INTERFACIAL CHARACTERISTICS OF RESIN-MODIFIED GLASS-IONOMER MATERIALS- A STUDY ON FLUID PERMEABILITY USING CONFOCAL FLUORESCENCE MICROSCOPY

The tooth interface with resin-modified glass-ionomer cements (RM GICs ) is poorly understood. This study examined the interface, especially with dentin. Cervical cavities in extracted teeth were restored with F uji II LC, Vitremer, Photac-Fil, or a conventional GIG, Fuji Cap II. F luorescent dye was placed in the pulp chambers for 3 hrs before the sp ecimens were sectioned. Examination of the tooth/material interface wi th a confocal microscope showed that dye uptake by the restoration var ied among materials. A ''struetureless'', non-particulate, highly-stai ned layer of GIC was observed next to dentin in Fuji Il LC. This layer varied in width, was prominent where the dentin tubules were cut ''en d-on'' and in areas closer to the pulp, and was not seen adjacent to e namel. Vitremer showed minimal dye uptake, and the ''structureless'' l ayer was barely discernible. Photac-Fil showed more uniform uptake and absence of this layer. Cracking of enamel was also noted with these m aterials. The conventional GIC did not show any dye uptake, presence o f a ''structureless'' layer, or enamel cracking. We elucidated the pot ential mechanisms involved in the formation of a ''structureless'' int erfacial layer in Fuji II LC by studying the variables of cavity desig n, surface pre-treatment, water content of the tooth, time for it to d evelop, early finishing, and coating of the restoration. This layer, t he ''absorption layer'', is probably related to water flux within the maturing cement, depending on environmental moisture changes and commu nication with the pulp in a wet tooth. The ''micropermeability model'' was useful in this study of the interfacial characteristics of RM GIC s.