Hardness and Wear Resistance of Dental Biomedical Nanomaterials in a Humid Environment with Non-Stationary Temperatures

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Abstract

This study discusses a quantitative fatigue evaluation of polymer–ceramic composites for dental restorations, i.e., commercial material (Filtek Z550) and experimental materials Ex-nano (G), Ex-flow (G). Their evaluation is based on the following descriptors: microhardness, scratch resistance, and sliding wear. In order to reflect factors of environmental degradation conditions, thermal fatigue was simulated with a special computer-controlled device performing algorithms of thermocycling. Specimens intended for the surface strength and wear tests underwent 10 ⁴ hydrothermal fatigue cycles. Thermocycling was preceded by aging, which meant immersing the specimens in artificial saliva at 37 °C for 30 days. Microhardness tests were performed with the Vickers hardness test method. The scratch test was done with a Rockwell diamond cone indenter. Sliding ball-on-disc friction tests were performed against an alumina ball in the presence of artificial saliva. A direct positive correlation was found between thermocycling fatigue and microhardness. The dominant mechanism of the wear of the experimental composites after thermocycling is the removal of fragments of the materials in the form of flakes from the friction surface (spalling). Hydrothermal fatigue is synergistic with mechanical fatigue.

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Thermal cycling procedures for laboratory testing of dental restorations.

Craig M. Gale, B W Darvell (1999)

Exposure of restorations in extracted teeth to cyclic thermal fluctuations to simulate one of the many factors in the oral environment has been common in many tracer penetration, marginal gap and bond strength laboratory tests. Temperature changes used have rarely been substantiated with temperature measurements made in vivo and vary considerably between reports. Justification and standardization of regimen are required. An assessment of reports describing temperature changes of teeth in vivo is followed by an analysis of 130 studies of laboratory thermal cycling of teeth by 99 first authors selected from 25 journals. A clinically relevant thermal cycling regimen was derived from the in vivo information, and is suggested as a benchmark standard. Variation of regimens used was large, making comparison of reports difficult. Reports of testing the effects of thermal cycling were often contradictory, but generally leakage increased with thermal stress, although it has never been demonstrated that cyclic testing is relevant to clinical failures. However, should this be done, the standard cyclic regimen defined is: 35 degrees C (28 s), 15 degrees C (2 s), 35 degrees C (28 s), 45 degrees C (2 s). No evidence of the number of cycles likely to be experienced in vivo was found and this requires investigation, but a provisional estimate of approximately 10,000 cycles per year is suggested. Thermal stressing of restoration interfaces is only of value when the initial bond is already known to be reliable. This is not the case for most current restorative materials.

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The effect of filler loading and morphology on the mechanical properties of contemporary composites.

Kanyin Ong, Jang-Kyo Kim, Osamu Okuno (2002)

Little information exists regarding the filler morphology and loading of composites with respect to their effects on selected mechanical properties and fracture toughness. The objectives of this study were to: (1) classify commercial composites according to filler morphology, (2) evaluate the influence of filler morphology on filler loading, and (3) evaluate the effect of filler morphology and loading on the hardness, flexural strength, flexural modulus, and fracture toughness of contemporary composites. Field emission scanning electron microscopy/energy dispersive spectroscopy was used to classify 3 specimens from each of 14 commercial composites into 4 groups according to filler morphology. The specimens (each 5 x 2.5 x 15 mm) were derived from the fractured remnants after the fracture toughness test. Filler weight content was determined by the standard ash method, and the volume content was calculated using the weight percentage and density of the filler and matrix components. Microhardness was measured with a Vickers hardness tester, and flexural strength and modulus were measured with a universal testing machine. A 3-point bending test (ASTM E-399) was used to determine the fracture toughness of each composite. Data were compared with analysis of variance followed by Duncan's multiple range test, both at the P<.05 level of significance. The composites were classified into 4 categories according to filler morphology: prepolymerized, irregular-shaped, both prepolymerized and irregular-shaped, and round particles. Filler loading was influenced by filler morphology. Composites containing prepolymerized filler particles had the lowest filler content (25% to 51% of filler volume), whereas composites containing round particles had the highest filler content (59% to 60% of filler volume). The mechanical properties of the composites were related to their filler content. Composites with the highest filler by volume exhibited the highest flexural strength (120 to 129 MPa), flexural modulus (12 to 15 GPa), and hardness (101 to 117 VHN). Fracture toughness was also affected by filler volume, but maximum toughness was found at a threshold level of approximately 55% filler volume. Within the limitations of this study, the commercial composites tested could be classified by their filler morphology. This property influenced filler loading. Both filler morphology and filler loading influenced flexural strength, flexural modulus, hardness, and fracture toughness.

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Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? A literature review.

Maurizio D'Amario, Mario Capogreco, Roberto Gatto … (2014)

In vitro tests continue to be an indispensable method for the initial screening of dental materials. Thermal cycling is one of the most widely used procedures to simulate the physiological aging experienced by biomaterials in clinical practice. Consequently it is routinely employed in experimental studies to evaluate materials' performance. A literature review aimed to elucidate test parameters for in vitro aging of adhesive restorations was performed. This study aims to assess whether or not a standardized protocol of thermal cycling has been acknowledged from a review of the literature. An exhaustive literature search, examining the effect of thermal cycling on restorative dental materials, was performed with electronic database and by hand. The search was restricted to studies published from 1998 to August 2013. No language restrictions were applied. The search identified 193 relevant experimental studies. Only twenty-three studies had faithfully applied ISO standard. The majority of studies used their own procedures, showing only a certain consistency within the temperature parameter (5-55°C) and a great variability in the number of cycles and dwell time chosen. A wide variation in thermal cycling parameters applied in experimental studies has been identified. The parameters selected amongst these studies seem to be done on the basis of convenience for the authors in most cases. A comparison of results between studies would appear to be impossible. The available data suggest that further investigations will be required to ultimately develop a standardized thermal cycling protocol.

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Journal

Journal ID (nlm-ta): Materials (Basel)

Journal ID (iso-abbrev): Materials (Basel)

Journal ID (publisher-id): materials

Title: Materials

Publisher: MDPI

ISSN (Electronic): 1996-1944

Publication date (Electronic): 10 March 2020

Publication date Collection: March 2020

Volume: 13

Issue: 5

Electronic Location Identifier: 1255

Affiliations

[1 ]Department of Mechanics and Machine Building, University of Economics and Innovations in Lublin, Projektowa 4, 20-209 Lublin, Poland; daniel.pieniak@ 123456wsei.lublin.pl

[2 ]The Main School of Fire Service, Faculty of Safety Engineering and Civil Protection, Slowackiego 52/54, 01-629 Warsaw, Poland; awalczak@ 123456sgsp.edu.pl

[3 ]Department of Materials Engineering, Faculty of Mechanical Engineering, Lublin University of Technology, Nadbystrzycka 36, 20-618, Lublin, Poland; m.walczak@ 123456pollub.pl

[4 ]Department of Automation, Faculty of Mechanical Engineering, Lublin University of Technology, Nadbystrzycka 36, 20-618, Lublin, Poland

[5 ]Department of Conservative Dentistry with Endodontics, Medical University of Lublin, Karmelicka 7, 20-080 Lublin, Poland; agata.niewczas@ 123456umlub.pl

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[* ]Correspondence: k.przystupa@ 123456pollub.pl

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Daniel Pieniak https://orcid.org/0000-0001-7807-3515

Krzysztof Przystupa https://orcid.org/0000-0003-4361-2763

Article

Publisher ID: materials-13-01255

DOI: 10.3390/ma13051255

PMC ID: 7085084

PubMed ID: 32164254

SO-VID: 61610844-6abc-4a62-a551-3b98901a9b47

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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

Hardness and Wear Resistance of Dental Biomedical Nanomaterials in a Humid Environment with Non-Stationary Temperatures

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HLA-G and immune tolerance in pregnancy

Most cited references 68

Thermal cycling procedures for laboratory testing of dental restorations.

The effect of filler loading and morphology on the mechanical properties of contemporary composites.

Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? A literature review.

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