RESUMO
STATEMENT OF PROBLEM: Improved stability of the adhesive interface can be obtained using crosslinkers. However, research on the use of crosslinkers in root dentin is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of crosslinkers on the proteolytic activity of root dentin and on the bond strength of resin-cemented fiber posts. MATERIAL AND METHODS: Single root canals were obtained from premolars (n=48) and endodontically treated before being divided into 4 groups: deionized water (control), 0.5 mol/L carbodiimide, 5% proanthocyanidin, or 5% glutaraldehyde. After removing the canal sealer, the dentin was etched with phosphoric acid, followed by water rinsing and the application of the crosslinkers for 60 seconds. Fiber posts were cemented using an adhesive (Single Bond 2) and resin cement (RelyX ARC). The roots were then transversally sectioned to obtain 1 mm thick specimens from the cervical, middle, and apical thirds and then aged for 24 hours or 9 months. Nine roots per group were used for the push-out test and 3 for determining the proteolytic activity of the root dentin by in situ zymography. Bond strength data were submitted to a mixed-model ANOVA and Bonferroni tests (α=.05). RESULTS: Only proanthocyanidin negatively affected the 24-hour bond strength. After 9 months, a significant decrease in bond strength was seen for all groups, except for the crosslinked treated specimens from the cervical third of the root canal. Intense gelatinolytic activity was detected in the control group after 24 hours but was inhibited in the crosslinker-treated groups. Proteolytic activity was also not detected after 9 months for the groups treated with the crosslinkers, irrespective of the root canal third. Conversely, proteolytic activity increased for the specimens from the control group. CONCLUSIONS: Although no proteolytic activity was detected in the hybrid layers along the entire root canal, dentin biomodification with crosslinkers was effective in preventing bond strength loss only in the cervical third.
Assuntos
Reagentes de Ligações Cruzadas/química , Colagem Dentária , Adesivos Dentinários/química , Técnica para Retentor Intrarradicular , Carbodi-Imidas , Cavidade Pulpar , Dentina , Glutaral , Humanos , Proantocianidinas , Proteólise , Cimentos de ResinaRESUMO
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.
RESUMO
OBJECTIVES: To evaluate the effect of EDC on elastic modulus (E), MMPs activity, hydroxyproline (HYP) release and thermal denaturation temperature of demineralized dentin collagen. METHODS: Dentin beams were obtained from human molars and completely demineralized in 10 wt% H3PO4 for 18 h. The initial E and MMP activity were determined with three-point bending and microcolorimetric assay, respectively. Extra demineralized beams were dehydrated and the initial dry mass (DM) was determined. All the beams were distributed into groups (n=10) and treated for 30 s or 60 s with: water, 0.5 M, 1 M or 2 M EDC or 10% glutaraldehyde (GA). After treatment, the new E and MMP activity were redetermined. The beams submitted to DM measurements were storage for 1 week in artificial saliva, after that the mass loss and HYP release were evaluated. The collagen thermal denaturation temperature (TDT) was determined by DSC analysis. Data for E, MMP activity and HYP release were submitted to Wilcoxon and Kruskal-Wallis or Mann-Whitney tests. Mass loss and TDT data were submitted to ANOVA and Tukey tests at the 5% of significance. RESULTS: EDC was able to significantly increase collagen stiffness in 60s. 10% GA groups obtained the highest E values after both 30 and 60s. All cross-linking agents decreased MMP activity and HYP release and increased TDT temperature. Significant differences were identified among EDC groups after 30 or 60 s of cross-linking, 1M or 2M EDC showed the lowest MMP activity. SIGNIFICANCE: Cross-linking agents are capable of preventing dentin collagen degradation. EDC treatment may be clinically useful to increase resin-dentin stability.
Assuntos
Reagentes de Ligações Cruzadas/química , Dentina/química , Varredura Diferencial de Calorimetria , Humanos , Técnicas In VitroRESUMO
Objetivo: Avaliar o efeito da clorexidina (CLX) na umectabilidade da dentina hígida e afetada por cárie por um sistema adesivo convencional simplificado. Material e Método: Foram preparadas superfícies planas de dentina em 60 molares hígidos, dos quais 30 foram artificialmente cariados. Para cada condição de substrato, hígido e afetado por cárie, as superfícies foram divididas em 3 grupos (n=10): com smear layer (SL), sem SL impregnada com água e sem SL impregnada com CLX. A remoção da SL foi realizada pela aplicação de ácido fosfórico por 15 s. Sobre a dentina desmineralizada foram aplicados 20 uL de água destilada ou digluconato de CLX a 2% por 60 s. Em seguida, uma gota do sistema Single Bond 2 foi depositada sobre cada superfície. Ângulos de contato entre a superfície da dentina e o adesivo foram mensurados por meio de um goniômetro e os dados submetidos aos testes de ANOVA e Tukey (?=0,05). Resultados: Maiores ângulos de contato foram obtidos sobre a dentina hígida em comparação a afetada por cárie (p<0,05), independente do tratamento da superfície. Para ambos os substratos, ângulos de contato estatisticamente superiores foram obtidos para a dentina coberta com SL (p<0,05). A remoção da SL resultou em redução significante dos ângulos (p<0,05) e nenhuma diferença foi encontrada entre os ângulos produzidos sobre a dentina desmineralizada impregnada por água ou por CLX (p>0,05). Conclusão: A umectabilidade da dentina afetada por cárie foi maior do que a da dentina hígida, sendo que a mesma não foi influenciada pela aplicação de clorexidina.
Aim: To evaluate the effect of chlorhexidine (CHX) on the wettability of sound and caries affected dentin by a simplified adhesive system. Material and Methods: Flat coronal dentin surfaces were produced on 60 sound molars, 30 of which were artificially decayed. The teeth were divided randomly into 3 groups (n = 10) with smear layer (SL), without SL impregnated with water and without SL impregnated with chlorhexidine. The SL removal was performed by phosphoric acid etching for 15 s. 20 uL of distilled water or 2% chlorhexidine digluconate were applied on the demineralized dentin for 60 s. Then, a drop of Single Bond 2 was deposited on each surface. Contact angles between dentin surface and adhesive was measured by means of a goniometer and data were submitted to ANOVA and Tukey tests (? = 0.05). Results: Higher contact angles were obtained on sound versus caries affected dentin (p <0.05), regardeless of the surface treatment. For both substrates, contact angles statistically higher were obtained for dentin covered with SL (P <0.05). The SL removal resulted in significant reduction of the angles (P <0.05) and no difference was found among angles produced on demineralized dentin impregnated with water or chlorhexidine (p> 0.05). Conclusion: Caries affected dentin wettability was higher than sound dentin and that characteristic was not influenced by chlorhexidine application.