The inviolability of the mandibular intercanine distance is an old orthodontic dogma that continues to be reinforced by current research (see clinical publications). Osteotomy techniques to narrow or angulate the symphysis are known, but infrequently used. Symphysial widening without recurring to osteodistraction techniques is practically impossible. Immediate widening by osteotomy techniques would cause gingival trauma and denudation of the necessary bone graft and osteosynthesis material. Osteodistraction demolishes the dogma of not violating the intercanine width.
In the clinical setting, anterior mandibular widening by osteodistraction has been generally accomplished with tooth-borne devices (see clinical publications). Similar problems as with tooth-borne expanders used in surgically assisted rapid palatal expansion have been encountered in the experimental setting, e.g.:
- device loosening;
- tipping of teeth and segments;
- more dental expansion in relation to skeletal widening. (see clinical publications)
TMD a bone borne device fixed on the symphysial surface, avoids these problems.
Three models are available which expand 12 mm:
- for infants;
- for adults with a bulky chin;
- for adults with a flat chin.
Two models are available which expand 20 mm:
- for adults with a bulky chin
- for adults with a flat chin
- No loss of anchorage since the footplates are fixed with 2 monocortical and 1 bicortical screw, at both sides of the midline.
- No or very little skeletal relapse since the actions of expansion and retention are immediately on the bone.
- No periodontal membrane compression or root resorption since the teeth are left untouched.
- At the end of the distraction, the occlusion plane can be fully controlled.
- The activation mechanism is extramucosal. It is easy accessible for activation; it helps to control the activation rate and it is helpful in case of a mechanical problem. It does not interfere with callus formation and maturation. Removal is possible without denudation of the newly formed bone.
- Differential expansion is possible by activating one rod more than the other.
- Trans Mandibular Distraction allows for symphyseal distraction along an arched segment, without the fear for instability of the fixation or for translational condylar movements, due to the joint in the middle part of the rods.
- The Trans Mandibular Distractor is maximally tissue compatible, since it is entirely made of titanium grade 2.
- The labial sulcus incision can be kept to 15 mm and the subperiosteal dissection can be performed medial to the mentalis muscles.
Recommondations for the surgeon
If brackets are already placed before the surgery, it is recommended to make a diastema of 1 - 2 mm between the centrals prior to the operation. This will prevent hiaotrogenic damage to the central teeth or sockets during the splitting of the mandible.
Towards the end of the activation, check carefully the occlusion and the angle of the teeth. This can be corrected by activating the lower screw more than the upper (or vice-versa).
Recommendations for the orthodontist
Orthodontic appliances can be placed before or after the operation. In case the appliances are placed before the operation, the arch wire has to be cut in two during the operation.
Fixation to posterior teeth of the incisors is needed to prevent them from drifting towards the distracted area, "Floating teeth phenomena ".
Orthodontic alignment can start 6 weeks or longer after the end of activation.
Instructions to communicate to the patient
- Once a week, the device and occlusion has to be checked by the surgeon and/or the orthodontist.
- Slight pressure might be felt at the beginning of the activation and towards the completion.
- If the device is loosened in any stage, patient has to see the surgeon as soon as possible.
- Changes in the occlusion will appear while activating. This will be solved by alignment of the teeth.