No abstract

H3PO4 doped polyaniline was synthesized by a single‐step chemical polymerization method using ammonium persulfate as an oxidizing agent. The material characterization was done by SEM, UV–vis spectroscopy and thermogravimetric analysis (TGA). The pellets of the synthesized material were used to study the electrical properties, using a four‐probe method. The room temperature electrical conductivity is found to be 0.2201 S/cm. The electrical resistance in response to the varying humid environment (ranging between 20 and 100% RH) is recorded to evaluate the sensitivity of the H3PO4 polyaniline samples toward humidity. The resistance of the samples is found to vary by three orders of magnitude for 20–100% RH and is found to decrease with increasing humidity. The response and recovery time are observed to be 12–14 and 26–30 sec, respectively. Copyright © 2007 John Wiley & Sons, Ltd.

Aim: To find the marginal fit of the porcelain fused to metal crowns by two different margin designs (shoulder and chamfer) and two commercially available base metal alloys. Material and Methods:Tooth preparation of first central incisor for porcelain-fused-to-metal crown with shoulder margin and second incisor for porcelain-fused-to-metal crown with chamfer margin was done. Wax pattern of the same was prepared. Impression of both prepared ivorine incisors was made by light body impression material and poured with pattern resin. Both the patterns were invested and casted with cobalt chromium alloy for making master dies. Two wax patterns of unprepared central incisors were fabricated, one with shoulder margin and another with chamfer margin. These patterns were then cut back to the size of the coping. Four rings were invested. In each ring ten patterns, five with shoulder margin and five with deep chamfer margin were sprued together to ensure that each group would pass through the same investing and casting procedure, followed by ceramic firing and measurement.

Aims and objective: Making of a definitive, secondary or wash/final impression of displaceable flabby tissues with minimum or no displacement of tissue by using window impression technique. Background: Denture fabrication on flabby ridges is testing situations for a clinician as it adversely affects retention and stability of complete dentures. The difficulties encountered in these patients need to be overcome by modified techniques in denture fabrication that are not time consuming and make use of materials that are easy to use. Materials and Methods: This window impression technique, uses a custom tray with a window over flabby tissues and a mucostatic impression material to minimize distortion of tissues while making a impression. First, an accurate record of the denture supporting and limiting structures is made except for the mobile tissues which are recorded in second step using light body Polyvinyl siloxane impression material in the window area of special tray. Conclusion: The use of window impression technique helps in maintaining the contour and recording the details of the tissues without displacing the flabby tissues. Hence, it improves the prognosis for complete denture without surgical removal of hyperplastic tissues.

Aim:The aim of the study was to evaluate the dimensional accuracy of three combinations of polyvinyl siloxane impression material by doublemix single-step impression technique. Materials and methods: Metal master model was made according to the ADA specification no. 19; ISO 4823:2000/AMD 2007. Impressions were made using perforated custom-made metallic trays of 2 mm and 4 mm spacing, the impression materials used were putty, heavy body, regular body and light body. A total of 30 impressions were made by single-step technique and poured in die stone to obtain resultant cast. Ten impressions were made of each combination of polyvinyl siloxane (PVS). Three dimensions (interabutment distance, height and diameter) on resultant cast were measured and compared with metal master model. The results were statistically analyzed and tabulated. Results: Diameter of abutment, the height of abutment and interabutment distance in each group were larger in dimensions as compared with metal master model. The dimensional discrepancies of group I, group II and group III casts when compared with the master model were significantly different from each other. The least difference was found in group I. Conclusion:The one-step putty-light body combination (group I) produced the most accurate stone casts compared with one-step heavy body-light body and regular body-light body combinations. Clinical significance: In everyday dental practice, impression making is imperative. Hence, by doing this study, we tried to find out which material combination is suitable to give us predictable and accurate results.