A photoelastic study of the effect of loops in arch wire and orthodontic elastics in relief of Curve of Spee / 대한치과교정학회지

Multiloop Edgewise Archwire(MEAW) is effective in relief the Curve of Spee in mandibular arch but up & down orthodontic elastics must be used with it. The purpose of this study was to analyse the effect of orthodontic elastics, like as up & down elastics, Class II elastics, and Class III elastics, and the effect of L loop in Multioop Edgewise Archwire. 1. Intrusive force of MEAW in anterior teeth was reduced and uprighting force in premolars was increased by up & down elastics. 2. Uprighting force was significantly increased with Class III elastics in multiple L loop arch wire. 3. The force of Class II elastics made molars tip mesially and Curve of Spee deep.

Cephalometric analysis of postsurgical behavior of mandibular prognathism

No abstract available.

The effects of heat treatment on the mechanical properties of the elgiloy wire / 대한치과교정학회지

Heat treatment which removes internal stress enhances the mechanical properties of the orthodontic arch wire. The main purpose of this experiment was to investigate the effects of the heat treatment on the mechanical properties of the Elgiloy wire. The Elgiloy wire, 0.016" X 0.022" and 0.018" X 0.025", were heat treated in an electric oven for 5, 10 and 15 minutes at selected temperatures between 300 and 900degreesC. Tensile strength and load deflection rate were measured to reveal the changes of mechanical property at various con?ditions, and each specimen was observed under metallurgic microscope. Also to trace the precipitation material due to overheat treatment, a qualitative analysis was carried out with EDS system. It was found that heat treatment at a low temperature caused an increase in the tensile strength and bending resistance, and a maintenance in the fibrous in the tensile strength and bending resistance, and a maintenance in the fibrous structure of both sizes of wire. The changes observed in properties and appearance were probably due to the relief of internal stresses incurred in the metal during cold working. In both sizes of wire the tensile strength and the bending resistance continued to decrease at high temperature, and the fibrous structure continued to disappear then was not observed at 900degreesC. The carbide precipitation founded in grain boundary at 750degreesC probably was other elements carbide (Ni, Co) except Cr. The grain growth was observed at 1100degreesC. Optimum heat treatment for the 0.016" X 0.022" Elgiloy wire was 10 minutes at 500degreesC, and for the 0.018" X 0.025" Elgiloy wire it was 5 to 15 minutes at 500degreesC.

The effects of heat treatment on mechanical properties and metal release from heat-treated orthodontic archwires / 대한치과교정학회지

The purpose of this study was to evaluate the effects of heat treatment on mechanical properties in 0.016" x 0.022" blue Elgiloy wires and to measure the amounts of nickel and chromium released from the wires in artificial saliva. Ultimate tensile strength, yield strength and elongation were measured with universal testing machine (Instron). and the amounts of nickel and chromium released from the sample were measured with atomic absorption spectrophotometer after one week immersion in the artificial saliva. Ultimate tensile strength and yield strength were progressively increased below 1000degreesF, but elongation was decreased. And the results were reversed above 1100degreesF. After heat treatment of the sample for 9 minutes at 1000degreesF, the maximum tensile strength and yield strength were 213.6kg/mm2, 140.1kg/mm2, respectively. Both tensile strength and yield strength were decreased progressively above 1100degreesF. Elongation was appeared the minimum value (8.6%) after heat treatment for 9 minutes and 12 minutes at 1000degreesF. There was a pronounced increase in nickel and chromium liberation with increasing time and temperature. The maximum amounts of nickel and chromium released form the sample were 4.947microgram/cm2, 3.088microgram/cm2, respectively after heat treatment for 12 minutes at 1300degreesF. Heat treatment is applied to orthodontic wires, especially cobalt-chromium alloys, for the purpose of stress-relievning and hardening. When the heat-treatment of orthodontic wires, the heating procedure should be well controlled in order to have no effect on corrosion resistance and mechanical properties.

A photoelastic study of the stress distribution by multiloop edgewise arch wire / 대한치과교정학회지

The purpose of this study was to investigate the force mechanism of Multiloop Edgewise Arch Wire and the intensity and distribution of stresses with vertical and intermaxillary elastics. The obtained results were as follows. 1. When plain wires were inserted and vertical and intermaxillary elastics were used in the upper and lower arch, the stresses of the anterior and posterior ends of wires were observed greatly but the stresses of the premolar were very small. 2. When MEAW were inserted in upper and lower arch, the upper 1st and 2nd premolar and the lower 1st premolar were extruded greatly. 3. In the area of the upper 1st molar and the lower 2nd premolar and the lower 1st molar, any stresses were not observed. 4. The vertical elastic counteracted the intrusion force of the MEAW in the anterior teeth but could not affect on posterior teeth. Using with the Class II elastics, the distal tipping force and extrusion force were exerted in the upper anterior teeth and the intrusion forces of the lower anterior teeth were relieved. Using with the Class III elastics, the extrusion force were exerted in the upper and lower anterior teeth, the distal tipping force were increased in the lower posterior teeth. 5. The Class II elastic counteracted the anterior intrusion force of the MEAW and extruded and tipped mesially the lower 2nd molar. The intrusion force of the MEAW also could not overcome the extrusion force of the class II elastics. 6. When the Class III elastics were engaged, the upper 2nd molar was extruded in spite of the intrusion forces of the MEAW and the extrusion forces of the lower anterior teeth and distal tipping forces in the posterior teeth were observed.

A cephalometric study on the position of the hyoid bone in cleft lip and palate individuals / 대한치과교정학회지

This comparative study was undertaken to investigate the position of the hyoid bone in unilateral cleft lip and palate individuals. The materials for this study consisted of 35 subjects with surgically repaired unilateral cleft lip and palate (25 males, 10 females) and 40 subjects with normal facial morphology (20 males, 20 females). Cephalometric measurements of unilateral cleft and palate individuals were compared with those of non-cleft individuals. The conclusions of this study were obtained as follows: 1. To the anterior cranial base, the hyoid bone in unilateral cleft lip and palate individuals was located downward as compared with non-cleft individuals. 2. To the mandible, the hyoid bone in unilateral cleft lip and palate individuals was located backward as compared with non-cleft individuals. 3. The distance between the dorsum of the tongue and the inferior border of the hard palate in unilateral cleft lip and palate individuals was longer than that in non-cleft individuals. 4. Unilateral cleft lip and palate individuals showed no significant difference in the distance between the hyoid bone and the dorum of the tongue as compared with non-cleft individuals.

The shear bond strength of two adhesives bonded to composite resin and glass ionomer cement restorations / 대한치과교정학회지

If the bond strength is sufficient to resist orthodontic force, orthodontic brackets can be bonded to restorations. Orthodontic brackets were bonded to composite resin and glass ionomer cement restorations wtih no-mix adhesive or glass ionomer cement. The shear bond strength of adhesives bonded to restorations was studied in vitro. Orthodontic brackets were bonded to 10 extracted natural teeth, 40 composite resin restorations and 40 glass ionomer restorations. The surfaces of composite resin restorations were roughened or applied with bonding agent (Scothbond) after surface roughening. The surfaces of glass ionomer cement restorations were conditioned with acid etching or applied with Scotchbond to etched surface. The adhesive was no-mix resin or glass ionomer cement. The shear bond strength was measured. The results were as follows: 1. Orthodontic brackets could be bonded to composite resin restorations effectively as they could be bonded to acid etched enamel with no-mix adhesive. The shear bond strength was sufficient to resist orthodontic force and was not affected by bonding agent greatly. 2. The shear bond strength of no-mix adhesive bonded to acid etched glass ionomer cement restorations was sufficient to resist orthodontic force. However, the fracture risk of glass ionomer cement restorations was increased during debonding. The bonding agent couldn't increase the shear bond strength greatly. 3. The shear bond strength of glass ionomer cement bonded to glass ionomer cement restorations was lower than that of no-mix adhesive. The shear bond strength was sufficient to resist orthodontic force and was greatly decreased by bonding agent. 4. The shear bond strength of glass ionomer cement bonded to composite resin restorations was too low to resist orthodontic force.

A comparative study of mandibular tooth development between Angle Class I malocclusion group and Angle Class III malocclusion group / 대한치과교정학회지

The purpose of this study was to compare mandibular teeth development of Angle Class I malocclusion group with that of Angle Class III malocclusion group. The studied subjects consisted of 217 Angle Class I malocclusion patients and 235 Angle Class III malocclusion patients. Two study methods were used. One was to evaluate tooth development degree by means of Nolla stage method, the others was to measure tooth length on panoramic radiograph. The following results were obtained, in 7, 8 and 9 years, tooth development of Angle Class III malocclusion group was significantly faster than that of Angle Class I malocclusion group. in 6 year and 10, 11, 12, 13, 14 years, the difference of tooth development degree between Angle Class III malocclusion group was not significant.

Metal release from brackets and archwires / 대한치과교정학회지

The purpose of this experiment was to measure the amounts of nickel and chromium released from a simulated orthodontic appliance in artificial saliva. Simulated mandibular half-arch orthodontic appliances were composed of American Iron and Steel Institute type 304 brackets, Permachrome, Elgiloy, Australian wire, T.M.A. and Nitinol. The amounts of nickel and chromium released from sample were measured with atomic absorption spectrophotometer after 3, 6, 9, 12, 15 days. The cumulative amounts of nickel released from Permachrome, Elgiloy, Australian wire and T.M.A. reached a plateau after 6 days. But the cumulative amounts of nickel released from Nitinol increased continuously. Significant amounts of both nickel and chromium were solubilized from the simulated orthodontic appliances into artificial saliva. After 15 days, total cumulative amounts of nickel were 152.15microgram, 150.27microgram, 134.74microgram, 114.67microgram and 93.39micron from the Elgiloy, Australian wire, Nitinol, Permachrome and T.M.A., respectively. Total cumulative amounts of chromium from Permachrome, Australian wire, Elgiloy, Nitinol and T.M.A. were 100.83microgram, 83.64microgram, 81.61microgram, 14.90microgram and 12.43microgram, respectively. The result showed that nickel released from Elgiloy and chromium released from Permachrome were more than any others.

A histologic study on the effect of laser on the periodontium of the orthodontically moved tooth of rat / 대한치과교정학회지

This study was performed to evaluate the effect of low-power laser irradiation on the periodontium of the orthodontically moved tooth of rat. The experimental materials were 30 male rats. Orthodontic appliances were placed bilaterally between maxillary first molar and incisor teeth and the force was 1 Oz. Experimental animals were divided into eight groups as follows: no movement, 1st, 2nd, 3rd, 5th, 7th, 14th, and 28th day groups. In all experimental animals except no movement group, low-power laser was irradiated on the unilateral maxillary first molar (experimental side), but on the contralateral side, only orthodontic force was applied (control side). The histologic effects of laser on the periodontium of the orthodontically moved tooth on the consecutive experimental days were as follows: In the experimental side, by the biostimulating effect of laser, 1. Hyalinized tissue was formed later and eliminated earlier than in the control side. 2. Undermining bone resorption was occurred earlier than in the control side. 3. More osteoid tissue was deposited and calcified earlier than in the control side. 4. The most prominent changes were formation of new blood vessels and dilatation of old blood vessels.

The increase of enamel crack in debonding teeth / 대한치과교정학회지

The aim of this study was to clarify whether bonding/debondmg procedure will affect the occurance of enamel crack. The frequency of enamel crack was compared between before-bonding and after-debonding on 200 human extracted teeth Each facial surface of the tooth was divided in 9 fragments A presence of crack, which was classified by its direction as vertical, horizontal and oblique crack, was surveyed in each fragment. Number of all cracks in facial surface was 1355 at before-bonding, and 1605 at after-debonding, so it revealed significant increase rate of 18.5%, but compared by fragment, cracks were significantly increased in OC, OD, CC and GC fragments. All kinds of cracks were significantly increased, especially increase rate of oblique crack reached 54.9%. The increase rate of cracks was not superior at any fragment or region, but some evidence was seen in CC fragment. Judging from the above, increase of crack is unavoidable with bonding/debonding procedures.

Experimental study of the effects on the growth of mandibular condyle following cyclophosphamide administration in rat / 대한치과교정학회지

In this study, effects of cyclophosphamide on the growth of the mandibular condyle head were investigated with Spraque-Dawley rats of the 28 days of age. Rats were devided into four groups. Three were used as experimental groups, and one as control. Each rat in experimental group was injected intraperitoneally with cyclophosphamide repeatedly three times, 20mg/kg for the first group, 40mg/kg for the second, and 60mg/kg for the third each time. Rats in control group were injected with physiological salime in the same method. Rate in each group were sacrificed at 5, 10, and 15 days following the 1ast injection. The specimens were stained with H-E, toluidine blue, PAS, and alcian blue. The results were as follows; 1. In experimental group, with increasing the injection doses, the thickness of the condylar cartilage from the transitional zone to the hypertrophic zone became thinner in control group. 2. Weaker metachromasia to toluidine blue and less positive reaction to PAS were seen. 3. In promary marrow cavity the fewer trabecular was formed, the direction of trabecular formation became obscuerer, and the lower density of bone was resulted in.

A case report of mandibular prognathism treated with the labiolingual appliances / 대한치과교정학회지

A boy (Hellman dental age III B) with mandibular prognathism was treated by means of the labiolingual appliance and the chin cap. Following results were obtained; 1) Except the problem of development, most of treatment objectives were achieved after 8 months of active treatment. 2) The axial inclinations of upper and lower incisors were changed by the treatment. 3) The most notable change was the reduction of genial angle. 4) The patient has retained the good occlusal stability till after 18 months of retention.

A case report of orthodontic treatment of cleft palate accompany teeth congenital missing / 대한치과교정학회지

19 years old female had untreated Veau classification class II cleft palate with ectopic eruption of upper right lateral incisor and congenital missing of lower lateral incisors. Upper left lateral incisor, left first molar aid lower left first molar were root restswithperiapicalpathologiclesions. So all root rests were extracted and prosthodontic rehabilitation after orthodontic treatment was planned. She was treated by means of multibanded system with face bow. After 23 months all orthodontic correction were achieved and, as soos as debanding procedure was done she was referred to oral surgeon and prosthodontist for surgical operation and bridge construction.