OBJECTIVES: This study aimed to observe the color rebound and rebound rates of non-pulp discolored teeth within 1 year after routine internal bleaching to guide clinical practice and prompt prognosis. METHODS: In this work, the efficacy of bleaching was observed in 20 patients. The color of discolored teeth was measured by using a computerized colorimeter before bleaching; immediately after bleaching; and at the 1st, 3rd, 6th, 9th, and 12th months after bleaching. The L*, a*, and b* values of the color of cervical, mesial, and incisal parts of the teeth were obtained, and the color change amounts ΔE*, ΔL*, Δa*, and Δb* were calculated. The overall rebound rate (P*) and the color rebound velocity (V*) were also analyzed over time. RESULTS: In 20 patients following treatment, the average ΔE* of tooth color change was 14.99. After bleaching, the neck and middle of the teeth ΔE* and ΔL* decreased in the 1st, 3rd, 6th, 9th, and 12th months, and the differences were statistically significant. Meanwhile, from the 9th month after bleaching, the rebound speed was lower than that in the 1st month, and the difference was statistically significant. The incisal end of the tooth ΔE* and ΔL* decreased in the 6th, 9th, and 12th months after bleaching, and the differences were statistically significant. No significant difference was found in the rebound speed between time points. However, this rate settled after the 9th month, with an average color rebound rate of 30.11% in 20 patients. CONCLUSIONS The results indicated that internal bleaching could cause a noticeable color change on pulpless teeth. The color rebound after bleaching was mainly caused by lightness (L*), which gradually decreased with time, and it was slightly related to a* and b*. The color of the teeth after internal bleaching rebounded to a certain extent with time, but the color rebound speed became stable from the 9th month. Clinically, secondary internal bleaching can be considered at this time according to whether the colors of the affected tooth and the adjacent tooth are coordinated and depending on the patient's needs.
Humans ; Tooth Bleaching/methods* ; Tooth, Nonvital/drug therapy* ; Color ; Tooth Discoloration/drug therapy* ; Tooth ; Hydrogen Peroxide/therapeutic use* ; Tooth Bleaching Agents/therapeutic use*

Objective: To investigate the effect of permeable resin on the surface structure, microhardness and color of tooth enamel after bleaching. Methods: Premolars extracted for orthodontic needs were selected (provided by the Department of Oral and Maxillofacial surgery of the first affiliated Hospital of Zhengzhou University) and randomly divided into A, B and C 3 groups. Each group was randomly divided into control subgroup, resin subgroup, bleaching subgroup and combined subgroup. Samples in the control subgroup did not receive any treatment. Those in the bleaching subgroup and combined subgroup were treated with cold light whitening. Those in the resin group and combined group were treated with permeable resin. Samples in the group A were observed by scanning electron microscope immediately after treatment and 2 weeks after treatment, and the microhardness of samples in the group B was measured before treatment, immediately after treatment and 2 weeks after treatment (the sample size of each time point was 8 in each subgroup). In group C, chromaticity was measured and chromatic aberration (ΔE value) was calculated before treatment, immediately after treatment and 1 and 2 weeks after treatment (10 samples in each subgroup). Results: Scanning electron microscope showed that the enamel surface of the resin subgroup and the combined group was smooth immediately after treatment, which was basically the same as that of the control subgroup, but covered with resin, and microporous defects and mineral deposits could be seen on the surface of the bleaching subgroup. Two weeks after treatment, the enamel surface of each subgroup was smooth, there was no obvious difference. Immediately after treatment, the microhardness of the control subgroup, resin subgroup, bleaching subgroup and combined subgroup were (354±33), (364±21), (411±30) and (350±17) HV, respectively (F=9.39,P<0.05). The microhardness of the bleaching subgroup was significantly higher than that of the other subgroups (P<0.05). There was no significant difference in microhardness among the four subgroups before treatment and 2 weeks after treatment (F=0.34, 2.75, P>0.05). Immediately after treatment, the ΔE values of the control subgroup, resin subgroup, bleaching subgroup and combined subgroup were 0.00±0.00, 2.29±1.86, 7.20±1.94 and 8.00±0.88, respectively (F=74.21,P<0.05); except that there was no significant difference between bleaching subgroup and combined subgroup (P>0.05), there were significant differences among the other subgroups (P<0.05). There was no significant difference in ΔE value among control subgroup, resin subgroup and bleaching subgroup at each time point (F=1.66, 0.30, 0.96, P>0.05). The difference in the combined subgroup immediately after treatment was significantly higher than that at 1 and 2 weeks after treatment (t=4.73, 4.23,P<0.05), but there was no significant difference between 1 and 2 weeks after treatment (t=0.75, P>0.05), and the color tended to be stable. Conclusions: When whitening healthy enamel, simple cold light whitening or cold light whitening combined with permeation resin can achieve whitening effect.
Color ; Dental Enamel ; Hardness ; Humans ; Hydrogen Peroxide/pharmacology* ; Tooth Bleaching/adverse effects* ; Tooth Bleaching Agents/pharmacology*

OBJECTIVES: The aim of the present study was to evaluate the effect of whitening mouth rinses alone and in combination with conventional whitening treatments on color, microhardness, and surface roughness changes in enamel specimens. MATERIALS AND METHODS: A total of 108 enamel specimens were collected from human third molars and divided into 9 groups (n = 12): 38% hydrogen peroxide (HP), 10% carbamide peroxide (CP), 38% HP + Listerine Whitening (LW), 10% CP + LW, 38% HP + Colgate Plax Whitening (CPW), 10% CP + CPW, LW, CPW, and the control group (CG). The initial color of the specimens was measured, followed by microhardness and roughness tests. Next, the samples were bleached, and their color, microhardness, and roughness were assessed. Data were analyzed through 2-way analysis of variance (ANOVA; microhardness and roughness) and 1-way ANOVA (color change), followed by the Tukey post hoc test. The Dunnett test was used to compare the roughness and microhardness data of the CG to those of the treated groups. RESULTS: Statistically significant color change was observed in all groups compared to the CG. All groups, except the LW group, showed statistically significant decreases in microhardness. Roughness showed a statistically significant increase after the treatments, except for the 38% HP group. CONCLUSIONS: Whitening mouth rinses led to a whitening effect when they were used after conventional treatments; however, this process caused major changes on the surface of the enamel specimens.
Dental Enamel ; Humans ; Hydrogen Peroxide ; Molar, Third ; Mouth ; Tooth Bleaching Agents ; Tooth Bleaching ; Tooth ; Urea

There has been increasing use of the H₂O₂-based teeth bleaching agents. The purpose of this study was to evaluate the bleaching effectiveness of the laser irradiation combined with nitrogen doped-TiO₂ nanoparticles (NPs) on the stained resin. Nitrogen (N) doped-TiO₂ NPs were prepared under sol-gel method. Light absorbance, X-ray diffraction patterns of NPs, and bleaching of methylene blue and stained resins were evaluated. For bleaching of stained resin, NPs-containing gel was used. For irradiation, light of two different wavelengths was used. Unlike TiO₂, N-TiO₂ showed high absorbance after 400 nm. N-TiO₂, which have used TiN as a precursor, showed a new rutile phase at the TiN structure. For methylene blue solution, N-TiO₂ with 3% H₂O₂ resulted in the greatest absorbance decrease after laser irradiation regardless of wavelength. For stained resin test, N-TiO₂ with 3% H₂O₂ resulted in the greatest color difference after laser irradiation, followed by group that used N-TiO₂ without 3% H₂O₂.
Methods ; Methylene Blue ; Nanoparticles ; Nitrogen ; Tin ; Tooth Bleaching Agents ; X-Ray Diffraction

OBJECTIVES: To examine the tooth whitening effects of a 3% hydrogen peroxide gel.METHODS: Twenty participants were given experimental tooth whitening gels containing 3% hydrogen peroxide, and another 20 participants, who served as the control group, were given tooth whitening gels that contained no hydrogen peroxide. Both groups used their respective whitening agents for 1 week, and tooth lightness was examined at baseline and 4 and 7 days after the experiment.RESULTS: Compared with the control group, in the experimental group, lightness values, determined using VITA classical A1-D4® and VITA SYSTEM 3D-MASTER®, were significantly increased after using the 3% hydrogen peroxide whitening agent (P < 0.01) both 5 and 7 days post-application (P < 0.05).CONCLUSIONS: The study findings confirmed that an improved tooth whitening effect could be expected with the use of a new type of whitening gel containing 3% hydrogen peroxide.
Bleaching Agents ; Gels ; Hydrogen Peroxide ; Hydrogen ; Tooth Bleaching ; Tooth ; Toothpastes

OBJECTIVES: This study evaluated the effects of a bleaching agent on the composition, mechanical properties, and surface topography of 6 conventional glass-ionomer cements (GICs) and one resin-modified GIC. MATERIALS AND METHODS: For 3 days, the specimens were subjected to three 20-minute applications of a 37% H2O2-based bleaching agent and evaluated for water uptake (WTK), weight loss (WL), compressive strength (CS), and Knoop hardness number (KHN). Changes in surface topography and chemical element distribution were also analyzed by energy-dispersive X-ray spectroscopy and scanning electron microscopy. For statistical evaluation, the Kruskal-Wallis and Wilcoxon paired tests (a = 0.05) were used to evaluate WTK and WL. CS specimens were subjected to 2-way analysis of variance (ANOVA) and the Tukey post hoc test (α = 0.05), and KH was evaluated by one-way ANOVA, the Holm-Sidak post hoc test (a = 0.05), and the t-test for independent samples (a = 0.05). RESULTS: The bleaching agent increased the WTK of Maxxion R, but did not affect the WL of any GICs. It had various effects on the CS, KHN, surface topography, and the chemical element distribution of the GICs. CONCLUSIONS: The bleaching agent with 37% H2O2 affected the mechanical and surface properties of GICs. The extent of the changes seemed to be dependent on exposure time and cement composition.
Compressive Strength ; Dental Materials ; Glass Ionomer Cements ; Hardness ; Microscopy, Electron, Scanning ; Spectrum Analysis ; Surface Properties ; Tooth Bleaching Agents ; Water ; Weight Loss

Tooth bleaching agents contain powerful oxidizing agents, which serve as the main part of bleaching agents because of its release of effective bleaching component. It has been a hot topic whether tooth bleaching agents exert negative influence on oral health. In order to provide train of thoughts and reference for further clinical researches and treatments, this review paper focuses on bleaching agents' effects on the growth of oral microbes and the formation of biofilms.
Bacteria ; drug effects ; growth & development ; Biofilms ; drug effects ; growth & development ; Humans ; Hydrogen Peroxide ; Mouth ; microbiology ; Oral Health ; Oxidants ; pharmacology ; Tooth Bleaching ; Tooth Bleaching Agents ; pharmacology

OBJECTIVEUsing tooth whitening agents (bleaching clip) in vitro and acidic drinks, we conducted a comparative study of the changes in enamel surface morphology, Ca/P content, and hardness.

METHODSTooth whitening glue pieces, cola, and orange juice were used to soak teeth in artificial saliva in vitro. Physiological saline was used as a control treatment. The morphology of the four groups was observed under a scanning electron microscope (SEM) immediately after the teeth were soaked for 7 and 14 d. The changes in Ca/P content and microhardness were analyzed.

RESULTSThe enamel surfaces of the teeth in the three test groups were demineralized. The Ca/P ratio and the average microhardness were significantly lower than those of the control group immediately after the teeth were soaked (P < 0.05). The Ca/P ratio and microhardness gradually increased after 7 d. No significant difference was observed between the control group and the test groups after 14 d (P > 0.05).

CONCLUSIONBleaching agents caused transient demineralization of human enamel, but these agents could induce re-mineralization and repair of enamel over time. Demineralization caused by bleaching covered a relatively normal range compared with acidic drinks and daily drinking.

Dental Enamel ; Hardness ; Humans ; Hydrogen Peroxide ; Saliva, Artificial ; Surface Properties ; Tooth Bleaching ; Tooth Bleaching Agents

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.
Animals ; Biomimetic Materials ; analysis ; therapeutic use ; Cattle ; Ceramics ; analysis ; chemistry ; Chemical Phenomena ; Color ; Colorimetry ; Dental Enamel ; drug effects ; ultrastructure ; Electron Probe Microanalysis ; Glass ; analysis ; chemistry ; Hardness ; Hydrogen Peroxide ; pharmacology ; Hydrogen-Ion Concentration ; Microscopy, Electron, Scanning ; Protective Agents ; analysis ; therapeutic use ; Random Allocation ; Solubility ; Spectroscopy, Fourier Transform Infrared ; Time Factors ; Tooth Bleaching ; methods ; Tooth Bleaching Agents ; pharmacology ; Water ; chemistry ; X-Ray Diffraction

OBJECTIVETo investigate the effects of three differently concentrated at-home bleaching agents on the structure and the structure-related mechanical properties of human enamel.

METHODSSixty enamel specimens were randomly divided into four groups and treated with 10% carbamide peroxide (CP), 15% CP, 20% CP and distilled water, respectively. The bleaching process was 8 h/day for 14 consecutive days. Baseline and final atomic force microscopy (AFM) surface detection, Raman spectroscopy, attenuated total reflectance-infrared spectroscopy (ATR-IR), microhardness and fracture toughness (FT) measurements were carried out before and after bleaching experiments.

RESULTSCP didn't change the morphology of enamel. Meanwhile, the three bleached groups and the control group had no significant difference in root mean square detection (P = 0.774), ν(2)CO(3)(2-) : ν(1)ν(3)PO(4)(3-) (P = 0.263) and microhardness (P = 0.829). The percentage of relative Raman intensity in the three bleached groups and the control group were (105.74 ± 11.34)%, (104.46 ± 8.83)%, (99.52 ± 9.32)% and (97.62 ± 7.46)%, respectively. There was no significant difference among them (P = 0.062). However, the percentage of laser-induced fluorescence in the three bleached groups and the control group were (20.86 ± 7.23)%, (22.14 ± 7.34)%, (21.10 ± 7.59)% and (100.78 ± 3.70)%, respectively. There was significant difference between either of the bleached groups and the control group (P < 0.001). Moreover, FT declined significantly in the three groups (P = 0.024, P = 0.005, P = 0.013) when compared with the control group.

CONCLUSIONSUnder in vitro condition, three differently concentrated at-home bleaching agents wouldn't induce the demineralization and the decline of microhardness on enamel. However, the decrease of FT on enamel seemed to be inevitable after bleaching.

Dental Enamel ; drug effects ; Dose-Response Relationship, Drug ; Hardness ; drug effects ; Humans ; Microscopy, Atomic Force ; Peroxides ; administration & dosage ; pharmacology ; Random Allocation ; Spectrophotometry, Infrared ; Spectrum Analysis, Raman ; Surface Properties ; Tooth Bleaching ; Tooth Bleaching Agents ; administration & dosage ; pharmacology ; Tooth Demineralization ; chemically induced ; Urea ; administration & dosage ; analogs & derivatives ; pharmacology