A comparative study on investment casting of dental crowns for veterinary dentistry by using ABS patterns with and without wax coating

The fused deposition modelling (FDM) assisted investment casting (IC) is one of the commercially established routes for fabrication of biomedical parts requiring high precision. In past two decades number of studies has been reported on use of thermoplastic and wax based FDM patterns for IC of dental crown (DC) in human dentistry. But hitherto little has been reported on comparison of Ni-Co-Cr based DC prepared by using FDM printed virgin acrylonitrile butadiene styrene (ABS) pattern and wax coated ABS pattern for veterinary patients (VP). In this work, first molar and canine teeth in left side of lower mandible of a 3-year German Shepherd male dog has been prepared by using virgin ABS and wax coated ABS patterns followed by IC of Ni-Co-Cr alloy. The result of study suggests that wax coated ABS samples-based DC has better surface hardness, grain structure, surface roughness (Ra) and controlled surface porosity thus may be used as commercial manufacturing strategy. The results have been supported with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis.

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.

Ergative–Absolutive Patterns in Tongan: An Overview

Tongan (Polynesian) shows ergative-absolutive (ERG-ABS) patterns in morphology as well as syntax, but the ERG-ABS pattern is not consistent throughout the language. Noun morphology shows a split between clitic pronouns and other types of nouns. In syntax, three phenomena show an ERG-ABS contrast: (a) relativization using the gap strategy is limited to ABS and ERG-relatives require resumption; (b) coordinate reduction applies only if the gap and the antecedent are in the same case, be it ABS or ERG; and (c) only ABS, but not ERG, can serve as the antecedent of the null SE anaphor. No single factor can account for all three of these phenomena and at least two of the three patterns are shown to be better viewed as PF-phenomena. The data suggest that syntactic ergativity should be understood as a construction-specific phenomenon rather than a language-specific property.

Direct Fabrication of IC Sacrificial Patterns via Rapid Prototyping Approaches

Patterns made from conventional wax materials in the Investment Casting (IC) process can easily be distorted, damaged, or broken in transportation or routine handling or due to exposure to heat. Alternatively, the strength and toughness of most Rapid Prototyping (RP) materials virtually eliminates this drawback due to their resistance to heat, humidity, and post curing. The current study is conducted to investigate the feasibility of using RP processes such as FDM and MJM to fabricate IC patterns from Acrylonitrile Butadine Styrene (ABS) and acrylate based materials respectively to be used directly in IC process. Evaluation of the effects of different internal pattern designs of the RP parts are conducted based on the thermal analysis approach and burnout properties of the RP patterns. Ceramic shell molds are fabricated on both RP patterns and subsequently placed in an oven which is gradually heated to 1000°C. The decomposition temperature and the residual ash of the RP pattern materials is determined and analyzed. Results show that the acrylate pattern ofMJMdecomposes rapidly compared to the ABS pattern from the FDM process. It is also observed that quasi and square hollow internal structures show better collapsibility or burnout properties, with no cracks, compared to cross pattern and cross hatch designs.