Bite Classifications

Understanding bite classifications is essential in dentistry. This classification system is primarily based on the alignment of the first permanent molars in centric occlusion, influenced by the skeletal relationship between the maxilla, mandible, and cranial base. A comprehensive diagnosis and treatment plan necessitate assessing dental and skeletal conditions in all spatial planes.

Dr. Edward Angle, born in 1855, revolutionized orthodontics and introduced a foundational classification system. Angle's system categorizes malocclusions into three main classes:

Class I:

Ideal occlusion, according to Dr. Angle, is marked by the alignment of the first molars, where the upper mesio-buccal cusp fits precisely into the lower buccal groove. This alignment signifies a Class I occlusion, characterized by a proper molar relationship. Additionally, in Class I, the upper canine cusp aligns with the space between the lower canine and first premolar.

Class II:

A Class II malocclusion occurs when the upper first molar's mesio-buccal cusp lies anterior to the lower molar's buccal groove. This positioning results in a distal (posterior) placement of the lower molar's buccal groove concerning the upper molar's cusp. Class II malocclusions are further subdivided based on the position of the incisors:

Division 1: Protrusion of upper anterior teeth with a large overjet.
Division 2: Retroclination of upper anterior teeth with a deep overbite.

Aligners combined with sequential distalization and Class II elastics can effectively treat Class II malocclusions of up to 3 mm.

Class III:

In Class III malocclusions, the upper first molar's mesio-buccal cusp is distally positioned compared to the lower molar's buccal groove. Similarly, the upper canine cusp lies distally concerning the space between the lower canine and first premolar. Treatment strategies for Class III malocclusions depend on whether a skeletal component is present, typically involving interproximal reduction (IPR), retroclination of lower incisors, proclination of upper incisors, and the use of Class III elastics.

Malocclusion Types

Malocclusion refers to the misalignment or improper relationship between the teeth of the upper and lower dental arches as they come together when the jaws close.

Common Types of Malocclusions:

Crowding: This occurs due to a mismatch between the arch length and tooth size, leading to overlapping and displacement of teeth in various directions. Crowding can be categorized as mild (up to 3 mm), moderate (3 to 5 mm), and severe (over 5 mm). Treatment strategies consider factors like soft tissues, facial profile, malocclusion type, dental positions, and the degree of crowding. Mild crowding may be addressed with expansion and proclination, while moderate to severe crowding may require additional techniques and auxiliary tools to achieve the desired outcome.
Spacing: This is characterized by gaps between teeth and missing interproximal contacts, often resulting from tooth size discrepancies, missing teeth, or habits. Mild spacing might be managed with aligners alone, moderate spacing with retraction, and severe cases may need various techniques including aligners and auxiliary supports. Post-treatment retention and monitoring of any detrimental habits are crucial to prevent relapse.
Deep Bite: This condition features excessive vertical overlap of the upper incisors over the lower incisors. It can result from multiple factors and might be corrected with aligners if not overly severe. Deep bites have significant functional implications.
Open Bite: In this condition, there is a lack of contact between the anterior or posterior teeth of the opposing arches. An anterior open bite means the front teeth do not make contact in centric occlusion, while a posterior open bite, less common, involves the back teeth. Open bites may be either dental or skeletal in nature, influenced by soft tissue profiles, arch forms, and jaw angles. Treatment might involve retroclining initially proclined incisors and may require comprehensive evaluation to ascertain the cause, whether dental, skeletal, muscular, or other. Monitoring for the development of a posterior open bite during treatment is crucial, as it may necessitate immediate corrective action.
Crossbite: A crossbite is when the upper teeth (anterior or posterior) are situated palatally relative to the lower teeth. Identifying whether a crossbite is dental or skeletal is essential for appropriate treatment planning. Dental crossbites, often linked to individual tooth misplacements, can generally be corrected with aligners. Skeletal crossbites, associated with discrepancies in arch width, might require initial treatment with other devices like fixed expanders or surgical intervention.

Tongue Thrust

Tongue thrust, also known as reverse swallow or immature swallow, refers to an orofacial muscular imbalance where the tongue protrudes actively through the front teeth during swallowing and speech, a condition typically recognized by professionals as a true tongue thrust. When the tongue passively protrudes between the front teeth while resting (as may occur with an overly large tongue), this is considered a postural phenomenon or pseudo-thrust. It is important for doctors to assess the size of the tongue and any tongue thrusting habits before starting treatment for patients with significant anterior spacing and severe proclination.

Causes of Tongue Thrust

Tongue thrusting can be caused by several factors, including:

Neuromuscular imbalance
An enlarged tongue
Habitual thumb sucking
Enlarged tonsils
Hereditary factors

Solutions for Tongue Thrust

In treating an anterior open bite, it is crucial to ascertain the underlying cause—whether it is environmental, such as from a large tongue, or from a hyperactive tongue thrusting against the teeth. Correctly identifying and addressing the root cause of an anterior open bite enhances the success and retention stability of the treatment. Although consulting a speech therapist might help address neuromuscular imbalances, correcting the environmental factors or the open bite to accommodate a large tongue in the oral cavity without it exerting excessive pressure on the teeth might also be effective without therapeutic intervention. Treatments for correcting an open bite may include the use of clear aligners, reverse-curve archwires, vertical elastics, or orthognathic surgery, depending on the severity of the issue. A long-term retention strategy is recommended to maintain the stability of the treatment results.