Maximum tensile resistance of
non-adjusted and adjusted expansion
screws in the locking part of unassisted
mandibular advancement splint 
- Uthai Uma, D.D.S., Dip. Thai Board of Oral Diagnostic Sciences (Occlusion and Orofacial Pain)
- Supranee Vichiennet, D.D.S., Dip. Thai Board of Oral Diagnostic Sciences (Occlusion)
- Phanomporn Vanichanon, D.D.S., M.S. (Restorative Dentistry-Occlusion), M.Sc. (Health Development), Dip. Thai Board of Occlusion and Orofacial Pain*
Abstract :
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.
(CU Dent J. 2018;41:23-32)
Keywords :
expansion screw; mandibular advancement; maximum tensile resistance; UMA splint