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PubMed1993

Chromium content in human skin after in vitro application of ordinary cement and ferrous-sulphate-reduced cement.

The amount of chromium found in human skin after in vitro application of cement suspensions on full-thickness human skin in diffusion cells was investigated. Cement suspensions made from ordinary Portland cement or Portland cement with the chromate reduced with added ferrous sulphate were used. The cement suspensions were either applied on the skin surface under occlusion for 48 h or applied repeatedly every 24 h for 96 h. No statistically significant difference in chromium content of skin layers between skin exposed to ordinary Portland cement, skin exposed to cement with added ferrous sulphate and unexposed skin was observed, despite a more permeable skin barrier at the alkaline pH of the cement suspensions, i.e., pH 12.5. Increased chromium levels in epidermis and dermis were seen when ordinary Portland cement was applied as a suspension with added sodium sulphate (20%) on the skin surface for 96 h. The content of water-soluble chromium in ordinary Portland cement may vary due to the alkali sulphate content of the cement.

Cementation↗
PubMed1992

Revision of cemented fixation and cement-bone interface strength.

Interfacial shear strength between poly(methyl methacrylate) (PMMA) bone cement and cancellous bone was measured in bone samples from human proximal femora. Samples were prepared with fresh cement-bone, fresh cement inside a mantle of existing cement and with fresh cement-revised bone surfaces. Push-out tests to measure shear strength caused failure only at bone-cement interfaces; revised bone interfaces were 30 per cent weaker (P < 0.02) than primary interfaces. The clinical relevance is that revision of cemented joint arthroplasties may necessitate removal of components with sound cement-bone fixation. The practice of removing all traces of PMMA cement may not yield the optimal fixation; adhesion of fresh cement to freshly prepared surfaces of the existing cement might also be considered where circumstances are favourable.

Bone Cements↗
PubMed1994

The cement-canal prosthesis. A new cementation technique studied in cadaver femora.

This report presents the cement-canal prosthesis. Acrylic cement is injected through the prosthesis by means of an integrated drill hole system. A second canal system within the prosthesis allows suction from the cavities, which could form in the mantle during cement injection. In an experimental study using 36 human cadaveric femora, 3 cement implantation pressures (0.5 bar, 1.0 bar and 1.5 bar) were used. A conventional cementing technique served as a control. Compared to the controls, a deeper penetration of bone cement into cancellous bone was found. Increasing cement pressure led to deeper cement penetration. The average depths of the cement layer were 2.2 mm at 0.5 bar implantation pressure, 2.9 mm at 1.0 bar and 3.9 mm at 1.5 bar. A cement mantle without voids was achieved by this technique, whereas control specimens showed a wide variability in cement defects.

Bone Cements↗
PubMed2003

[Influence of proximal stem geometry and stem-cement interface characteristics on bone and cement stresses in femoral hip arthroplasty: finite element analysis].

PURPOSE OF THE STUDY: The combined effects of proximal canal filling and stem-cement surface characteristics on stresses in the cement and bone in femoral hip arthrosplasty were investigated by finite element analysis. MATERIAL AND METHODS: Our finite element study of a femoral implant fitted with a stainless steel stem was based on a set of 4 models with decreasing metaphyseal fill, designed to simulate loading before the occurrence of any deterioration in the cement-bone interface. Thus, the cement was represented fully bonded to the bone. The implant-cement interface was modeling in the bonded and debonded states. First a vertical load was applied to the implant to simulate the conditions of the bearing phase of gait. Second, a rotational load was applied to the implant. Torsional loading tests were found to be satisfactory for studying variations in shape of the proximal portion of femoral implants because they simulate the most critical loading conditions such as stair climbing or chair rising. RESULTS: With the bonded implant-cement surface, bone stresses were rather distal, whereas they were mainly proximal with the debonded implant-cement interface. Under rotational loading, debonded implants produced less normal tensile and shear stresses in the proximal portion of the cement mantle. In contrast, compressive cement stresses were higher with debonded implants. In the debonded state, the rotational stability of the implant was found to be closely related to the degree of metaphyseal fill. CONCLUSION: In conclusion, the use of implants with a debonded metal-cement interface and with optimal metaphyseal filling should preserve the cement-bone interface from excessive shear and tensile stresses, while providing good rotational stability.

Arthroplasty, Replacement, Hip↗
PubMed1989

[Self-setting apatite cement. 8. Dissolution and remineralization behavior of 45Ca-apatite cement].

Self-setting apatite cement hardens into a mass of single phase apatite when mixed with diluted phosphoric acid. Structurally this mass consists of two types of apatite, i.e. the seed apatite used as a setting accelerator and the matrix apatite formed afterward in the reaction of dicalcium phosphate dihydrate (DCPD) and tetracalcium phosphate (Te-CP). To investigate the dissolution behavior of self-setting apatite cement in detail, two types of 45Ca labeled apatite cement were prepared. In one, the seed apatite was labeled with 45Ca (45Ca-HAp cement) and in the other the matrix apatite was labeled with 45Ca through use of 45Ca-DCPD (45Ca-DCPD cement). Solubility, estimated from the concentration of 45Ca released in 1 mM of organic acid (e.q. acetic, lactic, or citric acid) with initial pH adjusted to 4.0 at 37 degrees C, was approximately zero for 45Ca-HAp cement, whereas the solubility of 45Ca-DCPD cement was approximately the same as unlabeled cements used so far. This finding suggests that dissolution of the matrix apatite governs dissolution of the set cement, though comparison of X-ray diffraction patterns and electron micrographs of the seed apatite and apatite in the set cement showed no essential difference in crystallinity and crystal shape. The fact that the matrix apatite was formed by enveloping the seed apatite may account for the preferential dissolution of matrix apatite. In synthetic saliva labeled with 45Ca having a degree of supersaturation with respect to apatite comparable to rest saliva, 45Ca concentration in solution decreased once the cement pellet was introduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Apatites↗
PubMed1988

The cemented kinematic-II and the non-cemented porous-coated anatomic prostheses for total knee replacement. A prospective evaluation.

One hundred and sixty consecutive total knee arthroplasties were performed in 143 patients: 110 procedures, with a cemented kinematic-II prosthesis and fifty procedures, with a non-cemented porous-coated anatomic prosthesis. Each patient was evaluated before the operation and six weeks and three, six, twelve, and twenty-four months postoperatively. At a minimum twenty-four-month follow-up, the average Hospital for Special Surgery knee-rating score for the patients who had a cemented kinematic-II prosthesis was 9 points higher than the average score for the patients who had a non-cemented anatomic implant (88 points and 79 points). At the same follow-up period, the maximum flexion of the knees that had a cemented kinematic-II prosthesis was greater than that of the knees that had a non-cemented anatomic prosthesis (106 degrees and 97 degrees). In addition, the rate of reoperation for the patients who had a cemented kinematic-II replacement was 4 per cent, compared with 12 per cent for the patients who had a non-cemented anatomic prosthesis. On the basis of this prospective, non-randomized clinical review of unselected patients, we concluded that the results with the cemented kinematic-II prosthesis were superior to those with the non-cemented anatomic prosthesis at a minimum twenty-four month follow-up; however, these superior results may be related to the use of cement or to differences in the designs of the prostheses, the ages of the patients, or the postoperative management of the two groups of patients.

Arthritis, Rheumatoid↗
PubMed1996

Porosity reduction in bone cement at the cement-stem interface.

The fatigue failure of bone cement, leading to loosening of the stem, is likely to be one mode of failure of cemented total hip replacements. There is strong evidence that cracks in the cement are initiated at voids which act as stress risers, particularly at the cement-stem interface. The preferential formation of voids at this site results from shrinkage during polymerisation and the initiation of this process at the warmer cement-bone interface, which causes bone cement to shrink away from the stem. A reversal of the direction of polymerisation would shrink the cement on to the stem and reduce or eliminate the formation of voids at this interface. We have investigated this by implanting hip prostheses, at room temperature or preheated to 44 degrees C, into human cadaver femora kept at 37 degrees C. Two types of bone cement were either hand-mixed or vacuum-mixed before implantation. We found that the area of porosity at the cement-stem interface was dramatically reduced by preheating the stem and that the preheating temperature of 44 degrees C determined by computer analysis of transient heat transfer was the minimum required to induce initial polymerisation at the cement-stem interface. Temperature measurements taken during these experiments in vitro showed that preheating of the stem caused a negligible increase in the temperature of the bone. Reduction of porosity at the cement-stem interface could significantly increase the life of hip arthroplasties.

Bone Cements↗
PubMed1992

Effects of temporary cementation on permanent cement retention to composite resin cores.

This in vitro study compared the effects on retention of base metal cylindrical retainers placed on composite resin cores when pretreated with eugenol and noneugenol temporary cements. Sixty composite cores and base metal cylindrical retainers were tested. The cores were pretreated with eugenol and noneugenol temporary cements before eventual cementation with resin and zinc phosphate cements. Cemented core retention was measured by application of a compressive force to the cores in an Instron machine. Differences were found between the two permanent cements. Pretreatment with eugenol cement reduced retainer retention with resin cements, but had no effect with zinc phosphate cement. Pretreatment with noneugenol cement did not reduce retainer retention.

Cementation↗
PubMed2003

Fracture resistance of teeth restored with two different post-and-core designs cemented with two different cements: an in vitro study. Part I.

OBJECTIVE: The purpose of this in vitro study was to investigate fracture resistance in teeth restored with cast post and cores with and without ferrule and using two different luting cements. METHOD AND MATERIALS: Forty intact maxillary premolars were endodontically treated after their crowns were removed at 2.00 mm from the cementoenamel junction. Specimens were embedded in acrylic resin blocks in aluminum cylinders, 4.00 mm apical to the cementoenamel junction. Twenty specimens were ferruled, and half of the posts and cores were cemented with zinc-phosphate cement, while the other half was cemented with resin cement. The same procedures were followed for the nonferruled group. Loads were applied at an angle of 45 degrees and measured with a universal testing machine. ANOVA and Tukey test were used for statistical analyses; a significance level was established at 5%. RESULTS: Ferruled specimens showed greater resistance than nonferruled ones, regardless of the cement used. There was no statistical difference between the group of specimens cemented with resin cement and without ferrule and the ferruled groups. The non-ferruled group with zinc-phosphate cement showed the poorest results. CONCLUSION: A 2.00-mm cervical ferrule is important for fracture resistance of restored teeth, and resin cement has a better performance.

Analysis of Variance↗
PubMed1986

[In vitro immune response to acrylic cement particles in patients with cemented joint replacements].

Immunological reaction to bone cement in tissue could be considered one of the important causes to induce the loosening of the prosthesis in patients with cemented prostheses. To study whether or not bone cement is immunogenic in human in vitro, the effect of acrylic cement particles on specific or non-specific blastformation reaction of peripheral blood mononuclear cells (PBM) or of non-adherent cells (NAC) was studied. Acrylic cement particles showed neither mitogenic nor cytotoxic effect on human PBM. No statistically significant enhancing effect of acrylic cement particles was found on specific or non-specific blastformation reaction of PBM or NAC from patients with cemented prostheses. No significant difference in those reactions to cement was seen between patients with loosened prostheses and with non-loosened prostheses. In some cases, however, acrylic cement particles showed significant enhancing effects on some macrophage-dependent blastformation reaction systems. As many of them were patients with cemented prostheses, it is highly possible that bone cement could induce significant macrophage-dependent immunological reaction in some particular population.

Adult↗
PubMed2005

Influence of cement viscosity and cement mantle thickness on migration of the Exeter total hip prosthesis.

The effect of bone cement viscosity and cement mantle thickness on the migration of the Exeter total hip prosthesis was studied in a prospective, randomized, double-blind clinical Roentgen Stereophotogrammetric Analysis study. Forty-one cemented total hip arthroplasty in 39 patients were included and randomized into a low/medium Simplex P cement group and a high-viscosity Simplex AF cement group. At time of stem introduction, 5 minutes after mixing, the Simplex AF was more viscous than Simplex P. No statistical difference existed between the 2 cement groups, for neither translation nor rotation migration data. Subsidence of the stem at 2-year follow-up was 1.1 +/- 0.56 mm for Simplex AF cement and 1.5 +/- 1.00 mm for Simplex P cement. The mean rotation of the acetabular components about the sagittal axis was 1.7 degrees +/- 3.8 degrees in the Simplex AF group and 0.7 degrees +/- 2.1 degrees for the Simplex P group. No effect of cement mantle thickness on migration of neither the acetabular cups nor the femoral stems was found. Although there were no differences in migration data for the cups and the stems, 2 acetabular cups in the Simplex AF group (almost 10%) were revised because of mechanical loosening. Because of these findings, we suggest caution before using this new high-viscosity bone cement for fixation of acetabular components.

Acetabulum↗
PubMed2001

Evaluation of cement stresses in finite element analyses of cemented orthopaedic implants.

Stress analysis of the cement fixation of orthopaedic implants to bone is frequently carried out using finite element analysis. However the stress distribution in the cement layer is usually intricate, and it is difficult to report it in a way that facilitates comparison of implants for pre-clinical testing. To study this problem, and make recommendations for stress reporting, a finite element analysis of a hip prosthesis implanted into a synthetic composite femur is developed. Three cases are analyzed: a fully bonded implant, a debonded implant, and a debonded implant where the cement is removed distal to the stem tip. In addition to peak stresses, and contour and vector plots, a stressed volume and probability-of-failure analysis is reported. It is predicted that the peak stress is highest for the debonded stem, and that removal of the distal cement more than halves this peak stress. This would suggest that omission of the distal cement is good for polished prostheses (as practiced for the Exeter design). However, if the percentage of cement stressed above a certain threshold (say 3 MPa) is considered, then the removal of distal cement is shown to be disadvantageous because a higher volume of cement is stressed to above the threshold. Vector plots clearly demonstrate the different load transfer for bonded and debonded prostheses: A bonded stem generates maximum tensile stresses in the longitudinal direction, whereas a debonded stem generates most tensile stresses in the hoop direction, except near the tip where tensile longitudinal stresses occur due to subsidence of the stem. Removal of the cement distal to the tip allows greater subsidence but alleviates these large stresses at the tip, albeit at the expense of increased hoop stresses throughout the mantle. It is concluded that a thorough analysis of cemented implants should not report peak stress, which can be misleading, but rather stressed volume, and that vector plots should be reported if a precise analysis of the load transfer mechanism is required.

Biocompatible Materials↗
PubMed1996

Cement-within-cement revision hip arthroplasty; should it be done?

The complete removal of the cement mantle at revision arthroplasty can be extremely difficult. Some authors advise a 'cement-within-cement' revision technique in which a new layer of cement is applied to the old before insertion of the femoral component. We could find no long-term clinical data regarding the success of this procedure. In a simple biomechanical study, we examined the strength of the cement-to-cement interface in conditions likely to prevail in vivo. We found that the presence of a thin layer of blood and marrow debris at the interface weakened the cement-to-cement bond by 80% to 85%. These biomechanical findings and additional photomicrographic evidence do not support the practice of cement-within-cement revision arthroplasty.

Bone Cements↗
PubMed1996

Enamel fluoride levels after orthodontic band cementation with glass ionomer cement.

The aim of this investigation was to examine the fluoride uptake by enamel after application of glass ionomer cement for orthodontic band cementation compared with zinc phosphate cement. The study was conducted on 21 children whose mean age was 14 years. All the children were reared in the Middle Anatolian cities where the water fluoride concentration was below the level of 0.50 ppm. The subjects were randomly divided into three groups. The first experimental group, had seven subjects whose teeth were topically fluoridated with 2 per cent NaF solution, before orthodontic band cementation with zinc phosphate cement. The second experimental group also had seven subjects whose orthodontic bands were cemented with glass ionomer cement. The third group, consisted of seven control subjects and no dental procedures were performed in this group. All the participants were followed for 3 months and at the end of this period maxillary first premolars, which were in the ninth developmental stage according to Nolla (1960), were extracted for orthodontic purposes. The enamel fluoride concentrations were determined on the left maxillary first premolars at three successive etch depths by means of a fluor ion electrode, whereas the calcium concentrations were determined with an atomic absorption spectrophotometer. The results of this investigation showed that in both cementation groups enamel fluoride concentrations at three successive etch depths were highly increased compared with the control group. However, the difference between the cementation groups was not statistically significant.

Adolescent↗
PubMed2005

Short-term retentive values of zirconium oxide posts cemented with glass ionomer and resin cement: an in vitro study and a case report.

OBJECTIVE: This paper presents the results of an investigation focusing on the retention of all-ceramic posts. The aim of the study was to evaluate the influence of two luting agents--a glass-ionomer cement (Ketac Cem) and a resin cement (Panavia F)--on the retention of a prefabricated ceramic post (Cerapost) after different pretreatment techniques in vitro. METHOD AND MATERIALS: Forty freshly extracted incisors and canines were treated endodontically. The root canals were filled with laterally condensed gutta-percha and sealer. The teeth were assigned to 1 of 4 groups, each containing 10 specimens: sandblasted/nonsandblasted post cemented with glass-ionomer cement and sandblasted/nonsandblasted post cemented with resin cement. Tensile tests were carried out. The specimens were also quantitatively analyzed under a scanning electron microscope. RESULTS: The retentive strengths of posts, sandblasted and nonsandblasted, and cemented with Panavia F resin cement, were significantly increased as compared to those cemented with Ketac Cem. CONCLUSION: Both the luting agent and the post-surface pretreatment had a significant influence on the retention of the ceramic post.

Adult↗
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↗