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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 13  |  Issue : 6  |  Page : 1003-1006  

Evaluation of effect of aluminum oxide on flexural strength and surface roughness of conventional heat-cure denture base resin


1 Department of Prosthodontics and Crown and Bridge, Hazaribag College of Dental Sciences and Hospital, Hazaribagh, Jharkhand, India
2 Department of Prosthodontics and Crown and Bridge, Buddha Institute of Dental Sciences and Hospital, Patna, Bihar, India

Date of Submission22-Mar-2021
Date of Decision24-Jun-2021
Date of Acceptance16-Apr-2021
Date of Web Publication10-Nov-2021

Correspondence Address:
Madhu Ranjan
Department of Prosthodontics and Crown and Bridge, Hazaribag College of Dental Sciences and Hospital, Hazaribagh, Jharkhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpbs.jpbs_216_21

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   Abstract 


Purpose: Acrylic denture base tends to fracture frequently during their service due to poor strength. The surface roughness of denture base is a critical property because denture base with rough surface will cause accumulation of food particles ,thereby leading plaque retention . Microbes such as candida albicans are seen inhabitating the surface. Materials and Methods: Conventional heat cure denture base reins(DPI) and heat cure denture base resin with incorporation of 15wt% aluminium oxide was studied in two groups with 20 samples each. A mold of size 65 mm × 10 mm × 3 mm (ISO Standard) was obtained by investing brass rectangles. About forty specimens were prepared. Specimens were divided into two groups (n = 20) coded A and B. Group A was the control group (n = 20) without addition of aluminum oxide. Group B was the experimental group (n = 20) with addition of 15 wt % aluminum oxide. All the specimens were stored in distilled water for 14 days. The flexural strength was measured using a three-point bending test in a universal testing machine, and the surface roughness was measured using contact-type profilometer. Results: Incorporation of 15wt% aluminum oxide leads to a significant increase in flexural strength and surface roughness of conventional heat-cure denture base resin.

Keywords: Denture base resin, flexural strength, surface roughness


How to cite this article:
Ranjan M, Chatterjee U, Gupta A, Pandey S, Anand R, Keshri M. Evaluation of effect of aluminum oxide on flexural strength and surface roughness of conventional heat-cure denture base resin. J Pharm Bioall Sci 2021;13, Suppl S2:1003-6

How to cite this URL:
Ranjan M, Chatterjee U, Gupta A, Pandey S, Anand R, Keshri M. Evaluation of effect of aluminum oxide on flexural strength and surface roughness of conventional heat-cure denture base resin. J Pharm Bioall Sci [serial online] 2021 [cited 2022 Jun 25];13, Suppl S2:1003-6. Available from: https://www.jpbsonline.org/text.asp?2021/13/6/1003/330013




   Introduction Top


Polymethyl methacrylate (PMMA) is the most commonly used material in fabrication of dentures though it is still insufficient in fulfilling the ideal requirements of appliances.[1] Improvement on mechanical properties of denture base materials was tried to be achieved either by mechanical reinforcement of acrylics through metal inserts, inclusion of fibers, modification of chemical structure by addition of crosslinking agents, and copolymerization with rubber.[1],[2],[3],[4]

Reinforcement of ceramic particles has been found to be biocompatible and also restores esthetic of denture.[5] The surface roughness of denture base is a critical property because denture base with rough surface will cause accumulation of food particles ,thereby leading plaque retention. M icrobes such as candida albicans are seen inhabitating the surface.[6]

Although it has been found that addition of aluminum oxide at low concentration develops high strength acrylic resin, there is no study evaluating its effect on surface roughness. This study is conducted to use aluminum oxide fillers that were added to heat-cure PMMA and evaluate its effect on denture base flexural strength and surface roughness. The hypothesis of the study is that adding aluminum oxide would increase the flexural strength and surface roughness compared to the control group.


   Materials and Methods Top


Specimen preparation

A mold of size 65 mm × 10 mm × 3 mm (ISO 1567 Standard) was obtained by investing brass rectangle. A conventional heat-cured resin was used as a matrix and aluminum oxide powder with a size of 50 μm as a reinforcing agent. The acrylic specimens were fabricated by packing the acrylic resin into the stone molds contained in the denture flasks and curing them for 1.5 h at 70°C. The specimens were then deflasked. After removal, the specimens were trimmed and ground with silicon carbide paper to obtain a polished surface. Total forty specimens were fabricated and were divided into two groups (n = 20) coded A and B. Group A was the control group without addition of aluminum oxide. Group B was the experimental group with addition of 15 wt% aluminum oxide.

Aluminum oxide powder was mixed with resin powder and liquid monomer to get uniform mixture. The oxide–resin powder was mixed with monomer in a mixing jar with a close-fitting lid.

Flexural strength testing

After the rectangular specimens were deflasked, the edges were trimmed and polished. Prior to flexural strength testing, the dimension of each specimen was measured with Vernier calipers. Specimens were stored in distilled water for 14 days before testing. The flexural strength testing was done using a three-point bending test in a universal testing machine [Figure 1]. The specimens were placed on the center of device in such a way that the loading wedge was set to travel at a crosshead speed of 5 mm/min, engaged at the center of the upper surface of the specimens. Specimens were loaded until fracture occurred completely. The following formula was used for computing the flexure strength:
Figure 1: Universal testing machine

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FS – Flexural strength (MPa)

I – The distance between the supporting wedges

b – Width of the specimen

d – Depth or thickness of the specimen (mm)

P – The maximum load at the point of fracture.

Surface roughness testing

After deflasking, specimens were visually inspected to have a smooth surface without voids and porosity. Specimens were polished with silicon carbide papers. Evaluation of surface roughness is done using contact-type profilometer (atomic force microscope [AFM]) [Figure 2]. The profilometer probe interacts with the substrate through a raster scanning motion. AFM operates on the principle that a nanoscale tip is attached to a small cantilever which forms a spring. As the tip contacts the surface ,the cantilever bends and bending is detected using a laser diode and a split photodetector. This bending is indicative of the tip –sample interaction force. In contact mode, the tip is pressed into the surface and an electronic feedback loop monitors the tip-sample interaction force to keep the deflection constant throughout raster scanning.
Figure 2: Atomic force microscope (Contact type Profilometer)

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The reflected laser beam is tracked by a position-sensitive photodetector that picks up the vertical and lateral motion of prob.

Data analysis

Descriptive analysis was performed to calculate the mean and the standard deviation. Paired t-test was performed for statistical analysis of flexural strength and surface roughness to compare the mean values. P < 0.05 was taken to be statistically significant.


   Results Top


The mean and standard deviation values for flexural strength and surface roughness are presented in [Table 1] and [Table 2], respectively. The mean flexural strength values of PMMA and PMMA with aluminum oxide were found to be 77.30 ± 2.45 and 79.31 ± 2.02, respectively. The mean surface roughness values of PMMA and PMMA with aluminum oxide were found to be 153.68 ± 1.73 and 416 ± 2.32, respectively.
Table 1: Comparison of flexural strength microscopic polyangiitis of polymethyl methacrylate versus polymethyl methacrylate with aluminum oxide

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Table 2: Comparison of surface roughness of polymethyl methacrylate versus polymethyl methacrylate with aluminum oxide

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   Discussion Top


The acrylic resin materials should exhibit a high proportional limit to resist plastic deformation and exhibit fatigue resistance to endure repeated masticatory loads.[7],[8] Mullarky RH[8] studied the reinforcement of acrylic resin with aramid fibers. Finding was increased fatigue resistance of the aramid fiber-reinforced acrylic resin denture base material. The yellow-colored fibers were difficult to mask within the denture, resulting in thick acrylic resin denture. Ellakwa et al.[9] have reported that reinforcing high-impact acrylic resin with untreated Al2O3 powder at concentrations of 5%–20 wt% resulted in increases in both the flexural strength and thermal diffusivity of this high-impact acrylic resin. It was also concluded seen that hardness increased in proportion to the weight percentage of the Al2O3 filler. The hardness significantly increased after incorporating 2.5 and 5 wt% Al2O3.

This present study is in agreement with previous investigators, who concluded that reinforcing acrylic resin with filler particles produced improvement in flexural strength of acrylic resin. Addition of 15 wt% of aluminum oxide leads to a significant increase in strength. This increase in FS can be explained on the basis of transformation toughening. The most stable hexagonal alpha phase aluminum oxide is the strongest and stiffest of the oxide ceramics. Therefore, it is expected that when aluminum oxide particles disperse in a matrix, they increase its strength. This increase in strength may be due to strong ionic interatomic bonding. [10]

The surface roughness of denture base is important, as it affects the oral health of tissues. The surface roughness threshold for acrylic resin is 0.2 μm, below which no significant decrease in bacterial colonization occurs.[11],[12]


   Conclusion Top


The flexural strength and surface roughness property of the heat-cure denture showed significant changes after the addition of filler particle. Incorporating 15 wt% aluminum oxide powder to heat-cure resin resulted in a significant increase in the flexural strength of denture base resin and surface roughness.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Meng TR Jr., Latta MA. Physical properties of four acrylic denture base resins. J Contemp Dent Pract 2005;6:93-100.  Back to cited text no. 1
    
2.
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. 2
    
3.
Darbar UR, Huggett R, Harrison A. Denture fracture – A survey. Br Dent J 1994;176:342-5.  Back to cited text no. 3
    
4.
Carroll CE, von Fraunhofer JA. Wire reinforcement of acrylic resin prostheses. J Prosthet Dent 1984;52:639-41.  Back to cited text no. 4
    
5.
Ruffino AR. Effect of steel strengtheners on fracture resistance of the acrylic resin complete denture base. J Prosthet Dent 1985;54:75-8.  Back to cited text no. 5
    
6.
Mullarky RH. Aramid fiber reinforcement of acrylic appliance. J Clin Orthod 1985;19:655-8.  Back to cited text no. 6
    
7.
Jagger DC, Harrison A, Jandt KD. The reinforcement of dentures. J Oral Rehabil 1999;26:185-94.  Back to cited text no. 7
    
8.
Johnston EP, Smith DE. Flexural fatigue of 10 commonly used denture base resins. J Prosthet Dent 1981;48:478-83.  Back to cited text no. 8
    
9.
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. 9
    
10.
Clarke DA, Ladizesky NH, Chow TW. Acrylic resins reinforced with highly drawn linear polyethylene woven fibres. Construction of upper denture bases. Aust Dent J 1992;37:394-9.  Back to cited text no. 10
    
11.
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. 11
    
12.
Abdul M, Jaber R. Effect of aluminium oxide on the surface roughness and hardness of acrylic resin denture base. Tikrit J Dent Sci 2015;32-38  Back to cited text no. 12
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

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