Since ancient times, there have been attempts to alter bone growth in quantity and direction to create beautiful smiles by moving teeth or remodelling the shapes of the bones with various appliances. Initially, orthodontists focused primarily on moving the teeth while allowing the alveolar bone to naturally remodel, often overlooking the alveolar topography. However, in the 21st century, orthodontists have widened their horizons of treatment approaches and wider age range with more adult patients seeking treatment than before. Limitations in traditional orthodontic techniques and the duration of therapy often create barriers to the patient’s willingness to accept orthodontic treatment. Therefore, an interdisciplinary approach to treatment, in conjunction with the principles of tissue engineering and regenerative surgery, has evolved to allow the manipulation of alveolar bone for rapid tooth movement. Harnessing the cellular regulators of tooth movement is possible by inducing inflammation and chemical mediators through surgery; however, the safety and health of the tissue and biological side effects must be carefully considered.

Experts in the domains of periodontics and orthodontics have synergised to produce a systems and techniques of biologically sophisticated, optimal and predictable response of the alveolar bone to enhance tooth movement. Collectively, they represent variable methods, which are denoted as peri-orthodontic surgery. To create biologically optimal and predictable tooth movement, an understanding of periodontal tissues and their response to force combined with surgically induced inflammation is required. Surgically facilitated orthodontic techniques using corticotomies and single- or multiple-tooth osteotomies to enhance orthodontic movements are gaining widespread popularity. These clinical methods provide promising concepts which empower orthodontists to enable better treatment for complex dentofacial problems in a relatively shorter duration. Such techniques have significantly reduced side effects like root resorption and relapse, resulting in more stable outcomes. The need and scope of accelerated orthodontics are given in Table 94.1 .

Various forms of surgical interventions to enhance alveolar bone response to orthodontic force for enhancing the rate of tooth movement have been used for more than a hundred years. The concept of corticotomy was described in the dental literature as early as 1892. Farrar was the first to report the use of his ‘positive system’, a specialised screw to retract the canine into the first premolar extraction space. Around the turn of the 20th century, Codivilla performed the first limb lengthening procedure, utilising external skeletal traction following an oblique osteotomy of the femur. Ilizarov, a Russian orthopaedic surgeon, developed a single-stage procedure to lengthen long bones and later popularised distraction osteogenesis. In 1959, Kole was the first to describe the use of corticotomies to accelerate orthodontic tooth movement. In 1973, Snyder first described Ilizarov’s technique to extend a surgical osteotomy of the canine model. McCarthy et al. were among the pioneers who used the principles of distraction osteogenesis in the craniofacial skeleton. In 1998, Liou and Huang introduced the concept of distraction osteogenesis in tooth movement. However, it was Ferguson and Wilcko who affirmed that by moving teeth through a surgical healing site, tensional stresses on the teeth act synergistically with the growth factors and redefine local bone mass. They called it periodontally accelerated osteogenic orthodontics (PAOO) or accelerated osteogenic orthodontics (AAO), or more popularly, it is called Wilckodontics (WO). Iseri et al. developed a concept of rapid movement of the canines in the dentoalveolar segment in conformity with the principles of distraction osteogenesis. Other techniques have been evolved to accelerate tooth movement. Piezocision-assisted orthodontics is a minimally invasive sophisticated surgical system that enhances bone inflammation, thereby speeding orthodontic tooth movement. Alikhani et al. introduced micro-osteo-perforations (MOP) in the alveolar bone to stimulate the expression of inflammatory mediators, which facilitate an increase in the rate of tooth movement ( Table 94.2 ).

The terminologies used to denote the process of rapid orthodontic movement are listed in Table 94.3 . A new classification of surgically facilitated orthodontic treatment is given in Figure 94.1 .

Surgically facilitated orthodontic tooth movement (SFOTM).

The alveolus is composed of lamellar bone, which is organised into cortical plates which is a compact bone and trabecular bone which is a spongy bone. In a stable biological state, the processes of bone apposition and mineralisation are in equilibrium. The remodelling of trabecular bone occurs at a significantly faster rate than that of cortical bone, primarily due to differences in their surface-to-volume ratios.

Rapid tooth movement following surgery could be attained through corticotomy, in which only the cortical bone is cut, and the medullary bone is intact, or osteotomy, where both the cortical and medullary bone are cut to create a new bone segment.

After corticotomy, the alveolar bone temporarily becomes demineralised, mainly due to the release of calcium deposits from the spongy bone, which is associated with increased osteoclastic activity. This process is known as alveolar osteopenia . Following alveolar osteopenia, new bone osteoid is deposited and supplemented with a bone graft. Healing and remodelling are natural biological responses to injury and surgery in both hard and soft tissues.

The procedures associated with corticotomies resemble those involved in bone fracture healing and consist of three distinct phases: the reactive phase, the reparative phase and the remodelling phase ( Fig. 94.2 ).

The three phases of healing.

Source: Reproduced with permission from Buschang HP, Phillip MC, Ruso S. Accelerating tooth movement with corticotomies: is it possible and desirable? Semin Orthod 2012;18:286–294 .

The reactive phase, which lasts approximately 2 weeks, is characterised by the constriction of blood vessels to minimise bleeding, followed by the formation of a haematoma or blood clot. During this phase, the cells within the haematoma, as well as some nearby cells, undergo necrosis, ^, resulting in the formation of a loose aggregate composed of fibroblasts, intercellular substances and various supporting cells, interwoven with small blood vessels that constitute the granulation tissue. ^,

Following this, the reparative phase commences, during which periosteal cells located near the injury site and fibroblasts within the granulation tissue differentiate into chondroblasts, subsequently producing hyaline cartilage. ^,

The periosteal cells distal to the injury site develop into osteoblasts and form woven bone. These processes result in a mass of hyaline cartilage and woven bone called the callus. The hyaline cartilage and woven bone are then replaced by lamellar bone as the tissue becomes mineralised. The duration between callus formation and mineralisation lasts 1–4 months. ^,

The remodelling phase involves the transformation of bone into functionally competent, mature lamellar bone, a process that takes between 1 and 4 years. Harold Frost observed a direct correlation between the extent of injury and the intensity of the physiological healing response. The more severe the injury, the more rapid and intense the regional healing response becomes. This phenomenon was termed as regional acceleratory phenomenon (RAP).

When a tooth moves through a healing surgical site, the stress it generates on the surrounding teeth works together with growth factors to reshape the local bone mass. Decortication releases marrow cells, stimulates the formation of new blood vessels and exposes the body’s own mesenchymal cells to growth factors. This process introduces a therapeutically induced micro-strain into the bone. This mechanical tension is directly transferred to the nuclear cytoskeleton, which brings about conformational changes in the nuclear DNA and alters the cytoskeletal shape and protein synthesis. This induces osteo-induction. Mechanical signals are converted into biochemical events via osteocyte-canaliculi syncytium. Thus, by using the concept of tissue engineering, we get a newly engineered bone mass ( Fig. 94.3 ). The RAP effect of a corticotomy has a finite period of bone activation, which peaks 1–2 months after corticotomy and extends up to 2–4 months. ^{, ,} Biological stimulus pathways indicate that surgical side effects in humans range from 2 to 3 months, during which 4–6 mm of tooth movement can be expected to occur.

(A) Diagrammatic comparison of steady state versus RAP induced bone resorption with hypertrophied osteocytes and increased number of osteoclasts. (B) Shows cutting cone and secondary osteon formation. (C) 3D diagram shows osteocytic osteolysis within the lamellar bone and illustrates a cutting cone formation and the formation of a secondary osteon.

Source: Reproduced with permission from Prof. Donald J Ferguson, European University College, Dubai Healthcare City, UAE.

Hence, one can say that the quantum of tooth movement could be doubled in the duration of RAP.

In osteotomy-facilitated rapid tooth movement, a reparative callus is formed between the edges of two bones, which are split by an osteotomy. The initial formation of the callus is followed by an application of distraction force, which gradually pulls the bone segment apart, which will hold the callus under tension, aligning the inter-segment gap tissue parallel to the direction of distraction. Tension stress in the gradually stretched tissues produces alterations at cellular and subcellular levels, which in turn stimulates the differentiation of mesenchymal cells into osteoblasts. The tension also enhances the formation of capillaries and, therefore, enhances bone formation.

The technique involves selective decortications of the alveolar bone in the area of desired tooth movement. They primarily focus on weakening the cortical bone–tooth interface. Some techniques suggest buccal and lingual corticotomies followed by bone grafting to facilitate bone expansion. The corticotomies appear to supercharge traditional orthodontic treatment by inducing a state of bone turnover and transient osteopenia, followed by a faster rate of orthodontic tooth movement ( Fig. 94.6 ). CFOT can be broadly grouped into:

• 1.

  Selective alveolar decortication (SAD) and

• 2.

  PAOO or AOO. This technique is popularly known as Wilckodontics.

The process by which corticotomies bring about faster tooth movements.

Source: Reproduced with permission from Buschang HP, Phillip MC, Ruso S. Accelerating tooth movement with corticotomies: is it possible and desirable? Semin Orthod 2012;18:286–294.

Indications and contraindications of CFOT are tabulated in Table 94.5 .

Periodontally accelerated osteogenic orthodontics/accelerated osteogenic orthodontics/wilckodontics

This technique combines SADs in a linear or punctate pattern supplemented with a bone graft. It is performed under local anaesthesia as an outpatient procedure. A total thickness mucoperiosteal flap is reflected labially and lingually using sulcular releasing incisions. The flap should be carefully reflected beyond the apices of the teeth to avoid injury to the neurovascular complex(es) exiting the alveolus and to allow adequate decortication around the apices. Selective alveolar decortication is performed in the form of lines and cuts up to 0.5 mm in depth over all the teeth to be moved. Then, an adequate bio-absorbable bone graft material is spread over the injured bone. This bone graft provides lateral alveolar augmentation with growth factors and bone morphogenetic protein (BMP) substances. Flaps are then repositioned and sutured into place. Sutures should be left in place for at least 2 weeks, and tooth movement should be started 1 or 2 weeks after surgery ( Fig. 94.7 ).

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