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Herausnehmbarer Zahnersatz auf Basis von 3-D-gedrucktem Polyamid-12 (PA-12) Untersuchung von Oberflächenbeschaffenheit und Glanzwert bei Valplast®-Prothesen
Abstract and Figures
Diese In-vitro-Studie untersucht die Oberflächenbeschaffenheit von additiv gefertigten Prüfkörpern (n = 20) aus Polyamid-12. Dazu wurden aus dem Prothesenkunststoff Valplast® (Valplast, Westbury, USA) Proben über die Fused Filament Fabrication (FFF) gefertigt und Rauheitswerte sowie der Glanzwert im Sinne eines Ausgangswerts ermittelt. Anschließend wurden die Oberflächen der Proben vergütet (A: nach Herstellerangaben, B: konventionelle zahntechnische Politur (Goldstandard)) und von jeder Gruppe erneut Rauheitswerte (Rp, Rv, Rz) sowie Glanz bestimmt und mit dem Ausgangswert verglichen. Des Weiteren wurde mithilfe des Drei-Punkt-Biegeversuchs der Elastizitätsmodul der additiv gefertigten Proben aus Valplast® bestimmt, zum Vergleich mit Literaturangaben für konventionell gefertigte Proben (Thermopressverfahren).
Die statistische Auswertung zeigte signifikante Unterschiede zwischen beiden Nachbearbeitungsverfahren sowie beider Verfahren zum Ausgangswert bezüglich Oberflächenrauheit und Glanz. Eine Diskrepanz zwischen den zwei Fertigungsverfahren hinsichtlich des Elastizitätsmoduls konnte nicht beobachtet werden.
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Currently, there is minimal clinical data regarding biofilm composition on the surface of denture bases and the clinical tissue compatibility. Therefore, the aim of this experimental study was to compare the bacterial colonization and the tissue compatibility of a hypoallergenic polyamide with a frequently used PMMA resin tested intraorally in a randomized split-mouth design. Test specimens made of polyamide (n = 10) and PMMA (n = 10) were attached over a molar band appliance in oral cavity of 10 subjects. A cytological smear test was done from palatal mucosa at baseline and after four weeks. The monolayers were inspected for micronuclei. After four weeks in situ, the appliance was removed. The test specimens were immediately cultivated on non-selective and selective nutrient media. All growing colonies were identified using VITEK-MS. The anonymized results were analyzed descriptively. A total of 110 different bacterial species could be isolated, including putative pathogens. An average of 17.8 different bacterial species grew on the PMMA specimens, and 17.3 on the polyamide specimens. The highest number of different bacterial species was n = 24, found on a PMMA specimen. On the two specimens, a similar bacterial distribution was observed. Micronuclei, as a marker for genotoxic potential of dental materials, were not detected. This study indicates that the composition of bacterial biofilm developed on these resins after four weeks is not influenced by the type of resin itself. The two materials showed no cytological differences. This investigation suggests that polyamide and PMMA are suitable for clinical use as denture base material.
Design work related to the implementation of new elements requires the use of 3D CAD modelling techniques and rapid prototyping, which makes it possible to accelerate the deployment of new solutions significantly. In this paper, six successful assembly parts are 3D printed with advanced polylactic acid (PLA+) using the fused deposition modeling (FDM) method and are expressed by the arithmetic mean surface roughness, Ra. The surface roughness was measured in three different angular directions 0º, 45º and 90º during the investigation along with various independent process parameters of nozzle diameter (0.5, 0.3, 0.2 mm), layer height (0.3, 0.2, 0.1 mm) and other dependent variables, i.e., nozzle temperature (220°C), print speed (30 mm/s) and infill density (0%). Experimental results show that nozzle diameter and layer height play a major role in terms of part quality finish, build time and ultimately part cost. Nozzle diameter and a layer height of 0.3 mm and 0.1 mm, respectively, represent the optimal manufacturing process parameters that can be selected. The surface roughness behaviour does not change and remains relatively constant and follows a similar trend with minor variations for both 45° and 90° measuring angle. Whereas, the surface roughness values are susceptible to 0° measuring direction to the build orientation as compared to other angles.
Purpose: Some patients experience adverse reactions to poly(methyl methacrylate)-based (PMMA) dentures. Polyamide (PA) as an alternative to PMMA has, however, not been well documented with regard to water sorption and water solubility. The aim of this in vitro study was to measure water sorption and water solubility of two PA materials compared with PMMA, and to evaluate the major components released from the PA materials and the effect on hardness of the materials.
Methods: Ten discs (40.0 mm diameter, 2.0 mm thick) of each material (PA: Valplast and Breflex; PMMA: SR Ivocap HIP) were prepared according to manufacturers’ recommendations. The specimens were tested for water sorption and water solubility, according to a modification of ISO 20795-1:2008. Released substances were analysed by gas chromatography/mass spectrometry (GC/MS).
Results: There were statistically significant differences among the materials regarding water sorption, water solubility and time to water saturation. Breflex had the highest water sorption (30.4 μg/mm³), followed by PMMA-material (25.8 μg/mm³) and Valplast (13.6 μg/mm³). Both PA materials had statistically significant lower water solubility than the PMMA. Both PA had a net increase in weight. Analysis by GC/MS identified release of the compound 12-aminododecanolactam from the material Valplast. No release was found from the Breflex material.
Conclusions: The PA denture materials show differences in water sorption and solubility, but within the limits of the standard requirements. The PA showed a net increase in weight after long-term water sorption. The clinical implications of the findings are not elucidated.
The purpose of this article was to review the biocompatibility, physical, and mechanical properties of the polyamide denture base materials. An electronic search of scientific papers from 1990-2014 was carried out using PubMed, Scopus and Wiley Inter Science engines using the search terms “nylon denture base” and “polyamide denture base”. Searching the key words yielded a total of 82 articles. By application of inclusion criteria, the obtained results were further reduced to 24 citations recruited in this review. Several studies have evaluated various properties of polyamide (nylon) denture base materials. According to the results of the studies, currently, thermo-injectable, high impact, flexible or semi-flexible polyamide is thought to be an alternative to the conventional acrylic resins due to its esthetic and functional characteristics and physicochemical qualities.
It would be justifiable to use this material for denture fabrication in some cases such as severe soft/ hard tissue undercuts, unexplained repeated fracture of denture, in aesthetic-concerned patients, those who have allergy to other denture base materials, and in patients with microstomia.
Although polyamide has some attractive advantages, they require modifications to produce consistently better properties than the current polymethyl methacrylate (PMMA) materials. Moreover, since there is a very limited knowledge about their clinical performance, strict and careful follow-up evaluation of the patients rehabilitated with polyamide prosthesis is recommended.
Objectives:
Polyamide-12 (PA) is a flexible material suited for denture bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity.
Methods:
PA specimens (Valplast) of 40×10×2 mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine (n=10) were measured using the CIE L*a*b* color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles, n=15) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling (n=10).
Results:
Tukey's HSD test (P<0.05) revealed statistically significant color changes of PA in red wine (ΔE=4.27 after 12 days, ΔE=6.90 after 12 days) and coffee (ΔE=3.93 after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845 MPa and not affected by thermocycling (Tukey's HSD test, P>0.81). Dry specimens showed significantly decreased elasticity (P<0.001). Mean surface roughness (PA 0.20 μ m, PMMA 0.28 μ m) did not change significantly after thermocycling or storage (Mann-Whitney U-test, 0.16<P<0.65).
Significance:
PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.
The roughness of intraoral hard surfaces can influence bacterial plague retention. The present review evaluates the initial surface roughness of several intraoral hard materials, as well as changes in this surface roughness as a consequence of different treatment modalities.
Articles found through Medline searches were included in this review if they met the following criteria: 1) stated threshold surface roughness values and reputed change in surface roughness due to different manipulation techniques; or 2) included standardized surface conditions that could be compared to the treated surface.
Recently, some in vivo studies suggested a threshold surface roughness for bacterial retention (Ra = 0.2 micron) below which no further reduction in bacterial accumulation could be expected. An increase in surface roughness above this threshold roughness, however, resulted in a simultaneous increase in plaque accumulation, thereby increasing the risk for both caries and periodontal inflammation. The initial surface roughness of different dental materials (e.g., teeth, abutments, gold, amalgam, acrylic resin, resin composite, glass ionomer or compomer and ceramics) and the effect of different treatment modalities (e.g., polishing, scaling, brushing, condensing, glazing or finishing) on this initial surface roughness were analyzed and compared to the threshold surface roughness of 0.2 micron. The microbiological effects of these treatment modalities, if reported, are also discussed and compared to recent in vivo data.
Based on this review, the range in surface roughness of different intraoral hard surfaces was found to be wide, and the impact of dental treatments on the surface roughness is material-dependent. Some clinical techniques result in a very smooth surface (compressing of composites against matrices), whereas others made the surface rather rough (application of hand instruments on gold). These findings indicated that every dental material needs its own treatment modality in order to obtain and maintain a surface as smooth as possible.
To determine a threshold of detection value for surface roughness of restorations by patients using their tongue.
Samples of composite resin were finished with differing grades of abrasive. The surface roughness (Ra) was measured and representative scanning electro-micrographs taken. These were compared with labial enamel. Twenty-five volunteers were asked to rank them in order of perceived roughness using the tip of their tongue.
These showed that the 60% of volunteers were able to rank the specimens correctly, and were able to distinguish differences in roughness values from between 0.25 and 0.50 microm. This range encompasses that of natural enamel.
The subjects were able to distinguish lower roughness values than have previously been reported. It is concluded that when finishing restorations the surface should have a maximum roughness 0.50 microm if it is not to be detected by the patient.
Für die Auswahl geeigneter Kunststoffe ist es hilfreich, die physikalisch-technischen Eigenschaften der Materialien zu kennen. Entsprechend den Gruppen Duroplaste, Thermoplaste, Elastomere und Schäume werden die Eigenschaften aufgelistet und Anwendungsbereiche erläutert.
Der Inhalt
• Einteilung
• Herstellung
• Normung
• Eigenschaften ausgewählter Kunststoffe
• Duroplaste
• Thermoplaste
• Gummi (Elastomere)
• Kunststoff-Schäume
Die Zielgruppen
• Studierende
• Ingenieure
Der Autor
Dr.-Ing. Bernd Schröder war bis 2011 Professor an der Hochschule für Technik und Wirtschaft in Aalen.
The purpose of this study was to compare the resistance to wear of six commonly used orthotic appliance materials. These materials were: SR Ivocap (Ivoclar Vivadent, Inc., Amherst, NY), Eclipse (Dentsply International, York, PA), ProBase (Ivoclar Vivadent), Valplast (Valplast International Corp., Oceanside, NY), Impak (CMP Industries LLC, Albany, NY), and Clearsplint (Astron Dental Corp., Lake Zurich, IL). Twelve cylindrical specimens of each material were fabricated per manufacturer instructions. Occlusal wear was simulated in a custom-made wear simulator with each specimen receiving four wear scars in a two-body wear simulation using a 1.5 mm tungsten-carbide tipped stylus at 40 newtons for 2500 cycles at 1 Hz, while immersed in 37 degrees C distilled water (n = 48). The specimens were evaluated before and after wear testing using a three-dimensional (3D) noncontact profilometer (Proscan 2000, Scantron Corp., Eagan, MN). A mean change in volume was determined for each orthotic material. Results found that Clearsplint material displayed the greatest amount of volume loss/wear, while SR Ivocap, Eclipse, and ProBase materials had the least amount of wear. Valplast and Impak performed more moderately. Based upon this wear knowledge, practitioners are able to more reliably choose the appliance material necessary for their various patients.
Thermoplastic resin clasps have been used for esthetic denture rehabilitation. However, details of the design of the clasps have never been thoroughly clarified. This study investigated the retentive forces of thermoplastic resin clasps for non-metal clasp dentures. The retentive forces of all thermoplastic resin clasps depended on the elastic modulus of each resin, undercuts, thickness, and widths of the tested. A clasp with more than 0.5 mm undercut and 1.0 mm thickness is needed for Valplast. Similarly, more than 0.25 mm undercut and 1.0 mm thickness and 0.5 mm undercut and 0.5 mm thickness are required for Estheshot and Reigning, respectively; thus, the recommended clasp arm thickness is 1.0 mm to 1.5 mm for Valplast and Estheshot and 0.5 mm to 1.0 mm for Reigning when the width of the retentive arm is 5.0 mm.
To investigate the mechanical properties of injection-molded thermoplastic denture base resins.
Four injection-molded thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were used in this study. The flexural strength at the proportional limit (FS-PL), the elastic modulus, and the Charpy impact strength of the denture base resins were measured according to International Organization for Standardization (ISO) 1567 and ISO 1567:1999/Amd 1:2003.
The descending order of the FS-PL was: conventional PMMA > polyethylene terephthalate, polycarbonate > two polyamides. The descending order of the elastic moduli was: conventional PMMA > polycarbonate > polyethylene terephthalate > two polyamides. The descending order of the Charpy impact strength was: polyamide (Nylon PACM12) > polycarbonate > polyamide (Nylon 12), polyethylene terephthalate > conventional PMMA.
All of the injection-molded thermoplastic resins had significantly lower FS-PL, lower elastic moduli, and higher or similar impact strength compared to the conventional PMMA. The polyamide denture base resins had low FS-PL and low elastic moduli; one of them possessed very high impact strength, and the other had low impact strength. The polyethylene terephthalate denture base resin showed a moderately high FS-PL, moderate elastic modulus, and low impact strength. The polycarbonate denture base resin had a moderately high FS-PL, moderately high elastic modulus, and moderate impact strength.
Six thermoplastic resins and conventional acrylic resin were examined to characterize their mechanical and physical properties, water sorption, solubility, flexural strength, modulus of elasticity, tensile strength and color stability. Thermoplastic resins for non-metal clasp dentures exhibiting low water sorption and solubility offer hygienic advantages. Since they have a low modulus of elasticity and are easily manipulated, these materials make it possible for larger undercuts to be used for retention compared to acrylic resin. Not all of the thermoplastic resins tested fractured after the bending test in contrast to the conventional denture base resin, which fractured when tested beyond its proportional limit. It was also found that clinically noticeable staining may occur on the polyamide resins and polyethylene terephtalate resins.
Mün-chen: Walter-Straub-Institut für Pharmakologie und Toxikologie der LMU
- F-X Reichl
Reichl F-X. Analytisches Gutachten zum
Eluationsverhalten von Valplast. Mün-chen: Walter-Straub-Institut für Pharmakologie und Toxikologie der LMU, o.J.
Grundwissen für Zahntechniker -Die Teilprothese. 2. Aufl. München: Neuer Merkur
- H H Caesar
- K M Lehmann
Caesar HH, Lehmann KM. Grundwissen
für Zahntechniker -Die Teilprothese. 2.
Aufl. München: Neuer Merkur, o.J.
Analytisches Gutachten zum Eluationsverhalten von Valplast. München: Walter-Straub-Institut für Pharmakologie und Toxikologie der LMU
- F-X Reichl
Reichl F-X. Analytisches Gutachten zum
Eluationsverhalten von Valplast. München: Walter-Straub-Institut für Pharmakologie und Toxikologie der LMU, o.J.