Ionic exchanges between glass ionomers and demineralised dentine

Abstract

Glass-ionomer cement has been used in the Atraumatic Restorative Technique (ART) for stabilisation of carious lesions. The infected layer or fully demineralised dentine is removed by dental hand instruments only and glass-ionomer cement is placed to restore the lesion leaving the affected layer or partly demineralised dentine underneath. There are many anecdotal and some published reports of the ability of these materials to remineralise partly demineralised dentine. The major objectives of this investigation are: 1. To scientifically demonstrate the ability of glass-ionomers to remineralise partly demineralised dentine in vivo and in vitro. 2. To determine the nature of the remineralisation process. 3. To determine those factors having greatest impact on the remineralisation process. Those objectives are partly met with the use of EPMA and an in vitro model, specially designed to simulate clinical conditions as closely as possible. With EPMA, it is possible to identify, quantify and trace the migration of different elements, found in glass-ionomer, into the partly demineralised dentine. The results lead to a better understanding of the possible mechanisms involved. There have been anecdotal and clinical reports on the remineralisation of carious dentine left at the base of glass-ionomer restorations. This was confirmed in a human in vivo study. The information derived from it was utilised in the design of an in vitro model to allow in depth study of the effects, on the remineralisation process, of the following two variables: 1. The level of remaining minerals in dentine 2. The length of contact with the glass-ionomer The results support the hypothesis that the close adaptation of glass-ionomer cement to demineralised dentine will lead to the uptake of apatite forming ions into dentine and lead to its remineralisation. The process involved first the diffusion then the precipitation of both strontium and fluorine from the glass ionomer into the partly demineralised dentine. This process is dependent on the glass-ionomer, the level of demineralisation of dentine and the time that it stays in contact with the glass-ionomer. The combination of Fuji VI with a treatment time of 42 days has the best potential for remineralisation. However, further study is required before the mechanism involved can be fully understood.