**1. Introduction**

The artificial replacement of completely missing teeth with restoration of form, function and esthetics is critical to improving quality of life among edentulous patients [1]. A majority of edentulous patients experience psychosocial problems due to criticism, embarrassment and low confidence levels. For decades, different techniques and materials, i.e., wood, ivory and metals, have been employed for artificial denture fabrication [2]. Polymethyl methacrylate (PMMA) polymer denture resin material has been the material of choice for denture fabrication for the last 50 years, and has gained widespread acceptance due to its simplified processing and equipment, functional longevity, ease of maintenance, cost-effectiveness and esthetics [3].

The longer life expectancy of the elderly population leads to a higher number of individuals needing an artificial removable prosthesis [4]. Edentulous patients may lack manual dexterity and be unable to remove denture plaque. Therefore, PMMA denture patients are more susceptible to mucosal infections from bacterial and fungal species. In addition to various bacteria, *Candida albicans* (fungi) are most commonly associated with denture-related oral infections [5]. In order to overcome denture-related infections, different denture cleansers are used to effectively remove stains and food debris from the denture bases [6]. At present, different PMMA denture cleaning and disinfection techniques include mechanical, chemical and physical methods. Mechanical methods used for denture cleaning include the use of a toothbrush with water [7]. In their study, Veres et al. [8] revealed that 60–90% of denture patients practice mechanical cleaning in association with products such as toothpaste, soap or water. However, use of an unsuitable toothbrush with a dentifrice may also lead to surface roughness, which allows more microbial colonization [9]. In order to overcome drawbacks of mechanical cleaning, soaking PMMA denture bases in chemical disinfecting agents has gained more acceptance in clinical dentistry due to antimicrobial activity [10]. Chemical agents commonly used for denture cleaning include sodium hypochlorite, glutaraldehyde and chlorine dioxide, 0.12% Chlorhexidine gluconate, sodium perborate and alkaline peroxide [11]. The prosthesis is commonly immersed in the chemical agent for a specific duration for plaque removal and disinfection [11]. Effervescent tablets yielding an alkaline peroxide dilution with water are the preferred denture cleansers [12]. However, chemical disinfecting agents used for denture cleaning are known to damage acrylic resin, initiate surface staining or discoloration, and have been reported to be have cytotoxic ingredients [11].

Apart from mechanical and chemical means of denture disinfection, microwave oven disinfection is an effortless and inexpensive method for PMMA dentures [13,14]. Microwave irradiation allows for disinfection of not just bacteria and fungal species, but can also eliminate viruses [8]. Microwave irradiation can be a convenient, quick and cost effective household method for disinfecting PMMA dentures [13]. Studies have revealed that microwave disinfection has more potency for denture disinfection compared to sodium hypochlorite alone [8]. However, limited evidence is available to validate the disinfection protocol and standards for microwave irradiation to be a standard disinfection technique for acrylic dentures.

Previous studies investigating microwave disinfection of acrylic polymers have utilized high power (650 to 1400 watts) and increased exposure times (3 min, 5 min, 8, min, 10 min) [12–14]. However, these irradiation parameters can result in physical damage to polymeric denture base resin, including its dimensional stability and mechanical properties [15]. Therefore, it is critical to assess the low power and duration protocol for microwave irradiation in comparison to chemical disinfection for acrylic denture resin disinfection. It is hypothesized that the bacterial disinfection (cleaning efficacy) of PMMA denture base resin with a cleaning tablet or with microwave irradiation at low power (watt) and duration (1, 2 and 3 min) will be comparable. Therefore, the present study aimed to evaluate the disinfection efficacy of denture cleaning tablets (sodium perborate) and microwave irradiation at low power and duration (1, 2 and 3 min) for *E. coli*, *S. aureus* and *S. mutans* cultured on the PMMA denture base polymer.
