ORIGINAL RESEARCH Year : 2023  |  Volume : 14  |  Issue : 1  |  Page : 36-38

Effect of addition of polymerized polymethyl methacrylate (PMMA) and zirconia particles on impact strength, surface hardness, and roughness of heat cure PMMA: An in vitro study

Duaa Subhi Rasan1, Firas Abdulameer Farhan2
1 MSc student, Karbala, Iraq
2 Prosthodontic Department, College of Dentistry, University of Baghdad, Bab Al-Muadham campus of the University of Baghdad, Baghdad, Iraq

Date of Submission23-Nov-2022Date of Decision09-Jan-2023Date of Acceptance11-Jan-2023Date of Web Publication20-Mar-2023

Correspondence Address:
Duaa Subhi Rasan
MSc student, Karbala
Iraq

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/denthyp.denthyp_151_22

Introduction: This study was designed to examine the effects of addition of the combination of polymerized polymethyl methacrylate (PMMA) and zirconia (ZrO2) particles to heat cure PMMA resin on impact strength, surface hardness, and roughness. Methods: The 70% (w/w) of polymerized PMMA powder (particle size: 0.70 µm) was mixed with 30% (w/w) of zirconia powder (ZrO2) (1 µm) to produce PMMA-ZrO2 filler. Ninety acrylic specimens created were divided into three groups containing 0% wt (Control group), 2% wt, and 4% wt, PMMA-ZrO2 filler. Ten specimens were used for impact strength, surface hardness and roughness test, blindly. Data were analyzed via one-way ANOVA and the Tukey post hoc test using R 3.6.3. Results: There was statistically significant difference among study groups regarding surface hardness and roughness (p < 0.001). Yet, nonsignificant difference was found on the subject of impact strength (p = 0.33). Post hoc test showed statistically significant difference for all pairwise comparisons as regards surface hardness and roughness (p < 0.05). Conclusion: The incorporation of PMMA-ZrO2 filler did not improve impact strength (resistance during an unexpected blows or dropping). Yet, increased surface roughness and hardness, concentration-dependently.

Keywords: denture base, impact strength, polymerized polymethyl methacrylate particles, polymethyl methacrylate resin, surface hardness, surface roughness, zirconia; zirconium oxide

How to cite this article:
Rasan DS, Farhan FA. Effect of addition of polymerized polymethyl methacrylate (PMMA) and zirconia particles on impact strength, surface hardness, and roughness of heat cure PMMA: An in vitro study. Dent Hypotheses 2023;14:36-8
How to cite this URL:
Rasan DS, Farhan FA. Effect of addition of polymerized polymethyl methacrylate (PMMA) and zirconia particles on impact strength, surface hardness, and roughness of heat cure PMMA: An in vitro study. Dent Hypotheses [serial online] 2023 [cited 2023 Mar 21];14:36-8. Available from: http://www.dentalhypotheses.com/text.asp?2023/14/1/36/372093   Introduction 

Polymethyl methacrylate (PMMA) resin is a well-known polymeric material utilized as a denture base material. This is because of the easy handling, reparability, and biocompatibility with oral tissues. PMMA resin was reported to have insufficient hardness and low-impact strength.[1],[2] The addition of fillers and fibers to PMMA is a popular method to enhance physical and mechanical properties.[3] The addition of polymerized PMMA particles to heat-cure acrylic resin decreased water solubility, water sorption, and residual monomer release.[4]

Metal oxides have piqued the interest of academics and scientists worldwide due to their diverse and promising uses in fields such as materials science, medicine, and industrial inspection.[5] A recent systematic review on influence of addition of zirconia on PMMA showed greater flexural strength than the control group, which can clearly affect users of complete denture. In addition, the impact resistance and surface hardness reduced in comparison with the control group.[6] Another recent systematic review and meta-analysis showed addition of zirconia on PMMA with concentration ranged 0.5 to 5 wt% enhances the flexural strength. [7],[8]

The current study aimed to examine the effects of addition of the combination of polymerized PMMA and zirconia particles to heat cure PMMA resin on impact strength, surface hardness, and roughness.

  Materials and methods 

The study was approved by the research ethics committee of the College of Dentistry/University of Baghdad (Ref. No. 755, January 2, 2023).

Balls of heat cure PMMA resin (Spofa Dental, Markova, Czech Republic) were created according to the manufacturer’s recommendation. The resulted PMMA balls were grounded by the mechanical grinding-milling machine (Silver Crest, Zhejiang, China) and sieved by the sieving machine (FRITSCH, GmbH, Germany) to produce a powder with an average of 0.70 µm particle. The 70% (w/w) of polymerized PMMA powder (0.70 µm) was mixed with 30% (w/w) of zirconia powder (ZrO2) (1 µm) (FIXANAL, Sigma. Aldrich, Germany) to produce PMMA-ZrO2 filler. The selection of particle sizes and the ratio of the addition of zirconia to PMMA resin were designated according to the pilot study. Ninety acrylic specimens were created and divided into three groups containing 0% Control group, 2% and 4% (w/w) PMMA-ZrO2 filler. Ten specimens were used for each test.

Specimen’s diamines were 65 mm × 10 mm × 2.5 mm according to ADA specification No. 12[9] for hardness and surface roughness tests, and for the impact strength test were 80 mm × 10 mm × 4 mm according to ISO, 179-1: 2010 (www.iso.org/standard/44852.html).

The Charpy impact strength test was used according to the standard test method ASTM D6110 (www.astm.org/d6110-18.html) using impact tester TMI No. 43-1 (Testing Machines Inc., Amityville, New York, USA). The shore D hardness test was employed according to the standard test method ASTM D2240 (www.astm.org/d2240-15r21.html) and ISO 868:2003 (www.iso.org/standard/34804.html) using Analoger Shore-Härteprüfer 311 x (Härteprüfer, ZwickRoell GmbH & Co., Germany). A portable roughness tester (TR220 Salu Tron, GmbH, Germany) was used to analyze the surface roughness according to ANSI/ADA specification No. 12-2002 (https://urlis.net/80y3976) equipped with a diamond surface analyzer. Before the test, all specimens were ultrasonically cleaned with alcohol to reduce physical and chemical contamination of the surfaces.

All tests were carried out blindly. Data were analyzed via one-way ANOVA and the Tukey post hoc test using R 3.6.3 software (R Foundation for Statistical Computing, Vienna, Austria).

  Results 

There was statistically significant difference among study groups regarding surface hardness and roughness (p < 0.001). Yet, nonsignificant difference was found on the subject of impact strength (p = 0.33). Post hoc test showed statistically significant difference for all pairwise comparisons as regards surface hardness and roughness (p < 0.05) [Figure 1].

Figure 1 Violin plot summarizes the center, spread, and density of date related to impact strength (kJ/m2) (green), surface hardness (blue), and surface roughness (µm) (pink).

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  Discussion 

In the current study, a mixture of polymerized PMMA and zirconia particles was added as a filler to improve the mechanical and physical properties of PMMA resin. To our knowledge, this is the first attempt in this regard. The impact strength values (resistance during an unexpected blows or) revealed a nonsignificant increase in the 2% and 4% PMMA-ZrO2 filler groups when compared to the control group. Surface hardness and roughness values increased with increasing PMMA-ZrO2 filler ratio.

Ayad N et al., reported addition of 5 and 15% zirconia to PMMA affected the impact strength and surface hardness nonsignificantly.[10] Ozdemir AK et al., showed addition of 1% colemanite to PMMA increased the impact strength.[11] Abdallah RM showed addition of 0.3 wt% halloysite nanotubes increased surface hardness.[12] Zhang XY showed addition of 3 wt% of nano-ZrO₂/aluminum borate whiskers increased surface hardness of PMMA.[13],[14] Hasanen A et al., showed the addition of 3%, 5%, and 7% SiO2 increased surface hardness and reduced impact strength.[15] Narrative review of Gad MM et al., reported the impact strength of PMMA increased via addition of glass fiber, Polyethylene and Polypropylene fiber, aluminum, TiO2, and carbon nanotubes. Surface hardness of PMMA will increase by the addition of aluminum, silanized nano TiO2, nano SiO2. In contrast, they reported addition of carbon nanotubes decreased surface hardness. Addition of silver–zinc zeolite, aluminum, fluoride glass, silanized nono-zirconia slightly increased surface roughness. Yet, addition of 3 wt% of silanized TiO2 significantly increased surface roughness of PMMA.[16],[17] Systematic review of Aldegheishem A et al., showed impact strength lean toward rise if the fillers are chemically fused and well dispersed in PMMA resin.[18]However, readers must note the limitations of in vitro studies, which cannot simulate clinical situations exactly. More long-time clinical studies are required to evaluate clinical effectiveness and safety of addition PMMA-ZrO2 filler to denture base resin.

Financial support and sponsorship

The study was not funded by any agency or organization.

Conflicts of interest

The authors declare that they do not have any conflict of interest.

 

  References 
1.Zafar MS. Prosthodontic applications of polymethyl methacrylate (PMMA): an update. Polymers 2020;12:2299.  
    2.Raszewski Z, Nowakowska-Toporowska A, Nowakowska D, Więckiewicz W. Update on acrylic resins used in dentistry. Mini Rev Med Chem 2021;21:2130-7.  
    3.Avinash B, Avinash BS, Shivalinga BM et al. Going green with ecofriendly dentistry. J Contemp Dent Pract 2013;14:766-9.  
    4.Al-Jmmal AY, Nada Z, Taqa AA. The effect of recycled polymethylmethacrylate on some physical and chemical properties of acrylic resin denture base. Int J Enhanc Res Sci Technol 2018;7:85-92.  
    5.Hussein NA, Ali NA. Synthesis and characterization of Ni2O3 as a phase of nickel oxide nanomaterial. Iraqi J Sci 2022;63:4733-9.  
    6.de Souza Leão R, de Moraes SLD, de Luna Gomes JM et al. Influence of addition of zirconia on PMMA: a systematic review. Mater Sci Eng C 2020;106:110292.  
    7.Chęcińska K, Chęciński M, Sikora M, Nowak Z, Karwan S, Chlubek D. The effect of zirconium dioxide (ZrO2) nanoparticles addition on the mechanical parameters of polymethyl methacrylate (PMMA): a systematic review and meta-analysis of experimental studies. Polymers 2022;14:1047.  
    8.Kareem S, Moudhaffer M. The effect of zirconium silicate nanopowder reinforcement on some mechanical and physical properties of heat cured poly methyl methacrylate denture base materials. J Bagh Coll Dent 2015;325:1-7.  
    9.Materials CoD, Devices. Revised American dental association specification no. 12 for denture base polymers. J Am Dent Assoc 1975;90:451-8.  
    10.Ayad NM, Badawi MF, Fatah AA. Effect of reinforcement of high impact acrylic resin with zirconia on some physical and mechanical properties. Rev Clín Pesq Odontol 2008;4:145-51.  
    11.Özdemir AK, Demir H, Doğan DÖ, Tuğut F, Hakan A. Effects of boron on the mechanical properties of polymethyl methacrylate denture base material. Eur Oral Res 2021;55:45-53.  
    12.Abdallah RM. Evaluation of polymethyl methacrylate resin mechanical properties with incorporated halloysite nanotubes. J Adv Prosthodont 2016;8:167-71.  
    13.Zhang X-Y., Zhang X-J., Huang Z-L., Zhu B-S., Chen R-R. Hybrid effects of zirconia nanoparticles with aluminum borate whiskers on mechanical properties of denture base resin PMMA. Dent Mater J 2014;33:141-6.  
    14.Katsikis N, Franz Z, Anne H, Helmut M, Andry V. Thermal stability of PMMA/silica Nano-and micro composite as investigated by dynamic-mechanical experiment. Polym Degra Stab 2007;22:1966-76.  
    15.Alnamel HA, Mudhaffer M. The effect of Silicon di oxide Nano −fillers reinforcement on some properties of heat cure polymethyl methacrylate denture base material. J Bagh Coll Dentistry 2014;26:32-6.  
    16.Alwan SA, Alameer SS. The effect of the addition of silanized Nano titania fillers on some physical and mechanical properties of heat cured acrylic denture base materials. J Bagh Coll Dentistry 2015;325:1-12.  
    17.Gad MM, Fouda SM, Al-Harbi FA, Näpänkangas R, Raustia A. PMMA denture base material enhancement: a review of fiber, filler, and nanofiller addition. Int J Nanomedicine 2017;12:3801.  
    18.Aldegheishem A, Al Deeb M, Al-Ahdal K, Helmi M, Alsagob EI. Influence of reinforcing agents on the mechanical properties of denture base resin: a systematic review. Polymers 2021;13:3083.  
    
  [Figure 1]