Nanomodification of mineral trioxide aggregate for enhanced physiochemical properties.

AIM: To analyse the physicochemical properties of a Nano white mineral trioxide aggregate (NWMTA) and compare it with white mineral trioxide aggregate (WMTA). METHODOLOGY: White mineral trioxide aggregate and NWMTA were prepared and mixed according to the manufacturer's instructions. Surface area of powder before hydration, setting time, X-ray diffraction and microhardness at pH values of 4.4 and 7.4 were evaluated by Brunauer-Emmett-Teller, ISO Specification no.6876, Vickers microhardness, and energy-dispersive X-ray spectroscopy equipped with X-ray colour (dot) map for both cements. anova and Mann-Whitney were used for statistical analysis at a significance level of 0.5. RESULTS: The mean ± SD of surface area and setting time were 1.8 ± 0.2 m(2) g(-1) and 43 ± 2 min for WMTA and 7.8 ± 1.2 m(2) g(-1) and 6 ± 1 min for NWMTA, respectively. Mean ± SD of Microhardness were 16 ± 2, 51 ± 1, 69 ± 1 and 81 ± 2 for WMTA at pH values of 4.4 and 7.4 and for NWMTA correspondingly. Numbers of open porosity over the surface were 88 ± 24 and 44 ± 13 for WMTA and NWMTA, respectively. Statistical tests revealed significant differences between the groups (P < 0.001) in surface area, setting time and surface hardness for both cements. Uniform distribution of strontium was only observed in NWMTA. However, other compounds were not significantly different. CONCLUSION: Increasing surface area of powder can reduce setting time and increase microhardness even at lower pH values after hydration.

Effects of three oral analgesics on postoperative pain following root canal preparation: a controlled clinical trial.

AIM: To compare the effects of single doses of three oral medications on postoperative pain following instrumentation of root canals in teeth with irreversible pulpitis. METHODOLOGY: In this double-blind clinical trial, 100 patients who had anterior or premolar teeth with irreversible pulpitis without any signs and symptoms of acute or chronic apical periodontitis and moderate to severe pain were divided by balanced block random allocation into four groups of 25 each, a control group receiving a placebo medication, and three experimental groups receiving a single dose of either Tramadol (100 mg), Novafen (325 mg of paracetamol, 200 mg ibuprofen and 40 mg caffeine anhydrous) or Naproxen (500 mg) immediately after the first appointment where the pulp was removed, and the canals were fully prepared. The intensity of pain was scored based on 10-point VAS before and after treatment for up to 24 h postoperatively. Data were submitted to repeated analysis of variance. RESULTS: At the 6, 12 and 24 h postoperative intervals after drug administration, the intensity of pain was significantly lower in the experimental groups than in the placebo group (P < 0.01). Tramadol was significantly less effective (P < 0.05) than Naproxen, and Novafen that were similar to each other (P > 0.05). CONCLUSION: A single oral dose of Naproxen, Novafen and Tramadol taken immediately after treatment reduced postoperative pain following pulpectomy and root canal preparation of teeth with irreversible pulpitis.

A new approach for locating the minor apical foramen using an artificial neural network.

AIM: To develop a new approach for locating the minor apical foramen (AF) using feature-extracting procedures from radiographs and then processing data using an artificial neural network (ANN) as a decision-making system. METHODOLOGY: Fifty straight single-rooted teeth were selected and placed in a socket within the alveolar bone of a dried skull. Access cavities were prepared and a file was place in the canals to determine the working length. A radiograph was taken to evaluate the location of the file in relation to the minor foramen and further checked after retrieving the tooth from the alveolar socket. The location of the file tip was categorized into: beyond the AF (long), within the root canal (short) and just at the minor AF (exact). Each radiograph was used to extract relevant features using K-means, Otsu method and Wavelet protocol. Thirty-six extracted features were used for training and the rest were used for evaluating the multi-layer Perceptron ANN model. RESULTS: Analysis of the images from radiographs (test samples) by ANN showed that in 93% of the samples, the location of the AF had been determined correctly by false rejection and acceptation error methods. CONCLUSION: Artificial neural networks can act as a second opinion to locate the AF on radiographs to enhance the accuracy of working length determination by radiography. In addition, ANN can function as a decision-making system in various similar clinical situations.

X-ray diffraction analysis of gamma 2 (Sn-Hg) phase in higher copper amalgams of varying mercury content.

Microstructures of high copper commercial amalgams containing varying amounts of mercury, ranging from 20% above to 25% below recommended values, were primarily investigated by x-ray diffraction. Mechanisms relating to the absence or presence of gamma 2 (Sn-Hg) phase in these amalgams were discussed in relation to the presence of copper and tin elements in their original alloys. The optimum mercury concentration in some amalgams was determined in order to keep them free of the gamma 2 (Sn-Hg) phase.

Measurement of resistance of amalgam mixes to condensation.

A method was designed to evaluate the resistance of amalgam mixes to condensation forces. For the purpose of classification with respect to the plasticity of amalgam, the optimum test condition was to apply 40 or 50 lb of static load at 30 sec after trituration.

Microstructure of dental amalgams containing high and low copper contents.

Microstructure of commercial dental alloys and their amalgams were studied primarily by x-ray diffraction, optical metallography, scanning electron microscopy, and x-ray energy dispersive spectroscopy. X-ray diffraction revealed more phases than normally reported in these materials. Presence of new phase was discussed and their formation mechanism understood. Some phases having interacting 2 theta degrees values with others were properly identified. Both new and conventional dental alloys and their amalgams, namely Tytin, Sybraloy, Dispersalloy, Kerr Spheraloy, Caulk Spherical, Shofu Spherical, and Caulk 20th Century Microcut were used to complete the investigation.

Initiation of cracks in dental amalgam.

The force required to initiate cracks in dental amalgam beams was measured and related to the microstructure. The force measured was dependent on age and on the distribution of phases on the tension side of the beam. The Ag-Cu phase is most resistant to failure in Dispersalloy and an experimental alloy.

Physical properties of dental silver-tin amalgams with high and low copper contents.

Newly developed amalgams such as Tytin, Sybraloy, and Dispersalloy had low static creep, high compressive strength, and similar values for both diametral tensile strength and dimensional change in comparison with conventional amalgams such as Kerr Spheraloy, Caulk Spherical, Shofu Spherical, and Caulk 20th Century Micro Cut. The data for physical properties were evaluated statistically, and the amalgams were ranked according to the numerical position assigned to each property.

Evaluation of alternative alloys to type III gold for use in fixed prosthodontics.

A study was done to evaluate the fit of castings made from commercially available alloys promoted by their manufacturers as cheaper alternatives to type III gold for use in fixed prosthodontics. Two nickel-chromium alloys, two silver-palladium alloys, two gold-silver-palladium alloys, a 50% gold alloy, and a type III conventional gold alloy (used as a basis of comparison) were evaluated. After optimum conditions for waxing, investing, and casting were determined experimentally, four crowns (two full crowns and two three quarter crowns) were cast from each alloy. The castings were cleaned by pickling or sandblasting and placed on their respective dies. Only one casting was made from each die. Ten judges were asked to evaluate the marginal fit and completeness of each casting on its die. The judges rated each casting and the ratings were converted into rankings. Type III gold and Forticast tied and were ranked first; Paliney CB was ranked second; Alborium and Albacast tied and ranked third; Aurolite CB was ranked fourth; and Jelenko Experimental and Howmedica III tied and ranked fifth. It was found that the nickel-chromium alloys produced castings that had a tight fit and showed marginal discrepancies even under conditions designed to yield maximum expansion of the investment. These nonprecious metal castings were judged inferior in terms of fit when compared with castings made from noble metal-and precious metal-containing alloys. Existing investments and techniques were adequate for all castings except those made from the nonprecious alloys. It was concluded that low (approximately lambda 50%) gold alloys and palladium-silver-gold alloys that are commerically available can be used as substitutes for type III gold alloy without any loss inthe quality of casting fit.

Microscopic observations of amalgams carved by different methods and subsequently polished.

Occlusal amalgam restorations placed in extracted deciduous molars were studied using an electron microscope. The fillings were carved only or both carved and burnished, and all were subsequently polished. Observations were made before and after polishing, and the results emphasized the effects of carving, burnishing, and polishing on the surface texture and marginal integrity of amalgam fillings.