Chulalongkorn University Dental Journal

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Objective: To test the vertical and horizontal tensile forces of the locking part of a novel Unassisted Mandibular Advancement (UMA) Splint. Materials and methods: Twenty samples, each comprising a lower piece and an upper piece with an expansion screw, were prepared. The samples were divided into 4 groups (n=5): 1) non-expanded screw group for vertical force test (NEVT), 2) 5-mm-expanded screw group for vertical force test (5EVT), 3) non-expanded screw group for horizontal force test (NEHT), and 4) 5-mm-expanded screw group for horizontal force test (5EHT). NEVT and 5EVT groups received a vertical tensile force whereas NEHT and 5EHT groups received a horizontal tensile force. The pulling forces were continuously applied until the sample fractured or disconnected. The mode of failure for each sample was also evaluated. Results: The mean maximum tensile force of NEVT group was 267.31 ± 13.26 N and 262.70 ± 11.68 N for 5EVT group. The mean maximum tensile force of NEHT group was 476.11 ± 100.08 N and 449.17 ± 95.87 N for 5EHT group. There was no significant difference between the mean maximum tensile forces of NEVT and 5EVT (p=0.576) as well as those of NEHT and 5EHT (p=0.675) analyzed by independent t-test. There were 3 modes of failure including upper piece distortion, upper piece fracture, and lower piece fracture. Conclusion: The maximum tensile forces of the locking part in the UMA splint were not significantly affected by screw expansion. The maximum tensile forces were higher than that of the clinical maximum mouth opening force and mandibular retrusive force.



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