A Method to Generate Exact Contour Files for Solid Freeform Fabrication

Existing methods to create contour files generate a polygonal approximation of the contours instead of an exact representation. This paper presents a method to generate exact contours from Constructive Solid Geometry (CSG) representations. The method preserves the accuracy of the contour files provided the primitives used to generate the CSG tree are polygonal or quadric objects. Due to the inclusion of quadric objects into the primitive set an additional effort to solve for the intersection points between two quadric curves is required. The paper also presents a method to convert piecewise quadratic contours to toggle point files for raster scanning solid freeform fabrication processes.Mechanical Engineerin

Preparation, Characterization and Optimization of Ibuprofen Ointment Intended for Topical and Systemic Delivery

Purpose: To develop an ibuprofen ointment with a potential for both topical and systemic delivery of the drug. Method: A co-solvency technique with a trial and error approach was used to develop a 10% ibioprofen ointment in petrolatum base, with the entire drug dissolved in the base. An insertion cell was used to evaluate drug release from the formulations. Further, factorial design multiple regression (FDMRA) analysis, a statistical optimization technique, was used in the optimization of the final formulation. Result: The desired ibuprofen ointments were developed. Release depended on vehicle and proportion of co-solvents. Best fit equations for optimization purposes including various fluxes (initial, steady-state and total) and diffusion coefficient as dependent variables and the concentrations of co-solvents as independent variables were obtained using SAS programme. Dependent variables strongly depended (

An overview of dentin bonding agents

From the past, there has been a lot of use of the bonding agents in restorative dentistry. Choosing of bonding systems has become a challenge for the clinicians as there was a lot of advances regarding the usage of bonding agents. Each successive modification in the formulae has led to the classification of the bonding system into many “generations”. During the past few years, these bonding agents have been replaced by the same systems that are used on dentin. This change occurred because of the benefit of bonding resin to both enamel and dentin. Extensive research is still on the way to develop the best adhesive system that can produce reliable and permanent bonds to dentin

The amazing spectrum of light – LASER

“In right light at right time everything is extraordinary”- says Aaron Rose. This is very true with respect to lasers. Discovery of lasers from the spectrum of light has revolutionized the technology in many fields. The word “LASER” means Light Amplification by Stimulated Emission of Radiation. They offer many useful clinical applications for general dentists in the diagnosis and treatment of patients. There are many clinical, aesthetic, and psychological reasons to use lasers. Herein we present a brief overview of “THE AMAZING SPECTRUM OF LIGHT

Self-sealing resin fixators in dentistry

Fixed indirect restorations bond to the prepared tooth surfaces with the use of a variety of luting agents depending upon the purpose of that rehabilitation. Success and failures of these restorations have been attributed to the quality of their bond with the tooth substrate. However, the advent of resin-based and self-adhesive resin luting agents have greatly changed this equation by altering the conventional bonding mechanisms and the durability of bond. The limited literature details of these self-adhesive resin luting agents require further exploration for the benefit of dental professionals. This review provides an overview of the composition, chemical interactions, favourable and unfavourable properties to be known for improving the scope of their utilization in dentistry

Design and Optimization of Fin Tube Evaporator By Varying Different Parameters

Evaporator is useful in air-conditioning or refrigerating to allow a compressed cooling chemical to evaporate from liquid to gas. This process is extensively use in many applications. In this paper, dissimilar shapes of fins in fin tube evaporator are modeled in 3D modeling software Pro/Engineer. The fins considered are rectangular fin, circular fin a internal finned. The mass flow rate and heat transfer rate are analyzed by CFD analysis completed in ANSYS. CFD analysis is completed by varying fluids R134A, R22 and R410 on all the models. The inputs of CFD analysis are velocity and pressure and the results determined are Pressure, Velocity, Mass Flow Rate, Heat Transfer Rate and Heat Transfer Coefficient

Evaluation of the antimicrobial activity of heat-cure denture base resin materials incorporated with silver nanoparticles

Background: Poly (Methyl methacrylic acid) based materials are the most widely used for the fabrication of removable complete and partial dentures. Certain microorganisms adhere to the tissue surface of a denture base, especially on palatal region, often leading to Denture stomatitis. Numerous attempts were made to treat the denture stomatitis with various antifungal agents showing variable success rates. This may be attributed to the loss of the drug rapidly into the saliva, inhomogeneous distribution of the drug and the development of resistance to antifungal therapy. Aim: This study was done to evaluate the effect of incorporating various concentrations of silver nanoparticles on the antimicrobial activity of heat-cure denture base resin materials. Methods: Silver nanoparticles were incorporated at various concentrations (0.5, 1.0, 2.0 and 5.0 wt%) into three heat-cure denture base materials. A total of 300 disc-shaped specimens (10 × 2 mm) of heat-cure acrylic resin were made using compression molding technique which comprises 100 specimens with each denture base material. Fifty specimens from each denture base materials were allocated to each microorganism used in the study which comprises into five groups with ten specimens (n=10) for each concentration such as control, 0.5wt%, 1.0wt%, 2.0wt% and 5.0wt% concentrations of silver nanoparticles. Antimicrobial activity of control and modified specimens were evaluated using direct contact method against C albicans, and S Mutans by counting the number of colony-forming units. The data were subjected to One way ANOVA and Tukey HSD tests for statistical analyses. Results: Significant(P<0.05) differences were observed in the antimicrobial activity against C albicans and S Mutans between the control and modified groups of heat-cure denture base resin materials. Conclusion: Silver nanoparticles are the favourable materials to incorporate into denture base materials as they exhibit superior antimicrobial activity

Solubility of glass ionomer cement in various acidic beverages at different time intervals: an in vitro study

Background: Glass Ionomer is a widely used cement in dentistry for luting and restoration purposes. This cement leaches a large amount of fluoride ions leading to an increase in the early solubility and disintegration in the oral fluids. The solubility of the cement is further aggravated when it is exposed to an acidic medium. Aim: This study aimed to evaluate the solubility of glass ionomer cement (GIC) in various acidic beverages at different time intervals. Materials and Methods: Four commercially available beverages and distilled water was used as immersion media. The pH of the beverages was measured using a digital pH meter. Glass ionomer cement discs were prepared and immersed in beverages for 1 day, 24 hours and 7 days. After completing the immersion time in each beverage for a specific period, the specimens were retrieved and weighed. The solubility was calculated by subtracting the weight at the specific immersion period from the initial weight of the specimen.   Results: Immersion in distilled water demonstrated less solubility compared to immersion in acidic beverages. Among the acidic beverages, GIC immersed in MAAZA showed the maximum solubility compared to the other beverages. One-Way ANOVA displayed a significant difference (p=0.000) among the beverages at different time intervals. Conclusions: This study found that the GIC immersed in fruit juices with preservatives showed more solubility at all time intervals compared to the immersion in carbonated drinks

Mineral Trioxide Aggregate: an overview of composition, properties and clinical applications

“Mineral trioxide aggregate” is a cementitious material, which is popular by its trade name MTA. It was first introduced in the year 1993 by Mohmoud Torabinejad at Loma Linda University in California, USA. MTA is a powder mixture of Portland cement clinker, bismuth oxide, and gypsum. It has gained a lot of importance in dentistry in recent years. This importance is because of its extensive use as apical restorative material as well as a medicament for Apexogenesis and Apexification treatment. As it sets by hydration process, the byproducts of insoluble calcium silicate hydrate and alkaline calcium hydroxide offer unique stability and potential to enhance hard tissue regeneration.  This article reviewed the composition, types, properties of MTA and also its applications in the practice of dentistry