Summary of findings:
This study provides important insights into the pattern of dental caries at tooth surface, tooth and individual level in a high-income country where dental caries, despite a recent decline, remains the most prevalent condition in childhood. Visualisation of the distribution of dental caries at different stages of carious process across every surface of permanent dentition in 12- and 15-year-old children from England, Wales, and Northern Ireland shows the burden of disease carried by each tooth, most notably first permanent molars. Examination of two diagnostic thresholds: clinical decay which includes enamel caries and represents the criteria used by clinicians examining and providing care; and obvious decay which relates to previous epidemiological survey thresholds and is consistent with the WHO oral health surveys basic methods [23], highlights the volume of initial caries lesions (enamel caries) in these children, particularly 12-year-olds. The relative merits of using both of these thresholds have been debated in Europe and interested organisations have produced a recent “Brussels Statement” setting out the needs of modern caries epidemiology in Europe and beyond [24]. It is clear from these data that using the clinical decay threshold provides a more complete and higher representation of disease at population level, with implications for both clinical care and health policy. The findings also highlight the importance of social and behavioural factors in particular.
Epidemiology implications:
It is very clear from these findings that the threshold of reporting dental caries level is important to consider in epidemiological studies, suggesting that surveys which just focus on obvious decay seriously under-report the prevalence of disease, which increases with age cohort. If epidemiological surveys focus on code CDHS 2V (which equals to ICDAS 4) and above as the diagnostic threshold for decay [14], they will miss at least 40% of the dental caries. Enamel lesions are reversible [10]. Data on the volume of enamel caries provide an indication of great preventive opportunity [25] and should be taken into account by clinicians.
Clinical implications:
If readers consider that the majority of lesions in 12-year-olds were in enamel, this suggests that progression of much future disease could be prevented by supporting young people to increase toothbrushing, fluoride application and lower sugar consumption to recommended levels. This presents a large opportunity for prevention early in adolescence. If we do not do this, we fail the children themselves, and the healthcare system, leading to higher disease treatment and retreatment, with its associated costs for individuals and government. Implementing national guidance such as Delivering Better Oral Health [26], can support these children effectively through managing risk. Examples include behavioural changes in swopping sugar sweetened beverages and snacks for healthy snacks, as outlined in the Change 4 Life programme, particularly between meals, is important [27].
Children: patterns within the oral cavity
The number of standing teeth, particularly sound untreated teeth in childhood is the foundation of maintaining a ‘functional dentition’ through adulthood [28]. The proportions of dental caries experience that involved enamel decay in all surfaces in 15-year-olds was around 10% lower than in 12-year-olds, whilst more lesions were treated or had obvious decay. Furthermore, the prevalence, level and intensity of decay increased by age with more surfaces, teeth and children affected in this cross-sectional survey. As expected, occlusal and buccal surfaces of first molars as well as lower second molars were most effected by dental caries and either restored or in need of dental intervention. This suggests that the surface-/tooth-level of caries prevalence exhibited overall symmetry. Left: right symmetry, which indicated similar propensity of decay affected for both sides of the same dentition can be observed in most tooth sites. While a sort of symmetry between upper and lower posterior sextants could be pointed out at the same time. The traditional view holds that mandibular molars are more vulnerable to dental caries comparing with their maxillary counterparts as indicated by Luan et al. [29] who conducted a ten year follow-up study among the Chinese population. Our results confirmed the same decay affected characteristic of second molars in both age populations which was in agreement with Macek’s finding [30]. Nevertheless, first molars which have been present in the oral cavity for over 6 years show little difference in clinical decay experience vertically or horizontally. Similar to our findings, Macek et.al. reported that maxillary and mandibular first molars had the same post eruptive tooth age among 19.5-year-olds in U.S., thus sharing similar relative susceptibility to dental caries [30]. Batchelor and Sheiham also suggested that occlusal fissured surfaces of the first molar teeth, and buccal pits sites on lower first molars could be grouped together according to their similar caries susceptibility [31].
Interestingly, symmetry of caries prevalence doesn’t illustrate these teeth/tooth surfaces necessarily suffered from same stages of caries simultaneously in a certain child, which hasn’t been emphasized before. The proportion of pupils with decayed lower second molars who’s upper second molars suffered from caries at the same time, increased from 47% in 12-years to 68% in 15-years with age cohort. It is quite possible that a tooth/surface is in a very early (subclinical) stage of caries which cannot be detected by clinical visual examination, meanwhile, its asymmetrical surface already progressed to more advanced signs (white spot or cavitation). The fact that caries occurs horizontally and certain vertically in the same type of teeth suggests that when an effect that reduces/increases the cariogenic process of one of the teeth in children, is likely to affect all the other 1 to 3 teeth as they grow older. This was supported by Batchelor and Sheiham’s findings that occlusal surfaces of second molars and buccal sites on mandibular second molars were in the same group in order of caries susceptibility when 5- to 16-year-olds were involved [31]. Similar risk horizontally and differences vertically seem to reduce with increasing length of time in the oral cavity.
What do the models tell us that will support clinical care and community action. Modelling these data suggests that dental caries prevalence at surface level for clinical/obvious decay thresholds was associated with similar but not identical dental behavioural and psychological factors in two age groups, albeit that not always significant. Sugar intake frequency, one of the most recognised dental caries risk factors were proved to be related with clinical/obvious decay experience (DAV/2VMFS) in this research, which is consistent with the finding of 4th National Oral Health Survey in China [2], and the body of evidence reported by Moynihan and colleagues in their important systematic review [32]. The WHO strongly recommends a reduced intake of free sugars (include monosaccharides and disaccharides added to foods and beverages by the manufacturer, cook or consumer, and sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates) to less than 10% of total energy intake throughout the life-course [6], affirmed within the UK [33-35]. Toothbrushing plays an important role in delivering fluoride toothpaste and should be advised in line with current evidence [26]. Whilst attending a dentist does not necessarily prevent disease it increasingly can assist with disease prevention in young people through delivery of fluoride varnish and fissure sealants, together with advice on fluoride and diet. There remains a lack of consensus on the relationship between dental anxiety and dental caries [36-38]. Dental anxiety was reported to predict caries incidence in 15- to 18-year olds [37], but not significantly associated with dental caries experience at age 12 to 15 [36]. Interestingly, between the different age-groups examined (12- and 15-year-olds), moderate dental anxiety was verified as a strongly protective factor in this study for the first time. This may possibly be explained by the fact that these children have had a heightened awareness of dentistry and other input such as orthodontic treatment (with possible extractions due to crowding) and greater preventive input: however, this should be investigated further. Overall, these findings suggest the importance of evidence-based preventive care supported by regular dental attendance, particular if dentists are practicing preventive and minimally invasive dentistry.
Variation in the significance of the findings of the analysis could relate to the year cohort, sampling or the instruments utilized for data collection. What is clear is that the same patterns are present across both ages. Importantly the patterns and trends were similar in relation to significant or tending towards significance in both adjusted models.
The limitations of the study include the fact that it used cross-sectional data and differences between study samples and excluded samples could be found which have implications for its representativeness. None-the-less the uptake of the self-complete questionnaire survey was high and the survey was innovative in providing the opportunity to compare the data retrospectively with past surveys to document a further decline in caries [25], as well as being epidemiologically innovative. Ideally, it would be good to have longitudinal data to provide a better representation of caries trajectories, as with the Dunedin study [39].
The present findings have very important implications for public health policy, starting with epidemiology. First, initial stage of dental caries occupied almost half of decay-experienced surfaces/teeth in children according to information of CDHS 2013. Thus, if epidemiological surveys just focus on obvious decay to achieve comparability with past surveys, the findings will seriously underestimate the prevalence of disease, and provide limited insight to the planning of health interventions. Reporting dental caries levels at the clinical decay threshold is increasingly important and possible, and the methodology used by the CDHS 2013 survey can be useful to other countries and should be replicated in the UK in future surveys. Second, The volume of enamel caries in both age-groups, highlight the really important opportunity to recognise and arrest progression of these non-cavitation lesions – if they are controlled many restorations and repeated restorations will be prevented with cost savings [24, 25]. Action is required to alter children’s risk of oral disease. Third, caries susceptibility follows a clear pattern with left: right symmetry, and certain upper: lower symmetry with these modest differences reducing with age. This tendency indicates high requirements of early dental interventions, i.e. pit and fissure sealing and preventive resin restoration, particularly in first molars and second molars whose asymmetrical teeth already infected by dental decay. Fourth, and finally, given the pattern of disease in society and multiple risk factors, further research needs to be addressed to explore a way of categorizing individuals into different dental caries affected patterns.