First Permanent Molar: First Indicator of Dental Caries Activity in Initial Mixed Dentition

Júlio Carlos NORONHA1
Maria de Lourdes de Andrade MASSARA1
Bernardo Quiroga SOUKI1
Andrea Paola de Assis NOGUEIRA2

1Departamento de Odontopediatria e Ortodontia, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil
2Dental Surgeon, Belo Horizonte, MG, Brasil

Braz Dent J (1999) 10(2): 99-104  ISSN 0103-6440

| Introduction | Material and Methods | Results | Discussion | Conclusion | Acknowledgments | References |

The objective of the present study was to investigate among children in the initial mixed dentition phase the presence of clinical signs that might eventually function as more sensitive indicators of the development of caries disease, denoted here as caries activity. On this basis, we investigated the relationship between salivary levels of mutans streptococci (MS) and decayed, missing and filled permanent and deciduous tooth surfaces (DMFS and dmfs) using microbiological, clinical and radiographic examinations in 81 schoolchildren aged 7-8 years. Whereas dmfs did not present a positive correlation, DMFS was significantly correlated with salivary MS levels. The first permanent molars of the schoolchildren studied comprised 87.3% of the affected surfaces recorded in the DMFS, suggesting that the development of new lesions was preferentially located on the surfaces of the first permanent molars. These results permit us to conclude that the first permanent molars function as first indicators of dental caries activity in the schoolchildren examined.

Key Words: first permanent molar, caries activity, mutans streptococci.


Human teeth and their surfaces present different degrees of susceptibility to dental caries disease. The frequency of involvement of dental surfaces by carious lesions varies with age range, with peaks of intensity occurring during certain stages of human life (Schlagenhauf and Rosendahl, 1990).
Side-by-side with the evaluation of patient risk to develop caries is the need for the earliest possible clinical identification of the beginning of caries activity. Clinically detectable caries activity represents the visible expression of a disequilibrium that has been affecting the patient as a whole for a certain period of time and is now locally manifested in his teeth. This caries activity, or the development of disease over time, involves two aspects, i.e., the beginning and the progression of the lesion. The beginning is quantitated on the basis of the number of new lesions occurring within a certain period of time and is expressed as incidence, whereas the progress of the disease must be recorded by measuring the size and extent of previously existing lesions (Von der Fehr, 1988). Thus, it seems to be of high clinical interest to locate the region of most common first appearance of carious lesions for each type of dentition. This region is assumed to be the one where the disease, initially showing no perceptible signs, first manifests its progression as the result of a disequilibrium suffered by the individual or as the result of an increase of a previously subclinical disequilibrium.
Mutans streptococci (MS) have been widely associated with the onset of dental caries (Hirose et al., 1993). Thus, the objective of the present study was to determine the existence of clinical signs that may eventually function as more sensitive indicators of the advance of carious activity among 7-8-year-old children of low socioeconomic-cultural level.

Material and Methods

We examined eighty-one 7-8-year-old children of low socioeconomic-cultural level regularly enrolled in the public school network or the periphery of Belo Horizonte, State of Minas Gerais, Brazil. The mothers of the children were interviewed in order to obtain information about the water supply used by the children (piped and fluoride-treated or not) and the use of medications that might interfere with the buccal microbiota.
The methodology used for clinical, microbiologic and radiographic examination was that described by Massara (1990). A previously trained examiner performed the microbiologic evaluation of saliva samples by the method of Kohler and Bratthall (1979), modified in terms of collection (unstimulated saliva) and culture medium (Schaeken et al., 1986). For clinical examination, the students were submitted to complete professional dental cleaning using appropriate brushing and flossing techniques. Each dental surface was dried and examined with the aid of artificial light, a buccal mirror and careful probing for fissure cleaning only. Bilateral interproximal dental radiographs were taken for each child and were evaluated by an examiner with no knowledge of the results of clinical examination, according to the following criteria: 1) intact surface: absence of a pathological radiolucent image in enamel and dentin; 2) lesioned surface: pathological radiolucent image reaching any depth of the enamel and/or dentin.
Data were first submitted to descriptive analysis by means of graphs, tables and correlation measurements and then analyzed statistically by the Mantel-Haenszel, chi-square and Kruskal-Wallis tests for comparison of salivary MS levels with the remaining variables (DMFS and dmfs indices). The level of significance was set at P<0.05.


The interviews with the childrenís mothers showed that all subjects used piped and fluoride-treated water in their homes. Only 3 children were taking antibiotics.
Only 30.9% of the children showed low MS levels (<20 colony forming units, CFU). Among the 69.1% with high MS levels (>20 CFU), 44.4% had salivary MS levels of 20-100 CFU (Table 1).
With respect to the total number of carious lesions (Figure 1), 70.4% of the children presented 1 to 7 surfaces affected by caries in permanent teeth, and 40.7% presented 8 to 17 affected surfaces in primary teeth. Only 2 children (2.5%) presented no carious or restored surfaces in their primary teeth, whereas 14 children (17.3%) presented no carious lesions in permanent teeth.
It should be pointed out that no child was free from caries. Only 11 children (13.6%) had access to dental treatment. None of the children showed loss of any permanent tooth or permanent teeth indicated for extraction.
To determine whether all other variables were related to the level of MS infection in primary or permanent teeth, we constructed dispersal diagrams that indicate the absence of a relation between any variable and the levels of MS infection.
Data analysis by the Kruskal-Wallis test showed a statistically significant relation between salivary MS levels and DMFS, but not between salivary MS levels and dmfs.


Salivary MS determination revealed that most of the 7-8-year-old children studied (69.1%) had more than 20 CFU as measured by the method employed (Table 1). Despite the relative paucity of information about the cariogenic buccal microbiota of the Brazilian population, especially among 7-8-year-old children, we observed that the present results agree with those reported in other studies (Hofling et al., 1986; Maltz et al., 1986; Buischi et al., 1989; Noronha et al., 1989).
Some investigators agree that quantitative differences exist in the incidence of MS among individuals of different age ranges (Bretz et al., 1990; Schlagenhauf and Rosendahl, 1990). The 7-8-year-old age range (initial mixed dentition) represents the period in which there is the highest probability of detecting elevated mean counts of these microorganims, especially compared to the age range of 9-12 years (Schlagenhauf and Rosendahl, 1990).
The present findings reveal a high percentage of affected individuals (Figure 1) similar to that reported by Bretz et al. (1990), since all schoolchildren had carious teeth. It should be pointed out that the objective of the present study was to determine the full prevalence of caries clinically expressed in the experimental group (lesioned surfaces), justifying the inclusion of lesions with and without cavitation (white spots) in the indices surveyed (DMFS and dmfs). DMFS, but not dmfs, was significantly correlated with salivary MS levels in the 7-8-year-old children of low socioeconomic-cultural level studied in the present investigation.
The prevalence of dental caries has been widely associated with MS levels (Bratthall, 1980; Alaluusua et al., 1989; Holbrook et al., 1989). However, the present results partially disagree with those obtained by these investigators since the dmfs variable was not significantly correlated with the MS levels detected whereas DMFS was significantly correlated with salivary MS levels (Kruskal-Wallis test), as also reported by Zickert et al. (1982) and Maltz et al. (1986).
At 7-8 years of age, only the permanent incisors and first molars are detected in addition to primary teeth. Among the permanent teeth affected by caries in the 81 schoolchildren studied, 87.3% corresponded to the first molars, which are known to be highly susceptible to caries attack. Thus, the present results suggest that the incidence of carious lesions in the first permanent molars may be related to the salivary MS levels.
It should be emphasized that Loesche and Straffon (1979) did not observe a relationship between total number of carious teeth and salivary MS levels but did observe a statistically significant correlation between DMFS index and salivary MS levels. The present results agree with this previous study, since no permanent tooth loss was observed in our study and therefore, the DMFS could be recorded as DFS. Thus, this index expressed the increase in carious disease that occurred in these patients.
Caufield et al. (1993) demonstrated the existence of an infectivity window, i.e., a period when the child is at higher risk to acquire MS, which is related to the presence of new dental surfaces in the buccal cavity, especially the first primary molars. In their study, Caufield et al. (1993) speculated about the possibility of the opening of a second window with the eruption of the first permanent teeth. This suggestion is further supported by the fact that the first permanent molars can express the development of caries disease with more sensitivity.
From the viewpoint of caries epidemiology, the eruption of the first permanent molar may be considered the most important event among children in the so-called group of initial mixed dentition (6-8 years) (Schlagenhauf and Rosendahl, 1990), since at this age the remaining permanent teeth are clearly less susceptible to the disease. In the present study, caries activity was mainly expressed by the incidence of carious lesions (incipient and cavitated) in the first permanent molars. The existence of this more sensitive indicator in this age range offers the possibility of a more rational orientation of preventive procedures such as professional and home dental cleaning, especially for teeth that have not yet reached the occlusal line (Carvalho et al., 1991). Thus, it is necessary to teach parents and children to brush their teeth with special attention to the more vulnerable surfaces.
The fact that the first permanent molar expresses the advance of caries with higher sensitivity also indicates that a tool for the measurement of the general perversity of the environment is available for this age range. This more fragile link in the chain of resistance to the development of caries disease may serve not only as a simple alert to the fact that only one tooth should be protected (with a dental sealant), but also as a warning that all the parameters that modulate the caries process are beginning to act in union and to overcome host resistance. Thus, it is imperative to increase the number of recall visits to the dentistís office in order to avoid the perpetuation of the disequilibrium (Noronha et al., 1994), which is clinically expressed as caries activity, i.e., the development of caries disease in the patient.


The first permanent molars can function as the first indicators of dental caries activity during the phase of initial mixed dentition.
Clinical control of the events occurring in the more vulnerable teeth may represent an important tool in programs of preventive maintenance, when a constant monitoring of the health-illness process in the patient is imperative.


The authors are grateful to Profs. Maria Auxiliadora Roque de Carvalho (UFMG), Isabel Yoko Ito (USP), Wagner Segura Marcenes (University College of London) and Fernando Borba de Araújo (UFRS) for valuable criticisms and suggestions. Research supported by Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), Brazil.


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Correspondence: Prof. Júlio Carlos Noronha, R. Manaus, 745, Santa Efigência, 30150-350 Belo Horizonte, MG, Brasil. Fax: +55-31-281-1681. E-mail:

Accepted May 25, 1999
Eletronic publication: April, 2000