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NIH: Consensus Development Conference on Diagnosis and Management of Dental Caries Throughout Life: Background

NIH organized conference that produced consensus statements on important and controversial topics in medicine and dentistry.

The Microbiology of Primary Dental Caries

Jason M. Tanzer, D.M.D., Ph.D., and Jill Livingston, M.S.:

This review was conducted to evaluate the implication of certain microorganisms in the causation of human tooth decay. It examines the evidence concerning bacterial species identified in both early and current literature to be involved in tooth decay, whether originally implicated by wild animal, experimental animal, or human data. It also discusses the source of this putative infection of humans. Attention is focused on the mutans streptococci, the sanguinis streptococci, other streptococci, the enterococci, the lactobacilli, and certain actinomycetes, all of which are resident in the human mouth.

There is an immense literature on this topic. The present review deals with studies of the microbial causes and associations with dental caries in humans, relying on cross-sectional, case-control, longitudinal, and interventional studies. It addresses tooth decay in young children having only deciduous (primary) dentition, older children and adolescents having mixed and permanent (secondary) dentitions, and adults and seniors, whose secondary dentition often presents varying degrees of root exposure. As such, patients and experimental subjects with incipient enamel lesions (white spots) and established cavitations (cavities) of the tooth crowns and root surface lesions are considered. Studies of so-called secondary or recurrent caries have been excluded from this review, as have studies done in vitro, in experimental animals, or with so-called in situ caries models.

Earlier studies have characterized the biological behavior of the implicated microorganisms. The essentials are summarized below.

Mutans streptococci colonize the host only after the first teeth erupt, and their preferential colonization site is the teeth (Carlsson, Grahnen, Jonsson, 1975; Catalanotto, Shklair, Keene, 1975); they are highly localized on the surfaces of the teeth, and their abundance in the plaque is highest over initial lesions (Duchin, van Houte 1978; Babaahmady, Challacombe, Marsh, et al., 1998); their level of colonization within the plaque is increased by sucrose consumption (Folke, Gawronski, Staat, et al., 1972; Staat, Gawronski, Cressey, et al., 1975); they synthesize molecules from sucrose that foster their attachment to the teeth (Freedman, Tanzer, 1974; Tanzer, Freedman, Fitzgerald, et al., 1974); they are rapid producers of acid from simple carbohydrates and are tolerant to low pH (Edwardsson, 1968; Tanzer, 1989); and they are recovered on cultivation of initial and established carious lesion sites (Clarke, 1924; Littleton, Kakehashi, Fitzgerald, 1970; Keene, Shklair, 1974). Interest in them grew after demonstration of their potency in induction and progression of carious lesions in a variety of experimental animals, including mono-infected gnotobiotes (Fitzgerald, Fitzgerald, 1981). Their virulence expression is strongly associated with consumption of carbohydrates, especially sucrose (Tanzer, Freedman, Fitzgerald, 1985; Kuramitsu, 1993).

Lactobacilli do not avidly colonize the teeth and may be transiently found in the mouth before the teeth erupt; they preferentially colonize the dorsum of the tongue and are carried into saliva by sloughing of the tongue�s epithelium (van Houte, Gibbons, Pulkkinen, 1972); their numbers in saliva appear to be a reflection of the consumption of simple carbohydrates by the host (Staat, Gawronski, Cressey, et al., 1975; Holbrook, de Soet, de Graaff, 1993); they too are highly acidogenic from carbohydrates and are acid-tolerant (Wood, 1961). They are often cultured from established carious lesions (Loesche, Syed, 1973). Some lactobacilli are cariogenic in experimental animals, and their cariogenicity is dependent upon consumption of carbohydrate-rich-diets.

Nonmutans streptococci of several types, including the sanguinis group of organisms, and S. salivarius, are extremely abundant in the mouth; some are tooth surface colonizers, some mucosal colonizers. Some are quite acidogenic from carbohydrates and are acid-tolerant (Guggenheim, 1968; Edwardsson, 1968; Nyvad, Kilian, 1990). Less evidence exists of their virulence in experimental animals.

Enterococci were the first bacteria shown experimentally to induce caries in gnotobiotic animals (Orland, Blayney, Harrison, et al. 1955). Carbohydrate users, acidogenic, and acid-tolerant, they are seldom abundant in the human oral cavity (Guggenheim, 1968; Edwardsson, 1968; Nyvad, Kilian, 1990).

Actinomycetes are abundant in the human mouth and induce root surface caries in hamsters and gnotobiotic animals (Jordan, Keys, Bellack, 1972). They are also carbohydrate users, but are not powerfully acidogenic or acid-tolerant.

Summary of Current Review

Table 1. Studies on the association of microorganisms and dental caries

Bacterial Group

Total

Interventional

Longitudinal/
Retrospective

Case-Control

Cross-Sectional

Mutans streptococci

189

25

59

20

85

Sanguinis/other streptococci

16

1

2

2

11

Enterococci

3

0

0

0

3

Lactobacilli

144

9

40

20

75

Actinomycetes

27

1

3

3

20

Randomized Clinical Trials on Mutans Streptococci

Twenty-five interventional studies which monitored the putative cariogenic flora and recorded their effects on caries scores were found in the literature. Several of these applied extremely complex strategies (e.g., Gunay, Dmoch-Bockhorn, Gunay, et al., 1998). Some focused on mitigation of the solubility of the teeth with fluorides, some on repair or sealing of the teeth, some on diet management and/or use of sugar substitutes and thus indirectly on changing the implicated tooth surface flora, and some focused directly on the flora with mechanical plaque control or use of antiseptic agents.

Since the questions for the present review are more straightforward, those multistrategic studies confound interpretations of antibacterial effects with demineralization effects. It is understandable that investigators wish to accept this problem because of the ethical need to offer patients at high risk the best available anticaries strategies. Nonetheless, multistrategy approaches to experimental interventions set a very high threshold for detection of the effects of intervention on the flora and the attribution of anticaries responses to them. Some notable studies have been less confounded, however.

Partial suppression of mutans streptococci by topical chlorhexidine use and dietary counseling in randomized Swedish children (Zickert, Emilson, Krasse, 1983) inhibited mutans streptococcal recoveries and carious lesion development during 3 years, while lactobacillus titers in saliva were not detectably affected.

Treatment of primiparous mothers with 3- to 8-month-old infants in a Swedish community, alternately assigned to treatment or control groups, was aimed at reduction of mutans streptococcal salivary levels by sucrose avoidance counseling, professional toothcleaning (and topical fluoride application), oral hygiene instruction, and excavation of large carious lesions if present, and�if test mothers had salivary mutans streptococcal levels that exceeded a pre-set threshold�by treatment with topical chlorhexidine. This strategy increased the time to colonization by mutans streptococci of young children, time to caries experience of those children, and severity of caries experience of those children (K�hler, Andreen, Jonsson, 1984). There was no significant difference in salivary lactobacilli. Preventive strategies were discontinued when children were detected as colonized. The study ran until children were 36 months old. Four years later, when the children were 7 years old, treated mothers had lower mutans streptococci and lactobacilli than control mothers (K�hler, Andreen, 1994). Far lower percentages of children of treated mothers carried mutans streptococci compared with children of control mothers. The children of test mothers who were carriers also had lower levels of mutans streptococci than control children. Twenty-three percent of the children of test mothers were caries free, compared to 9 percent of the children of control mothers, and total group caries experience for test and control children was 5.2 vs. 8.6 def.

A similar strategy was used to treat 50 to 60-year-old Swedish patients of private dentists (Rask, Emilson, Krasse, et al., 1988). Two randomized groups of high and low risk patients (defined by salivary mutans, salivary flow rate, and buffer capacity) were assigned the test protocol or served as controls who were given standard care as deemed appropriate by their dentists. At year�s end, the treated high risk group had lower caries increments and lower mutans and lactobacillus titers than high risk controls, but there was no difference between the two low risk groups. The intervention was discontinued. Four years later there was no difference in microbiological parameters or caries increment between the treated and untreated high risk and low risk groups, and the one-year differential benefits of the test intercession had been lost.

A 3-year study (Gisselsson, Birkhed, Bj�rn, 1988) of 12-year old Swedish children, using an intervention of chlorhexidine-impregnated dental floss treatment of approximal surfaces compared with placebo-impregnated floss or no floss resulted in about a 50 percent reduction of new DFS in the chlorhexidine-floss compared with the placebo-floss group, and about a 60 percent reduction compared with the no floss group. Chlorhexidine-impregnated floss effects were about 42 percent better than placebo-floss. Salivary monitoring (rather than approximal plaque monitoring) found no differences among the groups, as could be expected.

A 3-year intensive program (Carlsson, Struzycka, Wierzbicka, et al., 1988) focused on personalized education, excavation of cavities, fluoride varnish, professional toothcleaning, and oral hygiene instruction. Study participants were randomized by school class and had group instruction on sugar avoidance, toothbrushing, fluoride toothpaste use, and were provided brushes. The personalized program resulted in about a six-fold decline of new DFS in 10 to 12-year-old Polish children and, after 3 years, significant reductions of mutans and lactobacillus salivary counts.

A 2-year randomized group study of 13-year-old Swedish children (Lindquist, Edward, Torrell, et al., 1989) compared supervised chlorhexidine gel treatment to fluoride varnish, topical FeAlF professional application, or an untreated control group. The antibacterial treatment resulted in about a 50 percent reduction of new DFS when compared with the untreated controls and lesser but still substantial and significant DFS reductions compared with the fluoride groups. There was correlated reduction of salivary mutans streptococci in the chlorhexidine group.

Finnish children 10 to12 years old were randomized to either high content xylitol gum use or not, during the first experimental phase (Isokangas, Tenovuo, S�derling, et al., 1991). Two years later, when the controls were randomly recruited for evaluation, it was found that some had begun to use xylitol gum. Approximal plaque mutans levels were lower in the xylitol users, and continuous users of xylitol gum had lower decay scores 6 years after the beginning of their use than nonusers. Mutans streptococci were lower at approximal sites that were clinically and radiographically sound than at decayed sites.

The use of a xylitol chewing gum by Finnish mothers (S�derling, Isokangas, Pienih�kkinen, et al. 2000; Isokangas, S�derling, Pienih�kkinen, et al., 2000) until their children were 3 years old was recently reported to inhibit the colonization of their children and reduce the caries experience of those children during a 5-year period of observation. Mothers were randomized to either xylitol gum use, chlorhexidine varnish, or fluoride varnish applications. The children did not use the gum or receive varnish treatments. The probability of being caries free was 70 percent for nonmutans colonized children compared to about 25 percent for mutans colonized ones at 5 years of age, and the group mean dmf score for the xylitol intercession cohort was 0.83, while scores for the chlorhexidine and fluoride varnish groups were 3.22 and 2.87, respectively.

Sixty-four longitudinal (prospective and retrospective) and case control studies indicate an important role of mutans streptococci in caries. They examined the relationship between salivary titers or plaque relative abundance of mutans streptococci (and often simultaneously quantified other bacteria, especially lactobacilli, actinomycetes, and sanguis streptococci) as well as inception, prevalence, or incidence of carious lesions. Many studies used randomized subjects, some being dental or medical patients; some subjects were almost totally naive dentally. Some studies have used population samples, and some compared cohorts with high or low caries experience, fluoridated or nonfluoridated communities, diverse racial/ethnic groups, diverse socioeconomic groups, diverse methods of paying for dental health care, ambulatory and nonambulatory health status, and diverse ages. The longitudinal, case-control, and cross- sectional (not discussed here) studies involved all of the continents except Antarctica. Several of these diverse studies are cited here (deStoppelaar, van Houte, Backer-Dirks, et al., 1969; Edwardsson, Koch, Obriuk, 1972; Loesche, Straffon, 1979; Alaluusua, Renkonen, 1983; Loesche, Eklund, Earnest, et al., 1984; Kristoffersson, Grondahl, Bratthall, 1985; Lang, Holtz, Gusberti, et al., 1987; Kingman, Little, Gomez, et al., 1988; Wilson, Ashley, 1989; Russell, MacFarlane, Aitchison, et al., 1991; Disney, Graves, Stamm, et al., 1992; Bjarnason, K�hler, Wagner, 1993; Schroder, Widenheim, Peyron, et al., 1994; Drake, Hunt, Beck, et al., 1994; Alaluusua, Malmivirta, 1994; Sigurjons, Magnusdottir, Holbrook, 1995; Hallonsten, Wendt, Mejare, et al., 1995; Grindefjord, Dahloff, Nilsson, et al., 1995, 1996; Twetman, Petersson, 1996).

These and other reports, with few exceptions, support a strong positive statistical association of mutans streptococci with inception or incidence of carious lesions. They often report concomitant positive associations with lactobacilli, especially if saliva, rather than discrete plaque samples, were monitored. They sometimes reported negative associations of sanguinis streptococci with mutans streptococci and with lesions. Some suggest that S. sobrinus are favored in their ability to colonize by preexisting S. mutans colonization. There is also suggestion of an association between S. sobrinus and lactobacilli.

These studies often gathered data on other variables of interest � socioeconomic status, sucrose consumption (usually as food types or patterns of consumption), fluoride exposure, oral hygiene status, breast feeding or close personal contact between mothers and their children, and, especially, initial caries status. Some studies asked the clinical examiners to predict the decay experience of study participants.

Some of these studies focused on a related question�the prediction of caries as a function of the sum total of all or many of the variables of interest to cariologists�rather than the microbiological variables targeted in this review. When predictive values were estimated and when multiple regression models included other caries-associated variables (such as candy or soft drink consumption, oral hygiene, SES, and, especially, prior numbers of lesions) and included them in the prediction model, the amount of variance explained by the bacteria of interest became predictably smaller. Prediction of the dependent variable (caries score) by inclusion of the baseline caries score as an independent variable appears inherently tautological in the context of explaining causation of the disease (and is arguably a post hoc, ergo propter hoc problem).

Discernment of microbial etiology from several longitudinal (and cross-sectional) studies was undoubtedly blunted by using salivary (or pooled plaque) monitoring of mutans streptococci as a surrogate for small samples of plaque in areas of high caries risk, as knowledge of the biology of mutans streptococci and expected locations of carious lesions would have seemed to dictate.

Lactobacilli. All of the concerns about confounding and the ambiguity of interpretation in interventional clinical trials stated above for mutans streptococci are applicable to lactobacilli as well. Several of the random clinical trials that yielded data on mutans streptococci also evaluated changes in lactobacilli. Generally, they resulted in inconsistent evidence that inception of carious lesions in children or decreases of incidence were associated with lactobacillus titer changes in saliva (K�hler, Andreen 1994; Rask, Emilson, Krasse, et al., 1988; Carlsson, Struzycka, Wierzbicka, et al., 1988; Lindquist, Edward, Torell, et al., 1989).

Longitudinal and case-control studies are perhaps more informative. Lactobacilli are late colonizers of the mouth (Hemmens, Blayney, Bradel, 1946; van Houte, Gibbons, Pulkkinen, 1972; Carlsson, Grahnen, Jonsson, 1975; Schroder, Widenheim, Peyron, et al., 1994; Babaahmady, Challacombe, Marsh, et al., 1998). Lactobacilli are recovered from carious lesions, but they are later colonizers of those lesions than mutans streptococci (Loesche, Eklund, Earnest, et al., 1984; Crossner, Claesson, Johansson, et al., 1989; Holbrook, de Soet, de Graaff, et al., 1993). Some data suggest that they are favored in their ability to colonize by preexisting colonization by mutans streptococci, especially S. sobrinus. These data thus indicate that lactobacilli are not requisite for the development of lesions. Nonetheless, they may potently contribute to demineralization of the teeth once lesions are established on either crowns or roots (Boyar, Bowden, 1985; Ravald, Hamp, Birkhed, et al., 1986; Fure, Romaniec, Emilson, et al., 1987; Scheinin, Pienih�kkinen, Tiekso, et al., 1994; Grindefjord, Dahllof, Nilsson, et al., 1995; Mazengo, Tenovuo, Hausen, et al., 1996; Fure, 1998). Little information is available concerning the species of lactobacilli that colonizes the human tongue and teeth.

Nonmutans Streptococci. Essentially no data support a causative role for sanguinis streptococci or S. salivarius in human caries. In fact, some data suggest an inverse relationship in the abundance of sanguinis streptococci and mutans streptococci, and also that sanguinis streptococci are inversely related to lesion development (deStoppelaar, van Houte, Backer-Dirks, et al., 1969; Loesche, Straffon, 1979; Bowden, Ekstrand, McNaughton, et al., 1990; Emilson, Ravald, Birkhed, et al., 1993).

Enterococci. Essentially no human data support a significant role of enterococci in the development of human carious lesions or in their prevalence in the human mouth.

Actinomycetes. Actinomycetes are prevalent in the human mouth and are frequently found in association with both carious and sound root surfaces, as well as sound crown surfaces. Evidence of their role in root surface carious lesion induction from interventional, longitudinal, case-control, or cross-sectional data is variable and inconclusive. In fact, these data sometimes suggest that actinomycetes are more reflective of noncariogenic than cariogenic status, in contrast with mutans streptococci and lactobacilli.

Just as modern molecular and genetic methods are now used in forensic science, they are also used to trace the spread of infection. They provide perhaps the strongest evidence of the source of transmission of infection. That evidence will be briefly abstracted here. Nonetheless, other evidence of the source of transmission of the bacteria etiologically involved in caries from experimental and longitudinal studies is consistent with even more compelling genetic investigations. Convincing data on the source of infection by cariogenic bacteria almost entirely pertain to mutans streptococci (see table 2).

Table 2. Studies on the transmission of bacterial species implicated in dental caries

Bacterial Group

Total

Molecular and genetic tracing: bacteriocin/
mutacin/phage typing/
endonuclease mapping/
ribotyping

Interventional

Longitudinal/ Case-Control

Cross-Sectional

Mutans streptococci

40

17

 

8

13

1

Sanguinis/other streptococci

1

0

0

1

0

Enterococci

0

-

-

-

-

Lactobacilli

7

-

4

3

0

Actinomycetes

0

-

-

-

-

Study of mutans streptococci isolated from children and their parents/siblings/caretakers as to bacteriocin typing, phage typing, mutacin typing, endonuclease DNA mapping, and ribotyping establish that these bacteria are transmitted to humans early in their lives, mainly from their mothers (Berkowitz, Jordan, 1975; Berkowitz, Jones, 1985; Caufield, Ratanapridakul, Allen, et al., 1988; Kulkarni, Chan, Sandham, 1989; Caufield, Walker, 1989; Li, Caufield, 1995; Emanuelsson, Li, Bratthall, 1998; Redmo Emanuelsson, Wang, 1998; Gronroos, Saarela, Matto, et al., 1998). Only two reports suggest significant patrilineal transmission. While it is common for children to share more than one genotype or bacteriocin type of mutans with their mothers, failure to detect all of the types among mother/child pairs suggests that some may be lost with time. New genotypes have been reported to colonize children during longitudinal studies, suggesting that extrafamilial transmission also occurs.

Longitudinal study of children led investigators to propose the existence of a "window of infectivity" by mutans streptococci (Caufield, Cutter, Dasanayake, et al., 1993), but that concept does not appear well-supported. Children become colonized both before and after the "window" period (Aaltonen, Tenovuo, 1994; van Loveren, Buijs, Bokhout, et al., 1998; Straetemans, van Loveren, de Soet, et al., 1998; Mohan, Morse, O�Sullivan, et al., 1998). Also, as reported in essentially all of the studies of adults (cited above), virtually all dentate adults appear colonized to some degree by mutans streptococci. There are likely to be other events of transmission or, alternatively, the methods historically used to cultivate mutans streptococci may fail to detect transmission which has in fact occurred.

Interventional studies of transmission are clearly inhibited by the ethical impossibility of exchanging children with mothers shortly after birth. Nonetheless, controlled experiments aimed at altering the probability of transmission of mutans streptococci from mothers to their children support the concept that the mother is the usual source of transmission to her child (K�hler, Andreen, 1994; Brambilla, Felloni, Gagliani, et al., 1998; S�derling, Isokangas, Pienih�kkinen, et al., 2000).

There are few data on the source of transmission of lactobacilli to children. Despite the use of very specific selective media for the cultivation of lactobacilli, speciation of them is laborious and is usually not done in an epidemiological context. Also, the literature does not yield studies of the genetics of the lactobacilli in the mouth, vagina, and gastro-intestinal tract of mothers and their children. It is clear that while lactobacilli can be found in the mouths of infants, they appear to be transient and are not a common feature of the oral cavity until after teeth erupt or obturators are placed for cleft palate management. There is even less information on the source of colonization of the mouth by sanguinis group streptococci, enterococci, and actinomycetes. S. salivarius is long known to colonize the mouth, usually within a day of birth.

Conclusion

Evidence from the current review strongly supports a central role of the mutans group of streptococci in the initiation of caries on the smooth surfaces and fissures of the crowns of the teeth of adults and children, and suggests that they have a potent etiologic role in the induction of root surface caries. Lactobacilli are also implicated as important contributory bacteria in tooth decay, but their role in induction of lesions is not well supported. Evidence that other streptococci, enterococci, or actinomycetes are prominent etiological agents of dental caries in humans is equivocal at best. The mutans streptococci are spread vertically in the population, mostly but not exclusively from mothers to their children.

References

Aaltonen AS, Tenovuo J. Association between mother-infant salivary contacts and caries resistance in children: a cohort study. Pediatr Dent 1994;16:110�6.

Alaluusua S, Kleemola-Kujala E, Gronroos L, Evalahti M. Salivary caries-related tests as predictors of future caries increment in teenagers. A three-year longitudinal study. Oral Microbiol Immunol 1990;5:77�81.

Alaluusua S, Malmivirta R. Early plaque accumulation�a sign for caries risk in young children. Comm Dent Oral Epidemiol 1994;22 (5pt1):273�6.

Alaluusua S, Renkonen OV. Streptococcus mutans establishment and dental caries experience in children from 2 to 4 years old. Scand J Dent Res1983;91:453�7.

Babaahmady KG, Challacombe SJ, Marsh PD, Newman HN. Ecological study of Streptococcus mutans, Streptococcus sobrinus and Lactobacillus spp. at sub-sites from approximal dental plaque from children. Caries Res 1998;32:51�8.

Berkowitz RJ, Jones P. Mouth-to-mouth transmission of the bacterium Streptococcus mutans between mother and child. Arch Oral Biol 1985;30:377�9.

Berkowitz RJ, Jordan HV. Similarity of bacteriocins of Streptococcus mutans from mother and infant. Arch Oral Biol 1975;20:725�30.

Bjarnason S, K�hler B, Wagner K. A longitudinal study of dental caries and cariogenic microflora in a group of young adults from G�teborg. Swedish Dent J 1993;17:191�9.

Bowden GH., Ekstrand J, McNaughton B, Challacombe SJ. Association of selected bacteria with the lesions of root surface caries. Oral Microbiol Immunol 1990;5:346�51.

Boyar RM, Bowden GH. The microflora associated with the progression of incipient carious lesions of children living in a water-fluoridated area. Caries Res 1985;19:298�306.

Brambilla E, Felloni A, Gagliani M, Malerba A, Garcia-Godoy F, Strohmenger L. Caries prevention during pregnancy: results of a 30-month study. J Amer Dent Assoc 1998;129:871�7.

Carlsson J, Grahnen H, Jonsson G. Lactobacilli and streptococci in the mouth of children. Caries Res 1975;9:333�9.

Carlsson P, Struzycka I, Wierzbicka M, Iwanicka-Frankowska E, Bratthall D. Effect of a preventive program on dental caries and mutans streptococci in Polish schoolchildren. Commun Dent Oral Epidemiol 1988;16:253�7.

Catalanotto FA, Shklair IL, Keene HJ. Prevalence and localization of Streptococcus mutans in infants and children. J Amer Dent Assoc 1975;91:606�9.

Caufield PW, Cutter GR, Dasanayake AP. Initial acquisition of mutans streptococci by infants: evidence for a discrete window of infectivity. J Dent Res 1993;72:37�45.

Caufield PW, Ratanapridakul K, Allen DN, Cutter GR. Plasmid-containing strains of Streptococcus mutans cluster within family and racial cohorts: implications for natural transmission. Infect Immun 1988;56:3216�20.

Caufield PW, Walker TM. Genetic diversity within Streptococcus mutans evident from chromosomal DNA restriction fragment polymorphisms [published erratum appears in J Clin Microbiol 1989;27:1918]. J Clin Microbiol 1989;27:274�8.

Clarke K. On the bacterial factor in the aetiology of dental caries. Brit J Exper Pathol 1924;5:141�7.

Crossner CG, Claesson R, Johansson T. Presence of mutans streptococci and various types of lactobacilli in interdental spaces related to development of proximal carious lesions. Scand J Dent Res 1989;97:307�15.

de Stoppelaar JD, van Houte J, Backer-Dirks O. The relationship between extracellular polysaccharide-producing streptococci and smooth surface caries in 13-year-old children. Caries Res 1969;3:190�9.

Disney JA, Graves RC, Stamm JW, Bohannan HM, Abernathy JR, Zack DD. The University of North Carolina Caries Risk Assessment Study: further developments in caries risk prediction. Comm Dent Oral Epidemiol 1992;20:64�75.

Drake CW, Hunt RJ, Beck JD, Koch GG. Eighteen-month coronal caries incidence in North Carolina older adults. J Pub Health Dent 1994;54:24�30.

Edwardsson S, Koch G, Obrink M. Strep. sanguis, Strep. mutans and Strep. salivarius in saliva. Prevalence and relation to caries increment and prophylactic measures. Odont Rev 1972;23:279�96.

Edwardsson S. Characteristics of caries-inducing human streptococci resembling Streptococcus mutans. Arch Oral Biol 1968;13:637�46.

Ellen RP, Banting DW, Fillery ED. Longitudinal microbiological investigation of a hospitalized population of older adults with a high root surface caries risk. J Dent Res 1985;64:1377�81.

Emanuelsson IR, Li Y, Bratthall D. Genotyping shows different strains of mutans streptococci between father and child and within parental pairs in Swedish families. Oral Microbiol Immunol 1998;13:271�7.

Emilson C-G, Ravald N, Birkhed D. Effects of a 12-month prophylactic programme on selected oral bacterial populations on root surfaces with active and inactive carious lesions. Caries Res 1993;27:195�200.

Fitzgerald RJ, Fitzgerald DB. The microbiologic status of test animals in relation to caries research. In: Animal Models in Cariology, Tanzer JM (ed). Information Retrieval Inc.,1981, 89�95.

Folke LE,Gawronski TH, Staat RH, Harris RS. Effect of dietary sucrose on quantity and quality of plaque. Scan J Dent Res 1972;80:529�33.

Freedman ML, Tanzer JM. Dissociation of plaque formation from glucan-induced agglutination in mutants of Streptococcus mutans. Infect Immun 1974;10:189�96.

Fujiwara T, Sasada E, Mima N, Ooshima T. Caries prevalence and salivary mutans streptococci in 0-2-year-old children of Japan. Comm Dent Oral Epidemiol 1991;19:151�4.

Fure S, Romaniec M, Emilson C-G, Krasse B. Proportions of Streptococcus mutans, lactobacilli and Actinomyces spp in root surface plaque. Scand J Dent Res 1987;95:119�23.

Fure S. Five-year incidence of caries, salivary and microbial conditions in 60-, 70- and 80-year-old Swedish individuals. Caries Res 1998;32:166�74.

Gisselsson H, Birkhed D, Bj�rn AL. Effect of professional flossing with chlorhexidine gel on approximal caries in 12- to 15-year-old schoolchildren. Caries Res 1988;22:187�92.

Grindefjord M, Dahllof G, Nilsson B, Modeer T. Prediction of dental caries development in 1-year-old children. Caries Res 1995;29:343�8.

Grindefjord M, Dahllof G, Nilsson B, Modeer T. Stepwise prediction of dental caries in children up to 3.5 years of age. Caries Res 1996;30:256�66.

Gronroos L, Saarela M, Matto J, Tanner-Salo U, Vuorela A, Alaluusua S. Mutacin production by Streptococcus mutans may promote transmission of bacteria from mother to child. Infect Immun1998;66:2595�600.

Guggenheim B. Streptococci of dental plaques. Caries Res 1968;2:147�63.

Gunay H, Dmoch-Bockhorn K, Gunay Y, Geurtsen W. Effect on caries experience of a long-term preventive program for mothers and children starting during pregnancy. Clin Oral Invest 1998;2:137�42.

Hallonsten AL, Wendt LK, Mejare I, Birkhed D, H�kansson C, Lindvall AM, et al. Dental caries and prolonged breast-feeding in 18-month-old Swedish children. J Paediatr Dent 1995;5:149�55.

Hemmens ES, Blayney JR, Bradel SF. The microbic flora of the dental plaque in relation to the beginning of caries. J Dent Res 1946;25:95�205.

Holbrook WP, de Soet JJ, de Graaff J.Prediction of dental caries in pre-school children. Caries Res 1993;27:424�30.

Isokangas P, S�derling E, Pienih�kkinen K, Alanen P. Occurrence of dental decay in children after maternal consumption of xylitol chewing gum, a follow-up from 0 to 5 years of age. J Dent Res 2000;79:1885�9.

Isokangas P, Tenovuo J, S�derling E, Mannisto H, Makinen KK. Dental caries and mutans streptococci in the proximal areas of molars affected by the habitual use of xylitol chewing gum. Caries Res 1991;25:444�8.

Jordan HV, Keyes PH, Bellack S. Periodontal lesions in hamsters and gnotobiotic rats infected with Actinomyces of human origin. J Periodontal Res 1972;7:21�8.

Keene HJ, Shklair IL. Relationship of Streptococcus mutans carrier status to the development of carious lesions in initially cariesfree recruits. J Dent Res 1974;53:1295�8.

Kingman A, Little W, Gomez I, Heifetz SB, Driscoll WS, Sheats R, Supan P. Salivary levels of Streptococcus mutans and lactobacilli and dental caries experiences in a US adolescent population. Comm Dent Oral Epidemiol 1988;16:98�103.

K�hler B, Andreen I, Jonsson B. The earlier the colonization by mutans streptococci, the higher the caries prevalence at 4 years of age. Oral Microbiol Immunol 1988;3:14�7.

K�hler B, Andreen I, Jonsson B. The effect of caries-preventive measures in mothers on dental caries and the oral presence of the bacteria Streptococcus mutans and lactobacilli in their children. Arch Oral Biol 1984;29:879�83.

K�hler B, Andreen I. Influence of caries-preventive measures in mothers on cariogenic bacteria and caries experience in their children. Arch Oral Biol 1994;39:907�11.

Kristoffersson K, Grondahl HG, Bratthall D. The more Streptococcus mutans, the more caries on approximal surfaces. J Dent Res 1985;64:58�61.

Kulkarni GV, Chan KH, Sandham HJ. An investigation into the use of restriction endonuclease analysis for the study of transmission of mutans streptococci. J Dent Res 1989;68:1155�61.

Kuramitsu HK. Virulence factors of mutans streptococci: Role of molecular genetics. Crit Rev Oral Biol Med 1993;4:159�76.

Lang NP, Hotz PR, Gusberti FA, Joss A. Longitudinal clinical and microbiological study on the relationship between infection with Streptococcus mutans and the development of caries in humans. Oral Microbiol Immun 1987;2:39�47.

Li Y, Caufield PW. The fidelity of initial acquisition of mutans streptococci by infants from their mothers. J Dent Res 1995;74:681�5.

Lindquist B, Edward S, Torell P, Krasse B. Effect of different caries preventive measures in children highly infected with mutans streptococci. Scand J Dent Res 1989;97:330�7.

Littleton NW, Kakehashi S, Fitzgerald RJ. Recovery of specific "caries-inducing streptococci" from carious lesions in the teeth of children. Arch Oral Biol 1970;15:461�3.

Loesche WJ, Eklund S, Earnest R, Burt B. Longitudinal investigation of bacteriology of human fissure decay: epidemiological studies in molars shortly after eruption. Infect Immun 1984;46:765�72.

Loesche WJ, Straffon LH. Longitudinal investigation of the role of Streptococcus mutans in human fissure decay. Infect Immun 1979;26:498�507.

Loesche WJ, Syed SA. The predominant cultivable flora of carious plaque and carious dentine. Caries Res 1973;7:201�16.

Masuda N, Tsutsumi N, Sobue S, Hamada S. Longitudinal survey of the distribution of various serotypes of Streptococcus mutans in infants. J Clin Microbiol 1979;10:497�502.

Mazengo MC, Tenovuo J, Hausen H. Dental caries in relation to diet, saliva and cariogenic microorganisms in Tanzanians of selected age groups. Comm Dent Oral Epidemiol 1996;24:169�74.

Mohan A, Morse DE, O�Sullivan DM, Tinanoff N. The relationship between bottle usage/content, age, and number of teeth with mutans streptococci colonization in 6-24-month-old children. Comm Dent Oral Epidemiol 1998;26:12�20.

Nyvad B, Kilian M. Comparison of the initial streptococcal microflora on dental enamel in caries-active and in caries-inactive individuals. Caries Res 1990;24:267�72.

Orland FJ, Blayney JR, Harrison RW, et al. Use of the germfree animal technic in the study of experimental dental caries. I. Basic observations on rats reared free of all micro-organisms. J Dent Res 1955;50:259�72.

Rask PI, Emilson CG, Krasse B, Sundberg H. Effect of preventive measures in 50-60-year-olds with a high risk of dental caries. Scand J Dent Res 1988;96:500�4.

Ravald N, Hamp SE, Birkhed D. Long-term evaluation of root surface caries in periodontally treated patients. J Clin Periodontol 1986;13:758�67.

Redmo Emanuelsson IM, Wang XM. Demonstration of identical strains of mutans streptococci within Chinese families by genotyping. Eur J Oral Sci 1998;106:788�94.

Roeters FJ, van der Hoeven JS, Burgersdijk RC, Schaeken MJ. Lactobacilli, mutants streptococci and dental caries: a longitudinal study in 2-year-old children up to the age of 5 years. Caries Res 1995;29:272�9.

Russell JI, MacFarlane TW, Aitchison TC, Stephen KW, Burchell CK. Prediction of caries increment in Scottish adolescents. Comm Dent Oral Epidemiol 1991;19:74�7.

Scheinin A, Pienih�kkinen K, Tiekso J, Holmberg S, Fukuda M, Suzuki A. Multifactorial modeling for root caries prediction: 3-year follow-up results. Comm Dent Oral Epidemiol 1994;22:126�9.

Schroder U,Widenheim J, Peyron M, Hagg E. Prediction of caries in 1 1/2-year-old children. Swedish Dent J 1994;18:95�104.

Sigurjons H, Magnusdottir MO, Holbrook WP. Cariogenic bacteria in a longitudinal study of approximal caries. Caries Res 1995;29:42�5.

S�derling E, Isokangas P, Pienih�kkinen K, Tenovuo J. Influence of maternal xylitol consumption on acquisition of mutans streptococci by infants. J Dent Res 2000;79:882�7.

Staat RH, Gawronski TH, Cressey TE, Harris RS, Folke LEA. Effects of dietary sucrose levels on the quantity and microbial composition of human dental plaque. J Dent Res 1975;54:872�80.

Straetemans MM, van Loveren C, de Soet JJ, de Graaff J, ten Cate JM. Colonization with mutans streptococci and lactobacilli and the caries experience of children after the age of five. J Dent Res 1998;77:1851�5.

Sullivan �, Schroder U. Systematic analysis of gingival state and salivary variables as predictors of caries from 5 to 7 years of age. Scand J Dent Res 1989;97:25�32.

Tanzer JM, Freedman ML, Fitzgerald RJ, Larson RH. Altered virulence of mutants of Streptococcus mutans defective in polysaccharide synthesis. Infect Immun 1974;10:197�203.

Tanzer JM, Freedman ML, Fitzgerald RJ. Virulence of mutants defective in glucosyl transferase, dextran-mediated aggregation, or dextranase activity. In: Molecular Basis of Oral Microbial Adhesion. Mergenhagen S, Rosan B (eds). American Society for Microbiology 1985; 204�11.

Tanzer JM. On changing the cariogenic chemistry of coronal plaque. J Dent Res 1989;68(Spec Iss):1576�87.

Twetman S, Petersson LG. Prediction of caries in pre-school children in relation to fluoride exposure. Eur J Oral Sci 1996;104:523�8.

van Houte J, Gibbons RJ, Pulkkinen AJ. Ecology of human oral lactobacilli. Infect Immun 1972;6:723�9.

van Loveren C, Buijs JF, Bokhout B, Prahl-Andersen B, Ten Cate JM. Incidence of mutans streptococci and lactobacilli in oral cleft children wearing acrylic plates from shortly after birth. Oral Microbiol Immunol 1998;13:286�91.

Wilson RF, Ashley FP. Identification of caries risk in schoolchildren: salivary buffering capacity and bacterial counts, sugar intake and caries experience as predictors of 2-year and 3-year caries increment. Brit Dent J 1989;167:99�102.

Wood WA. Fermentation of carbohydrates and related compounds. In: The Bacteria. Gunsalus IC, Stanier RY (eds). Academic Press, 1961; p 59�149.

Zickert I, Emilson C-G, Krasse B. Correlation of level and duration of Streptococcus mutans infection with incidence of dental caries. Infect Immun 1983;39:982�5.

Abstracts Index