|Year : 2021 | Volume
| Issue : 6 | Page : 1003-1006
Evaluation of effect of aluminum oxide on flexural strength and surface roughness of conventional heat-cure denture base resin
Madhu Ranjan1, Ujjal Chatterjee2, Arya Gupta1, Souvir Pandey1, Rohit Anand1, Mritunjay Keshri1
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 Submission||22-Mar-2021|
|Date of Decision||24-Jun-2021|
|Date of Acceptance||16-Apr-2021|
|Date of Web Publication||10-Nov-2021|
Department of Prosthodontics and Crown and Bridge, Hazaribag College of Dental Sciences and Hospital, Hazaribagh, Jharkhand
Source of Support: None, Conflict of Interest: None
| 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 26];13, Suppl S2:1003-6. Available from: https://www.jpbsonline.org/text.asp?2021/13/6/1003/330013
| Introduction|| |
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. 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.,,,
Reinforcement of ceramic particles has been found to be biocompatible and also restores esthetic of denture. 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.
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|| |
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:
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.
The reflected laser beam is tracked by a position-sensitive photodetector that picks up the vertical and lateral motion of prob.
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|| |
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|| |
The acrylic resin materials should exhibit a high proportional limit to resist plastic deformation and exhibit fatigue resistance to endure repeated masticatory loads., Mullarky RH 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. 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. 
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.,
| Conclusion|| |
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
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]