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PubMed1990

Effect of a ZOE temporary cement on the bond strength of a resin luting cement.

This study was conducted to determine if a eugenol-based temporary cement affected the bond strength of a dual-cure cement to etched enamel. Dicor buttons were cemented to etched enamel surfaces after pretreatment with a non-eugenol containing cement, a eugenol containing cement and a control. This study concluded that shear bond strengths were unaffected by the temporary cement, provided the enamel surface was cleaned with pumice and etched with 37% phosphoric acid.

Acid Etching, Dental↗
PubMedDate not supplied

The influence of cement thickness on the tensile strength of two resin cements.

This study evaluated the influence of varying the cement thickness upon the tensile strength of nickel-chromium specimen cylinders cemented with Panavia Ex or Panavia 21 resin cements. A decrease in mean tensile strength of the resin-nickel-chromium alloy composite structure was recorded with an increasing cement thickness for both resin cements. Panavia 21 exhibited a significantly greater mean tensile strength than Panavia Ex at all cement thicknesses tested (P < .01).

Cementation↗
PubMed1994

A novel skeletal drug delivery system using self-setting calcium phosphate cement. 2. Physicochemical properties and drug release rate of the cement-containing indomethacin.

A novel drug delivery device based on a self-setting bioactive cement formed from tetracalcium phosphate and dicalcium phosphate has been developed and tested in vitro with indomethacin as a model drug. Equimolar mixtures of the calcium phosphate powders containing 2 and 5% of indomethacin were transformed into a hydroxyapatite after being mixed with a dilute phosphoric acid solution. X-ray diffraction and differential scanning calorimetry results suggested that indomethacin transformed into an amorphous form in the pores of the cement matrix as it hardened. In vitro drug release from cement pellets into a 0.1 mol/L phosphate buffer at pH 7.40 and 37 degrees C continued for > 3 weeks. Release from 2 and 5% drug-loaded cements followed the Higuchi model equation. The drug release profiles of 5% drug-loaded cements with different thicknesses (0.5, 1.0, and 1.5 g) overlapped up to 90% drug release, indicating that the drug concentration gradient in the pore was independent of the thickness of the cement as expected from the model equation.

Adsorption↗
PubMed1982

Cementing v. not cementing the Monk endoprosthesis.

In a retrospective study, 45 patients who had Monk hard-top endoprostheses inserted with cement because of fresh intracapsular fracture of the femoral neck, were compared with 61 patients with uncemented prostheses. The average age, age-distribution and the preoperative condition of the patients were well matched in the two groups. Thirty cemented and 39 uncemented cases were reviewed. The average time to follow-up was 29.9 months in the cemented group and 18.7 months in the uncemented group. A significantly lower mobility score and social performance score was found in the uncemented group when compared with the cemented one. No significant difference in the complaint of pain or in the range of movement of the hips was found between the two groups. On X-ray examination, no increased wear of the acetabular cartilage in the cemented group was found, but an increased tendency to loosening of the prosthesis was found in the uncemented group. In agreement with other studies it is concluded that the advantages to the patient with an intracapsular fracture of the femoral neck of having a cemented prosthesis outweigh the disadvantages.

Aged↗
PubMed1992

Influence of cement layer thickness on the adhesive bond strength of polyalkenoate cements.

The fracture toughness and yield stress values of model zinc polycarboxylate and glass polyalkenoate cements have been used to calculate plastic zone sizes. The size of the plastic zone at the crack tip in these materials has been used to predict whether cement layer thickness is likely to influence the adhesive bond strength. In the model zinc polycarboxylate cement studied, the plastic zone size was comparable to the cement layer thickness and had a pronounced influence on the shear bond strengths obtained. In contrast, the plastic zone sizes obtained for the glass polyalkenoate cements were much smaller and the shear bond strengths were found to be much less dependent on cement layer thickness.

Adhesiveness↗
PubMed1995

Blood perfusion and remodelling activity in canine tibial diaphysis after filling with a new bone cement compared to bone wax and poly(methyl methacrylate) cement.

Six dogs each had one tibia filled with standard poly(methyl methacrylate) (PMMA) bone cement and the contralateral tibia filled with a new methyl methacrylate-n-decyl methacrylate-isobornyl methacrylate (MMA-DMA-IBMA) bone cement (Boneloc) with lowered polymerization heat and monomer leakage. An additional six dogs each had one tibia filled with MMA-DMA-IBMA and the contralateral tibia filled with bone wax. There was a higher diaphyseal blood flow, measured with a microsphere technique, in the legs filled with MMA-DMA-IBMA than in those filled with PMMA. The wax-filled bones presented higher blood perfusion than those with MMA-DMA-IBMA. We found a tendency towards higher 99mtechnetium-labelled methylene diphosphonate (99mTcMDP) uptake, and autoradiograms revealed a tendency towards larger subperiosteal apposition and more blackening, both at the subperiosteal apposition and the cortex, in the bones filled with new bone cement in the first series, but in wax-filled bone in the second series. It is concluded that the new bone cement, compared to standard acrylic bone cement, seems to inhibit the vascular response and bone remodelling activity less, making earlier remodelling possible. However, the new bone cement still seems to inhibit bone blood perfusion compared to bone wax.

Animals↗
PubMed2006

The influence of capsule geometry and cement formulation on the apparent viscosity of dental cements.

OBJECTIVES: This work examines the influence of specific aspects of capsule design and cement formulation on the handling properties of the extruded glass polyalkenoate cement (GPC) pastes. METHODS: A commercial metal reinforced GPC, HiDense, and experimental GPCs were extruded using a tensometer at loads and rates maintained within end-user limits and the apparent viscosity of the cement paste was determined by applying Poiseuille's law. The influence of the extrusion procedure (mixing time and ram speed), capillary geometry (length and diameter) and cement composition (powder: liquid (P:L) ratio, tartaric acid content and poly(acrylic acid) molar mass) on the apparent viscosity of the cement paste was evaluated. RESULTS: The examined GPCs behaved as non-Newtonian, pseudoplastic materials and exhibited a yield stress. Variation of the geometry of the capsule capillary resulted in the apparent viscosity of HiDense increasing by 7% as the length increased from 5 to 15mm whilst halving the capillary diameter from 2 to 1mm resulted in a 63% decrease in the apparent viscosity and a 600% increase in the extrusion load. The apparent viscosity of the experimental GPCs was increased by an increase in the P:L ratio and, in general, by the PAA molar mass, whilst the concentration-dependent effect of (+)-tartaric acid (TAA) indicates a working time dependence on TAA content. CONCLUSIONS: Using this approach optimisation of the rheological properties can be achieved by manipulation of the capsule design and cement formulation due to the dependency of the apparent viscosity on the capillary diameter, TAA content, P:L ratio and poly(acrylic acid) molar mass.

Chemistry, Pharmaceutical↗
PubMed2005

VersaBond bone cement prospective randomized study of the clinical properties of a new bone cement in total knee replacement.

VersaBond is a newly developed bone cement. To investigate its clinical performance, VersaBond was compared to Palacos R in a prospective randomized study in total knee replacement. Fifty-nine patients (61 knees) undergoing total knee replacement were randomized to either VersaBond or Palacos R bone cement and followed for 24 months using radiostereometric analysis (RSA). Up to 2 years there were no significant differences in clinical performance between the two cements. The mean/median values for implant migration were very similar for the two bone cements, as were the dispersion, and distribution of outliers. Also the proportion "stable" and "continuously migrating" implants was similar between the two cements. The result of this study indicates that VersaBond bone cement will perform at least equally as well as Palacos R in total knee replacement as regards as aseptic loosening.

Aged↗
PubMed2002

Residual stress effects on fracture energies of cement-bone and cement-implant interfaces.

The effects of residual stresses, which are caused by the temperature difference arising after polymerisation of bone cement, on the fracture energies of cement bone and cement-implant interfaces have been examined by using both experimental and numerical works. Only fracture loads of the test specimen having interfacial cracks have been measured in the experimental stage. The values of fracture loads and temperature difference after polymerisation have been applied to finite element models of the test specimens to calculate critical J-integral values of these both interfaces in the numerical stage. In addition, fracture energies of bone and cement, have been obtained by experimentally, using three-point bending test method The results have shown that residual stresses can produce changes in the fracture energies of these bimaterial systems, especially in cement implant interface and J(Ic) values of interfaces are considerably smaller than the experimentally determined J(Ic) values of cement and bone.

Biocompatible Materials↗
PubMed2000

A stem design change to reduce peak cement strains at the tip of cemented total hip arthroplasty.

A series of 3-dimensional finite element models was created to assess different designs of the tip of the stems of cemented femoral components of total hip arthroplasty that would decrease the peak axial tensile cement strains developed near the tip. Features of stem design that would facilitate positioning the femoral component in a neutral position centered in uniform cement mantle of adequate thickness also were evaluated. These studies showed that a stem that had a narrow tip profile that would accept an externally applied polymethyl methacrylate centralizer shaped similar to a napkin ring and had a gradual transition zone to join the body of the implant achieved these objectives. Such a combination resulted in the reduction of the peak axial strains to less than half the magnitude of the peak strains around a conventional tip (830 vs 1,868 microstrain). The reduction in peak axial strains was to one third the magnitude of the strains developed adjacent to a stem with a hole drilled into the tip to accept the commonly used fin-type polymethyl methacrylate centralizer (830 vs 2,466 microstrain). These goals were achieved because a stem that is designed to accept a napkin ring-style centralizer i) has a lower bending stiffness at the tip of the implant, ii) allows room for a thicker cement mantle, and iii) avoids creating a stress riser adjacent to the edge of the drill hole. The peak cement strains adjacent to a stem of this design are well below the endurance limit of cement as long as the transition zone where the narrow tip meets the body of the implant is gradual.

Biomechanical Phenomena↗
PubMed2001

The effect of femoral prosthesis design on cement strain in cemented total hip arthroplasty.

Finite element studies show that the highest cement stresses are located at the most proximal and distal ends of the prosthesis. In vitro biomechanical and histologic analyses of autopsy-retrieved cemented femoral components show these areas to be associated with cement-prosthesis debonding. In this study, cement strains were measured in 2 geometrically different femoral stems in paired cadaver femora: A straight, collared, moderately tapered stem (Centralign) was compared with an anatomically curved, collarless, dramatically tapered stem (Scientific Hip Prosthesis [SHP]). Results showed that the maximum strain and the overall strain profile differed between the 2 stems. The Centralign had peak strains located at the most proximal gauge positions, whereas the peak strains of the SHP were located around the middle of the femoral stem. Minimization of cement strain, especially at the crucial proximal and distal areas of the stem, by altering component design may be able to reduce cement-prosthesis debonding and improve clinical results.

Arthroplasty, Replacement, Hip↗
PubMedDate not supplied

[Value of scintigraphy in aseptic loosening of cemented and cement-free hip endoprostheses].

Scintigraphic findings in 24 cemented and 25 cement-free prostheses were compared to determine the information value of scintigraphy in the diagnosis of loosening of total hip replacements. The scintigraphic findings were evaluated on the basis of specificity (indicates the percentage of complaint-free hips in which the scan is also negative) and sensitivity (indicates the percentage of clinically loosened hips in which the scan is also positive) in relation to the clinical diagnosis. For the cemented prostheses, the specificity value was 58% and the sensitivity 66%. The figures for the cemented prostheses were 15% and 83% respectively. On the basis of the authors' results it may be inferred that for cemented hip replacements the scan represents a valuable supplement to clinical and radiologic diagnosis. For the cement-free type of prostheses used by the authors, neither the scan nor radiology are suitable for diagnosing loosening; with these prostheses the findings obtained by clinical examination are the most reliable.

Bone Cements↗
PubMed2003

Comprehensive biocompatibility testing of a new PMMA-hA bone cement versus conventional PMMA cement in vitro.

For more than 50 years PMMA bone cements have been used in orthopaedic surgery. In this study attempts were made to show whether cultured human bone marrow cells (HBMC) show an osteogenetic response resulting in new bone formation, production of extracellular matrix (ECM) and cell differentiation when they were cultured onto polymerized polymethylmethacrylate (PMMA)-hydroxyapatite (HA), conventional PMMA bone cement being taken as reference. Biocompatibility parameters were collagen-I and -II synthesis, the detection of the osteoblast markers alkaline phosphatase (ALP) and osteocalcin, the number of adherent cells and the cytodifferentiation of immunocompetent cells. Cement surface structure, HA stability in culture medium and chemical element analysis of specimens were considered. Fresh marrow cells were obtained from the human femora during hip replacement. Incubation time was up to ten weeks. We used atomic forced microscopy (AFM) and scanning electron microscopy (SEM) for cement specimen analysis. Fluorescent activated cell sorter (FACS), immunohistochemical staining. SEM and light microscopy (LM) served us to judge the cellular morphology. Products of the extracellular matrix were analyzed by protein dot blot analysis, SEM energy dispersive X-ray analysis (SEM-EDX) and Ca2+/PO(4)3- detection. HA particles increased the osteogenetic potential of PMMA bone cement regarding the cellular production of collagen, alkaline phosphatase (AP), the number of osteoblasts and the cellular differentiation pattern in vitro. Both tested cements showed good biocompatibility in a human long-term bone marrow cell-culture system.

Bone Cements↗
PubMed1993

The bone-cement interface: histological observations on the interface of cemented arthroplasties within the immediate and late phases.

Undecalcified specimens of cemented arthroplasties obtained during the early and late phases were studied. On the tenth postoperative day, there was excellent interlocking of the cement with the soft and hard tissues of the bone: there was no necrosis of the bed of the implant: a neutrophilic and macrophagic inflammatory response, where present, was mild and focal. Samples of the bone-cement interface of well fixed components obtained (at autopsy or by biopsy) many years after implantation revealed a thin and quiescent fibrous interfacial membrane alternating with bone and osteoid (that is, segmental osseointegration) or a cartilaginous layer abutting on the cement. It is concluded that, firstly, modern cementation techniques are not associated with extensive necrosis of the underlying bone in the immediate postoperative period; secondly, monomeric and polymeric methylmethacrylate as such is not toxic to the tissues; and, thirdly, acrylic cement is osseointegrated when motion at the interface is at its minimum.

Aged↗
PubMed1992

Mixing does not improve mechanical properties of all bone cements. Manual and centrifugation-vacuum mixing compared for 10 cement brands.

Contemporary mixing methods--centrifugation, vacuum mixing with or without precompression--were compared with manual mixing by testing strength characteristics in accordance with a proposed revision of the international standard for bone cements as applied to 10 cement brands. Simplex brands and low-viscosity cements were the strongest, and were not improved by any of the vacuum-mixing procedures. Centrifuging was found unsuitable for low-viscosity cements. Without attaining the strength of the former, the cements best suited for auxiliary mixing methods were CMW-1 and Palacos brands, which improved 6-11 percent by either of the methods. The Sterivac system was generally found unacceptable, because about 20 percent of a cement package was retained in the mixing gear, and the application of precompression had no additional effect on compressive and bending strengths.

Acrylic Resins↗
PubMed2004

Cement penetration using a tibial punch cement pressurizer in total knee arthroplasty.

This study describes a new tibial cement punch pressurizer to enhance cement penetration into the metaphyseal cancellous bone of the tibial plateau. Thirty knees of 15 patients undergoing simultaneous bilateral total knee arthroplasty (TKA) were randomly selected to receive the tibial cement punch pressurizer on one side, with the opposite side serving as control. Using computerized and radiographic evaluation of both knees 2 weeks postoperatively, the punch pressurizer achieved 132 times better penetration of the cement. The tibial punch cement pressurizer offers a simple technique to provide reliable cement penetration and tibial component fixation in TKA.

Arthroplasty, Replacement, Knee↗
PubMed1992

[Intraoperative complications during cementation of hip arthroplasty. Avoiding air embolization during cementation].

Circulatory collapse is known to occur during cementation of hip arthroplasty. The pathogenesis is multifarious, but the most important cause is believed to be formation of air embolism during insertion and cementation of the femoral component followed by air embolism in the heart. Inserting the cement retrogradely with a cement gun following distal plugging of the femoral cavity with spongiosa and using a plastic catheter for suction drainage reduces the air embolisation. Cement producing as little heat as possible during the setting should be used. Maintaining anaesthesia with N2O air embolism and should be avoided during and after cementation. Pre- and intraoperative care of the patient's circulation and oxygenation is essential. The use of pulse oximetry, capnography and precordially recorded Doppler ultrasound are recommended for monitoring air embolism.

Anesthesia, Inhalation↗
PubMed1981

[Studies on the setting reaction of the zinc phosphate dental cement (3)--quantitative analysis for consumed zinc oxide through setting reaction of the cement (author's transl)].

Zinc oxide powder of zinc phosphate cement for dental use was mixed with various phosphoric acid for cement liquid contained Al3+ and not, and zinc oxide in each cement after setting was determined quantitatively Then, consumed zinc oxide through setting reaction was calculated. When zinc oxide powder was mixed with cement liquid contained Al3+, consumed zinc oxide through setting reaction was approximate half quantity of it mixed with liquid contained no Al3+. This result show that setting reaction of zinc phosphate dental cement is the interaction Al3+ and H2PO4- in cement liquid rather than simple neutralizing reaction, ZnO+H3PO4 or ZnO+H2PO4-.

Aluminum↗