H. DE CLERCK, S. SICILIANO, H. REYCHLER
BONE  ANCHORAGE :  AN ALTERNATIVE FOR CONVENTIONAL ORTHODONTIC ANCHORAGE

A new Bone Anchor was developed to increase orthodontic anchorage in the anterior or posterior region of the upper and/or lower jaw.  A 3 holes titanium miniplate is fixed by monocortical miniscrews.  A round bar is penetrating the soft tissues at the muco-gingival boarder.  A cylindrical fixation unit with a locking screw makes it possible to fix an auxiliary wire that connects the Bone Anchor with the fixed orthodontic appliance.
Since 3 years 119 Bone Anchors were placed in upper and lower jaw and used as anchorage in different orthodontic applications:
1. Distal movement of the anterior segment in premolar extraction cases.
2. Distal movement of the posterior and anterior segment in non-extraction cases.
3. Mesial movement of posterior teeth.
4. Intrusion of a single tooth or a group of teeth.
5. Uprighting of mesialised lower second and third molars.
6. Preprosthaetic orthodontics.
Six clinical trials were started with orthopaedic traction applied between 2 Bone Anchors placed on the zygoma and 2 Bone Anchors in the lower canine region to stimulate anterior growth of the maxilla in young skeletal class III patients.
Thanks to the section of the round connection bar penetrating the soft tissues, dental hygiene is very easy.  This reduces to a minimum the risks for local infection and loosening of the miniscrews. 
The surgical techniques and orthodontic applications will be illustrated by clinical cases.

 
P.DELCAMPE, J.MISINO, J.B.LECA, A.DURET, S.GIGON, J.B.KERBRAT, J.M.PERON.
TRANSPALATAL DISTRACTION : IS THERE AN AESTHETIC FACIAL CHANGE ?

Purpose : Until recently, transversal maxilla expansion in a skeletal adult, was primarily performed for Lefort I down-fracture. However, even with a prolonged retention of the palatal arch, this procedure had a significant relapse occurrence. Over a two year period, a transversal distraction of the maxilla was performed with a palatal device cemented on four teeth. The aim of the study was to assess the morphological benefit on the middle third of the face.

Method : Palatal distraction device is cemented to the first premolars and molars before the surgical procedure. Under general anaesthesia, a sagittal osteotomy of the maxilla is performed with a Lefort  I osteotomy. After section of the pterygoid-maxillary area, the curve osteotomy is torqued anteriorly to assure completeness of the osteotomy and fractures. Therefore, a real down-fracture is generally not necessary. The soft tissues are closed without any other fixation. On the third day, appliance activation is begun (1mm daily) until the desired expansion is achieved.

Results : Twelve cases were included in this study, six males and females(range 15 to 25 years). length of distraction from 7 to 15 mm. The procedure allowed increase of pyriform aperture with subjective improvement of nasal respiration. The paranasal area became "convex" which gave an excellent aesthetic result.

Conclusion The authors suggest that transversal expansion of the maxilla using Lefort  I osteotomy could provide morphological aesthetic benefit to the middle third of the face.

 
B.DEVAUCHELLE
BIORESORBABLE OSTEOSYNTHESIS IN ORTHOGNATIC SURGERY

More than 80 patients have been operated on in the field of orthognatic surgery, using resorbable plates and screws.
The authors  studied a serie of 40 patients with Lefort 1 osteotomy, using bioresorbable materials for osteosynthesis. The ability of use, the stability of the osteosynthesis, the complications and the cost will be here  analysed.
As results , it appeared that the bioresorbable material was very well tolerated, with only few complications.
The ability of use is rather  easy, and  needs some minimal  experience, because the tightening of the screws is different compared with the titanium materiel.
The stability of the osteosynthesis will be  analysed on radiography made just after surgery, six months later  and one year after surgical time .
Finally the use of such  material presented lot of advantages, not only in the field of orthognatic surgery, but for pediatric  craniofacial surgery, and perhaps we could use it to release  molecules such  as drugs or bioengeneeing products  around the osteosynthesis site.

 
H. OBWEGESER
MANDIBULAR ASYMMETRIES, DIAGNOSTIC AND TREATMENT PRINCIPLES

No other bone of the whole skeleton shows such a great variety of anomalies as the mandible does.  Mandibular asymmetries are the main reason for the large variation.  They present one of the most interesting chapter in the field of our speciality, because of its great possible aetiological varieties and possible variations of shape and often enough because  of their diagnostic and therapeutic difficulties.  One has to keep in mind that the mandible consists embryologically of two equal halves.  Both unite at the symphysis during the first years of life and develop equally under normal conditions.  But they can also grow independently and produce a different shape than the normal side does.  That means that one abnormality maybe existing on one half of the mandible only, or on both sides, equal or different in origin and shape.

Genetic and embryonic disturbance of growth, adverse postnatal events during growth periode or after growth has ceased and in particular abnormal growth regulation after birth, both during growth period as well as after growth termination, all these aetiological causes can present a great variation, and also often vertuy typical appearances of th shape of the affected mandibular half.

For diagnosing whether or not there exists an asymmetry and which side is causing the asymmetry a horizontal line between the supraorbital rims on the face or on the p.a. cephalogram is drawn with a perpendicular line to it at the middle of the forehead.  This  is a very good diagnostic help.  Even more affirmative is the facial planner of my nephew Joachim Obwegeser.

Diagnostically and therapeutically of greatest interest of all asymmetries of the mandible are those which are caused by condylar misregulation of growth, mostly starting during growing period, but occasionally also after growth has ceased.  I am of the opinion that the condyle holds underneath its surgace two growth regulators, one reponsible for producing length, the other for mass production to the same half of the mandible.  They can produce two typical hemimandibular abnormalities, either a hemimandibular hyperplasia or a hemimandibular elongation, both with very clearly different but typical shape abnormalities.  If both of them are hyperactive then they will produce a hybrid form, in excessive cases resulting in a grotesque shape of the mandible.  They can affect one mandibular side only or both, almost equally, but mostly in different degrees.  As long as these growth regulators are hyperactive they can be diagnosed scintigraphically after i.v. injection of Tc-99m-DPD.  A superficial resection of the condyle stops immediately the abnormal growth of the affected side.

The correction of the mandibular asymmetries depends on the cause of it, the age of the patient and on the shape of the abnormality.  When the abnormal growth, whether lack of it or surplus, begins in early childhood, the maxilla can also be involved.  In these cases the surgical correction will also have to include it.

In most cases of mandibular asymmetries orthodontic treatment can only deal with positioning the teeth into proper angulation of the respective base of the jaw but has very little chance to influence the actual growth of the mandible.

Litterature : H.L. Obwegeser, Mandibular Growth Anomalies, Springer-Verlag, 2001.