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ORIGINAL RESEARCH
Year : 2023 | Volume
: 14
| Issue : 1 | Page : 22-24
Assessment of Elongation Percentage, Tensile, and Tear Strength of Filler Particles: An In Vitro Study
Mays H Hasan, Abdalbseet A Fatalla
Department of Prosthodontic, College of Dentistry, University of Baghdad, Bab Al-Muadham campus of the University of Baghdad, Baghdad, Iraq
Correspondence Address:
Abdalbseet A Fatalla
Prosthodontic Department, College of Dentistry, University of Baghdad, Bab Al-Muadham campus of the University of Baghdad, 1417, Baghdad
Iraq
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/denthyp.denthyp_145_22
Introduction: We aimed to assess how the addition of nano tellurium oxide (TeO2) filler particles affected the elongation percentage, tensile strength, and tear strength of the maxillofacial silicone elastomer. Methods: Thirty samples were created by adding nano TeO2 powder (518.9 nm) at percentages of 0%, 3%, and 5% w/w into the RTV VST-50 silicon elastomer. Elongation percentage, tensile, and tear strength were assessed according to the specifications of ISO 37:2017 using a computerized universal testing device. Data were analyzed with one-way ANOVA and Tukey’s honest significant difference test using MedCalc 20.104. Results: There were statistically significant differences regarding elongation percentage, tensile, and tear strength among study groups (P < 0.001). All of the post hoc comparisons showed statistically significant differences (P ≤ 0.002). Conclusion: The addition of 5% and 3% nano TeO2 filler particle significantly increases the elongation percentage, tensile strength, and tear strength of maxillofacial silicone in comparison with the control group, concentration-dependently.
Keywords: Elongation percentage, maxillofacial silicone elastomer, nano filler particle, tear strength, tensile strength, tellurium oxide
Silicon elastomer is widely used for creating facial prostheses because of its biocompatibility, low chemical reactivity, maneuverability, and optical clarity.[1] Numerous studies looking at the mechanical characteristics of maxillofacial silicon materials showed that these materials were still far from having the optimal attributes to meet the demands of maxillofacial prostheses.[2],[3]
Both the physical and mechanical properties of Maxillofacial silicon elastomeric materials could be improved by using different reinforcement additives.
Due to their special characteristics, metal oxide fillers have been generally employed in several industrial and biological applications.[4] A number of experiments have been done to add reinforcing compounds to materials to improve their mechanical properties. In one study, TeO2, ZnO, and CeO2 fillers at concentrations of 2.0% and 2.5% improved the general mechanical properties of the silicone A-2186 maxillofacial elastomer, including elongation percentage, tear strength, and tensile strength.[2]
A recent systematic review and meta-analysis showed that 1.5% ZrSiO4, 3% SiO2, 1.5% Y2O3, 2–6% TiO2, 2–2.5% ZnO, 2–2.5% CeO2, 0.5% TiSiO4, and 1% Ag-Zn Zeolite can be employed to strengthen maxillofacial silicone elastomer. Nano fillers showed higher relative results for tensile strength, tear strength, and elongation at break when compared to micro fillers. Micro fillers revealed unpredictable results in mechanical properties, and a meta-analysis of elongation at break concluded against their use. [5]
Tellurium oxide (TeO2) is satisfactory for a variety of applications because of its exceptional features, which consist of a higher index of refraction, mechanical durability, and excellent chemical stability. [6],[7]
The current study’s objective is to assess how the addition of nano TeO2 filler particles affects the elongation percentage, tensile strength, and tear strength of the maxillofacial silicone elastomer.
Materials and methodsStudy protocol is approved by the Ethical Committee of College of Dentistry, University of Baghdad at January 12, 2022 (approval number: 742).
The sample size calculation was based on previous studies[8] (alph: 0.05, power: 0.90, and effect size f: 0.7, sample size for each group: 10) using G*Power software version 3.1.9.7 (www.gpower.hhu.de/).
TeO2 filler particles with a mean particle size of 518.9 nm (Sigma, Darmstadt, Germany) were added to the RTV VST-50 silicon elastomer (Factor II Inc., Lakeside, USA). A CO2 laser cutting device with a laser power of 150 watts (JL-1612 Jinan Link, Shandong, China) was used to cut acrylic sheets with a 2 and 4 mm thickness for the mold components. The bottom and cover sections were made from sheets of material with a thickness of 4 mm rather than 2 mm; this is equivalent to the thickness of the test specimens’ that has to be prepared for a specific test.[3]
To prevent TeO2 fillers from dispersing, a 10 m vacuum mixing system was employed (Multivac 3, Degussa, Germany). To avoid sucking up the filler, the vacuum was shut off for the first 3 minutes. Then, it was restarted for the following 7 minutes at 360 rotations per minute and under a vacuum of −10 bar. To create a homogeneous mixture with free bubbles, the silicon base (0% TeO2 w/w) or modified silicon (Base and TeO2) were combined with the silicon catalyst, and the vacuum mixer was used once again for 5 minutes.[9] Before pouring the silicon mixture into the mold and sealing it with screws and G-clamps, the mould was first painted with isolation medium, and allowed to dry.[3] According to the manufacturer’s instructions, 24 hours should pass while the silicon is left out on a bench at 23.2 °C and 50% humidity.
The mould was opened, the silicon material was carefully removed from it, and it was left to polymerize for 24 hours at room temperature (23°C).[10] Under running water, the samples were scrubbed meticulously, dried with paper towels, and completed with a scalpel blade no. 11 to remove any remaining debris.[11] Then, they were stored in optimum conditions for at least 16 hours before being put to the test.[12],[13],[14]
Thirty dump-bell-shaped samples were produced according to ISO 37: 2017 (www.iso.org/standard/68116.html).[15] Ten specimens served as the control group, with the remaining 20 specimens having 3% and 5% w/w TeO2 filler concentrations added. Elongation percentage, tensile strength, and tear strength were assessed blindly according to the specifications of ISO 37:2017 using a computerized universal testing device (WDW20, Laryee Technology Co., Beijing, China).[10]
Data were analyzed with one-way ANOVA and the Tukey’s honest significant difference test using MedCalc 20.104 (MedCalc Software Ltd., Ostend, Belgium).
ResultsThere were statistically significant differences among study groups (P < 0.001) regarding elongation percentage, tensile strength, and tear strength. All post hoc comparisons showed statistically significant differences (P ≤ 0.002) [Figure 1].
Figure 1 Violin plot visualized the distribution of the data and their probability density related to tensile strength (MPa), tear strength (kgf/cm), and elongation percentage.Tensile Strength Tear Strength Elongation Percentage
DiscussionFor maxillofacial silicone rubbers, excellent tear strength, high tensile strength, and good bulk elongation at break are considered key physical properties. The addition of fillers is considered extremely critical in order to have an acceptable level of reinforcement required to significantly improve the mechanical properties. Processing conditions, polymer grade, filler loading, filler properties (particle size or specific surface area, structure, and surface activity), and filler properties (structure, surface activity) all have a significant effect on reinforcement. [16]
TeO2 is well suited for a variety of applications because of its excellent chemical stability, mechanical toughness, high refractive index, and good optical nonlinearity.[6],[7]
To our knowledge addition of TeO2 into maxillofacial silicone rarely studies and reported in the literature. In this study, the null hypothesis was rejected because the addition of 5% and 3% TeO2 filler significantly increased the elongation percentage, tensile strength, and tear strength of maxillofacial silicone in comparison with the control group, concentration-dependently. Han et al. reported significantly higher tensile and tear strengths and percent elongation with the addition of 2.0% and 2.5% TeO2 into A-2186 silicone elastomer. [2]
However, the increase in tensile strength may be related to chemical and physical interactions between TeO2 particles and polymer chains. The cross-linking process, cross-link density, and interaction between polymer chains and fillers has a significant effect on the elongation and tensile strength of cured elastomeric silicones.[17] Furthermore, by adding fillers, the energy required to disrupt the polymer network can be converted into heat, which required the availability of a large amount of energy.[18]
The increase in tear strength may be due to the polymer’s ability to dissipate the strain energy near the site of the expansion fracture. Since the filler particles disperse energy within the matrix as the crack propagates, making cracking more difficult, significant pressure is required to completely rupture the polymer matrix. [19] Since shorter cure times increase the tear strength, the tear strength of elastomers increases if the matrix is slightly undercured.[20] The results of this study are consistent with previous studies showing that the tear strength of silicone elastomers is improved by adding filler particles.[2],[21],[22]
Readers must be aware of the inherent limitations of in vitro studies. The physical properties of maxillo-facial silicone elastomer may be altered after months of clinical usage or after pigment addition. More clinical trials are needed to assess the effectiveness and safety of the addition of TeO2 to maxillofacial silicone elastomers.
References
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