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The introduction of visible light polymerization in dentistry led to the development of a new generation of pit and fissure sealants. The purpose of this study was an overall evaluation of some in vitro characteristics of four new sealants (Delton LC, Helioseal, Pentra-Seal and Visioseal) in comparison with a chemically cured control (Delton). The results indicate that the monomer systems utilized in the new materials have already been used in dental polymer technology. The relatively new monomers TCDDMA/TCDMA were identified in one product. Camphoroquinone is used as a photoinitiator in all the light-cured systems which, after 40 s exposure, present better conversion than the control. The extent of oxygen inhibition was considerably reduced in the new sealants and the surface hardness was enhanced. Great differences were obtained in the penetration coefficient values; these, however, did not affect the enamel retention capacity of the materials tested. Consequently, light-cured sealants should be considered to be strongly compatible with the conventional chemically cured sealants from a laboratory aspect until more clinical evidence is available for their effectiveness in the prevention of pit and fissure decay.

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The purpose of this study was to assess the surface alterations induced by acid etching on two glass ionomer lining cements (Ketac Bond, G-C lining cement) and to evaluate their interface with a composite resin (Herculite XR) following various surface treatments. The changes in the surface composition and topography of the etched liners were studied by electron microprobe and ESCA analyses. The interfacial treatments performed on the ionomer surfaces were: (i) application of a bonding resin; (ii) 20-s acid etching and application of a bonding resin; (iii) application of a dental adhesive based on a chlorophosphate ester of BisGMA (Scotch-bond LC), without acid etching. The interfacial sealing efficiency of these treatments was studied by the silver nitrate microleakage technique combined with optical and electron microscopy. According to the results the etched surfaces of both the liners present excessive porosity with glass and matrix dissolution. Significant changes in the surface chemistry of the liners were detected indicating severe degradation. The microleakage study revealed interfacial gaps and fractures in the etched samples. The best results were obtained from the non-etched ionomer liners which were subjected to the adhesive treatment. The efficiency of acid etching as a necessary step in the 'layered' technique is seriously questioned.

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