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1. Introduction
Page 1
The oral cavity resides in the different environments of the tongue, tooth, palate, cheek,
and gingival sulcus that are colonized by different micro-organisms. More than 300
species of micro-organisms have been identified in the oral microflora that colonizes
the oral cavity and dentures. The host is generally able to maintain oral microbial
homeostasis employing specific and innate host defenses. These defense mechanisms
along with commensal organisms help to reduce colonization by opportunistic micro-
organisms. With the increase in the population of geriatric patients, systemic illnesses
related to elderly patients have been given major importance. Numerous studies have
suggested the correlation between denture plaque and systemic diseases[1]. Denture
cleaning is inadequate in aged patients, resulting in excessive dental plaque. The
formation of plaque on poorly cleaned dentures in the compromised elderly exposes the
wearer to the risk of infection by a variety of diseases, including aspiration pneumonia
and denture stomatitis. With the advent of modern-day healthcare facilities, there is a
spurge rise in geriatric population, with life expectancy reaching up to 69 years,
globally. In India itself, the mean age has risen to 68.5 years. There is a paradigm shift
in oral healthcare as well, with comparatively more number of individuals willing to
accept the removable dental prosthesis. Contrarily, removable dental prosthesis harbor
microbes which consequently can lead to an infectious condition like aspiration
pneumonia, asthma and stomatitis in elderly people [1]. Mixed infections of endogenous
anaerobic bacteria in the oral cavity are the main cause of aspiration pneumonia,
inadequate cleaning of the denture increases the number of microorganisms in saliva,
and denture plaque is a factor in microbial proliferation in the pharynx[1]. The etiology
appears to be multiparametric and includes old age with a concomitant decline of the
immune system, systemic diseases, smoking, continual wearing of removable dentures,
and poor oral hygiene leading to accumulation of denture plaque. Contamination by

2. Introduction
Page 2
yeast and bacteria (Candida spp., Streptococci, Staphylococci, MRSA) of denture
intaglio surfaces are known to be predisposing factors[2]. Since the aspiration of bacteria
in oropharyngeal secretions is an important risk factor for nosocomial pneumonia in the
elderly[3].
Healthy elderly denture wearers can experience difficulty in cleaning certain parts of
their dentures such as the interdental papillary area and basal surface. Efficient and
regular procedures for cleaning complete dentures are important for maintaining good
oral health and greater longevity of the prosthesis. There are mechanical and chemical
aids for denture cleaning like toothbrushing, soap water, hypochlorite, bicarbonate,
effervescent tablets[4]. Compared to other methods including the use of a denture
cleanser it was clarified that mechanical cleaning such as brushing was the best method
for removal of denture plaque[5]. Surveys have reported that complete denture wearers
have difficulty in cleaning their dentures so there is a need that we should find a more
efficient way to clean the denture just by rinsing in tap water[1,4]
Polymethyl methacrylate is a commonly used denture base resin. However, because of
high water absorption by polymethyl methacrylate denture base resin, the surface of
dentures is accountable for contamination with denture plaque[2]. PMMA is also
susceptible to deterioration, surface roughness following fatigue, microbial adherence,
and colonization by bacteria due to water absorption.
To Improve denture hygiene, some attention has been focused on the modification of
denture materials. Materials such as TEFLON have been used in an attempt to increase
resistance to microbial adhesion to the surface of the denture[5].
Nanotechnology has gained an outstanding boost because metals can be inflected into
their nanosize which can remarkably change their physical, chemical & optical

3. Introduction
Page 3
properties. Nanoparticles (1-100nm) forming clusters of atoms are being widely used
in medical & biological fields due to their good antimicrobial potential[6].
Metal nanoparticles due to their large surface area to volume ratios are seen to have
more favorable antibacterial properties, which has become an area of interest for the
researchers for developing new antimicrobials for resistant strains. The use of metallic
nanoparticles as growth inhibitors for various microorganisms can be applied in various
diverse medical devices[7].
The high photocatalytic and super hydrophilic effects of Titanium dioxide have been
reported and when applied to dentures they can be cleaned simply by rinsing with water.
The adhesion of streptococcus sanguinus and candida albicans to the denture base can
be inhibited by titanium oxide coating [1]. Two methods have been proposed for the
application of TiO2 to the denture base. One method is to mix TiO2 with resin[8]. This
approach causes weakening and color change (whitening) of the denture base. A
preferable option is to use the TiO2 coating method. Here, the photocatalytic effect may
be applied to the denture without changing the mechanical properties or color of the
denture base. The spray method with primer for TiO2 coating was previously used[1-4].
Kado et al [9] showed that bolus adhesion can be reduced by TiO2 coating. Arai et al [5]
observed that adhesion of Streptococcus sanguinus and Candida albicans to the denture
base can be inhibited by TiO2 coating. Moreover, Amano et al [10] reported that the
durability of TiO2 coating with a primer against 100 000 brushstrokes could be
achieved. Mori et al [2] reported that TiO2 coating increased resin gloss without causing
the color change. Based on experiments in animals, Tsuji et al [4] reported that the TiO2
coating of denture base acrylic resin did not irritate the oral mucosa or cause skin
sensitization. These inhibitory effects against the adhesion of the bolus, S sanguinus,
and C albicans are in vitro results.

4. Introduction
Page 4
Tsuji et al. [4] reported that results of the study on animals demonstrated that denture
base resin coated with TiO2 by using air spray gun does not cause irritation or
sensitisation of oral mucosa, skin or intracutaneous tissue and therefore good
biocompatibility for use in close proximity to oral mucosa and skin.
It has been reported that untreated aluminum oxide (Al2O3) powder develops physical
properties of high impact acrylic resin, (Ellakwa et al., 2008) there have been no
investigations regarding the effect of Al2O3 Nanopowder on the mechanical properties
of a conventional cold-cured acrylic resin[11].
Ansari et al [12] clarified Al2O3-NPs were clinically significant in developing an
efficacious antibacterial therapeutic regimen against the multi-drug resistant bacterial
infections.
Al2O3 NPs treated bacterial cells growth curves showed that the growth and
reproduction of bacterial cells were inhibited. The NPs also delays the growth at all
concentration of all the tested strain of S. aureus [13].
Therefore this study will aim to investigate different metal nanoparticle coating (TIO2&
AL2O3) on denture base resin to examine their effect on plaque adhesion and microbial
count.