Mechanical Reaction of Facial Skeleton to Rapid Palatal Expansion Devices using Laser Holography: An in vitro Study

Introduction: Rapid palatal expansion of the midpalatal suture is an effective method for the correction of transverse malocclusions. This study was conducted to compare the reaction of circum-maxillary sutures and center of resistance of molar to the Hyrax appliance with different degrees of activations and the Spring jet appliance using laser holography on a freshly macerated skull. Materials and methods: A freshly macerated skull with well-aligned teeth and intact dental arches was used as the experimental model. The Hyrax appliance and Spring jet appliances were fabricated and analyzed qualitatively and quantitatively by using double exposure hologram. Hyrax was activated two 1⁄4 turns, four 1⁄4 turns and eight 1⁄4 turns. The Spring jet is activated and double exposure hologram was recorded. Results: Results were obtained qualitatively by observing the fringes, and quantitatively by counting the number of fringes. The Spring jet showed fringes only in the first molar area, whereas the Hyrax showed fringes along the circum-maxillary sutures and the first molar area; and the number of fringes increased with the number of turns. Conclusion: Hyrax appliance activation produced mechanical reactions on the teeth, alveolar bone, maxilla and the circum-maxillary bones and sutures. The displacement and fringes increased progressively with two, four and eight turns activation of hyrax. The pattern of the fringes was more circular around the nasomaxillary complex and zygomaticomaxillary sutures, suggesting rotational displacement of the maxilla. The number and pattern of fringes produced by the Spring jet appliances suggest that it produces only dentoalveolar changes and minimal orthopedic affects.