The aim of this study was to evaluate the trans-enamel and trans-dentinal effects of a 35% hydrogen peroxide (H 2 O 2 ) 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% H 2 O 2 ; G2-35% H 2 O 2 + 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% H 2 O 2 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.

The aim of this study was to evaluate the effect of specific parameters of low-level laser therapy (LLLT) on biofilms formed by Streptococcus mutans, Candida albicans or an association of both species. Single and dual-species biofilms--SSB and DSB--were exposed to laser doses of 5, 10 or 20 J/cm(2) from a near infrared InGaAsP diode laser prototype (LASERTable; 780 ± 3 nm, 0.04 W). After irradiation, the analysis of biobilm viability (MTT assay), biofilm growth (cfu/mL) and cell morphology (SEM) showed that LLLT reduced cell viability as well as the growth of biofilms. The response of S. mutans (SSB) to irradiation was similar for all laser doses and the biofilm growth was dose dependent. However, when associated with C. albicans (DSB), S. mutans was resistant to LLLT. For C. albicans, the association with S. mutans (DSB) caused a significant decrease in biofilm growth in a dose-dependent fashion. The morphology of the microorganisms in the SSB was not altered by LLLT, while the association of microbial species (DSB) promoted a reduction in the formation of C. albicans hyphae. LLLT had an inhibitory effect on the microorganisms, and this capacity can be altered according to the interactions between different microbial species.

This study evaluated the cytotoxic effects of 2 mineral trioxide aggregate (MTA) cements - White-MTA-Angelus and a new formulation, MTA-Bio - on odontoblast-like cell (MDPC-23) cultures. Twenty-four disc-shaped (2 mm diameter x 2 mm thick) specimens were fabricated from each material and immersed individually in wells containing 1 mL of DMEM culture medium for either 24 h or 7 days to obtain extracts, giving rise to 4 groups of 12 specimens each: G1 - White-MTA/24 h; G2 - White-MTA/7 days; G3 - MTA-Bio/24 h; and G4 - MTA-Bio/7 days. Plain culture medium (DMEM) was used as a negative control (G5). Cells at 30,000 cells/cm(2) concentration were seeded in the wells of 24-well plates and incubated in a humidified incubator with 5% CO2 and 95% air at 37 degrees C for 72 h. After this period, the culture medium of each well was replaced by 1 mL of extract (or plain DMEM in the control group) and the cells were incubated for additional 2 h. Cell metabolism was evaluated by the MTT assay and the data were analyzed statistically by ANOVA and Tukey's test (alpha=0.05). Cell morphology and the surface of representative MTA specimens of each group were examined by scanning electron microscopy. There was no statistically significant difference (p>0.05) between G1 and G2 or between G3 and G4. No significant difference (p>0.05) was found between the experimental and control groups either. Similar cell organization and morphology were observed in all groups, regardless of the storage periods. However, the number of cells observed in the experimental groups decreased compared to the control group. MTA-Bio presented irregular surface with more porosities than White-MTA. In conclusion, White-MTA and MTA-Bio presented low cytotoxic effects on odontoblast-like cell (MDPC-23) cultures.

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ResumoIntrodução: Agentes promotores de ligações cruzadas têm sido investigados como inibidores da atividade enzimática da dentina, o que favoreceria a longevidade das restaurações adesivas. Objetivo: Avaliar o efeito do tratamento da dentina com proantocianidina (PA), em curtos períodos de tempo, na inibição da atividade de MMPs in situ. Material e método: Quarenta espécimes de dentina (1×1×6 mm) foram obtidos de molares hígidos e divididos em quatro grupos (n=10). Os espécimes foram condicionados com ácido fosfórico por 15 s, seguido de lavagem em água deionizada. A dentina condicionada foi tratada com: água, 5% PA por 5 s, 15 s ou 30 s. A atividade de MMP foi analisada colorimetricamente (SensoLyte®) e os dados de absorbância (412 nm) foram submetidos aos testes de ANOVA e Tukey (α=0,05). Resultado: Todos os períodos de tratamento foram capazes de reduzir a atividade de MMPs, sendo que os melhores resultados foram observados para a dentina tratada com PA por 15 s (63,1% redução) e 30 s (70,2%). O tratamento por 5 s foi capaz de inibir 39,9% das MMPs. Conclusão: A aplicação de PA sobre a dentina condicionada foi capaz de reduzir a atividade de MMPs mesmo em períodos de tempo extremamente curtos, como 5 s. No entanto, melhores resultados foram obtidos com os maiores períodos de tratamento.Descritores: Dentina; colágeno; metaloproteinase da matriz; proantocianidina. AbstractIntroduction: Collagen cross-linkers have been investigated as inhibitors of the enzymatic activity of dentin, therefore improving the longevity of adhesive restorations. Purpose: To evaluate the effect of etched dentin treatment with proanthocyanidin (PA) in short periods of time on the inhibition of dentin metalloproteinases (MMP) activity in situ. Material and method: Forty dentin specimens (1x1x6mm) were obtained from sound third molars and divided into 4 groups (n=10). The specimens were etched with 37% phosphoric acid for 15s and rinsed in deionized water. Then they were treated with the following solutions: water, 5% PA for 5s, 15s or 30s. The total MMP activity was analyzed by a colorimetric test (SensoLyte®). Absorbance data (412nm) were submitted to ANOVA and Tukey tests (α=0.05). Result: All treatment periods were able to reduce the total activity of MMPs. The best results were observed for dentine treated with PA for 15s (63.1% reduction) and 30s (70.2%). Treatment for 5s was capable of inhibiting only 39.9% of the total MMP activity. Conclusion: Application of PA on the etched dentin in extremely short periods of time reduced the MMPs activity of dentin, even after 5s. However, the best results were obtained for the longer periods.

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