Modelling childhood caries using parametric competing risks survival analysis methods for clustered data

Survival analysis of caries incidence in African-American school-aged children

OBJECTIVES

To conduct an assessment of time-dependent covariates related to dental caries of the permanent dentition among a low socioeconomic status, understudied cohort of children, incorporating time-dependent covariates through the application of extended Cox proportional hazards modeling.

METHODS

This study modeled the time to first cavitated dental caries in permanent teeth among school-aged children and assessed factors associated with this event. A cohort of 98 low socioeconomic status African-American children with mean age of 5.85 years at baseline was recruited in Uniontown, Alabama and followed prospectively for 6 years. None of these children had dental caries on permanent teeth at baseline, and oral examinations were performed annually. Caries-free survival curves were generated to describe time to event (having first decayed, filled, or missing permanent surface). Bivariate and multivariable extended Cox hazards modeling was used to assess the relationships between time-dependent and time-independent covariates and time to event.

RESULTS

Twenty-eight children (28.6 percent) had their first permanent tooth caries event during the 6-year follow-up. Multivariable results showed that greater consumption of water was associated with lower dental caries hazard, while previous primary tooth caries experience was associated with greater dental caries hazard after adjustment for frequency of consumptions of milk, added-sugar beverages, and 100 percent juice.

CONCLUSIONS

There was a global/overall significant caries protective effect of water consumption during the school-age period of child development.

The efficacy of screening for common dental diseases by hygiene-therapists: a diagnostic test accuracy study

Regularly attending adult patients are increasingly asymptomatic and not in need of treatment when attending for their routine dental examinations. As oral health improves further, using the general dental practitioner to undertake the "checkup" on regular "low-risk" patients represents a substantial and potentially unnecessary cost for state-funded systems. Given recent regulatory changes in the United Kingdom, it is now theoretically possible to delegate a range of tasks to hygiene-therapists. This has the potential to release the general dental practitioner's time and increase the capacity to care. The aim of this study is to compare the diagnostic test accuracy of hygiene-therapists when screening for dental caries and periodontal disease in regularly attending asymptomatic adults who attend for their checkup. A visual screen by hygiene-therapists acted as the index test, and the general dental practitioner acted as the reference standard. Consenting asymptomatic adult patients, who were regularly attending patients at 10 practices across the Northwest of England, entered the study. Both sets of clinicians made an assessment of dental caries and periodontal disease. The primary outcomes measured were the sensitivity and specificity values for dental caries and periodontal disease. In total, 1899 patients were screened. The summary point for sensitivity of dental care professionals when screening for caries and periodontal disease was 0.81 (95% CI, 0.74 to 0.87) and 0.89 (0.86 to 0.92), respectively. The summary point for specificity of dental care professionals when screening for caries and periodontal disease was 0.87 (0.78 to 0.92) and 0.75 (0.66 to 0.82), respectively. The results suggest that hygiene-therapists could be used to screen for dental caries and periodontal disease. This has important ramifications for service design in public-funded health systems.

Selective serotonin reuptake inhibitors and the risk of osseointegrated implant failure: a cohort study

Selective serotonin reuptake inhibitors (SSRIs), the most widely used drugs for the treatment of depression, have been reported to reduce bone formation and increase the risk of bone fracture. Since osseointegration is influenced by bone metabolism, this study aimed to investigate the association between SSRIs and the risk of failures in osseointegrated implants. This retrospective cohort study was conducted on patients treated with dental implants from January 2007 to January 2013. A total of 916 dental implants in 490 patients (94 implants on 51 patients using SSRIs) were used to estimate the risk of failure associated with the use of SSRIs. Data analysis involved Cox proportional hazards, generalized estimating equation models, multilevel mixed effects parametric survival analysis, and Kaplan-Meier analysis. After 3 to 67 mo of follow-up, 38 dental implants failed and 784 succeeded in the nonusers group, while 10 failed and 84 succeeded in the SSRI-users group. The main limitation of this retrospective study was that drug compliance dose and treatment period could not be acquired from the files of the patients. The primary outcome was that compared with nonusers of SSRIs, SSRI usage was associated with an increased risk of dental implants failure (hazard ratio, 6.28; 95% confidence interval, 1.25-31.61; p = .03). The failure rates were 4.6% for SSRI nonusers and 10.6% for SSRI users. The secondary outcomes were that small implant diameters (≤4 mm; p = .02) and smoking habits (p = .01) also seemed to be associated with higher risk of implant failure. Our findings indicate that treatment with SSRIs is associated with an increased failure risk of osseointegrated implants, which might suggest a careful surgical treatment planning for SSRI users.

Economic modeling of sealing primary molars using a "value of information" approach

The objective was to evaluate 2 primary molar sealant strategies for publicly insured children using an "expected value of perfect information" (EVPI) approach. We converted a 10,000-observation tooth-level cost-effectiveness simulation model comparing 2 primary molar sealant strategies - always seal (AS) and standard care (SC) - with a 1,250-observation child-level model. Costs per child per restoration or extraction averted were estimated. Opportunity losses under the AS strategy were determined for children for whom SC was the optimal choice. We determined the EVPI by multiplying mean opportunity losses by the projected incident population of publicly insured 3-year-olds in the US over 10 years with costs discounted at 2%. All analyses were conducted under assumptions of high and low intrachild correlations between at-risk teeth. The AS strategy cost $43.68 over SC (95% CI: -$5.50, $92.86) per child per restoration or extraction averted under the high intrachild correlation assumption and $15.54 (95% CI $7.86, $23.20) under the low intrachild correlation. Under high intrachild correlation, mean opportunity losses were $80.28 (95% CI: $76.39, $84.17) per child, and AS was the optimal strategy in 31% of children. Under low correlation, mean opportunity losses were $14.61 (95% CI: $12.20, $17.68) and AS was the optimal strategy in 87% of children. The EVPI was calculated at $530,813,740 and $96,578,389 (for high and low intrachild correlation, respectively), for a projected total incident population of 8,059,712 children. On average, always sealing primary molars is more effective than standard care, but widespread implementation of this preventive approach among publicly insured children would result in large opportunity losses. Additional research is needed to identify the subgroups of publicly insured children who would benefit the most from this effective and potentially cost-saving public health intervention.

Statistical power of multilevel modelling in dental caries clinical trials: a simulation study

Outcome data from dental caries clinical trials have a naturally hierarchical structure, with surfaces clustered within teeth, clustered within individuals. Data are often aggregated into the DMF index for each individual, losing tooth- and surface-specific information. If these data are to be analysed by tooth or surface, allowing exploration of effects of interventions on different teeth and surfaces, appropriate methods must be used to adjust for the clustered nature of the data. Multilevel modelling allows analysis of clustered data using individual observations without aggregating data, and has been little used in the field of dental caries. A simulation study was conducted to investigate the performance of multilevel modelling methods and standard caries increment analysis. Data sets were simulated from a three-level binomial distribution based on analysis of a caries clinical trial in Scottish adolescents, with varying sample sizes, treatment effects and random tooth level effects based on trials reported in Cochrane reviews of topical fluoride, and analysed to compare the power of multilevel models and traditional analysis. 40,500 data sets were simulated. Analysis showed that estimated power for the traditional caries increment method was similar to that for multilevel modelling, with more variation in smaller data sets. Multilevel modelling may not allow significant reductions in the number of participants required in a caries clinical trial, compared to the use of traditional analyses, but investigators interested in exploring the effect of their intervention in more detail may wish to consider the application of multilevel modelling to their clinical trial data.

Statistical methodology in oral and dental research: pitfalls and recommendations

OBJECTIVES

This study describes the pitfalls for commonly used statistical techniques in dental research and gives some recommendations for avoiding them. It also explores the potential of some of the newer statistical techniques for dental research.

METHODS

Each of the commonly used techniques e.g. descriptive statistics, correlation and regression, hypothesis tests (parametric and non-parametric) and survival analysis are explored with examples and recommendations for their use are provided. Common sources of error including those of study design, insufficient information, ignoring the impact of clustering and underuse of confidence intervals are outlined. The potential of statistical techniques such as multivariate survival models, generalized estimating equations and multilevel models are also explored.

CONCLUSIONS

Reviews of published dental research repeatedly identify statistical errors in the design, analysis and conclusions of the study. Educating researchers on common pitfalls and giving recommendations for avoiding them may help researchers to eliminate statistical errors. Developments in statistical methodology should be routinely monitored to ensure the most appropriate statistical methods are used in dental research.

Review of 36,537 patient records for tooth health and longevity of dental restorations

To develop an automatic system for utilizing electronic dental records, a data mining system to extract the diagnostic and treatment codes from the records for an intermediate file and automatic drawing of Kaplan-Meier-type survival curves was first created. Then this intermediate file was analyzed with SAS software for the scientific determination of Kaplan-Meier survival of tooth/surface-specific healthy time and survival of restorations in each permanent tooth, health center, and age cohort and also combined. All patients born in 1985, 1990 or 1995 in 28 health centers in Finland were analyzed. Patients classified as caries-active were those who had caries in any first permanent molar under the age of 8 years, while resistant patients did not have caries in these teeth before 10 years. In the younger age cohorts, a shortening of survival of caries-free teeth was seen. The shortest caries-free survival was seen in mandibular and maxillary molars in the youngest age cohort. Occlusal surfaces of molars determined their caries onsets and proximal caries occurred equally in molars, incisors and premolars, whereas canines or mandibular incisors did not have caries in these age cohorts. Caries-prone subjects had the shortest survival in all their teeth. The median longevity of all restorations was 11.7 years, with great variation between health centers and teeth. Because of the great variation between individual teeth, the tooth-specific approach seems appropriate in both caries epidemiology and material sciences.

A practice-based study on the effect of a short sucrose/xylitol exposure on survival of primary teeth caries free

BACKGROUND

In a randomized double-blinded clinical trial, preschool children used sucrose or xylitol chewing gum regularly for 2 months to study the preventive effect of xylitol on acute otitis media (AOM). Salivary mutans streptococci (sm) levels of the children were measured before the exposure. Those with ≥10(5) sm CFU in 1 mL saliva were considered to have high sm levels (sm+); and those with <10(5) CFU low sm levels (sm-).

AIM

This practice-based study aims to evaluate long-term dental effects of the sucrose/xylitol exposure on primary teeth.

DESIGN

For analyses, individuals were divided into sub groups according to their study group in the original AOM trial and baseline sm levels. Outcome events owing to dental caries of their all primary teeth were followed from dental records up to 12 years. Survival of teeth caries free was determined by Kaplan-Meier method and analysed statistically by Wilcoxon testing.

RESULTS

Survival of primary teeth caries free of children with high sm levels in the sucrose group was significantly shorter compared with all other groups when followed until shedding.

CONCLUSIONS

Two months' regular exposure to sucrose was sufficient to induce dental caries in primary teeth of children with elevated sm levels at baseline.

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.

Efficacy of a non-drilling approach to manage non-cavitated dentin occlusal caries in primary molars: a 12-month randomized controlled clinical trial

BACKGROUND. Despite the efficacy of non-drilling approaches to manage non-cavitated dentin occlusal lesions (NCDOL) in permanent teeth, there is no data validating this type of therapy in the primary dentition. AIM. To compare the efficacy of a traditional fissure sealant in managing NCDOL in primary molars. DESIGN. This study is a randomized controlled clinical trial with a split-mouth design. Thirty schoolchildren with two NCDOL were selected and divided into two groups. The experimental group received a resin-based fissure sealant, whereas the control group was treated with a conventional composite resin. Treatment efficacy was evaluated after 1 year by means of clinical and radiographic examinations. RESULTS. The two treatment modalities were found to be similarly effective in managing DONCL in primary molars. CONCLUSION. For the management of non-cavitated dentin occlusal caries in primary teeth, the invasive approach can be replaced with non-drilling fissure sealing techniques.

Association of cardiometabolic risk factors and dental caries in a population-based sample of youths

BACKGROUND

Cardiovascular disease (CVD) risk factors begin from early life and track onto adulthood. Oral and dental diseases share some risk factors with CVD, therefore by finding a clear relation between dental diseases and cardiometabolic risk factors; we can then predict the potential risk of one based on the presence of the other. This study aimed to compare the prevalence of dental caries between two groups of age-matched adolescents with and without CVD risk factors.

METHODS

In this case-control study, the decayed, missing and filled surfaces (DMFS), based on the criteria of the World Health Organization, were compared in two groups of equal number (n = 61 in each group) of population-based sample of adolescents with and without CVD risk factors who were matched for sex and age group.

RESULTS

The study participants had a median age 13 y 5 mo, age range 11 y 7 mo to 16 y 1 mo, with male-to-female proportion of 49/51. We found significant difference between the mean values of DMFS, body mass index, waist and hip circumferences, as well as serum lipid profile in the case and control groups. Significant correlations were documented for DMFS with TC (r = 0.54, p = 0.02), LDL-C (r = 0.55, p = 0.01) and TG (r = 0.52, p = 0.04) in the case group; with LDL-C (r = 0.47, p = 0.03) in the whole study participants and with TC in control s(r = 0.45, p = 0.04).

CONCLUSIONS

Given the significant associations between dental caries and CVD risk factors among adolescents, more attention should be paid to oral health, as one of the topics to be taken into account in primordial/primary prevention of cardiometabolic disorders.