Interfacial Characteristics of Resin-modified Glass-ionomer Materials: A Study on Fluid Permeability Using Confocal Fluorescence Microscopy

Abstract

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 Fuji II LC, Vitremer, Photac-Fil, or a conventional GIC, Fuji Cap II. Fluorescent dye was placed in the pulp chambers for 3 hrs before the specimens were sectioned. Examination of the tooth/material interface with a confocal microscope showed that dye uptake by the restoration varied among materials. A "structureless", non-particulate, highly-stained layer of GIC was observed next to dentin in Fuji II LC. This layer varied in width, was prominent where the dentin tubules were cut "end-on" and in areas closer to the pulp, and was not seen adjacent to enamel. Vitremer showed minimal dye uptake, and the "structureless" layer was barely discernible. Photac-Fil showed more uniform uptake and absence of this layer. Cracking of enamel was also noted with these materials. The conventional GIC did not show any dye uptake, presence of a "structureless" layer, or enamel cracking. We elucidated the potential mechanisms involved in the formation of a "structureless" interfacial layer in Fuji II LC by studying the variables of cavity design, surface pre-treatment, water content of the tooth, time for it to develop, early finishing, and coating of the restoration. This layer, the "absorption layer", is probably related to water flux within the maturing cement, depending on environmental moisture changes and communication with the pulp in a wet tooth. The "micropermeability model" was useful in this study of the interfacial characteristics of RM GICs.

Adhesive restorative materials: A review

“…However, the experimental evidence seems equivocal. Some workers [25][26][27] have demonstrated resin tags in the dentinal tubules, while others [28][29][30] did not appear to do so. The 'hybrid layer' of resin-dentine bonding was apparently observed by Pereira et al, 10,27 but could not be identified by Lin et al 25 or by Ramos and Perdigão.…”

Resin modified glass‐ionomers: Strength, cure depth and translucency

“…In the resin modified glass-ionomers the acid/base reaction will initially be a little slower than it would have been in a conventional glass-ionomer because the HEMA has replaced some of the normal water content and water is an essential component of the acid/base reaction. 7 At the same time, because of the incorporation of traces of camphorquinone and a tertiary amine in the formula, irradiation of the surface layer will initiate polymerization of the HEMA and this will be complete in less than one minute. This reaction is quite separate from the acid/base reaction but a high degree of cross linking will occur between the two matrices as the acid/base reaction continues.…”

Efficacy and micro-characterization of pathophysiological events on caries-affected dentin treated with glass-ionomer cements

“…In the unloaded specimens treated with Vitrebond Plus, elemental analysis ( Fig. 6C-EDX) showed P and Ca as main components, but lower fractions of Al, Na and Sr were also detected, which became integrated in this porous, nonparticulate, poly(HEMA)-rich hydrogel layer [47], the absorption layer [23]. This 7-10 µm thick structure [10] was first reported by Watson and Barlett (1994) [48] , and contains some of the ions released by the initial acid-base glass-ionomer reaction between the fluoro-aluminosilicate glass particles, hydroxyapatite and polyacids and is crucial for mediating the bond between RMGICs and dentin [10].…”

“…At the bottom of the absorption layer, hydroxyapatite that remained attached to individual collagen fibrils upon application of RMGIC (Vitrebond Plus) formed receptors for primary chemical bonding with polyalkenoic acids incorporated into the materials [16,50]. The deposition of this submicrom phase over the hybrid layer has been evidenced and can thus be regarded as a sub-layer of the earlier-documented absorption layer [23], identified as gel phase, gray intermediate or multilocular phase [16], which buffers the low pH [6].…”