Occlusal vertical dimension and dental implants [Oklüzyon dikey boyutu ve dental implantlar]

The determination of optimum occlusal vertical dimension (OVD) that is harmonious with the individuals' craniofacial system is important for prosthetic restorative procedures. The purpose of this article was to examine the importance of OVD for implant supported prosthetic restorations with two clinical reports. A computer aided literature review was conducted to define the articles about OVD and implant supported restorations. The review revealed that one-stage OVD increase with moderate to severe degrees (3-16 mm, mean: 7.3 mm) did not result in any complaints or temporomandibular disorders. Regaining the OVD did not result in relapse or any changes. Moderate alterations in the occlusal vertical dimension of patients are generally well tolerated when necessary for therapeutic purposes

Preliminary evaluation of titanium tetrafluoride as an alternative ceramic etchant to hydrofluoric acid

PubMed ID: 20011764Purpose: The etching of dental ceramics with a glassy matrix by means of hydrofluoric acid (HF) is highly effective and after the application of a silane coupling agent, a strong link between the adhesive and the ceramic is achieved. The purpose of this study was to investigate whether aqueous titanium tetrafluoride (TiF4) solution could be used as an alternative ceramic etchant or not. Materials and Methods: Seventy lithia-based all-ceramic specimens (IPS Empress 2, Ivoclar Vivadent) (diameter: 4 mm, height: 4 mm) were prepared and ultrasonically cleaned for 15 min in ethanol and deionized water, then divided into 1 control and 4 experimental groups (n = 14/group). The control group was acid etched with 4.9% HF for 20 s as described by the manufacturer. The experimental groups were treated with 2.5% TiF4 solution for 60 s, 2.5% TiF4 solution for 120 s and 5% TiF4 solution for 60 s, as well as 5% TiF4 solution for 120 s. Seven of the ceramic specimens in each group were luted to the other seven by a dual-curing cement (Variolink II, Ivoclar Vivadent,) with silane application (Monobond-S). After storage of luted specimens in deionized water at 37°C for 24 h, the specimens were embedded in plastic holders with cyanoacrylate, and the shear-bond strength (SBS) tests were performed with a Shimadzu universal testing machine at a crosshead speed of 0.5 mm/min. A one-way ANOVA and Bonferroni correction, followed by the Tukey test, were applied for statistical analysis. Scanning electron microscopic examination was performed to evaluate the pattern of debonding. Results: Significantly higher SBS values (p ? 0.05) were obtained for the control group (28.71 ± 9.74). The SBS for 2.5%-60 s (25.25 ± 5.13) and 2.5%-120 s TiF4 (22.65 ± 5.68) were significantly higher than 5%-60 s (16.77 ± 3.92) and 5%-120 s TiF4 (18.54 ± 3.52) groups (p ? 0.05). Differences between 60- and 120-s groups irrespective of TiF4 concentrations were insignificant (p > 0.05). Conclusion: Aqueous TiF4 solution exhibited similar shear bond strength values in comparison to commonly used HF and can be considered as an alternative ceramic etchant within the limitations of this preliminary report. © 2009 by Quintessence Publishing Co Inc

Influence of applied current density on the nanostructural and light emitting properties of n-type porous silicon

WOS: 000355326700002Effects of current density on nanostructure and light emitting properties of porous silicon (PS) samples were investigated by field emission scanning electron microscope (FE-SEM), gravimetric method, Raman and photoluminescence (PL) spectroscopy. FE-SEM images have shown that below 60 mA/cm(2), macropore and mesopore arrays, exhibiting rough morphology, are formed together, whose pore diameter, pore depth and porosity are about 265-760 nm, 58-63 mu m and 44-61%, respectively. However, PS samples prepared above 60 mA/cm(2) display smooth and straight macropore arrays, with pore diameter ranging from 900-1250 nm, porosity of 61-80% and pore depth between 63-69 mu m. Raman analyses have shown that when the current density is increased from 10 mA/cm(2) to 100 mA/cm(2), Raman peaks of PS samples shift to lower wavenumbers by comparison to crystalline silicon (c-Si). The highest Raman peak shift is found to be 3.2 cm(-1) for PS sample, prepared at 90 mA/cm(2), which has the smallest nanocrystallite size, about 5.2 nm. This sample also shows a pronounced PL, with the highest blue shifting, of about 12 nm. Nanocrystalline silicon, with the smallest nanocrystallite size, confirmed by our Raman analyses using microcrystal model (MCM), should be responsible for both the highest Raman peak shift and PL blue shift due to quantum confinement effect (QCE).Ege University, Research Project FoundationEge University [2013FEN058]This work is supported by the Ege University, Research Project Foundation: Project no: 2013FEN058

Evaluation of bond strength of various margin ceramics to a zirconia ceramic

PubMed ID: 18620791Objective: This study evaluated the bond strengths of four different margin ceramics based on fluoroapatite and feldspath to a zirconia ceramic. Methods: Zirconia cores (Zirconzahn) (N = 28, n = 7/margin ceramic group) were fabricated according to the manufacturers' instructions (diameter: 4 mm; thickness: 2 mm) and ultrasonically cleaned. Four different margin ceramics (thickness: 5 mm) (Cerabien Zr, Noritake; Ceramco PFZ, Ceramco; e.max, Ivoclar Vivadent and Triceram, Dentaurum) were vibrated and condensed in a stainless steel mould and fired onto their zirconia cores. After trying the specimens in the mould for minor adjustments, they were again ultrasonically cleaned and embedded in PMMA. The specimens were stored in distilled water at 37 °C for 1 week and shear bond strength (MPa ± S.D.) tests were performed in a universal testing machine (crosshead speed: 0.5 mm/min). Failure modes were recorded under SEM. Results: Significant effect of margin ceramic types were found on the bond strength values (P < 0.05). The mean bond strength values of Ceramco margin ceramic to zirconia was significantly lower (25.4 ± 4.5 MPa) (P < 0.05) than those of Cerabien (31.6 ± 6.4 MPa), e.max (35.9 ± 8.4 MPa), and Triceram margin ceramic (38.8 ± 7.1 MPa) systems. Conclusions: Margin ceramics, compatible with zirconia framework material tested in the present study, exhibited high bond strength values. Variations in thermal expansion coefficients might influence their bond strength values. © 2008 Elsevier Ltd. All rights reserved