RESUMO
PURPOSE: To evaluate the influence of a 2% chlorhexidine solution (CHX) on the bond strength and nano leakage of two self-etching adhesive systems on demineralized dentin over a 12-month period. MATERIALS AND METHODS: The middle dentin from sound third molars was exposed and demineralized in vitro. Twelve groups were formed using different adhesive systems (Clearfil Protect Bond [PB], Clearfil SE Bond [SE]) dentin treatment (with or without CHX application), and water-storage times (24 h, 6 and 12 months). Composite resin cylinders were bonded to the prepared dentin, and these specimens underwent microshear bond strength (µSBS) testing and nano leakage evaluation. µSBS data were submitted to a three-way ANOVA and Tukey's test. The failure mode and nano leakage were analyzed descriptively by score. RESULTS: There was a statistically significant interaction only between the adhesive system and CHX, and adhesive system and water-storage times. SE showed the lowest µSBS just at 24 h water-storage time regardless of CHX. A significant decrease in µSBS values after 6 months of water storage occurred in all of the groups and was maintained until 12 months. Adhesive failure increased with storage time. All groups showed nano leakage at the resin/dentin interfaces and an increased silver deposition was noticed after 6 and 12 months of water storage. The highest percentages of nano leakage were found in CHX groups. CONCLUSION: CHX did not interfere with µSBS values for either self-etching adhesive system, but water storage did. Bond strength decreased for both adhesive systems after 6 and 12 months, regardless of CHX application. Nano leakage increased with water-storage time and with CHX application.
Assuntos
Clorexidina/farmacologia , Colagem Dentária , Infiltração Dentária , Dentina/patologia , Desinfetantes/farmacologia , Cimentos de Resina/farmacologia , Análise de Variância , Análise do Estresse Dentário , Interações Medicamentosas , Humanos , Resistência ao Cisalhamento , Estatísticas não Paramétricas , Desmineralização do Dente/patologia , ÁguaRESUMO
OBJECTIVES: To characterize the mechanical and biological properties of a resin-modified glass ionomer cement (RMGIC) containing doxycycline hyclate. METHODS: The antibacterial effect of RMGIC containing 1.5, 3.0 and 4.5% doxycycline hyclate was assessed using two experiments - agar diffusion test for 24h and biofilm assay for 24h and 7 days - against some cariogenic bacteria. Briefly, base layers of BHI agar and 300µL of each inoculum were prepared in Petri dishes with 6 wells that were completely filled with materials. After 24h incubation, zones of bacterial growth inhibition were measured using a digital caliper. Biofilm assays were conducted using RMGIC specimens immersed in 24-well plates containing the inoculum in BHI broth. After 24h and 7 days, each specimen were removed, vortexed and the suspension diluted and inoculated in BHI plates for subsequent bacterial counting. Cytotoxicity tests used 50 specimens made in sterilized metal molds, including Vitrebond as positive control. Extracts from every specimen were applied on the MDPC-23 odontoblast-like cells for 24h. The MTT assay and SEM evaluation determined cell metabolism and morphology, respectively. 80 cylindrical specimens were made from the previously cited groups, and were submitted to testing with a universal testing machine (Instron 4411) using a crosshead speed of 1.0mm/min for compressive strength and 0.5mm/min for diametral tensile strength, respectively. Data from antibacterial and cytotoxic effects, and mechanical properties were submitted to appropriated statistical tests. RESULTS: All tested groups showed growth inhibition of all tested strains (p<0.05) in 24h for both microbiological tests, but only 4.5% doxycycline have antibacterial effect after 7 days. None of doxycycline concentrations caused toxic effect to the MDPC-23 cells or presenting alterations to mechanical properties. CONCLUSION: The incorporation of up to 4.5% doxycycline hyclate into RMGIC inhibits important oral microorganisms, without modifying biological and mechanical characteristics of the dental material, suggesting a new alternative for the treatment of dental caries.