Effect of Alum Disinfectant Solutions on Some Properties of a Heat-Cured Acrylic Resin

Journal of Research in Medical and Dental Science
eISSN No. 2347-2367 pISSN No. 2347-2545

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Research - (2021) Volume 9, Issue 5

Effect of Alum Disinfectant Solutions on Some Properties of a Heat-Cured Acrylic Resin

Sundus Abdul Alhussain Jasim and Shorouq M Abass*

*Correspondence: Shorouq M Abass, Department of Prosthodontics, College of Dentistry, University of Baghdad, Bab-Almoadham, Baghdad, Iraq, Email:

Author info »


Objective: The objective of the study was to investigate the effect of immersion in different disinfectant solutions, on hardness and surface roughness of a heat-cured acrylic resin. Materials and Methods: Specimens were immersed in distilled water, commercial alum in concentration 5%,10% and sodium hypochlorite1% for 60 hour and 180 hours (n=10). After periods of immersion, shore hardness and surface roughness were evaluated using shore D hardness tester (time TH210 shore D hardness tester) and roughness tester, respectively. The data were analyzed using one-way ANOVA and Tukey HSD test, at a level of significance of 5%. Results: The hardness mean values ranged from 82.856± 1.674 to 86.653 ± 1.226 and roughness main values from 0.177± 0.139to 1.923± 0.510. There is no difference in hardness and roughness between groups and times (p>0.05). Conclusions: Within the limitations of this study there is no deference between 5% and 10%alum disinfectant solution, it is possible to conclude that alum and sodium hypochlorite , as alternative disinfectant solutions for acrylic resin devices, did not promote effects on hardness and polishing of a heat-cured acrylic resin used for the fabrication of prostheses, neither in 60 hours nor180 hours .


Alum, Acrylic denture base specimens, Disinfection


For several years, the use of acrylic resin as a denture base material has been suggested. Ideally, denture base material should acquire some key physical attributes that include biocompatibility, large bond strength with artificial teeth, in addition to good mechanical properties [1]. The popular form of oral candidiasis is denture stomatitis, characterized by inflamed and erythematous mucosa that is covered by the denture [2] . Among complete denture users, the prevalence varies between approximately 20% and 80% [3,4]. Although it is multifactorial disease, the colonization of the inner surface of the denture by Candida albicans one of The main causative factors [5].

Denture will provide the suitable conditions for the adhesion and multiplication of C. albicans because it provide an aerobic and acidic condition in addition it will cover the supporting mucosa making it far away from the cleaning action of saliva and oral muscles, so the prosthetic surfaces will covered by C. albicans biofilms [6]. Due to the brittle nature of acrylic resins, mechanical cleaning is difficult and unreliable in controlling bacteria in dentures. As a result, immersing prosthetic surfaces in disinfectant solutions has become a standard method to enhance cleansing [7,8]. Glutaraldehyde and sodium hypochlorite are the most commonly available alternatives. The most commonly solutions, glutaraldehyde and sodium hypochlorite used [9]. However, these solutions possess a number of disadvantages, such as glutaraldehyde toxicity, metals corrosion, skin irritation and the staining of tissue by sodium hypochlorite [9,10]. As a result, there is a need to find alternate disinfectant solutions that do not harm the material's properties. Aluminum potassium sulfate is naturally available products that used for centuries in handling diseases of human and they encompass constituents of therapeutic value. Naturally available products are cheap, environmentally safer and easily available [11]. This solution is a promising disinfectant in medicine and the food industry. Aluminum potassium sulfate (alum) having chemical formula KAL (SO4).12H20 and generally having no odor, no color sold crystal that return white in color in air that used in food preservation and water purification. The recommendation by Counter Advisory Panel of U.S.A FDAs (Food and Drug Administration) to use alum as active ingredient part in mouth wash [12]. Aluminum potassium sulfate could be considered as a harmless material and has a low toxicity in laboratory animals [13]. As a result, the aim of this analysis was to see how various disinfectants affected the stiffness and roughness of a heat-cured acrylic resin.

Materials and Methods

Eighty heat cured acrylic resin specimens were fabricated, (major base 20, heat cure acrylic, ITALY), with dimension 65mm X 10mm 65x10x2.5mm specimens were polymerized by , immersion of the flask in the water bath. Short curing cycle was used following the ADA specification No. 12 [I4] for denture base materials. The cycle included putting the flask in the water bath for hour and a half at 70 C° and half an hour at 100 C°.

After the curing cycle is completed, the flask left to cool at room temperature then de-flasking was done and acrylic specimens were removed.

All acrylic specimens (except those prepared for surface roughness test) were finished to remove excess materials by using prosthetic engine with acrylic burs and stone burs with continuous water cooling to avoid over heating that might distort the specimens. The process of polishing was accomplished by using rouge placed in dental lathe machine with speed of 1500 rpm with continuous water cooling until glossy surface of specimens was obtained. According to the disinfectant and the amount of time submerged, the specimens were randomly divided into eight classes (n=10).

Immersion in disinfectant solutions

Each specimen was immersed in 10 m L of distilled water (control), Alum 5%-10%, 1 % sodium hypochlorite. The samples were maintained in solution for 60 hours and 180 hours, without interruption, in closed containers. None of the solutions was replaced during this period. After immersion, the specimens were washed in distilled water and dried with absorbent paper.

Surface hardness test

Shore D hardness test has been used in this study since it is the suitable one that used for acrylic resin materials [15]. Surface hardness test was performed using shore D hardness tester (Time TH210 Shore D hardness tester) (Figure 1).


Figure 1: Surface hardness test specimen's dimensions.

Surface roughness test

Surface roughness of acrylic resin can be affected by the feature of material itself, technique of polishing, and skill of the operator [16].

Surface roughness test I-Specimen

Espoo dimensions

For surface roughness test the acrylic specimens were made with the following dimensions (65x10x2.5) mm length, width, and thickness respectively according to instructions of device as shown in Figure (2). The specimens were kept in distilled water at 37 C° for 48 hours before establishing the test according to ADA specification No. 12 [14] (Figure 2).


Figure 2: Surface roughness test specimen's dimensions.

Statistical analysis

The obtained data from experimental tests was statistically analyzed using SPSS (Statistical Package for Social Science) version 20 which includes the following:

Descriptive statistics:

Ô?? Mean.
Ô?? Standard deviation (SD).
Ô?? Minimum (Min).
Ô?? Maximum (Max).

One way analysis of variance (ANOVA) test was used to assess the difference between more than two groups. If there was a statistically significant difference, then Tukey HSD test used to reveal the difference between each two groups.


Shore D hardness result are display in table ranging from 82.856 ± 1.674 to 86.653± 1.226.

There was no statistical significance between the groups and times. There was no significant statistical difference between the disinfectant solutions and times (p>0.05) (Tables 1 and 2). For the surface roughness test (Tables 3 and 4), values ranged from 0.177 ± 0.139 to 1.923 ± 0.510μm. In this study the results a statistically non-significant increase in surface hardness as compared with control group with acceptable level. surface roughness means value significant increase with acceptable limit. Mean values of surface roughness were (0.717) and (1.001pm) for 60-hour immersion. The Mean values of surface roughness were (1.234) and (1.923pm) for180 hour immersion.

Table 1: Descriptive and statistical test of hardness among groups by time using factorial analysis of variance (ANOVA).

Time Groups Minimum Maximum Mean ±SD F P value Partial eta square (Effect size)
60h Water 82.866 86.433 84.81 1.291 2.504 0.066^ 0.094
NAOHCL 81.924 86.6 84.806 1.647
5 % Alum 78.566 89 85.366 2.814
10 % Alum 84.333 89 86.653 1.226
180h Water 82.9 87.066 85.053 1.17 3.044 0.034* 0.113
NAOHCL 80.733 85.2 82.856 1.674
5 % Alum 80.633 88.466 83.373 2.159
10 % Alum 82.333 85.666 84.17 1.258

Table 2: Multiple pairwise comparisons of hardness between groups in the 180-h using Tukey honestly significant difference (Tukey HSD).

(I) Groups (J) Groups Mean Difference (I-J) P value
Water NAOHCL 2.197 0.0306*
5 % Alum 1.68 0.1444^
10 % Alum 0.883 0.6690^
NAOHCL 5 % Alum -0.517 0.9107^
10 % Alum -1.313 0.3378^
5 % Alum 10 % Alum -0.797 0.7356^

Table 3: Descriptive and statistical test of Roughness (µm) among groups by time using factorial analysis of variance (ANOVA).

Time Groups Minimum Maximum Mean ±SD F P value Partial Eta Squared
60h water 0.543 1.281 0.895 0.218 1.057 0.373^ 0.042
NAOHCL 0.56 0.971 0.717 0.139
5 % Alum 0.538 1.631 1.001 0.318
10 % Alum 0.77 1.279 0.954 0.18
180h water 0.622 1.823 10.234 0.432 6.468 0.001* 0.212
NAOHCL 1.206 2.751 1.923 0.51
5 % Alum 1.135 2.505 1.843 0.38
10 % Alum 0.992 2.718 1.683 0.618

Table 4: Multiple pairwise comparisons of roughness (µm) between groups in the 180 H using tukey honestly significant difference (Tukey HSD).

(I) Groups (J) Groups Mean Difference (I-J) P value
Water NAOHCL -0.6891 0.0008*
5 % Alum -0.6094 0.0036*
10 % Alum -0.4492 0.0508^
NAOHCL 5 % Alum 0.0797 0.9663^
10 % Alum 0.2399 0.5027^
5 % Alum 10 % Alum 0.1602 0.7858^


A home-made disinfection technique may be used to immerse plastic resin prosthetic appliances in solutions. However, these disinfectants interact with the characteristics of the polymer substance [17,18]. With this in consideration, the current research explored the effect of immersion in various disinfectants on the micro - hardness and roughness of a heat-cured resin. After immersion in alum 5% and10% Alum, these properties were no different from purified water, which was used as a monitor, and 1% sodium hypochlorite, which is considered the paradigm in disinfection.

Immersion of the acrylic resin for 60 to 180 hours replicates 10 minutes per day of disinfectant touch for one and three years, respectively. Since the immersion was persistent, the difficulty was more challenging than that encouraged by sporadic exposure. Recommended length of usage for an acrylic resin denture is five years, and the extrapolated period is ten years [18]. Therefore, in the current analysis, the acrylic resin properties were maintained following immersion in disinfectant solutions for a span of time equivalent to the functional life of the dentures. Among other considerations, such as occlusion and the state of the patient's residual ridge, the characteristics of acrylic resin have a significant effect on the usable life of the denture since tolerance and contamination are important to durability and are related to the material's efficiency [19].

For chemical disinfection of the denture base, several active agents have been used. Because of its broad-spectrum usefulness, sodium hypochlorite is considered the gold standard. Nonetheless, it has adverse side effects such as corrosive activity on plastics, denture staining, and an irritant effect on the skin [9,10]. Hydrogen peroxide, on the other hand, has antimicrobial effects due to its alkaline origin [20]. The use of hydrogen peroxide can result in color change and a reduction in flexural strength [21]. Finally, alum is a low-cost solution that has been shown to be effective against Candida albicans, Streptococcus mutans, Staphylococcus aureus, Escherichia coli, and Bacillus subtili [9,11]. In the case of C. In the presence of Candida albicans, the major organism implicated in denture stomatitis, alum behaved similarly to sodium hypochlorite and chlorhexidine, and outpaced sodium perboratebased tablets [10].

Immersion in solutions can cause the material to dissolve due to polymer degradation [17]. When a polymer is exposed to a solvent, it undergoes hydrolytic degradation because of the chemical reaction between the solution and the organic matrix in the available spaces between the polymer chain [17,18]. Furthermore, the active agents can cause accelerated chemical degradation [22], However, as previously found in a previous study [8], agents with acidic and alkaline activity did not produce a better chance than the hydrolytic solution. In the situation of hydrogen peroxide, this can be clarified by the selective diffusion of hydroxyl radicals [21].

The impact of polymer matrix deterioration is first seen as an increase in overall roughness [23- 25], which encourages microbe colonization [5]. Immersion in disinfectant solutions did not result in an improvement in roughness in the current sample, contrary to previous findings [26-28]. Furthermore, in the current analysis, roughness after immersion did not reach the 0.2 m mark, which is the bearable boundary for preventing Candida albicans stickiness [28,29]. The roughness of acrylic resin following immersion in alum or sodium hypochlorite for 60 or 180 hours shows little deviation from immersion in purified water or sodium hypochlorite for the same time spans.

In regard to the interaction with disinfectant solutions, the mechanical and rheological characteristics of the polymer substance are influenced by the density of the cross-links. The polymer matrix differs based on the form and structure of the acrylic resin and can include pigments, cross-linking agents, load, and fibers. The use of heat-curable acrylic resin with a cross-linking agent favored the preservation of microhardness and polishing.


Under the study’s limitations, it is possible to assume that using alum or sodium hypochlorite as a replacement disinfectant for acrylic resin has no short- or long-term harmful effects on the stiffness or polishing of heat-cured acrylic resin being used on, neither in the short nor long term.


Author Info

Sundus Abdul Alhussain Jasim and Shorouq M Abass*

Department of Prosthodontics, College of Dentistry, University of Baghdad, Bab-Almoadham, Baghdad, Iraq

Received: 20-Apr-2021 Accepted: 13-May-2021 Published: 31-May-2021