Malocclusion, or the misalignment of teeth and jaws, is a widespread concern. These bite issues can range from minor cosmetic irregularities to significant functional problems that affect chewing and speaking. Among the most common forms of vertical malocclusion is the deep bite, where the vertical overlap of the front teeth is far greater than is considered healthy. Addressing this misalignment is a primary objective in orthodontic treatment due to its potential long-term effects on oral health.
Defining Excessive Vertical Overlap
A deep bite is an excessive vertical overlap of the upper teeth over the lower teeth when the back teeth are closed, a measurement known as overbite. In a balanced bite, the upper front teeth should cover only about 10% to 25% of the visible surface of the lower front teeth, or approximately one to three millimeters. This normal overlap ensures proper function and protection for the teeth and gums.
When this vertical overlap surpasses 40% of the lower incisor crown height, or exceeds four millimeters, the condition is classified as a deep bite. Orthodontists classify the severity based on this metric. An overlap covering 30% to 60% is considered moderate, while a severe deep bite is one where the upper teeth cover the lower teeth by 60% or more, sometimes completely hiding them from view.
Primary Factors Contributing to Deep Bite Development
The development of a deep bite involves skeletal, dental, and habitual factors. Skeletal deep bites are frequently linked to genetic traits, such as a smaller-than-average lower jaw or a growth pattern that results in a short lower facial height. This disproportionate jaw size forces the upper teeth to overlap the lower ones more significantly.
Dental causes involve the vertical positioning of the teeth within the jawbones. The over-eruption (supra-eruption) of the front teeth or the under-eruption (infra-eruption) of the back teeth can both lead to a deep bite. The loss of posterior teeth can also cause the bite to collapse, allowing the front teeth to over-erupt as they attempt to maintain contact. Childhood habits, such as prolonged thumb-sucking, can also contribute to the misalignment by affecting the developing jaw structure.
Health and Functional Issues Caused by Deep Bites
Leaving an excessive vertical overlap untreated can lead to consequences for the teeth and surrounding tissues. The excessive wear and tear on the incisal edges of the teeth is a common issue. The constant, heavy contact between the upper and lower teeth can cause the enamel to wear down, potentially leading to chipping, fractures, and the exposure of the sensitive dentin layer beneath.
Direct trauma to the gingival tissue is another significant problem. In severe cases, the lower front teeth bite directly into the gum tissue, or palatal mucosa, located behind the upper front teeth. This chronic impingement causes inflammation, painful sores, and can result in gum recession, which threatens the periodontal health of the upper teeth.
A deep bite can also place undue strain on the temporomandibular joint (TMJ). The excessive overlap can force the lower jaw into an unnatural, retruded position during closure, disrupting the movement of the joint. This uneven distribution of force can result in symptoms of temporomandibular disorder, including chronic jaw pain, clicking, and persistent headaches.
Orthodontic Solutions for Correcting Deep Bites
The correction of a deep bite relies on two primary biomechanical strategies: the intrusion of the anterior teeth or the extrusion of the posterior teeth. Intrusion is the process of moving the front teeth vertically into the jawbone, which is favored for patients who show too much of their upper front teeth or gums when smiling. This movement can be achieved using specialized archwires in traditional braces, such as a reverse curve of Spee, or with auxiliary appliances like utility arches.
The extrusion of posterior teeth involves encouraging the back teeth to move vertically out of the jawbone, effectively opening the bite in the front. This approach is preferred for individuals with a short lower facial height to help lengthen the face vertically. A common device for facilitating this is an anterior bite plane, which is a removable or fixed acrylic appliance that the lower front teeth contact, disengaging the back teeth and allowing them to erupt.
Modern clear aligners can also correct deep bites, utilizing specific attachments and bite ramps bonded to the teeth to control the intrusive forces. In cases of severe skeletal discrepancy where the jawbones themselves are significantly misaligned, orthodontic treatment may be combined with orthognathic surgery, depending on the patient’s age, facial structure, and the exact cause of the excessive vertical overlap.