• 대한치과교정학회지
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• 제26권6호
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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)

• 대한치과교정학회지
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• 제52권6호
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• pp.432-438
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• 2022

Objective: To compare crown-root angulations of the permanent maxillary anterior teeth in skeletal Class I, Class II, and Class III Korean malocclusion patients using cone-bean computed tomography (CBCT) images. Methods: Sixty CBCT images were collected from orthodontic patients archive based on skeletal Class I (0˚< A point-nasion-B point angle [ANB] < 4˚), Class II (ANB ≥ 4˚), and Class III (ANB ≤ 0˚) to have 20 samples in each group. Mesiodistal crown-root angulation (MDCRA) and labiolingual crown-root angulation (LLCRA) were evaluated after orientation of images. Crown-root angulations were compared among Class I, Class II, and Class III groups and among the maxillary anterior teeth in each group. Results: LLCRAs of the maxillary central incisor and the lateral incisor were significantly lower in Class III group than those in Class I group. However, those of the canine showed no significant differences among groups. MDCRAs of the maxillary anterior teeth did not significantly differ among groups either. Conclusions: Our results suggest that skeletal Class III malocclusion might affect LLCRA of the maxillary incisors, especially the central incisor.

• 구강회복응용과학지
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• 제19권3호
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• pp.139-151
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• 2003

This study was to evaluate and to compare the compressive strength and the displacement effecting the abutment or the residual ridge which are transformed by the angle and the heights of the konus denture inner crown when restorating the unilateral konus denture by using the mandibular canine and the 1st premolar as an abutment. The author made 9 different models for different inner crown heights and konus angles. The inner crown height were divided to 5mm, 6mm, and 7mm and konus angles was divided to $4^{\circ}$, $6^{\circ}$, and $8^{\circ}$. And then in each model, 5kg of $15^{\circ}$ mesial load was stressed on the central fossa of the 1st premolar and the 1st molar. The stresses and displacement were measured using the finite element analysis. The results were as follows 1. The maximum compressive strength was shown on the connective area of the abutment and the denture base. 2. As the angle of the inner crown becomes increased, the compressive strength was shown smaller. 3. As the height of the inner crown becomes increased, the maximum compressive strength was shown smaller while the compressive strength of the root apex and the residual ridge showed larger. 4. When the stress was loaded only on the 1st premolar, the more compressive strength was concentrated on the root apex area of the 1st premolar. 5. When the stress was loaded only on the 1st premolar, the compressive strength was concentrated uniformly on the abutment and the residual ridge. 6. When the stress was loaded only on the 1st molar, the maximum displacement was shown on the distal part of the residual ridge.

• 대한치과교정학회지
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• 제25권4호
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• pp.453-463
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• 1995

측모두부 방사선 계측사진에서 일반적으로 사용하는 상악 중절치의 장축은 치근첨(Root Apex)과 절치단(Incisor Edge)를 연결한 선을 사용하지만 일부 부정교합 환자에서는 치관장축과 치근장축이 일치하지 않는 경우가 있으며 이 경우 두장축이 이루는 각을 치관-치근각도(Collum Angle)라 하며, 이 각도는 교정치료의 진단 및 치료과정에 고려되어져야 한다. 본 연구에서는 제 I 급 부정교합 환자 31명, 제 II급 1류 부정교합 환자 30명, 제 II 급 2류 부정교합 환자 31명, 제 III급 부정교합 환자 31명에서 치관-치근 각도를 계측하여 부정교합과의 상관관계를 알아보았으며, 측모두부 방사선 계측사진에서 사용되는 항목들과의 상관분석을 통하여 다음과 같은 결론을 얻었다. 1. 부정교합 분류에 따른 치관-치근 각도의 평균값은 제 I 급 부정교합에서는 $3.11^{\circ}{\pm}3.54^{\circ}$, 제 II급 1류 부정교합에서는 $1.23^{\circ}{\pm}2.41^{\circ}$, 제 II급 2류 부정교합에서는 $3.77^{\circ}{\pm}4.39^{\circ}$, 제 III급 부정교합에서는 $3.90^{\circ}{\pm}4.08^{\circ}$ 이었다. 2. 제 II급 1류 부정교합군의 치관-치근 각도와 제 II급 2류, 제 III급 부정교합군의 치관-치근 각도에 유의성 있는 차이가 나타났다. 3. 치관-치근 각도와 측모두부 방사선 계측사진에서 사용되는 다른 항목들과의 상관관계에서 제 I급 부정교합에서는 IMPA, 제 II급 1류 부정교합에서는 Wits, 제 II급 2류 부정교합과 제 III급 부정교합에서는 Overbite이 가장 큰 상관성을 보였다.

• 한국지반신소재학회논문집
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• 제15권2호
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• pp.13-24
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• 2016

얕은 토층의 무한사면 파괴가 예상되는 지역에서 안전율 계산에 영향을 주는 지역적 특징인 뿌리점착력을 고려하지 않은 무한사면 안전율은 뿌리점착력을 적용한 무한사면 안전율 보다 낮은 수치로 해석되는 경향이 있다. 따라서 합리적인 무한사면의 안전율을 계산하기 위하여 지역적 특징을 반영한 안전율 해석이 필요하다. 본 연구에서는 수목의 뿌리와 수관밀도가 무한사면의 안전율에 미치는 영향을 분석하기 위하여 기존 무한사면 안정해석 방법에 수관밀도를 고려한 뿌리 점착력 이론을 적용하여 안전율의 변화를 비교 분석하였다. 해석결과 뿌리점착력의 효과로 인하여 안전율이 증가하지만, 사면의 경사에 따라서 안전율의 증가량이 다른 것으로 분석 되었으며, 뿌리점착력의 보강 효과는 완만한 경사의 사면일수록 커지는 것으로 나타났다.

• 대한치과교정학회지
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• 제50권4호
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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.

• 한국지반환경공학회 논문집
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• 제17권6호
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• pp.13-21
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• 2016

기존의 토사재해 위험지역 예측은 토질특성과 경사만으로 분석되기 때문에 지역적 특징이 반영되어 있지 않다. 따라서 보다 합리적인 위험지 예측 분석을 위하여 해당지역의 특징을 반영한 토사재해 위험지 예측을 할 필요가 있다. 토사재해 위험지의 특징 중 하나인 수목의 뿌리는 토사 내 점착력을 증가시키는 작용을 하는 것으로 연구되어 왔으며, 수목의 종류에 따라 그 영향이 다른 것으로 알려져 있다. 또한, 지역에 따라 수목의 밀집 정도(수관밀도)가 다양하기 때문에 실제 수목의 분포를 고려하여 토사재해 위험지역 예측을 한다면 보다 합리적인 위험지 예측이 가능할 것이다. 본 연구에서는 세종시 괴화산 일대를 중심으로 수목의 수관밀도를 고려한 뿌리점착력을 사용하여 토사재해 위험지역 예측을 하였으며, 뿌리점착력을 적용하지 않은 토사재해 위험지역 예측 결과와 비교하였다.

• The Journal of Advanced Prosthodontics
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• 제13권5호
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• pp.333-342
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• 2021

PURPOSE. To evaluate the impact of five different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium (CoCr) crowns produced by computer-aided designing (CAD) and selective laser melting (SLM) processes. MATERIALS AND METHODS. Five preparation data were constructed, after which design crowns were obtained. Actual crowns were fabricated using an SLM process. After the data of actual crowns were obtained with structural light scanning, intaglio surfaces of the design crown and actual crown were virtually superimposed on the preparation. The fit-discrepancies were displayed with colors, while the root means square was calculated and analyzed with one-way analysis of variance (ANOVA), Tukey's test or Kruskal-Wallis test (α = .05). RESULTS. The marginal or internal color-coded images in the five design groups were not identical. The shoulder-lip and sharp line angle groups in the CAD or SLM process had larger marginal or internal fit discrepancies compared to other groups (P < .05). In the CAD process, the mean marginal and internal fit discrepancies were 10.0 to 24.2 ㎛ and 29.6 to 31.4 ㎛, respectively. After the CAD and SLM processes, the mean marginal and internal fit discrepancies were 18.4 to 40.9 ㎛ and 39.1 to 47.1 ㎛, respectively. The SLM process itself resulted in a positive increase of the marginal (6.0 - 16.7 ㎛) and internal (9.0 - 15.7 ㎛) fit discrepancies. CONCLUSION. The CAD and SLM processes affected the fit of CoCr crowns and varied based on the preparation designs. Typically, the shoulder-lip and sharp line angle designs had a more significant effect on crown fit. However, the differences between the design groups were relatively small, especially when compared to fit discrepancies observed clinically.

• 대한치과보철학회지
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• 제34권4호
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• pp.780-790
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• 1996

The endodontically treated tooth is generally restored with post and core, owing to the brittleness and the loss of large amount of tooth structure. Although there have been lots of studies about the endodontically treated teeth, the three-dimensional quantitative studies about the stress distribution of them are in rare cases. In this study, it was assumed that the coronal portion of the upper incisor had extensively damaged. After the root canal therapy it was post cored, and restored with PFG crown. The three-dimensional model, in which the root was supported with a normal alveolar bone, was constructed. Force was applied to the centric stop point with the angle of 135 degrees to the long axis of the tooth. Force was assumed to be 250N as functional maximum bite force of upper central incisors. The results analyzed with three-dimensional finite element method were as follows : 1. Stress was concentrated on the middle portion of the labial side dentin and the apical portion of the dentin. 2. Stress in the post was more concentrated on the post apex. 3. The displacement of the post at the post-cement interface was almost symmetrical la-bio-lingually. 4. It assumed that restoring extensively damaged tooth with a post-core and PFG crown is an adequate method of restoration.

• 대한치과교정학회지
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• 제49권3호
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• pp.161-169
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• 2019

Objective: To evaluate the effectiveness of the Frog appliance in three dimensions by using cone-beam computed tomography (CBCT) images. Methods: Forty patients (21 boys and 19 girls), averaged 11.7 years old, with an Angle Class II division 1 malocclusion were included in our study. They had either late mixed dentition or early permanent dentition, and the maxillary second molars had not yet erupted. All patients underwent CBCT before and after the treatment for measuring changes in the maxillary first molars, second premolars, central incisors, and profile. Paired-samples t-test was used to compare the mean difference in each variable before treatment and after the first phase of treatment. Results: The maxillary first molars were effectively distalized by 4.25 mm (p < 0.001) and 3.53 mm (p < 0.05) in the dental crown and root apex, respectively. The tipping increased by $2.25^{\circ}$, but the difference was not significant. Moreover the teeth moved buccally by 0.84 mm (p < 0.05) and 2.87 mm (p < 0.01) in the mesiobuccal and distobuccal cusps, respectively, whereas no significant changes occurred in the root apex. Regarding the anchorage parts, the angle of the maxillary central incisor's long axis to the sella-nasion plane increased by $2.76^{\circ}$ (p < 0.05) and the distance from the upper lip to the esthetic plane decreased by 0.52 mm (p = 0.01). Conclusions: The Frog appliance effectively distalized the maxillary molars with an acceptable degree of tipping, distobuccal rotation, and buccal crown torque, with only slight anchorage loss. Furthermore, CBCT image demonstrated that it is a simple and reliable method for three-dimensional analysis.