1. Get the Key for Tomorrow’s Dentistry
a symposium organized by the
KOREAN CARIES PREVENTION ASSOCIATION
and sponsored by
Danisco Cultor and Lotte Korea
Seoul April 22, 2001

2. The Influence and Mechanism of Xylitol on Mutans Streptococci
Luc Trahan, PhD
Groupe de Recherche en Écologie Buccale
Faculté de médecine dentaire
Université Laval
Québec, Canada

3. Principal Proposed Mechanisms of Action of Xylitol
Lack of acid production by plaque bacteria
Increased saliva secretion and salivary buffer capacity
Inhibition of demineralization of sound enamel
Remineralization of decalcified sites
Inhibition of acid production by MS from dietary sugars
Inhibition of MS growth
Selection of a new less virulent MS population
Reduction of the transmission / implantation of Ms

4. Aim and Content
Aim: To survey and summarize the influence and the mechanisms of action of xylitol on Mutans Streptococci
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Recent progresses on the mechanisms of action
Summary and take home messages

5. Content
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Inhibition of growth and acid production from sugars
Selection of a new MS population
Recent progresses on the mechanisms of action
Disturbed protein synthesis and reduced survival
Virulence properties
Summary and take home messages

6. The Caries Etiological Factors Constitute a Fragile Ecosystem
Xylitol
Plaque
Tooth
Sugar
CARIES
Saliva
Fluoride
Multiple
Factors
Sealant
Antiseptics

7. Modification of the Plaque Ecosystem by Sugar Consumption
SUGARS
(sucrose)
SUGARS
S M
S M
ACIDS
ACIDS

8. Ecological Plaque Hypothesis and Prevention of Caries
Environmental
changes
Ecological
shift
Fermentable
Sugar
Acid
Neutral pH
Low
S. oralis
S. sanguis MS
Lactobacilli
Remineralization
Demineralization
Marsh, P., 1991

9. Dietary Sugars: Source of Energy and Carbon for the Growth of Plaque Bacteria
OD (660 mm) 4 8 1 2 , 3 5
Sugar could be: sucrose glucose
lactose
mannitol
sorbitol
etc..
Xylitol
Time (hours)

10. Acidic End-products Generation from Dietary Sugars by Plaque Bacteria
Demineralization
Remineralization
Sugars
Xylitol
Sorbitol
Critical pH 19

11. Xylitol: a Caries Preventive 5C- Sugar Alcohol
CH2OH
H-C-OH
HO-C-H
SORBITOL
C6H14O6
CH2OH
H-C-OH
HO-C-H
XYLITOL
C5H12O5
CH2OH
C=O
HO-C-H
H-C-OH
FRUCTOSE
C6H12O6
A NATURAL 5 CARBON SUGAR
ALCOHOL (PENTITOL)

12. Dietary Sugar Utilization by Oral Streptococci
ATP
Glucan
Fructan
Sugar
ADP + +
Sugar~P
Fructose
Glucose
Sugar
ADP+PPi
ATP
Polysaccharides
reserves
PTS
Glucose~P
ADP
ATP
Sucrose
PEP
ADP
Pyruvate
ATP
Lactate
Lactic acid

13. Five-carbon Sugar Alcohols Utilization by Non-oral Bacteria
PERMEASE
2-Keto
pentose
Kinase
5-C alcohol
5-C alcohol
(xylitol)
2-Keto pentose~P
PTS DH
5-C alcohol~P
Epimerisation }
Carbohydrate pathways
Lactic acid
Acetic acid
Ethanol
etc...
± acidic
end-products
ADP
ATP

14. Incapacity for Oral Bacteria to Utilize 5-Carbon Sugar Alcohols
PERMEASE
2-Keto
pentose
Kinase
5-C alcohol
5-C alcohol
(xylitol)
2-Keto pentose~P 
PTS DH
5-C alcohol~P
Epimerisation  } 
Carbohydrate pathways
± acidic
end-products
Lactic acid
Acetic acid
Ethanol
etc...
ADP
ATP

15. Inducible Six-carbon Sugar Alcohols Utilization by Mutans Streptococci
Mannitol~P
Sorbitol~P
Mannitol
PTS mtl
ADP+PPi
ATP
Polysaccharides
reserves
Glucose~P
ADP
PTS sor
ATP
Sorbitol
PEP
Pyruvate
ADP
ATP
Lactate
Lactic acid

16. Content
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Inhibition of growth and acid production from sugars
Selection of a new MS population
Recent progresses on the mechanisms of action
Disturbed protein synthesis and reduced survival
Virulence properties
Summary and take home messages

17. Growth Inhibition of S. mutans Strains by Xylitol
ATCC 27352
GS5-2
Ingbritt
NTCC 10449
6715
8E3 (
fresh
isolate)
67.3 ( 82 76 85 84 68 33

18. Effect of Xylitol on Acid Production Rate by Resting Cells of S. mutans4 m o l e H + / 1 6 g c s ( d r y w i h t )
from glucose 3
Strain
% inhibition R
27352 X S
6715
Ingbritt 49 68 38 2 1
+ xylitol
from xylitol 1 2 3 4 M I N U T E S
Vadeboncoeur, C., 1983

19. Definition of MS Sensitivity to Xylitol
Xs wild type strains : xylitol-sensitive
Strains that are inhibited by xylitol
Xr natural mutants : xylitol-resistant
Strains that are not inhibited by xylitol
None of these strains ferment xylitol
and none produce acid from it.

20. Effect of the Addition of Xylitol to Growing XS and XR S. mutans
XR (± xyl)
+ xylitol
XS (+ H2O) , 7 , 6
XS (+ xyl) , 5 , 4 ) m n , 3 1 2 6 XS 6 ( 1 d D e t O a 8 , 2 l u m u 6 c c a l 4 o l i t y 2 x XR - C 4 1 , 1 1 2 3 4 5 6 T i m e ( h o u r s )
Trahan, L., 1985

21. S. mutans Constitutive Fructose-PTS also Transports Xylitol
XYLITOL~P
IIC
FRUCTOSE
XYLITOL
Constitutive
fructose-PTS
IIB ~
IIA P
PEP
Enzyme I
HPr(His~P)
HPr
FRUCTOSE
IIC
IIA
IIB
Enzyme I~P ~ ~
Pyruvate P P
Inducible
fructose-PTS
FRUCTOSE-1-~P
Benchabane, H., 1997

22. Xylitol Transport and Expulsion in S. mutans
Sugar
Xylitol Transport and Expulsion in S. mutans
PTS
Sugar~P
ADP
ATP
PEP
ADP
FRUCTOSE
PTS
Xylitol
ATP
Pyruvate
Xylitol~P
EXPULSION
Lactic
acid
Lactate Pi
Xylitol
Trahan L. 1996

23. Establishment and Consequences of a Xylitol Futile Cycle
Sugar
Establishment and Consequences of a Xylitol Futile Cycle
PTS
Sugar~P
ADP
ATP
PEP
ADP
FRUCTOSE
PTS
Xylitol
ATP
Pyruvate
Xylitol~P E
Lactic
acid
EXPULSION
Lactate Pi
Xylitol

24. Absence of Constitutive Fructose PTS Activity in Xr Mutants
Sugar
Absence of Constitutive Fructose PTS Activity in Xr Mutants
PTS
Sugar~P
ADP
ATP
PEP
ADP
Xylitol
FRUCTOSE
PTS
ATP
Pyruvate
Lactic
acid
Lactate

25. Effect of Xylitol and Xylitol-5-phosphate on Selected Glycolytic Enzymes in Vitro
% inhibition by
Enzyme
xylitol
xylitol 5-P
PGI
>90
6-PFK 50
1-PFK 10 PK
>90
LDH

26. Proposed Model of the Effect of Xylitol on S. mutans
Glycogen
PMF
Fructose-6-P
6-PFK
Glucose
PGI
Fructose-1,6-di-P
Glucose
Glucose-6-P -
DHAP
PTSman
GA3P + PK
LDH
Lactic
acid
PEP
Pyruvate
Lactate
1,3-DPG
PTSfru
2-PG -
3-PG
Xylitol
Xylitol-P
Xylitol
Trahan L., 1996

27. Content
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Inhibition of growth and acid production from sugars
Selection of a new MS population
Recent progresses on the mechanisms of action
Disturbed protein synthesis and reduced survival
Virulence properties
Summary and take home messages

28. In vitro Selection of XR Natural Mutants Following Growth in the Presence of Xylitol

29. In vivo Selection of XR Natural Mutants in Saliva and Plaque of Xylitol Consumers

30. Proportion of salivary natural XR MS strains in patients
Number of strains
% XR
Patients
Total XR XS
Controls 20 2 18 10 54 47
Xylitol-consumers 7 87

31. Occurrence in 1988 of XR Salivary Strains in Patients from the Ylivieska Xylitol Study (1982-1984)
Group
% XR
Controls
35.0 ± 6.4
Active consumers
82.5 ± 5.7
Former consumers N 16 14 13
74.6 ± 8.6

32. Effect of Xylitol Consumption on the Plaque Ecosystem
S M
XYLITOL

33. Content
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Inhibition of growth and acid production from sugars
Selection of a new MS population
Recent progresses on the mechanisms of action
Disturbed protein synthesis and reduced survival
Virulence properties
Summary and take home messages

34. Effect of a Heat or Xylitol Stress on 14C-labelled Protein Profile of S. mutans

35. Densitometric Analysis of Protein Profiles of Xr and Xs MS Strains After a Xylitol Exposure
Xs strain
Xr strain
Protein ID
Control
Xylitol
exposure
Control
Xylitol
exposure
HSP-70
1.00
1.08
0.53
HSP-60
0.82
0.54
71 kDa
1.00
0.58
1.00
1.16
63 kDa
1.00
0.57
1.00
1.11
57 kDa
1.00
1.37
1.00
1.03
53 kDa
1.00
0.53
1.00
0.95
50 kDa
1.00
1.48
1.00
0.95
40 kDa
1.00
1.09
1.53

36. Effect of a Xylitol Shock on the Survival Capacity of S. mutans 123.1
Number of surviving cells (CFU /mL)
S. mutans XS S. mutans XR
Control Xylitol X/C Control Xylitol X/C
3.51±0.13 x ±0.47 x ±0.68 x ±0.38 x
1.45±0.38 x ±0.09 x ±0.34 x ±0.42 x
3.07±0.60 x ±0.05 x ±0.39 x ±0.43 x
1, 2, 3 p<0.0003
4, 5, 6 p>0.11

37. Content
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Inhibition of growth and acid production from sugars
Selection of a new MS population
Recent progresses on the mechanisms of action
Disturbed protein synthesis and reduced survival
Virulence properties
Summary and take home messages

38. Preliminary Results on the Attenuated Virulence Properties of XR MS Strains Selected by Xylitol ...
When XR strains are compared with corresponding XS strains the accumulated evidence suggest:
a reduced acid production from sugars
a modified extracellular polysaccharides synthesis
a modified bacterial agglutination/aggregation capacity
an elevated glucan-binding protein C elevated 20 folds

39. Preliminary Results on the Attenuated Virulence Properties of XR MS Strains Selected by Xylitol
an increased dextran-dependent aggregation capacity
a reduced adherence to saliva coated hydroxyapatite and glass surfaces
a reduced cariogenicity in a rat model
an absence of DnaK and GroEL stress proteins response to a xylitol exposure
a larger bacterial cells shedding from plaque to saliva

40. Content
Background information on the dental plaque ecosystem and the utilisation of sugars by MS
Details of the effects of xylitol on MS
Inhibition of growth and acid production from sugars
Selection of a new MS population
Recent progresses on the mechanisms of action
Disturbed protein synthesis and reduced survival
Virulence properties
Summary and take home messages

41. Summary of the Effects of Xylitol on Mutans Streptococci ...
A variable intensity inhibition of growth on most fermentable sugars resulting from:
the establishment of an energy spending futile cycle
the strong inhibition of glycolytic pathway enzymes
An inhibition of acid production from dietary sugars also resulting from the above mentioned mechanisms

42. Summary of the Effects of Xylitol on Mutans Streptococci
A selection of XR MS strains with apparently less virulent properties
A disturbance of protein synthesis, including stress proteins DnaK and GroEL, resulting in a reduced capacity to survive further exposure to xylitol
A reduced capacity to be transmitted from mother to child

43. Clinical Benefits for Patients Chewing Xylitol Gum
The accumulated evidence suggests:
a reduced caries incidence via:
an increased saliva secretion and salivary buffer capacity
an inhibition of demineralization of sound enamel
a remineralization of decalcified sites
an inhibition of acid production from dietary sugars
a less acidogenic and less aciduric plaque ecosystem

44. The accumulated evidence suggests:
Additional Clinical Benefits from the Inhibitory Action of Xylitol on MS
The accumulated evidence suggests:
a reduction of:
plaque indices
the amount of plaque accumulated
the number of MS in plaque and saliva
the capacity to transmit MS strains
a selection of Xr MS strains with:
apparently less virulent properties
a loss of MS strains from plaque to saliva

45. Take Home Message # 1
Xylitol influences positively the plaque microflora in establishing ecological conditions less appropriate for the low-pH bacteria producing acidic end-products and thus beneficial for the patients
Long and/or frequent exposure to xylitol does not result, for oral bacteria, in adaptation to metabolize the sugar-alcohol

46. Take Home Message # 2
Xylitol is not only unfermentable by oral bacteria but it also inhibits most mutans streptococci
Biochemical mechanisms explaining the inhibition of the growth of, and acid production by, mutans streptococci have been well known for a few years
Knowledge on other mechanisms involving disturbed proteins synthesis by xylitol and reduced survival of MS to repeated exposures to xylitol is progressing

47. Take Home Message # 3
The occurrence of xylitol-resistant strains in xylitol consumers is explained by a simple selection of natural mutants
Xylitol-resistance of MS does not impair its use in caries prevention and is most probably beneficial for the patients
Knowledge of the hypothesized less virulent properties of xylitol-resistant strains is progressing

48. This presentation is the result of various studies conducted with numerous graduate students and colleagues from Québec and Finland
THANK YOU

49. A french speaking university founded in 1683
A campus with more than students
A Faculté de médecine dentaire since 1969 14