Size * Micrognathia Mandibular micrognathia is the condition when lower<unk>  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. This maybe because a posterior placing of the condylar head with regard to the skull or to a steep mandibular angle resulting in an evident<unk>  retrusion. The acquired type of micrognathia occurs after birth and usually is an effect of a disturbance to temporomandibular joint. Growth of mandible depends on the normally developing condyles and the muscle function For example, trauma or infection that affect mastoid, middle ear or the joint will result in ankylosis of temporomandibular joint leading to mandibular micrognathia. * Macronagthia Macronagthia is a condition of abnormally large<unk> s. The<unk>  size is usually proportion to the increase in skeleton size. It is usually due to excessive growth of the mandible and can have features including reverse maxillary to mandibular relationship, reverse overjet or absence of overbite. It can also be clinically presented when the glenoid fossa and condylar head is more anteriorly placed, causing mandibular prognathism. Macronagthism can be associated with other medical conditions :- 1. Paget's disease where there is overgrowth of the maxilla, cranium and mandible 2. Acromegaly, an endocrine disease, can present with enlargement of bones with growth potential such as the mandible, thickened soft tissues and facial features and spade-like hands * Macrogenia or Microgenia Macrogenia and microgenia occur when there is a normal skeletal relationship but the chin, skeletal and soft tissue components, failed to develop in proportion to the skeletal base, resulting in marked protrusive (macrogenia) or retrusive (microgenia) facial profile. Microgenia can be presented when there is inadequate bone depth at the apex of lower anteriors or the base of mandible and vice versa. Position * Transverse A transverse<unk>  position is known as Laterognathia. This term describes a lateral bite in the lower<unk>  and is often associated with a unilateral crossbite at an early age This can lead to bone development of an asymmetrical mandibular ramus resulting in asymmetry in the whole of the lower face. Treatment of laterognathism is either possible with orthodontic tooth movement or a surgical relocation of the lower<unk> . * Vertical One of the ways in which a<unk>  can develop abnormally is in the vertical dimension. Abnormal growth can occur in the maxilla and the mandible. The<unk>  is usually loosely used to refer to the mandible (considered the lower<unk> . However, the maxilla is also a<unk>  and should thus be referred to in this respect as well. The vertical<unk> es relating to the mandible are in relation to excessive vertical growth and excessive horizontal growth, measured by the maxillary-mandibular plane angle (MMPA). The vertical<unk> es relating to the maxilla are in relation to excessive downward displacement (EDD) and insufficient downward displacement (IDD). These terms used to previously be known as vertical maxillary excess and deficiency. This nomenclature changed because excess and deficiency typically refer to size. Whereas when assessing this clinically, one would measure the distance between the central incisors and the upper lip, which, in fact, denotes position rather than size. Therefore, in order to ‘harmonize with geometry’, EDD and IDD are now used widely. Vertical and Horizontal Mandibular Excess: Simply put, excessive vertical growth is the term used for when the mandible is considered ‘too far down. Whereas in excessive horizontal growth the opposite applies, where the mandible is growing in a more horizontal pattern, in relation to the maxilla. The primary cause of the above two<unk> es in adolescents is due to accelerated and slow mandibular growth. Resulting in either a longer lower face height appearance (vertical growth) or a shorter one (horizontal growth). The length between the columella (base of the nose) and menton (base of the chin) is the variable measurement. This is in relation to the length between the glabella (between eyebrows) and the columella. In a normal case, these lengths would be equal or without a major discrepancy. However, in excess vertical and horizontal growth, the proportions vary and do not equal. The development of the mandible is such that it ossifies in two primary ways; endochondrally and intramembranously. Almost the entire mandible is formed via intramembranous ossification, with just the condyle ossifying endochondrally. This allows the condyle to resist forces exerted on it. One way in which a vertical<unk>  can occur is if the condylar growth process is damaged, and thus the intramembranous growth continues along the posterior condylar margin, becoming predominant, thus resulting in a high angle type. Assessing a patient for vertical and horizontal excess The Maxillary Mandibular Plane Angle (MMPA) is important in assessing a patient for vertical<unk> . The important landmarks are the Frankfurt plane and the Mandibular plane. The Frankfurt plane is a line charted from the upper border of external auditory meatus to the lower border of the orbit. It is similar to the ala-tragus line however should not be confused with it. Whereas the Mandibular angle is a line measured along the natural lower border of the patient's mandible. The intersection of the Frankfurt and Mandibular plane is what determines the pattern of vertical growth. If the intersection occurs behind the occiput i.e. decreased angle, then the patient is considered to have horizontal growth. On the other hand, if the intersection occurs in front of the occiput, then the patient is considered to have vertical growth. The normal range is considered to be between 25 and 30 degrees in a typical Caucasian person. Those with excess vertical<unk>  growth are most often seen having an anterior open bite, as the mandible is growing away from the maxilla. Whereas those with excessive horizontal growth are seen as having an overbite. Excessive Downward Displacement and Insufficient Downward Displacement Here on, we will use interchangeably the terms vertical maxillary excess and deficiency with excessive and insufficient downward displacement. In order to understand its manifestations, we need to account for key landmarks such as: · Columella (CM)– The tissue that links the nasal tip to the nasal base, separating the nares. The inferior margin of the nasal septum · Subnasale (SN) – the junction of the upper lip and the columella · Stomion Superios (Sts) – the lower most point on the vermillion of the upper lip · Stomion (Sto) – The point of contact, when lips are competent, in the midline, between the top and bottom lip · Stomion Inferious (Sti) – the upper most point on the vermillion of the lower lip · Soft tissue mention (Me) – The most inferior point on the soft tissue outline of the chin The measurements of the upper lip and lower lip for each patient are ascertained by using the aforementioned landmarks. The length of the upper lip is measured from Sn to Sts. In a typical male and female this measures to 24mm and 21mm respectively (REF). The length of the lower lip is measured from Sti to Me. In a typical male and female this measures to 50mm and 46.5mm respectively. When considering EDD and IDD, the class of the skeletal base is a good adjunct. In other words, EDD and IDD can either appear camouflaged or apparent given the skeletal base and the soft tissue profile accompanying it. For example, the drape of the upper lip can mask the maxillary deficiency to such an extent that it presents as a normal soft tissue profile (REF). Para-nasal hollowing is a key indicator of underlying maxillary deficiency. It is most common in class III patients, but can also present in some class II cases, with bilateral maxillary retrusion. Assessing a patient for vertical and horizontal excess: Arguably the main observation to carry out in a patient to assess maxillary excess or deficiency is the upper incisor/gum show when at rest and smiling. In other words, the relationship between the upper lip and upper central incisors when at rest and smiling. Ensure the patient's head posture is correct and the lips are at rest to establish the resting lip line. Similarly, to assess the incisor/gum show on smiling, the patient needs to fully smile to allow the upper lip to rise to its maximum height. The average showing of the incisors when the lips are at rest is 1/3 of its clinical crown height. With maxillary excess, more than 1/3 of the incisors would show. When the patient smiles, maxillary excess would manifest as the entire clinical crown and a portion of the gums showing as well. This is regarded as a ‘gummy smile.’ As alluded to previously, the paranasal region is important to consider when assessing a patient for IDD or EDD. Observing the patient from the side view allows a
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