Jaw abnormality sagittally divides the face into five equal parts: 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. Mandibular micrognathia is the condition when lower jaw is smaller than normal. Failure of the ramus to develop will give rise to micrognathia.<ref name="Elsevier/Churchill Livingstone"></ref> 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,
Jaw coupling elements that do need to be inspected and replaced. Jaw coupling elastomers often have signature wear patterns, and failures can often be root caused based on the condition of the elastomer and hubs. Common failure causes include misalignment, over-torque, chemical exposure, temperature exposure, torsional vibrations, and hub failure. Jaw couplings are available in both straight tooth jaw and curved jaw design. The straight tooth design enables elastomers to be attached and removed radially, including a "not fail-safe" jaw elastomer in-shear design. For the elastomer in-shear design, the coupling hub teeth are no longer inter-meshed, so an elastomer failure will result