PAOO technique for the bimaxillary protrusion: Perio-ortho interrelationship

Abstract

An increasing number of adult patients have been seeking orthodontic treatment, and a short treatment time has been a recurring request. To meet their expectations, a number of innovative techniques have been developed to accelerate orthodontic tooth movement. Significant acceleration in orthodontic tooth movement has been extensively reported following a combination of selective alveolar decortication and bone grafting surgery with the latter being responsible for the increased scope of tooth movement and the long-term improvement of the periodontium. Six patients who have been diagnosed as class I malocclusion with bimaxillary protrusion were selected. A modified corticotomy procedure was carried out The active orthodontic treatment was begun within 1 week after surgery and follow up. All the patients reported the minmalpain and mild swelling 2 days following the surgical procedure. The mean treatment time for these patients was 17.4 months, with the distalization of the canines being mostly completed in 8.5 months. Periodontallyaccelerated osteogenicsorthodontic tooth movement procedure or selective alveolar decortications or corticotomy approach is one of the surgical techniques developed to reduce the time for orthodontic treatment. This newer approach is leading to short orthodontic treatment time and great patient acceptance.

INTRODUCTION

Periodontally accelerated osteogenic orthodontics (PAOO) technique is a combination of a selective decortication-facilitated orthodontic technique and alveolar augmentation.[1–3] With this technique, one teeth can be moved 2-3 times further in one third or one fourth of the time required for traditional orthodontic therapy 3-6. It can be used to treat moderate to severe malocclusions in both adolescents and adults and can also reduce the need for extractions.

Surgical intervention to affect the alveolar housing and speed tooth movement has been used in various forms for more than a hundred years. Heinrich Köle's publication in 1959[4] was the beginning for the surgically accelerated orthodontic tooth movement. Köle believed that it was the continuity and thickness of the denser layer of cortical bone that offered the most resistance to tooth movement. He theorized that by disrupting the continuity of this cortical layer of bone that he was actually creating and moving segments of bone in which the teeth were embedded. He believed that these outlined blocks of bone could be moved rapidly and somewhat independently of each other because they were connected by only less dense medullary bone, which would act as the nutritive pedicle and maintain the vitality of the periodontium. The blocks of bone were outlined using vertical interradicularcorticotomy cuts both facially and lingually and these were joined 10 mm supra-apically with an osteotomy cut through the entire thickness of the alveolus.[4]

Over time the supra-apical connecting osteotomy cuts used by Köle were replaced with corticotomy cuts. Gantes and coworkers in 1990[5] reported on corticotomy-facilitated orthodontics in fiac adult patients in whom space closing was attempted with merely orthodontic forces. The mean treatment time for these patients was 14.8 months, with the distalization of the canines being mostly completed in 7 months. The mean treatment time for the traditional orthodontic control group was 28.3 months. Wilcko and coworkers[1] reported that in a surface computed tomographic (CT) scan evaluation of selectively decorticated patients was that the rapid tooth movement was not the result of bony block movement, but rather to a transient localized demineralization-remineralization phenomenon in the bony alveolar housing consistent with the wound healing pattern of the regional acceleratory phenomenon (RAP), developed by Frost and Jee and described in the periodontal literature by Yaffe and coworkers.[6] The demineralization of the alveolar housing over the root surfaces apparently leaves the collagenous soft tissue matrix of the bone, which can be carried with the root surface and then remineralizes following the completion of the orthodontic treatment. They have also demonstrated that it is not the design of the selective alveolar decortication that is responsible for the rapid tooth movement[4] but rather the degree of tissue metabolic perturbation per se. Ferguson and coworkers have further defined this to be an osteopenic process.[5,6]

The role of periodontists in the PAOO is becoming increasingly important. It is important for the periodontist to know the details of the procedure to fulfill the need of the patient and thus helping the orthodontist in attaining the quicker and stable results.

The aim of this report is to present the rapid and effective modified alveolar corticotomy-facilitated orthodontic treatment of an adult case with severe malocclusion.

CASE REPORT

Six patients who have been diagnosed as class I malocclusion with bimaxillary protrusion were selected [Figure 1]. All the patients had a convex facial profile and maintained good oral hygiene. All of them reported to have good systemic health.

Figure 1.

Preoperative

Treatment objectives

The treatment objectives included correction of bimaxillary protrusion and correction of dental relationship. To attain the objectives, the extraction of upper and lower firac premolars with maximum anchorage mechanics was planned. All the patients were explained regarding the PAOO and the patient consent was obtained for the surgical corticotomies.

Surgical procedure

A modified corticotomy procedure was carried out under local anesthesia. A mucoperiosteal flap preserving the gingival margin was elevated beyond the apices of the lower incisor. The greatest mesiodistal width of the incisors guided the vertical bone cuts in the cortical bone from the gingival margin to 2-3 mm below the apices of the teeth. The vertical cuts were performed from the distal of the right lower canine to the distal of left canine with a 0.5-mm diameter stainless steel round bur. These vertical cuts were deepened in the cortical bone about 1.5-2 mm and extended to spongiosa. The vertical cuts were joined using the horizontal cuts. After bleeding control, bone graft was placed and the fl T was repositioned and closed with interrupted sutures [Figures 2–5]. The active orthodontic treatment was begun within 1 week after surgery. Similar surgical procedure was followed for the maxillary teeth [Figure 6] all the patients were given postopertative antibiotics and anti-inflammatory agents 5 days following the surgery.

Figure 2.

Maxillary anterior teeth coticotomy

Figure 5.

Postoperative left side

Figure 6.

Postoperative right side

Figure 3.

Bone graft placed

Figure 4.

Bone graft placed in the corticotomy site in the lower anteriors

The mean treatment time for these patients was 17.4 months, with the distalization of the canines being mostly completed in 8.5 months [Table 1]. In one case, there was mild subcutaneous hematoma, after maxillary anterior teeth corticotomy, which was subsided within a week. All the patients reported the pain and mild swelling 2 days following the surgical procedure.

Table 1.

Mean treatment period

DISCUSSION

Alveolar corticotomies have been commonly used in conjunction with orthodontics. Concerns about the possible risks of corticotomy procedure have led to the modification of this technique. The original technique described by Kole[4] included a combined interradicularcorticotomy and supra-apical osteotomy. Although the results of the Kole osteotomies were stable, pulp mortifications were not rare.[7] Later, the supra-apical osteotomy was replaced by corticotomy, and labial and lingual corticotomy cuts were used to circumscribe the roots of the teeth.[8,9] Park et al[10] introduced the alternative approach consisiting of incisions directly through the gingiva and bone using a combination of blades and a surgical mallet. While decreasing the surgical time (no flaps or sutures; only cortical incisions), this technique did not offer the benefits of bone grafting to increase periodontal support in the areas where expansive tooth movement was desired. In addition, the extensive hammering in office to perform the cortical incisions appears to certain patients to be somewhat aggressive. Moreover, dizziness and benign paroxysmal positional vertigo have been reported, following the use of the hammer and chisels in the maxilla.[11] Furthermore, Germac[12] introduced modified corticotomy technique. In which, labial and lingual supra-apical horizontal and lingual vertical cuts were not performed. Dibart[13] introduced a new, minimally invasive procedure, combining microincisions (peizocision) with selective tunneling that allows for hard- or soft-tissue grafting and piezoelectric incisions.

Reduction of orthodontic therapy time is considered to be an important goal in the management of malocclusions. Corticotomy has been proposed as an alternative to conventional orthodontic treatment in difficult adult cases for rapid tooth movement.[1] Chung et al[8] reported that the complete retraction of anterior teeth combined with corticotomy in a case with severe bimaxillary protrusion took less than 3½ months. According to the clinical observations of Duker,[14] the required position of the teeth after corticotomy could be achieved even earlier than 1½-3 months. Geramc[12] observed the total dramatical reduction in the orthodontic treatment time (16 months) when compared with the average treatment time for extraction therapy (31 months).[15,16] In corticotomy-facilitated orthodontics, the reduction of orthodontic treatment time by approximately 50% was observed.[5]

When responding to a traumatic stimulus, the bony tissues initially have a biologic stage called regional acceleratory phenomenon (RAP) characterized by a transient increase in bone turnover and a decrease in trabecular bone density.[6] After fractures or surgical osteotomies, the regional acceleratory phenomenon significantly stimulates healing and tissue reorganization by a temporary burst of localized tissue remodeling.[6] Alveolar corticotomies are surgical interventions limited to cortical bone that were suggested as an alternative to facilitate the treatment of complex occlusal problems.

Sebaoun and coworkers have analyzed the alveolar and periodontal response to selective alveolar decortication as a function of time and proximity to the injury in a rat model.[17] Since traditional orthodontic tooth movement per se will in itself stimulate a mild RAP response, tooth movement was thus intentionally not included in the experimental design. The Sebaoun and coworkers reported that selective alveolar decortication injury resulted in an overwhelming activating stimulus for both the catabolic process (resorption response) and the anabolic process (formation response) in the periodontium. This bone modeling behavior peaked at 3 weeks after decortication surgery at which timethe catabolic response (osteoclastic count) and anabolic response (apposition width and rate) were 3-folds higher. Additionally, adjacent to the injury the calcified spongiosa content of the alveolar bone decreased 2-fold and the PDL surface increased by 2-folds. Thus, there was a dramatic increase in the tissue turnover by the third week after decortication surgery, which dissipated to normal steady state by 11 weeks after surgery. The increased bone turnover was localized to the area immediately adjacent to the injury. Dynamics of the periodontium change in response to the decortication injury could thus be clarified. The PDL activity is enhanced by the decortication surgery, but it is the spongiosa that most likely plays the dominant role in rapid tooth movement. This may also have a positive impact onposttreatment settling and stability.

Generally, the conventional corticotomy techniques include both labial and lingual cuts, although the clinical healing was uneventful, some complications, such as subcutaneous hematomas of the face and the neck.[3] Overcompression of the periodontal ligament can lead to hyalinization necrosis, the removal of which can be associated with root resorption. In an evaluation of the PAOO data base, Machado et al reported a 1.1 mm reduction in apical root resorption of the maxillary central incisors.[18] Although some animal experiments and case reports regarding the effects of segmental alveolar movement after corticotomy revealed no damages in the pulp and no adverse effects on the periodontium of the teeth,[1] it was also reported that reactive inflammation of pulp and vacuolar degeneration in maxillary anterior teeth were observed after protraction with two-stage corticotomy in the maxilla.[7] There have been several reports regarding the adverse effects to the periodontium after corticotomy.[1] These reports range from no problems[1,14,19–21] to slightly interdental bone loss and decrease of attached gingiva[20] and periodontal defects observed in some cases with short interdental distance.[20]

In comparison to traditional orthodontics, the fact that, the teeth can be moved more rapidly with the corticotomy techniques, thus resulting in shortened treatment times, is certainly advantageous to the patient's periodontal health because less time in fixed appliances reduces patient “burnout” and substantially reduces the time available for relatively benign commensal bacterial biofilms to assume qualitative changes and convert to a destructive cytotoxic (“periodontopathic”) potential often seen when fixed appliances have remained on the teeth for more than 2-3 years.[22]

CONCLUSION

Corticotomy-facilitated orthodontics is an effective treatment alternative in adults with severe malocclusion to decrease the treatment time and increase the quality of treatment. The role of periodontist in assisting the orthodontists to achieve the desirable results in shorter period of time is increasing. The periodontist should choose appropriate corticotomy technique, according to the alveolar topography. To avoid complications and to assist accelerated orthodontic tooth movement.