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Methods: 10 patients were evaluated by conventional oral examination (COE) followed by direct visual fluorescence evaluation (DVFE) using VELscope. Areas clinically suspicious detected by COE or with positive DVFE (visual fluorescence loss (VFL)) have been further investigated using surgical biopsy. The association between COE and DVFE has also been assessed and compared with the gold standard, i.e. histopathology.
Results: Eight positive biopsies for malignant lesions were detected using COE and DVFE. Only one positive biopsy for a premalignant lesion was not in accordance with COE and DVFE. One of the lesions, determined on the VELscope and COE as a non-malignant lesion was also confirmed by the biopsy. Therefore, the VELscope system had a sensitivity of 100% and specificity of 50% in discriminating in situ normal mucosa from carcinoma or invasive carcinoma, compared with histology. The predictive positive value was 88.89% and the negative predictive value was 100% (95% confidence interval).
Conclusions: DFVE allows for simple and cost-effective margin determinations, in order to detect and screen oral precancerous and early cancerous disorders. We found that for the moment the VELscope system could not replace the histopathology procedure. Nonetheless, its usefulness for clinical examination was determined, as well as for monitoring oral lesions and guiding biopsies. Therefore, this method may add sensitivity to oral tissue examinations and be an effective adjunct procedure for high-risk patients.
MATERIALS AND METHODS: 25 preparations of frontal and lateral teeth were performed for 7 different patients. The impressions of the prosthetic fields were obtained both using a conventional optoelectronic system (Apolo Di, Syrona) and a Spectral Domain using OCT (Dental prototype, working at 860 nm). For the conventional impression technique the preparation margins were been prelevated by gingival impregnated cords. No specific treatments were performed by the OCT impression technique.
RESULTS: The scanning performed by conventional optoelectronic system proved to be quick and accurate in terms of impression technology. The results were represented by 3D virtual models obtained after the scanning procedure was completed. In order to obtain a good optical impression a gingival retraction cord was inserted between the prepared tooth and the gingival tissue for a better elevation of the tooth cervical margin preparation. Spectral OCT was enforced in order to observe the quality but also the advantages coming from this technology. No special preparation was performed for this operation.
CONCLUSION: Considering these aspects, OCT could be used as a valuable tool for dental impression technology, being non-invasive but also non-destructive on the marginal gingival tissue, in comparison with conventional optoelectronic technology where the gingival retraction cord is still mandatory.
Materials and methods. 24 all ceramic FPPs created with CAD/CAM technology were used. The models were scanned with Zeno Wieland Scanner, a one touch scanning machine which requires between 45-60 s for a full model scan. The scanner provides 3 axis-architecture and automatic data processing. The zirconia infrastructures resulted from milling zirconia green disks in Wieland units, followed by the deposition of ceramic masses and then by burning procedures. All the samples were assessed with a Time Domain Optical Coherence Tomography (TD-OCT) system working at a wavelenght of 1300 nm. Using OCT investigations, material defects were detected in the areas of maximal tension, i.e. the connectors, the oclusal, and the cervical areas. These samples with defects in the above areas have not been considered for the study further on. Finally, the samples were loaded in a MultiTest 5 i Mecmesin system and tested until fracture occurred. The MultiTest 5-i creates tensile and compression forces of up to 5 kN.
Results and discussions. All the test samples survived a dynamic load of 1.2 x 107 cycles and a thermal cycle mixer simulator version; signs of failure in terms of fracture lines were observed in all samples. The average value of the force necessary to break the FPPs obtained from the tests is 1750 N.
Conclusions. Conventional metal-ceramic fixed partial dentures are still considered the standard for edentulous spaces in the posterior region. Therefore, the resistance of metal-ceramic fixed partial dentures has served in this study as a guide for new ceramics tests. All the values from this study conducted in FPP with zirconia frames were much lower than the values reported for metal ceramic fixed partial dentures (i.e., 2500-3000 N), but higher that 1000 N, which is considered the lowest resistance point to be utilized in the rear region of the oral cavity.
Transmission functions of optical choppers for Gaussian beam distributions: modeling and simulations
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