The More Sm More Caries

The More Streptococcus mutans, the More Caries on Approximal Surfaces K.

KRISTOFFERSSONI, H.-G. GRONDAHL2, and

D.

BRATTHALLI *

lDepartment of Cariology, University of Lund, Malmd, Sweden; and 2Department of Oral Radiology, University of Gothenburg, Gothenburg, Sweden The relationship between the presence of Streptococcus mutans and caries on approximal tooth surfaces was studied in a group of 28 children who were 13 years old at baseline. 700 surfaces in the pre-molar and molar regions were studied. Sampling of S. mutans was performed with a toothpick method at the beginning of the study and after one and two years. From bite-wing radiographs, the approximal surfaces were recorded as caries-free, decayed, or restored. Progression of lesions during the two years was also studied. More new caries lesions and progressive caries lesions were found on surfaces positive for S. mutans than on surfaces without, and the more S. mutans, the more lesions. 52% of the surfaces with positive S. mutans findings at all three sampling occasions became various or had caries in a progressive form. Among the surfaces with no detectable S. mutans, the corresponding figure was 8%o. 80 out of the 530 surfaces diagnosed as intact at the start of the study became various over the two-year period. 69 of these were S. mutanspositive at the first and/or second sampling.

J Dent Res 64(1):58-61, January, 1985

Introduction. We have based the present study on the following facts: First, the number of longitudinal studies relating S. mutans to caries in humans is sparse, and the results are conflicting (Bowden et al., 1976; Burt et al., 1983; Gibbons et al., 1974; Ikeda et al., 1973; Kbhler et al., 1981; Loesche and Straffon, 1979; Mikkelsen and Poulsen, 1976). Second, the development of a system to monitor the initiation and progression of caries on approximal tooth surfaces by radiographs (Grdndahl et al., 1977; Pitts, 1983) allows for a much more detailed analysis of etiological factors than was possible in earlier studies. Third, the development of a simplified method for the determination and quantification of S. mutans on approximal surfaces (Keene et al., 1981; Kristoffersson and Bratthall, 1982) has made it possible to include a high number of surfaces in studies - a fact of special importance in areas with a declining caries incidence. The specific aims of our two-year study were: (1) to study whether approximal surfaces colonized with S. mutans showed differences in the initiation and progression of caries as compared with non-colonized surfaces; and (2) to study whether the amount of S. mutans on a specific surface was of importance for caries development.

Materials and methods. Twenty-eight children, 13 years of age at the start of the study, participated. They all attended the same school in Malmb, Sweden. The study spanned two years and included three sampling occasions at one-year intervals. During the study, the children took part in the routine dental care program, based on a yearly check-up by the local dentist. It was recommended that they use a fluoridated dentifrice, and the water in the region contained 0.1 ppm F. Received for publication July 30, 1984 Accepted for publication October 22, 1984 This investigation was supported by the Swedish Medical Research Council, Project No. 5999. *Mailing address: Department of Cariology, School of Dentistry, Carl Gustavs Vdg 34, S-214 21 Malmb, Sweden 58

Radiographic examination. -Bitewing radiographs, one on each side, were obtained at the baseline registration and again after 12 and 24 months. A specially made device was used to assure geometric reproducibility. It consisted of a collimating cylinder replacing the ordinary aiming device of the X-ray machine. A rod was firmly attached to the cylinder, and at the other end of the rod a removable filmholder was placed. The holder was fitted with a perpendicularly positioned, perforated flap. A piece of wax1 was placed on both sides of the flap, permitting an occlusal registration of the teeth of both jaws. The same X-ray machine (Oralix 65, Philips), operating at 65 kVp, was used at all examinations, and the films (Kodak Ektaspeed®§> ) were processed in an automatic developing machine. The same examiner read the radiographs from each examination without access to the results of the bacteriologic examinations. The approximal surfaces of the pre-molars and the molars and the distal surfaces of the cuspids were scored according to the following system (Grdndahl et al., 1977): 0 = radiographically sound 1 = radiolucency in the outer half of the enamel 2 = radiolucency in the inner half of the enamel 3 = radiolucency in the outer half of the dentin or at the enamel-dentinal junction 4 = radiolucency in the inner half of the dentin 5 = restored surface 6 = restoration with adjacent caries 7 = unreadable New lesions were noted for surfaces that increased from score 0 to scores of 1, 2, 3, 4, 5, or 6. A surface that decreased to score 0 from one of the caries scores kept the higher score throughout -that is, so-called "reversals" were not considered. Progression of a lesion was noted when a surface with a caries score at the first examination received a higher caries score at a later examination. A surface that showed transitions between scores after being scored 0 at a preceding examination was considered only as having received a new lesion and not as progression as well. 133 surfaces were unreadable either because of overlapping, or because they did not appear in the radiographs. These surfaces were excluded in the analysis of the results. Four restored surfaces that became carious (score 6) were also excluded, as were an additional four that went from score 3 to 5 without progression being observed. Sampling of S. mutans. -The approximal surfaces from the mesial surface of the second molar to the distal surface of the canine (= max 32 surfaces per child) were examined using a method described by Kristoffersson and Bratthall (1982): A triangular wooden toothpick was inserted into the interproximal space. Both sides of the toothpick were then immediately pressed against the surface of an MSB agar plate, selective for S. mutans (Gold et al., 1973). After two days of incubation (95% N2, 5% CO2 in 370 C), the colony-forming units (CFU), representing the mesial and distal surfaces of each interproximal space, were counted. 1 Alminax

Wax, Associated Dental Products, Ltd., Great Britain

S. MUTANS AND CARIES

Vol. 64 No. I

Results. Fig. 1 depicts, for each subject, the number of approximal surfaces with no detectable S. mutans and the number of surfaces on which S. mutans was found on at least one sampling. A total of 431 surfaces was positive for S. mutans at least once, while 244 were negative at all three samplings. Fig. 1 also shows the distribution of new and progressive caries lesions among the individuals, related to presence or absence of S. mutans. In two of the children, no new caries or progression of caries was registered during the two-year period. Most of the surfaces (88%), with new or progressive caries, had at least one positive S. mutans sample. The children had, on the average, 5.3 surfaces that progressed or became carious, the median value being 3. Fig. 2 demonstrates the distribution of different diagnoses among approximal surfaces varying with regard to the number of sampling occasions at which S. mutans was found. Of the surfaces with no detectable S. mutans at any of the sampling occasions (M-), 83% remained intact. Among the surfaces harboring S. mutans on all three sampling occasions (M+++), only 35% remained caries-free. Approximately half of the surfaces in the latter group became carious or showed progression of earlier established lesions. In the group of surfaces with no detectable S. mutans, the corresponding value was 8%. In Fig. 3, the surfaces are grouped according to diagnosis. For each diagnosis, the distribution of surfaces with regard to findings of S. mutans appears. Almost half of the surfaces (46%) that remained intact throughout the study period did not show detectable S. mutans at any of the samplings. On the other hand, approximately 90% of the surfaces developing new lesions and surfaces showing progression of caries harbored S. mutans on at least one sampling occasion. In these groups, the percentage of surfaces with S. mutans in all samplings was considerably higher (average, 30%) than in the group of intact surfaces

(8%).

Fig. 4 demonstrates that, with increasing numbers of

S. mutans CFU at the first and/or second sampling, the relative number of approximal surfaces that developed new caries lesions increased. Among the surfaces with no detectable S. mutans, 4% became carious, as opposed to almost 60% of the surfaces with > 75 CFU. Concerning S. mutans and progression of caries, the results show that 40% of the surfaces with no detectable S. mutans at the first and/or second sampling, and with caries at baseline (n=37), progressed. 70% of the surfaces that were carious at baseline and showing > 75 CFU S. mutans at one or both of the two first samplings (n=23) progressed. Of the 530 surfaces diagnosed as intact at the start of the study, 283 were positive and 247 negative for S. mutans. 80 of these 530 surfaces became carious over the twoyear period. Of these, 69 were S. mutans-positive at the first and/or second sampling. Of the remaining 11 surfaces, two became positive for S. mutans at the third sampling.

Discussion. Our results support the opinion expressed by, among that S. mutans is a others, Hamada and Slade (1980) micro-organism associated with the development of caries. Of the 97 surfaces which were positive for S. mutans at all sampling occasions, seven were restored. Of the remaining 90 surfaces, 52% showed either initiation of new caries or progression of caries during a two-year period. Of the 247 surfaces negative for S. mutans, the corresponding value was only 8%. Furthermore, the degree of colonization on each surface was of importance for development of caries. The risk for new caries lesions was more than four times higher when > 75 colonies were present, as compared with only 1-5 colonies. A similar role for S. mutans in fissure caries has been described by Loesche and Straffon (1979). In some recent studies, salivary numbers of S. mutans have been used as a diagnostic aid to select patients at risk of caries (Klock and Krasse, 1979; Kdhler et al., 1983; Zickert et al., 1982). Since S. mutans is known to colonize

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Fig. I1 The approximal surfaces for each individual presented as either S. mutans-negative or S. mutans-positive (at one or more sampling occasions). Surfaces with new, or progressive, caries during the course of study indicated. Filled surfaces at baseline excluded.

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Fig. 2 The distribution of different diaginoses of surfaces with different numbers of positive S. mutans samp]les. The surfaces were divided into the following groups: filled - suIfaces with a filling at baseline and no caries during the study; caries - surfaces with caries at baseline and with no progression during t-he study; progressive caries - surfaces with caries at baseline whici h showed progression during the study; new caries - surfaces whichwere intact at baseline but became carious during the study; and intaact -surfaces with no lesion or filling throughout the study. M-: S. mutans never detected. M+: S. mutans detected at one of thte samplings. M++: S. mutans detected at two of the samplings. bM+++: S. mutans detected at all three samplings. -

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Another explanation is that some caries lesions could have been caused by other bacteria with a cariogenic potential. A high number of intact surfaces without S. mutans 236 = 96%) remained free from new caries lesions. This 247

means that the predictive value of the absence of S. mutans is high. The predictive value when S. mutans is present, expressed as the relative number of surfaces with S. mutans that developed new caries lesions ( 69 = 24%), is much lower. However, the difference in risk suggests that S. mutans is a suitable target micro-organism for caries prophylactic measures. The results of this study were obtained in a population with a declining caries incidence. In the future, we think it would be interesting to obtain corresponding data of the relationship between S. mutans and caries in populations with different propensities for caries.

Acknowledgments.

50

We thank Miss Elisabet Hansson for technical assistance. REFERENCES

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the teeth in a localized way (Edman e t al., 1975; Duchin and van Houte, 1975), we also wainted to determine whether site-specific evaluations had a prognostic value. Fig. 1 shows that the number of sites Nwith S. mutants and the number of sites with developing carn were well spread among the 28 individuals. Some surfai:es became various without any observed history of S. mattans. One explanation could be that the sampling methodd was too crude or that the samplings were performed withl too-long intervals.

ces

BOWDEN, G.H.; HARDIE, J.M.; McKEE, A.S.; MARSH, P.D.; FILLERY, E.D.; and SLACK, G.L. (1976): The Microflora Associated with Developing Carious Lesions of the Distal Surfaces on the Upper First Premolars in 13-14-Year-Old Children. In: Microbial Aspects of Dental Caries, Stiles, H.M., Loesche, W.J., and O'Brien, W.J., Eds. Spec. Supply, Microbiol Abstr, pp. 223-241. BURT, B.A.; LOESCHE, W.J.; EKLUND, S.A.; and EARNEST, R.W. (1983): Stability of Streptococcus mutans and Its Relationship to Caries in a Child Population over 2 Years, Caries Res 17:532-542. DUCHIN, S. and VAN HOUTE, J. (1978): Relationship of Streptococcus mutans and Lactobacilli to Incipient Smooth Surface Dental Caries in Man, Arch Oral Biol 23:779-786. D.C.; KEENE, H.J.; SHKLAIR, I.L.; and HOERMAN, EDMAN, K.C. (1975): Dental Floss for Implantation and Sampling of Streptococcus mutans from Approximal Surfaces of Human

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(1974): Interdental Localization of Streptococcus mutans as Related to Dental Caries Experience, Infect Immun 9:481-488.

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Reduction of Streptococcus mutans Interdentally by Chlorhexidine Gel, Scand J Dent Res 90:417-422. KOHLER, B.; PETTERSSON, B.M.; and BRATTHALL, D. (1981): Streptococcus mutans in Plaque and Saliva and the Development of Caries, Scand JDent Res 89:19-25. KOHLER, B.; BRATTHALL, D.; and KRASSE, B. (1983): Preventive Measures in Mothers Influence the Establishment of Streptococcus mutans in Their Infants, Arch Oral Biol 28:225-231. LOESCHE, W.J. and STRAFFON, L.H. (1979): Longitudinal Investigation of the Role of Streptococcus mutans in Human Fissure Decay, Infect Immun 26:498-507. MIKKELSEN, L. and POULSEN, S. (1976): Microbiological Studies on Plaque in Relation to Development of Dental Caries in Man, Caries Res 10:178-188. PITTS, N.B. (1983): Monitoring of Caries Progression in Permanent and Primary Posterior Approximal Enamel by Bitewing Radiography. A Review, Community Dent Oral Epidemiol 11:228235. ZICKERT, I.; EMILSON, C.G.; and KRASSE, B. (1982): Effect on Caries Activity in 13-14-Year-Old Swedish Children of Measures Against Streptococcus mutans, Arch Oral Biol 27:861-868.