pH and effects on Streptococcus mutans growth of denture adhesives: an in vitro study

ObjectivesTo evaluate the pH and effects on Streptococcus mutans growth of denture adhesives. BackgroundThere is little information regarding the pH of contemporary adhesives and their influences on S.mutans growth. Materials and methodsThe adhesives tested were Polident((R)) cream, Protefix((R)) cream and Protefix((R)) powder. Samples of each adhesive were added to deionized water to produce solutions of 10.0, 5.0, 2.5 and 1.0% w/v (cream formulations) or 5.0, 2.5,1.0 and 0.5% (powder formulation). The pH values were measured immediately after preparation and at 1-, 2-, 3-, 6-, 12-, and 24-h intervals using a digital pH meter. Streptococcus mutans UA159 was inoculated in the Brain Heart Infusion medium with or without the adhesive extracts (control). Bacterial growth was observed by measuring absorption at 600nm every 1h for 12h using a spectrophotometer. ResultsThe tested adhesives generally remained relatively pH-stable over 24h, ranging from 5.5 to 7.0. There were no statistically significant differences in S.mutans growth rates between the extract-treated and control cultures (p>0.5). ConclusionsSome adhesives produce a pH below the critical pH of hydroxyapatite and may not be suitable for patients with natural teeth. None of the tested adhesives significantly affect S.mutans growth.