The Swedish dental health register - validation study of remaining and intact teeth

Poor oral health as defined by diseases of the oral cavity, foremost periodontitis and caries, and limited number of remaining intact teeth constitutes a major global health burden. The distribution of poor oral health is socially patterned as shown by large socioeconomic disparities in oral health within and between countries. [1, 2] There is limited data on oral health and its determinants in the Swedish population [3], but there are indications of major social disparities. [3‐8] A large part of the global population is not covered by dental health care, and in settings with high coverage the utilization varies across socioeconomic groups. Sweden has universal free dental health care services for children and young adults up to the year of their 23rd birthday. For adults, from the year they turn 24, dental health care services are financed by state subsidization and patient out-of-pocket payment and a small part by the county council for some specific group in the population. Dental care is to a large extent (60% in the year 2014) financed by the consumers of dental care. [9‐11]

Population-based registers facilitate high quality research provided that registration is complete and valid. There is a need for a national register with high coverage, completeness and validity to facilitate continuous monitoring of the distribution of dental health in the population, evaluation of dental health care treatment, and to enable studies of the association between dental health and other diseases. Sweden has a long tradition of nationwide population registers enabling population-based research of high quality. [12] In the other Nordic countries there has been national or regional registers on dental health foremost for children, including a Swedish register on dental implants and another for dental caries and periodontitis, but for long Sweden has not had a national register covering the adult population. [13‐16] However, in 2008 the Swedish Dental Health Register was initiated. The register contains individual data on dental health care reimbursed by the State to the whole adult (23 years and older) population of Sweden. [17]

The data collection is administered by the Swedish Insurance Agency as part of the administration of the reimbursement from the State to dental health care facilities for dental services provided to the population. Information on dental health care is monthly transferred to the National Board of Health and Welfare, which is responsible for keeping all national health data registers. The Swedish Dental Health Register is regulated under a legislation issued by the Swedish government and can among others be used for evaluation and planning of health care services, monitoring public health and for research. Electronic reporting is mandatory for the dental health professions. [18]

We aim to describe the content and the validity of reported number of teeth of the Swedish Dental Health Register and to report some descriptive data on dental health care utilization.

The Swedish Dental Health Register provides near to complete national data on dental health care to the adult Swedish population. The positive predictive value of reported teeth is high among those with at least 1 tooth up to 31 intact teeth reported to the register. However, we have pinpointed two major areas where the quality of the register has to be improved considerably; recording of no teeth and recording of all remaining and intact teeth (32 intact teeth). In a random sample the positive predictive value was less than 50% in these groups.

The high quality and validity of the Dental Health Register together with the complete nationwide coverage is a unique source for dental health care services research. This also provides our study with high precision and considerable power in the estimates of the dental health and dental health care utilization of the Swedish population. The four largest computerized reporting systems used in dental health care services in Sweden have predefined default values of either no teeth or 32 teeth. Hence, we hypothesize that some dentists and dental hygienists by routine just click the default value (0 or 32) instead of recording the actual correct number of remaining teeth. This is most probably the explanation of the low validity of 0 and 32 reported teeth. A possible improvement could be to have no default values and thus instead force the recorder to manually fill in the correct number of teeth. We have only validated the recorded number of teeth for that particular sampled dental visit. However, also taking previously recorded values of number of teeth into account would generate a higher concordance between recorded number of teeth and the correct number of teeth assessed by manual review. This indicates that there is no systematic misclassification of number of teeth due to patient or dentist or dental hygienist characteristics. The misclassification more seems to be non-differential. The overall response rate of the validation study was high (75%). However, we cannot totally rule out differential response rate between dentists and dental hygienists recording correctly and those recording less correctly which might have overestimated the quality of the reported number of remaining teeth. The clinical data reported to the register is number of remaining teeth, intact teeth, diagnoses and procedures. However, we have only validated remaining teeth and intact teeth. We argue that remaining intact teeth is a simple and very useful measure of oral health (if the data is correct) to use for dental health surveillance and thus the most important data to validate. However, in the future we hope that reported specific diagnoses and procedures will be validated.

The reform of dental care that was introduced in 2008 included increased governmental subsidies. [9‐11] For implementation of the dental reform, the Dental Health Register was introduced, making it necessary for the dentists to register their patients in a computerized system in order to get the subsidies paid out by the governmental agency in charge of the register. However, as the out-of-pocket payment can be substantial, patients with financial distress may opt not to seek dental health care when needed. We have no means to in a systematic way assess the oral health of those not registered in the register.

Until now the sources used for dental health research in Sweden have mainly been regional or local registers or specifically collected data in smaller studies; dental health in the population, [21‐23] utilization of dental health care services [24], socioeconomic differences in utilization of health care services, [3‐8, 25], risk factors for caries [26], dental health as a risk factor for other disease [27‐29]. The Dental Health Register, with data on utilization by age and sex and possible to link to socioeconomic factors is a valuable and very powerful source for public health policy planning and future research on these topics. Linking the Dental Health Register to other national data will generate unique possibilities for research not possible in many other settings. [12, 18, 30‐32]

For patients coded as having less than 32 remaining intact teeth but not being edentulous the reported number of remaining and intact teeth is to a very high degree correct. However, the correctness for those coded as edentulous or having 32 remaining intact teeth is low and varies substantially by age. The high validity of reported remaining and intact teeth in the Swedish Dental Health Register offers enormous potential for descriptive and analytical population-based dental health research.