ROLE OF THE ORTHODONTIST IN ORTHOGNATHIC SURGERY
Introduction
Initially intended for the treatment of major syndromes, orthognathic surgery has seen its indications multiply, thanks to the establishment of a dialogue between surgeon and orthodontist, and the reduction of surgical and post-surgical procedures. These orthodontic-surgical treatments retain precise indications , and should not be systematized.
It is the orthodontist who first examines the patient, and it is he who therefore establishes the indication for surgery. He will then accompany the latter before the intervention during the pre-surgical preparation, and systematically review the patient at the end of the hospitalization in order to perfect the occlusion.
1/Indication of surgical therapy:
Surgical treatment of dysmorphoses depends on certain criteria:
l -The severity of the dysmorphosis and the associated aesthetic damage.
2-The hereditary nature of the observed anomaly.
3-The usual evolutionary characteristics of this type of dysmorphosis . Thus, skeletal classes III, facial asymmetries, large vertical excesses tend most often to worsen during growth.
4- The type of growth of the patient, the estimation of which is somewhat random.
The indications for surgical-orthodontic protocols concern:
l- major syndromes: these major craniofacial anomalies, often accompanied by significant aesthetic damage, require complex and often early surgical protocols.
2- severe skeletal shifts which exceed the possibilities of alveolar compensation, or whose aesthetic repercussions require surgical restoration of facial balance and harmony.
3- orthodontic treatments with aesthetic risk: in some cases, malocclusion, in particular increased incisal overjet, provides support to the lips minimizing the repercussions of dysmorphosis on facial aesthetics. This is for example the case of class II division 1 in a hypo divergent skeletal pattern where the retraction of the maxillary incisors risks unfavorably hollowing out the nasomental profile.
4- relapses or therapeutic failures linked to unfavorable growth or a lack of cooperation during the orthopedic phase.
2/Role of the orthodontist in planning therapy:
The therapeutic strategy is based on clinical observation and analysis of complementary examinations. This dialogue is most often organized around occlusal and especially cephalometric simulations: pre-surgical setups. They allow us to visualize the impact of the different therapies envisaged, to assess their feasibility and to coordinate them.
ROLE OF THE ORTHODONTIST IN ORTHOGNATHIC SURGERY
2-1 Presurgical orthodontic preparation
Therapeutic calendar
Even when the surgical indication is made early, orthognathic surgery only occurs at the end of the decline, around 16 or 17 years of age in girls, 18 years of age in boys, in order to avoid the risks of relapse linked to unfavorable late mandibular growth, especially in class III and asymmetries.
Orthodontic preparation is most often carried out just before surgery, around 15 or 16 years of age depending on its estimated duration and the presumed date of the intervention.
Objectives of orthodontic preparation
This orthodontic phase fulfills four essential objectives :
1-Manage intra-arch problems: Like a classic orthodontic treatment, it ensures:
– resolution of crowding and correction of dental dystopias,
– the placement of included teeth;
– the restoration, if possible, of arch symmetry.
In the context of surgical-orthodontic treatment, the analysis of space requirements remains identical to that of classic orthodontic treatment. The choice of possible extractions and the methods of closing the spaces must, however, integrate the needs of alveolar decompensation.
-2 Lift alveolar compensations
The orthodontist must remove all alveolar compensations and give the surgeon the range of movement necessary for skeletal correction. He must therefore re-establish, at the level of occlusal relationships, a gap identical to the surgical movements envisaged.; He thus aggravates the inter-arch relationships by: the use of reverse maxillary tractions: TIM class II in classes III and TIM class III in classes II; reverse extraction choices: 15, 25, 34 and 44 in classes II and 14, 24, 35 and 45 in classes III.
In the sagittal direction, the lifting of the alveolar compensations aggravates the overjet and induces a displacement of the lips which increases the aesthetic prejudice. The patient must be informed before treatment of the aesthetic consequences of this phase which can be difficult to bear psychologically. The removal of the alveolar compensations concerns the three dimensions of space.
-3 Ensure the congruence of the arches
The most perfect possible intercuspidation at the end of the procedure is the guarantee of good post-surgical stability. Orthodontic preparation must therefore
harmonize the arch shapes, manage any transverse discrepancies and obtain optimal alignment. Pre-orthodontic surgical intermaxillary disjunction is indicated when the suture is ossified and there is a discrepancy in the maxillary and mandibular intercanine diameters. Like orthodontic disjunction, it provides space on the arch to correct certain maxillary crowding problems without extraction. It is similar to distraction.
In this case, the orthodontist must remove the transverse alveolar compensations and correct the vestibuloversion of the lateral sectors. It worsens the transverse occlusion and thus restores a bilateral reverse occlusion most often.
Most orthodontic finishing must be done before surgery to ensure this intercuspation goal.
4-Provide anchoring for the post-surgical retention device : Surgical arches, large rectangular arches with welded or clipped pins, constitute a reliable anchor that respects the periodontium for intraoperative intermaxillary blocking during osteosynthesis but especially during post-operative retention.
2-2 Pre-surgical assessment
In the absence of intermaxillary landmarks, the orthodontist checks the progress of the preparation by making models on which he assesses the congruence of the arches.
At the end of the orthodontic preparation, a new pre-surgical assessment is carried out based on the models and new X-rays or a CT scan of the patient. If the objectives of the orthodontic preparation have been achieved, the date of the intervention is set jointly by the orthodontist and the surgeon.
2-3The surgical palette: Let us quote for the record:
– Total maxillary osteotomies of Le Fort I, Le Fort II.
– Total mandibular osteotomies (DALPONT-OBWEGESER sagittal cleavage.
– Genioplasties for functional and aesthetic purposes.
– Surgery of the muscular environment (cheiloplasty, glossoplasty, etc.).
The surgeon must respect the play of the temporomandibular joint,
muscular balance, bone continuity and the neurovascular bundle. Restoring functional balance and aesthetic harmony of the face sometimes requires combining contour surgery (profiloplasty) or muscle strap surgery.
ROLE OF THE ORTHODONTIST IN ORTHOGNATHIC SURGERY
2-4 Post-surgical phase:
During this phase, four essential missions must be accomplished by the surgeon, the orthodontist and the associated multidisciplinary team.
Psychological support for the patient
This is the main risky phase of these treatments, even if in the long term the various studies highlight the benefits of these interventions: The radical transformation brought about by surgery can have major psychological repercussions. The patient no longer recognizes himself and must regain his image. The loss of proprioception aggravates this disorientation. In addition, the postoperative edema does not allow him to clearly understand the result obtained.
Monitoring and containment of the surgical result
Transient labiomental anesthesia is common in sagittal cleavage mandibular osteotomies. Recovery is more or less rapid.
The contention of osteotomies is currently mainly ensured by the osteosynthesis device , in particular miniature plates. Blocking by intermaxillary traction, of variable duration, perpetuates the intercuspidation
maximum obtained. They do not concern the posterior sectors of the arches in order to avoid any joint overload.
Establishing a new neuromusculoskeletal balance
The intervention disrupts the proprioceptive mechanisms and induces muscle contractures and incoordination. Intermaxillary tractions, in addition to their role of containment, relieve the orofacial musculature and secure the patient during this phase of incoordination. At the end of this phase of containment, careful physiotherapy allows a new neuromusculoskeletal balance to be established, functions to be re-educated and the amplitude of mandibular movements to be restored.
Rehabilitation of parafunctions or dysfunctions that have appeared or persisted may be necessary to maintain the stability of the result. Monitoring of the ATMs must be established by the occlusodontist during this phase in order to monitor their adaptation to the new anatomical and physiological conditions.
2-5 Orthodontic finishes
Classically, this phase of post-surgical orthodontics is limited (3 to 8 months depending on the authors and the cases), because most of the orthodontic finishing work was done before the operation. Its main aim is to establish the occlusion and to correct the parasitic effects of intermaxillary traction on the anterior and lateral torques and the last imperfections. (diastemas, rotation, etc.)
Conclusion
Thanks to the close collaboration between surgeon-orthodontist teams, to advances in surgical techniques and diagnostic imaging, orthognathic surgery provides increasingly effective solutions in the treatment of facial dysmorphoses. It helps to rebalance
the facial skeleton ensuring aesthetic reharmonization and functional normalization.
Distractions complete the range of osteotomies and open up other treatment possibilities.
One of the major difficulties for the orthodontist remains, in certain borderline cases, to assess early the need for intervention, the evolution linked to growth being uncertain.