Periodontal diseases, such as gingivitis and chronic periodontitis,are infectious diseases that are common in the adult population. InSweden, treatment is mostly provided in general dentistry by generaldental practitioners (GDPs) and dental hygienists (DHs). Thecare chain also comprises periodontists since they act as consultantsto the GDPs and DHs. Several studies have explored how cliniciansjudge, diagnose, and treat patients with different diseasesbut no previous study has explored how patients, with commonlyoccurring periodontal conditions in a population, are diagnosedand treated in general dentistry. Therefore the overall aim of thethesis was to study the treatment strategies applied by general dentistryclinicians to patients with common periodontal conditions.This thesis is based on five studies, where study I-IV are based on aquestionnaire and conducted using a quantitative approach while study V is based on in-depth interviews and conducted using aqualitative approach. The questionnaire in study I-IV comprised four simulated patientcases with different periodontal conditions. These four cases representthe periodontal status of the majority of middle-aged patientspresented in a general dentistry practice: 1) Generalised bone lossbut minimal signs of inflammation (well-maintained), 2) Generalisedbone loss and signs of inflammation (periodontitis), 3) Negligiblebone loss and minimal signs of inflammation (healthy), and4) Negligible bone loss but with signs of inflammation (gingivitis).The clinicians who participated in the studies were asked to judge each patient case as healthy or diseased, propose a diagnosis, evaluatetreatment needs, propose a treatment plan, and assess theprognosis.In study I, GDPs and DHs were combined in one group as generaldentistry clinicians (GDCs) and compared as to their judgement,proposed diagnosis and proposed treatment. Key findings: Three ofthe four patient cases was each judged as healthy by some GDCsand as diseased by others. The difference in judgement did not influencethe GDCs’ intention to treat or their proposed treatmentmeasures but did influence the estimated number of treatment sessions. In study II, GDCs were compared as to their prognostic assessment,treatment goals and estimation of treatment extent in termsof more or less treatment assigned to a given patient case in comparisonto the other patient cases (healthy patient case excluded).Key finding: The majority of GDCs was in general pessimistic intheir prognostic assessment and anticipated that all patient caseswere to experience a deterioration of their periodontal condition.The most common treatment goal, irrespective of the patient case,was to improve oral health awareness. The periodontitis patientcase was estimated to need the most treatment; slightly more thanthe gingivitis and the well-maintained patient cases where a similartreatment extent was estimated. In Study III, dental students (DSs) from Paris (DSP) and Malmö(DSM) were compared to each other as to judgement, diagnosis,treatment plans, and prognostic assessment. This was done in orderto discover if difference in educational background might influenceDSs’ treatment strategies. Key finding: The majority of bothgroups of DSs judged all the patient cases as diseased. DSPs proposedperiodontitis as a diagnosis more readily and estimated ahigher risk for disease progression in patient cases with no obviousbone loss (healthy and gingivitis patient cases). DSPs also recommendedmore treatment measures and estimated longer treatmenttime for all the patient cases than DSMs. In study IV, periodontists were primarily compared amongst eachother and secondly to GDPs as to their judgement, diagnosis, proposedtreatment plans, and prognostic assessment. Key findings:Both periodontists and GDPs varied in their judgement and proposeddiagnosis. The difference in periodontists’ judgement influencedtheir intention to treat and prognostic assessment. The GDPsintended to treat three out of four patient cases (except the periodontitispatient case) more often and were more pessimistic in theirprognostic assessment of patient cases with negligible bone lossthan the periodontists. In Study V, the phenomenon of lived experience of performing aperiodontal treatment in the context of general dentistry was describedby analysing interviews from three different DHs using thedescriptive phenomenological psychological method. Key finding:The periodontal treatment is perceived more as a standardisedworkflow than as an individually tailored treatment. The patients’oral hygiene and self-awareness are experienced as crucial partswhile the mechanical infection control is perceived as successfulbut sometimes difficult to perform. The DHs are experiencing aneed to be supportive of the patient but are sometimes doubtful ofthe patient’s ability to achieve and maintain a positive change inoral health behaviour.