In orthodontic treatments with aligners, one of the biggest challenges is distalizing lower molars (such as the 47) without relying on temporary anchorage devices (TADs). While TADs provide stable and predictable anchorage, it is possible to avoid their use by implementing advanced biomechanical strategies. Here, we analyze this topic based on a clinical simulation.
The Clinical Situation: Distalization of the 47
In the presented simulation, a distal force of 3.5 N is applied to a vertical attachment placed on the 47, while the effects on neighboring teeth, such as the 46, are observed. Although the primary goal is to move the 47 distally, the reaction force may cause side effects, such as a slight mesialization of the 46.
Is It Possible to Avoid a TAD?
Yes, but it depends on optimizing forces and the treatment plan design. Below, we describe how these cases can be managed:
1. Strategic Use of Elastics
Intra-arch elastics:
Place a cut in the aligner of the 44 and use an elastic connected between the 44 and the 17. This helps distribute forces toward the anterior arch and reduces the reaction force transmitted to the 46.
The force applied by the elastic should be moderate (2-4 oz, equivalent to 56-113 g). This provides additional anchorage and helps stabilize the lower arch during distalization.
2. Optimized Aligner Design
Beveled attachments:
Place beveled attachments oriented distally from the 43 until the 47.These help direct forces efficiently, maximizing distal movement while minimizing side effects such as tipping.
Aligner material:
Use aligners with greater stiffness (e.g., 0.75 mm thickness or materials such as PET-G) to ensure better biomechanical control.
3. Control Movement in Small Stages
Distalization of 3-4 mm should be divided into small increments of 0.20-0.30 mm per stage. This allows for controlled bone remodeling and minimizes the risk of secondary movements.
4. Constant Review of Anchorage
The success of distalization without a TAD depends on good natural anchorage provided by the anterior teeth. If you notice:
Significant mesialization of the 46: Consider reinforcing the anchorage design (e.g., using tighter elastics).
Instability of the 43 or 44: In such cases, the use of a TAD may be necessary to avoid loss of control.
Conclusion
Distalization of 4mm lower molars (such as the 47) without a TAD is possible if advanced biomechanical strategies are employed, including:
Strategically placed elastics.
Optimized stiffness aligners with specific cuts and attachments.
Controlled movement in small stages.
This approach is ideal for moderate cases, but for larger distalizations 4 mm or when natural anchorage is weak, the use of a TAD remains the most predictable option.
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