Secondary caries in dentine around composites: A wavelength-independent microradiographical study

Composite restorations are prone to develop secondary caries if a gap exists between tissue and restoration. The aim of this article was to quantify the effects of a fluoridating and non-F composite on secondary dentine caries in vitro as a function of time. The mineral loss in dentine was assessed in an artificial gap of 200 mu m width at the composite/dentine interface; the samples were demineralised in a carboxymethylcellulose gel (pH = 5, 37 degrees C) for 8 weeks. Once a week the mineral content of the samples was determined using non-destructive wavelength-independent microradiography (WIM). After 8 weeks transversal microradiography (TMR) was done on the samples to investigate the mineral distribution of the dentine lesions. The WIM results show that the fluoride-releasing composite decreased the dentine demineralisation statistically significantly with respect of the non-F control by approximately 45%. The mineral loss values are found to be strictly proportional to time; the demineralisation reduction is expected to continue over extended periods of clinical relevance. The TMR results show that the fluoridating composite reduced the mineral loss values significantly with respect to the non-F control by approximately 55%, but had a negligible effect on the lesion depth values. This study indicates that WIM is an accurate and reliable technique to measure in vitro secondary dentine caries next to a composite restoration as a function of time

CLOSING OF DENTINAL TUBULES BY GLUTARDIALDEHYDE TREATMENT, A SCANNING ELECTRON-MICROSCOPY STUDY

The properties of dentin are strongly influenced by the so-called smear layer. This layer is always present on the dentin surface after cutting, drilling, sawing, etc. The smear layer can be removed by various chemical treatments, such as those of acid etching or ethylenediaminetetraacetic acid (EDTA). These treatments remove the smear layer and open the tubules. In this paper, the effect on the smear layer of human dentin of treatment with a 2% glutardialdehyde (GDA) solution at pH 3.5 for 2 min and a 0.5-M EDTA solution at pH 7.4 for 4 min was investigated by scanning electron microscope (SEM). The dentin samples were dried by air or critical-point drying before SEM photography was employed. The number of open dentin tubules was quantified on micrographs of EDTA- and GDA + EDTA-treated dentin. The results show that the GDA treatment fixed part of the smear layer and the superficial dentin surface in such a way that at least 50% of the tubules remained closed after EDTA treatment. By closing the dentinal tubules, the GDA-fixed layer might have a positive effect on dentin hypersensitivity, root caries, and bonding of composite to dentin