Introduction
Class III malocclusion, commonly referred to as an underbite, occurs when the lower jaw (mandible) protrudes forward relative to the upper jaw (maxilla). This results in a reversed bite relationship, where the lower teeth are positioned in front of the upper teeth. Managing Class III malocclusion requires a strategic approach tailored to the patient’s age, skeletal growth potential, and severity of the condition.
Causes of Class III Malocclusion
Class III malocclusion can arise due to skeletal, dental, or functional factors, including:
1. Skeletal Causes
- Maxillary deficiency (underdeveloped upper jaw)
- Mandibular prognathism (overdeveloped lower jaw)
- Combination of both
2. Dental Causes
- Forward positioning of lower teeth (dental Class III)
- Backward inclination of upper teeth
3. Functional Causes
- Pseudo-Class III due to anterior crossbite or habitual forward positioning of the lower jaw
Diagnosis of Class III Malocclusion
A comprehensive evaluation includes:
1. Clinical Examination
- Assessing facial profile, jaw alignment, and functional shifts
- Evaluating overjet (horizontal relationship) and overbite (vertical overlap)
2. Radiographic Analysis
- Cephalometric X-rays to analyze skeletal discrepancies
- 3D imaging (CBCT scans) for complex cases
3. Digital Scans or Study Models
- Assessing dental arch alignment and bite relationship
Treatment Approaches for Class III Malocclusion
1. Early Treatment (Growth Modification in Children & Adolescents)
When diagnosed early, growth modification therapy can correct skeletal imbalances. Common approaches include:
A. Protraction Facemask Therapy (Reverse Pull Headgear)
- Best for children aged 6-10 years with maxillary deficiency.
- Applies forward traction on the upper jaw using a facemask and elastics.
- Often combined with a Rapid Palatal Expander (RPE) to stimulate maxillary growth.
B. Chin Cup Therapy
- Used to control excessive mandibular growth.
- Less effective for severe cases.
C. Functional Appliances (For Mild Cases)
- Appliances like the Frankel III or Bionator III help posture the mandible back in young patients.
2. Orthodontic Treatment (Braces & Aligners in Adolescents & Adults)
If skeletal growth modification is not possible, orthodontic treatment can manage Class III malocclusion by:
A. Fixed Braces (Metal or Ceramic Braces)
- Elastics or Class III mechanics (e.g., Class III rubber bands) are used to shift the upper and lower teeth into proper alignment.
- Temporary Anchorage Devices (TADs) can aid in moving teeth more effectively.
B. Clear Aligners (e.g., Invisalign)
- Suitable for mild to moderate dental Class III cases.
- Attachments and elastics may be used to improve results.
C. Tooth Extractions (For Severe Dental Class III Cases)
- Lower premolar extractions may be needed to allow retraction of the lower anterior teeth.
3. Surgical-Orthodontic Treatment (For Severe Skeletal Class III in Adults)
When jaw discrepancies are too severe for orthodontics alone, orthognathic surgery is required.
A. Mandibular Setback Surgery (Bilateral Sagittal Split Osteotomy – BSSO)
- The lower jaw is surgically repositioned backward.
B. Maxillary Advancement Surgery (Lefort I Osteotomy)
- The upper jaw is brought forward in cases of maxillary deficiency.
C. Bimaxillary Surgery
- In some cases, both jaws need surgical correction for optimal facial balance.
Retention & Post-Treatment Stability
After active treatment, retainers are crucial to maintain stability and prevent relapse:
- Fixed Retainers – Bonded retainers for long-term stability.
- Removable Retainers – Worn as per orthodontist’s instructions.
Conclusion
Managing Class III malocclusion requires a customized approach based on the severity of the case and the patient’s age. Early intervention with growth modification techniques can prevent the need for surgery, while orthodontics and orthognathic surgery are viable options for adolescents and adults with more severe skeletal discrepancies.
If you or someone you know has an underbite, consulting an orthodontist early can make treatment more effective and prevent complications.