bubble_chart Overview

Deep overbite is an abnormal vertical relationship between the upper and lower dental arches. It refers to the condition where the incisal edge of the upper front teeth covers more than one-third of the crown length of the lower front teeth, or the lower front teeth occlude on the lingual side of the upper front teeth by more than one-third.

bubble_chart Etiology

1. Systemic factors: Chronic systemic diseases during childhood can lead to underdeveloped jaws, incomplete eruption of posterior teeth, insufficient posterior alveolar height, while anterior teeth continue to erupt, resulting in excessive anterior alveolar height or forward and upward rotation of the mandible.

2. Genetic or congenital factors: Excessive development of the maxilla; forward and upward rotation of the mandible.

3. Severe buccolingual malposition of molars or excessive wear of posterior teeth, reducing vertical dimension.

4. Excessive tension in masticatory muscles, with high electromyographic activity during intercuspal position (ICP) clenching, inhibiting posterior alveolar bone growth.

5. Premature loss of multiple deciduous molars or first permanent molars, reducing intermaxillary distance and lacking masticatory stimulation, affecting jaw and alveolar development.

6. Congenital absence of some mandibular incisors or premature loss of deciduous canines, leading to abnormal anterior tooth contact and over-eruption.

bubble_chart Pathogenesis

It is mainly due to the improper coordination of the anterior and posterior alveolar or jaw bone height, resulting in an increased overbite of the upper and lower anterior teeth. There are three forms of manifestation:

Type I is characterized by normal height of the anterior alveolar or jaw bone, but insufficient height of the posterior alveolar or jaw bone.

Type II is characterized by excessive height of the anterior alveolar or jaw bone or upward rotation of the mandibular body, while the height of the posterior alveolar bone is normal.

Type III is characterized by excessive height of the anterior alveolar or jaw bone and insufficient height of the posterior alveolar or jaw bone.

bubble_chart Clinical Manifestations

The upper central incisors are vertical or inclined inward, with the lateral incisors inclined labially, or the upper incisors inclined inward while the canines incline labially, or all upper anterior teeth inclined inward, with an anterior overbite of less than 3 mm, sometimes 0–1 mm. Alternatively, the upper and lower anterior teeth may be crowded and inclined inward, forming a severe locked bite, which can cause biting on the lingual side of the upper incisors or the labial gingival tissue of the lower incisors, leading to acute or chronic periodontitis, alveolar bone resorption, and tooth mobility. The posterior teeth exhibit a neutral or distal occlusion, and both the upper and lower dental arches are shortened. In deep overbite cases, the compensatory curve of the upper dental arch and the sagittal curve of the lower dental arch form antagonistic arcs. Mandibular protrusion and lateral movements are restricted, with the mandible only capable of hinge-like opening and closing motions. Lateral movements can only occur after the distal surfaces of the upper canines have worn into grooves. Functional mandibular retrusion is present, with normal or excessive tension in the lip and masticatory muscles. In some cases, electromyographic activity is high during intercuspal position (ICP) clenching. Facial and jawbone development is generally good, often presenting a square facial shape. The lower third of the face is short, with a prominent mandibular angle and a low-angle mandibular plane. The facial appearance of deep overbite includes everted lower lips, forming deep horizontal chin wrinkles, a protruding chin, elevated nasal wings, and a shortened upper lip.

bubble_chart Diagnosis

Based on the degree of overbite, it is classified into 3 degrees:

Degree I: The upper anterior teeth cover more than 1/3 to 1/2 of the crown length of the lower anterior teeth; or the lower anterior teeth occlude on the lingual incisal 1/3 to 1/2 of the upper anterior teeth.

Degree II: The upper anterior teeth cover more than 1/2 to 2/3 of the crown length of the lower anterior teeth; or the lower anterior teeth occlude on the lingual incisal 1/2 to 2/3 of the upper anterior teeth (e.g., the cingulum).

Degree III: The upper anterior teeth completely cover the crowns of the lower anterior teeth, even biting on the labial gingival tissue of the lower anterior teeth; or the lower anterior teeth occlude on the lingual gingival tissue or hard palatal mucosa of the upper anterior teeth, thereby causing traumatic gingivitis or mucosal injury.

Specific diagnosis can be combined with cephalometric X-ray analysis.

bubble_chart Treatment Measures

For younger individuals who are still in the growth and development phase, a functional appliance with a flat bite plate (or inclined bite plate) and a double-curved lingual spring on the labial side of the upper front teeth is used to stimulate the continued growth of the posterior teeth and inhibit the elongation of the anterior teeth. However, the lingually inclined front teeth must first be corrected, followed by coordinating the lengths of the upper and lower dental arches to correct the relationship between the upper and lower jaws and the dental arches.

1. Treatment for Type I Deep Overbite: Maintain the height of the anterior alveolar bone and focus on increasing the height of the posterior teeth. Use a removable maxillary appliance with a flat bite plate and occlusal pad. Starting from the last tooth, gradually grind down the occlusal pad to allow each pair of teeth to elongate and make contact. After the posterior teeth have been elevated, correct the lingual displacement of the anterior teeth and the distal occlusion of the posterior teeth. For older individuals whose growth has ceased, treatment is extremely difficult. Wearing an occlusal pad and flat bite plate will not elevate the posterior teeth. After correcting the anterior teeth as much as possible, use a compound formula to increase the height of the posterior teeth and restore the occlusal height. However, this must be within the mandibular rest space; otherwise, temporomandibular joint and muscle symptoms may occur.

2. Treatment for Type II Deep Overbite: Maintain the height of the posterior alveolar bone and depress the anterior teeth. If the anterior overbite is not too deep, fixed or removable appliances can be used to push the upper and lower front teeth toward the labial side. For deeper overbites, after correcting the lingual displacement of the anterior teeth as described above, a finger spring can be soldered to the labial bow of the removable appliance to directly depress the teeth, or a pin spring can be soldered with a hook attached to the tooth for depression. If using fixed appliances like Edgewise or Begg for correction, the upper front teeth must first be pushed labially before proceeding with mandibular treatment.

3. Treatment for Type III Deep Overbite: Combine depressing the anterior teeth and elevating the posterior teeth. For younger individuals, use a removable appliance with a finger spring soldered to the labial bow to depress the upper front teeth. After the upper front teeth are depressed, add a flat bite plate to depress the lower front teeth and elevate the posterior teeth. Alternatively, the flat bite plate and upper finger spring can be used simultaneously. Fixed or functional appliances can also be used for correction.