CATEGORY 48 AUSTRALASIAN DENTIST LINICAL The correction of transverse maxillary deficiency can be an important component of an orthodontic treatment plan. Numerous factors can result in transverse maxillary deficiency including genetic, environmental, traumatic and functional, which includes abnormal habits such as mouth breathing. Various expansion appliances have been introduced with different force levels and duration of treatment, and the factors that influence the selection of these appliances to quantify the amount of skeletal or dental expansion depends on age, growth, amount of force and even the gender of the patient. Expansion may also be gradual or slow (3–14 months). The difference in expansion rates reflects differences in the frequencies of activation, the magnitude of applied force, the duration of treatment and the proportion of dentoalveolar to skeletal effects. HISTORY The history of expansion dates back to 1860 where Emerson C. Angell reported his first case of successfully splitting the maxilla using a jackscrew appliance, thus he was considered to be the father of rapid maxillary expansion. Later Farrar and Clark Godard (1893) stressed the effectiveness of transverse expansion of the palate with opening up of the mid-palatal suture. Lathamin (1971) believed that growth at the mid-palatal suture ceases at the age of 3 years which was contradicted in the year 1974 by Bjork and Skieller who did a study with implants which proved that growth at mid-palatal suture can continue up to 13 years of age. CLASSIFICATION OF EXPANSION (McNamara) 1. Orthodontic or Denal expansion u This is produced by conventional fixed appliances and different types of removable appliances. u Expansion is dentoalveolar in nature i.e., there is lateral movement of the buccal segments resulting in buccal tipping of the crowns and lingual tipping of the roots. u Aberrant soft tissue pressure from cheeks can cause relapse of the achieved expansion. 2. Orthodpedic or Skeletal expansion u Changes are produced mainly in the skeletal structures. u Less amount of dentoalveolar expansion. u Rapid maxillary expansion (RME) appliances are classical examples of true orthopaedic expansion. u RME causes separation of midpalatalmid-palatal suture resulting in effects on circumzygomatic and circummaxillary sutures. u After expansion, new bone is deposited in the mid-palatal suture. 3. Passive expansion u Intrinsic forces from the tongue play a major role. u With the use of buccal shields (e.g. Frankel), the forces from the labial and buccal musculature are prevented from acting on the dentition, which results in the widening of the arches, because the forces from tongue exert expansible forces on the arches. u Passive expansion is not achieved by mechanical appliances but by the vestibular or lip shields. Broadly classified into: Diagnosis The patient is evaluated for maxillary expansion using the following diagnostic records: 1. Orthodontic study model 2. A thorough clinical history 3. Radiographs – Orthopantomogram OPG – Lateral and PA view cephalogram – Occlusal radiographs. Sutures Mid Palatine Suture plays a key role in Maxillary expansion Infancy – Y-shape, Juvenile – T-shape, Adolescence – Jigsaw puzzle Normal palatal growth is completed by age of 6. Increasing interdigitation of the suture makes separation difficult to achieve after puberty. RAPID MAXILLARY EXPANSION APPLIANCES 1. Indications for RME u RME appliances are ideally indicated in growing individuals with severely constricted maxillary arches, involving airway impairment or mouth breathing tendencies. u Posterior cross bites with real or relative maxillary deficiency u Cleft patients u Along with face mask therapy, RME is used to loosen the maxillary sutural attachment in order to facilitate protraction of deficient maxilla. u Class III cases with minor maxillary deficiency u In interceptive orthodontic treatment mechanics. Dr Geoff Hall By Dr Geoffrey Hall Palatal Expansion in Child and Adult PA Cephalogram Sutures
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