Effect of Head Position on Linear Cephalometric Measurement Accuracy of Cone-Beam Computed Tomography

Objective This study aimed to assess the effect of head position on linear cephalometric measurements by cone-beam computed tomography (CBCT). Methods: CBCT scans of four human dry skulls were obtained by NewTom 3G volume scanner with alarge (15 x15 cm)field of view in 1 centric and 18 eccentric positions: 10°, 20°, and 30° tilt (right and left), 10°, 20°, and 30° rotation (right and left), 10°, 20°, and 30° extension and 10°, 20°,and 30° flexion. The distances between the selected landmarks namely the Nasion (N), Sella (Se), anterior nasal spine (AN S), Menton (Me), Gnathion (Gn), Gonion (Go), and Condylion (Co) were measured by two observers on maximum intensity projection reconstructions using the NNT Viewer software, and compared with the actual measurements (gold standard). The inter-class correlation coefficient (ICC) and the student’s t-test were used for statistical analysis. Results The mean inter-rater agreement was excellent for all head positions (ICC=96.89%). The maximum error in absolute mean measurements was 2.56 mm (P=0.03) The minimum error was for the N-Me line, which is a vertical line closest to the midline. Conclusion The greatest error was observed in 30° left ward rotation for the left CoGn linear measurement. Although this level of error may not be of clinical significance, it is suggested that clinicians acquire the scans in ideal head position to minimize distortion and errors

Effect of hydrofluoric acid concentration and etching time on the surface roughness of CAD/CAM ceramics

Introduction: Dental ceramics are considered as materials that can restore the appearance of natural teeth. Etching the inner surface of a ceramic restoration with hydrofluoric acid (HF) followed by using a silane coupling agent is a well-known and recommended method to increase the bond strength. The aim of etching on ceramic structure is to enhance the surface roughness (Ra) and energy and to cleanse the bonding area. The aim of this study was to evaluate the effect of different HF concentrations and etching times on the Ra of IPS e.max CADTM and Vita mark IITM. Material & Methods: Two HF concentrations (5% and 10%) and three etching times (20, 60 and 120 seconds) were evaluated. Etched patterns were observed by scanning electron microscopy (SEM) and Ra was measured using atomic force microscopy (AFM). Surface element analysis was performed using energy dispersive X-ray spectroscopy (EDAX). Data were analyzed on SPSS 20 using ANOVA and T-test. Results: The Ra had no significant difference among various Vita mark IITM specimens (P=0.973). Among IPS e.maxTM specimens etched with 5% HF, the AFM results showed that 20-s etching time had the lowest Ra and among those etched with 10% HF and 120-s etching time had the most Ra. In IPS e.maxTM specimens etched with acid for 20 s, a significant difference was observed in Ra of 5% and 10% acid concentrations (5% HF lower than 10% HF) (p=0.012). Conclusion: Among IPS e.maxTM specimens etched with 5% and 10% HF, increasing the etching time lead to higher Ra. For both IPS e.maxTM and Vita mark IITM, 20-s etching with 5% HF provides acceptable Ra for the bond

Production, Characterization and Application of Monolithic Biocarbon for Water Desalination

Desalination is a process of removing salts from saline solutions to produce fresh water. Currently, the challenges of desalination technology are high energy consumption and material cost. This project suggests sustainable and affordable ways to purify water via evaporation process under sunlight or capacitive deionization using monolithic biocarbon. Biocarbon was produced from woody biomass during 60 hours of slow pyrolysis. After pyrolysis, the macrostructure of wood is preserved in the produced biocarbon. The morphology, chemical composition, permeability and electro capacitance of biocarbon was measured. The effect of biocarbon amount, biocarbon particle size range, light intensity, light distance, salt concentration, and wood orientation on evaporation rate was studied. The use of monolithic biocarbon increased the evaporation rate 8 times higher from saltwater. The permeability of biocarbon and evaporation rate in axial and radial orientation was significantly different. The measured capacitance of biocarbon was 113 F/g in 1 M NH_4Cl solution.M.A.S

Tissue Characterization Using Optical Coherence Tomography

Optical coherence tomography (OCT) is a non-invasive imaging modality, which provides real-time near-histology resolution images. In dentistry, OCT has been used for early detection of carious lesions, malignant changes in the oral tissues and other indications. However, to the best of our knowledge there is no information regarding the ability of this imaging modality in differentiating between different types of tissues in the oral cavity. If OCT proves to be able to render information regarding the properties of tissues, it can be used to detect pathological changes at an early stage, which results in better treatment outcomes. In this study, we imaged five types of tissues, i.e., human enamel, human cortical bone, human trabecular bone, rat masseteric muscle and fatty tissue plus water and air using OCT (Axsun Inc. Billerica, MA). We then developed an algorithm to determine the intensity profile, pixel intensity values and histograms for each sample. The same tissues plus water and air were also imaged using cone beam computed tomography (CBCT) and gray scale values were measured for each tissue. The mean pixel intensity values and gray scale values for the OCT images and CBCT scans of each tissue were reported, respectively. A similar pattern was observed in the pixel intensity values and gray scale values in both imaging modalities. Therefore, within the limitations of this study, it was concluded that OCT can reliably differentiate between different tissues (hard and soft tissues) in vitro and the results are comparable to CBCT gray scale value

Artificial Intelligence (AI) for Detection and Localization of Unobturated Second Mesial Buccal (MB2) Canals in Cone-Beam Computed Tomography (CBCT)

The aim of this study was to develop a deep learning model to automatically detect and segment unobturated mesial buccal 2 (MB2) canals on endodontically obturated maxillary molars depicted in CBCT studies. Fifty-seven deidentified CBCT studies of maxillary molars with clinically confirmed unobturated MB2 canals were retrieved from a dental institution radiology database. One-hundred and two maxillary molar roots with and without unobturated MB2 canals were segmented using ITK-SNAP. The data were split into training and testing samples designated to train and evaluate the performance, respectively, of a convolutional neural network (CNN), U-Net. The detection performance revealed a sensitivity of 0.8, a specificity of 1, a high PPV of 1, and a NPV of 0.83 for the testing set, along with an accuracy of 0.9. The segmentation performance of unobturated MB2 canals, assessed using the custom metric, rendered a mean value of 0.3018 for the testing set. The current AI algorithm has the potential to identify obturated and unobturated canals in endodontically treated teeth. However, the AI algorithm is still somewhat affected by metallic artifacts, variations in canal calcifications, and the applied configuration. Thus, further development is needed to improve the algorithm and validate the accuracy using external validation data sets

Counterclockwise Drilling with Different Tapered Drills Condenses the Implant Bed—An Optical Coherence Tomography In Vitro Study

Background and Objectives: To evaluate the condensation and the microarchitecture of implant bed walls of sites prepared with counterclockwise drilling with tapered implant drills using optical coherence tomography. Materials and Methods: Four drill designs with different wall and tip angles were used. Polyurethane laminas resembling type IV bone microarchitecture were superimposed and clamped with a vice to simulate the coronal, middle, and apical aspects of the implant site. Twenty implant beds were prepared at 1200 rpm in clockwise (control) and counterclockwise (test) directions (N = 160). Optical coherence tomography (OCT) was used to evaluate the condensation and microarchitecture characteristics of the implant bed walls. The relative condensation was calculated using the Image J software Bone application. The microarchitecture was evaluated in reconstructed 3D volumes in XY, XZ, and YZ sections. Statistical analysis was performed using one-way ANOVA. Dunnet test was applied to determine differences between groups. Significance was set as p < 0.05. Results: Counterclockwise drilling (Test) condensed and changed the microarchitecture of the apical regions for all the implant beds in all of the groups when compared to clockwise drilling (control). The apical region of test groups showed the highest relative bone condensation (p = 0.026) when compared to controls. Conclusions: The direction of rotation (counterclockwise drilling) and not the design of tapered drills (tip and wall angles) is responsible for the condensation at the apical area observed in polyurethane blocks. The OCT method can be used for the evaluation of changes in density and microstructure of polyurethane blocks

Non-syndromic hypodontia in an Iranian orthodontic population

To investigate the prevalence, characteristics (ie, malocclusion, location, type), and sex distribution of hypodontia in an Iranian orthodontic population. A retrospective study was conducted using periapical and panoramic radiographs and study models of 1,751 subjects attending university orthodontic clinics (870 females, 881 males, age 9-27 years). The Chi-square test was used to analyze differences in the distribution of hypodontia, after stratification by sex and malocclusion type. A total of 197 congenitally missing teeth were observed in 160 patients (9.1%; 74 boys and 86 girls); there were no statistically significant differences between sexes (Chi-square = 0.832, P = 0.36). Hypodontia was more common in patients with Class III malocclusion (45.2%), and was more prevalent in the maxilla (71%) than in the mandible (29%). Maxillary lateral incisors (35.6%) and maxillary second premolars (13.0%) were the most commonly missing teeth, followed by mandibular lateral incisors (9.6%) and mandibular second premolars (8.2%). The prevalence of missing teeth was higher in the anterior segment (incisors and canines) than in the posterior segment (premolars and molars). The prevalence of oligodontia was 0.34%. The prevalence and characteristics of the most frequently missing teeth accorded with the findings of most studies conducted in other countries

Supernumerary teeth amongst Iranian orthodontic patients : a retrospective radiographic and clinical survey

Objective: To investigate the prevalence, characteristics (malocclusion, location, type) and gender distribution of supernumerary teeth (ST) in an Iranian orthodontic population. Material and methods: A retrospective study was carried out using radiographs (periapicals, panoramic) and study models of 1751 subjects (870 girls, 881 boys; age range 9–27 years). The Pearson chi-square test was used to determine differences in the distribution of ST when stratified by gender and malocclusion type. Results: Fourteen ST were found in 13 patients (six males, seven females), giving a prevalence rate of 0.74%. The prevalence rate of ST was higher in Class III malocclusions (5.2%) and was a rare finding among Class II malocclusions (0.1%). The occurrence rate of ST was higher in maxilla (78.5%) than in mandible (21.5%). The most common type of ST was the conical form (43%). We did not observe any late-developing paramolar or distomolar ST. Conclusion: The prevalence rate of ST in our study was 0.74% and ST were more common among Class III malocclusions

Study Motives and Career Choices of Iranian Medical and Dental Students

To compare the study motives and career choices of senior undergraduate medical and dental students in Iran. A cross-sectional questionnaire-based survey study involving final year medical and dental students from 4 dental and medical schools was conducted in 2010. The questionnaire was designed in three sections (Demographic details, motivational items and career choice items) and after confirming the validity and reliability of the questions, it was distributed among the students. Data were entered into SPSS; statistical analysis included logistic regression and multiple linear regression. The response rate was 62% (n=219) for medical and 64% (n=300) for dental students. The factor analysis identified six motivational items: "Social and professional status", "Health care and people", "Others recommendation", "personal interest and nature of occupation", "Occupational experience" and "Personal life". Medical students were more influenced by "Playing a role in community health" and "Personal interest". "Work independence" and "Social factors" however were two major influential factors among dental students. There were significant differences in important influences by age (Social and professional status, Others' recommendation), Parents education (Social and professional status, Health care and people, Personal life) and marital status (single >married: Occupational experience, married > single: Personal life). Engaging in postgraduate studies was the first career preference among 90.9% and 89.8% of dental and medical students respectively. Medical and dental students report a wide range of motivational factors in studying medicine/dentistry and future career plans which is affected by age, parents' education and marital status

Movement: A Clinical Investigation

Objectives: One major drawback of orthodontic treatment is its long duration due to slow tooth movement and the pain at the onset of treatment following application of forces. There is controversy regarding the efficacy of laser for decreasing the treatment time and pain of orthodontic treatment. The purpose of this study was to investigate the effect of low level diode laser on the rate of orthodontic tooth movement and the associated pain. Materials and Methods: In this double blind randomized controlled clinical trial, 12 or- thodontic patients referring to Shahid Beheshti School of Dentistry for first premolar ex- traction were randomly selected and allocated to gallium aluminum-arsenide laser (Ga,Al,As diode laser, 880 nm, 100 mW, 5 j/cm2, 8 points, 80 seconds, continuous mode) or control group. The patients initially underwent leveling and alignment using the sectional system. Force (150 gr) was applied to each canine tooth via sectional closing loops. The loops were activated every month. The rate of tooth movement and pain were monitored over the treatment period and recorded on days 1, 3, 7, 30, 33, 37, 60, 63 and 67. Two-way ANOVA was used for comparison of groups. Results: There was no significant difference in terms of tooth movement and pain scores between the irradiated and non-irradiated sides at any time point (P>0.05). Conclusion: Although laser enhanced orthodontic tooth movement in the upper jaw, we failed to provide solid evidence to support the efficacy of laser for expediting tooth move- ment or reducing the associated pain