Overdentures the realms of overshadowness or obliviousness

The overdenture is a predictable and valuable option in the treatment of a patient with multiple missing teeth. It aids by preservation of alveolar bone, teeth and supporting structures, maintenance of proprioceptive response and neuromuscular co-ordination, and enhances the quality of a prosthesis by improving the stability, retention and patient acceptance. Often while fabricating an overdenture with retained attachments it becomes mandatory to cast the wax pattern and by no means can that be judged for parallelism with the abutments. A lucid method of obtaining parallelism has been described, adjunct with significant improvement of bite force has been portrayed.Careful case selection and abutment preparation as well as periodic recall is the key to a successful over denture rehabilitation. This case report also depicts the tooth supported overdenture as a viable option with the use of a customized parallelometer which has its ease of use and cost effectiveness for determining parallelism of abutments using a prefabricated ball attachment system and deciphers the increase in bite force in a dynamic manner.

Numerical Simulation and Rapid Centrifugal Casting of Large Complex Thin-Walled Titanium Alloy Intermediate Casing Based on 3D Printed Pattern

Titanium alloy intermediate casing is a typical large casting, with many thin-walled and complex structures. It is a high cost and time-consuming process in the trial stage to manufacturing the wax pattern of the intermediate casing by metal mold. Rapid investment casting based on 3D printed patterns is the development direction of casting technology which integrates digitization and intelligence. In this study, selective laser sintering (SLS) technology was used to realize the rapid prototyping of polystyrene pattern in the precision casting of intermediate casing. A numerical simulation method was used to predict the filling process, solidification and casting defects of the intermediate casing. The simulation results show that the gating system for the casting of intermediate casting was reasonable, the number and size of gating risers met the open design requirements, and a sequential solidification of the casting could be realized. The titanium alloy intermediate casing with excellent metallurgical quality and size accuracy CT7 was successfully produced using centrifugal rapid casting technology.

Marginal misfit of heat-pressed milled wax-pattern and CAD/CAM crowns and its effect on stress distribution in implant-supported rehabilitations

Aim: To compare the marginal fit of lithium disilicate CAD/CAM crowns and heat-pressed crowns fabricated using milled wax patterns, and evaluate its effect on stress distribution in implantsupported rehabilitation. Methods: A CAD model of a mandibular first molar was designed, and 16 lithium disilicate crowns (8/group) were obtained. The crown-prosthetic abutment set was evaluated in a scanning electron microscopy. The mean misfit for each group was recorded and evaluated using Student’s t-test. For in silico analysis, a virtual cement thickness was designed for the two misfit values found previously, and the CAD model was assembled on an implant-abutment set. A load of 100 N was applied at 30° on the central fossa, and the equivalent stress was calculated for the crown, titanium components, bone, and resin cement layer. Results: The CAD/CAM group presented a significantly (p=0.0068) higher misfit (64.99±18.73 μm) than the heat-pressed group (37.64±15.66 μm). In silico results showed that the heat-pressed group presented a decrease in stress concentration of 61% in the crown and 21% in the cement. In addition, a decrease of 14.5% and an increase of 7.8% in the stress for the prosthetic abutment and implant, respectively, was recorded. For the cortical and cancellous bone, a slight increase in stress occurred with an increase in the cement layer thickness of 5.9% and 5.7%, respectively. Conclusion: The milling of wax patterns for subsequent inclusion and obtaining heat-pressed crowns is an option to obtain restorations with an excellent marginal fit and better stress distribution throughout the implant-abutment set.

A method of hollowing the obturator prosthesis and an overview on the pros and cons of the various materials used for hollowing

Prosthetic rehabilitation of a partial or total maxillectomy with an obturator is the most acceptable treatment option. The hollowing of the obturator prosthesis is beneficial as it reduces the stresses over the underlying and surrounding tissues. A simple technique of fabricating a hollow bulb obturator has been discussed in this article. At the step of the packing of a denture, the hollow wax pattern of the defect area is formed with modeling wax. This hollow wax pattern is filled with water and is allowed to freeze to form an ice block. This ice block is removed from the wax pattern and is interposed between two layers for heat-cured acrylic resin and is then cured. After processing the denture, the water is retrieved by making a small hole in denture base, which is packed after hollowing with a cold cure acrylic resin. A lightweight prosthesis with a uniform thickness was achieved with a readily available and easily retrievable material, i.e., ice.

Effect of Pouring Temperature and Heating of Ceramic Shells Mould on Projection of Thin Wall Castings

One of the research directions of this study is to determine the possibility of making precise, thin-walled castings from selected iron alloys. The scope of research work is aimed at determining the applicability of the casting process of selected iron alloys with the technology of wax pattern, for making precise castings with a wall thickness of less than 3 mm. The article presents the results of tests carried out for experimental castings with the shape of steps, characterized by different wall thicknesses: 1 mm, 5 mm, 10 mm, 25 mm. The castings were made of LH14, Gs42crMo4, L35H7MP2, LH26N9, 316L cast steel, and a new alloy marked “0”. The metal was smelted in an induction furnace with a capacity of 150 kg. The technology of ceramic shell mould used in the plant was used to make the experimental castings. Ceramic shell moulds were heated in a chamber furnace at a fixed temperature. The time of annealing the ceramic mould was constant in a ceramic form. The following parameters were variable during the tests: iron alloy, pouring temperature, and annealing temperature of the ceramic shell mould.

Application of Stereolithography Based 3D Printing Technology in Investment Casting

Advanced methods for manufacturing high quality parts should be used to ensure the production of competitive products for the world market. Investment casting (IC) is a process where a wax pattern is used as a sacrificial pattern to manufacture high precision casting of solid metal parts. Rapid casting is in turn, a technique that eases the IC process by combining additive manufacturing (AM) technologies with IC. The use of AM technologies to create patterns for new industrial products is a unique opportunity to develop cost-effective methods for producing investment casting parts in a timely manner. Particularly, stereolithography (SLA) based AM is of interest due to its high dimensional accuracy and the smooth surface quality of the printed parts. From the first appearance of commercially available SLA printers in the market, it took a few decades until desktop SLA printers became available to consumers at a reasonable price. Therefore, the aim of this review paper is to analyze the state-of-the-art and applicability of SLA based 3D printing technology in IC manufacturing, as SLA based AM technologies have been gaining enormous popularity in recent times. Other AM techniques in IC are also reviewed for comparison. Moreover, the SLA process parameters, material properties, and current issues are discussed.

The use of 3D printing technologies in art casting

The paper presents one of the roles of additive manufacturing used for preparing an art casting. Based on the virtual model (CAD), a casting pattern was 3D printed, based on which the wax pattern was made and in the final step an art casting was made.

3D Printing Technology with Plastic Materials for Hip Implant Master Patterns Manufacturing

This paper describes a hip implant model designed to assess the Fused Deposition Modeling (FDM) process for manufacturing investment casting master patterns. In addition, an indirect approach toward manufacturing master pattern via silicone rubber moulding in conjunction with 3D Printing process manufactured hip implant master pattern has been investigated. The dimensional accuracies of the manufactured AM master patterns and the wax pattern are presented. Finally, cost and lead time comparisons carried out between FDM ABS pattern manufacturing, indirect pattern manufacturing via silicone rubber moulding and conventional pattern manufacturing by metal mould are also presented.

An Experimental Examination on Ice Pattern for Casting Process

The casting process has come to wide range of use in manufacturing process. Wooden, aluminum and wax are mostly used materials for pattern in the casting. However, it contains some limitations such as expansion of wax pattern, cracks in ceramic, complexity limitation in wooden pattern and removal of wooden pattern from sand mold etc., in the light of this, the work attempts to use ice pattern for mold making and sublimating ice pattern to create cavity in the mold for pouring. Ice pattern can be produced with aid of rapid freeze prototyping (RFP) or by traditional ice mold method. Integration of RFP/Traditional ice mold method with sublimated ice in casting process allows the quick creation of complex metal parts. Here, mold is produced by ice pattern and then ice pattern is removed by sublimation process (sublimation is the process of direct conversion of solid phase to vapor phase of matters) to create cavity. The advantages of no parts geometric complexity problems , No need of parting line design, less complex limitation, sound casting, clean and less cost of process operation, and better performance. This paper will present our creation study on sublimation of ice pattern in greensand for mold making for casting, and results of the cast piece obtained from sand casting process.