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University of Groningen

Xilitol and dental caries.

Smits, Marten Titus

IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below.

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1987

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Smits, M. T. (1987). Xilitol and dental caries. [s.n.].

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xylitol and dental caries

M.T. Smits

(3)

XYLITOL AND DENTAL CARIES

(4)

STELLINGEN BEHORENDE BIJ HET PROEFSCHRIFT

"XYLITOL AND DENTAL CARIES"

1

Voor modelmatige weergave van de relatie tussen cariës en haar etiologische factoren, dient aan figuur 1.1. uit dit proefschrift de voorkeur te worden ge­

geven boven de (gemodificeerde) trias van Keyes.

Keyes PH, Int Denl J 12: 443-464 (1962)

König KG, Karies und Kariesprophylaxe·. München, Goldman (1971) Dit proefschrift

Il

De geringe cariësloename op buccale en linguale vlakken bij proefpersonen die een xylitol-dieet gebruiken, kan worden verklaard door de goede toegankelijk­

heid van deze vlakken voor xylitol en de effecten van xylitol op hel_ re- en dcmineralisatieproces.

Scheinin A, Banoczy J, Acta Ddont Scand 43: 321-325 (1985) Dit proefschrift

lll

De bevinding dat xylitol geen remmende werking heeft op de sucrose fermentatie door microorganismen, mag niet leiden tol de conclusie dal toevoeging van xy­

litol aan sucrosehoudend snoepgoed geen cariësremmend effect heeft.

Lutz D and Gulzow HJ, Caries Res 13: 132-136 (1979) Dit proefschrift

IV

De remmende invloed van xylitol op hel cariësproces kan worden verklaard uit de effecten van xylitol op (i) plaque, op (ii) speeksel en op (iii) het de- en remineralisatieproces.

Dit proefschrift

V

Een hoge correlatie lussen DMF-scores en Plaque-scores wil niet zeggen dat een hoge plaque score in een individu een hoog cariësrisico inhoudt.

Grenby TH, Basharaat AH, Gey KF, Br Dent J 152: 339-343 (1982) VI

Labo ra tor iumonderzoek naar de hechtsterkte van etsbruggen heeft een geringe voorspellende waarde voor de hechtsterkte die onder klinische omstandigheden· wordt bereikt.

Veen H van der, Bronsdijk AE, Poel ACM van de, Ned Tijdschr Tandheelk 93:

471-476 (1986)

(5)

VII

Gezien de huidige kennis met betrekking tot preventie en progressie van gla­

zuurcariës en de toenemende levensverwachting van de bevolking dient nu nader onderzoek te worden verricht naar de bchandclnoodzaak van dcntinccariës.

VIII

Omdat bij de tandheelkundige studie en beroepsuitoefening het begrip kwaliteit een belangrijke rol speelt, verdient het aanbeveling het bock "Zen and the art of motorcyclc maintainancc" als verplichte literatuur in het onderwijs op te nemen.

IX

Schrijven zonder tekstverwerker is als rekenen zonder rekenmachine: je moet zonder kunnen, maar het gaat gemakkelijker met.

X

Zolang rivaliteit de productiv itci t bevordert, dient "incompatibili té d' hu­

meur" in een bedrijfssituatie als gewenst te worden beschouwd.

XI

Een baanloze tandarts verliest wel zijn vakkennis, maar niet zijn handvaardig­

heid.

XII

Omdat tijdens fietsen en douchen in het algemeen goede ideeën ontstaan, dienen door de universiteit aan "assistenten in opleiding" salaris-aanvullende subsi­

dies te worden verstrekt op fiets en douchevoorzieningen.

XIII

Nadat in 1986 enkele verkeerstechnische aanpassingen in Groningen gereed zijn gekomen, behoort het Noorden des lands wat fileproblematiek betreft echt bij de randstad.

Martin Smits, 27 mei 1987

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Cover: Er ik van Ommen

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RlJKSUNlVERSlTElT TE GRONINGEN XYLITOL AND DENTAL CARIES

proefschrift.

ter verkrijging van het doctoraat in de Geneeskunde

aan de Rijksuniversiteit te Groningen op gezag van de

Rector Magnificus Or. E. Bleumink in het openbaar te verdedigen op

woensdag 27 mei 1987 des namiddags te 4.00 uur

door

Marlen Titus Smits geboren te Leeuwarden

(8)

Promulurcs

Paranimfen

Prof. Dr. J. Arcnds

Prof. Dr. A. C.M. van de Poel

Han de Ruiter Marjoke Vervoorn

(9)

VOORWOORD

Velen hebben de afgelopen 5 jaar op diverse wijzen bijgedragen aan hel tot stand komen van dit proefschrift. Enkelen wil ik hier met name noemen.

Prof. Dr. J. Arends en Prof. Dr. A.C. M. van de Poel bedank ik beide voor de plezierige en constructieve wijze waarop ze hun promotorentaak hebben verricht,

Dr. A. Bär voor de waardevolle gesprekken over verscheidene fa­

cetten van het onderzoek,

De leden van de promotiecommissie, Prof. Dr. J.M. ten Cate, Prof.

Dr. G. Boering en Prof. Dr. J.J. ten Bosch voor de vlotte beoor­

deling van het manuscript,

Dr. D.J. Purdell-L ewis voor het verbeteren van het engels van het manuscript en zijn adviezen,

Lidy Kingma en Alie Wollman voor hun onvermoeibare inzet bij het typen en verzorgen van de lay-out van het manuscript,

Erik van Ommen voor ontwerp en uitvoering van de omslag en, samen met Henk Flanderijn voor het tekenen van de figuren en de deskun­

dige hulp bij het persklaar maken van het manuscript,

Jan Schuthof, Jan Ruben en Marianne van der Kuijl voor alle labo­

ratoriumhulp,

Kai Leimbach, Mart Flach en Tom Linthorst voor hun bijdrage aan de experimenten van hoofdstuk 4.

Verder bedank ik hier alle proefpersonen die aan de klinische experimenten hebben meegewerkt -zonder hen was er geen getal op papier gekomen- en de medewerkers van het laboratorium voor orga­

nische chemie (Prof. Dr. Kelloch) voor het verstrekken van mole­

cuulmodellen.

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Daarnaast bedank ik iedereen met wie ik de afgelopen jaren indi- viduccl

cultuur zonder 1984", groep

of in groepen heb samengewerkt, voor hun bijdrage aan de waarbinnen dit proefschrift lol stand kwam. ln het bij­

noem ik hier "de slafgrocp onderwijs in de Dl fase 1981-

"de stafgroep onderwijs lT-345 1985-1987", "de cariologie- 1982-1983" en de medewerkers van de vakgroepen PPS en Malaria Technica,

In een voorwoord wordt de belangrijkste persoon meestal als laat­

ste genoemd. Van deze gewoonte wijk ik niet af en bedank hier Anneke Brockcma voor al haar activiteiten als copromovendus.

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- CONTENTS -

XYLITOL AND DENTAL CARIES

l . lntroduction and aim of the invcstigation 1. 1. lntroduction

1.2. Xylitol

2. Xylitol and dental caries: a literature review

3.

4.

2. l. Introduction

2. 2. Epidemiological and rat studies 2. 3. Effect of xylitol on plaque 2. 4. Effect of xylitol on saliva 2. 5. Effect of xylitol on enamel 2. 6. Conclusions

lnfl uence of xylitol on surface Changes in enamel hardness 3. l. Abstract

3. 2. lntroduction

3. 3. Material and Methods 3. 4. Results

3. 5. Discussion

lnfluence of xylitol on surface Fluoride uptake in enamel

4.1. lntroduction

4. 2. Material and Methods 4. 3. Results

4. 4. Discussion

softened

softened

enamel

enamel

in vivo

in vivo ( 1 )

( 2) 13 13 14 18 18 20 21 29 32 33

36 36 36 37 39 45

48 48 48 52 59

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5. Enamel demineralization in artificial grooves (1) Lesion formation in vitro

5. 1. Abstract 5. 2. Introduction

5. 3. Material and Methods 5. 4. Results

5. 5. Discussion

6. Enamel demineralization in arti ficial grooves (2) In fluence of xylitol on enamel in plaque free and plaque covered conditions in vivo

7.

6. 1. Abstract 6. 2. Introduction

6. 3. Material and Methods 6. 4. Results

6. 5. Discussion General discussion Summary

Samenvatting Re ferences

63 63 63 65 67 69

72 72 73 73 77 81 85 91 96

102

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LIST OF FIGURES 1. l

1. 2 2. l 3.1 3. 2 4. 1 4. 2 4.3

Factors involved in dental caries

Chemical structure of xylitol, sorbitol and sucrose pH changes in plaque after eating a snack

Microhardness of enamel in vivo

Polarized light microscopie picture of softened enamel Preparation of enamel bleeks for fluoride analysis Thickness measurement of enamel layers for fluoride analysis

Mean fluoride content in enamel

4.4 Relation between microhardness and fluoride conten t of enamel

4. 5 4. 6

5. l 5. 2 5. 3 6. 1 6. 2 6. 3 7. l

Fluoride profiles in enamel

Relation between fluoride data obtained from two tech­

niques

Creation of an artificial groove in enamel

Position of lesion depth measurements on tooth sec­

tions

Lesion depth in enamel after demineralization in vitro Measurement position s on tooth sections

Two enamel bleeks mounted in a prosthesis

Polarized light picture of enamel lesions in a groove Factors involved in dental caries

15 16 26 42 45 50 51 53 54 55 58 64 66 68 7 4 7 6 7 8 91

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LIST OF TABLES

1 I. l Xylitol effect in human epidemiological dies

1 I. 2 Xylitol effect on plaque 1 I. 3 Xylitol effect on saliva 11. 4 Xylitol effect on enamel

111. l Composition of the toothpastes 111. 2 Outline of the experiment

111. 3 Enamel microhardness in vivo (examples) 111. 4 Mean enamel microhardness in vivo

111. 5 Relative changes in enamel microhardness lV. l Composilion of the toothpastes

and rat stu-

lV. 2 Mean fluoride content in softened enamel ( abrasive technique)

1 V. 3 Mean fluoride content in sound and softened enamel (Secondary Ion Mass Spectroscopy)

lV.4 Relation between abrasive and S lMS technique

V. l Mean lesion depth in enamel after demineralization in vitro

V l. l Mineral loss from enamel in vivo V l. 2 Lesion depths in enamel in vivo

V l l.l Fluoride uptake in enamel from toothpaste slurries in vitro

19 22 31 32

39 40 41 43 44 49 52

65 59

67 7 9 80

88

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CHAPTER 1

INTRODUCTION AND AIM OF THE INVESTIGATION

1.1. lntroduction

The purpose of th.is investigation was to study the effect of xylitol on initial enamel caries.

Dental caries is a disease which is characterized by localized destruction of the dental hard tissues by metabolites produced by oral micro-organisms [Nik.iforuk, 1985; Thylstrup and Fejerskov, 1986].

During the caries proces tooth mineral is lost from the tooth en­

amel to the den tal plaque and saliva. Th is process is cal led enamel demineralization. Eventually demineralization leads to the formation of cavities in enamel and, later on, in the under­

lying dentine. ln the init.ial phase of enamel caries, the demin­

eralized areas can be repaired ( "healed") by redeposition of tooth mineral from plaque and sal.iva. This is called remineral- ization. Alternating periods of demineralization and remineral­

ization of tooth enamel occur each day. The delicate equilibrium between de- and remineralization is influenced by the presence of fluoride, calcium, phosphates and other elements in plaque, sal­

iva and tooth enamel.

Conditions favouring demineralization can be characterized by low concentrations of fluoride, calcium and phosphate and a low pH near the enamel surface under plaque. Remineralization can occur if concentrations of fluoride, calcium and phosphates and the pH are higher.

De- and remineralization depend on the presence of these ions in plaque near the enamel surface and are influenced by several factors such as

(1) the microflora in plaque and saliva -13-

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Chapler l: lnlroduclion

(2) □ral hygiene (3) dielary habits

( 4) social and cullural variables [Jenny et al. , 1974; Ruiken, 1983].

This wide range of factors involved in the eliology of dental caries is shown schematically in figure 1. 1.

The car.ies process, lhe result of .imbalance between de- and re­

m.ineralization, can be influenced extens.ively by changing one of these factors, for example by m.inimizing the sucrose content of the daily d.iet.

The results of a large scale caries experiment, the Vipeholm stu­

dies were published in 1957 [Gustafsson et al. ]. lt was shown that caries increases if sucrose containing foods are frequently consumed between meals. These findings did not lead to a wide­

spread reduction in sugar consumption, probably because of the important psychological and cul tural role of sugar, i ts sweet tasle and other properties.

These and other results stimulated the search for noncariogenic sweeteners and a considerable amount of research has been carried out on sweet-tasting carbohydrates such as sorbitol, xylitol and mannitol.

The studies on xylitol have shown eipecially interesling results ( chapter 2) . The effects of xylitol on dental caries were, therefore further investigaled in this thesis.

S everal physical and chernical properties of xylitol are described in the next paragraph and cornpared with these of sucrose and sor­

bitol.

1. 2. Xylitol

Xylitol is a sugar substitute aften used in the formulation of non-cariogenic sweet foods. Xylitol is found naturally in sever­

al foods, such as plums, strawberries, mushrooms and cauliflower, in concentralions varying up to 1 weight percent. The sweet

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Chaplcr 1: lntroduction

social and cultural factors oral hygiëne

saliva plaque

de

diet

Fig. l. l. This figure shows a simpli fied model of dental car ies. The model shows the relalion belween several important factors, or subsys­

lems, involved in the caries process.

The mineral loss from loolh enamel is the net resull of rcminer­

alizalion (REMIN) and demineralization (DEMIN), occuring al lhe in­

ter face belween enamel and plaque ( the lhickness of lhe plaque layer varies from O up to approximalely 2 mm). DEMIN and REMIN are delermined directly by the concenlralion of several ions, such as calcium (Ca), phosphale (P) and fluoride and the pH al the inter­

face. The olher factors in lhis figurc indireclly influence lhe conccnlrations of the ions at the interface. For inslance, social and cullural factors influence oral hygiene measures and dietary habils. These can influence sali vary composi tion and flow, which in turn can effect the amounl and (microbial) composilion of plaque. This influences the ion concenlrations al the plaque-enam­

el interface and ullimately DEMIN and REMIN and thercby denlal carics. Changing one factor in lhis system of relaled subsystems, for instance the use of sugar in foods, can resull in a subslantial incrcasc or dccrease in dental caries.

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Chapter 1: lntroduction

taste of xy litol is a little weaker than that of sucrose. Xyli­

tol occurs as a natural intermediate in the carbohydrate metabo­

lism of man in amounts o f between 3-10 g / day in healthy sub- jects. lntestinal problems in the f orm of osmotic diarrhoea can occur, but only when large quantities of xylitol are taken oral ly [Mäkinen, 197 8]. Most adu lts can consume 30-60 g xylitol per day without side eff ects. After adaptation human subjects have taken in 200-400 g xylitol daily without side ef f ects which would dif ­ f er from those caused by equivalent amounts of fructose or su­

crose [Mäkinen , 1978].

The chemical f ormulae of xylitol, sorbito l and sucrose are given in figure 1. 2. Sucrose is a disaccharide, consisting of glucose and f ructose in a double r.ing structure [ Pigman and Horton, 1970]. Xylitol and sorbitol .are bath relatively small polyols, with f ive and six carbon atoms respectively.

Fig. l. 2. Chemical structure and formulae of xylitol (le ft) and sorbitol (right) and the chemical formula of sucrose (under).

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Chapter 1: lntroduction

Complete substitution of dietary sucrose by xylitol in the Turku studies resulted in nearly 100�� caries reduction after three years [Scheinin et al., 1975a]. Addition of xylitol chewin g gum to a normal sucrose conta.ining diet also caused a significant caries reduction after 1 year [S cheinin et al. , 1975b].

The followin g explanations have been suggested in the literature to explain the car.ies reducing effect of xylitol.

( i) The effect of xylitol on the quantity and "quality" of p laque

( ii) The effect of xylitol on the flow and composit.ion of saliva (iii) Recently some investigations indicated that xylitol may be involved in the enamel de- and remineralization process

directly.

Aims of the investigation

The experimen ts described in this examine the influence of xylitol on zation in vivo.

thesis were enamel de-

all and

designed to reminerali- Therefore, two in vivo experiments were

xylitol containin g toothpastes to examine remincralization and one with xylitol examine the effect on demineralization.

-17-

carried out. One with the effect on enamel dippin g solutions to

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CHAPTER 2

XYLITOL AND DENTAL CARIES:

A LITERATURE REVIEW

2 .1. Introduction

Since 1970 more than 10 0 experiments have been carried out to elucidate the role of xylitol in dental caries.

These experiments will be considered under four headings:

a) epidemiological studies and rat experiments, b) studies on dental plaque,

c) studies on saliva and

d) re- and demineralization investigations.

Comparison of the results of different studies is aften complex because of differences in experimental conditions (such as dif­

ferent control groups) and differences in data presentation. The data of each study have therefore been summarized in tables 11.1 to 11.4 with respect to:

- method of research.

- duration of the experiment. This parameter varies from several minutes in laboratory studies to 3 years in epidemiological trials.

form of xylitol use. Xylitol can be employed in in vivo exper­

iments in the form of xylitol containing ( food) products, such as chewing gum and sweets, xylitol rinse solutions, or xylitol based toothpastes. The xylitol dosage in different studies varies from the addition of small amounts of xylitol to a norm­

al sucrose containing diet, up to the complete substitution of dietary sucrose, e. g. approximately 30 g. xylitol per day.

Partial substitution of dietary sucrose by xylitol occurs when sucrose containing dietary components are replaced by xylitol containing ingredients.

- the control group(s) . In some studies the xylitol effect was

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Chapter 2: Literature review

compared with a sucrose control; in other studies the xylitol effect was compared with a water or sorbitol control group or with baseline data from before the experimental period.

- the effects measured. To enable comparisons to be made the re­

sults of each study were recalculated in this thesis to per­

centage effect using data from tables, figures and text in the papers ment.ioned.

Table 11.1. Xylitol effect in epidemiological and rat studies.

* denotes a statistically significant effect ref denotes the literature reference

(g = gram, d = day, gums = chcwing gums, F = fluoride, Sorb = sorbitol, nc = not computable)

--EPlDEMl0L0GlCAL STUDIES--

ref period form of xilitol use compared with effect�ó 1 3 year 17 g/d added normal d.iet (Hungary) -45 * 2 2 year 17 g/d added normal diet (Hungary) -37 * 3 3 year 50 g/d substituted normal diet (Turku) -100 * 4 1 year 4 gums/d added 4 sucrose gums/d (Turku) -130 * 11 3 year 4 gums/d (F+Sorb) added 4 sucrose (+F) gums/d

(Thailand) -nc

12 3 year 4 gums/d (F+Sorb) added normal d.iet + F-rinse

(French Polynesia) 0 --RAT STUDIES--

ref period tipe of xilitol use compared with effcct�ó 5 15 day 6"' ,o substitution sucrose free diet -48 * 6 21 3"' ,o added normal diet -15

6 21 3"' ,o added (odd days) normal d.iet -50 *

6 21 3"' ,o added (odd days) starch added diet -25 *

7 96 5"' ,o added normal diet +18 8 60 2.5-30% substitution saccharose diet 0 8 60 2.5-30% substitution fructose diet 0 9 21 l□�ó added water added diet -20 *

9 21 l□�ó added normal diet -27 *

10 20 5% substitution normal diet +15

Refcrences: (1) Scheinin et al. , 1985a; (2) Scheinin et al. , 1985b; (3) Scheinin et al. , 1975a; (4) Scheinin et al. , 1975b; (5) Leach and Green, 1981; ( 6) Le ach and Green, 1980; ( 7) Havenaar et al. , 1983; (8) Kar le and Gehring, 1976; (9) Gey and Kinkel, 1978; (10) Navia et al. , 1974; (11) 8armes et al. , 1985; (12) Khambanonda et al. , 1983.

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Chapter 2: Literature review

2.2. Epidemiological investigations and rat studies

Table II. 1 shows the resul ts of six epidemiological studies and six rat experiments. The table shows the calculated effect (ef­

fect%) of the "form of xylitol use" with respect to different control groups, noted in the columm "compared with". In this column a "normal diet" denotes a (standardized) sucrose contain­

ing diet. Negative values in the column effect% indicate a caries reduction, positive values a caries increase.

Epidemiological studies: In one study complete substitution of sucrose by xylitol resulted in l0m� caries reduction after 3 years [Scheinin et al., 1975a]. In the xylitol group of this ex­

periment the area of white spot lesions decreased. In the sucrose group the area of white spot lesions showed a significant in­

crease [Rekola, 1986].

In the other experiments xylitol was employed in the form of chewing gum or sweets additional to a normal sucrose containing diet. This resulted in caries reductions varying from 37 to 130%

after one to three years, when compared with a sucrose control.

The reduction of 130% in the xylitol group in one study [Scheinin et al., 1975b] means that at the end of the experimental period less teeth were Decayed, Missing or Filled (DMF) than at the start of the experiment.

Rat studies: In most rat experiments caries is measured as the total number of decayed fissures (references 5 to 9 in table 11.l) or the total number of buccal lesions (reference 10 in table 11.1). This means that no distinction is made between different stages of les ion format ion, such as "enamel caries",

"caries up to the dentine-enamel-junction" and "dentine caries".

The addition of 6 percent xylitol to a sucrose free diet leads to 48% reduction of fissure caries after 15 days [Leach and Green, 1981]. Addition of xylitol to a sucrose

lead to a significant caries reduction

containing diet can also of 20-50% if a suitable

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Chapter 2: Literature review

rat feeding pattern is chosen [Leach and Green, 1980; Gey and Kinkel, 1978]. Other feeding patterns or concentrations of xylitol and sucrose do significantly not influence fissure caries. One study [Havenaar et al., 1983] shows a statistically insignificant increase of the total number of fissure lesions.

The number of deep lesions has however significantly decreased.

The caries reduction in epidemiological and rat studies can be explained by the effect of xylitol on the quantity or "quality"

of plaque and saliva or by direct interaction of xylitol with enamel during de- and remineralization.

ation is needed

More specific inform-

1) to elucidate the mechanism of caries reduction by xylitol, 2) to determine whether caries reduction is specific for xylitol

onl y or also for other non-fermentable carbohydrates and sweeteners.

2.3. Effect o f xylitol on dental plaque

Table 11. 2. shows the results of 19 studies on the effects of xylitol on the quantity and "quality" of dental plaque.

sults are divided into effects on a) growth of microorcjanisms, b) acid production,

C) plaque pH,

d) amount of plaque, e) plaque adhesiveness,

The re-

f) plaque content with respect to proteins, carbohydrates, cal- cium and phosphates.

Growth of microorganisms

Several laboratory studies have shown that partial or complete substitution of sucrose by xylitol in the growth medium reduces the growth of many strains of Streptococcus mutans by between 33 and 100�� [ Gauthier et al., 1984; Mühleman et al., 1977; Scheie et

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Chapter 2: Literature review

Table 11.2. Xylitol effect on plaque: growth of microorganisms, acid pro­

duction, plaque pH, plaque weight, plaque score, plaque adhes­

iveness and plaque content.

* denotes a statistically significant effect ref. denotes the literature reference nc denotes "not computable"

--GROWTH OF MICROORGANISMS--

( SM= strains of S. mutans, mo = strains of other microorganisms, susp = suspension of microorganisms)

ref period t}:'.pe of X}:'.litol use compared with e ffec t�Ó 11 SM 12 hrs 0.5-2% substitution 0. 2% sucrose susp -70 * 11 SM 12 hrs 0. 5-2% added 2�ó sucrose susp 0 16 SM 12 hrs 50' ,o added l�ó sucrose susp -33/-85*

20 SM 24 min l"' ,o subst l sucrose susp -100 * 21 SM 12 hrs l"' ,o added + fluoride added 0. 2% glucose susp -nc 16 mo 12 hrs 5"' ,o added l "' ,o sucrose susp -0/-17 28 SM 14 d 10 chewing gums/d added 10 fructose ch gums/d -90 * 28 SM 14 d 10 chewing gums/d added 10 sorbitol ch gums/d -90 * 28 mo 14 d 10 chewing gums/d added 10 fructose ch gums/d 0 28 mo 14 d 10 chewing gums/d added 10 sorbitol ch gums/d 0 29 mo l year 4 chewing gums/d added 4 sucrose ch gums/d 0

--ACID PRODUCTION--

( pl = plaque suspension, SM = suspension of S. mutans, mo = suspensions of other microorganisms)

ref period t}:'.pe of X}:'.litol use compared with effect%

12 pl 5 min l�ó substi tut ion 1% sucrose in susp -100 * 13 pl 22 hrs 0. 8% substitution 0.8% sucrose in susp -99 * 13 pl 22 hrs 0. 8% substitution 2. 5�ó NaCl in susp + l 20 SM 24 min l "' ,o substitution l "' ,o sucrose susp -100 * 16 SM 12 hrs 5"' ,o added l "' ,o sucrose susp -38/-69*

16 mo 12 hrs 5"' ,o added l "' ,o sucrose susp 0 --PLAQUE PH--

ref period t}:'.pe of X}:'.litol use compared with effect�ó 15 77 d 6 chewing gums/d added baseline value -nc * 20 90 min lO�ó added 0. l�ó sucrose (rinse) -nc * 20 90 min 10% + 0. 1% sucrose added 0. l�ó sucrose (rinse) O"' ,o 26 5 min 1 o, ,o + l"' ,o glucose added l "' ,o glucose ( rinse) -nc * 26 65 min l�� + Uó glucose added 1 ., ,o glucose ( rinse) -nc * -continued on next page-

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( table 11. 2. continued)

--PLAQUE WEIGHT-- ( W = wetweight; D = dryweight; gums = chewing gums) ref

14 W 17 W 18 W 22 W 23 W 23 W 27 W 27 W 24 W 19 D

ref 20 17 19 22 27 27 27 27

23 25 29

ref 22 14

period 28 d

4 d 4 d 90 d 3 d 3 d 3 d 3 d 12 d 3 d

period 4 d 2 d 3 d 90 d 3 d 3 d 3 d 3 d 3 d 60 d l year

type of xylitol use 6-10 gums/d added 10 gums/ d added 10 gums/ d added 20% toothpaste added 6 gums/d added 6 gums/d added 5 gums/d substitution 5 gums/d substitution 6 rinses/d added 6 gums/d added

compared with baseline value

10 placebo gums/d 10 sorbitol gums/d 20% sorbitol dentifr 6 sucrose gums/d no gum

sucrose free diet 5 sucrose gums/d (in

sucrose free diet) 6 sucrose rinses/d 6 placebo gums/d --PLAQUE SCORE--

type of xylitol use 10 gums/d added 6 rinses/d added 6 gums/d added 20% toothpaste added 5 gums/d added 5 gums/d added 5 gums/d substitution 5 gums/d substitution 6 gums/d added 20 g/d added

4 chewing gums/d added

compared with 10 placebo gums/d 6 water rinses/d 6 placebo gums/d 20% Sorb. toothpaste no gum

5 sucrose gums/d sucrose free diet 5 sucrose gums/d (in

sucrose free diet) no gum

normal diet 4 sucrose gums/d --PLAQUE ADHESIVENESS--

effcct�ó -50 * -30 * -20 * -40 D * -25 -10 -35 * -40 * - 5

effcct�ó -10 D

D D - 5 -10 -10 -25 - 4 -nc -60

*

* *

period type of xylitol use comparcd wi th effcct�ó 90 d

28 d 20�ó toothpaste 6-10 gums/d added

-23-

20% sorbitol toothpaste D 6-10 sorbitol gums/d -nc

-continued on next page-

*

(28)

(table 11.2. continued)

--PLAQUE C0NTENT--

(Pr = protein; In = invertase; Re = reducing sugars; Su = sucrose; Ex = extracellular polysaccharides; Ch = carbohydrates; Ca = calcium; Ph = phosphorus)

ref 17 19 22 24 23 17 17 22 17 19 24

22 19 24 24 22

Pr Pr Pr Pr In Re Su Ex Ch Ch Ch

Ca Ca Ca Ca Ph

period 4 d 3 d 90 d 12 d 3 d 4 d 4 d 90 d 4 d 3 d 12 d 90 d 3 d 12 d 12 d 90 d

type of xylitol use 10 gums/ d added 6 gums/d added 20% toothpaste added 6 rinses/dadded 6 gums/d added 10 gums/d added 10 gums/d added 20% toothpaste added 10 gums/ d added 6 gums/d added 6 rinses/d added 20% toothpaste added 6 gums/d adqed 6 rinses/d added 6 rinses/d added 20% toothpaste added

compared with 10 placebo gums/d 10 placebo gums/d 20% sorbitol toothpaste 6 sucrose rinses/d normal diet

10 placebo gums/d 10 placebo gums/d 20 sorbitol paste 10 placebo gums/d 6 placebo gums/d 6 sucrose rinses/d 20% sorbitol toothpaste 6 placebo gums/d 6 sucrose rinses/d 6 cyclamate rinses/d 20% sorbitol toothpaste

effect��

0 0 -15 0

*

-45

*

0 0 0 0 +1:5 -35

*

+10 0 +35

*

+50

*

0 References: (11) Gauthier et al., 1984; (12) Maki et al., 1983; (13) Mäkinen en Virtanen, 1978; (14) Rekola, 1982; (15) Graber et al., 1982;

(16) Vadeboncoeur et al. , 1983; (17) Birkhed et al. , 1983; (18) Topitsoglou et al. , 1983; (19) Grenby et al. , 1982; (20) Mühleman et al. , 1977; (21) Scheie et al. , 1986; (22) Mäkinen et al., 1985; (23) Mouton et al. , 1975;

(24) Hurttia et al. , 1984; (25) Pakkala et al., 1981; (26) Waler and Rölla, 1983; (27) Plüss, 1978; (28) Loesche et al., 1984; (29) Larmas et al. , 1975.

(29)

C hapter 2: Literature review

al. , 1986]. The growth of other micro-organisms is only slightly affected if at all [Vadeboncoeur et al., 1983]. These effects have all been observed in laboratory studies after test periods of between 20 minutes and 12 hours.

The effect of xylitol containing chewing gum on the number of S. mutans and other microorganisms in plaque was examined in an in vivo experiment. The addition o f 10 pieces o f xylitol chewing gum per day to a normal sucrose containing diet resulted in a significant reduction in the number of S. mutans, compared wi th fructose or sorbitol containing chewing gum after 14 days. The number of Lactobacilli and S. Sanguis was not affected by addition of xylitol [L oesche et al. , 1984; Larmas et al. , 1975].

Acid production

Xylitol addition to suspensions of human dental plaque or suspen­

sions of microorganisms (denoted in table I I. 2 as substitution) does not result in acid production [Maki et al. , 1983; Mäkinen and Virtanen, 1978; Mühleman et al. , 1977]. Addition of a mix­

ture of xylitol and sucrose to suspensions of Streptococcus mu­

tans results in less acid production (38-69�ó) than addition of the same amount o f sucrose without xylitol [Vadeboncoeur et al. , 1983]. Addition of the same mixture to suspensions of other mi­

croorganisms ( Streptococcus salivarius, S. sanguis, Actinomyces, Lactobacillus) did not af fect acid production [Vadeboncoeur et al. , 1983]. These results show that xylitol is non-acidogenic in suspensions of plaque or microorganisms and only anti-acidogenic with respect to some strains of micro-organisms. Addition of xylitol to sucrose containing plaque suspensions has no effect on acid production. These effects were all recorded in vitro after test periods o f from several minutes to 22 hours.

Plaque pH

Figure 2. 1. shows the mean interproximal pH changes o f 5 person�

in the 120 minutes following eating a chocolate wafer cookie [Jensen, 1986].

-25-

(30)

C hapter 2: Literature review

The pH of dental plaque shows a slight raise if six sticks of xy­

litol chewing gum are used per day for 77 days [Graber et al.

1982].

The pH drop in four day old p laque is influenced significan tly by the presence of xylitol. Rinsing with a solution of glucose and xylitol results in a smaller pH drop than rinsing with a glucose sol ution only [Waler and Rölla, 1983] .

interproximal plaque pH

7

6

5

4

3

0

20 40

chocolate water cookie

60 80 100 120

time (minutes)

Fig. 2.1. Interproximal pH changes after eating a chocolate wafer cookie.

Mean and standard deviation over five human volunteers. [ Jensen, 1986].

(31)

C haptcr 2 : Litcraturc review

Amount o f plaque (plaque wcight and plaque score)

The effect of xylitol cont aining chcwing gum on the total wcight o f dcnta l plaque has been dctcrmined in sevcral in vivo studies a ftcr pcriods of 3 to 28 days. Chcwing 6 to 10 picccs o f xylitol containing gum a day results in a 10-50% rcduction in the plaque wet wcight a fter 28 days, compared to the p laque wet wcight at the start of the experiment [Rcko la, 1982 ; Mouton et al . , 1975 ;

P lüss, 197 8 ) . Howcvcr, comparab lc results have been found with xy litol- free chcwing gums [Ainamo et al. , 197 7 ) .

l f the e f fect o f xylitol containing chcwing gum is comparcd with the effect of the samc chewing gum without xy litol addition (dc­

notcd in tablc 1 1. 2 as placebo gum), a reduction is found in pla­

que wet wcight o f 30% [Birkhcd et a l. , 198 3 ) and in dry wcight o f 5�� [Grcnby et al., 1982 ) .

Rcgular usc plaque ( wc t al ., 198 3 ) .

of xylitol chcwing gum for 4 days leads to 2 0 % lcss wcight) than sorbitol chewing gum [ T opitsoglou et Xylitol chcwing gum addcd to a normal sucrose con- taining dict leads to 40% rcduct ion of wet plaque wcight a ftcr 3 days comparcd with sucrose chcwing gum [Mouton et al ., 197 5 ) . Rinsing with a xylito l so lution resu lts in a 40�� rcduction o f plaque wet weight whcn compared with sucrose rinscs a fter 12 days [ H u rttia et a l . , 198 4 ) .

. Toothbrushing with xylito l bascd toothpastes does not resu lt in a rcduction o f plaque wet weight whcn compared with a sorbito l based toothpastc a fter 90 days [Mäkincn et al. , 1985 ) .

Another possible technique to dctcrmine the amount of plaque in the oral cavity is the use o f plaque scoring indices, such as the Plaque I ndex [Löe, 1967 ) . Several in vivo experiments have shown that rinsing with

bascd toothpastcs, measurably reduce mcnts [Birkhed et

xylito l solutions, toothbrushing with xylitol or chewing xylitol containing gum does not the plaque score, compared to con trol trcat­

al., 19B 3 ; Mühlcman et a l., 197 7 ; Grenby et - 2 7 -

(32)

Chapter 2: Literature review

al. , 1 982; Mäkinen et 1975]. One study showed

al. , 1985 ; Plüss, 1978 ; Mouton et a l . , a 2 5 % reduction in the plaque index when xylitol chewing gum was added to a sucrose free diet for 3 days when compared with sucrose containing chewing gum [P lüss 1978 ] . Another study , however , showed 60�� reduction of plaque score if 20 gram xylitol was added to a normal (sucrose containing ) diet for 60 days [Pakkala et al. , 198 1].

lt can be concluded from these results that addition of xylitol to the diet causes a reduction in the total weight of plaque in the oral cavity after a period of only a few days. T he amount of plaque covered tooth surface(s) is however only reduced if large amounts of xylitol are added to the diet , or if xylitol is added to a sucrose free diet.

Combining these two findings , ' reduction of total plaque weight ' and ' no reduction in the plaque covered area ' , leads to the con­

clusion that the addition of xylitol to the diet may well result in a reduction in the thickness of the plaque layer on tooth sur­

faces.

Plaque adhesiveness

T he adhesiveness of plaque onto tooth surfaces has been studied by spraying water on plaque in the mouth after periods using xy­

litol containing or xylitol free chewing gum or toothpaste. The effect of xylitol can be determined by comparing the plaque scores of the surfaces before and after spraying. The use of xy­

litol containing toothpastes does not result in a decrease in ad­

hesiveness , compared with sorbitol containing toothpastes after a period of 90 days [Mäkinen et al. , 1985]. However , chewing 6 to 10 pieces xylitol containing chewing gum a day results in a sig­

nificant decrease in plaque adhesiveness , compared with sorbitol containing chewing gum, after 28 days [Rekola , 1982].

(33)

Chapter 2: Lilerature review

P laque c o ntent with respect to pr oteins, c arb o hydrates, c alcium and phosph ates

Chewing xylitol containing c hewing gum d oes not result in a lower c oncentration of proteins or carb o hydrates in dental pla que, c om­

pared with placebo c hewing gum a f ter peri o ds o f 3 or 4 d ays [Grenby et al. , 1982; Birkhed et al. , 1983]. T h e invertase a ct­

ivity in dental pla que decreases signif ic antly 3 days af ter a d d ­ i n g xylito l b ased chewing gum to a norma l sucrose containing diet

[ Mouton et al. , 1975]. T h e use of xylitol b ased toothpastes does not, however, c hange the concentration o f proteins, extracellular polysach arides, c alcium or phosphates i n pla que when c ompared with sorbitol b ased toothpaste a f t er 90 d ays [ Mäkinen et a l . , 1985 ].

Rinsing with a xylitol solution c ombined with a normal sucrose c ontaining diet , results in a 15�� decrease in the protein c o n­

centration and a 35% d ecrease in the c arb ohydrate concentration in pla que when c ompared with sucrose c ontaining soluti ons a f ter 12 days [ Hurttia et al. , 1984]. T he same study a lso shows a sig­

ni f i cant increase o f 35-50% in the c alcium c oncentration in pla que a f ter rinsing with xylito l, compa red to rinsing with su­

crose or cyclamate [Hurttia et a l. , 1984].

T he use o f xylito l containing chewing gum results in a statist­

i c ally non-signi f ic ant increase o f 10% in the c a lcium concentra­

tion in pla que, compared with pla cebo chewing gum a f ter 3 d ays (Grenby et a l . 1982).

2 . 4 . Ef f ect of xylitol on sal i v a

S a liva i s t h e secretion product o f t h e salivary glands in the oral c avity. lt contains inorganic i ons, small organic molecules and proteins dissolved in water . T h e composition of saliva varies b etween glands and varies with the rate o f f low and severa l other f a ctors [Jenkins, 197 8]. T he mixture of the sec reti on products of the salivary glands, pla que meta b o lites, mi cro-organisms and f o o d products in the oral c avity is a f ten c a lled " oral f luid " .

-29-

(34)

Chapter 2: L iterature review

Table 11. 3 shows the re sults of 8 studie s on the e ffect of xyli­

tol on the composition of saliva.

Xylitol containing chewing gurn doe s not peroxi de conce ntration of who l e sal iva, chewing gum after 4 days [Birkhed e t al. ,

affect the prote in or compare d with placebo 1983]. The amount of Streptococcus mutans in saliva decrease s significantly after a period of 3 years if 15 to.20 g. xylitol , in the form of swe ets , is added daily to a normal sucrose containing diet, comparing with a control group without swe ets adde d [Banocz y e t al. , 1986].

Addition of 2 0 g xylitol per day, in the form of table ts , to the die t resu l ts in a significant increase in the concentration of ammonia (45%) and cyanide ( 30 0%) in saliva, after 60 days. T here was , howe ver , no change in the concentration of prote ins , sialic acid , arginino and lactoporo�idaso [Pakkala e t al. , 1981 ] .

Rinsing with a xylitol solution causos a slight raiso in salivary pH aftar 6 minutos, comparo d with rinsing with water [Mä kine n and Mäkino n , 197 8]. Rinsing with a xylitol solution doos not affect the calcium and phosphate conco ntration or the peroxidase activ­

ity in wholo saliva after 32 minute s [Mäkinon and Mäkinen , 197 8].

0the r salivary parameters , such as oxigen use , count of Lactoba­

cillus and inve rtase activity , did not change significantly after the use of xylitol [Lutz and Gulz ow., 197 9; Loe sche e t al. , 1 984;

Mä kine n et al. , 1985; Mäkinen and Scheinin, 1975 ( 2X) ].

Apart from the effects of xylitol on the composition of saliva, the use of xylitol food products also increases the rate of sal­

ivary fl ow [Le ach and Gre e n , 1981] and thoreby the salivary buf­

fering syste ms. The e ffect on the rate of salivary flow is , how­

e ve r, a normal physiological reaction re lated to the presence of food in the mouth [Jenkins , 197 8] , and not uniquely relate d to xylitol containing products.

(35)

Table 11.3 . Xylitol effect on saliva

ref param 31 0xUse 33 S Mut 36 S Mut 36 S Mut 36 Lactb 34 37 38 32 35 38 37 35

37 32 34 34 34 34 34 35 35

L ase Inver lnver Per0x Per0x Per0x pH pH

Pr Pr Pr Arg Cyan Amm Si ac Ca pH

*

denotes a statistically significant effect ref denotes the literature reference

param denotes salivary parameter tested (0xUse = oxigen use, S mut = count of S mutans, Lactb = count of Lactobacil lus, Inver

= invertase, L ase = lactoperoxidase, Per0x = peroxidase, Pr = protein, Arg = arginine, Cyan = cyanide, Amm = ammonia, Si ac

= sialic acid, Ca = calcium, Phos = phosphorus) period

5 hrs 3 yrs 14 d 14 d 14 d 60 d 90 d l year

4 d 32 min

l year 6 min 90 d 90 d 4 d 60 d 60 d 60 d 60 d 60 d 32 min 32 min

type of xylitol

0 . 1-10% in saliva susp 17 g/d added

10 chewing gums/d added 10 chewing gums/d added 10 chewing gums/d added 20 g/d added

20% toothpaste added 4 chewing gums/d added 10 gums/d added rinse

4 chewing gums/d added rinse

20% toothpaste added 20% toothpaste added 10 gums/d added 20 g/d added 20 g/d added 20 g/d added 20 g/d added 20 g/d added rinse

rinse

compared with 1% sucrose normal diet

10 fructose gums/d 10 sorbitol gums/d 10 sorbitol gums/d normal diet

20% sorbitol paste 4 sucrose gums/d 10 placebo gums/d water rinse 4 sucrose gums/d water rinse 20% sorbitol paste 20% sorbitol paste 10 placebo gums/d normal diet normal diet normal diet normal diet normal diet water rinse water rinse

-nc 0

*

-90

*

-90 * -90

*

0 0 0 0 D 0 +nc 0

0 0 0 0 +300 +45 0

0 0

*

* *

References: (31) Lutz and Gulzow, 1979; (32) Birkhed et al . , 1983, (33) Banoczy et al. , 1986; (34) Pakkala et al . , 1981; (35) Mäkinen and Mäkinen, 1978; (36) Loesche et al., 1984; (37) Mäkinen et al. , 1985; (38) Mäkinen and Scheinin, 197 5 .

-31-

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Chapter 2: Literature review

2 . 5. E f fect o f xyl i to l on enamel d i rectly

Tab le 11.4 s hows the results o f 5 studies on the e f fect o f xy litol on

employ the

the de- and reminera lization o f enamel. Two studies intra-oral cariogenicity test ( ICT) to determine the ef fect of xy l itol on enamel deminera lization in an in vivo model.

Table 1 1. 4. Xylitol effect on enamel in vivo and in vitro

* denotes a statistically significant effect ref denotes the literature reference

( ICT = Intra-or al Cariogenicity Test, VHN = Vickers Hardness Number, DEM = demineralization, REM = remineralization, visc = viscosity)

ref period -- ---

41 ICT 5 d 41 ICT 5 d 42 ICT 7 d 42 ICT 7 d 43 VHN 10 d ref period -- ---

44 DEM 21 d 45 REM 7 d 45 REM 7 d 45 REM 7 d

--IN VIVO--

xylitol compared with

5�� added 50, ,o sucrose + normal diet 5��+5�� sucrose added 50, ,o sucrose + norrnal diet

3"' ,o added 3"' ,o sucrose + normal diet

30, ,o added oo, ,o sucrose + normal diet 20 g/d added normal diet

--IN VITRO-- type of

450 g/1 20 g/1 20 g/1 20 g/1

xylitol use substitution substi tution substitution substitution

compared with

0 g xylitol/1, pH 4 . 5 0 g xylitol/1, pH 7

3Og-sorbitol/l (low visc)

3Og sorb/1 (high visc)

effect��

-95

*

+30 -57

*

-15 >-100

*

effect%

-50

*

-35 +25

*

-50

*

References: (41) Pearce and Gallagher, 1979; (42) Koulourides et al., 1976;

(43) Scheinin et al. , 1981; ( 44) Arends et al. , 1984; ( 45) Vissink et al. , 1985.

In this type o f investigation enamel s labs are mounted in an intra-ora l appl iance and covered with gauze, to ensure that pla­

que accumul ates on the enamel sur face. The appliance is placed in a test sol ution containing either x y l itol, sucrose or water several times a day. The degree of enamel deminera lization can be estimated b y measuring the penetration depth o f a Knoop dia­

mond under a standardized laad before and a fter the test period.

Use of a xy l itol solution results in 5 7 -9 5 % reduction in penetra-

(37)

C hapter 2 : Li tera t ure review

t ion depth compared wit h a sucrose solution after 5 -7 days ICT.

A tost solution containing a mixt ure of 5% xylitol and 5% sucrose has a comparablo ef fec t on enamel demineralization as a tes t so­

lution con taining 5 % sucrose [Pearce and Gallagher, 197 9 ) . A 3%

xylitol solution leads to comparable results as a 0% sucrose so­

lution [Koulourides et al., 1976 ).

I t is not clear from ICT experiments whether the c hanges in enam­

el hardness are due to direc t interac tion o f xylitol with de- and remineralization process or due to an indirec t effect v i a c hanges in t he plaque on the enamel surface.

I n another study enamel slabs were mounted intra-oral ly in buc cal c avities and 20 grams of xylitol added to the daily diet. T his resulted in hardening of enamel after 10 days, while continuous demineralization was found in the control group [Sc heinin et al. , 1981 ) .

I n vitro demineralization o f enamel (determined as lesion depth a fter 21 days) can be reduced if xylitol is added to the deminer­

alizing solution [ Arends et al., 1984 ) . Addition of xylitol to the rominoralizing solution leads to extra remincralization, measured as rchardcning, of 35-50�� compared to the addition of sorbitol after 7 days in vitro [Vissink et al., 1985 ) .

One in vitro study showod penctration of xylitol i n demineralized enamel up to considcrablc depths ncar the lcsion front [Arcnds et al., 1984 ) .

2 . 6 . Conclusion s

S o veral experimcnts on t he influonce o f xylitol on carics have been desc ribed in the first part of this c hapter. Epidemiologie­

al and animal studies have shown a slower rato of increase in the DMF index if xylitol containing products are added to the diet.

T he addition of other sucrose substitutes, suc h as sorbitol and mannitol [Maller, 197 3 ) , fructose [Sc heinin et al. , 197 5b] and Lycasin [Frostell et al. , 1 97 4 ) also lead to a slowing of the DMF increase, but not to the same degroe as xylitol. This leads to

-33-

(38)

Chapter 2 : Literature review

the first concl usion on the e ffect of xylitol.

( 1) Xylito l addition to the diet reduces caries progression.

The fol l owing comments should however be made.

Proof, in a scientific sense, of such a specific effect of a pre­

ventive regime in epidemiological caries trials, is not possible [Barmes et al. , 1985]. The various probl ems in these studies, such as those relating to the data, control groups, examiner calibration, participant drop-out, baseline di f ferences b etween test-groups etc, make the eval uation of probab l e or possib l e ef­

fectiveness difficult.

In the past decade the same prob l ems have bedevi l ed the epidemio­

logical investigations on fl uoridation of drinking water and have l ead to doubtfull concl usions on the preventive e ffect of water fluoridation and " The mystery of declining tooth decay" [Diesen­

dorf, 1986].

lf however, concl usion ( 1) on the caries reducing effect of xylitol is accepted, then what are the mechanisms involved?

Several suggestions have been made to explain the anticariogenic­

ity of xylitol , such as the infl uence of xylitol on the product­

ion of saliva or on the composition of dental plaque. These e ffects have been investigated in the studies mentioned in table

1 1. 2 and 1 1. 3 and can be summarized as follows:

(2) Xylitol addition infl uences the growth, metabolism and/or acid production of some microorganisms in vivo.

(3) Xylitol addition influences plaque thickness, plaque com­

position and/or the microflora in plaque (reduces the number o f S. mutans and increases S. sanguis) .

( 4) Xylitol addition reduces the number of S.mutans in saliva.

These results show that the addition of xylitol a ften coincides with a change in the quantity or quality of plaque and saliva.

These studies only suggest a causal relation between the shift in properties of saliva and plaque and the caries reduction found in

(39)

C hapto r 2: Litoraturo review

the opidomiologi c a l studies. Further invostigation is noodod on the effo cts of these (slight) c hanges in plaque and saliva on enamel do- and rominorali z ation.

T he ef fect of xylitol on en amel de- and rominer a lization ( tabla II. 4) has boen invostigatod in only very few oxporimonts.

Two in vivo oxporiments are describod in this thesis which o lu­

c i date the role of xylitol in this context.

-35-

(40)

C HAPTER 3

I NFLUENCE O F XYLITOL ON SURFACE SOFTENED ENAMEL IN VIVO ( 1 ) CHANGES IN ENAMEL HARDNESS

3. 1 . Abstract

This chapter describes the effect of xylitol and fluoride on re­

mineralization of surface softened human enamel in vivo . Surfacc softened enamel blocks were mounted in the lowcr prosthcses of 20 full denture-wcaring participants. These participants used xyli­

tol- and/or fluoride-containing toothpastcs during 4 -wcek pe­

riods. Knoop hardness measurcments were cmployed to estimatc the degree of remineralization in each period. After 26 days of toothpaste use it was found that the enamel defccts rehardenc d substantial ly and that the hardness of sound enamel was ap­

proached. The changes of enamel hardness were not significantly affected by the prescnce of xylitol and/or f luoride in the tooth­

pastcs.

3 . 2 . Introduction

Scveral in vivo studies have shown the caries-rcducing effect of xylitol when it ( partial ly) substitutes dietary sucrose [Schcinin et al. , 1975a, b ; Mäkincn and Virtancn, 1978 ; Lcach and Green, 1980 ) . Possible causes for this effect are the infl uence of xy- litol on plaque formation, on micro-organisms, on saliva compo­

sition and saliva production or directly on th� enamel. Recently some i nvestigations indicated that xyl itol may be involved in enamel de- and remineralization proccsses [Arends et al . , 1 984 ; Scheinin et al . , 1981 ).

This chapter has been published previously in Carics Ros 19: 528-535 (1985)

" lnflucnce of xylitol and/or fluoride containing toothpastes on the rcmincral­

ization of surfacc softcned enamel defects in vivo", M.T. Smits and J. Arends.

Published with permission of S . Kargcr AG , Basel.

(41)

Chapter 3 : Changes in enamel micro-hardness in vivo

The purpose of this s t udy is to est i ma t e the effect of xyli tol­

and fluoride-con taining toothpas t es on t he in v i vo rem ineraliza­

t i o n of surface soft ened enamel. These shal low enamel defects can be remineral ized in v ivo in a relatively short period. Ex­

tens ive remineralization has been repor ted with i n 4 weeks if a 1 , 5

□□-

ppm fl uoride-con taining toothpas te is used [Gelhard , 1982].

I n this s t udy the eff ect of 4 different toothpastes was tes ted.

One pas te was on glyce r ine base, another on xyl itol base, the third paste contained glycer ine and fluoride and the fourth contained xylito l and fluoride. Reminera lization of the shall ow enamel defects was followed using micr o hardness techniques. l t is assumed t hat a decrease o f inden tation l engths dur ing a test per iod indicates enamel remineralization and t hat an increase in indentation lengths ind icates enamel demineralization [F eagin et al. , 1969; Gel hard and Arends, 1984a, b ] .

3 . 3 . Material s and Methods

Enamel treatment and hardness determinations

160 extracted permanent human incisors, canines and premolars were col lected from several dental prac titioners in the G roningen a r ea (nonfluori dated) and stored in tap water with some thymol added.

T he buccal s urfaces were ground flat and polis hed on waterproof s ilicon carbide abrasive paper (gr it 1 , 200 ) . With a sectioning machine the flattened surfaces were c ut i n rectangular enamel b locks of + 15 mm2 These blocks were separately embedded in a crylic resin (RR, De Trey ) with exception of the polished enamel sur face. The s urface was then partially (about one third) covered with nail varnish and placed in a 0. 1-M potassium acetate solution at pH 5. 0 during 8 h (s t i rring speed ± 12 5 rpm) . Subse­

quently the varnish was r e moved.

H ardness measurements were employed t o est i mate the degree of surface softening. Five indentations we r e made w i th a L eitz mini-

-37-

(42)

Chapter 3 : Changes in enamel micro-hardness in vivo

l aad hardness tester at 500 g laad , bath in the sound enamel part and in the so ftened sur face of the specimens. The laad on the Knoop diamond was always perpend icular to the polished enamel surface. The length o f the Knoop indentations was measured with an accuracy of l µm ( in this study equivalent to about 1%). l n this chapter all hardness data wil l be given in the form of indentation lengths under 500 g laad.

Participants

2 1 patients , all wearing full denture protheses , participated voluntarily. They were chosen at random out of the group of pa­

tients at the university dental clinic. After the experiment the results of l participant had to be left out because she had not followed a l l brushing instructions . The remaining group of 20 participants consisted o f 9 men and 11 wamen, aged 41-6 5 (mean age 5 5

±

6 . 2 years) .

0utline of the experiment

Two enamel b locks were placed with acrylic resin in the right hand side o f each lower denture. Prior to this, hardness me­

asurements were carried out in the sound and softened enamel. The indentation length in sound enamel is denoted by 50 and the in­

dentation length in softened enamel is denoted by 10

Be fore participants started to use a toothpaste, all blocks were conditioned in the oral environment for 2 days. During this period th e participants brushed twice daily with tap water only.

After this 2-day conditioning period -thus before using a tooth­

paste- hardness measurements were carried out again . These i ndentation lengths are denoted for sound enamel by 5 and for softened enamel by l

Then .the participants started to use a toothpaste and brushed twice daily. After 8 days of toothpaste use, hardness measure­

ments were repeated. The measured va lues for sound and so ftened enamel are denoted by 510 and 110. After 26 days of toothpaste use the ha rdness was measured again. The indentation values are

(43)

Chapter 3: Changes in enamel micro- hardness in vivo

now denoted for sound and softened enamel by s28 and 128.

This clinical toothpaste experiment was done with four pastes (double-blind) . The pastes are denoted by G , X , GF and XF. The details of each paste are given in table 111. 1.

Table I l l . I . Composition of the toothpastes

Toothpaste Contents

G base paste + 35�ó glycerine ( 85�ó) X base paste + 35�ó xylitol

GF base paste + 35�ó glycerine ( 85�ó) + 500 ppm F (NaF) XF base paste + 35�ó xylitol + 500 ppm F (NaF) The base paste consisted of: mucilago (2.2%); dicalcium phospha te ( 22. 5%) ; tensid ( 2. 5�ó); aroma/Sacharine-Na ( l. 5�ó) ; titandioxid (1. 0%). The actual ionic fluoride (F-) content in pastes GF and XF was found to be 485 ppm be fore and a fter the experiment.

The experiment was carried out using a random black design.

Thus , l participant used the toothpastes G , X , GF and XF (each 26 days) in periods 1- 4. Another participant used the pastes X , GF , XF and G , in period 1-4 etc. For each period 2 new enamel blocks were placed in the prothesis. The outline of the experiment for l participant is given in table 1 1 1. 2.

3 . 4 . R e s u l t s

The results of this experiment are presented in two farms :

(l) results of 2 participants as examples of changes in the enamel hardness after the use of different toothpastes

(2) results of the changes in the hardness of sound and softened enamel a fter the use of four toothpastes averaged over 20 participants.

-39-

(44)

C hapter 3: Changes in enamel micro- hardness in vivo

Table 111. 2. 0utline of the experiment for one typical part­

icipant Time

days

0

2 10

28

Events

enamel bleeks placed; con- ditioning period of 2 days start brushing with one toothpaste GF

test period finished; enamel bleeks removed

Microhardness measurements sound enamel

so s2 s10 520

softened enamel

10 12 110 120 This procedure was repeated for toothpastes G, X and XF.

Examples of changes in enamel hardness during the use of di ffer­

ent toothpastes

In table 1 1 1. 3. the indentation lengths in sound and softened en amel in ble eks l and 2 are given for four toothpastes used by participante no. 9 and 20.

lenght of five indentations. Each va l ue is the mean indentation I n participant 9 there was i ndentation length reduction in soft- ened enamel for each toothpaste. T he indentation lenght in so ftened enamel approximated the indentation length in sound enamel a fter 28 days except for black 1 in the XF group and black 2 in the G group.

In participant 20 there was ha rdly any reducti on o f the indenta­

tion lenght i n softened enamel in 6 out of 8 ble eks. T he softened enamel in the other bleeks showed dive rgent results: (1) the indentation lengths in black l during the use of xylitol paste showed an increase from 2 26 to 327 µm; (2) the indentation lengths in black 2 during the use of xylitol and fluoride paste showed a slight reduction by 17 µm from 207 to 190 µm .

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