In vivo evaluations of the neutralizing effect of a hydroxyl ion-releasing resin composite and a prophylactic gel on plaque acidogenicity : measured by the microtouch method

Abstract: The prevalence of dental caries has decreased dramatically in most developed countries since the sixties and the number of remaining teeth in adults has increased during the last decades. Elderly as a group will during aging become an increasing risk group for caries. Especially older individuals with hyposalivation are at increased risk for coronal and root caries and need increased oral care. A large part of the time spent by the dental team is occupied by prevention and treatment of secondary caries, which is the main reason of replacement or repair of restorations. Traditionally, prevention of caries is directed against the different risk factors of the individual such as oral hygiene, intake of fermentable carbohydrates, cariogenic microflora and oral dryness. In some restorative materials the release of fluoride can be used to decrease the risk of secondary caries alone or in combination with other preventive methods. New alternative preventive methods are necessary to complete traditional methods in order to decrease the caries risk in elderly and/or to prevent secondary caries. Addition of methods with buffering properties have been suggested and developed to supplement the biological buffering capacity of saliva. The neutralizing effects of a hydroxyl ion-releasing resin composite and a prophylactic gel containing buffering properties on dental plaque acidogenicity was evaluated by the microtouch method. In this method, a skin reference electrode was validated in comparison with a glass capillary reference electrode and used in the subsequent studies. Change of plaque acidogenicity on proximal surfaces of aged restorations of the hydroxyl ion-releasing resin composite was compared intra-individually a conventional hybrid resin composite and a non-filled enamel proximal surface. Relative frequencies of cariogenic microorganisms in plaque on these surfaces were studied. The effect of a single application of the prophylactic gel with buffering substances was evaluated on plaque acidogenicity in healthy individuals with low and normal salivary secretion rate. It was compared intra-individually with the same gel without buffering substances. The effect of multiple applications of the prophylactic gel on plaque acidogenicity was studied in institutionalized elderly individuals with subjectively reported oral dryness and compared intra-individually with the same gel without buffering substances. Major results and conclusions from the studies are: • The use of the skin reference electrode, in combination with the microtouch electrode, showed high validity in comparison with the conventional glass capillary reference electrode • The hydroxyl ion-releasing composite resin countered plaque acidogenicity fall at two time points of the aged restorations and maintained it at levels where lesser demineralization occurs. No influence of the ion-release on the amount of cariogenic plaque microorganisms on the resin composite surface was observed • A single application of the prophylactic gel with buffering substances showed a neutralizing effect of plaque pH in healthy individuals with normal salivary secretion rate. No effect was observed in low secretion rate individuals. • Multiple applications of the prophylactic gel did not neutralize dental plaque acidogenicity in elderly individuals with subjective oral dryness