Background: Periodontitis and obesity are among the most common human diseases. It is known that, due to the increased serum levels of proinflammatory cytokines in overweight and obese people, a negative physiological condition, which may promote periodontal disease, arises. This work aims to determine the degree of influence of the treatment success of overweight patients, with a Body-Mass-Index value over 25kg/m, on the conservative treatment of the Vienna Periodontal Treatment Concept.<br />Materials & Methods: The total number of subjects in this retrospective longitudinal case-control study was 555. In all patients, extensive periodontal status was recorded in connection with the Vienna Periodontal Treatment Concept, followed by treatment at the University Clinic of Dentistry Vienna. Probing depths were recorded on each tooth using a 6-point measurement at three times: t1 (periodontal status) before therapy, t2 (re-evaluation) at least 6-8 weeks after therapy, and t3 (recall) 12 months after re-evaluation. In addition, age, sex, smoking status, weight and height were documented in the anamnesis sheet. According to an anthropometric determination of the body mass index, the subjects were devided in three groups 1. normal and underweight (278 subjects, BMI < 25kg/m), 2. overweight (172 subjects, BMI 25kg/m- 29.99kg/m ) and 3. obese (105 volunteers, BMI > 30kg/m). The hypotheses were performed at a significance level of = 0.05 using IBM SPSS® managing multiple regression analyzes with repeated measures, as well as multiple variance analyzes (MANOVA).<br />Results: The answer to the main hypothesis regarding a difference in therapeutic success between the three BMI categories was unable to identify any significant differences between the three groups. Treatment success was also significantly observed in the maintenance phase (Rev-Rec) for all BMI groups. When comparing the BMI categories, a significantly higher ST level for BMI > 30 kg/m could be determined compared to BMI 25-29.99kg/m (p = .042) and BMI < 25kg/m (p = .032). In addition, these differences in obese patients tended to last across all observation periods for all tooth groups and significantly (p = .017) in the anterior region. With regard to tooth loss, BMI group patients > 30 kg/m started with significantly fewer (p <.001) teeth than patients in the 25-29.99kg/m group, and those with significantly less compared to the group < 25 kg/m. In addition, significant differences (p's <.01) in tooth loss with attention to the course of therapy were assessed between all BMI categories. Adipose and obese had significantly fewer teeth than normal weight at all times. The individual predictors of age, sex, smoking and diabetes mellitus provided no significant explanatory value for the decrease in probing depths.<br />Discussion: Overweight per se played a minor role on the outcome of conservative periodontitis therapy in general. However, the comparison with obesity showed significant differences in ST levels at the start of therapy and in the anterior region during the maintenance phase. This fact suggests a negative impact of a pathological BMI of > 30kg/m and higher on the periodontal disease itself. The question remains whether the increased early tooth extractions of groups > 25kg/m during therapy and thus a loss of pathological ST from the data can falsify the results.