• Anatomy and Cell Biology
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• 제56권4호
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• pp.474-481
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• 2023

The dental characteristics created by acquired dental treatments can be used as age estimators. This pilot study aimed to analyze the correlation between the number of teeth observed for dental characteristics and chronological age and to develop new non-invasive age estimation models. Dental features on panoramic radiographs (420 radiographs of subjects aged 20-89 years) were classified and coded. The correlation between the number of teeth for each selected code (codes V, X, T, F, P, and L) and age was observed, and multiple regression was performed to analyze the relationship between them. Eleven regression models with various combinations of dental sextants were presented. The model with the data from both sides of the posterior teeth on both jaws showed the best performance (root mean square error of 14.78 years and an adjusted R² of 0.461). The model with all teeth was the second-best. Based on these results, we confirmed statistically significant correlations between certain dental features and chronological age. We also observed that some regression models performed sufficiently well to be used as adjunctive methods in forensic practice. These results provide valuable information for the design and performance of future full-scale studies.

• Imaging Science in Dentistry
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• 제42권3호
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• pp.175-182
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• 2012

Purpose: The aim of this study was to provide sex-matched three-dimensional (3D) statistical shape models of the mandible, which would provide cephalometric parameters for 3D treatment planning and cephalometric measurements in orthognathic surgery. Materials and Methods: The subjects used to create the 3D shape models of the mandible included 23 males and 23 females. The mandibles were segmented semi-automatically from 3D facial CT images. Each individual mandible shape was reconstructed as a 3D surface model, which was parameterized to establish correspondence between different individual surfaces. The principal component analysis (PCA) applied to all mandible shapes produced a mean model and characteristic models of variation. The cephalometric parameters were measured directly from the mean models to evaluate the 3D shape models. The means of the measured parameters were compared with those from other conventional studies. The male and female 3D statistical mean models were developed from 23 individual mandibles, respectively. Results: The male and female characteristic shapes of variation produced by PCA showed a large variability included in the individual mandibles. The cephalometric measurements from the developed models were very close to those from some conventional studies. Conclusion: We described the construction of 3D mandibular shape models and presented the application of the 3D mandibular template in cephalometric measurements. Optimal reference models determined from variations produced by PCA could be used for craniofacial patients with various types of skeletal shape.

• The Journal of Advanced Prosthodontics
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• 제9권1호
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• pp.31-37
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• 2017

PURPOSE. The purpose of this study was to analyze the influence of the platform switching concept on an implant system and peri-implant bone using three-dimensional finite element analysis. MATERIALS AND METHODS. Two three-dimensional finite element models for wide platform and platform switching were created. In the wide platform model, a wide platform abutment was connected to a wide platform implant. In the platform switching model, the wide platform abutment of the wide platform model was replaced by a regular platform abutment. A contact condition was set between the implant components. A vertical load of 300 N was applied to the crown. The maximum von Mises stress values and displacements of the two models were compared to analyze the biomechanical behavior of the models. RESULTS. In the two models, the stress was mainly concentrated at the bottom of the abutment and the top surface of the implant in both models. However, the von Mises stress values were much higher in the platform switching model in most of the components, except for the bone. The highest von Mises values and stress distribution pattern of the bone were similar in the two models. The components of the platform switching model showed greater displacement than those of the wide platform model. CONCLUSION. Due to the stress concentration generated in the implant and the prosthodontic components of the platform switched implant, the mechanical complications might occur when platform switching concept is used.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제40권
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• pp.4.1-4.4
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• 2018

Background: Along with the advances in technology of three-dimensional (3D) printer, it became a possible to make more precise patient-specific 3D model in the various fields including oral and maxillofacial surgery. When creating 3D models of the mandible and maxilla, it is easier to make a single unit with a fused temporomandibular joint, though this results in poor operability of the model. However, while models created with a separate mandible and maxilla have operability, it can be difficult to fully restore the position of the condylar after simulation. The purpose of this study is to introduce and asses the novel condylar repositioning method in 3D model preoperational simulation. Methods: Our novel condylar repositioning method is simple to apply two irregularities in 3D models. Three oral surgeons measured and evaluated one linear distance and two angles in 3D models. Results: This study included two patients who underwent sagittal split ramus osteotomy (SSRO) and two benign tumor patients who underwent segmental mandibulectomy and immediate reconstruction. For each SSRO case, the mandibular condyles were designed to be convex and the glenoid cavities were designed to be concave. For the benign tumor cases, the margins on the resection side, including the joint portions, were designed to be convex, and the resection margin was designed to be concave. The distance from the mandibular ramus to the tip of the maxillary canine, the angle created by joining the inferior edge of the orbit to the tip of the maxillary canine and the ramus, the angle created by the lines from the base of the mentum to the endpoint of the condyle, and the angle between the most lateral point of the condyle and the most medial point of the condyle were measured before and after simulations. Near-complete matches were observed for all items measured before and after model simulations of surgery in all jaw deformity and reconstruction cases. Conclusions: We demonstrated that 3D models manufactured using our method can be applied to simulations and fully restore the position of the condyle without the need for special devices.

• 대한치과기공학회지
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• 제41권4호
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• pp.287-293
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• 2019

Purpose: To evaluate the accuracy of the 3D printed die models and to investigate its clinical applicability. Methods: Stone die models were fabricated from conventional impressions(stone die model; SDM, n=7). 3D virtual models obtained from the digital impressions were manufactured as a 3D printed die models using a 3D printer(3D printed die models;3DM, n=7). Reference model, stone die models and 3D printed die models were scanned with a reference scanner. All dies model dataset were superimposed with the reference model file by the "Best fit alignment" method using 3D analysis software. Statistical analysis was performed using the independent t-test and 2-way ANOVA (α=.05). Results: The RMS value of the 3D printed die model was significantly larger than the RMS value of the stone die model (P<.001). As a result of 2-way ANOVA, significant differences were found between the model group (P<.001) and the part (P<.001), and their interaction effects (P<.001). Conclusion: The 3D printed die model showed lower accuracy than the stone die model. Therefore, it is necessary to further improve the performance of 3D printer in order to apply the 3D printed model in prosthodontics.

• 대한소아치과학회지
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• 제51권1호
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• pp.55-65
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• 2024

This study aimed to assess the accuracy of tooth widths, intermolar widths, and arch lengths acquired through two intraoral scanners, including iTero Element Plus Series (Align Technology, Santa Clara, CA, USA) and Trios 4 (3Shape, Copenhagen, Denmark), specifically on mixed dentition. A total of 30 subjects were divided into 2 groups, each undergoing both alginate impressions and intraoral scanning using either the iTero or Trios scanner. The plaster models were measured with a caliper, while the digital models were measured virtually. In the iTero group, all tooth width measurements exhibited differences compared to the plaster values, except for maxillary left lateral incisors (p = 0.179), mandibular right (p = 0.285), and left (p = 0.073) central incisors. The Trios group did not display significant differences in any of the tooth width measurements. Intermolar width comparisons for both groups indicated differences, except for mandibular primary canine to primary canine values (p = 0.426) in the iTero group. Regarding arch length, the mandibular anterior, maxillary right, and left arch lengths in the iTero group demonstrated larger caliper values than those of iTero. Conversely, in the Trios group, all parameters showed smaller caliper values, especially in upper anterior, maxillary right, mandibular right, and mandibular left arch lengths with significance (p = 0.027, 0.007, 0.003, and 0.047, respectively). Despite the differences between the two groups, digital models might be clinically suitable alternatives for plaster models. Pediatric dentists should carefully assess these differences, as a comprehensive evaluation would result in precise orthodontic treatment planning and favorable outcomes for young patients with mixed dentition.

• 한국콘텐츠학회논문지
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• 제12권10호
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• pp.357-364
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• 2012

치과용 스캐너를 기반으로 하는 디지털 모형은 기존의 전통적인 석고모형을 대체할 만큼 발전되고 있다. 본 연구의 목적은 디지털모형의 정확도와 신뢰도를 평가하고자 하였다. 상악의 전악모형을 주 모형으로 설정하여 주 모형으로부터 석고모형을 제작하였고(N=10), 치과용 백색광 스캐너를 이용하여 10개의 디지털모형 데이터를 채득하였다. 제작된 두 실험군(석고모형, 디지털모형)을 1명의 검사자가 2회에 걸쳐서 6곳의 계측지점을 측정하였다. 짝 표본 t-검정과 급내 상관계수을 이용하여 통계적인 분석을 하였다. 실험결과 측정값의 검사자 내 신뢰도는 급내 상관계수 결과 두 실험군 0.75에서 0.87의 범위를 보였다. 석고모형과 디지털 모형의 평균 오차값은 0.11mm에서 0.23mm의 범위를 나타내었고, 모든 계측지점에서 통계적으로 유의한 차이를 보였다(P<0.05). 본 실험결과 모든 계측지점에서 적정수준의 정확성은 확보되지 않았으나, 선행연구에 비추어 볼 때 임상적인 효용성은 검증되었다. 추가적으로 임상적인 사례를 통해 평가되어야 할 것으로 사료된다.

• 구강회복응용과학지
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• 제31권4호
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• pp.316-328
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• 2015

목적: 보관 조건과 석고 주입 시간에 따라 알지네이트 인상체로부터 제작된 모형의 정확성을 알아보고자 하였다. 연구 재료 및 방법: 채득된 알지네이트 인상체는 습도가 유지되는 항습조에 보관하는 것과 진료실 내의 공기 중에 노출되는 상태로 보관 조건을 달리하였다. 보관 조건에 따라 각각 즉시, 채득된 후 10분, 30분, 180분, 360분으로 나누어 보관한 후에 석고 모형을 제작하였다. 제작된 석고 모형을 3D 레이저 스캐너로 삼차원 디지털 모형을 구성하였고 구성된 디지털 모형의 참고점에서 거리를 측정하여 변형률을 비교하였다. 또한 각 실험군의 삼차원 디지털 평균 모형을 제작한 후 중첩을 시행함으로써 표면 변위가 발생한 부위와 크기를 확인하였다. 결과: 인상 채득 즉시 제작한 모형의 변형률이 가장 작게 나타났고, 공기 중에 보관한 인상체보다 항습조에 보관한 인상체의 변형률이 작게 나타났다. 석고 주입 시간이 증가함에 따라서 변형률도 증가하였으며, 석고 주입 시간이 180분을 지나면 보관 조건에 관계없이 대구치 부위에서 변형률과 표면 변위가 증가한다. 결론: 알지네이트 인상체로부터 제작된 모형의 정확성을 위해서는 인상 채득 후, 즉시 모형을 제작해야 한다. 보관이 필요한 경우에는 100% 상대습도가 유지되는 항습조를 이용하고, 보관 시간은 180분을 넘지 않도록 해야 정확한 모형을 얻을 수 있다.

• The Journal of Advanced Prosthodontics
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• 제5권3호
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• pp.326-332
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• 2013

PURPOSE. The purpose of this study was to compare stress distributions of implant-supported crown placed in fibula bone model with those in intact mandible model using three-dimensional finite element analysis. MATERIALS AND METHODS. Two three-dimensional finite element models were created to analyze biomechanical behaviors of implant-supported crowns placed in intact mandible and fibula model. The finite element models were generated from patient's computed tomography data. The model for grafted fibula was composed of fibula block, dental implant system, and implant-supported crown. In the mandible model, same components with identical geometries with the fibula model were used except that the mandible replaced the fibula. Vertical and oblique loadings were applied on the crowns. The highest von Mises stresses were investigated and stress distributions of the two models were analyzed. RESULTS. Overall stress distributions in the two models were similar. The highest von Mises stress values were higher in the mandible model than in the fibula model. In the individual prosthodontic components there was no prominent difference between models. The stress concentrations occurred in cortical bones in both models and the effect of bicortical anchorage could be found in the fibula model. CONCLUSION. Using finite element analysis it was shown that the implant-supported crown placed in free fibula graft might function successfully in terms of biomechanical behavior.

• 대한치과기공학회지
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• 제34권2호
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• pp.121-128
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• 2012

Purpose: The aim of this study was to determine the reliability and accuracy of measurements in digital models(CEREC$^{(R)}$ AC) compared to stone models. Methods: A master model(500B-1, Nissin Dental Product, Japan) with the prepared upper full arch tooth was used. Conventional impression and then stone model(n=10) were produced from this master model, and on the other hands, digital impressions were made with the CEREC$^{(R)}$ AC intra-oral scanner(n=10). One examiner measured two times the intercanine, intermolar distance, dental arch length. The stone model were measured using a digital caliper. The t-student test for paired samples and intraclass correlation coefficient(ICC) were used for statistical analysis. Results: The measurement of two methods showed very good reliability. At the intra-examiner reliability of measurement, ICC at the stone and CEREC$^{(R)}$ AC model were 0.81 and 0.94. The mean difference between measurements made directly on the stone models and those made on the CEREC$^{(R)}$ AC model was 0.20~0.28mm, and was statistically significant(P=0.001). Conclusion: These in vitro studies show that accuracy of the digital impression is similar to that of the conventional impression. These results will have to be confirmed in further clinical studies.