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At least 73 records · Page 4Linked to original sources
PubMed2006

[Surface pretreatment for prolonged survival of cemented tibial prosthesis components: full- vs. surface-cementation technique].

Aseptic loosening of tibial components due to degradation of the interface between bone cement and metallic tibial shaft component is still a persistent problem, particularly for surface-cemented tibial components. The surface cementation technique has important clinical meaning in case of revision and for avoidance of stress shielding. This study was done to prove crack formation in the bone cement near the metallic surface when this is not coated. We propose a newly developed coating process by SiOx-PVD layering to avoid crack formation. A biomechanical model for a vibration fatigue test was done to prove that crack formation can be significantly reduced in the case of coated surfaces. It was found that coated tibial components showed a highly significant reduction of cement cracking near the metal/bone cement interface (p < 0.01) and a significant reduction of gap formation in the metal-to-bone cement interface (p < 0.05). Coating dramatically reduces hydrolytic- and stress-related crack formation at the prosthesis metal/bone cement interface. This leads to a more homogenous load transfer into the cement mantle which should reduce the frequency of loosening in the metal/bone cement/bone interfaces. With surface coating of the tibial component it should become possible that surface-cemented TKAs reveal similar loosening rates as TKAs both surface- and stem-cemented. This would be an important clinical advantage since it is believed that surface cementing reduces metaphyseal bone loss in the case of revision and stress shielding for a better bone health.

Arthroplasty, Replacement, Knee↗
PubMed1993

The effect of post adaptation in the root canal on retention of posts cemented with various cements.

This laboratory study compared the retention of prefabricated posts in well-fitting and loose-fitting post canals using different cement materials. Eighty-three human teeth were prepared for post placement. One of zinc phosphate cement, polycarboxylate cement, glass ionomer cement or resin cement was used to cement each post in place. A tensile force was applied to remove each post and the separation force was recorded. Posts cemented with the resin cement were the most difficult to dislodge. Posts cemented into loose-fitting canals exhibited greater resistance to dislodgment than posts cemented into well-fitting canals irrespective of the type of cements used.

Dental Cements↗
PubMed2000

Prevention of fibrous layer formation between bone and adhesive bone cement: in vivo evaluation of bone impregnation with 4-META/MMA-TBB cement.

We have studied a new adhesive bone cement, that consists of 4-methacryloyloxyethyl trimellitate anhydride (4-META) and methylmethacrylate (MMA) as monomers, tri-n-butyl borane (TBB) as the initiator, and polymethylmethacrylate powder (4-META/MMA-TBB cement). This cement has shown remarkable adhesive properties to bone in vitro. In this study, we assessed the interface in vivo periodically. The femora of rabbits were fenestrated and filled with either the 4-META/MMA-TBB cement or a conventional polymethylmethacrylate cement. The animals were killed after 1, 4, 12, and 24 weeks to analyze the interface by optical microscopy and transmission electron microscopy. Optical microscopic examinations showed that the cured 4-META/MMA-TBB adhesive cement bonded to bone directly for 24 weeks, whereas a fibrous tissue layer was observed between the bone and cured conventional cement at 12 weeks after the operation. The transmission electron microscopy views of 4-META/MMA-TBB cement bonded to bone demonstrated a unique "hybridized bone" with the cement in the subsurface of the substrate in every case. The formation of the hybridized bone indicates the bonding mechanism of the adhesive cement to bone, which prevents the fibrosis intervention between bone and cement. These results suggest that the biomechanical and adhesive properties of 4-META/MMA-TBB cement make it a useful bone-bonding agent in orthopedic surgery.

Animals↗
PubMed1993

Stress transfer at the femoral bone/bone cement interface as a function of the cement thickness.

When a cement canal prosthesis is used as the femoral component in total hip replacement (THR), the penetration depth of the bone cement can be varied according to the cement implantation pressure. Using experimental data which give a relation between the pressure applied to the cement at implantation and the resulting shape of the cement layer, a three-dimensional finite element study was performed to calculate the stress distribution at the bone/bone cement interface. The calculations show that the interface stresses increase with increasing depth of penetration by the cement layer. The explanation of this effect is that as the bone cement penetrates further into the cancellous bone, the cancellous bone is stiffened and can no longer act as a soft interposition between cortical bone and bone cement. From these results and from the clinical requirement that as little bone as possible be destroyed in any kind of allo-arthroplasty, we conclude that the penetration depth of bone cement into cancellous bone in THR should be minimized to the depth necessary in order to achieve sufficient initial stability of the implant. The results show that a cement-canal prosthesis meets these requirements if a cement implantation pressure of 1.0 bar is used.

Bone Cements↗
PubMed2007

The role of cement viscosity on cement-bone apposition and strength: an in vitro model with medullary bleeding.

We compared the mechanical and morphological characteristics of cement-bone structures created with either standard- or low-viscosity cement using a human cadaver model that simulated intramedullary bleeding. The goal is to determine if the viscosity of the cement would affect the strength of the cement-bone interface and the degree of apposition between the cement and bone. The tensile strength of cement-bone constructs with standard-viscosity cement (2.42 +/- 1.55 MPa) was 21% stronger than with low-viscosity cement (2.00 +/- 1.51 MPa, P = .034). Cement-bone apposition was positively correlated (r2 = 0.29, P <. 0001) with the strength of the interface. There was 15% greater apposition between cement and bone (P = .036) for standard-viscosity cement. Low-viscosity cement may be less effective in displacing bone marrow and in preventing hemodynamic backflow, resulting in less apposition and a weaker interface.

Aged, 80 and over↗
PubMed1997

Tensile strength of the cement-bone interface depends on the amount of bone interdigitated with PMMA cement.

An experimental investigation was performed to (1) determine the general mechanical behavior and in particular, the post-yield behavior of the cement-bone interface under tensile loading, (2) determine where interface failure occurs, and (3) determine if the mechanical properties of the interface could be related to the density of bone at the interface and/or the amount of cement-bone interdigitation. Seventy-one cement-bone test specimens were machined from human proximal femurs that had been broached and cemented using contemporary cementing techniques. The amount of cement-bone interdigitation was documented and the quantitative computed tomography equivalent mineral density (QCT density) of the bone with cement was measured. Specimens were loaded to failure in tension under displacement control and exhibited linear elastic behavior with some reduction in stiffness until the peak tensile stress was reached (1.28 +/- 0.79 MPa). A substantial amount of strain softening (negative tangent stiffness) with an exponential-type decay was found after the peak stress and continued until there was complete debonding of the specimens (at 0.93 +/- 0.44 mm displacement). Interfacial failure most often occurred at the extent of cement penetration into the bone (56% of specimens) or with small spicules of cement left in the bone (38% of specimens). The results showed that the post-yield tensile behavior contributes substantially to the energy required to cause failure of the cement-bone interface, but the post-yield behavior was not well correlated with the amount of interdigitation or density of bone. Linear regression analysis revealed a moderate (r2 = 0.499, p < 0.0001) positive relationship between the tensile strength of the cement-bone interface and the quantity of bone interdigitated with the cement.

Adult↗
PubMed1998

Effect of geometrical cement size on in vitro and in vivo indomethacin release from self-setting apatite cement.

The relationship between in vitro and in vivo indomethacin (IMC) release from a self-setting bioactive apatite cement and cement size were investigated. Differently sized apatite cements (total weight, 500 mg); either 64 of the small size (2 mm diameter x 2 mm thickness), sixteen of the medium size (4 mm x 2 mm) or one of the large size (15 mm x 2 mm) were obtained from cement bulk powder containing tetracalcium phosphate, dicalcium phosphate dihydrate and hydroxyapatite. In vitro IMC release from the 1, 2 and 5% drug-loaded apatite cement systems in simulated body fluid (SBF) (pH 7.25) at 37 degrees C increased with increasing concentrations of IMC and with decreasing geometrical size of the cement. The plots of in vitro IMC release per unit area against the square root of time increased with increasing IMC concentrations, but not with decreasing geometrical size of the cement. After subcutaneous (s.c.) implantation of differently sized 1% IMC-loaded cements in male Wistar rats, the plasma IMC concentration and the area under the curve increased with decreasing cement diameter. The in vivo IMC release profiles of the cement were deconvoluted from the plasma IMC profiles after s.c. administration of IMC solution. The plots of in vivo IMC release per unit area against the square root of time suggested that the initial release from all 1% drug-loaded cements was very rapid, slowed after one day, but continued for over two weeks. The relationship between the in vitro release in SBF and the in vivo release in rats of IMC-loaded cements was linear.

Animals↗
PubMed2004

Cement penetration and stiffness of the cement-bone composite in the proximal tibia in a porcine model.

PURPOSE: To assess the stiffness of the cement bone composite and the depth and uniformity of cement penetration into the surface of the tibial component during total knee reconstruction in a porcine model. METHODS: The effectiveness of 3 protocols were compared: 2 commonly used cementing techniques-finger-packing of cement on the cut surface followed by impaction, and coating of the undersurface of the prosthesis with cement followed by impaction-and a new method using a tibial cement-pressurising device. Cement penetration was measured by computed tomography; stiffness was determined by hydraulic penetration testing. RESULTS: Cement penetration at a depth of 1 mm was significantly greater following coating the undersurface of the prosthesis than following finger-packing (p=0.008). There was no significant difference at deeper levels or between the tibial-pressurising device group and either of the 2 other groups at any level (p>0.3 in all cases). Differences in surface stiffness by tibial plateau region were found in tibiae that had been cemented using finger-packing and in those that had had their undersurface coated, but not in tibiae that had been cemented using the tibial-pressurising device. CONCLUSION: The tibial cement-pressurising device eliminated regional differences in stiffness seen with other cementing methods. Elimination of these differences by using this device should reduce micromotion and the incidence of aseptic loosening of tibial base plates in total knee arthroplasty.

Analysis of Variance↗
PubMed2000

Bond strength of brackets cemented with light-cured glass-ionomer cements to contaminated enamel.

PURPOSE: To examine the effect of contamination on the bond strength of orthodontic brackets cemented with either a commercial (Fuji Ortho LC) or an experimental light-cured glass-ionomer cement to enamel, and the effect of etching times on the bond strength. MATERIALS & METHODS: Simulated metal brackets were applied with the cements to bond polished and etched (37% phosphoric acid) bovine enamel with and without contamination by water, human saliva, and blood. After 1-day water immersion, the shear bond strengths were measured. The fractured surfaces were examined using SEM. Additional tests were conducted on: (1) the Knoop hardness of the contaminated cements, (2) the HEMA composition of the cements, (3) the viscosity of the cements, and (4) the intensity of transmitted visible light through the contaminants. The results were compared by ANOVA and Duncan's tests at P=0.05. RESULTS: Water and saliva reduced the bond strength to polished and etched enamel, except for the bond strength of Fuji Ortho LC to polished enamel. The blood contamination produced poor bond strengths to polished and etched enamel. The experimental cement showed higher bond strengths to polished enamel with water and saliva contamination than Fuji Ortho LC. The bond strength of the experimental cement to etched enamel with and without contamination were comparable to those of Fuji Ortho LC. SEM micrographs revealed that the specimens exhibiting high bond strengths to polished and etched enamel mainly had cement-enamel interface failure and cement-metal mesh interface failure, respectively. Fuji Ortho LC had higher HEMA concentration than the experimental cement. The highest viscosity was measured with blood, followed by saliva and water. Blood contamination, showing the highest attenuation of the light intensity, reduced Knoop hardness of the experimental cement and Fuji Ortho LC.

Acid Etching, Dental↗
PubMedDate not supplied

Acetabular cement compactor. An experimental study of pressurization of cement in the acetabulum in total hip arthroplasty.

To improve cement fixation of acetabular components for total hip arthroplasty, a new instrument, the acetabular cement compactor, was devised. Measurements in human cadaveric acetabula show that the cement intrusion pressure is significantly and substantially increased by the acetabular cement compactor. The depth of cement intrusion is greatly improved when the compactor is used, as compared with finger packing. The impression casts of the acetabular cement are superior when the cement is inserted using the acetabular cement compactor. Occlusion of the orifice of the keying holes permits generation of high pressure in the cement within them. This can be achieved by using the keying-hole seal. Pressurization of the acetabular cement used in the dough stage by the acetabular cement compactor substantively improves acetabular cement fixation.

Acetabulum↗
PubMed2003

The effect of cement type and mixing on the bi-axial fracture strength of cemented aluminous core porcelain discs.

OBJECTIVES: Luting agents in current use include zinc phosphate, zinc polycarboxylate, conventional glass-ionomer, resin-modified glass-ionomer and resin composite cements. Dental cements may be used in practice with a wide range of mixing ratios. Accordingly, the impact of cement type and mixing on the strength of alumina reinforcing porcelain was investigated. METHODS: Standard Vitadur-N core porcelain disc specimens were coated with different cement types of varying mixing ratios to produce a luting thickness. Sets of 25 coated specimens were stored at 37+/-1 degrees C for 24h prior to testing. Mean fracture strengths, standard deviations and associated Weibull Moduli (m) were determined using bi-axial fracture (ball-on-ring). RESULTS: The strength data for porcelain discs coated with different cement types manipulated at the consistency indicated for luting all-ceramic crowns showed little variation in magnitude and consistency. The plots of survival probability against strength for specimens coated with acid-base cements appear to develop a slight asymmetry at the lower values of strength. This effect was more pronounced for acid-base cements prepared at mixing ratios below that recommended for luting purposes. SIGNIFICANCE: The corrosive acidic environment of acid-base cements may have extended pre-existing flaws in the porcelain discs producing the asymmetry in the survival distributions. Resin composite cements appear to enhance the strength of the porcelain disc specimens possibly by healing the surface imperfections. This may increase their scope of application over acid-base cements to include the luting of all-ceramic restorations.

Aluminum Oxide↗
PubMed2004

Influence of mixing method on the cement temperature-mixing time history and doughing time of three acrylic cements for vertebroplasty.

Acrylic cements are increasingly being used to augment osteoporotic vertebrae in a procedure called vertebroplasty. Two significant factors that may complicate the use of acrylic cements are: (a) short handling time, which may result in insufficient filling of the vertebra; and (b) exothermic setting (curing) behavior, which may result in thermal damage of the surrounding tissue. It has been previously reported that mixing the cement components under oscillation, as compared to manual mixing, increases the handling time. More specifically, it seems that oscillatory mixing slows down the cement polymerization process and, consequently, widens the time window during which cement is injectable. However, the effect of oscillatory mixing on the exothermic setting behavior of cement undergoing polymerization has not been examined. In this study, the exothermic setting behavior of three commercially available acrylic cements--Antibiotic Simplex, DP-Pour&trade, and Vertebroplastic--were examined for both manual and oscillatory mixing methods. For each combination of cement and mixing method, the parameters that were measured were the exothermic setting curve (and hence the cement setting temperature and setting time) and the cement doughing time. It was found that oscillatory mixing had no significant effect on any of these parameters. Based on the results of this study, it can be concluded that, for the tested cements, the setting process is a reaction-controlled process rather than a diffusion-controlled one. Clinically, this implies that oscillatory mixing may be used to increase the working period for acrylic cements without increasing the risk of thermal damage to surrounding tissue.

Bone Substitutes↗
PubMed2006

Evaluation of stainless steel crowns cemented with glass-ionomer and resin-modified glass-ionomer luting cements.

PURPOSE: To evaluate in vitro and in vivo conditions of stainless steel crowns (SSC) cemented using one luting glass-ionomer cement (Aqua Meron) and one luting resin-modified glass-ionomer cement (Vitremer). METHODS: In the in vitro part of this study, retentive properties of SSCs cemented using Aqua Meron and Vitremer on extracted primary first molars were tested. In addition, two specimens of each group were used to evaluate the tooth hard tissue-cement, within the cement itself, cement-SSC, and tooth hard tissue-cement-SSC under scanning electron microscope (SEM). In the in vivo part of this study, 152 SSCs were placed on the first or second primary molars of 86 children, and cemented using either Aqua Meron or Vitremer. The crowns were examined for retention. In addition, the clinical views of the crowns were recorded with an intraoral camera. RESULTS: No significant difference was found between the mean retentive forces of Aqua Meron and Vitremer (P> 0.05). SSCs cemented with Aqua Meron and Vitremer had an average lifespan of 26.44 and 24.07 months respectively. Only one (0.66%) of 152 SSCs was lost from the Aqua Meron group during post-cementation periods. Nineteen of the 152 SSCs (12.5%) had dents or perforations.

Cementation↗