A malocclusion, often called a “bad bite,” is a common dental term for any misalignment of the upper and lower teeth when the mouth is closed. Dental professionals use Angle’s Classification, a standardized system based on the relationship between the first permanent molars, to categorize these discrepancies. This classification helps determine the nature and severity of the issue for treatment planning. The Class II malocclusion is one of the most frequently diagnosed types of alignment issues.
Defining the Class II Bite
A Class II bite is characterized by the lower dental arch being positioned backward relative to the upper arch when the jaws are closed. This condition is often visually identified by a noticeable protrusion of the upper front teeth, commonly referred to as an “overbite” or “buck teeth.” Technically, the classification is defined by the relationship between the first molars, where the mesiobuccal cusp of the upper first molar sits forward of the buccal groove of the lower first molar.
A Class II bite features an increased overjet, which is the horizontal projection of the upper incisors beyond the lower incisors. While a normal overjet measures between 2 and 5 millimeters, this distance is significantly greater in Class II cases, sometimes exceeding 9 millimeters. This malocclusion is divided into two types: Division 1, where the upper front teeth are flared outward, and Division 2, where the upper central incisors are tipped inward, often resulting in a deep bite.
Class II malocclusions can be due to a skeletal discrepancy, a dental discrepancy, or a combination of both. A skeletal Class II involves a structural imbalance between the size or position of the jaws, often an underdeveloped lower jaw (mandibular retrusion) or an overgrown upper jaw (maxillary protrusion). A dental Class II means the teeth themselves are positioned incorrectly within otherwise properly aligned jaws.
Underlying Causes and Contributing Factors
The development of a Class II bite is multifactorial, arising from an interplay between genetics and environmental influences. Heredity plays a significant role, as the size and shape of the facial bones and jaws are inherited. Genetic factors can lead to skeletal disproportion, such as inheriting a smaller lower jaw size combined with a normal-sized upper jaw.
Environmental factors contribute to the malocclusion, particularly in younger patients. Prolonged oral habits, such as thumb sucking or extended pacifier use past early childhood, exert constant pressure on the developing teeth and jawbones. This pressure can push the upper front teeth forward and restrict the forward growth of the lower jaw, exacerbating the Class II relationship. The premature loss of deciduous (baby) molar teeth can also allow permanent molars to drift forward, contributing to the dental component of the malocclusion.
Health and Functional Implications
Leaving a Class II malocclusion uncorrected can lead to functional and health complications. The significant protrusion of the upper incisors increases the risk of dental trauma, especially from falls or sports injuries, because the teeth are unprotected by the lips. The risk of injury is considerably elevated in patients with an overjet greater than 3 millimeters.
The misalignment interferes with normal oral function, making it difficult to properly bite and chew certain foods. This inefficiency may sometimes lead to digestive issues. The incorrect jaw relationship can also contribute to speech impediments, such as lisping.
Furthermore, the misaligned bite can cause uneven and excessive wear on specific teeth over time. The strain from this misalignment can also place stress on the temporomandibular joints (TMJ), potentially leading to discomfort or dysfunction.
Treatment Approaches
The approach to correcting a Class II bite depends heavily on the patient’s age and whether the malocclusion is primarily skeletal or dental. For growing children (ages 7 to 11), early intervention, known as Phase I treatment, focuses on growth modification. Appliances like headgear can restrict the forward growth of the upper jaw, while functional appliances such as the Herbst or Forsus encourage the forward positioning of the lower jaw.
Once a patient is in adolescence and most of their permanent teeth have erupted, comprehensive treatment often begins. This Phase II treatment typically involves fixed appliances, commonly known as braces, or clear aligners to move the teeth into their correct positions. The use of specialized elastics is frequently incorporated to pull the upper teeth backward and the lower teeth forward, effectively correcting the molar relationship.
For adults, or in severe skeletal cases where growth is complete, treatment options are limited to dental camouflage or orthognathic surgery. Dental camouflage uses orthodontics, sometimes with tooth extractions, to align the teeth within the existing jaw structure, masking the skeletal issue. For significant skeletal discrepancies, orthognathic surgery (jaw surgery) is required to physically reposition the upper and/or lower jaw to achieve a correct and stable bite relationship.