Chemical and mechanical resistance of novel experimental hybrid coatings on dentin permeability.

This study aimed to evaluate the capacity of novel experimental hybrid coatings (HC) to reduce dentin permeability and to verify their resistance to erosive and abrasive challenges. Dentin disc specimens (1 mm thick) were treated with 0.5 M EDTA solution and randomly allocated into three experimental groups (n = 10): Control (Saliva); Concentrated Hybrid Coating (TEOS/GPTMS/Y-APS); and Diluted Hybrid Coating (1:3 ratio with distilled water). Dentin permeability was assessed by hydraulic conductance in the following experimental time periods: post-EDTA, post treatment, post erosion (5 min in 0.05 M citric acid solution, pH = 3.8), and post abrasion (toothbrushing for 3,900 cycles). Dentin permeability percent was calculated with respect the values of post-EDTA for each experimental time. The morphology of the surface of extra dentin specimens was examined by scanning electron microscopy (SEM) in the same time periods (n = 3). Permeability data were analyzed by two-way repeated measures ANOVA and Tukey tests (p < .05). Both HC presented significantly lower dentin permeability than control post treatment and post erosion (p < .05), without difference between them (p > .05). Post abrasion, there were no significant difference among groups (p > .05). Post treatment and post erosion, the HC seemed to flow into the tubules, occluding them, while the tubules in control remained opened. Post abrasion, the tubules appear to be occluded in all groups. In conclusion, the experimental hybrid coatings were capable of reducing dentin permeability after treatment. They were also able to resist to erosive and abrasive challenges, with the advantage of forming thinner and colorless films that can be potentially used to treat dentin hypersensitivity.

A novel application of nano eggshell/titanium dioxide composite on occluding dentine tubules: an in vitro study.

To synthesize Nano eggshell-titanium-dioxide (EB@TiO2) biocomposite and to evaluate its effectiveness in occluding opened dentine tubules. EB@TiO2 was synthesized and characterized using X-ray diffraction (XRD), and Transmission Electron Microscope (TEM). Sixteen simulated bovine dentine discs were prepared and randomly assigned into four groups according to the following treatment (n = 4): Group 1: No treatment; Group 2: eggshell powder; Group 3: EB@TiO2; Group 4: Sensodyne. These were then agitated in a solution of 1g powder and 40mL water for 3hours. Thereafter, each dentine discs from the respective groups were post-treated for 5 min with 2wt% citric acid to test their acid resistant characteristics. Scanning Electron Microscope (SEM) was used to observe the effectiveness of occluded dentine pre-and post-treatment. The cytotoxicity of the synthesized EB@TiO2 was tested using NIH 3T3 assay. ANOVA was used to evaluate the mean values of the occluded area ratio and the data of MTS assay. This was followed by a multi-comparison test with Bonferroni correction (α = .05). The XRD confirmed that EB@TiO2 was successfully modified through ball-milling. The TEM revealed the presence of both spherical and irregular particle shape powders. The SEM result showed that EB@TiO2 could effectively occlude open dentine tubules. Equally, the result demonstrated that EB@TiO2 exhibited the highest acid resistant stability post-treatment. NIH 3T3 assay identified that EB@TiO2 had little effect on the NIH 3T3 cell line even at the highest concentration of 100µg/ml. This study suggests that the application of EB@TiO2 effectively occluded dentine tubules and the occlusion showed a high acid resistant stability.

A novel application of nano eggshell/titanium dioxide composite on occluding dentine tubules: an in vitro study

Abstract To synthesize Nano eggshell-titanium-dioxide (EB@TiO2) biocomposite and to evaluate its effectiveness in occluding opened dentine tubules. EB@TiO2 was synthesized and characterized using X-ray diffraction (XRD), and Transmission Electron Microscope (TEM). Sixteen simulated bovine dentine discs were prepared and randomly assigned into four groups according to the following treatment (n = 4): Group 1: No treatment; Group 2: eggshell powder; Group 3: EB@TiO2; Group 4: Sensodyne. These were then agitated in a solution of 1g powder and 40mL water for 3hours. Thereafter, each dentine discs from the respective groups were post-treated for 5 min with 2wt% citric acid to test their acid resistant characteristics. Scanning Electron Microscope (SEM) was used to observe the effectiveness of occluded dentine pre-and post-treatment. The cytotoxicity of the synthesized EB@TiO2 was tested using NIH 3T3 assay. ANOVA was used to evaluate the mean values of the occluded area ratio and the data of MTS assay. This was followed by a multi-comparison test with Bonferroni correction (α = .05). The XRD confirmed that EB@TiO2 was successfully modified through ball-milling. The TEM revealed the presence of both spherical and irregular particle shape powders. The SEM result showed that EB@TiO2 could effectively occlude open dentine tubules. Equally, the result demonstrated that EB@TiO2 exhibited the highest acid resistant stability post-treatment. NIH 3T3 assay identified that EB@TiO2 had little effect on the NIH 3T3 cell line even at the highest concentration of 100µg/ml. This study suggests that the application of EB@TiO2 effectively occluded dentine tubules and the occlusion showed a high acid resistant stability.

Effects of EDTA gel and chlorhexidine gel on root dentin permeability.

The aim of this study was to evaluate the effect of 24% ethylenediaminetetraacetic acid (EDTA) gel and 2% chlorhexidine gel (CHX) in dentin permeability and smear layer removal from root canals instrumented with NiTi rotary system using histochemical staining and scanning electron microscopy (SEM) analysis. Overall, 43 premolars were classified into two experimental groups, EDTA (n = 20) and CHX (n = 20), and a negative control (NC) (n = 3). All specimens were instrumented and the irrigant solutions were used after each file change. The EDTA group received a final rinse with 5-ml 1% NaOCl followed by a 5-ml 0.9% saline solution; the CHX group received a final rinse with 10-ml 0.9% saline solution; and the negative control group received a final rinse with only 0.9% saline solution. Fifteen teeth from each group were prepared for histochemical staining and evaluation of dentin permeability using the image-scanning software Axion Vision (v.4.8.2). Five remaining teeth were prepared for analysis using SEM for morphological analysis. The study found that 24% EDTA gel increased the permeability of dentin in all thirds evaluated and also demonstrated an increased cleaning ability, with dentinal walls free of smear layer and open dentinal tubules, as compared to 2% CHX gel. It was concluded that EDTA was efficient in cleaning the dentinal tubules and increased dentin permeability.

Effect of two desensitizing agents on dentin permeability in vitro.

OBJECTIVE: The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. MATERIAL AND METHODS: GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. RESULTS: PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. CONCLUSIONS: The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

Effect of two desensitizing agents on dentin permeability in vitro

Abstract Objective The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. Material and Methods GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. Results PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. Conclusions The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

Avaliação in vitro de novos produtos na diminuição da permeabilidade dentinária antes e após desafios ácidos / In vitro evaluation of new products in regarding dentin permeability reduction before and after acid challenge model

Objetivo: avaliar in vitro a efetividade de aplicações sucessivas de diferentes produtos utilizados para o tratamento da hipersensibilidade dentinária cervical na redução da permeabilidade dentinária, assim como avaliar a resistência destes produtos a desafios ácidos. Material e métodos: foram utilizados 72 terceiros molares humanos íntegros para a preparação de 72 amostras, que foram ligadas a um sistema de pressão hidráulica para mensurar a permeabilidade dentinária após os seguintes passos: 1) preparação da amostra; 2) tratamento com ácido fosfórico a 37% durante 30 segundos; 3) cinco aplicações dos produtos testados; 4) primeiro desafio ácido; 5) segundo desafio ácido; e 6) terceiro desafio ácido. As amostras foram divididas aleatoriamente em seis grupos (n=12), de acordo com os tratamentos propostos: Desensibilize Nano P, Clinpro XT, dentifrício Colgate Sensitive Pró-Alívio, dentifrício Duraphat, dentifrício Sensodyne Repair e após restauração com resina composta (grupo-controle). Conclusão: que todos os produtos testados foram capazes de promover a redução da permeabilidade dentinária significativamente, sendo que os grupos Clinpro XT, Desensibilize Nano P e controle mantiveram esses níveis reduzidos estatisticamente até o terceiro desafio ácido, enquanto que os dentifrícios Duraphat, Sensodyne Repair e Colgate Sensitive Pró-Alívio mantiveram essas reduções estatisticamente significativas até o segundo desafio ácido.

Objective: to evaluate in vitro the effectiveness of successive applications of different products used for the treatment of cervical dentinal hypersensitivity, reducing dentin permeability, as well as to evaluate the resistance of these products, acids challenges. Material and methods: 72 intact human third molars were used for the preparation of 72 samples were bound to a hydraulic pressure system to measure the dentin after the following steps: 1) sample preparation; 2) treatment with 37% phosphoric acid for 30 seconds; 3) 5 applications of the products tested; 4) first challenge acid; 5) second challenge acid; 6) third challenge acid. The samples were randomly divided into 6 groups (n=12) according to the proposed treatments: Desensibilize Nano P, Clinpro XT, toothpaste Colgate Sensitive Pro-Relief, Duraphat toothpaste, toothpaste Sensodyne Repair and after restoration with composite resin (control group). Conclusion: all products tested were able to significantly promote the reduction of dentin, and the Clinpro XT groups Desensibilize Nano P and control these reduced levels remained statistically to the third challenge acid, while toothpaste Duraphat, Sensodyne Repair and Colgate Sensitive Pro-Relief kept these statistically significant reductions to the second challenge acid.

Effects of different desensitizing treatments on root dentin permeability.

The objective of this study was to evaluate the effects of diode laser and a desensitizing dentifrice on dentin permeability. Fifty-two root dentin fragments were obtained (5 × 5mm) and treated with 24% EDTA gel. The samples were divided into 4 groups (n = 13): G1, control (no treatment); G2, diode laser (λ = 908 nm, 1.5 W, continuous mode, 20s); G3, application of abrasive dentifrice for 1 minute (Elmex Sensitive Professional (International Gaba); and G4, application of abrasive dentifrice for 1 minute followed by irradiation with diode laser. Ten samples per group were immersed in 2% methylene blue solution for 4h. The specimens were washed, longitudinally sectioned, observed under optical microscopy, photographed and assessed based on the degree of dye leakage. The remaining samples were observed under scanning electron microscopy (SEM). The leakage data were subjected to ANOVA test, followed by Tukey's t-test (α = 5%). Groups 2, 3 and 4 showed less dye penetration than the control group (p < 0.05), but were similar among each other. SEM images showed that dentinal tubules were open in G1, and fused and occluded in G2. Group 3 showed dentinal tubules that were occluded by the metal ions from the toothpaste. G4 presented similar characteristics to G3, and the presence of fused dentin. The diode laser and the dentifrice were effective in reducing dentinal permeability, and the combination of the two treatments did not show better results than either one used alone.

Longitudinal Effect of Surface Treatments Modified by NaOCl-Induced Deproteinization and Nd:YAG Laser on Dentin Permeability.

OBJECTIVE: The purpose of this study was to evaluate dentin permeability after dentin hypersensitivity treatments: fluoride, adhesive system, and collagen deproteinization with and without Nd:YAG laser exposure, and after erosive and abrasive challenges. MATERIALS AND METHODS: Dentin permeability was assessed by measuring dentinal fluid flow using a permeability device. Eighty bovine dentin specimens (6 mm diameter/1 mm thickness) had permeability measured in the presence of the smear layer and after removal of the smear layer by ethylenediaminetetraacetic acid (EDTA). They were then divided into eight groups according to treatment (n = 10): Group C, control; Group L, Nd:YAG laser; Group F, fluoride; Group FL, fluoride plus Nd:YAG laser; Group A, adhesive; Group AL, adhesive plus Nd:YAG laser; Group D, 10% NaOCl plus adhesive; and group DL, NaOCl plus adhesive plus Nd:YAG laser. Nd:YAG laser was irradiated at 60 mJ/pulse/10 Hz/47.7 J/cm2/1 W and applied freehanded without contact for 60 sec. Permeability was measured 24 h after the treatments. The specimens were exposed to erosive and abrasive challenges for 5 days. Erosive challenge was done by immersion in Coca-Cola, four times a day/90 sec each. After the first and last erosive challenge of the day, the abrasive challenge was conducted by brushing the specimens (24,000 cycles/3.8 cm range/200 g weight), and permeability was measured again. Results were analyzed statistically using two factor ANOVA and Tukey tests (α = 0.05). RESULTS: With the exception of groups FL and A, all treatments reduced permeability. A significant reduction in permeability was seen when the treatments were combined with laser exposure. The association of adhesive and Nd:YAG laser led to the lowest rate of permeability after 24 h. NaOCl-induced deproteinization associated with Nd:YAG laser showed the lowest permeability rate after erosive/abrasive challenges. CONCLUSIONS: Dentin hypersensitivity treatments reduced dentin permeability when associated with Nd:YAG laser, even after erosive/abrasive challenges.

Combined effect of fluoride varnish to Er:YAG or Nd:YAG laser on permeability of eroded root dentine.

OBJECTIVE: This study evaluated the combined effect of fluoride varnish to Er:YAG or Nd:YAG laser on permeability of eroded root dentine. DESIGN: Sixty slabs of bovine root dentine (2×2×2mm) were eroded with citric acid 0.3% (pH 3.2) during 2h and then kept in artificial saliva during 24h. Specimens were randomly assigned in 6 groups (n=10), to receive the following treatments: fluoride varnish; fluoride varnish+Er:YAG laser; fluoride varnish+Nd:YAG laser; non-fluoride varnish; non-fluoride varnish+Er:YAG laser; non-fluoride varnish+Nd:YAG laser. The Er:YAG (100mJ, 3Hz) and Nd:YAG (70mJ, 15Hz) were applied for 10s. Specimens were subjected to further erosive challenges with citric acid 0.3% 4×/day, during 1min, for 5 days, remaining in artificial saliva between cycles. Dentin permeability was then assessed. Two-way ANOVA demonstrated no significant interaction between laser and varnish (p=0.858). RESULTS: No effect was also detected for the main factor varnish (p=0.768), while permeability of eroded root dentin was significantly lower when such substrate was laser-irradiated, no matter the laser source (p<0.001). CONCLUSIONS: This study concluded that Er:YAG and Nd:YAG lasers can be employed to control the permeability of eroded root dentin, regardless of fluoride varnish application.

Effects of different desensitizing treatments on root dentin permeability

Abstract The objective of this study was to evaluate the effects of diode laser and a desensitizing dentifrice on dentin permeability. Fifty-two root dentin fragments were obtained (5 × 5mm) and treated with 24% EDTA gel. The samples were divided into 4 groups (n = 13): G1, control (no treatment); G2, diode laser (λ = 908 nm, 1.5 W, continuous mode, 20s); G3, application of abrasive dentifrice for 1 minute (Elmex Sensitive Professional (International Gaba); and G4, application of abrasive dentifrice for 1 minute followed by irradiation with diode laser. Ten samples per group were immersed in 2% methylene blue solution for 4h. The specimens were washed, longitudinally sectioned, observed under optical microscopy, photographed and assessed based on the degree of dye leakage. The remaining samples were observed under scanning electron microscopy (SEM). The leakage data were subjected to ANOVA test, followed by Tukey's t-test (α = 5%). Groups 2, 3 and 4 showed less dye penetration than the control group (p < 0.05), but were similar among each other. SEM images showed that dentinal tubules were open in G1, and fused and occluded in G2. Group 3 showed dentinal tubules that were occluded by the metal ions from the toothpaste. G4 presented similar characteristics to G3, and the presence of fused dentin. The diode laser and the dentifrice were effective in reducing dentinal permeability, and the combination of the two treatments did not show better results than either one used alone.

Demineralization and hydrogen peroxide penetration in teeth with incipient lesions.

The aim of this study was to evaluate the demineralization and hydrogen peroxide (HP) penetration in teeth with incipient lesions submitted to bleaching treatment. For analysis of HP penetration, sound and demineralized enamel/dentin discs were placed in artificial pulp chambers containing acetate buffer solution. After bleaching treatment, this solution was subjected for analysis of optical density by spectrophotometry and the disc surfaces were analyzed with scanning electron microscopy (SEM) and polarized light microscopy (PLM). The remaining discs were subjected for cross-sectional hardness analysis at different depths. Data were analyzed by repeated measures ANOVA and PLSD Fisher test (a=0.05). It was observed that previously demineralized teeth showed greater HP penetration (p<0.05). The bleaching treatment caused changes to a depth of 20 µm in sound enamel and up to 90 µm in demineralized enamel. SEM and PLM images revealed that the bleaching treatment caused superficial changes that were considerably more accentuated in previously demineralized teeth. It may be concluded that the enamel mineralization level influences HP penetration and the bleaching agent contributed to increase the demineralization depth.

Demineralization and Hydrogen Peroxide Penetration in Teeth with Incipient Lesions

The aim of this study was to evaluate the demineralization and hydrogen peroxide (HP) penetration in teeth with incipient lesions submitted to bleaching treatment. For analysis of HP penetration, sound and demineralized enamel/dentin discs were placed in artificial pulp chambers containing acetate buffer solution. After bleaching treatment, this solution was subjected for analysis of optical density by spectrophotometry and the disc surfaces were analyzed with scanning electron microscopy (SEM) and polarized light microscopy (PLM). The remaining discs were subjected for cross-sectional hardness analysis at different depths. Data were analyzed by repeated measures ANOVA and PLSD Fisher test (a=0.05). It was observed that previously demineralized teeth showed greater HP penetration (p<0.05). The bleaching treatment caused changes to a depth of 20 µm in sound enamel and up to 90 µm in demineralized enamel. SEM and PLM images revealed that the bleaching treatment caused superficial changes that were considerably more accentuated in previously demineralized teeth. It may be concluded that the enamel mineralization level influences HP penetration and the bleaching agent contributed to increase the demineralization depth.

O objetivo deste estudo foi avaliar a desmineralização e a penetração do peróxido de hidrogênio (HP) em dentes com lesões incipientes submetidos ao tratamento clareador. Para analisar a penetração do peróxido de hidrogênio, discos de esmalte/dentina hígidos e desmineralizados foram posicionados em câmaras pulpares artificiais contendo solução tampão de acetato. Após o tratamento clareador, esta solução foi submetida à análise da densidade óptica no espectrofotômetro e as superfícies dos discos foram analisadas por meio de microscopia eletrônica de varredura (MEV) e microscopia de luz polarizada (MLP). Os discos restantes foram submetidos à análise de microdureza transversal em diferentes profundidades. Os dados foram submetidos aos testes ANOVA e teste PLSD Fisher (= 5%). Observou-se que os dentes previamente desmineralizados mostraram maior penetração de HP (p<0,05). O tratamento clareador causou alterações em uma profundidade de 20 μm em esmalte hígido e até 90 μm em esmalte desmineralizado. As imagens obtidas em PLM e MEV mostraram que o tratamento clareador promove alterações superficiais no esmalte, sendo mais pronunciadas em dentes previamente desmineralizados. Foi concluído que o nível de mineralização do esmalte influencia a penetração do PH e que o agente clareador contribuiu para o aumento da profundidade de desmineralização.

Transdentinal cytotoxicity of experimental adhesive systems of different hydrophilicity applied to ethanol-saturated dentin.

The aim of this study was to evaluate the transdentinal cytotoxicity of experimental adhesive systems (EASs) with different hydrophilicity and dentin saturation solutions on odontoblast-like cells. One hundred 0.4-mm-thick dentin discs were mounted in in vitro pulp chambers and assigned to 10 groups. MDPC-23 cells were seeded onto the pulpal side of the discs, incubated for 48h. The EASs with increasing hydrophilicity (R1, R2, R3 and R4) were applied to the occlusal side after etching and saturation of etched dentin with water or ethanol. R0 (no adhesive) served as controls. R1 is a non-solvated hydrophobic blend, R2 is similar to a simplified etch-and-rinse adhesive system and R3 and R4 are similar to self-etching adhesives. After 24h, cell metabolism was evaluated by MTT assay (n=8 discs) and cell morphology was examined by SEM (n=2 discs). Type of cell death was identified by flow cytometry and the degree of monomer conversion (%DC) was determined by infrared spectroscopy (FTIR) after 10s or 20s of photoactivation. Data were analyzed by the Kruskal-Wallis and Mann-Whitney tests (α=0.05). Dentin saturation with ethanol resulted in higher necrotic cell death ratios for R2, R3 and R4 compared with water saturation, although R2 and R3 induced higher SDH production. Photoactivation for 20s significantly improved the %DC of all EASs compared with 10s. A significant positive correlation was observed between the degree of hydrophilicity and %DC. In conclusion, except for R1, dentin saturation with ethanol increased the cytotoxicity of EASs, as expressed by the induction of necrotic cell death.

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.

Chemical treatment of the intra-canal dentin surface: a new approach to modify dentin hydrophobicity.

OBJECTIVE: This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS). MATERIAL AND METHODS: An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA). The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT). RESULTS AND CONCLUSIONS: Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system.

Influence of type of bur and acid etching on dentin hydraulic conductance.

The aim of this study was to compare ex vivo filtration rate (hydraulic conductance) in human dentin discs mechanically treated with diamond and carbide burs of different grain size with or without acid etching. Method: 60 healthy third molars, recently extracted from patients aged 18-30 years, were cleaned, disinfected (0.1% thymol) and embedded in epoxy resin blocks. Dentin discs were obtained by cutting the occlusal surface with cylindrical rotary instruments, forming nine groups containing 12 specimens each: 1: fine grain (FG); 2: medium grain (MG); 3: coarse grain (CG); 4: carbide (C) burs; 5: FG with acid etching (AE); 6: MG with AE; 7: CG with AE; 8: C with AE; 9: only AE. Hydraulic conductance was determined in the experimental model under constant pressure of 200mm H2O. No difference in hydraulic conductance was observed among dentin discs treated with different types of burs (p = 0.5). Differences were found in the hydraulic conductance of etched and non-etched dentin discs (p < 0.001). The type of mechanical bur treatment does not affect dentin hydraulic conductance. Acid etching significantly increases dentin hydraulic conductance.

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).

Chemical treatment of the intra-canal dentin surface: a new approach to modify dentin hydrophobicity

Objective: This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS). Material and Methods: An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA). The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT). Results and Conclusions: Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system.

Influence of type of bur and acid etching on dentin hydraulic conductance. / Influence of type of bur and acid etching on dentin hydraulic conductance.

The aim of this study was to compare ex vivo filtration rate (hydraulic conductance) in human dentin discs mechanically treated with diamond and carbide burs of different grain size with or without acid etching. Method: 60 healthy third molars, recently extracted from patients aged 18-30 years, were cleaned, disinfected (0.1

thymol) and embedded in epoxy resin blocks. Dentin discs were obtained by cutting the occlusal surface with cylindrical rotary instruments, forming nine groups containing 12 specimens each: 1: fine grain (FG); 2: medium grain (MG); 3: coarse grain (CG); 4: carbide (C) burs; 5: FG with acid etching (AE); 6: MG with AE; 7: CG with AE; 8: C with AE; 9: only AE. Hydraulic conductance was determined in the experimental model under constant pressure of 200mm H2O. No difference in hydraulic conductance was observed among dentin discs treated with different types of burs (p = 0.5). Differences were found in the hydraulic conductance of etched and non-etched dentin discs (p < 0.001). The type of mechanical bur treatment does not affect dentin hydraulic conductance. Acid etching significantly increases dentin hydraulic conductance.