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Table of Contents
ORIGINAL ARTICLE
Year : 2019  |  Volume : 6  |  Issue : 3  |  Page : 56-58

Effect of adding aluminum oxide on the flexural strength of heat-cured poly (methyl methacrylate) denture base resin


1 Private Practise/Former Post Graduate, Dr. G D Pol Foundation's Yerala Medical Trust's Dental College and Hospital, Mumbai, Maharashtra, India
2 Professor and Head, Dr. G D Pol Foundation's Yerala Medical Trust's Dental College and Hospital, Mumbai, Maharashtra, India
3 Senior Lecturer, Dr. G D Pol Foundation's Yerala Medical Trust's Dental College and Hospital, Mumbai, Maharashtra, India
4 Reader, Dr. G D Pol Foundation's Yerala Medical Trust's Dental College and Hospital, Mumbai, Maharashtra, India
5 Private Practise, Department of Prosthodontics, Dr. G D Pol Foundation's Yerala Medical Trust's Dental College and Hospital, Mumbai, Maharashtra, India

Date of Submission23-Sep-2019
Date of Acceptance24-Sep-2019
Date of Web Publication25-Nov-2019

Correspondence Address:
Dr. Saumil Chetan Sampat
103/104, Cairo CHS, Skyline Oasis, Premier Road, Vidyavihar West, Mumbai - 400 086, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/INPC.INPC_48_19

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  Abstract 


Background: Apart from its numerous advantages, poly (methyl methacrylate) (PMMA) has certain limitations such as its low strength, brittle on impact, poor thermal conductivity, and resultant low flexural strength. This study is, therefore, planned to investigate the flexural strength of heat-cured PMMA denture base resin with the addition of different percentage of aluminum oxide powder.
Materials and Methods: A total of 120 specimens of PMMA (DPI® Heat Cure) of standard dimension (64mm x 10mm x 2.5mm) as per the American Dental Association specification No. 12/International Standards Organization specification No. 1567 for the determination of flexural strength were prepared: 30 for each of the four study groups. Aluminum oxide powder was added in specific percentage (5%, 15%, and 25% by weight) to the polymer component of heat-cure denture base resin as per the different subgroups.
Results: The results of this study showed that the highest mean flexural strength was for specimens in Subgroup A, i.e., PMMA reinforced with 5% aluminum oxide powder by weight, with a mean value of 124.39 Mpa.
Conclusions: Among the experimental group, the highest mean flexural strength of 124.39 Mpa was found with Subgroup A (5%) followed by Subgroup B (15%) which was 116.83 Mpa. The least flexural strength of 95.81 Mpa was found with Subgroup C (25%).

Keywords: Aluminum oxide, fillers, flexural strength, poly (methyl methacrylate)


How to cite this article:
Nahata N, Das RD, Sampat SC, Banga P, Dole V, Murkey SN. Effect of adding aluminum oxide on the flexural strength of heat-cured poly (methyl methacrylate) denture base resin. Int J Prev Clin Dent Res 2019;6:56-8

How to cite this URL:
Nahata N, Das RD, Sampat SC, Banga P, Dole V, Murkey SN. Effect of adding aluminum oxide on the flexural strength of heat-cured poly (methyl methacrylate) denture base resin. Int J Prev Clin Dent Res [serial online] 2019 [cited 2019 Dec 10];6:56-8. Available from: http://www.ijpcdr.org/text.asp?2019/6/3/56/271527




  Introduction Top


Introduction of poly (methyl methacrylate) (PMMA) resins by Dr. Walter Wright in 1937 revolutionized the use of denture base resins.[1] The properties that have contributed to the success of this material as a denture base resin are its ease of processing, its color-matching ability, lightweight, ease in handling and repair, accurate fit with better stability, and low cost.[2],[3] However, they are susceptible to fracture after prolonged clinical use because of certain limitations such as low thermal conductivity, brittle on impact, and resultant low flexural strength.[4] Therefore, different approaches have been proposed to improve the mechanical properties of PMMA by incorporating metal forms (wires, plates, or meshes), polyaramid fibers, carbon fibers, glass fibers, polyethylene fibers, chopped PMMA fibers, sapphire whiskers, ceramic powders, and alumina. With several conflicting data reports, an in-vitro study was conducted to evaluate the effect of adding aluminum oxide in varying percentages by weight on the flexural strength of a heat-cured PMMA denture base resin.

Standardization of samples

A brass metal mold with five prefabricated die spaces measuring 64 mm × 10 mm × 2.5 mm was fabricated, according to the International Standards Organization specification 1567 and American Dental Association specification No. 12. This mold was used to prepare thirty samples for each group. All samples after processing were then stored in distilled water for 50 h before testing.

Grouping of test specimens

Preparation of samples for the control group (Group I)

Group I was the control group consisting of thirty samples of PMMA without any filler.

Preparation of samples for the experimental group (Group II)

Group II was the experimental group that was divided into three subgroups consisting of thirty samples each with different percentage of aluminum oxide, respectively, i.e.,

  • Subgroup A: 5% of aluminum oxide in PMMA
  • Subgroup B: 15% of aluminum oxide in PMMA
  • Subgroup C: 25% of aluminum oxide in PMMA.


Testing of samples

The samples of the control group as well as each subgroup were subjected to flexural strength test at the “Material Science Department, Indian Institute of Technology, Powai, Mumbai, India.” A three-point bending test on Instron® universal testing machine was used. Individual samples were removed from the water bath and were dried. Midline and a line 25 mm from it on both sides were marked on the individual sample. These lines helped in the positioning of samples on the three-point bending machine.


  Results Top


This study was carried out to evaluate the flexural strength of heat-cured PMMA denture base resin with the addition of different percentage of aluminum oxide powder. The data were analyzed and subjected to one-way ANOVA followed by the Bonferroni correction for posthoc analysis with time. The statistics revealed that the mean flexural strength (MPa) for Subgroup A was the highest (124.39 MPa) [Graph 1], followed by that for Subgroup B (116.84 MPa) [Graph 2], then control group (97.66 MPa) [Graph 3] and Subgroup C (95.82 MPa) [Graph 4]. The standard deviations were comparable and are revealed through box plots presented in [Graph 5].




  Discussion Top


High flexural strength is important for the clinical success of a denture. Tissue-borne prosthesis is subjected to constant repetitive stresses due to mastication and parafunctional contacts.[5],[6],[7],[8],[9],[10] Hargreaves[9] and Jagger et al.[11] have also stated that flexural fatigue stress exerted by the repeated masticatory forces is the primary cause of PMMA denture base fracture and that it is prone to impact failure with time. Hence, PMMA denture base resin should have a high proportional limit to counteract plastic deformation and also possess fatigue resistance to withstand these repeated functional loads. Various studies are documented in the literature pertaining to reinforcement of PMMA with numerous types of inserts in an attempt to enhance its mechanical properties. Some of the materials used are metal forms (wires, plates, or meshes), polyaramid fibers,[10],[11] carbon fibers, glass fibers,[11] polyethylene fibers, chopped PMMA fibers, and sapphire whiskers.[8],[12] The incorporation of ceramic particles in various dental materials has been studied and found to be biocompatible, and it also improves mechanical properties. In addition, the white color of the ceramic powder is not expected to compromise esthetic appearance. Aluminum oxide, more commonly known as alumina, has strong ionic interatomic bonds that lead to several advantageous qualities. Researchers[13] have documented that incorporating higher concentration of aluminum oxide in their study caused decrease in flexural strength.


  Conclusions Top


Among the experimental group, the highest mean flexural strength of 124.39 Mpa was found with Subgroup A (5%) followed by Subgroup B (15%) which was 116.83 Mpa. The least flexural strength of 95.81 Mpa was found with Subgroup C (25%).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest



 
  References Top

1.
Peyton FA. History of resins in dentistry. Dent Clin North Am 1975;19:211-22.  Back to cited text no. 1
    
2.
Craig R, Powers J. Prosthetic application of polymers. In: Restorative Dental Materials. 11th ed.. Mosby, St. Louis. Missouri 2002. p. 636.  Back to cited text no. 2
    
3.
Arora N, Jain V, Chawla A, Mathur VA. Effect of addition of sapphire (aluminium oxide) on the flexural strength, thermal diffusivity and water sorption of heat polymerized acrylic resin. Int J Prosthet Rest Dent 2011;1:21-7.  Back to cited text no. 3
    
4.
Powers JM, Sakaguchi RL. Craig's Restorative Material. 12th ed.. St. Louis, Missouri: Elsevier; 2006. p. 518-26.  Back to cited text no. 4
    
5.
Anusavice KJ. Phillips's Science of Dental Materials. 10th ed.. St. Louis, Missouri: Saunders; 1996. p. 254-62.  Back to cited text no. 5
    
6.
Saritha MK, Shadakshari S, Nandeeshwar DB, Tewary S. An in vitro study to investigate the flexural strength of conventional heat polymerised denture base resin with addition of different percentage of aluminium oxide powder. Asian J Med Cli Sci 2012;1:80-5.  Back to cited text no. 6
    
7.
Vojdani M, Bagheri R, Khaledi AA. Effect of aluminium addition on flexural strength, surface hardness and roughness of heat polymerized acrylic resin. J Dent Sci 2012;7:238-44.  Back to cited text no. 7
    
8.
Grant AA, Greener EH. Whisker reinforcement of poly (methyl methacrylate) denture base resins. Austin Dent J 1967;12:29-33.  Back to cited text no. 8
    
9.
Hargreaves AS. Polymethylmethacrylate as a denture base material in service. J Oral Rehabil 1975;2:97-104.  Back to cited text no. 9
    
10.
Vallittu PK, Lassila VP, Lappalainen R. Transverse strength and fatigue of denture acrylic-glass fiber composite. Dent Mater 1994;10:116-21.  Back to cited text no. 10
    
11.
Jagger DC, Harrison A, Jandt KD. The reinforcement of dentures. J Oral Rehabil 1999;26:185-94.  Back to cited text no. 11
    
12.
Ellakwa AE, Morsy MA, El-Sheikh AM. Effect of aluminum oxide addition on the flexural strength and thermal diffusivity of heat-polymerized acrylic resin. J Prosthodont 2008;17:439-44.  Back to cited text no. 12
    
13.
Sehajpal SB, Sood VK. Effect of metal fillers on some physical properties of acrylic resin. J Prosthet Dent 1989;61:746-51.  Back to cited text no. 13
    




 

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