Biomedical subjects

Kwangchul Choy

Publications and source records attributed to Kwangchul Choy.

2 recordsLinked to original sources

PubMed2006

Initial changes of centres of rotation of the anterior segment in response to horizontal forces.

This study investigated the changes in the initial centres of rotation (Crot) of the upper six anterior teeth in response to a horizontal load. Six upper anterior teeth were extracted, splinted as a unit, and embedded in dental stone after the roots were uniformly coated with silicone. An aluminium fixture was bonded to the anterior segment and three linear variable differential transformers (LVDTs) were attached to measure the microdisplacement of the segment. A pulley and dead weight assembly were used to apply a 200 g occluso-gingivally varying horizontal force to the segment. The changes in the Crot for the anterior segment to the horizontal load were recorded. The results showed that the centre of resistance (Cres) of the upper anterior segment was located 14.5 mm apical and 9.5 mm distal from the incisal edge of the central incisors. A linear functional axis (a trace of the measured Crot) was recorded. The functional axis maintained an angle of 14.5 degrees to the vertical axis of the anterior segment passing through the Cres of the segment. The Crot constant, which determines the tipping sensitivity of the segment, was 23 mm(2). The results demonstrate that the upper anterior segment may be slightly intruded when a horizontal force is applied and is less prone to tipping than a single tooth.

Humans↗

PubMed2002

Controlled space closure with a statically determinate retraction system.

We designed a variant of a cantilever spring, the statically determinate retraction system, and studied its mechanical characteristics. This novel system consisted of a single-force cantilever arm made of 0.017 x 0.025-inch titanium molybdenum alloy wire for active retraction and a passive rigid stabilizing unit. Since the active component for space closure is a cantilever, it is simple to measure the force system of the spring with a force gauge (ie, the system is a statically determinate system). A torque tester apparatus was used to examine the property of this retraction spring with a helix at the posterior and a simple bend at the anterior. Both a standard shape and modified shapes of the spring were studied. At full activation, the standard spring delivered 163 g with a load-deflection rate of six g/mm. When the magnitude of the anterior bend of the spring was increased, the horizontal component of the force increased more than the vertical component. In contrast, when the posterior bend of the spring increased, the vertical component of the force increased more than the horizontal component. A clinical case presented here clearly demonstrates the versatility and applicability of the spring.

Adult↗