Changes in longitudinal craniofacial growth in subjects with normal occlusions using the Ricketts analysis / 대한치과교정학회지

OBJECTIVE: This study was designed to define the Korean norm values for the Ricketts analysis. METHODS: In this longitudinal study, lateral cephalograms of 31 subjects with normal occlusion were taken biennially from ages 9-19 years. Cephalometric measurements were performed. Parameters for which the 10-year change did not exceed one standard deviation were defined as unchanged. The means and standard deviations for the measured parameters were determined for each age group. RESULTS: No significant changes in growth were observed in the molar relationship, incisor overjet, incisor overbite, mandibular incisor extrusion, interincisor angle, lower incisor tip (B1) to A point-Pogonion (A-PO) plane, upper incisor tip (A1) to A-PO plane, B1 inclination to A-PO, A1 inclination to A-PO, B1 inclination to Frankfurt plane (FH), convexity, lower facial height, facial axis, maxillary depth, maxillary height, palatal plane to FH, cranial deflection, ramus Xi position, or porion location. Continual changes over the 10 years of growth were observed in the maxillary first molar distal position to pterygoid true vertical plane, facial depth, mandibular plane to FH, anterior cranial length, mandibular arc, and corpus length. CONCLUSIONS: Clinicians can apply the Korean norms at age 9 as determined in this study when using the Ricketts analysis. The patient's age at the beginning of treatment and their sex should be taken into consideration when drawing visual treatment objectives.

Finite element analysis of peri-implant bone stresses induced by root contact of orthodontic microimplant / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the biomechanical aspects of peri-implant bone upon root contact of orthodontic microimplant. METHODS: Axisymmetric finite element modeling scheme was used to analyze the compressive strength of the orthodontic microimplant (Absoanchor SH1312-7, Dentos Inc., Daegu, Korea) placed into inter-radicular bone covered by 1 mm thick cortical bone, with its apical tip contacting adjacent root surface. A stepwise analysis technique was adopted to simulate the response of peri-implant bone. Areas of the bone that were subject to higher stresses than the maximum compressive strength (in case of cancellous bone) or threshold stress of 54.8MPa, which was assumed to impair the physiological remodeling of cortical bone, were removed from the FE mesh in a stepwise manner. For comparison, a control model was analyzed which simulated normal orthodontic force of 5 N at the head of the microimplant. RESULTS: Stresses in cancellous bone were high enough to cause mechanical failure across its entire thickness. Stresses in cortical bone were more likely to cause resorptive bone remodeling than mechanical failure. The overloaded zone, initially located at the lower part of cortical plate, proliferated upward in a positive feedback mode, unaffected by stress redistribution, until the whole thickness was engaged. CONCLUSIONS: Stresses induced around a microimplant by root contact may lead to a irreversible loss of microimplant stability.

Optimization of orthodontic microimplant thread design / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to optimize the thread pattern of orthodontic microimplants. METHODS: In search of an optimal thread for orthodontic microimplants, an objective function stability quotient (SQ) was built and solved which will help increase the stability and torsional strength of microimplants while reducing the bone damage during insertion. Selecting the AbsoAnchor SH1312-7 microimplant (Dentos Inc., Daegu, Korea) as a control, and using the thread height (h) and pitch (p) as design parameters, new thread designs with optimal combination of h and p combination were developed. Design soundness of the new threads were examined through insertion strain analyses using 3D finite element simulation, torque test, and clinical test. RESULTS: Solving the function SQ, four new models with optimized thread designs were developed (h200p6, h225p7, h250p8, and h275p8). Finite element analysis has shown that these new designs may cause less bone damage during insertion. The torsional strength of two models h200p6 and h225p7 were significantly higher than the control. On the other hand, clinical test of models h200p6 and h250p8 had similar success rates when compared to the control. CONCLUSIONS: Overall, the new thread designs exhibited better performance than the control which indicated that the optimization methodology may be a useful tool when designing orthodontic microimplant threads.

Finite element analysis of cortical bone strain induced by self-drilling placement of orthodontic microimplant / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion in a self-drilling manner. METHODS: A 3D finite element method was used to simulate the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) into 1 mm thick cortical bone. The shape and dimension of thread groove in the center of the cortical bone produced by the cutting flute at the apical of the microimplant was obtained from animal test using rabbit tibias. A total of 3,600 analysis steps was used to calculate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. RESULTS: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, were observed in the peri-implant bone along the whole length of the microimplant. Level of strains in the vicinity of either the screw tip or the valley part were similar. CONCLUSIONS: Bone strains from a microimplant insertion in a self-drilling manner might have a negative impact on the physiological remodeling of cortical bone.

Evaluation of potency of panoramic radiography for estimating the position of maxillary impacted canines using 3D CT / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the potency of panoramic radiography for the detection of maxillary impacted canines. METHODS: Twenty-five patients were selected, comprised of 7 males (mean age: 10.9 years, range: 8.5 - 14.5 years) and 18 females (mean age: 10.9 years, range: 8.2 - 15.7 years). In total, thirty-five maxillary impacted canines were estimated. The position of the canine and root resorption of adjacent teeth were evaluated on panoramic radiography and 3D CT. RESULTS: Except for angulation to the occlusal plane, the other parameters, such as tooth length, crown width, vertical distance and lateral shift showed larger values on panoramic radiography compared to 3D CT. In palatally impacted cases, the angulation of canine was smaller, and the vertical distance to the occlusal place was larger on panoramic radiography than 3D CT. For labially impacted canines, tooth length, crown width, and angulation to the occlusal plane were similar for the two methods. The sensitivity for detecting root resorption on panoramic radiography was calculated as being 33.3% of 3D CT. CONCLUSIONS: The position of labially impacted canines can be effectively estimated using panoramic radiography, but palatally impacted canines need further investigation such as 3D CT for proper diagnosis.

A cephalometric and dental cast study of obstructive sleep apnea patients / 대한치과교정학회지

To evaluate the cephalometric and dental characteristics of obstructive sleep apnea (OSA) patients, 23 OSA patients and 15 control, non-OSA, patients who visited the Sleep Disorder Clinic Center, Keimyung University were investigated. Patients who suffered from apnea-hypopnea episodes over 10 times per hour were diagnosed as having OSA after polysomnograph testing. Impressions were taken with alginate. Cephalometric radiographs were taken at maximum intercuspation. The dental cast measurements, including transpalatal width, intercanine width, intermolar width and palatal depth did not differ between the control and OAS groups and did not have a positive correlation with the apnea-hypopnea index (AHI). Upper airway width was statistically narrower than the control group. Upper airway width had a low negative correlation with AHI, but, lower airway width had a low positive correlation, and, the higher the AHI score, the longer the mandibular border to hyoid distance.

A study on the dental arch characteristics of bialveolar protrusion patients using a three-dimensional digital model / 대한치과교정학회지

Recent beauty trends have caused an increase in the number of bialveolar protrusion patients seeking treatment of lip protrusion. But studies of these patients are not common. Studies using their dental models are especially rare. Dental models have been measured manually or through a computer by digitizing two dimensional images of models. Nowadays, we are able to study dental models more easily and accurately by utilizing the three-dimensional (3-D) laser scanner in dentistry. An investigation was carried out to evaluate the characteristics of the dental arch in a bialveolar protrusion group in comparison with a normal group using 3-D digital models. The normal group was composed of 20 subjects who were selected from students of the School of Dentistry, Kyungpook National University. The bialveolar protrusion group was composed of 20 subjects who visited for treatment at the Department of Orthodontics, Kyungpook National University Hospital. Tooth size, arch width and arch length were measured digitally, and arch shape and the shape of the palate were drawn. Based on the results of this study, the differences of the arch characteristics in the bialveolar protrusion group were that the size of the teeth was larger, mandibular canine width and 1st premolar width were wider, and arch length was longer than in the normal group. And there were differences in the arch shape and the shape of palate between the bialveolar protrusion and normal groups.

Comparison of histologic observation and insertional and removal torque values between titanium grade 2 and 4 microimplants / 대한치과교정학회지

The purpose of this study was to evaluate the light microscopic features and the maximum insertional and removal torque value of microimplants, made from titanium grade 2 or 4, in the tibia of 6 rabbits. First, the maximum torque values of microimplants at implantation were measured. After 2, 8, and 12 weeks of healing time, the microimplant-containing segments of tibia of 2 rabbits were removed and the maximum removal torque of each microimplant were measured. Comparisons of histologic examination and insertional and removal torque values were carried out for the two groups of microimplants. Removal torque values were significantly increased in both groups after 8 and 12 weeks as compared to 2 weeks after implantation. Other values measured did not show any statistically significant differences and there were no histological differences between grade 2 and 4 titanium. Based on these results, this study showed that there were no significant differences between grade 2 and 4 titanium. It seems better to use grade 4 titanium for making microimplants because grade 4 titanium is mechanically harder than grade 2 titanium and has similar retention.

Elastic force degradation of synthetic elastomeric chain / 대한치과교정학회지

The purpose of this study was to evaluate the force degradation rate of synthetic elastomeric chains during space closing phase of orthodontic treatment. Two kinds of synthetic elastomeric chains(RMO, 3M) were selected which were commonly used in clinics. All of the samples were extended and tested for 4 weeks under the simulated intraoral condition. The results can be summarized as follows : 1. Time related residual force showed typical logarithm function. Residual force after 4 weeks was 41.2~64.6 % of original force, and difference between two kinds of elastomeric chain existed. 2. Elastic force decreased greatly during first 10 minutes, so 20~25 % of original force disappeared. After that, this decreasing tendency was diminished significantly, average rate of elastic force after 1 week to 4 weeks were 1.5 % demonstrating rather constant force. 3. Even though the same brand of elastomeric chiain was used, as extension rate of elastomeric chain increased, force degradation rate increased by decreasing of residual force.

The effect of a static magnetic field of Nd-Fe-B magnet on alkaline phosphatase activity of MC3T3-E1 cells / 대한치과교정학회지

more efficient tooth movement. The purpose of this study was to evaluate the effect of different static magnetic fields of ND-Fe-B magnet on MC3T3-E1 cells by measuring the alkaline phosphatase activity and observing the amount of stained alkaline phosphatase. For measuring of alkaline phosphatase activity, MC3T3-E1 cells were seeded in first and third row of 12 well culture plate. And Nd-Fe-B magnets were positioned under the first column of first and third row to apply different static magnetic fields(first column:100mT ; second column:4.6mT ; third column:0.5mT ; forth column:0.0mT) to the cells for 7, 13, 19, and 25 days. For staining of alkaline phosphatase, MC3T3-E1 cells were seeded in 100mm culture plates. And Nd-Fe-B magnets were positioned under the corner of plates to apply different static magnetic fields(magnet side:100mT ; the opposite side:0.5mT) to the cells for 7, 13, 19 and 25 days. The results were as follows : 1. ALP activity was increased until day 19 in biochemical determination as well as in histochemical staining. 2. The application of higher magnetic field(100mT) suppressed ALP activity at day 13, 19, 25. On the contrary, the application of the lower magnetic field(4.6mT, 0.5mT) significantly enhanced the ALP activity. 3. Consistent with enzyme assay, histochemical staining of ALP also demonstrated that higher magnetic field(100mT) suppressed ALP activity, lower one(0.5mT) enhanced.

The effects of salivary contamination on tensile bond strength of resin modified glass ionomer cements in bonding brackets / 대한치과교정학회지

The purposes of this study were to evaluate applicability of resin modified glass ionomer cements and to determine the effect of salivary contamination on the tensile bond strength. Fourty extracted human permanent premolars were prepared for bonding and standard edgewise brackets were bonded with Ortho-One, Fuji Ortho LC, Vitremer and Advance. Fourty extracted human permanent premolars were contaminated with saliva, dried and bonded with same materials above. The tensile bond strength was tested by Instron testing device after storage in normal saline at 37degrees C for 24 hours from bonding. The results were as follow : 1. The tensile bond strength of Ortho-one group was 7.68 1.76, Advance group was 7.87 2.80, Fuji Ortho LC group was 4.99 +/-2.53, Vitremer group was 2.80 0.88 MPa. The tensile bond strength in contaminated condition of Ortho-One group was 4.12 1.67, Advance group was 5.37 0.68, Fuji Ortho LC group was 4.41 1.61, Vitremer group was 2.60 1.10 MPa.. 2. Salivary contamination did not affect the tensile bond strength when compared with the uncontaminated enamel group in Fuji Ortho LC and Vitremer (p>0.05) and there was great significant difference in the tensile bond strength of Ortho-One and Advance. 3. Advance, Ortho-One and Fuji Ortho LC seemed to have clinically a proper bond strength.

A new method of tooth positioner fabrication using modified T.A.R.G. to measure the inclination and angulation of individual teeth / 대한치과교정학회지

In this article, we introduce a new method of tooth positioner fabrication using modified T.A.R.G. to measure the inclination and angulation of individual teeth. In finishing stage of orthodontic treatment with a fixed appliance, we anticipate that tooth positioner fabricated using the described construction method provides the movement of individual tooth into a desired position; corrected inclination and angulation of teeth, extrusion, intrusion, rotation and so on.

Changes in CGRP-immunoreactive nerve fibers during expansion of midpalatal suture of the rat / 대한치과교정학회지

Midpalatal suture expansion if often used for patients having narrow maxillary arch, cleft palate, respiratory handicap with narrow nasal cavity. CGRP has been known as a modulator of pain transmission in central nervous system and a local effector to peripheral tissue causing vasodilation, increase of blood flow, modulation of immunesystem, regulation of macrophagic function and stimulation of bone formation. To investigate changes of CGRP-immunoreactive nerve fibers in midpalatal suture during the expansion, immunohistochemical study was performed by using rats. Experimental rats (10 weeks, 250 gm) were divided into five groups (control, 1, 4, 7, 14 days group (each n=4) and applied orthodontic force (approximately 200gm) to upper anterior incisors. Frozen sections of midpalatal suture area were immunostained by using rabbit antisera. The results were as follows: The CGRP-immunoreactive nerve fibers were hardly observed in control group. In 1 day group, the CGRP-immunoreactive nerve fibers were more increased around the vessels than control group. In 4 days group, the CGRP-immunoreactive nerve fibers were more increased than control group, but nor more increased than 1 day group. Vascular diameter was more enlarged. In 7 days group, especially, hematoxilin affinity of cells was remarkable and cells were arranged along the bone margin. The CGRP-immunoreactive nerve fibers were more reduced than 4 days group and vascular diameter was also reduced. In 14 days group. the CGRP-immunoreactive nerve fibers were similar to those of 7 days group and the irregularity of bone margin was almost recoverd. In Conclusion, the CGRP-immunoreactive nerve fibers may be related to intial neurogenic inflammatory reaction in expanding mid-palatal suture.

The retrospective study on the prognosis of Class III malocclusion treatments / 대한치과교정학회지

The purpose of this study was to predict the prognosis of class III malocclusion treatments. 25 patients selected for this study were devided into two groups by the stability of dentitional, skeletal and soft tissue profile improvement. One was stable group which consisted of 12 children and the other was relapse group with 13 children. Various measurements in initial lateral cephalogram were calculated and analyzed by t-test, correlation coefficient and discriminant analysis. The results of this study were summarized as follows: 1. In both stable and relapse groups, there was not distinct difference in the antem-posterior skeletal relationship(P<0.05). 2. As the result of wits, AB to occlusal plane angle and occlusal plane to mandubular plane angle, the occlusal plane of relapse group was stopper than that of the stable group. 3. In correlation coefficient analysis, the overjet and the occlusal plane to mandibular plane angle showed significant correlations (P<0.001, P<0.01). 4. The discrminant function was obtained from three major influential measurements; overjet, AB to occlusal plane angle and articular angle, and this function could discriminate correctly in 88% of these samples.

The frictional resistance of tin ion-plated Co-Cr orthodontic wire / 대한치과교정학회지

The effectiveness of TiN ion-plating was examined with TiN ion-plated Co-Cr wires(016", 016"X.022") on three different types of bracket(TiN ion-plated metal bracket, ceramic bracket and plastic bracket). Maximum static frictional forces and characteristic curves obtained from the frictional characteristic graph, were compared and surface roughness of wires and bracket slots before and after friction experiment was observed by SEM. The obtained results were as follows. · The frictional forces of TiN ion-plated wires were significantly lower than those of non ion-plated wires(P<0.O5 ).· On the effect of wire shape, the frictional forces of round wires were significantly lower than those of rectangular wires(P<0.05). · As the result of the SEM observation on the wires and bracket slots after the friction experiment, the surface of non ion-plated wires was rougher than that of TiN ion-plated ones. · The difference between the static frictional forces and the kinetic frictional forces was not significant in case of the TiN ion-plated round wires, but the static frictional forces were a little higher than the kinetic frictional forces in the TiN ion-plated rectangular wires. · The static frictional forces were much higher than the kinetic frictional forces in the case of non ion-plated wires.

The effect of ligation method on the frictional force between orthodontic bracket and archwire / 대한치과교정학회지

The frictional force has been considered as an harmful factor in an active unit where tooth movement occurs, but as an advantageous factor in anchor unit that resist tooth movement. That is, efficient tooth movement is planned by using ligation methods that have low levels of bracket-wire frictional force and the anchorage control can be achieved by using ligation methods that have high levels of bracket-wire frictional force that result in binding of the bracket accompanied by little or no tooth movement. The purpose of this study was to evaluate the frictional force generated between bracket and wire in accordance with the methods of ligation, the material of ligation and the passage of time under artificial saliva. Tested were 0.017X0.022 inch stainless steel wires in standard edgewise twin brackets for upper central incisors in a 0.018-inch slot The wires were ligated into the brackets with elastomeric modules and stainless steel ligatures. Whole tie, half tie, twisting tie and double overlay tie were done with elastomeric modules. With 0.009-inch stainless steel ligature whole tie and half tie were done by needle holder and whole tie by ligature tying plier. With 0.012-inch stainless steel ligature whole ties were done by needle holder. Whole tie groups of elastomeric module were kept in artificial saliva bath at 37degress C for 28 days. The frictional force was recorded by means of an Instron universial testing instrument (4202 INSTRON, Instron Co., U.S.A.) at initial, 7, 14, 21, and 28 days. The results for ligated samples in a simulated oral environment revealed the following: In elastomeric module whole tie, 28 days group was significantly greater mean static frictional force than any other group but there were no significant differences among any other group (p>0.05). Elastomeric module twisting ties were significantly greater mean static frictional forces than any other ligation method but there were no significant differences between twisting tie and double overlay tie (p>0.05). Twisting tie, double overlay tie, whole tie, half tie showed differences in decreasing order. Stainless steel half tie produced lower mean static frictional forcee than whole tie, ligation by ligature tying plier produced greater mean static frictional force than by needle holder and ligation with 0.012-inch stainless steel ligature produced greater mean static frictional force than with 0.009-inch stainless steel ligature (p0.05).

The angulation and inclination of individual tooth to FH plane in normal occlusion / 대한치과교정학회지

The purpose of this study was to obtain the angulation and inclination of FACC of all teeth to FH plane. Study models of 31 persons with normal occlusion were selected and mounted on the semiadjustable articulator for this study. Using TARG. with a little modified method, the angulation and inclination of FACC of all teeth to FH plane were measured and then the measurements were analyzed statistically. The obtained results were as follows. Mean, standard deviation, maximum value, and minimum value of the angulation and inclination of FACC of upper and lower teeth were obtained. The FACC in both upper and lower arch was progressively lingually-inclined from anterior teeth to posterior teeth. In the angulations of FACC of upper teeth, central and lateral incisor showed similar value. Yet, the FACC of the rest was progressively distally-angulated -from the canine to posterior teeth. The FACC in lower arch was progressively mesially-angulated from anterior teeth to posterior teeth. The angulation and inclination of FACC of any tooth in both upper and lower teeth correlated strongly and positively with the angulation and inclination of FACC of adjacent tooth.

The physical properties of tin ion-plated Co-Cr (elgiloy) orthodontic wires / 대한치과교정학회지

To estimate the possibility of clinical application of TiN ion-plated Elgiloy(Co-Cr wire), measurements of tensile strength and hardness were made on the four tempers on each of the manufactured Elgiloy, the (heat-treated) Elgiloy for 30 minutes at 250degrees C and the TiN ion-plated Elgiloy. For comparison, the tensile strength and hardness of Stainless Steel wires were also measured. The following are the results of the study: · In the 4 tempers, tensile strength was the greatest in the TiN ion-plated group, followed by the heat-treated Elgiloy group and the manufactured Elgiloy group, but no statistical difference was noticed between heat-treated and manufactured Elgiloy groups(P<0.05). · In each temper, tensile strength- of ion-plated Elgiloy increased- about l0kgf/mm` in comparison with the values of the manufactured Elgiloy. · In yellow, green and red tempers except the blue, hardness was the greatest in ion-plated group. In the blue temper, there was no statistical difference between heat: treated and manufactured Elgiloy groups(P<0.05). · In each temper, hardness of ion-plated Elgiloy increased about 50-90VHN in comparison with the values of the manufactured Elgiloy. · The tensile strength of Stainless Steel wire was similar to that of the red temper of manufactured Elgiloy and the green temper of ion-plated Elgiloy.

The effect of a static magnetic field on the bone nodule formation of MC3T3-E1 cells / 대한치과교정학회지

To evaluate the effect of a static magnetic field on the bone producing potential of MC3T3 El cells, the alkaline phosphatase activity was measured after the cells having been cultured under 76.4mT static magnetic field using a SmCos magnets for 5days, 7days, lldays, 15days and 2ldays for each cell culture group. Also, the amount of bone nodule stained with Alizarin red S was observed. The results were as follows. · The alkaline phosphatase activity of the 7, 11, and 15 days group among the experimental groups was decreased as compared with the control groups, and the decrease of alkaline phosphatase activity in the 11 days group was the most evident among them. · Any stained bone nodules of both groups had not been observed until the 11th day. The stained bone nodules in the control groups were found on the 15th day, but not in the experimental groups. The stained bone nodules were observed in both groups on the 21st day, but the control groups have more bone nodules than the experimental groups.

The effects of surface treatment of dental nickel-chromium alloy on tensile bond strength / 대한치과교정학회지

This study was conducted to evaluate the tensile bond strength by bonding the dental bracket with Super-bond after treating the surface of dental Nickel-Chromium alloy with sandblasting, sandblasting & tin-plating, respectively, and tin-plating. 10 pieces of Nickel-Chromium alloys with brackets bonded with Super-bond without their surface treatment were sampled as a control group, 20 pieces of Nickel-Chromium alloy brackets bonded with Super-bond after treating them with sandblasting as group I, 20 pieces of Nickel-Chromium alloys tin-plated and bonded with Super-bond after sandblasting as group II, and then 20 pieces of alloys with brackets bonded with Super-bond after tin-plating as group III. The result of those examination and comparison is summarized as follows: 1. Group I showed the mean tensile bond strength of 14.41+/-2.24MPa which was highest among 4 groups, followed by group III( 13.59+/-L51MPa ), group II( 12.27+/-1.45MPa ), and control group( 10.50+/-1.57MPa ), respectively. However, it was shown that them was no statistically significant difference between group I and III, group III and II, and group II and control group( P>005 ). 2. The main failure pattern of those brackets showed that 70% of the control group had an adhesive failure at the bracket Superbond interface, and 30% at the Nickel-Chromium alloy-Superbond interface, while other groups did the adhesive failure at the bracket-Superbond interface. 3. When examined under SEM, it was shown that adhesives were mostly attached to the surface of the Nickel-Chromium alloy for all groups while a considerable quantity of adhesives were attached to the bracket base. Then, those samples treated only with sandblasting showed the most even and remarkable roughness of their surface.