• Journal of Periodontal and Implant Science
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• 제36권1호
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• pp.61-68
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• 2006

The factors influencing long-term prognosis of teeth must be carefully considered. Among these, attachment level is strongly associated with tooth loss. The purpose of the present study was to estimate pattern of attachment loss based on attachment area in extracted teeth. 197 satisfied the criteria for assessment after staining. The protocol described by Waerhaug(l975) was performed. An indir ect method, based on digital image abstracted from digital camera and digital imaging software program, was used to calculate the root surface area and the attachment loss area. The data were analysed using SPSS. Except maxillary central incisior and mandibular canine, no statistical significant differences between each root surfaces were observed in anterior teeth. In posterior teeth, statistical significant differences in palatal surface of maxillary molar and mandibular molar compared with others were observed. Statistical significant difference in buccal surface compared with others was lowly observed in single and multi rooted. This study did not reveal progressive loss pattern of attachment area in each root surface but clarified root surface that has relative high loss rate of attachment area at extraction. Thus understanding this pattern of attachment loss is helpful for dentist to treat the periodontitis.

• 대한심미치과학회지
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• 제29권1호
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• pp.13-24
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• 2020

임플란트 술식은 그 동안 많은 발전을 하였고, 자연치를 대체할 훌륭한 치료법임에는 부인할 수 없지만 치주인대가 존재하지 않는 구조적 한계점, 발치 직후 시작되는 bundle bone의 흡수는 자연치와 같은 적절한 emergence profile을 만들어내기 어려울 수 있고 이는 심미적인 결과로 이어질 수 있다. 만약 해당 환자의 구강 내에 건전한 제3대구치가 있고, 결손부위의 염증상태가 심각하지 않으면 건전한 제3대구치를 결손된 부위로 이식하여 치아를 재건할 수 있다. 성공적인 자가치아이이식술은 저작기능을 회복하고, 자가치아를 이용하기에 생체 친화적이며, 치조골의 흡수를 예방하는 훌륭한 치료이기 때문에 가능하기만 하다면 첫번째 치료로 충분히 고려될 수 있을 것이다.

• 대한치과교정학회지
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• 제14권2호
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• pp.249-261
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• 1984

This study was to investigate the fitness of the dental arch line to the parabola, and to estimate correlation between the parabola and some ratios of the dental arch measurements. The sample was consisted of the 64 plaster casts showing normal occlusion which was taken from males and females of Korea, aging from 15 to 18 years. The photos of occlusal surface of the plaster casts were taken, and 38 landmarks on the film were selected. The 3 dental arch lines on each dental arch were imaged. One is the dental arch line passing the points of the most buccal surfaces of the teeth, another is that passing the buccal cusp tips of the posterior teeth and the incisal edges, and the other is that passing the midpoints of the teeth. The landmarks on the film were digitized, and measurements and statistics were performed by the IBM computer. The results were as follows; 1. The fitness of the dental arch to the parabola was very good. The fitness of thor upper dental arch was above $91\%$, and that of the lower dental arch was $93\%$. 2. The dental arch line passing the points of the most buccal surfaces of teeth was best fit to the parabola, the buccal cusp tip arch line and the midpoint arch line in order. 3. Correlation between the ratio of oblique molar dental height to molar width and the parabola was very high. 4. The ratio of oblique molar dental height to molar width was devided into 4 groups by the quartiles, and mean parabolic equations and curves were calculated and drawn.

• 대한소아치과학회지
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• 제4권1호
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• pp.7-18
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• 1977

The author carried out to determine the normal range of eruptive time, average age and order of eruption of primary teeth in korean infants. The examimation was given to 1757 healty infants(Male 1032, female 725) from afterbirth 4 months to 32 months. The results was as fallows. 1. The eruption of primary teeth was 0.57 months earlier in male than in female. 2. The average month of eruption of primary teeth was as follows; Upper primary central is $9.66{\pm}0.19$ months Upper primary lateral is $11.58{\pm}0.18$ months. Upper primary canine is $18.06{\pm}0.32$ months. Upper first primary molar is $16.45{\pm}0.29$ months. Upper second primary molar is $24.28{\pm}0.51$ months. Lower primary central is $7.50{\pm}0.12$ months. Lower primary lateral is $12.87{\pm}0.16$ months. Lower primary camine is $18.82{\pm}0.34$ months. Lower first primary molar is $17.66{\pm}0.37$ months. Lower second primary molar is $23.89{\pm}0.51$ months. 3. The eruptive order of the korean is different from that of the American and same to that of Japanese. 4. There is no significant right and left arch. 5. Generally, the eruption of primary teeth on the upper is 1.08 months earlier than on the lower; but the upper central is 2.16 months later than the lower and the upper second primary is 0.39 months later than the lower.

• 대한소아치과학회지
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• 제42권3호
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• pp.257-263
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• 2015

매복치는 유치열기보다 영구치열기에서 더 높은 빈도로 발생한다. 가장 흔하게 이환되는 치아는 상하악 제3대구치들이며, 하악 제1대구치의 매복은 비교적 드문 편이다. 매복치의 치료방법은 자발적 맹출을 위한 지속적인 검사, 외과적 노출술, 외과적 노출 후 아탈구, 교정적 견인, 그리고 외과적 재위치술 등이 있으며 이 모든 치료가 실패한다면 치아를 발거하는 것을 고려할 수 있다. 첫 번째 증례는 8세 남아로서 매복된 하악 제1대구치에 폐쇄장치를 이용한 감압술을 시행하였으며, 정기적인 검진을 통해 치아의 맹출이 관찰되었다. 두 번째 증례는 12세 남아로서 매복된 하악 제1대구치의 외과적 노출술을 시행 후 치아의 맹출이 관찰되지 않아 가철성 장치를 이용한 교정적 정출술을 시행하였으며 이 후 정상적인 치아의 맹출이 관찰되었다.

• 대한치과기공학회지
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• 제46권2호
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• pp.36-41
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• 2024

Purpose: This study aimed to generate virtual mandibular left first molar teeth using deep convolutional generative adversarial networks (DCGANs) and analyze their matching accuracy with actual tooth morphology to propose a new paradigm for using medical data. Methods: Occlusal surface images of the mandibular left first molar scanned using a dental model scanner were analyzed using DCGANs. Overall, 100 training sets comprising 50 original and 50 background-removed images were created, thus generating 1,000 virtual teeth. These virtual teeth were classified based on the number of cusps and occlusal surface ratio, and subsequently, were analyzed for consistency by expert dental technicians over three rounds of examination. Statistical analysis was conducted using IBM SPSS Statistics ver. 23.0 (IBM), including intraclass correlation coefficient for intrarater reliability, one-way ANOVA, and Tukey's post-hoc analysis. Results: Virtual mandibular left first molars exhibited high consistency in the occlusal surface ratio but varied in other criteria. Moreover, consistency was the highest in the occlusal buccal lingual criteria at 91.9%, whereas discrepancies were observed most in the occusal buccal cusp criteria at 85.5%. Significant differences were observed among all groups (p<0.05). Conclusion: Based on the classification of the virtually generated left mandibular first molar according to several criteria, DCGANs can generate virtual data highly similar to real data. Thus, subsequent research in the dental field, including the development of improved neural network structures, is necessary.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.452-456
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• 2013

PURPOSE. The aim of this study was to evaluate the repeatability of the digitizing of silicon rubber impressions of abutment teeth by using a white light scanner and compare differences in repeatability between different abutment teeth types. MATERIALS AND METHODS. Silicon rubber impressions of a canine, premolar, and molar tooth were each digitized 8 times using a white light scanner, and 3D surface models were created using the point clouds. The size of any discrepancy between each model and the corresponding reference tooth were measured, and the distribution of these values was analyzed by an inspection software (PowerInspect 2012, Delcamplc., Birmingham, UK). Absolute values of discrepancies were analyzed by the Kruskal-Wallis test and multiple comparisons (${\alpha}$=.05). RESULTS. The discrepancy between the impressions for the canine, premolar, and molar teeth were $6.3{\mu}m$ (95% confidence interval [CI], 5.4-7.2), $6.4{\mu}m$ (95% CI, 5.3-7.6), and $8.9{\mu}m$ (95% CI, 8.2-9.5), respectively. The discrepancy of the molar tooth impression was significantly higher than that of other tooth types. The largest variation (as mean [SD]) in discrepancies was seen in the premolar tooth impression scans: $26.7{\mu}m$ (95% CI, 19.7-33.8); followed by canine and molar teeth impressions, $16.3{\mu}m$ (95% CI, 15.3- 17.3), and $14.0{\mu}m$ (95% CI, 12.3-15.7), respectively. CONCLUSION. The repeatability of the digitizing abutment teeth's silicon rubber impressions by using a white light scanner was improved compared to that with a laser scanner, showing only a low mean discrepancy between $6.3{\mu}m$ and $8.9{\mu}m$, which was in an clinically acceptable range. Premolar impression with a long and narrow shape showed a significantly larger discrepancy than canine and molar impressions. Further work is needed to increase the digitizing performance of the white light scanner for deep and slender impressions.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2001년도 추계학술대회(제116회) 및 13회 Workshop 제3회 한ㆍ일 치과보존학회 공동학술대회 초록집
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• pp.574.1-574
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• 2001

Maxillary first molar, the "6-year molar", is the tooth largest in volume and most complex in root and root canal anatomy. Therefore, maxillary first molar is possibly the most treated, least understood. It is the posterior tooth with the highest endodontic failure rate and unquestionably one of the most important teeth. The earliest permanent posterior tooth to erupt, the mandibular first molar seems to be the most frequently in need of endodontic treatment.(omitted)

• 대한치과보철학회지
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• 제22권1호
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• pp.109-122
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• 1984

The purpose of this study was to analyze the magnitude and mode of the stress distribution induced in the supporting alveolar bone and periodontal ligament and, to determine the displacement of abutment teeth and telescope denture base by applying chewing force to the telescope denture quantitatively and qualitatively. Two finite element models of telescope denture that were restored the missing mandibular second molar with two abutment teeth which were constructed. In two different models, parallel and tapering type telescope crowns were constructed. These finite element models of two cases used for these experiment were a two-dimensional mesiodistal section of the mandibular second bicuspid and first molar. Chewing force of 25Kg that was devided in the ratio of 45/155 (29%) in bicuspid and 55/155 (35.5%) in molars was applied to telescope denture and abutment teeth respectively. The displacement of the telescope denture base and abutment teeth and the stress distribution in the periodontal ligament and alveolar bone were analized to investigate the influence of chewing force acting on the telescope denture and abutment teeth. The results were as follows: 1. Abutment teeth displaced mesially and the magnitude of displacement of abutment teeth in vertical direction were more than that of horizontal direction in two cases. The displacement of abutment teeth on the telescope denture treated with tapering type telescope crown were less than that of the parallel type crown. 2. The displacement of the telescope denture base that were treated with parallel type telescope crown were less than that of treated with tapering type telescope crown. 3. The stress induced in the alveolar bone and periodontal ligament on abutment teeth that treated with parallel type telescope crown were more than that of treated with tapering type telescope crown and more stress induced in the alveolar bone than in the periodontal ligament. 4. In the telescope denture, the magnitude of displacement of abutment teeth and stress induced in the periodontal ligament and alveolar bone were within physiologic limit.

• Journal of Oral Medicine and Pain
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• 제19권1호
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• pp.57-72
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• 1994

This study was undertaken to obtain the data age determination following the eruption of individual cusps of the first molars in the point of forensic odontology. 532 children (294 male and 238 female, born between April, 1989 and March, 1986) from a kindergarten and a primary school in a reesidential district in Seoul were studied. The eruption state of the first molar was divides into 6 stages according to the degree of exposure of individual cusps, and correlation between the stage and age was stastically analysed. The results of the study lead to following conclusions : 1. The most frequently seen eruption sequence of cusps for the upper first molar was mesibuccal cusp, mesiopalatal cusp, distobuccal cusp, mesiodistal cusp, distopalatal cusp. As for the lower first molar : mesiobuccal cusp, mcsiolingual cusp, distobuccal cusp, distolingual cusp. 2. The time of eruption was earlier in the female ethan in the male, but it was stastically remarkable only in upper and lower parts of the right and the left teeth of subjects age between 6.0 and 6.5 and upper part of the right and the left teeth of subjects age over 7.5 3. The eruption of the lower first molar was comparatively earlier than that of the upper first molar and there was no significant stastical difference between the right and the left first molars in the time of eruption. 4. There was no noticeable difference in the eruption sequence of cusps, irrespective of sex and side. 5. The eruption of the upper first molar is started at the age of about 6.4 and complete the age of about 7.1 and as for the lower first molar, it is from 6.3 to 7.0