Effects of Different Surface Treatments of Woven Glass Fibers on Mechanical Properties of an Acrylic Denture Base Material.

Silanized glass fibers are popular reinforcements of acrylic denture base materials. To increase the number of surface hydroxyl groups and to improve interfacial adhesion between the matrix and reinforcements, acid or base treatments of glass fibers are commonly performed before the silanization. However, limited data are available on the effect of these treatments on the mechanical properties of acrylic matrix composite materials used for denture base applications. In this work, before the silanization of a woven glass fiber fabric (GF) with 3-(trimethoxysilyl) propyl methacrylate, activation pretreatments using HCl and NH4OH aqueous solutions have been performed. To characterize the glass surface, FTIR spectroscopy was used. Specimens of cured acrylic denture base resin and composites were divided into five groups: (1) cured acrylic denture base resin-control group; (2) composite with non-silanized GF; (3) composite with silanized GF; (4) composite with NH4OH activated and silanized GF; (5) composite with HCl activated and silanized GF. The flexural and impact properties of specimens were evaluated by means of three-point-bending tests and Charpy impact testing, respectively. The residual reactivity of the samples was analyzed using differential scanning calorimetry. The results of mechanical testing showed that acid and base pretreatments of the glass fabric had a positive effect on the flexural modulus of prepared composites but a negative effect on their impact strength. Possible interfacial adhesion mechanisms and the diffusion control of isothermal cure reactions due to vitrification have been discussed.

Plantaris tendon: a novel graft for anterolateral ligament reconstruction and additional reinforcement for anterior cruciate ligament autografts in combined reconstructive procedures.

The anterolateral ligament is recently recognized as an important structure in restoring rotational stability of the anterior cruciate ligament-deficient knee. Biomechanical and clinical studies confirmed the benefits of concurrent anterior cruciate ligament and anterolateral ligament reconstruction. However, present techniques mostly use hamstring tendons autografts and therefore additionally disrupt the knee biomechanics. The plantaris tendon is a well known and accessible graft and has excellent biomechanical properties for anterolateral ligament reconstruction. The present paper describes a new combined anterior cruciate ligament and anterolateral ligament reconstruction technique using plantaris tendon and semitendinosus tendon.Level of evidence V (Case report).

Comparison of Mechanical Properties of 3D-Printed, CAD/CAM, and Conventional Denture Base Materials.

PURPOSE: To evaluate and compare the mechanical properties (flexural strength and surface hardness) of different materials and technologies for denture base fabrication. The study emphasized the digital technologies of computer-aided design/computer-aided manufacturing (CAD/CAM) and three-dimensional (3D) printing. MATERIALS AND METHODS: A total of 160 rectangular specimens were fabricated from three conventional heat-polymerized (ProBase Hot, Paladon 65, and Interacryl Hot), three CAD/CAM produced (IvoBase CAD, Interdent CC disc PMMA, and Polident CAD/CAM disc), one 3D-printed (NextDent Base), and one polyamide material (Vertex ThermoSens) for denture base fabrication. The flexural strength test was the three-point flexure test, while hardness testing was conducted using the Brinell method. The data were analyzed using descriptive and analytical statistics (α = 0.05). RESULTS: During flexural testing, the IvoBase CAD and Vertex ThermoSens specimens did not fracture during loading. The flexural strength values of the other groups ranged from 71.7 ± 7.4 MPa to 111.9 ± 4.3 MPa. The surface hardness values ranged from 67.13 ± 10.64 MPa to 145.66 ± 2.22 MPa. There were significant differences between the tested materials for both flexural strength and surface hardness. There were also differences between some materials with the same polymerization type. CAD/CAM and polyamide materials had the highest flexural strength values. Two groups of CAD/CAM materials had the highest surface hardness values, while a third, along with the polyamide material, had the lowest. The 3D-printed materials had the lowest flexural strength values. CONCLUSIONS: Generally, CAD/CAM materials show better mechanical properties than heat-polymerized and 3D-printed acrylics do. Nevertheless, a material's polymerization type is no guarantee of its optimal mechanical properties.

A study of the flexural strength and surface hardness of different materials and technologies for occlusal device fabrication.

STATEMENT OF PROBLEM: With the emergence of digital technologies, new materials have become available for occlusal devices. However, data are scarce about these different materials and technologies and their mechanical properties. PURPOSE: The purpose of this in vitro study was to investigate the flexural strength and surface hardness of different materials using different technologies for occlusal device fabrication, with an emphasis on the digital technologies of computer-aided design and computer-aided manufacturing (CAD-CAM) and 3D printing. MATERIAL AND METHODS: A total of 140 rectangular specimens were fabricated from two 3D-printed (VarseoWax Splint and Ortho Rigid), 2 CAD-CAM-produced (Ceramill Splintec and CopraDur), and 3 conventional autopolymerizing occlusal device materials (ProBase Cold, Resilit S, and Orthocryl) according to ISO 20795-1:2013. Flexural strength and surface hardness were determined for 10 specimens of each tested material using the 3-point bend test and the Brinell method. The data were analyzed using descriptive statistics and 1-way ANOVA with Bonferroni corrections (α=.05). RESULTS: Surface hardness values ranged from 28.5 ±2.5 MPa to 116.2 ±1.6 MPa. During flexural testing, neither the CopraDur nor the VarseoWax Splint specimens fractured during loading within the end limits of the penetrant's possible movement. Flexural strength values for other groups ranged from 75.0 ±12.0 MPa to 104.9 ±6.2 MPa. Statistical analysis determined significant differences among the tested materials for flexural strength and surface hardness. CONCLUSIONS: Mechanical properties among different occlusal device materials were significantly different. Acrylic resins were less flexible than polyamide and nonacrylic occlusal device materials for 3D printing but had higher and more consistent values of surface hardness. Clinicians should consider the different mechanical properties of the available materials when choosing occlusal device materials.

Femoral head wear and metallosis caused by damaged titanium porous coating after primary metal-on-polyethylene total hip arthroplasty: a case report.

Excessive metal femoral head wear has been described only as revision surgery complication after primary ceramic-on-ceramic total hip arthroplasty (THA). Here, we present the first case of metal femoral head wear after primary metal-on-polyethylene THA. A 56-year-old woman was referred to our outpatient clinic 17 years after primary right-sided THA, experiencing pain and decreased right hip range of motion. Radiographic examination revealed acetabular cup dislocation, eccentric femoral head wear, damaged titanium porous coating of femoral stem, metallosis, and pseudotumor formation. Endoprosthetic components were extracted, but further reconstruction was impossible due to presence of large acetabular bone defect. Macro- and micro-structure of extracted components were analyzed. Acetabular liner surface was damaged, with scratches, indentations, and embedded metal debris particles present on the entire inner surface. Analysis of metal debris by energy-dispersive spectroscopy showed that it consisted of titanium and stainless-steel particles. Femoral head was gravely worn and elliptically shaped, with abrasive wear visible under scanning electron microscope. No signs of trunnionosis at head/neck junction were observed. Microstructure of femoral head material was homogeneous austenitic, with microhardness of 145 HV 0.2, which is lower than previously described titanium hardness. In conclusion, detached titanium porous coating of femoral stem can cause stainless-steel femoral head wear in primary metal-on-polyethylene THA. As soon as such detachment becomes evident, revision surgery should be considered to prevent devastating complications.

Plantaris Tendon Autograft Can Restore Patellar Stability in Adolescent Medial Patellofemoral Ligament Reconstruction: A Technical Note.

Medial patellofemoral ligament reconstruction is a standard treatment option for patients with patellar instability. The main purpose of this study was to determine whether isolated anatomic medial patellofemoral ligament reconstruction using double folded, four-strand plantaris tendon autograft restores patellar stability in adolescent patients. Plantaris tendon autografts were harvested through proximal approach and used in four adolescent patients. A four-strand autograft was prepared in a double-limbed configuration and fixed on the patella and the femur with suture anchors and interference screws, respectively. The mean Kujala score improved significantly from 44 ± 24 SD (range, 19 to 69) points preoperatively to 94 ± 10 SD (range, 78 to 100) points postoperatively (P< 0.001). All patients reported excellent subjective outcomes and returned to their pre-injury level of sporting activities. The use of a four-strand plantaris tendon autograft in isolated anatomic medial patellofemoral ligament reconstruction can restore patellar stability in adolescents.

Laser Powder Bed Fusion Parameters Optimization for Enhanced Mechanical Properties of EOS Co-Cr Dental Alloy.

This research explores how variations in laser powder bed fusion (LPBF) parameters-laser power (P), scanning speed (v), and base plate preheating temperature (ϑp)-affect the mechanical properties of the EOS Co-Cr SP2 dental alloy. A central composite design (CCD) was used to optimize the process parameters. Mechanical testing focused on crucial properties for dental applications, including yield strength (Rp0.2), elongation (ε), toughness (KVa), and flexural strength (Rms). Microstructural analysis was conducted using light and electron microscopy, while XRD identified microstructural phases. Statistical analysis (ANOVA, Scheffé post hoc test, α = 0.05) revealed significant effects of P, v, and ϑp on the mechanical properties. Response surface models (RSMs) were developed, and optimal parameters were determined to achieve maximum toughness and flexural strength. Maximum values were obtained with laser power above 205 W and base plate preheating at 310 °C. The mathematical model predicted toughness values with less than 5% deviation from experimental results, indicating high accuracy.

Shear bond strength in zirconia veneered ceramics using two different surface treatments prior veneering.

Aim of the study was to assess the effect of different surface treatments on the shear bond strength (SBS) of the veneering ceramics to zirconia core. In a shear test the influence of grinding and sandblasting of the zirconia surface on bonding were assessed. Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA). There was a significant difference between the groups considering shear bond strength (SBS) values, i.e. ground and sandblasted samples had significantly higher SBS values than only ground samples (mean difference = -190.67; df = 10, t = -6.386, p < 0.001). The results of the present study indicate that ground and sandblasted cores are superior to ground cores, allowing significantly higher surface roughness and significantly higher shear bond strength between the core and the veneering material.

Antibacterial activity of silver doped hydroxyapatite toward multidrug-resistant clinical isolates of Acinetobacter baumannii.

Bacteria Acinetobacter baumannii is a persistent issue in hospital-acquired infections due to its fast and potent development of multi-drug resistance. To address this urgent challenge, a novel biomaterial using silver (Ag+) ions within the hydroxyapatite (HAp) lattice has been developed to prevent infections in orthopedic surgery and bone regeneration applications without relying on antibiotics. The aim of the study was to examine the antibacterial activity of mono-substituted HAp with Ag+ ions and a mixture of mono-substituted HAps with Sr2+, Zn2+, Mg2+, SeO32- and Ag+ ions against the A. baumannii. The samples were prepared in the form of powder and disc and analyzed by disc diffusion, broth microdilution method, and scanning electron microscopy. The results from the disc-diffusion method have shown a strong antibacterial efficacy of the Ag-substituted and mixture of mono-substituted HAps (Sr, Zn, Se, Mg, Ag) toward several clinical isolates. The Minimal Inhibitory Concentrations for the powdered HAp samples ranged from 32 to 42 mg/L (Ag+ substituted) and 83-167 mg/L (mixture of mono-substituted), while the Minimal Bactericidal Concentrations after 24 h of contact ranged from 62.5 (Ag+) to 187.5-292 mg/L (ion mixture). The lower substitution level of Ag+ ions in a mixture of mono-substituted HAps was the cause of lower antibacterial effects measured in suspension. However, the inhibition zones and bacterial adhesion on the biomaterial surface were comparable. Overall, the clinical isolates of A. baumannii were effectively inhibited by substituted HAp samples, probably in the same amount as by other commercially available silver-doped materials, and such materials may provide a promising alternative or supplementation to antibiotic treatment in the prevention of infections associated with bone regeneration. The antibacterial activity of prepared samples toward A. baumannii was time-dependent and should be considered in potential applications.

Plantaris tendon is valuable graft for the medial patellofemoral ligament reconstruction: A biomechanical study.

BACKGROUND: Medial patellofemoral ligament (MPFL) reconstruction is a standard treatment option for selected patients with patellar instability. Although frequently performed, the optimal graft source for the procedure has not yet been established. This study aimed to determine whether a two-strand plantaris tendon construct possesses the biomechanical properties needed to act as an MPFL reconstruction graft. METHODS: Thirty paired plantaris and gracilis tendons were harvested from 15 cadavers, mean age at death of 42.7 years. All specimens were frozen and maintained at -20 °C until biomechanical testing. Prior to mechanical testing, specimens were thawed at room temperature. The two-strand plantaris tendon and two-strand gracilis tendon constructs were created and secured in a uniaxial tensile testing machine in a triangular-shaped mode. Biomechanical properties for tensile testing to failure were determined using validated method. Results obtained were compared with the previously published data on native MPFL biomechanical properties. RESULTS: The mean maximal force was 220.3 ± 108.1 N and 448.1 ± 117 N for the two-strand plantaris tendon construct and two-strand gracilis tendon construct, respectively. Significant differences were observed between all biomechanical properties of two-strand plantaris tendon and two-strand gracilis tendon constructs. The mean maximal force of a two-strand plantaris tendon construct and a two-strand gracilis tendon construct were greater than the mean maximal force of the native MPFL reported in all previous studies. CONCLUSIONS: This study suggests that, due to its biomechanical properties, the two-strand plantaris tendon graft is suitable as a graft for MPFL reconstruction.

The Effects of Three Remineralizing Agents on the Microhardness and Chemical Composition of Demineralized Enamel.

This study aimed to determine the effects of three different varnish materials (containing casein phosphopeptide-amorphous calcium phosphate, nano-hydroxyapatite, and fluoride) on enamel. Thirty-three extracted human third molars were used for specimen preparation. These were demineralized using phosphoric acid. Three experimental groups (n = 11) were treated with 3M™ Clinpro™ White Varnish, MI Varnish®, and Megasonex® toothpaste, respectively, every twenty-four hours for fourteen days. Analysis of the microhardness of the specimens' enamel surfaces was carried out via the Vickers method, and by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis was performed at three stages: at baseline value, after demineralization, and after the period of remineralization. Data were subjected to Scheffe's post hoc test. The mean microhardness values (HV0.1) obtained for the group of samples treated with MI Varnish® were higher compared with the other two groups (p = 0.001 for both comparisons), while the first and third groups did not differ significantly from each other (p = 0.97). SEM analysis showed uneven patterns and porosities on all samples tested. EDS results showed an increase in the mineral content of the examined samples, with the highest mineral content observed in the MI Varnish® group. It can be concluded that MI Varnish® use has a better remineralization effect on enamel than the other two materials.

Additively Manufactured Commercial Co-Cr Dental Alloys: Comparison of Microstructure and Mechanical Properties.

Laser-powder bed fusion (LPBF) is one of the preferred techniques for producing Co-Cr metal structures for dental prosthodontic appliances. However, there is generally insufficient information about material properties related to the production process and parameters. This study was conducted on samples produced from three different commercially available Co-Cr dental alloys produced on three different LPBF machines. Identically prepared samples were used for tensile, three-point bending, and toughness tests. Light microscopy (LM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses of microstructure were performed after testing. Differences were observed in microstructures, which reflected statistically significant differences in mechanical properties (one-way analysis of variance (ANOVA) and Scheffé post hoc test (α = 0.05)). The material produced on the 3D Systems DMP Dental 100 had 24 times greater elongation ε than the material produced on the Sysma MySint 100 device and the EOS M100 machine. On the other hand, the material produced on the EOS M100 had significantly higher hardness (HV0.2) than the other two produced materials. However, the microstructure of the Sysma specimens with its morphology deviates considerably from the studied group. LPBF-prepared Co-Cr dental alloys demonstrated significant differences in their microstructures and, consequently, mechanical properties.

Comparison of shear bond strengths of different types of denture teeth to different denture base resins.

PURPOSE: To determine the shear bond strengths of different denture base resins to different types of prefabricated teeth (acrylic, nanohybrid composite, and cross-linked) and denture teeth produced by computer-aided design/computer-aided manufacturing (CAD/CAM) technology. MATERIALS AND METHODS: Prefabricated teeth and CAD/CAM (milled) denture teeth were divided into 10 groups and bonded to different denture base materials. Groups 1-3 comprised of different types of prefabricated teeth and cold-polymerized denture base resin; groups 4-6 comprised of different types of prefabricated teeth and heat-polymerized denture base resin; groups 7-9 comprised of different types of prefabricated teeth and CAD/CAM (milled) denture base resin; and group 10 comprised of milled denture teeth produced by CAD/CAM technology and CAD/CAM (milled) denture base resin. A universal testing machine was used to evaluate the shear bond strength for all specimens. One-way ANOVA and Tukey post-hoc test were used for analyzing the data (α=.05). RESULTS: The shear bond strengths of different groups ranged from 3.37 ± 2.14 MPa to 18.10 ± 2.68 MPa. Statistical analysis showed significant differences among the tested groups (P<.0001). Among different polymerization methods, the lowest values were determined in cold-polymerized resin.There was no significant difference between the shear bond strength values of heat-polymerized and CAD/CAM (milled) denture base resins. CONCLUSION: Different combinations of materials for removable denture base and denture teeth can affect their bond strength. Cold-polymerized resin should be avoided for attaching prefabricated teeth to a denture base. CAD/CAM (milled) and heat-polymerized denture base resins bonded to different types of prefabricated teeth show similar shear bond strength values.

Mechanical Properties of High Viscosity Glass Ionomer and Glass Hybrid Restorative Materials.

OBJECTIVES: to determine the mechanical properties of hybrid and high-viscosity glass ionomer cements. Compressive strength and hardness of three glass ionomer cements (GIC) were measured: Ketac ™ Universal Aplicap ™, EQUIA Fil® and EQUIA FORTE Fil®, and the SEM sample analysis were performed. MATERIALS AND METHODS: The samples for measuring the compressive strength were prepared using silicone molds with standard dimensions of 6 mm x 4 mm and stored in deionized water for five days, while the samples for hardness measurement were prepared using Teflon molds with a cylindrical opening in the middle, dimensions 2 mm in height and 5 mm in width. For each material, one sample was made (n = 1) and stored in deionized water at 37ºC for 25 days. A representative sample of each material was analyzed using SEM. For the comparison of obtained values, the ANOVA test was used, while Tukey test was used for the multiple comparison. RESULTS: There were no significant differences between the compressive strength of the three tested materials (p <0.05). The hardness values were: 157 HV0,2 for Ketac ™ Universal Aplicap ™, 47 HV0,2 for EQUIA Fil® and 39 HV0,2 for EQUIA FORTE Fil®, respectively, and were significantly different, implying that Ketac ™ Universal Aplicap ™ has much higher hardness values than the other materials tested. SEM sample analysis revealed similar fracture modes of the tested materials. CONCLUSION: It was concluded that there were no statistically significant differences in compressive strength and fracture modes between the tested materials, while Ketac ™ Universal Aplicap ™ hardness results were significantly higher than the ones measured for EQUIA Fil® and EQUIA FORTE Fil®.

Bioactive Ti + Mg composites fabricated by powder metallurgy: The relation between the microstructure and mechanical properties.

Metallic implant materials are biomaterials that have experienced major development over the last fifty years, yet some demands posed to them have not been addressed. For the osseointegration process and the outcome of endosseous implantation, it is crucial to reduce the stress shielding effect and achieve sufficient biocompatibility. Powder metallurgy (PM) was utilized in this study to fabricate a new type of titanium (Ti) + magnesium (Mg) bioactive composite to enable stress-shielding reduction and obtain better biocompatibility compared with that of the traditional Ti and Ti alloys used for dental implants. Such composites are produced by well-known cost-effective and widely used PM methods, which eliminate the need for complex and costly Ti casting used in traditional implant production. The relation between the microstructure and mechanical properties of as-extruded Ti + (0-24) vol% Mg composites was investigated with respect to the Mg content. The microstructure of the composites consisted of a biodegradable Mg component in the form of filaments, elongated along the direction of extrusion, which were embedded within a permanent, bioinert Ti matrix. As the Mg content was increased, the discrete filaments became interconnected with each other and formed a continuous Mg network. Young's modulus (E) of the composites was reduced to 81 GPa, while other tensile mechanical properties were maintained at the values required for a dental implant material. The corrosion behavior of the Ti + Mg composites was studied during immersion in a Hank's balanced salt solution (HBSS) for up to 21 days. The elution of Mg pores formed at former Mg sites led to a further decrease of E to 74 GPa. The studied compositions showed that a new Ti + Mg metallic composite should be promising for load-bearing applications in endosseous dental implants in the future.

Titanium Ions Release from an Innovative Titanium-Magnesium Composite: an in Vitro Study.

BACKGROUND: The innovative titanium-magnesium composite (Ti-Mg) was produced by powder metallurgy (P/M) method and is characterized in terms of corrosion behavior. MATERIAL AND METHODS: Two groups of experimental material, 1 mass% (Ti-1Mg) and 2 mass% (Ti-2Mg) of magnesium in titanium matrix, were tested and compared to commercially pure titanium (CP Ti). Immersion test and chemical analysis of four solutions: artificial saliva; artificial saliva pH 4; artificial saliva with fluoride and Hank balanced salt solution were performed after 42 days of immersion, using inductively coupled plasma mass spectrometry (ICP-MS) to detect the amount of released titanium ions (Ti). SEM and EDS analysis were used for surface characterization. RESULTS: The difference between the results from different test solutions was assessed by ANOVA and Newman-Keuls test at p<0.05. The influence of predictor variables was found by multiple regression analysis. The results of the present study revealed a low corrosion rate of titanium from the experimental Ti-Mg group. Up to 46 and 23 times lower dissolution of Ti from Ti-1Mg and Ti-2Mg, respectively was observed compared to the control group. Among the tested solutions, artificial saliva with fluorides exhibited the highest corrosion effect on all specimens tested. SEM micrographs showed preserved dual phase surface structure and EDS analysis suggested a favorable surface bioactivity. CONCLUSION: In conclusion, Ti-Mg produced by P/M as a material with better corrosion properties when compared to CP Ti is suggested.

Effects of Wire EDM on the Microstructure of P/M Titanium Samples.

PURPOSE: Commercially pure titanium (CP Ti) has been recognized in dentistry for its biocompatibility, good mechanical properties and corrosion resistance. Conventional manufacturing processes can affect surface quality and result in poor bonding of dental ceramics to CP Ti. This is why powder metallurgy (P/M) and wire electro-discharge machining (WEDM) are being introduced in the manufacturing process. The aim of this study was to evaluate the effect of WEDM on the surface composition and microstructure of P/M CP Ti samples produced for bond strength testing according to ISO 9693. MATERIALS AND METHODS: Eight samples of P/M CP Ti, dimensions according to ISO 9693, were made using WEDM and divided in two groups (untreated and grinded). Microanalyses of chemical composition and microstructure of both groups were made using SEM, EDS and XDR. RESULTS: SEM and EDS analysis of untreated samples showed a thin layer on surfaces with fractures in it. Grinded samples showed homogenous structure with no layer and no fractures. XDR analysis showed high level of oxides on the surface of untreated samples, while after grinding only pure α-phase was found. CONCLUSION: WEDM is a suitable method of sample production for ISO 9693 if accompanied by grinding with silicon carbide papers P320-P4000.