Introduction: One of the fractal analysis methods to examine the structure of a texture is fractal dimension (F.D.) measurement. F.D is a quantitative method to show the complexity of a structure using a number. The aim of this study was to determine the effect of different exposure conditions, voltages and angle of x-ray tube on F.D. values of mandibular bone. Methods: This lab-trial analytical research was conducted on ten healthy, non-fracturing human mandibles. Periapical digital images were obtained by the Peri-Apical Focus (Planmeca, Finland) with a constant time of 0.2 seconds and changes in exposure conditions and angle of the tube. Periapical radiographs were obtained with 2 kV voltages of 60, 70, with2 mA of 400, 500, and 3 tube angles of -5, 0, +5 degrees. Data was analyzed by SPSS version 16 software and Kolmogorov–Smirnov test, mann whitney testand ANOVA test. Results: No significant difference was observed in fractal mean values between 60 and 70 kVp and among 5-, 0, 5+ degrees in all 10 mandibles.There was a significant difference between the 400 and 500 mA just in one case (p≤0.05). Conclusion: Considering the incompatibility of the amount of calculated fractal dimension from kVp, mA and tube angle, this method can be used as a useful tool in dentistry to examine the structure of spongy bone and its changes in various pathological conditions. Then, standardize the periapical imaging technique to compare it is not necessary.
Objectives: The aim of this study was to determine the effect of different scan delays and different kVps on the diagnostic accuracy of inter-proximal caries detection in photostimulable phosphor plates (PSPs). Materials and Methods: 45 non-cavitated extracted human posterior teeth were radiographed using the DIGORA® PSPs (Soredex Corporation, Helsinki, Finland). The plates were exposed at 60 kVp and 70 kVp were scanned immediately, 10 min, 30 min, 1h, 6 h, 24 h and 48 h after exposure. In between the exposure and the scan period, the plates were stored in light-tight boxes. The true presence of caries was determined by sectioning the teeth mesiodistally. The accuracy was expressed as the area under ROC curve (AZ). The AZs were compared using SPSS version17 software and repeated measurement test. Kappa was used to measure inter and intra observer agreement. Results: There was no significant difference between caries detection AZs of the images that were scanned immediately and within 30 min after exposure at 60 kVp and 70 kVp (P >0.05). The immediately scanned AZ at 60 kVp was significantly higher than the AZs with 6 h, 24 h and 48 h scan delays (P <0.05). the immediately scanned AZ at 70Kvp was significantly higher than the AZs of 1 h, 6 h, 24 h and 48 h (P <0.05). Conclusions: PSP scanning should not be delayed higher than 30 min in order to have an accurate proximal caries detection. Longer delays may cause loss of quality of images.
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