Temporary Materials Research Articles

3D Printing Temporary Crown and Bridge by Temperature Controlled Mask Image Projection Stereolithography

Traditionally, the fabrication of temporary teeth restorations must go through multiple processes such as moulding, curing and post finishing, which requires extensive expertise of dentists. In addition, the handmade temporary restorations are usually unable to precisely fit the patient’s teeth due to limited formability of material. To address the problem, a three-dimensional (3D) printing technology named temperature controlled mask image projection based stereolithography (TCMIP-SL) is presented for dental materials in this paper, with aim to build customized temporary crown and bridge quickly for its use in dental offices. We first studied the photo-polymerization performance of commercial materials that are commonly used in dental industry. Then we discussed the temperature effect on curing performance and rheology of dental composite material. Based on the studies, we further developed our TCMIP-SL process by integrating a material coating system with controllable heating, so that the coated thin film of dental composite material can be selectively cured using high resolution patterned light beam. Several test cases are performed to demonstrate the TCMIP-SL process can 3D print high viscous temporary crown material with fast speed and high resolution.

Evaluation of retention of two implant supported ceramic crowns using two temporary cements

Aim: The purpose of this in vitro study was to evaluate the effect of two temporary cements (Resin based cement and Eugenol Free Zinc oxide cement) on the retention of two titanium implant supported crowns made of (Polymer infiltrated hybrid glass ceramic and Yttrium stabilized tetragonal zirconia).Materials and methods: 20 dummy implants were inserted in epoxy resin blocks. The twenty blocks were divided according to the crown material into two groups (n=10): Group I: VITA ENAMIC™ crowns, Group II: BurxZir™ zirconia crowns. Each group were further sub-divided into two sub-groups (n=5), according to the temporary cement material used (Sub-group A: crowns cemented with DentoTemp™ cement, Sub group B: crowns cemented with Tempbond NE™ cement). The crowns were fabricated with CAD-CAM technology. Each crown had two wings on the mesial and distal surfaces to aid in retention analysis. The crowns were cemented to the titanium abutments and then retention was measured using uni-axial tensile force test.Results: DentoTemp™ cement showed a higher retentive values with both crown materials. The retentive values of the DentoTemp™ temporary cement was significantly higher than those of the Tempbond NE™ cement when used with BruxZir™ Zirconia crowns.Conclusions: Resin based temporary cement showed significantly higher retention results than non-eugenol temporary cement while the difference in crown material showed no significant difference.

The influence of different immersion time intervals and disinfection of tissue conditioner functional impression materials on the surface roughness of stone cast

Tissue conditioners are used as a functional impression material, to re-condition the denture-bearing mucosa abused by ill-fitting dentures and as a temporary lining material for immediate dentures. The immersion of tissue conditioners in disinfectant prior to pouring the impression can significantly affect the properties of dental stone depending on the duration of immersion. The present study aims to evaluate the effect of immersion time of tissue conditioner on the surface roughness of dental stone. Thirty specimens of tissue conditioner stone casts were prepared on cylindrical split aluminum with a lower hollow ring designed to receive the tissue conditioner and an upper ring adjusted to receive the stone mix. The thirty specimens of tissue conditioner were divided into 3 equal groups of 10 specimens according to the storage period (1hr, 24hrs and 48hrs). The three groups were subdivided into two subgroups: subgroup (a) 2% chlorhexidine (CHX) solution were sprayed on the surface of tissue conditioner specimens prior to pouring with dental stone materials while the other subgroup (b) specimens were poured with dental stone but without using (CHX) disinfection. The dental stone mixture was poured into molds and stored at room temperature for 60 minutes. The stone casts were then separated from the tissue conditioner and the surface roughness values of these dental stone casts was determined. Our results revealed a significant higher means values of surface roughness of groups (IIa and IIIa) when chlorhexidine was used compared to groups (IIb and IIIb). Comparison between subgroups (a and b) showed a statistical significance between (IIa and IIb) and (IIIa and IIIb). Based on the obtained results it can be concluded that the optimum time for using tissue conditioner as functional impression is from 24 to 48 hours after immersion. The use of 2% chlorhexidine solution disinfectant had adverse effect on surface roughness of dental stone.

Seeking congruency in digital optimisation and constructability in fabric formed ice shells utilising bending active frames

Fabric formed structures are widely used to produce structural forms through the use of a temporary rigid framing to support a flexible membrane as formwork. Recent research has sought to introduce flexible support systems for fabric formwork so that they may participate in the parametric behaviour of fabric, while providing useful constraints for design. In the project presented here, a bending active frame is used to create a fabric formed ice shell using this approach. A focus is placed on the use of ice as a temporary structural material that allows for the iterative accumulation of mass during construction, as well as an analogous material for speculating about the use of other more permanent liquid-to-solid materials (like concrete). This project presents novel construction methods seeking to establish a meaningful link between digital optimisation design techniques and the often incongruent realities that must be confronted to build such a structure.

A comparative evaluation of vertical marginal fit of provisional crowns fabricated by computer-aided design/computer-aided manufacturing technique and direct (intraoral technique) and flexural strength of the materials: An in vitro study.

Background:With the advent of new provisional crown materials, it has become imperative to evaluate their marginal fit and strength to select the ideal provisional crown material.Aim:The purpose of this in vitro study was to evaluate and compare the vertical marginal fit and flexural strength of provisional crowns prepared using computer-aided design-computer-aided manufacturing (CAD-CAM) temporary material versus those fabricated using bis-acrylic composite-based autopolymerizing resin material.Materials and Methods:Eighty samples were divided into two equal Groups (I and II). Group I consisted of forty samples that were evaluated for flexural strength and Group II consisted of forty samples that were evaluated for their vertical marginal fit. Group I was subdivided as Group IA, i.e., bis-acrylic composite-based autopolymerizing resin material (Protemp™ 4) blocks and Group IB, i.e., CAD/CAM provisional material blocks. Similarly, Group II was subdivided as Group IIA, i.e., bis-acrylic composite-based autopolymerizing resin material (Protemp™ 4) crowns and Group IIB, i.e., CAD/CAM provisional material crowns. Marginal adaptation was evaluated using stereomicroscope and image analyzing software to measure the amount of marginal gap. For flexural strength, all specimens were subjected to a standard compression load in the universal testing machine until fracture occurred. Data were analyzed using Student's t-test (P = 0.001).Results:CAD/CAM provisional crowns showed better marginal adaptation (34.34 μm) as compared to bis-acrylic composite-based autopolymerizing resin material (Protemp™ 4) crowns (63.42 μm) (P < 0.001). The flexural strength of CAD/CAM blocks (94.06 megapascals [MPa]) was not statistically different from bis-acrylic composite-based autopolymerizing resin material (Protemp™ 4) blocks (101.41 MPa) (P > 0.001).Conclusion:Protemp™ 4 and CAD/CAM provisional materials have comparable flexural strength. However, the marginal fit of temporary crowns fabricated by CAD/CAM was found to be superior to the ones fabricated using bis-acrylic composite-based autopolymerizing resin material (Protemp™ 4).

In situ evaluation of surface roughness and micromorphology of temporary soft denture liner materials at different time intervals.

To perform an in situ evaluation of surface roughness and micromorphology of two soft liner materials for dentures at different time intervals. The surface roughness of materials may influence the adhesion of micro-organisms and inflammation of the mucosal tissues. The in situ evaluation of surface roughness and the micromorphology of soft liner materials over the course of time may present results different from those of invitro studies, considering the constant presence of saliva and food, the changes in temperature and the pH level in the oral cavity. Forty-eight rectangular specimens of each of the two soft liner materials were fabricated: a silicone-based material (Mucopren Soft) and an acrylic resin-based material (Trusoft). The specimens were placed in the dentures of 12 participants (n=12), and the materials were evaluated for surface roughness and micromorphology at different time intervals: 0, 7, 30 and 60days. Roughness (Ra) was evaluated by means of a roughness tester. Surface micromorphology was evaluated by scanning electron microscopy. Analysis of variance for randomised block design and Tukey's test showed that surface roughness values were lower in the groups using the silicone-based material at all the time intervals (P<.0001). The average surface roughness was higher at time interval 0 than at the other intervals, for both materials (P<.0001). The surface micromorphology showed that the silicone material presented a more regular and smoother surface than the acrylic resin-based material. The surface roughness of acrylic resin-based and silicone-based denture soft liner materials decreased after 7days of evaluation, leading to a smoother surface over time. The silicone-based material showed lower roughness values and a smoother surface than the acrylic resin-based material, thereby making it preferred when selecting more appropriate material, due its tendency to promote less biofilm build-up.

Effect of Incorporation of Antifungal Agents on the Ultimate Tensile Strength of Temporary Soft Denture Liners.

To investigate the ultimate tensile strength of temporary soft denture liners modified by minimum inhibitory concentrations (MICs) of antifungal agents for Candida albicans biofilm (SC5314) determined in previous microbiological research. Dumbbell-shaped specimens (n = 7) with a central cross-sectional area of 6 × 3 × 33 mm were produced by Softone and Trusoft, without (control) or with incorporation of drugs in powder form at MICs for C. albicans biofilm (per g of material powder): nystatin (0.032 g), chlorhexidine diacetate (0.064 g), ketoconazole (0.128 g), miconazole (0.256 g), and itraconazole (0.256 g). After plasticization, specimens were immersed in distilled water at 37°C for 24 hours, 7 or 14 days, and then tested in tension in a universal testing machine at 40 mm/min. Data of tensile strength (MPa) and elongation percentage (%) were submitted to 3-way ANOVA and Tukey's test (α = 0.05). At the end of 14 days, the tensile strength for both materials was significantly lower in the groups modified by miconazole and itraconazole compared to the other groups (p < 0.0001), which showed no significant difference between them (p > 0.05). After 7 and 14 days in water, miconazole and itraconazole added into both materials resulted in significantly lower elongation percentages compared to the other antifungal agents and control (p < 0.0001), which were similar to each other (p > 0.05). The addition of the nystatin, chlorhexidine, and ketoconazole at MICs for C. albicans biofilm resulted in no harmful effects on the tensile strength and elongation percentage of the temporary soft denture liner materials up to 14 days.

Removal of temporary cements following an immediate dentin hybridization approach: a comparison of mechanical and chemical methods for substrate cleaning

This study evaluated the microshear bond strength (μSBS) of a composite resin cement to a pre-hybridized dentinal substrate exposed to two kinds of temporary materials; the influence of different cleaning techniques was investigated. Dentinal surfaces were conditioned with an etch-and-rinse adhesive system to obtain an immediately-sealed (IDS) layer. Each surface was divided into quadrants and covered (1) with an eugenol-free (NE_Group) or (2) with a resin-based provisional agent (CL_Group). After storage, the temporary cement was removed by using one of the following methods: (1) Hand-scaler [S]; (2) Alumina air-abrasion [SB]; (3) Glycine-powder air-abrasion [Gly]; (4) D-Limonene chemical solvent [Or]. A new IDS layer was then created; polyethylene tubes were placed on dentin surfaces and filled with a dual-cure resin cement. A universal testing machine was used for the μSBS tests; conditioned surfaces were analyzed at SEM. Means and SD were calculated; a two-way ANOVA (a: 0.05) was performed to detect significant differences among groups. For NE groups, mean μSBS values (MPa) were: 21.6 ± 6.6 [NE_NoT]; 20.7 ± 4.5 [NE_Or]; 20.1 ± 6.6 [NE_SB]; 19.1 ± 5.3 [NE_S]; 17.8 ± 2.2 [NE_Gly]. No significant differences were found among tested treatments within NE (p: 0.5493). For CL groups, mean μSBS values (MPa) ranged from 15.8 ± 2.8 (CL_S50) to 19.4 ± 2.9 (CL_Gly). Cleaning of the substrate with glycine air-abrasion statistically improved μSBS values with respect to aluminum-oxide (CL_SB: 15.8 ± 2.8) or scaling (CL_S: 16.0 ± 2.4). The application of the IDS technique was effective for preservation of freshly-cut dentin from adverse effects of temporary materials. Glycine air-abrasion is suggested when a temporary resin cement is adopted.

Intraoral Device for Optimal Antifungal Delivery in a Rat Model.

Antifungal agents incorporated into temporary denture resilient liners as drug carriers and delivery have been suggested as an alternative treatment for denture stomatitis. However, to test the in vivo biocompatibility of this protocol, standardization of an intraoral device for optimal drug delivery is required. Standardized criteria were produced to adjust an acrylic intraoral device (IOD) for rats feasible for denture stomatitis treatment by sustained drug-delivery based on minimal inhibitory drug concentrations (MICs) of antifungals for Candida albicans biofilm. Adjustments methodological involved diet, impression technique, type of retention device to the palate and histopathological analysis. 115 Wistar rats were tested without IOD, with devices without relining or relined with temporary resilient material (Trusoft) modified or not by drugs at MICs (nystatin-0.032g/mL; chlorhexidine diacetate-0.064g/mL; ketoconazole-0.128g/mL). The animals were sacrificed after 7 or 14 days from the IOD installation. Paste diet enabled the best animal survival conditions. The IODs that most satisfactorily remained in position were those designed only to the posterior palatal mucosa and cement-retained in molars, being all obtained from impressions highly detained and individual. In both periods, Trusoft without/with drugs showed good performance. Only histological samples from hard/soft tissues were considered appropriate for region of interest-RI determination (n=12), which corresponded to the area restricted to the first molars between the palatal neurovascular bundles. Final samples of all groups allowed a standardized descriptive histopathological analysis in both periods. The methodological standardization of this rat model resulted in IODs for optimal antifungal delivery for denture stomatitis treatment.

Transient Fiber Mats of Electrospun Poly(Propylene Carbonate) Composites with Remarkable Mechanical Strength.

Polymers with a triggered decomposition are attractive for an array of applications ranging from patterning to transient packaging materials, as well as for environmental protection. This work showed for the first time UV and thermally triggered transience in fiber mats using poly(propylene carbonate) (PPC) composites. The electrospun PPC-composite fiber mats combine excellent decomposition performance (because of the high surface to volume ratio) with high stiffness and thus represent a new class of materials enabling innovative applications, such as transient filter materials and short-time plant protection materials, as well as temporary lightweight materials for aerospace engineering. Thermally and UV-triggerable additives (protected acids or base) have been used in different concentrations to tune the transience performance of the fiber mats over a wide range (75-212 °C). The addition of organo-modified clay (OMMT) enhanced mechanical stability and prevented shrinkage at room temperature. Different annealing methods have been used to improve the mechanical properties even further (tensile strength = 2-12 MPa, Young's modulus = 55-747 MPa) making these fiber mats attractive for a broad field of applications. An Ashby plot of Young's modulus versus degradation temperature for electrospun fiber mats is shown, revealing much lower degradation temperatures with higher moduli for PPC composites compared to other electrospun polymers.

In-vivo microbiologic evaluation of polytetrafluoroethylene and cotton as endodontic spacer materials.

Spacers are commonly placed between the canal orifice and the temporary material between endodontic treatment appointments. This prevents the temporary restoration material from obstructing the canal orifices and allows for easy removal. Various endodontic spacers are currently used, including polytetrafluoroethylene (PTFE) tape. Previous in-vitro studies have demonstrated the advantages of using PTFE over using cotton; however, no in-vivo studies have demonstrated this. Hence, the purpose of this study was to evaluate which spacer showed less bacterial leakage between endodontic treatments. Fifty patients participated in the study and were randomly assigned to either the cotton or the PTFE group. Root canal treatments were completed in two appointments. Cotton and PTFE spacers were collected after a 2- to 4- week time interval between the first and second appointments. Samples were incubated on agar plates for 48 hours and then evaluated for presence of microbial growth. Colony forming units (CFUs) were counted for each of the samples. The results were analyzed using nonparametric statistical tests. Fifteen of the 24 cotton spacers and two of the 24 PTFE spacers were positive for bacterial growth. Cotton fibers exposed to the oral environment could potentially wick contaminants into the pulp chamber. The tendency of cotton to distort under masticatory forces may allow disruption of the temporary material's marginal seal. Based on the results of this study, the use of PTFE is strongly recommended over cotton as an endodontic spacer material. PTFE performed better than cotton in this in-vivo microbial study.

Enhancing Well Performance by In-Stage Diversion in Unconventional Wells

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 180985, “Enhancing Well Performance by In-Stage Diversion in Unconventional Wells: Physics and Case Studies,” by F.E. FragachÁn, M. Pordel Shahri, D.M. Arnold, A.G. Babey, and C.S. Smith, Weatherford, prepared for the 2016 SPE Argentina Exploration and Production of Unconventional Resources Symposium, Buenos Aires, 1–3 June. The paper has not been peer reviewed. Developments in nondamaging, degradable diverters with outstanding plugging efficiency have opened new opportunities for protecting existing fractures by plugging them and then fracturing zones that were previously bypassed because of inefficient zone coverage or refracturing zones that were inefficiently fractured initially. With multistage operations becoming the industry norm, operators need easily deployable diversion technologies that will protect previously stimulated perforations and enable addition of new ones. This paper reviews several aspects of the use of in-stage diversion. Introduction to Degradable Diverters Polymer-based degradable diverters are temporary materials that are useful in some oil and gas operations, primarily to enable fluids to flow into areas of the reservoir where fluid dynamics would normally exclude them. While standard mechanical diverters work well for zonal isolation, they must be physically removed from the well after the workover job has been completed. Degradable diverters have performed an important role for many decades, but they cannot meet operational requirements to stay intact for weeks or even hours. Perforation balls or degradable ball sealers will fall away from perforations without continuous application of pressure. Rock salt and flakes will dis-solve after a few hours. High temperatures degrade the material faster. The suite of degradable diverter products consists of polymers of varying chemistries that provide good blocking and sealing when applied to the well but that can also degrade across a wide temperature range to monomer species that will be nondamaging to hydrocarbon-bearing formations. Diversion applications with degradation times between a few hours and a few days in temperatures from 80 to 325°F can be achieved by the selection of appropriate polymer chemistry. Despite the unique design of these various polymers, the success of applying this technology in the field for use as a temporary diverter is heavily dependent on sound engineering and geomechanical design that enables the creation of a seal over existing flow pathways that can withstand differential pressures up to and exceeding 8,000 psi and yet can completely degrade in a controlled amount of time after the completion of the intervention.

Mechanical properties of materials used for temporary fixed dentures – in vitro study

Abstract Objectives. The objective of the research was to define the mechanical properties of currently marketed temporary filling materials. Methods. Eight temporary filling materials: Boston, Dentalon, Protemp II, Revotek LC, Structure 2, Structure 3, UniFast LC, UniFast Trad were used to make 5 samples each of measurements 2 × 2 × 25 mm, in order to define the flexural strength, and 10 rings each of measurements 2 × 5 mm, in order to carry out the Vickers micro-hardness test. After preparation, the samples were stored in distilled water of temperature of 370°C, for 7 days. Subsequently, flexural strength and Vickers hardness testing was undertaken. Results. Composite temporary materials showed considerably better mechanical properties, both in flexural strength and in Vickers micro-hardness testing. Conclusions. the best mechanical properties, both in terms of flexural strength, as well as Vickers micro-hardness test can be observe among composite materials.

Evaluation of the flexural properties of a new temporary splint material for use in dental trauma splints

The present study evaluated the flexural properties of a new temporary splint material, G-Fix, for use in dental trauma splints in comparison with other resin materials. Four types of resin materials were considered in the present study: MI Flow II, light-cured composite resin (MI); G-Fix, light-cured resin for splinting teeth (GF); Super-Bond C&B, adhesive resin cement (SB); and Unifast III, self-cured methyl-methacrylate resin (UF). The flexural properties of these four materials were tested according to ISO 4049. The flexural strength significantly increased in the order of UF (64.9 MPa)<SB (76.5 MPa)<GF (94.3 MPa)<MI (161.2 MPa). The elastic modulus significantly increased in the order of UF (2.11 GPa) ≒ SB (2.23 GPa)<GF (2.62 GPa)<MI (7.39 GPa). A splint made of GF may be more flexible than a composite splint, which is categorized as a rigid splint.

Surface Properties of Temporary Soft Liners Modified by Minimum Inhibitory Concentrations of Antifungals.

Evaluating the addition of minimum inhibitory concentrations (MICs) of antifungals for Candida albicans biofilm on the hardness and roughness of temporary denture soft liners. Specimens (n=8; 36×7×6 mm) of tissue conditioner (Softone) and resilient liner (Trusoft) were produced either without (control) or with incorporation of drugs at MICs: nystatin (0.032 g/mL), chlorhexidine diacetate (0.064 g/mL), ketoconazole (0.128 g/mL), miconazole (0.256 g/mL) and itraconazole (0.256 g/mL). Specimens were stored in distilled water at 37 °C for 24 h, 7 days and 14 days prior to the hardness/roughness measurements. Data were analyzed by 3-way ANOVA and Tukey HSD test (α=0.05). The addition of the antifungals into both materials demonstrated no evident hardness change or decrease of this property compared with the control, except for miconazole in Softone, which increased the hardness after 14 days (p=0.003). The addition of nystatin into both materials, chlorhexidine in Trusoft and ketoconazole in Softone resulted in no significant changes of roughness compared with the control, after 7 days and 14 days (p>0.05). In these periods, itraconazole increased the roughness of both materials (p<0.001). The addition of all antifungals, except for the miconazole in Softone, resulted in no deleterious effects on the materials' hardness over the evaluation time. The MICs of nystatin in both temporary soft lining materials, ketoconazole in Softone and chlorhexidine in Trusoft resulted in no deleterious effects for roughness up to 14 days.

In-vitro performance of CAD/CAM-fabricated implant-supported temporary crowns.

The aim of this study was to investigate the in-vitro performance and fracture resistance of a temporary computer-aided designed and computer-aided manufactured polymethylmethacrylate (CAD/CAM-PMMA) material as implant or tooth-supported single crown with respect to the clinical procedure (permanently bonded/temporarily cemented). Sixty-four crowns were fabricated on implants or human molar teeth simulating (a) labside procedure on prefabricated titanium-bonding base ([TiBase] implant crown bonded in laboratory, screwed chairside), (b) labside procedure ([LAB] standard abutment and implant crown bonded in laboratory, screwed chairside), (c) chairside procedure ([CHAIR] implant crown bonded to abutment), and (d) reference ([TOOTH] crowns luted on prepared human teeth). Crowns were made of a CAD/CAM-PMMA temporary material (TelioCAD, Ivoclar-Vivadent). For investigating the influence of fixation, half of the crowns were permanently (P) or temporarily (T) bonded. Combined thermal cycling and mechanical loading (TCML) was performed simulating a 5-year clinical situation. Fracture force was determined. Data were statistically analyzed (Kolmogorov-Smirnov test, one-way ANOVA; post hoc Bonferroni, α=0.05). All restorations survived TCML without visible failures. Fracture results varied between 3034.3 (Tooth-P) and 1602.9N (Tooth-T) [TOOTH], 1510.5 (TiBase-P) and 963.6N (TiBase-T) [TiBase], 2691.1 (LAB-P) and 2064.5N (LAB-T) [LAB], and 1609.4 (Chair-P) and 1253.0N (Chair-T) [CHAIR]. Tested groups showed significantly (p<0.001) different fracture values. Failure pattern was characterized by fractures in mesial-distal, buccal-oral, or mixed (mesial-distal/buccal-oral) directions, with differences for the individual groups. Temporary CAD/CAM crowns showed no different in-vitro performance but provided different fracture results that depended on cementation, screw channel, and type of abutment. All bonded and screwed PMMA crowns were in a range where clinical application seems not restricted.

Analysis of the THM behaviour in a clay-based engineered barrier system (EBS): modelling of the HE-E experiment (Mont Terri URL)

To understand the complex thermo-hydro-mechanical (THM) processes and their evolution in a clay-based engineered barrier systems (EBS) during the closure phase of a geological repository for radioactive waste, a 1:2 scale in situ heating experiment (HE-E experiment) has been ongoing since 2011 in the Mont Terri Rock laboratory. Based on the experimental data, a fully coupled THM 3D simulation using the finite-element program OpenGeoSys was carried out. The main objectives of the simulation were to interpret the experimental observations, to understand the thermally induced THM interactions and to analyse the different material properties. Five experimental phases were numerically interpreted, in order to take into account the changes in the temporary material properties during experimental operations. These included the tunnel excavation, the ventilation, the emplacement of the bentonite EBS, the heating phase and the phase after shutdown of the heater. A non-isothermal Richards’ flow model was used to take into account the evaporation and vapour diffusion during the heating. The material behaviours of EBS in association with the saturation-dependent thermal conductivity and the water retention behaviour under high temperatures were analysed in detail. The strong thermal, hydraulic and mechanical anisotropic properties of the Opalinus Clay were described by a transversely isotropic model.

치과 CAD-CAM용 임시 수복재의 색 안정성 비교 연구

치과 CAD-CAM용 임시 수복재의 색 안정성 비교 연구

가설기자재 품질관리제도의 비교·분석에 관한 연구

가설기자재 품질관리제도의 비교·분석에 관한 연구

Topology optimization considering overhang constraints: Eliminating sacrificial support material in additive manufacturing through design

Additively manufactured components often require temporary support material to prevent the component from collapsing or warping during fabrication. Whether these support materials are removed chemically as in the case of many polymer additive manufacturing processes, or mechanically as in the case of (for example) Direct Metal Laser Sintering, the use of sacrificial material increases total material usage, build time, and time required in post-fabrication treatments. The goal of this work is to embed a minimum allowable self-supporting angle within the topology optimization framework such that designed components and structures may be manufactured without the use of support material. This is achieved through a series of projection operations that combine a local projection to enforce minimum length scale requirements and a support region projection to ensure a feature is adequately supported from below. The magnitude of the self-supporting angle is process dependent and is thus an input variable provided by the manufacturing or design engineer. The algorithm is demonstrated on standard minimum compliance topology optimization problems and solutions are shown to satisfy minimum length scale, overhang angle, and volume constraints, and are shown to be dependent on the allowable magnitudes of these constraints.