We present some of our recent investigations in Dental Medicine using Optical Coherence Tomography (OCT). Time Domain (TD), Spectral Domain (SD), and Swept Source (SS) OCT in-house developed systems are being used, for both ex vivo and in vivo investigations in the oral cavity. We study ex vivo the interface between the tooth and the dental sealant and demonstrate the limitations of the X-rays investigations that are now the gold standard for such procedures. Using OCT, defects in the interface that cannot be identified in radiographs can be determined both as position and magnitude. The drilling process of teeth can also be characterized in real time using OCT, to monitor the remaining dentin thickness (RDT) in order to avoid opening the pulp chamber. We demonstrate in this respect that an RDT of 0.5 mm is the minimum value to assure the integrity of the dentin wall between the drilled cavity and the pulp chamber; at an RDT of 0.3 mm or less a fracture is initiated, the dentin is punctured and endodontic treatment must follow. In vivo OCT investigations in the oral cavity were also performed (i.e., for metalloceramic prostheses and for ceramic inlay tooth interfaces), with the low cost, light weight and versatile handheld probes with 1D galvoscanners that we have developed and applied for a range of in-house developed OCT systems, in various clinical applications. They are briefly discussed, as well as some of our current and future work in the field, including for studies of soft tissue in the mouth.
Introduction: Evaluating the health status of the gingival tissue represents an important objective in the daily practice.
Inflammation changes the microcirculatory and micromorphological dynamics of human gingiva. Aim: The purpose of
this study was to evaluate the microcirculation in subjects with moderate gingivitis and healthy gingiva by using laser
Doppler flowmetry (LDF). Material and Methods: Recordings of the gingival microcirculation (GM) were taken from 20
healthy gingival sites and from 20 sites with moderate gingivitis. The gingival blood flows in the gingivitis group before
treatment was significantly different from those in the healthy gingiva group. Signals were recorded with the aid of a
laser Doppler MoorLab instrument VMS-LDF2 probe VP3 10 mm S/N 2482. Three consecutive determinations of the
GM were registered for each site, as follows: before the initial therapy, at 24 hours after the initial therapy and then, 7
days after the initial therapy. The data were processed using the statistical analysis software SPSS v16.0.1. Results: The
results of this preliminary study showed statistically significant differences among the GM values recorded before and
after the initial therapy. Conclusions: LDF could be a useful, noninvasive, sensitive, reproducible, and harmless method
for measuring gingival blood flow (gingival microcirculation) in humans.
The aim of this retrospective clinical study was to examine the survival time of endodontically treated teeth (ETT) and the factors that may influence the failure risk, over a period of up to 7 years. The files of 67 patients that received metal free post and core restorations using a standardized technique were analyzed. The survival probability was assessed using Kaplan-Meyer analysis and Log Rank (Matel-Cox). Cox regression was used to assess the risk of failure and to identify possible covariates. The average survival time of the ETT was 6.6 Years. The cumulative failure rate was 5.82% for all type of the restored endodontically treated teeth. The main failure type was encountered in the cervical area of the teeth, and due to the extensive hard tissue loss, the teeth were extracted.
Oral squamous cell carcinoma (OSCC) constitutes 90% of oral cancer. Early detection is a cornerstone to improve survival. Interaction of light with tissues may highlight changes in tissue structure and metabolism. We propose optical coherence tomography (OCT), as a non-invasive diagnosis method, being a new high-resolution optical technique that permits tri-dimensional (3-D), real-time imaging of near surface abnormalities in complex tissues. In this study half of the excisional biopsy was directed to the pathologist and the other half was assigned for OCT investigation. Histopathology validated the results. Areas of OSCC of the buccal mucosa were identified in the OCT images. The elements obserced included extensive epithelial down-growth, the disruption of the basement membrane, with areas of erosion, an epithelial layer that was highly variable in thickness and invasion into the sub-epithelial layers. Therefore, OCT appears to be a highly promising imaging modality.
The efforts aimed at early diagnosis of oral cancer should be prioritized towards developing a new screening instrument, based on optical coherence tomography (OCT), to be used directly intraorally, able to perform a fast, real time, 3D and non-invasive diagnosis of oral malignancies. The first step in this direction would be to optimize the OCT image interpretation of oral tissues. Therefore we propose plastination as a tissue preparation method that better preserves three-dimensional structure for study by new optical imaging techniques. The OCT and the synchrotron radiation computed microtomography (micro-CT) were employed for tissue sample analyze. For validating the OCT results we used the gold standard diagnostic procedure for any suspicious lesion – histopathology. This is a preliminary study of comparing features provided by OCT and Micro-CT. In the conditions of the present study, OCT proves to be a highly promising imaging modality. The use of x-ray based topographic imaging of small biological samples has been limited by the low intrinsic x-ray absorption of non-mineralized tissue and the lack of established contrast agents. Plastination can be used to enhance optical imagies of oral soft tissue samples.
This study was performed in order to evaluate in vivo the applicability of Laser Doppler Flowmetry (LDF) in recording the gingival blood flow and to assess the changes of gingival blood flow following gingival reshaping performed with Er:YAG and 980 nm diode lasers. The LDF evaluation was performed on 20 anterior teeth, which underwent reshaping of gingiva, corresponding to 5 female patients (4 anterior teeth/patient), aged between 20 and 35. One part of the mouth was treated with Er:YAG laser (LP, VLP modes, 140 - 250 mJ, 10 - 20 Hz, using cylindrical sapphire tips) and other part with 980 nm diode laser (CW, 4 W, contact mode and saline solution cooling). The gingival blood flow was monitored using a MoorLab laser Doppler equipment (Moor Instruments Ltd., Axminster, UK) with a straight optical probe, MP3b, 10 mm. The data were processed using statistical analysis software SPSS v16.0.1. The investigation showed an evident decrease in perfusion for both areas in comparison with the baseline values 24 hours after treatment. The microvascular blood flow increased significantly after 7 days in both areas but mostly in diode area (p<0.001). After 14 days for the Er:YAG area the blood perfusion returned to the initial value. The results in diode area remained at a high level after 14 days. Both lasers proved efficiency in the surgical treatment of gingival tissue. Moreover, Laser Doppler Flowmetry is adequate for recording changes in gingival blood flow following periodontal surgery.
Bone grafting is a commonly performed surgical procedure to augment bone regeneration in a variety of orthopaedic and maxillofacial procedures, with autologous bone being considered as the "gold standard" bone-grafting material, as it combines all properties required in a bone-graft material: osteoinduction (bone morphogenetic proteins – BMPs - and other growth factors), osteogenesis (osteoprogenitor cells) and osteoconduction (scaffold). The problematic elements of bone regenerative materials are represented by their quality control methods, the adjustment of the initial bone regenerative material, the monitoring (noninvasive, if possible) during their osteoconduction and osteointegration period and biomedical evaluation of the new regenerated bone. One of the research directions was the interface investigation of the regenerative bone materials and their behavior at different time periods on the normal femoral rat bone. 12 rat femurs were used for this investigation. In each ones a 1 mm diameter hole were drilled and a bone grafting material was inserted in the artificial defect. The femurs were removed after one, three and six months. The defects repaired by bone grafting material were evaluated by optical coherence tomography working in Time Domain Mode at 1300 nm. Three dimensional reconstructions of the interfaces were generated. The validations of the results were evaluated by microCT. Synchrotron Radiation allows achieving high spatial resolution images to be generated with high signal-to-noise ratio. In addition, Synchrotron Radiation allows acquisition of volumes at different energies and volume subtraction to enhance contrast. Evaluation of the bone grafting material/bone interface with noninvasive methods such as optical coherence tomography could act as a valuable procedure that can be use in the future in the usual clinical techniques. The results were confirmed by microCT. Optical coherence tomography can be performed in vivo and can provide a qualitative and quantitative evaluation of the bone augmentation procedure.