Time domain optical coherence tomography investigation of bone matrix interface in rat femurs

The materials used to fabricate scaffolds for tissue engineering are derived from synthetic polymers, mainly from the polyester family, or from natural materials (e.g., collagen and chitosan). The mechanical properties and the structural properties of these materials can be tailored by adjusting the molecular weight, the crystalline state, and the ratio of monomers in the copolymers. Quality control and adjustment of the scaffold manufacturing process are essential to achieve high standard scaffolds. Most scaffolds are made from highly crystalline polymers, which inevitably result in their opaque appearance. Their 3-D opaque structure prevents the observation of internal uneven surface structures of the scaffolds under normal optical instruments, such as the traditional light microscope. The inability to easily monitor the inner structure of scaffolds as well as the interface with the old bone poses a major challenge for tissue engineering: it impedes the precise control and adjustment of the parameters that affect the cell growth in response to various mimicked culture conditions. The aim of this paper is to investigate the interface between the femur rat bone and the new bone that is obtained using a method of tissue engineering that is based on different artificial matrixes inserted in previously artificially induced defects. For this study, 15 rats were used in conformity with ethical procedures. In all the femurs a round defect was induced by drilling with a 1 mm spherical Co-Cr surgical drill. The matrixes used were Bioss and 4bone. These materials were inserted into the induced defects. The femurs were investigated at 1 week, 1 month, 2 month and three month after the surgical procedures. The interfaces were examined using Time Domain (TD) Optical Coherence Tomography (OCT) combined with Confocal Microscopy (CM). The optical configuration uses two single mode directional couplers with a superluminiscent diode as the source centered at 1300 nm. The scanning procedure is similar to that used in any CM, where the fast scanning is en-face (line rate) and the scanning in depth is much slower (at the frame rate). The results showed open interfaces due to the insufficient healing process, as well as closed interfaces due to a new bone formation inside the defect. The conclusion of this study is that TD-OCT can act as a valuable tool in the investigation of the interface between the old bone and the one that has been newly induced due to the osteoinductive process. © 2013 SPIE

New metallic nanoparticles modified adhesive used for time domain optical coherence tomography evaluation of class II direct composite restoration

Non invasive investigation in class II fillings, such as optical coherence tomography (OCT), is slowly entering in the usual dental arsenal of the direct restoration analysis. Working at more than 2 mm depth inside the samples could lead to problems related to the evaluation of the adhesive layer. At this level is difficult to point out the area with adhesive or adhesive with aerie inclusions. For this reason a new metallic Nanoparticles modified dental adhesive is used in order to increase the scattering of the normal adhesive and gain a good contrast on the OCT investigation. The validation of the results were done with SEM and EDAX procedures. In conclusion, noninvasive evaluations methods like OCT, especially OCT working in Time Domain mode, have a great capability to evaluate the interfaces between dental structure, resin fillings and dental adhesive when a metallic Nanoparticles modified adhesive is used

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

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. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onl

Confocal microscopy combined with time domain optical coherence tomography and micro computer tomography in interface evaluation of class II direct composite restoration

Class II cavities are often a challenge for dentists. There are a lot of procedures that can be used in order to fill this type of cavity and also a lot of problems concerning marginal adaptation, especially when composite materials are used. The aims of this study are to evaluate the integrity and marginal adaptation of class II direct composite fillings. There were used 32 samples for orthodontic reasons. Metallographic evaluation was used as the invasive methods. Micro computer tomography, confocal microscopy and optical coherence tomography were used as noninvasive methods. The conclusions pointed out the fact that noninvasive evaluation methods have great capability to accomplish a high quality characterization of the class II direct composite restorations

Scanning electron microscopy or optical coherence tomography for the evaluation of the glass fiber reinforced acrylic resin?

Aesthetics and strength are two major criteria for dental materials today. Objective: Easy evaluation of the bond between acrylic resin and glass fbers. Materials and methods: Pre-impregnated woven E-glass fbres (Stick® Net, Stick Tech Ltd Oy) and unidirectional pre-impregnated E-glass fbres (StickTM) were used to reinforce a conventional heat-curing denture base resin (Meliodent, Heraeus Kulzer GmbH&Co.KG) - ISO 1567:1999 (E). The samples were 12 Stick reinforced, 12 Stick net reinforced (Stick tech, Finland) and 12 were un-reinforced (control). Optical coherence tomography (OCT) investigation was performed in the Department of Applied Optics, School of Physical Sciences University of Kent, UK. SEM micrographs of the fractured specimens were taken using a SEM microscope (TESLA BS 343 A) in the Department of Materials Testing - ISIM Timisoara, Romania. The samples were in vacuum gold plated. Results: The SEM images were taken at 48× 55?, 120× 55?, 240× 55?, 480× 55? magnifcations for each sample. The OCT micrographs were taken at 670 nm and 1300 nm. The penetration depth is in micron range up to 2 mm. For each sample investigated at 670 nm, 61 de slices per stuck were taken and for each sample investigated at 1300 nm, minimum 100 slices per stuck were taken. Conclusions: Both methods are useful for the bond in between acrylic resin and glass fbers evaluation. SEM is more laborious than OCT which is able to obtain many precise images in steps up to 1 ?

Handheld scanning probes for optical coherence tomography

We report the design of two handheld scanning probes for Optical Coherence Tomography (OCT). The probes are equipped with a one-dimensional (1D) galvanometer scanner (GS), offering cross-sectional capabilities with OCT. One of the variants of the probe is tested in the lab, including in vivo on healthy volunteers

Dentistry investigations of teeth and dental prostheses using OCT

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. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only