Is α-Tocopherol or Sodium Ascorbate Effective as Antioxidant on Fracture Resistance of Bleached Teeth?

AIM: To evaluate the effect of two antioxidant formulations (sodium ascorbate and α-tocopherol) on fracture resistance of endodontically treated teeth. MATERIALS AND METHODS: Sixty human premolars were endodontically treated and divided into six groups (n = 10): G1 (negative control)-unbleached and restored with composite resin; G2 (positive control)-bleached in three sessions, using hydrogen peroxide (15 H2O2) plus titanium dioxide (TiO2) nanoparticles, photoactivated by LED laser system and restored with composite resin; G3-bleaching similar to G2, after the use of 10% sodium ascorbate gel for 24 hours and restored with composite resin; G4-similar to G3, but with the use of 10% sodium ascorbate solution and restored with composite resin; G5 and G6-similar to G3, but with the use of 10% α-tocopherol in alcohol or carbopol, respectively, and was also restored. A mechanical fracture resistance test was performed and the Kruskal-Wallis test was used to evaluate the results (α = 0.05). RESULTS: No statistical difference was observed in fracture resistance between groups (p > 0.05). Regarding the antioxidant and pharmaceutical formulation applied, no statistical difference was detected in any comparison (p > 0.05). The frequency of fractures considered favorable was higher in G1 and G3 compared to the other groups. CONCLUSION: The endodontically treated teeth bleached with 15 H2O2 plus TiO2 nanoparticles and photoactivated with the LED laser did not decrease the fracture resistance and the use of sodium ascorbate or α-tocopherol did not increase the crown fracture resistance. CLINICAL SIGNIFICANCE: The literature reports a significant reduction in the bond strength of restorations on the bleached dentin. Therefore, the use of antioxidant agents may have a promising effect on fracture resistance of endodontically treated teeth.

Efeito citotóxico de géis clareadores com diferentes concentrações de peróxido de hidrogênio aplicados diretamente sobre a dentina / Cytotoxic effects of a bleaching gel with different concentrations of hydrogen peroxide applied directly on dentin

Objetivo: Avaliar os efeitos citotóxicos de agentes clareadores com diferentes concentrações de PH sobre células odontoblastóides, quando aplicados diretamente sobre a superfície de dentina humana. Material e método: Cinquenta discos de dentina (0,5 mm de espessura) foram adaptados em câmaras pulpares artificiais (CPAs) e células MDPC-23 foram semeadas na superfície pulpar dos discos. Cinco grupos (n=10) foram estabelecidos: G1: 7,5% PH; G2: 20% PH; G3: 35% PH; G4: gel sem PH; G5: DMEN (controle). Os produtos foram aplicados na superfície oclusal dos discos por 2x de 15 minutos. A viabilidade (ensaio de MTT) e a morfologia celular (MEV) foram avaliadas imediatamente após o clareamento. Os dados de viabilidade celular foram submetidos ao teste de Kruskal-Wallis e Mann-Whitney (α=0,05). Resultados: Redução significante na viabilidade celular em relação ao controle (G5) foi observada para todas as concentrações de PH (p<0,05), associada a intensas alterações na morfologia celular. Entretanto, nenhuma diferença significante foi observada entre as três concentrações de PH. Também, não houve diferença estatística entre o grupo controle e o grupo gel sem PH (G5 e G4). Conclusão: Todas as concentrações de PH causaram efeitos citotóxicos de severos sobre as células MDPC-23, quando aplicados diretamente sobre a dentina. Entretanto, a intensidade do efeito tóxico não foi influenciada pela concentração de PH no agente clareador. Relevância clínica: Apesar das limitações deste estudo in vitro, os resultados indicam que o clareamento dental não deve ser realizado diretamente em áreas com exposição da dentina.

Objective: To evaluate the cytotoxic effects of bleaching gels with different concentrations of hydrogen peroxide (HP) on odontoblast-like cells, when applied directly on dentin. Material and method: Fifty dentin discs (0.5 mm thick) were adapted in artificial pulp chambers (APC) and MDPC-23 cells were seed on the pulpal side. The discs were divided into 5 groups (n=10): G1: HP 7.5%; G2: HP 20%; G3: HP 35%; G4: gel with no HP; and G5: no treatment (control). The gels were applied on the occlusal side of the discs for 2x of 15 min. Cellular viability (MTT assay) and morphology (SEM) were analyzed immediately after the bleaching procedure. Data of cellular viability were submitted to Kruskal-Wallis and Mann-Whitney tests (α=0.05). Results: Significant reduction in cellular viability was seen for all HP concentrations in comparison to the control (G5). However, no statistical significant difference was seen among the concentrations of HP. Likewise, there was no statistical difference between the control group (G5) and the group where the gel with no HP was applied (G4). Conclusion: All HP concentrations caused severe cytotoxic effects on the odontoblast-like cells when applied directly on dentin. However, the intensity of the cytotoxic effect was not influenced by the concentration of the HP included in the bleaching gel. Clinical significance: Within the limitations of this in vitro study, the results strongly indicate that dental bleaching procedures should not be performed directly on areas of dentin exposure.

Contaminação mercurial: risco ocupacional ao cirurgião-dentista / Mercury contamination: occupational risk of the dental surgeon

Introdução e objetivo: O mercúrio é um material amplamente usado na prática odontológica, contudo trata-se de um dos mais perigosos poluentes ambientais e ocupacionais. Nesse sentido, este estudo tem como objetivos analisar diversos aspectos referentes à contaminação mercurial, com base em trabalhos existentes na literatura, e demonstrar os riscos que o mercúrio causa quando manuseado de forma inadequada. Revisão de literatura: Algumas recomendações são efetuadas, pertinentes ao manuseio e à aplicação do mercúrio no ambiente do consultório odontológico, já que um sem-número de restaurações de amálgama está sendo substituído por material estético, podendo ocorrer inalação do vapor de mercúrio. Muitos cirurgiões-dentistas não se preocupam com os riscos que esse elemento químico pode causar à saúde. Conclusão: O mercúrio pode produzir efeitos tóxicos locais ou sistêmicos ao organismo, pela inalação de vapores durante o preparo do amálgama ou mesmo quando da sua substituição.

Introduction and objective: Mercury is a widely used material in dental practice. However, it is one of the most dangerous environmental and occupational pollutants. Thus, the aim of this study is to analyze several aspects of mercury contamination, based on a literature review, in order to demonstrate the risks related to mishandling of mercury. Literature review: Some recommendations are stated regarding the handling and application of mercury in the dental office environment, once aesthetic materials have been replacing a large number of amalgam restorations. This could lead to mercury vapor exposure, a chemical risk to the health that many dental professionals do not always consider. Conclusion: Mercury can produce local or systemic toxic effects on the organism through vapor inhalation during amalgam preparation or during its replacement

Occurrence of talon cusp on a geminated maxillary central incisor: a case report.

This article reports an uncommon case of talon cusp on a geminated permanent maxillary central incisor, including details of the clinical and radiographic findings and treatment. A 28-year-old woman presented at the university dental clinic, and intraoral examination revealed a maxillary central incisor of abnormal size with a prominent accessory cusp on the lingual aspect. The case was diagnosed as talon cusp on a geminated tooth. Early diagnosis of this anomaly is important since it may cause clinical problems such as esthetic concerns, caries and tooth crowding. In the present case, these anomalies did not complicate the subsequent endodontic treatment.

Influence of different dentin etching times and concentrations and air-abrasion technique on dentin microtensile bond strength.

PURPOSE: To determine the influence of different dentin treatments on the microtensile bond strengths of adhesive resins to dentin. METHODS: Fifteen human molars were ground to 600-grit to obtain flat root-dentin surfaces. Five different dentin treatments were evaluated: Group 1--10% phosphoric acid for 30 seconds; Group 2--37% phosphoric acid for 15 seconds; Group 3--air-abrasion for 10 seconds followed by 10% phosphoric acid for 30 seconds; Group 4--air-abasion for 10 seconds followed by 37% phosphoric acid for 15 seconds. The dental adhesive (OptiBond Solo Plus) was applied according to manufacturer's instructions and followed by composite (Z100) application to provide sufficient bulk for microtensile bond testing. All samples were placed in distilled water for 24 hours at 37 degrees C, thermocycled for 500 cycles in distilled water at 10 degrees C and 50 degrees C, and serially sliced perpendicular to the adhesive surface and subjected to tensile forces (0.5 mm/minute). Additional samples were prepared for SEM to observe the adhesive interface. RESULTS: Group 2 exhibited significantly (P < 0.05) lower bond strength values than all other treatments. The bond strengths of the different conditions were (in MPa): Group 1: 43.0 +/- 16.1; Group 2: 29.2 +/- 8.3; Group 3: 48.1 +/- 14.2; Group 4: 41.0 +/- 9.3. The dentin treated with phosphoric acid 37% for 15 seconds showed the lowest values of microtensile bond strength. The results obtained with Groups 1, 3 and 4 were statistically similar.