An underbite, medically known as a Class III malocclusion, occurs when the lower front teeth and jaw extend beyond the upper front teeth. This misalignment, where the bottom teeth protrude instead of being slightly overlapped by the upper teeth, can progress over time.
How Underbites Change Over Time
Underbites can worsen with age, particularly during periods of significant jaw growth. The lower jaw, or mandible, may continue to grow disproportionately compared to the upper jaw, leading to a more pronounced underbite. This accelerated growth often occurs during the pubertal growth spurt in early to mid-teenage years. While jaw growth generally stabilizes by late adolescence or early adulthood, the misalignment can become more severe if left unaddressed.
There are two main types of underbites: skeletal and dental. A skeletal underbite involves a discrepancy in the size or position of the jaw bones, such as an oversized lower jaw or an underdeveloped upper jaw. This type is more likely to worsen with continued jaw growth. In contrast, a dental underbite primarily involves the positioning of the teeth, where the lower teeth are angled forward without a significant underlying jawbone issue.
Effects of an Underbite on Oral Health
An underbite can lead to various health issues beyond its visible impact. Difficulty chewing and biting food is a common problem, as misaligned teeth cannot properly break down food. This affects digestion and can lead to discomfort or pain during meals. Speech impediments are also frequently associated with underbites, as the altered jaw and tooth position can make it challenging to articulate sounds like “s,” “z,” “t,” “d,” “n,” and “l.”
Improper alignment can cause excessive wear on tooth enamel, particularly on the front teeth, increasing the risk of chipping, breakage, and decay. This wear can necessitate restorative dental work. An underbite can also strain the temporomandibular joints (TMJ), which connect the jaw to the skull. This strain can result in jaw pain, headaches, earaches, and clicking sounds when moving the jaw, potentially leading to chronic TMJ disorders.
Addressing Underbites at Different Ages
Addressing underbites involves various approaches, with the patient’s age significantly influencing options and outcomes. Early intervention during childhood, before puberty, is recommended because jaw bones are still developing and more amenable to guidance. Orthopedic appliances like palate expanders (to widen the upper jaw) and reverse-pull headgear (to encourage forward upper jaw growth) can direct jaw development. This proactive treatment can reduce the complexity and invasiveness of future corrections.
For adolescents, who still have jaw growth potential, treatment often involves braces to align the teeth and correct the bite. Braces might be combined with other orthodontic appliances or tooth removal to create space. The goal is to achieve proper alignment while taking advantage of any remaining growth.
In adults, where jaw growth has ceased, correcting a significant skeletal underbite requires a comprehensive approach. Braces align teeth, but for pronounced jaw discrepancies, orthognathic surgery (jaw surgery) is often necessary. This surgery repositions the upper or lower jaw, or both, for proper alignment. While treatment is possible at any age, complexity and invasiveness increase with age due to hardened adult jaw bones.