Many adult patients with malocclusions are reluctant to undergo traditional orthodontic procedures due to the prolonged treatment time, which usually increases the probability of suffering from other concomitant diseases, including dental caries, decalcification, root resorption, gingival recession and other periodontal diseases. In this context, PAOO technology has been introduced to satisfy adult patients’ demand for shorter treatment times without compromising the results. Indeed, orthodontic tooth movement involves the compression of the periodontal ligament, accelerating the kinetics of crestal bone resorption and reconstruction in what is known as the “periodontal phenomenon” . Thus, it is necessary and, indeed, highly significant to explore the effect of the PAOO procedure on periodontal status in adult patients, particularly in patients with bone fenestration and dehiscence, which is a periodontal hazard in itself. Based on our current study, the PAOO technique was demonstrated to be beneficial to periodontal tissues in terms of soft and hard tissue augmentation; thus, PAOO may represent a safe and efficient treatment for orthodontic patients with bone fenestration and dehiscence.
As a novel technology to shorten the treatment period without compromising orthodontic results, PAOO is heavily relied on in the comprehensive treatment of patients with occlusal and aesthetic issues. PAOO was first introduced by Wilcko in 2001 based on the RAP theory . The author assumed that surgical trauma in healthy tissues could cause osteopenia, reduce bone resistance to tooth movement, and allow tooth movement to be accelerated. More importantly, the PAOO procedure was identified as an effective treatment with minimal root resorption and bone dehiscence compared with conventional orthodontic treatment.
In our current study, there were no significant differences in BI, PD or KGW (between baseline and 3, 6 and 12 months postoperatively). These findings were in line with a previous study conducted by Miyamoto T et al., in which periodontal parameters remained stable after the implementation of PAOO surgery supplemented with deproteinized bovine bone mineral with 10% collagen (DBBM-C) or without DBBM-C . BI and PD are closely related to plaque biofilm and gingival inflammation; keratinization of the gingiva is of great significance because it enables periodontal tissues to resist external stimulation, and the ability to resist inflammation was identified to be positively related to KGW. All of the patients which recruited in our study are people with bone fenestration and dehiscence. According the presented study, the KGW of orthodontic patients without bone fenestration and dehiscence had significantly difference (0.48 ± 1.84 mm) after augmented corticotomy-assisted orthodontics (ACAO) compared with traditional orthodontic patients. In addition, traditional orthodontic patients even appeared new gingival recession . Based on the data obtained from our present study, good control of plaque could be achieved with good oral hygiene habits, and PAOO did not increase the risk of gingival inflammation because the reduced time with a fixed appliance did not facilitate the conversion of commensal bacterial biofilms to destructive periodontopathic biofilms . In addition, the proportion of teeth with a thick gingival phenotype was increased from 43.6% (at baseline) to 63.3% (12 months postoperatively) in the present study; these encouraging results may be the results of the guided bone regeneration procedure, which aims to promote periodontal bone regeneration. The gingival thickness was found to be positively correlated with the alveolar bone width. The increase in bone thickness (at the mid-root and crestal levels) observed in the present study may have given rise to the increase in the thick gingival phenotype . In general, a thick gingival phenotype was correlated with a relatively good clinical therapeutic effect, which indicated a relatively promising therapeutic effect of PAOO in patients with bone fenestration and dehiscence. Gingival recession is a common complication in orthodontic treatment, and it was reported that approximately 15% of patients suffered development or aggravation of gingival recession after orthodontic treatment . However, in this particular study, 112 tooth sites without gingival recession before the treatment remained free of gingival recession 12 months after the operation. In fact, a significantly reduction in GRL was recognized at the gingival recession sites at the end of the observation period. The significant reduction of gingival recession and covering of the exposed root may be correlated with the use of coronally advanced flaps. Additionally, the improved stability of the periodontium was considered to be a result of managing bone dehiscence and fenestration, which can decrease the possibility of periodontal tissue recession . Collectively, these data indicated that the PAOO procedure does not increase the risk of gingival recession and tissue inflammation in patients with bone fenestration and dehiscence, and to a certain degree, applying PAOO technology may be beneficial to gingival recession sites.
In addition to the reduced periodontal concerns, the PAOO procedure was observed to facilitate an increase in bone volume. A previous study reported that the alveolar bone height and width both increased significantly after the implementation of the PAOO procedure. Additionally, a recent study conducted by Liu and colleagues demonstrated that PAOO treatment can provide adequate graft stabilization characterized by superior coronal augmentation and favourable vertical volume . Coscia et al. revealed that PAOO could remarkably increase the horizontal ridge thickness (at the mid-root and apex levels) of the lower anterior teeth, while no significant change in vertical alveolar bone was identified . In our current study, the bone height and width (at the mid-root and crestal levels) were increased markedly compared with the baseline values, although the increase at the apical level was not statistically significant. The observed increase in bone thickness and height could be positively related to bone grafting and the RAP .
According to the recent survey, VBH was partially determined by the design of surgical incisions with tension-free design, having adequate membrane coverage and the augmented grafting material displacement and leakage [36, 37]. All of the patients recruited in our study used deproteinized bovine bone material (Bio-Oss, Geistlich, Wolhuser, Switzerland) combined with the collagen membrane (Geistlich). There are two reasons for using collagen membranes: decreasing the leakage of bone materials and preventing epithelial cells from affecting osseointegration. Fibroblasts as well as bone-forming cells are able to attach to, proliferate on and migrate over collagen membranes, which would help to achieve better functional periodontal regeneration [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 . 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 .
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 . However, significant root resorption was not identified in the current study, which was in accordance with previous findings . 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 .
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 .