bubble_chart Overview

Anterior deep overjet refers to the maximum horizontal distance from the incisal edge of the lower anterior teeth to the labial surface of the upper anterior teeth exceeding 3mm. This is a relatively common malocclusion in clinical practice, often accompanied by anterior deep overbite.

bubble_chart Etiology

1. Bad Habits Long-term habits such as thumb-sucking, finger-sucking, biting the lower lip, or licking the upper front teeth exert continuous labial pressure on the upper front teeth, easily causing them to tilt labially. Simultaneously, the lower front teeth may tilt lingually and become crowded, leading to excessive anterior overjet. Persistent thumb-sucking may also contribute to abnormal jaw development.

2. Local Obstacles in Tooth Replacement or Eruption

(1) Congenital absence of lower front teeth: Clinically, the absence of 1–2 lower incisors can reduce the anterior segment of the lower dental arch, causing retraction of the lower arch and deep anterior overjet. This may further lead to habits like lip-biting or mouth-breathing, worsening the malocclusion.

(2) Premature loss of primary molars: Promoting lactation. Early loss of molars can shrink the anterior segment of the lower dental arch, increasing anterior overjet.

(3) Supernumerary teeth: Extra teeth in the upper anterior region may enlarge the dental arch or cause labial displacement of the upper incisors, resulting in excessive deep overjet.

(4) Abnormal eruption sequence: If the upper second permanent molar erupts before the lower second permanent molar, or the upper first permanent molar erupts earlier than the lower first permanent molar, or the upper second permanent molar erupts before the upper canine, it may lead to a distal step, causing deep anterior overjet.

3. Distal Step A distal step relationship between the upper and lower second primary molars can result in deep anterior overjet.

4. Mouth Breathing Due to partial nasal obstruction from respiratory diseases, mouth breathing often replaces nasal breathing, gradually forming a habit. Over time, relaxed lip muscles reduce normal labial pressure on the upper front teeth, while elongated buccal muscles compress the dental arch, narrowing it and forming a high palatal vault. This leads to deep anterior overjet combined with maxillary or dental arch protrusion.

5. Systemic Diseases or Calcium-Phosphorus Metabolism Disorders (e.g., Rickets) Weak muscle and ligament tension can cause narrowing of the upper dental arch, upper tooth protrusion, and distal malocclusion.

6. Genetic Factors Deep anterior overjet is often accompanied by significant skeletal deformities, such as excessive maxillary development or underdeveloped mandible. {|109|}

bubble_chart Diagnosis

1. Dental Type: The relationship between the upper and lower jaws, as well as with the craniofacial structure, is generally normal, meaning the molar relationship is neutral. The deep overjet is primarily caused by labial displacement of the upper front teeth or lingual displacement of the lower front teeth, or a combination of both mechanisms, without significant skeletal abnormalities. The prognosis for this type of deep overjet is favorable.

2. Functional Type: Mainly caused by a neuromuscular reflex leading to functional retrusion or backward positioning of the mandible. The maxillary development is generally normal, with a distal molar relationship, but when the mandible is protruded to a neutral molar relationship, the upper and lower dental arches are essentially harmonious. The prognosis for this type of malocclusion is uncertain.

3. Skeletal Type: Primarily due to abnormal development of the upper and lower jaws, resulting in a distal malocclusion relationship, with the posterior teeth mostly in a distal relationship. Based on the mechanism of formation, it can be further divided into three scenarios, with specific diagnoses aided by cephalometric X-ray analysis.

(1) Maxillary protrusion with normal mandibular development.

(2) Normal maxillary development with mandibular deficiency or retrusion.

(3) Maxillary protrusion combined with mandibular deficiency or retrusion.

4. The degree of overjet can be classified into three levels based on severity.

- Degree I Deep Overjet: The maximum horizontal distance from the incisal edge of the upper front teeth to the labial surface of the lower front teeth is 3–5 mm.

- Degree II Deep Overjet: 5–7 mm.

- Degree III Deep Overjet: Over 7 mm.

Severe cases may exceed 10 mm.

bubble_chart Treatment Measures

1. Eliminate the causes of disease as early as possible, such as breaking various bad habits, treating systemic diseases including nasal respiratory diseases, and extracting supernumerary teeth.

2. Correction of malocclusion

(1) Treatment objectives: The treatment objectives for this deformity mainly depend on the manifestation of the malocclusion. In most cases, deep overbite of the anterior teeth can be fully corrected, and some cases may also require reduction of the deep overbite. Correction of the posterior occlusion is also important, though not all cases require it. Severe deformities caused by skeletal or muscular factors are relatively difficult to fully correct; the treatment objectives for such cases should be adjusted accordingly. Some severe adult cases require combined orthodontic and orthognathic surgical treatment.

The main treatment objectives are: ① Alleviate dental crowding and local misalignment; ② Reduce anterior deep overbite; ③ Reduce anterior overjet; ④ Correct posterior distal malocclusion.

(2) Extraction issues during treatment: Anterior overjet is often accompanied by labial inclination of the upper incisors and sometimes combined with crowding. Therefore, extraction is often necessary to reduce anterior overjet and other issues.

Extraction serves four main purposes: ① Alleviate crowding in the dental arch; ② Provide space for retraction of anterior teeth in the upper arch; ③ Provide space for intermaxillary traction and correction of molar relationships in the lower arch; ④ Provide space to relieve deep overbite.

Post-extraction treatment mainly involves alleviating crowding, reducing overbite and overjet, and correcting posterior occlusion. The correction of the first two aspects can be referred to in relevant chapters. Here, only the reduction of overjet and correction of posterior occlusion are introduced.

(3) Reducing overjet: Overjet is usually reduced by retracting the anterior segment of the upper arch, which requires sufficient space for retraction. In a few cases, overjet reduction is achieved by advancing the lower incisors.

The method used to retract the upper anterior teeth mainly depends on the severity of Class II skeletal discrepancy. In Grade I discrepancies, simple incisor tipping can achieve good incisor relationships. When extraction of the first premolars is required, the canines are usually first moved distally to approximate the second premolars, followed by lingual displacement of the upper incisors to reduce overjet. If the overjet is small, removable appliances can be used for correction. If the overjet is large and significant tipping is required, extraoral anchorage reinforcement or intermaxillary traction with fixed appliances is used (Figure 1).

A. The canines need to be sufficiently retracted. To prevent mesial movement of the posterior teeth, extraoral anchorage or other reinforcement methods can be used.

B. No anchorage reinforcement is needed. The dashed line indicates the extracted tooth.

Figure 1: Canine retraction and anchorage

For anterior overjet with severe Class II skeletal discrepancies, simple incisor tipping is insufficient due to the significant retraction required. Instead, bodily movement or tipping followed by root torque is used (Figure 2).

Figure 2: Methods for reducing anterior overjet

Overjet reduction can be achieved through bodily movement of the incisors (A), or initial tipping (B) followed by root torque (C).

A key feature after correcting anterior overjet is the balance between incisor position and muscular forces. The overjet should at least be reduced to a point where the lower lip rests in front of the upper incisors.

(4) Correction of posterior occlusion: When anterior deep overbite is accompanied by a distal molar relationship, whether it is necessary to correct the posterior teeth to a neutral occlusion is controversial. The generally accepted view is to establish good functional occlusion in the posterior teeth, with a cusp-fossa relationship. If conditions permit, efforts should be made to achieve a neutral posterior occlusion. Under limited conditions, it is preferable to form a distal relationship with cusp-fossa alignment rather than a distal contact relationship with cusp-to-cusp alignment. There are four basic methods to achieve the above treatment goals.

1) Distal movement of upper posterior teeth to form a neutral occlusion: This requires a larger jaw to accommodate all teeth, along with significant distal displacement, often necessitating intermaxillary or extraoral traction. Occasionally, success can be achieved after extracting the upper second permanent molars (Figure 3A).

Figure 3 Methods for correcting distal cusp-to-cusp relationships of posterior teeth

A. Non-extraction intermaxillary or extraoral traction

B. Extraction of four first premolars and intermaxillary traction to close extraction spaces

C. If lower teeth are aligned, only upper premolars are extracted, with intermaxillary traction to close spaces and correct anterior tooth relationships

2) Mesial movement of lower posterior teeth to form a neutral occlusion: Often achieved by extracting four first premolars in both jaws. Intermaxillary traction can be used to move upper anterior teeth backward and lower posterior teeth forward (Figure 3B).

3) Mesial movement of upper posterior teeth to form a distal cusp-to-fossa relationship: This primarily suits Angle Class II Division 1 malocclusion with intact lower arches and distal cusp-to-cusp molar relationships. Extract the first premolars in the upper jaw and use intramaxillary traction to retract upper anterior teeth and move upper posterior teeth forward into the extraction spaces (Figure 3C).

4) Guiding the mandible forward to form a neutral occlusion: This mainly applies to functional deep overbite malocclusions where the maxilla is essentially normal, the lower arch is intact but in a distal retruded position. Functional appliances can correct distal molar relationships.

3. For adult patients with severe skeletal deformities accompanying deep overbite, combined surgical orthodontics and orthodontic treatment are necessary for success.