Stannous Fluoride and Its Effects on Oral Microbial Adhesive Properties in Vitro Kazuo Ota, DDS, Susumu Kikuchi, DDS, Ddsc John W
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PEDIATRICDENTISTRY/Copyright © 1989 by The AmericanAcademy of Pediatric Dentistry Volume1 I, NumberI Stannous fluoride and its effects on oral microbial adhesive properties in vitro Kazuo Ota, DDS, Susumu Kikuchi, DDS, DDSc John W. Beierle, PhD Abstract The effect of sodiumand stannous fluoride compoundson examined by scanning and transmission electron the coherence of Streptococcus mutans was examined. Both microscopy. commercialand reagent grade preparations were t~sted on S. In a clinical study, White and Taylor (1979) also mutans, strain 6715. Test fluoride aliquots at various reported a significant reduction in plaque from daily concentrations were added to sucrose suspensions of S. rinsing with 0.1% SnF2. Klock et al. (1985) further mutansat a starting microbial suspensionsequivalent to 25% examined the effects of twice-daily mouthrinses with transmission as read in a spectrophotometer. Test samples either SnF2 or sodium fluoride (NaF) in adults and were rotated at 35°, 80 rpmin an incubated orbital shaker. reported that after 1 year of rinsing with SnF2patients Analysis at 560 nmat various time periods, wasperformed to had fewer Streptococcus mutans/ml saliva, a lower determine increases in %T as a function of aggregate incidence of caries, and less gingivitis than those formation. SnF2 preparationsroutinely inhibited coherenceat participants rinsing with NaF. Long-term clinical concentrations as low as .001%, whereas NaF showed no studies by Leverett et al. (1986) suggested that 0.1% SnF~ effects on microbialcell-to-cell coherence. caused 4-5 times as muchextrinsic stain as 0.05% NaF after a 28-month mouthrinsing period, but there were Prevention and control of dental plaque by daily no statistically significant differences between the 2 rinsing with fluoride-containing solutions is widely fluoride groups in terms of total DMFS. used. The major efforts in fluoride mouth rinsing have Early plaque formation is considerably enhanced by been directed to treatment strategies that strengthen S. mutans species cohering to one another after adhering enamel or affect cariogenic bacteria. Although these to a tooth surface. The cohesion-adhesion is at least fluoride effects traditionally have been considered to be partly due to glucan production and its coating of cells mainly the result of a physiochemical interaction with after sucrose utilization. These substances act as part of enamel, there is evidence that fluoride also alters the biological "glue" enhancing bacterial adherence. bacterial metabolism at low concentrations, and is Levan and other microbial components may also play a bacteriocidal at higher concentrations (Loesche et al. part in bacteria-to-bacteria binding. 1975; Hamilton 1977). Therefore, the comparative The purpose of this study was to investigate qualities of various fluoride complexes on the oral stannous fluoride complexes on oral microbial adhesive microbial ecosystem has been a topic of interest over the properties and also to compare the stannous and the years. sodium ion forms of fluoride compounds. Konig (1959) studied the effects of topically administered stannous fluoride on the accumulation of Materials and Methods plaque on rat molars in vivo. Not only was enamel Bacterial cultures of S. mutans, strain 6715, solubility and caries reduced, but extensive plaque (American Type Culture Collection [ATCC]25175, Lot inhibition was noted as well. Tinanoff et al. (1976) 0585 S) were inoculated into a nutrient broth made of further showed that there is more suppression of tryptose phosphate broth and Todd Hewitt broth 2:1 by bacterial colonization on enamel by SnF2 than by NaF volume and incubated 16-20 hr at 35° C. The bacterial with mouthrinses at a concentration of 100 ppm F-, in cultures then were centrifuged at 3000 rpm x g for 10 vivo. Mouthrinsing was performed either once or twice rain, after which the supernatant was decanted from the a day for up to 7 days. The enamel specimens were Pediatric Dentistry: March,1989 N Volume11, Number1 21 solid pellet The pellet was mixed in a saline wash and time to determine characteristics of effects of fluoride- centrifuged again for 10 min to remove residual spent containing solutions on the aggregation of S. mutans media. All test and control solutions were maintained at (Fig 1). 2pH 4.0 in phthalate buffer. This pH was used since SnF Other aggregation assays were performed using was found not to autoprecipitate in the experimental chemically pure fluoride reagents in addition to the time sequences required and microbial adherence was commercial product mixtures, ACTand Gel-Kam. The noted to be well promoted within the pH range 4.0-6.0 aggregation analyses usually were completed by 90 min (Beierle et al. 1979). A volumeof a 1.0% sucrose in 0.05 at which time maximumcohesion was sustained. M phthalate buffer, pH 4.00 solution was added to the pellet which was resuspended to a concentration 120. equivalent to 25%transmittance in a spectrophotometer (Model DB -- Beckman; Irvine, CA) at 560 nm. Gel- 100 Kam® (Scherer Lab Inc; Dallas, TX) was selected representative of a stannous fluoride-containing 80- product and ACT® (Johnson & Johnson Products Inc; New Brunswick, NJ) as a representative of a sodium 60- fluoride-containing product. The SnF2 rinse (Gel-Kam) was diluted with pH 4.00 phthalate buffer solution (1:3) 40- immediately before use to produce a stock 0.1% solution. The NaF mouthrinse (ACT) was used as 20- stock solution at a concentration of 0.05%. These starting stock solutions were used in testing as 0 ~ ~o 4’s ~o 7~ ~’o ~o 11o no interfering precipitation occurred in controls minutes analyzed for the required 120 min necessary to complete ¯ 1.0 % SUCROSE the analyses. A 4.5-mi aliquot of the 25%T bacterial ....... ~,~....... 0.005% NaF ( ACT ~ ÷ SUCROSE suspension made up in sucrose was added to 60 x 15- ...... "~ ........ 0.01 ~ SnF2 ( Gel - Kam) ¯ SUCROSE mmplastic Petri dishes (#1007 -- Falcon Plastics; ~~ SALINE Oxnard, CA) and 0.5 ml aliquots of each fluoride- FIG1. Aggregationprofiles of S. mutansin the presenceof sucrose, containing solution then were added to make a final saline, and fluoride preparations. volume of 5.0 ml. Varying dilutions of fluoride were made up to final concentrations from 0.01 to 0.005%. All 1.0% sucrose test solutions were adjusted to a pH of 4.00 with 0.005% NaF(ACT) + sucrose phthalate buffer. Control 25%T suspensions of bacteria 0.01% SnF2 (Gel-Kam)+ sucrose without fluoride additives were analyzed in 1% sucrose Saline solutions or in with 0.85%saline solutions. The test Petri dishes were then rotated in a gyratory shaker (Model Results GS-8 -- New Brunswick Environmental Shaker; New ° The coherence of S. mutans is greatly enhanced in the Brunswick, NJ) at 80 rpm at 35 C. presence of sucrose compared to that of saline (Fig 1). Triplicate samples of each group were analyzed in a Coherence was noted to start rapidly and the adherence spectrophotometer to assess bacterial aggregation at assays generally were completed at the end of 1 hr. The time points ranging from 0 to 120 min. All experiments addition of ACT solution containing 0.005% NaF were performed a minimumof 3 separate times in order showed no substantial differences over that of the to substantiate findings. sucrose control aggregation assay. The addition of Gel- This aggregation assay is based on the detection of Kam containing 0.01% SnF2, however, did reveal a increased percentage of transmission as a function of significant reduction in the ability of S. mutansto cohere. increased microbial cohesion (Beierle et al. 1979). Photographs of the various aggregates detected after The highest percentage of transmissions obtained 60 rain in Figure 1 show the various coherent masses was arbitrarily set to 100%and all other values then (Figs 2a-d). The aggregates of S. mutans shaken in were corrected to 100%T as well, with a starting point of sucrose consistently were viewed as being compact, 0%T. Actually, all test samples started at 25%T which rounded, and distinctly visible, ranging from 1 to 2 mm allowed for adequate microbial numbers for coherence in diameter (Fig 2a). Whencompared to samples rotated to occur in the rotary suspension shaking procedure. in saline (Fig 2b) the plates were seen to contain turbid, The mean value and standard deviation were milky suspensions of nonaggregated bacteria. When calculated and plotted as corrected percentage of T vs. these viable suspensions were viewed at 630x 22 EH:ECT OF .SNF2 ON .S. MUTANS:Ota et al. Again, no inhibition of cohesion of S. mutans was noted, even at concentrations higher than that found in stock solutions of ACT. Interestingly, S. mutans was continually noted to adhere slightly better in sucrose solutions in all concentrations tested ranging from IO'1 to lQ-8% NaF. Similar experiments were performed with Gel-Kam containing SnF, to determine if any differences existed when using the stannous vs. the sodium form of fluoride compound. The Gel-Kam preparation demon- strated reduction in coherence at SnF, concentrations as low as 0.001% (Fig 5, next page). This finding contrasted sharply with the lack of effect detected in a01% SnFi (Q«l-K«n)+ SUCROSE preparations using NaF (Figs 3,4). When reagent grade SnF2 was FIG 2. Aggregates of S. mutans at 60 min exposed to various reagents. utilized in place of the Gel-Kam preparation, similar effects on magnification by polarized light or interference cohesion in the same concentration range were noted microscopy the streptococci were found to be mainly in (Fig 6, next page). single cell suspension or in pairs. Bacteria rotated in saline barely cohered past that noted at the initial time Discussion of dispersion. The process of adherence of oral microbes to enamel Starting cultures were dispersed by vigorous surfaces or to various dental materials is of considerable agitation on a vortex mixer followed by trituration interest (Fujioka et al.