RESUMO
The aim of this research was to analyse the long-term clinical behaviour of two dental materials applied as filling under silver amalgam restorations: glass-ionomer cement (GIC) and composite resin with adhesive system (CR). In this study, 117 posterior teeth (29 premolars and 88 molars) were selected with carious lesions which resulted in great loss of dentin and cusps with unsupported enamel. After caries removal, cavities were prepared and totally filled with GIC or with CR. In a following visit, new cavities were prepared, leaving the employed filling material as a base and support for the enamel, which were then restored with silver amalgam. Restorations were evaluated periodically after 6 months and up to 5 years. Both fracture and pulpal involvement rates were low. Although differences could be observed in the behaviour of the materials, statistical survival estimation showed that the performances of GIC and CR as filling material were similar. There was a significant association both between kind of tooth (molar or premolar) and long-term survival of the restorations; and between degree of unsupported enamel and the same long-term survival. Our results confirmed that the technique in which GIC or CR are used as filling under silver amalgam restorations is clinically acceptable.
Assuntos
Resinas Compostas , Amálgama Dentário , Restauração Dentária Permanente/métodos , Cimentos de Ionômeros de Vidro , Traumatismos Dentários/prevenção & controle , Adolescente , Adulto , Dente Pré-Molar , Polpa Dentária/lesões , Humanos , Estudos Longitudinais , Dente Molar , Modelos de Riscos Proporcionais , Análise de Sobrevida , Fraturas dos Dentes/prevenção & controleRESUMO
This study was conducted to investigate the possibility of using sewage as an organic substrate for the growth of sulphate reducing bacteria (SRB) and to acclimatise anaerobic sludge to produce sulphide from sulphate reduction, with a view to metal precipitation. The experiments were carried out in a continuous bench-scale bioreactor (13 1 UASB reactor) operated with hydraulic retention times (HRT) of 11 and 19 hours. The feed solution used was composed of the liquid part of the sewage (organic matter) supplemented with nickel sulphate and sodium sulphate. The results showed that it was possible to acclimatise anaerobic sludge for production of sulphide by sulphate reduction. A relation between the available COD and the concentration of sulphate reduced by SRB was observed. High nickel removal efficiency (96%) was obtained during the whole operation (320 days). However, the process required very strict control of the organic load available (sewage) in the solution and, if necessary, the addition of a complementary organic carbon source, in order to maintain a constant level of metal removal. The SRB were not affected by the HRT values studied and were installed and maintained in the system; however, granular sludge was not observed. The micrographs confirmed the presence of iron and nickel sulphides and also a mixed bacterial culture in the anaerobic sludge. The EDS spectrum of the sludge showed that nickel was retained in the sludge predominantly as a nickel sulphide.
Assuntos
Bactérias Anaeróbias/fisiologia , Reatores Biológicos , Metais Pesados/química , Esgotos/química , Esgotos/microbiologia , Sulfatos/química , Sulfetos/química , Precipitação Química , HumanosRESUMO
PURPOSE: To compare the retention of a multi-use bonding agent (OptiBond) to a conventional sealant (Delton) used as pit and fissure sealants. MATERIALS AND METHODS: An informed consent was obtained from 38 subjects aged 11-17 yrs. Delton, a self-cured sealant, was applied to 86 teeth, and OptiBond, a dual-cure glass filled adhesive, was applied to 85 teeth, under cotton roll isolation and saliva ejector. Each subject received both sealing materials, randomly assigned to the sides of the mouth. The sealed teeth were followed up to 30 months. Clinical evaluation was performed by two examiners and the retention was classified as failure or success. RESULTS: Statistical analysis based on a stratified Cox proportional hazards regression model indicated that OptiBond had better clinical performance than Delton (P < 0.001).