Biomedical Engineering Reference
In-Depth Information
culture reflect the biomass present on the oral surfaces, but this is not the number of yeast
cells included in oral biofilms. Colony forming units (CFU) counted on the agar medium
represented only a small part of the cells harvested by the cotton, as assessed by three
successive spreadings of the same cotton that provided similar data (in the range interval of
0.1 logarithmic units). Furthermore, two successive swabs of the same oral surface yielded
similar quantities of yeast cells (in the range interval of 0.5 logarithmic units).
Finally, investigators themselves can influence the hygiene behavior of the subjects under
study. The study previously quoted (Vanden Abbeele et al., 2008) also analyzes the effect of
the oral care program. In the absence of any hygiene advice, a second denture swabbing
taken in 46 patients after an interval of one week demonstrated only minor variations, thus
minimizing the hygiene-stimulation effect produced by pursuing the collection of samples.
Repeated sampling (at one-week intervals) of 46 different healthy denture-wearers
demonstrated yeast counts remaining in the same range (±1 logarithmic unit) for more than
85% of the denture swabs and mucosa samples. Values below the lower limit (-1 logarithmic
unit) occurred in less than 15% of denture and mucosa swabs. This was attributed to
behavioral changes in hygiene practice following the investigators' first visit. By contrast, a
hygiene program including a placebo oral gel (tested to be inactive
in vitro
) led to a decrease
of yeast carriage after two weeks.
6. Conclusion
Yeasts belonging to the
Candida
genus usually colonize the human oral cavity.
In vivo
and
in
vitro
studies have shown
Candida
incorporation into biofilms covering different biomaterials
and devices such as dentures. These biofilms may indicate an increased risk factor for
invasive candidosis when the host immune system is compromised. Daily denture brushing
is recommended to all denture (and other device) wearers in order to prevent the
development of
Candida
biofilm. Family members and healthcare workers must assume this
task when there is a deficiency in dexterity and/or a loss of autonomy, especially in elderly
and disabled persons. In case of candidosis in denture-wearers, decontamination of
dentures is mandatory. Antimycotics such as azoles or nystatin must be reserved for
curative treatment of infected patients; they are less active against
Candida
biofilms on
dentures and could lead to emergent resistance if applied daily to dentures in order to
prevent yeast colonization. Nevertheless, few studies, if any, integrate all aspects of denture
care: welfare of denture-wearers, prevention of candidosis, biomaterial defects after
decontamination processing, and possible
Candida
biofilm development. Daily brushing of
dentures remains the key recommendation. A better understanding of
Candida
biology in
the oral environment will provide new tools to control
Candida
biofilms, the possible
development of more appropriate biomaterials for dentistry (or surface improvements), and
better management of biomaterial use in the oral cavity. Further investigations in this field
will require cooperation among dentists, biologists, and engineers.
7. Acknowledgment
The author reports no conflicts of interest in this work. The author wishes to thank the
students from the
Haute Ecole Francisco Ferrer
(Medical Biology section) and the
Université
Libre de Bruxelles
(Faculty of Medicine, Dentistry section) in Brussels who enthusiastically
participated in studies on biofilm biology in the frame of their final memory or doctorate.
