• 대한치과교정학회지
• /
• 제24권3호
• /
• pp.649-658
• /
• 1994

The purpose of this study was to evaluate the association between incisor root resolution and sex, age, extraction, the magnitude and direction of tooth movement. The sample consisted of 189 randomly selected orthodontic patients, receiving standard edgewise orthodontic treatment in three private orthodontic onces at San Francisco. Pre-treatment and post-treatment periapicals and cephalometric radiographs were digitized. Measurements and superimpositions were made utilizing a computerized cephalometric analysis program. The variables were statistically analyzed. The results were as follows: 1. Mean apical root resorption values were $0.77{\pm}2.08mm$ for upper right central incisor, $0.88{\pm}2.11mm$ for upper left central incisor, $-0.05{\pm}2.09mm$ for lower right central incisor and $0.11{\pm}1.85mm$ for lower left central incisor. Apical root resorption of upper incisor was greater than lowers. 2. No correlation was found between sex and apical root resorption. 3. Apical root resorptions in adolescents were smaller than those in adults. 4. Apical root resorption was not affected by extraction. 5. Apical root resorption values of upper incisor were correlated to the horizontal and vertical movement of apex; Apical root resorption values of lower incisor were correlated to the vertical movement of apex.

• 대한치과교정학회지
• /
• 제20권2호
• /
• pp.227-245
• /
• 1990

The purpose of this study was to analyze the reorganization of periodontal ligament after collagenase treatment with autoradiography. The author compared the collagenase-treated experimental group and no-treated experimental group with control group. Fourty eight Sprague-Dawley rats were divided into nine groups, including normal control and immediate group. Closed coil springs were used between the upper incisors and the first molars with 100 grams. Collagenase and $^3H-proline$ were adminstered and the samples were sacrificed and sectioned. After being dipped into the NTB-3 emulsion the samples were analyzed with light microscope under H/E stain. Data were analyzed by t-test and ANOVA. The results were as follows: 1) Generally collagenase-treated groups got more $^3H-proline$ uptake than no-treated groups. 2) Compared with normal control group, collagenase-treated group had the same $^3H-proline$ uptake in amount at 21th day. 3) Among cemento-enamel junction, middle, apex areas, cementa-enamel junction area of collagenase-treated group arrived at normal control level earlier than no-treated group. 4) Cemento-enamel junction area had the most $^3H-proline$ incorporation amount in no-treated group, but apex area had the most in collagenase group.

• Imaging Science in Dentistry
• /
• 제50권3호
• /
• pp.183-192
• /
• 2020

Purpose: This study was performed to assess the accuracy of preoperative cone-beam computed tomography (CBCT), when justified for other reasons, in locating the apical foramen and establishing the working length. Materials and Methods: Six electronic databases were searched for studies on this subject. All studies, of any type, were included if they compared measurements of working length with preoperative CBCT to measurements using an electronic apex locator (EAL) or histological reference standard. Due to the high levels of heterogeneity, an inverse-variance random-effects model was chosen, and weighted mean differences were obtained with 95% confidence intervals and P values. Results: Nine studies were included. Compared to a histological reference standard, CBCT indicated that the apical foramen was on average 0.40 mm coronal of its histological position, with a mean absolute difference of 0.48 mm. Comparisons were also performed to an EAL reference standard, but the conclusions could not be considered robust due to high levels of heterogeneity in the results. Conclusion: A low level of evidence is produced suggesting that preoperative CBCT shows the apical foramen to be on average 0.40 mm coronal to its histological position, with a mean absolute difference of 0.48 mm.

• Restorative Dentistry and Endodontics
• /
• 제43권1호
• /
• pp.2.1-2.10
• /
• 2018

Objectives: To determine the effect of size and insertion depth of irrigation needle on the amount of apical extruded debris and the amount of penetration depth of sealer using a confocal laser scanning microscope (CLSM). Materials and Methods: Twenty maxillary premolars were assigned to 2 groups (n = 10), according to the size of needle tip, 28 G or 30 G. Buccal roots of samples were irrigated with respective needle type inserted 1 mm short of the working length (WL), while palatal roots were irrigated with respective needle type inserted 3 mm short of the WL. Prepared teeth were removed from the pre-weighed Eppendorf tubes. Canals were filled with F3 gutta-percha cone and rhodamine B dye-labeled AH 26 sealer. Teeth were transversally sectioned at 1 and 3 mm levels from the apex and observed under a CLSM. Eppendorf tubes were incubated to evaporate the irrigant and were weighed again. The difference between pre- and post-weights was calculated, and statistical evaluation was performed. Results: Inserting needles closer to the apex and using needles with wider diameters were associated with significantly more debris extrusion (p < 0.05). The position of needles and level of sections had statistically significant effects on sealer penetration depth (p < 0.05 for both). Conclusions: Following preparation, inserting narrower needles compatible with the final apical diameter of the prepared root canal at 3 mm short of WL during final irrigation might prevent debris extrusion and improve sealer penetration in the apical third.

• 대한치과교정학회지
• /
• 제52권1호
• /
• pp.42-52
• /
• 2022

Objective: This study compared soft tissue changes after extraction of the four premolars followed by maximum retraction of the anterior teeth according to the type of anterior teeth movement: tipping and translation. Methods: Patients who had undergone orthodontic treatment involving the extraction of four premolars were retrospectively selected and divided into either the tipping (n = 27) or translation (n = 26) groups based on the retraction of the incisor root apex and the axis changes of the incisors during the treatment period. Lateral pre- and post-treatment cephalograms were analyzed. Results: There were no significant differences between the tipping and translation groups before treatment. The retraction amounts of the root apex of the upper and lower incisors in the tipping group were 0.33 and 0.26 mm, respectively, and 5.02 and 5.31 mm, respectively, in the translation group (p < 0.001). The posterior movements of soft tissue points A and B in the tipping group were 0.61 and 1.25 mm, respectively, and 1.10 and 3.25 mm, respectively, in the translation group (p < 0.01). The mentolabial sulcus angle increased by 5.89° in the tipping group, whereas it decreased by 8.13° in the translation group (p < 0.001). Conclusions: An increased amount of retraction of the incisor root apex led to the increased posterior movement of soft tissue points A and B, and this appeared more distinct in cases involving the lower incisor and lower lip.

• 대한소아치과학회지
• /
• 제27권4호
• /
• pp.564-572
• /
• 2000

치아매복에 의한 미맹출시 치아 매복의 방향과 위치 치근단의 완성정도, 맹출공간의 존재여부, 매복치 주변에 과잉치, 치아종, 낭종 등의 존재여부 등에 따라 발치, 교정적 견인, 외과적 자가이식중 어떤 술식을 시행할 것인지 결정하게 된다. 자가 치아이식은 치아의 위치가 교정력을 가할 수 없는 위치에 존재하거나 치아이동이 제한을 받게 되어 통상적인 치료가 불가능할 경우에 발거에 앞서 고려할 수 있다. 자가치아이식의 예후는 치근의 완성도, 외과적 시술능력 환자의 나이, 근관치료, 고정기간과 형태, 치주인대의 보존, 저장 방법 등에 영향을 받는다. 특히 이식 수여부의 골의 결손이 너무 클 경우 치아의 동요도를 감소시키고 골치유를 빠르게 하기위해 골이식을 고려할 수 있다. 치아 미맹출을 주소로 본원에 내원한 증례들로 상악과 하악의 여러 부위에서 과잉치, 치아종, 이소맹출 등의 다양한 원인요소들이 발견되었다. 자가치아이식전 필요시 공간확보를 행하고, 과잉치 및 치아종의 발거로 인해 골결손이 클 때, 탈회냉동건조골과 자가골 이식을 시행하였다. 치아고정은 $2\sim3$주정도 시행하고 $3\sim4$주 후 방사선적 검사와 임상검사후 근과치료의 필요성을 결정하고 정기적인 검사를 시행한 결과 치근흡수소견 등의 비정상적인 소견은 보이지 않고 정상적인 치유소견을 관찰할 수 있었다.

• 대한치과보철학회지
• /
• 제31권4호
• /
• pp.580-610
• /
• 1993

The purpose of this study was to analyse the deflection and stress distribution at the supporting bone and it's superstructure by the alteration of angulation between implant and it's implant abutment. For this study, the free-end saddle case of mandibular first and second molar missing would be planned to restore with fixed prosthesis. So the mandibular second premolar was prepared for abutment, and the cylinder type osseointegrated implant was placed at the site of mandibular second molar for abutment. The finite element stress analysis was applied for this study. 13 two-dimensional FEM models were created, a standard model at $0^{\circ}$ and 12 models created by changing the angulation between implant and implant abutment as increasing the angulation mesially and distally with $5^{\circ}$ unittill $30^{\circ}$. The preprocessing decording, solving and postprocessing procedures were done by using FEM analysis software PATRAN and SUN-SPARC2GX. The deflections and von Mises stresses were calculated under concentrated load (load 1) and distributed load(load 2) at the reference points. The results were as follows : 1. Observing at standard model, the amount of total deflection at the distobuccal cusp-tip of pontic under concentrated load was largest of all, and that at the apex of implant was least of all, and the amount of total deflection at the buccal cusp-tip of second premolar under distributed load was largest of all, and that at the apex of implant was least of all. 2. Increasing the angulation mesially or distally, the amounts of total deflection were increased or decreased according to the reference points. But the order according to the amount of total deflection was not changed except apex of second premolar and central fossa of implant abutment under concentrated load during distal inclination. 3. Observing at standard model, the von Mises stress at the distal joint of pontic under concentrated load was largest of all, and that at the apex of implant was least of all. The von Mises stress at the distal margin of second premolar under distributed load was largest of all, and that at the apex of Implant was least of ail. 4. Increasing the angulation of implant mesially, the von Mises stresses at the mesial crest of implant were increased under concentrated load and distributed load, but those were increased remarkably under distributed load and so that at $30^{\circ}$ mesial inclination was largest of all. 5. Increasing the angulation of implant distally, the von Mises stresses at the distal crest of implant were increased remarkably under concentrated load and distributed load, and so those at $30^{\circ}$ distal inclination were largest of all.

• 대한치과보철학회지
• /
• 제35권4호
• /
• pp.674-696
• /
• 1997

There're many cases that should be reconstructed with post and core when clinical crown is destructed. But this post and core restoration may cause damaging stress on the teeth. Previous finite element study was restricted to normal bone model relatively close to cemen-toenamel junction. Moreover, the test of a model with diminished bone support was rare. The purpose of this study is to test the effects of alveolar bone loss on the magnitude, stress distribution and displacement of post reconstructed teeth. In this study, it was assumed that the coronal portion of upper incisor was severely destructed. After conventional endodontic treatment, it was restored with post and core. The PFM restoration was made on it. This crown was cemented with ZPC. Alveolar bone was classified by 4 types of bone, such as normal, 2 mm, 4 mm, 6 mm bone, according to the bone loss. Meanwhile, the material of post are divided into 2 types of materials, such as gold, co-cr. Force was applied to two directions. One was fuctional maximum bite force (300 N) applied to the spot just lingual to the incisal edge with the angle of 45 degree to the long axis of the tooth, and the other one was horizontal force (300 N) applied to the labial surface. The results analyzed with three dimensional finite element method were as follows : 1. Stress was concentrated on the adjacent dentin of the post apex, one third portion of the post apex and the labial & lingual mid-portion of the root in all case. The stress of middle third of the root was apparently concentrated on the labial aspect. 2. The stress on adjacent dentin of the post apex and one third of the post apex increased as alveolar bone height moved apically. This increase was dramatic beyond 4 mm bone loss model. 3. The stress of the post apex was spreaded to the middle third of the post and greater than gold post in the case of metal post. 4. The displacement of the neck of post was the greatest in one of the post-cement interface and this increased as alveolar bone height moved apically. Besides the displacement of the metal post is slightly lower than one of the gold post.

• Journal of Periodontal and Implant Science
• /
• 제34권1호
• /
• pp.19-28
• /
• 2004

Tooth is the most important element in esthetic consideration on facial area. Tooth alignment which is in harmony with gingiva, lips, and face is also key element. The purpose of this study was to give a clinical discipline for restoration of gingival contour, which contains a ratio of maxillary 6 anterior teeth, research for gingival contour etc., in case of rehabilitation of maxillary anterior teeth. 300 Dankook university dental school students ,who is their twenties and free from periodontitis, participate in this study. The result was from each 70 males and females who had normal occlusion and tooth alignment. Length, width and length/width ratio of maxillary 6 anterior teeth were 0.74-0.81 in male, 0.81-0.84 in female. There was significant difference between male and female. The most deepest position of gingiva in maxillary central incisor and canine was located in distal part of teeth and maxillary lateral incisor was middle portion. In maxillary central incisors, gingival line of the most deepest point appeared significant difference between male and female (p<0.01) whereas there was no difference in lateral incisors and canines. Distance between interdental papilla apex and the most deepest portion appeared significant difference between male and female. Distance of the deepest position of gingiva is statistically significant except maxillary central incisors and lateral incisors. Standard deviation and mean of the width of labio-lingual were measured in cervical area and there was a significant difference both male and female.(p<0.01) From this result, we could get the mean of maxillary anterior gingival line and these results have great value in clinical guidance in studying maxillary anterior teeth.

• 대한소아치과학회지
• /
• 제33권4호
• /
• pp.704-709
• /
• 2006

이소맹출은 발육과정 중 그 발생지에서의 정상적 맹출 경로에서 벗어난 치아의 맹출을 의미한다. 이소맹출의 극단적인 형태로 전위가 있는데 이것은 두 치아의 위치가 서로 바뀐 것이다. 이러한 이소맹출 및 전위된 치아의 치료는 치아가 맹출되는 방향, 치근단의 완성정도, 맹출공간의 존재여부 등에 따라 단순한 관찰에서 외과적 노출 후 교정적 견인까지 매우 다양하며, 위치 이상이 심한 경우에는 외과적 자가이식이나 발치를 고려할 수 있다. 이중 자가치아이식은 치아를 구강내의 한 위치에서 다른 발치와나 외과적으로 형성된 치조와로 이동시키는 술식으로, 치아가 교정력을 가할 수 없는 위치에 존재하거나 치아 이동에 제한이 있어 통상적인 치료가 불가능할 경우 발거에 앞서 고려할 수 있는 술식이다. 본 증례들은 교정적 견인 및 배열이 어렵다고 판단되는 이소맹출하는 상악 측절치와 상악 견치를 자가이식함으로써 심미적, 기능적으로 양호한 결과를 얻을 수 있었다.