Caries Epidemiolgy And Sealant Assessment Methods In Chinese Children

Backgrounds:This research was taken place in China, among school children of second grade students; the overall aim of this research was to monitor the caries prevalence and experience in primary dentitions, the natural course of cavitated primary dentitions and to investigate the most appropriate evaluation method for assessing sealant retention in newly erupted permanent molars over time.The first part consisted of two epidemiological studies. Epidemiological studies of trends in dental caries prevalence have shown different patterns around the world. Several developed countries have experienced a steady reduction in dental caries prevalence since the1980s. However, trends in low-and middle-income countries are unclear. Studies covering dental caries in school children in various countries are numerous In China, children’s need for dental care is characterized by the high prevalence of dental caries in primary dentition. Considering that over the past decades the economy in China has increased steadily, it is not unlikely to think that a cohort effect in caries prevalence might be present in the society of China. This warrants the necessity of monitoring the prevalence and severity of dental caries, particularly in young children. The first epidemiological study used a time-lag design to compare caries prevalence and caries experience in primary dentitions in two cohorts of children. Meanwhile, in China, dental-mindness is not much developed yet. Regular dental check-up visists are relatively rare. Data for China show96.7%of cavitated primary teeth among5-year-olds were left untreated. It is of interesting to investigate the natural course of the cavitated primary teeth within the Chinese health care system over time. And this was the aim of the second epidemiogical study.Sealants have been shown to be effective in preventing the occurrence of the carious lesions in pits and fissures, and the integrity and retention of the sealant should be evaluated periodically, to ensure its effectiveness over time. In2008. a comparative sealant trial started in Wuhan, the results of the caries lesion preventive effects and sealant retention rates after2years have been published. Direct visual clinical examination was the method used for evaluation of the previous study. However, it is not possible to recall or reassess sealants after a while and it may introduce assessment bias in epidemiological studies. Compared to the direct method, indirect methods like colour photographs, radiographs and replica cause less observe bias. They further permit assessment for all cases under standard conditions by designated examiners whether it concerns cases from different geographic areas or if the same case is examined at different times. In addition, indirect methods have the potential to increase the efficiency and effectiveness of dentists working in the primary oral care environment, thereby freeing up resources to improve access to oral care and reduce oral health inequalities. Recently, the reliability of colour photographs in detecting developmental defects in enamel and in carious lesions have been investigated and found very reliable. And the replica method is regarding to be more sensitive in measuring the level of retention and degradation of dental sealants over time. However, few studies have compared and validate the visual clinical examination, replica method and the colour photographs with regard to sealant retention assessment over time. For this purpose, studies in this part were carried out and aimed to investigate the most appropriate evaluation method for assessing sealant retention.Part I:Epidemiological Study:Surveillance on the primary dentitionStudy1:Caries experience in primary dentitions and presence of plaque in two cohorts of children from an economically fast-growing country over a time lag of four yearsObjectives. The aim of the present study was to test the hypothesis that dental caries prevalence and caries experience in primary dentitions has increased over4years and, to compare the presence of plaque in permanent teeth in child cohorts over4years. Methods:A time-lag study design was used comprising two cohorts of children aged6-8-years from the same5primary schools in Wuhan examined in2007and2011. Two calibrated examiners visually assessed the dentitions according to the ART caries criteria and plaque accumulation according to the Greene&Vermillion Index. ANOVA, t-test and Chi-Square test were used to test for differences between dependent and independent variables. Results:The2007-sample consisted of991and the2011-sample of1114children. The prevalence of dental caries (d3mft) was68.3%in2007and67.2%in2011, while that of d2mft was78.5%in2007and71%in2011(p<0.001). The mean d3mft score was2.8in2007and3.1in2011(p=0.09), while the mean d3mfs score was5.0in2007and7.3in2011(p<0.001). The d3-component of the d3mft index was75%in2007and68%in2011, while the f-component was21%in2007and26%in2011. The hypothesis was not accepted. The proportion of children with plaque code3(extensive coverage) was higher in2011(21.8%) than in age mates in2007(5.7%). Conclusions:There were no obvious signs that dental caries prevalence had been increased in primary dentitions of this child population between2007and2011. But as the mean caries experience scores at surface level were higher in2011than in2007, monitoring caries prevalence remains essential but should start at an earlier age than this study covered. Health and educational authorities should collaborate in setting up programmes aimed at ensuring good oral health for school children.Study2:What happened to cavitated primary teeth over time? A3.5-year prospective cohort study in China.Objectives:Data for China show that among5-year-olds96.7%of cavitated primary teeth were left untreated. The aim of this study is to report on the course of cavitated primary teeth within the Chinese healthcare system over an observational period of3.5years. Methods:Selection of high caries risk children for inclusion in a sealant comparison study was based on cavitated dentine lesion presence in their primary teeth. Although children had been advised to seek restorative care, at the6-month sealant evaluation point many of these cavitated dentine lesions had not been treated. This necessitated monitoring of these cavitated teeth, which was done every6months until exfoliation. In the course of this monitoring, exfoliated teeth, restored teeth, teeth with a cavity left open, those having caused toothache (symptom) and those having (had) an abscess or fistulae (symptom) were recorded. Care-seeking instruction was given at every evaluation point. The ANOVA, t-test and Kaplan-Meier survival method were used in analysing the data. Results:A total of1012cavitated primary teeth in305children ranging7.6-9.3years old, were followed for3.5years. A total of92.9%of the cavitated primary teeth were left open, while7.1%were restored at some stage during the observation period.98.5%of the restored and95.5%of cavitated teeth left open exfoliated.93.9%of restored teeth and81.5%of cavitated primary teeth left open exfoliated without any sign of a symptom. Having (had) toothache was the symptom most frequently related both to exfoliated restored teeth and to exfoliated cavitated teeth left open. Restored primary teeth survived statistically significantly longer than cavitated primary teeth left open:1.99±0.07years and1.68±0.03years, respectively. Conclusion:The large majority of cavitated primary teeth in this child population exfoliated without symptoms.Part Ⅱ:Clinical trial:Evaluation of Sealant assessment methodsStudy3:Comparison between visual clinical examination and replica method assessments of sealant retention over a2year periodObjectives:To compare the level of agreement and the survival rate of sealant retention of different sealing materials over a period of two years assessed according to the visual clinical examination and the replica method.Methods:Sealant retention data were obtained from clinical examination and replicas from one and the same sealed tooth at baseline and at0.5.1and2years evaluation points of307children, and compared for agreement using kappa-coefficients. Survival curves of retained sealants in occlusal surfaces were performed using the traditional categorization (fully and partially retained versus completely lost sealants) and the modified categorization (fully and partially retained versus completely lost sealants including those pits and fissures that had≥1pit re-exposed) according to the Kaplan-Meijer method. Results: The kappa-coefficients for the agreement test between both assessment method over the combined three evaluation points was0.36for the traditional and0.38for the modified categorization of retention. More sealant retention was observed from replicas than through visual clinical examination according to both categorizations of determining retention. For the traditional categorization, cumulative survival curves for the three times of evaluation were statistically significantly higher when assessed from replicas (p=0.004) but not according to the modified categorization (p=0.47). Significance:More retained sealant material was observed using the replica method than through the visible clinical examination during the two year evaluation period. The modified categorization of determining partial retention and completely lost sealant material appears to be more appropriate for calculating the survival rate of sealant retention than the traditional manner.Study4:Validation of three different methods for assessing sealant retentionObjective:To test the hypothesis that the color photograph method has a higher level of validity for assessing sealant retention than those obtained from the visual clinical examination and replica methods.Methods:From a sample of sealed1st molars, retention was assessed according to the visual clinical examination and from colour photographs by the same two evaluators, and from replicas by two other evaluators. Scores of the three methods were compared against consensus scores derived from assessing retention from SEM images (gold standard). Presence or absence (survival) of retained sealants in occlusal surfaces was determined according to the traditional categorization (fully and partially retained versus completely lost sealants) and to the modified categorization (fully retained and those having≥1pit covered with the sealant material versus completely lost sealants, that included those pits and fissures that had≥1pit re-exposed). Percentage of agreement, sensitivity, specificity and Youden-index scores were calculated. Results:Kappa-coefficients for inter-consistency reliability of data obtained from the three methods were high/substantial. Comparing sealant retention assessment scores of visual clinical examinations and colour photographs with those of the SEM images was performed on112teeth for replicas on43teeth. The highest mean Youden-index score for presence/absence of sealant material was observed for the colour photograph method, followed by that of the replica method whilst the visual clinical examination method scored lowest. The mean Youden-index score for the survival of retained sealants was highest for the colour photograph method for both the traditional (0.867) and the modified (0.747) category of determining sealant retention, with the visual clinical examination method having the lowest Younden-index score (0.730-0.053). Conclusions:Assessing sealant retention from colour photographs appears to be a valid method while the visual clinical examination appears not to be a valid method anymore.Study5:Detecting carious lesions and assessing sealant retention through visual clinical examination and from colour photographs after4yearsObjective:To compare the level of agreement of carious lesion development and that of sealant retention as assessed according to the visual clinical examination and the colour photograph methods. Methods; Data from retained sealant and presence of carious lesions were obtained from visual clinical examination and from colour photographs from the same sealed teeth after4-years by two examiners. Kappa-statistics were applied to calculate agreement. Survival rates of retained sealants in occlusal surfaces were estimated, using the traditional (completely gone versus fully and partially retained sealants) and the modified categorization (completely gone sealants, which included pits and fissures system that had≥1pit re-exposed, versus fully retained and partially retained sealants). Results:The prevalence of dentine carious lesions was too low. The kappa-coefficients for detecting carious lesions for both assessment methods by the two examiners were0.65(CI:0.56-0.74) and0.70(CI:0.62-0.78) and they were0.71(CI:0.64-0.79) and0.80(CI:0.74-0.87) for assessing sealant retention. Survival rates of retained sealants between the visual clinical examination and the colour photograph methods for both types of categorization were not statistically significantly different. Conclusion:The colour photograph method is not different in detecting carious lesions but appears more sensitive in assessing sealant retention than the visual clinical examination after4years.