in a more horizontal pattern, in relation to the maxilla. the primary cause of the above two abnormalities 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 jaw abnormality 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 jaw abnormality. 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 jaw 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 clearer perspective. a lack of bony support for the soft tissues in this region will subsequently produce the depression, known as paranasal hollowing. this indicates a low level antero-posterior maxillary deficiency. maxillary deficiency usually manifests as an increased naso-labial angle, although this is not a credible indication due to factors such as a short upper lip and/or proclined incisors. another method to predict if a patient has maxillary deficiency is by the ‘scleral show and eyelid shape.’ the lower eyelid normally rests at the inferior border of the iris, without any sclera showing. if there is any sclera showing, then this is a good sign of infraorbital rim deficiency and maxillary antero-posterior deficiency, two manifestations that are usually seen in class iii patients. orientation when a jaw is abnormally oriented, malrotations occur. these malrotations are classified according to the axis on which the abnormal rotation occurs. when a jaw is malrotated around the transverse facial axis, it is said to have abnormal pitch. when malrotated around the anteroposterior axis, the jaw has an abnormal roll, a condition also known as cant. finally, when a jaw is malrotated around the vertical axis, it has abnormal yaw. it can occur in maxilla and/or mandible and could result due to abnormal growth of the jaws in itself or as compensatory growth. shape shape refers to figure, the geometric characteristic of an object that is not size, position, or orientation 5. a jaw with abnormal shape is said be distorted. completeness completeness means the wholeness of the jaw. when failure of tissues to fuse together that are forming early in pregnancy, defect can happen and jaw is incomplete. for example, cleft lip and palate when one of the jaw's embryological processes failed to fuse together or the agenesis of the condylar process of the mandible, which may be seen in hemifacial microsomia. clinically, cleft palate presents as opening in the palate that can affect the front palate only or extending from the front to the back palate. cleft lip is presented clinically with opening of the upper lip which can be a small slit on the upper lip or large opening connected to the nose. the cleft can be unilateral on the upper lip or bilaterally. cleft lip can happen together with cleft palate. palatal clefts are one of the most common congenital abnormalities which occur in 1:2500 live births. embryologically, palate formation takes place in two stages, with the primary palate formed after 6th week followed by secondary palate formation between sixth and eighth weeks. the palate will fuse with the medial nasal process to form the roof of the mouth in order to complete the developmental process. however, if this process is incomplete that is when developmental defect occur. initially, it is just a common oro-nasal cavity within the embryo with nothing to separate the nose and mouth cavity. this space is occupied with tongue. the primary palate formed when medial nasal prominences fused together to form the intermaxillary segment to demarcate the oral from the nasal components. the formation of secondary palate starts with the growing of tissues vertically and mesially forming the right and left lateral palatal shelves. on the week 8, the tongue will be withdrawn downwards and the right and left lateral palatal shelves will be rapidly elevated, flipped into a horizontal orientation and fuse together from the front to the back two. the right and left lateral palatal shelves contact or fuse with each other at the midline to form the secondary palate two. a lot of growth factors are actively involved in the signalling to the tissues during craniofacial development. these growth factors function to control the cells proliferation, survival and apoptosis. some of the growth factors that can be implicated in the facial development resulting in craniofacial defect are bmp, fgf, shh, wnt and endothelins. one of the environmental factors that has been identified in mice study to have link to cleft lip is teratogen which can interfere the molecular signalling between the growth factors. however, the exact mechanism is still not clear. another environmental factors that has been actively involved in studies to prevent cleft lip and palate occurrences is the intake of folic acid during pregnancy. 0.4 mg folic acid intake per day has been shown to reduce one third risk of cleft lip (with or without cleft palate) in babies. however, it seems had no apparent effect on the risk of cleft palate alone. there are also studies in mice and dogs reported the protective effect of folic acid supplementation to prevent cleft lip palate occurrence. treatment jaw abnormalities are commonly treated with combined surgical (orthognathic surgery) and orthodontic treatment. the procedure is carried out by oral and maxillofacial surgeons and orthodontists in close collaboration. in most cases, the orthodontist will first align the teeth with braces or other appliances, which may worsen the occlusion until after the surgery. this is carried out to show the full degree of abnormality, and to create sufficient space for full correction in the bones. orthognathic surgery, also known as corrective jaw surgery, is performed to normalise dentofacial deformity and reposition part/all of the upper and/or lower jaws to improve occlusion stability and facial proportions. it is the 'mainstay treatment for patients who are too old for growth modification and for dentofacial conditions that are too severe for either surgical or orthodontic camouflage.' the surgery usually involves gaining access to the bone from inside the mouth, revealing and moving the bone into a correct functional position, and fixing it in position with metal plates and screws. these plates are most often left in the bone, but at times require removal due to infection, which would require another operation. most orthognathic surgeries are performed inside the mouth without any external scarring. mandibular surgery there are numerous surgical techniques available to correct the position of the mandible. the most popular of these techniques is the sagittal split osteotomy which "enables the body of mandible to be moved forwards or backwards by sliding the split ramus and angle".: 203 this provides a lot of bone overlap for healing. damage to the inferior alveolar bundle is avoided by sectioning the buccal and retromolar cortex of the mandible and the cancellous bone is carefully split. after the mandible has been repositioned, screws or mini-plates can be used to fix the mandible directly. this is instead of fixing it indirectly with intermaxillary fixation (imf).: 203 genioplasty reduction or augmentation of the chin may be carried out either on its own or as part of a mandibular or maxillary orthognathic operation.: 203 maxillary surgery the le fort classification (which is used for fracture description) generally describes the surgical techniques which are used for maxillary surgery.: 203