In orthodontic treatment, few principles are as foundational—and as often overlooked—as anchorage. Without sufficient anchorage, retraction forces may move the wrong teeth, disrupt occlusion, or lead to mid-treatment failure. Simply put, anchorage systems determine whether your space closure plan will succeed or self-destruct.
In this article, we break down the major types of anchorage systems used in orthodontic retraction, their clinical indications, and how to choose the right one for each case.
What Is Anchorage in Orthodontics?
Anchorage refers to resistance to unwanted tooth movement. When applying force to retract teeth, Newton’s third law ensures that an equal and opposite force is generated—if not properly managed, this can cause posterior teeth to drift forward instead of moving anterior teeth backward.
Anchorage systems provide the biomechanical counterbalance needed to direct force efficiently.
Classification of Anchorage Systems
Anchorage systems can be classified by several criteria:
A. By Location
- Intraoral anchorage: Uses teeth, palate, or alveolar bone
- Extraoral anchorage: Includes headgear or facemasks
B. By Support Type
- Dental anchorage: Uses teeth as support units
- Skeletal anchorage: Uses mini-screws (TADs), plates, or implants
C. By Control Mechanism
- Passive anchorage: Resistance is provided without active force (e.g., Nance button)
- Active anchorage: Actively counteracts force through resistance or engagement (e.g., TAD with coil spring)
D. By Magnitude of Anchorage Demand
- Minimum anchorage: Posterior teeth allowed to drift forward
- Moderate anchorage: Balanced tooth movement
- Maximum anchorage: Posterior teeth must remain stationary
Common Anchorage Devices and Their Uses
| Anchorage Type | Device | Indication |
|---|---|---|
| Dental | Transpalatal Arch (TPA) | Moderate anchorage in upper arch |
| Dental | Nance Button | Maximum anchorage in non-growing patients |
| Dental | Lower Lingual Holding Arch | Mandibular molar anchorage |
| Skeletal | Mini-screws (TADs) | High control in adults or complex retraction |
| Skeletal | Mini-plates | Extreme anchorage in surgical or asymmetrical cases |
| Extraoral | Headgear | Orthopedic control, growing patients |
How to Choose the Right Anchorage System
Choosing the right system depends on clinical factors such as:
- Anchorage Demand
- Extraction cases often need moderate to maximum anchorage
- Patient Age and Compliance
- Extraoral systems need cooperation, whereas skeletal systems do not
- Space Available and Esthetic Needs
- Mini-screws can be hidden; headgear cannot
- Vertical and Sagittal Control
- Some anchorage systems also influence bite depth or molar tipping’
Clinical Case Types and Recommended Anchorage
Case 1: Bimaxillary Protrusion (Extraction of 1st Premolars)
- Goal: Maximum anterior retraction
- Anchorage: Bilateral mini-screws between 2nd premolars and 1st molars
Case 2: Mild Crowding with Extraction
- Goal: Space closure with minor anchorage concern
- Anchorage: Passive TPA + group ligation of molars
Case 3: Deep Bite with Posterior Open Bite Tendency
- Goal: Control vertical dimension during retraction
- Anchorage: TADs with intrusive force vectors + reverse curve archwire
Case 4: Asymmetrical Arch or Crossbite
- Goal: Unilateral or segmented retraction
- Anchorage: Mini-plate on affected side + reinforced ligation on opposite side
Tips for Effective Anchorage Control During Retraction
- Anchor Before You Pull
- Set anchorage systems before applying retraction force
- Reinforce Consistently
- Monitor TPA tightness, mini-screw integrity, and headgear wear time
- Don’t Rely on Ligatures Alone
- Group ligation may seem secure but often fails under sustained force
- Minimize Friction
- Low-friction brackets reduce anchorage demand by enhancing force efficiency
- Watch for Anchorage Loss Early
- Use progress models or cephalometric analysis to track molar drift
When Anchorage Fails
Despite best intentions, anchorage loss can occur and derail your treatment plan:
- Posterior teeth shift forward while space seems to close
- Midline shifts develop unexpectedly
- Incisors fail to reach planned position
What to do:
- Reinforce with skeletal anchorage mid-treatment
- Re-open space with open coil and reattempt retraction
- Evaluate for compliance or biomechanical flaws
Final Thoughts
In retraction mechanics, anchorage is not a suggestion—it’s a necessity. Without proper anchorage systems, even the best force systems fail.
Take time to plan your anchorage before you begin space closure. Know your patient’s needs, your biomechanical options, and your backup plans.
“He who controls the anchor, controls the case.”
Next Episode: Reinforcing Anchorage: Tools, Techniques, and Mini-screw Mastery
