An underbite, known scientifically as an Angle Class III anomaly, is one of the most complex and visually striking jaw irregularities. This condition goes far beyond a simple aesthetic issue with the teeth; it affects facial harmony, chewing function and, in the long term, the health of the jaw joint as well. At the Foxxi clinic, using the most advanced diagnostic and therapeutic procedures, we offer evidence-based treatment plans to achieve the perfect functional and aesthetic result.

What exactly is an underbite, and what causes it?

An underbite, medically known as mandibular prognathism, occurs when the lower teeth bite in front of the upper teeth.[1] This irregularity affects not only the position of the teeth but most often arises from a difference in the size and position of the jawbones.[1][2][3]

The scientific background:

Genetic predisposition: In a significant proportion of cases, an underbite is caused by genetic factors. The inherited predisposition determines the growth potential of the jawbones.
Growth disharmony: The problem most often arises from the jawbones growing at different rates. This can mean overgrowth of the lower jaw (mandible), underdevelopment of the upper jaw (maxilla), or a combination of the two.[4]
Functional causes: In certain cases, an incorrect tongue position during swallowing or other functional irregularities may also contribute to the development or worsening of an underbite.

The appearance and consequences of an underbite

An Angle Class III anomaly determines not only the bite but the character of the entire face.

Typical external features:

The lower lip and chin become more prominent and protrude forward.
The facial profile may become concave.
The nasolabial fold may deepen, while the upper lip may appear sunken.

Functional and health-related consequences:

Chewing difficulties: Biting into and grinding food may become difficult.
Speech problems: The formation of certain sounds may be imprecise.
Jaw joint complaints (TMJ): Due to improper loading, clicking and pain may develop in the jaw joint.
Increased tooth wear: Because of the abnormal contacts, the teeth may wear down prematurely.

The most effective therapy: surgical orthodontics

While in childhood, during the active phase of growth, it is still possible to influence the growth of the jawbones with special orthodontic appliances, in adulthood an already established bony discrepancy can only be corrected effectively and stably by combining orthodontics with jaw surgery, in what is known as orthognathic surgical treatment.[3][5]

This is a precisely planned, multi-stage process in which the orthodontist and the head and neck surgeon work closely together.

Pre-surgical orthodontics (approx. 1–1.5 years): In this phase, a fixed orthodontic appliance is used to move the teeth into their ideal position within their own jawbone. The goal is for the dental arches to fit together perfectly after surgery. During this phase the bite may temporarily appear even worse, but this process is essential for a successful operation.
The jaw operation (orthognathic surgery): The procedure is performed under general anaesthesia, inside the oral cavity, so no external scars remain. The most commonly used procedure on the lower jaw is the bilateral sagittal split osteotomy (BSSO). During this, the oral surgeon makes precise bone cuts that allow the lower jaw to be moved backward or forward, or to be rotated. If necessary, a correction is also carried out on the upper jaw (Le Fort I osteotomy) to achieve ideal facial and bite harmony. The bones are fixed in their new position with tiny titanium plates and screws.
Post-surgical orthodontics (approx. 6–10 months): The aim of the fine-tuning after surgery is to set the bite perfectly and to ensure a stable end result.

Why is the surgical solution the best choice?

Combined orthodontic-surgical therapy not only aligns the teeth, but eliminates the root of the problem: the positional irregularity of the jawbones. The result is a stable, functionally perfect bite and an aesthetically harmonious facial profile, which significantly improves quality of life and boosts self-confidence.

This article was written by the Foxxi team, reviewed by Dr. Magyar Dominika Ph.D., orthodontic specialist

Scientific sources used:

Park, J. U., & Baik, S. H. (2001). Classification of Angle Class III malocclusion and its treatment modalities. International journal of adult orthodontics and orthognathic surgery, 16(1), 19–29.
Popescu, M. V., et al. (2010). Correlations between the occlusal plane angle and the risk of relapse after surgical orthodontic treatment of Angle Class III anomalies. Revista de chirurgie oro-maxilo-facială şi implantologie, 1(1), 18-23.
Ngan, P., & Moon, W. (2015). Evolution of Class III treatment in orthodontics. American Journal of Orthodontics and Dentofacial Orthopedics, 148(1), 22-36.
Reyneke, J. P., & Tsakiris, P. (2019). The bilateral sagittal split osteotomy: its role in modern orthognathic surgery. Oral and Maxillofacial Surgery Clinics, 31(4), 479-492.
Kaán László Miklós (n.d.). Az orthodontiai kezelések optimális időzítése. Semmelweis University, Department of Paediatric Dentistry and Orthodontics.
Gábris Katalin (n.d.). Az orthodonciai anomáliák diagnosztizálása és kezelési lehetőségei. Semmelweis University.