This thesis deals with epidemiological data regarding periodontaldisease from two different Swedish populations (Jönköping andSkåne).BackgroundThe studies focus on periodontal disease, a disease affecting a largepart of the adult population. Periodontitis is a complex inflammatorydisease, often chronic, which affects the tissues supporting the teeth– the periodontium. The biofilm that adheres to the hard surfaces of the teeth initiate an inflammation in the supporting tissues. Insusceptible individuals, the inflammation may cause the destructionof the periodontium (periodontitis). Individuals with severeperiodontitis – between 5-15% in different populations – show arange of clinical signs and symptoms, such as bleeding gums, mobileand drifting teeth, the loss of interdental papillae, and eventually theloss of teeth. This may affect the function of the dentition and theaesthetic appearance of the individual. Despite this, the disease isoften considered to be silent. AimsThe overall aim was to study periodontitis prevalence and severityin two Swedish adult populations, and to describe the changes overtime. Further aims were to examine the effect of an individual’ssense of coherence on periodontitis and to analyse the impact ofperiodontitis on oral health-related quality of life.In order to examine this, a series of four different studies wereperformed with the following specific aims: I) to investigate the prevalence, severity, extent of marginal bone loss and subjectcharacteristics in the adult population in the county of Skåne, Sweden;II) to assess trends over 40 years regarding the prevalence and severityof periodontitis in an adult Swedish population; III) to investigatethe impact of periodontal disease experience on quality of life, inan adult Swedish population, using the OHIP-14 questionnaire;and finally IV). To investigate how an individual’s level of senseof coherence correlates with their periodontitis experience, in twodifferent random samples, ten years apart. MethodsOne cross-sectional clinical study in Skåne and five cross-sectionalclinical studies in Jönköping, repeated every ten years, were performedwith random samples of the adult populations. Both study protocolsincluded questionnaires regarding demographic as well as healthand oral health-related factors, as well as patient-related outcomemeasures, such as oral health related quality of life and sense ofcoherence.ResultsThe prevalence of severe periodontitis experience was elevenpercent across the two study populations. There was no differencein periodontitis prevalence according to gender. It was also shownthat subjects with severe periodontitis suffered from worse quality oflife compared to subjects without periodontitis. Regarding the senseof coherence, no difference could be observed between the differentdegrees of periodontitis experience. ConclusionThe main findings over time were the increase of periodontally healthyindividuals and the retention of more teeth among subjects with severeperiodontal disease. Also, individuals with advanced periodontitisexperience worse quality of life compared to periodontally healthyindividuals.