A well-aligned bite, or occlusion, is important for chewing, speaking, and overall dental health. When the upper and lower teeth do not align properly, this is termed a malocclusion, or a “bad bite.” Dentists and orthodontists use Angle’s Classification, based on the position of the first permanent molars, to categorize these relationships. This system divides malocclusions into three main categories. Class 2 malocclusion is a frequently observed type requiring orthodontic intervention, involving a distinct relationship between the upper and lower jaws that affects dental function and facial appearance.
Defining the Class 2 Jaw Relationship
Class 2 malocclusion is defined by the front-to-back relationship of the upper and lower first permanent molars. In a normal Class 1 bite, the mesiobuccal cusp of the upper first molar fits directly into the buccal groove of the lower first molar. A Class 2 diagnosis occurs when the lower molar is positioned too far back (distal) relative to the upper molar. Specifically, the upper molar cusp sits forward of the lower molar groove. This discrepancy makes the lower jaw appear retruded compared to the upper jaw. This posterior positioning often results in an increased overjet, which is the horizontal protrusion of the upper front teeth over the lower front teeth.
Subdivisions of Dental Class 2
The molar relationship defines the Class 2 diagnosis, but the position of the upper incisors determines its two main subtypes: Division 1 and Division 2. These divisions have different visual characteristics and functional problems. The primary feature separating them is the difference in incisor inclination.
Division 1
Class 2 Division 1 is the more common presentation, characterized by upper incisors that are tipped forward (proclined). This forward inclination leads to a pronounced overjet, often resulting in the appearance of “buck teeth.” Patients frequently have difficulty achieving a complete lip seal because of the protrusion. The lower lip may rest behind the upper incisors, inadvertently pushing them further forward and worsening the overjet. This condition also carries an increased risk of trauma to the exposed upper front teeth.
Division 2
Class 2 Division 2 involves a unique arrangement of the front teeth despite the underlying Class 2 molar relationship. The upper central incisors are tipped inward (retroclined) toward the palate. This inward tipping often results in a deep overbite, where the upper front teeth severely overlap the lower front teeth vertically. The lateral incisors may be tipped forward to escape the inward pressure. Since the central incisors are tipped back, the overjet is often minimal, masking the skeletal discrepancy. This deep bite can sometimes cause the lower incisors to bite into the gum tissue, potentially leading to soft tissue damage.
Underlying Factors Contributing to Class 2
The development of a Class 2 malocclusion results from an interaction between inherited growth patterns and environmental influences. Causes are separated into skeletal factors, relating to jaw size and position, and functional factors, involving muscle forces and oral behaviors. Understanding the specific origin helps determine the most effective treatment approach.
Skeletal Factors
Skeletal factors are often the dominant cause, accounting for the underlying jaw discrepancy. The most common issue is mandibular retrognathism, meaning the lower jaw is underdeveloped or positioned too far back relative to the skull base. Less frequently, the condition is caused by maxillary prognathism, where the upper jaw is positioned too far forward or is excessively large. Both situations result in the distal positioning of the lower molars, leading to the Class 2 diagnosis. Genetic differences contribute significantly to the development of these inherited growth patterns.
Environmental and Functional Factors
Environmental and functional factors can influence or worsen the severity of the malocclusion. Persistent non-nutritive sucking habits, such as prolonged thumb or pacifier use past age four, directly influence tooth position. The force exerted can push the upper incisors forward, increasing the overjet and contributing to a Division 1 presentation. Abnormal tongue positioning, like a tongue thrust, or low muscle tone in the lips can also create an imbalance of forces that displaces teeth. Additionally, early loss of baby teeth in the upper arch can allow permanent molars to drift forward, contributing to the Class 2 dental relationship.
Correcting Dental Class 2 Alignment Issues
Correcting a Class 2 malocclusion involves a planned sequence of treatments dependent on the patient’s age and skeletal growth status. Treatment goals focus on achieving a stable Class 1 molar relationship and proper alignment of the front teeth. The approach is often phased for growing children to maximize the use of natural growth spurts.
Phase I: Growth Modification
Early intervention, known as Phase I treatment, is initiated in children during their mixed dentition phase while they are still growing. This stage focuses on growth modification, using specialized appliances to encourage the forward movement of the lower jaw. Functional appliances, such as the Twin Block or the Herbst appliance, are designed to posture the mandible forward, stimulating growth and redirecting the bite. Headgear is also used in Phase I to restrain or slow the forward growth of the upper jaw.
Phase II: Comprehensive Orthodontics
Once jaw growth is complete, typically in adolescence or adulthood, treatment shifts to comprehensive orthodontics (Phase II). This phase uses fixed appliances, like traditional braces or clear aligners, to precisely align the teeth within the arches. For mild to moderate skeletal discrepancies, the orthodontist may use inter-arch elastics or temporary anchorage devices to move the teeth into a Class 1 relationship. This process is sometimes called “dental camouflage,” where teeth are repositioned to hide the underlying skeletal discrepancy.
Orthognathic Surgery
For adults or patients with a severe skeletal discrepancy, where growth modification is no longer possible and dental camouflage is insufficient, orthognathic surgery may be necessary. This involves a surgical procedure to physically reposition the upper jaw, the lower jaw, or both, to achieve a proper skeletal relationship. The surgery is preceded and followed by comprehensive orthodontics to ensure the teeth fit together correctly once the jaws are moved.