A Confocal Microscopic Study of Some Factors Affecting the Adaptation of a Light-cured Glass Ionomer to Tooth Tissue

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Abstract
Vitrabond consists of a conventional glass ionomer, in conjunction with a light-curing resin and hydroxy-ethylmethacrylate. This study, which used a tandem scanning reflected light microscope for confocal imaging, looked at factors affecting the adaptation of this material to tooth tissue. Wedge-shaped cervical cavities were cut and restored in three ways: (1) Vitrabond was applied as a thin sub-base and either extended onto the enamel margin or kept clear of it. P50 resin composite was then placed, following phosphoric-acid-etching of the enamel margins. (2) The dentin surfaces were conditioned with Scotchprep (maleic acid), then with the Vitrabond, the enamel was etched, and the Scotchbond 2 adhesive applied prior to addition of the P50. (3) Vitrabond was applied alone in bulk, with and without Scotchprep acid-dentin conditioning with a 1:1 (normal) and 3:1 powder:liquid ratio (P:L). Adaptation of the Vitrabond was excellent when maleic acid was used for conditioning of the dentin. When the Vitrabond was used with P50 but extended onto the enamel, the enamel margin occasionally failed. Enamel invariably fractured when the Vitrabond was used alone in bulk. An increase in the P:L ratio decreased contraction gaps when the dentin was not conditioned, but Vitrabond failed cohesively when the dentin was conditioned. The Vitrabond was very susceptible to shrinkage on dehydration. This study suggests that Vitrabond should only be applied to dentin in thin layers, should not be extended onto enamel margins, and should not be allowed to dehydrate. Maleic acid conditioning of the dentin improved adaptation.