A malocclusion is a misalignment of the teeth and jaws that affects the proper meeting of the upper and lower dental arches. While a small degree of overlap is necessary for a functional bite, any significant deviation can compromise oral health and function. The two most commonly recognized forms of this misalignment are the overbite and the underbite. Determining which condition is inherently “worse” requires comparing their functional consequences and the complexity involved in their correction. Both can cause problems if left untreated, but they present different challenges.
Understanding Overbites and Underbites
An overbite, technically known as a Class II malocclusion, occurs when the upper front teeth excessively overlap the lower front teeth vertically. A slight overlap of one to two millimeters is considered normal. When the upper teeth cover the lower teeth by more than three to four millimeters, it is classified as a deep overbite. This condition often results from a lower jaw that is too far back or too small compared to the upper jaw, creating a convex facial profile.
An underbite, or Class III malocclusion, presents the opposite relationship: the lower jaw protrudes, and the lower front teeth rest in front of the upper front teeth. This reverse overlap deviates from the normal biting pattern and can be caused by an oversized or forward-positioned lower jaw, an underdeveloped upper jaw, or a combination of both. Underbites are less common than overbites, occurring in less than six percent of orthodontic cases compared to nearly 20 percent for Class II. Both conditions can be classified as either dental, involving only tooth positioning, or skeletal, involving a mismatch in the size or position of the jawbones.
Comparative Health and Functional Consequences
The consequences of severe overbites and underbites extend beyond aesthetics, affecting chewing, speech, and joint health. A deep overbite can lead to trauma and excessive wear on the lower front teeth. These teeth may contact the gum tissue behind the upper front teeth or the roof of the mouth. This repeated contact can strip gum tissue from the back of the upper teeth or cause painful sores and ulcers on the palate, potentially leading to tooth loss. Furthermore, a deep overbite can strain the temporomandibular joint (TMJ), leading to discomfort, headaches, and jaw pain.
In contrast, an underbite accelerates wear on the front teeth due to direct, edge-to-edge or reverse contact between the upper and lower incisors. This abnormal contact pattern can lead to chipping, cracking, and premature enamel loss. Underbites also impact chewing efficiency, making it difficult to bite into certain foods with the front teeth and often causing uneven chewing on the back teeth. The misalignment can also affect tongue placement, potentially leading to speech impediments such as lisps.
While both malocclusions can result in TMJ issues, speech difficulties, and uneven tooth wear, the skeletal nature of many underbites often makes them functionally more disruptive. The significant forward position of the lower jaw in a severe Class III malocclusion can interfere with proper food breakdown and may even be linked to obstructive sleep apnea. Ultimately, the severity of the skeletal discrepancy determines the functional impact, and Class III malocclusions are considered to present a greater challenge to the entire chewing system.
Differences in Correction and Treatment Difficulty
The perceived “worseness” of a malocclusion is often related to the complexity, duration, and invasiveness of the required treatment. Overbite correction, especially for dental cases, can often be addressed effectively with traditional orthodontic methods like braces or clear aligners. For growing patients with a skeletal Class II issue, functional appliances like the Herbst or Twin Block are used to encourage the forward growth of the lower jaw. These interventions aim to reduce the need for surgery later in life by harnessing the body’s natural growth potential.
Underbite treatment often necessitates more complex and aggressive interventions, particularly when the issue is skeletal. Early intervention, known as Phase I orthodontics, is considered important for Class III cases to guide jaw development before growth is complete. This early phase might involve a reverse-pull headgear or a facemask to encourage the forward growth of the underdeveloped upper jaw. Delaying treatment for a skeletal underbite beyond the late mixed dentition stage can significantly limit the possibility of non-surgical correction.
For severe skeletal discrepancies in adult patients where jaw growth is complete, the likelihood of needing orthognathic surgery is higher with an underbite than with a comparable overbite. Underbite correction may require procedures like mandibular setback or maxillary advancement to physically reposition the jawbones. While severe overbites can also require surgery, the need for combined surgical-orthodontic treatment is a more common feature of severe Class III malocclusions. This contributes to the perception that underbites are more challenging and costly to manage.