Fibre Bragg Grating Sensors For Sutural Expansion Assessment In Rapid Palatal Expanders: An Ex-Vivo Validation

This study presents the development and validation of a fibre Bragg gratings (FBGs)-based sensor system for the assessment of strain in the midpalatal suture in subjects using rapid palatal expanders (RPEs). The ex-vivo experiments were made by means of positioning two RPEs in a porcine palatal region. The RPEs used were the Hyrax, a tooth-borne expander and MARPE (microimplant-assisted rapid palatal expansion), a bone-borne expander. In order to define the regions in the palatal region for the sensors positioning, a finite-element analysis was performed in a porcine head subjected to the loadings caused by an RPE. In addition, a strain transfer model was used to obtain a correction coefficient that approximates the strain estimated by the FBG to the actual strain in the structure under shear and normal stress. Results show high linearity in the sensors characterisation tests with the advantages of compactness, intrinsic safe operation and multiplexing capabilities of FBGs. In the RPE analysis, a higher strain was estimated in the anterior region, which is in accordance with the simulation and previously reported results, where MARPE showed a higher strain (with an exponential pattern) than Hyrax as the number of activations increase.