• The korean journal of orthodontics
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• v.33 no.5 s.100
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• pp.359-370
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• 2003

The purpose of this study was to evaluate the bond strength of orthodontic brackets bonded to metal bar with chemically cured adhesive (Ortho-one, Bisco Co, USA) in various types and directions of force application. Three types of metal bracket with different bracket base configurations; Micro-Loc base(Tomy Co, Japan), Chessboard base(Daesung Co, Korea), Non-etched Foil-Mesh base(Dentaurum, Germany); were used in this study. Peel, shear, tensile bond strengths were measured by universal testing machine and compared each other. The peel force directions applied were $0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;60^{\circ},\;75^{\circ},\;90^{\circ}$ And then, in consideration of the different surface area of the bracket bases, the bond strength Per unit area were calculated and compared. The results obtained were summarized as follows: 1. The bond strengths according to the types and the directions of the forces were greatest at the shear forces in all three bracket base configuration groups(p<0.01). 2. As the peel force direction grew higher in degree, peel bond strength decreased. The Patterns of peel bond strength change according to force direction was similar in all three bracket base configurations. The minimum bond strength was 60 degree-peel bond strengths in all three bracket base configurations. 3. In Micro-Loc base group, minimum peel bond strength$(_{60}PBS)$ was in $29\%$ level of shear bond strength and $52\%$ level of tensile bond strength. In Chessboard base group, $_{60}PBS$ was in $34\%$ level of shear bond strength and $61\%$ level of tensile bond strength. In Non-etched Foil-Mesh base group, $_{60}PBS$ was in $34\%$ level of shear bond strength and $55\%$ level of tensile bond strength. 4. The bond strengths per unit area were lowest in Non-etched Foil-Mesh base group and highest in Chessboard base group(p<0.05). However, there were no differences in shear bond strength, tensile bond strength, $75^{\circ}\;and\;90^{\circ}$ per unit area between Micro-Loc and Chessboard base groups.

• The korean journal of orthodontics
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• v.33 no.6 s.101
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• pp.437-451
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• 2003

The purpose of this study was to measure maximum bite force and to investigate its relationship with anteroposterior, vertical, and transverse facial skeletal measurements. From among the dental students at the College of Dentistry, forty subjects (26 male and 14 female) were selected. With two sets of strain gauge, maximum bite force at the right and left first molars and anterior teeth was measured in the morning and afternoon. After taking lateral and posteroanterior cephalograms, fifty and nineteen variables were evaluated, respectively Paired t-tests and an independent t-test were done and correlation coefficients were obtained. 1. The maximum bite force at the first molars was $68.0\pm13.9kg$. in males and $55.6\pm10.5kg$ in females (p<0.05) while the force at the anterior teeth was $8.4\pm4.9kg\;and\;1.1\pm3.4kg$ respectively (p<0.05). 2. Some tendency for a greater value of maximum bite force at the preferred side was observed but not statistically significant (p>0.05). 3. Significant difference was observed between the strong bite force group and the weak bite force group in some cephalometric and other measurements (p<0.05). N-S-Ar, S-Ar-Go, FH-Hl, IMPA and MMO showed a significant difference in posterior maximum bite force (P). N-S-Ar and FH-H1 also showed a significant difference in anterior maximum bite force (A). 4. Several cephalometric variables showed some correlation with maximum bite force (p<0.05). N-S-Ar, S-Ar-Go, UGA, FH-H6, FH-H1, body weight and MMO were significantly correlated with posterior maximum bite force (P). Go-Me, P-1 and IMPA were significantly correlated with anterior maximum bite force (A).

• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.303-312
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• 2004

An unfavorable tipping movement can occur during the retraction of anterior teeth because orthodontic force is loaded by brackets positioned far from the center of resistance. To avoid this unfavorable movement, a compensating curved wire or lingual root torque wire is used. The purpose of this study is to investigate, using photoelastic material, the distribution of initial stress associated with the retraction of the incisors according to the degree of the compensating curve, to model changes associated with tooth ud alveolar bone structure. The following results were obtained by analysis of the polarizing plate of the effects of initial stress resulting from retraction of the anterior teeth: 1. When the incisors were retracted using combination archwire or sliding mechanics, the maximal polarizing pattern of the apical area decreased as the degree of the compensating owe increased from 0 to 15 to 30. 2. When the incisors were retracted by the combination archwire or sliding mechanics, the maximal polarizing pattern of the canine and premolar area increased as the degree of the compensating curve increased from 0to 15to 30. 3. A lower degree of polarizing patterns were associated with the combination archwire technique than the sliding mechanics technique at a given force. The above results indicate that there is no significant difference between the combination loop archwire technique and sliding mechanics, for the retraction of maxillary anterior teeth with decreased lingual tipping tendency by a compensating curve on the arch wire. However, the use of sliding mechanics is more effective for the prevention of lingual inclination of the anterior teeth, because the hook used in sliding mechanics is closer to the center of resistance of the maxillary anterior teeth.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.230-236
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• 2020

In this study, an adhesive tape with water and impact resistance for mobile devices was developed using a UV-curable urethane acrylate based polymer as a substrate. The substrate fabricated by UV-curable materials shows hydrophobicity and poor wettability, which significantly deteriorates the interface-adhesions between the substrate and acrylic adhesive. In order to improve the interface adhesion, 3-glycidoxy-propyl trimethoxysilane (GPTMS), a silane coupling agent having epoxy functional groups, was selected and incorporated into UV-curable urethane acrylate based polymer resins in various contents. The changes of the chemical composition according to the contents of GPTMS was studied with Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) to know the surface bonding properties. Also mechanical properties of the substrate were characterized by tensile strength, gel fraction and water contact angle measurements. The peel strengths at 180° and 90° were measured to compare the adhesion between the substrate and adhesive according to the silane coupling agent contents. The mechanical strength of the urethane acrylate adhesive tape decreased as the silane coupling agent increased, but the adhesion between the substrate and adhesives increased remarkably at an appropriate content of 0.5~1 wt%.