Class II problems represent abnormal relationships in which the upper jaw and teeth project ahead of the lower jaw. This is called "overjet." Class II patients usually exhibit a convex facial profile with a deficient chin prominence. Typically, a Class II problem is inherited and results in a shorter than normal lower jaw. Other factors, such as persistent thumb sucking can aggravate these problems. Correction of this disorder generally requires influencing facial growth to bring the upper and lower jaws and teeth into their proper position.
Crowding of the teeth is the most common problem associated with the need for orthodontic care. Although many factors contribute to the dental crowding, this problem usually stems from a discrepancy between space available in each jaw and the size of the teeth. Aside from aesthetic considerations, poor alignment of teeth may be associated with periodontal problems and an increased risk of dental decay due to difficulty in maintaining proper oral hygiene.
Excessive vertical overlapping of incisor teeth called "deepbite" or "overbite" is generally found in association with a discrepancy between the length of the upper and lower jaws. It usually results in excessive eruption of either the upper or lower incisors, or both. Associated problems include: 1) excessive display of gum tissue, 2) lip protrusion or entrapment, 3) biting the roof of the mouth and 4) incisor wear.
Spaces between teeth are another common problem associated with the need for orthodontic care. Like crowding, spacing may be related to a tooth-to-jaw-size disharmony. Gum tissue attachment called "frenum" is also a common cause of spacing between the front teeth. Excessive vertical overlap of the front teeth as well as incisor protrusion may lead spacing. Other contributing factors include atypical or unusually narrow teeth, and missing or impacted teeth.
Posterior crossbites usually result from a constricted upper jaw or unusually wide lower jaw. A narrow upper jaw will often force a patient to move their lower jaw forward or to the side when closing into a stable bite. When closed into this accommodated position, the lower teeth are located outside the upper teeth. This posturing may result in an incorrect fuctional position of the lower jaw with accompanying facial assymetry.
