BACKGROUND Advancements in medical care have enabled more children born preterm to survive and develop as healthy individuals alongside their full-term peers. However, a higher frequency of medical health problems, cognitive and behavioural disturbances, including problems in school, has been reported. There is limited knowledge about how this affects preterm children (PT) in dentistry, and few studies have evaluated behavioural problems related to dental treatments and oral health in PT as compared with full-term control children (C). AIMS The overall objective was to investigate behavioural problems related to dental treatments and the oral health in PT born between 23 and 32 weeks of gestation as compared with full-term C. Specific aims were to analyze behaviour management problems (BMP), dental fear and anxiety (DFA), prevalence of Molar-Incisor Hypomineralization (MIH), oral hygiene, gingival health, and dental caries in PT and full-term C. MATERIALS AND METHODS The study group comprised all children born between 23 and 32 weeks of gestation in the catchment area of the University hospitals of Lund and Malmö in southern Sweden. The subjects in Papers I-III were PT and matched full-term C, followed from preschool years to adolescence. In Paper IV, a new group of children, living in the city of Malmö was identified, the subjects being 10-to-12-year old PT and matched full-term C. Information about dental treatment, oral health and oral health related factors were obtained from dental records, interviews, questionnaires and clinical examinations. RESULTS OF THE FOUR PAPERS: Paper I: BMP and dental caries was studied in 187 PT and 187 C, based on notes in dental records at 3 and 6 years of age, and during the preschool period (3-6 years). At age 3, but not at age 6, the prevalence of BMPat dental examinations were more common in PT than in C. At various kinds of dental treatments during the preschool period, PT presented more frequently with BMP. No differences were found regarding dental caries. Paper II: Parents of 153 PT and 153 C were interviewed on two occasions, two years apar (preschool period and early school years) regarding experience of their child's dental care, oral health behaviour and medical health. BMPwere reported more common in PT than in C during preschool period but not during the early school years. PT also reported more medical health problems than C. Paper III: AT 12-14 years of age, 109 PT and 108 C toop art in a questionnaire study, including, the Children's Fear Survey Schedule--Dental Subscale (CFSS-DS) to measure the level of DFA, oral health behaviour and medical health. Few PT and C reported DFA. PT reported more daily use of dental floss and use of extra fluorid supplements than C. Further, PT reported more medical health problems than C. Paper IV: Eighty-two PT and 82 full-term C, aged 10 to 12 years, were clinicaly examined regarding the prevalence and severity of MIH as well as their levels of oral hygiene and gingival health. In addition, BMP and dental caries were recorded. MIH was more common in PT than in C. Low gestational age and low birth weight increased the risk of MIH. PT had more plaque and gingival inflammation and presented more BMP than C. No difference in caries prevalence was found. CONCLUSIONS AND IMPLICATIONS In 3-to-10-year old PT and matched full-term C, and based on dental records and parental reports, it was concluded that BMP were more common in PT than in C during the preschool period. The difference decreased with increasing age and during the early school years there were no differences between the groups. However, at clinical examination at the age of 10-12 years, PT presented with BMP more frequently than C. During adolescence, based on the youngsters' own viewpoints, few PT and C reported DFA. The clinical examination at 10-12 years of age showed that PT had a higher prevaleance of Molar-Incisor Hypomineralization (MIH) than C, and low gestational age and low birth weight increased the risk of MIH. At this age, PT also had less favorable oral hygiene and gingival status than C. Problems with toothbrushing were more commonly reported in PT than in C during the preschool period. During adolescence, PT reported more daily use of dental floss and extra fluoride supplements than C. Regarding caries prevalence, there were no differences between the group in either the primary or in the permanent dentition. In contrast, PT had more medical health problems, persisting from preschool period in adolescence than C. The results in this thesis indicate more behavioural problems related to dental treatment and more oral health problems in PT than in C. Therefore, PT require special attention from the dental services, with treatment planning and prevention strategies from an early age. Collaboration between medical and dental health care professionals is advocated in order to ensure good oral health in PT.