The thesis focuses on periodontal-orthodontic treatment of adult subjects with periodontal disease.

Aims: The overall aim of this thesis was to explore the effects, risks and benefits of periodontal-orthodontic treatment on periodontal tissues in subjects with periodontal disease.

Methods: The research was conducted through a systematic literature review (Study 1), a randomised controlled trial (Study 2) and cone beam computed tomography examinations (Studies 3 and 4). The clinical part of the thesis was designed as a randomised controlled trial, which aimed to compare two periodontal treatment timing strategies regarding the effect of orthodontic treatment on periodontal status (Study 2). Fifty subjects with periodontal disease were randomly assigned either to the test (periodontal treatment simultaneous with orthodontic treatment) or control group (periodontal treatment before the start of orthodontic treatment). Initial treatment included oral hygiene instruction, supra- and sub-gingival debridement and was performed for all study patients. Nonsurgical and subsequent surgical periodontal treatment was performed at different time points for the test and control groups. Orthodontic treatment was performed with a straight-wire appliance. Clinical attachment level (CAL) change was chosen as a primary outcome variable. All patients were examined by cone beam computed tomography (CBCT) before and after orthodontic treatment to explore the extent of external apical root resorption (EARR) (Study 3) and changes in alveolar bone levels (ABL) (Study 4).

Results: The findings in the systematic literature review yielded absence of randomized controlled trials orcontrolled clinical trials on comprehensive orthodontic treatment in subjects with periodontal disease. No difference in CAL change, EARR and ABL was found whether orthodontic treatment was performed simultaneously with (test group patients) or after (control group patients) periodontal treatment. Results yielded a median CAL change (sites CAL ≥4 mm) of 0.4 mm (Q1, Q3: 0.19, 0.61). Gain in clinical attachment level was observed in 22 (88%) patients in both treatment groups. CAL remained unchanged in an average of 3/4 of the sites; CAL gain was observed in an average of 1/4 of the sites. Root lengths were shortened in a median of 80.7% (Q1, Q3: 68.0, 90.0) of orthodontically moved teeth with a mean EARR of 1.2 mm (SD 0.44). EARR of <2 mm was observed in 82% of teeth. ABL levels remained unchanged on a mean of 69.3% (SD 8.8) of surfaces, ABL improved on a mean of 15.6% (SD 7.4) of surfaces, more on the mesial and distal, and ABL decreased on a mean of 15.1% (SD 7.5) of surfaces, more on the buccal and lingual.

Conclusions: Based on the results of the present research it can be concluded that periodontal-orthodontic treatment under optimal conditions (experienced clinicians and patients with excellent oral hygiene routines overtime), if needed, could be included in the rehabilitation of patients with periodontal disease without deleterious effects. However, there are two important prerequisites: meticulous personal oral hygiene of the patient and optimal sub-gingival control of inflammation before and throughout the combined treatment.