CCR7 expression on peripheral blood lymphocytes is up-regulated following treatment of multiple sclerosis with interferon-beta

A prospective study of the expression of the chemokine receptor CCR7 was performed in 11 relapsing-remitting multiple sclerosis (MS) patients during 12 months of interferon-beta (IFNbeta) treatment. The results show increased expression of CCR7 on peripheral blood lymphocytes (PBL) of MS patients receiving IFNbeta treatment as well as lymphocytes from healthy subjects treated with IFNbeta in vitro. Our results suggest that in addition to modulating the expression of adhesion molecules, the mode of action of IFNbeta also involves the control of the chemokine receptor CCR7. The net effect is a key change in the control of lymphocyte traffic between immune organs and the central nervous system (CNS) and a shift from CCR7 negative effector T cells to CCR7 positive central memory T cells.     

Static strength of molar region direct technique glass fibre-reinforced composite fixed partial dentures

The aim of this study was to determine static fracture force of fibre-reinforced composite (FRC) fixed partial dentures (FPD) with different retainer designs. The fabrication simulated the process to make directly made 3-unit maxillary molar FPD. Four types of retainers were tested (n = 5): conventional crown preparation (1.2 mm axially and 2.0 mm occlusally), slot preparation (3.5 mm high x 3.5 mm wide x 1 mm deep), no preparation with broad fibre abutment contact, and combination of the slot and broad fibre contact were performed. The FPD contained unidirectional E-glass FRC veneered with particulate reinforced composite. Dimensions of the FPDs were homogenized. FPDs were stored at 1 week 37 degrees C deionized water, thermocycled between 5 degrees C and 55 degrees C (5000 cycles, dwell time 10 s) and statically loaded to failure. The slot retainer design yielded the lowest mean load to initial and final failure (FF) (1284 and 1313 N, respectively), the crown retainer the highest mean load to initial failure at 1755 N, and the combination retainer resulted in the highest mean load to FF (1836 N) (anova, P < 0.001; Tukey multiple comparisons, 0.05 significance level). The results of this study suggest that the fabrication of direct FRC FPD does not necessarily require extensive preparation for the retainers.     

Assessment of CAD-CAM polymers for digitally fabricated complete dentures

Statement of problemInformation on the mechanical properties of the materials used for manufacturing computer-engineered complete dentures is scarce.PurposeThe purpose of this in vitro study was to evaluate the mechanical properties of 3 prepolymerized polymethyl methacrylate (PMMA) resins used in the fabrication of computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete dentures (CDs), as well as 2 denture base polymers used for conventionally fabricated CDs.Material and methodsThree CAD-CAM materials were evaluated: Degos Dental L-Temp, IvoBase CAD, and Zirkonzahn Temp Basic Tissue. Two materials used for conventionally manufactured dentures were also included as controls (Palapress and Paladon 65). Each material type was sectioned into bars for flexural strength, nanohardness, elastic modulus, and surface microhardness evaluation (n=8/material). Half of the specimens were stored in water for 30 days, while the other half was dry-stored. A 2-way ANOVA was conducted to detect the effect of material and storage on the evaluated properties (α=.05). Linear contrasts were conducted to compare the differences among the 3 types of CAD-CAM material and the conventional ones.ResultsMaterial type and storage had a significant influence on the flexural strength, nanohardness, elastic modulus, and surface hardness of the materials investigated (P<.001). The post hoc Scheffé test for flexural strength revealed a nonsignificant difference in the interaction between Degos L-Temp and Paladon (P=1.000). In terms of nanohardness, no difference was found when comparing Palapress with Paladon, as well as IvoBase CAD with Zirkonzahn Temp Basic (P=1.000). A nonsignificant interaction in terms of surface hardness was also found between IvoBase CAD and Palapress (P=.575).ConclusionsThe tested materials showed variation in their mechanical properties, with satisfactory behavior of the CAD-CAM materials. However, the results obtained when testing the materials used for the conventional fabrication of complete dentures suggest that their use might still be advisable.     

The effect of chlorhexidine and dimethyl sulfoxide on long-term sealing ability of two calcium silicate cements in root canal

ObjectivesTo evaluate the long-term effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) on the sealing ability and biomineralization of two different calcium silicate cements (CSC) in root canal.MethodsSixty human third molar root canals were obturated with ProRoot MTA or Biodentine. Before obturation the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage was tested after three days and after six months. After additional six months (12 months after root filling) the roots were cut into 2 mm thick dentine discs. The discs were stored in artificial saliva for one year. The bond strength was measured with the push-out method, and the failure mode was evaluated with a stereomicroscope. The most apical disc of each tooth was used for Vickers hardness test.ResultsNo significant differences between the groups was found in initial microleakage. The leakage increased significantly during the 6-month storage in all groups except in Biodentine-CHX group and Biodentine-DMSO group. CHX and DMSO irrigation significantly increased the leakage with ProRoot MTA with time, but there was no statistically significant difference compared to the ProRoot MTA-control group at six months’ time point. CHX significantly reduced the push-out bond strength of ProRoot MTA. With Biodentine irrigation with CHX or DMSO resulted with significantly higher push-out strength compared to the Biodentine control group. Fracture analysis showed statistically significant difference in the distribution of the fractures between the groups, but neither CHX nor DMSO change the fracture pattern statistically significantly. With Vickers hardness test ProRoot MTA with and without DMSO as the final irrigant showed significantly higher dentin hardness than any Biodentine-group.SignificanceConsidering that aging increased the leakage in all groups except with Biodentine-DMSO and the differences in the push-out strength and surface microhardness data, it appears that the time-related biomineralizing effect of MTA and Biodentine does not improve sealing to dentin. CHX significantly reduced ProRoot MTA bond strength and increased pure adhesive failures with both cements.     

Bonding of lithium-disilicate ceramic to enamel and dentin using orthotropic fiber-reinforced composite at the interface

Objective. To evaluate the effect of orthotropic fiber-reinforced composite (FRC) at the interface on bonding of lithium-disilicate ceramic to dentin and enamel using different adhesive systems. Material and Methods. Dentin and enamel surfaces were ground occlusally on human molar teeth. Ceramic blocks of IPS Empress 2 (Ivoclar-Vivadent) were fabricated. Following acid etching and silane treatment of the ceramics, the teeth were divided into two groups (dentin and enamel). Ceramic blocks were bonded to the tooth substance with or without a layer of FRC and dual-polymerizing composite cement (Duolink). Total-etching (etchant (Etch 37) with adhesive (One Step Plus)) and self-etching (self-priming etchant (Tyrian SPE) with adhesive (One Step Plus)) systems were used, with five test specimens in each group. The cement was polymerized with a LED curing unit (Elipar Freelight LED 2) with standard mode of 40 s. The specimens were thermocycled for 6000 cycles and tested with the microtensile tester at a rate of 5 mm/min. Fracture mode analyses were done by light microscope and with SEM. The data were analyzed using three-way analysis of variance (ANOVA). Results. ANOVA showed that enamel had statistically significant (p<0.001) higher bond strength values than dentin. Bond strength values were significantly higher (p=0.012) with the total-etching system than with the self-etching system. The existence of FRC also had a minor effect on bond strength values (p=0.013). Conclusions. The enamel and total-etching system provided more reliable bonding than dentin and the self-etching system. Use of an FRC layer at the interface did not improve bond strength values, but instead changed fracture pattern behavior.     

Accuracy of three-dimensional finite element modeling using two different dental cone beam computed tomography systems

The aim of this study is to evaluate the accuracy of dental ceramic object three dimensional (3D) finite element model constructed directly from two different dental cone beam computed tomography (CT) systems. CT scanned one 10.0 × 10.0 × 20.0 mm block and one 8.0 × 10.0 × 40.0 mm block of an 8-step wedge. All 3D finite element (FE) models were created from CT images. Each 3D FE model measured the length of the directions X, Y, and Z that corresponded to an original specimen using the measurement function between two points on the Mechanical Finder software package. The measurements and practical value were compared with the CT image and the accuracy of the reproduced measurements was examined. No significant differences were found between Alphard-3030 on the Z axis and ProMax 3D on the Y axis of the block. In addition, there were also no significant differences observed between Alphard-3030 on the Y axis and ProMax 3D on the X axis compared with Alphard-3030 on the Z axis and ProMax 3D on the Y axis for the step-wedge. The results suggest that measurement of the dimensions of cone beam CT images could be useful in applications where both good reproducibility and accuracy of FE models are required.     

Influence of increment thickness on dentin bond strength and light transmission of composite base materials

Clinical Oral Investigations - Bulk-fill resin composites (BFCs) are gaining popularity in restorative dentistry due to the reduced chair time and ease of application. This study aimed to evaluate...     

Mechanical properties of oligomer-modified acrylic bone cement

The aim of this study was to determine the mechanical properties of acrylic bone cement modified with an experimental oligomer filler, based on an amino acid of trans-4-hydroxy-L-proline synthesized in the laboratory. The test specimens were tested either dry, or after being stored in distilled water or in simulated body fluid (SBF) for 1 week and then tested in distilled water. The three-point bending test was used to measure the flexural strength and flexural modulus of the cement, and the compression tests were used to measure the compression strength and modulus. One test specimen from each group was examined under a scanning electron microscope (SEM) to determine the nature of the oligomer filler in the polymethylmethacrylate-polymethylacrylate copolymer-based (PMMA-PMA/PMMA) polymer blend. In dry conditions, the flexural strength of the test specimens tested in air was 66 MPa, and the compression strength was 93 GPa (p<0.001) for the plain bone cement. For the test specimens including 20 wt% of oligomer filler, the flexural strength was 37 MPa, and the compression strength was 102 MPa(p<0.001) in dry conditions. The storage in wet conditions (in distilled water and the SBF) decreased the flexural strength of the test specimens with 20 wt% of oligomer filler (p<0.001) by 60% and the flexural modulus by 44% compared to the plain bone cement specimens stored in the same conditions. The reduction in compression strength in wet conditions was 32%, and that of the compression modulus was 30% (p<0.001). No significant differences were found between test specimens stored in distilled water or SBF (ANOVA, p<0.001). In the SEM examinations, random voids were observed in the oligomer-PMMA-PMA/PMMA polymer blend after water or SBF storage. The results suggest that both water and SBF storage decrease the mechanical properties of the PMMA-PMA/PMMA bone cement modified with oligomer, while at the same time, there was porous formation in the bone cement structure.