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Updated: May 15, 2026
Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition
Published on: February 23, 2024
Biomechanical analysis of implant anchorage versus class II elastics in maxillary anterior retraction with clear
Haoxian He1, Xinming Yang1, Shujuan Lu1
1Department of Orthodontics, Shenzhen Stomatology Hospital, Shenzhen, P.R. China.
Background:
Clear aligners are widely used for their esthetic advantages, yet anchorage control in extraction cases remains challenging, often leading to the "roller-coaster effect"-characterized by anterior tipping, extrusion, and posterior mesial drift. Evidence comparing anchorage strategies to mitigate this effect is limited. This study used iterative finite element analysis to evaluate two anchorage modalities during maxillary anterior retraction with clear aligners.
Methods:
Three-dimensional models of maxillary teeth, periodontal ligaments, alveolar bone, and aligners were constructed from cone-beam CT data. An improved displacement-driven iterative simulation (10 iterations, 2 mm total retraction post-first premolar extraction) compared three conditions: control (M1), implant anchorage (M2), and Class II elastics (M3). Tooth displacement, inclination, occlusal plane rotation, and periodontal ligament stress were analyzed.
Results:
Both implant anchorage and Class II elastics effectively reduced posterior mesial movement, yet vertical control differed markedly between them. Implant anchorage minimized anterior extrusion and produced canine intrusion, whereas Class II elastics aggravated the roller-coaster effect through greater anterior extrusion and more pronounced lingual tipping. It also limited clockwise rotation of the anterior occlusal plane most effectively, while the control group exhibited the largest counterclockwise rotation of the posterior occlusal plane. Periodontal ligament stress distribution in the anterior region further highlighted these differences: it showed higher tensile stress peaks with Class II elastics but greater compressive stress at the palatal mid-root areas with implant anchorage.
Conclusions:
Implant anchorage is biomechanically preferable for hyperdivergent or deep-bite patients requiring strong vertical control. Class II elastics necessitate overcorrection to offset adverse effects. The iterative approach effectively reveals long-term biomechanical trends and supports personalized treatment planning, pending clinical validation.
