They allow for the appraisal of shape and size of jaws and teeth. This can be valuable for the long-term evaluation of development and for the follow up of treatment results. Depending on the type of jaw abnormality, a face bow record for transfer on to the articulator, can sometimes be appropriate for the patient. Radiographs - Radiographic investigations should be based on individual needs and used in conjunction to the clinical examination. As with all other dental radiographs, the benefit gained for the patient with the radiograph must be weighed against the radiation dosage of taking it. In the assessment of jaw abnormalities, the most common radiographs taken used to be the dental panoramic tomography and lateral cephalometry. With the advancement in technology, the use of 3D imaging e.g. Cone Beam Computed Tomography (CBCT) has gained popularity for the use of radiographic examinations of facial bones for purpose of planning complex orthognathic surgery, especially involving significant facial asymmetry. A 3D facial construction model can be utilised in more complex malocclusion to help plan management. Classification
Size
MicrognathiaMandibular micrognathia is the condition when lower jaw is smaller than normal. Failure of the ramus to develop will give rise to micrognathia. Micrognathia can be classified as either congenital or acquired. Clinical appearance of some patients with congenital type of mandibular micrognathia can have a severe retrusion of the chin but by actual measurements, the mandible maybe be found to be within the normal limits of variation.
It checks for the alignment of the soft tissue nasion, the middle part of the upper lip at the vermillion border, and the chin point. If present, it is necessary to distinguish between a false and true asymmetry. A false asymmetry arises due to occlusal interferences, which results in a lateral displacement of the mandible, producing a cross-bite in the anterior/buccal region. Elimination of the displacement will return the mandible to a centric position. On the other hand, a true asymmetry indicates unequal facial growth on the left or right side of the jaws. Elimination of any occlusal cross-bites is not only difficult, but unlikely to improve the facial asymmetry. The assessment of the transverse components of the facial width is best described by the "rule of fifths", which sagittally divides the face into five equal parts:
Each transverse fifth should be an eye distance in width. The middle fifth is marked by the inner canthus of both eyes. The medial three-fifths of the face is marked from the outer canthus of the eye frames
The outer two-fifths of the face is measured from the lateral canthus to lateral helix of the ear, which represents the width of the ears. Tests
It is insufficient to derive at a diagnosis of jaw deformity solely based on the clinical examination. Hence, additional information is gathered from diagnostic tests, which may include dental model analyses and radiographic imaging studies. Dental Model Analyses - Study models for analysis can be made by taking dental impressions, or by 3D intra-oral scanning.