Periodontally accelerated osteogenic orthodontics: An interdisciplinary approach for faster orthodontic therapy.

Periodontally accelerated osteogenic orthodontics is a relatively new procedure designed to minimize the time taken for orthodontic treatment. The orthodontist avails of the aid of a periodontist to perform decortication of the bone and places bone graft for rapid orthodontic correction of malocclusion. A PubMed search was carried out to identify papers describing the procedure, and the data were organized in the current format.

The correction of irregular teeth can take a prolonged period of time, thus depending upon various factors such as good patient compliance for obtaining optimal results. There is now a growing need to provide quick fix solutions to the problem of malocclusion.

Periodontally accelerated osteogenic orthodontic (PAOO) treatment is also known as alveolar osteogenic orthodontics or Wilckodontics. It mainly focuses on enhancing the manner in which the periodontium responds to applied forces and on providing for more intact periodontium and increased alveolar volume to support the teeth and overlying soft tissues during retention.

History

surgery.[1] laid the foundation for this procedure by recommending surgical remodeling of the alveolar ridge in order to correct occlusal abnormalities. Where selective alveolar decortication was performed to accelerate orthodontic tooth movement, and bone graft was placed to add volume. The regional osteopenia that occurs by this manipulation allows the orthodontist to give patients an accelerated rate of orthodontic tooth movement and when grafts are placed. The movement of the teeth maintains the osteopenic state past the usual 4-6 months naturally induced by decortication or even some adjacent soft tissue surgery.[23]

Murphy[4] has referred the ability to morph bone with orthodontic tooth movement done in conjunction with periodontal bone activation and alveolar augmentation as “in vivo tissue engineering.” The surgical component of the PAOO technique is an in-office procedure, that has similar level of morbidity as other orthodontic-related surgeries such as third molar removal, bicuspid extractions, gingival grafting, and it certainly carries lesser morbidity than orthognathic surgery.

Frost[5] in his study reported of a physiologic response, called the regional acceleratory phenomenon (RAP) as a response to osseous insult in endochondral long bones. Yaffe et al.[6] also described the same phenomenon in the mandible following periodontal flap surgery.

Wilcko et al.[7] have reported that in an evaluation of corticotomized patients, the small outlined blocks of bone lost their structural integrity due to demineralization of the alveolar bone over root prominences. This apparent demineralization occurred in close approximation to the circumscribing corticotomy cuts both on the pressure side of the teeth and on the tension side of the teeth. The initial alveolar demineralization and subsequent remineralization was consistent with the cascading physiologic events associated with RAP. The facilitated tooth movement subsequent to a corticotomy-based surgery can thus be attributed to a physiologically based periodontal ligament mediated process.[8]

Wilcko et al.[9] have further reported that the remineralization phase of the RAP was complete in adolescents at roughly 2 years post corticotomy surgery, however similar results could not be observed in adult patients, which was likely due to the decreased recuperative potential of adult bone in comparison to adolescent bone. It has also been suggested that the operative signal transduction converting mechanical signal to biochemical events is mediated by the osteocyte-canalliculi syncytium,[1011] that further elaborates on the simplistic events described in the “pressure-tension” model.

Procedure makes, it a better alternative to orthognathic surgery in cases like mandibular skeletal Class-III malocclusion. It also offers better anchorage due to a difference in support around the anchored tooth and the tooth to be moved; furthermore, the treatment window of approximately 4 months provided due to this procedure provides a decrease time duration for orthodontic therapy.

Surgical Technique

The typical PAOO treatment starts with a thorough orthodontic and periodontal evaluation. It is the duty of the orthodontist to formulate and coordinate the treatment plan. In order for the treatment to be successful, no active disease should be present at the time of the surgery, and any infections if diagnosed must be resolved prior to the start of surgical procedure.

The patient must be made aware of the limitations of the procedure and potential complications in the final outcome, and explained about compliance, especially in regard to keeping up with the orthodontic adjustment appointments every 2 weeks.

Decortication

Orthodontic bracket and a light arch wire are placed ideally 1 week prior to the surgery. The surgery is typically performed under general anesthesia. Full-thickness flaps are reflected both facially and lingually around all the teeth regardless of the teeth that are to be activated. Regional osteopenia can result from simply elevation a mucoperiosteal flap,[6] but a more intense and regulated decalcification through variable degrees of decortication is favoured [Figure 1]. This surgical manipulation provides the orthodontist with a “force-friendly” environment to promote normal bone repair. Decorticating the alveolus also stimulates local angiogenesis, which is important because mesenchymal stem cells are also present in artery walls, smaller vessels and may even enter the general circulation.[121314]

Figure 1

A schematic of the cortical scarification or decortication pattern

Bone Activation

The alveolar bone is activated over the root prominences in the direction of the intended tooth movement; usually, the bone in the direction away from which the teeth are being moved should also be activated. Ideally, a thin layer of bone should cover the root prominence in the direction of the intended tooth movement. In order to move a tooth through the long axis of the alveolus an ostectomy is performed through the entire thickness of the alveolus. In most other tooth movements, the bone activation is performed with a combination of corticotomy cuts or intramarrow penetrations that extend through the cortical layer of bone and only to some extent into the medullary bone.[8]

Placement of Bone Grafts

The bone activation is followed by the placement of the particulate bone graft material facially and lingually over the activated bone [Figure 2]. This fact is important, because bone morphogenetic proteins in allografts may further increase the osteogenic potential[15] as they bind to heparin sulfate, heparin and the type IV collagen in the endothelial basement membrane.[16] Concentrations of growth factor can be altered by adding recombinant growth factor (recombinant human bone morphogenetic protein-2) directly into the grafted bone, using absorbable collagen sponges.[1718] Xenografts and synthetic material may be “osteoconductive,” but it may not be adequate just to establish a scaffold for bone growth. While the best evidence suggests an important role for growth factors, we cannot categorically rule out the possibility that volumetric distension of the periosteum itself is an important factor in achieving clinical results, as it too is a functional matrix of bone.[1920212223]

Figure 2

Procedure for periodontally accelerated osteogenic orthodontic: (a) Decortication done, (b) Bone graft placed, (c) Sutures placed, (d) Continuing with orthodontic therapy

In case of the maxilla, when only the anterior teeth are being activated bone grafts can still be used on the buccal aspect of the upper posterior teeth to lessen the likelihood of dark buccal corridors. The amount of the bone grafting material used depends on the extent of preexisting alveolar deficiencies:

The anticipated increase in the dentoalveolar deficiency, and

The amount of lower facial recontouring that one is attempting to achieve

A thin layer of highly reactive bone is very conducive to tooth movement. The opposite of this, a thicker layer of relatively quiescent bone, would thus favor posttreatment stability[8]

A reduction of at least 50% in volume is to be anticipated as the particulate grafting materials are eliminated and replaced by the patient's own natural bone. The bone grafts maintain the space between the periosteum and the activated bone and any micro-movement of the graft must be minimized to obtain optimal results.

Rothe et al.[24] have reported that patients with thinner mandibular cortices are at increased risk for dental relapse. The bone grafting procedure or alveolar augmentation that is performed in conjunction with the bone activation at the time of PAOO surgery will provide for additional alveolar volume over vital root surfaces.[8] In addition, the increased tissue turnover and the complex interplay between demineralization and remineralization subsequent to the bone activation contributes to posttreatment stability through memory loss and improved bite settling.[25]

Flap Closure and Postoperative Care

The integrity of the flaps needs to be appreciated; therefore, incisions vertically and at the base of the flaps need to be avoided as much as possible. The continuity of the flap function as a pouch to hold the compact bone graft material in place that helps minimizes the micro-movement of the graft particles. The goal of the treatment is to achieve increased alveolar volume, but not to have the new bone formation occur so rapidly as to impede the tooth movement.

Therapeutic levels of bone morphogenic proteins would be potentially challenging in this regard, but growth factors that stimulate soft tissue maturation of the overlying flap can also have a positive influence on the bone development through a secondary action.

Nonresorbable, nonwicking sutures are used, which are maintained in place for a minimum period of 2 weeks to allow time for the establishment of the epithelial attachment. The patients should be checked after 4-5 days following the surgery to make sure that the sutures have remained intact.

The patients must not take nonsteroid anti-inflammatory drugs beyond the 1st week postsurgically. Which are prostaglandin inhibitors and can reduce the sterile inflammatory process that is required to ease the rapid tooth movement.

The orthodontic adjustments are generally performed at 2-week intervals. Any major movement requiring orthodontic force is not performed at least until 2 weeks following the surgery to give the RAP a chance to take effect.

Advantages

Less time in brackets

Accelerated treatment time

Less risk of post orthodontic gingival recession and subsequent cervical abrasion

Greater post orthodontic stability and retention

Less risk of root resorption

Less risk of an unfavorable crown to root ratio

Less furcation invasion

Less relapse.

Disadvantages

An expensive procedure

It is a mildly invasive surgical procedure, and like all surgeries, it has its risks

Mild to moderate pain and swelling, and the possibility of infection is seen

Not recommended in Class-III malocclusion.

Contraindications

Bone loss

Root damage

Periodontal disease

Class-III malocclusion

Rheumatoid arthritis.

Summary and Conclusion

The PAOO technique can present the practitioner with the ability to carry out treatments in an in-office setting that would have previously been unimaginable. It is an interdisciplinary collaboration that has integrated the use of traditional orthodontic tooth movement in conjunction with periodontal tissue engineering and regenerative surgery.

The result of this interdisciplinary amalgamation has been rapid orthodontic tooth movement with drastically shortened treatment times and also an increased scope of treatment with reduced side-effects such as root alveolar bone,[19] relapse,[26] inadequate alveolar bone[27] and bacterial factors like caries and infection.

The application of PAOO treatment should not be considered a treatment of last resort, and also in teeth that have become ankylosed as a result of blunt trauma or previous luxation should not be considered. This technique can be used to treat cases of borderline dental Class-III occlusion; however, severe skeletal Class-III situations cannot be adequately addressed with this technique.[26]

The movement brought about with the PAOO technique is dentoalveolar in nature and as such the surrounding periodontium must be healthy. Therefore, reduced alveolar vitality can be caused from the use of bisphosphonates or from a prolonged corticosteroid therapy, which precludes the use of this technique. However, in systemically healthy individuals even severe malocclusion can be adequately managed.

Age is not considered a limiting factor for PAOO technique. In fact, due to the ability to increase the tissue turnover rate by two- to three-fold by PAOO treatment, this can be viewed as a boon for older population.