Prevention and control of common dental diseases highly depends on individual behavior, and during the last decades, individuals have increasingly been required to take responsibility for their own oral health. In Finland the rate of toothbrushing and dental visits were first surveyed nationwide in 1971 by interviews with a sample of 1063 individuals, drawn to represent the total population aged 15 yr and over. At the time, 68% of the 829 dentulous interviewees claimed to brush at least once a day. Using another sample of 1006 interviewees, drawn in the same manner, in 1990 the brushing rate was found to have increased to 91% in 853 dentulous subjects. Daily brushing was more frequent among women (98%) than men (83%). The most distinct positive change regarding brushing frequency was found among men and those with only elementary education. In 1971 the interval between the two most recent dental visits was 1 yr or less for 44% of all the interviewees and for 25% it was more than 5 yr. In 1990, 53% of the interviewees had visited a dentist within a year and the visiting interval was more than 5 yr for 16%. The youngest subjects were the most frequent visitors: 60% of them in 1971 and 74% in 1990. The results indicate a clear trend toward more frequent brushing in Finland. However, this trend regarding dental visits does not seem to be equally remarkable.

The validity of the age assessment method based on the "Radiographic Atlas of Skeletal Development of the Hand and Wrist" by Greulich and Pyle (1st edition 1950) has been frequently questioned. The purpose of this study was to examine the reliability of this widely used method and to compare it to various dental and other skeletal age assessment methods. Forty-seven Finnish children of known ages below 16 years, who perished in Thailand in the Southeast Asian Tsunami on 26 December 2004 were examined. Every victim repatriated to Finland underwent a complete forensic autopsy including CT-scan, toxicological screening, and diatom analysis in order to establish the cause of death, as well as DNA testing and dental examination for the verification of the identification established in Thailand. Age assessment was performed by dental and skeletal methods. The average difference between the age assessment values obtained by the Greulich and Pyle method, and the chronological age was 9.7 months. In addition to the Greulich and Pyle method, an alternate skeletal method, Tanner and Whitehouse 2, resulted in an average age difference of 10.3 months. Dental age assessment methods were based either on the eruption (Nyström method, 8 cases, average age difference 5.6 months), or the development of the crown and roots (Demirjian method, 33 cases, average age difference 5.2 months and ABFO method, 7 cases, average differences 12.6 months). Dental methods proved to be most accurate in childhood until the teeth-with the exception of wisdom teeth-have erupted and root development is completed. In adolescence, however, the validity of skeletal methods improves considerably.

In Finland, forensic age assessment is strictly regulated by legislation. According to the Aliens Act (301/2004) and the amendment of the Act (549/2010), the police authorities, the frontier guard authorities, and the immigration authorities have the right to refer asylum seekers to the University of Helsinki, Department of Forensic Medicine, for age assessment. These assessments are especially performed to solve if the person is of major age, the cutoff being 18 completed years. The forensic age assessment is largely based on dental development, since the special permit of the Radiation and Nuclear Safety Authority (STUK) to the Department of Forensic Medicine of the University of Helsinki, allowing the use of ionizing radiation for non-medical purposes, includes dental and hand X-rays. Forensic age assessment is always performed by two forensic odontologists. In 2015, the total number of forensic age assessment examinations was 149, and the countries of origin of the asylum seekers were most commonly Iraq, Afghanistan, and Somalia. The current legislation on forensic age assessment has been well received and approved. Radiological and other examinations can be performed in different parts of Finland, but the forensic odontologist at the University of Helsinki is always involved in the process and ensures joint quality standards for the forensic age assessment.

The WM and SM were similar in their age prediction performances, and the use of the WM in dental age assessment in the Somali population is justified.

Estimation of an individual’s age has important applications in forensics. In young individuals, it often relies on separate evaluations of permanent teeth (PT) and third molars (TM) development. Here, we analysed the age prediction performance of combined information from PT and TM in an unusual sample of healthy Somalis, born and living in Finland. PT development was staged according to Demirjian et al. ( Hum Biol , 1973) and TM development according to Köhler et al. ( Ann Anat , 1994), using panoramic radiographs from 803 subjects (397 males, 406 females) aged 3–23 years. A sex-specific Bayesian age-estimation model for the multivariate distribution of the stages conditional on age was fitted on PT, TM and PT and TM combined. The age-estimation performances were validated and quantified. The approach combining PT and TM only overestimated age with an ME of − 0.031 years in males and − 0.011 years in females, indicating the best age prediction performance.