Dr. Cristian O. Zaharia Profile

Dr. Cristian O. Zaharia

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Publications (7)

Proceedings Article | 6 May 2022 Paper

The evaluation of dental adhesives augmented with magnetic nanoparticles

Carina Sonia Neagu, Andreea Codruta Cojocariu, Cristian Zaharia, Mihai Romînu, Meda-Lavinia Negruţiu, Virgil-Florin Duma, Cosmin Sinescu

Proceedings Volume 12170, 121700G (2022) https://doi.org/10.1117/12.2613382

KEYWORDS: Adhesives, Teeth, Magnetism, Composites, Optical coherence tomography, Scanning electron microscopy, Interfaces, Nanoparticles, Collagen, Human-machine interfaces

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Proceedings Article | 5 March 2018 Paper

Dental impression technique using optoelectronic devices

Cosmin Sinescu, Souman Barua, Florin Ionel Topala, Meda Lavinia Negrutiu, Virgil-Florin Duma, Alin Gabriel Gabor, Cristian Zaharia, Adrian Bradu, Adrian Podoleanu

Proceedings Volume 10591, 105910M (2018) https://doi.org/10.1117/12.2281775

KEYWORDS: Optical coherence tomography, Teeth, Tissues, Optoelectronics, 3D modeling, Optoelectronic devices, Tissue optics, Geometrical optics, Dentistry, Microscopes

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INTRODUCTION: The use of Optical Coherence Tomography (OCT) as a non-invasive and high precision quantitative information providing tool has been well established by researches within the last decade. The marginal discrepancy values can be scrutinized in optical biopsy made in three dimensional (3D) micro millimetre scale and reveal detailed qualitative and quantitative information of soft and hard tissues. OCT-based high resolution 3D images can provide a significant impact on finding recurrent caries, restorative failure, analysing the precision of crown preparation, and prosthetic elements marginal adaptation error with the gingiva and dental hard tissues. During the CAD/CAM process of prosthodontic restorations, the circumvent of any error is important for the practitioner and the technician to reduce waste of time and material. Additionally, OCT images help to achieve a new or semi-skilled practitioner to analyse their crown preparation works and help to develop their skills faster than in a conventional way. The aim of this study is to highlight the advantages of OCT in high precision prosthodontic restorations.

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.

Proceedings Article | 5 March 2018 Paper

New ways of combating demineralization: link between classic and allopathic medicine

Laura Idoraşi, Sandra Andreea Secoşan, Alexandru Ogodescu, Cosmin Sinescu, Cristian Zaharia, Adrian Tudor Stan, Adrian Podoleanu, Meda-Lavinia Negruţiu

Proceedings Volume 10591, 105910K (2018) https://doi.org/10.1117/12.2281725

KEYWORDS: Teeth, Optical coherence tomography, Medicine, Inspection, Silver, Optical inspection, Visualization, Dental caries, Pharmacy, Dentistry

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Proceedings Article | 22 March 2016 Paper

OCT and shear-force evaluations of zirconia Fixed Partial Prosthesis processed with a conventional CAD/CAM technology

C. Zaharia, A. Gabor, C. Sinescu, F. Topala, M. Negrutiu, C. Levai, V. Duma, A. Bradu, A. Gh. Podoleanu

Proceedings Volume 9670, 967010 (2016) https://doi.org/10.1117/12.2192980

KEYWORDS: Ceramics, Zirconium dioxide, Optical coherence tomography, Resistance, Scanners, Metals, Connectors, Computer aided design, Manufacturing, Combustion

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Introduction. Dental ceramics show better biocompatibility and aesthetic properties in dental constructs with regard to metals. However, they also have an insufficient mechanical stability, as well as low resistance limits due to their fragility. Taking into account these aspects, glass infiltrated with ceramic materials such as alumina (i.e., zirconiareinforced ceramics) is being nowadays considered a better material for full fixed partial prostheses (FPPs) than ceramics: the former has a higher mechanical resistance, which makes it more appropriate for restoration areas, where there is an increased mechanical stress. The interest for zirconia is growing due both to its resistance and to the possibility to develop such prostheses using the CAD/CAM technology.

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.

Proceedings Article | 22 March 2016 Paper

OCT evaluation of single ceramic crowns: comparison between conventional and chair-side CAD/CAM technologies

A. Gabor, A. Jivanescu, C. Zaharia, S. Hategan, F. Topala, C. Levai, M. Negrutiu, C. Sinescu, V.-F. Duma, A. Bradu, A. Gh. Podoleanu

Proceedings Volume 9670, 96700Z (2016) https://doi.org/10.1117/12.2191907

KEYWORDS: Ceramics, Optical coherence tomography, Scanners, In vitro testing, Fabrication, Epoxies, Interfaces, Medicine, Teeth, Manufacturing

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Proceedings Article | 22 March 2016 Paper

Influence of scanning system and dentist's level of training in the accuracy of digital impressions

Simona Hategan, Alin Gabor, Cristian Zaharia, Cosmin Sinescu, Meda Lavinia Negrutiu, Anca Jivanescu

Proceedings Volume 9670, 967014 (2016) https://doi.org/10.1117/12.2189683

KEYWORDS: Titanium dioxide, Coating, Teeth, Cameras, Manufacturing, Imaging systems, Systems modeling, Adhesives, Dentistry, Medicine

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Background: The principal aim of our study was to evaluate digital impressions, taken with spray powder and powderfree scan systems, in order to determine the influence of the dentist’s commitment to training as a critical factor regarding quality.

Material and method: Two digital intraoral impression systems from the same manufacture (Sirona) : Apollo DI and CEREC Omnicam, were used to scan 16 crown preparations on teeth on a typodont maxillary model. Because an Apollo Di intraoral camera is a powder system, an adhesive was applied before using the powder spray. Three groups were used to scan the crown preparations in order to determine coating thickness homogeneity. One group consisted of senior year dental students, a second consisted of prosthodontics residents, and the third consisted of prosthodontics specialists. The same procedure was applied with a CEREC Omnicam intraoral camera, which is a powder-free system. By using the two systems software parameters we were able to determine the scanning precision.

Results: Homogeneity scores for Apollo Di regarding the spray layer was significantly thinner for all dental surfaces in the first group, while the second group had thinner coatings for buccal and distal surfaces. For the third group, the crown preparations were coated more homogeneously than the first two groups. The powder-free system CEREC Omnicam can, to a degree, mask the lack of experience in direct optical impressions by avoiding the poor quality coating, which can lead to defective marginal adaptation of definitive restoration.

Conclusions: The dentist’s lack of experience can be mitigated, and partially avoided, by using powder-free systems. At the same time, the dentist can give more time towards learning how to integrate computerized fabricated restoration into the practice. The commitment to training is a critical factor in the successful integration of the technology. In addition, scanning marginal preparation details needs time in order to develop technical and manual skills.

Proceedings Article | 14 January 2014 Paper

Different matrix evaluation for the bone regeneration of rats' femours using time domain optical coherence tomography

Laura-Cristina Rusu, Meda Lavinia Negrutiu, Cosmin Sinescu, Bogdan Hoinoiu, Cristian Zaharia, Lavinia Ardelean, Virgil-Florin Duma, Adrian Podoleanu

Proceedings Volume 8925, 89250V (2014) https://doi.org/10.1117/12.2045849

KEYWORDS: Bone, Interfaces, Optical coherence tomography, Curium, Confocal microscopy, Medicine, Spherical lenses, Directional couplers, Diodes, Tissue engineering

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