Fixed orthodontics is the elected treatment in any age permanent dentition patients.
In fact, in most of cases only with a fixed appliance is possible to achieve a precise and controlled dental movement.
When patient needs an invisible treatment the answer is a fixed lingual treatment, that could be realized with or without brackets. The appliance is so bonded on the lingual aspect and this is why it is not visible.
At first lingual fixed orthodontic without brackets was deviced to solve relapse of previous classic brackets treatment that didn’t want anymore a brackets therapy. Then was applied to treat malocclusion in patients never treated before because it does not produce tongue and soft tissues pains and phonetics diseases that usually occurred with a lingual brackets therapy.
With fixed lingual orthodontic without brackets it is possible to treat every kind of malocclusions by means of orthodontic wires directly bonded on the lingual aspect of the teeth, like the active retainers, but also other devices, like the mini-screws. Mini-screws are a recent innovation in orthodontic treatment and have a large application also in conventional brackets therapy, because they allowed a maximum skeletal anchorage and a faster dental movement.
The following clinical case is an example of dental and skeletal second class treated by means of this innovative therapy.
The patients, a 25 years old female, presented at a clinical examination (fig. 1-6)
- an edge to edge molar and canine and a scissor bite between 24-34 on the left side
- an edge to edge canine and a previous extraction of tooth 46 with mesialization and inclination of tooth 47 on the right side
The x-ray evaluation (fig. 7-10) showed a skeletal second class with a proclination of the lower incisors on the mandibular plane of 6 degrees.
The second class treatment with inter-maxillary elastics was not advised because of the excessive lower incisors proclination (+6 on the mandibular plane).
To avoid the upper first bicuspids extraction we decided to distalize the upper lateral sector from canine to the second molars on both sides.
The upper third molars were extracted few weeks later the orthodontic appliance positioning. The space generated by the distalization was used to level the frontal teeth. In the lower arch it was necessary teeth levelling, uprighting and mesialization of tooth 47.
The distalization was accomplished by using 2 mini-screws as anchorage, applied between lateral incisor and canine on both sides. To simplify and better explain the procedure, after the mini-screws insertion it was taken a silicon impression of the upper arch and the system was reproduced on the model cast.
The applied mini-screws had a cylindrical shape, 8 mm length and 1,5 mm wide. Screws head has two holes crossed to each other that allows the sliding of the wires. In the holes given into the impression by the mini-screws head, we placed the same two mini-screws applied into the mouth so to reproduce the identical position (fig.11-16).
Two .016-.016 inches stainless steel sectional were modelled to slide on one side in the hole of the mini-screws and to be bonded on the other side on the palatal surface of the first molar (fig. 17-18).
The distalization force was realized by means of a coil spring compressed between the mini-screws and the gingival handle of the sectional (fig.19).
This system, that was not based on patient’s collaboration and that avoid the proclination of the lower incisor because of the skeletal anchorage, produced a controlled force of quite 400gr on both sides.
For the mini-screws insertion procedure it is important to control that one of the two hole is parallel to the occlusal plane so allowing the sectional sliding during teeth distalization.
The sectional gingival handle was modelled to applied the force near the occlusal third of the first molars roots and more near as possible to the resistance center to have a body movement.
The connection realized by a fiberglass from canine to the second molar on both sides contributed to move occlusally the resistance center increasing the body movement.
After a first step this fiber connection was removed, to continue only the molar distalization (fig. 20-21-21a-21b).
Further coil activations were realized applying flowable resin on the sectional handle and light-cured it in the meanwile an utility probe activated the coil in contraction by reducing its length.
After molar distalization (fig.22-26) it take place the bicuspids distalization, connected to each other.
Two bands and a trans-palatal bar were applied to anchorage the molars in the achieved position. The trans-palatal bar was activated in de-rotation an in slight contraction, to correct the buccal movement produced by the lingual-buccal force vector of the distalization system (fig. 27-31).
In the lower arch was bonded a .014 inches stainless steel arch from 36 to 45, and a .016-.016 stabilization sectional on 44 e 45, as 47 up-righting anchorage. The up-righting was realized positioning a buccal tube on the molar and a sectional, first in Ni-Ti and then in stainless steel, that moved from the occlusal slot of the tube and directly bonded on the 45 buccal surface. The mesialization was accomplished with a sliding mechanic by means an elastic chain and a lingual chain was applied to control the molar rotation (fig. 32-34).
Then it was applied on the lingual surfaces from 33 to 35 an active retainer to move buccally and intrude the 34, to solve the scissor bite, meanwhile a stainless steel stabilization sectional connected 35 to 36.
After lateral sectors distalization in the upper arch was applied an active retainer to level the frontal teeth (fig 34b). The retainer was modelled and activated as previously explained in the article.
The following pictures showed the first class closure reached at the end of the therapy (fig. 35-39).
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