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. 2024 Jul 20;16(7):e64971.
doi: 10.7759/cureus.64971. eCollection 2024 Jul.

Comparative Evaluation of Microhardness and Polymerization Shrinkage in Residual Zirconia Reinforced Provisional Restorations: An In Vitro Study

Himaja Naina  1 , Vidyashree V Nandini  1 , Dilip M Kumar  1 , Russia Marimuthu  1 , Shiney Boruah  1 , Naveen S Raj  1
Affiliations

Comparative Evaluation of Microhardness and Polymerization Shrinkage in Residual Zirconia Reinforced Provisional Restorations: An In Vitro Study

Himaja Naina et al. Cureus. .

Abstract

Aim The aim of this study is to evaluate and compare the microhardness and polymerization shrinkage of polymethyl methacrylate reinforced with residual zirconia. Materials and methods A total of 360 resin samples were fabricated, with dimensions of 12 mm × 12 mm × 3 mm and 12 mm × 8 mm × 6 mm. Zirconia dust (40% by weight) was added to 180 of these samples. The study included four groups: Group A (autopolymerizing acrylic resin), Group H (heat-polymerizing acrylic resin), Group ZA (autopolymerizing acrylic resin with zirconia dust), and Group ZH (heat-polymerizing acrylic resin with zirconia dust). Each group consisted of 90 samples, with 45 samples used for evaluating microhardness and 45 samples for assessing polymerization shrinkage. Results Group ZH exhibited the highest microhardness at 6.06 ± 0.31 GPa. It also recorded the lowest shrinkage values, measuring 52.11 ± 3.21 mm³. Tukey's honestly significant difference test revealed that microhardness was significantly higher in Group ZA (4.53 ± 0.29 GPa) compared to Group A (3.51 ± 0.25 GPa). However, Group H (5.42 ± 0.26 GPa) demonstrated greater hardness than Group ZA. Regarding shrinkage, the addition of zirconia dust resulted in reduced values, with Group ZA (73.93 ± 3.55 mm³) showing less shrinkage compared to Group A (91.9 ± 6.38 mm³). Similarly, Group ZH (52.11 ± 3.21 mm³) had lower shrinkage than Group H (66.71 ± 5.97 mm³). Group A exhibited the highest shrinkage among all the groups. Conclusion Within the limitations of this study, it can be concluded that there is an increase in hardness and a decrease in shrinkage values of the resin with the addition of zirconia dust in heat and autopolymerizing acrylic resin used for the fabrication of provisional restorations. Zirconia-incorporated heat-activated resin showed superior microhardness and decreased shrinkage values. Although the addition of residual zirconia to autopolymerized samples demonstrated better hardness, it was observed that pure heat-polymerized samples showed greater hardness. Reusing computer-aided design and computer-aided manufacturing powder waste can cut down on economic losses and aid in environmental sustainability.

Keywords: cad-cam residual; cad-cam waste; green dentistry; milling dust; residual zirconia.

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Conflict of interest statement

Human subjects: All authors have confirmed that this study did not involve human participants or tissue. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. Wax patterns of samples for testing microhardness
Figure 2
Figure 2. Wax patterns of samples for testing polymerization shrinkage
See this image and copyright information in PMC

References

    1. A simple solution to recycle and reuse dental CAD/CAM zirconia block from its waste residuals. Ding H, Tsoi JK, Kan CW, Matinlinna JP. J Prosthodont Res. 2021;65:311–320. - PubMed
    1. New perspectives for recycling dental zirconia waste resulting from CAD/CAM manufacturing process. Gouveia PF, Schabbach LM, Souza JCM, et al. J Clean Prod. 2017;152:454–463.
    1. Flexural strength of heat-polymerized polymethyl methacrylate denture resin reinforced with glass, aramid, or nylon fibers. John J, Gangadhar SA, Shah I. J Prosthet Dent. 2001;86:424–427. - PubMed
    1. Anusavice J, Shen C, Rawls HR. Elsevier. Vol. 506. Elsevier; 2014. Phillip’s Science of Dental Materials - 1st South Asian Edition; p. 509.
    1. Oliver-Pharr indentation method in determining elastic moduli of shape memory alloys—a phase transformable material. Kan Q, Yan W, Kang G, Sun Q. J Mech Phys Solids. 2023;5:1–7.

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