Journal of Clinical Periodontohgy 1983: 10: 636-642

Key words: Denial curies - enamel micrulwrdncss - loulhigh ^uc

AcceplL'd for publication May 4, 1983

roic die: - plaque pll - pownlial cariogemciiy.

sucrose dietary patternsHANS GRAF

Department of Periodontology, Dentai Clinics, University of Berne, Berne, Switzerland

Abstraci. In vivo daytime plaque pH telemetry during 2 week periods was combined with measurementof changes in enamel microhardness and analysis of microbial plaque composition in 2 human subjects.Well defined sucrose rich and sucrose poor diets were used as variables. During the 2 weeks of the highsucrose diet (50-80 g/day), a high cariogenic acid attack calculated from pH changes in "Proton hours"was associated with a marked progressive decrease in enamel microhardness. The low sucrose diet (2-6g/day) showed a low "Proton hour" acid attack during the entire 2 weeks. The decrease in enamelmicrohardness, however, was low only during the first week. After day 7 a marked decrease could beobserved. It could not beexplainedby the glycolytic activity of the plaque, which was low. ^mutans was present in all microbial samples.

"Dental caries is a multifactorial disease involv-ing 3 principal factors: host (particularly salivaand teeth), microflora, and their substrate (i.e.diet). A fourth dimension: time, or frequencywhen considering diet, plays an intergral role"(Newbrun 1979). An adequate test for measur-ing cariogenicity of food would have to takeinto account all these factors. So far, such asingle test has not been found. In vitro tests donot properly measure hosl factors; humanplaque pH determinations show acidogenicitybut not necessarily cariogenicity and animalexperiments are limited in value, e.g. due lofood preference and other factors. Clinical trialson humans are difficult to perform and may beregarded as unethical.

Intraoral pH telemetry of interdental plaquepH (Graf & Muhlemann i966) during longerexperimental periods seems to be suitable todetermine the cariogenic acid attack, capable ofenamel demineraUzation. Recent improve-ments of the method in the laboratories of theinvestigator have made it possible to followplaque pH up to 19 days in lhe same interdental

area. It is, therefore, feasible to record pHchanges in the same plaque area during 2 weeks.

Surface microhardness measurements onsample enamel surfaces exposed to the samenaturally grown plaque near the pH measuringsite should reveal demineralization proportion-al to calcium loss. The microhardness test is asensitive method to detect early changes to theenamel surface of the initial caries lesion (Kou-lourides et al. 1976).

Analysis of the microbial composition of theplaque growing on the pH glass microelectrodeand the adjacent enamel slabs with regard toStreptococcus mutans and sanguis and to Laclo-bacilH may provide evidence for its odontopa-thie potential.

The hypothesis to be tested was that conven-tional diets with high or low sucrose contentconsumed in identical time patterns have differ-ent cariogenic potentials. The glycolytic activityof plaque calculated from pH drops, integratedover time and expressed in "Proton hours" maybe correlated with decreases in enamel micro-hardness.

CARIOGENICITY OF DIETARY PATTERNS 637

Material and Methods

2 adult human subjects, both male, aged 61 and72 years respectively, participated with informedconsent in the study. Except for spaces ofmissing teeth, suitable for the incorporation ofan experimental partial denture, their generaland oral health was good.

Subject T had an average stimulated salivaryflow of 1.3 ml/min and was fitted with a lowerpartial denture. Subject W had an averagestimulated salivary flow of 20 ml/min andreceived an upper partial denture. In bothdentures a pH glass microelectrode and 6enamel slabs were fixed facing the vestibuium.Electrodes and slabs were subsequently coveredwith a piece of Dacron patch fabric (Koulou-rides et al. 1976; Fig. 1). The registration systemof pH telemetry has been described elsewhere(Joss 1979).

The enamel slabs were obtained from ortho-dontically extracted premolars. They were cutto pieces of about 2X2 mm, polished flat andmounted in an acrylic block that could beremoved from the denture for microhardnesste.sts on a Frank-Durotest machine. Knoophardness (Knoop et al. 1939) was calculatedfrom diamond impressions with 100 g force andof 30 sec duration according to the formula:

14230 • KKNH

(K —testing force in g; L —diagonal length in

Fig. 1. Upper and lower free end saddles of experimen-ta! partial dentures with pH glass microelectrode(arrow) and 6 enamel slabs for microhardness testscovered with Dacron patch fabric.

The initial hardness was assessed on theevening preceding the start of the experiments.

At the beginning of each experimental periodthe glass electrode surface and the enamel slabswere free of plaque. A well balanced averageSwiss diet, composed, analyzed, and suppliedby the University hospital service, was the onlypermitted food and beverage intake. The diet ofthe first experiment (2 weeks) contained mini-mal sucrose quantities (2-6 g/day). In thesecond experiment the sucrose intake was highin sucrose (50-80 g/day). The time pattern ofeating was identical for the 4 weeks. Breakfast,lunch and dinner were consumed under super-vision. Between meals only 1 cup of tea withartificial sweetener was allowed. After a pauseof 1 day the second period with the sucrose richdiet was started. The cup of lea was sweetenedwith sucrose. Ail meals were prepared in thehospital kitchen. Based upon an exact analysisthe daily consumed amount of sucrose wasdetermined. There was no food intake at night.

The subjects were allowed to brush theirnatural teeth with a nonfluoride dentifrice oncea day while the experimental partial denturewas removed and kept in a moist environmentof 35° C.

Plaque pH was monitored every day for atleast 11 h. On days 3, 5, 7, 9, 11 and 13 of eachexperiment 1 ename! slab, being exposed toplaque growth from day 0 on, was subjected tomicrohardness tests. At the same time plaque

638 GRAF

1 0 " 11*

1 DAY OLD PLAQUE

3 DAY OLD PLAQUE

7 DM OLD PLAQUE

11 DAY OLD PLAQUE

Fig. 2. Telemetrically recorded pH of 1, 3, 7 and 11 day old plaque with sucrose rich (thin line) and sucrose poor(thick line) diet from subject with experimental lower partial denture. pH drops after intake of meals can berecognized at regular intervals.

CARIOGENICITY OF DIETARY PATTERNS 639

SUCROSE RICH DIET SUCROSE POOR DIET

NOOP HARDNESS DIFFEnEKC&

Fig. 3, Total sucrose intake, cariogenic acid attack in "Proton hours" and enamel microhardness changes insubject with experimental lower partial denture during 2 weeks of sucrose poor and 2 weeks of sucrose rich diet.

samples were collected from the fabric coveringthe enamel slabs and analyzed for Strepiococcusmulans. Streptococcus sanguis and Lactohacilli.The microbiologic methods are described else-where {Kusy &. Zwyssig 1980).

In order to evaluate the quantitative influ-ence of the acid attack the pH values wereconverted into a relative H*-ion concentration:

pH7:lpH 6:10pH 5.100pH 4:1.000pH 4:10.000

The duration of the acid attack was calculatedin "Proton hours" (Joss 1979} according to thefollowing definition:

1 Proton hour —pH 7 during 1 hour

The continuous pH registration served to calcu-late the corresponding "Proton hours" every 12min over each daytime of 11 h. The calculateddaily values were added over the 13 experimen-tal days.

Results

An example of the daytime pH changes isshown for 1,3,7 and 11 day old plaque in Fig. 2.These curves served for the calculation of the"Proton hour" acid attack. A summary of theresults from each subject is shown grahically inFigs. 3 and 4.

The sucrose rich diet was associated in bothsubjects with a marked cumulative acid attack

640 GRAF

SUCROSE RICH" DIET SUCROSE POOR DIET

10TAL SUCROSE IKIAKE

pnoiOn HOURS

Fig. 4. Total sucrose intake, cariogenic acid attack in "Proton hours" and changes in enamel microhardness insubject with experimental upper partial denture during 2 weeks of sucrose poor and 2 weeks of sucrose rich diet.

up to 20.231, respectively 50.522 "Protonhours". The enatnei microhardness decreasedgradually from the initial value to the varioussample times corresponding to the acid attackand the amount of sucrose intake (last sampledifferences 155.8, respectively 105.0 KNH).

The sucrose poor diet was associated in bothsubjects with a Sow attack up to 7.010, respec-tively 3.673 "Proton hours", corresponding tothe low sucrose intake. The differences inenamel microhardness were low or notchanging up today 7 ( — 5.7, respectively +0.20KNH). During the second week of the lowsucrose diet pattern enamel hardness changeddramatically decreasing by KNH 192.1 respec-tively 86.5. The microbiological results showedthat Streptococcus mutans was present in allsamples and varied between 3-66 %. The analy-

sis of Streptococcus sanguis and Salivarius wasinconsistent.

Discussion

The combination of daytime pH telemetry andenamel microhardness determination assessingpotential cariogenicity during 2 week periodslimited the number of subjects due to suitabilityand availability. Statistics were not possible andthe results have to be considered as individualobservations only. Technical questions and ademanding experimental design restrict conclu-sions from the results. Details of the study arediscussed by Kusy & Zwyssig (1980).

It couM, however, be cJearJy shown that thecariogenic acid attack calculated in "Protonhours" was significantly lower with a sucrose

CARIOGENICITY OF DIETARY PATTERNS

poor as compared with a sucrose rich diet. With

the low sucrose diet, enamel microhardness

started to decrease significantly only after 7

days. The total amount of sucrose ingested with

the low sucrose diet corresponded at that time

with the amount eaten on the first day of the

sucrose rich period. Enamel hardness was

markedly lowered with the sucrose rich diet

already after 3 days.

The pronounced decrease in the enamel

hardness during the second week of the sucrose

poor diet cannot readily be explained, e.g. by a

corresponding "Proton hour" acid attack. It

may be that other mechanisms than acid demin-

eralization contributed to this phenomenon.

The attempt to find correlations of microbiai

plaque composition was not successful. Strep-

tococcus mil tans was present in all samples.

However, the other results were inconsistent.

The reason, most likely, lies in the nonstandard-

ized sampling technique and not in the cultiva-

ting and evaluation methods.

Further experiments with the combination of

in vivo quantitative assessment of glycolytic

activity of human dental plaque and enamel

microhardness measurements under well con-

trolled dietary patterns of week long duration

may lead to a better understanding of the

dynamic aspects of the initial mechanisms of

caries development.

Acknowledgements

This study was supported by Grant No. 580

from the Nutrition Foundation Inc.

The author wishes to express his thanks to A.

Antczak, A. Joss, P. Hotz, D. Kusy, I. Moser

and J. M. Zwyssig for their excellent coopera-

tion.

Zusammenfassung

Kariogenes Potential sacchavosearmer und saccharose-re icher DiatWahrend zweimal 2 Wochen wurde an 2 Probandentagstiber das Plaque-pH telemetrisch gemessen und

gJeichzeitig die Veranderungen der Zahnschmelznii-kroharte und der mikrobieiien Plaquezusammenset-zung verfoigt. !n den ersten 2 Wochen erhidten dieProbanden eine sehr genau kontrollierte saccharose-arme, in den zweiten 2 Wochen eine saccharosereicheDiiit. Bis zum siebenten Tag des Versuchs war dieMenge der eingenommenen Saccharose direkt mildem kariogenen Saureangriff, gemessen in Protonen-stunden, und der relativen Abnahme der Schmelzmi-krohiirte korreliert. Im weiteren Veriauf des Experi-mentes zeigte sich eine starkere Variation der Mess-werte. Trotz minimaler Saccharoseeinnahme konntczum Beispiel eine starkere Schmelzharteabnahmebeobachtet werden. In samtlichen Plaqueproben liesssich der kariogene Keim Streptococcus mutans nach-weisen; sein prozentuales Vorkommen konnte jedochnicht mit dem kariogenen Saureangriff oder derSchmelzmikroharie korreliert werden.

Resume

Cariogenese potentielle des regimes pauvres ou richesen saccharoseLe pH de la plaque dentaire de 2 individus a etemesure in vivo par telemetrie au cours de la journeedurant des periodes de 2 semaines, tandis que lesvariations de microdurete de l'email etaient mesureeset la composition de la plaque microbienne analysiee.Les variables utilisees etaient des regimes stricts richesou pauvres en saccharose. Durant ies 2 semaines deforte consommation de sacchaTose {50-80 g/jour) uneattaque acide tres cariogene evaluee d'apres les varia-tions de pH en "heures Proton" (heures avec pH 7) aete associee a une diminution progressive marquee dela microdurete de l'email. Avec la faibie consomma-tion de saccharose (2-6 g/jour) une faibie attaqueacide en "heures Proton" a ete observee pendant les 2semaines. Toutefois la diminution de la microduretede l'email n'etait faibie que durant la premieresemaine. Apre.s le jour 7, une importante diminutionnon attribuable a la faibie activite glycolitique de laplaque pouvait etre constatee. Le Streptococcus mu-tans etait present dans tous les echantillons micro-biens.

References

Graf, H. & Muhiemann, H. R, (1966) Telemetry ofplaque pH from interdental area. Helvetica Odonto-logica Acta 10, 94-101.

Joss, A. (1979) pH-Transducer for dental researchapplication. Department of Periodoniology, Uni-versitv of Berne.

GRAF

Knoop, F. et al. (1939) A sensitive pyramidal dia-mond tool for indentation measurements. Journalof the A'ational Bureau of Standards 23, 39-61.

Koulourides, T., Bodden, R., Keller, S,, Manson-Hing, L., Lastra, J. & Housch, T. (1976) Cario-genidty of nine sugar tests with an intraoral de-vice in man. Caries Research 10, 427-441,

Kusy, D. & Zwyssig, J, M. (1980) Potentielle Kario-genizitat gemessen mit in vivo Langzeit-pH-Teie-metrie, Schmelzmikrohartebestimmung und mi-krobieUer Plaquezusammensetzung. MedizinischeDissertation, Universitat Bern.

Newbrun, E, (1979) Criteria indicative of cariogeni-

city or non-cariogenicity of foods and beverages.In Health and Sugar Substitutes, ed, Guggenheim,B. Proceedings of the ERGOB Conference on sugarsubstitutes. Basel: S, Karger.

Address;

Hans GrafDepartment of PeriodontohgyDental ClinicsUniversity of BerneCH-30W BerneSwitzerland