Finite element study on modification of bracket base and its effects on bond strength.

OBJECTIVE: This article aims to analyze the difference in stresses generated in the bracket-cement-tooth system by means of a peel load in single and double-mesh bracket bases using a three-dimensional finite element computer model. MATERIAL AND METHODS: A three-dimensional finite element model of the bracket-cement-tooth system was constructed and consisted of 40,536 bonds and 49,201 finite elements using a commercial mesh generating programmer (ANSYS 7.0). Both single and double-mesh bracket bases were modified by varying the diameter from 100-400 µm progressively, and the spacing between the mesh wires was kept at 300 µm for each diameter of wire. A peel load was applied on the model to study the stresses generated in different layers. RESULTS: In case of double-mesh bracket base, there was reduction in stress generation at the enamel in comparison to single-mesh bracket base. There was no difference in stress generated at the bracket layer between single and double-mesh bracket bases. At the impregnated wire mesh (IWM), layer stresses increased as the wire diameter of the mesh increased. CONCLUSION: Results show that bracket design modification can improve bonding abilities and simultaneously reduce enamel damage while debonding. These facts may be used in bringing about the new innovative bracket designs for clinical use.

Finite element study on modification of bracket base and its effects on bond strength

OBJECTIVE: This article aims to analyze the difference in stresses generated in the bracket-cement-tooth system by means of a peel load in single and double-mesh bracket bases using a three-dimensional finite element computer model. MATERIAL AND METHODS: A three-dimensional finite element model of the bracket-cement-tooth system was constructed and consisted of 40,536 bonds and 49,201 finite elements using a commercial mesh generating programmer (ANSYS 7.0). Both single and double-mesh bracket bases were modified by varying the diameter from 100-400 µm progressively, and the spacing between the mesh wires was kept at 300 µm for each diameter of wire. A peel load was applied on the model to study the stresses generated in different layers. RESULTS: In case of double-mesh bracket base, there was reduction in stress generation at the enamel in comparison to single-mesh bracket base. There was no difference in stress generated at the bracket layer between single and double-mesh bracket bases. At the impregnated wire mesh (IWM), layer stresses increased as the wire diameter of the mesh increased. CONCLUSION: Results show that bracket design modification can improve bonding abilities and simultaneously reduce enamel damage while debonding. These facts may be used in bringing about the new innovative bracket designs for clinical use. .

OBJETIVO: o objetivo do presente artigo é analisar a diferença entre as tensões geradas na interface braquete-cemento-dente por meio do teste peel load em bases de braquete de malha simples e dupla e do método de elementos finitos tridimensional. MÉTODOS: foi construído um modelo de elementos finitos do sistema composto pela interface braquete-cemento-dente. Esse modelo consistiu de 40.536 nós e 49.201 elementos finitos. A análise foi feita com a ajuda do programa ANSYS 7.0. Tanto a base de braquete de malha única quanto a de malha dupla sofreram modificações no diâmetro, que variou de 100 a 400µm, progressivamente. O espaço entre os fios das malhas foi mantido a 300µm para o diâmetro de cada fio. O teste peel load foi aplicado ao modelo para investigar as tensões geradas nas diferentes camadas. RESULTADOS: quando comparadas às bases de braquetes de malha simples, as bases de braquetes de malha dupla geraram menos tensão no esmalte dentário. Não foram detectadas diferenças entre as tensões geradas na superfície dos braquetes com bases de malha simples e dupla. Na malha de fios impregnados (MFI), houve um aumento na tensão com o aumento do diâmetro dos fios que compõem a malha. CONCLUSÃO: os resultados revelam que as modificações no desenho do braquete podem aumentar a colagem e, ao mesmo tempo, minimizar os danos causados no esmalte durante o processo de descolagem. Esses fatos podem ser utilizados no desenvolvimento de desenhos de braquetes inovadores, destinados à utilização clínica. .

An experimental study of arch perimeter and arch width increase with mandibular expansion: a finite element method.

AIMS: The objective of this study was to estimate the increase in arch perimeter associated with mandibular lateral expansion, To estimate the increase in intermolar width with mandibular lateral expansion and to find out the changes of tooth inclination with mandibular expansion. MATERIALS AND METHODS: The mandibular bone with dentition of indian skeletal specimen was obtained. The computer tomogram (CT) slices of the mandible were taken. Finite element model (FEM): Numerical representation of the geometry was created by dividing the geometry into finite number of elements and the elements were connected together with nodes at the junction. RESULTS: The result of the study showed when 10° of lateral expansion was applied to the lower buccal segment at the center of rotation found at 4.3 mm below the root apex of first molar, a space of 1.3 mm between the canine and first premolar, and thus an increase in arch perimeter of 2.6 mm. CONCLUSION: The tip of the mesiolingual cusp of the first molar moved 4.2 mm laterally, resulting in a change in intermolar width by 8.4 mm. Three-dimensional simulation showed that 1 mm of intermolar expansion increased the arch perimeter by 0.30 mm. CLINICAL SIGNIFICANCE: As the finite element method evolves and scientists are able to more clearly define physical properties of biological tissues, more accurate information can be generated at the level that other analytical methods cannot fully provide data.This result would be of value clinically for prediction of the effects of mandibular expansion.

Are ratings of dentofacial attractiveness influenced by dentofacial midline discrepancies?

AIMS: To assess the attractiveness of dentofacial midline discrepancies during smiling, and to determine if the ratings were influenced by the gender of the judges. METHODS: Twenty non-dental undergraduate students (10 males, mean age: 33.5 years; 10 females, mean age: 31.2 years) and 20 orthodontists (10 males, mean age: 36.6 years; 10 females, mean age: 34.3 years) assessed frontal photographs of the same smiling adult female with coincident midlines, and images of the same person with the upper dental midline shifted 2 mm and 4 mm to the right and left of the facial midline. The judges scored the attractiveness of the smile using 5-point scale. RESULTS: Both the students and the orthodontists considered that the images were less attractive as the dentofacial midline discrepancy increased. More orthodontists than undergraduate students, and more female orthodontists than male orthodontists, considered a 4 mm discrepancy between the dental and facial midlines as unattractive. CONCLUSION: Dental to facial midline discrepancies reduce dentofacial attractiveness. Discrepancies of 2 mm or more are likely to be noticed by both orthodontists and non-dental university students. Orthodontic treatment objectives should include correction of the dental midline discrepancies to within 2 mm of the facial midline.

Epstein-Barr virus-associated gastric carcinoma in southern India: A comparison with a large-scale Japanese series.

Epidemiological and clinicopathological features of Epstein-Barr virus (EBV) associated gastric carcinoma was compared in India and Japan, two countries differing markedly in gastric cancer incidence. Using in situ hybridization assay, the presence of EBV-encoded small RNA (EBER) was examined in 215, and 2,011 gastric cancer cases in Kerala, India, and Japan, respectively. Ten cases (5%), all males, in the Indian series were EBER-positive. This frequency was similar to that in the Japanese series (6.2%). As was the case with Japanese series, the EBV-associated gastric carcinoma in the Indian series was observed most frequently in the middle part of the stomach (1 in antrum, 4 in middle part, 2 in cardia, and 3 unknown), and, histologically, the diffuse type Lauren's classification (8 cases) was more common than the intestinal type (2 cases). Virus subtyping by PCR-RFLP revealed that all of the 10 EBV strains isolated from the EBER-positive Indian cases were subtype A, and wild-type F for Bam HI F region. In Bam HI I region, 8 cases were type C and the remaining 2 cases were type D. In either series, there was no significant difference in the frequency of tumors with p53 overexpression between EBER-positive and -negative cases. However, the proportion of cells with p53 overexpression in EBER-negative tumors was significantly higher than that in EBER-positive tumors regardless of histological type in both series. In conclusion, the frequency and major clinicopathological features of EBV-associated gastric carcinoma in south India were similar to those observed in Japanese series although gastric cancer incidence in these two countries differs markedly.

Carcinoma of the pancreas presenting as an orbital tumor: a case report.

Metastasis to the orbit from pancreatic adenocarcinoma is rare. A 38-year-old man with metastatic adenocarcinoma of the right orbit at initial examination is described. Two months later he was diagnosed with a pancreatic primary tumor. The incidence and pattern of orbital metastasis in carcinomas is briefly discussed.

Radiation-induced acute immediate nuclear abnormalities in oral cancer cells: serial cytologic evaluation.

OBJECTIVE: To evaluate the dose-response relationship of nuclear abnormalities in tumor cells collected by serial scrape smears from oral cancer patients on fractionated radiotherapy. STUDY DESIGN: The study included 31 patients with squamous cell carcinoma of the oral cavity treated by radiotherapy (60 Gy in 25 fractions; 2.4 Gy per fraction). Serial scrape smears were taken from each tumor before treatment and after delivery of various fractions, usually 2 (4.8 Gy), 5 (12.0 Gy), 8 (19.2 Gy) or 12 (28.8 Gy). The smears were stained by Giemsa stain and evaluated by light microscopy, and the number of micronucleated, binucleated, nuclear budded and multinucleated cells were scored. Their relation to cumulative dose was analyzed by Kruskal-Wallis one-way analysis of variance. The results were expressed in terms of 1,000 mononucleated cells. RESULTS: Even before treatment, most of the tumors showed various abnormally nucleated cells, and, despite the high intertumoral variation (as indicated by the high variance), all of them showed statistically significant dose-related increases. The mean values before treatment and after irradiation with 28.8 Gy, respectively, were 2.8 and 19.5 (P < .0001) for micronucleated cells, 1.5 and 8.5 (P < .000001) for nuclear budded cells, 8.2 and 35.5 (P < .0001) for binucleated cells, and 3.7 and 16.8 (P < .0001) for multinucleated cells. When the different types of nuclear abnormalities were combined and analyzed as "abnormally nucleated cells," the mean count before treatment and after 28.8 Gy were 7.9 and 44.9 (P < .00001), respectively. CONCLUSION: The study showed that radiation-induced micronucleation, multinucleation, binucleation and nuclear budding in oral cancer cells has statistically significant dose-related increases that become evident in the initial few days of radiotherapy and that they can be differentiated well by cytology. This dose-response relationship and the high intertumoral variations suggest that serial assay of these changes has potential use for radiosensitivity prediction.

Correlation of lectin binding with lymph node metastasis in oral cancers.

Lymph node metastasis is an important factor that influences the treatment policy and prognosis of oral cancers. The cell membrane is known to play a role in the metastatic process. The aim of the present study was to evaluate the relationship of lectin binding frequency of oral cancer cells to their capacity to metastasize to the lymph node. Smears collected from tumours of 66 untreated patients were stained with Jackfruit lectin (JFL) conjugated with horseradish peroxidase (HRP), with diaminobenzidine dihydrochloride (DAB) as the visualant. The frequency of cells showing lectin binding was evaluated. The results showed that tumours with a high frequency of JFL binding cells had higher risk of lymph node metastasis (RR = 1.5). It was also found that a combined score integrating the percentage of lectin binding cells with known clinical parameters, like primary tumour size, local invasion and histological subgroup, had better utility than any of these individually in assessing risk of lymph node metastasis. The density of sugar residues on the cell surface may be of importance in determining the lymph node metastatic potential of oral cancers, and the present study suggests the need for further research in this area.

Evaluation of visual inspection as a screening test for cervical cancer.

Visual inspection of the uterine cervix by paramedical personnel has been proposed for the early detection of cervical cancer, as an alternative to routine cytology screening in developing countries. We evaluated the performance of this procedure in detecting precursor lesions and cancer in a study involving 2843 married women in Kerala, India. Two thresholds were used to define a positive test. In the lower one, any abnormality was considered as positive. The cut-off point for the high threshold was one or more of the high-risk findings: bleeding on touch, suspicious growth/ulcer and hard, irregular, oedematous cervix. A Pap smear was performed on all subjects, and a biopsy was done for those with moderate dysplasia and above. A combination of cytology and histology findings was used as the 'gold standard'. Using the low threshold, 1279 (45%) women were positive on visual inspection, and with the higher threshold 179 (6.3%) were positive. There were six moderate dysplasias, nine severe dysplasias, ten carcinomas in situ and 13 invasive carcinomas. With the lower threshold, sensitivity and specificity to detect moderate dysplasia and above were 65.8% and 55.3% respectively; the values for severe dysplasia and above were 71.9% and 55.3% respectively and for invasive cancer were 92.3% and 55.2% respectively. With the higher threshold, the sensitivity decreased considerably (28.9% to detect moderate dysplasia lesions, 31.3% for severe dysplasia and 53.8% for clinical cancer) and the specificity increased to approximately 94%. At a lower threshold, the sensitivity was not satisfactory, and the test was highly non-specific; at a higher threshold sensitivity was even lower. Thus, the test characteristics of visual inspection are not very promising either as a preselection procedure for cytology or as a low-technology measure for cervical cancer screening in developing countries.

Serial cytological assay of micronucleus induction: a new tool to predict human cancer radiosensitivity.

BACKGROUND AND PURPOSE: The micronucleus test, generally done in cultured tumour cells irradiated in vitro, has not gained wide acceptance in predicting human cancer radiosensitivity. The purpose of this study was to see if micronucleus assay by serial scrape smear cytology can predict oral cancer radiosensitivity. MATERIALS AND METHODS: Forty nine oral cancer patients given radiotherapy (60 Gy/25 fractions/5 weeks) form the study population. Serial scrape smears were taken from their tumours before treatment and after delivery of 2, 5, 8 and 12 fractions, stained by Giemsa and the number of micronucleated cells (MNC) noted. The patients were grouped to those who developed tumour recurrence ('Resistant') and those who did not ('Sensitive'), and the pattern of micronucleus induction compared. RESULTS: Both groups of tumours had MNC even before treatment, with statistically significant dose-related increase with radiotherapy. The sensitive group had a higher mean increase in MNC count than the resistant group (6.1 times and 3.6 times the pre-treatment value, respectively) and better correlation with dose (r = 0.54 vs. 0.43). The increase in MNC count occurred earlier in the resistant group than in the sensitive, the TMNC (time for the pre-treatment value to double) being 3.3 days and 7.6 days, respectively. Also, the resistant group showed a plateauing of the MNC count which the sensitive group lacked. CONCLUSIONS: The higher MNC induction in the sensitive tumours suggests the usefulness of the assay as a test of radiosensitivity. The differing patterns of MNC increase suggest that differences in proliferation rate is an important cause of tumour failure. Serial cytological assay of micronucleus induction can identify both radiosensitivity and proliferation characteristics of tumours, and thus may turn out to be a useful test of radiocurability.

Significance of AgNOR count in differentiating malignant cells from reactive mesothelial cells in serous effusions.

OBJECTIVE: To distinguish reactive mesothelial cells from malignant cells in serous effusions using silver staining of nucleolar organizer regions (AgNOR) applied to ethanol-fixed cytologic preparations. STUDY DESIGN: One hundred aspirated samples of benign and malignant effusions were studied using the one-step silver staining method. Eight cytologically atypical samples were also included in the study. RESULTS: In malignant cells the mean AgNOR count was 4.72 +/- 0.76 (+/- SD), and the AgNORs were irregular in shape, while in benign mesothelial cells AgNORs were comparatively larger, single dots with a mean count of 1.92 +/- 0.23. Of the cytologically atypical samples, five were in the malignant range. The others were within benign limits. Repeat cytology of the second aspirate confirmed that finding. CONCLUSION: AgNOR study appears to be clinically useful as an additional diagnostic tool for use in ascitic and pleural fluid samples when the cytologic diagnosis is difficult.

Differential expression of jackfruit-lectin-specific glycoconjugates in metastatic adenocarcinoma and reactive mesothelial cells-a diagnostic aid in effusion cytology.

Distinguishing reactive mesothelial cells from adenocarcinoma cells in serous effusions on the basis of morphological criteria alone is often difficult. Interest has therefore been focused on identifying reliable methods to supplement the conventional cytological techniques. Plant lectins have been reported as diagnostic markers for malignant cells. We studied 51 aspirated samples of benign and malignant effusions using horseradish-peroxidase-conjugated jackfruit lectin. No significant difference was observed between the cells of pleural and peritoneal fluids. The reactively proliferated mesothelial cells of benign effusions showed a predominance of mild staining while moderate and intense staining was predominant in malignant effusions. Intense and irregular lectin binding was observed in macrophages irrespective of the cause of effusion. The lectin staining method therefore appears to have some clinical significance as an additional diagnostic aid for use in effusion cytology.

Role of sputum cytology in the diagnosis of mediastinal germ cell tumor.

A rare case of germ cell tumor of the mediastinum infiltrating the lung and metastasizing to the supraclavicular lymph node in a 25-year-old male is presented. The patient presented with a history of superior vena cava syndrome and chest roentgenograms revealed an abnormal mediastinum. Primary positive diagnosis was made cytologically on sputum specimens. The peculiar cell type found in the Papanicolaou stained sputum smears were correlated with fine needle aspiration cytology of lung and lymph node, and confirmed the histologic pattern of the tumor metastasizing to the lymph node. To our knowledge, the present case is the first report of a primary mediastinal seminoma (germinoma) infiltrating the lung and diagnosed by sputum cytology. These results suggest the usefulness of sputum examination as an adjunctive diagnostic procedure in the detection of patients with possible lung infiltrated germinal neoplasms.