Dental caries and its determinantsamong recent immigrants trom ruralEthiopiaSgan-Cohen LID, Steinberg D. Zusman SP. Sela MN; Dental caries and its determiti-ants atnong recent itnmigtanls frotn rural Flhiopia. Comtnunity Detit Oral Epidemiol1992; 20; .338-42.

Abstract Adults (35-45 yr old) and children (5 and 12 yr old) reeently arrived inIsrael from rural areas in Ethiopia wet-e cxatiiitied. Caries levels wet-e low; e.g.DMF'T = 0.31 among 12-yt--(-)kls olds, and 1.27 amongst adults. The 5-yt--olds wet-e86.X"/) caries-free, while 12-yr-olds were 81 .^"/<t atul adults 54"/ii earies-IVee respeelively.Aeeording to inlet-view data, the diet in Ethiopia had beeti based (->n loeal agricultut--al products and was almost sugar-fi-ee. The mean total eount of salivary bacteria, asdetert-nined on blood agar. was 3.4 x 10"; tnean eount of Streptococcus viridatts. otit-nitjs salivarius, was 6.7 x 10'; and mean count of .V. tiitttatis. as determined on mitissalivarius wilh baeilracin, was 1.7 x 10'. These levels wet-e all high and wet-e nolsignificantly different IVotn a eontrol group of 20 Ist-aelis. The tneati tiutnbet- oflactobaeilli, on Rogosa agar. was 2.75 x 10'', whieh was signifieantly higher thatiamong the eontrols (3.6 x 10'). Salivary pH levels were generally sitnilar between theEthiopian group and the eontrols. Salivary flow was sigiiincantly higher for theEthiopians (1.93 ml/min) than for controls (1.16 ml/min). Low levels of caries inthis population ean be attributed to an almost sugat--ft-ee diet and high salivat-ynow, but not to the composition of oral tnicrollora.

Harold D. Sgan-Cohen',Doron Steinberg^Shiomo P. Zusman'and Michaei N.'Department ol Conimunity Dentistry,'Department ot Orat Biology. HebrewUniversity-Hadassah School ol Dentaltvtedicine, tounded by the Atpha OmegaFraternity. 'Department ol Dental Health. IsraelMinistry ot Heallh. Jerusalem, Israel

Key words: dental caries; epidemiology; saliva-diet; lactobacitli; S, mutans

H, D. Sgan-Cohen. Community Dentistry.Faculty ot Oenlat Medicine, IHebrewUniversity-Hadassati. PO, Box 1172. Jerusalem91010. Israel

Accepted lor publication 21 February 1992

Chatiging populations in the past havebeen subject to extensive dental epidemio-logic t-eseareh aimed al describing and ex-plaining the evolution of health and dis-ease patterns (1 5). In reeent years dentalreseareh has been eharaeterized by an in-ct-ea.sed understanding of eotnplex biolog-ic and environtnental etiologies (6). Coti-curt-ently. decteases in the pt-evalence ofdental earies among "western developed"eoutitries have beeti leported (7). Theteat-e few opportutiities available today toutilize the current understanding of cariesetiology among "utiderdeveloped" eul-tures. Therefore it wasconsidered ofinter-est to study a popttiation of itntnigrantsfrom l-.thiopian rural t-egions who had ar-rived in Israel in 1991.

This population had tnigrated frotn atraditional, rural cultui-e (absenee of elec-tricity, home water supply, matiufaeturedfoods, shops, ete.), traditional health be-havior and services (no university traineddoctors, denlists, etc.), and had beentnoved, within 48 h, to Israel, a eountrywith a typieal "western" diet, cultut-e,health behavior and health cat-e. It wasdeetned important to examine ihese peo-

ple as soon as possible aftet- tlieit- itnmi-gration, i.e. befot-e any possible eulturaland biologic "c(-itilatninatioti".

Curt-etitly. earies fottnation is tlioitghtlo be due to the repeated attack by acidsproduced by plaque bacteria on enamel.Factots affecting plaque pH ehanges iti-clude; the buffering eapaeity of saliva,fiow talc of saliva, Huoride pt-esence andcontent in etiatnel atul plaque, total fer-mentable carbohydrate cotitent. thephysieal form of food including factorsthat affeet otal retention, and concetilra-tion of aeidogenie baeteria (8).

The objeetives of Ihe pt-csetil studywet-e Iherefot-e to detertiiitie the ptev-alenee of dental earies, lluoride sitpplc-mentation and lluot-osis, and to establishIhe dietary patterns, the niierobial con-tent of saliva, salivary How rates and plllevels in recetit immigrants IVotn ruralEthiopia.

Materiai and metiiods

Popitlatioti On arrival in Israel, immi-gratits had beeti plaeed in absorptioticenters throughout the eountry. atul one

of lhe two iti .lerusalem was chosen asthe location of the present study. No evi-.dencc itidicatctl any difference in p(-)puki-lioti distribution iti the varii-ius locationsLhe study cctiler hottsed apptoxitnatcl-v1000 subjeets who wet-e examined witbin1 tnotitli of arrival. Al Ihal lime idciiiifi-calioti documents had not beeti distrib-uted and niatiy heallh. social, and adtnin-isltalive aclivilies wete taking place. Thesurvey was C(-)tiducled with full aulhori-zation of all involved agencies atul withinthe cotislraitils (->f llic exisling cotidilions

The study populatioti was composedof 5 6-and 12-yi--okl ehildren and 35 45-yt--(-ikl adttlts who were judged to be sys-tetnically healthy, the.se age groups hav-itig been recommended by WilO forwotkl oral heallh dala bank sittdy (9). Onthe six oeeasions lhe center was visitedby examiners, all subjects tlicti pt-esentorigitialing from tutal villages in Ethio-pia were asked to participate. Explana-tions weie provided via an interpreterand IOO'̂ ei-)ti.sen( was obtained. Adultimmigrants wete dentally exatnined andititerviewed iti a room desigtiated for thispurpose. Chiklteti were exatnitied iti the

Caries atid deiermitiatits iti rival Ethiopian itittiiigratits 339

ad hoc "kindergarten and school" at-eawithin the eenlet-.

All parlieipatits wet-e informed of anypathology found and referred to the Ha-dassah Sehool of Dental Medieine wherefree firsl aid tt-ealmetit was provided.

'With t-espect to salivary and bacterialvariables, 20 hospital employees, aged35-^5 yt-. set-ved as eotitrols. For slalisli-cal analyses. Student's /-test was em-ployed, and 95'M> confidence intervalswere calculated for (he percentage of car-ies-frcc itulividiials (10).

E.xamitiers Clitiical data wct-c diag-nosed by two calibt-ated specialists itidental public health who were eoneur-rently involved in an on-goitig tiationaldental health sut-vey. Examiners wereaided by ]-)t-ett-ained t-eeorders and inlet--pretets. Dietary behavior interviews wet-econducted by ati Israeli-trained regis-tered dental hygienist of Ethiopian origin-who had been specifically instructed forth is purpose.

Salivat-y samples wete colleeted by twoexperieneed ot-al mierobiologists, assistedby two dental students, from subjectschoseti for baeterial atid salivary exatni-nations.

Detitctl earies recordittg - With subjeetsseated, caries was recot-dcd with the aidof optimal lighting, dental tnirrots andsicl<le-shaped explorers as recommendedby the World Health Organization (11).A m o n g 5 6-yt--olds. the percent ol caries-free individuals (priniary and permanenldentitions) was noted and lhe DMFTindex (permanent teeth) was employedfor 12-yr-old ehildten and adults. Thitdn-iolars wete tiot included in the exatnina-t ion . Only leeth cleatly extracted due tocar ies were recot-ded as "M".

Salivary tiieasitrctiicttts The partiei-p a n t s wet-e itistrueted lo rinse theirm o n t h s with tap water for 30 seeondsand then, avoiding swallowing, to expec-to ra te for 1 miti into a gt-aduated plastietest tube. Measutetnent was for 1 niiti (ino r d e r to nieasiirc paramelers not de-scribed here) and thereafter the averaget low per mitiute was ealeulated for thewhole group. The control group wasstudied by Ihe satne method and there-fore the compat-isoti was tegatded as val-id. The amount of saliva was measured.and the saliva placed on iee and trans-ferred to lhe labotaloty. whete it wasdivided into two separate tubes. Initialsalivary pH was measured by pH meter(Hanna instruments, Israel) in the first of

the tubes. Saliva was incubated at 37 Cfollowing the addition of 2"/a suerose.Salivary pH was then tneasut-ed in 30-min intervals over 3 h. Plaeement underoil was nol den-ianded as saliva eollectedill this study was imstimulaled and Ihet-c-fot-e the atnount of bicarbonate (the tnainsoui-ee of COj) was eonsidered to be low(12). The proeedure was identieal for theEthiopian and control groups.

Bacteriological variables - Aliquotsamples from the second saliva tube wereinnoculated by means of a Spiral plater(13) on three speeilic tiiedia. viz; Bloodagar for the deleclioti of lolal bacterialcounis. mitis salivarius agar for Strepto-eoeeus viridatis. and mitis salivarius withbacitracin (14) for S. timtatis counts. Ro-gosa agar (DIFCO) was used for thequantitative evaluation of lactobacilli.

Diet recording Dielat-y behaviot- wastecot-ded in detailed intet-views of 20mothers. These women were instruetedto describe a typical 1-day diet diarywhieh included meals and all between-meal eating and drinking habits of thefamily. Etnphasis was placed on all foodsusually consumed, and their ingtedients.

Resuits

Amotig 5 6-yt--olds. 68 children were ex-amined in the "kindergarten" ai-ea. 54"/nmales and 46'Mi fetnales. Both dentitiotisvvet-e studied and 86.8% of lhe subjeclswete found lo be earies-free (79%-95"'!ial the 95"^ eonfidence level).

Among 12-yr-olds. only 33 subjectswet-e exatnined as sotne ofthese ehildt-enwct-e absetit at the lime of exatnitialion.Het-e. 60"'o wet-e tnale and 40"/,. fetnale.wilh 8l.8"o being caries-IVee (63"'!i-93%al lhe 95% confidenee level), with aDMFT of 0.31. as described in Table 1.

Among the 70 adults examined (59%males. 4l"/o females). 54".'(i were deemedcat-ies-IVee (34'Xi-58% at the 95%. confi-dence level), wilh a mean DMFT seoreof 1.27 (Table 1). Of ihc lotal populationIhe mean DMFT seore of t-nales was 0.73(SD=L61) and of females 1.85 (SD =1.97). These data were signifieantly dif-

ferent at a statistical level of/ '<0.02. Onaverage, adults had 0.56 missing teeth(SD = 0.95), of wliieh 0.23 teeth weremissing due to earies, as judged both byelinical exat-nination and questioi-iirig ofpatients.

Data in Table 2 summarize the eountsof different baeteria examined in Ethiopi-an immigrant subjeets and in eontrols.As is evident, the mean total counis ofsalivary baeteria were 3.4x10* in thestudy group and 1.1 7 x 10* in controls,there being no signifieant differences.Furthermore, bolh the total eounts ofvtridatis stt-eptococci atid of S. tiiutattswere high in the two groups but againno signifieanl differenees were noted (5.Yiridatis = 6.1 X \0^ and S. tnutatis =1.74x10' in the Ethiopian group, and1.69 X 10' and 1.15 x 10' respectively ineotitrols). The number of laelobacilli wassignifieantly higher in the study group(2.75x10'') than in the controls (3.6 x10'), with F<0.001.

The t-esults of salivary pH measure-tnetits are summarized in Table 3. As canbe seen, the itiitial pH in the Iwo groupswas nol dissimilar (6.48 + 0.4 in the studygroup and 6.39+ in the eontrols). It canalso be seen that, while the drop in sali-vary pH lollow-ing incubation with 2%suerose in the Ethiopian gtoup washighly significant ( f< 0.001) after 30 minineubation, the pH drop in the eontrolgroup was not significant after 30 and 60min but only after 1.5 h (/'< 0.001).

The results of salivary flow data, mea-sut-ed in 51 Ethiopians and 20 controls,are pt-esented in Table 4. As is evident,the tnean flow- rate of the Ethiopiangroup, 1.93 ml/min. was significantlyhigher than that of controls. 1.16 ml/min (P<0.005). Furthet-more. Ethiopiantnales demonstrated a significantly high-er salivary How level of 2.2 ml tnin aseompared to 1.65 ml/min among females(/>< 0.005).

None of ihc examinees had e\'er visiteda denlist before. Some had had teelh ex-traeted (for undetermined reasons, notneeessarily caries) by village "teeth ex-traetors" and none had ever cleaned teeth

Table 1. Dislribulion of caries according lo mean DML'T (and its coii-iponents; D. M. L). and"o of population earies-free. by age

Age(yr)

12.V̂ 45

n

337t)

C'aries-t'ree " o

81.854.0

MeanDMLT

0.311,27

SD

0,821.55

MeanD

0,281.04

SD

0.771,68

MeanM

0 030,23

SD

0,18

MeanL

0t)

SD

00

340 StiAN-CoiitiN nv

Table 2. Bacterial counts In saliva'

EthiopianMeanSD

Controls tMeanSD

Total bac.-

itnmigrants (/; = 70)3.4 X 10»5.8 X 10"

/I = 20)1.1 X 10"1.3 X 10»

.V, viriihtits'

6,7 X 10'1.1 X 10"

1.7 X 10'1.3 X 10'

.V. ttttttatt.s'^

1.7 X 10'4.4 X It)'

1.1 X 10'1.5 X 10'

Lactob;

2.7 X2.2 X

3.6 X2.7 X

icilli^

10'10-*

10'10'

' Number of bacteria per 1 ml saliva.• Counis on hlood agar.' Counts on mitis salivaruis agar.'' Counts on milis salivarius hacitracin agat-.' Counis on Rogosa agar.

wilh a toothbrush or toothpaste. Thetnost common oral hygiene method (re-ported almost universally) was rigorousrinsing with water after eating and clean-ing wilh special olive tree "chewingsticks". No topical lluoride was utilizedand no signs of lluorosis were evident.

The dietary pattertis wete very dil-fetent to those of "western" eultures. Allfoods wet-e hotiie pt-oduced and stronglyspiced, bttt no sugar was added as it wasrat-ely available in the villages. It wasstated that the staple foods consisted ofgrains and pulses (chickpeas, corn, etc.)pan "fried" (without oil) over a fire and.served in a "solid" (not softetied) state.Special home fried or baked "pita" typebreads from local wheats and brans weredipped in spicy sauces. Adults oftendratik strong, coarsely home-groutui (un-sweetened) coffee, this being a traditionalcomponent of all social meetings, whichoccurt-ed several titnes a day. Men alsodtaiik home-made beer, wotnen waterand herb teas, and childt-en drank watet-and milk (in the morning, fresh from thecow). Milk was accutnulated during theweek and cheeses wete pt-epat-ed for theweekend. Very little fruit or vegetableswere eonsumed as these wct-e availableonly about onee a week (or less) frotnthe towns.

fable 3, .Salivary pH measurements hy time

0 0.5 1.0 1.5 2.0 2.5 3.0

Ethiopian imtnigrants (/i = 70)Mean 6.5 6.2 6.1 6.0 5.9 5,8 5.7SD 0.4 0.5 0.6 t),6 t),X 0.8 t).H

Controls (/; = 2t))Mean 6.4 6..̂ 6,2 6.0 5,9 5.8 5.7SD 0.2 0.3 0.3 0.4 0.5 0.5 0.5

' p l l at time 0 and 30 min intervals followingsucro.se challenge.

Discussion

The ptesetil sludy population frotn ruralEthiopia offered a unique opporluiiity toexamine, at firsl hand, a cotnmunily inthe process of chatiging citltut-c pattcttis.Very low earies levels were found.

The plaque pH level has been de-scribed as the most important variable indetermining the detnineralization/retniti-eralization dynamic process surroundinglhe leeth (6). The availability ofa earbo-hydt-ate-rieli diet tnay be expected to gen-et-ate, together with appt-opriate mi-crofiot-a, ati acidic cfi'cct oti plaque withresultanl demitietalizalioti of tooth ealei-utn phosphate. Saliva, in contrast, is themain soutee of caleium and phosphatefor both tooth and plaque, and thereforeis lhe main factor t-esponsible for tetnin-cralizatjon (15). Detital teseat-eh has tra-ditionally implieated the degree of infee-tion with mutans streptococci and lacto-bacilli in the developtnent of earies, atulit has been suggested that the levels ofthese miet-oorganistns at-e earies risk indi-catots (16).

Epidetniologic tescat-ch conductedthroughout the world has detnotistratedIhat populations adhering to diets basedon loeal agricultural products, low insugar cotitent, have a low earies ptev-

Table 4. Salivary How measurements (in ml/ian immigrants and controls.

hy gender

EthiopianH

MeanSD

Controls//MeansSD

Males

immigrants29

2.20,98

141,16t),49

L'emales

1.650,74

61.150,44

Tolal

511.930,S6

2t)1.160.50

alence (1-5). Otice expo.sed lo "western"eivilizalion. the.se chatigitig societies bavedemonstrated signifieant inereases in car-ies levels. The caries prevalence has bcei-it-eported to be rising among Ethiopianpopulations over a period of about 16 yrpatallcling an increase in sugar eot-isump-tion. In Addis Ababa, earies was foiu-idto be twice as high as iti the less devel-oped provinces and was attribitted tohigh sugar eotisumpti(-iti iti itrbatichildt-en (17). A t-eeent sludy of 12-yr-oldselioolelnldten iti tutal Cihana detnon-strated a DMF'L level of 0.2 witb 8 8 ' ^of the populalion carics-IVee (18). Tbeselevels, which wete sitnilar lo those foundin Ihc ptescnt rural population (0.3 andH2"At t-espeetively), wete differctil fromGliaiian urban childten, who dcmon-strated signifieantly mote disease (18).

A tccenl nalional caries pt-evalencesurvey in Israel it-idicaled 41.3'̂ ;) of sub-jecls caries-free al 5 6 yr of age, com-parcd lo approximately 87'/o in lhe pt-es-ent study. Amotig l2-yt--okl Israelis21.2% were earies-lree wilh a DMF'T of3, as cotnpated lo about ^2"/» caries-freeatid a DMFT of 0.31 iti Ethiopian immi-grants (19). A ptevioits literatut-e t-eviewin Ist-ael teported 2.1'Xi earies-lVee and9.6 DMF'T amongst l8-yt--olds as com-pared to 54'!4i carics-IVee atul a tneatiDMFT of 1.27 atnong 35-45-yt--olds inthe present study (20).

The epidetniology of deereasing cariesover the last two decades, throughoutthe western world, has frequently beenatttibuted to fiuoride (21). LJtiforttinatelvthei-e was no possibility of assessing thuRuoride levels of water eotisutned by tbepresent study population while in Flthio-pia but during their elinieal examinationno evidence of even tniki llttotosis wasnoted (II). Such sytnptotns would havebeeti expected if lluoride was a significantdelerminani of Ihe extremely low carieslevels (22, 23).

The tesults of the present study re-vealed high salivaty levels of mutansstreptococci among both the rural Ethio-pians and cotilt-ols. Salivary levels of lae-lobacilli in eotitrols were high, atid inEthiopian itntnigt-ants eveti higher. Re-seat-eh eonducted oti devek-tpitig popula-tions in M(-)/,ainbique, Sudan, atul 'Lbai-land (tutal tegion) have t-evealed lowlevels of earies despite high levels ofmutans stteptoeoeci atul lactobacilli(24-26). As a result, it has bccti speculat-ed that the abundance of mutatis sttepto-

Caries and delerttiinants in rttrttl Ethioptatt itntitigratits 341

cocci in a low caries population may beexplaitied by the ptesetiee of non-eario-gcnie stt-aitis, but this possibility has notbeen conllrtned in a Sudanese rttialpopulatioti (26). Re.seatchers have sug-gested that Afrjcan populaliotis wilh pre-existing widespt-ead levels of mulansstreptococci and lactobacilli. bul beforeintroduclion of suerose lo lhe diet, maybe on lhe verge ofa earies epidemic (27).

Resting salivat-y pH levels wet-e alsosimilar for test and control groups.A m o n g Ethiopians, the pH drop aflersucrose challenge was signifieantly mot-ein-in-iedialc. This tnay be telaled to thehigher laelobacilli levels amotig F'lliio-p ians .

Tlie indepcndenl variables tiiosl signi-ficanlly dilTet-etil bclweeti llie two groupsw e r e salivary fiow (higher among the ini-n-iigi-ants) and diet composition (lowersuga r cotilenl for immigtants). ll is ofimporlance to note that vvitliin the F'thio-p i an group, atnong males, salivary Howw a s significantly higher and caries prev-alence signifieantly lower than for theit-fen-iale eounterparts.

The dielaty data ft-otii ihis populationit-idicated a metui cxttetncly low in extrin-sic sugars. Moreovet-, the catbohydt-alescot-isumed wet-e in a "hat-detied" physiealforn-i whieh is knowti tiol to facililalcfood tetetition. but stimulates chewing.a n d thereby salivary fiow. This currctitd a t a appcat-s lo be eotisislent with thetheory Ihal caries experience, on a "cottti-try to countt-y" level, is telated to sugat-consumption. but not lo mulans strepto-cocci , nor to watei- fiuotide level (28).

Results of this study elearly indicatethe efieet of diet on the prevalence ofdenta l earies. The variables available tom a n in controlling caries have tradition-ally itieltidetl otal hygiene ineasut-es. reg-u la r dental tteattiient. fiuot-ide utilizationand diet. Atnotig the present populatiotin o n e of the above, besides diet, eould beimplicated in the exttemely low cariesprevalence. These data are consistctitwi th ptcvious Ethiopian immigrant re-search in Israel which dctnotislraled low-car ies prevalence, but did tiol itivesligalerelated determinants, olher than to as-s u m e that diet tnay have a role (29).

Despite a world trend towards a eariesdecrease, comtnotily attt-ibtited to lino-ride usage, ftttther detilal health promo-tion recomtnetuiatiotis should iticludc adecrease iti sitgat- consutiiptioti (30). andthe present dala appear lo stiengthen this

understanding, ln order to avoid a de-eliiie in ihc dental health of these newitntnigrants, an oral health protnotionprogtam should be designed and imple-mented to avoid a potential decline itiheallh, which has oecurt-ed in most olherehatigitig soeielies. This should includeihc traditional and tested cotnponents ofcaries pt-evetition; heallh edueation, fiuo-rides. diet control, ot-al hygiene, and fis-sut-e sealatiis. where possible and appro-priate. Data of this study clearly indicatethat a major behaviotal variable ihalshould be addt-essed is diel. Israeli publichealth workers should thetefote iticludciti the edueation ofthese immigrants, theadvisability ofa high-sugar diet which isdestrtietive both to dental and getietalhealth. Although such a course wouldbe difiicitlt. the attempt should be tnadebefot-e il is too late.

.•lckttimlcit.i;tttcttts file authors wish to tliankRoNit HANAOR. LAVt ARON. ZviA Pi;rnT andlltRV-t Suousst. I'or their important assistanee.

References

1. NtiiMANN IIH. DtSAt v-o NA. Caries itiIndians of the Mexican Cordillera, thePeruvian Andes and at the Atnazon Head-waters. Rr Dent ./ 1958; 104: 13 6.

2. ORAN.lt P. NORtSKtN .IN. OstiORN TWB.fhe effect of diet upon dental cat-ies in theSouth Al'riean Bantu. .S" .4fr .1 Med Sei1935; /.- 57 62.

3. PRtc-t- WA. Eskitiio and Indian field stud-ies in Alaska and Canada, ./ADA 1930;2.1- 417 37,

4. Ltsittlti L.I. A field survey ofdental condi-tions, periodontal disease, and enamel de-t'ects in Tristan da Ciinha. Hr Dettt .1 1968;125: 447 53.

5. Pt;t;it;Rst-,N PO. Investigations inlo dentaleonditions of about 300t) ancient atidmodern Ciiccnlandcrs. Dettt Rcc 1938; .W,191,

6. Kl t;tNtit;t<ci 1. CttAn;R.tt:t; R. DtNtt'titv AI.. LITecls of saliva and dietary eating hah-its oti the pH and detiiinerali/ation-remin-eialization potential iil'dental plaque. In;LtiAtti SA. Lt;)tiAR WM. cd. Dcntitteraliza-tion and rctnittcrctlizatiott of the teeth. Ox-t'ot-d; IRL Press. 1983.

7. D(-)VV-Nt;R MC, Clianging patterns of dis-ease in the western world. In; GiUKitN-ttt;tM B. ed. Cariology today. Ba.sel; Katgei-.1984.

8. SritAiH-n.it; CI--. .li;Nst;N ML", Comparisonof methods tor monitoring ehanges iti thepH of human detilal plaque, ./ Dent Res1982; 61: 1117 25,

9. A<:(-.t;RYti 'X. Goals for oral health in theyear 2000; cooperation between WHO.LDl and the national denial associations.Int Dent .1 1983; A\- 55 9,

10. Pt;AR.soN ES. HARII.HV. liiontetric tables

for stiitisticiittts. Canihridge; UnivetsityPress. l')58.

11, World Health Organization. Otal heallhsurveys, hasie tnethods. Geneva; WHO.19X7.

12, DAVVB C , The effects of tlow rate anddut-ation of stimulation on the concentra-tions of protein and lhe main eleclrolylesin human suhmandihular saliva, ArehOtal liiol l'-)74; 19: 887 95.

13, .lARVts B, LA(-H V H . W(K)t) .IM, Evalua-tion of the spit-al plate ti-iaker for the enu-meration of n-iicroorganisms in foods. ./App Baet \^11: 4i: 149 52.

14, Got tl OG. .loRHAN H'V. VAN Hoini; .1. Amedium for the selcetive cultivation of S.ttttaatis. .Ateh Otal Biol 1973; IS: 1357-64.

15, MANtitt. ID. Impact of .saliva on dentalcaries. Conipeiut Cotitin Edue Dettt 1989;Suppl 13; 476 81.

ir-i, Bt;t(.itnoN D. The value of .salivarv bacte-rial counts in the prediction of earies activ-ity. In; .lottNsoN NW. ed. Ri.sk markers fororal diseases. Dental Caries. Cambridge;Cambridge Lhiiversity Press. 1991.

17. Hoit.ovVAV P,l. The role of sugar in theaetiology of dental caries. ./ Dent 1983;//.- 189'99.

18. Atl^o-^'ot^o C. Wit t tAMs SA. CURZONML.I, Dental caries experience in Ghanaamong 12-year-old urban and ruralschoolchildren. Citries Res 1991; 2.̂ ",311 4.

19. ZADIK D. ZUSMAN SP. Ki;t MAN AM. Car-

ies prevalenee in 5- and 12-ycar-oldchildren in Istael, Conttttitttitv Detit OratEpidettiiot 1992; 2t): 54 5,

20. CiORtxiN M. SARNAT H . SciAN-CoiitN HD.MANN .1. Trend of earies prevalence inchildren and young adults in Israel, Cottt-tttttnity Detit Otat Epidemiot 1990; /<S'- 108.

21. BRiiNi,t,t.t; .IA. CARt.os .IP. Recent trendsiti dental caries in U.S. children and Iheefteet of water fluoridation. ./ Dent Res1990; 69 (Spec Iss); 723 7.

22. RtoRDAN P.I. Dental caries and lluorideexposure in Western Australia../ Dent Res1991; 70: 1029 34.

23. Rt(-iRt-)AN P.I. BANKS .IA. Dental tluorosisand tliioride exposure in Westet-n Austral-ia, ./ Dent Res 1991; 70: 1022-28.

24. HRATTHAt.t D. St;RtNIRA(-H R. CAR1.S.SONp. LI;KH'AN(1HI S. Streptoeoccus tttutansand dental caries in urban and rutalschoolchildren in Thailand. CotntntitiityDent Orut Epidetniol 1986; 14: 21A 6,

25. CARI.SSON P. Ot.SSON B. BRATTllAtt D.The relationship hetween the bacteriumStreptococcus tnutatis in t h e sa l iva a n d

dental earies in children in Mo/amhique..(/-(-/( Oral Biol 1985; M): 265 8.

26. CARt .SSON P. CiANtXHlR IA. OlSSON B.RtCKARtissoN B. AnnAS K. High prev-alence of mutans streptococci in a popula-tion with extremely low prevalence ofden-tal caries. Oral Microhiot Imttttittol 1987;2.- 121 4,

27. BHGIITON D. MAN.U L. BAti UM 'V. EljKR-

SKOV O. .loUNSoN NW. Wit roN .IMA. As-sociations hetween salivat-y levels of Strep-tococctts ttttaatis. Streptococcus sobrinus.Laetobacillus. and caries expct-iencc inKetiyan adole.sccnts, ./ Dent Res 1989; 6S:1242 (1.

342 Sc;AN-Coiir;N in- AL.

28. BRATTHALI. D. The global epidemiologyof mutans streptococci. In; JOHNSON NW.ed. Risk markers for orat diseases. Dentatcaries. Cambridge; Cambridge UnivetsityPress. 1991.

29. SARNAI H . CoiiiiN S. GAt H. Changingpatterns ofdental caries in Ethiopian ado-lescents who immigrated to Israel. Coin-ttitmity Dent Otat Epidetttiol 1987; 15:286 8.

30. Siti;tttAM A. Why free sugars e o n s u m p t j o , ,should be below 15 kg per person peryear in industrialised countries; the dciU;ilevidence. Br Dent .1 1991; 171: 63 5