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PubMed1999

Interface gap after implantation of a cemented femoral stem in pigs.

We studied the interface gap around cemented femoral stems. Fresh pig femora were used. Bone cement mixed under vacuum or at atmospheric pressure was injected into the femoral canal and a cobalt chrome stem was then implanted. The femora were sectioned transversely from the minor trochanter and distally by using a high-pressure water cutter. Most of the interfaces had intimate contact. However, in all specimens, small gaps were found at the bone-cement and cement-stem interfaces. The gaps at the interfaces between the bone and cement and the cement and stem were measured, using a computerized video digital system. They occupied about 10% of the circumference at the bone-cement interface and about 15% of the circumference at the cement-stem interface, irrespective of the mixing procedures. Most gaps were less than 100 mu at the interfaces. In conclusion, cemented implants in the animal model showed that small gaps are found at the interfaces directly after implantation. These gaps may be weak points and initiate debonding when loading the prostheses.

Animals↗
PubMed2004

The effects of initial hemostatic period on the mechanical strength and transformation of apatite cement.

It is well known that apatite cement causes inflammatory response if it is exposed to blood before setting. In this respect, the hemostatic procedure is very important. However, it has not been clarified how initial hemostasis affects the other basic properties of apatite cement. In the present study, the effect of initial hemostasis on the setting reaction was simulated by allowing the apatite cement paste to be hardened in an incubator for 1 to 30 minutes and then immersed in saline up to 7 days. We found faster transformation of apatite cement to apatitic mineral and higher mechanical strength of the set mass when the cement paste underwent a longer pre-hardening period. We also found that earlier exposure of apatite cement to saline resulted in a set mass with larger porosity. It is thought that the larger porosity of the cement is caused by the penetration of liquid into the cement paste, thus leading to lower mechanical strength and slower transformation of the apatite cement to apatitic mineral. We concluded, therefore, that hemostatic procedure is important not only to prevent inflammatory response but also to obtain a set mass with higher mechanical strength and faster transformation to apatitic mineral.

Analysis of Variance↗
PubMed2004

Histopathological and cell enzyme studies of calcium phosphate cements.

New types of self-setting calcium phosphate cement (N-CPC), which do not contain tetracalcium phosphate, were recently developed. N-CPCs harden in 10 minutes with phosphate solution as the cement liquid, and form hydroxyapatite as the set product. The objectives of the present study were to evaluate the biocompatibility (Study I) and cell enzyme activity of N-CPCs and a conventional CPC (Study II). Four experimental cements were tested: (1) dicalcium phosphate anhydrous (DCPA) and calcium oxide; (2) DCPA and calcium hydroxide; (3) tricalcium phosphate and calcium carbonate; and (4) DCPA and tetracalcium phosphate. Phosphate solution was used as the cement liquid for cements (1)-(3), and water for cement (4). Sintered hydroxyapatite particles (5) were used as a control. The test materials were implanted subcutaneously in rats. Four weeks after operation, the animals were sacrificed and histopathological observations were performed. Cements (2) and (3) showed no inflammatory reaction, and were surrounded only by very thin fibrous connective tissues. The histopathological reactions of N-CPCs were nearly identical and were similar to (4) and (5). In addition, effects of alkaline phosphatase (ALP-ase) activity--invoked by the presence of cements (3) and (4)--on osteoblast-like cells derived from dog alveolar bone were also examined because ALP-ase activity is closely related to new bone formation. These results indicated that (3) and (4) were highly compatible with subcutaneous tissues and suggested that these cements may enhance new bone formation.

Acid Phosphatase↗
PubMed2002

Current state of cement fixation in THR.

The author surveys important landmarks in the development of total hip arthroplasty, with an accent on implant fixation using acrylic cement. He explains why he personally opted for hybrid prostheses, combining a cemented stem and a cementless socket, in patients over sixty years. Excellent cementless, sockets have been available for a long time; on the femoral side, the first steps were difficult, but several cementless, stems were subsequently developed, which provided excellent long term results. This historical evolution resulted in a very uneven use of cemented versus cementless stems from one country to another in Europe. Cemented implants have enjoyed a renewed popularity over the past few years as a result of several factors, including economical factors. The author discusses the conditions for optimal fixation of a cemented stem; these conditions are not always met satisfactorily, as a number of surgeons obviously stick to a crude cementing technique. The author describes the role of the stem geometry and surface finish, as well as the possible influence of a centralizer; he explains why, based on a correct analysis of the available data, discredit has been unduly cast on cemented stems made of titanium alloy. He insists on one important although often disregarded factor: the specific type of cement used, as better results have clearly been achieved with certain cements than with others. He insists on the necessity to take into account all the elements involved, in order to avoid making erroneous conclusions. He also insists on one very important variable, the quality of the surgical technique. Total hip arthroplasty is likely to make further progress in the future, although we are likely now in the asymptotic portion of an ascending curve. Further improvement in clinical results will result from improvement of currently existing systems and optimization of surgical technique, rather than from the continuous designing of new implants.

Alloys↗
PubMed2002

Conduction analysis of cement interface temperature in total knee arthroplasty.

We applied an axisymmetric model of the tibia to a finite element method and analyzed the heat conduction from bone cement in total knee arthroplasty using numerical simulation with the finite element analysis software, ABACUS. We hypothesized the thermal necrotic map of bone. Moreover, we suggested a method for preventing thermal necrosis of bone using this simulation. We adopted an initial temperature of 32?C and a cement layer of 3mm to our simulation and analyzed heat conduction. The maximum temperature into the cement layer was 65?C and 56?C at the bone-cement interface 200 sec after the start of heat generation. Bone necrosis was observed approximately 2mm from the bone-cement interface. To thin the cement layer, the maximum temperature and bone necrotic area reduced. At a cement layer of less than 1mm no bone necrotic area was observed. To lower the initial temperature of the bone surface, the maximum temperature and bone necrotic area was also reduced. At an initial temperature of less than 28?C we did not find any bone necrosis. Even if we hypothesized pouring cold water around the prosthesis, the maximum temperature did not reduce at any time, neither did the necrotic area reduce. We should make the cement layer as thin as possible and cool the bone before cementing to prevent thermal bone necrosis.

Arthroplasty, Replacement, Knee↗
PubMed2002

Morphological and chemical characterization of the dentin/resin cement interface produced with a self-etching primer.

PURPOSE: The purpose of this study was to analyze a resin cement/dentin interface by comparing the diffusion of a resin cement into dentin surfaces pretreated with a self-etching primer with or without pretreatment by conventional acid etching. MATERIALS AND METHODS: Dentin surfaces of 8 unerupted human third molars were treated with a self-etch primer (Panavia 21) with or without conventional phosphoric acid pretreatment. Panavia 21 resin cement was applied according to manufacturer's instructions. Dentin/resin cement interface sections from each tooth were examined with scanning electron microscopy and micro-Raman spectroscopy. RESULTS: When the self-etch primer was used following conventional acid pretreatment, the resin cement did not penetrate to the depth of the zone of demineralized dentin, leaving a substantial area of exposed dentin matrix at the dentin/cement interface. In contrast, there was substantial resin cement diffusion throughout the demineralized dentin when the self-etch primer was used without acid etching pretreatment. CONCLUSION: The in vitro evaluation of resin cement penetration throughout the zone of demineralized dentin is an important step in identifying sites of exposed dentin matrix that may promote postoperative sensitivity and may leave the dentin/resin cement interface vulnerable to premature degradation under clinical conditions. In this study, the self-etch primer used alone produced substantial resin cement penetration and left no exposed dentin matrix at the dentin/resin cement interface.

Acid Etching, Dental↗
PubMed2003

Cement particles containing radio-opacifiers stimulate pro-osteolytic cytokine production from a human monocytic cell line.

Proponents of the biological theory of aseptic loosening have in recent years tended to concentrate on the production and distribution of particulate ultra-high-molecular-weight polyethylene (UHMWPE) debris around the potential joint space. However, mechanical loading of cemented implants with the differing elastic moduli of metal stems, polymethylmethacrylate (PMMA) cement and bone can result in relative micromotion, implying the potential for production of metal and PMMA particles from the stem-cement interface by fretting wear. In order to investigate the production and biological reactivity of debris from this interface, PMMA and metal particulate debris was produced by sliding wear of PMMA pins containing barium sulphate and zirconium dioxide against a Vaquasheened stainless steel counterface. This debris was characterised by SEM, energy-dispersive analysis by X-ray (EDAX) and image analysis, then added to cell cultures of a human monocytic cell line, U937, and stimulation of proosteolytic cytokines measured by ELISA. Large quantities of PMMA cement debris were generated by the sliding wear of PMMA pins against Vaquasheened stainless steel plates in the method developed for this study. Both cements stimulated the release of pro-osteolytic TNFalpha from the U937 monocytic cell line, in a dose-dependent fashion. There was a trend towards greater TNFalpha release with Palacos cement than CMW cement at the same dose. Palacos particles also caused significant release of IL-6, another pro-osteolytic cytokine, while CMW did not. The particulate cement debris produced did not stimulate the release of GM-CSF or IL1beta from the U937 cells. These results may explain the cytokine pathway responsible for bone resorption caused by particulate PMMA debris. Radio-opaque additives are of value in surgical practice and clinical studies to quantify the relevance of these in vitro findings are required before the use of cement containing radio-opacifier is constrained.

Biocompatible Materials↗
PubMed2003

Bond strength of resin cement to dentin and to surface-treated posts of titanium alloy, glass fiber, and zirconia.

PURPOSE: To determine the effect of surface treatments on bond strength of two resin cements (ParaPost Cement and Panavia F) to posts of titanium alloy (ParaPost XH), glass fiber (ParaPost Fiber White), and zirconia (Cerapost), and to dentin. MATERIALS AND METHODS: After embedding, planar surfaces of posts (n = 9 to 14) and human dentin (n = 10) were obtained by grinding. The posts received one of three surface treatments: 1. roughening (sandblasting, hydrofluoric acid etching), 2. application of primer (Alloy Primer, Metalprimer II, silane), or 3. roughening followed by application of primer (sandblasting or etching followed by primer, Cojet treatment). ParaPost Cement and Panavia F were bonded to the post and dentin specimens, and the bonded specimens were placed in water at 37 degrees C for 7 days. The specimens were debonded in shear. RESULTS: Panavia F had significantly higher bond strength to ground ParaPost XH, Cerapost, and dentin than did ParaPost Cement. Most surface treatments resulted in an improved bond strength of resin cements to the posts. Compared to the ground control, Cojet treatment and sandblasting were the most effective treatments. Etching of Cerapost with hydrofluoric acid with and without silane treatment significantly decreased the bond strength of Panavia F to the post. CONCLUSION: The bond strength of resin cements to the posts was affected by the material of the post, the surface treatment of the post, and by the type of resin cement. The bond strength of resin cement to dentin was influenced by the type of resin cement.

Acid Etching, Dental↗
PubMed2006

Three-dimensional finite element analysis of weakened roots restored with different cements in combination with titanium alloy posts.

BACKGROUND: It is very difficult and relatively unpredictable to preserve and restore severely weakened pulpless roots. To provide much needed benefit basis for clinical practice, this study was carried out to analyze the stress distribution in weakened roots restored with different cements in combination with titanium alloy posts. Finite element analysis (FEA) was employed in the study. METHODS: A pseudo three-dimensional model of a maxillary central incisor with flared root canal, theoretically restored with titanium alloy posts in combination with different cements, was established. The analysis was performed by use of ANSYS software. The tooth was assumed to be isotropic, homogenous and elastic. A load of 100 N at an angle of 45 degrees to the longitudinal axis was applied at the palatal surface of the crown. The distributions of stresses in weakened roots filled with cements of different elastic modulus were analyzed by the three-dimensional FEA model. RESULTS: Several stress trends were observed when the stress cloud atlas obtained in the study was analyzed. With the increase of the elastic modulus of cements from 1.8 GPa to 22.4 GPa, the stress values in dentin decreased from 39.58 MPa to 31.43 MPa and from 24.51 MPa to 20.76 MPa (respectively, for maximum principle stress values and Von Mises stress values). When Panavia F and zinc phosphate cement were used, the stress peak values in dentin were very small with no significant difference observed, and the Von Mises stress values were 20.87 MPa and 20.76 MPa respectively. On the other hand, maximum principle stress value and Von Mises stress value in cement layer increased with the increase of the elastic modulus of cements. CONCLUSIONS: The result of this study demonstrated that elastic modulus was indeed one of the important parameters to evaluate property of the cements. Our three-dimensional FEA model study also found that the cement with elastic modulus similar to that of dentin could reinforce weakened root and reduce the stress in dentin. Thus, it may be a better choice for the restoration of weakened roots in clinical practice.

Adult↗
PubMed1992

The mechanism of loosening of cemented acetabular components in total hip arthroplasty. Analysis of specimens retrieved at autopsy.

Late aseptic loosening of cemented acetabular components is governed by the progressive, three-dimensional resorption of the bone immediately adjacent to the cement mantle. This process begins circumferentially at the intraarticular margin and progresses toward the dome of the implant. Evidence of bone resorption at the cement-bone interface was present even in the most well-fixed implants before the appearance of lucent lines on standard roentgenographic views. The mechanical stability of the implant was determined by the three-dimensional extent of bone resorption and membrane formation at the cement-bone interface. The leading edge of the membrane is a transition zone from regions of membrane interposition between the cement and the bone to regions of intimate cement-bone contact. Histologic analysis revealed that progressive bone resorption is fueled by small particles of high density polyethylene (HDP) migrating along the cement-bone interface and bone resorption occurs as a result of the macrophage inflammatory response to the particulate HDP. Evidence in support of a mechanical basis for failure of fixation was lacking. The mechanism of late aseptic loosening of a cemented acetabular component is therefore biologic in nature, not mechanical. This is exactly opposite to the mechanism of loosening on the femoral side of a cemented total hip replacement, which is mechanical in nature.

Acetabulum↗
PubMed1991

[Study of root canal cements comprising calcium aluminate. First report on cytotoxicity].

We prepared new root canal cements for trial. These cements were comprized of calcium aluminate and calcium hydroxyde for setting in a root canal and a bioabsorbable property. The biocompatibility of these cements were then evaluated with kinds of cytotoxicity tests and were compared with three kinds of root canal cements on the market such as Calvital (CV), Canals (CA) and Neodyne (ND). As a result of the millipore filter test using HeLa cells, three kinds of trial cements and CV showed moderate cytotoxicity at every stage. The toxicity of CA and ND were related to the period of administration and the two products showed severe cytotoxicity 24 hours after the administration. The cell growth inhibition test using L-929 cells revealed that the inhibition of the three kinds of trial cements was based on a strong alkalinity caused by calcium hydroxyde and the inhibition on the cell growth was related to the calcium hydroxyde content in these cements. However, the inhibition of these cements was smaller than that of CV and they showed no inhibition in the last stage of the cell culture, while CA and ND caused the mild inhibition. Therefore, we have concluded that these trial cements are useful for root canal filling because they have better affinity to the cultured cells than CV, CA and ND.

Aluminum↗
PubMedDate not supplied

[Glass ionomer cementing in stomatological practice].

Glass ionomers cements represent a cement system which develops by a reaction between a polyalchenic acid, usually a homo- or a copolymer of acrylic acid and a ion donor, usually an aluminium fluorosilicate glass. Introduction of these ionomers in the stomatological practice was determined by their remarkable adherence to dentin, by pulpal and parodontal biocompatibility, and because of the fact that they deliver continuously fluorine over a long period of time. These cements provide a good marginal sealing of the obturation. In the last years a new generation of glass ionomers cements has been introduced, that "Cormat" cements, in which the glass powder is intimately linked to a pure silver metallic powder by a synthetization process, and this provides a greatly increased resistance to abrasion, as compared to conventional glass ionomer cements. Presently glass ionomer cements have become increasingly known in the stomatological practice and they are used preferentially for base obturations, under obturations with composites on lateral teeth, in the treatment of mylolysis and for coronary erosions determined by brushing, which do not need preparation of retention cavities. They are also used for coronary reconstruction, and the treatment of atopical microcavities of occluding decay processes on the lateral teeth that have induced limited enamel losses. The perspective of these cements in the stomatological practice depends however on an improved translucency, which, for the present at least, does not match that of silicates and composites, as well as on an improved resistance to bending, and even the "Cormat" cements are inferior to silver amalgam which is used in the obturation of classical class II cavities.

Dental Alloys↗
PubMed1989

[Self-setting apatite cement. VII. Barium-apatite as radio-opaque medium].

Addition of barium hydroxyapatite (BaAp) successfully bestowed clinically acceptable radioopacity to the self-setting apatite cement consisting of an equimolar mixture of tetracalcium phosphate and dicalcium phosphate dihydrate. To accelerate the setting reaction which was retarded by Ba2+ released from BaAp at a lower pH during first stage of spatulation with 20 mM phosphoric acid, calcium hydroxyapatite (CaAp) was added to the cement mixture. At about 20 wt% of BaAp and 20 wt% CaAp, the setting reaction proceeded at a neutral or weak alkaline pH, which is one of the most promising aspects of the self-setting cement and assures that this type of cement may be the least irritating of the dental cements presently available. The cement spatulated at L/P = 0.4 set within 10 minutes and its radiopacity was comparable to or more than that of tooth enamel. The wet compressive strength of the set cement stored for one day in synthetic saliva at 37 degrees C was approximately 100 kgf/cm2. Although this value is almost one fourth that of 40 wt% CaAp cement, this cement appears to be strong enough to apply as root canal filling material.

Barium↗
PubMed1988

[Antibiotic-loaded orthopedic cements. Pharmacokinetics and bone level].

A mechanical study in the laboratory of 10 types of cement has shown that the characteristics of low viscosity antibiotic-loaded cements are comparable with those of standard cement without antibiotic and of standard viscosity. A study of the release of Gentamycin in 26 patients treated by total hip replacement showed that the concentration of antibiotic in the drainage fluid was much greater than the minimum inhibitory concentration whereas the low blood concentration gave no risk of ototoxicity or nephrotoxicity. This method of administration achieved antibiotic concentrations in the tissues in contact with the prosthesis 10 times greater than those obtained by injection. In sheep, the intra-osseous concentration was studied in 32 femora after insertion of low viscosity Gentamycin-loaded cement. The levels remained raised to 4 times the minimum inhibitory concentration for up to one year after operation, even with cements with a low concentration of antibiotic of 0.6 g/dose. The concentrations obtained in the drainage fluid, in the peri-prosthetic tissues and especially in bone, confirm the effectiveness and the prolonged action of antibiotic therapy by cement and its value in the revision of infected prostheses and in prophylaxis in primary surgery. This justifies the further study of combinations of cement with new antibiotics with a broader spectrum than Gentamycin since there is no concern with the cements currently in use that the mechanical quality is less than that of standard cement.

Animals↗
PubMed1987

Cement disease.

Does "cement disease" exist? The bony environment surrounding a loosened cemented prosthesis is an abnormal pathologic condition which, if left unattended, will progress to a total failure of the joint including an inhibition of function and immobilizing pain. That biomaterial properties of the cement used for fixation also contribute to the pathologic state separates this disease from other modes of loosening. This leads inevitably to the conclusion that "cement disease" does exist. Methyl methacrylate has revolutionized the treatment of severe joint dysfunction. There can be no doubt that improving surgical technique, cement handling, and the cement itself will continue to improve the results and reduce the incidence of failure due to loosening. Cement is undoubtedly satisfactory for elderly patients with low activity levels and relatively short life expectancies. However, because of the inherent biologic and biomechanical properties of methyl methacrylate, it is unlikely that it can be rendered satisfactory in the long run for the young, the active, or the overweight patient, for whom alternatives are currently being sought. In such cases, the elimination of "cement disease" can only occur with the elimination of cement. Alternatives include the search for other grouting materials and the development of prostheses with satisfactory surfaces for either press-fit or biologic ingrowth.

Age Factors↗
PubMed1986

Variations in the density of bone cement after centrifugation.

Barium sulfate added to bone cement to provide radiopacity has a density about four times greater than that of polymerized radiolucent bone cement. Because centrifugation might make a clinically significant change in the distribution of barium sulfate, this process was studied. Radiolucent and radiopaque Simplex-P bone cement (Howmedica, Inc., Rutherford, New Jersey) were mixed with and without cooling and centrifuged for two or four minutes at 2,000 g or 1,000 g (gravity acceleration). The density of sections of the hardened bone cement was measured using the Archimedes principle. Erythromycin and colistin were added to cement batches to test whether or not centrifugation affected the distribution of antibiotics. Direct and radiographic observation and density measurements (cooled specimens, 2,000 g, p less than 0.01) verified that barium sulfate does accumulate at the bottom of the centrifugation tubes. Thin sections of the bone cement revealed that only larger particles (20-100 micron) of barium sulfate were deposited at the bottom. No evidence of redistribution of antibiotics after centrifugation was seen. It is recommended that Simplex-P bone cement be reformulated to eliminate concern about inhomogeneities that arise from centrifugation. Further, it is recommended that cooled, centrifuged antibiotic cement be used for long-stem revision hip surgery, where longer setting times are necessary, and room temperature cement for "fresh" hip surgery. A total centrifuge time of two minutes with a 2,000 g maximum force is recommended.

Anti-Bacterial Agents↗
PubMed1994

Effect of bone mineral particles on the porosity of bone cement.

Bone particle-impregnated bone cement is investigated in vitro, which could be used to improve fixation between bone and cement interface by ingrowth of tissues that may replace bone particles. Inorganic bone particles (150-300 microns diameter) were mixed with regular bone cement powder by 0, 10, 20, and 30% by weight and implanted into the pre-drilled intramedullary canal (11cm long, 10mm diameter) of canine femur. A 4mm diameter, 10mm long stainless steel rod was implanted to simulate the prosthesis. The specimens were cut into 2mm thick discs transversely along the long axis of the bone and ground to examine with a confocal laser microscope. Diametral tensile strength tests were performed for the 0, 10, 20, and 30% bone particle impregnated bone cement discs without the intramedullary implant. Present results show that mixing bone particles with bone cement decreased the number of pores and porosity but increased the size of pores. The analysis of porosity distribution showed no significant difference between bone cement and bone particle-impregnated bone cement. Also, the strength of the bone particle-impregnated bone cement decreased linearly with increased amount of bone particles in spite of the decreased percent porosity. Using a bone particle-impregnated bone cement along with a pre-coated implant could be one of the solutions to the problems in the fixation of total joint arthroplasty.

Animals↗
PubMed1994

An in vitro study of femoral intramedullary pressures during hip replacement using modern cement technique.

Five femora (four cadaveric and one plastic) were used to measure the intramedullary pressures simultaneously at two different locations along the proximal femur during the insertion of bone cement and the femoral component using modern cement technique. The pressures were monitored by transducers located at the midpoint of each femoral stem (P1), and just beyond the tip of the femoral stem proximal to a cement plug (P2). Transient increases in intramedullary pressure were noted during the initial compaction of the bone cement using a conventional device. However, during insertion of the femoral component, the pressures at P1 and P2 increased dramatically to peak pressures exceeding 2385 mm Hg at P1 and 3710 mm Hg at P2 respectively. These pressure elevations were not sustained; eight to 10 minutes after prosthesis insertion, the pressures decreased to below baseline levels in all five femora. This probably resulted from contraction of the cement during the curing phase. Transient elevations of intramedullary pressure to levels greater than 100 times capillary pressure are produced during hip replacement using modern cement technique. The highest pressures are generated during insertion of the femoral component rather than during the cement compaction step. These findings suggest that the use of a cement compactor to improve intrusion of the cement into bone is probably unnecessary.

Bone Cements↗