Light transmittance of CAD/CAM ceramics with different shades and thicknesses and microhardness of the underlying light-cured resin cement

OBJECTIVES: The aim of this in vitro study was to evaluate the effects of the thickness and shade of 3 types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials. MATERIALS AND METHODS: A total of 120 specimens of 2 shades (A1 and A3) and 2 thicknesses (1 and 2 mm) were fabricated using VITA Mark II (VM; VITA Zahnfabrik), IPS e.max CAD (IE; IvoclarVivadent), and VITA Suprinity (VS; VITA Zahnfabrik) (n = 10 per subgroup). The amount of light transmission through the ceramic specimens was measured by a radiometer (Optilux, Kerr). Light-cured resin cement samples (Choice 2, Bisco) were fabricated in a Teflon mold and activated through the various ceramics with different shades and thicknesses using an LED unit (Bluephase, IvoclarVivadent). In the control group, the resin cement sample was directly light-cured without any ceramic. Vickers microhardness indentations were made on the resin surfaces (KoopaPazhoohesh) after 24 hours of dark storage in a 37°C incubator. Data were analyzed using analysis of variance followed by the Tukey post hoc test (α = 0.05). RESULTS: Ceramic thickness and shade had significant effects on light transmission and the microhardness of all specimens (p < 0.05). The mean values of light transmittance and microhardness of the resin cement in the VM group were significantly higher than those observed in the IE and VS groups. The lowest microhardness was observed in the VS group, due to the lowest level of light transmission (p < 0.05). CONCLUSION: Greater thickness and darker shades of the 3 types of CAD/CAM ceramics significantly decreased the microhardness of the underlying resin cement.

Evaluation of linear measurements of implant sites based on head orientation during acquisition: An ex vivo study using cone-beam computed tomography

PURPOSE: This study evaluated the effect of various head orientations during cone-beam computed tomography (CBCT) image acquisition on linear measurements of potential implant sites. MATERIALS AND METHODS: Six dry human skulls with a total of 28 implant sites were evaluated for seven different head orientations. The scans were acquired using a Hitachi CB-MercuRay CBCT machine. The scanned volumes were reconstructed. Horizontal and vertical measurements were made and were compared to measurements made after simulating the head position to corrected head angulations. Data was analyzed using a two-way ANOVA test. RESULTS: Statistical analysis revealed a significant interaction between the mean errors in vertical measurements with a marked difference observed at the extension head position (P<0.05). Statistical analysis failed to yield any significant interaction between the mean errors in horizontal measurements at various head positions. CONCLUSION: Head orientation could significantly affect the vertical measurements in CBCT scans. The main head position influencing the measurements is extension.

Radiographic evaluation of the maxillary sinus prior to dental implant therapy: A comparison between two-dimensional and three-dimensional radiographic imaging

PURPOSE: This study was performed to evaluate the diagnostic efficacy of panoramic radiography and cone-beam computed tomography (CBCT) in detecting sinus pathology. MATERIALS AND METHODS: This study was based on a retrospective evaluation of patients who had undergone both a panoramic radiograph and a CBCT exam. A total of 100 maxillary sinuses were evaluated. Four examiners with various levels of expertise evaluated the images using a five-point scoring system. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic efficacy of the two modalities. The image analysis was repeated twice, with at least two weeks between the evaluation sessions. Interobserver reliability was assessed using Cronbach's alpha, and intraobserver reliability was assessed using Cohen's kappa. RESULTS: Maxillary sinus pathology was detected in 72% of the patients. High interobserver and intraobserver reliability were observed for both imaging modalities and among the four examiners. Statistical analyses using ROC curves demonstrated that the CBCT images had a larger area under the curve (0.940) than the panoramic radiographs (0.579). CONCLUSION: Three-dimensional evaluation of the sinus with CBCT was significantly more reliable in detecting pathology than panoramic imaging.

The reliability of tablet computers in depicting maxillofacial radiographic landmarks

PURPOSE: This study was performed to evaluate the reliability of the identification of anatomical landmarks in panoramic and lateral cephalometric radiographs on a standard medical grade picture archiving communication system (PACS) monitor and a tablet computer (iPad 5). MATERIALS AND METHODS: A total of 1000 radiographs, including 500 panoramic and 500 lateral cephalometric radiographs, were retrieved from the de-identified dataset of the archive of the Section of Oral and Maxillofacial Radiology of the University Of Connecticut School Of Dental Medicine. Major radiographic anatomical landmarks were independently reviewed by two examiners on both displays. The examiners initially reviewed ten panoramic and ten lateral cephalometric radiographs using each imaging system, in order to verify interoperator agreement in landmark identification. The images were scored on a four-point scale reflecting the diagnostic image quality and exposure level of the images. RESULTS: Statistical analysis showed no significant difference between the two displays regarding the visibility and clarity of the landmarks in either the panoramic or cephalometric radiographs. CONCLUSION: Tablet computers can reliably show anatomical landmarks in panoramic and lateral cephalometric radiographs.

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

Accuracy of the methodology section of graduate and post-graduate theses in Shahid Beheshti medical university, school of dentistry from March 2009 to October 2011

The purpose of this study was to investigate the histologic interaction Theses are among the most important research sources of the universities and should be authored according to the international standards of scientific writing. The present study aimed at determining the accuracy of the methodology section of graduate and post-graduate theses conducted in Shahid Beheshti Medical University, School of Dentistry from March 2009 to October 2011. In this descriptive cross-sectional study all approved theses of the Shahid Beheshti Medical University, School of Dentistry from March 2009 to October 2011 were evaluated according to the international check lists. For data analysis, SPSS version 16.0 software, ANOVA and independent ttest were used. A total of 101 theses with observational design and 72 with experimental design were evaluated. The mean conformity of observational theses with STROBE check list was 75%. The highest conformity was observed in the complete description of inclusion and exclusion criteria [95%] while the lowest conformity was observed in the bias control [48%]. The mean conformity of the interventional theses with all the items of CONSORT checklist was 62%. The highest conformity was found in complete description of the type and process of intervention [90.3%] whereas the lowest conformity was found in allocation concealment mechanism [88%]. No significant correlation was found between the presence of a consulting professor and academic ranking of the thesis instructor and the mean score of thesis. In observational theses, the lowest conformity was observed in the description of the bias control; whereas, in interventional theses the lowest conformity was detected to be in allocation concealment mechanism