A comparison between different methods for prediction of caries activity B. KLOCK AND B. KRASSF Department ofCariology, University of Gothenburg, Gothenburg, Sweden

Klock, B. & Krasse, B.: A comparison between different methods for prediction of caries activity, Scand,J. Dent. Res. 1979: 87: 129-1S9. Abstract - The aim of the study was to find out if any of the following factors, alone or in combination, could be used for prediction of caries activity: salivarj' S. mulans, salivary lactobacilli, butler capacity, saliva secretion rate, salivary pH, the amount of plaque and the caries frequency. The patient material consisted of 300 children betvt^een 9 and 12 years old. The increment of caries after 1 and 2 years was compared widi all the above factors registered at baseline. Only the factors caries frequency and S. mutans showed a significant correlation to caries activity. In one of the tests the lactobacillus count approached significance. The combination of high numbers of incipient smooth surface lesions, S. mutans and lactobacilli gave a mean value of caries activity almost three times that of the whole group (8.4 versus 3,1). Keywords: dental caries; saliva; Streptococcus mutans. Bjorn Klock, Faculty of Odontology, Fack, S-400 33 Gothenburg, Sweden. Accepted for publication 19 October 1978.

Different microbial ,and salivary factors have been associated with the development of caries. The microbial factors which have been studied most are the numbers of Streptococcus mutans and lactobacilli (for reviews see 7, 21). The corresponding salivary factors are the secretion rate, the pH and the buffer capacity (for a review see 22). The amount of plaque has also been associated with the caries process (for a

review see 32). For selection of children at high risk for caries the previous history of caries (caries frequency) has been used (2,14). In the present study the increment of caries in schoolchildren has been correlated with the above factors and the aim of the investigation was to find out if any of the factors, alone or, in combination, registered once at the start of the study, was correlated to caries activity, i.e. the

KLOCK AND KRASSE

130

number of new carious lesions per unit time, and consequently could be used for prediction of the caries risk.

Material and methods In the autumn term of 1973, all 9-12-year-old children on the island of Tjorn, a communit)' outside Gothenburg, Sweden, were examined. The total number of children studied was 645. Some of the children received special preventive measures in addition to the ordinary preventive program used in the school dental ser\'ice. These measures included professional toothcleaning, dietarv and oral hygiene instruction, topical fluoride application and sealing of pits and fissures. The children were examined after 1 and 2 years with regard to caries activity (13). The 300 children belonging to the control groups constituted the patient material in the main part of the present study. Owing to occasional illness and removal Irom the community, the number of children remaining after 1 and 2 years was 279 and 271, respectively.

LABORATORY EXAMINATION During the autumn school term saliva samples were collected and the secretion rate, the pH and buffer capacity {final pH) (8) were detennined. In the same samples the number of S. mutatis and lactobacilli was counted. All details of the methods used have been given in an earlier paper (12).

CLINICAL EXAMINATION In January 1974 all the children were examined clinically and radiographically. The caries frequency, in terms of decayed and filled surfaces in the mixed and the permanent dentition [12), was recorded. The decayed surfaces were divided into incipient stnooth surface lesions and lesions with macroscopic delects. The incipient smooth surface lesions included visible decalcified spots of tbe enamel (caries without defect) and well-defined decalcified areas of the proximal surfaces not penetrating more than one-third of the enamel

in the radiograph, and which could not be verified as cavities on inspection by mirror and probe. The lesions with macroscopic defects included pit and fissure caries and defects of the enamel and dentin which did not show characteristics of hypoplasia or erosion (9). The amount of plaque (Pl I score) was recorded according to the method of SILNESS& LOE(30).

The various factors mentioned above, i.e. S. mutans and lactobacilli/ml saliva, buffer capacity (final pH) (8), saliva secretion rate, saliva pH, Pl I score and caries frequency, alone or in combination, were correlated to the caries activity in these children during the 1st and 2nd year. Statistical

methods

— The following

cor-

relations and analyses were performed betvveen the caries activity and the various factors investigated at the start of the study: 1] Correlation coefficient (r,^,^,) = cov (x, y) and

partial

correlations

according

to

MORRISON (25).

2) A non-parameiric partial correlation analysis was performed, in order to eliminate the effect of these factors one at a time, in the following way. The material was divided into groups according to the value of the factor in cjuesdon (23). Within each such group the correlation between the caries activity and another factor, significandy correlated to the caries activity, was determined by Pitman's test variable (3). The results from the different groups were then pooled to a summarizing test. 3) Student's i-test was applied to test the caries activity in the children on both sides of threshold values commonly used to select persons at high risk for caries and the (-test was also used to find out if preventive measures could reduce the caries activity significantly in children at high risk for caries.

Results The correlations between the various factors examined at the start of the study and the number of new carious lesions during the 1st and the 2nd year were weak

PREDICTION OF CARIES ACTIVITY

131

Table 1

2nd year. It should be stressed that the rvalues were very low but, owing to the large number of individuals, an r-value above +0.157 means a significant correlation (P 10^ Incipient smooth surface lesions > 11 (permanent dentition) 2. S. mutans > 10' Lactobacilli > 10* Incipient smooth surtace lesions > 11 (mixed dentition) 3. S. mutans > IO' Incipient smooth surface lesions > 11 (permanent dentition) 4. Incipient smooth surface lesions > 1 i (permanent dentition) 5. S. mutarii

No. of children

Carious lesions

10

8.4±3.3

13

6.9 ±4.2

22

5.6±3.9

53

5,2±3.7

5.1±3.0

> 10'

6. Incipient smooth surface lesions > 11 (mi\et3 dentition)

control groups are identical to the two t:op groups in Table 6, while the children in the four experimental groups originate from the 345 children given special preventive measures once or twice a montJi (13).

Discussion Of the different factors studied, the number of incipient smooth surface lesions showed the best correlation to

72

4,4-±S.7

caries activity. Notie of the salivarj' factors was correlated to the increment of caries but of the microbial factors the number of 5. mutans showed a significant correlation to the caries activity both years. For the number of lactobacilli and the plaque index score the difference between the groups approached the level of significance during the 2nd year. In other studies the clinical caries exatnination has been found to be a good predictor of caries activity (2,14) and the observed correlation between 5. mutans

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136

Table 7 Number of rum carious lesions during 2nd year of study in six groups. Four of them were given special preventive measures once or twice a month. Control groups (None) are identical with thefirstgroups in Table 6 Preventive measures

Combination lactors None (control) S. mutans > 10'^ 1 Lactobacilli > 10* Incipient smooth > surface lesions > 11 (permanent dent,) J 5. mutans > 10" 1 Lactobacilli > 10* i incipient smooth f surface lesions > 11 (mixed dent) J

' 8,4 3,4 10

•"•

s,d, n

"

s.d, n

'6.9 4,2 13

X

Twice a month

Once a month

1,9

"

"

0,6" 1,4 5

*

0,4^ 1,1 8

1,9 8

* ft* A

1,8 1,7 11

Student's i-test: "F

A comparison between different methods for prediction of caries activity.

A comparison between different methods for prediction of caries activity B. KLOCK AND B. KRASSF Department ofCariology, University of Gothenburg, Goth...
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