Background

At present, the considerable number of adult orthodontic patients is driving demand for aesthetics-centred, function-oriented and fast-paced treatment, which poses a great challenge in clinical practice [1,9]. An accumulating body of research has indicated that PAOO has advantages over traditional orthodontic methods in terms of accelerated tooth movement up to 3 to 4 times, increased scope of orthodontic therapy, abridged treatment duration, sustainable alveolar bone augmentation, increased range of tooth movement, reduced root resorption and enhanced stability of the postorthodontic mandibular irregularity index for at least 10 years [8, 10,11,12]. To our knowledge, although the research to date has indicated that PAOO is a safe, time-consuming and effective treatment, most of the studies were case reports, [13,14,15] and there is a lack of systematic studies to ascertain whether PAOO is safe or detrimental to the periodontal tissues of adults, especially in patients with bone dehiscence and fenestration.

Bone dehiscence (a defect that extends to the cervical surface of the root, leading to marginal alveolar bone loss) and fenestration (a window that affects the root surface but is still bordered by bone along its coronal aspect) are the most common alveolar bone defects [16, 17]. A previous study noted that Class II and Class III subjects showed a high prevalence of bone defects surrounding the anterior mandibular teeth, with rates of up to 41.11% and 45.02%, respectively [18]. These defects usually lead to root exposure, gingival recession and even treatment relapse or failure, which pose challenges in orthodontic treatment [19, 20]. Therefore, shortening the duration of orthodontic treatment and decreasing severe sequelae are of great significance for orthodontic patients, especially adults with bone fenestration and dehiscence, which are also aesthetically significant issues that are time consuming to treat. PAOO has been regarded as a promising therapeutic strategy with minimal side effects in terms of root resorption and bone defect risks [16].

Therefore, the present study was designed to examine the clinical efficacy of PAOO in adult patients with bone fenestration and dehiscence. Periodontal status was evaluated by the bleeding index (BI), probing depth (PD), keratinized gingiva width (KGW), gingival recession level (GRL) and gingival phenotype at baseline and 3, 6 and 12 months postoperatively. Bone volume was also measured during the follow-up period, with the aim of providing guidance for the clinical application of PAOO therapy.

Methods

Study design

The present single-centre, retrospective study included 54 recruited subjects who were prescribed PAOO surgery by the Department of Periodontology, School of Stomatology, ** Sutures for Stabilization of Osseous Grafts With Resorbable Membranes for Buccal Ridge Augmentation: A Technique Report. J Oral Implantol. 2017;43(4):283–90." href="/article/10.1186/s13005-022-00344-z#ref-CR38" id="ref-link-section-d41782544e1688">38, 39]. Most studies have demonstrated periodontal regeneration following the combination approach. A systematic review showed histologically superior healing following the combination of barrier membranes and grafting materials when compared with barrier membranes alone or grafting materials alone [40]. Additionally, to avoid more invasive and less predictable regenerative procedures, stem cells of different origins, such as induced pluripotent stem cells (iPSCs), have been proposed as possible alternatives. IPSCs have the potential to proliferate and differentiate into all cell types derived from the three primary germ layers (ectoderm, endoderm and mesoderm), making them a potential alternative resource for the regeneration of either mineralized tooth components or supporting tissue. In addition, to avoid more invasive and less predictable regenerative procedures, Stem cells of different origins such as induced pluripotent stem cells (iPSCs) were proposed as possible alternative. IPSCs have potential for proliferation and differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm, which could be proposed as alternative in regeneration either of mineralized tooth components or supporting tissue [41].

Root resorption, an undesirable sequela of traditional orthodontic treatment with a long treatment. Thus, the average orthodontic treatment time for adults is 18.7 to 31 months duration, is usually attributed to hyalinizing necrosis of the periodontal ligament and commonly identified in adults [6]. However, significant root resorption was not identified in the current study, which was in accordance with previous findings [28]. Based on the current understanding, after PAOO surgery is performed, cortical incision initiates the RAP to reduce the resistance to tooth movement, leading to a decrease in the orthodontic treatment time and a reduction in root resorption.

The present study, combined with previously published data show that, as a technology combines corticotomy-facilitated orthodontics, alveolar augmentation, and periodontal treatment, PAOO treatment facilitates the management of pre-existing bone fenestration and dehiscence, further improving the periodontal stability. PAOO differs from prior techniques by the additional step of alveolar bone grafting. It is this additional step that is believed to be responsible for the increased postoperative alveolar bone amount, which enhances the long-term orthodontic stability. All of the surgeries in our study were done on the buccal side. The surgery would done on the lingual/palatal side sometimes when patients undergoing lingual orthodontics or the need of lingual inclination of the anterior incisors. However, there lack of the study about lingual PAOO may due to the risk of violating important lingual anatomic structures. Nahm et.al showed that augmented corticotomy on the palate was beneficial for bodily movement in a bialveolar patient with an extremely thin alveolar bone housing [42].

The present study, combined with previously published data, shows that PAOO treatment, as a technology that combines corticotomy-facilitated orthodontics, alveolar augmentation, and periodontal treatment, improves periodontal stability by facilitating the management of pre-existing bone fenestration and dehiscence. However, although the present study demonstrated favourable results based on the outcomes obtained, there still exist some limitations, and the long-term clinical efficacy of PAOO in adult patients with bone fenestration and dehiscence remains unknown. In addition, although the quantity of new bone was ascertained, the quality of the newly formed bone also needs to be measured and analysed. In future studies, we will expand the dataset and continue the study along with histologic analysis to strengthen the basic theory and clinical basis for the proper use of PAOO.

Finally, suitable protective measures must be identified with regard to clothing, operating protocols, disinfection of environments, and management of waiting rooms and front offices under the circumstances of the COVID-19 pandemic [43].

Conclusion

The data obtained in the present study show that PAOO may represent a promising, safe, and effective treatment for adults with bone fenestration and dehiscence; it can result in improved periodontal health and simultaneously facilitate the repair of bone dehiscence and fenestration on the labial aspect of the mandibular anterior area, which can also be beneficial to soft tissue. However, further clinical investigations should be performed over a long follow-up period to evaluate long-term stability after PAOO.