Biomedical Engineering Reference
In-Depth Information
which includes the resistance to antimicrobial agents at concentrations that approach 1000 times
greater than that required to kill planktonic microorganisms
[12,13]
. This is of particular signifi-
cance in the development of nanoantimicrobials and the extrapolation of in vitro findings.
10.2.2
Oral biofilms and disease
10.2.2.1
Dental caries and periodontal disease
Dental caries is a destructive condition of the dental hard tissues that can progress to inflammation
and death of vital pulp tissue, and if untreated it may lead to the eventual spread of infection to the
periapical area of the tooth and beyond. The disease process involves acidogenic plaque bacteria,
including Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus spp.
[14]
, whereas the
periodontal diseases can involve both the soft and hard tissues and are initiated by components of the
plaque biofilm that develop on the hard root surface adjacent to the soft tissues of the supporting peri-
odontium. Periodontal disease may be confined to the gingiva (gingivitis) or extend to the deeper sup-
porting structures with destruction of the periodontal ligament and the alveolar bone that supports the
teeth (periodontitis). This loss of attachment, with associated periodontal pocket formation, may ulti-
mately lead to loosening and loss of the affected teeth. P. gingivalis, Tannerella forsythia, and
T. denticola are now regarded as the major pathogens in advancing periodontitis
[15]
.
Prevention of dental caries and periodontal diseases is traditionally targeted at mechanical or
nonspecific control of the plaque biofilm because this is the precipitating factor. The use of antimi-
crobial agents represents a valuable complement to mechanical plaque control
[16]
. Such strategies
should ideally control plaque biofilm formation without significantly affecting the biological equi-
librium within the oral cavity. However, actual periods of exposure to antimicrobial agents during
tooth brushing and mouth rinsing can be very short and may amount to about 30 s, rather than the
recommended 2 min
[17]
.
10.2.2.2
Peri-implantitis
Implant systems are increasingly being used to replace missing teeth and most integrate with bone
without complications. Small amounts of plaque consisting mainly of Streptococcus and
Actinomyces spp. will accumulate on successful implants. However, in peri-implantitis, anaerobic
gram-negative organisms predominate
[18]
. This infection is a key cause of dental implant failure
whereby the induced inflammatory changes in the soft tissues surrounding oral implants lead to a
progressive destruction of the supporting bone (classified as peri-implantitis and seen in up to 43%
of implant-treated subjects) or soft tissues (classified as peri-implant mucositis and seen in up to
50% of implant-treated subjects)
[19]
. Current forms of treatment are often inadequate and may
result in chronic infection requiring implant removal and costly resective and regenerative proce-
dures in an attempt to restore and reshape the implant supporting tissue
[19]
. The incorporation of
nanoparticles into implant coatings may well offer useful osteoconductive and antimicrobial func-
tionalities to prevent dental implant failure.
10.2.2.3
Candidiasis
The development of candidiasis, including denture stomatitis (chronic atrophic candidiasis), which
can affect up to 65% of edentulous individuals
[20]
involves the formation of a biofilm. Despite
the use of antifungal drugs to treat denture stomatitis, infection can often recur. Chandra et al.
[20]
,
