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Anterior Open Bite Dilemma

 

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Pakistan has a very low prevalence of anterior open-bites as compared to Central Asia, Eskimos, Eastern Europe and Northern Turkey populations. In general, Anterior Open Bite (AOB) cases are difficult to control, retain and treat orthodontically with conventional braces. Luckily, Pakistani population has prevalence towards class 1 and 2 malocclusions with deep overbite, which has a completely different orthodontic approach as compared to skeletal openbites. There are 2 AOB categories; one Skeletal the other Dental. The Dental open bite is easier to treat and is found in young patients with obstruction to the normal development of the overbite due to local factors, like habits such as thumb sucking. Unfortunately the treatment of older cases with more severe skeletal AOB’s is more difficult and less successful. In the inexperienced hand AOB treatment may cause problems of failure, deterioration of esthetics due to excessive gingival show on smiling, and poor stability of the achieved results due to over -erupted anterior teeth. Currently surgery could be acknowledged as the main and most efficient treatment option in these cases. In Orthodontic books, AOB can be defined as “the teeth in the anterior portion of the maxilla and mandible are vertically apart and lack the overlapping necessary for the incisive function with the mandible in closed position”. Or defined as no occlusal contacts of the incisors neither in habitual occlusion nor following forward sliding of the lower dental cast having always at least two occlusal contacts on the molars bilaterally in the sagittal plane. The incidence of anterior open bite was found to be 4.2% percent in 6-year old children while this percentage dropped to 2.5% percent in 14-year old children. The decrease in the anterior open bite was attributed to the self-correction of the open bite as the habits causing it gradually disappear with age. Etiology of AOB AOB is mostly due to heredity and the major disposing factors are unfavorable growth such as excessive vertical facial growth, excessive posterior dental growth, defective anterior growth of the dentoalveolar complex, vertical skeletal growth discrepancies, and long face syndrome. Vertical skeletal growth discrepancies include vertical eruption of the maxillary molars and alveolus that subsequently hinges the mandible down and back, under development of the middle cranial fossa height producing an elevation of the glenoid fossa, and inadequate alveolar growth in the anterior portion of the maxilla. The long face syndrome is characterized by a pronounced increase in the lower facial height.In these cases we find more posteriorly directed growth pattern of the mandibular condyle expressed as vertical growth at the chin. The mandibular position is affected by the anterior and posterior facial height growth. Differences between the anterior facial height and posterior facial height growth lead to rotational and positional changes in the mandible that greatly affects the position of the chin. Anterior facial height is generally affected by the eruption of the maxillary and mandibular posterior teeth, as well as the amount of sutural lowering of the maxilla. As for the posterior facial height it is most affected by the lowering of the temporomandibular fossae and condylar growth. Genetics and heredity are also major causes but also many functional, postural, and growth-related factors have been identified. Even weaker masticatory muscles are present in high angle cases and hypothesized that this less biting force is a major factor in developing a long face. Openbite could also be due to nasopharyngeal obstructive disorders such as allergy, septum deviation, and large conchae. These conditions could force the mandible into a lower position to open the air space, and thus affect the growth accordingly.

May 19, 2013

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