Maxillary molar distalization with clear aligners and infrazygomatic anchorage – promising biomechanics, modest results
Published on: Nov 1, 2025
Can we finally improve distalization with aligners?
Shen C, Zhou S, Wang Q, Bowman SJ, Chung CH, Li C. AJODO 2025; DOI:10.1016/j.ajodo.2025.09.011 provides one of the most detailed CBCT-based evaluations to date of maxillary molar distalization using clear aligner therapy (CAT) supported by infrazygomatic temporary skeletal anchorage devices (TSADs).
The rationale is familiar: sequential molar distalization with aligners alone typically results in limited movement and significant distal tipping. Adding skeletal anchorage might, in theory, enhance bodily movement and reduce unwanted effects. This retrospective analysis aimed to quantify both the amount and efficacy of such movements and to see whether CBCT data confirm the expectations from digital treatment planning.
Study Participants
Twenty-one adult patients (38 sides) treated with Invisalign and infrazygomatic TSADs were included, each with ≥1 mm of programmed first molar distalization. Pretreatment and post-retraction CBCTs and intraoral scans were compared with ClinCheck prescriptions.
Results
The median achieved molar distalization was modest: 0.8–1.05 mm at the first molar and 0.95–1.25 mm at the second molar. These values were only about one third of the prescribed movements (median 3.05 mm). Efficacy dropped further as the programmed distalization increased, suggesting a nonlinear response beyond roughly 2–3 mm of intended distal shift.
Despite the limited amount of movement, the quality of tooth movement was favorable. CBCT revealed minimal distal tipping and mesial-out rotation, indicating more controlled, bodily translation compared with aligners alone. Intrusion of 1–1.6 mm was consistently observed—an expected side effect of the infrazygomatic vector, which exerts a downward and backward force on the molars. This vertical control could be advantageous in high-angle or Class II cases. On the other hand, significant buccal expansion and crown torque were noted, implying inadequate transverse control despite the use of rectangular attachments.
Clinical Implications
Clinically, these data confirm that adding TSADs can improve the type of molar movement, but not necessarily the amount. The practical benefit seems to lie in enhanced bodily control and intrusion, not in generating more distalization. The study also documents the poor predictability of aligner planning for posterior movement—median efficacy near 30%—a sobering statistic for digital treatment promises.
Methodological Considerations
From a methodological standpoint, the study is careful and technically impressive. The use of both CBCT and intraoral superimpositions adds robustness, though inherent biases remain. The retrospective design limits control for compliance and clinician variation, and sample heterogeneity (1–5.6 mm planned movement) complicates interpretation. The authors rightly point out that further randomized trials are needed, particularly with standardized distalization ranges and defined clinical equivalence margins.
Takeaway for Clinicians
For clinicians, the takeaway is pragmatic: infrazygomatic TSADs in combination with clear aligners can improve root control and vertical stability of distalizing molars, but one should not expect large distal shifts. Overreliance on the digital prescription without mechanical anchorage control remains risky. The approach is elegant biomechanically, but biologically constrained.
Reference
Shen C, Zhou S, Wang Q, Bowman SJ, Chung CH, Li C. Maxillary molar distalization with clear aligner therapy and infrazygomatic temporary skeletal anchorage devices. Am J Orthod Dentofacial Orthop. 2025; DOI:10.1016/j.ajodo.2025.09.011.