• Imaging Science in Dentistry
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• 제51권4호
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• pp.399-406
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• 2021

Purpose: This in vitro study measured and compared 3 intraoral scanners' accuracy (trueness and precision) with different span lengths. Materials and Methods: Three master casts were prepared to simulate 3 different span lengths (fixed partial dentures with 3, 4, and 5 units). Each master cast was scanned once with an E3 lab scanner and 10 times with each of the 3 intraoral scanners (Trios 3, Planmeca Emerald, and Primescan AC). Data were stored as Standard Tessellation Language (STL) files. The differences between measurements were compared 3-dimensionally using metrology software. Data were analyzed using 1-way analysis of variance with post hoc analysis by the Tukey honest significant difference test for trueness and precision. Statistical significance was set at P<0.05. Results: A statistically significant difference was found between the 3 intraoral scanners in trueness and precision (P<0.05). Primescan AC showed the lowest trueness and precision values(36.8 ㎛ and 42.0 ㎛;(39.4 ㎛ and 51.2 ㎛; and 54.9 ㎛ and 52.7 ㎛) followed by Trios 3 (38.9 ㎛ and 53.5 ㎛; 49.9 ㎛ and 59.1 ㎛; and 58.1 ㎛ and 64.5 ㎛) and Planmeca Emerald (60.4 ㎛ and 63.6 ㎛; 61.3 ㎛ and 69.0 ㎛; and 70.8 ㎛ and 74.3 ㎛) for the 3-unit, 4-unit, and 5-unit fixed partial dentures, respectively. Conclusion: Primescan AC had the best trueness and precision, followed by Trios 3 and Planmeca Emerald. Increasing span length reduced the trueness and precession of the 3 scanners; however, their values were within the accepted successful ranges.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.239-244
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• 2022

Purpose: Despite the proliferation of numerous morphometric and anthropometric methods for sex identification based on linear, angular, and regional measurements of various parts of the body, these methods are subject to error due to the observer's knowledge and expertise. This study aimed to explore the possibility of automated sex determination using convolutional neural networks(CNNs) based on lateral cephalometric radiographs. Materials and Methods: Lateral cephalometric radiographs of 1,476 Iranian subjects (794 women and 682 men) from 18 to 49 years of age were included. Lateral cephalometric radiographs were considered as a network input and output layer including 2 classes(male and female). Eighty percent of the data was used as a training set and the rest as a test set. Hyperparameter tuning of each network was done after preprocessing and data augmentation steps. The predictive performance of different architectures (DenseNet, ResNet, and VGG) was evaluated based on their accuracy in test sets. Results: The CNN based on the DenseNet121 architecture, with an overall accuracy of 90%, had the best predictive power in sex determination. The prediction accuracy of this model was almost equal for men and women. Furthermore, with all architectures, the use of transfer learning improved predictive performance. Conclusion: The results confirmed that a CNN could predict a person's sex with high accuracy. This prediction was independent of human bias because feature extraction was done automatically. However, for more accurate sex determination on a wider scale, further studies with larger sample sizes are desirable.

• Imaging Science in Dentistry
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• 제52권1호
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• pp.19-25
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• 2022

Purpose: This study evaluated the distance from the posterior root apices to the maxillary sinus floor (MSF) and the frequency of roots touching or protruding through the MSF using cone-beam computed tomography (CBCT). Materials and Methods: This study included 100 subjects divided into different vertical and anteroposterior skeletal growth patterns. On CBCT images, the distance from the posterior root apices to MSF was measured and the frequency of roots touching or protruding through the MSF was evaluated using NNT software (version 5.3.0.0; ImageWorks, Elmsford, NY, USA). Results: No statistically significant differences were found in the distance from the posterior root apices to the MSF among vertical skeletal groups (P>0.05). The palatal roots of the first molar and the palatal, mesio-buccal and disto-buccal roots of the second molars had significantly less distance from MSF in skeletal class II than in class III (P<0.05). The high-angle group had the highest frequencies of roots touching or protruding into the maxillary sinus (49.8%); the lowest proportion of these roots was found in skeletal class III (28.3%) and the highest proportion in class II (50.3%). Males had shorter distances from the posterior root apices to the MSF and higher frequencies of roots protruding through or touching the MSF than females. Conclusion: Anteroposterior skeletal growth patterns and sex affected the distances from the maxillary posterior roots to the MSF. The frequency of roots protruding into or touching the sinus was affected by both vertical and anteroposterior skeletal groups and sex. These findings have implications for dental practice.

• Imaging Science in Dentistry
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• 제53권1호
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• pp.21-26
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• 2023

Purpose: A fully digital approach to oral prosthodontic rehabilitation requires the possibility of combining (i.e., registering) digital documentation from different sources. This becomes more complex in an edentulous jaw, as fixed dental markers to perform reliable registration are lacking. This validation study aimed to evaluate the reproducibility of 1) intraoral scanning and 2) soft tissue-based registration of an intraoral scan with a cone-beam computed tomography (CBCT) scan for a fully edentulous upper jaw. Materials and Methods: Two observers independently performed intraoral scans of the upper jaw in 14 fully edentulous patients. The palatal vault of both surface models was aligned, and the inter-observer variability was assessed by calculating the mean inter-surface distance at the level of the alveolar crest. Additionally, a CBCT scan of all patients was obtained and a soft tissue surface model was generated using patient-specific gray values. This CBCT soft tissue model was registered with the intraoral scans of both observers, and the intraclass correlation coefficient(ICC) was calculated to evaluate the reproducibility of the registration method. Results: The mean inter-observer deviation when performing an intraoral scan of the fully edentulous upper jaw was 0.10±0.09 mm. The inter-observer agreement for the soft tissue-based registration method was excellent(ICC=0.94; 95% confidence interval, 0.81-0.98). Conclusion: Even when teeth are lacking, intraoral scanning of the jaw and soft tissue-based registration of an intraoral scan with a CBCT scan can be performed with a high degree of precision.

• Imaging Science in Dentistry
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• 제53권1호
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• pp.77-82
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• 2023

Purpose: This study evaluated anatomical variations in the root canals of the lower premolars and molars in a Brazilian sub-population using cone-beam computed tomography (CBCT). Materials and Methods: In total, 121 CBCT images of patients were selected from a database. All images contained lower first and second premolars and molars on both sides of the arch, fully developed roots, and no treatment, resorption, or calcifications. In each image, the root canals of the lower premolars and molars were evaluated according to the Vertucci classification in On-Demand 3D software in the multiplanar reconstruction with dynamic navigation. Twenty-five percent of the images were re-assessed to analyze intraobserver confidence with the kappa test. Data were statistically evaluated with linear regression to evaluate the correlations of anatomic variations with age and sex, and the Wilcoxon test to analyze the laterality of variations, with a significance level of 5%. Results: The intraobserver agreement (0.94) was excellent. In general, the root canals of lower premolars and molars showed a higher prevalence of type I than other Vertucci classification types, followed by type V in premolars and type II in molars. When the molar roots were evaluated separately, type II was more frequent in mesial roots and type I in distal roots. Although age showed no correlations with the results, sex and laterality showed correlations with tooth 45 and the lower second premolars, respectively. Conclusion: The lower premolars and molars of a Brazilian sub-population showed a wide range of root canal anatomic variations.

• Anatomy and Cell Biology
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• 제56권2호
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• pp.185-190
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• 2023

The root canal morphology undergoes aging-related changes, and relevant quantitative analyses have not yet been reported. We compared the cone beam computed tomography (CBCT) and micro-computed tomography (microCT) scans of extracted mandibular incisors to check the accuracy of morphological measurements. Thereafter, the root canal morphology and aging-related changes in the mandibular incisors of Japanese individuals were assessed using CBCT. Six extracted teeth were fixed in a phantom head and imaged using CBCT and micro-CT. The correlation between the findings of the two imaging modalities was examined. Further, CBCT reconstructed images of the mandibular incisors of 81 individuals were observed. Age-related changes of the root canals were compared between participants aged <30 years and those aged ≥30 years. The CBCT and micro-CT findings regarding the root canals of the extracted teeth coincided in 94.4% of the cases. Mandibular incisors exhibiting two root canals in either cross-section accounted for 9.9% of central incisors and 12.4% of lateral incisors. Mandibular central incisors with two root canals were observed in two (6.3%) individuals aged <30 years and six (12.2%) aged ≥30 years. Mandibular lateral incisors with two root canals were observed in one (3.1%) individual aged <30 years and nine (18.4%) aged ≥30 years. CBCT allows accurate evaluation of complex root canal morphologies and is useful for endodontic preoperative assessment. Mandibular incisors have more frequent occurrence of two root canals with aging.

• Journal of Oral Medicine and Pain
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• 제48권4호
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• pp.152-158
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• 2023

Purpose: This pilot study aimed to evaluate changes in joint space (JS) using cone-beam computed tomography (CBCT) images of patients diagnosed with temporomandibular joint (TMJ) osteoarthritis (OA) and to determine the association between occlusal changes and JS. Methods: CBCT images were used to measure the anterior, superior, and posterior JSs of the sagittal plane. The differences in JS values over time and between groups were compared. The percentage change in the anteroposterior position of the mandibular condyle between groups was also analyzed. Results: Thirty-four subjects (mean age=43.91±20.13), comprising eight males (23.5%) and 26 females (76.5%), were divided into 18 patients with no change in occlusion (NCO) and 16 patients with a change in occlusion (CO) during TMJ OA. The JS measurements of the study subjects showed a decrease in anterior joint space (AJS) values over time. There was no difference in JS measurements between the groups at T1 and T2. AJS values measured at T1 were lower in the CO group than in the NCO group, but the difference was not statistically significant. In both groups, a posterior position of the mandibular condyle was initially observed with high frequency. However, there is a statistically significant difference in CBCT images taken after occlusal changes, with an increased frequency of condyles observed in the anterior or central positions. Conclusions: In conclusion, AJS decreased over time in TMJ OA, and the mandibular condyle became more anteriorly positioned with occlusal changes. Therefore, clinicians should diligently monitor mandibular condyle morphology and JS using CBCT, along with the patient's clinical symptoms, to treat and control TMJ OA effectively.

• 대한치과보철학회지
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• 제48권2호
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• pp.128-134
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• 2010

연구목적: 본 연구에서는 건강기능식품인 $PostPlant^{TM}$ Calcium을 임플란트 식립 환자에게 투여하고, 투여하지 않은 군과 비교하여 그 유효성과 안정성을 평가하여 투여 후 골밀도의 변화 및 골유착 기간의 단축 여부를 평가하고자 하였다. 연구 재료 및 방법 임플란트 식립 후에Post$PostPlant^{TM}$ Calcium을 투여한 실험군은 18명의 환자를 대상으로 25개의 임플란트를 식립하였고, 투여하지 않은 대조군에서는 7명의 환자에게 9개의 임플란트를 식립하여 관찰하였다. 일차수술 후, 이차수술 후, 6개월 후에 $Osstell^{TM}$ Mentor, $Periotest^{(R)}$를 이용하여 임플란트 안정성을 비교 분석하였고, 일차수술후, 1, 3, 6개월 후에 방사선 사진 촬영을 시행하여 임플란트 주위 골밀도를 측정하여 비교 분석하였다. 결과:1. $Osstell^{TM}$ Mentor의해 측정된 ISQ 값은 측정 결과 시간이 경과함에 따라 실험군, 대조군 모두 수치가 높아지는 경향을 보였다. 실험군의 측정값이 대조군에 비해 더 높은 수치를 보였으며, 식립 6개월 후에 실험군과 대조군 간에 통계적으로 유의한 차이가 관찰되었다 (P< .05); 2. $Periotest^{(R)}$ 측정 결과 시간이 경과함에 따라 실험군, 대조군 모두 수치가 낮아지는 경향을 보였으며, 실험군이 대조군에 비해 더 낮은 수치를 나타내었으나 각 군간에 통계적인 유의성은 없었다. 3. 골밀도 측정 결과 시간이 경과함에 따라 실험군, 대조군 모두 골밀도 수치가 증가하는 경향을 보였으며, 실험군이 대조군에 비해 더 높은 수치를 나타내었으나 각 군간에 통계적인 유의성은 없었다. 결론:임상적으로 임플란트 식립 후 환자가 $PostPlant^{TM}$ Calcium을 장기간 복용하는 것이 임플란트 안정성을 높이고, 골유착을 성공적으로 이루는데 도움을 줄 수 있다고 사료된다.

• 대한치과교정학회지
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• 제39권5호
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• pp.300-309
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• 2009

본 연구는 Cone-beam CT의 MPR이미지상에서 하악골 평면에 대한 하악 제1대구치와 견치의 편위측과 비편위측의 높이와 각도차이 그리고 FH 평면에 대한 상악 제1대구치와 견치의 편위측과 비편위측의 높이와 각도차이를 계측함으로써 안면비대칭자에서 이부편위에 따른 편위측과 비편위측의 제1대구치와 견치의 높이와 협설측 경사도를 CBCT를 이용하여 분석하고 그 관련성을 알아보는 데 있다. 연구대상은 하악골의 이부편위를 동반한 안면비대칭 환자 50명(여자 29명, 남자 21명, 평균나이 24세 4개월)으로 하였다. 대조군으로 평균나이 25세 7개월인 20명(남자 11명, 여자 9명)을 분석하였다. 결과는 이부편위에 대해 FH 평면에 대한 상악 제1대구치의 편위측과 비편위측의 길이 및 각도 차이(편위측 - 비편위측)는 대조군에 대해 통계적으로 유의한 차이가 존재하였다 (p < 0.01). 비대칭군에서 상악 제1대구치 각도는 편위측이 비편위측보다 평균 $8.62\;{\pm}\;5.95^{\circ}$ 컸다 (p < 0.01). 상악 견치의 경우에도 편위측과 비편위측의 각도차이가 평균 $4.48\;{\pm}\;5.05^{\circ}$로 통계적으로 유의한 차이가 존재하였다 (p < 0.01). 하악골 평면에 대한 하악 제1대구치의 수직 길이와 각도는 편위측과 비편위측에서 통계적으로 유의할 만한 차이가 존재하였다 (p < 0.01). 각도의 차이는 평균 $-11.92\;{\pm}\;5.79^{\circ}$로 나타났다. 이부편위에 대한 상하악 제1대구치와 견치의 수직거리 및 각도의 Pearson 상관분석 및 회귀분석 결과, FH 평면에 대한 상악 제1대구치의 편위측과 비편위측의 각도차이(${\Delta\angle}UM6$-FH plane (dev.-ndev.))는 통계적으로 유의한 양의 상관관계를 나타내었고, 하악골 평면에 대한 하악 제1대구치의 편위측과 비편위측의 각도차이(${\Delta\angle}LM6$-Mn plane (dev.-ndev.))는 통계적으로 유의한 음의 상관관계를 나타내었다. 이상의 결과에서 이부편위를 동반한 하악골 비대칭이 존재하는 경우, 이부가 편위되는 방향으로 상하악 제1대구치의 치아장축의 각도가 변화되는 것으로 나타났다.

• 한국방사선학회논문지
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• 제7권1호
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• pp.17-24
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• 2013

본 연구는 파노라마 표준 촬영에서 환자의 피폭 선량을 측정하여 방사선 생물학적 위험인자를 평가하고 환자의 피폭 선량 저감화 방안을 제시하고자 하였다. 피폭 선량의 측정 오차를 최소화하기 위하여 각 OSL 선량계의 교정상수를 구하였으며 파노라마 표준 촬영에서 간접적으로 포함되는 좌 우측 수정체와 갑상선, 직접적으로 포함되는 상 하 입술, 하악골 첨부, 촬영 중심점을 대상으로 ICRP에서 권고하는 인체 모형 표준 팬텀을 이용하여 측정하였다. 측정 결과, 촬영 중심점의 선량이 $413.67{\pm}6.53{\mu}Gy$로 최대였으며 상 하 입술의 경우 각각 $217.80{\pm}2.98{\mu}Gy$, $215.33{\pm}2.61{\mu}Gy$이었다. 또한 파노라마 표준 촬영에서 간접적으로 포함되는 좌 우측 수정체의 등가선량은 각각 $30.73{\pm}2.34{\mu}Gy$, $31.87{\pm}2.50{\mu}Gy$이었으며 하악골 첨부 및 갑상선의 등가선량은 $276.73{\pm}14.43{\mu}Gy$, $162.07{\pm}4.13{\mu}Gy$이었다. 결론적으로 측정된 피폭 선량은 방사선 생물학적 효과를 유발할 수 있었으며 치과 의료기관의 파노라마 표준 촬영에서 환자의 피폭 선량에 대한 저감화 방안으로 국제기구에서 권고하고 있는 방사선 방어 원칙에 대한 정당한 해석과 제도적 뒷받침(regulation)이 필요하다. 이에 파노라마 검사에 의한 피폭 선량은 기술적 경제적 측면뿐 만 아니라 사회적 인자를 고려하여 합리적으로 용인 가능한 수준까지 최소화하기 위한 체계화된 프로토콜의 제정과 주변 결정 장기를 방어하기 위한 방사선 보호 기구에 대한 추가적 연구가 필요할 것으로 판단되었다.