PubMed Health⌕ Search

Biomedical subjects

Jung-Yul Cha

Publications and source records attributed to Jung-Yul Cha.

4 recordsLinked to original sources
PubMed2007

Friction of conventional and silica-insert ceramic brackets in various bracket-wire combinations.

OBJECTIVE: To compare the level of friction resistance (FR) of conventional and silica-insert ceramic brackets using various bracket-wire combinations and angulations. MATERIALS AND METHODS: Four types of ceramic brackets were examined: (1) polycrystalline alumina bracket (PCA-C), (2) polycrystalline alumina bracket with a stainless steel (SS) slot (PCA-M), (3) polycrystalline alumina bracket with a silica layer (PCA-S), and (4) monocrystalline sapphire bracket (MCS). A conventional SS bracket was used as the control. The static and kinetic FR in four bracket-wire angulations (0 degrees, 5 degrees, 10 degrees, and 15 degrees) was examined using SS and beta-titanium (beta-Ti) orthodontic wires, 0.019 x 0.025 inches in size, under elastic ligature in the dry state. RESULTS: The FR generated by the PCA-S bracket was significantly lower than that generated with the other ceramic brackets, and was similar to that of the SS bracket. The PCA-S bracket showed the lowest FR with both the SS and the beta-Ti wires at zero bracket angulation. The FR to sliding increased rapidly and nonlinearly when the bracket wire angulation was >5 degrees. The PCS-S bracket showed the lowest FR from 5 degrees to 15 degrees of angulation. The MCS bracket demonstrated the highest increase in FR from 0 degrees to 15 degrees of angulation, showing the highest FR at 15 degrees of angulation. CONCLUSION: PCA-S showed minimal FR among the ceramic brackets, and was comparable to the conventional SS bracket. The silica layer and rounded edges of the ceramic slot lowered FR considerably.

Aluminum Oxide↗
PubMed2004

Orthodontic treatment with growth hormone therapy in a girl of short stature.

The purpose of this article is to review the characteristics of craniofacial morphology in children of short stature and the effects of human growth hormone (HGH) therapy on the craniofacial complex. Changes in body height, facial growth, and dental maturity of a 9-year-old girl who received HGH therapy during orthodontic treatment were observed. Orthodontists need to understand the skeletal characteristics of the craniofacial complex of short-stature patients before beginning orthodontic treatment and consider how the differences between chronologic and skeletal ages affect the timing and method of orthodontic treatment. If short-stature children are undergoing HGH therapy, its cranioskeletal effect should be considered; if possible, it is better to delay orthodontic treatment until HGH is finished. However, if orthodontic treatment is performed, the following should be considered: (1) HGH therapy affects the growth of the mandible more than the growth of the maxilla, (2) the amount and pattern of growth during HGH administration are unpredictable, and (3) HGH therapy rarely affects dental maturity.

Adolescent↗
PubMed2003

Mechanical and biological comparison of latex and silicone rubber bands.

Latex rubber bands are routinely used to supply orthodontic force. However, because the incidence of allergic reactions to latex is rising, the use of nonlatex alternatives is increasing, and assessing the mechanical properties of the replacement products is becoming more important. The purposes of this study were to compare the mechanical properties of latex and silicone orthodontic rubber bands through static testing under dry and wet conditions, and to compare their biologic (cytotoxic) properties. Three brands of latex and 1 brand of silicone rubber bands were tested. When extended to 300% of the lumen diameter, the silicone group had an initial force equal to 83% of the product specifications; this was the lowest of the 4 groups. All 4 brands showed notable amounts of force degradation at the 300% extension when subjected to saliva immersion; this approximated a 30% force decay over 2 days. The latex bands all followed a similar pattern of force degradation, whereas the silicone bands showed a greater increase in force decay as the extension length increased. The silicone bands were less cytotoxic than 2 of the 3 types of latex. Although the silicone bands showed the least discrepancy of force degradation between air and saliva conditions, the amount of the force decay was the greatest. Therefore, great improvements in the physical properties of the silicone band are required before they can be considered an acceptable replacement for latex.

Analysis of Variance↗