A great many adult patients with malocclusions show reluctance to the traditional orthodontic procedure due to the drawn out treatment time, which usually increase the probability of suffering from other concomitant diseases including dental caries, decalcification, root resorption, gingival recession and other periodontal diseases. Under this context, PAOO technology has been introduced to satisfy the adult patient demand of shorter treatment time without compromising results. Indeed, Orthodontic tooth movement involves the compression of periodontal ligament, further activating the kinetics of crestal bone resorption and reconstruction, which thereby is considered a “periodontal phenomenon” . Thus, it is prerequisite and of great significance to explore the effect of PAOO procedure on the periodontal status in adult patients; in particular, patients with bone fenestration and dehiscence, which in itself is a periodontal hazard. Based on our current study, PAOO technique were demonstrated to be beneficial to the periodontal tissues in terms of soft and hard tissue augmentation, which 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 carries a big weight in the comprehensive treatment for patients with occlusal and esthetic issues. PAOO was firstly introduced by Wilcko in 2001 based on the RAP theory , the author assumed that the surgical trauma in healthy tissues could cause osteopenia, reduce the bone resistance to tooth movement and further allow for the tooth acceleration movement. More importantly, PAOO procedure was identified to be an effective treatment with minimal root resorption and bone dehiscence when compared with the conventional orthodontic treatment. However, when the orthodontic patients in themselves are involved in bone dehiscence and fenestration, it is not clear whether PAOO is still applicable and beneficial to the periodontal tissues, in view of this, the present study was conducted.
In our current study, there were no significant difference in BI, PD and KGW (between at the baseline, postoperative 3, 6 and 12 months), which was in line with the previous study conducted by Miyamoto T et al, periodontal parameters were identified to remain stable after the implementation of PAOO surgery supplied by deproteinized bovine bone mineral with 10% collagen (DBBM-C) or without . BI and PD are closely related to plaque biofilm and gingival inflammation; keratinized gingiva is of great significance for periodontal tissues to resist external stimulation, and its ability to resist inflammation was identified to be positively related to the KGW . Based on the data obtained from our present study, well-controlled plaque could be achieved with good oral hygiene habits, and PAOO didn’t increase the risk of gingival inflammation, for the reduced time within fixed appliance not facilitate the conversion of commensal bacterial biofilms to destructive periodontopathic organisms . In addition, the proportion of teeth with thick gingival phenotype was increased from 43.6% (at baseline) to 63.3% (12 months post-surgery) in the present study, this encouraging results may be the results of GBR procedure, which aimed to periodontal bone regeneration, and the gingival thickness was identified to be positively correlated with the alveolar bone width, then the increase of bone thickness (at mid-root and crestal level) observed in the present study may lead to the increase of thick gingival phenotype . In general, thick gingival phenotype was correlated with a relatively well clinical therapeutic effect, which indicated a relatively promising therapeutic effect of PAOO in patients with bone fenestration and dehiscence. Gingival recession is a commonly complication in orthodontic treatment and it was reported that about 15% of the patients suffer development or aggravation of gingival recession after orthodontic implementation . However, in this particular study, 112 teeth sites without gingival recession before the treatment demonstrated no developing gingival recession 12 months after the operation. On contrary, a significantly reduction in GRD was recognized in the gingival recession sites at the end of observation period. The significant effect on reducing the gingival recession and covering the exposed root may be correlated with the coronally advanced flap technology. 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 obtained 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, performing PAOO technology may be beneficial to the gingival recession sites.
In addition to the reduced periodontal concerns, PAOO procedure was identified to facilitate the increase of bone volume. A previous study reported that both the alveolar bone height and width was increased significantly after the implementation of PAOO procedure. Also, a recent study conducted by Liu and colleagues demonstrated that PAOO treatment can provide adequate graft stabilization in terms of superior coronal augmentation and favorable vertical volume . Coscia et al revealed that PAOO can remarkably increase the horizontal ridge thickness (at the mid-root and apex level) of lower anterior teeth, while no statistical change within vertical alveolar bone was identified . In our current study, the bone height and width (at the mid-root and crestal level) were increased markedly compared with the baseline records, although the increase in apical level was not statistically significant. The observed increase in bone thickness and height could be positively related to the bone grafting and the RAP phenomenon .
Root resorption is an undesirable sequelae of traditional orthodontic treatment associated with a long treatment duration , usually attributed to the hyalinization necrosis of periodontal ligament, and commonly identified in adults. However, significant root resorption was not identified in the current study, which was in accordance with the previous findings . Based on the current understanding, after PAOO surgery performed, cortical incision initiates the RAP phenomenon to reduce the resistance to tooth movement, leading to the decrease of the orthodontic treatment time and reduce of 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. However, Although the present study demonstrated favorable results based on the outcomes obtained, there still exists some limitations, the long-term clinical efficacy of PAOO in adult patients with bone fenestration and dehiscence remains unknown. Besides, although the quantity of new bone was identified, the quality of the newly formed bone also needs to be measured and analyzed. In the future studies, we will expand the data pool and continue the study along with histologic analysis, to provide more basic theory and clinical basis for the proper use of PAOO.