Three-Dimensional Force Measurements During Rapid Palatal Expansion in Sus scrofa

Abstract

Rapid palatal expansion is an orthodontic procedure widely used to correct the maxillary arch. However, its outcome is significantly influenced by factors that show a high degree of variability amongst patients. The traditional treatment methodology is based on an intuitive and heuristic treatment approach because the forces applied in the three dimensions are indeterminate. To enable optimal and individualized treatment, it is essential to measure the three-dimensional (3D) forces and displacements created by the expander. This paper proposes a method for performing these 3D measurements using a single embedded strain sensor, combining experimental measurements of strain in the palatal expander with 3D finite element analysis (FEA). The method is demonstrated using the maxillary jaw from a freshly euthanized pig (Sus scrofa) and a hyrax-design rapid palatal expander (RPE) appliance with integrated strain gage. The strain gage measurements are recorded using a computer interface, following which the expansion forces and extent of expansion are estimated by FEA. A total activation of 2.0 mm results in peak total force of about 100 N—almost entirely along the direction of expansion. The results also indicate that more than 85% of the input activation is immediately transferred to the palate and/or teeth. These studies demonstrate a method for assessing and individualizing expansion magnitudes and forces during orthopedic expansion of the maxilla. This provides the basis for further development of smart orthodontic appliances that provide real-time readouts of forces and movements, which will allow personalized, optimal treatment.

Sutural loading in bone‐ versus dental‐borne rapid palatal expansion: An ex vivo study

“…The differences between the 2 groups can be attributed to the differences in anchorage and the point of force application. In the DRPE, expansion force is applied through the teeth, and some of the expansion force will be dissipated by the PDL and through dental tipping 5‐9,16 . This explains the excessive strains recorded at the alveolar bone and the delayed MPS opening in the DRPE.…”

“…In the DRPE, expansion force is applied through the teeth, and some of the expansion force will be dissipated by the PDL and through dental tipping. [5][6][7][8][9]16 This explains the excessive strains recorded at the alveolar bone and the delayed MPS opening in the DRPE. Additionally, the attachment points of the expander and the anchor teeth are vertically and laterally farther from the MPS, which will potentially result in less efficient mechanical loading of the suture.…”

“…This separates the midpalatal suture (MPS) resulting in bone formation along the sutural edges 3,4 . The expansion force associated with expansion is relatively high (~100N), 5 which when delivered to the teeth rather than the bone itself, results in undesired side effects, including tipping of the anchor teeth and alveolar bone, possible dehiscence, and long‐term instability 5‐9 …”

“…side effects, including tipping of the anchor teeth and alveolar bone, possible dehiscence, and long-term instability. [5][6][7][8][9] Maxillary expansion is dependent on the maturation status of the intermaxillary suture. 10 As patient age, the suture increases in complexity and eventually fuses.…”

Moving towards precision orthodontics: An evolving paradigm shift in the planning and delivery of customized orthodontic therapy

“…To allow optimal and individualized treatment, it is essential to measure the 3D forces delivered by the expander. By combining experimental measurements of strain in the palatal expander with 3D finite element analysis, 3D forces have recently been measured . Such an approach may be used to monitor how the magnitude and direction of forces are disseminated to teeth and bones in either tooth or bone‐anchored expanders, and the information utilized for optimized activation of the device.…”