A new method for fabrication of nanohydroxyapatite and TCP from the sea snail Cerithium vulgatum

Biphasic bioceramic nanopowders of hydroxyapatite (HA) and β-tricalcium phosphate (TCP) were prepared from shells of the sea snail Cerithium vulgatum (Bruguière, 1792) using a novel chemical method. Calcination of the powders produced was carried out at varying temperatures, specifically at 400°C and 800°C, in air for 4 hours. When compared to the conventional hydrothermal transformation method, this chemical method is very simple, economic, due to the fact that it needs inexpensive and safe equipment, because the transformation of the aragonite and calcite of the shells into the calcium phosphate phases takes place at 80°C under the atmospheric pressure. The powders produced were determined using infrared spectroscopy (FT-IR), X-ray diffraction, and scanning electron microscopy (SEM). The features of the powders produced along with the fact of their biological origin qualify these powders for further consideration and experimentation to fabricate nanoceramic biomaterials. © 2014 O. Gunduz et al

Wettability characteristics of an Al2O3/SiO2-based ceramic modified with CO2, Nd:YAG, excimer and high-power diode lasers

Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of an Al2O3/SiO2 based ceramic was found to effect significant changes in the wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330 respectively. In contrast, interaction with excimer laser radiation resulted an increase in the contact angle to 1210. Such changes were identified as being due to: (i) the melting and partial vitrification of the Al2O3/SiO2 based ceramic surface as a result of interaction with CO2, Nd:YAG HPDL radiation. (ii) the surface roughness of the Al2O3/SiO2 based ceramic increasing after interaction with excimer laser radiation. (iii) the surface oxygen content of the Al2O3/SiO2 based ceramic increasing after interaction with CO2, Nd:YAG and HPDL radiation. The work has shown that the wettability characteristics of the Al2O3/SiO2 based ceramic could be controlled and/or modified with laser surface treatment. In particular, whether the laser radiation had the propensity to cause surface melting. However, a wavelength dependance of the change of the wetting properties could not be deduced from the findings of this work

Calcium phosphate formation from sea urchin - (brissus latecarinatus) via modified mechano-chemical (ultrasonic) conversion method

This study aims to produce apatite structures, such as hydroxyapatite (HA) and fluorapatite (FA), from precursor calcium phosphates of biological origin, namely from sea urchin, with mechano-chemical stirring and hot-plating conversion method. The produced materials were heat treated at 800 °C for 4 hours. X-ray diffraction and scanning electron microscopy (SEM) studies were conducted. Calcium phosphate phases were developed. The SEM images showed the formation of micro to nano-powders. The experimental results suggest that sea urchin, Brissus latecarinatus skeleton could be an alternative source for the production of various mono or biphasic calcium phosphates with simple and economic mechano-chemical (ultrasonic) conversion method

Hydroxyapatite scaffolds produced from cuttlefish bone via hydrothermal transformation for application in tissue engineering and drug delivery systems

An increase in life expectancy due to improvements in healthcare, in parallel with high percentage of injures, because of traffic accidents and sport activities, has emerged as the primary reasons for the replacements of lost, infected, and damaged bones. Combined with tissue engineering, this is an area of great interest to regenerative medicine. Novel scaffolds development, providing a suitable environment that can favor osteoinduction for the newly formed bone is needed. Composite porous hydrogels, based on alginate and chitosan with the dispersed phase from powders of bioceramics, such as hydroxyapatite (HAp), are recently developed for this reason. This work presents a reverse and novel approach, where these two popular hydrogels are infiltrated in a 3D HAp-scaffold. More specifically, HAp is obtained from aragonite from cuttlefish bone via hydrothermal transformation. This reinforcement of HAp with alginate or chitosan hydrogels, through infiltration method gives to the final product proper mechanical potential for hard tissue regeneration. The structure of the produced scaffolds resembles the microstructure and the texture of the natural bone. These advanced scaffolds are easily handled by the surgeon while maintaining their porous structure during the implantation process to promote the regeneration of newly formed bone tissue. In particular, once such a scaffold is implanted in an area where the bone tissue is lost, biological liquids will be able to penetrate into the pores of the lyophilized composite scaffold. The polymeric matrix will then be dissolved and the remaining HAp, or its precursor compounds, which will eventually transform into HAp, will promote osteoinduction. The worldwide availability and the low cost of cuttlefish bone, along with their biological-natural origin are attractive features making them highly sorted material used in the preparation of advanced scaffolds containing HAp for applications in biomedicine. The optimization of the fabrication technique is required to unravel the endless potential of biomaterials, shedding light on this promising interdisciplinary field, which includes both tissue engineering and drug delivery system approaches. © Springer Nature Singapore Pte Ltd 2019

Effect of Bonding Agent on Metal-Ceramic Bond Strength between Co-Cr Fabricated with Selective Laser Melting and Dental Feldspathic Porcelain

Purpose: To investigate the effect of bonding agent on the bonding strength between Co-Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain. Materials and Methods: The experiments were conducted according to ISO 9693 and the conventional protocols for the production of metal-ceramic dental restorations. After Al2O3 air-particle abrasion, metal substrates of Co-Cr dental alloy specimens were bonded, using bonding agent (25 specimens), with dental porcelain positioned in layers (opaque, dentin, enamel). Control specimens (25) were also produced without bonding agent. Bonding strength was measured using 3-point bending tests, and the results were statistically analyzed using the t-test and Weibull statistics. Elemental (by SEM/EDS) and crystallographic analyses (by XRD) were conducted on the bonding agent, along cross sections of alloy-porcelain interfaces, and on fracture surfaces. Results: Cohesive fracture occurred (on the porcelain side). The application of the bonding agent decreased the average bonding strength (from 42.27 ± 5.85 to 36.25 ± 3.26 MPa, P = 0.00006), attributed to the nonexisting reaction between the TiO2-rich bonding agent and the Co-Cr alloy, but it increased the Weibull modulus (from 7.84 to 12.16), which reflects the reliability of the bond in the tested metal-ceramic specimens. Conclusions: Although the application of bonding agent slightly decreased the bonding strength, all the measured values of the metal-ceramic specimens produced by the SLM technique, with or without the bonding agent, are markedly higher than the minimum value required by ISO 9693 (25 MPa). Moreover, the use of bonding agent favors the increase of the Weibull modulus. © 2019 by the American College of Prosthodontist

Crystallization of leucite in potassium-alumino-silicate glasses

Leucite crystals were successfully precipitated in a glass matrix which had the precise stoichiometric composition of leucite (KAISi(2)O(6)). Potassium silicate compound was first produced. Then, alumina was added to obtain the potassium aluminosilicate glass. Crystallization took place at 1550 degrees C for 24 h in air with a heating rate of 3 degrees C/min. The resultant material comprised a glass matrix where dense round polycrystalline clusters (200-300 mu m) of leucite were homogenously dispersed, seemingly acting as crack arresters. The leucite crystals (similar to 2-4 mu m thick and similar to 10 mu m long) were well-interlocked one to the other. The produced glass-ceramics exhibited good aesthetics with regards to their potential in dental applications