Comparative Experimental Evaluation of Orthodontic Appliances for Maxillary Arch Expansion

Abstract

Background/Objectives: The orthodontic treatment of posterior crossbite using appliances for gradual maxillary expansion is crucial to ensure proper transversal jaw relationships as much as occlusal functionality. The aim of this study was to analyze forces and torques generated by different appliances for maxillary expansion. Methods: Measurements were conducted for the Wilson^® 3D^® Quadhelix (WQH) and Wilson^® 3D^® Multi-Action Palatal Appliance (WPA) across various sizes and compared to the Remanium^® Quadhelix (RQH). Activations were set to 8 mm for the WQH and RQH and 6 and 8 mm for the WPA. Rotations and root torque were simulated via an activation of 10° for arches. A total of eight test series were conducted. Results: The WPA displayed the highest force and torque values for all movements, far surpassing recommended guideline values (expansion 8.5->15.0 N/46.3-86.5 Nmm, rotation 3.1-6.1 N/40.7-61.4 Nmm, torque 3.9-5.1 N/22.4-29.7 Nmm), and the WQH displayed the lowest values (expansion 2.7-12.6 N/11.1-39.6 Nmm, rotation 0.1-1.7 N/23.0-32.2 Nmm, torque 0.9-2.9 N/3.4-10.5 Nmm). Appliances with the smallest transverse dimensions exhibited the highest force and torque maxima. Conclusions: This study underscores the importance of understanding biomechanical principles in orthodontics for minimizing unintended tooth movements, providing detailed insights into the force systems of appliances acting in the transverse plane, and establishing a foundation for future clinical investigations to validate these in vitro findings.

Keywords: arch expansion; orthodontic forces; posterior crossbite; quadhelix; torque.

Figure 1

The three appliances investigated for the resulting forces and torques induced by experimental expansion, rotation, and root torque. Wilson^® 3D^® Quadhelix (left, (A)), Wilson^® 3D^® Multi-Action Palatal Appliance (middle, (B)), Remanium^® Quadhelix (right, (C)). A Rocky Mountain Orthodontics^® (RMO) lock, pre-welded for vertical insertion, used for the molar bands of the Wilson^® 3D^® appliances (left, (D)). An Orthorama^® (Dentaurum) lock bonded directly to the Frasaco teeth for the horizontal insertion of the Remanium^® Quadhelix (right, (E)).

Figure 2

The forces measured in Newtons (N) (A) and torques measured in Newton-millimeters (Nmm) (B) exerted by the Wilson^® 3D^® Multi-Action Palatal Appliance (WPA) during expansion activation recorded by the OMSS are presented in columns corresponding to each appliance size, ranging from 32 mm to 56 mm. Forces exceeding 15 N, which surpassed the measurement capacity of the OMSS’s sensors, are highlighted in red. Exemplified force and torque components during an expansion movement with a WPA size of 32 mm (C). A total of n = 5 specimens per appliance variant and size were analyzed.

Figure 2

The forces measured in Newtons (N) (A) and torques measured in Newton-millimeters (Nmm) (B) exerted by the Wilson^® 3D^® Multi-Action Palatal Appliance (WPA) during expansion activation recorded by the OMSS are presented in columns corresponding to each appliance size, ranging from 32 mm to 56 mm. Forces exceeding 15 N, which surpassed the measurement capacity of the OMSS’s sensors, are highlighted in red. Exemplified force and torque components during an expansion movement with a WPA size of 32 mm (C). A total of n = 5 specimens per appliance variant and size were analyzed.

Figure 3

Forces measured in Newtons (N) (A) and torques measured in Newton-millimeters (Nmm) (B) exerted by the Wilson^® 3D^® Quadhelix (WQH) across sizes ranging from 25 to 40 mm and for the Remanium^® Quadhelix (RQH) across sizes ranging from 36 to 40 mm. A total of n = 5 specimens per appliance variant and size were analyzed.

Figure 3

Forces measured in Newtons (N) (A) and torques measured in Newton-millimeters (Nmm) (B) exerted by the Wilson^® 3D^® Quadhelix (WQH) across sizes ranging from 25 to 40 mm and for the Remanium^® Quadhelix (RQH) across sizes ranging from 36 to 40 mm. A total of n = 5 specimens per appliance variant and size were analyzed.