• Journal of the korean academy of Pediatric Dentistry
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• v.4 no.1
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• pp.28-34
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• 1977

The present study was undertaken to evaluate gingivitis and oral hygiene status of the crowned teeth comparing to controlled teeth by use of P. M. A. Index and Oral Hygiene. Index in children from $3\frac{1}{2}$ to $7\frac{1}{2}$ years old. The results were as followings. 1. In P. M. A. Index, satisfactory crowned teeth (1.53) showed statistically significant increment compare to the controlled teeth (0.68) (P<0.01). 2. In P. M. A. Index, unsatisfactory crowned teeth (2.22) showed statistically significant increment compare to the controlled teeth (0.70) (P<0 01). 3. In Oral Hygiene Index, satisfactory crowned teeth (1.49) showed statistically nonsignificant increment compare to the controlled teeth (1.27). 4. In Oral Hygiene Index, unsatisfactory crowned teeth (1.62) showed statistically nonsignicant increment compare to the controlled (1.39) 5. The severity of gingivitis following Oral Hygiene Index showed higher in crowed teeth than the controlled teeth. 6. The severity of giginvitis showed the highest in the unsatisfactory crowned teeth, the next was the satisfactory crowned teeth, and the controlled teeth showed the lowest.

• Journal of Technologic Dentistry
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• v.35 no.4
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• pp.415-424
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• 2013

Purpose: This study is to present a standard value for clinical crown angulation and inclination required in laboratory process and see if the value can be used for actual laboratory process. Methods: In order to find out a standard value for clinical crown angulation and inclination, this study made a study model of normal occlusion of 21 females in twenties. The clinical crown angulation and inclination of both six-maxillary and six-mandibular anterior teeth are measured by Set-up Model Checker. From the measured value above, the mean and standard deviation of the twelve teeth are obtained, and then the mean of the teeth between right and left side is calculated. Results: Each clinical crown angulation of maxillary central incisor, lateral incisor, and canine is like this; $1.0^{\circ}{\pm}1.3^{\circ}$, $3.0^{\circ}{\pm}1.3^{\circ}$, and $5.0^{\circ}{\pm}1.4^{\circ}$. In case of mandibular, each degree is like this; $0.6^{\circ}{\pm}1.1^{\circ}$, $1.5^{\circ}{\pm}1.1^{\circ}$, and $4.1^{\circ}{\pm}1.1^{\circ}$. Each clinical crown inclination of maxillary central incisor, lateral incisor, and canine is like this; $6.1^{\circ}{\pm}1.8^{\circ}$, $4.5^{\circ}{\pm}1.9^{\circ}$, and $-6.2^{\circ}{\pm}1.4^{\circ}$. In case of mandibular, each degree is like this; $0.3^{\circ}{\pm}1.5^{\circ}$, $0.3^{\circ}{\pm}1.8^{\circ}$, and $-7.5^{\circ}{\pm}1.8^{\circ}$. Conclusion: As the result, the mean value for clinical crown angulation and inclination can be referred to actual laboratory process. However, the mean value is different from those of the precedent study and an unsatisfied one for adopting the standard value.

• The Journal of the Korean dental association
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• v.12 no.2
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• pp.131-134
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• 1974

The author had studied the masticatory effience on three different types; on missing of the first molar, on replacing the missed first molar with crown & bridge and on natural dentition. This study was made from the parched soybeans as testfood by means of mesh technique. As a result of this study on 25 of natural dentitions, 20 of crown & bridges and 25 of missing of the first molars, the following were come out. 1. Masticatory efficiency of natural dentitions was 75.8%, that of crown & bridges was 66.4%, and that of missing of the first molars was 43.7%. 2. Difference of masticatory efficiency of crown & bridges to natural dentitions was 9.4%, that of natural dentitions to missing teeth was 32.1%, and that of crown & bridges to missing teeth was 22.7%.

• The Journal of Advanced Prosthodontics
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• v.6 no.3
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• pp.171-176
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• 2014

PURPOSE. The aim of this study was to determine the absolute value of the root/crown ratio (R/C ratio) using panoramic radiographs (PRGs) in a healthy Korean population. MATERIALS AND METHODS. In total, 99 patient radiographs (of 50 males and 49 females subjects; aged 16 to 24 years old) were examined, and 2,770 teeth were analyzed. Crown lengths and root lengths were measured with modified Lind's measurements using PACS tools by two examiners in two separate sessions two months apart. All data were analyzed using SPSS. The independent t-test was used to assess for gender differences, and the paired t-test was used to compare both arches with a significance level of P<.05. RESULTS. The mean R/C ratios varied from 1.29 to 1.89 (male: 1.28-1.84; females: 1.31-1.94). The highest R/C ratios were recorded for the mandibular canines (1.89), followed by the maxillary canines (1.79). The lowest R/C ratios were recorded for the maxillary second molars (1.31). In comparison with the maxillary teeth (1.29-1.78), the mandibular teeth yielded the higher R/C ratio (1.47-1.89), and this difference was significant in the females (P<.05). The difference between the genders was not statistically significant, except for the maxillary central incisors, mandibular canines and mandibular first premolars. CONCLUSION. These data may enhance the understanding of the clinical R/C ratio as a useful guideline for determining the status of teeth and the ethnic difference.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.341-353
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• 1987

The purpose of this study was to investigate the gingival response to the location of the crown margin and the gingival response to the period of crown placement. Twenty one patients were selected for this study. The patients fitted into the research condition. The crown margins of anterior teeth were located at crest and supragingivally. The crown margins of posterior teeth were located at crest, subgingivally and supragingivally. Plaque index and gingival index were measured before tooth preparation and 1 week,4 weeks, 6 weeks after crown placement. The results were as follows: 1. There was no significance in the gingival response to the location of crown margin in short term period. 2. As the period of crown placement was extended, plaque index and gingival index were gradually increased. 3. Plaque index and gingival index of tooth surfaces were increased in the order of the interproximal surfaces, lingual surfaces and buccal or labial surfaces.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.94-104
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• 2000

A kinematically admissible velocity field for near-net shape forging of a crown gear form is proposed. This takes into account the profiled shape of the teeth chosen by approximating these kinematically as radially straight taper teeth, (rectangular and trapezoidal teeth). The upper bound to the forging load, the relative forging pressure and the deformed configurations, with both the initially solid circular cylindrical and hollow billets, are predicted using the velocity field at varying incremental punch movements considering differing frictional factors. These and other results are given and commented upon.

• Restorative Dentistry and Endodontics
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• v.7 no.1
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• pp.33-40
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• 1981

The more civilized, the more incidence had happened in our daily life, particularly in industrial factories, by traffic accident, and in sports, etc. in the dental field. The accidental trauma is usually involved the teeth and surronuding tissues. And the author intended to study of the traumatic injuries of anterior teeth by individual tooth, age, sex, cause of trauma, and how they were treated. The following results were obtained: 1. The patients with traumatic injuries of the anterior teeth were 1.8% among the total dental out-patients. 2. By the age group, the twenties was most frequent in both sexes, and the teenagers next. 3. The predominant causes of traumatic injuries in the dental field were traffic accident (23.4%), fighting (19.2%), falling (18.5%), and sports (7.3%). 4. In the classification of injuries of the teeth, uncomplicated crown fractures (31.2%), subluxations (14.7%), and the complicated crown fractures (13.2%) were presented. 5. By the individual tooth in the traumatic cases, the upper cental incisors were most frequently injuried (49.8%). 6. In the treatments fillings and endodontic treatments (33.2%), splints (13.5%), extractions (11.7%) were main after care method.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.2
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• pp.389-400
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• 1996

In Class II amalgam restoration in deciduous molar, failure rate and incidence of recurrent caries are high as children become older. In order to preserve deciduous molars till the physiologic exfoliation time, stainless steel crown is a choice of the treatment. As a result of a careless treatment, such as overhanging margin, poor marginal adaptation, poor proximal contour and inadequate mesiodistal width give rise to interfering eruption of the adjacent teeth, recurrent caries and chronic gingival irritation and insufficient arch length respectively. In this study, 252 s.s. crowned teeth extracted due to physiologic exfoliation or periapical lesion. The purpose of this study is to analyze the marginal adaptation of stainless steel crown to the deciduous molar in order to obtain better clinical result. The results were as follows : 1. Between the length of s.s. crown and the marginal gap of crown, positive correlations were shown. 2. Largest amount of marginal gap was shown at buccal side in upper deciduous molars and lower first deciduous molar, lingual side in lower second deciduous molar. But no significant diffrence were found statistically compared to second most largest one. 3. Incidence of exposed restoration and recurrent caries were higher in proximal surface than buccal/lingual surface. And extension of restoration below the margin of s.s. crown gives rise to higher rate of recurrent caries. 4. Defect of contour was found in 34%, frequently found in lower 1st deciduous molar and upper 1st deciduous molar. 5. Marginal polishing defects were found in 23%. 6. Ledge was formed in 10% especially in lower 1st deciduous molar and lower 2nd deciduous molar. 7. 16% of the teeth had wear facet due to traumatic occlusion, 7% of them had occlusal perforation.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.557-564
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• 2008

Purpose: Various methods are used in clinical crown lengthening procedure, Esthetic is more important in anterior region than in posterior region. Therefore when performing clinical crown lengthening procedure in esthetic region, clinicians should choose method which doesn't impair esthetic. Surgical extrusion could be a good method to achieve esthetic results. Material and Methods: Two patients were scheduled to clinical crown lengthening procedure in esthetic region. Teeth were extruded with periotome carefully to the intended level. Extruded teeth were anchored with sutures. Sutures are removed after 7day. Restorations were seated after extruded teeth were stabilized. Result: Five to six months later, both cases showed favorable esthetic outcome that were harmonious with adjacent teeth. Conclusion: When clinicians are to do clinical crown lengthening procedure in esthetic region, predictable esthetic outcome could be achieved with surgical extrusion.

• The Journal of Korean Academy of Prosthodontics
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• v.9 no.1
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• pp.17-22
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• 1969

Intra-oral films of 155 patients were taken on the areas of Gold Crown-Bridges, S. P. Bridges and Partial Dentures. And the author observed periodontal ligaments widening rates, the presence of periapical lesions and the alveolar bone patterns on the Partial Denture Saddle portions. The results were as follows : 1. Periodontal ligaments a) Periodontal ligaments widening rate increased obviously with the duration of wearing those prosthetic appliances. b) Periodontal ligaments widening rate was the highest in partial denture wearing patients, and then that of S. P. Crown Bridge patients, Gold Crown Bridge wearing females, Gold Crown Bridge males were the sequences. 2. Periapical lesions a) Periapical lesions increased with the wearing duration of those prosthetic appliances. But they did not increase in proportion to the duration. Periapical lesions were about the same in the teeth with those appliances showing relatively higher rate in Partial Denture abutment teeth and the lowest in Gold-Bridge abutment teeth. 3. Alveolar bone of Partial Denture saddle portion One third of all(32%) were normal with their smooth and compact bone pattern so that they were considered to perform normal function.