• Restorative Dentistry and Endodontics
• /
• v.26 no.6
• /
• pp.464-484
• /
• 2001

When restoring a tooth, the dentist tries to choose the ideal material for existing situation. One criterion that is considered is its suitability for restoring coronal strength. As more tooth structure is removed, the cusps are weakened and susceptible to fracture. Further, this increased deformation may cause the formation of intermittent gaps at the margin between the hard tissue and the restoration, facilitating marginal leakage. The improvements in ceramic materials now make it possible for alternatives to amalgams, composites, and cast metal to be of offered for posterior teeth. Of the materials used, ceramics most closely approximates the properties of enamel. The introduction of computer-aided design/computer-aided manufacture(CAD/CAM) systems to restorative dentistry represents a major technological breakthrough. It is possible to design and fabricate ceramic restorations at a single appointment. Additionally, CAD/CAM systems eliminate certain errors and inaccuracies that are inherent to the indirect method and provide an esthetic restoration. The aim of this investigation was to study the loading characteristics of CAD/CAM ceramic inlay and to compare the stress distribution and displacement associated with different designs of cavity(the isthmus width and cavity depth). A human maxillary left first premolar was prepared with standard mesio-occlusal cavity preparation, as recommended by the manufacturer Ceramic inlay was fabricated with CEREC 2 CAD/CIM equipment and cemented into the prepared cavity. Three dimensional model was made by the serial photographic method. The cavity width was varied $\frac{1}{3}$, $\frac{1}{2}$ and $\frac{2}{3}$ of intercuspal distance between buccal and lingual cusp tip. The cavity depth was varied 1.5mm and 2.3mm. So six models were constructed to simulate six conditions. A point load of 500N was applied vertically onto the first node of the lingual slope from the buccal cusp tip. The stress distribution and displacement were solved using ANSYS finite element program(Swanson Analysis System). (omitted)

• The korean journal of orthodontics
• /
• v.46 no.5
• /
• pp.310-322
• /
• 2016

Objective: The aim of this study was to determine the optimal loading conditions for pure intrusion of the six maxillary anterior teeth with miniscrews according to alveolar bone loss. Methods: A three-dimensional finite element model was created for a segment of the six anterior teeth, and the positions of the miniscrews and hooks were varied after setting the alveolar bone loss to 0, 2, or 4 mm. Under 100 g of intrusive force, initial displacement of the individual teeth in three directions and the degree of labial tilting were measured. Results: The degree of labial tilting increased with reduced alveolar bone height under the same load. When a miniscrew was inserted between the two central incisors, the amounts of medial-lateral and anterior-posterior displacement of the central incisor were significantly greater than in the other conditions. When the miniscrews were inserted distally to the canines and an intrusion force was applied distal to the lateral incisors, the degree of labial tilting and the amounts of displacement of the six anterior teeth were the lowest, and the maximum von Mises stress was distributed evenly across all the teeth, regardless of the bone loss. Conclusions: Initial tooth displacement similar to pure intrusion of the six maxillary anterior teeth was induced when miniscrews were inserted distal to the maxillary canines and an intrusion force was applied distal to the lateral incisors. In this condition, the maximum von Mises stresses were relatively evenly distributed across all the teeth, regardless of the bone loss.

• The korean journal of orthodontics
• /
• v.38 no.1
• /
• pp.13-30
• /
• 2008

Objective: The objective of this study was to evaluate the displacement pattern and the stress distribution of the finite element model 3-D visualization during symphyseal widening according to the osteotomy position, osteotomy type, and distraction device. Methods: The kinds of distraction devices used were tooth-borne type, hybrid type, bone-borne type and tooth-borne type $30^{\circ}$ angulated, and the kinds of osteotomy design were vertical osteotomy line between the central incisors and step osteotomy line through the symphysis. Results: All reference points of the mandible including the condyles were displaced laterally irrespective of the osteotomy position, osteotomy method and distraction device. The anteroposterior or vertical displacements showed small differences between the groups. The widening pattern of the osteotomy line in the tooth-borne type of device was v shaped, and that of bone-borne type was a reverse v shape. However, the pattern in the hybrid type was parallel. The lateral displacement of the mandibular angle by the bone-borne device was more remarkable than the other types of devices. The displacement by the $30^{\circ}$ angulated tooth-borne type was different between the left and right sides in both the transverse and anteroposterior aspects. Conclusion: The design of the distraction devices and osteotomy line can influence the displacement pattern and the stress distribution during mandibular symphyseal distraction osteogenesis procedures.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.38 no.1
• /
• pp.62-67
• /
• 2011

Early eruption refers to an accelerated eruption of a tooth beyond the normal eruption period. The clinical findings of an early erupted tooth with little formation of crown and/or root include severe mobility, pain on chewing, hypocalcification of the enamel, and inclination, displacement, and rotation of the tooth. The radiographic findings include underdeveloped root and insufficient bone support. Early eruption of a permanent tooth can cause several complications such as chronic trauma, pain, edema, an increased rate of premolar impaction and tooth displacement and/or rotation. Therefore, when a permanent tooth erupts earlier than its normal eruption period with accompanying symptoms, appropriate treatments should be done as soon as possible. A female patient of age 7 without any systemic disease was referred from a local dental clinic with chief complaint of severe mobilities and pain in both upper first premolars. According to the clinical and radiographic examinations, the permanent teeth erupted earlier with barely formed roots, severe mobilities, edema, and pain. This case is to report the successful accomplishment of root formations and stabilization of teeth after applying intraoral fixed appliances using bands and spurs for 14 months.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.5
• /
• pp.34-42
• /
• 2008

• Journal of the korean academy of Pediatric Dentistry
• /
• v.40 no.1
• /
• pp.53-59
• /
• 2013

In an intra-alveolar root fracture (IARF) of a primary tooth with severe mobility and displacement, extraction and periodic-follow-up is the choice of recommended treatments because of the fear of aspiration of the mobile tooth and the possibility of damage in the permanent succeeding tooth. However, repositioning and splinting are presented as a fresh proposal recently. In case of extracting a primary incisor, many problems occur; esthetic problems; functional problems such as pronunciation and mastication; space loss; and psychological and social problems. Therefore, the best treatment is conservation of the primary tooth. The aim of this report was to suggest the conservative treatment of an Intra-alveolar root fracture of the primary central incisors with severe mobility and displacement based on two cases that describe the diagnoses, treatments and follow-ups (mean period: 27-month). All cases have been treated by reduction and immobilization by resin wire splint (RWS) (mean period: 6-week). Both cases were followed up until the successors were erupted. There have been no complications such as pain, pulp necrosis, periapical lesion, displacement of permanent tooth germ, eruption disturbance and etc.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.25 no.2
• /
• pp.399-408
• /
• 1995

The purpose of this study was to obtain information on the clinical and radiographic features of the dentigerous cysts in the jaws. For this study, the authors examined and analysed the clinical records and radiographs of 233 patients who had lesions of dentigerous cyst diagnosed by clinical and radiographic or histopathological examinations. And the obtained results were as follows: 1. Dentigerous cysts occurred the most frequently in the 2nd decade(38.2％) and occurred more frequently in males(67.4％) than in females(32.6％). 2. The most common clinical symptom was swelling of the jaw(33.9％), and the lesions were treated by the method of surgical removal. 3. The type of lesions was mainly observed as central type(72.5％), and size of the lesion was most frequently observed 2 - 2.9cm in the widest length. 4. The lesions were most frequently observed well-defined outline with hyperostotic border(49.8％), and smooth margin(73.4％), and homogeneous lesional radiolucency(79.4％). 5. Cortical thinning and expansion of the lesions(82.0％) were observed, and their direction were most frequently observed toward buccal side(64.0％). 6. The effect on the causative tooth were observed as tooth displacement(41.2％) and delayed root development(l9.3％), and the distance between cemento-enamel junction and lesional wall attachment of the causative tooth was mainly observed as below 2mm(79.6％). 7. The effect on the adjacent tooth were observed as loss of lamina dura(66.8％), root resorption(33.9％), and tooth displacement(31.5％). 8. The effects on the adjacent anatomic structures were observed as displacement of the mandibular canal(46.5％) and maxillary sinus or nasal cavity(72.2％).

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.24 no.1
• /
• pp.95-105
• /
• 1994

The aim of this study was to evaluate the clinical, radiographic and histopathologic features of 23 cases of solitary bone cyst by means of the analysis of radiographs and biopsy specimens in 23 persons visited the Department of Oral and Maxillofacial Radiology, School of Dentistry, Kyung Hee University and Chunbuk National University. The obtained results were as follows; 1. The incidence of solitary bone cyst was almost equal in males(52.2%) and in females(47.8%) and the prevalent age of the solitary bone cyst were the second decade(47.8%) and the third decade (21.7%). 2. In the signs and symptoms of solitary bone cyst, pain or tenderness revealed in 17.4%, swelling revealed in 13.0%, pain and swelling revealed in 21.7%, paresthesia revealed in 4.4% and 43.5% were asymptom and the tooth vitality involved in the solitary bone cyst, 76.5% were positive and 23.5% were either positive or negative. 3. In the location of the solitary bone cyst, 47.8% present posterior region, 21.7% present anterior region, 21.6% present anterior and posterior region, 4.4% present condylar process area. 4. In the hyperostotic border of the solitary bone cyst, 47.8% were seen entirely, 21.8% were seen partialy, and 30.4% were not seen. 5. In the change of tooth, 59.1% were intact, 18.2% were loss of the alveolar lamina dura, 13.6% were root resorption 4.55% were tooth displacement, 4.55% were root resorption and tooth displacement. 6. In the change of cortical bone of the solitary bone cyst, 39.1% were intact and 60.9% were thinning and expansion of cortical bone. 7. In the histopathologic findings of 9 cases, 33.3% were thin connective tissue wall, 11.1% were thickened myxofibromatous wall, 55.6% were thickened myxofibromatous wall with dysplastic bone formation.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.23 no.2
• /
• pp.255-264
• /
• 1993

The purpose of this study was to obtain some informations for the radiographic differential diagnosis between dentigerous cysts and unicystic ameloblastomas in the mandible. The authors observed and compared the clinico-radiographic features of 38 cases of dentigerous cyst and 32 cases of unicystic ameloblastoma associated with impacted mandibular molar. The obtained results were as follows: Dentigerous cysts occurred the most frequently in the 3rd decade, but unicystic ameloblastomas in the 2nd decade, and both lesions occurred with slight predilection in males. Average of lesional size of unicystic ameloblastomas was larger than that of dentigerous cysts, and lesions of over 25㎠ were only in unicystic ameloblastomas. Cortical thinning and expansion were more frequently observed in unicystic ameloblastomas at 72.9% than in dentigerous cysts at 15.8%. Dentigerous cysts showed smooth border at 89.5%, but unicystic ameloblastomas showed smooth border at 53.1% and scalloped border at 46.9%. Dentigerous cysts showed well-defined outline at 81.6%, but unicystic ameloblastomas showed well-defined outline at 53.1% and moderate-defined outline at 46.9%. In both lesions, the mandibular 3rd molar was the most frequent causative tooth. Average of distance between the cemento-enamel junction and lesional wall attachment of the causative tooth was longer in unicystic ameloblastomas than in dentigerous cysts. Severe displacement of causative tooth was more frequent in unicystic ameloblastomas at 62.5% than in dentigerous cysts at 23.7%. Dentigerous cysts showed homogeneous lesional radiolucency at 89.5%, but unicystic ameloblastomas showed inhomogeneous lesional radiolucency at 53.1%. Root resorption of adjacent tooth and displacement of mandibular canal were more frequent in unicystic ameloblastomas at 65.2% and 61.5% than in dentigerous cysts at 15.8% and 38.1% respectively.

• The Journal of Korean Academy of Prosthodontics
• /
• v.34 no.4
• /
• pp.780-790
• /
• 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.