗结束时、治疗结束半年及1年时采用Vitalescence美学修复比色板对四环素牙进行比色,记录牙齿漂白前后的色阶变化及疗程,计算治疗有效率,并评价疗效稳定性。结果1）3组患者轻度四环素牙治疗后均有较好的牙色改善,美白有效率均为100%;治疗组与对照2组中、重度四环素牙治疗后牙色改善及美白有效率好于对照1组（P<0.05）,治疗组与对照2组间无统计学差异（P>0.05）,但治疗组轻、中、重度四环素牙的治疗疗程较对照2组分别缩短了43%、46%和49%。2）3组患者轻、中、重度四环素牙的美白疗效依次减弱（P<0.05）。3）对照1组半年后及1年后的美白有效率与治疗结束时有统计学差异（P<0.01）,而治疗组和对照2组半年后及1年后的美白有效率与治疗结束时无统计学差异（P>0.05）。结论冷光美白技术与NGVB协同治疗轻、中度四环素牙可以在较短的疗程内取得令人满意的美白效果,并提高美白效果的长期稳定性。     

Effects of carbamide peroxides on wear resistance and color change of enamel opposing porcelain

PURPOSE: This study evaluated the effects of a simulated 1- and 2-week night guard bleaching technique using various bleaching gel concentrations on wear resistance and color change of human enamel opposing a feldspathic porcelain substrate. MATERIALS AND METHODS: VMK 68 feldspathic porcelain was formed into 15-mm disks (n = 63) and fired according to manufacturer's recommendations. Enamel cusps were formed and shaped from extracted third molars and treated with 1 of 3 bleaching materials for 7 or 14 days. Specimens were kept at 37 degrees C in 100% humidity. The control group was subjected to identical conditions but with water replacing the bleaching gel between and during bleaching treatments. After simulated bleaching, the enamel cusp specimens were subjected to 3-body wear testing opposite a highly polished porcelain substrate. Enamel wear was evaluated using optical scanning methods, and color was measured with a small-aperture colorimeter. Data were subjected to a one-way repeated- measure analysis of variance and various post hoc statistics. RESULTS: Results indicated that the within effect of treatment time (7 or 14 days) did not significantly affect (p = 0.13) the size of the resulting enamel wear facet, whereas the between effect of bleaching concentration was significant (p = 0.01). Statistical analysis of unbleached control groups suggests that between-group differences can be explained by variations in wear rates of the 3 enamel groups, not by the concentration differences in bleaching gels. All bleaching treatments resulted in significant color changes (p = 0.04) compared to the unbleached control, but the bleach concentration did not significantly influence the magnitude of color change (p = 0.81). CONCLUSIONS: A simulated night guard vital bleaching treatment of 1 or 2 weeks had no significant effect on the wear resistance of human enamel in vitro. The increased bleaching treatment time and concentration did not significantly affect the amount of enamel color change.     

In vitro evaluation of the cytotoxicity of a bleaching agent

Abstract— Cell cultures of L929 and BHK21/C13 cells were used to evaluate the toxicity of a newly introduced bleaching agent (Colgate Platinum) compared to hydrogen peroxide, an established bleaching agent. The cell reaction was determined by a quantitative technique at 24 h and 72 h. Both bleaching materials had a dose-dependent effect on cell viability. Concentrations of hydrogen peroxide causing a 50% decrease in cell number (50% inhibition dose-ID_Jo) were calculated as 0.00034% after 24 h and 0.00001% after 72 h in L929 cells. The ID₅₀ of hydrogen peroxide was found to be 0.00016% after 24 h and 0.00007% after 72 h in BHK21/ C13 cells. The ID₅₀ of Colgate Platinum was 0.00074% after 24 h and 0.00045% after 72 h in L929 cells and 0.00055% after 24 h and 0.00024% after 72 h in BHK21/C13 cells. The results showed that, in vitro , both bleaching agents were cytotoxic to fibroblasts and the new bleaching agent was less toxic than hydrogen peroxide.     

外漂白对牙体硬组织影响的研究进展

外漂白是牙美白的主要方法之一。外漂白是否会造成牙体硬组织的破坏以及破坏程度如何一直是人们关注的话题。本文从漂白后牙体硬组织的表面形态、矿物含量改变方面对外漂白对牙体硬组织的影响作一综述。     

Clinical comparison of two self-directed bleaching systems

PURPOSE: This randomized clinical trial compared the clinical efficacy and tolerability of 2 marketed self-directed vital tooth-whitening systems. MATERIALS AND METHODS: Balancing for baseline tooth color, self-reported coffee/tea use, and age, 57 adult volunteers were randomized to either a whitening strip containing 6% hydrogen peroxide or a tray-based 10% carbamide peroxide/dentifrice/mouth rinse combination system. Following the manufacturer's directions, the strip group bleached twice daily for 30 minutes, whereas the tray group bleached twice daily for 20-30 minutes, preceded by tooth brushing with a whitening dentifrice and followed by mouth rinsing with a whitening solution. Treatment extended for 14 days, with evaluation at day 7 and again at day 14. Whitening response was measured objectively as L*a*b* from standardized digital images of maxillary anterior teeth. Tolerability was assessed by oral examination and subject interview. Efficacy comparisons were made using analysis of covariance, whereas tolerability was compared using the nonparametric Wilcoxon rank-sum test. RESULTS: Both treatments resulted in statistically significant (P < 0.01) improvements from baseline for all color parameters. For between-group comparisons, the 6% hydrogen peroxide strips yielded a nearly 3-fold reduction in yellowness (deltab*), a nearly 2-fold improvement in lightness (deltaL*), 2.6 times greater redness reduction (deltaa*), and a more than 2-fold change in overall color (deltaE*) compared to the tray-based combination system. Between-group comparisons were statistically significant for the all color parameters at both the day 7 and day 14 evaluations (P < 0.001). In general, 7-day use of the whitening strips provided significantly greater color improvement relative to the combination dentifrice/gel/rinse system at day 14. In addition, the groups differed significantly (P < 0.05) in bleaching tolerability severity-days, with the strip system demonstrating better overall tolerability compared to the combination system. CONCLUSIONS: The single-step 6% hydrogen peroxide strips demonstrated better overall clinical response, in terms of both tooth-whitening efficacy and tolerability, than the multiple-step tray-based combination system.     

国产美白胶对牙齿白色度的影响

目的评价美白胶漂白剂对离体牙色度的影响，确定其漂白效果是否可靠。方法采用白色度参数为检验指标，用数字摄影连续记录离体牙表面及其剖面在使用美白胶以及另外2种漂白剂时的颜色变化，使用图像处理软件记录牙体组织的L＊a＊b＊值，并按照白色度W（Lab）=100-[（100-L）^2＋a^2＋b^2]^1/2。的公式计算出各实验对象在漂白前后以及漂白过程当中的白色度。计算所得结果进行配对T检验以及单因素方差分析。结果关白胶与作为对照组的Poladay、PolaOffice均使牙齿表面及剖面的白色度明显上升，在使牙齿白色度增加幅度上关白胶与Poladay（过氧化氢7．5％）相同。且高于PolaOffice（过氧化氢35％）。剖面观肉眼未见美白胶导致牙体硬组织透明性改变。结论美白胶作为牙齿漂白剂效果可靠，同时本实验证明美白胶与其它牙齿漂白剂均可以快速渗透到牙体硬组织内部。对全层组织发挥作用。     

Effect of bleaching versus repolishing on colour and surface topography of stained resin composite

Background: The aim of this study was to examine the effect of ozonated gel, carbamide peroxide bleaching agent and polishing paste on the colour and surface topography of stained resin composite. Methods: Ninety disc‐shaped resin composite specimens were used in this study. They were randomly divided into three groups of 30 specimens each according to the immersion solutions used, i.e., tea, cola or artificial saliva. Each group was further subdivided into three equal subgroups (n = 10) according to the type of whitening treatment applied; 30% carbamide peroxide, ozonated KY gel or polishing paste. Colour and surface roughness was measured at baseline, after immersion, also following whitening procedures by using a stereomicroscope. The results were recorded, tabulated and statistically analysed. Results: The colour values of artificial saliva displayed the highest statistically significant mean colour difference compared to cola and tea. However, there was no statistically significant difference in surface roughness. Also, a superior whitening effect was demonstrated with ozonated gel. Ozonated gel showed statistically significant lowest roughness compared to both carbamide peroxide and polishing paste. Conclusions: Immersion solutions have a positive influence on the colour of resin composite. Also, ozonated gel is an efficient bleaching agent with the least adverse effect on surface roughness.     

Sealing evaluation of the cervical base in intracoronal bleaching

Abstract –  Discoloration of non-vital teeth is an esthetic deficiency frequently requiring bleaching treatment. The purpose of this study was to evaluate in vitro the cervical base efficacy in order to prevent or to minimize the leakage along the root canal filling and into the dentinal tubules. Thirty-eight extracted single-root human teeth were used, which were biomechanically prepared, filled, and divided into three experimental groups: G1, a cervical base was applied (3 mm of thickness) below the cemento-enamel junction, with resin-modified glass-ionomer cement (Vitremer); G2, the base was done with glass-ionomer cement (Vidrion R); and G3 (Control), did not receive any material as base. A mixture of sodium perborate and hydrogen peroxide 30% was placed inside the pulp chamber for 3 days, and the access opening was sealed with Cimpat. This procedure was repeated thrice. Soon after this, a paste of calcium hydroxide was inserted into the pulp chamber for 14 days. All teeth were covered with two layers of sticky wax, except the access opening, and immersed in blue India Ink for 5 days. The results did not show statistically significant differences between the three groups concerning the leakage inside the dentinal tubules. Regarding the apical direction, a statistical difference ( anova P  < 0.05) was observed among the experimental group G1 and control group G3. No statistically significant difference was observed between G2 and G3 groups. Therefore, the placement of a cervical base before internal bleaching procedures is still recommended.