Background: Accurate recording of implant location is required for a successful definitive restoration. Aim: This study was conducted to compare the accuracy of two implant impression techniques (direct and indirect) in transferring implant positions to the master casts in comparison to implant position in patients' mouth using radiographic imaging. Materials and Methods: Ten completely edentulous male patients were selected. 2 Root-form implants 3.7 mm in diameter and 16 mm in length were utilized in this study in the canine regions. For each patient two special trays were fabricated, one for the registration of direct impression technique and the other for the indirect impression technique. Cone beam computed tomography (CBCT radiograph) was done for all patients, the casts obtained from direct and indirect implant impression techniques were taken to evaluate the accuracy of the two impression techniques in comparison with the patients' radiographs regarding the distance between the implants. The horizontal dimensional accuracy of the impression techniques was determined by measuring the inter-implants' distance in the x-axis between the copings. Measurements were done on radiographic images of the following; casts obtained from direct impression technique, casts obtained from indirect implant impression technique and radiographs of patients. Results: The mean and SD values of casts radiographs obtained from both impression techniques and from patients' radiographs were calculated. Group I (Deviation of distance between direct impression technique and patients' radiograph) had a mean value of 1.45mm (SD 0.03); Group II (Deviation of distance between indirect impression technique and patients' radiograph) had a mean value of 2.08 mm (SD 0.04). The direct impression technique showed more accurate results. Conclusion: Casts obtained from the direct impression technique were significantly more accurate than those obtained from indirect impression technique. Comparison of both impression techniques retrieved from patients in relation to patients' CBCT provided more reliable results than in vitro studies. So this study suggests that direct impression technique is more accurate.

Introduction Thyroid nodules are highly prevalent in the general population; therefore, it is crucial to discriminate benign from malignant nodules. A practical thyroid imaging reporting and data system (TI-RADS) for thyroid nodules and ultrasound elastography are valuable tools not only for characterization of nodules but also for the selection of tumors for fine-needle aspiration cytology (FNAC). Objective This study aimed to evaluate the diagnostic accuracy of US evaluation in the prediction of malignant thyroid nodules and evaluate the role of the elastography score, strain ratio (SR), and the TI-RADS scoring system as non-invasive tools in differentiation between malignant and benign thyroid nodules. Material and methods A total of 1269 patients were evaluated between February 2017 and April 2020 by a single expert thyroid ultrasound operator. The final diagnosis was achieved from cytological and/or histological evaluation and follow-up for at least 1 year. Results There were 1088 females and 181 males with a mean age of 44 ± 10 SD. The final diagnosis was 1197 benign nodules and 72 malignant nodules. Most malignant nodules were scored elastography score 4 (83.3%) and TI-RADS category 5 (86.11%). We found that nodules with antero-posterior to transverse (A-P/T) diameter > 1, have 21 times more risk to be malignant than those with A-P/T diameter < 1, patients with solitary thyroid nodules have 4.5 times to develop malignancy compared to those with multinodular goiter (MNG), nodules with absent halo have 4 times more risk of malignancy. Furthermore, microcalcifications in thyroid nodules increase the risk of malignancy 9 times compared to those without calcifications. SR was found to be an excellent discriminator to differentiate between benign and malignant nodules with P < 0.001. Also, we found that for every unit increase in SR, the risk of malignancy increased by 20%. We reported that the accuracy of ultrasonography in the detection of malignant thyroid nodules had a sensitivity of 89%, specificity of 98%, 70% PPV, and 99.3% NPV, with an overall accuracy of 97.2%. Conclusion The application of ultrasonographic non-invasive criteria for thyroid nodules in clinical practice might significantly reduce the number of unnecessary FNAC. Elastography, SR, and TI-RADS classification could be good predictors for malignant thyroid nodules.