The size of provider-specific variation in the diagnosis of caries is fairly low. The size of the variability is dependent on the level of diagnostic uncertainty, which is coherent with the practice style hypothesis.

There are few longitudinal studies in which the development of caries over a long period of time has been studied for different age groups. Such studies are important because they can provide information to assess future needs for dental care and the implications if the development of caries is different for patients in different age groups. We describe changes in caries during the period 2003-2012 for several birth cohorts in Norway, using longitudinal data collected annually for each individual during a period of 10 years. The data set included patients born during the period 1940-1989 who received regular dental care in the public dental services in the county of Hedmark - altogether 7,519 patients. Information about caries was obtained from the electronic patient records. Nearly 90% of the patients had no caries for at least 5 years during the 10-year study period, and nearly 50% had no caries for at least 8 years. This pattern was similar for all birth cohorts. The mean number of carious teeth per patient decreased from 2003 to 2012. This decrease was particularly large at the end of the period and among the oldest birth cohorts, i.e. those born in the periods 1940-1949 and 1950-1959. Our findings indicate that the need for restorative treatment is reducing, particularly in the older age groups. Fewer dentists and more dental hygienists may be needed in the future to provide routine follow-up and care.

We identified a fairly strong family effect, which confirms that the family is an important arena in which the dental health of the children is formed. An improvement in dental health for one of the siblings was associated with a positive effect on the dental health of the other sibling, and vice versa.

Public dental officers in Norway show a high degree of homogeneity with regard to longevity of restorations. Further improvements in the longevity of restorations can most likely be achieved by preventing secondary caries and by improving the physical properties of materials.

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