Effect of Nisin-based pretreatment solution on dentin bond strength, antibacterial property, and MMP activity of the adhesive interface.

OBJECTIVE: To evaluate the effect of a Nisin-based dentin pretreatment solution on microtensile bond strength, antibacterial activity, and matrix metalloproteinase (MMP) activity of the adhesive interface. MATERIALS AND METHODS: 100 human molars were sectioned to expose dentin. The teeth were assigned to five groups (n = 20), according to the dentin pretreatment: 0.5%, 1.0%, or 1.5% Nisin; 0.12% chlorhexidine (positive control), and no solution (negative control), and divided into 2 subgroups: no aging, and thermomechanical aging. Specimens were etched with 37% H3PO4 for 15 s and submitted to the dentin pretreatment. Then, they were bonded with an adhesive (Adper Single Bond 2) and a resin composite for microtensile bond strength (µTBS) evaluation. Antibacterial activity against Streptococcus mutans was qualitatively examined using an agar diffusion test. Anti-MMP activity within hybrid layers was examined using in-situ zymography. Data were analyzed with two-factor ANOVA and post-hoc Tukey's test (α = 0.050). RESULTS: For µTBS, significant differences were identified for the factors "solutions" (p = 0.002), "aging" (p = 0.017), and interaction of the two factors (p = 0.002). In the absence of aging, higher µTBS was observed for the group 0.5% Nisin. In the presence of aging, all groups showed similar µTBS values. All Nisin concentrations were effective in inhibiting the growth of S. mutans. Endogenous MMP activity was more significantly inhibited using 0.5% and 1.0% Nisin (p < 0.050). CONCLUSION: 0.5% and 1.0% Nisin solutions do not adversely affect resin-dentin bond strength and exhibit a potential bactericidal effect against S. mutans. Both concentrations effectively reduce endogenous gelatinolytic activity within the hybrid layer. CLINICAL RELEVANCE: The use of 0.5% and 1.0% Nisin solutions for dentin pretreatment potentially contributes to preserving the adhesive interface, increasing the longevity of composite restorations.

Influence of chlorhexidine, propolis, pulpal pressure simulation, and aging on dentin bond strength.

The present study evaluated the bond strength (µTBS) of dentin treated with chlorhexidine and propolis subjected to simulated pulpal pressure (SPP) and thermocycle aging. One hundred and twenty healthy human molars were sectioned to obtain 2 mm of dentin thickness and were divided into two groups (n = 60): SPP (15 cm H2 O) and no SPP (Control group). Dentin surfaces were conditioned with 37% phosphoric acid for 15 s and were divided according to the dentin treatment (n = 20): Control; Chlorhexidine gluconate (0.2% for 30 s) and Propolis (aqueous propolis extract for 30 s). Half of the specimens were submitted to 15,000 thermocycle aging (5 ± 2°C and 55 ± 2°C). The samples were sectioned into beams and submitted to µTBS. Data were analyzed by three-way ANOVA (SPP × Dentin treatment × Thermocycle aging) and the Tukey's tests (p < .001). With regard to the SPP, ANOVA revealed that the Control group (32.98 MPa) had significantly higher values of µTBS when compared to the SPP (29.19 MPa). With regard to Thermocycle aging, no aging (34.05 MPa) had significantly higher values of µTBS when compared to the aging (28.12 MPa). With regard to the dentin treatment, Propolis and Chlorhexidine did not statistically influence the results (p > .05). The SPP and thermocycle aging negatively influenced the bond strength between the dentin and resin; the 0.2% chlorhexidine digluconate and aqueous propolis extract solutions did not interfere in the bond strength between the resin and dentin. The use of chlorhexidine and propolis as a dental treatment may not influence the dentin bond strength, but SPP and thermocycle aging may damage the longitudinal dentin bond strength. RESEARCH HIGHLIGHTS: Chlorhexidine and propolis as a dental treatment may not influence the dentin bond strength. Simulated pulpal pressure and thermocycle aging may damage the longitudinal dentin bond strength.

Desenvolvimento de solução de desinfecção cavitária à base de nisina e suas implicações na interface adesiva / Development of a nisin-based cavity disinfection solution and its implications for the adhesive interface

Este trabalho desenvolveu uma solução de desinfecção cavitária à base de Nisina, um peptídeo utilizado para conservação de alimentos, avaliou a consequência dessa aplicação nas propriedades mecânicas e biológicas da interface adesiva. Utilizou-se 100 dentes humanos hígidos e recém-extraídos, divididos em 2 grupos: I (Corte Imediato), C (Ciclagem Termomecânica). Os espécimes foram submetidos envelhecimento mecânico (120.000 ciclos) e térmico (5.000 ciclos) para avaliar os resultados da resistência de união de maneira imediata e pós ciclagem. Foram subdivididos de acordo com a concentração de Nisina aplicada (n=10): controle (sem aplicação de solução de Nisina ­ SB), controle positivo (aplicação de Digluconato de Clorexidina 0,12% - CP), solução de Nisina com concentração 0,5% (N05), solução de Nisina com concentração 1,0% (N1) e solução de Nisina com concentração 1,5% (N1,5). A superfície de esmalte foi removida dos espécimes, expondo a superfície dentinária. A Nisina, assim como a Clorexidina, foi aplicada após condicionamento ácido e antes da aplicação do adesivo (Single Bond). A resina composta (Filtek Z250) foi aplicada através da técnica incremental. Foram avaliadas a resistência de união, através de teste de microtração, de maneira imediata e longitudinal, e a atividade antibacteriana através do teste de difusão em ágar. Uutilizou-se a microscopia confocal laser para avaliar a penetrabilidade da Nisina modificada por Rodamina na dentina e a atividade gelatinolítica por meio da zimografia in situ. Os espécimes resultantes da microtração foram avaliados em microscopia eletrônica de varredura (MEV). Os resultados obtidos foram submetidos ao teste estatístico de normalidade, e ao teste ANOVA, seguido do teste de Tukey (5%). Os resultados do teste de microtração (p=0,0016) foram, em Mpa: I 26,04±2,11A e C 25,24±1,08B. Nos subgrupos foram: SB 26,69±3,56AB, CP 25,09±3,43ª , N0525,09±3,43A,N125,54±2,24A, N1,524,44±1,49. Na microscopia confocal laser, foi confirmada a penetrabilidade da Nisina no substrato a partir da análise das imagens. Os resultados obtidos foram submetidos à análise estatística, sendo eles: CP119,98±12,17ª, N05 124,13±12,47ª, N1 176,37±7,04B, N1,5 233,50±9,87C. A inibição de MMPs foi submetida a teste estatístico: SB2226,70±14,85D, CP171,78±4,97C, N05 129,96±3,97B, N1 120,31±3,74B e N1,5 109,54±4,21ª. Observou-se que a Nisina não causou diminuição significativa da resistência de união, enquanto o grupo C apresentou resultados menores comparados ao grupo I. Observou-se que a Nisina possui capacidade de inibição de Streptococcus através do teste de difusão em ágar. A Nisina também foi capaz de penetrar no substrato e inibir metaloproteinases, sem alterar o modo de fratura das restaurações. Sendo assim, os resultados obtidos demonstram que a Nisina possui características interessantes para a evolução de estudos posteriores envolvendo desinfecção cavitária. (AU)

This work developed a cavity disinfection solution based on Nisin, a peptide used for food preservation, evaluated the consequence of this application on the mechanical and biological properties of the adhesive interface. 100 healthy and recently extracted human teeth were used, divided into 2 groups: I (Immediate Cutting), C (Thermomechanical Cycling). The specimens underwent mechanical aging (120,000 cycles) and thermal aging (5,000 cycles) to evaluate bond strength results immediately and after cycling. They were subdivided according to the applied Nisin concentration (n=10): control (no application of Nisin solution - SB), positive control (application of 0.12% Chlorhexidine Digluconate - CP), Nisin solution with 0 concentration .5% (N05), Nisin solution with 1.0% concentration (N1) and Nisin solution with 1.5% concentration (N1.5). The enamel surface was removed from the specimens, exposing the dentin surface. Nisin, like Chlorhexidine, was applied after acid etching and before application of the adhesive (Single Bond). Composite resin (Filtek Z250) was applied using the incremental technique. The bond strength was evaluated through microtensile test, immediately and longitudinally, and the antibacterial activity through the agar diffusion test. Confocal laser microscopy was used to assess the penetrability of Nisin modified by Rhodamine in dentin and the gelatinolytic activity by means of in situ zymography. The specimens resulting from microtraction were evaluated in scanning electron microscopy (SEM). The results obtained were submitted to the statistical test of normality, and to the ANOVA test, followed by the Tukey test (5%). The results of the microtensile test (p=0.0016) were, in Mpa: I 26.04±2.11A and C 25.24±1.08B. The subgroups were: SB 26.69±3.56AB, CP 25.09±3.43ª, N0525.09±3.43A N125.54±2.24A, N1.524.44±1.49. In confocal laser microscopy, the penetrability of Nisin in the substrate was confirmed based on image analysis. The results obtained were submitted to statistical analysis, as follows: CP119.98±12.17ª, N05 124.13±12.47ª, N1 176.37±7.04B, N1.5 233.50±9.87C. The inhibition of MMPs was submitted to a statistical test: SB2226.70±14.85D, CP171.78±4.97C, N05 129.96±3.97B, N1 120.31±3.74B and N1.5 109.54 ±4.21a. It was observed that Nisin did not cause a significant decrease in bond strength, while group C showed lower results compared to group I. It was observed that Nisin has the ability to inhibit Streptococcus through the agar diffusion test. Nisin was also able to penetrate the substrate and inhibit metalloproteinases, without altering the fracture mode of the restorations. Thus, the results obtained demonstrate that Nisin has interesting characteristics for the evolution of further studies involving cavity disinfection (AU)

Minimal intervention in dentistry: which is the best approach for silorane composite restoration repairs?

BACKGROUND: This study aimed to evaluate surface treatments, adhesives and composites for repairing silorane based restorations. MATERIAL AND METHODS: One hundred and twenty truncated cones (2 mm smaller diameter and 4 mm larger diameter) made of silorane composite were divided in 12 groups according with the surface treatment (diamond bur and oxide aluminum abrasion), the adhesive (Adper Scothbond Multipurpose (3M ESPE), Ecusit (Voco) and Filtek P90 Adhesive (3M ESPE)). Each group was subdivided in two according with the composite used for repair (methacrylate and silorane). The repair was made with a second truncated cone build over the first one and bond strength assssed by tensile strength. Data were submitted to ANOVA 3-way and Tukey's test (p<0.05). RESULTS: There was difference only for the adhesives and the composites, with conventional adhesives (Adper Scothbond Mutipurpose) and methacrylate-based composites (Filtek Z350) presenting superior tensile strength compared to the silorane ones (P90 Adhesive system and composite). CONCLUSIONS: Therefore, it must be concluded that silorane composite can be repaired with methacrylate base composites and adhesives. Key words:Silorane composites, composites, bond strength, minimal intervention.