• The korean journal of orthodontics
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• v.35 no.6 s.113
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• pp.451-458
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• 2005

Cephalometric superimposition is unable to evaluate tooth movement along the occlusal plane and the errors of photographing and superimposition of the occlusogram is also inevitable. The purpose of the present study was to evaluate the rotational movements of the maxillary posterior teeth following space closure after extraction of maxillary first premolars. using 3D dental images. In 19 adult females. analysis of rotational movements of the maxillary posterior teeth was performed between the initial and final 3D dental images superimposed on the maxillary hard palate. The results showed a diversity of rotational movements of posterior teeth. The causes of various rotational movements may be different rotation of molars in each case at the beginning of treatment. individual characters of the dental arch and tooth morphology. The results of the study indicate that accurate evaluation of rotational movements of posterior teeth following space closure after extraction of premolars using 3D dental images can be obtained through the subdivision of tooth movement during the initial aligning, space closure and finishing stages.

• The korean journal of orthodontics
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• v.41 no.4
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• pp.255-267
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• 2011

Objective: The purpose of this study was to confirm the reliability of a cone beam computed tomography (CBCT)-generated panoramic view based on a CBCT 3D image and to find the most helpful 2D panoramic image compared with CBCT 3D image when examining the mesiodistal tooth axis. Methods: A test model was constructed according to cephalometric norms. The test model was repeatedly repositioned for CBCT and panoramic radiographic imaging. Panoramic radiographs were acquired at each of the following 3 occlusal plane positions: $-5^{\circ}$, $0^{\circ}$, and $+5^{\circ}$. Measurements of mesiodistal tooth axis in CBCT 3D image, CBCT-generated panoramic view, and panoramic radiographs were compared. Results: Compared with the CBCT-generated panoramic view, CBCT 3D image showed significant difference in the mesiodistal tooth axis in the premolars and no significant difference in the mesiodistal tooth axis in the incisors and canines. Mesiodistal tooth axis on the CBCT-generated panoramic view was significantly different from that on panoramic radiographs. Conclusions: CBCT-generated panoramic view can be a useful tool for evaluating mesiodistal tooth axis.

• The korean journal of orthodontics
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• v.37 no.2 s.121
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• pp.150-158
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• 2007

Objective: The aim of this study was to determine the relationship between the status of a unilateral palatally impacted maxillary canine (as seen on the panoramic radiograph) and the orthodontic treatment duration. Methods: A total of 36 subjects were chosen (8 males and 28 females, $13.7{\pm}2.5$ years). All patients had undergone orthodontic traction of the impacted canine after a closed flap surgery. The position of impacted canine on the panoramic radiograph was traced and calculated with regard to the treatment duration. Results: The canine overlap over the lateral incisor (COGr) had significant statistical difference between the short-term and the long-term treatment duration groups (divided by average treatment time of 21 months) (p<0.05). Multiple regression indicated that the variables of significance (with treatment duration as the dependent variable) were the canine vertical height from the occlusal plane $(HCV,\;r^2=0.115;\;p<0.05)$ and the mandibular anterior width $(MnDW,\;r^2=0.142;\;p<0.05)$. The treatment duration, the canine angle to the incisor midline (CA), and HCV decreased from primary dentition (under 12 yrs) to permanent dentition (15 yrs). Howerer, these increased again at the adolescent ages (over 16 yrs). Conclusion: These findings suggested that orthodontic treatment of a palatally impacted canine would show good prognosis at an age of early permanent dentition with the canine showing smaller CA and HCV.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.77-87
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• 2010

Skeletodental asymmetries are common and asymmetric orthodontic treatments are very difficult to correct successfully. The cause of asymmetries can be the skeletal asymmetry, dental, or functional, or combinations of these causes. Skeletodental asymmetries can be the result of congenital factors, such as hemifacial microsomia and environmental factors, such as trauma. Optimal treatment outcome of the severe facial asymmetry requires the orthognathic surgery. Mild asymmetry problem can be treated by only orthodontic treatment. The orthodontic treatment of asymmetry is usually difficult. Facial asymmetry orthodontic treatment are primarily based on proper diagnosis and careful treatment planning. Side effects of asymmetric elastic to treat midline discrepancies are canted occlusal plane, tipped incisors and unesthetic results. In the management of dental arch asymmetries, the clinician should select the appropriate force system and the appliance design necessary to address the asymmetry while minimizing undesirable side effects. This report presents treatment strategies for the treatment of skeletodental asymmetry. In this case report, the clinical case with midline discrepancies treated by optimal mechanics is described. Through diagnosis and strategic treatment mechanics can obtain proper midline correction with minimal side effects.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.218-226
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• 2018

In partial edentulous patients, implant-assisted removable partial denture which provide additional retention and support by placing a small number of implants in strategic positions might be suitable treatment. This case of patient with loss of maxillary posterior teeth and moderate to severe wear of residual dentition, three implants were placed in the maxillary anterior edentulous area and then surveyed bridges were made including remaining anterior natural teeth. Posterior edentulous area was restored with distal extension removable partial denture (RPD). In addition, the worn mandibular natural teeth were restored with fixed prostheses. As a result, reduced vertical dimension and collapsed occlusal plane were rehabilitated, and improved functionally and aesthetically. The purpose of this case was to report the results of three-year follow-up of full mouth rehabilitation with anterior implant surveyed bridges and distal extension RPD.

• Imaging Science in Dentistry
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• v.44 no.4
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• pp.257-262
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• 2014

Purpose: This study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT). Materials and Methods: Forty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., $0^{\circ}$), $+10^{\circ}$, $+12^{\circ}$, $-12^{\circ}$, and $-10^{\circ}$ with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant. Results: The differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of $-12^{\circ}$, -0.66 to -0.11 at $-10^{\circ}$, -0.51 to +0.19 at $0^{\circ}$, -0.64 to +0.08 at $+10^{\circ}$, and -0.64 to +0.1 at $+12^{\circ}$. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9. Conclusion: Changing the slice orientation in the range of $-12^{\circ}$ to $+12^{\circ}$ reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.2
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• pp.237-248
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• 1993

Although pantograph has been used to investigate whether the determinents of the mandibular movement were possible contributing factors of TMJ click, there was the problems to understand the role of tooth morphology upon the occurrence of click because of using appliance without tooth contacts. There Were advantages to evaluate the effects of tooth morphology upon the mandibular movements, because intraoral tracing device(Functiograph$^{(R)}$) had been obtained maintaining occlusal contact between the upper and lower natural teeth during mandibular movement. The purpose of this study was to record the mandibular eccentric movement quantitatively performed in 20 adult control subjects and 20 adult subjects with TMJ click and to investigate the effects of occlusion upon the occurrence of TMJ click. The obtained results were as follows : 1. The average ICP-P distance was $3.07{\pm}0.73mm$ in subjects with TMJ click, $2.14{\pm}0.85mm$ in control subjects. There was a statistical significance between subjects with TMJ click and control subjects(P<0.001). 2. The average ICP-P distance was $3.07{\pm}1.14mm$ in subjects with TMJ click, $2.61{\pm}0.96mm$ in control subjects. There was a statistical significance between subjects with TMJ click and control subjects(P<0.05). 3. The average distance of right and left lateral movement was not statistically significant between subjects with TMJ click and control subjects. 4. The average lateral displacement from midline during RCP was $0.75{\pm}0.54mm$ subjects with TMJ click, $0.16{\pm}0.17mm$ in control subjects. There was a statistical significance between subjects with TMJ click and control subjects(P<0.001). 5. The average lateral displacement from midline during protrusive movement was $0.88{\pm}0.54mm$ in subjects with TMJ click, $0.20{\pm}0.23mm$ in control subjects. There was a statistical significance between subjects with TMJ click and control subjects(P<0.001). 6. The average angle of right and left lateral movement was $144.2{\pm}20.20^{\circ}$ in subjects with TMJ click, $138.15{\pm}20.09^{\circ}$ in control subjects. There was a statistical significance between subjects with TMJ click and control subjects(P<0.05).

• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.1-13
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• 2001

The extraction lot orthodontic treatment can be adopted for aligning crowded dentition, improving facial esthetics and solving a skeletal discrepancy as alternative for a surgical option. Mandibular second premolar extraction was often selected as treatment plan when there we very little or no space shortage in lower arch or limited retraction of the lower incisors was required. The primary object of this study was evaluate a pretreatment condition and examine the amount of tooth movement ior a mandibular second premolar extraction in growing patients. Pretreatment and posttreatment lateral cephalograms of 14 cases that had their four first premolar extracted (4/4 group), 15 cases with upper first and lower second premolar extraction (4/5 group) were selected. Structural method superimposition was conducted to evaluate a difference of dental change between 4/4 and 4/5 group. The results were as follows, 1. Pretreatment factor for 4/4 extraction or 4/5 extraction choice included maxillary incisor axis to occlusal plane, Class II molar relationship, IMPA and interincisal angle. 2. The amount of molar anterior movement in 4/5 group was greater than that of 4/4 group(p<0.05). 3. There was no significant difference between 4/4 group and 4/5 group in aspects of maxillary tooth movement(p<0.05).

• Imaging Science in Dentistry
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• v.42 no.3
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• pp.139-146
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• 2012

Purpose: An individual surgical stent fabricated from computed tomography (CT) data, called a CT-guided stent, would be useful for accurate installation of implants. The purpose of the present study was to introduce a newly developed CT-guided stent with a simple design and evaluate the accuracy of the stent placement. Materials and Methods: A resin template was fabricated from a hog mandible and a specially designed plastic plate, with 4 metal balls inserted in it for radiographic recognition, was attached to the occlusal surface of the template. With the surgical stent applied, CT images were taken, and virtual implants were placed using software. The spatial positions of the virtually positioned implants were acquired and implant guiding holes were drilled into the surgical stent using a specially designed 5-axis drilling machine. The surgical stent was placed on the mandible and CT images were taken again. The discrepancy between the central axis of the drilled holes on the second CT images and the virtually installed implants on the first CT images was evaluated. Results: The deviation of the entry point and angulation of the central axis in the reference plane were $0.47{\pm}0.27$ mm, $0.57{\pm}0.23$ mm, and $0.64{\pm}0.16^{\circ}$, $0.57{\pm}0.15^{\circ}$, respectively. However, for the two different angulations in each group, the $20^{\circ}$ angulation showed a greater error in the deviation of the entry point than did the $10^{\circ}$ angulation. Conclusion: The CT-guided template proposed in this study was highly accurate. It could replace existing implant guide systems to reduce costs and effort.

• Journal of Periodontal and Implant Science
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• v.32 no.1
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• pp.41-49
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• 2002

The aim of this study was to compare periodontal conditions around mesially tipped molars by a tipping degree. Patients who had been consecutively treated at the Department of Periodontology, Chonbuk National University Hospital from October 1999 to August 2001 were assessed with radiographs taken at their molar regions. Of all molars investigated, 142 molars of 116 patients tipped mesially more than 10 degrees to the line perpendicular to an occlusal plane were selected for the study. The tipped molars were divided into 2 groups with a reference to a tipping degree, i.e., 66 slightly tipped(group 1 : <$30^{\circ}$) and 76 severely tipped molars (group 2 : ${\geq}30^{\circ}$). Probing depth(PD), plaque retention index(PRI) at mesial surfaces of tipped molars and tooth mobility(TM) were recorded at the clinical examination. Tipping degree(TD) and alveolar bony defect(ABD) at the mesial surface of the molars were measured in a radiograph. The results showed that no statistical differences were found between groups in all measured variables. In Pearson correlation analysis performed in the same group, a positive relationship was shown between PRI and PD in the group 1 and, in the group 2, between PRI and PD as well as PRI and ABD(p < 0.01). However, no statistically significant relationship was found between TD and all other variables in both groups. Within limitations of this study, it may be concluded that tipping degree did not seem to influence periodontal conditions, i.e., PD, ABD and TM of mesially tipped molars per se, but plaque presence/absence seemed to mainly affect the periodontal conditions of the tipped molars.