Characterization of novel calcium hydroxide- mediated highly porous chitosan- calcium scaffolds for potential application in dentin tissue engineering

The aim of this study was to develop a highly porous calcium- containing chitosan scaffold suitable for dentin regeneration. A calcium hydroxide (Ca[OH]2) suspension was used to modulate the degree of porosity and chemical composition of chitosan scaffolds. The chitosan solution concentration and freezing protocol were adjusted to optimize the porous architecture using the phase- separation technique. Scanning electron microscopy/energy- dispersive spectroscopy demonstrated the fabrication of a highly porous calcium- linked chitosan scaffold (CH- Ca), with a well- organized and interconnected porous network. Scaffolds were cross- linked on glutaraldehyde (GA) vapor. Following a 28- day incubation in water, cross- linked CH scaffold had no changes on humid mass, and CH- Ca featured a controlled degradability profile since the significant humid mass loss was observed only after 21 (26.0%) and 28- days (42.2%). Fourier- transform infrared spectroscopy indicated the establishment of Schiff base on cross- linked scaffolds, along with calcium complexation for CH- Ca. Cross- linked CH- Ca scaffold featured a sustained Ca2+ release up to 21- days in a humid environment. This porous and stable architecture allowed for human dental pulp cells (HDPCs) to spread throughout the scaffold, with cells exhibiting a widely stretched cytoplasm; whereas, the cells seeded onto CH scaffold were organized in clusters. HDPCs seeded onto CH- Ca featured significantly higher ALP activity, and gene expressions for ALP, Col1, DMP- 1, and DSPP in comparison to CH, leading to a significant 3.5 times increase in calcium- rich matrix deposition. In sum, our findings suggest that CH- Ca scaffolds are attractive candidates for creating a highly porous and bioactive substrate for dentin tissue engineering.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155906/1/jbmb34586.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155906/2/jbmb34586_am.pd

Bond strength of a resin cement to high-alumina and zirconia-reinforced ceramics:The effect of surface conditioning

Purpose: The aim of this study was to evaluate the effect of two surface conditioning methods on the microtensile bond strength of a resin cement to three high-strength core ceramics: high alumina-based (In-Ceram Alumina, Procera AllCeram) and zirconia-reinforced alumina-based (in-Ceram Zirconia) ceramics. Materials and Methods: Ten blocks (5 x 6 x 8 mm) of In-Ceram Alumina (AL), In-Ceram Zirconia (ZR), and Procera (PR) ceramics were fabricated according to each manufacturer's instructions and duplicated in composite. The specimens were assigned to one of the two following treatment conditions: (1) airborne particle abrasion with 110-mu m Al(2)O(3) particles + silanization, (2) silica coating with 30 lam SiO(x) particles (CoJet, 3M ESPE) + silanization. Each ceramic block was duplicated in composite resin (W3D-Master, Wilcos, Petropolis, RJ, Brazil) using a mold made out of silicon impression material. Composite resin layers were incrementally condensed into the mold to fill up the mold and each layer was light polymerized for 40 s. The composite blocks were bonded to the surface-conditioned ceramic blocks using a resin cement system (Panavia F, Kuraray, Okayama, Japan). One composite resin block was fabricated for each ceramic block. The ceramic-composite was stored at 37 degrees C in distilled water for 7 days prior to bond tests. The blocks were cut under water cooling to produce bar specimens (n = 30) with a bonding area of approximately 0.6 mm(2). The bond strength tests were performed in a universal testing machine (crosshead speed: 1 mm/min). Bond strength values were statistically analyzed using two-way ANOVA and Tukey's test ( Results: Silica coating with silanization increased the bond strength significantly for all three high-strength ceramics (18.5 to 31.2 MPa) compared to that of airborne particle abrasion with 110-mu m Al(2)O(3) (12.7-17.3 MPa) (ANOVA, p <0.05). PR exhibited the lowest bond strengths after both Al(2)O(3) and silica coating (12.7 and 18.5 MPa, respectively). Conclusion: Conditioning the high-strength ceramic surfaces with silica coating and silanization provided higher bond strengths of the resin cement than with airborne particle abrasion with 110- mu m Al(2)O(3) and silanization