Prognathism in humans can be due to normal variation among phenotypes. In human populations where prognathism is not the norm, it may be a malformation, the result of injury, a disease state or a hereditary condition. Prognathism is considered a disorder only if it affects mastication, speech or social function as a byproduct of severely affected aesthetics of the face.

Clinical determinants include soft tissue analysis where the clinician assesses nasolabial angle, the relationship of the soft tissue portion of the chin to the nose, and the relationship between the upper and lower lips; also used is dental arch relationship assessment such as Angle's classification.

Cephalometric analysis is the most accurate way of determining all types of prognathism, as it includes assessments of skeletal base, occlusal plane angulation, facial height, soft tissue assessment and anterior dental angulation. Various calculations and assessments of the information in a cephalometric radiograph allow the clinician to objectively determine dental and skeletal relationships and determine a treatment plan.

Prognathism is less prevalent in East Asians and Caucasians. It is not to be confused with micrognathism, although combinations of both may be found. It affects the middle third of the face, causing it to jut out, thereby increasing the facial area, similar in phenotype of archaic hominids and apes. Mandibular prognathism is a protrusion of the mandible, affecting the lower third of the face. Alveolar prognathism is a protrusion of that portion of the maxilla where the teeth are located, in the dental lining of the upper jaw. Prognathism can also be used to describe ways that the maxillary and mandibular dental arches relate to one another, including malocclusion (where the upper and lower teeth do not align). When there is maxillary and/or alveolar prognathism which causes an alignment of the maxillary incisors significantly anterior to the lower teeth, the condition is called an overjet. When the reverse is the case, and the lower jaw extends forward beyond the upper, the condition is referred to as retrognathia (reverse overjet).

Not all alveolar prognathism is anomalous, and significant differences can be observed among different ethnic groups.

Harmful habits such as thumb sucking or tongue thrusting can result in or exaggerate an alveolar prognathism, causing teeth to misalign. Functional appliances can be used in growing children to help modify bad habits and neuro-muscular function, with the aim of correcting this condition.

Alveolar prognathism can also easily be corrected with fixed orthodontic therapy. However, relapse is quite common, unless the cause is removed or a long-term retention is used.

Unilateral crossbite involves one side of the arch. The most common cause of unilateral crossbite is a narrow maxillary dental arch. This can happen due to habits such as digit sucking, prolonged use of pacifier or upper airway obstruction. Due to the discrepancy between the maxillary and mandibular arch, neuromuscular guidance of the mandible causes mandible to shift towards the side of the crossbite. This is also known as Functional mandibular shift. This shift can become structural if left untreated for a long time during growth, leading to skeletal asymmetries. Unilateral crossbites can present with following features in a child

- Lower midline deviation to the crossbite side

- Class 2 Subdivision relationships

- Temporomandibular disorders

Retrognathia (or retrognathism) is a type of malocclusion which refers to an abnormal posterior positioning of the maxilla or mandible, particularly the mandible, relative to the facial skeleton and soft tissues.

A retrognathic mandible is commonly referred to as an overbite, though this terminology is not used medically.

A jaw abnormality is disorder in the formation or shape of the jaw. It can involve malocclusion.

Types include:

- Micrognathism

- Prognathism

- Retrognathism

- Pierre Robin syndrome

Dental open bite occurs in patients where the anterior teeth fail to touch. However, this is not accompanied by the skeletal tendency of having an open bite. Thus this type of open bite may happen in patients who have horizontal or hypodivergent growth pattern. These patients have normal jaw growth and do not have the long face syndrome. The anterior open bite in these patients may be caused by Macroglossia, Tongue thrusting habit or digit sucking habits. Some of the characteristics of a dental open bite include:

- Normal lower anterior facial height

- Horizontal/Hypodivergent growth pattern

- Occlusal plane diverges after the premolar contact

- Under-eruption of the anterior incisors

- Over-eruption of the posterior incisors

- Proclined upper and lower incisors

- No vertical maxillary excess or gummy smile

- Presence of habits such as thumb sucking, tongue thrusting

- Spacing between anterior incisors due to their proclination

Bjork defined posterior crossbite as a malocclusion where the buccal cusps of canine, premolar and molar of upper teeth occlude lingually to the buccal cusps of canine, premolar and molar of lower teeth. Posterior crossbite is often correlated to a narrow maxilla and upper dental arch. A posterior crossbite can be unilateral, bilateral, single-tooth or entire segment crossbite. Posterior crossbite has been reported to occur between 7–23% of the population. The most common type of posterior crossbite to occur is the unilateral crossbite which occurs in 80% to 97% of the posterior crossbite cases. Posterior crossbites also occur most commonly in primary and mixed dentition. This type of crossbite usually presents with a "functional shift of the mandible towards the side of the crossbite". Posterior crossbite can occur due to either skeletal, dental or functional abnormalities. One of the common reasons for development of posterior crossbite is the size difference between maxilla and mandible, where maxilla is smaller than mandible. Posterior crossbite can result due to

- Upper Airway Obstruction where people with "adenoid faces" who have trouble breathing through their nose. They have an open bite malocclusion and present with development of posterior crossbite.

- Prolong digit or suckling habits which can lead to constriction of maxilla posteriorly

- Prolong pacifier use (beyond age 4)

This version of macrostomia is less severe because it does not affect the facial muscles and is not associated with any soft tissue or bone deformities. A small cleft(s) extends from the mouth and can be repaired surgically.

Clefts in this variant are slightly more severe than the ones seen in simple macrostomia. It also does not have bone deformities, but it does include minor soft tissue deformities. The defining feature is muscle diastasis which is separation of the masseter. This phenotype can also be partially corrected with surgery.

Patient with skeletal open bites that accompany dental open bites may have Adenoid faces or Long face syndrome. They are said to have what is known as "Hyperdivergent Growth Pattern" which includes characteristics such as:

- Increased Lower Anterior Facial Height

- Occlusal plane diverges after the 1st molar contact

- May accompany dental open bite

- Narrow nostrils with upturned nose

- Dolicofacial or Leptoprosopic face pattern

- Constricted maxillary arch

- Bilateral Posterior Crossbite

- High and narrow palatal vault

- Presence of crowding in teeth

- Mentalis muscle strain upon forcibly closing of lips

- Possible gummy smile with increased interlabial gap

Cephalometric analysis features of skeletal open bite may include:

- Increased Frankfurt-Mandibular Plane angle

- Steep Occlusal Plane Angle

- Increased SN-MP Angle

- Short Mandibular ramus

- Increased mandibular body length

- Downward and backward position of mandible

- Increased gonial angle

- Proclined upper incisors, retroclined or upright lower incisors

- Posterior part of maxilla is tipped downwards

- Posterior facial height equals 1/2 of anterior facial height

- Increased hard tissue Lower Anterior Facial Height

- Increased total anterior facial height

- Short mandibular ramus

Viken Sassouni developed Sassouni analysis which indicates that patient's with long face syndrome have 4 of their bony planes (mandibular plane, occlusal plane, palatal plane, SN plane) steep to each other.

Symptoms that may be associated with condylar resorption include:

- Occlusion

- Anterior open bite

- Receding chin

- Clicking or popping when opening or closing the jaw

- Pain when opening or closing the jaw

- Limited jaw mobility

Overbite medically refers to the extent of vertical (superior-inferior) overlap of the maxillary central incisors over the mandibular central incisors, measured relative to the incisal ridges.

The term overbite does not refer to a specific condition, nor is it a form of malocclusion. Rather an absent or excess overbite would be a malocclusion. Normal overbite is not measured in exact terms, but as a proportion (approximately 30–50% of the height of the mandibular incisors) and is commonly expressed as a percentage.

Macrognathism is the condition of abnormally large jaws. It is also called "megagnathia" (antonym: micrognathia).

There are no symptoms, and no signs can be elicited on examination. Medical imaging such as traditional radiography or computed tomography is required to demonstrate the defect. Usually the defect is unilateral, but occasionally can be bilateral.

Malocclusion is a common finding, although it is not usually serious enough to require treatment. Those who have more severe malocclusions, which present as a part of Craniofacial Anomalies, may require orthodontic and sometimes surgical treatment (orthognathic surgery) to correct the problem. Correction of malocclusion may reduce risk of tooth decay and help relieve excessive pressure on the temporomandibular joint. Orthodontic treatment is also used to align for aesthetic reasons.

Malocclusions may be coupled with skeletal disharmony of the face, where the relations between the upper and lower jaws are not appropriate. Such skeletal disharmonies often distort sufferer's face shape, severely affect aesthetics of the face, and may be coupled with mastication or speech problems. Most skeletal malocclusions can only be treated by orthognathic surgery.

Other kinds of malocclusions can be due to tooth size or horizontal, vertical, or transverse skeletal discrepancies, including skeletal asymmetries. Long faces may lead to "open bite malocclusion", while short faces can be coupled to a "Deep bite malocclusion". However, there are many other more common causes for open bites (such as tongue thrusting and thumb sucking), and likewise for deep bites. Upper or lower jaw can be overgrown or undergrown, leading to Class II or Class III malocclusions that may need corrective jaw surgery or orthognathic surgery as a part of overall treatment, which can be seen in about 5% of the general population.

By far, the two most common symptoms described are pain and the feeling that teeth no longer correctly meet (traumatic malocclusion, or disocclusion). The teeth are very sensitive to pressure (proprioception), so even a small change in the location of the teeth will generate this sensation. People will also be very sensitive to touching the area of the jaw that is broken, or in the case of condylar fracture the area just in front of the tragus of the ear.

Other symptoms may include loose teeth (teeth on either side of the fracture will feel loose because the fracture is mobile), numbness (because the inferior alveolar nerve runs along the jaw and can be compressed by a fracture) and trismus (difficulty opening the mouth).

Outside the mouth, signs of swelling, bruising and deformity can all be seen. Condylar fractures are deep, so it is rare to see significant swelling although, the trauma can cause fracture of the bone on the anterior aspect of the external auditory meatus so bruising or bleeding can sometimes be seen in the ear canal. Mouth opening can be diminished (less than 3 cm). There can be numbness or altered sensation (anesthesia/paraesthesia in the chin and lower lip (the distribution of the mental nerve).

Intraorally, if the fracture occurs in the tooth bearing area, a step may seen between the teeth on either side of the fracture or a space can be seen (often mistaken for a lost tooth) and bleeding from the gingiva in the area. There can be an open bite where the lower teeth, no longer meet the upper teeth. In the case of a unilateral condylar fracture the back teeth on the side of the fracture will meet and the open bite will get progressively greater towards the other side of the mouth.

Sometimes bruising will develop in the floor of the mouth (sublingual eccymosis) and the fracture can be moved by moving either side of the fracture segment up and down. For fractures that occur in the non-tooth bearing area (condyle, ramus, and sometimes the angle) an open bite is an important clinical feature since little else, other than swelling, may be apparent.

Although it may be asymptomatic, symptoms usually are more likely to be present and more severe with larger tongue enlargements. Signs and symptoms include:

- Dyspnea - difficult, noisy breathing, obstructive sleep apnea or airway obstruction

- Dysphagia - difficulty swallowing and eating

- Dysphonia - disrupted speech, possibly manifest as lisping

- Sialorrhea - drooling

- Angular cheilitis - sores at the corners of the mouth

- Crenated tongue - indentations on the lateral borders of the tongue caused by pressure from teeth ("pie crust tongue")

- Open bite malocclusion - a type of malocclusion of the teeth

- Mandibular prognathism - enlarged mandible

- Mouth breathing

- Orthodontic abnormalities - including diastema and tooth spacing

A tongue that constantly protrudes from the mouth is vulnerable to drying out, ulceration, infection or even necrosis.

It is a classed as a pseudocyst, since there is no epithelial lining or fluid content. This defect is usually considered with other cysts of the jaws, since it can be mistaken for such on a radiograph.

Overbite is often confused with overjet, which is the distance between the maxillary anterior teeth and the mandibular anterior teeth in the anterior-posterior axis.

"Overbite" may also be used commonly to refer to Class II malocclusion or retrognathia, though this usage can be considered incorrect. This is where the mesiobuccal cusp of the maxillary first molar is situated anterior to the buccal groove of the mandibular first molar; in other words, the mandible (lower jaw) appears too far behind the maxilla. A person presenting with Class II malocclusion may exhibit excessive overbite as well, or may have the opposite problem, which is referred to as openbite (or apertognathia). In the case of apertognathia, the teeth do not overlap enough or at all. The upper teeth protrude past the lower teeth.

This type of fractured mandible can involve one condyle (unilateral) or both (bilateral). Unilateral condylar fracture may cause restricted and painful jaw movement. There may be swelling over the temporomandibular joint region and bleeding from the ear because of lacerations to the external auditory meatus. The hematoma may spread downwards and backwards behind the ear, which may be confused with Battle's sign (a sign of a base of skull fracture), although this is an uncommon finding so if present, intra-cranial injury must be ruled out. If the bones fracture and overlie each other there may be shortening of the height of the ramus. This results in gagging of the teeth on the fractured side (the teeth meet too soon on the fractured side, and not on the non fractured side, i.e. "open bite" that becomes progressively worse to the unaffected side). When the mouth is opened, there may be deviation of the mandible towards the fractured side. Bilateral condylar fractures may cause the above signs and symptoms, but on both sides. Malocclusion and restricted jaw movement are usually more severe. Bilateral body or parasymphysis fractures are sometimes termed "flail mandible", and can cause involuntary posterior movement of the tongue with subsequent obstruction of the upper airway. Displacement of the condyle through the roof of glenoid fossa and into the middle cranial fossa is rare. Bilateral condylar fractures combined with a symphyseal fracture is sometimes termed a guardsman's fracture. The name comes from this injury occurring in soldiers who faint on parade grounds and strike the floor with their chin.

The general presentation is of a skin-covered nodule, papule, or nodule of the skin surface, usually immediately anterior to the auricle. However, it may be anywhere within the periauricular tissues. Bilateral presentation can be seen.

Most often natal teeth are mandibular central incisors. They have little root structure and are attached to the end of the gum by soft tissue and are often mobile.

Brachygnathism or colloquially Parrot Mouth, is the uneven alignment of the upper and lower teeth in horses. In serious cases, the upper teeth protrude beyond the lower teeth. Problem with parrot mouth occur if the molars at the back of the mouth are also uneven, resulting in large hooks forming on the upper molars and the rear of the lower back molars. Horses with parrot mouth often require dental treatment at least every six months to remove the hooks and maintain alignment.

The equivalent conditions in humans are termed retrognathism or prognathism depending on whether the lower jaw is too far back or too far forward respectively.

Condylar resorption, also called idiopathic condylar resorption, ICR, and condylysis, is a temporomandibular joint disorder in which one or both of the mandibular condyles are broken down in a bone resorption process. This disorder is nine times more likely to be present in females than males, and is more common among teenagers.