Comparative evaluation of the forces produced by tongue on circummaxillary sutures in skeletal Class III malocclusion with maxillary hypoplasia using tongue crib with that of facemask therapy - A FEM study

Abstract

Background: Class III malocclusion has the lowest incidence when compared to other malocclusions. Class III malocclusion can be present in retrognathic maxilla, prognathic mandible or a combination. Various modalities have been used in treatment. Facemask with expansion is an effective appliance used for protraction in case of retrognathic mandible; although it is effective, dentists have to deal with patient compliance. Efforts have been directed to simplify the design of appliance to redirect growth. The finite element method can be used to simulate conditions to check various hypothesis. Methods: A finite element method (FEM) study was performed in two important steps: generation of model and model analysis. A tongue force of 4-6 pounds was applied to cribs (Group I) based on the frequency of swallowing per day (minimum to maximum). In facemask therapy (Group II), a downward force at 30 degrees along with transverse expansion of 1N was applied. Mean values of both sides were considered. Results: Von-Mises stresses in Group I and Group II showed a non-significant difference (p=0.535). Displacement in Group I and Group II showed a significant difference (p=0.0001). Maximum amount of displacement was seen in maxillary dentition on canines and incisors, and minimum stress was seen on posterior teeth in both interventional therapies, even though the Von-Mises stresses generated were different in both groups. Overall displacement in both Group I and Group II was similar. Conclusions: Both modalities were effective in the treatment of Class III malocclusion. The force transmission varied and overall displacement was similar in both modalities, which implies both modalities are effective in treating Class III malocclusion.