Effect of a new desensitizing material on human dentin permeability.

OBJECTIVES: Resin-modified glass ionomers (RMGI) have demonstrated clinical success providing immediate and long-term relief from root sensitivity. RMGIs have been recently introduced as paste-liquid systems for convenience of clinical usage. The objective of this study was to measure the ability of a new paste-liquid RMGI to reduce fluid flow through human dentin, compared to an established single-bottle nanofilled total etch resin adhesive indicated for root desensitization. METHODS: Dentin permeability was measured on human crown sections on etched dentin, presenting a model for the exposed tubules typical of root sensitivity, and permitting measurement of the maximum permeability. In the first two groups, the etched dentin was coated with either the RMGI or adhesive, and permeability measured on the coated dentin. In a third group, a smear layer was created on the dentin with sandpaper, then the specimens were coated with the RMGI; permeability was measured on the smeared and coated dentin. Specimens from each group were sectioned and examined via scanning electron microscopy (SEM). RESULTS: Both the resin adhesive and the new paste-liquid RMGI protective material significantly reduced fluid flow through dentin, and exhibited excellent seal on dentin with either open tubules or smear-layer occluded tubules. The RMGI infiltrated the smear layer with resin during placement, penetrated dentin tubules, and formed resin tags. SIGNIFICANCE: The RMGI was equivalent to the adhesive in its ability to reduce fluid flow and seal dentin. It is therefore concluded that the new RMGI and the adhesive show the potential to offer excellent sensitivity relief on exposed root dentin.

Effect of a new liner/base on human dentin permeability.

OBJECTIVES: Resin-modified glass ionomers (RMGI) have demonstrated clinical success in their ability to minimize post-operative sensitivity of restorations. RMGIs have been recently introduced as paste-liquid systems for convenience of clinical usage. The objective of this study was to measure the ability of a new paste-liquid RMGI liner/base to reduce fluid flow through human dentin. METHODS: Dentin permeability was measured on human crown sections on etched dentin, using etched dentin as a model for the exposed tubules typical of root sensitivity, and permitting measurement of the maximum permeability. In the one group, the etched dentin was coated with the RMGI, and pre- and post-treatment permeability was measured on the coated dentin. In the second group, a smear layer was created on the dentin with sandpaper, then the samples were coated with the RMGI; permeability was measured on the smeared and coated dentin. Samples from each group were sectioned and examined via scanning electron microscopy (SEM). RESULTS: The new paste-liquid RMGI liner/base significantly reduced fluid flow through dentin, and exhibited excellent seal on dentin with either a smear layer or open tubules. SEM images show evidence that the RMGI infiltrated the smear layer with resin during placement, penetrated dentin tubules, and formed resin tags in acid-etched dentin. CONCLUSIONS: Based on these results, combined with previous research on adhesion and microleakage, it is concluded that the new RMGI liner/base should minimize post-operative sensitivity in restorations.

Inhibition of dentin demineralization adjacent to a glass-ionomer/composite sandwich restoration.

OBJECTIVE: To evaluate, in vitro, dentin caries inhibition ability of a composite restoration with glass-ionomer liners in an open-sandwich configuration. METHOD AND MATERIALS: Rectangular dentin cavities (n = 5) were restored with a composite and glass-ionomer liner in an open-sandwich configuration where the liner was applied up to the cavity margin. Liners used were 3 resin-modified glass-ionomers (Vitrebond, 3M ESPE; Vitrebond Plus, 3M ESPE; Fuji Lining LC Paste Pak, GC) and a conventional glass-ionomer (Ketac Bond, 3M ESPE). The control group was a composite restoration (Filtek Z250, 3M ESPE) without a liner. Specimens were immersed in lactic acid gel for 3 weeks to create a demineralized lesion before being subjected to microradiographic analysis. The width of the area where the demineralization was completely inhibited at the restoration interface was measured. The total mineral loss (DeltaZ) was determined at 0.25 and 1.0 mm from the cavity margin. RESULTS: An inhibition zone was observed at the interface of all open-sandwich restorations but not in Filtek Z250. DeltaZ at 0.25 mm of all the open-sandwich restorations was significantly less than that of Filtek Z250 (analysis of variance, Scheffe's S, P < .05). At 1.0 mm, only the open-sandwich restorations in Vitrebond and Vitrebond Plus groups had significantly less DeltaZ than Filtek Z250. CONCLUSION: Under an in vitro demineralization challenge, glass-ionomer liners in an open-sandwich restoration exhibited pronounced inhibition zones at the dentin margin and lowered the amount of mineral loss in the vicinity of 0.25 mm from the restoration interface.

Long-term adhesion and mechanism of bonding of a paste-liquid resin-modified glass-ionomer.

OBJECTIVES: The contribution of chemical bonding of the polycarboxylic acid in classical powder/liquid conventional glass ionomers (GI) and resin-modified glass-ionomers (RMGI) has been attributed to the excellent long-term bond strengths and clinical retention. RMGIs have been recently introduced as paste/liquid systems for convenience of clinical usage. The objective of this study was to investigate the long-term bond strengths and mechanism of adhesion of paste-liquid RMGI in order to ascertain whether similar characteristics are retained. METHODS: Long-term shear adhesion to dentin and enamel was measured on two paste-liquid RMGIs and one powder/liquid RMGI. Scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses were carried out on the paste-liquid RMGI Vitrebond Plus (VBP) and compared with the classical powder/liquid RMGI Vitrebond (VB). RESULTS: VBP maintains adhesion to dentin and enamel over long times; its long-term adhesive performance is equivalent to VB. FTIR data confirm that VBP exhibits the carboxylate crosslinking reaction of a true glass ionomer. SEM images show evidence of micromechanical bonding at the interface between VBP and the tooth. XPS and FTIR data show that the methacrylated copolyalkenoic acid component present in VB and VBP chemically bonds to the calcium in HAP. SIGNIFICANCE: The new paste-liquid RMGI liner, VBP, shows equivalent adhesion to its powder-liquid predecessor, VB. The adhesion mechanism was attributed to micromechanical and chemical bonding. This chemical bond is a significant factor in the excellent long-term adhesion of these materials.