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Transcript of ORTHODONTIC APPLIANCES
Treatment of mandibular deficiencies INDICATIONS: CONTAR-INDICATIONS: The use of bionator for correction of genetically inherited mandibular deficiencies has limited results. Surgery is usually a better option for these cases.
Some specific types of Bionator and Activator appliance have a tendency to open the bite and increase anterior lower face height. For this reason, its use is not recommended in patients with minimum overbite or with an open bite and long anterior lower face height.
In forcing the patient to bite in a forward position, the lower incisors are in continuous contact with a lingual ramp which can result in proclination of these teeth with prolonged use. Therefore the use of these appliance are contraindicated in patients with pre-existing proclined lower incisors (i.e.high lower incisors to mandibular plane angle).
The use of the activator or bionator appliance is not recommended for non-complaint patients. The success of these appliances relies on the patient’s willingness to wear the appliance. In case of a non-complaint or mentally-challenged patients, its use is contra-indicated.
Bionator can create a dual bite, especially in the first weeks of treatment; therefore therapy requires careful evaluation and regular recall.
Bionator therapy is usually recognized as being the Phase 1 of treatment. Patients need to be aware that a Phase 2 (phase of fixed appliance therapy) may be needed following Phase 1 in order to get proper interdigitation and good occlusion TYPES OF BIONATORS: Standard Bionator (to open bite)
helps in the advancement of the mandible. The mandibular anterior teeth are prevented from super erupting due to the acrylic coverage over them. As a result, the posterior teeth are allowed to erupt and open the bite. An expansion screw may be added for extra expansion if needed. Standard Bionator (to maintain bite) helps in the advancement of the mandible. However, the acrylic covers over both the occlusal surfaces of posterior teeth and over the mandibular anteriors in order to prevent unwanted eruption of the teeth. An expansion screw may also be added for extra expansion if needed. Functional components: 1- Deep lingual flange extensions
In the bionator and activator appliances, the most important functional components are the deep lingual flange extensions contacting the alveolar mucosa below the mandibular molars and behind the lower incisors. It modifies the way the child bites down and repositions the mandible in a more forward position. The functional components therefore generate forces by altering posture of the mandible, which in turn favours mandibular growth to reposition it in a more forward position.
Vertical control components: 2- Acrylic bite block (anterior and/or posterior)
An acrylic block is placed in between the teeth in order to control vertical growth. As the child bites down in a new forward position, disocclusion of posterior teeth will cause eruption of selected posterior teeth and restrain eruption of the anterior teeth.
The eruption path of the posterior teeth can be controlled by the orthodontist.
- Facets or flutes can be trimmed into the appliance to direct erupting posterior teeth mesially or distally.
- Flutes can be replaced by a plastic shelves to restrict eruption of upper posterior teeth and allow eruption of lower posterior teeth instead. Stabilizing components: 3- Labial Bow
A labial bow crossing the maxillary incisor teeth is used to help guide the appliance into proper position and not tip the upper incisors lingually. In order to avoid lingual tipping, the labial bow is adjusted so that it does not touch the anterior maxillary teeth when the appliance is seated in position.
Clinical and laboratory steps
1st appointment: 1- Impressions:
The impression technique for functional appliance fabrication is similar to the ordinary alginate impression in orthodontics. The impression should represented a well delineated capture of the areas of the alveolar mucosa on which the lingual flange will be located, and the impression should not overextended in the vestibule areas. 2- Bite registration
The wax construction bite is the most important element of the Bionator, as it determines the relative position of the joined upper and lower acrylic parts of the appliance. The wax is softened and firmly seated on the upper teeth, and the mandible is slowly guided forward to the desired position (4-6 mm of protrusion is recommended) and the bite is recorded. Make sure that the dental midlines are on while taking the bite registration. The Bionator is supposed to exert a three-dimensional effect; consequently the construction bite must provide three-dimensional control.
2nd appointment – Appliance delivery: Trim excess acrylic with acrylic burs in order to be able to insert the appliance and seat it in patient’s month. Adjust labial bow with proper pliers. The labial bow should be crossing the midline of the maxillary teeth and should not be in contact with the maxillary incisor when patient is in occlusion. Give patient and parents instructions on proper oral hygiene and appliance instructions (see instructions to assist patient section). 1st recall should be 2 weeks post delivery in order to evaluate patient compliance and the soft tissue and appliance condition. Recall patient every 4 to 6 weeks to evaluate compliance, progression of treatment and monitor possible dental side-effects of appliance.
Timing of treatment: Therapy should coincide with periods of active growth
Therapy should usually begin in middle to late mixed dentition
Therapy may be started earlier if patient is compliant
The success rate of the Bionator is very limited in non-growing persons Standard Bionator (to close bite) helps in the advancement of the mandible. The acrylic coverage over the occlusal surfaces of the posterior teeth allows the anterior teeth to erupt and therefore close the bite.