The comparison of torque values in two types of miniscrews placed in rabbits: tapered and cylindrical shapes: Preliminary study / 대한치과교정학회지

OBJECTIVE: This study compared the stability of cylindrical miniscrews (Cy, 7 mm in length) with that of tapered miniscrews (Ta, 5 mm in length), using torque values to determine if the healing time before loading affects the stability of the miniscrew and if the insertion torque is associated with the removal torque measured after a few weeks of healing. METHODS: Ta and Cy with different thread lengths were placed in the tibias of 12 female New Zealand white rabbits (body weight: 3.0 - 3.5 kg), and the maximum insertion torque values (ITV) were measured. No orthodontic forces were applied so as to allow us to determine the pure effects of the different shapes. After 3 different healing periods (2, 4, and 6 weeks), maximum removal torque values (RTV) were measured immediately before the rabbits were sacrificed. RESULTS: No miniscrews were loosened. There were no significant differences in ITV or RTV between the Ta and Cy nor were there any significant differences in the ITV and RTV between the 3 groups, which had different healing periods. There was a correlation between the ITV and RTV. CONCLUSIONS: Shorter Ta showed similar stability as Cy, as determined by torque values. This result strongly suggests that the tapered shape is more advantageous than the cylindrical shape. The RTV did not increase significantly over time. It is recommended that a miniscrew be loaded immediately; waiting a few weeks before loading should be avoided. The correlation between the ITV and RTV suggests that the ITV can be used to estimate a screw's future stability.

Fracture resistance of crown-root fractured teeth repaired with dual-cured composite resin and horizontal posts / 대한치과보존학회지

The purpose of this study was to investigate the fracture resistance of crown-root fractured teeth repaired with dual-cured composite resin and horizontal posts. 48 extracted human premolars were assigned to control group and three experimental groups. Complete crown-root fractures were experimentally induced in all control and experimental teeth. In the control group, the teeth (n=12) were bonded with resin cement and endodontically treated. Thereafter, the access cavities were sealed with dual-cured composite resin. In composite resin core - post group (n=12), the teeth were endodontically treated and access cavities were sealed with dual-cured composite resin. In addition, the fractured segments in this group were fixed using horizontal posts. In composite resin core group (n=12), the teeth were endodontically treated and the access cavities were filled with dual-cured composite resin without horizontal posts. In bonded amalgam group (n=12), the teeth were endodontically treated and the access cavities were sealed with bonded amalgam. Experimental complete crown-root fractures were induced again on repaired control and experimental teeth. The ratio of fracture resistance to original fracture resistance was analyzed with Kruskal-Wallis test. The results showed that teeth in control and composite resin core - post group showed significantly higher resistance to re-fracture than those in amalgam core group (p < 0.05). The resistance to refracture was high in the order of composite resin - post group, control group, composite resin group and bonded amalgam group. Within the scope of this study, the use of horizontal post could be beneficial in increasing the fracture resistance of previously fractured teeth.

A study on the treatment of anterior open bite with midpalatal miniscrews / 대한치과교정학회지

Recently several techniques have been reported for the treatment of anterior open bite in adults characterized by molar intrusion with skeletal anchorage. In this study, five adult patients who had anterior open bite malocclusion were selected to undergo upper molar intrusion with midpalatal miniscrew to close the open bite. The aim of this study is (1) to validate true intrusion of molars in adults (2) to test the usefullness of midpalatal miniscrews as anchorage for intruding upper molars (3) to evaluate the skeletal and dental changes of open bite closure. The results are as follows. (1) All had true intrusion of the maxillary molars. Mean amount of molar intrusion was 3.4mm(range 1.5-5mm). (2) No movement of midpalatal miniscrew occurred during their use. (3) Open bite closure was achieved for all 5 patients. The mandible closed and B-point rotated anteriorly and upward. The mandibular plane angle and the occlusal plane angle decreased.

A study on the bone thickness of midpalatal suture area for miniscrew insertion / 대한치과교정학회지

The midpalatal suture area has some advantages for supporting miniscrews : it has no specific anatomical structure, it is composed of thick cortical bone, and covered with attached gingiva. So it is suitable area for inserting miniscrews. However, the midpalatal suture area appears thinner when seen in ceph. As a result, Clinicians can misunderstand that inserting miniscrews cause the problem, both the risk of perforation and the decrease of stability. The purpose of this article is measuring the vertical bone thickness of the midpalatal suture area for inserting miniscrews. The total of 25patient (male : 13, female : 12), who are in their twenties, were taken CT. The vertical bone thickness of the midpalatal suture area was measures from the transverse section of CT. As a result, We reached a conclusion from the differences of each area. It is as follows : 1. There is no significant difference between the thickness of male group and that of female group. 2. In coronal section, Bone thickness becomes thinner from the midpalatal suture to Left & Right side, in sagittal section, Bone thickness becomes thinner from incisive foramen to PNS. 3. The area that is within 3mm of left and right from the midpalatal suture area transversely and within 25mm backward from the incisive foramen sagittaly is enough for inserting miniscrews.

A Comparison of pre and post-surgical characteristics in skeletal Class III malocclusion patients using counterpart analysis / 대한치과교정학회지

Enlow's counterpart analysis explains the complex with anatomic and developmental characteristics where craniofacial aspect of individuals has been developed. Counterpart analysis does not compare individual measurement with the normal value from the average of majority but analyzes by comparison of values that each individual has. In this study we examined surgical changes in skeletal Class III malocclusion patients(male 40, female 40) and compared them with normal occlusion patients using counterpart analysis. The results indicated that : 1. Skeletal anterior-posterior discrepancy was relieved by shortening of the ramus width(B3). 2. The ramus alignment(R3, R4) was displaced posteriorly and the occlusal plane angle(R5) was rotated clockwise. 3. Skeletal Class III pattern was relieved in the post-operative group, but differences in the level of the cranium(R1, R2) was remaining compared to the normal occlusion patients. 4. In the comparison of surgery methods, the two-jaw surgery group presented changes in the maxillary length(A4), ramus alignment(R3,R4) and occlusal plane angle(R5) compared to the one-jaw surgery group, but the differences were not significant. In the past study about Korean skeletal Class III patients, the skeletal characteristics are upward backward rotation of the cranial base, posterior displacement of the maxilla, forward inclination of the ramus and lengthening of the mandibular body, but in this study, skeletal Class III pattern was relieved by shortening of the ramus width and maxillary advancement by orthognathic surgery, because orthognathic surgery is usually performed on limited areas in the maxilla and the mandible.

The use of miniscrew as an anchorage for the orthodontic tooth movement / 대한치과교정학회지

Anchorage in orthodontics is very important factor for orthodontist to treat malocclusion from diagnosis and treatment planning to end of treatment. Skeletal anchorage like miniscrew is supposed to be more effective method in anchorage control than conventional anchorage which needs patient's good cooperation. So this article will be mentioned about various clinical application of miniscrew through the general investigation and case reports about orthodontic use of miniscrew, specially about screwing area and clinical consideration of miniscrew's screwing on midpalate. The changes of treatment philosophy and methods by using skeletal anchorage were summarized and following results were obtained. 1. The orthodontic anchorage changed from relative concept to absolute one. 2. Bodily movement of teeth gets easier and determinate force system is possible on biomechanical consideration. 3. Some part of treatment that needs surgical intervention is possible by just orthodontic treatment.

A cephalometric study in patients with obstructive sleep apnea after use of oral appliance / 대한치과교정학회지

It is well known that oral appliance could improve respiratory difficulty in patients with obstructive sleep apnea (OSA). To evaluate the effect of oral appliance, polysomnography and cephalometry were performed in OSA patients before and after oral appliance was used. Twenty four OSA patients were included in this study. Respiratory difficulty index (RDI) was obtained from polysomnography and the movement of soft palate, tongue, posterior pharygeal wall, hyoid bone, and mandible and the variables of the facial pattern were measured on the cephalogram. The changes of cephalometric parameters were compared to the RDI changes and the correlation was tested. After oral appliance was used, RDI decreased from 46.8 to 13.3. There was significant relationship between RDI improvement and the anterior movement of the mandible and superior movement of the hyoid bone. In 8 patients whose RDI was most improved, RDI improvement rate was correlated with the anterior movement of the on tongue and anterior-posterior (AP) diameter of the airway at the levels between the lower portion of the soft palate and epiglottis. These results could conclude that anterior movement of the tongue and superior movement of the hyoid bone would be favorable cephalometric parameters for the improvement of OSA.

Study on maxillofacial growth and physical development of growing children / 대한치과교정학회지

Orthodontic patients are individuals that grow and develop : therefore selection of the proper time for orthodontic trdatment is considered to be one of the most difficult and yet difficult foctor. Since the development of cephalometric X-ray, amount and pattern of craniofacial growth change with aging could be predicted and became useful in the process of orthodontic treatment. The relationship between the mean values of cephalometric measurements and body helght and weight was studied among the groups(boys and girls) of Koream childern from the ages 0f 3-years to 12-years. 126 boys and 90 girls with no abnormality in growth and development and no history of orthodontic treatment from the ages of 3 years were chosen as subjects: Cephalometric X-ray were takem for 2 years and hard tissue analysis based on Burstone's COGS, which was divided into measurements of 6 parts (Cranial base, Maxillar and Mandible, Vertical measurements, Horizontal measurements, Basal bone relationchip, Dental measurements.) The relationship between craniofacial growth and body height & weight was studied. The following conclusions were obtained : 1. The maximum growth in the measurements of cranial base, N-Ar(FH) corresponded with the age the maximum increasein body height & weight in both boys and girls. 2. Gonual angle gradually decreased with in both boys and girls. 3. N-ANS(L) showed greater amount of growth than ANS-Me(L), and this had greater influence on facial profile. 4. N-A-Pogdegrees decreased with aging, and mandibular growth exceeded maxillary growth in amount and rate. 5. Length of Y-axis increased, but Y-axis to FH plane remained condtant. This show that mandible grows at a constant angulation to cranial base. 6. As permanert teeth erupt, interincisal angle deceased.

A study on the mandibular growth prediction and size of the frontal sinus / 대한치과교정학회지

This author tried to find if the size of the frontal sinus can be used as a diagnostic aid to predict the mandibular growth pattern in growing patients-in lateral cephalogram utilizing the fact the the frontal sinus completes its growth in earlier stage but the mandible continues to grow until later. At this study, the 228 samples were divided into 3 groups as skeletal Class I , II, III malocclusions and three indicies(ANB, APDI, Wits) were measured which hidicate the mandibular body length and the antero-posterior relationship of maxilla and mandible to evaluate their relations with frontal sinus. And results were obtained as followings. 1. The size of frontal sinus is highly related to ANB, APDI, Wits and mandilar body length(p<0.001) 2. the size of the frontal sinus of the Cl III malocclusion group was on the lateral cephalogram larger than Cl I and C1 II group.

Comparision of two cephalometric superimposition methods nasion-sella line method and anterior cranial base method / 대한치과교정학회지

Spatial change of craniofacial structures from growth or orthopedic force is usually evaluated by cephalometric superimpositions at different points in time.As the evaluation can be changed according to cephalometric superimposition method,selection for correct superimposition method is very important. Double registration of nineteen pairs of female lateral head films,their growth period is average 3.7 years and age is average 10.7 years, were performed by two observers. Comparisions was made between two methods and the results revealed the following; 1. NS line and ACE superimpositions are not markedly different in reliability due to almost same registration error of them. 2. The investigation was undertaken to examine interobserver difference. In NS line method, there is no significance in all measurements. In ACE method, significant difference was revealed in 4 measurements of 7 measurements was 3. In the investigation of intermethod difference, there is no significance between NS line and ACB superimpositions

Treatment effect of protraction head gear on skeletal Class III malocclusion / 대한치과교정학회지

Before 1970, mandibular overgrowth was known as main cause of skeletal Class III malocclusion in growing children ; however, recent study reports that many skeletal Class III malocclusion patients also show maxillary deficiency. Since 1972, when Delaire re-accommodated Protraction Head Gear (P.H.G.), many researchers have reported that skeletal Class III discrepancies could be corrected through use of P.H.G., which induces anterior movement of maxilla and change in mandibular growth pattern into infero-posterior direction ; nevertheless, it is very difficult to predict resultant changes of orofacial region. The purpose of this study was to find out what treatment effect P.H.G. has on different study samples. Author divided 51 skeletal Class III malocclusion patients with maxillary deficiency who were treated with P.H.G. into different study groups depending on sex, treatment beginning age, intraoral appliance, and facial growth pattern. By doing so, following results were obtained. 1. Treatment beginning age and Sex Four age groups (5.8 to 8 year-old, 8 to 10 year-old, 10 to 12 year-old, 12 to 14 year-old) were compared, and no significant difference was observed. (p<0.05) There was no significant difference between the sex groups, either. (p<0.05) 2. Intraoral appliance Treatment effects of study groups that used R.P.E.(mean age of 10.2) and Labio-Lingual appliance(mean age of 8.9) were compared. There was no significant difference depending on the type of intraoral appliance that was used. (p<0.05) 3. Facial growth pattern 1) Amounts of SNB and ANB corrections were smaller in clockwise growth pattern group than those in normal or counterclockwise growth pattern group. (p<0.05) 2) Amounts of increase in Wits appraisal and mandibular plane angle were greater in counterclockwise growth pattern group than those in normal or clockwise growth pattern group.(p<0.05) 3)Amounts of increase in articular angle were greater in counter lockwise growth pattern group than those in clockwise growth pattern group. (p<0.05)

Diagnosis and treatment plan of maxillary impacted canine / 대한치과교정학회지

Upper canine is important because it protects and maintains the stability of the dental arch and also, joins the anterior with the posterior teeth. The incidence of impaction of upper canine is the second most frequent next to the third molar because it takes a long period of time to develop, and has a complicated path of eruption, and erupts lately. After the age of 10, clinical and radioglaphic examination can be used in revealing the possibility of impaction and efforts should be put to reduce the side effects. To prevent impaction, selective extraction of primary canine at the age of 8 to 9 could be considered and prolonged retention of primary canine in oral cavity should be avoided at this time. Once the impaction is iden, the first stage of the treatment is to localize the lesion by radiographic examination and According to the severity, orthodontic traction or autotransplantation should be considered and comprehensive diagnosis and treatment plan of malocclusion should be established. Generally, labial impaction is due to arch length discrepancy and palatal impaction is due to malposition or morphologic pathosis of lateral incisors rather than arch length discrepancy. In surgical procedure, peridontal problems should be considered and the minimum amount of bone and soft tissue shold be reduced and direct bonding method of many attachment methods should be recommended. Especially in traction of labially impacted canine, it should be guided to erupt through the keratinized zone and proper forced magnitude should be applied. The importance of periodontal condition should always be in mind following the patient education to mintain the good oral hygiene at each stage of treatment. Properly managed impacted canine can provide function and esthetic by proper diagnosis and treatment if extraction of canine is not indicated.