24 March 2020

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Are temporary anchorage devices truly effective in the treatment of skeletal open bites?

Davide Elsido

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Open bite  is considered as a deviation in the vertical relationship of the maxillary and mandibular dental arches, characterized by a lack of contact between opposing segments of teeth. Open bite develops because of interaction of many etiologic factors, both hereditary and environmental in nature.
Treatment of skeletal open bite is regarded as one of the most complicated and challenging treatments in the orthodontic specialty. Control of the vertical dimension and the height of the posterior dentoalveolar regions is considered the most important factor in successfully treating patients with skeletal open bite and hyperdivergency. For the correction of anterior open bite with a steep mandible and excessive molar height, intrusion of the posterior teeth is generally the best option. However, intrusion of the molar teeth is quite difficult to obtain with traditional mechanics.

In recent years, temporary anchorage devices (TADs) have been increasingly used for skeletal open bite patients because they provide absolute molar intrusion, which used to be impossible with traditional orthodontic mechanics combined with intra- or extra-oral anchorage. Moreover, with the use of TADs, the vertical correction of the posterior dentoalveolar region without unfavorable side effects has become possible. The infrazygomatic crest has been used successfully to provide skeletal anchorage for the intrusion of the maxillary posterior teeth.

In a recent issue of European Journal of Dentistry an article was published about a clinical study to evaluate the effects of temporary anchorage devices (TADs) in the treatment of skeletal open bites and to compare the results with untreated controls. 

A total of forty patients with skeletal anterior open bites were assigned to two groups of twenty each. The mean chronological age for the treatment group (14 female, 6 male) was 16.68 ± 2.80 years old, compared with 16.63 ± 2.83 years old for the control group (11 female, 9 male). Titanium miniplates fixed bilaterally to the infrazygomatic crest area were used as TADs and intrusive forces were applied to the posterior teeth with Ni-Ti coil springs. In the study, the appliance and the mechanics successfully intruded the upper molars.

They attained 3.59 mm of true molar intrusion. This amount of intrusion, to a large extent, was obtained by buccal intrusive forces. After intrusion of the molars, autorotation of the mandible has been reported by several authors. This result was also true for this study because intrusion of the maxillary molars caused a significant anterior rotation of the mandible. The mandibular plane closed by an average of 2.25°, resulting in 3 mm of upward and forward movement of the chin.

TADs have opened up a new era in the management of severe dentofacial deformities, in which surgery had been the only option. With the successful intrusion of the maxillary molars, the mandible automatically rotates anteriorly, resulting in open-bite closure. To sum up, mild to moderate skeletal anterior open bites could easily be treated with TADs  without orthognathic surgery. With the rigid anchorage of miniplates, true molar intrusion of up to 4 mm was achieved. With molar intrusion, anterior rotation of the mandible and a significant reduction in anterior face height were determined.

For additional informations:  Are temporary anchorage devices truly effective in the treatment of skeletal open bites?