Characterization by electron spin resonance spectroscopy of reactive oxygen species generated by titanium dioxide and hydrogen peroxide

The influence of reactive oxygen species (ROS) on the surface modification of titanium implants and osseointegration is unclear. The aim of this study was to evaluate the ability of titanium dioxide (TiO2) to generate ROS in the presence of H2O2 and to determine whether any ROS thus generated play a role in osseointegration, as measured by electron spin resonance (ESR) spin-trapping with 5,5-dimethyl-1-pyrolline-N-oxide (DMPO). We demonstrate that TiO2 together with H2O2 generated hydroxyl radicals (HO*), as shown by a time-dependent increase in the spin concentration of the ESR signal for the DMPO-OH spin adduct, indicating HO* generation. Interestingly, irradiated TiO2 with H2O2 generated the superoxide (O2*-), as shown by an increase in the spin concentration of the signal for the DMPO-OOH spin adduct, indicating O2*- generation during the period of irradiation (0-5 min). These results suggest that ROS generated from the TiO2 layer may be involved in creating appropriate conditions for the osseointegration of dental implants into alveolar bone tissues.     

微弧氧化法在纯钛表面生成含羟基磷灰石陶瓷膜的研究

目的：利用微弧氧化法在纯钛表面直接生成含羟基磷灰石的陶瓷膜。方法：通过微弧氧化技术,采用双相脉冲电源,以0．4mol／L醋酸钙和0．2mol／L磷酸二氢钠为电解液体系,设定脉冲频率为60Hz,正相电流密度为20A／dm^2,处理时间分别为5rain、10min、20min、30min、60min,在纯钛表面制备陶瓷膜。利用扫描电镜观察膜层的表面形貌,能谱仪分析氧化膜的元素组成,X射线衍射仪分析膜层的相组成,电涡流涂层测厚仪测量膜层的厚度。结果：以0．4mol／L醋酸钙和0．2mol／L磷酸二氢钠为电解液体系,经微弧氧化处理后,在纯钛表面形成含有Ti、O、Ca和P元素的微孔结构的氧化膜,该膜由锐钛矿型TiO2、金红石型TiO2及羟基磷灰石组成。随微弧氧化反应时间的延长,膜层增厚,膜层表面微孔孔径增大,数量减少,粗糙度增大。钛元素的相对含量减少,Ca、P元素相对含量增加,O元素变化不明显。钛、锐钛矿型TiO2和金红石型TiO2的衍射峰逐渐减弱,羟基磷灰石的衍射峰逐渐增强。结论：应用微弧氧化技术,以0．4mol／L醋酸钙和0．2mol／L磷酸二氢钠为电解液体系,在纯钛表面能直接生成含有羟基磷灰石成份的微孔结构的陶瓷膜。     

Reactive oxygen species participation in experimentally induced arthritis of the temporomandibular joint in rats

In the temporomandibular joint (TMJ), it has been hypothesized that mechanical stresses lead to the oxidative stress of articular tissues. It has also been postulated that cells pertinent to arthritis-including endothelial cells and synovial cells-when stimulated by mechanical stresses and/or pro-inflammatory cytokines, promote oxidative damage. To determine the involvement of reactive oxygen species (ROS) in the diseased joint, we studied the generation of ROS in synovial fluid (SF) from interleukin-1alpha (IL-1alpha)-induced TMJ arthritis by electron spin resonance (ESR) spectroscopy, using the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The TMJ arthritis was experimentally induced in rats by the injection of human recombinant IL-1alpha into the TMJ; control rats were treated with normal saline solution. We found that the detected radicals in the collected SF were identified as a 1:2:2:1 quartet, characteristic of the hydroxyl radical-DMPO spin adduct. The ESR signal intensity of the hydroxyl radical-DMPO spin adduct in the SF from IL-1-treated rats was significantly higher than that from the control rats (P < 0.01). The results of ESR study also showed that hydroxyl radical (HO*) was increased in a time-dependent fashion in the presence of superoxide anion radical (O2*-) scavenger superoxide dismutase (SOD); the formation of DMPO-HO* was strongly inhibited by the iron chelater deferoxamine. We could measure higher levels of free iron (Fe2- and Fe3-) in the SF from TMJ arthritis than in that from controls (P < 0.05). Analysis of the data obtained from the present study suggests that the HO* radical detected in SF from IL-1-induced TMJ arthritis is generated via a modified Haber-Weiss reaction (biological Fenton reaction) in which O2*- can subsequently result in the production of H2O2 through dismutation reaction by SOD. Thus, HO* may be generated from the reaction of resultant H2O2 with free iron ions. The results presented here provide the first evidence of involvement of ROS in IL-1-induced TMJ arthritis.     

Hydrogen peroxide tooth-whitening (bleaching) products: review of adverse effects and safety issues

Hydrogen peroxide in the form of carbamide peroxide is widely used for tooth whitening (bleaching), both in professionally- and in self-administered products. Adverse effects have become evident. Cervical root resorption is a possible consequence of internal bleaching and is more frequently observed in teeth treated with the thermo-catalytic procedure. Tooth sensitivity is experienced in 15-78% of patients undergoing external tooth bleaching. However, clinical studies addressing other adverse effects are lacking. Direct contact with hydrogen peroxide induces genotoxic effects in bacteria and cultured epithelial cells, but the effect is reduced or totally abolished in the presence of metabolising enzymes. Several carcinogenesis studies, including the hamster cheek pouch model, indicate that hydrogen peroxide (H(2)O(2)) might possibly act as a promoter. Until further clinical research is concluded to address the question of possible carcinogenicity, it is recommended that: tooth-bleaching products using concentrated H(2)O(2) should not be used without gingival protection; that H(2)O(2) containing products should be avoided in patients with damaged or diseased soft tissues. For nightguard vital bleaching, minimal amounts of low dose H(2)O(2) (including in the form of carbamide peroxide) are preferred, thereby avoiding prolonged and concentrated exposures.     

钴铬合金表面铁离子掺杂二氧化钛膜的制备

目的在钴铬合金表面制备Fe3+掺杂二氧化钛薄膜。方法采用溶胶-凝胶法在钴铬合金表面制备Fe3+掺杂二氧化钛膜,利用扫描电镜、原子力显微镜、X射线衍射仪、傅立叶红外光谱仪、X射线能谱仪分别表征薄膜的表面和横断面形貌、晶相结构及元素成分,并通过划痕法和磨损实验测试膜基结合强度及薄膜的耐磨性。结果钴铬合金试样表面形成一层厚约267~310 nm、平整致密的金黄色透明薄膜,薄膜成分为锐钛矿型二氧化钛,其主要元素成分有O、Ti、Fe。膜基结合力平均值为68.37 N,同等磨损实验条件下,镀膜试样的失重量约为未镀膜者的2/5。结论溶胶-凝胶法在钴铬合金表面制备Fe3+掺杂二氧化钛薄膜光滑平整,具有良好的膜基结合力与临床应用价值。     

Antioxidant and pro-oxidant properties of chlorhexidine and its interaction with calcium hydroxide solutions

AIM: To evaluate the antioxidant and pro-oxidant properties of chlorhexidine (CHX). METHODOLOGY: The scavenging and generation of reactive oxygen species (ROS) by CHX in the presence or absence of saturated Ca(OH)(2) solutions was evaluated. The reaction emitted chemiluminescence in the presence of lucigenin thus was determined by a luminometer to evaluate the levels of ROS production. Changes in DNA conformation were analysed by agarose gel electrophoresis. Paired Student's t-test was used to compare the difference between groups. RESULTS: Chlorhexidine (0.00002-0.02%) effectively scavenged 56-88% of the superoxide radicals generated by the xanthine/xanthine oxidase reaction. Through analysis of PUC18 DNA conformation changes, CHX was shown to be a mild scavenger of hydroxyl radicals generated by H(2)O(2) plus FeCl(2). However, CHX (>0.083%) decreased the mobility of PUC18 plasmid DNA with potential production of DNA-DNA cross-link and severe DNA breaks (presence of DNA smear) at further higher concentrations. Furthermore, CHX induced ROS production including H(2)O(2) and superoxide radicals in 0.1N NaOH (pH = 12.76) or Ca(OH)(2) (pH = 12.5) solutions. CONCLUSION: Chlorhexidine exhibited both antioxidant and pro-oxidant properties under different conditions. These events are possibly involved in the killing of root canal and periodontal microorganisms when CHX and Ca(OH)(2) were used in combination or separately. Potential genotoxicity and tissue damage when extruded into the periradicular tissue and at higher concentrations should be considered during periodontal and endodontic practice.     

Determination of reactive oxygen species generated by phorbol 12-myristate 13-acetate-stimulated oral polymorphonuclear cells from healthy human volunteers without any dental problems

Human oral polymorphonuclear cells (OPMNs) play an important role in the defence of oral cavity from bacteria by releasing reactive oxygen species (ROS). The purpose of the study is to determine ROS generated by OPMNs collected from healthy volunteers without any dental problems by applying a luminol analogue 8-amino-5-chloro-7-phenylpyrido[3,4-d]pyridazine-1,4-(2H,3H)dione sodium salt-dependent chemiluminescence (CL) response in combination with radical and ROS scavengers. In the CL response induced by OPMNs primed with phorbol 12-myristate 13-acetate, 0.23 M 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap, 12.5 U/ml of super oxide dismutase (SOD) as a superoxide anion (O(2)(·-)) scavenger, and 0.96 M dimethyl sulfoxide (DMSO) as a hydroxyl radical ((·)OH) scavenger inhibited the response by approximately 90%, 70%, and 60%, respectively. The inhibitory effects were obtained in a range of concentrations where viability of the OPMNs exposed to DMPO, SOD, and DMSO were more than 70%. Electron spin resonance-spin trapping analysis confirmed that at least O(2)(·-) and (·)OH were generated via primed OPMNs. Furthermore, the addition of both 12.5 U/ml of SOD and 0.96 M DMSO inhibited the CL response by more than 90%, which was in accordance with the inhibition rate obtained by the addition of DMPO. Therefore, it is suggested that around 90% of the CL response is induced by free radicals, and at least around 70% of the radicals are SOD-inhibitable, meaning that they are originally derived from O(2)(·-). In addition, some of the (·)OH are generated independently of O(2)(·-) because if all of the (·)OH were formed through dismutation of O(2)(·-), only 70% of the CL response would be inhibited by the combination of SOD and DMSO as was inhibited by SOD alone. The present study suggests that OPMNs in health individuals have an ability to generate free radicals, which consist mainly of O(2)(·-), (·)OH and possibly an intermediate ROS derived from O(2)(·-) and (·)OH.     

Manganese oxide increases bleaching efficacy and reduces the cytotoxicity of a 10% hydrogen peroxide bleaching gel

Clinical Oral Investigations - The study aims to assess the effects of a 10% H2O2 bleaching gel with different MnO2 concentrations on the bleaching efficacy (BE), degradation kinetics (DK) of H2O2,...     

Bleaching using 30% hydrogen peroxide and sodium hydrogen carbonate

This study investigated the bleaching efficacy of a mixture of sodium hydrogen carbonate (NaHCO(3)) and 30% hydrogen peroxide (H(2)O(2)), the latter being an active ingredient in in-office bleaching products. A commercially available 35% H(2)O(2)-based in-office bleaching product was used as a control and for comparison. Enamel surfaces after bleaching were evaluated for post-bleaching color change, Vickers hardness, surface roughness, erosion depth, and surface morphology (SEM images). The bleaching efficacy of 30%H(2)O(2)-NaHCO(3) was comparable to that of control, and favorable results over the control were obtained after bleaching with 30%H(2)O(2)-NaHCO(3), lower increase in surface roughness, smaller erosion depth, and reduced extent of enamel erosion based on SEM images. These results were obtained because an addition of NaHCO(3) to H(2)O(2) changed the initially low pH to a higher one.     

Additive effects of TEGDMA and hydrogenperoxide on the cellular glutathione content of human gingival fibroblasts.

OBJECTIVES: Only few data are available about cytotoxic effects of leachable dental resin compounds in combination with hydrogen peroxide (H(2)O(2)) segregated from dental bleaching agents. Therefore, the purpose of this study was to evaluate the effects of various concentrations of triethylene-glycol dimethacrylate (TEGDMA) and H(2)O(2) on intracellular glutathione levels (GSH) and viability of human gingival fibroblasts (HGF) that are primary target cells of cytotoxic actions of these substances. METHODS: HGF were grown in 96-well plates for 24h, treated with various concentrations of TEGDMA (0.5-5.0mM) for 24h and subsequently for 90min with 0.2mM H(2)O(2) or culture medium (control). The relative intracellular GSH concentration was determined using a fluorescence assay with monobromobimane. Readings were normalized to cell numbers, which were determined by a propidium iodide assay. Data were statistically analyzed by t-test and ANOVA with Tukey's post test. A significance level of p<0.05 was used. RESULTS: Exposure to TEGDMA reduced the viability of HGF at concentrations > or =1.0mM. TEGDMA induced a decrease of the GSH pool in a concentration-dependent manner (p<0.05). The depletion of GSH was correlated with a reduction of viability (p<0.05) and the total cell number. Furthermore, a significant decrease of the intracellular GSH content was found when cells were exposed to TEGDMA in combination with H(2)O(2), compared to experiments without H(2)O(2). SIGNIFICANCE: We conclude from our findings that TEGDMA and H(2)O(2) have additive adverse effects on GSH metabolism and cell viability.     

Heme oxygenase‐1 mediates nicotine‐ and lipopolysaccharide‐induced expression of cyclooxygenase‐2 and inducible nitric oxide synthase in human periodontal ligament cells

Pi S‐H, Jeong G‐S, Oh H‐W, Kim Y‐S, Pae H‐O, Chung H‐T, Lee S‐K, Kim E‐C. Heme oxygenase‐1 mediates nicotine‐ and lipopolysaccharide‐induced expression of cyclooxygenase‐2 and inducible nitric oxide synthase in human periodontal ligament cells. J Periodont Res 2010; 45: 177–183. © 2010 John Wiley & Sons A/S Background and Objective: Although heme oxygenase‐1 (HO‐1) plays a key role in inflammation, its anti‐inflammatory effects and mechanism of action in periodontitis are still unknown. This study aimed to identify the effects of HO‐1 on the proinflammatory mediators activated by nicotine and lipopolysaccharide (LPS) stimulation in human periodontal ligament (PDL) cells. Material and Methods: The production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) was evaluated using Griess reagent and an enzyme immunoassay, respectively. The expression of inducible nitric oxide synthase (iNOS), cyclooxygenase‐2 (COX‐2) and HO‐1 proteins was evaluated by Western blot analysis. Results: Lipopolysaccharide and nicotine synergistically induced the production of NO and PGE₂ and increased the protein expression of iNOS, COX‐2 and HO‐1. Treatment with an HO‐1 inhibitor and HO‐1 small interfering RNAs blocked the LPS‐ and nicotine‐stimulated NO and PGE₂ release as well as the expression of iNOS and COX‐2. Conclusion: Our data suggest that the nicotine‐ and LPS‐induced inflammatory effects on PDL cells may act through a novel mechanism involving the action of HO‐1. Thus, HO‐1 may provide a potential therapeutic target for the treatment of periodontal disease associated with smoking and dental plaque.     

Development of in vitro tooth staining model and usage of catalysts to elevate the effectiveness of tooth bleaching.

OBJECTIVES: Whole blood or tea was frequently used to stain the teeth for measuring the effectiveness of different bleaching materials. However, the components of blood or tea cannot be quantitatively determined and variability might exist among different brands of tea. The purpose of this study was to develop a reproducible in vitro tooth-staining model to simulate the intrinsic discoloration of teeth and evaluate the ability of two catalysts to enhance the bleaching activity of H(2)O(2). METHODS: Rhodamine B, Orange II, Fe(III) phthalocyanine, and tea were used to stain the tooth specimens for 4-72 h and subsequently bleached by H(2)O(2) for 4-72 h. The process was photographed using a digital stereoscopic microscope and a digital camera. The image was transformed to get L*, a*, b* values of CIE Lab system with image processing software. The catalytic ability of light irradiation plus addition of Fe/Sodium-Y or Mn/Sodium-Y for specimens stained by Orange II was evaluated in test tubes and in extracted tooth model. RESULTS: The color of specimens stained by Rhodamine B could not be sufficiently recovered after bleaching by H(2)O(2). In addition, the reaction of Fe(III) phthalocyanine with H(2)O(2) in test tubes was too fast to be monitored. Light activation plus use of Fe/Sodium-Y or Mn/Sodium-Y could significantly accelerate the bleaching efficiency of H(2)O(2). SIGNIFICANCE: Orange II was the most appropriate dye for tooth staining among the dyes used in this study. Addition of Fe/Sodium-Y or Mn/Sodium-Y plus light irradiation could elevate the bleaching efficacy of H(2)O(2) for those specimens stained by Orange II.     

Induction of calcium phosphate precipitation by titanium dioxide

Titanium powder and various titanium dioxides were tested for their capacity to reduce the induction time for calcium phosphate precipitation from supersaturated solutions. Only after a pretreatment aimed at increasing its oxide surface layer was titanium powder found to accelerate the precipitation from solutions containing 2 mmol/L CaCl2, 2 mmol/L KH2PO4, 50 mmol/L Hepes, pH 7.2, and to induce precipitation from metastable solutions containing 1.2 mmol/L CaCl2, 1.2 mmol/L KH2PO4, 50 mmol/L Hepes, pH 7.2, at 37 degrees C. Even stronger effects were found when suspensions of the titanium dioxides anatase or rutile (10-50 micrograms/mL) were added to these solutions. TiO2 appeared to serve as a reactive substrate for secondary nucleation at a wide range of calcium-to-phosphate ratios and concentrations, even in the presence of 40 mg/mL bovine serum albumin, which completely inhibited precipitation in control incubations. These results suggest that the oxide surface layer of titanium implants may induce calcium phosphate precipitation in the metal-to-bone interface, which may play a role in the integration of such implants in bone.     

纯钛种植体表面多孔结构的制备与分析

目的：利用喷砂、双重酸蚀和H2O2法构建粗化、改性种植体表面并对其形貌进行分析。方法：商业纯钛片经磨平、喷砂、清洗后分为6组,分别采用不同方法进行处理,从而得到不同的表面形貌。用扫描电镜（FSEM）观察表面形貌,能谱分析表面元素组成,X射线衍射（XRD）分析表面成分。结果：钛片表面经喷砂、超声清洗后．表面嵌有大量的喷砂颗粒,经低浓度HF／HNO3酸蚀后,仍有部分残留;同时,钛片表面形成大量纳米级孔洞。经高浓度HF／HNO3酸蚀后完全去除喷砂颗粒,钛片表面形成大量微米级孔洞。钛片再经HCl和H2SO4混合液酸蚀后,可以完全去除喷砂颗粒,同时得到多级孔洞结构。H2O2法处理,可使粗化表面得到锐钛矿晶相结构的TiO2层。结论：通过改变HF／HNO3浓度,可以得到不同孔径的孔洞;双重酸蚀处理,可以完全去除喷砂颗粒,并得到多级孔洞结构。H2O2法可将粗化表面的非晶态TiO2结晶转变为锐钛矿晶相结构。     

Effect of smear layer removal on bleaching of human teeth in vitro

The purpose of this study was to evaluate objectively in vitro the effectiveness of bleaching artificially discolored teeth with or without the smear layer present using sodium perborate mixed with sterile water or 35% hydrogen peroxide (H2O2). Seventy fully developed maxillary anterior teeth were artificially stained with human hemoglobin and separated into one control and four experimental groups. After the smear layer was removed on half the experimental teeth and left intact on the other half, all of the teeth were bleached intracoronally with sodium perborate and 35% H2O2 or sodium perborate plus water. The bleaching agents were applied twice over a 6-day period. The changes in tooth shade were objectively analyzed using a SP78 sphere spectrophotometer at 1, 30, and 60 days postbleaching. The presence or absence of the smear layer did not significantly influence the outcome of bleaching (p > 0.05). The teeth bleached with sodium perborate and 35% H2O2 were significantly lighter than the teeth bleached with sodium perborate and sterile water (p < 0.0001) at each experimental period. Based on the findings of this study, it is not advantageous to remove the smear layer before intracoronal bleaching.     

Cytotoxicity of intracanal bleaching agents on periodontal ligament cells in vitro

Intracoronal bleaching of nonvital teeth is a simple and conservative procedure for esthetic restoration of discolored teeth. However it is possible that damage to the periodontal ligament may occur if the bleaching agents contact this tissue. The purpose of this study was to examine the cytotoxicity of intracanal bleaching agents on human periodontal ligament (PDL) cells in vitro. Three bleaching agents, 30% hydrogen peroxide (H2O2), 2.0 g/ml sodium perborate (SP) solution, and 2.0 g/ml SP in H2O2, were diluted from 10(-3) to 10(-7) with Eagle's minimal essential medium and incubated with PDL cells isolated and cultured from extracted teeth. Cytotoxicity was assessed quantitatively by determining the amount of lactic dehydrogenase activity released from the cells after exposure to the agents for 24 or 72 h. Dose-response curves were plotted, and TD50 values (dilution causing the release of 50% of control lactate dehydrogenase activity) and 95% confidence limits determined. The rank order of the TD50 values after exposure for 24 h was SP in H2O2 (most toxic) > H2O2 > SP solution (least toxic). After 72 h SP in H2O2 still produced the greatest cytotoxic effect. However the SP solution was more cytotoxic than H2O2 at this time point. It is concluded that the mixture of SP with H2O2 was the most toxic to the PDL cells in vitro.     

不同结晶水过硼酸钠牙冠内漂白的体外研究

目的 比较不同结晶水过硼酸钠与３０％过氧化氢或蒸馏水结合的漂白功效。方法 ６６颗单根管牙人工染色后行不同结晶水含量的过硼酸钠分别与３０％过氧化氢和蒸馏水结合后的冠内漂白术，并在第１、３天置换漂白剂。结果 ６天后完全漂白的成功率达６３．６４％￣８１．８２％，不同结晶水过硼酸钠的漂白效果无显著差异；过硼酸钠与３０％过氧化氢或蒸馏水结合的漂白效果无显著差异。结论 与一般漂白剂相比，过硼酸钠的漂白时间较短     

含漱口泰及1.5% H2O2对减少超声洁牙产生的细菌性气雾的研究

目的 了解口泰３及１．５％Ｈ２Ｏ２漱口对减少超声洁牙产生的细菌性气雾的作用。方法 在患者胸前约离口腔２４ｃｍ处和置普通需氧平板及ＣＤＣ血琼脂平板，用空气沉降法收集细菌１ｍｉｎ，分组对超声波洁牙经口泰及１．５％Ｈ２Ｏ２漱口前后产生的气雾作需氧菌和厌氧菌测定。结果 口泰漱口后，气雾中的需氧菌减少７３７ＣＦＵ，厌氧菌减少７４９ＣＦＵ；１．５％Ｈ２Ｏ２漱口后，气雾中的需氧菌减少３５５ＣＦＵ，厌氧菌减少了４     

Effects of hydrogen peroxide bleaching strips on tooth surface color, surface microhardness, surface and subsurface ultrastructure, and microchemical (Raman spectroscopic) composition

OBJECTIVE: This study examined the effects of hydrogen peroxide tooth bleaching strips on the surface hardness and morphology of enamel and the ultrastructure and chemical composition of enamel and dentin in vitro. METHODOLOGY: Sound human molars were ground and polished to prepare a uniform substrate for bleaching treatments. A cycling treatment methodology was employed which alternated ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching treatments included commercial Crest Whitestrips bleaching strips, which utilize hydrogen peroxide in a gel as the in situ bleaching source at 6.0 and 6.5% concentrations of H2O2. Control treatments included an untreated group. Crest Whitestrips bleaching included treatment exposures simulating 2x the recommended clinical exposures (28 hours bleaching). Surface color measurements were taken prior to and following bleaching to ensure tooth bleaching activity. The effects of bleach on physical properties of enamel were assessed with microhardness measures. Ultrastructural effects were classified by surface and subsurface confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) techniques. In addition, the effects of bleaching on tooth microchemical composition was studied in different tooth regions by coincident assessment of Raman spectroscopic signature. RESULTS: Color assessments confirmed significant ex vivo tooth bleaching by Whitestrips. Surface microhardness and SEM measures revealed no deleterious effects on the enamel surfaces. CLSM micromorphological assessments supported the safety of hydrogen peroxide bleaching strips both on surface and subsurface enamel, DEJ, and dentin ultrastructure. Raman spectroscopy analysis demonstrated no obvious effects of bleaching treatments on the microchemical composition of enamel and dentin. CONCLUSION: These results confirm that tooth bleaching with hydrogen peroxide whitening strips does not produce changes in surface/subsurface histomorphology or in surface microhardness and ultrastructure of treated teeth. In addition, for the first time, these results confirm the safety of hydrogen peroxide bleaching strips to tooth microchemical composition as measured by Raman spectroscopy.     

Bleaching gel mixed with MI Paste Plus reduces penetration of H2O2 and damage to pulp tissue and maintains bleaching effectiveness

Clinical Oral Investigations - MI Paste Plus remineralizer (Rem) strengthens dental structures after bleaching. We investigated the effect of Rem on the penetration of hydrogen peroxide (H2O2),...