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PubMed2002

Influence of cement viscosity on cement interdigitation and venous fat content under in vivo conditions: a bilateral study of 13 sheep.

In a sheep model permitting standardized bilateral, simultaneous cement pressurization, we studied the effect of different cement viscosities on fat and bone marrow intravasation and cement penetration in vivo. High viscosity cement (Palacos) was used on one side and low viscosity cement (Osteopal) on the other. Catheters were inserted into both external iliac veins to collect blood during bilateral simultaneous cement pressurization. After bone preparation and pulsatile lavage, both femora were filled with cement followed by simultaneous cement pressurization. A quantitative fat analysis of the blood collected was done. We used microradiographs to determine cement penetration in a left versus right comparison of both viscosity groups. The low viscosity cement yielded lower rates of cement penetration despite adequate and sustained pressurization. Cement applied at low viscosity state seems to take the path of least resistance into the venous system before more deeper cement penetration can occur. The use of high viscosity cement ran a higher risk of fat embolism, but improved cement interdigitation.

Animals↗
PubMed1997

The effects of cement-stem debonding in THA on the long-term failure probability of cement.

The damage accumulation failure scenario is one of the most prominent ones of cemented THA reconstruction, and involves the accumulation of mechanical damage in materials and interfaces due to repetitive dynamic loading eventually resulting in gross loosening. This study addresses this scenario by combining finite element techniques with the theory of continuum damage mechanics, to analyze the damage accumulation process in the cement mantle. It was investigated how damage accumulation was affected by stem-cement debonding, and what the effects of a layer with poor bone quality around the cement mantle were. For the unbonded stem, it was determined if clinical migration rates can be explained by failure of the cement mantle, and whether cement failure promotes the formation of a pathway for debris at the stem-cement interface. It was found that stem-cement debonding not only elevated the initial stress levels with a factor of about two to three as demonstrated in earlier studies, but remained to have an impact on the failure process of the cement mantle. Stem-cement debonding accelerated the failure process by a factor of four, and promoted the formation of a pathway for debris at the stem-cement interface, particularly when the bone support to the cement mantle was reduced. The amount of subsidence was only substantial when the damaged cement mantle was surrounded by a layer of bone with reduced stiffness. This study supports the hypothesis that the survival of cemented THA is enhanced by a firm and lasting bond between the stem and the cement mantle, although this may be difficult to realize clinically.

Bone Cements↗
PubMedDate not supplied

Cement-mantle thickness affects cement strains in total hip replacement.

Bone cement is commonly used to affix femoral implants to the bone during total hip reconstruction. Previous studies suggest that the expected life of a cemented femoral implant may depend on the thickness of the cement mantle surrounding the implant and the implant geometry. The purpose of this study was to determine whether different cement-mantle thicknesses and femoral stem sizes affected strain patterns in the bone cement around cemented femoral stems. Two different sizes of cobalt-chromium stems were cemented into composite femora with varying cement-mantle thickness. Strain gages were embedded in the cement mantle and the implanted stems were loaded axially and under conditions simulating walking and standing. An increase in stem size with the same cement-mantle thickness (approximately 2.2 mm) caused a 65% decrease in proximal medial cement strains. Increasing cement mantle thickness from 2.4 to 3.7 mm caused substantial strain reductions in the distal cement (40-49%). We conclude that increased cement-mantle thickness around femoral stems may increase the fatigue life of a bone-implant system by reducing peak strains within the cement.

Bone Cements↗
PubMedDate not supplied

Short-term aseptic loosening of the femoral component in canine total hip replacement: effects of cementing technique on cement mantle grade.

OBJECTIVES: To evaluate the effects of different cementing techniques on radiographic cement mantle grade and short-term aseptic loosening of the femoral component in canine total hip replacement (THR). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Radiographs of 284 dogs that had THR. METHODS: Immediate postoperative radiographs of 284 dogs that had cemented THR were reviewed by 4 surgeons and 1 radiologist and assigned a cement mantle grade using a 4-grade classification system. Dog age and weight at surgery, cementing technique (1st, 2nd, 3rd generation), complications (type and timing), and follow-up time were retrieved and analyzed. RESULTS: Mean cement mantle score for 2nd generation technique was significantly higher than 3rd generation technique and both were significantly higher than 1st generation technique (P<.001). Aseptic loosening was the 2nd most common complication observed with an incidence of 2.1%. Mean time from surgery to last follow-up examination was 122 days. No statistically significant difference in incidence of aseptic loosening was identified among different cement mantle grades or cementing techniques. CONCLUSIONS: Advanced cementing techniques resulted in better cement mantles based on grading of immediate postoperative radiographs, however grading did not predict short-term aseptic loosening. Cementing technique seemingly did not affect the incidence of short-term aseptic loosening of the femoral component for dogs in this study. CLINICAL RELEVANCE: Our study suggests that advances in cementing technique may result in improvements in the radiographic grade of cement mantles. With respect to aseptic loosening of the femoral component, our data only suggest that short-term (3 months-3 years) loosening cannot be predicted by immediate postoperative radiographic evaluation of cement mantle.

Animals↗
PubMedDate not supplied

Effects of adhesive liner and provisional cement on the bond strength of nickel/chrome/beryllium alloy cemented to dentin.

OBJECTIVE: Treating teeth with adhesive agents before placing a provisional restoration can prevent tooth sensitivity. This study evaluated the bond strength of resin cements to dentin treated with 2 adhesive agents and 2 provisional cements. METHODS AND MATERIALS: Extracted human molars were prepared by exposing dentin and were treated with either Prime & Bond NT or Clearfil SE Bond. After a simulated impression technique, the teeth were provisionalized with either a eugenol or noneugenol temporary cement. Teeth were cleaned for bonding by either mechanical removal of the cement or use of an acid conditioner. Panavia F and Calibra resin cements were used to cement nickel/chrome/beryllium alloy to the tooth surfaces, and the specimens were debonded. Mean shear bond strengths for each group were calculated. RESULTS: Mean shear bond strengths ranged from 26.6 +/- 5.8 MPa for Calibra bonded to dentin treated with Prime & Bond NT, a noneugenol cement, and mechanically cleaned, to 10.6 +/- 4.4 MPa for Panavia F bonded to unlined (no adhesive) dentin treated with a eugenol cement and mechanically cleaned. Of the 14 groups tested, significant differences were observed related to the adhesives and resin cements. Both temporary cements reduced the bond to dentin not treated with a resin adhesive. Use of an acid conditioner for cleaning the temporary cement also reduced bond strengths in all groups. CONCLUSIONS: Placement of a dentin adhesive before provisionalization may prevent the temporary cement from affecting the bond of the final resin cement to the tooth. For the products used in this study, use of phosphoric acid to clean the tooth surface is not recommended.

Cementation↗
PubMed2004

Crowns cemented on crown preparations lacking geometric resistance form. Part II: effect of cement.

PURPOSE: This study evaluated the effect of different cements on resistance to dislodgment of crowns cemented on preparations lacking geometric resistance form. MATERIALS AND METHODS: A preparation that offered no geometric resistance form, with 20 degrees total occlusal convergence (TOC), 0.9 mm wide shoulder finish line, and a 2.5 mm axial wall height was created on an ivorine tooth using a milling machine. Ten metal test specimen die replicas and 10 standardized metal crowns with recipient sites for the application of external forces through a universal testing machine were fabricated. The crowns were cemented on the dies under 5 and 10 kg external loads, the marginal openings measured, loaded to dislodgment, and cleaned of cement. The process was repeated using zinc oxide and eugenol (ZOE), zinc phosphate (ZPh), resin modified glass ionomer (RMGI), and composite resin (CR) cements. RESULTS: Marginal openings under 5 kg cementation loads were 74.63 (+/-15.04) for ZOE, 75.98 (+/-18.20) microm for ZPh, 98.58 (+/-22.62) microm for RMGI, and 105.82 (+/-20.07) microm for CR cements respectively; under 10 kg cementation loads they were 57.62 (+/-15.86) microm, 59.55 (+/-15.41) microm, 95.00 (+/-19.52) microm, 101.30 (+/-12.52) microm respectively. Oblique dislodgment forces, measured with a Universal testing machine, were 40.18 (+/- 6.76) N for ZOE, 215.65 (+/-45.79) N for ZPh, 165.43 (+/-19.53) N for RMGI, and 181.54 (+/-30.75) N for CR respectively when crowns were cemented under 5 kg loads. The corresponding values for 10 kg loads were 38.62 (+/-4.19), 274.86 (+/-54.22), 139.70 (+/-21.71), and 160.40 (+/-21.21) respectively. Only zinc phosphate cement produced statistically enhanced resistance when crowns were cemented under 10 kg force (p value = 0.035). CONCLUSIONS: Under the conditions of the present study only crowns cemented with zinc phosphate displayed increased resistance to dislodgment on preparations lacking resistance form.

Cementation↗
PubMed2000

[Effects of the cementing technique on cementing results concerning the coxal end of the femur].

The purpose of this study was to determine the influence of jet-lavage and cement pressurising techniques upon cement penetration into proximal femoral cancellous bone. In a cadaver study 60 left human cadaver femora were used for implantation of cemented stem components. Four different groups of cementing techniques were generated, the allocation to the groups was randomized. Bone lavage was carried out either using jet-lavage or manual syringe lavage, cement application differed with regard to the amount of pressurisation used. Five different stem designs were used. Radiographs were taken and horizontal sections were obtained at predefined levels (2 cm) using a diamond saw. Microradiographs were taken and analysed using image analysis to assess cement penetration into cancellous bone. In an additional study the influence of jet-lavage (1000 ml) versus syringe lavage (1000 ml) was studied in 11 paired human cadaver femora. The specimens were imbedded in specially designed pots. Bone cement was applied in a retrograde manner and subjected to a standard pressure protocol with a constant force of 3000 N. The analysis protocol was identical to the main experiment. Both jet-lavage and pressurisation of bone cement significantly improved the penetration of cement into cancellous bone (p = 0.027 and p = 0.003, respectively). In the presence of strong, dense cancellous bone the findings were more pronounced. In the additional comparative study cement intrusion was significantly better (p < 0.001) in the jet-lavage group. We did not observe an influence of the stem type upon outcome (penetration). The use of jet-lavage yields significantly improved cement penetration and should be regarded mandatory in cemented total hip arthroplasty. High pressurising techniques are effective means to improve the interdigitation between cancellous bone and cement, but should only be administered in combination with jet-lavage to reduce the risk of thrombo-embolic complications.

Arthroplasty, Replacement, Hip↗
PubMed2003

Effects of pre-cooling and pre-heating procedures on cement polymerization and thermal osteonecrosis in cemented hip replacements.

Numerical studies were performed to investigate bone cement polymerization, temperature history and thermal osteonecrosis in cemented hip replacements with finite element methods. In this paper, the effects of pre-cooling and pre-heating of the prosthesis and/or the cement prior to implantation were simulated. It was found that the cement polymerization initiated near the bone-cement interface and progressed toward the prosthesis when both the cement and prosthesis were initially at room temperature. When the prosthesis and/or cement were pre-cooled, a reduction of the peak temperature at the bone-cement interface resulted, and this may reduce thermal osteonecrosis. However, this also slowed the polymerization process, and may result in a weaker bone cement. If the prosthesis was significantly initially heated, bone cement polymerization reversed reaction direction, started from the cement-prosthesis interface and proceeded toward the bone. Such polymerization direction may reduce or eliminate the formation of voids at the cement-prosthesis interface. Numerical results also showed that pre-heating seemed unlikely to produce significant thermal damage to the bone. The method of pre-heating the prosthesis prior to implantation may decrease the likelihood of cement-prosthesis loosening and increase the life of total hip arthroplasty.

Arthroplasty, Replacement, Hip↗
PubMed1984

Cement distribution and bond strength in cemented posts.

Rods of lucite were drilled to receive a No. 5 parapost to a depth of 4 mm and 7 mm. Posts were fitted and cemented either by coating the post with cement or by placing the cement in the prepared hole with a lentulo spiral in a low-speed hand-piece and then inserting the pre-coated post. Photographs were taken to determine the distribution of the cement. The lentulo spiral distributed the cement along the entire length of the preparation, but coating alone did not distribute the cement evenly. The tensile strength with these two methods of post cementation was also compared in four groups of extracted teeth. In Groups IA and IIA, the post preparation was rinsed with 2 ml of 5.25% NaOCl and dried with paper points and blasts of air. In Group IA, the post was coated with zinc phosphate cement and seated. In Group IIA, the cement was placed into the post space with a lentulo spiral in a slowly rotating hand-piece; the post was then coated and seated. In Groups IB and IIB, the post preparation was rinsed with 1 ml of 17% Na2 EDTA followed by 1 ml of 5.25% NaOCl to remove the smeared layer at the dentin-cement interface. The posts were then cemented as in IA and IIA. Under the conditions of this experiment, the following conclusions can be drawn: Placing cement into the preparation with a lentulo spiral increased the tensile strength and the overall cement distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Cementation↗
PubMed1997

Effects of cement creep on stem subsidence and stresses in the cement mantle of a total hip replacement.

In cemented total hip prostheses, the role of creep of the acrylic cement (polymethyl methacrylate, [PMMA]) in increasing or decreasing the chance of failure of the cement mantle is a subject of ongoing controversy. In the present study we used a three-dimensional finite-element model of a cemented stem to assess the influence of cement creep on subsidence of the stem, and on the stress and strain in the cement under cyclic load, both in the short and long term. The cement layer was assigned the shear and bulk creep moduli of Zimmer regular PMMA cement, which were obtained experimentally. The stem-cement interface was modeled either as (1) completely bonded, (2) completely debonded with friction, or (3) completely debonded and frictionless. Under the cyclic load some cement creep occurred with all three bonding conditions, allowing additional subsidence of the stem and a decrease in the stress components within the cement. During the unloaded period the full recovery of the preload conditions could be reached with the completely bonded and with the frictionless interfaces. With the frictional interface there was residual cement creep, residual stresses within the cement, and residual subsidence of the stem during the unloaded period; however, the reduction of the stress was at most 13% and the subsidence was about 0.46 mm. The much larger subsidence of debonded stems that is often observed clinically might be attributed to the factors which were not included in the present model, such as circumferential bone remodeling.

Biocompatible Materials↗
PubMed1998

Effects of prosthesis surface roughness on the failure process of cemented hip implants after stem-cement debonding.

Retrieval studies suggest that the loosening process of the cemented femoral components of total hip arthroplasties is initiated by failure of the bond between the prosthesis and the cement mantle. Finite element (FE) analyses have demonstrated that stem-cement debonding has stress-producing effects in the cement mantle. High interface friction, which corresponds to a degree of surface roughness, reduces these stresses. In experiments, however, debonded rough stems produced more cement damage than polished ones; in the Swedish Hip Register polished stems were clinically superior with respect to stems with a mat surface finish. The purpose of the present study was to investigate this contradiction. For this purpose, global and local FE models with debonded stem-cement interfaces were used to study the effects of prosthesis surface roughness on the cement stresses on a global scale and microscale, respectively. Similar to earlier numerical studies, the global FE model predicted that an increased surface roughness of the stem reduced the stresses in the cement mantle. The local model provided insight in the load-transfer mechanism on a microscale and could explain the experimental and clinical findings. The local cement peak stresses around the asperities of the surface roughness profile increased with increasing surface roughness and decreased again beyond a particular roughness value. Cement abrasion is caused by localized stresses in combination with micromotion. From this study it can be concluded that to minimize cement abrasion, debonded stems should either have a polished microstructure to minimize the local cement stresses or have a profiled macrostructure to minimize micromotions at the stem-cement interface.

Arthroplasty, Replacement, Hip↗
PubMed1994

A novel skeletal drug delivery system using self-setting calcium phosphate cement. 7. Effect of biological factors on indomethacin release from the cement loaded on bovine bone.

The use of self-setting bioactive calcium phosphate cement containing indomethacin as a model drug in bovine bone was investigated by means of an in vitro drug release test, mercury porosimetry, and scanning electron microscopy (SEM). Calcium phosphate cements containing 2 and 5% indomethacin after being mixed with dilute phosphoric acid were applied to defect sites and the medullary cavity of bovine bone and transformed into hydroxyapatite. The in vitro drug release from the cement loaded on the defect site into a simulated body fluid (SBF) containing 2.5 mM Ca2+ and 1.0 mM HPO4(2+) or 0.1 M phosphate buffer at pH 7.25 and 37 degrees C continued for more than 3 weeks. The release profiles of the drug-loaded cements in phosphate buffer were linear using the Higuchi plot; however, that was not the case for SBF. The drug release in SBF was much lower than that in phosphate buffer. The total pore volume of the cement after the drug release test in SBF was lower than its initial value. However, the pore size of 0.1-0.01 microns after drug release in phosphate buffer was higher than that seen in SBF. The micropore distribution results suggested that hydroxyapatite crystallized from SBF and the pore volume in the cement decreased after drug release. However, in phosphate buffer it appeared to dissolve. The SEM observations for cements loaded on the bone after drug release in phosphate buffer suggested that there was a boundary layer between the cement and natural bone, but this was not the case in SBF, where the cement bonded with the natural bone. The drug release rates from the cement-loaded bone were significantly higher than those from cement loaded on the dissolution holder. The results suggested that cement formation and drug release were affected by the presence of protein from natural bone. The drug release rates from the cement loaded on the defective bone were slower than those from the medullary cavity.

Animals↗
PubMed1997

In vivo study of calcium phosphate cements: implantation of an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste.

alpha-Tricalcium phosphate (alpha-TCP)/dicalcium phosphate dibasic (DCPD)/tetracalcium phosphate monoxide (TeCP) cement was implanted in paste form into soft tissue (rate subcutaneous sockets) and bone tissue (defects in rabbit mandibles) to evaluate the setting behaviour of the cement and tissue responses to the cement. A histological study of the soft tissue implants revealed thin fibrous capsule formation, the appearance of multinucleated giant cells on and close to the cement surface, and small clusters of the cement near the main part of the set cement which were formed by the migration of the paste while setting. X-ray diffraction (XRD) analysis of the implanted cement showed peaks for hydroxyapatite (HA) which increased as the implant period increased. Histology and microradiography of the bone tissue implants showed well-set cement without migration, active bone formation around the cement and direct bone union to it. However, the cement disappeared from the implant site in 4 of 16 specimens where intense bleeding seemed to wash away the implants while setting. From the results of the present study, we concluded that the cement is well tolerated, especially by bone tissue. This may be related to the fact that the cement sets producing HA. The cement is a promising material as a bone substitute; however, there is a problem of migration while setting in soft tissue and of exclusion from the bone defects by intense bleeding.

Animals↗
PubMed1993

[Blood lamination in bone cement--effect of cementing technique].

The quality of the cement layer influences the long-term survival of cemented endoprostheses. However, blood and fluid laminations within the cement layer, which can form during implantation of endoprostheses, lead to the deterioration of bone cement. Since the bone cement is the weakest part in the construction consisting of prosthesis, bone and bone cement, further weakening of the bone cement should be avoided if possible. By means of in vitro studies, three different cementing techniques were tested, measuring quantitatively the amount of fluid within the cement layer after implantation. The least amount of fluid within the cement layer was found in the cement-canal technique, and the highest amount in anterograde cement injection. Retrograde cement injection led to intermediate values.

Biomechanical Phenomena↗
PubMed2000

A comparison of 2 modern femoral cementing techniques: analysis by cement-bone interface pressure measurements, computerized image analysis, and static mechanical testing.

Modern cementing techniques aim to improve microinterlock and to reduce aseptic loosening. The Norwegian and Swedish Arthroplasty Registers have shown an increased risk of revision using reduced-viscosity cement. We have compared 2 modern cementing techniques using retrograde insertion of normal-viscosity and reduced-viscosity cements. Laboratory-simulated arthroplasty was performed in paired human femora. Performance was evaluated by measuring pressures generated during cementation, cement penetration, and shear strength of the prosthesis-cement and bone-cement interfaces. Large differences exist between these 2 modern techniques. Despite no statistical differences between the pressure measurements with the 2 techniques, greater penetration of reduced-viscosity cement was found proximally, with a trend toward increased penetration of the more viscous cement distally. Areas of greater cement penetration with reduced-viscosity cement proximally produced higher values of ultimate shear strength. Both techniques showed a progressive increase in the shear strength as the level of the section progressed toward the tip of the prosthesis. There is a trend with both techniques for the distal fixation to be stronger.

Arthroplasty, Replacement, Hip↗
PubMed1993

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

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

Dental Cements↗