Role of the orthodontist in orthognathic surgery
Introduction
Maxillofacial surgery targets both hard and soft tissues to improve aesthetics and function, and requires close collaboration between the surgeon and orthodontist.
The objective of this course is to identify the place of orthodontics in the orthodontic-surgical symbiosis.
Definition
Orthognathic surgery is a surgical treatment aimed at correcting dysmorphia due to growth disorders of the maxilla and mandible (hard and soft tissue).
- The different types of orthognathic surgery (hard): 2-1) Interventions on the maxilla
2-1-1) Total maxillary osteotomy: The most classic displacement is done by a “Lefort I, II, III” type osteotomy.
-It allows movement of this arch in the 3 directions of space: Advancement, retraction, impaction and lowering, derotation (advancement on one side and retraction on the other), expansion or contraction by surgical disjunction.
Lefort I Lefort II Lefort III Figure 1: “Lefort I, II, III” type osteotomies
2-1-2) Segmental osteotomy: The procedure is limited to the anterior alveolar sector, or to the alveolar sector as a whole. It is indicated for the treatment of: upper alveolar protrusion, dental open bite associated with hyperdivergence of the maxillomandibular bases and excess vertical height with gummy smile.
Role of the orthodontist in orthognathic surgery
Figure 2: Osteotomy with segmentation and extraction of two premolars to correct a bony open bite associated with a proalveolus.
2-2) Interventions on the mandible
2-2-1) Total osteotomies: they may involve: the ascending branch , the horizontal branch and/or the mandibular angles. Indications: true lower prognathia, micrognathia, laterognathia, mandibular anomalies of the vertical direction (posterior and/or anterior vertical excess).
Role of the orthodontist in orthognathic surgery
Figure 3: Advancement osteotomy Figure 4: Retraction osteotomy
2-2-2) Segmental osteotomies: indicated for:
– Inferior proalveolus or retroalveolus
– The supra or infra-lower incisor-canine alveolus
2-2-3) Genioplasties: macrogenia, microgenia or asymmetry of the chin
- Indications for orthodontic-surgical treatment:
– Major malformation syndromes (Crouzon syndrome, Brodie syndrome, etc.)
– Severe skeletal shifts in all three spatial directions at the end of growth
-Strong dentate-alveolar compensations
– Major aesthetic disturbances
- The role of the orthodontist in orthognathic surgery: 4-1) Phase 1: preparatory or planning and information
During this phase, the patient is examined separately by the two specialists, in order to:
-To classify problems according to their degrees of seriousness.
-To better explain the specificities of their treatment.
The orthodontist, for his part, carries out a thorough clinical examination with additional documents (photos, casts and x-rays) in order to develop a precise diagnosis and an appropriate orthodontic treatment plan;
After the synthesis of the solutions envisaged, the treatment plan is established jointly as well as the practical aspects of the overall care, emphasizing the pre and post surgical phases.
4-2) Phase 2: “pre-surgical orthodontics”:
-It is done by fixed equipment which will include attachments up to the 2nd molar with lingual devices placed preoperatively and intended to achieve bimaxillary blocking.
-The duration of this orthodontic preparation varies depending on the case, between 6 to 14 months.
- Decompensation :
It helps correct alveolar anomalies associated with the shift of the bone bases.
-In the case of retromandibulia, the upper incisors become palatoverted and the lower incisors become vestibuloverted. To achieve sufficient surgical mandibular advancement and obtain a Class I canine and molar occlusion, it is essential to decompensate (correct) the position of the incisors by increasing the anterior overjet. (Class III TIM).
CL II compensated Class II decompensated After surgery
Figure 5: Treatment of compensated class II
-Conversely, in the case of retromaxillary or promandibulia , wearing class II TIMs is essential.
- Transverse coordination of the arches :
It is necessary to know from the outset, to predict the existence or not of a transverse shift and its origin: dental or skeletal, this in order to know the nature of the treatment: orthodontic, by segmental or expansive surgery.
- Leveling and correction of dental crowding:
-As in conventional orthodontics, the extent of dental crowding must be assessed in both arches in order to decide the best way to arrange these arches (with or without extraction)
– Avulsion of the included DDS is done at least 6 months before the operation, thus avoiding the risk of bone fracture during cleavage.
4-3) Phase 3: “Intraoperative orthodontics”
-Maxillomandibular blocking: Surgical arches must ensure maxillomandibular blocking. It is therefore necessary that the orthodontist has taken care of (glued or banded) all the teeth.
-A 3 mm high gingival hook welded or clipped on the gingival side in brass (.032″) or steel must be placed opposite each interdental papilla, on both arches. These hooks allow for metal blocking during the installation of the osteosynthesis system and possibly ensure occlusion by maxillomandibular elastics during bone consolidation (45 days postoperatively).
– Cross-sectional control: if an increase or decrease in the scope
If an arcade is necessary, it is essential to plan for it when constructing the arches.
In the maxillary arch, it is classic to place a loop between the two central incisors and behind the canines (these loops can thus be opened as desired intraoperatively to be adapted to the new arch perimeter).
Figure 6: Placement of gingival hooks
Role of the orthodontist in orthognathic surgery
Figure 7: Anterior bimaxillary blockade
4-4) Phase 4: “post-surgical orthodontic treatment”:
The objective of this phase is:
-To assess the oral opening and the condition of the device after surgery.
-To monitor the recovery of the ICM in RC after removal of the retention splint, the duration of this step should not exceed 6 to 8 weeks.
-To control the transverse direction using a palatal bar or rigid vestibular arch
-To find the same occlusal objectives (static and dynamic) of a conventional orthodontic treatment:
-close small residual diastemas
-obtain correct intercuspation
-in case of segmental surgery and if a divergence has been performed; parallelize the dental axes;
-obtain an aesthetic dental result
-Neuromuscular rebalancing
4-5) Phase 5: “containment and additional treatments”:
This involves perfecting and finishing the results obtained after surgery with their maintenance, the duration and type of retention of which vary depending on the initial malocclusion.
Conclusion
The orthodontist plays a key role in the orthodontic-surgical treatment of maxillary dysmorphia; by arranging and coordinating the dental arches before surgery and ensuring the finishing and stability of the results at the end of treatment.