– Validity of response to a postal questionnaire, answered by 216 persons, was studied by comparing data from the respondents on the occurrence of dentures and on the number of remaining teeth with data recorded by a clinical examination. Information, collected in a personal interview on gingival disease, was compared with clinical records. Reliability was studied by examining the agreement between data from the questionnaires and from the interviews concerning time interval since the last dental visit. The information on the occurrence of dentures proved to be highly valid, while the reported number of teeth were less likely to conform with the clinical records. A slight tendency towards overreporting of remaining teeth was found. Conceivably, the greatest proportion of overestimates was caused by confusion concerning the counting of fractured teeth and roots. Gingival disease was markedly underreported. At the clinical examination, all subjects with some teeth showed signs of gingival disease, but only every fourth person reported having experienced “gum disease”. Information about time interval since the last dental visit was found to be reliable.

The oral hygiene, the gingival condition, pocket depth, and the incidence of caries on crowned teeth were studied during a period of 5 years in a group of patients (114) who had been treated with fixed dental prostheses. Prior to the prosthetic treatment, the patients received periodontal treatment. During the study, the subjects participated in an oral hygiene program. Crown margins were located sub-gingivally, at the gingiva and supra-gingivally. When the crown margins were located sub-gingivally, there was an increase in Gingival Index scores 2, and in pocket depth, compared to supra-gingival placement. An improvement of gingival health was recorded where the crown margins were located supra-gingivally. Caries lesions developed on 3.5% of the tooth surfaces which had recieved crowns.

Utilization rates, types of dental services received and reports on number of teeth present were studied through seven sets of cross-sectional data collected in 1973, '77, '79, '81, '83 and '85. Personal interviews performed by trained interviewers were held with nationwide probability samples, each of 1500 persons covering the Norwegian population aged 15 and above. During the 12-yr period, the percentage of the samples reporting to have 20 or more teeth increased from 63 in 1973 to 74 in 1985, while the percentage of edentulous subjects dropped from 16 to 12. The time interval since the last dental visit decreased continuously: in 1973, 58% of the sample reported to have paid a dental visit during the last year, in 1983, 70%. Correspondingly, a higher proportion of the samples stated they were regular treatment attenders (52% in 1973 and 67% in 1985), while the proportion of "irregulars" dropped. Although the regularity of the visits probably was somewhat overreported, the favorable trend was substantiated by the information on services received: extractions, denture services and fillings diminished, while preventive and "other" services gained importance. Possible explanations and implications for dental practice and education are discussed.

The purpose of this paper was to review some global aspects of dental caries epidemiology. Existing data show that caries activity has increased, often rapidly, in developing countries in recent years while marked reductions have occurred in some industrialized countries during the last 10-15 years. Changes in the prevalence of a multifactorial disease like dental caries are difficult to explain but the obvious ones seem to coincide either with increased intake or refined sugar-containing products or with increased use of fluorides. Furthermore it would appear that restorative treatment along has little impact on caries activity when viewed in a life long perspective. Experience, the existing geographic distribution of oral health problems and resources to cope with them suggest an urgent need for co-operation in dental education and research between developing and industrialized countries to develop acceptable cost-effective preventive programs in countries where caries activity is higher or increasing rapidly.