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From Orthodontically Driven Corticotomy to Orthodontically Driven Osteogenesis: Tissue Engineering to Enhance Orthodontic Treatment, Guided by the Orthodontist
Federico Brugnami1 and Alfonso Caiazzo2
1 Private Practice Limited to Periodontics, Oral Implants and Adult Orthodontics, Rome, Italy
2 Department of Oral and Maxillofacial Surgery, Practice Limited to Oral Surgery and Implants, Centro Odontoiatrico Salernitano, Italian Society of Oral Surgery and Implants (SICOI), MGSDM Boston University, Salerno, Italy
Introduction
Corticotomy‐facilitated therapy is a technique that aims to enhance the healing process at the molecular level of DNA and stem cells, without creating any anatomical fragments or separate parts. Tissue engineering involves combining two elements: “Tissue,” which refers to a collection of cells with a common purpose, and “Engineering,” which involves marshaling natural forces and manipulating them to achieve a predetermined design (Williams and Murphy, 2008). It is worth noting that in oral surgery and orthodontic literature, “corticotomy” is often confused with “osteotomy.”
While corticotomy refers to the cut of the cortices, osteotomy involves the cut through the entire thickness and potentially creating a mobilized segment of bone and teeth. Suya proposed that the tooth embedded within a block of medullary bone served as the handle by which the less‐dense medullary bone surrounding the teeth was moved block by block (Suya, 1991). However, the Wilcko brothers demonstrated that movement results from a cascade of transient localized reactions in the bony alveolar housing leading to bone healing rather than the repositioning of tooth–bone blocks (Wilcko et al., 2001) (Figure 6.1).
In this book, we will delve into the work of the Wilcko brothers, who developed the innovative technique of combined corticotomy surgery with alveolar grafting for accelerated osteogenic orthodontics (AOO), later changed to periodontally accelerated osteogenic orthodontics (PAOO®). The orthodontically driven corticotomy (ODC) concept emphasizes the central role of the Orthodontist in guiding the process, using the powerful tool of regenerative corticotomy (RC), osteogenic orthodontics (OO), orthodontically driven osteogenesis (ODO), and PAOO® interchangeably, based on the latest scientific evidence confirming their osteogenic potential (Brugnami et al., 2018, 2021).
Surgical Techniques: The Beginning of Tissue Engineering in Orthodontics
As described in previous chapters, corticotomy was initially developed as an in‐office alternative to orthognathic surgery. However, it was invasive, technically demanding, time‐consuming, and not patient‐friendly (Kole, 1959). The surgery has been modified for years, especially after Suya’s publication (Suya, 1991), to make it gradually less invasive and comparable to a full mouth periodontal surgery (Wilcko et al., 2001). More recently, it has been modified so that it can be done flapless (Dibart et al., 2009). Thanks to advancements in surgical techniques, patients can now benefit from more applicable and acceptable procedures. The innovative work of the Wilcko brothers and their PAOO® technique has dramatically improved the field. Corticotomy is not solely used to accelerate orthodontic treatment but also to enhance it. Adding a bone graft to the decorticated area can significantly modify the alveolar foundation, greatly expanding treatment options. (Wilcko et al., 2001). The field of bone engineering is advancing rapidly with the introduction of a groundbreaking technique known as ODO. This innovative approach is revolutionizing orthodontic treatment by enabling the modification and shaping of the alveolar basis. With its numerous advantages, including the ability to address crowding without premolar extraction, create a stronger periodontium, reduce the risk of root resorption, facilitate broader movements, and improve differential anchorage of teeth, ODO offers a comprehensive solution to many orthodontic challenges. Additionally, it can potentially correct transverse and mild sagittal discrepancies and even modify the lower third of the face (Wilcko et al., 2003). In other words, it exponentially expanded the scope of orthodontics, and the speed merely became a marketing bonus to enhance patient acceptance. The treatment was much faster than the traditional one, but the other advantages overtook speed.
Surgical Strategies: Single Flap Corticotomy (SFC) and Tunnel Regenerative Corticotomy (TURC)
SFC slightly modifies the PAOO® protocol (Brugnami et al., 2021). It involves only a single full‐thickness flap elevation in the anticipated direction of the orthodontic movement. It is typically a vestibular flap, and we named it SFC. For example, only the vestibular flap is elevated for decrowding, one of the most common orthodontic problems where corticotomy is used (Brugnami et al., 2010). For arch expansion, the same approach would be utilized. On the other hand, if a lingualization is planned, a single flap on the lingual side can be performed (Figure 6.2a–c). The same is valid for the TURC approach but in a flapless fashion.
The surgical techniques used are described in Chapter 3. Cone‐beam computed tomography (CBCT) scans become critical depending on the type and entity of movement and the periodontal biotype to evaluate 3D alveolar bone morphology and the indications for corticotomy and bone grafting. If the anticipated movement extends beyond the alveolar bone surrounding the tooth (i.e., expansion or proclination) or the bone is <1 mm, the combination of corticotomy and bone graft is strongly suggested.
In the SFC, only one flap is elevated by definition. In most instances, it is also segmental and performed only in the area where the expected movements will occur. It is the base of the concept of ODC.
Corticotomy/surgical decortication: Authors suggest a combination of rear‐vented high‐speed, rotary surgical instrumentation under copious irrigation for speed and outlining of corticotomy (Figure 6.3a, b) and piezoelectric scalpel for refinement and small interproximal corticotomies, especially in the presence of root proximities(Figure 6.4a, b). Some authors suggested that a piezoelectric scalpel could be superior to burs regarding postoperative swelling (Sivolella et al., 2011). In contrast, others have observed a higher temperature and surgical length increase than rotative instruments (Maurer et al., 2008). Up to this point, there is no definitive evidence that piezoelectric scalpels are comparable or superior to classical rotary instruments (Cassetta et al., 2012) and become a matter of personal preference for the surgeon. A piezoelectric scalpel, for instance, becomes much more practical and safe for the surgeon in the flapless approach compared to a rotating bur (Figure 6.5).
The design of decortication is not relevant, but we try to overcome the fact that we do not elevate both flaps by deepening the interproximal cuts of at least 3 mm in the buccolingual direction and being at least 3 mm from the level of bone crest in the apico‐coronal direction. We thin the alveolar bone surrounding the tooth in the direction of movement we anticipate.
It is a crucial part of the corticotomy, which is often neglected and difficult to perform in a flapless manner (Figure 6.6).
Bone grafting and membranes have been extensively discussed in Chapter 3. Slow resorption bovine xenograft or freeze‐dried allograft should be the preferred grafting choice (Figure 6.7a–c).
Autogenous and demineralized freeze‐dried bone grafts, which are more rapidly resorbed, should be avoided unless utilized with a membrane or in layers with slow‐resorbing grafting material acting as a membrane (see Chapter 7). Calcium sulfate and other quick resorbing materials, such as autogenous bone grafts, should be avoided as they have shown limited stability even in a short period (Figure 6.8a–d).
The volume of the graft material used is dictated by the direction and amount of tooth movement predicted by the alveolar bone’s pretreatment thickness and the alveolar bone’s need for labial support.
Near the margin, the lingual and buccal plates are very thin. When the tooth is inclined, it will cause stress and potential resorption at the marginal cervical level in the direction of rotation and on the opposite apical side. Delivering a bone graft where the bone is thin and where the anticipated movement will cause resorbing stress is crucial.
A tunnel approach to grafting that does not mobilize the coronal part of the gingival complex, as described in Chapter 3, is wholly contraindicated for these reasons. The mucoperiosteal component, which has limited stretching potential, will push the graft apically (Figures 6.9a, b, 6.10a–c).
Since most SFCs, as already described, are done in sextants or quadrants, the mobility of the flap may be inferior compared to a complete arch design when elevation has been carried out, as described in Chapter 3. This is limiting the quantity of bone graft we can deliver (0.5 cc for approx 3–4 teeth) and still achieving a tension‐free re‐approximation of the flap. We often try to overcome the lesser volume of graft, following the principle of guided bone regeneration (GBR), and place a resorbable collagen membrane over the graft (Figure 6.11a–c).
Care should be taken to avoid fixation pins that may interfere with orthodontic movements (Figure 6.12).
A membrane will also enhance the possibility of true bone regeneration, compared to a fibrous encapsulation of at least the most superficial layers of the graft.
Only in rare cases, where the thickness of cortical plates in the direction of movements is more than 2 mm (which is not frequent), and the entity of anticipated movement is minimal, bone grafting can be avoided.
The segmental and/or sequential approach to the surgery allows multiple surgeries in sextant according to the orthodontic treatment plan. Contrary to the “classical” Wilcko technique and surgical design, it is, in fact, optional to combine different mechanics to take as much a possible advantage of the regional acceleratory phenomenon (RAP). It will be the RAP that will be initiated according to the orthodontic treatment plan. The segmental approach also amplifies the duration of the rap. Being performed when the actual orthodontic movements take place, according to the orthodontic treatment plan and mechanic, the 4‐month window of opportunity is well spent while correcting other problems (Figure 6.13a–e).
Being aware of potential challenges when considering different surgical approaches is essential. For example, with the piezocision technique, precisely grafting a tunnel can be difficult. It can lead to the graft material being displaced at the midroot level if it has not been delivered under the keratinized attached gingiva. The TURC approach can be used to overcome this challenge. This approach involves mobilizing the mucogingival complex around the tooth’s neck to achieve a coronal displacement. It allows the graft to be placed without tension and the risk of apical displacement. In severe crowding with minimal bony bases, more than the piezocision method may be required. In such cases, a SFC in a segmental fashion can be a less invasive option, allowing for adequate grafting and stimulation of the RAP (Figures 6.14a–d, 6.15a–c, 6.16–6.19).
The Concept of Orthodontically Driven Corticotomy (ODC): From ODC to ODO
Surgical Strategies in ODO: Segmental, Sequential, Segmental, and Sequential Approaches
Segmental Approach
This passage delves into the concept of ODC and the various surgical strategies that can be utilized in this treatment. The segmental approach to corticotomy was initially introduced by Mostafa in 1985 and was later employed in 2007 to showcase how corticotomy could alter tooth anchorage and achieve bodily distalization of upper molars without requiring accessory anchorage (Spena et al., 2007; Figures 6.20–6.23