A Comparison of the Marginal Accuracy of Metal Copings Made with Three Different Brands of Nickel-Chromium Alloys and Various Sprue Designs: An Vitro Study.

Introduction: It is important to construct the sprue in a way that ensures that the mold gets an appropriate supply of metal at the right speed. Many manufacturers now offer sprue designs that have not been advocated in textbooks or publications for their normal use. Aim: The goal of this research was to compare the sprue design's marginal fit to that of the other designs. Methods: During this investigation, we attempted to see whether the fabrication of metal copings could be improved. Three sprue designs were used in this research for the assessment of casting accuracy: normal cylindrical, funnel-shaped, and cuboidal or flattened sprue forms. Results: The mean marginal disparity of nickel-chromium (Ni-Cr) alloy copings made by three distinct brands was determined to be statistically insignificant. Conclusion: Within the limitation of the study, it was concluded that the marginal accuracy of metal copings fabricated with three different brands of Ni-Cr alloy did not reveal a statistically significant result. However, out of the three different sprue designs, that is, cylindrical, cuboidal, and funnel shape, the marginal accuracy of cylindrical and cuboidal sprue designs was found to be better than that of the funnel shape sprue design because the funnel shape sprue design is narrow at the point of attachment, thereby increasing the flow pressure and decreasing the turbulence of the molten metal.

Evaluation of Microleakage Using Dye-penetration Method in Three Different Composite Resin Core Build-up Materials: An In Vitro Study.

AIM: Aim of the current research is to establish and assess the microleakage in bulk-fill composite, nanohybrid ormocer-based resins, and nanofilled composite resin core build-up materials employing the dye-penetration technique. MATERIALS AND METHODS: Sixty human mandibular first premolar teeth with a solitary root canal without dental caries were chosen for this research. Each specimen was subjected to decoronation of 2 mm from the cementoenamel junction (CEJ), following which the root canal treatment procedure was rendered complete. A space for the post was made for all the 60 samples. Following positioning of the post, specimens were allocated into one of the following three investigational groups (20 specimens in every group) on the basis of the core build-up materials used as group I: bulk-fill composites, group II: nanohybrid ormocer-based resins, and group III: nanofilled resin composites. Direct composite was used for core build-up and subjected to light-curing. Following this, the specimens were immersed in 1% methylene blue solution for 24 hours interval. Each section was evaluated for dye diffusion employing a stereomicroscope with software at a magnifying power of 40× and surface contact between dentin and base of the material was evaluated under scanning electron microscope. RESULTS: Nanohybrid ormocer-based composites exhibited the least microleakage at 1.12 ± 0.14, in pursuit by nanofilled composite resins at 1.79 ± 0.09, and finally the bulk-fill composites at 2.85 ± 0.11, amid the investigational groups studied. A statistically significant difference amid the three dissimilar cores buildup substances was found upon analysis of variance. CONCLUSION: Despite the study limitations, this research came to a conclusion that each of the three investigated core build-up substances exhibited microleakage. However, amid the three, nanohybrid ormocer-based composites depicted the lowest amount of microleakage in pursuit by the nanofilled resins and the bulk-fill composites. CLINICAL SIGNIFICANCE: Core build-up is an important requirement as the remaining tooth substance following root canal treatment reduces and needs reinforcement with core build-up to sustain the tooth structure and provide resistance. A vital mandate for enduring efficiency of the restoration in the mouth is high-quality adhesive bond of these agents to cavity walls with diminished microleakage.

Comparison between Mineral Trioxide Aggregate Mixed with Water and Water-based Gel Regarding Shear Bond Strength with Resin-modified Glass Ionomer Cement and Composite.

AIM AND OBJECTIVE: To compare between mineral trioxide aggregate (MTA) mixed with water and water-based gel regarding shear bond strength with resin-modified glass ionomer cement (RMGIC) and composite. METHODS AND MATERIALS: In this study, 40 blocks of cylindrical shape were prepared with acrylic. These blocks were divided into four groups with each group consisting of 10 blocks: group-1A: MTA + distilled water + composite, group-1B: MTA + distilled water + RMGIC, group-2A: MTA + polymer + composite, and group-2B: RMGIC + MTA + polymer. After that, a universal testing machine was used for the measurement of shear bond strength. The acrylic blocks were placed under this machine. A blade with a knife-edge was used to provide a crosshead speed of 1 mm/minute. This was continued till bond of MTA in both forms (distilled water/gel) and restorative material failed. RESULTS: It was observed that a statistically significant difference was found between MTAw + composite and MTAg + composite resin but no statistically significant difference between MTAw + RMGIC and MTAg + RMGIC with p ≥ 0.05. It was found that a statistically significant difference was present between the RMGIC and composite groups within the same MTA type with p ≤ 0.05. CONCLUSION: It was concluded from the present study that MTA with a water-based gel has a better shear bond strength than composite resin and RMGIC materials. CLINICAL SIGNIFICANCE: It has been found that MTA has different properties when it is mixed with polymer and water. Very few studies have been conducted in the past to compare MTA mixed with water and water-based gel regarding the shear bond strength with RMGIC and composite.

Comparison of Dimensional Accuracy of Three Different Impression Materials Using Three Different Techniques for Implant Impressions: An In Vitro Study.

AIM: To compare the dimensional accuracy of polyether, polyvinyl siloxane, and polyether polyvinyl siloxane hybrid impression materials using closed tray, open tray splinted, and open tray nonsplinted coping impression techniques and to find out the best suitable impression material and technique combination for implant impressions. MATERIALS AND METHODS: The sample size of the study was 45. The combinations of materials and techniques were divided into nine groups, namely polyvinyl siloxane with closed tray, polyvinyl siloxane with open tray nonsplinted copings, polyvinyl siloxane with open tray splinted copings, polyether with closed tray, polyether with open tray nonsplinted copings, polyether with open tray splinted copings, polyvinyl siloxane-polyether hybrid with closed tray, polyvinyl siloxane-polyether hybrid with open tray nonsplinted copings, and polyvinyl siloxanepolyether hybrid with open tray splinted copings. Five samples of each group were evaluated. A total of 45 impressions were taken. A stainless steel master metal framework with three internal hex implants was fabricated and used to generate the samples. A common condensation silicone putty spacer was applied over the impression copings attached to the implants, which was then duplicated. All trays were fabricated on this duplicated silicone die using light cure acrylic resin. Trays to be used for open tray techniques had their top removed for gaining access to screws of the impression copings. Splinting of coping for OS group was done using pattern resin. Impressions were poured, and master cast was generated. Interimplant distance was measured using stereomicroscope and an image analyzing software. RESULTS: Open nonsplinted technique resulted in significantly better replication of implant positions compared to open splinted and closed techniques. Hybrid impression material depicted significantly better dimensional accuracy than polyether and polyvinyl siloxane. Hybrid open nonsplinted depicted least mean difference in interimplant distance, followed by hybrid open splinted and polyether open splinted groups. Polyvinyl siloxane closed tray showed maximum difference in interimplant distance in comparison with other groups. CONCLUSION: Polyvinyl siloxane-polyether hybrid impression material and open nonsplinted technique gave best replication of implant positions on the master cast. CLINICAL SIGNIFICANCE: Accuracy of impressions and casts is of great importance for the fabrication and long-term clinical success of precisely fitting implant-retained prostheses.