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PubMed2003

Sustainable development of the cement industry and blended cements to meet ecological challenges.

The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and--at the same time--uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

Construction Materials↗
PubMed2005

Micromotion in cemented rotating platform total knee arthroplasty: cemented tibial stem versus hybrid fixation.

INTRODUCTION: Improving the longevity and reliability of cemented total knee arthroplasty (TKA) remains a major step to achieve. It is still unclear, whether a cemented tibial stem reduces micromotion of the tibial tray and produces therefore a better initial stability or not. The higher conformity of rotating platform design and the possible rotary forces to the tibial platform may produce higher micromotion when the tibial stem remains cementless (hybrid fixation). MATERIALS AND METHODS: An in vitro study was performed using the PFC mobile bearing tibial tray (DePuy, Warswa, IN, USA) to test the hypothesis that the addition of cement surrounding the tibial stem reduces micromotion of the tibial tray in cemented TKA with mobile bearing design. Ten tibial trays with mobile design were implanted in sawbones with a 3-mm cement mantle beneath the baseplate of the tibial tray and with or without the cemented stem. Tibial trays were loaded additionally in the ventral, lateral, medial and posterior positions with 2,500 N using the Zwick Z010 instrumentation and HBM pick up Hottinger Baldwin. RESULTS: In this study, a significant increased mean maximum liftoff was found when only cementing the tibial baseplate (hybrid fixation), compared to the fully cemented tibial tray (P<0.02). CONCLUSION: In conclusion, the stem of mobile bearing tibial components should be cemented to provide increased micromotion and earlier loosening.

Arthroplasty, Replacement, Knee↗
PubMed2006

Inferior stability of a biodegradable cement plug. 122 total hip replacements randomized to degradable or non-degradable cement restrictor.

INTRODUCTION: Modern cementing technique demands high intramedullar cement pressure to create an optimum fixed cement support of the femoral stem. Pressure resistant, stable closure of the canal therefore is absolutely necessary. Biodegradable cement restrictors, if corresponding to above mentioned attributes, could be of immense advantage in case of potential revision surgery. MATERIAL AND METHODS: A prospective, randomized trial was performed on a consecutive series of 130 patients who underwent primary cemented total hip arthroplasty due to hip arthrosis to compare a degradable cement restrictor and a non-degradable cement restrictor in their ability to resist distal migration during stem insertion. RESULTS: The median cement plug length measured 27 mm (range -12 to 126 mm, 95% confidence interval (CI) 20-33 mm) in the biodegradable restrictor group and 15 mm (range 0-61 mm, 95% CI 12-18 mm) in the non-degradable restrictor group (P=0.003). A significant effect of the relationship between the difference of restrictor size and the diameter of the femoral canal on length of cement distal of the tip of the stem in between the two groups was evident (P=0.031). CONCLUSION: The results indicate insufficient intramedullary plug fixation of the degradable restrictor probably due to the elastic material properties which also may lead to inferior precision in restrictor size choice.

Absorbable Implants↗
PubMed1994

Effect of increasing cement space on cementation of artificial crowns.

In this study, the effect of cement space on cementation with an artificial crown and machined die was investigated. Spacing was varied in increments of 10 microns, and the dies were cemented in the crown by a force of 25 N with either zinc phosphate cement or a silicone fluid. Separation of the artificial crown and die was measured relative to complete seating without cement. A silicone fluid of 10.6 Pa seconds viscosity was used first with seating times from 168 seconds (SD 8.8 seconds) with no spacing to 2.1 seconds (SD 0.07 second) with 50 microns spacing. Unless 40 microns of spacing was used, the zinc phosphate cement did not allow the artificial crown to seat to less than 30 microns seating discrepancy, and it was suggested that particles in the cement caused this effect. The seating discrepancy ranged from 368 microns (SD 10 microns) without spacing to 29 microns (SD 1 micron) with 50 microns spacing. It was concluded that providing cement space substantially facilitated seating of crowns during cementation.

Cementation↗
PubMed1997

Enhanced strength in cemented stem fixation using adhesive acrylic cement as a metal coating material.

One cause of aseptic loosening of cemented total hip arthroplasty is mechanical weakness at the interface between the metal stem and the cured bone cement. Adhesive acrylic bone cement containing 4-methacryloyloxyethyl trimellitate anhydride (4-META) was applied as a metal coating material to increase the strength of the cemented fixation. The 4-META cement has 2-3 times greater tensile bond strength to metals than does commercial acrylic bone cement. The shear strength of the coated metals fixed with bone cement was approximately 4 times greater in SUS-304 and 3 times greater in titanium (Ti) alloy than those of uncoated metals, and this strength did not decrease after 1 week's immersion in saline. The coating process using the 4-META cement can be performed at normal room temperature, so that metal stems for bone cement fixation could be coated during the course of an operation resulting in potentially improved results of total hip arthroplasty.

Biocompatible Materials↗
PubMed1997

Integrated system for preparation of bone cement and effects on cement quality and environment.

We developed a prepacked mixing system for the preparation of bone cement. The system is based on mixing and collection of bone cement under a vacuum and serves as both the storage and mixing device for the cement components, thereby minimizing the exposure of the operating staff to the monomer and the risk for contamination of the cement during preparation. We evaluated the system using Palacos R and Simplex P. The cement produced was compared with cement obtained from a commercially available mixing system. Temperature evolution during curing, handling characteristics, density, and porosity of the cement obtained were analyzed. The results showed that the experimental system produces cement with physical properties (i.e., setting times and temperature, porosity, and density) equal to or better than those obtained with commercially available systems. Reducing the amount of monomer in the experimental system led to a reduction of the curing temperature without compromising the physical properties of the cements.

Biocompatible Materials↗
PubMed1994

A novel skeletal drug-delivery system using self-setting calcium phosphate cement. 4. Effects of the mixing solution volume on the drug-release rate of heterogeneous aspirin-loaded cement.

The effect of the mixing solution volume was investigated on the in vitro drug-release rate of a novel drug-delivery device based on a self-setting bioactive calcium phosphate cement containing aspirin as a model drug. Equimolar mixtures of metastable calcium phosphate powders containing various proportions (3-40 w/w %) of seed hydroxyapatite crystals transformed into hydroxyapatite after being mixed with dilute phosphoric acid. The drug release from cement pellets in vitro into a 0.1 mol/L phosphate buffer at pH 7.40 and 37 degrees C by the rotating disk method continued for more than 1 week. The drug-release rate from the cement increased with increasing volumes of mixing solution. The relationship between the liquid/powder ratio and the porosity of the cement was a straight line, indicating that the cement porosity depended on the amount of the mixing solution, but was independent of the amount of seed crystals. Drug release from the cement followed the modified Fick's law, with the rate increasing with the amount of mixing solution, since the porosity depended on the amount. The tortuosity of the cements was estimated from the modified Fick's equation, and the relationships between the drug release rate and the tortuosity of the pore in the drug-loaded cement in the plots were nonlinear. The results suggested that the drug-release rates from the cement were controlled by the drug diffusion in the pores.

Aspirin↗
PubMed2005

Probabilistic analysis of the influence of the bonding degree of the stem-cement interface in the performance of cemented hip prostheses.

The long-term behavior of the stem-cement interface is one of the most frequent topics of discussion in the design of cemented total hip replacements, especially with regards to the process of damage accumulation in the cement layer. This effect is analyzed here comparing two different situations of the interface: completely bonded and debonded with friction. This comparative analysis is performed using a probabilistic computational approach that considers the variability and uncertainty of determinant factors that directly compromise the damage accumulation in the cement mantle. This stochastic technique is based on the combination of probabilistic finite elements (PFEM) and a cumulative damage approach known as B-model. Three random variables were considered: muscle and joint contact forces at the hip (both for walking and stair climbing), cement damage and fatigue properties of the cement. The results predicted that the regions with higher failure probability in the bulk cement are completely different depending on the stem-cement interface characteristics. In a bonded interface, critical sites appeared at the distal and medial parts of the cement, while for debonded interfaces, the critical regions were found distally and proximally. In bonded interfaces, the failure probability was higher than in debonded ones. The same conclusion may be established for stair climbing in comparison with walking activity.

Cementation↗
PubMed1998

Effect of cement modulus on the shear properties of the bone-cement interface.

Shear tests of the bone-cement interface were performed in vitro using two types of bone cement, standard poly(methyl methacrylate) (PMMA) and a reduced-modulus formulation with poly(butyl methacrylate) beads in a methyl methacrylate matrix (PBMMA). Tests of shear properties were also calculated on cancellous bone and on each cement alone. The tests were done using the Iosipescu shear test method which generates a pure shear force in a zero-moment section of the specimen. With this method, shear properties can be determined at specified locations throughout the specimen. Tests were performed across the entire interface region, specifically in the middle of the region of cement bone interdigitation and at both the bone and cement ends of that region. Ultimate shear strengths and shear moduli were calculated. The shear modulus of the PBMMA is less than 3% that of PMMA. The strength and modulus of cancellous bone had a direct relation to the apparent density of the bone, as did the strength and modulus of the bone-composite interface and the composite region. Strength and modulus were dictated by the bone at the bone-composite interface, and by the cement at the cement composite interface. Through the composite region, the stiffer of the two materials in the composite determined the shear properties. Reduced-modulus bone cement substantially decreases the interfacial shear stresses at the bone-cement interface which should decrease the rate of resorptive bone remodelling at this interface.

Animals↗
PubMed2001

The use of handheld cement sample as a guide to the setting of in situ cement mantle.

During cemented joint arthroplasties, it is necessary to monitor the hardening of the cement to know when it is soft enough to allow insertion of the prosthesis but viscous enough to maintain bone interlock. Most often, a small piece of cement is left out and checked for hardening. These cement pieces are exposed to different fates, which include being held in the hand, held between fingers and kneaded, and left on the instrument table. The value of any of these techniques for predicting the cement's hardening has not been investigated formally. During 9 total hip arthroplasties, polymethyl methacrylate bone-cement was used in cementing the femoral component. Three 1-cm(3) samples collected from each operation site were exposed to the aforementioned 3 different conditions. The fingertip-held and kneaded cement specimens most closely predicted the time to setting of the cement mantle at the operation site.

Adult↗
PubMedDate not supplied

Effects of thermocycling on the tensile bond strength between resin cement and dentin surfaces after temporary cement application.

PURPOSE: In a previous study the authors found that 2 of 3 tooth conditioners examined were able to reduce the negative effect of temporary cement on the bond strength between resin cement and teeth. The aim of this study was to evaluate the bond durability with the conditioners, as well as their capability for temporary cement dissolution. MATERIALS AND METHODS: After eliminating the temporary cement with a curette from the bovine dentin surface, a conditioner (ethyl dihydrogen phosphate, EP; or methacryloxyethyl dihydrogen phosphate, MEP) was applied to the surface and a resin cement was adhered. Tensile bond strength measurement, scanning electron microscopic observation, and energy-dispersive analysis were carried out without thermocycling and after thermocycling. RESULTS: The tensile bond strength gradually decreased with an increase in the number of thermocycles. However, specimens treated with EP or MEP showed significantly higher tensile bond strength values compared to those that did not receive conditioner application (P < 0.0001); EP showed significantly higher tensile bond strength values compared to the specimens that did not receive both temporary cement and conditioner application (P < 0.0001). The scanning electron microscopic, energy-dispersive, and solubility analyses suggest that both conditioners have the capability of dissolving temporary cement remnants. CONCLUSION: Both EP and MEP have potential value as conditioners to reduce the negative effect of temporary cement on the bond strength between resin cement and dentin and to improve the bond durability.

Analysis of Variance↗
PubMed2004

Indications, methods, and results of cemented, hybrid, and cement-free implantation of THR.

THR has become one of the most widely performed operations in orthopaedic surgery. In Germany, more than 180,000 THRs are currently done annually with increasing tendency. We use four different types of endoprostheses: (1) cemented, (2) cement-less, (3) hybrid (cement-free implanted socket and cemented stem), and (4) hemi-endoprosthesis (cemented stem without socket). A total number of 600 patients were included in a prospective follow-up study during 5 to 20 years, with a mean follow-up period of 10 years. The relevant question of whether to use a cemented, hybrid, or cement-free version of THR is, in our opinion, no longer a concern. All the methods have their advantages, disadvantages, indications, and contraindications. After the "Endler-era", significant differences are not noted between the groups of cemented, hybrid, and cement-less implants that impact on the clinical results and loosening rates.

Adult↗
PubMed1993

Effects of variation of cement thickness on bone and cement stress at the tip of a femoral implant.

With the resurgence of the use of bone cement in total hip arthroplasty, a renewed concern in techniques or designs that may reduce cement fixation failure has arisen. Analysis of the stresses at the tip of the prosthesis may suggest strategies to reduce loosening. Using a three-dimensional finite element model this study analyzed stresses in the bone, cement, and prosthesis near the tip of a femoral component as a function of cement thickness. A section of an idealized circular femoral shaft with implant prosthesis and cement was modeled with loading conditions representing the stance phase of gait. Increasing cement thickness is predicted to significantly reduce stress in the cement mantle of a femoral implant. Tensile stress is reduced by fifty percent while shear stress is reduced at least twelve percent. Peak tensile stresses occur on the medial side at the tip of the prosthesis in a transverse direction, indicating likelihood of failure due to debonding. Local shear stress peaks also occur at the tip. Shear stresses in the cement mantle are in the same range as the tensile stresses and must be considered when analyzing the possible modes of failure. However, the mode of failure in shear is complex, and shear strength of the stem-cement interface is unknown at present.

Bone Cements↗
PubMed1996

Visualization of cement exocytosis in the cypris cement gland of the barnacle Megabalanus rosa

Cementation to substrata during permanent attachment concludes the planktonic larval phase in many sessile marine invertebrates, including barnacles. However, the neural control and the mechanism of cement secretion from cement organs are poorly understood. In the present study, using isolated cement glands from cyprids of Megabalanus rosa, we have visualized cement secretion and demonstrated the stimulatory effect of dopamine and noradrenaline on such secretion. The abrupt disappearance of secretory granules and subsequent omega-figure formation indicated that exocytosis was the major mode of cement secretion. Exocytosis was localized at the apical surface of cement-secreting cells and lasted for over 30 min. Dopamine and noradrenaline also activated the directional transport of secretory granules to the sites of exocytosis. Glyoxylic acid staining provided histochemical evidence for catecholaminergic innervation to the cement glands. These results suggest that gradual, localized exocytotic secretion of cement triggered by catecholaminergic neurones is a key mechanism during permanent attachment by barnacle cyprids.

Journal Article↗
PubMed1994

Retention of posts cemented with various dentinal bonding cements.

This investigation evaluated the retention of preformed posts with four different cements: C & B Metabond, Panavia, All-Bond 2, and Ketac-Cem. Sixty intact maxillary canines were selected for the study. The clinical crowns were removed and endodontic therapy done on each root, which was then prepared to receive prefabricated posts. The 60 samples were divided into four groups of 15, and the posts in each group were cemented with one of the four cements. The roots were mounted in acrylic resin blocks and the posts were separated from the canals with an Instron testing machine. Analysis of the forces needed to dislodge the posts with analysis of variance and Student-Newman-Keuls test disclosed that C & B Metabond cement was the most retentive (p < 0.05). No difference in retention was recorded between Ketac-Cem and Panavia cements. All-Bond 2 cement was the least retentive of cements.

Analysis of Variance↗
PubMed2002

Residual stresses at the stem-cement interface of an idealized cemented hip stem.

During the operation of total hip arthroplasty, when the cement polymerizes between the stem implant and the bone, residual stresses are generated in the cement. The purpose of this study was to determine whether including residual stresses at the stem-cement interface of cemented hip implants affected the cement stress distributions due to externally applied loads. An idealized cemented hip implant subjected to bending was numerically investigated for an early post-operative situation. The finite element analysis was three-dimensional and used non-linear contact elements to represent the debonded stem-cement interface. The results showed that the inclusion of the residual stresses at the interface had up to a 4-fold increase in the von Mises cement stresses compared to the case without residual stresses.

Bone Cements↗
PubMed1998

Comparative laboratory investigation of dual-cured vs. conventional glass ionomer cements for band cementation.

This laboratory study compared the mean tensile bond strength, mode of band failure, and survival time of orthodontic bands cemented with dual-cured cement or conventional glass ionomer cement. Survival time was assessed following application of mechanical stress in a ball mill. Mean tensile bond strength was significantly higher for bands cemented with the dual-cured cement (p < 0.01), and mean survival time was significantly greater. Bands cemented with glass ionomer failed mainly at the cement/band interface. The results suggest that dual-cured cement is superior to glass ionomer for band cementation.

Chi-Square Distribution↗