Impact of transparent tray-based application of bioactive glasses desensitizer on the permeability of enamel and dentin to hydrogen peroxide: an in vitro study.

BACKGROUND: To investigate the effect of transparent tray-based application of bioactive glasses (BGs) desensitizer on the permeability of enamel and dentin to hydrogen peroxide (H2O2). METHODS: Freshly extracted human first premolars were divided into 6 groups (n = 8). Group A and B: without pretreatments; Group C and E: treated with BGs desensitizer only; Group D and F: treated with BGs desensitizer dispensed with a transparent tray. After roots and pulp tissues of the treated tooth specimens were thoroughly removed, acetate buffer was added into pulp chambers and the treated specimens were immersed in distilled water (Groups A, E, and F) or 30% H2O2 (Groups B, C, and D) for 30 min at 37 °C. The amount of H2O2 in the pulp chamber of each group was measured using ultraviolet-visible spectrophotometry. RESULTS: In control groups (Group A, E, and F), H2O2 was not detected. The amount of pulpal H2O2 in Group B, C, and D were 21.149 ± 0.489 µg, 9.813 ± 0.426 µg, and 4.065 ± 0.268 µg respectively. One-way ANOVA analysis indicated that significant differences existed in these groups (F = 459.748, p < 0.05). CONCLUSIONS: The effect of BGs desensitizer in reducing the permeability of enamel and dentin to H2O2 could be enhanced when dispensed with a transparent tray.

Hydrogen peroxide penetration into the pulp chamber and dental permeability after bleaching.

This study sought to quantify the concentration of hydrogen peroxide (HP) in the pulp chamber and evaluate changes on dental permeability after bleaching with 3 HP concentrations (10%, 35%, and 50%). This study was divided into 2 experiments and the bleaching treatments consisted of 3 applications of HP for 30 minutes during a single session. The first experiment tested HP penetration into the pulp chamber of 4 experimental groups (n = 10) of bovine crowns, which were divided by HP concentration: an unbleached control group (0% HP), 10% HP, 35% HP, and 50% HP. Acetate buffer solution was placed into the pulp chamber and after each application of HP. This solution was collected to determine spectrophotometrically the concentration of HP that reached the pulp chamber. The second experiment evaluated dental permeability. Bovine crowns were divided into 3 groups (n = 10). The crowns were connected to a permeability device and the initial permeability was measured at 10 psi. Three different concentrations of HP gels (10%, 35% and 50%) were applied to the buccal enamel surfaces and the dental permeability was measured after the first, second, and third applications of HP. The data were analyzed by 2-way ANOVA and Tukey test (P ≤ 0.05). All concentrations of HP reached the pulp chamber, although no significant differences were noted between the 3 concentrations tested (P > 0.05). However, the increase of dental permeability in the group that received 50% HP was significantly higher than the 10% HP group (P < 0.05). The results indicate that the HP bleaching treatments increased dental permeability.

Infiltration of natural caries lesions in relation to their activity status and acid pretreatment in vitro.

This study aimed at testing how active and inactive enamel caries lesions differ by their degree of resin infiltration, and whether the choice of acid pretreatment plays a crucial role. Four examiners assessed 104 human molars and premolars with noncavitated enamel lesions and classified them as 'active' or 'inactive' using the Nyvad criteria. Forty-five teeth were included in this study after independent unanimous lesion activity assessment. Lesions were cut perpendicularly into 2 halves. Each half lesion was pretreated with either 15% hydrochloric acid or 35% phosphoric acid. The lesions were infiltrated after staining with rhodamine isothiocyanate. Thin sections of 100 µm were prepared and the specimens were bleached with 30% hydrogen peroxide. The specimens were then counterstained with sodium fluorescein, subjected to confocal laser scanning microscopy and analyzed quantitatively. Outcome parameters were maximum and average infiltration depths as well as relative penetration depths and areas. In active lesions no significant difference of percentage maximum penetration depth and percentage average penetration depth between lesions pretreated with hydrochloric or phosphoric acid could be observed. In inactive lesions, however, phosphoric acid pretreatment resulted in significantly lower penetration compared to hydrochloric acid pretreatment. Surface conditioning with hydrochloric acid led to similar infiltration results in active and inactive lesions. Moreover, inactive lesions showed greater variability in all assessed infiltration parameters than did active lesions. In conclusion, caries lesion activity and acid pretreatment both influenced the infiltration. The use of phosphoric acid to increase permeability of the surface layer of active lesions should be further explored.

Low toxic effects of a whitening strip to cultured pulp cells.

PURPOSE: To assess the trans-enamel and trans-dentin toxicity of a 10% hydrogen peroxide (HP) whitening strip to odontoblast-like cells (MDPC-23). METHODS: Enamel surfaces of enamel/dentin discs adapted to artificial pulp chambers were subjected to two 30-minute whitening strip applications to obtain indirect extracts (DMEM + bleaching components that diffused across enamel and dentin). The extracts were applied for 1 hour to the cells for 1 or 5 days. A bleaching gel with 35% HP was used as the positive control. Cell viability (MTT assay) and morphology (SEM) as well as the quantity of HP in the extracts were assessed. RESULTS: Discrete cell viability reduction (21.9%) associated with slight alterations in cell morphology occurred after application of the extracts for 5 days to the MDPC-23 cells (Tukey's test; P < 0.05). Lower enamel/dentin diffusion of HP was observed after the use of the whitening strip compared with the bleaching gel (Mann-Whitney; P < 0.05).

Quantification of peroxide ion passage in dentin, enamel, and cementum after internal bleaching with hydrogen peroxide.

The aim of this study was to evaluate the amount of peroxide passage from the pulp chamber to the external enamel surface during the internal bleaching technique. Fifty bovine teeth were sectioned transversally 5 mm below the cemento-enamel junction (CEJ), and the remaining part of the root was sealed with a 2-mm layer of glass ionomer cement. The external surface of the samples was coated with nail varnish, with the exception of standardized circular areas (6-mm diameter) located on the enamel, exposed dentin, or cementum surface of the tooth. The teeth were divided into three experimental groups according to exposed areas close to the CEJ and into two control groups (n=10/group), as follows: GE, enamel exposure area; GC, cementum exposed area; GD, dentin exposed area; Negative control, no presence of internal bleaching agent and uncoated surface; and Positive control, pulp chamber filled with bleaching agent and external surface totally coated with nail varnish. The pulp chamber was filled with 35% hydrogen peroxide (Opalescence Endo, Ultradent). Each sample was placed inside of individual flasks with 1000 µL of acetate buffer solution, 2 M (pH 4.5). After seven days, the buffer solution was transferred to a glass tube, in which 100 µL of leuco-crystal violet and 50 µL of horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to Kruskal-Wallis and Dunn-Bonferroni tests (α=0.05). All experimental groups presented passage of peroxide to the external surface that was statistically different from that observed in the control groups. It was verified that the passage of peroxide was higher in GD than in GE (p<0.01). The GC group presented a significantly lower peroxide passage than did GD and GE (p<0.01). It can be concluded that the hydrogen peroxide placed into the pulp chamber passed through the dental hard tissues, reaching the external surface and the periodontal tissue. The cementum surface was less permeable than were the dentin and enamel surfaces.

The use of a 'bleach-etch-seal' deproteinization technique on MIH affected enamel.

AIMS: To ascertain whether deproteinization pretreatment of molar-incisor hypomineralization (MIH) enamel affects resin sealant infiltration. DESIGN: Thirty one extracted MIH teeth were divided into three sections and randomly allocated into the Control (etch and FS), Treatment 1 (5% NaOCl, etched and fissure sealed), and Treatment 2 (5% NaOCl and fissure sealed with no etch) groups. Two hundred seventy nine sealant tag/enamel grade observations were recorded by scanning electron microscopy. RESULTS: Control and Treatment 1 were similar in their outcomes, and Treatment 2 was markedly different. There was no statistical evidence to suggest that there was any difference between Treatment 1 and the Control Treatment (95% CI, 0.52, 1.51; P = 0.6). There was a marked difference between Treatment 2 and the Control Treatment (95% CI, 0.07, 0.25; P < 0.001). All treatments also demonstrated a high-predicted probability of obtaining 'poor' sealant tags (Control = 47%, Treatment 1 = 49%, and Treatment 2 = 40%). CONCLUSIONS: The findings suggest that there was no significant difference in the tag quality between the conventional technique (Control) and the 'bleach-etch-seal' technique (Treatment 1). There was no benefit in pre-treating with NaOCl alone (without etch) before sealing. This research also showed that there was a high-predicted probability of obtaining 'poor' sealant tags in MIH enamel, regardless of which of the three treatments was used.

Effect of dentifrices against hydrochloric acid-induced erosion.

PURPOSE: This in vitro investigation assessed whether different dentifrices would be capable of controlling the enamel erosion progression caused by HCl. MATERIALS AND METHODS: Sixty bovine enamel slabs were covered with acid-resistant varnish, except for a 2.5-mm2 circular area on the labial surface. According to a complete block design, the experimental units were immersed in HCl solution (pH 1.2; 0.1M). After storage in artificial saliva for 1 h, specimens (n = 15) were exposed to different dentifrices: Sensodyne Cool Gel (1100 ppm F), Sensodyne ProNamel (1450 ppm F), and PrevDent 5000 (5000 ppm F). The control group was immersed in deionised water. Following five cycles of erosive challenge, the slabs were prepared for porosity evaluation using solutions of copper sulfate and rubeanic acid. RESULTS: ANOVA demonstrated no difference in the enamel porosity as a function of the dentifrice employed (P = 0.5494). CONCLUSION: The damage caused by a simulated intrinsic erosive challenge seems unable to be controlled by fluoridated dentifrices, even when this ion is found in elevated concentrations.

In vivo effects of fluoride on enamel permeability.

This in vivo study evaluated the effects of topical fluoride application on enamel by repeated scanning electron microscopy analysis of replicas. Baseline fluid droplets were employed as qualitative indication of enamel permeability. CaF(2)-like globules were detected in vivo after fluoride application and were not found after professional brushing, ultrasound action, or chemical extraction. Absence of water permeability of enamel was demonstrated even after removal of CaF(2)-like globules. Droplets reappeared within 1 h in sodium fluoride-treated teeth, but they did not reappear even after 1 week following topical enamel treatment with acidulated phosphate fluoride. Teeth treated with an acidulate fluoride-free solution showed lack of CaF(2)-like globules and no droplets for at least 1 week as detected in acidulate phosphate fluoride-treated teeth. The caries-preventing action of fluoride may be due to its ability to decrease permeability and diffusion pathways. CaF(2)-like globules seem to be indirectly involved in enamel protection over time maintaining an impermeable barrier, and phosphoric acid seemed to play an unexpected fluoride-independent preventive role.

Transenamel and transdentinal cytotoxicity of carbamide peroxide bleaching gels on odontoblast-like MDPC-23 cells.

AIM: To evaluate the transenamel and transdentinal cytotoxicity of bleaching gels based on carbamide peroxide (CP) on odontoblast-like cells after different contact times of the products with enamel. METHODOLOGY: Enamel/dentine discs were obtained from bovine incisors and placed in artificial pulp chambers. Bleaching gels containing 10% or 16% CP were applied for 8 h day(-1) on the enamel side of the discs during periods of 1, 7 or 14 days. Deionized water and artificial saliva served as controls. The extracts (culture medium plus bleaching gel products that diffused through the discs) were collected and applied on previously cultured MDPC-23 cells for 1 h. Cell metabolism was evaluated by the MTT assay, and the data were analysed statistically by one-way anova and Tukey's test (α=0.05). Cell morphology was analysed by SEM. RESULTS: There was no significant difference (P>0.05) between the controls and the groups bleached with 10% CP gel. In the groups bleached with 16% CP gel, however, cell metabolism decreased significantly (P<0.05) by 40.32%, 30.16% and 26.61% at 1, 7 and 14 days, respectively. There was no significant difference (P>0.05) between 1, 7 or 14 applications of the gels for either of the CP concentrations. CONCLUSION: Regardless of the number of applications on an enamel surface, the 10% CP bleaching gel did not cause transenamel and transdentinal cytotoxicity to the MDPC-23 cell cultures. However, diffusion of products from the 16% CP gel through enamel and dentine and cytopathic effects to the pulp cells occurred even after a single application of this product on enamel.

Enamel susceptibility to coffee and red wine staining at different intervals elapsed from bleaching: a photoreflectance spectrophotometry analysis.

OBJECTIVE: This study aimed to investigate bleached enamel susceptibility to coffee and red-wine staining at different time periods after bleaching. BACKGROUND DATA: Although hydrogen peroxide is effective for dental bleaching, little is known regarding color stability immediately after bleaching. MATERIALS AND METHODS: Fifty-four standardized bovine enamel slabs were obtained and assigned to the following treatments (n = 9): (CO) control: sound enamel surface submitted only to bleaching with 35% hydrogen peroxide (HP); (C30') enamel submitted to HP and coffee immersion at 30 min after bleaching; (C150') enamel submitted to HP and coffee immersion at 150 min after bleaching; (W30') enamel submitted to HP and red-wine immersion at 30 min after bleaching; and (W150') enamel submitted to HP and red-wine immersion at 150 min after bleaching. The color of treated enamel was determined by means of photoreflectance spectroscopy at baseline (T(0)) and after the described treatments (T(f)), and data were statistically analyzed with ANOVA and Tukey tests (p < 0.05). RESULTS: No differences were observed between the exposure times of 30 and 150 min after bleaching for both beverages (p > 0.05). Although coffee did not stain the surface, red wine significantly darkened previously bleached enamel (p < 0.05). CONCLUSION: Bleached enamel was susceptible to red-wine staining at both 30 and 150 min after bleaching procedures, whereas coffee did not interfere with the bleaching process.

Influence of chemical activation of a 35% hydrogen peroxide bleaching gel on its penetration and efficacy--in vitro study.

OBJECTIVES: The aim of this study was to evaluate the effects of chemical activation of hydrogen peroxide (HP) gel on colour changes and penetration through the tooth structure. METHODS: One hundred and four bovine incisors were used. One dentine (CD) disc and one enamel-dentine (ED) disc were prepared from each tooth. They were positioned over artificial pulpal chambers and the bleaching was performed with an experimental 35% HP gel. Two control and six experimental groups were prepared. In the positive control group (PC) no chemical activator was used. In the negative control group (NC) the specimens did not receive any bleaching. Each experimental group received a different chemical activator (manganese gluconate-MG; manganese chlorite-MC; ferrous sulphate-FS; ferrous chlorite-FC; and mulberries root extract-MRE). After the bleaching procedure a sample of solution was collected from the artificial pulpal chamber and the HP concentration was measured. The data were analysed using ANOVA, Tukey's, and Dunnett's tests. RESULTS: The groups MG and FS showed a significantly lower penetration of HP than the PC group. For the parameter Delta E, all the groups, with the exception of the group MRE, showed a significantly higher means in relation to the PC group in ED colour. For dentine colour, just the groups MG and FS had significant differences in relation to PC. CONCLUSIONS: The addition of MG and FS decreases the penetration of HP. The chemical activation using metal salts tested was effective in increasing the bleaching effect.

Trans-enamel and trans-dentinal cytotoxic effects of a 35% H2O2 bleaching gel on cultured odontoblast cell lines after consecutive applications.

AIM: To evaluate the trans-enamel and trans-dentinal cytotoxic effects of a 35% H(2)O(2) bleaching gel on an odontoblast-like cell lines (MDPC-23) after consecutive applications. METHODOLOGY: Fifteen enamel/dentine discs were obtained from bovine central incisor teeth and placed individually in artificial pulp chambers. Three groups (n = 5 discs) were formed according to the following enamel treatments: G1: 35% H(2)O(2) bleaching gel (15 min); G2: 35% H(2)O(2) bleaching gel (15 min) + halogen light (20 s); G3: control (no treatment). After repeating the treatments three consecutive times, the extracts (culture medium + gel components that had diffused through enamel/dentine discs) in contact with the dentine were collected and applied to previously cultured MDPC-23 cells (50 000 cells cm(-2)) for 24 h. Cell metabolism was evaluated by the MTT assay and data were analysed statistically (alpha = 5%; Kruskal-Wallis and Mann-Whitney U-test). Cell morphology was analysed by scanning electron microscopy. RESULTS: Cell metabolism decreased by 92.03% and 82.47% in G1 and G2 respectively. G1 and G2 differed significantly (P < 0.05) from G3. Regardless of halogen light activation, the application of the bleaching gel on the cultured odontoblast-like cells caused significantly more severe cytotoxic effects than those observed in the nontreated control group. In addition, significant morphological cell alterations were observed in G1 and G2. CONCLUSION: After three consecutive applications of a 35% H(2)O(2) bleaching agent, the diffusion of the gel components through enamel and dentine caused severe toxic effects to cultured pulp cells.

Indirect cytotoxicity of a 35% hydrogen peroxide bleaching gel on cultured odontoblast-like cells.

The aim of this study was to evaluate the trans-enamel and trans-dentinal effects of a 35% hydrogen peroxide (H2O2) bleaching gel on odontoblast-like cells. Enamel/dentin discs obtained from bovine incisors were mounted in artificial pulp chambers (APCs). Three groups were formed: G1- 35% H2O2; G2- 35% H2O2 + halogen light application; G3- control. The treatments were repeated 5 times and the APCs were incubated for 12 h. Then, the extract was collected and applied for 24 h on the cells. Cell metabolism, total protein dosage and cell morphology were evaluated. Cell metabolism decreased by 62.09% and 61.83% in G1 and G2, respectively. The depression of cell metabolism was statistically significant when G1 and G2 were compared to G3. Total protein dosage decreased by 93.13% and 91.80% in G1 and G2, respectively. The cells in G1 and G2 exhibited significant morphological alterations after contact with the extracts. Regardless of halogen light application, the extracts caused significantly more intense cytopathic effects compared to the control group. After 5 consecutive applications of a 35% H2O2 bleaching agent, either catalyzed or not by halogen light, products of gel degradation were capable to diffuse through enamel and dentin causing toxic effects to the cells.

Permeability of different groups of maxillary teeth after 38% hydrogen peroxide internal bleaching.

This study evaluated the influence of internal tooth bleaching with 38% hydrogen peroxide (H2O2) on the permeability of the coronal dentin in maxillary anterior teeth and premolars. Seventy teeth (14 per group) were used: central incisors (CI), lateral incisor (LI), canines (C), first premolars (1PM) and second premolars (2PM). Pulp chamber access and transversal sectioning at 2 mm from the cementoenamel junction were performed and the specimens were divided into 2 groups (n= 7): a) no treatment and b) bleaching with 38% H2O2. The bleaching agent was applied to the buccal surface and to the pulp chamber for 10 min. This procedure was repeated 3 times. The specimens were processed histochemically with copper sulfate and rubeanic acid, sectioned longitudinally, and digitalized in a scanner. The area of stained dentin was measured using Image Tool software. Data were analyzed statistically by ANOVA and Tukey's HSD test (alpha=0.05). There was statistically significant difference (p<0.001) among the untreated groups, CI (0.23 +/- 0.26) having the lowest permeability and LI (10.14 +/- 1.89) the highest permeability. Among the bleached groups, dentin permeability was increased in all groups of teeth except for 2PM. It may be concluded that bleaching with 38% H2O2 affected dentin permeability near the pulp chamber in maxillary anterior teeth and in first and second premolars.

Indirect cytotoxicity of a 35 percent hydrogen peroxide bleaching gel on cultured odontoblast-like cells

The aim of this study was to evaluate the trans-enamel and trans-dentinal effects of a 35 percent hydrogen peroxide (H2O2) bleaching gel on odontoblast-like cells. Enamel/dentin discs obtained from bovine incisors were mounted in artificial pulp chambers (APCs). Three groups were formed: G1- 35 percent H2O2; G2- 35 percent H2O2 + halogen light application; G3- control. The treatments were repeated 5 times and the APCs were incubated for 12 h. Then, the extract was collected and applied for 24 h on the cells. Cell metabolism, total protein dosage and cell morphology were evaluated. Cell metabolism decreased by 62.09 percent and 61.83 percent in G1 and G2, respectively. The depression of cell metabolism was statistically significant when G1 and G2 were compared to G3. Total protein dosage decreased by 93.13 percent and 91.80 percent in G1 and G2, respectively. The cells in G1 and G2 exhibited significant morphological alterations after contact with the extracts. Regardless of halogen light application, the extracts caused significantly more intense cytopathic effects compared to the control group. After 5 consecutive applications of a 35 percent H2O2 bleaching agent, either catalyzed or not by halogen light, products of gel degradation were capable to diffuse through enamel and dentin causing toxic effects to the cells.

O objetivo deste estudo foi avaliar os efeitos citotóxicos de um agente clareador com 35 por cento de peróxido de hidrogênio (H2O2) sobre células da linhagem odontoblástica. Foram confeccionados discos de esmalte/dentina obtidos de incisivos bovinos, os quais foram posicionados em câmaras pulpares artificiais (CPAs). Três grupos foram formados: G1: gel clareador; G2: gel clareador + luz halógena e G3: controle. Após 5 aplicações consecutivas do gel clareador sobre o esmalte, os extratos foram obtidos e aplicados por 24 h sobre as células. Foram realizadas avaliações do metabolismo celular, morfologia das células e expressão total de proteína. O metabolismo celular para G1 e G2 reduziu em 62,09 por cento e 61,83 por cento, respectivamente. A redução do metabolismo celular foi estatisticamente significante quando se comparou G1 e G2 com G3. A expressão de proteína total reduziu em 93,13 por cento e 91,80 por cento para G1 e G2, respectivamente. As células em G1 e G2 apresentaram importantes alterações morfológicas após contato com os extratos. Foi possível concluir que independente da catalização ou não do gel clareador por luz halógena, os componentes que se difundiram através dos tecidos duros do dente após sua quinta aplicação sobre o esmalte, causaram intensos efeitos citotóxicos para as células.

Permeability of different groups of maxillary teeth after 38 percent hydrogen peroxide internal bleaching

This study evaluated the influence of internal tooth bleaching with 38 percent hydrogen peroxide (H2O2) on the permeability of the coronal dentin in maxillary anterior teeth and premolars. Seventy teeth (14 per group) were used: central incisors (CI), lateral incisor (LI), canines (C), first premolars (1PM) and second premolars (2PM). Pulp chamber access and transversal sectioning at 2 mm from the cementoenamel junction were performed and the specimens were divided into 2 groups (n= 7): a) no treatment and b) bleaching with 38 percent H2O2. The bleaching agent was applied to the buccal surface and to the pulp chamber for 10 min. This procedure was repeated 3 times. The specimens were processed histochemically with copper sulfate and rubeanic acid, sectioned longitudinally, and digitalized in a scanner. The area of stained dentin was measured using Image Tool software. Data were analyzed statistically by ANOVA and Tukey's HSD test (?=0.05). There was statistically significant difference (p<0.001) among the untreated groups, CI (0.23 ± 0.26) having the lowest permeability and LI (10.14 ± 1.89) the highest permeability. Among the bleached groups, dentin permeability was increased in all groups of teeth except for 2PM. It may be concluded that bleaching with 38 percent H2O2 affected dentin permeability near the pulp chamber in maxillary anterior teeth and in first and second premolars.

Este estudo avaliou a influência do clareamento interno com peróxido de hidrogênio (H2O2) a 38 por cento na permeabilidade da dentina coronária de dentes anteriores superiores e pré-molares superiores. Quatorze incisivos centrais (IC), incisivos laterais (IL), caninos (C), primeiros (1PM) e segundos (2PM) pré-molares foram seccionados transversalmente e distribuídos em 2 grupos (n=7) sendo: G1: não receberam tratamento e, G2: clareados com aplicação de gel na face vestibular e câmara pulpar por 10 min, repetido 3 vezes. Os espécimes foram processados histoquimicamente por meio de imersão em sulfato de cobre e ácido rubeânico e digitalizados em escaner. A área corada foi aferida (Programa Image Tool). Os dentes que não receberam tratamento, apresentaram diferença estatisticamente significante (p<0,001), sendo o ICS (0,23 ± 0,26) e o ILS (10,14 ± 1,89) os grupo com os menores e os maiores valores de permeabilidade, respectivamente. Quando clareados, a permeabilidade coronária dos grupos dentais foi aumentada, exceto no grupo do 2PM. Concluiu-se que a permeabilidade da dentina coronária nos dentes anteriores superiores e primeiros pré-molares foi alterada pelo clareamento dental interno.

Enamel susceptibility to red wine staining after 35% hydrogen peroxide bleaching.

Concern has been expressed regarding the staining of enamel surface by different beverages after bleaching. This study investigated the influence of 35% hydrogen peroxide bleaching agents on enamel surface stained with wine after whitening treatments. Flat and polished bovine enamel surfaces were submitted to two commercially available 35% hydrogen peroxide bleaching agents or kept in 100% humidity, as a control group (n = 10). Specimens of all groups were immersed in red wine for 48 h at 37 degrees C, immediately, 24 h or 1 week after treatments. All specimens were ground into powder and prepared for the spectrophotometric analysis. Data were subjected to two-way analysis of variance and Fisher's PLSD test at 5% significance level. The amount of wine pigments uptake by enamel submitted to bleaching treatments was statistically higher than that of control group, independently of the evaluation time. Results suggested that wine staining susceptibility was increased by bleaching treatments.

Fluoropolymers as low-surface-energy tooth coatings for oral care.

A range of low-surface-energy fluoropolymers has been synthesised and their effectiveness as dental-care coatings for plaque, stain and erosion prevention has been evaluated using a series of oral care models employing pressed discs of calcium hydroxyapatite or sections of human teeth. Since the blocking of dentinal tubules is a key mechanistic strategy in the treatment of dentine hypersensitivity, the capability of these non-permanent fluoropolymer coatings to occlude the pore structure of human dentine and to reduce the outward flow of simulated dentinal fluid has also been investigated. Several of the fluoropolymer coatings have been found to inhibit bacterial adhesion but no correlation has been established between anti-adhesion efficacy and fluorine content or surface energy. All the fluoropolymers have been seen to reduce stain uptake by pellicle-coated HA discs, with homopolymers being considerably more effective than copolymers. Some fluoropolymer coatings have also been shown to inhibit the acid demineralisation of hydroxyapatite discs and to reduce dentine permeability. Coatings of the 2:1 copolymer of 1H,1H,2H,2H-perfluorodecyl acrylate and 2-hydroxyethyl acrylate are most promising, exhibiting significant anti-adhesion and anti-erosion efficacy and reducing dentine permeability to a level that is comparable with that achieved with the standard treatment employed in commercial anti-sensitivity formulations.

Effect of pre-etching enamel on fatigue of self-etch adhesive bonds.

OBJECTIVE: A previous study found that the shear bond strength (SBS) to bovine enamel for the self-etching adhesive Adper Prompt-L-Pop (PLP) was 75% of that found with the etch-and-rinse material SingleBond, while the comparative value for the shear fatigue limit (SFL) was only 58% at 10(5) load cycles. Resin penetration into the enamel surface was substantially less for PLP but it was not conclusive that this was the reason for the lower results cited above. The objective of this study was to determine if pre-etching enamel would substantially improve the SBS and SFL of the PLP adhesive over those found in the previous study. MATERIALS AND METHODS: All test methods were the same as for the previous study. SBS measurements were conducted for composite bonds to bovine enamel using a phosphoric acid pre-etch with the PLP adhesive (PLP-10) and for a conventional enamel-bonding adhesive (EB). Fatigue testing was done with the same test fixtures, load cycling at 2Hz up to a maximum of 10(5) cycles at four selected peak load values between 35 and 60% of the respective bond strengths. Fatigue limits were determined from the data obtained. SEM analysis of resin penetration of the enamel surface was carried out for each adhesive. RESULTS: A significantly greater SBS and SFL were found for EB (SBS: 30.4MPa; SFL: 15.6MPa) than for PLP-10 (SBS: 20.2MPa; SFL: 9.9MPa). Compared with previously found results, the pre-etching of enamel had no significant improvement in SBS and only slight improvement in SFL. Resin tag penetration of the enamel surface for PLP-10 was similar to that previously found for PLP alone, suggesting that the porosity created by phosphoric acid was effectively removed by the acidic PLP adhesive. SIGNIFICANCE: Unlike some self-etching adhesives reported in the literature, pre-etching enamel did not improve the performance of the Prompt-L-Pop adhesive.