The aim of this study is to evaluate in a prospective, randomized, controlled clinical trail the effectiveness of preorthodontic piezotomy combined with a buccal bone augmentation (in other name periodontlly accelerated osteogenic orthodontics: PAOO)in the prevention of gingival recession, and in the acceleration of orthodontic tooth movement (OTM).

Patients presenting teeth crowding in mandibulary or maxillary front area, without ongoing periodontal disease, who require OTM with incisor proclination, are included in the study. Patients are randomly allocated into test and control groups. Individuals in both groups receive before OTM a buccal bone augmentation in order to further increase the bony envelope where to teeth are intended to move. Test subjects receive a selected decorticalistation of the buccal bone with a piezosurgical device (piezotomy), while control patients are augmented without piezotomy. 1 week postsurgical multibond orthodontic appliances are bonded to initiate OTM. Teeth movement are measured on cephalometric X-ray images, where an initial and a final (at the end of the nivellation phase) cephalogramm is compared with each other. Buccal bone dimensions are measured on initial and 6th month's postoperatively CBCT images. The investigators' hypothesis is that the buccal bone thickness can be significantly increased, which might prevent the development of gingival recessions. This means, that in both groups the initial and final bone volumes will be comparable without significant difference. It is also hypothesized that the bone changes will not differ significantly between the two groups. However, piezotomy in the test group might have an additional benefit throughout regional acceleratory phenomenon, reducing the duration of OTM.

Inclusion Criteria:

• tooth crowding exceeding a 5mm lack of space (originating from the discrepancy between the overall mesiodostal length of the teeth and the length of the dental arch present at the time of the evaluation)
• thin bone morphotype (buccal width of the cortical layer must be under 1mm)
• incisor proclination in order to eliminate crowding without compensatory extractions.
• informed consent

Exclusion Criteria:

• ongoing periodontitis
• Pregnant women.
• Participation in another clinical study within 30 days prior to study start.
• Alcoholism, drug dependency, heavy smoking (>5 cigarettes/day).
• Known infection with HIV, HBV, or HCV.
• Patients requiring chemo- or radiotherapy.
• Previous or current radiotherapy of the head.
• Uncontrolled or insulin-dependent diabetes mellitus
• Clinically relevant osteoporosis or systemic disease affecting bone metabolism
• Clinically relevant cardiovascular disease e.g., decompensated cardiac insufficiency, hemodynamically relevant heart valve defects, or myocardial infarction during the last three months.
• Clinically relevant blood coagulation disorder.
• Previous or current treatment with systemic corticosteroids (within 2 months prior to screening visit) of more than 5 mg/day prednisone equivalent.
• Previous or current therapy with bisphosphonates at least for 30 days within the last 12 months before screening visit

The persons responsible to measure on the cephalogramms and CBCTs are blinded to the study design