Background: Orthodontic treatment can greatly impact the periodontium, especially in dentitions with a thin periodontal phenotype. Orthodontic tooth movement can result into iatrogenic sequelae to these vulnerable anatomic conditions, such as development and exacerbation of bony dehiscence or fenestration defects, which can manifest loss of periodontal support and gingival recession (GR). This systematic review aimed to investigate whether periodontal phenotype modification therapy (PhMT) involving hard tissue augmentation (PhMT-b) or soft tissue augmentation (PhMT-s) has clinical benefits for patients undergoing orthodontic treatment. Methods: An electronic search was performed in two major databases for journals published in English language from January 1975 to January 2019 and a hand search of printed journals was also performed to identify human clinical trials reporting clinical and radiographic outcomes of patients receiving orthodontic treatment with or without hard and soft tissue augmentation procedures. Data were extracted and organized into tables for qualitative assessment. Results: Eight studies were identified evaluating the outcomes of PhMT in patients undergoing orthodontic therapy. Six studies evaluated patients receiving PhMT-b via corticotomy-assisted orthodontic therapy (CAOT) and simultaneous bone augmentation while the other two received PhMT-s before tooth movement. No studies investigated PhMT-b alone without CAOT and most studies focused on the mandibular anterior decompensation movements. There was high heterogeneity in the study design and inconsistency of the reported outcomes; therefore, a meta-analysis was not performed. Evidence at this moment supports CAOT with hard tissue augmentation accelerated tooth movement. However, only two studies provided direct comparison to support that CAOT with PhMT-b reduced the overall treatment time compared with conventional orthodontic treatment. No periodontal complications or evidence of severe root resorption were reported for both groups. Four studies provided radiographic assessment of the PhMT-b and demonstrated increased radiographic density or thicker facial bone after the treatment. Two studies reported an expanded tooth movement. One study reported an increase in keratinized tissue width post-CAOT plus PhMT-b, while another study with a 10-year follow-up showed a lower degree of relapse using the mandibular irregularity index when compared with conventional tooth movement alone. Two studies examined the effect of PhMT-s before orthodontic treatment. Unfortunately, no conclusions can be drawn because of the limited number of studies with contradicting outcomes. Conclusions: Within the limited studies included in this systematic review, PhMT-b via particulate bone grafting together with CAOT may provide clinical benefits such as modifying periodontal phenotype, maintaining or enhancing facial bone thickness, accelerating tooth movement, expanding the scope of safe tooth movement for patients undergoing orthodontic tooth movement. The benefits of PhMT-s alone for orthodontic treatment remain undetermined due to limited studies available. However, PhMT-b appears promising and with many potential benefits for patients undergoing orthodontic tooth movement. There is a need for a higher quality of randomized controlled trials or case control studies with longer follow-up to investigate the effects of different grafting materials and surgical sites other than mandibular anterior region.
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