Emerging Dental Applications of Raman Spectroscopy - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 264

11.6.2 Raman Spectroscopy of Dental Caries

Clinical Problem

Caries is the clinical term for tooth decay and most people are familiar with
the term cavities. Cavities are actually advanced clinical endpoints of tooth
decay whereby regions of tooth structure and integrity have deteriorated to
the point that the structure collapses to form a hole or cavity. Dental caries
results from the destruction of tooth structure due to acid leaching of cal-
cium and phosphate ions from minerals of the tooth (i.e. a process known as
demineralization) resulting in a porous weak structure. The acid is secreted
from bacteria that harbour in dental plaque biofilm formed on tooth surfaces.
Dental caries is a chronic infectious disease that is experienced by most in-
dividuals at some point in their life [33]. Caries is the most common chronic
disease in childhood. Despite the decline in the incidence of caries in the west-
ern world due to improved prevention methods such as water fluoridation and
fluoride in toothpastes and mouth rinses, there are still large segments of the
population who suffer from this disease. With appropriate oral health hygiene,
caries is deemed a preventable disease. However, where prevention is not pos-
sible, it is still feasible to repair the early uncavitated caries lesion through
conservative non-surgical treatment strategies such as fluoride for remineral-
ization, sealants and anti-microbials. Unfortunately, when cavitation occurs,
the only treatment option is surgical intervention involving drilling and plac-
ing of fillings. Current diagnostic clinical methods involving visual inspection
and tactile examination with the dental explorer rely on subjective clinical
criteria such as colour, softness and resistance to removal. Furthermore, car-
ious lesions that are visible on conventional dental radiographs have already
30-40% mineral loss before they are detected radiographically and thus are
already more advanced lesions [34].
Early dental caries (incipient lesions) are non-cavitated and limited to the
outer enamel surface. Clinically, these lesions are identified as visible “white
spots” when the tooth is air-dried (Fig. 11.1). The incipient lesion is known
as a subsurface lesion since the surface appears intact. However, histological
investigations have shown that below the surface, there are zones that vary
in porosity (voids from mineral loss) as well as biochemical composition (e.g.
fluoride, water and carbonate content) [29]. The enamel caries can vary from
a depth of

∼ 100-250 μ m (for incipient caries) to entirely through the enamel

( 1 . 5 mm deep), at which point the cavitated lesion has extended into the

underlying dentin [35]. The diagnostic challenge remains early caries detection
and the focus has been on caries lesions that form on the tooth crown affecting
the enamel. The remainder of the discussion will therefore concentrate on
enamel caries.

∼

Conventional Raman Spectroscopy of Dental Caries

The application of Raman spectroscopy for studying dental caries began
about a decade ago. At that time, the team of Hill and Petrou used Raman