• The korean journal of orthodontics
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• v.26 no.1 s.54
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• pp.105-111
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• 1996

Most of orthodontic cases are treated with extraction of certain teeth, which influence the pre-eruptive movement of the lower third molar The purpose of this study was to evaluate the positional change of lower third molar following orthodontic treatment. Pre- and post-treatment pantomograms of 163 orthodontic patients (77 nonextraction group, 78 first premolar- extraction group, 8 second molar- extraction group) were analyzed in terms of the mesiodistal and buccolingual angles of lower third molar. The results were as follows. 1. The change of the mesiodistal angle of lower third molar by orthodontic treatment was significant in second molar-extraction group. 2. The mesiodistal angle of lower third molar in pre-treatment was significantly correlated to the mesiodistal angle in post-treatment and/or the change of the mesiodistal angle by treatment. 3. The change of the buccolingual angle of lower third molar by orthodontic treatment was significant in non -extraction group or first premolar-extrction group. 4. The change of the buccolingual angle of lower third molar by treatment was significantly correlated to the mesiodistal angle in post-treatment, the change of the mesiodistal angle by treatment, the buccolingual angle in pre-treatment or the buccolingual angle in post-treatment.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.125-130
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• 2016

PURPOSE. The purpose of this study was to determine the effect of changes in the horizontal plane angle on the mesiodistal width ratios of the maxillary anterior teeth during the acquisition of frontal view photographs, derive these ratios for Korean adults on the basis of the data obtained, and analyze them using the Golden Proportion as a reference. MATERIALS AND METHODS. In experiment I, 30 plaster casts were mounted on an articulator and positioned on the angle-measuring device with a center setting of $0^{\circ}$. The device was rotated to $10^{\circ}$ in $1^{\circ}$ increments in a counterclockwise direction. At each angle, photographs were obtained and analyzed. Experiment II was based on 60 patients who visited the Department of Prosthodontics at Kyungpook National University Dental Hospital from February 2012 to February 2015. The patients were divided into three groups [Male (M), Female (F), Total (M + F)]. Frontal views were obtained for all groups and analyzed. RESULTS. From $1^{\circ}$ to $10^{\circ}$, the relative mesiodistal width ratios for the maxillary anterior teeth showed no significant differences from those at $0^{\circ}$. In all three groups, the relative width ratio of the maxillary central incisor was smaller than that specified in the Golden Proportion; the opposite was true for the canine. CONCLUSION. Our results suggest that the mesiodistal width ratios of the maxillary anterior teeth do not follow the Golden Proportion in Korean adults, and that a change in the horizontal plane angle from $1^{\circ}$ to $10^{\circ}$ during frontal photography does not affect these ratios.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.121-130
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• 1997

This study was aimed to help the construction of naturally dental prosthesis by investigation of the factors affecting on the attrition position and attrition angle of maxillary canines. Therefore 163 complete cast of maxillary and mandibular extracted from the student of K. college were subjected for this study, and result through the study are as follows. 1. None attrite rate of the maxillary canine was 7%, of examined teeth. 2. Throughout mesiodistal attrition of 1) Throughout mesiodistal attrition area of the maxillary canines showed that mesial area and mid area of cusp was more frequence in attrition than distal area of it. 2) Sex, dental arch type, vertical overlap, horizontal overlap, did not affect significantly to throughtout mesiodistal attrition statistically 3. Througout labiolingual attrition area 1) Throughout labiolingual attrition area of the maxillary canines showed that attrition of the from lingual to labioncisal edge was more frequence than it of linguoincisal edge 2) It showed that attrition of the from lingual to labioincisal edge was more frequence when the length of horizontal overlap is shorter, by horizontal overlap 3) The attrition of the from lingual to labioincisal edge in maxillary left canines showed that male was more frequence in attrition than female. 4) Dental arch type, vertical overlap, did not affect signioficantly to labiolingual attrition, statistically. 4. Attrition angle 1) It showed that average attrition angle of the maxillary right canines were $19{\pm}11.02$ dagree, and it of left canines were $18{\pm}11.83$ degree. 2) It showed that famale have a bigger attrition angle than male, by sex. 3) It showed that attrition angle was bigger when the length of horizontal ovelap is bigger, by horizontal overlap.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.391-403
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• 1993

For the purpose of investigating mesiodistal axial inclination of posterior teeth in normal occlusion group, open bite and deep bite group and investigating the correlationship between the axial inclination of posterior teeth and overbite of anterior teeth, a cephalometric study was performed on the subjects consisted of normal occlusion group(40), open bite group(71 : Angle's Class I, Class II, division 1 25, Class III 25) and deep bite group(64 : Angle's Class I 23, Class II, division 1 21, Class III 20). Mesiodistal axial inclination of posterior teeth to occlusal, mandibular and palatal plane were measured. The findings of this study were as follows : 1. Upper and lower posterior teeth were more mesially inclined to occlusal plane in open bite group than in deep bite group. 2. Lower posterior teeth were more mesially inclined in deep bite group than in open bite group in Angle's Class II, division 1 malocclusion but there were no significant differences in Angle's Class I and Class III malocclusion. 3. There was no significant correlationship between the axial inclination of posterior teeth to each plane and overbite of anterior teeth in open bite group. 4. There was a significant correlationship between the axial inclination of upeer and lower second premolar to occlusal plane and overbite of anterior teeth in Angle's Class I, Class II, division 1 and Class III malocclusion.

• Imaging Science in Dentistry
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• v.35 no.1
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• pp.25-31
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• 2005

Purpose : To evaluate the stability of the segmental occlusal plane and anatomical line as the reference line for measuring the mesiodistal tooth angulation in panoramic radiography and to determine the mean angle and the range of the mesiodistal tooth angulation in Korean population with normal occlusions. Materials and Methods : Twenty nine subjects (15 men, 14 women) with normal occlusion were selected. A total of 29 panoramic radiograms were taken at normal head position and then 10 images of 5 subjects selected were repeatedly taken with repositioning 2 times at each of the head down (V-shaped occlusion) and up (horizontal occlusion) for evaluation of stability of adopted reference lines by using PM2002CC (Planmeca, Finland). The images were traced with adoption of two test reference lines and the long axes of the teeth. The mesial angles formed by each reference line and the long axes of the teeth were measured and analyzed. Results : With anatomical reference line, the mesiodistal tooth angulations of the molars showed the significant difference by over 5 degree between the normal and each changed head position. With segmented occlusal reference line, deviations of mesiodistal tooth angulations by the two changed head positions were less than 1 degree. The means, standard deviations, and maximum and minimum values of mesiodistal tooth angulations to segmental occlusal reference line on panoramic radiography were determined. Conclusion : It would appear that mesiodistal tooth angulations to segmental occlusal plane as reference line in panograms are predictable as standards of normal occlusion and useful for evaluation of tooth arrangement between adjacent teeth.

• The korean journal of orthodontics
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• v.21 no.3
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• pp.673-683
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• 1991

This research was performed to find out the adaptation patterns of maxillary and mandibular posterior teeth to the changes in relationships of vertical skeletal components, which constitute the skeletofacial complex. For this research, 61 adult malocclusion patients were chosen as subjects according to the Hellman's dental age with normally ranged FMN-A-B angle. These subjects were divided into 4 groups in maxilla and 3 groups in mandible according to mesiodistal inclinations of teeth. Following results were obtained after studying the relationships of the vertical skeletal components between each group. 1. Inspire of the fact that the FMN-A-B angle was within a normal range, the degree of mesiodistal inclinations of maxillary and mandibular posterior teeth showed differences in relation to the anteroposterior relationships of maxilla and mandible. In case where the FMN-A-B angle was large, the mesial inclinations of maxillary posterior teeth showed more increase from the posterior to the anterior, whereas in mandible it showed overall decrease. 2. The degrees of mesial inclinations of mandibular posterior teeth were increased when the angulations of lower facial height, occlusal plane angle and mandibular plane angle were greater. 3. The patterns of mesial inclinations of maxillary posterior teeth were varied according to the angulation of lower facial height. If relatively large, it showed more increase from the posterior to the anterior and it was decreased nearly consistent when the angulation was small. 4. The degrees of mesial inclinations of maxillary posterior teeth were decreased as the lower facial height, palatal plane angle, occlusal plane angle and the mandibular plane angle became greater.

• Journal of Technologic Dentistry
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• v.18 no.1
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• pp.117-127
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• 1996

This study was aimed to help the construction of esthetic dental prosthesis by investigation of the factors affecting on the atterition position and attrition angle of maxillary lateral incisors. Therefore 197 complete cast of maxillary and mandibualar extracted form the student of K. college were subjected for this study, and result throught the study are as follows. 1. None attrite rate of the maxiilary right lateral incisors was about 16.2% and that of the maxillary left lateral incisors was about 32.4% of examined teeth. 2. Throught mesiodistal attrition area 1) It showed that right lateral incisors was the most frequence in attrition of mesial area of incisal edge, and left lateral incisors was the most frequence in attrition of mesial and mid area of incisal edge. 2) It showed that square type arch was more frequence in attrition of all incisal edge, and ovoid type arch was more frequence in the attrition of mid area of incisal edge, and ovoid type arch was more frequence in the attrition of mid area of incisal edge, and taper type arch was more frequence in the attrition of mesial area of incisal edge than it of average frequence of right lateral incisors, by dental arch type. 3) It showed that square type arch was more frequence in the attrition of all area and mid area of incisal edge, and ovoid type arch was more frequence in the attrition of mid area of incisal edge, and taper type arch was more frequence in the attrition of mesial and distal area of incisal edge than it of average frequence of left lateral incisal, by dental arch type. 4) Sex, vertical overlap, horizontal overlap, incisal guide angle, did not affect significantly to throughout mesiodistal attrition, statistically 3. Throughout labiolingual attrition quantity. 1) It showed that throughout labiolingual attrition quantity was more attrition in order of taper type arch < ovoid type arch < square type arch, by dental arch type. 2) It showed that throughout labiolingual attrition qauntity was more attrition when the length of horizontal overlap is shorter than it of other, by horizontal overlap. 3) Throughout labiolingual attrition quantity of right lateral incisors showed that male was more attrition than it of female. 4) Vertical overlap, incisal guide angle, sex on left lateral incisors did not affect significantly to throughout labiolingual attrition, statistically. 4. Attrition angle 1) It showed that average attrition anlge of right lateral incisors were $30{\pm}13.02$ degree, and it of left lateral incisors were $26{\pm}13.37$ degree. 2) It showed that taper type arch have a bigger attrition angle than it of average of lateral incisors, and square tape arch have a smaller attrition angle than it of average of lateral incisors, by dental arch type. 3) It showed that horizontal overlap of 2.1mm above have a bigger attrition angle than it of average, by horizontal overlap. 4) It showed that female have a bigger attrition angle it of male, by sex.

• The korean journal of orthodontics
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• v.50 no.4
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• pp.229-237
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• 2020

Objective: To evaluate the construction reproducibility of a composite tooth model (CTM) composed of an intraoral-scanned crown and a cone-beam computed tomography (CBCT)-scanned root. Methods: The study assessed 240 teeth (30 central incisors, 30 canines, 30 second premolars, and 30 first molars in the maxillary and mandibular arches) from 15 young adult patients whose pre-treatment intraoral scan and CBCT were available. Examiner-Reference (3 years' experience in CTM construction) and Examiners-A and Examiner-B (no experience) constructed the individual CTMs independently by performing the following steps: image acquisition and processing into a three-dimensional model, integration of intraoral-scanned crowns and CBCT-scanned teeth, and replacement of the CBCT-scanned crown with the intraoral-scanned crown. The tooth axis angle in terms of mesiodistal angulation and buccolingual inclination of the CTMs constructed by the three examiners were measured. To assess the construction reproducibility of CTMs, intraclass correlation coefficient (ICC) assessments were performed. Results: The ICC values of mesiodistal angulation and buccolingual inclination among the 3 examiners showed excellent agreement (0.950-0.992 and 0.965-0.993; 0.976-0.994 and 0.973-0.995 in the maxillary and mandibular arches, respectively). Conclusions: The CTM showed excellent construction reproducibility in mesiodistal angulation and buccolingual inclination regardless of the construction skill and experience levels of the examiners.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.21-32
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• 2010

The convergence angle of a prepared tooth is a very important factor in the retention and resistance of a crown restoration. But various intraoral environments and clinician's techniques make it difficult to obtain the ideal inclination. Therefore, in this study, clinical convergence angle of a prepared tooth was investigated. The data was collected from the patient models of prosthodontic residents and the patient models of general practitioners. The images of mesiodistal and buccolingual surfaces were taken with a digital camera to evaluate the convergence angle on 'ImageJ' program. The images were classified according to the criteria (1. Clinician group, 2. Position in the dental arch, 3. The purpose of abutment preparation)and then analyzed. The mean convergence angle of a prepared tooth for Korean clinicians was $15.02^{\circ}$ (${\pm}10.13^{\circ}$). 1. It was significant in the convergence angle between the general practitioner group and the prosthodontic resident group(p<0.05). 2. It was significant between the mesiodistal and buccolingual surface in the the prosthodontic resident group(p<0.05). 3. For the general practitioner group, it was significant when anteriors and premolars were compared with molars(p<0.05). For the prosthodontic resident group, it was significant when anteriors and premolars were compared with molars (p<0.05). 4. When divided into upper and lower arches, for the general practitioner group, it showed significant difference in the buccolingual aspect(p<0.05). Also in the prosthodontic resident group, it showed significant difference in the buccolingual aspect(p<0.05). 5. Dividing left and right sides of the arches, there was no significant difference in the general practitioner group and the prosthodontic resident group(p>0.05). 6. In the general practitioner group, it was significant in the mesiodistal axial convergence angle of single crown abutment and 3 unit bridge abutment(p<0.05). In the prosthodontic resident group, it was significant in the mesiodistal and overall axial convergence angle of single crown abutment and 3 unit bridge abutment(p<0.05). Clinical convergence angle of prepared tooth in Korea was included in agreement with other studies investigating convergence angle that ranged from 10 to 22 degrees, achieved in clinical practice.

• The korean journal of orthodontics
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• v.26 no.6
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• pp.657-666
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• 1996

Orthopantomogram is commonly used to evaluate root parallelism. "Good parallelism" between roots is widely accepted as one of the guidelines of a successful orthodontic treatment. In case there was a large angle between crown axis and root axis, and if we valued only the position of crown in establishing occlusal relationship without considering of the situation of root, the problem of root arrangement between adjacent teeth would be occurred. The estimate of root parallelism in mesiodistal direction before and after orthodontic treatment must be emphasized. The intent of this study was to determine the clinical importance and correlation of the angle between crown axis and root axis. Orthopantomograms of 105 orthodontic patients being treated in Yonsei university were used in this study. Twenty-eight teeth in both maxilla and mandible were selected and analyzed quantitively to evaluate the angle between crown axis and root axis, and obtain the correlationship among the individual teeth. The results are as follows: 1. Among the teeth presenting normal distribution, the maxillary right canine showed the largest mean value( $5.73{\pm}4.42^{\circ}$), which was composed of the crown-root angles, and the mandibular left lateral incisor showed the smallest mean value( $0.60{\pm}3.76^{\circ}$). 2. The crown-root angles of the maxillary incisors and the first molars, and the mandibular central incisors and the first molars didn't show normal distribution and the ranges of these angles were dispersed. 3. Significant differences were present between the crown axis and the root axis except for lower first premolars. (p<0.05) 4. No significant difference was present for the crown-root angle between right and left side, (p<0.05) 5. No significant difference was present for the crown-root angle between male and female except for lower left first premolar. (p<0.05) 6. In the upper right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine. In the upper left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor. In the lower right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, first molar and second molar. In the lower left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine, first molar and second molar. (p<0.05)