Comparative antibacterial effects of chlorhexidine and stannous fluoride-amine fluoride containing dental gels against salivary mutans streptococci
ILKKA OSTELA, LAURA KARHUVAARA AND JORMA TENOVUO Department of Cariolog)', Institute of Dentistry, University of Turku, Turku, Finland
Ostela I, Karhuvaara L, Tenovuo J: Gomparative antibacterial effects of chlorhexidine and stannous fluoride-amine fluoride containing dental gels against salivary mutans streptococci. ScandJ Dent Res 1991; 99: 378-83. Abstract - F'orty-five young adults were divided into three groups of equal size and given a professional toothcleaning (3 times during 1 wk) with dental gels containing either chlorhexidine (GHX, 1%), or a SntVamine Ouoride (AmF) combination (F" content 1.20%). The control group received toothcleaning with a placebo gel. The study was done double blind. The number of salivary mutans streptococci was monitored for 11 wk after the gel treatment using both mitissalivarius-bacitracin agar plates and the chairside method based on the adhesion of mutans streptococci on plastic strips (Dentocult-SM Strip mutans). Professional toothcleaning with a GHX gel was clearly most effective ( ? < 0.001) but the ba.seline levels of streptococci returned in 1 1 wk. SnfVAmF gel also reduced significantly (P< 0.001) mutans streptococci but recolonization occurred already in 7 wk. Placebo gel, i.e. professional toothcleaning as such, did not show any statistically significant effect on the numbers of salivary mutans streptococci. None of the treatments affected the levels of lactobacilli or the total aerobic flora in saliva samples. Professional toothcleaning with a GHX gel, or with a SnF^,-AmF gel, can be regarded as an alternative to the commonly used, but more patience demanding, application of gel in mouth trays at home for individuals with high caries activity. Key words: chlorhexidine; fluorides; mutans streptococci; preventive dentistry. Jorma Tenovuo, Department of Cariology, Institute of Dentistry, University of Turku, LemminkSisenkatu 2, SF-20520 Turku, Finland. Accepted fbr publication 16 January 1991.
Ghlorhexidine (GHX) has a broad spectrum of topical antimicrobial activity (1). One of the major indications for its use in dentistry has been the reduction of oral mutans streptococci (2). For this purpose, GHX has been
incorporated into mouthwashes (3), dental gels (4-6), or varnishes (7-9). Reduction in the numbers of mutans streptococci by GHX has led to a concomitant decline in caries incidence (10-12).
ANTIMIGROBIALS AND MUTANS STREPTOCOCCI
379
done three times during 1 wk. After all the followup saliva samples had been analyzed for mutans streptococci and lactobacilli, the code of the three gels was opened. Group A had received treatment with a SnFj-AmF gel containing 1.20% F" (17; Gel No. 1), group B with 1 % GHX gel, and group C with a placebo gel (with no active antimicrobial ingredients). All the gels were kindly provided and coded for this study by GABA International, Basel, Switzerland. The initial salivary levels (mean + SD, log CFU/ml) of mutans streptococci did not differ significantly between the three groups: group A 4.38 ±0.70, group B 3.95 ±0.81, and group G 4.55 ±0.74. Neither did the initial levels of salivary lactobacilli or total aerobic flora differ between the groups (Table 1). Parafiin wax-stimulated whole saliva samples were collected just before the first gel treatment and then, in an identical way, 1, 2, 7, and 11 wk after the last gel application. All saliva samples were collected at noon with no eating, drinking or smoking for 1 h prior to the sampling. Bacterialproeedures - Bacterial analyses were done in two different ways. First, 100 |ll of saliva were immediately transferred into tubes containing 1 ml of tryptic soy broth (Oxoid, Basingstoke, UK) supplemented with 20% glycerol. The samples were stored at — 20°G, then thawed and vortexed Subjects and methods vigorously for 20 s, using sterile glass beads. To Subjects - Thirty-two female and 13 male dental determine the mutans streptococci levels, the susstudents (age 22.1 + 1.7 yr, mean + SD) volun- pension was diluted 1:10 and 1:100 and 20 |xl were teered for this study, which was approved by the pipetted in duplicate on mitis-salivarius (MS) agar Ethical Committee ofthe Medical Faculty of Tur(Difco Laboratories, Detroit, MI) plates, with ku University. All subjects were healthy, all had a 15% sucrose and 0.2 U bacitracin per ml. The full dentition with no dentinal caries, they had colonies were counted after an incubation period taken no antimicrobial medication before the of 2 days in a CO, atmosphere at 35°C. Numbers study, and took no systemic antibiotics during the of mutans streptococci in fresh saliva samples were study. Also antimicrobial mouthwashes were not also determined using the new Dentocult SM Strip allowed during the study period. The subjects were mutans test (19), manufactured by Orion Diagrandomly assigned to three test groups of equal nostica, Espoo, Finland. Salivary lactobacilli were size, each group receiving similar treatment but cultured anaerobicaliy on a selective Rogosa mediwith diflerent test gels. The study was done douum for 3 days at 35°G. The total aerobicflorawas ble-blind. studied by plating duplicate samples on blood agar Design of the study -• The subjects were given a (Oxoid, 5% bovine blood) and incubating for 2 professional toothcleaning with the experimental days in a CO, atmosphere at 35°C. Aerobic incudental gel using rotating rubber cups and dental bation was chosen because Gram-positive aerobes (loss. The treatment was done by a dentist and it are, in general, more susceptible to GHX than lasted for 5 min per subject each time. Just before Gram-negative anaerobes (1). the treatment, the students brushed their teeth Statistical analyses - The differences in logm bactewithout any toothpaste. No eating, drinking or rial counts within and between the groups were smoking was allowed for 1 h before the treatment. analyzed by the analysis of variance for repeated For each subject, professional toothcleaning was measures (BMDP 4V).
Because stannous fluoride (SnF9; 5, 13, 14) and amine fluoride (AmF; 15) also exhibit .significant antibacterial properties against oral mutans streptococci and lactobacilh, their combination has been studied as a possibility to combat oral cariogenic bacteria (16, 17). Although in vitro studies have shown SnFj-AmF combinations to be as effective as GHX against mutans streptococci (16, 17), SnF,-AmF solution with a low total F~ content (0.025%) did not prevent plaque accumulation, nor the growth of oral mutans streptococci (18). This was clearly in contrast to a GHX solution (0.12%). In the present study we have analyzed how a higher concentration of SnFj-AmF (1.20% F~), incorporated into a dental gel, affects the in vivo levels of salivary mutans streptococci and lactobacilli. This concentration of SnF,AmF was chosen because in our previous in vitro study (17) it was as effective as 1% GHX gel, which we used as a positive control in the present study.
OSTELA ET AL.
380
Results Professional toothcleaning with a CHX gel reduced significantly (/"< 0.001) the levels of salivary mutans streptococci but SnFj-AmF gel 'was somewhat less effective (Fig. 1). The results slightly differed whether the mutans streptococci were analyzed by the conventional agar technique or by the chairsidc method: the recolonization of mutans streptococci seemed to be slower if the bacteria were assayed by the method based on their adherence on plastic strips than if quantitated on MSB agar plates (Fig. 1). Professional
cleaning with a placebo gel did not affect the total level of mutans streptococci in sahva although a slight, but non-significant, decrease was found on plastic strips (Fig. 1). When quantitated by the agar plates, the recolonization of mutans streptococci occurred with CHX in 11 weeks but with SnF2AmF gel in 7 wk. However, already 2 wk after the gel treatments the differences between the groups were statistically non-signifiicant. None of the test gels affected significantly the growth of lactobacilli or the total aerobic flora in the mouth during the 11-wk study period (Table 1).
Table 1 Effect of professional toothcleaning with SnF.j-AmF, chlorhexidine and placebo gets on numbers of salivary tactobacilli and total aerobes (mean + SD, n = 15 in each group). Differences between or within grottps were slatislically not signiftcanl
Lactohacilli' Mean
Gel
SD
Total aerobic fiora' Mean
SD
6P
5,0 CONTROL
MS (log CFU/ml) 4,0
Chlorhexidine
Pretreatment Posttrcatment" 1 2
7 11
6.60
0.83
7.50
0.40
6.32 6.80 6.72 6.82
0.65 0.67 0.65 0.62
7..M 7.64 7.68 7.68
0.35 0.40 0.30 0.44
6.39
0.73
7.62
0.27
6.52 6.53 6.66 6.67
0.82 0.60 0.69 0.50
7.73 7.59 7.75 7.60
0.36 0.22 0.31 0.25
6.11
0.79
7.70
0.34
6.33 6.39 6.46 6.46
0.73 0.69 0.75 0.92
7.69 7.65 7.75 7.73
3,0 MS (scale units)
20
Pretreatment Posttreatment" 1 2 7 II Placebo
Pretreatment Posttreatmcnf^ 1 2 7 11
12
'log CFU/ml. ^wk after professional toothcleaning.
7
11
POST-TREATMENT(WEEKS) PRETREATMENT
0.37 0.45 0.46 0.52
Fig. 1. Effect of professional toothcleaning with placebo (control), SnFj-AmF and chlorhexidine (CHX) gels on numbers of salivary mutans streptococci on MSB agar plates (A), or on their adherence to plastic strips (B). Values are mean + SD, n= 15 in each group.
ANTIMICROBIALS AND MUTANS STREPTOCOCCI
Discussion
381
saliva samples. The combination of SnF, and AmF is stable (24) but according to our results this type of product should be regarded only as an alternative to those patients who, for some reason (allergy etc.), are unable to use chlorhexidine for targeted antistreptococeal treatment. However, in future studies SnFj-AmF gel should be studied as an alternative to fiuoride varnishes: both have a high fiuoride content, have to be applied in the dental office but, in contrast to varnishes (25), the SnF.;-AmF combination reduces the numbers of oral mutans streptococci. It seemed that the quantitation of mutans streptococci based on their adhesion on plastic strips showed longer inhibitory effect than methods based on their cultivation on agar plates. In the present study, the pattern of regrowth in agar is in accordance with the extensive studies by EMILSON ei al. (21). The difference between the two methods may be due to the known inhibitory effect of both chlorhexidine and fiuoride on the adherence of oral streptococci (6, 26). However, for some unknown reason the placebo treatment also tended to reduce slightly, but non-significantly, the adherence of mutans streptococci. Further studies of the distribution of mutans streptococci between plaque and saliva after various antimicrobial treatments may provide more information of how these treatments actually work in vivo.
A large number of studies have shown that chlorhexidine (1%) gel is effective in reducing the number of oral mutans streptococci (2). Usually, ehlorhexidine gel has been applied by individually designed mouth trays and the patient has done the treatments at home according to the instructions given in the dental office (20, 21). This type of treatment is demanding for patients who have high caries activity and poor cooperation the reasons why they are thought to benefit from chlorhexidine in their dental prophylaxis. Use of chlorhexidine as a toothpaste is somewhat less effective than its use in dental trays (6). The present study showed that also professional toothcleaning with a chlorhexidine gel is an effective way to reduce the numbers of oral mutans streptococci. Because no such effect was found with the placebo gel, it is clear that the reduction was not due to the professional cleaning as such. This is in accordance with KRISTOFFERSSON et al. (22) who found that the effect of an intensive professional cleaning program on tnutans streptococci was only transient and the recolonization to the baseline levels occurred in less than 30 days. Our results suggest that professional toothcleaning with chlorhexidine gel may be a useful alternative for a more patient-demanding use of gel in dental trays at home. Although the decline in salivary mutans streptococci lasted only 1-2 Acknowledgmenls - This study was supported by months, professional flossing with chlorhexi- the Finnish Dental Society and the Academy of dine gel at regular intervals has reduced Finland. Drs. JAAKKO TIEKSO, SATU KivEL.ii and significantly approximal caries increment in TUNA JARVINEN are gratefully acknowledged for help in clinical and statistical work, and Orion a 3-yr study (23). Diagnostica (Espoo, Finland) for providing the Although in vitro tests have shown SnFo- Dentocult-SM tests. AmF gel to be even slightly niore potent inhibitor o^Streptococcus mutans and S. sobrinus than chlorhexidine (17), the in vivo situation References was not the same. SnF.,-AmF gel was significantly antistreptococcal but less effective 1. GJERMO P. Chlorhexidine and related comthan chlorhexidine. None of the gels had pounds. J Dent Res 1989; 68: Spec Iss: 1602any effect on the total aerobic fiora of whole
382
OSTELA ET AL.
2. KRASSE B , EMILSON C-G. Reduction of Strep-
tococcus mutans in humans. In: HAMADA S et al., eds. Molecular microbiology and immunobiology of Streptococcus mutans. A m s t e r d a m : Elsevier, 1986; 381-91. 3. SPETS-HAPPONEN S, MARKKANEN H , POLLANEN L,
KAUPPINEN
T , LUOMA
H . Salivary
Streptococcus mutans count and gingivitis in children after rinsing with a chlorhexidinefluoride solution with and without strontium. Scand J Dent Res 1985; 93: 329-35. 4. EMILSON C-G. Effect of chlorhexidine gel treatment on Streptococcus mutans population in human saliva and dental plaque. Scand J Dent Res 1981; 89: 239-46. 5. ScHAEKEN MJM,
D E JONG
MH,
FRANKEN
HCM, VAN DER HOEVEN JS. Effects of highly concentrated stannous fluoride and chlorhexidine regimens on human dental plaque flora. J Dent Res 1986; 65: 57-61. 6. OsTELA I, TENOVUO J, SODERLING E , LAMMI
E, LAMMI M . Effect of chlorhexidine-sodium fluoride gel applied by tray or by toothbrush on salivary mutans streptococci. Proc Finn Dent Soc 1990; 86: 9-14. 7. K E T J E N S H M A M . Microbiolog)' attd preventive trectlment of root surjctce caries. Thesis, Nijmegen, 1987. 8. SANDHAM HJ, BROWN J, PHILLIPS HI, CHAN
KH. A preliminary report of long-term elimination of detectable mutans streptococci in man. J Dettt Res 1988; 67: 9-14. 9. ScHAEKEN MJM, D E HAAN P. Effects of sustained-release chlorhexidine acetate on the human dental placiue flora. J Dent Res 1989; 68: 119-23. 10. LUOMA H^-MURTOMAA H , NUUJA T , et al. A
simtiltaneous reduction in caries and gingivitis in a group of school children receiving chlorhexidine-fluoride applications. Results after 2 years. Caries Res 1978; 12: 290-8. 11. ZICKERT I, EMILSON C-G, KRASSE B . Effect
ly applied, on Streptococcus mutans, Streptococcus sanguis and lactobacilli in dental plaque and saliva. Scand J Dent Res 1983; 91: 123-9. 14. KLOCK B , SERLING J, KINDER S, MANWELL
MA, TiNANOFF N. Comparison of effect of SnF.j and NaF mouthrinses on caries incidence, salivary S. mutans and gingivitis in high caries prevalent adults. Scand J Dent Res 1985; 93: 213-7. 15. KAY HM, WILSON M . The in vitro effects of amine fluorides on plaque hd^ctma.. J Periodontol 1988; 59: 266-9. 16. MEURMAN J H , JousiMiES-SoMER H, SUOMALA P, ALALUUSUA S, TORKKO H , ASIKAINEN S.
Activity of amine-stannous fluoride combination and chlorhexidine against some aerobic and anaerobic oral bacteria. Oral Microbiol Imnntnol 1989; 4: 117-9. 17. OsTELA I, TENOVUO J. Antibacterial activity of dental gels containing combinations of amine fluoride, stannous fluoride, and chlorhexidine against cariogenic bacteria. Scand J Dent Res 1990; 98: 1-7. 18. ETEMADZADEH H , MEURMAN J H , MURTOMAA H, TORKKO H , LAPPI L , ROOS M . Effect on
plaque growth and salivary microorganisms of amine fluoride - stannous fluoride and chlorhexidine containing mouthrinses. J Clin Periodonlol 1989; 16: 175-8. 19. JENSEN B, BRATTHALL D . A new method for
the estimation of mutans streptococci in human saliva. J Dent Res 1989; 68: 46871. 20. MALTZ M , ZICKERT I, KRASSE B . Effect of
intensive treatment with chlorhexidine on number of Streptococcus mutans in saliva. Scatid J Dettt Res 1981; 89: 445-9. 21. EMILSON C-G, LINDCJVIST B , WENNERHOLM K .
Recolonization of human tooth surfaces by Streptococcus mutans after suppression by chlorhexidine treatment. J Dent Res 1987; 66: 1503-8.
of caries-preventive measures in children highly infected with the bacterium Strepto22. KRISTOFFERSSON K , AXELSSON P, BRATTHALL coccus mutans. Arch Oral Biol 1982; 27: D. Effect of professional tooth cleaning pro861-8. gram on interdentally localized Streptococcus 12. LiNDqvisT B, EDWARD S, TORELL P, et al. Efmutans. Caries Res 1984; 18: 385-90. fect of different caries preventive measure in 23. GissELssoN H, BIRKHED D , BJORN A - L . Effect children highly infected with mutans strepof professional flossing with chlorhexidine gel tococci. Scand J Dent Res 1989; 97: 330-7. on approximal caries in 12- to 15-year-old 13. SvANBERG M, WESTERGREN G . Effect of schoolchildren. Caries Res 1988; 22: 187SnF.j administered as mouthrinses or topical92.
ANTIMICROBIALS AND MUTANS STREPTOCOCCI 24. MiJHLEMANN HR,
SAXER U , MORMANN W .
Reduction of plaque and gingivitis by stannous fluoride stabilized with amine fluoride. Caries Res 1981; 15: 186 (only). 25. ZICKERT I, EMILSON C-G. Effect of fluoride-
containing varnish on Streptococcus mutans
383
in plaque and saliva. Scand J Dent Res 1982; 90: 423-8. 26. MEURMAN JH. Ultrastructure, growth, and adherence of Streptococcus mutans after treatment with chlorhexidine and fluoride. Caries Res 1988; 22: 283-7.
ILKKA OSTELA, LAURA KARHUVAARA AND JORMA TENOVUO Department of Cariolog)', Institute of Dentistry, University of Turku, Turku, Finland
Ostela I, Karhuvaara L, Tenovuo J: Gomparative antibacterial effects of chlorhexidine and stannous fluoride-amine fluoride containing dental gels against salivary mutans streptococci. ScandJ Dent Res 1991; 99: 378-83. Abstract - F'orty-five young adults were divided into three groups of equal size and given a professional toothcleaning (3 times during 1 wk) with dental gels containing either chlorhexidine (GHX, 1%), or a SntVamine Ouoride (AmF) combination (F" content 1.20%). The control group received toothcleaning with a placebo gel. The study was done double blind. The number of salivary mutans streptococci was monitored for 11 wk after the gel treatment using both mitissalivarius-bacitracin agar plates and the chairside method based on the adhesion of mutans streptococci on plastic strips (Dentocult-SM Strip mutans). Professional toothcleaning with a GHX gel was clearly most effective ( ? < 0.001) but the ba.seline levels of streptococci returned in 1 1 wk. SnfVAmF gel also reduced significantly (P< 0.001) mutans streptococci but recolonization occurred already in 7 wk. Placebo gel, i.e. professional toothcleaning as such, did not show any statistically significant effect on the numbers of salivary mutans streptococci. None of the treatments affected the levels of lactobacilli or the total aerobic flora in saliva samples. Professional toothcleaning with a GHX gel, or with a SnF^,-AmF gel, can be regarded as an alternative to the commonly used, but more patience demanding, application of gel in mouth trays at home for individuals with high caries activity. Key words: chlorhexidine; fluorides; mutans streptococci; preventive dentistry. Jorma Tenovuo, Department of Cariology, Institute of Dentistry, University of Turku, LemminkSisenkatu 2, SF-20520 Turku, Finland. Accepted fbr publication 16 January 1991.
Ghlorhexidine (GHX) has a broad spectrum of topical antimicrobial activity (1). One of the major indications for its use in dentistry has been the reduction of oral mutans streptococci (2). For this purpose, GHX has been
incorporated into mouthwashes (3), dental gels (4-6), or varnishes (7-9). Reduction in the numbers of mutans streptococci by GHX has led to a concomitant decline in caries incidence (10-12).
ANTIMIGROBIALS AND MUTANS STREPTOCOCCI
379
done three times during 1 wk. After all the followup saliva samples had been analyzed for mutans streptococci and lactobacilli, the code of the three gels was opened. Group A had received treatment with a SnFj-AmF gel containing 1.20% F" (17; Gel No. 1), group B with 1 % GHX gel, and group C with a placebo gel (with no active antimicrobial ingredients). All the gels were kindly provided and coded for this study by GABA International, Basel, Switzerland. The initial salivary levels (mean + SD, log CFU/ml) of mutans streptococci did not differ significantly between the three groups: group A 4.38 ±0.70, group B 3.95 ±0.81, and group G 4.55 ±0.74. Neither did the initial levels of salivary lactobacilli or total aerobic flora differ between the groups (Table 1). Parafiin wax-stimulated whole saliva samples were collected just before the first gel treatment and then, in an identical way, 1, 2, 7, and 11 wk after the last gel application. All saliva samples were collected at noon with no eating, drinking or smoking for 1 h prior to the sampling. Bacterialproeedures - Bacterial analyses were done in two different ways. First, 100 |ll of saliva were immediately transferred into tubes containing 1 ml of tryptic soy broth (Oxoid, Basingstoke, UK) supplemented with 20% glycerol. The samples were stored at — 20°G, then thawed and vortexed Subjects and methods vigorously for 20 s, using sterile glass beads. To Subjects - Thirty-two female and 13 male dental determine the mutans streptococci levels, the susstudents (age 22.1 + 1.7 yr, mean + SD) volun- pension was diluted 1:10 and 1:100 and 20 |xl were teered for this study, which was approved by the pipetted in duplicate on mitis-salivarius (MS) agar Ethical Committee ofthe Medical Faculty of Tur(Difco Laboratories, Detroit, MI) plates, with ku University. All subjects were healthy, all had a 15% sucrose and 0.2 U bacitracin per ml. The full dentition with no dentinal caries, they had colonies were counted after an incubation period taken no antimicrobial medication before the of 2 days in a CO, atmosphere at 35°C. Numbers study, and took no systemic antibiotics during the of mutans streptococci in fresh saliva samples were study. Also antimicrobial mouthwashes were not also determined using the new Dentocult SM Strip allowed during the study period. The subjects were mutans test (19), manufactured by Orion Diagrandomly assigned to three test groups of equal nostica, Espoo, Finland. Salivary lactobacilli were size, each group receiving similar treatment but cultured anaerobicaliy on a selective Rogosa mediwith diflerent test gels. The study was done douum for 3 days at 35°G. The total aerobicflorawas ble-blind. studied by plating duplicate samples on blood agar Design of the study -• The subjects were given a (Oxoid, 5% bovine blood) and incubating for 2 professional toothcleaning with the experimental days in a CO, atmosphere at 35°C. Aerobic incudental gel using rotating rubber cups and dental bation was chosen because Gram-positive aerobes (loss. The treatment was done by a dentist and it are, in general, more susceptible to GHX than lasted for 5 min per subject each time. Just before Gram-negative anaerobes (1). the treatment, the students brushed their teeth Statistical analyses - The differences in logm bactewithout any toothpaste. No eating, drinking or rial counts within and between the groups were smoking was allowed for 1 h before the treatment. analyzed by the analysis of variance for repeated For each subject, professional toothcleaning was measures (BMDP 4V).
Because stannous fluoride (SnF9; 5, 13, 14) and amine fluoride (AmF; 15) also exhibit .significant antibacterial properties against oral mutans streptococci and lactobacilh, their combination has been studied as a possibility to combat oral cariogenic bacteria (16, 17). Although in vitro studies have shown SnFj-AmF combinations to be as effective as GHX against mutans streptococci (16, 17), SnF,-AmF solution with a low total F~ content (0.025%) did not prevent plaque accumulation, nor the growth of oral mutans streptococci (18). This was clearly in contrast to a GHX solution (0.12%). In the present study we have analyzed how a higher concentration of SnFj-AmF (1.20% F~), incorporated into a dental gel, affects the in vivo levels of salivary mutans streptococci and lactobacilli. This concentration of SnF,AmF was chosen because in our previous in vitro study (17) it was as effective as 1% GHX gel, which we used as a positive control in the present study.
OSTELA ET AL.
380
Results Professional toothcleaning with a CHX gel reduced significantly (/"< 0.001) the levels of salivary mutans streptococci but SnFj-AmF gel 'was somewhat less effective (Fig. 1). The results slightly differed whether the mutans streptococci were analyzed by the conventional agar technique or by the chairsidc method: the recolonization of mutans streptococci seemed to be slower if the bacteria were assayed by the method based on their adherence on plastic strips than if quantitated on MSB agar plates (Fig. 1). Professional
cleaning with a placebo gel did not affect the total level of mutans streptococci in sahva although a slight, but non-significant, decrease was found on plastic strips (Fig. 1). When quantitated by the agar plates, the recolonization of mutans streptococci occurred with CHX in 11 weeks but with SnF2AmF gel in 7 wk. However, already 2 wk after the gel treatments the differences between the groups were statistically non-signifiicant. None of the test gels affected significantly the growth of lactobacilli or the total aerobic flora in the mouth during the 11-wk study period (Table 1).
Table 1 Effect of professional toothcleaning with SnF.j-AmF, chlorhexidine and placebo gets on numbers of salivary tactobacilli and total aerobes (mean + SD, n = 15 in each group). Differences between or within grottps were slatislically not signiftcanl
Lactohacilli' Mean
Gel
SD
Total aerobic fiora' Mean
SD
6P
5,0 CONTROL
MS (log CFU/ml) 4,0
Chlorhexidine
Pretreatment Posttrcatment" 1 2
7 11
6.60
0.83
7.50
0.40
6.32 6.80 6.72 6.82
0.65 0.67 0.65 0.62
7..M 7.64 7.68 7.68
0.35 0.40 0.30 0.44
6.39
0.73
7.62
0.27
6.52 6.53 6.66 6.67
0.82 0.60 0.69 0.50
7.73 7.59 7.75 7.60
0.36 0.22 0.31 0.25
6.11
0.79
7.70
0.34
6.33 6.39 6.46 6.46
0.73 0.69 0.75 0.92
7.69 7.65 7.75 7.73
3,0 MS (scale units)
20
Pretreatment Posttreatment" 1 2 7 II Placebo
Pretreatment Posttreatmcnf^ 1 2 7 11
12
'log CFU/ml. ^wk after professional toothcleaning.
7
11
POST-TREATMENT(WEEKS) PRETREATMENT
0.37 0.45 0.46 0.52
Fig. 1. Effect of professional toothcleaning with placebo (control), SnFj-AmF and chlorhexidine (CHX) gels on numbers of salivary mutans streptococci on MSB agar plates (A), or on their adherence to plastic strips (B). Values are mean + SD, n= 15 in each group.
ANTIMICROBIALS AND MUTANS STREPTOCOCCI
Discussion
381
saliva samples. The combination of SnF, and AmF is stable (24) but according to our results this type of product should be regarded only as an alternative to those patients who, for some reason (allergy etc.), are unable to use chlorhexidine for targeted antistreptococeal treatment. However, in future studies SnFj-AmF gel should be studied as an alternative to fiuoride varnishes: both have a high fiuoride content, have to be applied in the dental office but, in contrast to varnishes (25), the SnF.;-AmF combination reduces the numbers of oral mutans streptococci. It seemed that the quantitation of mutans streptococci based on their adhesion on plastic strips showed longer inhibitory effect than methods based on their cultivation on agar plates. In the present study, the pattern of regrowth in agar is in accordance with the extensive studies by EMILSON ei al. (21). The difference between the two methods may be due to the known inhibitory effect of both chlorhexidine and fiuoride on the adherence of oral streptococci (6, 26). However, for some unknown reason the placebo treatment also tended to reduce slightly, but non-significantly, the adherence of mutans streptococci. Further studies of the distribution of mutans streptococci between plaque and saliva after various antimicrobial treatments may provide more information of how these treatments actually work in vivo.
A large number of studies have shown that chlorhexidine (1%) gel is effective in reducing the number of oral mutans streptococci (2). Usually, ehlorhexidine gel has been applied by individually designed mouth trays and the patient has done the treatments at home according to the instructions given in the dental office (20, 21). This type of treatment is demanding for patients who have high caries activity and poor cooperation the reasons why they are thought to benefit from chlorhexidine in their dental prophylaxis. Use of chlorhexidine as a toothpaste is somewhat less effective than its use in dental trays (6). The present study showed that also professional toothcleaning with a chlorhexidine gel is an effective way to reduce the numbers of oral mutans streptococci. Because no such effect was found with the placebo gel, it is clear that the reduction was not due to the professional cleaning as such. This is in accordance with KRISTOFFERSSON et al. (22) who found that the effect of an intensive professional cleaning program on tnutans streptococci was only transient and the recolonization to the baseline levels occurred in less than 30 days. Our results suggest that professional toothcleaning with chlorhexidine gel may be a useful alternative for a more patient-demanding use of gel in dental trays at home. Although the decline in salivary mutans streptococci lasted only 1-2 Acknowledgmenls - This study was supported by months, professional flossing with chlorhexi- the Finnish Dental Society and the Academy of dine gel at regular intervals has reduced Finland. Drs. JAAKKO TIEKSO, SATU KivEL.ii and significantly approximal caries increment in TUNA JARVINEN are gratefully acknowledged for help in clinical and statistical work, and Orion a 3-yr study (23). Diagnostica (Espoo, Finland) for providing the Although in vitro tests have shown SnFo- Dentocult-SM tests. AmF gel to be even slightly niore potent inhibitor o^Streptococcus mutans and S. sobrinus than chlorhexidine (17), the in vivo situation References was not the same. SnF.,-AmF gel was significantly antistreptococcal but less effective 1. GJERMO P. Chlorhexidine and related comthan chlorhexidine. None of the gels had pounds. J Dent Res 1989; 68: Spec Iss: 1602any effect on the total aerobic fiora of whole
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E, LAMMI M . Effect of chlorhexidine-sodium fluoride gel applied by tray or by toothbrush on salivary mutans streptococci. Proc Finn Dent Soc 1990; 86: 9-14. 7. K E T J E N S H M A M . Microbiolog)' attd preventive trectlment of root surjctce caries. Thesis, Nijmegen, 1987. 8. SANDHAM HJ, BROWN J, PHILLIPS HI, CHAN
KH. A preliminary report of long-term elimination of detectable mutans streptococci in man. J Dettt Res 1988; 67: 9-14. 9. ScHAEKEN MJM, D E HAAN P. Effects of sustained-release chlorhexidine acetate on the human dental placiue flora. J Dent Res 1989; 68: 119-23. 10. LUOMA H^-MURTOMAA H , NUUJA T , et al. A
simtiltaneous reduction in caries and gingivitis in a group of school children receiving chlorhexidine-fluoride applications. Results after 2 years. Caries Res 1978; 12: 290-8. 11. ZICKERT I, EMILSON C-G, KRASSE B . Effect
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MA, TiNANOFF N. Comparison of effect of SnF.j and NaF mouthrinses on caries incidence, salivary S. mutans and gingivitis in high caries prevalent adults. Scand J Dent Res 1985; 93: 213-7. 15. KAY HM, WILSON M . The in vitro effects of amine fluorides on plaque hd^ctma.. J Periodontol 1988; 59: 266-9. 16. MEURMAN J H , JousiMiES-SoMER H, SUOMALA P, ALALUUSUA S, TORKKO H , ASIKAINEN S.
Activity of amine-stannous fluoride combination and chlorhexidine against some aerobic and anaerobic oral bacteria. Oral Microbiol Imnntnol 1989; 4: 117-9. 17. OsTELA I, TENOVUO J. Antibacterial activity of dental gels containing combinations of amine fluoride, stannous fluoride, and chlorhexidine against cariogenic bacteria. Scand J Dent Res 1990; 98: 1-7. 18. ETEMADZADEH H , MEURMAN J H , MURTOMAA H, TORKKO H , LAPPI L , ROOS M . Effect on
plaque growth and salivary microorganisms of amine fluoride - stannous fluoride and chlorhexidine containing mouthrinses. J Clin Periodonlol 1989; 16: 175-8. 19. JENSEN B, BRATTHALL D . A new method for
the estimation of mutans streptococci in human saliva. J Dent Res 1989; 68: 46871. 20. MALTZ M , ZICKERT I, KRASSE B . Effect of
intensive treatment with chlorhexidine on number of Streptococcus mutans in saliva. Scatid J Dettt Res 1981; 89: 445-9. 21. EMILSON C-G, LINDCJVIST B , WENNERHOLM K .
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of caries-preventive measures in children highly infected with the bacterium Strepto22. KRISTOFFERSSON K , AXELSSON P, BRATTHALL coccus mutans. Arch Oral Biol 1982; 27: D. Effect of professional tooth cleaning pro861-8. gram on interdentally localized Streptococcus 12. LiNDqvisT B, EDWARD S, TORELL P, et al. Efmutans. Caries Res 1984; 18: 385-90. fect of different caries preventive measure in 23. GissELssoN H, BIRKHED D , BJORN A - L . Effect children highly infected with mutans strepof professional flossing with chlorhexidine gel tococci. Scand J Dent Res 1989; 97: 330-7. on approximal caries in 12- to 15-year-old 13. SvANBERG M, WESTERGREN G . Effect of schoolchildren. Caries Res 1988; 22: 187SnF.j administered as mouthrinses or topical92.
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