MA. Souissia (Dr), M. Ben Rejeb*b (Dr), J. Bouguilaa (Dr), H. Khochtalic (Pr)a Service ORL et chirurgie maxillo-faciale, CHU la Rabta, Tunis, TUNISIE ;

b Service de Chirurgie maxillo-faciale et esthétique CHU Charles Nicole, Tunis, TUNISIE ;c Service de Chirurgie Maxillo-faciale et Esthétique de Sahloul, Sousse, TUNISIE

Class III skeletal malocclusion: Tips and traps

Introduction:Class III skeletal malocclusion may present several etiologies, among which maxillary deficiency is the most frequent. This type of malocclusion is usually treated with association of orthodontics and orthognatic surgeryRelapse after surgery always has been a circumstance with which maxillofacial surgeons have had to deal.This study reviews the stability of orthognathic movements in Class III skeletal malocclusion using traditional osteotomies and fixation and compares them to what is currently in the literature.

Materials et methods :In this report we present our experience in clinical 40 cases in which the orthodontic surgical treatment was indicated for correction of the class III skeletal malocclusion (34% among different types of orthognatic surgery). A review of the literature is done to complete this presentation.

Results :The most frequent indication was Bimaxillar osteotomy (19).Maxillary advancement with our without rotation movement in asymmetric cases (14). Retrusion and anticlockwise rotation of the mandible were indicated in some cases(7).2 cases of relapse in the isolate SSBO, with end to end incisive relationship.Good occlusal function.

Case 1:

Orthodentic treatment : 22 months(leveling,alignment,alveolo dental decompensation).

Clinical cases

Maxillary advancement: 7 mmMaxillary impaction: 4mmMandibular setback (obwegeser/Daplont): 3mm

Case 2:

Concave face with an nterincisive point shift

Maxillary advancement: 3 mmBilateral sagittal split osteotomy mandibular symetrisation

Case 3:

A segmental orthodontic alignment by a sub apical osteotomy.Maxillary advancement.

In a Class III malocclusion, the mandibular teeth occlude the maxillary teeth by more than a half.This dental relationship is very often associated with a skeletal Class III disharmony involving the middle and lower thirds of the face, and sometimes the cranial base.Therapeutic alternatives for dentoskeletal Class III malocclusions include:orthopedic treatment in growing patients Surgery in adults:Maxillary advancementBilateral sagittal split osteotomy mandibular setbackBoth +/- Genioplasty.Complementary surgery such as Glossecoplasty in real macroglossy.It is fortunate that in most cases, relapse is within the ability of the orthodontist to finish the occlusion.Whether it is caused by muscle pull and function, lack of rigidity in fixation, or postsurgical growth, relapse is still known to occur.Maxillary advancement:Whether using maxillomandibular fixation and wire osteosynthesis or rigid internal fixation, maxillary advancement is a stable movement.According to data from the University of North Carolina, during the first postoperative year a 2- to 4-mm relapse movement occurred in 20% of patients, with 80% of patients experiencing no relapse(1). Long-term follow up (1–5 years postoperative) revealed similar results. Ten percent of patients who had undergone a maxillary advancement had mild relapse at A point . If large maxillary advancement is planned, the use of a step osteotomy with bone grafts placed within the step may prevent backward movement and facilitate rigid fixation(2).

Skeletal and dental malocclusion class IIIMaxillary retrusion

Discussion:

1-Proffit W, Phillips C. Physiologic responses to treatment and postsurgical stability. In: Contemporary treatment of dentofacial deformity. St. Louis (MO): Mosby; 2003. p. 646–76.

2-Perciaccante V, Bays R. Maxillary orthognathic surgery. In: Miloro M, editor. Peterson’s principles of oral and maxillofacial surgery. Hamilton, Ontario (Canada): BC Decker, Inc.; 2004. p. 1179–204.

Bilateral sagittal split osteotomy mandibular setback:Evaluation of stability after mandibular osteotomy is as complicated as in the maxilla.instability is multifactorial, and many issues can lead to what may be termed relapse or instability in mandibular surgery:Fixation failure; Slippage at the osteotomy site; Errors in condylar positioning;Condylar sag; Fossa/Condylar remodeling or resorption; Orthodontic movement; Growth.

The direction of the tendency for relapse in BSSO setback is anterior. Relapse has been reported from 4.35% to 62%The meta analysis by Bays and Bouloux found a relapse range of 10% to 62%, with a mean relapse of 22% in the anterior direction at a mean followup of 28 months.Factors cited to contribute to instability in the BSSO setback include :The magnitude of the setback; Patient ageBrachiocephalic facial pattern; Rigid fixationDistal rotation of the proximal fragment; Concomitant maxillary surgery; Late mandibular growth; Segment incompatibility that does not allow passive fit; Condylar positioning; Opening of the gonial angle.

Surgical tricks:Maxillary advancement > Bilateral sagittal split osteotomy mandibular setback.Osteotomy with bone grafts in maxillary advancement. Controle condylar positioning+++ Prevent distal rotation of the proximal fragmentPassive fit of bone segments Pterygoid muscules desinsertionAssociated Golssoplasty

Orthodontico-surgical stability hierarchy : According to Profitt+++ Maxillary impaction.

Mandibular advancement.Maxillary advancement.Maxillary impaction+mandib advancement.Maxillary advancement+Mandible recession.Mandibular recession.Maxillary lowering.

- - - Maxillary expansion.

Conclusion:A correct diagnosis (skeletal, occlusal and orofacial dysfunctions), planning as well as an appropriate execution of the treatment plan are determinant factors for having success and long-term stability in classIII skeletal malocclusion.

Déclarations d’intérêt : Pas de conflit d’intérêtE-Mail : benrejebmarouen@gmail.com , Souissi_ma@yahoo.fr