Interactions of delmopinol with constituents of experimental pellicle

Anti-plaque agents in the prevention of biofilm-associated oral diseases

The prevention of dental caries and periodontal diseases is targeted at the control of dental plaque. In this context, chemical agents could represent a valuable complement to mechanical plaque control. The active agents should prevent biofilm formation without affecting the biological equilibrium within the oral cavity. Depending on the goals of the preventive measures, various strategies may be considered. Anti-plaque agents with properties other than bactericidal or bacteriostatic activities may be used in primary prevention. In this approach, a modest antiplaque effect may be sufficient or even desirable, as it would decrease the side effects of the active agent. Antimicrobial agents are best indicated in secondary and tertiary prevention, as the objectives are to restore health and to prevent disease recurrence. The rational is to prevent or delay subgingival recolonization by pathogenic micro-organisms. The development of in vitro oral biofilm models certainly represents a major advance for studying and testing oral anti-plaque agents in recent years. The results of these studies have shown that chlorhexidine, hexetidine, delmopinol, amine fluoride/stannous fluoride, triclosan, phenolic compounds, among others, may inhibit biofilm development and maturation as well as affect bacterial metabolism.

Effects of various antiplaque agents on fructosyltransferase activity in solution and immobilized onto hydroxyapatite

Fructosyltransferases (FTFs) are extracellular enzymes which synthesize fructans from sucrose. Cell free FTFs are found in the dental plaque biofilm as well as in saliva. Fructans play an important role in the progression of dental caries, mainly by serving as an extracellular nutrition reservoir for bacteria. The objective of the present study was to compare the effects of several antiplaque agents on the synthesis of fructans by FTF immobilized on hydroxyapatite (HA) or in solution. The effect of chlorhexidine, cetylpyridinium chloride, sodium lauryl sulfate and Tween on FTF activity was tested using radioactive assays. Their effect on fructan structure was tested using circular dichrosim-optical rotative dispersion (CD-ORD) analysis and Fourier transform infrared (FT-IR) spectroscopy. Our results show that the antiplaque agents tested had an inhibitory effect on FTF activity both in the immobilized phase and in solution, although the inhibitory effect was more pronounced in solution. Structural changes in fructans, due to the presence of the antiplque agents, were recorded as additional C-H or O-H bands demonstrated in FT-IR analysis. However, non-significant changes in peak location were detected in CD-ORD spectrum between fructans synthesized in solution and on HA surfaces, and after treatment with the different antiplaque agents. Our study shows that several antiplaque agents may affect FTF activity and the synthesis of fructans by FTF, immobilized on hydroxyapatite or in solution.

Regulation of fructosyltransferase activity by carbohydrates, in solution and immobilized on hydroxyapatite surfaces

We tested the effect of several carbohydrates on the activity of cell-free fructosyltransferases (FTF) in solution and immobilized onto hydroxyapatite (HA) and found an inhibitory dose-dependent effect of glucose on FTF activity, both on the surface and in solution. Glucose at 160 mM inhibits FTF activity by 75% both on HA and in solution. Fructose at 160 mM inhibited FTF activity by 25% in solution and by 15% on HA. Levan inhibited FTF activity by 30% in solution, while dextrans and inulin had a limited effect on FTF activity. Circular dichroism and infrared analysis demonstrated no major changes in the chemical structure of fructans synthesized by cell-free FTF on HA and in solution, in the presence or absence of glucose. However, as verified by size-exclusion chromatography, glucose inhibited the synthesis of high molecular-weight fructans. The results indicate that glucose, a byproduct of the FTF enzymatic reaction, is the main carbohydrate affecting FTF activity. Selective inhibition of high molecular-weight fructan production by glucose, may indicate that two mechanisms are involved in the synthesis of fructans, both in solution and on the surface.

Antibacterial effect of chlorhexidine on bacteria adsorbed onto experimental dental plaque

The most common method used to examine the antibacterial effect of antiplaque agents is the minimal inhibitory concentration (MIC) method, which is tested on bacteria in suspensions. Examining the antibacterial effect on bacteria adsorbed onto dental surfaces models is not as popular, although it is clear that such models reflect the conditions in the oral cavity far more accurately than the conventional MIC method. The antibacterial effect of chlorhexidine (CHX) on bacteria adsorbed onto experimental dental plaque model was investigated. Hydroxyapatite beads were coated with human saliva. Next, cell-free fructosyltransferase (FTF) and glucosyltransferase (GTF) were adsorbed onto the beads, and sucrose was added to allow the synthesis of polysaccharide by the surface-bound enzymes. Following adsorption of Streptococcus sobrinus to the experimental dental plaque (EDP), the EDP was exposed to CHX at concentrations between 0.008 to 0.0002% at pH values of 5.5, 6.5, and 7.5. After 150 min incubation, growth of the adsorbed bacteria was measured by their incorporation of 3H-uridine or 3H-thymidine. Comparison of bacterial growth on the EDP with that in suspension showed that the surface-bound bacteria were less sensitive to CHX than were the bacteria in suspension. At all tested CHX concentrations, the antibacterial effect was independent of pH. In addition, under our experimental conditions, the use of 3H-uridine as an indicator of bacterial viability proved to be more sensitive than 3H-thymidine. The antibacterial effect of an agent in a model closely mimicking the tooth surface should generate results that are more relevant to the in vivo conditions than are conventional methods, thus bearing significant information concerning clinical applications of CHX.

Effect of local application of delmopinol hydrochloride on developing and early established supragingival plaque in humans

The aim of the study was to investigate the effect of delmopinol hydrochloride on the development of dental plaque and on newly established plaque. In addition, the influence of this compound on the composition of the microbiota colonizing the gingival mucous membrane was studied. 14 healthy male volunteers took part. After a 3 week pre-experimental period of intense oral hygiene, the participants refrained from all oral hygiene for 14 days. The buccal surfaces of cuspids and bicuspids on one side of the jaws were treated with a 1% aqueous solution of delmopinol hydrochloride (applied with a paint brush) 2 x a day for 7 days, while the contralateral side received placebo solution. On day 7, the application procedures were changed in that the test compound was applied on the teeth previously treated with placebo and vice versa. Plaque development was assessed clinically and by photo-based planimetric determination. The clinical recordings revealed that 89.3% of the placebo-treated surfaces displayed visible plaque on day 7, compared to 6.0% of the delmopinol hydrochloride treated surfaces. Delmopinol hydrochloride treatment of the previously placebo-treated surfaces resulted in a decrease in the number of surfaces with visible plaque from 89.3% on day 7 to 6% on day 14. These results were confirmed by the planimetric data. No significant change in the composition of the mucosal flora was observed during the experimental period. The present results indicate that delmopinol hydrochloride markedly reduces the formation of dental plaque on a clean tooth surface exposed to conditions which favour bacterial colonization. Furthermore, the substance appears to possess plaque-dissolving properties.

The effect of milk and casein proteins on the adherence of Streptococcus mutans to saliva-coated hydroxyapatite

Experiments sought to determine the nature of the binding of milk proteins to hydroxyapatite (HA) and to saliva-coated hydroxyapatite (sHA), and to determine the effect of milk and casein on the adherence of Streptococcus mutans GS-5 to sHA. The binding of radiolabelled alpha-casein to HA was reduced when incubated simultaneously with parotid saliva, and enhanced in the presence of milk. The binding of beta- and kappa-casein to HA was unaffected by the presence of parotid saliva and enhanced by the presence of milk. The in vitro bacterial adherence of Strep. mutans GS-5 to sHA beads was reduced when beads were coated with milk instead of buffer, or when bacteria were added to sHA in the presence of milk instead of buffer. Casein proteins (alpha, beta, kappa) added to sHA simultaneously with bacteria inhibited the adherence of Strep. mutans GS-5 to sHA. kappa-Casein, when bound to sHA, inhibited streptococcal adherence to sHA; alpha- and beta-casein, when bound to sHA, had no effect on streptococcal adherence. Fractionation of kappa-casein by anion-exchange chromatography revealed the anti-adherence activity of kappa-casein was mediated primarily by a 40,000 mol. wt. glycoprotein-containing fraction. These data show that milk, particularly kappa-casein fractions, can modulate the adherence of Strep. mutans GS-5 to SHA surfaces in vitro.

The relative efficacy of 0.1% and 0.2% delmopinol mouthrinses in inhibiting the development of supragingival dental plaque and gingivitis in man

Delmopinol, a 3-alkyl substituted N-hydroethyl morpholine, has shown potential as a mouthrinse for the management of dental plaque and treatment of gingivitis. Delmopinol has been shown to possess plaque inhibitory activity in several previous studies. The aims of this study were to: 1) compare the antiplaque, antigingivitis efficacy and safety of 0.1% and 0.2% delmopinol-containing mouthrinses (DMP) in a 2-week, randomized, parallel arm, vehicle controlled study; and 2) determine if a dose response antiplaque, antigingivitis effect could be found in this type of formulation. One hundred and thirty-three male subjects were randomly assigned to one of three groups, 0.1% DMP, 0.2% DMP, or vehicle control mouthrinses. At baseline all subjects received a clinical examination consisting of an intraoral soft tissue, plaque (Turesky modification of Quigley-Hein plaque index), and gingival index (modified gingival index) evaluations, and received a thorough oral prophylaxis. All subjects refrained from all forms of oral hygiene for the next 2 weeks, except for the use of the assigned mouthrinse. Subjects rinsed for 1 minute with their assigned mouthrinse twice daily under supervision for 2 weeks. Following 2 weeks of mouthrinse use, plaque and gingivitis scoring and soft tissue examinations were repeated. The results showed the mean plaque index at the 2-week examination was statistically related to the baseline value (P < 0.0003, ANOVA) and the concentration of DMP (P < 0.0001, ANOVA). In contrast, the gingivitis index was not related to the concentration of DMP (P > 0.05, ANOVA). No adverse effects were noted or reported during this clinical trial.