Journal of Dental Medicine

This article presents a comparative clinical study of digital imaging, as a new technology, and conventional method for X - Ray absorption in lens and thyroid.Clinical examination was performed on 50 patients with an average of 28 years among the cases who were reffered to the department of rediology, Islamic Azad universiy of IRAN in 1999.Two pocket dosimeters were used to meausre the dose rate. One was placed on the skin of thyroid region and the other on the eyes.The results revealed that the absorbed dose in RVG was significantly lower than conventional method (P<0.0001).Digital imaging, as a new technology, is in a state of rapid development.It is a likely that RVG will substute conventional radiography within the near future.

Background and Aim: Proper shaping and cleaning of the root canal system is one of the most important aspects of endodontic treatment. To estimate the canal length before instrumentation in endodontic treatment, traditionally, conventional radiographic techniques and recently Direct Digital Radiography (DDR) are applied. The application of computer technology to radiography has allowed less exposure time, image acquisition, manipulation, storage, retrieval, and transmission to remote sites in a digital format, elimination of wet processing and considerable reduction in the time lapse between image acquisition and display. The purpose of this study was to compare the accuracy of DDR versus conventional radiography in estimating endodontic file lengths of curved canals in first mandibular molars.

Materials and Methods: In this test evaluation study, fourty extracted human first mandibular molars with root curvature were selected.Samples were divided into two groups: With root curvature less than 25 and more than 25. Samples were mounted in plaster blocks and canal lengths were estimated by using DDR and conventional radiographs. Regression analysis and correlation coefficient were used to calculate statistical differences between the groups with P<0.05 as the limit of significance.

Results: Conventional radiography was more precise in canals with less than 25 degrees curvature (P=0.160). While, DDR was more precise for canals with curvature more than 25 degrees (P=0.605). However, these differences were not statistically significant.

Conclusion: The image quality of DDR system has improved to the point that it can now be used for estimating canal lengths, even for curved canals, with accuracy comparable to that of conventional radiography.

Background and Aims: Internal derangement of the Temporomandibular joint (TMJ) is the most common form of Temporomandibular disorders, which represents an abnormal internal strucural and functional change of the disk, as well as an abnormal relationship of the disk to the condyle, glenoid fossa and articular eminence when the teeth are in the closed- mouth position. The aim of this study was to evaluate the correlation between eminence steepness and condyle disk movements in TMJs affected by internal derangements using magnetic resonance imaging (MRI).

Materials and Methods: In this cross-sectional study, digital MRI files of 90 joints belong to 45 patients in open and closed-mouth positions were evaluated. Patients were subdivided into two groups: 64 individuals with anterior disk displacement with reduction and 26 individuals with anterior disk displacement without reduction. Appropriate oblique sagittal sections were selected and printed. Outlines of the fossa, eminence, condyle and disk were traced on matte acetate sheets and evaluated by an oral and maxillofacial radiologist and a postgraduate student of oral and maxillofacial radiology. Disk rotation, condyle rotation, condyle translation and eminence steepness were measured. The data were analyzed using T-test.

Results: In this study, no significant difference was found in measurements between the two groups, (for steepness P=0.64, for Disc rotation P=0.77, for condyle rotation P=0.28 and for condyle translation P=0.12). Disk rotation showed statistically significant correlation with eminence steepness in the anterior disk displacement with reduction group
(P=0.034). Although this correlation was weak (r=0.27) no statistically significant correlations were found between other variables and eminence steepness in this group (for condyle rotation P=0.3 and for condyle translation P=0.98). Disk rotation and condyle translation had statistically significant relationship in the anterior disk displacement without reduction group (P=0.011, r=-0.49). In addition, a significant difference was found between disk rotation and condyle rotation in this group (P=0.004, r=0.54). The relationship between other variables and eminence steepness were not statistically significant (for disc rotation P=0.06, for condyle rotation P=0.72 and for condyle translation P=0.73).

Conclusion: According to the results of the present study, there is no obvious relationship between eminence steepness and movements of the condyle- disk assembly in patients with TMJ internal derangements. Therefore, the hypothesis that a steep articular eminence of the TMJ is a predisposing factor for disk displacement without reduction could not be verified. Performing prophylactic Eminectomy as a part of patient treatment plan is doubtful and need further evaluations.

Background and Aims: The purpose of this in vitro study was to assess the effect of two different surface treatments on the contrast ratio of IPS e.max press ceramic submitted to accelerated aging.

Materials and Methods: Ten ceramic (IPS e.max Press) disks (10-mm diameter and 1.5-mm thick) were fabricated according to the manufacturer's recommendations. The samples were randomly divided into 2 groups (n=5): polishing and glazing. Contrast ratio ware obtained with a spectrophotometer before and after accelerated aging. The contrast ratio (CR=Yb/Yw), was defined as the ratio of illuminance (Y) of the test material when it is placed on the black background (Yb) to the illuminance of the same material when it is placed over a white background (Yw), was determined. The data were statistically analyzed by two-way analysis of variance (P<0.05).

Results: All specimens of IPS e.max press ceramic showed significant increase in CR after 300-hour accelerated aging time (P=0.005). Polished samples showed significantly higher opacity compared with that of the glazed ones (P=0.018).

Conclusion: Within the limitations of this study, it may be concluded that the glazed specimens showed higher stability in their translucency than the polished specimens.

Background and Aims: Because of high prevalence of TMJ dysfunctions , increased promotion of diagnostic and treatment methods is necessary. In many cases, in addition to disc position, morphology of other joint components such as articular eminence can be changed and therefore the probable correlation between disc position and morphology of hard tissue components can be used for prediction of internal derangements. The aim of this study was to evaluate the correlation between the position of disc and morphology of articular eminence of TMD`s patients using magnetic resonance imaging (MRI).

 Materials and Methods: In this cross sectional study by evaluation of digital MRI files, ultimately 78 joint images were identified which had sufficient quality and resolution for review. Then the MRI images, were observed and evaluated by 3 oral and maxillofacial radiologists to determine the disc position (normal, anterior displacement with and without reduction, and posterior displacement) and morphology of articular eminence (Box, Sigmoid, Flattened). Ultimately the results that were reported at least by 2 observers were included as the final results and were recorded in the check list. Data were analyzed using Chi-Square test and Fisher test.

 Results: In this study, no case of posterior disc displacement was found and therefore was excluded from the study. Articular eminence morphology (Flattened versus Sigmoid) showed statistically significant correlation with anterior disc displacement with and without reduction (P-values for anterior displacement with and without reduction were 0.03 and 0.002, respectively). No significant difference was found between the sigmoid and box types in relationship with disc displacement (P-values for anterior displacement with and without reduction were 0.72 and 0.70. In this study, no significant difference between the anterior disc displacement with reduction and anterior disc displacement without reduction in relationship with the morphological changes of articular eminence in any of the cases were found.

 Conclusion: The results showed that flattening of articular eminence had significant relationship with anterior disc displacement.