Biological and mechanical degradation affecting the surface properties of aesthetic restorative

To evaluate the roughness (Ra), Knoop hardness (KHN) and change of color (ΔE) of esthetic restorative materials (Filtek Z350-composite nanoparticle; Empress Direct-composite nanohybrid and IPS e.Max-ceramic) subjected to contact with the Streptococcus mutans biofilm (biological degradation) associated with abrasion generated by tooth brushing (mechanical degradation). Methods: Ten specimens of each material were prepared, and the surface properties initial were evaluated. All specimens were exposed to Streptococcus mutans inoculum; after 7 days, surface properties were evaluated. The specimens were submitted to a 30,000 toothbrushing cycles, using a toothpaste slurry, then, surface properties were evaluated again. Data were analyzed by Proc-Mixed, One-way ANOVA, Tukey-Kramer and Tukey's tests (α = 0.05). Results: At the baseline, ceramic showed the highest Ra and KHN values; after the biological degradation the composites showed increased Ra, but KHN did not change; after the mechanical degradation, Empress showed decreased Ra and Z350 showed similar Ra, the KHN increased to both composites, and all materials had increased lightness after the mechanical degradation. Conclusions: The results suggest that, when exposed to Streptococcus mutans biofilm and toothbrush abrasion, the ceramics undergoes minimal degradation and the composites exhibited variable degradation, depending on the composition of the material (AU)

Effectiveness of casein phosphopeptide-amorphous calcium phosphate and lysozyme, lactoferrin, and lactoperoxidase in reducing Streptococcus mutans counts in dentinal caries.

This study compared the capacity of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) to that of a combination of lysozyme, lactoferrin, and lactoperoxidase (LLL) in root canal disinfectant for reducing the Streptococcus mutans counts from dentinal caries. Forty human permanent third molars were selected, and flat dentin surfaces were created. Carious lesions were induced using a microbiological model. The specimens were randomly divided into 2 groups (n = 20) according to the type of agent used: group 1, CPP-ACP; group 2, LLL. The S mutans counts were performed before application and after the first, second, and third applications of the agents. The duration of each application was 3 minutes. Carious dentin specimens were homogenized, diluted, and seeded onto mitis salivarius-bacitracin plates for viable counts of S mutans. Results showed that there was no significant reduction in the number of S mutans in group 1 after the applications of CPP-ACP (P > 0.05). In group 2, a significant reduction of S mutans was observed after the third application of LLL (P < 0.01). These results indicate that 3 applications of LLL enzymes can be used to reduce the number of S mutans in dentinal caries lesions.

Efficacy of a bioactive material and nanostructured desensitizing on dentin hypersensitivity treatment / Eficácia de um material bioativo e dessensibilizante nanoestruturado no tratamento da hipersensibilidade dentinária

Introduction: Dentin hypersensitivity is a frequent occurrence in dental practice. It is clinically characterized by acute, short, and temporary pain in response to mechanical, chemical, thermal, or osmotic stimuli resulting from dentin exposure. Objective: To compare in vivo the effect of an experimental crystalline bioactive material and nanostructured desensitizing on the pain assessment among patients with cervical dentin hypersensitivity. Material and method: Thirty patients were selected for this study, who were randomly assigned to two groups (n=15) in a split-mouth design. Each patient received two treatments: group 1 (fluoride gel and bioactive material) and group 2 (fluoride gel and nanostructured desensitizing). Pain analyses were performed using a visual analogue scale, ranging 0-10. Baseline pain measurement was performed prior to initial treatment (T0) and new measurements were carried out weekly for 3 weeks (T1, T2, and T3) before materials were reapplied. Final pain analysis was performed 3 months after initial treatment (T4). Degree of pain reduction was calculated using the formula T0 - Tperiod after treatment. The data of the pain measurements were analyzed using 2-way repeated measure ANOVA and Tukey’s test (α=0.05). Result: Regardless of evaluation period, there was no statistical difference on pain reduction between the treatments (p>0.05). The degree of pain was reduced significantly in each evaluated period for all tested treatments (p<0.05), by approximately three degrees after 3 months. Conclusion: The tested desensitizing materials were effective on dentin hypersensitivity reduction.

Introdução: A hipersensibilidade dentinária é uma ocorrência frequente na prática clínica; clinicamente caracterizada por dor aguda, curta e temporária, em resposta ao estímulo mecânico, químico, térmico ou osmótico causada pela exposição dentinária. Objetivo: Comparar in vivo o efeito de um material bioativo cristalino experimental e um dessensibilizante nanoestruturado na avaliação da dor de pacientes com hipersensibilidade dentinária cervical. Material e método: Trinta pacientes foram selecionados para este estudo, que foram randomicamente divididos em dois grupos (n=15) em um desenho experimental de boca dividida. Cada paciente recebeu dois tratamentos: grupo 1 (flúor gel e material bioativo) e grupo 2 (flúor gel e dessensibilizante nanoestruturado). As análises de dor foram realizadas usando uma escala visual analógica, variando de 0-10. A mensuração da dor inicial foi realizada previamente ao tratamento inicial (T0) e novas análises foram realizadas semanalmente durante 3 semanas (T1, T2 e T3) antes da reaplicação dos materiais. A análise final da dor foi realizada 3 meses após o início do tratamento (T4). O grau de redução de dor foi mensurado pela fórmula: T0 - Tperíodo após tratamento. Os dados das mensurações de dor foram analisados pela ANOVA para medidas repetidas 2 critérios e teste de Tukey (α=0,05). Resultado: Independente do período de avaliação, não houve diferença estatística entre todos os tratamentos na redução da dor (p>0,05). O grau de dor reduziu significativamente em cada período avaliado para todos os tratamentos testados (p<0,05), aproximadamente três graus após 3 meses. Conclusão: Os materiais dessensibilizantes testados foram efetivos na redução da hipersensibilidade dentinária.

Bond Strength of Experimental Low-viscosity Resin Materials to Early Enamel Caries Lesions: Effect of Diluent/Solvent Addition.

PURPOSE: To evaluate the effect of different concentrations of monomers and solvents/diluents on the microtensile bond strength (µTBS) bond strength of experimental low-viscosity resins (infiltrants) to enamel caries-like lesions (ECLL). MATERIALS AND METHODS: Flat enamel blocks obtained from sound human third molars were submitted to ECLL formation and randomly distributed into 9 groups (n = 10): G1: TEG-DMA 100%; G2: TEG-DMA 80%, ethanol 20%; G3; TEG-DMA 80%, HEMA 20%; G4: TEG-DMA 75%, UDMA 25%; G5: TEG-DMA 60%, UDMA 20%, ethanol 20%; G6: TEG-DMA 60%, UDMA 20%, HEMA 20%; G7: TEG-DMA 75%, bis-EMA 25%; G8: TEG-DMA 60%, bis-EMA 20%, ethanol 20%; G9: TEG-DMA 60%, bis-EMA 20%, HEMA 20%. After etching with 37% phosphoric acid for 60 s, experimental infiltrants were actively applied and photocured for 60 s, then stored in 100% humidity (24 h, 37°C). Hourglass-shaped specimens were obtained and the µTBS test performed (MPa). The fracture patterns were assessed by SEM. Data were submitted to two way-ANOVA and Tukey's tests (α = 0.05). RESULTS: The highest µTBS value was observed for G4 (TEG-DMA/UDMA, 19.18 MPa) and the lowest for G5 (TEG-DMA/UDMA/ethanol, 9.00 MPa). A significant decrease in µTBS was observed for all groups containing ethanol (G2, G5, and G8). The addition of HEMA did not affect µTBS values. Most groups showed a high frequency of mixed failure between infiltrant and enamel. CONCLUSION: The addition of bis-EMA or UDMA to TEG-DMA-based infiltrants did not improve bond strength to carious enamel. The ethanol addition negatively affected the bonding strength of infiltrants to enamel caries-like lesions, regardless of the resin matrix composition of the infiltrant.

Evaluation of polymerization characteristics and penetration into enamel caries lesions of experimental infiltrants.

OBJECTIVES: To evaluate the properties of experimental infiltrant blends by comparing them with the commercial infiltrant Icon(®) and penetration homogeneity into enamel caries lesions. METHODS: Groups were set up as follows: G1 (TEGDMA 100%); G2 (TEGDMA 80%, Ethanol 20%); G3 (TEGDMA 80%, HEMA 20%); G4 (TEGDMA 75%, BisEMA 25%); G5 (TEGDMA 60%, BisEMA 20%, Ethanol 20%); G6 (TEGDMA 60%, BisEMA 20%, HEMA 20%); G7 (TEGDMA 75%, UDMA 25%); G8 (TEGDMA 60%, UDMA 20%, Ethanol 20%); G9 (TEGDMA 60%, UDMA 20%, HEMA 20%) and Icon(®). Ten specimens were comprised by each group for the following tests (n=10): degree of conversion (DC), elastic modulus (EM), Knoop hardness (KH), and softening ratio (SR). Infiltrant penetration was evaluated using confocal microscopy (CLSM). Data were subjected to two-way ANOVA and a Tukey's test (5%). Data comparing experimental materials and Icon(®) were analysed using ANOVA and Dunnett's test (5%). RESULTS: The highest DC values were found in G1, G7, G8, and G9. The lowest DC values were found in G2, G4, G5, and G6. EM and KHN were significantly lower in HEMA and with ethanol addition for all blends, except for G9. There was no significant difference among the groups regarding SR, and it was not possible to take KHN readings of G2, G5, and G8 after storage. There was no significant difference among groups for infiltrant penetration into enamel lesions. CONCLUSIONS: The addition of hydrophobic monomers and solvents into TEGDMA blends affected DC, EM, and KHN. UDMA added to TEGDMA resulted in an increase in DC, EM, and KHN. Overall, solvents added to monomer blends resulted in decreased properties. The addition of hydrophobic monomers and solvents into TEGDMA blends does not improve the penetration depth of the infiltrants.