What is bone-anchored orthodontics (bone-anchored ortho) and when is it a viable treatment option?

Bone-Anchored Orthodontics: Applications and Treatment Options

Bone-anchored orthodontics is a specialized technique that uses skeletal fixation devices directly attached to bone to provide absolute anchorage for orthodontic tooth movement, eliminating the need for patient compliance and overcoming limitations of traditional orthodontic anchorage methods.

Types of Bone Anchoring Devices

Several types of bone anchoring devices are used in orthodontics, each with specific applications:

1. Miniscrews (Temporary Anchorage Devices)

• Small titanium or stainless steel screws (typically 2mm diameter)
• Placed in inter-radicular spaces or extra-alveolar locations
• Success rates ranging from 61-100% 1
• Advantages:
  • Minimally invasive placement
  • Immediate loading capability
  • No patient compliance required
  • Can be placed in various locations

2. Miniplates

• Base plates fixed with mono-cortical screws
• Higher success rates (91.4-100%) 1
• Advantages:
  • Greater stability for complex movements
  • Can withstand heavier forces
  • Useful in cases requiring significant tooth movement

3. Palatal Implants

• Placed in the palatal region
• Success rates of 74-93.3% 1
• Advantages:
  • Good stability
  • Hidden from view
  • Useful for maxillary molar distalization

4. Extra-Alveolar Bone Screws

• Larger diameter (2mm) stainless steel screws
• Placed in basilar bone of the infra-zygomatic crest or mandibular buccal shelf
• Advantages:
  • Can retract entire dentition
  • Rotate either arch
  • Recover impacted teeth with lever arm springs 2

Clinical Applications and Indications

Bone-anchored orthodontics is particularly valuable in:

1. Complex Malocclusions:

   • Severe crowding requiring maximum anchorage
   • Skeletal discrepancies that would otherwise require orthognathic surgery
   • Dental asymmetries requiring unilateral tooth movement 2

2. Atypical Treatment Plans:

   • When conventional anchorage systems are insufficient
   • When treatment plans need modification due to unforeseen factors 3

3. Impacted Tooth Recovery:

   • Using lever arm springs anchored to infra-zygomatic crest or mandibular buccal shelf bone screws 2

4. Clear Aligner Therapy Enhancement:

   • Providing anchorage for tooth movements difficult to achieve with aligners alone 2

5. Denture Retention in Patients with Bone Loss:

   • Even two strategically placed implants can dramatically improve retention in patients with significant bone loss 4

Advantages Over Traditional Anchorage

• Provides absolute anchorage, overcoming reaction forces and moments
• Eliminates dependence on patient cooperation
• Allows for more predictable tooth movement
• Reduces treatment time in complex cases
• Can be used in patients with insufficient teeth for traditional anchorage 5

Potential Complications and Considerations

• Failure rates: While generally successful, failure rates vary by device type (miniscrews having the highest variability) 1
• Common minor complications: Granulations, acute gingivitis, gingival recession 6
• Anatomical limitations: Placement depends on bone quality and thickness 6
• Technical sensitivity: Proper placement technique is crucial for success

Clinical Decision-Making Algorithm

When considering bone-anchored orthodontics:

1. Assess anchorage requirements:

   • Is absolute anchorage necessary?
   • Will traditional anchorage methods be sufficient?

2. Evaluate bone quality and quantity:

   • Use cone-beam computed tomography to assess potential placement sites
   • Consider bone height, density, and proximity to vital structures

3. Select appropriate device type:

   • Miniscrews for moderate anchorage needs in adequate bone
   • Miniplates for heavy forces or poor bone quality
   • Palatal implants for maxillary molar movements
   • Extra-alveolar screws for whole arch movements

4. Determine optimal placement location:

   • Based on biomechanical requirements
   • Considering soft tissue health and accessibility

5. Plan loading protocol:

   • Immediate vs. delayed loading based on primary stability
   • Force magnitude and vector considerations

Future Directions

The field of bone-anchored orthodontics continues to evolve, with promising developments including:

• Integration with clear aligner therapy for complex movements
• Improved materials and designs for higher success rates
• Simplified placement protocols for wider clinical adoption 2

Bone-anchored orthodontics represents a significant advancement in orthodontic treatment, providing solutions for cases that were previously challenging or impossible to treat with conventional methods.