• Journal of the Korea Society of Computer and Information
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• v.23 no.3
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• pp.17-23
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• 2018

In this paper, we propose the automatic detection method which find the middle part of tooth crown to start individual tooth segmentation. There have been many studies on the automation of individual tooth segmentation, but there are still many problems for full automation. Detection of middle part of tooth crown used as initial information for individual tooth segmentation is closely related to performance, but most studies are based on the assumption that they are already known or they can be represented by using a straight line. In this study, we have found that the jawbone curve is similar to the tooth alignment curve by spatially analyzing the CT image, and propose a method to automatically detect the middle part of tooth crown. The proposed method successfully uses the jawbone curves to successfully create a tooth alignment curve that is difficult to detect. As the middle part of tooth crown is in the form of a tooth alignment curve, the proposed method detects the middle part of tooth crown successfully. It has also been verified by experiments that the proposed method works well on real dental CT images.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.290-300
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• 1995

Tooth mobility is one of the most important clinical parameters in examination, diagnosis, prognosis and treatment planning procedure. In order to determine the differences of tooth mobility according to radiographical bone level, clinical root length, clinical crown/root ratio, and bleeding on probing, 90 male adults with periodontal disease and 10 male adults with periodontal health($25{\sim}45$ years old) were selected through clinical examinations including occlusal relationship, probing depth, attachment level, and bleeding on probing. On the mandibular anterior teeth, standard periapical radiographs were taken, and tooth mobility was measured by Periotest(Siemens Co., Germany). The radiographic bone level of individual tooth was evaluated as coronal 1/3, middle 1/3, and apical 1/3 to anatomical root length, and clinical crown length from incisal edge to bone level and clinical root length from bone level to root apex were measured with Boley gauge, and subsquently clinical crown/root ratio was calculated. The difference of tooth mobility(Periotest value) according to radiographical bone level, clinical root length, clinical crown/root ratio, and bleeding on probing was statistically analyzed by unpaired Student t-test. Tooth mobility was significantly higher in bleeding group than non-bleeding group on probing in the teeth radiographic bone level of middle 1/3, with clinical root length longer than 6mm, and with clinical crown/root ratio over 0.3(p<0.01). But there was no statistical difference in tooth mobility between bleeding group and non-bleeding group on probing in the teeth with radiographic bone level of apical 1/3, with short clinical root length less than 5mm, and with clinical crown/root ratio under 0.2(p>0.05). The results note that the tooth mobility depends on clinical root length, clinical crown/root ratio and gingival inflammation, and in the teeth with relatively good alveolar bone support gingival inflammation is one of the most important factors that affect tooth mobility.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.10 no.2
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• pp.84-88
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• 2014

Traditional method of pulpectomy for a necrotic primary anterior tooth was done on lingual side. But it could not recover the discoloration of crown effectively. For the purpose of treating the discoloration of crown after lingual pulpectomy, additional methods of crown restoration were needed like : celluloid crown, open-faced crown, rasin-faced crown. Neverthless, these kinds of complete coverage methods had some disadvantages such as possibility of tooth fracture by increased tooth preparation. In order to overcome the shortcomings of lingual pulpectomy, labial treatment could be considered as an alternative. It is a method that treats necrotic pulp through the labial access opening. After finishing the pulp treatment, discolored labial tooth structure was removed extending from access opening. Discoloration of deep area could be masked effectively using opaque sealant. Cavity on labial side was restored with composite resin. This labial approach method has several advantages. First, it gives a direct vision for effective pulp treatment which is also very useful for children with poor behavior. Second, most of lingual tooth structure could be saved and occlusal contact of lingual surface remains undisrupted. Only nonfunctional discolored labial surface may removed. Third, complete removal of discolored part of a labial tooth and immediate resin restoration could be done effectively after pulp treatment. Moreover, it also could be used for pulp treatment having serious dental caries on labial surface with sound lingual tooth structure. This report presents cases with discolored upper anteior primary tooth, approaching labial side with successful restoration.

• Imaging Science in Dentistry
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• v.42 no.3
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• pp.197-200
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• 2012

Gemination, a relatively uncommon dental anomaly, is characterized by its peculiar representation as a tooth with a bifid crown and a common root and root canal. It usually occurs in primary dentition. To come across gemination in a supernumerary tooth is a rare phenomenon. The purpose of this paper is to present a unique case of hyperdontia wherein gemination in an impacted supernumerary tooth resulted in a trifid crown unlike the usual bifid crown. The role of conventional radiographs as well as computed tomography, to accurately determine the morphology and spatial location, and to arrive at a diagnosis, is also emphasized in this paper.

• Journal of Oral Medicine and Pain
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• v.13 no.1
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• pp.13-21
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• 1988

The author studied the vertical height of tooth crown and the amounts of alveolar bone resorption with age. All 84 subjects(44 male, 40female) who visited Dental hospital of Wonkwang University with no history of sever periodontal disease and no experience of periodontal surgery. 84 subject were divided into 3 groups by age, that is, group I(28-32yrs), group II(38-42yrs), and group III(48-52yrs). Informal radiogram with bite wing film(horizontal angulation : $0^{\circ}$, vertical angulation : $+5^{\circ}~+10^{\circ}$) were taken on premolar and molar area. The distances from cusp tip to cementoenamel junction (vertical height of tooth crown) and from cementoenamel junction alveolar crest(amount of alveolar bone resorption) were measured, and then recorded data from 946 teeth were statistically analysed. This study was undertaken to obtain the data for age estimation by the changes of tooth crown height and alveolar bone resorption in the point of forensic odontology. The obtained results were as follows : 1. The average crown height of mandibular right 1st. molar was 7.1mm in group I, 6.7mm in group II, and 6.6mm group III, and the average amount of alveolar bone resorption on mandibular right 1st. molar were 1.8mm in group I, 2.5mm in group II, and 3.0mm in group III. Ratio of tooth crown height to amount of alveolar bone resorption was 4.0:1 in groupI, 2.7:1 in group II, and 2.2:1 in group III, the ratio was decreased with age. 2. In comparison with upper teeth and lower teeth in ipsilateral side, the average value of tooth crown height and amount of alveolar bone resorption were slightly higher in upper arch than those in lower arch, but there was not a statistically significant difference. 3. The ratio of height of tooth crown to amount of alveolar bone resorption was decreased with age, and which depended mainly upon the change of amount of alveolar bone resorption rather than the change of tooth crown height.

• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.298-298
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• 2000

Seven years old male lion in Everland Zoo has three fractured canine tooth. To avoid the risk of a possible fracture with pulp exposure after restroration of largest abration defects, endodontic therapy was performed. The pulp chamber was filled with calcium hydroxide, zinc oxide cement and gutta percha. We also installed the Crown prosthesis was installed in fractured canine tooth to protect the tooth and to improve the cosmetics and function of the tooth. The lion could eat in one day and there were no any signs of dental problem. It is the obvious prophylactic procedure for wild animal is the inclusion of an oral examination at every opportunity to handle the animal. It is considered that crown prosthesis after endodontic therapy was useful for maintaining normal physiological function and for provention of additional fracture or complication.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.968-974
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• 1996

Intra-alveolar transverse crown & root fx. provokes many problems in treatment. Conventionally, extraction of the injured tooth and its prosthodontic restoration has been the treatment of choice. Though orthodontic extrusion could be an alternative treatment, there would be a situation it's inadequate to apply. Loss of natural tooth would be a psychological damage to the patient, of course. This report describes a replantation method of tooth in case of intra-alveolar transverse crown & root fracture. The fractured tooth was extracted, rotated, then replanted. Fixation and esthetic restoration was done. And then endodontic treatment was followed. Continuing follow-up of its function and endodontic status is required.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.781-787
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• 1997

In spite of the improvements of the techniques in the field of preventive dentistry, many children still present with extensive destruction of primary anterior teeth. Not only the practioner must consider the pulp state of the primary incisor, but also restore the form, function and esthetics of the tooth. Restorative treatment of primary incisor tooth requires durability, retention and esthetics. Stainless steel crowns used in restoring primary anterior teeth is retentive and durable in comparison with the composite resin, celluloid crown. But they are not esthetic. To enhance the esthetics of the anterior stainless steel crown without reducing its superior retention, an open-face stainless steel crown has been suggested. Several authors have suggested cutting away the labial portion of the stainless steel crown and placing the composite resin in that area. By following this technique, the practioner can prepare a retentive, durable, and esthetic restoration for primary teeth which have suffered from extensive loss of teeth structure. In addition, the single missing primary anterior teeth can be successfully restored by soldering the stainless steel crown together. Open-face stainless steel crown is indicated in the areas of large interproximal lesions involving incisal edge, crown fracture with pulp exposure and congenital malformation of the teeth. By this technique, the practioner can restore primary anterior teeth successfully regardless of the amount of remaining tooth structure, bruxism habit and presence of attrition. In this case, rampant caries with extensive loss of tooth structure and single missing of primary anterior tooth hart been successfully treated with open-face stainless steel crown.

• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.232-237
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• 2017

Dentists often place post and core buildups on endodontically treated abutments for crown and bridge restorations. This article analyzes the bio-mechanical purposes, advantages and disadvantages of placing a core or a post and core in an endodontically treated tooth and reviews literature on post and core biomechanics. The author assesses the scientific rationale of the claim that the main purpose of a post is to retain a core, or the claim that posts weaken teeth. More likely, the main function of a post is to help prevent the abutment, on which a crown is cemented, from fracturing such that the abutment separates from the tooth root, at a fracture plane that is located approximately and theoretically at the level of the crown (or ferrule) margin. A post essentially improves the ferrule effect that is provided by the partial fixed denture prosthesis. This paper also explores the difference between bio-mechanical failures of crowns caused by lack of retention or excess taper, versus failures due to a sub-optimal ferrule effect in crown and bridge prostheses.

• Imaging Science in Dentistry
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• v.43 no.4
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• pp.295-301
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• 2013

The author experienced 8 cases of pericoronal radiolucency involving an incomplete tooth crown that had not developed to form the cemento-enamel junction, and the underdeveloped crown sometimes appeared to be floating within the radiolucency radiographically. The first impression was that these cystic lesions had odontogenic keratocysts, but half of them turned out to be dentigerous cysts histopathologically. There has been no report concerning odontogenic cysts involving an incompletely developed crown. The purpose of this paper is to report that dentigerous cysts may develop before the completion of the cemento-enamel junction of a developing crown.