|
Abstract:
|
Dental caries persists to be the most predominant oral disease in spite of
remarkable progress made during the past half- century to reduce its prevalence.
Early diagnosis of carious lesions is an important factor in the prevention and
management of dental caries. Conventional procedures for caries detection involve
visual-tactile and radiographic examination, which is considered as “gold standard”.
These techniques are subjective and are unable to detect the lesions until they are
well advanced and involve about one-third of the thickness of enamel. Therefore, all
these factors necessitate the need for the development of new techniques for early
diagnosis of carious lesions. Researchers have been trying to develop various
instruments based on optical spectroscopic techniques for detection of dental caries
during the last two decades. These optical spectroscopic techniques facilitate noninvasive
and real-time tissue characterization with reduced radiation exposure to
patient, thereby improving the management of dental caries. Nonetheless, a costeffective
optical system with adequate sensitivity and specificity for clinical use is
still not realized and development of such a system is a challenging task.Two key techniques based on the optical properties of dental hard tissues are
discussed in this current thesis, namely laser-induced fluorescence (LIF) and diffuse
reflectance (DR) spectroscopy for detection of tooth caries and demineralization.
The work described in this thesis is mainly of applied nature, focusing on the analysis
of data from in vitro tooth samples and extending these results to diagnose dental
caries in a clinical environment. The work mainly aims to improve and contribute to
the contemporary research on fluorescence and diffuse reflectance for discriminating
different stages of carious lesions. Towards this, a portable and compact laser-induced
fluorescence and reflectance spectroscopic system (LIFRS) was developed for point
monitoring of fluorescence and diffuse reflectance spectra from tooth samples. The
LIFRS system uses either a 337 nm nitrogen laser or a 404 nm diode laser for the
excitation of tooth autofluorescence and a white light source (tungsten halogen lamp)
for measuring diffuse reflectance.Extensive in vitro studies were carried out on extracted tooth samples to
test the applicability of LIFRS system for detecting dental caries, before being tested
in a clinical environment. Both LIF and DR studies were performed for diagnosis of
dental caries, but special emphasis was given for early detection and also to
discriminate between different stages of carious lesions. Further the potential of LIFRS system in detecting demineralization and remineralization were also assessed.In the clinical trial on 105 patients, fluorescence reference standard (FRS)
criteria was developed based on LIF spectral ratios (F500/F635 and F500/F680) to
discriminate different stages of caries and for early detection of dental caries. The
FRS ratio scatter plots developed showed better sensitivity and specificity as compared
to clinical and radiographic examination, and the results were validated with the blindtests.
Moreover, the LIF spectra were analyzed by curve-fitting using Gaussian
spectral functions and the derived curve-fitted parameters such as peak position,
Gaussian curve area, amplitude and width were found to be useful for distinguishing
different stages of caries. In DR studies, a novel method was established based on
DR ratios (R500/R700, R600/R700 and R650/R700) to detect dental caries with
improved accuracy. Further the diagnostic accuracy of LIFRS system was evaluated
in terms of sensitivity, specificity and area under the ROC curve. On the basis of
these results, the LIFRS system was found useful as a valuable adjunct to the clinicians
for detecting carious lesions. |