Analytic approaches to longitudinal caries data in adults

Predictors of tooth loss in Brazilian older adults: An 8-year follow-up

OBJECTIVE

To investigate the risk factors for tooth loss after 8 years among community-dwelling older adults in a southern Brazilian city.

METHODS

In 2004, 388 dentate community-dwelling older adults from Carlos Barbosa, southern Brazil, were selected using simple random sampling. In 2012, the follow-up consisted of 199 (51.3%) participants. Data collection comprised an interview with data about socio-demographic, behavioural and access to services and an oral examination. The outcome variable of this study is the ratio between the sum of the teeth lost during the 8-year period of follow-up, and the sum of the teeth present in 2004, per person, modelled through binomial regression analysis.

RESULTS

Being older (IOR = 1.03, 95% CI: 1.00-1.06), living in a rural area (IOR = 1.56, 95% CI: 1.17-2.07), earning two or more monthly minimum wages (IOR = 1.46, 95% CI: 1.09-1.96), living alone (single, widowed or divorced; IOR = 1.36, 95% CI: 1.00-1.85), having more gingival bleeding sites (IOR = 1.01, 95% CI: 1.00-1.02) and wearing partial removable prosthesis (IOR = 2.82, 95% CI: 2.15-3.71) were risk factors for tooth loss. Approximately 48% of the participants lost one or more teeth over the 8-year follow-up period.

CONCLUSION

Socio-demographic, economic and clinical variables were associated with the risk for tooth loss. This might be a result of social determinants of health influencing people's access to oral health care, oral health behaviours and oral health status. Public policy aimed at older adults living in rural areas, living alone and using removable dentures may contribute to reducing the risk of tooth loss.

Efficiency Issues among Statistical Methods for Demonstrating Efficacy of Caries Prevention

Although repeated tooth-surface-specific information is commonly collected during a longitudinal caries clinical trial, traditional methods often make limited use of the repeated measures. Newer methods of analysis, such as methods based on time-to-event and methods for longitudinal or clustered data, have the potential to increase the efficiency of the statistical analysis. We compare a range of analytical methods from the traditional analysis based only on the number of caries onsets to newer methods that incorporate time at risk and surface-specific information, such as Poisson regression methods for clustered data, with respect to the efficiency of treatment comparisons. Under most circumstances, the greatest gain in efficiency associated with time-to-event methods will be due to the ability of subjects to contribute caries onsets to the analysis until they are lost from the study. Incorporating the number of surfaces at risk, the surface time at risk, and surface-specific characteristics will typically produce only a modest gain in efficiency.

The Role of Risk Factors in the Identification of Appropriate Subjects for Caries Clinical Trials: Design Considerations

In seeking new and more effective therapies to delay or prevent caries development, investigators must design clinical trials focused on high-risk populations with a predictable incidence of caries over a limited period of time. In children and adolescents, the strongest predictors of caries incidence appear to be baseline levels of caries activity (present caries, e.g., dmfs, DMFT, caries lesions in first molars). Other predictors of caries risk typically include oral hygiene level, counts of cariogenic micro-organisms in plaque and saliva, fluoride history, sucrose intake, and parent's socio-economic level. This paper will briefly review existing literature to address the most useful and relevant prognostic factors for predicting future caries onset. The relative merits of identifying high-risk subjects based on these factors, either singly or in combination, will be explored in terms of statistical efficiency. Particular attention will focus on the advantages of covariate adjustment in the context of survival-based methods for the analysis of caries data. Further, with the advent of more sophisticated diagnostic procedures ( e.g., quantitative light fluorescence) to screen and monitor study subjects for caries activity, there is the potential for earlier states of lesion initiation and progression (or regression) to be detected, with, therefore, improved experimental sensitivity to treatment effects. The validity of risk assessment and outcome measurement on the basis of these new diagnostic tools vs. more conventional methods will be examined.

Effect of Fluoridated Sealants on Adjacent Tooth Surfaces: A 30-mo Randomized Clinical Trial

A double-blind randomized clinical trial was performed in 6- to 7-yr-old schoolchildren to evaluate, in a 30-mo period, whether the caries increment on the distal surface of the second primary molars adjacent to permanent first molars sealed with fluoride release compounds would be lower with respect to those adjacent to permanent first molars sealed with a nonfluoridated sealant. In sum, 2,776 subjects were enrolled and randomly divided into 3 groups receiving sealants on sound first molars: high-viscosity glass ionomer cement (GIC group); resin-based sealant with fluoride (fluoride-RB group); and a resin-based sealant without fluoride (RB group). Caries (D1 - D3 level) was recorded on the distal surface of the second primary molar, considered the unit of analysis including only sound surfaces at the baseline. At baseline, no differences in caries prevalence were recorded in the 3 groups regarding the considered surfaces. At follow-up, the prevalence of an affected unit of analysis was statistically lower (p = .03) in the GIC and fluoride-RB groups (p = .04). In the GIC group, fewer new caries were observed in the unit of analysis respect to the other 2 groups. Incidence rate ratios (IRRs) were 0.70 (95% confidence interval: 0.50, 0.86; p < .01) for GIC vs. RB and 0.79 (95% confidence interval: 0.67, 0.89; p = .005) for fluoride-RB vs. RB [Corrected]. Caries incidence was significantly associated with low socioeconomic status (IRR = 1.18; 95% confidence interval: 1.10, 1.42; p = .05). Dental sealant high-viscosity GIC and fluoride-RB demonstrated protection against dental caries, and there was evidence that these materials afforded additional protection for the tooth nearest to the sealed tooth (clinical trial registration NCT01588210).

Racial disparities in trajectories of dental caries experience

OBJECTIVES

This study charted the trajectories of dental caries, including decayed teeth, missing teeth and filled teeth among older Americans over a 5-year period. In particular, it focused on racial differences in the levels of and rates of change in dental caries experience.

METHODS

Data came from the Piedmont Dental Study. The sample included 810 older Americans who were dentate at the baseline with up to 4 repeated observations between 1988 and 1994. Hierarchical linear models were employed in depicting intrapersonal and interpersonal differences in dental caries experience.

RESULTS

Different measures of caries outcomes exhibited distinct trajectories. On average, the number of decayed teeth decreased over time, whereas missing teeth increased. In contrast, the number of filled teeth remained stable during a 5-year period. Relative to their white counterparts, older black Americans had more decayed teeth and missing teeth but fewer filled teeth. Blacks and whites differed in the levels of dental caries but not in their rates of change except for missing teeth. Even when demographic and socioeconomic attributes were adjusted, racial variations in dental caries experience remained significant.

CONCLUSIONS

Although significantly correlated, various dental caries outcomes move along different paths over time. In view of the persistent racial disparities in dental caries trajectories, future interventions to minimize such variations among older Americans in the levels of and the rates of change in dental caries experience are clearly warranted.

Assessment of dental caries predictors in 6-year-old school children - results from 5-year retrospective cohort study

Background

This was a retrospective cohort study undertaken to assess the rate and pattern of dental caries development in 6-year-old school children followed-up for a period of 5 years, and to identify baseline risk factors that were associated with 5 years caries experience in Malaysian children.

Methods

This 5-years retrospective cohort study comprised primary school children initially aged 6 years in 2004. Caries experience of each child was recorded annually using World Health Organization criteria. The rates of dental caries were recorded in prevalence and incidence density of carious lesions from baseline to final examination. Risk assessment was done to assess relative risk for caries after 5 years in children with baseline caries status. Simple and multiple logistic regression analysis were performed to identify significant independent risk factors for caries.

Results

The sample consisted of 1830 school children. All components of DMFT showed significant differences between baseline and final examination. Filled teeth (FT) component of the DMFT showed the greatest increases. Results revealed the initial baseline caries level in permanent dentition was a strong predictor for future caries after 5 years (RR=3.78, 95% CI=3.48-4.10, P<0.001). Logistic regression analysis showed significant association between caries occurrence and residence (urban/rural) (OR=1.80, P<0.001). However, it was not significantly associated with gender and ethnicity. The incidence density of caries, affected persons (ID_p) observed from baseline and after 5 years was 5.80 persons/100 person-year of observation. The rate of new caries-affected tooth (ID_t) in the period from baseline and after 5-years was 0.76 teeth/100 teeth-year of observation.

Conclusion

The majority of 12-year-old school children (70%) were caries-free and most of the caries were concentrated in only a small proportion (30%) of them. We found that the presence of caries in permanent teeth at the age of 6 years was a strong predictor of future caries development in this population. The strong evidence of early permanent teeth caries at six years old to predict future caries incidence at 12-year-olds, which could be obtained at almost no cost, questions the need for and cost-effectiveness of expensive technology-based commercial caries predictions kits.

Sense of coherence and four-year caries incidence in Finnish adults

This study assesses whether sense of coherence (SOC) predicts incidence of tooth decay over 4 years and the role of dental behaviours in explaining the effect of SOC on incidence of tooth decay. Data from 994 adults who participated in both the Health 2000 survey and the Follow-Up Study of Finnish Adults' Oral Health were analysed for this study. At baseline, participants provided information on demographic characteristics, education level, the SOC scale and dental behaviours (tooth brushing frequency, dental attendance and sugar intake frequency). The 4-year incidence of tooth decay was calculated using data from baseline and follow-up clinical oral examinations. Baseline SOC was significantly related to 4-year incidence of tooth decay after adjustment for demographic factors and education (relative risk: 0.79, 95% CI: 0.63-0.98). This effect was fully attenuated after further adjustment for the three dental behaviours. Tooth brushing frequency and dental attendance were the only dental behaviours significantly related to incidence of tooth decay. This prospective study suggests that SOC predicts incidence of tooth decay and that dental behaviours may help explaining why adults with strong SOC have lower risk of developing tooth decay than those with weak SOC.

Six months of high-dose xylitol in high-risk caries subjects--a 2-year randomised, clinical trial

Objectives

The hypothesis was that the daily use of a high dose of a xylitol chewing gum for 6 months would reduce the increment of decayed permanent first molar surfaces (ΔD₆S) in high-risk schoolchildren after 2 years.

Methods

In this randomised, clinical trial, 204 schoolchildren with a high caries risk were assigned to two experimental groups, xylitol and non-xylitol. Caries status, salivary mutans streptococci, and lactobacilli were re-evaluated 2 years later in 74 xylitol-treated and 83 non-xylitol-treated schoolchildren. Differences in mean ∆D₆S between groups registered at baseline and at follow-up were evaluated using the nonparametric Mann–Whitney U test.

Results

Outcome was the development of detectable carious lesions initial (D₁–D₂) and manifest (D₃) in the permanent first molars. In the xylitol group, the difference in proportion of children with decayed first permanent molars at baseline and follow-up was 1.43 % for manifest lesion and 2.86 % for initial lesions; while in the non-xylitol group was 10.26 % (p < 0.01) and 16.66 % (p < 0.01), respectively. A statistically significant difference regarding means was also observed in the non-xylitol group: the ∆D₆S for manifest lesion was 0.18 (p = 0.03) and 0.67 (p = 0.02) for initial lesion.

Conclusion

The use of a chewing gum containing a high dose of xylitol for a period of 6 months has been shown to produce a long-term effect on caries development in high caries-risk children.

Clinical relevance

A school-based preventive programme based on 6 months’ administration of a high dose of xylitol via chewing gum proved to be efficacious in controlling caries increment in high-risk children.

A model for the analysis of caries occurrence in primary molar tooth surfaces

Recently methods of caries quantification in the primary dentition have moved away from summary 'whole mouth' measures at the individual level to methods based on generalised linear modelling (GLM) approaches or survival analysis approaches. However, GLM approaches based on logistic transformation fail to take into account the time-dependent process of tooth/surface survival to caries. There may also be practical difficulties associated with casting parametric survival-based approaches in a complex multilevel hierarchy and the selection of an optimal survival distribution, while non-parametric survival methods are not generally suitable for the assessment of supplementary information recorded on study participants. In the current investigation, a hybrid semi-parametric approach comprising elements of survival-based and GLM methodologies suitable for modelling of caries occurrence within fixed time periods is assessed, using an illustrative multilevel data set of caries occurrence in primary molars from a cohort study, with clustering of data assumed to occur at surface and tooth levels. Inferences of parameter significance were found to be consistent with previous parametric survival-based analyses of the same data set, with gender, socio-economic status, fluoridation status, tooth location, surface type and fluoridation status-surface type interaction significantly associated with caries occurrence. The appropriateness of the hierarchical structure facilitated by the hybrid approach was also confirmed. Hence the hybrid approach is proposed as a more appropriate alternative to primary caries modelling than non-parametric survival methods or other GLM-based models, and as a practical alternative to more rigorous survival-based methods unlikely to be fully accessible to most researchers.

Caries, gender and socio-economic change in the Xavante Indians from Central Brazil

BACKGROUND

The oral health conditions of indigenous peoples in Amazonia are closely associated with ecological and dietary changes related to interaction with non-Indians.

AIM

The study investigated the incidence of caries in an indigenous community from Central Brazil focusing on gender differences.

SUBJECTS AND METHODS

The research was conducted among the Xavante Indians and was based on longitudinal data collected in two surveys (1999 and 2004). The study included 128 individuals, 63 (49.2%) males and 65 (50.8%) females, divided in four age brackets (6-12, 13-19, 20-34, 35-60 years of age). The DMFT (decayed, missing and filled teeth) index and incidences (difference between 1999 and 2004) were calculated for each individual. The proportion of incidence was also calculated. Differences in caries risk between gender and age brackets were compared by parametric and non-parametric tests.

RESULTS

There were statistically significant differences in relation to caries incidence between age brackets and gender. The greatest incidence was observed in the 20-34 age bracket, which presented 3.30 new decayed teeth, twice the risk of the 6-12 age bracket (p<0.01), chosen as reference. While females in most age groups did not show higher risk for caries when compared to males, there was a 4.04-fold risk in the 20-34 age bracket (p<0.01).

CONCLUSION

It is concluded that factors related to the social functions of each sex (gender issues) and differential access to information, health services, and education may help to understand the differences observed in the incidence of caries.

Risks for Early Childhood Caries Analyzed by Negative Binomial Models

Because of the high incidence of early childhood caries (ECC), a longitudinal study to identify risk factors from the prenatal period to the child’s first birthday among 9- to 18-month-old children was conducted with negative binomial modeling. Overall, 495 children had dental examinations at ages 9, 12, and 18 months. Mothers were interviewed during the 2nd trimester of pregnancy and when the children had dental examinations. The highest incidence of caries was found among children who were born to mothers with ≥ 10 decayed teeth and who never received calcium supplements during pregnancy, and children who were not fed supplementary foods at age 3 months, had sweet-tasting foods at 5 months, started snacking at 5 months, had sugary snacks, had soft drinks, and did not have their teeth brushed daily at 9 months. Thus, prenatal care and child-rearing-practices during and after birth are important risk factors for the incidence and incremental rate of ECC.

Computed online determination of life-long mean index values for carious, extracted, and/or filled permanent teeth

OBJECTIVE

The purpose of this study was to develop and test a data-mining system for the online determination of mean DS, M, and FS or DMFS values per subject at different ages from electronic patient records at two health centers to see if there are north-south differences in oral health in Finland.

MATERIAL AND METHODS

The mean index values were determined at two health centers using the codes of dental charts and progress notes of electronic dental records during the digital era of more than 10 years in a total of 153,619 subjects of all ages. Extracted teeth, as well as sound, carious, and restored tooth surfaces, were recorded from the dental charts. Treatments were then additionally registered from progress notes of the records when performed.

RESULTS

The cumulative DS and FS values were similar in subjects under the age of 20 years at both health centers. In adults, caries was more abundant in northern Finland, where there was a higher number of restored surfaces (>40) registered, compared to only 30 in southern Finland at the age of 40 years. A high increase in the number of extractions began at age 45 in the north compared to age 70 in the south. These changes were clearly reflected in the DMFS index.

CONCLUSIONS

Online determination of health parameters is a feasible methodology. The results revealed that north-south regional differences in dental health still occur in adults in Finland, but not in subjects younger than 20 years of age.

Chlorhexidine and Preservation of Sound Tooth Structure in Older Adults

The Trial to Enhance Elderly Teeth Health (TEETH) was designed to test the impact of regular rinsing with a 0.12% chlorhexidine (CHX) solution on tooth loss, and the causes of tooth loss (caries, periodontal disease and trauma) were also investigated. This paper reports on the effectiveness of a 0.12% CHX solution for controlling caries using a tooth surface (coronal and root) survival analysis. A total of 1,101 low income elders in Seattle (United States) and Vancouver (Canada), aged 60-75 years, were recruited for a double-blind clinical trial and assigned to either a CHX (n = 550) or a placebo (n = 551) mouth rinse. Subjects alternated between daily rinsing for 1 month, followed by weekly rinsing for 5 months. All sound coronal and root surfaces at baseline were followed annually for up to 5 years. At each follow-up examination, those tooth surfaces with caries, restored, or extracted were scored as 'carious'. The hazard ratio associated with CHX for a sound surface to become filled, decayed, or extracted was 0.87 for coronal surfaces (95% confidence interval: 0.71-1.14, p = 0.20) and 0.91 for root surfaces (95% confidence interval: 0.73-1.14, p = 0.41). These findings suggest that regular rinsing with CHX does not have a substantial effect on the preservation of sound tooth structure in older adults.

A longitudinal study of early childhood caries in 9- to 18-month-old Thai infants

OBJECTIVE

To examine the rate and pattern of early childhood caries (ECC) development and to investigate the transitional changes of the carious lesions during a follow-up period of 3-9 months.

METHODS

A longitudinal observational community-based survey of 599 children, 9-18 months old. The children's dental examinations were first carried out at the age of 9 months with re-examination at 12 and 18 months by five dentists using standardized methods. The affected rates of dental caries were determined for prevalence, incidence density for risk of caries per person (IDp) and risk by surface (IDs). Changes in dental status over time were explored from unerupted (U) to sound (S), including enamel caries (D1), dentine caries (D2) and caries involving pulp (D3) by computing transitional probabilities.

RESULTS

The prevalence of caries was 2.0%, 22.8% and 68.1% among 9-, 12- and 18-month olds, respectively. The IDp observed for newly affected children 9-12 and 12-18 months old was 10.32 and 15.70 persons/100 person-months, respectively. The IDs for children 9-12 months old was 2.17 newly affected surfaces/100 surface-months whereas it was 2.22 surfaces/100 surface-months for children 12-18 months old. The buccal surface of maxillary incisors was the most affected (44.9%) followed by lingual, mesial and distal surfaces, respectively. The transitional probability of caries progression ranged between 1.79% and 15.38% during the follow-up period from 9 to 12 months old. It was 3.43-39.60% from 12 to 18 months old.

CONCLUSIONS

An extremely high caries-affected rate was found among the study children even before the age of 18 months. The buccal surface of the maxillary incisors was the most affected. The teeth acquired caries at 3-6 months after initial eruption and carious lesions developed continuously over time.

For debate: problems with the DMF index pertinent to dental caries data analysis

The Decayed, Missing, Filled (DMF) index has been used for over 50 years and is well established as the key measure of caries experience in dental epidemiology. Despite its long history of use, there is debate about the most appropriate number of surfaces to include for a missing tooth. Assigning the maximum possible value for the 'M' component of DMFS (Surfaces) leads to overestimation of an individual's caries experience, and in any associated comparisons of in-caries experience, whereas assigning the minimum possible value for the 'M' component has the opposite effect. Alternative methods of assigning the number of caries-affected surfaces for an extracted tooth are considered. The net caries increment and adjusted caries increment (common methods of correction of the crude increment measure for reversals) are discussed, along with incidence density, a measure of caries extent. Problems exist with the adjusted caries increment, particularly among cohorts with low mean baseline caries experience. Development of an alternative method of estimating the relationship of 'true' and 'examiner' reversals is advocated, as well as greater utilization of incidence density in dental epidemiology.

Caries incidence and increments in Adelaide nursing home residents

The objective of The Adelaide Dental Study of Nursing Homes was to quantify coronal and root caries incidence and increments in residents of Adelaide nursing homes. A longitudinal design was used to conduct dental inspections, completed by calibrated dental examiners, for residents of 7 randomly selected nursing homes at both baseline and at one-year follow-up. The nursing home residents in this study were very functionally dependent, medically compromised, cognitively impaired and behaviorally difficult older adults. The coronal caries surface incidence was 64.4% and root caries surface incidence was 48.5%. There were 72.1% of residents who had coronal and/or root caries increments between baseline and one-year. The coronal and root caries increments in these residents were high (adjusted caries increment = 2.5 coronal and 1.0 root surfaces), and were many times greater than that reported from a longitudinal study of community-dwelling older adults in Adelaide. Residents with eating and nutritional problems developed high levels of new caries. Both coronal and root caries incidence and increments were high in these nursing home residents over the one-year follow-up period.

Caries incidence and increments in community-living older adults with and without dementia

OBJECTIVES

The Oral Health of Older Adults with Dementia was instigated in the late 1990s to quantify and compare coronal and root caries incidence and increments in community-living older Australians with and without dementia.

METHODS

A longitudinal design was used to conduct dental inspections at baseline and one-year, for two groups of randomly selected community-living older adults--one group of 116 people with dementia and a comparison group of 116 people without dementia.

RESULTS

At one-year there were 103 dementia and 113 (112 dentate) non-dementia participants. Coronal and root surface caries incidence was higher for dementia participants (p < 0.05). Dementia participants had higher coronal and root caries adjusted caries increments (ADJCI) (p < 0.01). Both coronal and root ADJCI were evident in half of dementia participants, compared with one-quarter of non-dementia participants. Dementia participants with higher coronal ADJCI were those who had visited the dentist since baseline, who were taking neuroleptics with high anticholinergic adverse effects, and whose carer had high carer burden score (p < 0.01). Dementia participants with higher root ADJCI were those needing assistance with oral hygiene care and whose carers had difficulties with oral hygiene care (p < 0.05). Baseline characteristics predictive in linear regression for: (1) coronal caries increments among all participants were--dementia participants, those with cognitive testing scores indicative of moderate-severe dementia, those with private health insurance; (2) root caries increments among all participants were--dementia participants, and those who had > or = 1 decayed/filled root surface at baseline. Among dementia participants, being male was the baseline characteristic predictive in logistic regression for coronal caries increments, and having > or = 1 decayed coronal surface was the baseline characteristic predictive for root caries increments.

CONCLUSIONS

Coronal and root caries incidence and increments were significantly higher in the community-living older adults with dementia over the one-year follow-up period. Dementia participants had high levels of coronal and root caries increments; characteristics related to high caries increments included sex (males), dementia severity (moderate-severe), high carer burden, oral hygiene care difficulties, use of neuroleptic medication (with high anticholinergic adverse effects) and previous experience of caries.

Caries risk analysis: considering caries as an individual time-dependent process

AIM

To estimate the probability that a tooth does not develop a cavitated lesion (= end-stage caries) within time periods of interest. Additionally it was of interest to assess the heterogeneity between patients, in relation to the time periods required for their teeth to develop a cavitated lesion.

DESIGN

A prospective study using patient data of a clinical pedodontic course.

SAMPLE AND METHODS

Forty-one patients who had been followed for at least 3 years were selected. Before initiation of therapy, affiliation to a specific risk group was checked. Nine individuals who had belonged to a high-risk group on test were excluded. Of 1968 teeth, 1378 were eligible for data evaluation. The statistical techniques applied originate from time-to-event analysis methods, including a parametric frailty approach providing estimates of the relative caries risk for each individual to develop a cavitated lesion.

RESULTS

In the selected group of patients the probability that a tooth remained free of a cavitated lesion within five years ranged from 0.89 to 0.95 applying a 95% confidence interval. In the present sample the true caries risk of the patients to develop a cavitated lesion varied considerably although such variation was not expected from the individual examinations at baseline.

CONCLUSION

The frailty model accounts sufficiently for the heterogeneity of each patient. The applied time-to-event methods facilitated reliable estimation of both the probability that a tooth remains free of a cavitated lesion within a certain time and the relative caries risk of an individual to develop a cavitated lesion.

A re-analysis of a caries clinical trial by survival analysis

The decline in caries prevalence, the increases in the level of fluoride exposure, and the lack of placebo control subjects have complicated caries clinical trials in recent times. There has been a substantial increase in the numbers of subjects required for the detection of statistically significant differences between dental products, and hence, the cost of these trials has grown enormously. This study uses a new statistical approach to the analysis of the data from these trials with the ultimate aim of providing a more sensitive method of analysis. The new approach uses survival analysis, where the outcome measure is the survival time of an individual tooth surface. It exploits recent developments in the analysis of clustered survival data where survival times within the same cluster or subject are correlated. To illustrate, the new method of analysis was used for the North Wales, UK, caries clinical trial. It is concluded that survival analysis uses most of the data available in a caries clinical trial, an outcome measure that is easily understood and may lead to a more sensitive method of analysis.

Methodological issues in longitudinal epidemiologic studies of dental caries

As longitudinal epidemiologic studies of dental caries address increasingly complex research questions, approaches to analysis of data from those studies have become more sophisticated. This review examines methods available for analyzing and reporting data from such studies. Traditional analytic methods utilize the DMFS increment as the outcome measure in longitudinal studies of caries. However, two other outcome measures may be needed to address some research issues: cumulative incidence, which quantifies caries risk; and incidence density, which quantifies caries rate. Four major analytic decisions have to be addressed when computing DMFS increment: examiner misclassification ("reversals"), teeth lost due to caries, findings from more than two examinations, and multiple events such as caries initiation and progression. We present a uniform approach for enumerating caries events that permits the same analytic decisions made in calculating DMFS increment to be applied to cumulative incidence and incidence density calculations. In view of the variety of analytic decisions that must be made when enumerating events in longitudinal studies of caries, authors should specify how all potential changes in caries status were handled. Furthermore, if a study uses more than one outcome measure, the same decisions for enumerating events should be used when computing those measures.

Caries prediction: a review of the literature

For over a decade researchers have been looking for the formula that will allow caries prediction. The purpose of this summary is to review recent multifactorial prediction models for adults and children with the aim of identifying the most successful and consistent methods. Conclusions from this review include the following: Clinical variables, especially past caries experience, are confirmed as the most significant predictors of future caries development. The status of the most recently erupted/exposed surface is the most successful measure of past caries experience. Bacterial levels are included in the most accurate prediction models. Sociodemographic variables are most important to caries prediction models for young children and older adults.

Caries frequency in permanent teeth before and after discontinuation of water fluoridation in Kuopio, Finland

The piped water of Kuopio, Finland, was fluoridated in 1959. Owing to strong opposition by different civic groups, water fluoridation was stopped at the end of 1992.

OBJECTIVES

The aim of this study was to examine the consequences of the discontinuation on dental health.

METHODS

In 1992 and 1995, independent random samples of all children aged 6, 9, 12 and 15 years were drawn from Kuopio and Jyväskylä, a nearby low fluoride town whose distribution of demographic and socio-economic characteristics was fairly similar to Kuopio's. The total number of subjects examined was 550 in 1992 and 1198 in 1995. Caries was registered clinically and radiographically by the same two calibrated dentists in both towns.

RESULTS

In 1992, the mean DMFS values were lower in the fluoridated town for the two older age groups, the percentage differences for 12- and 15-year-olds being 37% and 29%, respectively. For the two younger age groups no meaningful differences could be found. In 1995, the only difference with possible clinical significance was found in the 15-year-olds in favor of the fluoridated town (18%). In 1995, a decline in caries was seen in the two older age groups in the nonfluoridated town. In spite of discontinued water fluoridation, no indication of an increasing trend of caries could be found in Kuopio. The mean numbers of fluoride varnish and sealant applications decreased sharply in both towns between 1992 and 1995. In spite of that caries declined.

CONCLUSIONS

These findings suggest that the decline of caries has little to do with professional preventive measures performed in dental clinics.