Cone-beam computed tomography (CBCT) is one of the most useful diagnostic techniques in dentistry but it involves
ionizing radiation, while swept source optical coherence tomography (SS-OCT) has been introduced recently as a
nondestructive, real-time, high resolution imaging technique using low-coherence interferometry, which involves no
ionizing radiation. The purpose of this study was to evaluate the ability of SS-OCT to detect the pulp horn (PH) in
comparison with that of CBCT. Ten extracted human mandibular molars were used. After horizontally removing a half of
the tooth crown, the distance from the cut dentin surface to PH was measured using microfocus computed tomography
(Micro CT) (SL) as the gold standard, by CBCT (CL) and by SS-OCT (OL). In the SS-OCT images, only when PH was
observed beneath the overlying dentin, the distance from the cut dentin surface to PH was recorded. If the pulp was exposed,
it was defined as pulp exposure (PE). The results obtained by the above three methods were statistically analyzed by
Spearman's rank correlation coefficient at a significance level of p < 0.01. SS-OCT detected the presence of PH when the
distance from the cut dentin surface to PH determined by SL was 2.33 mm or less. Strong correlations of the measured
values were found between SL and CL (r=0.87), SL and OL (r=0.96), and CL and OL (r=0.86). The results showed that
SS-OCT images correlated closely with CBCT images, suggesting that SS-OCT can be a useful tool for the detection of
PH.
Apicoectomy is performed for the management of apical periodontitis when orthograde root canal treatment is not
possible or is ineffective. Prior to the surgery, cone beam computed tomography (CBCT) examination is often performed
to evaluate the lesion and the adjacent tissues. During the surgical procedure, the root apex is resected and the resected
surface is usually observed under dental operating microscope (DOM). However, it is difficult to evaluate the details and
the subsurface structure of the root using CBCT and DOM. A new diagnostic system, swept source optical coherence
tomography (SS-OCT), has been developed to observe the subsurface anatomical structure. The aim of this study was to
observe resected apical root canals of human maxillary premolars using SS-OCT and compare the findings with those
observed using CBCT and DOM. Six extracted human maxillary premolars were used. After microfocus computed
tomography (Micro CT; for gold standard) and CBCT scanning of the root, 1 mm of the apex was cut perpendicular to
the long axis of the tooth. Each resected surface was treated with EDTA, irrigated with saline solution, and stained with
methylene blue dye. The resected surface was observed with DOM and SS-OCT. This sequence was repeated three
times. The number of root canals was counted and statistically evaluated. There was no significant difference in the
accuracy of detecting root canals among CBCT, DOM and SS-OCT (p > 0.05, Wilcoxon test). Because SS-OCT can be
used in real time during surgery, it would be a useful tool for observing resected apical root canals.
Autofluorescence of healthy and inflamed human pulpal tissues was observed by confocal laser microscopy. In this preliminary study, photodynamic diagnosis (PDD) was applied to diagnose pulpal disease. The ability to accurately diagnose pulpal pathology prior to pulpectomy would be very beneficial. Clinically, however, we are unable to perform biopsy to detect pathological changes. Therefore, this study was performed using healthy, acutely and chronically inflamed human pulpal tissues to detect pathological changes in pulpal tissues. Following excision, pulpal tissues were rapidly frozen and standard cryosections were prepared. Autofluorescence of pulpal tissues was observed using a confocal laser microscope to examine whether there were any differences in autofluorescence intensities between healthy and inflamed pulpal tissues. Several combinations of excitation and detection wavelengths were tested to observe autofluorescence from pulpal tissues; the excitation wavelengths ranged from 488nm to 633nm, and the detection wavelengths were longer than 505 nm.
Autofluorescence was detected in both healthy and inflamed groups. With this technique, it may be possible to diagnose pulpal pathology without biopsy, and might be applicable to photodynamic diagnosis (PDD) and photodynamic therapy (PDT) in root canal treatment.
The aim of this study was to determine the appropriateness of Nd:YAG laser irradiation for root canal
preparation. Tooth crowns were removed from single-rooted human teeth and a quartz optical fiber (diameter 400 μm)
was inserted into the root canal orifice towards the apical foramen. The length of the fiber within the root canal was
measured, and the irradiating length determined. Root canals were then filled with 3% TiO2 emulsion solution (a
photosensitizer) and irradiated using a pulsed Nd:YAG laser at 600 mJ/pulse (pulse frequency; 5 or 10 pps). During laser
irradiation, the fiber was moved coronally from the apical region towards the canal orifice at a rate of 1 mm/s. Contact
microradiographs (CMR) were taken before and after laser irradiation. Each root was then halved longitudinally, and the
root canal surface observed by scanning electron microscopy (SEM).
The CMR images of the tooth revealed that the root canal was slightly enlarged as a result of treatment.
Carbonization of the root canal dentin was not seen, but a smear layer and melted dentin were observed by SEM.
Nd:YAG laser irradiation using TiO2 emulsion solution appears to be a useful tool for root canal preparation.
A direct non-histological means of pulpal diagnosis remains elusive to clinical practice. Clinical vitality testing remains limited to electric, thermal criteria, or laser Doppler flowmetry. The goal of these investigations was to determine the feasibility of using light-induced fluorescence as a non-invasive modality for pulpal evaluation. Such a capability would, for example, permit expanded use of pulpotomy/pulpectomy techniques. Clinically healthy and diseased human extirpated pulpal tissues were used in this study. After excision, they were rapidly frozen and standard cryosections prepared. Measurement of tissue excitation/emission characteristics was performed using spectrographic analysis. A low-light level fluorescence microscopy system was then used to image autofluorescence localization and intensity at optimal excitation/detection parameters. Excitation/detection parameters used in this study included 405/605, 405/635, 405/670, 440/550, and 440/635. Autofluorescence intensities in healthy tissues were significantly stronger than those in diseased tissues at optimal parameters. It is postulated that autofluorescence characteristics are related to pathology- related structural changes in the pulp. This work provides the basis for further investigation into the relation between autofluorescence, histology and clinical symptoms.
The aim of this study was to determine the effects of varying parameters of Er:YAG laser irradiation with and without water spray cooling on root canal dentin in vitro. After horizontally removing tooth crowns from extracted human teeth, roots were axially sectioned into thin slices, exposing the root canal surface. An Er:YAG laser delivered 10-30 J/cm2 into a 0.4-mm diameter laser spot on the root canal surface .Single pulses of different lengths were applied with and without water spray cooling/irrigation, and sequences of 3 pulses at a repetition rate of 30 Hz were applied at selected pulse parameters. The irradiated samples were investigated using confocal laser scanning microscopy (CLSM). At most irradiation conditions, root canal dentin surface was ablated. 3D images from CLSM revealed that the cavity walls were not smooth. Depths, diameters and micro surfaces of the cavities revealed a significant different between the cavities.
A histopathological study was performed on the tooth pulp of mongrel dogs after cavity preparation using the conventional high speed method (control group) and the newly developed Er:YAG laser system (laser group, output energy: 100 mJ, 150 mJ, and 200 mJ/pulse). All samples were divided into two groups (deep cavity and shallow cavity) according to the remaining dentin thickness (RDT) and histopathologically evaluated. After 1, 2, 4, 7 and 28 days postoperatively, there was no histopathological difference between the control group and the laser group. Er:YAG laser irradiation with three different output energies made little difference in the degree of pulpal damage. In the deep cavities, damage of the pulp was more remarkable than the shallow cavities in all groups. The efficacy of cutting rate in the laser group was not very different from the control group.
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