Epidemiological trends, predictive factors, and projection of tooth loss in Germany 1997–2030: part I. missing teeth in adults and seniors

Dental caries and periodontal diseases are the most common oral diseases and the main cause of tooth loss [1]. From an epidemiological point of view, caries experience has been continuously declining since the 1990s in Germany, both in children, adolescents, and among adults, which has a subsequent impact on the rate of tooth loss, especially in the first half of life [2]. The number of periodontally affected teeth, however, has been increasing in parallel [3], with the majority of these teeth being retained long term, also into higher age. Concomitantly, the older population segment is growing, while younger groups are shrinking. Overall, there is a strong indication for oral health gains in a large segment of the life curve on an individual level, but a compression of morbidity in elderly individuals and also older population segments [4].

Tooth loss is a very robust oral-epidemiological health marker, as it is relatively easy to measure. It is highly relevant to patients. Tooth loss is thus an epidemiological key variable and is also used to assess the quality of a dental healthcare [5]. Tooth loss exceeding a certain number of teeth has a significant impact on chewing function, nutrition, speech, and esthetics. This is even more true for complete tooth loss (edentulism), which is the final event of tooth loss and has a specific impact on both quality of life and therapy options. Edentulism is, at least in many high-income countries, a phenomenon of the older population [6‐8].

There are only a few longitudinal studies that can identify trends in tooth loss and associate them with trends in caries experience and prevalence, or extent and severity of periodontal disease [9‐12]. Cross-sectional surveys may be used as an alternative for identifying trends, but require the consideration of possible cohort effects. Such cross-sectional studies are frequently used for epidemiological population monitoring and for deducing interventions in healthcare planning.

The present study is the first part of a report on tooth loss in Germany. The aim of this study was [1] to illustrate the past trends in tooth loss and edentulism in Germany in the past quarter century on the basis of data from three waves of German oral health studies, [2] to evaluate factors that can predict tooth loss and edentulism at the population level, and [3] to use these predictors to forecast tooth loss and edentulism in the year 2030. This first report is devoted to tooth loss in particular. This is clinically relevant for all adult age groups. In a second paper, we report on edentulism in more detail, focusing on seniors (Fig. 1).

The Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis (TRIPOD) initiative developed a transparent set of suggestions for the reporting of studies developing, validating, or updating a prediction model, whether for diagnostic or prognostic purposes. The reporting of this study (part 1 and part 2) follows the TRIPOD statement [10].

The overall characteristics of the sampled cohorts in 1997, 2005, and 2014 are displayed in Table 1. While sex proportions remained relatively stable in both age groups over time, education level increased. Smoking decreased mainly in younger adults, but not in younger seniors.

MT and the prevalence of tooth loss decreased with time in both age groups. While MT decreased by nearly 50% in both age groups between 1997 and 2014, the prevalence of tooth loss decreased by 20% in younger adults, but only by 2% in younger seniors.

All predictors were significantly associated with MT (Table 2); that are the age per life year, sex, educational level, smoking behavior, and the cohort (DMS wave). With each year of age, MT increased in younger adults by 0.195 teeth and in younger seniors by 0.509 teeth. MT was also higher in females than males, those from low versus medium and high educational level, and in current versus former and never smokers. The model was robust when split-sample coefficients were tested in the other half of the sample (the predicted prevalence in the different waves deviated by < 2% when compared to reported prevalence).

The yielded coefficients were then applied to project MT and tooth loss prevalence in 2030 (Table 3). The projected MT in younger adults was 1.3 and was 5.6 in younger seniors. Predicted prevalence of tooth loss for the year 2030 in younger adults and younger seniors is 50% and 65%, respectively. In absolute terms, these were 36 and 65 million fewer MT in 2030 compared with 1997, respectively. The reduction in MT was higher in those from a lower than medium and high educational level.

Looking at tooth loss in relation to the dental arch, it is noticeable that the general decrease in tooth loss over time has occurred equally in both age groups and in anterior and posterior teeth, respectively. Interestingly, the anterior tooth loss in younger seniors is more pronounced than in the posterior area, whereas the distribution in younger adults is almost symmetrical (Appendix Table 4).

This study describes trends in tooth loss in adults and younger seniors in Germany as measured by repeated waves of a population-representative cross-sectional survey. In our sample and based on nearly 6000 participants, the strongest predictors for MT (and edentulism, see part II) were the cohort, patients’ age, and education level as well as smoking status. In this respect, our findings are in line with previous evaluations of tooth loss [20, 21].

In addition to the known risk factors that can lead to tooth loss, so-called dental generations can also be identified which, as a result of cohort effects, orally represent the current state of health technology in dental care. Our findings regarding the different “dental generations” [22] demonstrate the association between the caries decline and tooth loss. The adults sampled into DMS IV and DMS V (2005, 2014) have benefitted from the wide availability of fluoride toothpaste and preventive programs (fluoride varnish and sealant application in dental practice and group prophylaxis in kindergartens and schools) installed in the late 1970s and 1980s, respectively. In contrast, the adults sampled into DMS III (1997) and the seniors of DMS V had experienced higher caries increments and had been mainly treated restoratively, eventually leading to the final endpoint of the disease, tooth loss. The seniors from DMS III and IV had even entered adulthood with some missing teeth; the extent then increased even further up until age 65–74 years. The three cohorts of the DMS thus represent the “denture,” the “filling,” and the “fluoride” generation: given the chronic-cumulative nature of dental diseases, the endpoint tooth loss can be used to characterize them.

Edentulism can be considered a special case of tooth loss, namely the state after the final “target event.” Despite the closeness of tooth loss and edentulism, there exist clear epidemiological distinctions between these two states. For example, their prevalence is highly different; while tooth loss is highly prevalent in both age groups, edentulism is practically nonexistent among adults. Moreover, the changes observed over time (1997–2014) between both states are remarkable: While the prevalence of tooth loss decreased by one quarter in younger adults (from 77 to 57%), it was almost unchanged in younger seniors (from 98 to 96%). This was also reflected in trends on edentulism, which halved (from 22 to 12%) in younger seniors but remained stable (from 1 to 0.8%) in younger adults (see part II of this paper). It is thus relevant to evaluate both states separately, also given the different treatment needs and subjective impact emanating from them.

Our findings can be contrasted with that from other studies. In accordance with our data, one Finnish study reported a significant decrease of MT between 1978 and 1997, together with a decrease in prevalence from 80 to 60%. The number of adults with reduced dentition (MT > 6) decreased from 26 to 14% with time [23, 24]. A Swedish study reported that between 1975 and 1997, the number of adults with tooth loss decreased from 23 to 10%, whereas this number remained almost constantly among younger seniors (at 25%) [25]. Globally, severe tooth loss in the permanent dentition has been nearly halved since 1990 from almost 40 to 20%, again in line with our data [26].

This study has a number of strengths and limitations. One strength is that the available data are highly intrinsically consistent, as all three examinations were developed, collected, and evaluated by the same study center. Second, the used analytic method for the projection had been tested, validated, and applied to project edentulism, too (see part II); the present study supplements this method from a binary to a continuous outcome and helps to describe the oral health status in Germany in more depth. As limitation, it was not possible to draw testable, causal connections from our analysis given the (repeated) cross-sectional character of the underlying data. Thus, no analysis as to the reasons of tooth loss and the associated pathways, involving dental caries and periodontitis, was possible. Rather, this is a descriptive analysis and projection. The future wave of the DMS in 2021 will, for the first time, allow re-examining the participants of the DMS V and will thus be the first population-representative longitudinal oral health observation in Germany. Second, only a limited number of predictor variables were used in our study, mainly dictated by the availability of predictions of these variables in 2030, whereby the percentage of explained variance (R-squared) fluctuates, depending on the incorporated DMS waves, between 7.8% and 13.5% for the adult group, and between 7.7% and 8.9% for the senior group. These R² values thus appear moderately strong at best. While it was thus not able to reliably predict the individual tooth loss, the findings (from the validation) clearly demonstrate the ability to predict tooth loss on population level. In any case, our projection is only as robust as the predictions of these variables are, and prone to unforeseen social or demographic but also economic etc. changes. Third, our model was validated only in the population it was developed in using the split-sample technique; it will most likely be less accurate when applied to other populations. Thus, a different morbidity dynamic with regard to tooth loss in Germany could emerge in the medium term if global migration continues and, in addition, Germany will compensate for the lack of skilled workers in the future through a targeted immigration policy. An epidemiological study of oral health and access of older migrants in Germany has shown that the number of missing teeth of migrants is only insignificantly higher than that of non-migrants of the same age (70.2 yrs. of age) (MT migrants 14.4 vs. MT non-migrants 12.6; p = 0.301) (27). However, as this is a first orienting study, it is not possible to assess with certainty how tooth loss will develop in Germany in the future in times of global migration and immigration. Fourth, our primary outcome was the extent of tooth loss (MT), not the prevalence. The model for the prediction of prevalence was not validated; the projected prevalence should thus be regarded with caution. Last, only two selected age groups were analyzed. Our absolute estimates are not able to catch the burden of tooth loss in the whole German population. Given the expected demographic shift and the only recently measured oral health status of older seniors (in the DMS V), assessing and projecting tooth loss in the very old seems highly relevant, too, and should be performed in future studies. Especially in this age group, linking tooth loss data with general health or further socio-demographic parameters is of interest, also to gauge causal (bi-directional) pathways and to determine the subjective impact of (also non-severe) tooth loss (and tooth replacement). The Study of Health in Pomerania (SHiP), for example, links tooth loss and further general health data [27]. Eventually, a further triangulation with qualitative sociological research might also assist a deeper interpretation of tooth loss findings.

In conclusion, and within the limitations of this study, a robust and continuous decrease in tooth loss in the German population has occurred between 1997 and 2014. Based on our projection, this trend will become more dynamic by the year 2030, with around 50% of adults not having experienced any tooth loss in 2030, while young seniors will possess more teeth than they have previously lost. This decrease is likely to reduce the need for tooth replacement treatments, while the challenges of retaining more teeth for longer (for example, with regard to periodontal diseases and root caries) will need to be actively addressed.