C. Vanloveren et al., PLAQUE COMPOSITION, FLUORIDE TOLERANCE AND ACID PRODUCTION OF MUTANS STREPTOCOCCI BEFORE AND AFTER THE SUSPENSION OF THE USE OF FLUORIDE TOOTHPASTES, Caries research, 29(6), 1995, pp. 442-448
Although fluoride toothpastes are widely used for caries prevention, l
ittle is known about the impact of fluoride dentifrices on plaque comp
osition. Also the issue of adaptation of mutans streptococci to grow i
n vivo in a fluoride environment has received little attention. Such a
n adaptation may be of interest as it has been suggested that adapted
mutans streptococci may show reduced glycolytic activity thereby being
less cariogenic. In the present experiments the impact of the suspens
ion of the use of fluoride toothpastes on plaque composition, fluoride
tolerance and acid production of mutans streptococci was studied. Poo
led plaque samples from the lingual surfaces of the lower incisors wer
e collected from individuals (n = 13) just before and 7 weeks after th
ey had replaced their fluoride toothpastes (0.1-0.15% F) with a non-fl
uoride one. The samples were analysed for fluoride and the numbers and
proportions of streptococci, Streptococcus mutans, Streptococcus sobr
inus, Actinomyces species, and lactobacilli, respectively. The fluorid
e tolerance of the mutans streptococci was estimated by culture of the
plaque samples on TYCSB agar supplemented with of 0, 1, 2, 3, 4, and
5 mmol/l fluoride (NaF) at pH 7.2. From each plaque sample six S. muta
ns strains were isolated for the measurement of the rate of acid produ
ction (Vap) at pH 7 in the presence of 0, 5, and 10 mmol/l F. The over
night final pH was measured in cultures of the S, mutans strains with
excess of glucose and 0, 5, and 10 mmol/l F. The results showed that t
he removal of the fluoride pressure from plaque did not affect the num
bers or proportions of the various species and genera of bacteria. The
fluoride tolerance of the mutans streptococci, and the Vap or the ove
rnight final pH of the isolated strains had not changed. These results
suggest that the use of fluoride toothpaste had not affected plaque c
omposition, nor fluoride tolerance or acidogenicity of mutans streptoc
occi. Probably the amount of fluoride delivered by fluoride dentifrice
s to dental plaque is too low to induce such adaptations.