Technological improvements and the progress of new adhesive materials have led to the development of minimally
invasive restorations, like overlays; these are also indicated in the treatment of pathological tooth wear caused by
bruxism. In this study we evaluated the marginal adaptation of Tizian overlays through two non-invasive methods:
digital microscopy and confocal laser scanning microscopy. 12 maxillary first premolars were extracted and prepared for
overlays. The Tizian overlays were cemented with Variolonk II (Ivoclar Vivadent). The marginal adaptation of each
specimen was analyzed, on all four surfaces, with a digital microscope at 40x to 800x magnification ratio; we also used
a confocal laser scanning microscope, at 10x magnification, in Z mode, with 10 μm slices and a resolution of 1020 x
1024. The exposure time per pixel was 8 μs and the wavelength of the laser was set at 405 nm, corresponding to a blue
light laser. We concluded that confocal laser scanning microscopy, with its a higher horizontal and vertical resolution
with regard to digital microscopy, and with its volumetric reconstructions capability of the sample image, is therefore a
more appropriate method for this particular dental field, i.e., to investigate the marginal adaptation of Tizian overlays.
"Table tops"/occlusal veneers are partial crowns that allow for the biomimetic restoration of worn teeth in bruxing
patients. The biomimetic approach includes a CAD/CAM composite resin for the manufacturing of the "table tops", for
example Tizian, which is a zirconia reinforced composite (Schutz Dental Group). In the present study we prove the value
of a fast swept source optical coherence tomography (SS-OCT) system in the evaluation of the marginal fit of Tizian
"table tops". 12 maxillary first premolars were extracted and minimally invasive prepared for "table tops". The Tizian
"table tops" were then adhesively cemented on the natural teeth with Variolink II (Ivoclar Vivadent). A SS-OCT system
has been used to evaluate the marginal and internal adaptation of Tizian "table tops". The SS (Axsun Technologies,
Billerica, MA) has a central wavelength of 1060 nm, a sweeping range 106 nm (quoted at 10 dB), and a 100 kHz line
rate. The depth resolution of the system, measured experimentally in air was 10 μm. The same samples were analyzed by
using a micro-computed tomography (μCT) system, in order cu confirm the data obtained by using OCT. The imaging
system used for this study offers good spatial resolutions in both directions, transversal and longitudinal, of around 10
μm, a high sensitivity, and it is also able to acquire entire 3D volumes as fast as 2.5 s. Once the full dataset has been
acquired, rendered high resolutions en-face projections could be produced. With it, the "table top" – cement – abutment
tooth interfaces were observed on both C-scans as 2D images and also in the 3D reconstructions; the system was able to
detect several open interfaces, which were confirmed on the μCT images. The SS-OCT system allows for an efficient
evaluation of biomimetic Tizian "table tops".
Erosion is the progressive loss of tooth substance by chemical processes that do not involve bacterial action. The affected teeth can be restored by using IPS e.max Press “table tops”, which replace the occlusal surfaces. In this study we applied a fast in-house Swept Source Optical Coherence Tomography (SS OCT) system to analyze IPS e.max Press “table tops”. 12 maxillary first premolars have been extracted and prepared for “table tops”. These restorations were subjected to 3000 alternating cycles of thermo-cycling in a range from -10°C to +50°C; mechanical occlusal loads of 200 N were also applied. Using SS OCT we analyze the marginal seal of these restorations, before and after applying the mechanical and thermal strain. The characteristics of the SS OCT system utilized are presented. Its depth resolution, measured in air is 10 μm. The system is able to acquire entire volumetric reconstructions in 2.5 s. From the dataset acquired high resolution en-face projections were also produced. Thus, the interfaces between all ceramic “table tops” and natural teeth were analyzed on the cross-sections (i.e., the B-scans) produced and also on the volumetric (tri-dimensional (3D)) reconstructions, several open interfaces being detected. The study therefore demonstrates the utility of SS OCT for the analysis of lithium disilicate glass ceramic “table tops”.
The teeth affected by pathologic attrition can be restored by a minimally invasive approach, using Tizian overlays. In this study we prove the advantages of a fast swept source (SS) OCT system in the evaluation of Tizian overlays placed in an environment characterized by high occlusal forces. 12 maxillary first premolars were extracted and prepared for overlays. The Tizian overlays were subjected to 3000 alternating cycles of thermo-cycling (from -10°C to +50°C) and to mechanical occlusal overloads (at 800 N). A fast SS OCT system was used to evaluate the Tizian overlays before and after the mechanical and thermal straining. The SS (Axsun Technologies, Billerica, MA) has a central wavelength of 1060 nm, sweeping range of 106 nm (quoted at 10 dB) and a 100 kHz line rate. The depth resolution of the system, measured experimentally in air was 10 μm. The imaging system used for this study offers high spatial resolutions in both directions, transversal and longitudinal of around 10 μm, a high sensitivity, and it is also able to acquire entire tridimensional (3D)/volume reconstructions as fast as 2.5 s. Once the full dataset was acquired, rendered high resolutions en-face projections could be produced. Using them, the overlay (i.e., cement) abutment tooth interfaces were remarked both on B-scans/two-dimensional (2D) sections and in the 3D reconstructions. Using the system several open interfaces were possible to detect. The fast SS OCT system thus proves useful in the evaluation of zirconia reinforced composite overlays, placed in an environment characterized by high occlusal forces.
Non-carious cervical lesions (NCCL) are defined as the loss of tooth substance at the cemento-enamel junction and are caused by abrasion, erosion and/or occlusal overload. In this paper we proved that our fast swept source OCT system is a valuable tool to track the evolution of NCCL lesions in time. On several extracted bicuspids, four levels of NCCL were artificially created. After every level of induced lesion, OCT scanning was performed. B scans were acquired and 3D reconstructions were generated. The swept source OCT instrument used in this study has a central wavelength of 1050 nm, a sweeping range of 106 nm (measured at 10 dB), an average output power of 16 mW and a sweeping rate of 100 kHz. A depth resolution determined by the swept source of 12 μm in air was experimentally obtained. NCCL were measured on the B-scans as 2D images and 3D reconstructions (volumes). For quantitative evaluations of volumes, the Image J software was used. By calculating the areas of the amount of lost tissue corresponding to each difference of Bscans, the final volumes of NCCL were obtained. This swept source OCT method allows the dynamic diagnosis of NCCL in time.
Early diagnosis of occlusal overload is an important issue in dental medicine. The high occlusal forces can cause
irreversible damage to the dental hard tissues. Our study proposes the early microstructural characterization of occlusal
overloaded bicuspids, with abnormal crown morphology, by en face optical coherence tomography (eFOCT). The dental
samples were investigated using an eFOCT system operating at 1300 nm in B-scan and C-scan mode. The eFOCT
images obtained from these teeth visualized cracks, which didn't reach the tooth surface. The μCT and histological
images confirmed the microstructural defects identified on eFOCT images. In conclusion, eFOCT is a promising
imaging method for the early diagnosis of occlusal overload on bicuspids with normal crown morphology and for the
prophylaxis of dental wear.
Aim and objectives. Abfraction is the pathological loss of cervical hard tooth substance caused by biomechanical
overload. High horizontal occlusal forces result in large stress concentrations in the cervical region of the teeth. These
stresses may be high enough to cause microfractures in the dental hard tissues, eventually resulting in the loss of cervical
enamel and dentin. The present study proposes the microstructural characterization of these cervical lesions by en face
optical coherence tomography (eFOCT).
Material and methods: 31 extracted bicuspids were investigated using eFOCT. 24 teeth derived from patients with
active bruxism and occlusal interferences; they presented deep buccal abfractions and variable degrees of occlusal
pathological attrition. The other 7 bicuspids were not exposed to occlusal overload and had a normal morphology of the
dental crowns.
The dental samples were investigated using an eFOCT system operating at 1300 nm (B-scan at 1 Hz and C-scan mode at
2 Hz). The system has a lateral resolution better than 5 μm and a depth resolution of 9 μm in tissue. OCT images were
further compared with micro - computer tomography images.
Results. The eFOCT investigation of bicuspids with a normal morphology revealed a homogeneous structure of the
buccal cervical enamel. The C-scan and B-scan images obtained from the occlusal overloaded bicuspids visualized the
wedge-shaped loss of cervical enamel and damage in the microstructure of the underlaying dentin. The high occlusal
forces produced a characteristic pattern of large cracks, which reached the tooth surface.
Conclusions: eFOCT is a promising imaging method for dental abfractions and it may offer some insight on the
etiological mechanism of these noncarious cervical lesions.
Aim and objectives. The morphology and position of the temporo-mandibular disc are key issues in the diagnosis and
treatment of arthrogenous temporo-mandibular disorders. Magnetic resonance imaging and arthroscopy are used today to
identify: flattening of the pars posterior of the disc, perforation and/or adhesions in the pars intermedia of the disc and disc
displacements. The present study proposes the investigation of the temporo-mandibular joint disc by optical coherence
tomography (OCT).
Material and methods. 8 human temporo-mandibular joint discs were harvested from dead subjects, under 40 year of age,
and conserved in formalin. They had a normal morphology, with a thicker pars posterior (2,6 mm on the average) and a
thinner pars intermedia (1mm on the average). We investigated the disc samples using two different OCT systems: an
en-face OCT (time domain (TD)-OCT) system, working at 1300 nm (C-scan and B-scan mode) and a spectral OCT system
(a Fourier domain (FD)-OCT) system , working at 840 nm (B-scan mode).
Results. The OCT investigation of the temporo-mandibular joint discs revealed a homogeneous microstructure. The longer
wavelength of the TD-OCT offers a higher penetration depth (2,5 mm in air), which is important for the analysis of the pars
posterior, while the FD-OCT is much faster.
Conclusions: OCT is a promising imaging method for the microstructural characterization of the temporo-mandibular
disc.
The aim of this study is the early detection and monitoring of occlusal overload in bruxing patients. En-Face Optical
coherence tomography (eF-OCT) and fluorescence microscopy (FM) were used for the imaging of several anterior teeth
extracted from patients with light active bruxism. We found a characteristic pattern of enamel cracks, that reached the
tooth surface. We concluded that the combination of the en-Face OCT and FM is a promising non-invasive alternative
technique for reliable monitoring of occlusal overload.
Excessive dental wear (pathological attrition and/or abfractions) is a frequent complication in bruxing patients. The parafunction causes heavy occlusal loads. The aim of this study is the early detection and monitoring of occlusal overload in bruxing patients. En-face optical coherence tomography was used for investigating and imaging of several extracted tooth, with a normal morphology, derived from patients with active bruxism and from subjects without parafunction. We found a characteristic pattern of enamel cracks in patients with first degree bruxism and with a normal tooth morphology. We conclude that the en-face optical coherence tomography is a promising non-invasive alternative technique for the early detection of occlusal overload, before it becomes clinically evident as tooth wear.
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