• 한국생산제조학회지
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• 제20권3호
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• pp.284-291
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• 2011

Numerical experiments on biological interfacial layer, DEJ by finite element software ABAQUS have been conducted to study its fracture behavior including crack bridging / arresting characteristics in the model. Crack growth simulation has been carried out by numerical tool, XFEM, devoted to study cracks and discontinuities. The fracture toughness of DEJ has been estimated before and after crack bridging. The implications of bridging in numerical study of fracture behavior of DEJ-like biological interface have been discussed. It has been observed that the results provided by the numerical studies without proper accommodation of bridging phenomenon can mislead. This study can be helpful for understanding the DEJ-like biological interface in terms of its fracture toughness, an important material characteristics. This property of the material is an important measure that has to be taken care during design and manufacturing processes.

• 치위생과학회지
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• 제7권4호
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• pp.207-211
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• 2007

많은 연구에서 대구치의 백악법랑 경계부에 나타나는 법랑돌기의 발현이 치주질환과 밀접한 연관성을 보인다고 하였다. 이 연구는 서울대학교 치과병원에 내원한 환자에서 발거된 치아 660개 중 법랑돌기의 관찰이 가능하고, 제 1, 2대구치의 구별이 가능한 530개의 치아를 대상으로 치면별, 치아별 법랑돌기의 발현빈도를 알아보고자 시행하였다. 법랑돌기의 관찰이 용이하도록 깨끗이 세정한 후, 8배 전자확대경을 이용하여 상, 하악 제 1, 2대구치의 협면, 근심면, 원심면, 설면(구개면)에 나타나는 법랑돌기를 조사하였다. 법랑돌기의 발현빈도는 상악에서 45.49%, 하악에서 39.62%로, 하악에서보다 상악에서 높았으며, 제1대구치는 45.22%, 제2대구치는 39.89%로, 제2대구치보다 제1대구치에서 더 높게 나타났다. 또한 치면별 발현빈도는 전체 대상치아의 협면에서 가장 높게 나타났으며, 상악 제1대구치 협면에서 78.27%, 상악 제2대구치 협면에서 81.23%, 하악 제1대구치 협면에서 76.86%, 하악 제2대구치 협면에서 70.3%의 발현율을 보였다. 이 연구의 결과는 이전의 보고에 비해 높은 법랑돌기의 발현빈도를 보여주고 있으며, 이는 8배 전자확대경을 이용한 관찰에 의한 결과로 생각된다.

• 대한치과의사협회지
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• 제56권1호
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• pp.8-16
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• 2018

Purpose: The aim of in vitro study was to compare the diagnostic accuracy to detect non-cavitated enamel caries on smooth surface by using four kinds of the QLF devices. Materials and Methods: A total of 52 human permanent premolars and molars were used. Fluorescence images were captured by the QLF devices (Inspektor Pro, QLF-D, Qraycam, and Qraypen). Fluorescence loss of the QLF was calculated. The severity of lesions was categorized into the following 3 scores using polarized light microscopy: normal (S), enamel demineralization to outer half of enamel (D1), and inner half of the enamel up to the dentin-enamel junction (D2). The Kruskal-Wallis test was used to compare the fluorescence loss among the QLF devices. Spearman rank correlation coefficient between histological scores and fluorescence loss of the devices was calculated. The sensitivity, specificity, and area under the receiver operating curve (AUROC) were calculated to compare their diagnostic accuracies. Results: The correlation coefficients between histological scores and the fluorescence loss of the devices showed 0.77 to 0.81 (P < 0.001). All histological scores, the fluorescence loss among the devices showed no statistical difference. Among the devices, sensitivity, specificity, and AUC values of the fluorescence loss showed 0.84 to 0.94, 0.76 to 0.90, and 0.90 to 0.92, respectively. Conclusions: All QLF devices had no difference with excellent diagnostic accuracies to detect non-cavitated enamel caries on smooth surface.

• Journal of Korean Dental Science
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• 제4권1호
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• pp.1-5
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• 2011

Purpose: Exact knowledge of the location and dimension of the pulp chamber help to maintain the pulp healthy during operative procedure and also reduces the risk of perforation of pulp chamber during root canal treatment. This in-vivo study was carried out to measure critical morphology of pulp chamber of mandibular molar using intra-oral periapical radiograph. Materials and Methods: Mandibular molar teeth of 56 patients were evaluated. The mandibular molar teeth whose pulp chamber was not violated by caries, restoration, fracture crown and those having closed apex were included in the study. The intraoral periapical radiographs were taken with paralleling angle technique using radio-opaque grid with 1 mm space. This grid was placed directly on the film. Results: In 94% of the mandibular first molars specimens the pulp chamber ceiling was at the level of the cemento-enamel junction. The measurements showing the lowest percentage variance were buccal cusp to furcation (approximately 11%) and buccal cusp to pulp chamber ceiling (approximately 15%). The distance from the cusp tip to pulp chamber ceiling height was approximately 6.0 mm, the distance from the pulpal floor to the furcation was approximately 3.0 mm, and the average height of a pulp chamber was 1.5 to 2.0 mm. Conclusion: The exact knowledge of distances of pulp chamber from various anatomical landmarks helps in proper assessment of root canals and ultimately avoids the failure of root canal treatment.

• 대한치과의사협회지
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• 제48권4호
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• pp.297-307
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• 2010

Noncarious cervical lesions(NCCLs) are characterized as structural defects found on the tooth surface of the cement-enamel junction. Loss of tooth structure through noncarious mechanisms may vary in etiology and clinical presentation for each individual but presently many clinician now classify this as tooth failure of abfraction due to the stress applied in the cervical area of the tooth under oral physiological and pathological loads. In the current study, we investigated the stress distribution of maxillary premolar with NCCL using simulated 3D finite element analysis. The results were as follows: 1. In the sound maxillary premolar, the stresses were highly concentrated at cervical enamel surface of the mesiobuccal line angle, asymmetrically. 2. Once the lesion has been formed, the highest stress concentration was observed around the apex of the wedge shaped lesion. 3. In four types of NCCL, the patterns of stress distribution were similar and the peak stress was observed at mesial corner and also stresses concentrated at lesion apex. 4. Lesion cavity modification of rounding apex, reduced stress of lesion apex. 5. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin.

• 대한소아치과학회지
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• 제38권3호
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• pp.290-295
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• 2011

치아형성 과정 중 치배 주위의 물리적 작용이나 대사 환경의 변화로 치아 발생은 영향을 받을 수 있다. 유치열기에 가해진 외상은 계승 영구치의 발생에 장애를 초래시킬 수 있는 가장 대표적인 물리적 요인으로 이로 인한 합병증으로 계승 영구치의 법랑질 변색 및 저형성증이 가장 흔히 발생하고 드물게 매복, 이소 맹출, 치근 형성 정지 및 치근 만곡 등이 나타난다. 본 증례에서는 만 6세 5개월의 여자 어린이 환자가 안면부 외상을 주소로 내원하여 상악 좌우 유중절치의 정출성 탈구, 상악 우측 유측절치의 함입성 탈구, 상악 좌측 유측절치의 구개측 측방 탈구로 진단되었고, 상악 치은부의 열상과 상악 전치부의 치조골 골절이 관찰되었다. 내원 당일 치과 응급실에서 동요도가 심한 상악 좌우 유중절치의 발치 후 치은 봉합술을 시행하였다. 24개월 정기 검진 중 방사선 사진 상에서 상악 좌,우측 측절치의 백악 법랑 경계(Cemento enamel junction, CEJ) 근방에 치근 만곡이 관찰되었고 상악 중절치 치근의 치관부 1/3부위에서 치근 형성이 정지되고 있는 양상이 관찰되었다. 치조골 골절이 어린이에서 흔하게 나타나는 외상의 유형은 아니나 본 증례에서와 같이 치근 발육이상 등 여러 합병증을 일으킬 수 있으므로 외상을 입은 환아에서 치조골 골절 여부에 대한 면밀한 검사 및 주기적인 검진은 예후 예측 및 향후 치료에 있어서 중요할 것이다.

• Current Optics and Photonics
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• 제6권1호
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• pp.86-91
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• 2022

Two-photon fluorescence microscopy was performed on the enamel-dentin junction area of a human tooth using a femtosecond pulsed laser. We obtained a clear image contrast between the bright dentin and dark tubules with the autofluorescence generated from the endogenous fluorophores in dentin. The autofluorescence shows a broad spectrum due to complex cross links between dentinal collagens, which extend from blue to orange wavelengths (470-590 nm), but a gradual autofluorescence loss in photobleaching was observed for a long-term exposure under strong excitation. For increasing excitation power, we found that two-step decay becomes significant in the spectrally integrated autofluorescence.

• International Journal of Oral Biology
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• 제42권4호
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• pp.155-161
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• 2017

Teeth and bones are highly mineralized tissues containing inorganic minerals such as calcium phosphate, and a growing number of evidences show that their mineral content is associated with many diseases. Although the quantification of mineral contents by micro-computed tomography(micro- CT) has been used in diagnosis and evaluation for treating bone diseases, its application for teeth diseases has not been well established. In this study, we attempted to estimate a usefulness of a high-resolution micro-CT in analysis of human teeth. The teeth were scanned by using the Skyscan 1172 micro-CT. In order to measure tooth mineral content, beam hardening effect of the machine was corrected with a radiopaque iodine-containing substance, iodoacetamide. Under the maximum resolution of $6.6{\mu}m$, X-ray densities in teeth and hydroxyapatite standards were obtained with Hounsfield unit (HU), and they were then converted to an absolute mineral concentration by a CT Analyzer software. In enamel layer of cusp area, the mean mineral concentration was about $2.14mg/mm^3$ and there was a constant mineral concentration gradient from the enamel surface to the dentinoenamel junction. In the dentin of middle 1/3 of tooth, the mean mineral concentration was approximately $1.27mg/mm^3$ and there was a constant mineral concentration gradient from the outer of root to the pulp side, ranging from 1.3 to $1.06mg/mm^3$. In decay region of dentin, the mineral content was gradually decreased from the intact inner side to the decayed surface. These results suggest that high-resolution micro-CT can be as a useful tool for non-invasive measurement of mineral concentration in teeth.

• 대한소아치과학회지
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• 제32권1호
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• pp.152-157
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• 2005

Hypophosphatemia rickets는 비타민 D의 치료량에 내성을 갖기 때문에 Vitamin D-resistant rickets(VDRR)라고도 명명되며, 이는 요세관으로부터 무기질 인산의 재흡수가 감소됨으로써 혈청 칼슘농도는 정상이나 인산농도가 낮고 alkaline phosphatase가 약간 증가되기 때문에 쉽게 진단되는 구루병의 한 형태이다. 이러한 Hypophosphatemia rickets의 임상적인 소견으로 양다리가 휘는 것. 작은 키, 척추측만. 손목과 발목부위의 팽대가 나타나며 구강내 소견으로는 자발적인 치성농양의 높은 발생률, 맹출 지연, 근단공의 폐쇄지연, 얇고 저형성된 법랑질, 명확히 인지하기 힘든 치조백선, 확대된 치수강, 법랑상아경계까지 연장된 치수각 등이 있다. 본 증례는 유치의 상실과 그에 따른 치료를 위해 본원 소아과에서 의뢰된 비타민 D저항성 구루병 환아의 임상소견과 그 치과적 치료에 대해 보고하는 바이다.

• Restorative Dentistry and Endodontics
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• 제42권2호
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• pp.87-94
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• 2017

Objectives: Chitosan has been widely investigated and used. However, the literature does not refer to the shelf life of this solution. This study evaluated, through the colorimetric titration technique and an analysis of dentin micro-hardness, the shelf life of 0.2% chitosan solution. Materials and Methods: Thirty human canines were sectioned, and specimens were obtained from the second and third slices, from cemento-enamel junction to the apex. A 0.2% chitosan solution was prepared and distributed in 3 identical glass bottles (v1, v2, and v3) and 3 plastic bottles (p1, p2, and p3). At 0, 7, 15, 30, 45, 60, 90, 120, 150, and 180 days, the specimens were immersed in each solution for 5 minutes (n = 3 each). The chelating effect of the solution was assessed by micro-hardness and colorimetric analysis of the dentin specimens. 17% EDTA and distilled water were used as controls. Data were analyzed statistically by two-way and Tukey-Kramer multiple comparison (${\alpha}=0.05$). Results: There was no statistically significant difference among the solutions with respect to the study time (p = 0.113) and micro-hardness/time interaction (p = 0.329). Chitosan solutions and EDTA reduced the micro-hardness in a similar manner and differed significantly from the control group (p < 0.001). Chitosan solutions chelated calcium ions throughout the entire experiment. Conclusions: Regardless of the storage form, chitosan demonstrates a chelating property for a minimum period of 6 months.