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Dental Caries Experience: A Two-generation Study1 Faculty of Dentistry, McGill University, 3640 University Street, Montreal, Quebec, Canada H2A 3B2; and 2 Faculty of Medicine, Université de Montréal, Montreal, Canada; Correspondence: * corresponding author, christophe.bedos{at}mcgill.ca
The life-course framework stresses the importance of social, psychosocial, and biological factors in early life on the development of later disease. From this perspective, the association between edentulousness of mothers and their children’s caries risk has not been studied. Therefore, a sample of 6303 mother-child pairs was randomly selected in Quebec (Canada). Mothers (6039 dentate and 264 edentulous) completed a self-administered questionnaire, and their children, aged 5 to 9 years, were clinically examined. Bivariate analyses and multiple logistic regressions showed that edentulous mothers’ children are more likely to experience caries on both primary [OR = 1.7 (1.3–2.3)] and permanent [OR = 1.4 (1.0–2.0)] dentitions when compared with dentate mothers’ children. These results are independent of socio-economic status, age, gender, and children’s oral-health-related behaviors. Our study is the first to show that edentulous mothers’ children constitute a group at risk of caries. It also highlights the need for a better understanding of the mother-child transmission of risk.
Key Words: life-course • epidemiology • caries • edentulism • mother-child.
In recent decades, public health research has increased its focus on the social determinants of health and illness. This has led to the emergence of theoretical approaches stressing the social context and its interaction with biological and psychological factors (Watt, 2002). The life-course framework is one of these new approaches. It points out the importance of early life for adult disease through a ‘programming during critical periods of development’ or an ‘accumulation of risk through the life course’ (Kuh and Ben-Shlomo, 1997). It provides insights into the effects of various adverse environments or psychosocial stresses associated with socio-economic position that vary by the time and duration of exposure. Recent evidence from the life-course framework has suggested that exposure to adverse environments during the life-course contributes additively to caries and periodontal health. In a New Zealand Birth Cohort, all measures of dental health, caries, oral hygiene, bleeding, and loss of periodontal attachment at age 26 showed a graded relation with childhood socio-economic status (Poulton et al., 2002; Thomson et al., 2004). Similarly, a cross-sectional study that collected information retrospectively found that 13-year-olds whose families experienced material deprivation had high levels of caries (Nicolau et al., 2003a) and gingivitis (Nicolau et al., 2003b). It is thus relevant that we consider parent-related factors and the influence of the latter on their children’s oral health. Chen (1986) observed a strong relationship between mothers’ preventive behaviors and those of their children, suggesting a modeling effect. More recently, researchers identified an association among mothers’ toothbrushing regularity (Mattila et al., 2000), mothers’ gingival condition (Sasahara et al., 1998), and their children’s experience of caries. As well, several studies reported a correlation between parents’ and children’s experiences of caries, with Ringelberg showing higher mother-child than father-child correlations (Ringelberg et al., 1974; Garn et al., 1976; Grytten et al., 1988). However, the association between mothers’ edentulousness and their children’s caries risk does not seem to have been explored previously. In the province of Quebec, Canada, the life-course framework raised concern about the influence that edentulous parents may have on their children’s caries experience. Indeed, caries (Brodeur et al., 2000) and edentulism (Brodeur et al., 1995) have long been public health problems in Quebec: In 1993, for instance, 14% of adults in the 35- to 44-year age group had already lost all their teeth. Since edentulous adults might have multiple risk factors, whether determinants or consequences of edentulism, we raised the hypothesis that edentulous mothers’ children might be at high risk of caries. Since this association has not been shown previously, we set out to compare the dental status of children whose mothers were edentulous with that of children whose mothers were fully or partially dentate.
Sample The sample comes from the Study on the Oral Health of Quebec Students Aged 5–6 and 7–8 Years, 1998–99. The main goal of this cross-sectional study, co-directed by the Université de Montréal and the Montréal-Centre Public Health Department, was to draw a portrait of the oral health status of Kindergarten and Grade 2 schoolchildren in the province of Quebec. We randomly selected 9930 children aged 5 to 8 from a list provided by the board of education. This procedure was stratified by region, residence area, and socio-economic status of the residence area. Each family received one questionnaire, and the parents decided who would answer it. They were also asked to send the completed questionnaire to their child’s school. Among the 8430 parents who returned their completed questionnaire (85%), the vast majority agreed to have their child examined, so we obtained 7382 parent-child pairs. Mothers completed 87% of the questionnaires; we excluded other respondents, such as fathers and spouses. The final sample was thus composed of 6303 mother-child couples. Of the 6303 mothers, 264 (4.2%) were edentulous.
Data Collection The children were interviewed and clinically examined in their school by research teams composed of a public health dentist and a dental hygienist. Each dental team followed the same procedure. Every child selected was greeted in an empty classroom during class time and was first asked his/her name and then a few questions regarding his/her dental health-related behaviors: "Did you brush your teeth yesterday?" In the case of a positive answer, the interviewer then asked: "How many times?" The interview continued: "Did you snack yesterday before going to bed?" If the answer was "yes", the interviewer asked the child to describe the snack. To determine whether the snack was cariogenic, the interviewer had a list of cariogenic foods that included sodas, treats, etc. The team then conducted an ADA type 3 examination (lamp, mouth mirror, explorer; no x-ray) to record a DMF index on permanent and primary teeth. The child was asked to lie on a portable dental chair while the dentist recorded the indices and the hygienist collected the data. Prior to data collection, the 13 dentists in charge of the clinical examinations throughout Quebec participated in a three-day-long calibration session in Montreal. For the measurement of dmfs and DMFS indices—which record experience of caries on primary and permanent teeth, respectively—the percentage of agreement between the examiners and the gold standard examiner was between 83% and 100%, the intraclass correlation coefficient was between 93% and 100%, and the kappa statistics were between 92% and 98%.
Statistical Analyses
The two groups studied differed slightly, since edentulous mothers tended to be older, and had incomes and education levels lower than those of dentate mothers (Table 1  ). They also differed in terms of children’s age: The proportion of 7- and 8-year-old children was higher in the edentulous mothers group than in the dentate mothers group.
On primary teeth, children of edentulous mothers experienced significantly more caries than did dentate mothers’ children (Table 2 ): The percentage of caries-free children was lower in the edentulous group, and the mean dmfs was higher. On permanent teeth (Table 3), although there was no significant difference between the two groups at age six, we observed the same pattern as on primary teeth at ages seven and eight. At age eight, for instance, 62.4% of children were caries-free on permanent teeth in the edentulous mothers group vs. 74.2% in the dentate mothers group (p = 0.01).
The multiple logistic regression analyses showed that, when adjusted for social, demographic, and children’s oral-health-related behavior variables, the association between mothers’ dental status and their children’s experience of caries was maintained. On primary teeth (Table 4 ), edentulous mothers’ children were 1.7 times more likely to experience caries, regardless of adjustment for children’s oral-health-related behavior variables (steps 2, 3). On permanent teeth, the OR was 1.4 in both cases.
To our knowledge, our study is the first to show that edentulous mothers’ children have more caries than do dentate mothers’ children. This occurs on primary as well as on permanent teeth, even when adjusted for important determinants such as socio-economic status, age, gender, and children’s dental-care-related behaviors. Several limitations of our study, however, must be taken into consideration. We did not have information on the mothers’ "tooth loss pathway" and thus did not take into account the process by which they lost their teeth, and the time since they became toothless. Regarding the tooth loss process, Burt and Eklund (1999) reported, in an extensive literature review, that caries is generally the main cause of edentulism before 50 years of age. We believe that periodontal disease did not contribute significantly to edentulism in our sample, because of the relatively young age of the mothers and the very high prevalence of caries in Quebec (Brodeur et al., 2000). The fact that we lacked information on the fathers’ dental status was another limitation, even though researchers (Ringelberg et al., 1974; Garn et al., 1976) have shown that mother-child correlations are higher than father-child correlations in terms of DMF indices. Finally, we lacked complete information on children’s fluoride exposure; however, since water fluoridation is the exception in Quebec, toothpaste is the main source of fluoride, and we took it into account in our models through the "toothbrushing" variable. Although our data provided limited information on the processes that could lead the children of edentulous mothers to be more susceptible to caries, it is important to discuss, from a life-course perspective, biological/genetic and behavioral/lifestyle hypotheses that could explain our results. A first hypothesis is the mother-child transmission of genetic factors. Indeed, studies conducted on twins raised apart strongly suggest a genetic contribution to the incidence of caries (Boraas et al., 1988; Conry et al., 1993). A systematic review of the literature (Shuler, 2001) reported evidence that this genetic contribution was related to the structure of dental enamel and the immunologic response to cariogenic bacteria. Caries susceptibility could also be related to salivary characteristics, such as flow rate and buffering capacity (Leone and Oppenheim, 2001). Little is known, however, about the host genetic factors that may influence caries susceptibility. Another biological hypothesis is related to fetal growth. Barker and his colleagues (Barker, 1992) hypothesized that chronic disease could be "biologically programmed" in utero or early infancy. According to them, a stimulus such as impaired maternal nutrition could have lasting effects on the structure or function of organs. Numerous studies (Sheiham et al., 2001; Allen and McMillan, 2002) have showed that edentulism is associated with poor diet: Edentulous people tend to consume fewer vegetables and less dietary fiber (Joshipura et al., 1996; Nowjack-Raymer and Sheiham, 2003) but more sweet snacks (Johansson et al., 1994) than those with natural teeth. It is thus possible that impaired maternal nutrition may have an effect on fetal growth and birthweight and, subsequently, on caries susceptibility. On this subject, however, research remains inconclusive: Low birthweight was recently associated with DMF-T at adolescence (Nicolau et al., 2003a), whereas a previous systematic review found no relationship between low birthweight and subsequent caries (Burt and Pai, 2001). The behavioral/lifestyle hypotheses also need to be examined, even though, in the regression models, we controlled for 3 child-related behavioral variables: snacking at night, toothbrushing, and visiting the dentist. These indicators, indeed, are limited and cannot fully account for the complex behaviors related to oral health and disease. As a consequence, we believe that behavioral/lifestyle pathways should be explored. One hypothesis is that nutritional habits and taste are transmitted from mother to child. Whether it is the result of preferences for certain types of food or the consequence of impaired masticatory function related to edentulism, the edentulous mothers’ diet might have a negative influence on their children’s diet. For instance, it has been reported that children’s intakes of snack food are correlated with that of their mothers (Longbottom et al., 2002), and that mothers tend not to offer their children food they themselves dislike (Skinner et al., 2002). In terms of preventive behaviors, a strong relationship between children’s preventive dental behaviors (brushing, flossing, preventive visits to the dentist) and those of their mothers has been described (Chen, 1986). It has also been shown that parents’ oral health behavior can affect not only their children’s oral health behavior, but also their gingival and dental health (Okada et al., 2002). Relying upon Bandura’s social learning theory, Chen (1986) suggested that children may acquire their dental behaviors by direct observation and modeling of their mothers’ behaviors. From a life-course perspective, we could hypothesize that children of edentulous mothers inherit a low "behavioral capital", defined by Schooling and Kuh (2002) as "the accumulation of positive individual attributes" that could "affect educational aspirations" as well as "the choice of health behaviours. In conclusion, our study revealed that edentulous mothers’ children constitute a group at risk of caries in Quebec. They experience more caries than do dentate mothers’ children, and these differences appear early in life. Although we do not know if these differences continue into adolescence and into adulthood, this is likely, when one considers that inequalities in oral health tend to persist from infancy to adulthood. A life-course perspective suggests that both edentulous mothers and their young children constitute a target for oral health promotion programs that aim to prevent current and future caries in these children. This study also highlights the need for research to improve our understanding of the etiology of caries and the complex biological and behavioral pathways related to the mother-child transmission of risk.
This study was supported by grants from the Ministère de la Santé et des Services Sociaux du Québec, the Canadian Institutes of Health Research (CIHR), and the Fonds de Recherche en Santé du Québec (FRSQ). The authors also thank Drs. Marie Olivier, Mike Benigeri, and Alissa Levine for their contributions, as well as Ms. Elke Love. Received for publication October 19, 2004. Revision received May 19, 2005. Accepted for publication July 11, 2005.
Journal of Dental Research, Vol. 84, No. 10,
931-936 (2005) This article has been cited by other articles:
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ABSTRACT
INTRODUCTION
