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S. Nares (ed.)Advances in Periodontal Surgeryhttps://doi.org/10.1007/978-3-030-12310-9_14
14. Surgically Facilitated Orthodontic Therapy
CorticotomyAccelerated orthodonticsInterdisciplinary dentofacial therapyPeriodontics-orthodonticsBone grafting
It is widely accepted that diseases of the oral cavity have effects which reach past the head and neck area and may significantly impact the general health of the patient. Whether it is malocclusion, caries, attrition, erosion, periodontitis, deficient dentoalveolar bone volume, mucogingival discrepancies, or the impairment of craniofacial structural integrity, patients often find themselves at risk for systemic comorbidities. Increasingly, the underdeveloped or compromised airway and the myriad health impairments this may cause have become an emerging focus of dentistry. Deficiencies in dentoalveolar bone volume (relative to the dentition) and discrepancies in skeletal relationships can reduce oral cavity and oropharyngeal airway volume. Dentoalveolar volume deficiencies are manifesting with increasing prevalence as dental crowding, inappropriately compensated arch forms, and malocclusion.
Surgically facilitated orthodontic therapy (SFOT) uses corticotomies and decortication within the dentoalveolar and alveoloskeletal bone complex to stimulate the regional acceleratory phenomenon (RAP) [1–6] and upregulate bone remodeling in order to facilitate tooth movement as a part of orthodontic decompensation measures. It also generally includes efforts consistent with guided periodontal tissue regeneration (where fenestrations or dehiscence’s are present) and/or dentoalveolar bone augmentation. This treatment modality is based on addressing the etiology of the core problem and is aimed at achieving a physiologically sound and homeostatic resolution. The harmonization of tooth-to-tooth, tooth-to-jaw, jaw-to-jaw, and jaws-to-face relationships, when implemented appropriately, can provide the patient with stable, sustainable esthetics and function.
SFOT is emerging as a pivotal component of interdisciplinary dentofacial therapy (IDT) for the improvement of overall health. However, SFOT is demanding for both patient and treating clinician. It requires a high level of training, focus, attention, and communication by and among all members of the interdisciplinary team as well as thorough communication with the patient about the realistic expectations and outcomes from the therapy.
This chapter discusses SFOT as an integral component of contemporary IDT to establish, enhance, or recreate the underlying homeostatic physiology in order to enhance and facilitate more predictable and sustainable dentofacial outcomes.
14.2 Developmental Impact of Human Evolution and Culture on the Cranio-dentofacial Complex
Dental compensations result from a skeletal disharmony and are commonly seen whenever anterior-posterior or transverse maxillo-mandibular discrepancies are present [11, 12]. The positions of teeth within the mouth represent a homeostatic relationship between the opposing forces of the lips, tongue, oral musculature, and alveolar bone. Dental crowding generally results from a deficiency in dentoalveolar bone volume and associated arch-length deficiency.
Patterns of facial disharmony/skeletal malocclusion and benefit from periodontal-orthodontic therapy involving corticotomy and dentoalveolar bone augmentation (i.e., SFOT/PAOO®)
Malocclusion anatomic description
Treatment planning challenges and opportunities
Treatment options using SFOT prior to OGS
Transverse maxillary deficiency
Highly prevalent malocclusion case type
Usually presents with excess curve of Wilson
Typical correction involves SARPE, which decreases buccal alveolar bone
SFOT/PAOO® allows more optimal decompensation and correction of excess curve of Wilson as well as idealizes axial inclination of teeth by augmenting buccal alveolar bone
Skeletal movement needed with OGS may become purely expansion with improved decompensation (if possible)
SFOT/PAOO® to expand and increase buccal alveolar boundary conditions (i.e., orthodontic walls) laterally, allowing decompensation to occur through buccal root torque
LeFort I osteotomy OGS may reduce the need for tipping to optimize posterior articulation
Skeletal Class II, division 2 dentofacial disharmony malocclusion with severely upright or retroclined maxillary incisors
Notoriously difficult cases to decompensate due to thick crestal bone
May require 20° of torque, exceeding orthodontic capabilities
The use of SFOT/PAOO® induces RAP, which can help achieve more ideal decompensation for the orthodontist because the teeth move in a demineralized bone matrix, which facilitates movement, may improve the predictability of tooth movement, and decreases treatment time
SFOT/PAOO® to induce RAP and allow decompensation to occur in a demineralized bone matrix while augmenting the dentoalveolar bone complex
OGS thereafter to align skeletal discrepancies once decompensation is corrected and inter/intra-arch dimensions are aligned for such correction
Skeletal Class II or III dentofacial disharmony malocclusion with maxillary incisor proclination requiring labial root torque
Crown is in a relatively good position
Root position is unfavorable and requires movement
Dentoalveolar bone volume is limited to accomplish ideal decompensation
Proclination requires labial root torque while holding incisor crown position
Risk is pushing roots out of the alveolar bone and exceeding the alveolar boundary conditions (i.e., orthodontic walls)
Conventional correction may include extraction and/or skeletal anchorage for maximum space closure
Conventional correction necessitates increasing a negative overjet and a larger skeletal correction
If OGS is needed, one-jaw surgery may now become a double-jaw procedure
SFOT/PAOO® to develop dentoalveolar bone and augment/enhance alveolar boundary conditions (i.e., orthodontic walls), facilitating tooth movement and expanding tooth movement capabilities
Skeletal Class III den-tofacial disharmony malocclusion cases with protrusive and retroclined mandibular incisors
Very limited alveolar bone to move teeth safely
“Teeth on a pedestal” presentation on CBCT cross section/sagittal view
Decompensation of mandibular incisor position is impossible with labial crown torque as it can create dehiscences and periodontal problems
Conventional OGS therapy includes antero-posterior reduction genioplasty, which may not look favorable and does not correct the dentoalveolar bone deficiency/volume etiologic problem
SFOT/PAOO® to provide dentoalveolar bone and alveoloskeletal bone augmentation and to allow proclination of mandibular incisors to occur
Skeletal Class II den-tofacial disharmony malocclusions with mandibular incisor proclination needing labial root torque
Severely proclined mandibular incisors requiring decompensation for future OGS
Limited dentoalveolar bone to accomplish labial root torque movement while allowing roots of teeth to be placed in bone
Typical plan: extract and decompensate for OGS
Not an ideal plan when patient has an ideal Holdaway ratio or no additional overjet is needed for desired skeletal correction
If the patient has obstructive sleep apnea, this condition might become worse before becoming better
SFOT/PAOO® to enhance orthodontic decompensation and apply labial root torque and place roots in bone for decompensation
OGS thereafter to correct skeletal discrepancy
An escalating prevalence of malocclusions over the last 250 years [15, 16] correlates with increased consumption of highly processed foods , decreased breastfeeding [18–20], and a uniformly soft diet fed to infants and toddlers. This is theorized to result in a failure to develop forward tongue and lip muscular habits, which perpetuates a reduced oral cavity volume (OCV). Impaired development of craniofacial-respiratory structures may manifest as deficient dentoalveolar bone [21, 22] as well as impaired development of the maxilla and mandible (i.e., hypoplasia and/or retrognathia).
The teeth develop independently of the soft tissue structures and require a specific bone volume for proper alignment within the dental arch. When there are discrepancies between the available dentoalveolar bone volume and the size of the teeth, intraoral forces may move teeth into abnormal positions to compensate (i.e., dental compensations) for the skeletal imbalance, and dental crowding and malocclusions can occur . Crowding may also be accompanied by alveolar dehiscences and fenestrations . Deficiencies in dentoalveolar bone volume and discrepancies in the relationship between the alveolus and skeletal base may limit the extent to which teeth can be safely “decompensated.” These deficiencies and discrepancies narrow the “orthodontic walls” or reduce the orthodontic boundary conditions within which teeth can be safely moved without iatrogenic harm to the periodontium [13, 14].
The impact on oropharyngeal airway volume is an emerging focus of contemporary IDT. The most common manifestation of a suboptimal airway space is sleep-disordered breathing conditions and obstructive sleep apnea (OSA), which has reached epidemic proportions in both adults [25, 26] and children [27, 28]. Intuitively, a larger oral cavity volume should make it easier for air to pass through the upper respiratory track and improve a patient’s ability to breathe. However, the evidence about how directly oral cavity volume may impact these diseases is somewhat equivocal and inconclusive. An increased tongue-to-oral cavity volume has been found to predispose patients to sleep-disordered breathing . Other research suggests that the extraction of four bicuspids does not influence sleep apnea conditions or esthetic perceptions of changes in facial profile, though it would seem to decrease the oral cavity volume [30, 31]. More directed and definitive research is needed in order to more decisively discern the relationship between oral cavity volume and breathing disorders.
14.2.1 Embryogenesis of the Craniofacial Skeleton
A thorough understanding of embryologic and developmental processes leading to craniofacial anatomic development is essential to appreciate—and therapeutically reestablish—the homeostatic balance essential for sustainable craniofacial stability and esthetics. This is particularly true if one is to be successful at sustainable bone regeneration or augmentation/construction efforts.
Unfortunately, it is not possible to discuss the details of embryogenesis of the craniofacial skeleton nor the impact of epigenetic processes influencing individual response to SFOT surgery in this chapter, but rather to indeed acknowledge its vital role in surgical planning. As such, the reader is encouraged to consider the indicated references for further background and study [32–48].
14.2.2 Biology of Corticotomy-Assisted Orthodontic Tooth Movement
The regional acceleratory phenomenon (RAP) was first described by Harold Frost in 1983 in response to bone injury (specifically, fracture healing) . The four key events include osteopenia, vasculoneogenesis leading to bone resorption and formation, activation of normal biologic processes from chemical signals sent by inflammatory cells, and a duration of 6–12 weeks during which RAP is present. In the context of SFOT, corticotomy and dentoalveolar bone decortication surgery has been shown to result in a coupled demineralization-remineralization of bone through which teeth are moved [1–6]. Zimmo et al. published a systematic review summarizing the history and research supporting the safety of SFOT, its efficacy in the IDT setting, and the pivotal role of the RAP in accelerating tooth movement and alveolar augmentation . The implications of combined therapy (surgery and tooth movement) include (1) a bypass of the lag phase (rate-limiting step in orthodontia) whereby the osteoblastogenesis-osteoclastogenesis coupling mechanism occurs earlier, (2) there is a reduction in the risk of hyalinization of the periodontal ligament, and (3) a reversible osteopenia occurs with no pathologic loss of bone density, mass, or volume .
14.2.3 Facially Prioritized Interdisciplinary Workflow
Contemporary goals of facially prioritized IDT contribute to a global/comprehensive treatment approach with a restoratively driven and airway-centric context and can be compartmentalized into four relationships. These include Tooth-to-tooth, tooth-to-jaw, jaw-to-jaw, and jaws-to-face .
Tooth-to-tooth planning is critical to (re)establish and maintain a homeostatic intermaxillary relationship, which includes anterior protected articulation schemes, an absence of fremitus, optimized arch forms, and interdental relationships. These relationships are critical to the success of restorative dentistry and dental implant therapy.
Teeth-to-jaw/s planning is most effective when cases are envisioned in terms of reproducible case-type patterns, as described by Mandelaris et al.  and shown in Table 14.1. A key overall objective of this phase is to increase dentoalveolar bone availability so that teeth can be decompensated and arch forms expanded, thus increasing oral cavity volume and optimizing airway conditions.
Facial bone is often very thin,: most often 1 mm or less . This lack of buccal bone has been described as the “human problem.” Orthodontic boundary conditions/orthodontic walls are limited and unable to accommodate more advanced tooth movement, as the modulus of elasticity of alveolar bone (in vivo, in humans) has yet to be determined [14, 49]. A key part of SFOT treatment planning involves CBCT imaging to establish pretreatment risk to the periodontium and determine realistic tooth movement possibilities without iatrogenic harm (i.e., bone loss). Care must be taken to evaluate the regional anatomical characteristics of the individual patient. Pretreatment orthodontic simulation software systems, such as SureSmile®, provide a distinct advantage compared to conventional 2D planning or even 3D planning that does not account for the changes in the dentoalveolar compartment (but only displays the tooth-to-tooth relationship).