PSI - Issue 74

Hrubanová A. et al. / Procedia Structural Integrity 74 (2025) 33–37 Anna Hrubanová / Structural Integrity Procedia 00 (2025) 000–000

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material of the silicone obturator, silicone impression materials are a preferable option as they are specifically designed for safe use within the oral cavity. However, there are multiple options available which can be suitable for the protective obturator. Some studies already compared the tensile mechanical properties (Re et al. 2015; Lu, Nguyen, and Powers 2004; Wezgowiec et al. 2022), tear strength (Lu, Nguyen, and Powers 2004; Singer et al. 2022) or the effect of disinfectants on mechanical properties (Wezgowiec et al. 2022; Hrubanová et al. 2024) of elastomer impression materials, even though the materials are usually compared only based on their elastic recovery (Wezgowiec et al. 2022; Singer et al. 2022; Ud Din et al. 2023; Jamani, Harringhton, and Wilson 1989), since they are used for precision impressions. In this study, comparison of mechanical properties and micro-structure of four silicone impression materials was done to determine the suitable options for protective silicone obturator fabrication. 2. Materials and Methods Four silicone impression materials were selected for comparison with regard to the classification of elastomeric impression materials (Wassell, Barker, and Walls 2002); one material from each class was selected for material properties comparison (Tab.1).

Table 1. Elastomeric impression materials Elastomeric impression material

Manufacturer

Condensation silicone

Zetaplus (Zhermack)

Addition silicones (polyvinylsiloxane)

Elite HD+ Putty Soft (Zhermack) Permlastic Regular Body (KERR)

Polysulfide Polyether

Impregum Soft (3M)

2.1. Specimen preparation and tensile testing The shape of the uniaxial tensile specimens was based on ISO 527-2. The two-part moulds for specimen preparation were 3D-printed (Prusa i3 MK3S+) from PLA material. The elastomeric impression materials were prepared according to the manufacturers’ instructions; Elite HD+ Putty is composed of two clay-like components – the base component and the catalyst – which can be mixed manually. A similar mixing technique was used for the Zetaplus material which also consists of a clay-like base component and a paste catalyst. The two remaining materials were provided as two paste-like components (base and catalyst) and had to be mixed on a special mat using a spatula. After mixing the two components, the material was inserted into the mould, pressed, and left to harden according to the manufacturers’ instructions. In total, 40 uniaxial specimens were prepared, 10 from each material class. A similar procedure was used for the preparation of specimens intended for micro-CT scanning. The specimens were tested 24 hours after preparation. Each specimen was marked with contrast dots which were later used for deformation analysis using Digital Image Correlation (DIC). Thickness measurements were carried out using a digital thickness indicator at 5 different locations within the testing area; the mean value was considered for further analysis. A custom-made tensile testing device (Camea s.r.o, CZ) was used for testing and each specimen was tested until failure. The engineering stress-strain curves were considered for further analysis. Micro-CT Rectangular specimens (18 mm x 18 mm) of each impression material with thicknesses of 1.5 mm and 2.5 mm were scanned using a micro-CT device (GE phoenix v|tome|x L240, GE Sensing & Inspection Technologies GmbH, Wunstorf, Germany). Two different thicknesses were chosen, so that the porosity could be evaluated independently of specimen thickness. All specimens were scanned simultaneously; polystyrene layers were inserted between each specimen so that they are clearly separated in the micro-CT images for subsequent analysis. Due to its low density, polystyrene is not visible in micro-CT images and it helps to maintain the gap between specimens. A silicone cylinder 2.2.