Evaluation of optical coherence tomography in detecting initial enamel erosion bin vitro and in vivo studies / Azwatee Abdul Aziz
Introduction: Enamel erosion is a problem of increasing clinical concern and early detection is difficult. A reliable tool that is able to detect minute changes on the enamel surface is indispensable. Optical Coherence Tomography (OCT) has significant potential for non-invasive, non-ionizing d...
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| Format: | Thesis |
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2019
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| Online Access: | http://studentsrepo.um.edu.my/12613/ http://studentsrepo.um.edu.my/12613/4/azwatee.pdf |
| Summary: | Introduction: Enamel erosion is a problem of increasing clinical concern and early
detection is difficult. A reliable tool that is able to detect minute changes on the enamel
surface is indispensable. Optical Coherence Tomography (OCT) has significant potential
for non-invasive, non-ionizing detection of the earliest signs of enamel erosion. Hence,
the overarching goal of this study is to assess the potential of OCT to detect initial enamel
erosion that could be used in clinical trials and oral health survey.
Aims: For the in vitro study, to evaluate the effect of early dental biofilm on OCT
backscattered intensity, and to evaluate the effect of dental water-jet on acid-induced
softened human enamel surfaces. For the in vivo study, to explore the utility of OCT in
detecting initial enamel erosion, in vivo.
Methods: In vitro study, 80 enamel specimens were prepared, exposing 2 x 4mm2
window. At baseline (t1), specimens were subjected to acid challenge (citric acid for 30
min) and divided into four groups; (1) Control (immersed in de-ionised water for 3-days),
(2) 1-Day_Biofilm, (3) 2-Day_Biofilm, and (4) 3-Day_Biofilm. Specimens from group
2, 3 and 4 were inoculated to produce early laboratory-cultivated biofilm for 1, 2 and 3
days, respectively. All specimens were then subjected to water-jet (WJ) for 20 sec. Swept
Source OCT (SS-OCT) was used to scan the specimens at baseline (t1), post-erosion (t2),
with biofilm (t3) and post-WJ (t4) time points. Surface Microhardness (SMH) was
measured at t1 and t2. Repeated measures ANOVA was used to compare the data between
time points, within each group. The in vivo study involved a two-phase (A and B) study
with 22 subjects. In Phase-A, subjects were instructed to swish a total of 250 ml orange
juice for 10 min, three times per day with three-hour interval for three consecutive days.
In Phase B, the same protocol was followed with an addition of gum chewing for 15 min
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after each swishing. OCT measurements were taken before and after each swishing,
totalling of six time points per day (t1 � t6). Data was analysed using repeated measures
ANOVA and paired t-test. The level of significance was set at p<0.05 for all studies.
Results: The in vitro results showed statistically significant increase (p<0.05) in Supra?surface integrated reflectivity (IRbiofilm) between t2 and t3 for all groups. Subsurface
integrated reflectivity (IRsub) results showed significant decrease (p<0.05) in 2-Day
Biofilm group, however, a significant increase (p<0.05) was shown in 3-Day Biofilm
group, between t2 and t3. Results also showed a significant reduction in SMH (p<0.05) at
t2, however, the reduction in enamel thickness (D) was not statistically significant. IRbiofilm
mean values showed no significant differences at t4 (p>0.05) amongst all groups. The in
vivo results revealed that there was a statistically significant increase in IR after repeated
acid challenge (p<0.05) in day-1 of Phase B, at t1, t2 and t3.
Conclusions: In vitro, biofilm on the enamel surface showed some effects on the OCT
backscattered intensity. Results also showed that WJ application did not cause surface
loss of softened enamel and the biofilm was not adequately removed. In vivo results
showed higher intensities observed from the B-scans following acid challenges indicated
that OCT could detect initial enamel erosion, however, quantitatively there was no
significant difference. Thus, this study provides support for further development of OCT
to be used as a tool to detect minute changes of the initially eroded enamel surface.
Keywords: In vivo, initial erosion, optical coherence tomography, biofilm, dental water
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