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Year : 2015  |  Volume : 4  |  Issue : 1  |  Page : 21-23

The effect of aluminum oxide addition on the flexural strength of heat activated acrylic resin: An in vitro study

Department of Prosthodontics, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India

Date of Web Publication16-Mar-2015

Correspondence Address:
Dr. Jyothi Atla
Department of Prosthodontics, Sibar Institute of Dental Sciences, Takkellapadu, Guntur - 522 509, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2277-8632.153307

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Aim: This study was done to investigate the effect of adding 5-20% aluminum oxide (Al 2 O 3 ) powder by weight on the flexural strength of heat-polymerized acrylic resin.
Materials and Methods: A total of 50 specimens of heat-polymerized acrylic resin were fabricated and were divided into five groups (n = 10). Group A was the control group (unmodified acrylic resin specimens). The specimens of the remaining four groups i.e., Groups B, C, D and E were reinforced with Al 2 O 3 powder to achieve loadings of 5%, 10%, 15% and 20% by weight. Specimens were stored in distilled water for 1 week and the flexural strength of the specimens was tested in a universal testing machine (5 mm/min crosshead speed). Results were analyzed by one-way analysis of variance. Weibull analysis was used to calculate the Weibull modulus, characteristic strength and the required stress for 1% and 5% probabilities of failure.
Results: The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 92.01, 114.46, 116.77, 123.11 and 129.72, for Groups A, B, C, D and E, respectively. The flexural strength increased significantly with the incorporation of Al 2 O 3 .
Conclusion: Al 2 O 3 fillers are potential components to be added in denture bases to provide increased flexural strength. Adequate flexural strength of denture base is quite essential for the longevity of the prosthesis.

Keywords: Aluminum oxide, denture bases universal testing machine, flexural strength, heat activated acrylic resin

How to cite this article:
Anne G, Bindu Oliganti SH, Atla J, Budati S, Manne P, Chiramana S. The effect of aluminum oxide addition on the flexural strength of heat activated acrylic resin: An in vitro study. J NTR Univ Health Sci 2015;4:21-3

How to cite this URL:
Anne G, Bindu Oliganti SH, Atla J, Budati S, Manne P, Chiramana S. The effect of aluminum oxide addition on the flexural strength of heat activated acrylic resin: An in vitro study. J NTR Univ Health Sci [serial online] 2015 [cited 2023 Feb 4];4:21-3. Available from: https://www.jdrntruhs.org/text.asp?2015/4/1/21/153307

  Introduction Top

Polymethyl methacrylate (PMMA) introduced in 1937 by Dr. Walter Wright, was considered to be the near ideal denture base material due to its various advantages. [1] However low impact strength of an acrylic resin is a potential disadvantage. Besides its high hardness and good thermal properties, aluminum oxide (Al 2 O 3 ) was proved to be biocompatible material which makes it the material of choice to reinforce acrylic resins in order to improve its strength properties. [2] The present in vitro study was done to evaluate the flexural strength of heat cure acrylic resin reinforced with Al 2 O 3 in various proportions.

  Materials and Methods Top

As per the ISO 1567 standards a Teflon die measuring 65 mm 3 × 10 mm 3 × 3 mm 3 [Figure 1] was prepared and flasked to obtain mould space for acrylic specimens preparation. [3],[4] Heat cure acrylic resin was then proportioned with aluminum oxide at various concentrations. Packing, curing and acrylization of the specimens were done in a conventional way. A total of fifty specimens were prepared and the specimens were divided into five groups namely A, B C, D and E, each` group consisted of 10 samples. Group A was the control group whereas the B, C, D and E groups consisted of specimens reinforced with Al 2 O 3 at 5, 10, 15 and 20 weight % respectively.
Figure 1: Teflon dyes for acrylic specimen preparation

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Flexural strength of the specimen was determined by using a 3-point bending testing device in universal testing machine Instron (Model 5565, Canton) [Figure 2]. The specimens were centered on the device in such a way that the loading wedge was set to travel at a cross head speed of 5 mm/min, engaged at the centre of the upper surface of the specimens [Figure 3]. Specimens were loaded until fracture occurred completely.
Figure 2: Universal testing machine

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Figure 3: Specimens being subjected to three point bending test

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The results were analyzed using one-way analysis of variance (ANOVA) which was used to determine whether significant differences existed between the means of the experimental groups. Weibull analysis was used to calculate the weibull modulus, characteristic strength and the required stress for 5% and 95% probabilities of failure.

  Results Top

Mean value and standard deviation values of A, B, C, D and E groups are presented [Table 1].
Table 1: The Mean and Standard Deviation Values

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One-way ANOVA analysis showed the F value of 20.54667. Since P < 0.05 there is a significant difference in the flexural strength between the different groups [Table 2].
Table 2: The Anova One-Way Test for Flexural Strength

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Weibull analysis depicted the strength of 5% and 95% probability of failure of all the Groups A, B, C, D and E [Table 3].
Table 3: Weibull Analysis of The Flexural Bond Strengths (In MPA)

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  Discussion Top

Despite of the fact that we have landed up in a very modern era of dentistry, the continuous search for an ideal denture base material ever remained as a challenge. [5] In the 1850's vulcanite, a hardened rubber became the most widely used denture base material. [6] Acrylic resins represent approximately 95% of the denture base materials that are now being used in the field of prosthodontics. [3] It is considered to be the popular denture base material because of its advantages such as esthetics, dimensional stability, ease in manipulation and processing. [1],[7] However, its properties like low strength and thermal conductivity, polymerization shrinkage differs it from being an ideal denture base material. Several efforts are being made to improve its properties.

Fracture of the dentures made from acrylic resin is an unresolved problem and fracture occurs in spite of metal reinforcement. [8],[9] According to Kelly fatigue failure was a real problem in well-fitting maxillary dentures occluding against natural mandibular teeth. [10] A study by John et al., showed that 68% of the acrylic resin dentures fracture within a few years after fabrication, which may be primarily because of impact or fatigue failure. [1] Impact fatigue may occur outside the mouth when the denture is dropped accidentally whereas flexural fatigue may occur in the mouth due to repeated flexing from chewing. [1] This ultimately fractures the dentures in the mouth and causes inconvenience to both the dentist and the patients. So in order to overcome these failures many authors tried reinforcing PMMA with various materials likely glass, aramid and nylon fibers.

The present study was done by reinforcing PMMA with Al 2 O 3 powder which was widely recommended by many of the authors due to its positive properties like its abundancy, inexpensiveness, good thermal properties, high hardness and refractoriness. [11],[12] However, few limitations of the use of this material includes a decrease in tensile strength, toughness, decreased esthetic appearance when used in higher proportions (>25%). [11],[13]

  Conclusion Top

Within the limitations of the study the following conclusions can be drawn. Incorporating Al 2 O 3 powder from 5% to 20% by weight into conventional heat polymerized denture base resin resulted in an increase in the flexural strength. Significant enhancement in the flexural strength values were seen with an increase in the weight proportions of Al 2 O 3 .

  References Top

John J, Gangadhar SA, Shah I. Flexural strength of heat-polymerized polymethyl methacrylate denture resin reinforced with glass, aramid, or nylon fibers. J Prosthet Dent 2001;86:424-7.  Back to cited text no. 1
Kawahara H, Yamagami A, Nakamura M Jr. Biological testing of dental materials by means of tissue culture. Int Dent J 1968;18:443-67.  Back to cited text no. 2
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. 3
Jagger DC, Jagger RG, Allen SM, Harrison A. An investigation into the transverse and impact strength of "high strength" denture base acrylic resins. J Oral Rehabil 2002;29:263-7.  Back to cited text no. 4
Yadav NS, Elkawash H. Flexural strength of denture base resin reinforced with aluminium oxide and processed by different processing techniques. J Adv Dent Res 2011;2:119-21.  Back to cited text no. 5
Rueggeberg FA. From vulcanite to vinyl, a history of resins in restorative dentistry. J Prosthet Dent 2002;87:364-79.  Back to cited text no. 6
Smith DC. Recent developments and prospects in dental polymers. J Prosthet Dent 1962;12:1066-78.  Back to cited text no. 7
Vallittu PK. A review of fiber-reinforced denture base resins. J Prosthodont 1996;5:270-6.  Back to cited text no. 8
Kim SH, Watts DC. The effect of reinforcement with woven E-glass fibers on the impact strength of complete dentures fabricated with high-impact acrylic resin. J Prosthet Dent 2004;91:274-80.  Back to cited text no. 9
Kelly E. Fatigue failure in denture base polymers. J Prosthet Dent 1969;21:257-66.  Back to cited text no. 10
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. 11
Grant AA, Greene EH. Whisker reinforcement of polymethyl methacrylate denture base resins. Aust Dent J 1967;12:29-33.  Back to cited text no. 12
Messersmith PB, Obrez A, Lindberg S. New acrylic resin composite with improved thermal diffusivity. J Prosthet Dent 1998;79:278-84.  Back to cited text no. 13


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3]

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