Introduction

Oral Microflora at Major Life Stages

While bad breath is frequently associated with food related odors such as garlic and onion, the primary source of oral malodor is the oral microflora.¹   Most treatment modalities for bad breath involve targeting microbial plaque, whether it is through conventional oral hygiene practices or incorporation of antimicrobial ingredients into oral care products.

The oral microflora changes with age of the host.²  An infant begins life with a sterile oral cavity and rapidly acquires its initial microorganisms from its mother.  The child then transitions into the acquisition of other species from the environment with the eruption of teeth, onset of puberty, and progression to adulthood.  Oral disease processes, including caries and periodontal disease, also influence the makeup of the oral microflora in any given patient.  Once the teeth are lost, edentulous adults return to an oral microflora that closely resembles that of the infant prior to the eruption of teeth.²

The presence of dentures in edentulous patients creates yet another environment with its own microflora.  Several studies have examined denture plaque both on the denture surface itself and the underlying supporting tissues.^3-7  Collectively, these reports have revealed a denture plaque composition similar to plaque on the tooth surface or at the junction of the tooth and the gingiva.

The difference between plaque isolated from the denture acrylic versus the supporting tissues is negligible and in fact appears to be a continuous heterogeneous intermicrobial matrix.^3,6  Intersubject variability is quite high regardless of the sample collection method used, so it is less important to focus on the strict quantitation of microorganisms as it is to focus on the general trend for predominance of one species over another.  Ultrastructural studies performed using the transmission electron microscope have demonstrated an electron-dense layer on the surface of the denture acrylic which resembles acquired dental pellicle and appears to mediate the adherence of the denture plaque mass to the denture itself.³

Gram-positive cocci were the predominant bacteria isolated from both the palatal mucosa and the surface of the denture, with a mean prevalence ranging from 60-70% of the total plaque composition.⁶  The next most frequently isolated group were the Gram-positive rods, with a prevalence of no more than 23%.  Speciation of the isolated microorganisms reveals Streptococcal species including: S. milleri, S. mutans, S. salivarius, along with Staphylococcus aureus constituting the Gram-positive facultative cocci.  This is followed by the Gram-positive rods: Actinomyces israelii, A. viscosus, and, subsequently, Veillonella parvula, a Gram-negative cocci.  Gram-negative rods such as Bacteroides species and Fusobacterium are only rarely isolated.⁵  This is important because these Gram-negative rods are often associated with oral diseases/conditions in adults, including periodontal disease and oral malodor.

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Citation Number: Vol. 3, No. 4, Page 002