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PubMed2004

Initial stability of cemented femoral stems as a function of surface finish, collar, and stem size.

BACKGROUND: The optimum surface roughness of cemented femoral stems used for total hip replacement is a subject of controversy. While rougher surfaces provide stronger cement adhesion, it has been hypothesized that polished, tapered, noncollared stems settle into the cement mantle, providing improved stability. However, the effects of surface finish on the stability of straight, cemented stems tapered only in the coronal plane are not known. METHODS: Using composite model femora, we assessed the initial stability of a straight, cemented femoral stem as a function of surface roughness, the presence or absence of a collar, stem size, and the resultant cement thickness under simulated walking and stair-climbing loads. Otherwise identical stems were manufactured with polished or rough surfaces, with or without a collar, in two different sizes. We isolated these three variables and compared their relative contributions to the motion at the stem-cement interface throughout cyclic loading. We defined three indicators of stability: per-cycle motion, rate of migration, and final migration. RESULTS: Surface roughness had a greater influence on per-cycle motions than did the presence or absence of a collar or cement thickness. Specifically, in the medial-lateral direction, per-cycle motion of polished stems was 43 micro m greater than that of rough stems (p < 0.01). None of the per-cycle motions decreased over the 77,000 load cycles. In contrast, with all stems, the rate of migration decreased over the course of cyclic loading, but the rate of migration of the polished stems was greater than that of the rough stems. Final migrations of the stems over the course of loading were generally distal, medial, and into retroversion. Compared with rough stems, polished stems had 8 to 18 micro m more axial migration (p < 0.001), 48 micro m more anterior-posterior migration (p < 0.001), and 0.4 degrees more rotational migration (p = 0.01). CONCLUSIONS: and CLINICAL RELEVANCE: The results indicated that, for cemented, straight femoral stems tapered only in the coronal plane, a rough surface offers the advantage of less per-cycle motion. These results may apply to widely used cemented stem designs based on the profile of the original Charnley femoral component, which has approximately parallel anterior and posterior aspects.

Arthroplasty, Replacement, Hip↗
PubMed2004

Effects of dorsal flanges on fixation of a cemented total hip replacement femoral stem.

BACKGROUND: Although current designs of cemented femoral stems for total hip replacement include both those with and those without a flanged shape at the proximal end, the influence of anteroposterior dorsal flanges on the fixation of the stem is not completely understood. The purpose of this study was to assess the effects of flanges on femoral stem stability and load transfer to the femur with use of an in vitro model. METHODS: We measured femoral surface strains and three-dimensional micromotion in synthetic femora under cyclic loading with four types of stems: those with flanges and those without flanges in two sizes each. The four types of stems were otherwise identical; that is, all of them were straight, polished, and collarless. Stem-cement micromotion measurements and strain measurements were repeated with three stems of each type, whereas bone-cement micromotion measurements were made with one stem of each type. RESULTS: Flanges had a greater influence on femoral strains and micromotion than did the difference in the cement thickness resulting from the different stem sizes. Specifically, the flanged stems produced greater strains on the medial femoral surface but smaller strains on the anterior surface than did the non-flanged stems. Flanged stems achieved tighter mechanical interlock within the cement, but these stems increased bone-cement micromotion. Specifically, the motion per cycle of flanged stems within the cement mantle was smaller than that of non-flanged stems, whereas the motion per cycle of the cement mantle within the femoral canal was greater with the flanged stems than with the non-flanged stems. CONCLUSIONS: Flanges on a total hip femoral stem increase the interlock between the stem and the cement and decrease the proximal-medial stress-shielding. However, these advantages occur with increased bone-cement interface motion, which may be detrimental to the survival of the implant.

Adult↗
PubMed1994

Tensile bonding strength of the cement-prosthesis interface.

A widely held belief among orthopedic surgeons is that there is no adhesion between polymethylmethacrylate bone cement and metal. However, a bond does form between the cement and the standard grit-blasted implant finish. Moreover, it has been shown that disruption of this bond or "debonding" of this interface is a major factor in the initiation of failure of some cemented total joint arthroplasties. It is the purpose of this study to determine the tensile pull-off strength of the bone cement-implant surface interface. A 1.27 cm (0.5 in) layer of Simplex-P bone cement was cured between two Co-Cr-Mo pins of 2.22 cm (0.875 in) diameter which had the standard implant finish on the surface that was interfaced with the cement. The specimens were tested in an MTS machine in stroke control with a cross head rate of 1 in per minute. The maximum load to failure was recorded. Bonding of the cement to the surface does occur. The tensile pull-off strength of the bone cement-implant surface interface is approximately 5 MPa. Other studies have shown that maintaining this bond between the stem and cement is important in maintaining the stability of cemented total joint arthroplasties.

Adhesiveness↗
PubMed1993

A basic study of a new adhesive lining cement applied emulsion of hydrophobic polymer.

To diminish the effect of water on the adhesive durability of lining cement, an experimental lining cement using a hydrophobic polymer as the cement liquid was studied. The polymers were styrene-butadien-alkyl acrylate copolymer (SBA copolymer) and carboxylated styrene-butadien-alkyl acrylate copolymer (CSBA copolymer) and were used as aqueous emulsions. The cement powder consisted of alkaline silicate and calcium disilicate. The pH values of the immersion water of the cement prepared from emulsion of SBA copolymer (SBA cement) was almost the same as that of calcium hydroxide cement. The compressive and diametral tensile strengths of SBA cement gradually increased over time in water. The bond strengths of cement prepared from the CSBA copolymer emulsion containing five percent carboxyl groups by weight were superior to those of calcium hydroxide cement.

Acrylic Resins↗
PubMed2002

Properties of encapsulated and hand-mixed zinc phosphate dental cement.

PURPOSE: Dental cements can be supplied as loose powder and liquid or as encapsulated syringes. This study assessed the compressive strength of a recently marketed zinc phosphate encapsulated cement compared with a hand-mixed system according to the American Dental Association Specification. MATERIALS AND METHODS: The mean fracture strength, standard deviations and associated Weibull Moduli (m) of the encapsulated and hand-mixed cements were determined by compressive fracturing 30 cylindrical specimens (height 6.0 +/- 0.1 mm, diameter 4.0 +/- 0.1 mm). Scanning electron microscopy was employed to assess crack growth from indentations and cement morphology. Image analysis was used to investigate the influence of mixing regime on pore distribution within the cement samples. RESULTS: The compressive strength data showed variation in magnitude and reliability ranging from 42 +/- 8 MPa (m = 5.2 +/- 1.0) for the encapsulated cement filled directly from the capsule to 71 +/- 11 MPa (m = 6.3 +/- 1.3) for the hand-mixed cement. The encapsulated cement matrix was extensively porous, consisting of pores between 0.1-0.5 microm diameter, compared with the non-porous hand-mixed cement matrix. Larger pores (over 18 microm diameter) were related to air entrapment in the encapsulated cement on mixing while small pores (0.1-0.5 microm diameter) were indicative of vaporization porosity commonly seen with exothermic reactions.

Air↗
PubMed2002

[An in vitro study of the tensile strength of a new titanium root post with respect to the type of luting cement used].

BACKGROUND: Assessing the retentive capabilities of a new titanium root post (Optipost, Komet-Gebr. Brasseler, GmbH and Co. KG Lemgo, Germany) with a decreasing diameter shape (turret like) and how these can be improved by the choice of fixing cement. METHODS: The tensile strength was assessed in relation to the type of cement used. The following cements were tested: Compolute composite cement (Espe), C/B Crown & Bridge Luting Composite (Bisco), Diamond Link cement (DRM) with Harvard cement as a control. The cementing procedures laid down by the manufacturers were followed in the case of each cement. The results of the traction tests were analysed and compared statistically and a SEM evaluation of the root/cement and cement/post interface was carried out. RESULTS: The results showed that the highest absolute mean value (best performance) was Diamond Link cement (46.48+/-14.31 kg) which also came out best in the statistical analysis (Scheffe Test p=0.007). Analysis of the samples at the SEM confirmed the results of the traction tests. CONCLUSIONS: The characteristic < > form of the Optipost root post and the sanding of the surface would appear to be important factors which, together with the adhesive cementing technique, lead to a high decementing resistance.

Biocompatible Materials↗
PubMedDate not supplied

Borderline indications for use of cement in total joint replacements.

In order to delineate the borderline indications for the cemented and uncemented total hip replacements, we need to evaluate the existing success rates with these procedures. The long term success rates with cemented total hip replacements done using an intramedullary methylmethacrylate plug, doughy Simplex bone cement introduced in a retrograde fashion via a cement gun, and collared cobalt-chrome femoral components with rounded corners were reviewed at eleven year follow-up. The patients ranged in ages from 20 to 84 years (mean 57 years). Among the 105 patients in the group followed up at a minimum of 10 years 97% of the femoral components remained rigidly fixed. These results suggest that the cemented femoral components give satisfactory results to the vast majority of patients over eleven years. Further improvements in the use of cement for prosthetic fixation were made since then. The strength of the cement-prosthesis interface is now considerably enhanced by precoating the prosthesis industrially with a thin layer of methacrylate and or by using texture prosthesis. The strength of cement is considerably improved by techniques such as centrifuging the cement after mixing, or mixing the cement in vacuum. These techniques appear promising and may further enhance the fixation of the prostheses to the skeleton.

Adult↗
PubMed2004

[Evaluation of results after reimplantation of total hip arthroplasty cemented cup].

PURPOSE OF THE STUDY: The aim of the study is to evaluate the results achieved after the replacement of a loosened or broken cemented cup by another cemented cup and to specify conditions under which such procedure may be successful. MATERIAL: In the period of 1992-1997, 158 revision surgeries of total hip arthroplasty were performed at the authors' Department. In 69 patients (57 women, 12 men) the cemented cup was replaced by another cemented cup and the original femoral monocomponent with the 32 mm head diameter the surface of which was not damaged was left in place. METHODS: The indication for operation was loosening of Degree 2 or 3 of the classification after Krbec et al. The surgery was performed from the Watson-Jones or Bauer approach. The cup was always revised with the use of the Palacos cement in combination with antibiotics by the cementing technique of 2nd generation. Augmentation was used in 11 cups. The original femoral component was always returned to the original cemented bed and a cement mantle was added in the proximal part in 15 patients. Poldi cups were replaced in all patients of the followed up cohort (63 times loosening--91%, 6 times breakage--9%) using 3 types of cups for revision surgery (Poldi--44 times, Ultima--20 times, SPC--5 times). During the period of March through December 2001, 48 patients were followed up in the out-patient department. The clinical condition was evaluated on the basis of the Harris Hip Score and a radiograph was made to monitor changes in the position of the cup, linear wear, the presence and size of the radiolucent zone. RESULTS: The results were evaluated in 48 patients (40 women and 8 men) with the average interval of 63 months after revision of the cup (range, 46 to 112 months). However, the clinical and radiograph evaluation of the condition was made only in 45 patients. Three patients re-operated on in 2001 were not included in the evaluation. The Harris Hip Score was on average 78 points (range, 51 to 97 points). Radiographs did not show any change in the position of the cup. The linear wear up to 1 mm was revealed in 4 cups and above 1 mm in 1 cup (11% of the evaluated patients). The radiolucent line in zone III after DeLee and Charnley was present in 4 cups, in zones II and III in another 4 patients, i.e. in total in 8 of 45 cups (18%). DISCUSSION: The group of 45 followed-up patients may be considered a sufficiently representative sample of the original 69-member cohort (minimally 7 patients died in the follow-up period, 3 patients were not included in the evaluation). With regard to the average follow-up of 63 months the results may be considered as medium-term. The average interval between primary total hip arthroplasty and revision of 130 months is comparable with the results of similar studies by other authors. The results of the clinical evaluation on the basis of Harris Hip Score are not convincing (range, 51 to 97 points, average 78 points). Radiographs showed a radiolucent zone in 8 cups (18%). Another 3 patients were at the time of evaluation after a repeated revision of the cup for loosening (at the interval of 22 to 34 months). CONCLUSION: A good integration of the cemented cup used in revision of the loosened cemented cup of total hip arthroplasty was evident only in infrequent cases of a perfectly preserved acetabulum both from the viewpoint of shape and structure. The evaluation of other patients of the followed-up cohort, however, produced rather unconvincing results. On this basis and also on the basis of their experience in the use of cementless cups in revision of total hip prostheses the authors recommend to prefer a cementless implant in the revision of the cup.

Aged↗
PubMed2004

Cementing constrained acetabular liners in revision hip replacement: clinical and laboratory observations.

During revision hip arthroplasty, removal of a well-fixed, ingrown metal acetabular component may not be possible. Therefore, a new polyethylene liner can be cemented into the existing shell via the cement locking mechanism. This technique is well recognized, and the cement locking mechanism has proved to be sufficiently strong and durable for clinical use. A constrained polyethylene liner is designed to reduce the risk of hip dislocation by capturing the femoral head. However, there are increased shear forces created at the liner interface as the dislocation is resisted. If a constrained liner is cemented into an ingrown acetabular component, then there is the theoretical risk that these increased shear forces will damage the cement locking mechanism, thus leading to failure of the construct. There are a few clinical series in which a constrained liner has been used with the cement locking mechanism. Overall, the failure rate of the cement locking mechanism is no greater if a constrained liner instead of a standard liner is used. The cement locking mechanism can be strengthened by roughening the backside of a smooth polyethylene liner to improve the cement-polyethylene interface, or by using an all-polyethylene acetabular component that is designed to be used with cement. Whether a smooth metal shell needs to be roughened as well is a matter of debate.

Arthroplasty, Replacement, Hip↗
PubMed2006

Effect of polymerization mode of adhesive and cement on shear bond strength to dentin.

PURPOSE: To investigate the shear bond strength to dentin when two resin adhesive systems in light-cure, dual-cure, and auto-cure modes were used with three resin cements. This was done to determine the degree of compatibility that exists when resin products with different polymerization mechanisms are used together. METHODS: Three hundred non-carious human molars were divided into 30 test groups in which Prime & Bond NT and ScotchBond Multi-Purpose were used as adhesives with Calibra, Nexxus and Variolink cements to attach Rexillium III posts to flattened dentin surfaces. Debonding was achieved with an Instron testing machine and mean shear bond strengths were determined for each test group. The data were subjected to three-way ANOVA and post-hoc LSD testing to determine whether significant differences existed between the test groups. RESULTS: Bond strengths achieved were affected by the adhesive, the cement, and the cement curing mode. In general, the auto-cure application of the three cements demonstrated reduced shear bond strengths, both with respect to the different adhesives and their curing modes as well as compared to the dual-cure technique of the same cement. Additionally, Prime & Bond NT demonstrated considerably more variability than ScotchBond Multi-Purpose when used with both dual-cure and auto-cure varieties of the three cements. The bond strengths of resin cements depend on the curing mode of the cement and the adhesive. Unlike with direct light-cured resin composites, combining adhesive systems and dual-cured resin cements from different manufacturers may be contraindicated.

Adhesives↗
PubMed2006

Effect of low O2-gas transmission rate barrier films on knoop hardness and toothbrush abrasion of resin cements.

PURPOSE: To investigate the influence of utilizing films with different oxygen transmission rates (O2-GTR) on Knoop hardness and toothbrush abrasion of resin cements for luting. METHODS: Four dual-activated, composite-type resin cements, and a chemically activated PMMA-type resin cement, were used. Three different types of barrier films (Techbarrier HI, Harden Film N130, and Lix-2) were used. Resin cement was mixed and inserted into a cylindrical mold (4 mm in diameter, 3 mm in height), then chemically activated. The specimens were stored in the dark at 37 +/- 1 degrees C, 90 +/- 5%RH conditions for 1 hour. Knoop hardness on the top surface of the resin cement was measured with a microhardness tester. The top surface of specimens (8 mm in diameter, 3 mm in height) polymerized under the same conditions were used for toothbrush abrasion testing. One-way ANOVA followed by Tukey HSD test (P< 0.05) were done. RESULTS: When the cement surface was covered by low O2-GTR film, a significant increase in Knoop hardness and resistance to toothbrush abrasion was observed for the dual activated, composite-type resin cements, but not for the chemically activated PMMA type resin cement. From the results of this study, the use of low O2-GTR matrix barrier films for the dual activated, composite-type resin cements could be effective in eliminating the oxygen inhibited layer on the cement surface.

Hardness↗
PubMed2006

Antimicrobial properties of erythromycin and colistin impregnated bone cement. An in vitro analysis.

Deep surgical site infection is a devastating consequence of total joint arthroplasty. The use of antibiotic impregnated bone cement is a well-accepted adjunct for treatment of established infection and prevention of deep orthopaedic infection. It allows local delivery of the antibiotic at the cement-bone interface and sustained release of antibiotic provides adequate antibiotic coverage after the wound closure. Preclinical testing, randomised and clinical trials indicate that the use of antibiotic-impregnated bone cement is a potentially effective strategy in reducing the risk of deep surgical site infection following total joint arthroplasty. The purpose of this study was to assess antibacterial activity of erythromycin and colistin impregnated bone cement against strains of organisms' representative of orthopaedic infections including Gram-positive and Gram-negative aerobic organisms: Staphylococcus aureus, coagulase-negative Staphylococci, Enterococcus sp., Proteus sp., Klebsiella sp., Pseudomonas sp., and Escherichia coli. Pre-blended Simplex P bone cement with the addition of erythromycin and colistin (Howemedica Inc) was mixed thoroughly with 20ml liquid under sterile conditions to produce uniform cylindrical discs with a diameter of 14mm and thickness of 2mm. 24-48 hour agar cultures of Staphylococcus aureus, coagulase-negative Staphylococci, Enterococcus sp.,Proteus sp., Klebsiella sp.,Pseudomonas sp., and Escherichia coli were used for the agar diffusion tests. The agar plates were streaked for confluent growth followed by application of erythromycin and colistin impregnated bone cement disc to each agar plate. The plates were incubated at 30 degrees C and examined at 24, 48, 72 hours, and four and five days after the preparation of the impregnated cement. The susceptibility of Staphylococcus aureus to the control discs was most clearly demonstrated showing a distinct zone of inhibition. The zone observed around coagulase-negative Staphylococci, Klebsiella sp., Pseudomonas sp., and Escherichia coli were also significant. However, there was no zone of inhibition or signs of antibacterial activity at the cemented surface were detected around discs with Enterococcus sp. and Proteus sp. The results showed that Simplex P bone cement with the addition of erythromycin and colistin was effective against most of the broad spectrum organisms encountered during total joint arthroplasty. The activity of Simplex P bone cement impregnated with erythromycin and colistin is mainly during the first 72 hours.

Anti-Bacterial Agents↗
PubMed1991

[Histamine release and cardiovascular reactions to implantation of bone cement during total hip replacement].

Cardiovascular reactions to acrylic bone cement in patients with total hip replacement are a common complication. Hypotension and arrhythmias are the most frequently observed symptoms. Elderly patients with fractures of the femoral neck constitute a special risk group. In some patients these reactions can be fatal. The mechanisms suggested to explain these reactions are embolism of air, polymer or fat, reaction to the heat, and toxic or vasodilating effects of the acrylic monomer. In a pilot study and in a case report a significant rise of the plasma histamine was described following cementation of the femur. We therefore performed an investigation to find whether application of bone cement to the femur caused histamine release in elective hip surgery, and, independently of this, also investigated whether premedication with H1- + H2-antagonists had any effect on the cardiovascular reactions due to bone cement implantation into the femoral shaft in elderly patients with hip fracture. METHODS. Part I. In all, 40 patients, scheduled for elective surgical hip replacement were anesthetized by general or epidural anesthesia. Patients were continuously monitored by ECG. Blood pressure was recorded noninvasively at 2-min intervals during the study. Blood samples for the determination of the plasma histamine were taken immediately before implantation of the bone cement into the femur, and 2, 5, and 10 min after. Part II. A further group of 20 patients aged greater than or equal to 70 years with fractures of the femoral neck and in whom total hip replacement was planned were included in the study. In this group, 10 patients were randomly assigned to receive 4 mg clemastine + 400 mg cimetidine i.v. about 15 min before implantation of the bone cement. All patients were operated on under general anesthesia. ECG was monitored continuously and blood pressure was monitored at 2-min intervals during the study. Changes of the blood pressure and heart rate and therapeutic interventions following the implantation of the bone cement were documented. RESULTS. Part I. In 11 of the 40 patients (27.5%) plasma histamine increased by greater than 0.5 ng/ml (9 patients greater than 1 ng/ml). In comparable groups (patients with a control systolic blood pressure less than or equal to 130 mmHg) the histamine responders showed a significantly greater reduction in systolic blood pressure (-5.7 +/- 14.7 vs -17.7 +/- 8.6 mmHg). Part II. In the control group we observed a significantly greater fall in systolic blood pressure than in premedicated patients (41.5 +/- 25.4 vs 11.0 +/- 13.4 mmHg). In the control group 7 of the 10 patients required therapeutic interventions, while in the premedicated group only one therapeutic intervention was necessary (P less than 0.05). DISCUSSION. We have demonstrated that the implantation of acrylic bone cement into the femur may increase plasma histamine by greater than 1 ng/ml. In elderly patients with preexisting cardiac diseases or/and hypovolemia even moderate histamine release can cause serious, sometimes potentially fatal, cardiovascular complications. In this special risk group with hip fractures we found a significant reduction in the frequency of cardiovascular reactions to bone cement implantation in patients premedicated with H1 + H2 antagonists. Because we also observed significant falls in systolic blood pressure in premedicated patients, we assume that the pathogenesis of cardiovascular reactions to bone cement implantation is multifactorial. It may be that potentially lethal complications only occur if two or more of the predisposing factors (hypovolemia, myocardial insufficiency, arrhythmia, embolism, histamine release) are present simultaneously. Pre- and intraoperative measures therefore have to be instituted to eliminate all possible risk factors.

Aged↗
PubMedDate not supplied

Does the thickness of the resin cement affect the bond strength of a fiber post to the root dentin?

This study aimed to evaluate the influence of cement thickness on the bond strength of a fiber-reinforced composite (FRC) post system to the root dentin. Eighteen single-rooted human teeth were decoronated (length: 16 mm), the canals were prepared, and the specimens were randomly allocated to 2 groups (n = 9): group 1 (low cement thickness), in which size 3 FRC posts were cemented using adhesive plus resin cement; and group 2 (high cement thickness), in which size 1 FRC posts were cemented as in group 1. Specimens were sectioned, producing 5 samples (thickness: 1.5 mm). For cement thickness evaluation, photographs of the samples were taken using an optical microscope, and the images were analyzed. Each sample was tested in push-out, and data were statistically analyzed. Bond strengths of groups 1 and 2 did not show significant differences (P = .558), but the cement thicknesses for these groups were significantly different (P < .0001). The increase in cement thickness did not significantly affect the bond strength (r2 = 0.1389, P= .936). Increased cement thickness surrounding the FRC post did not impair the bond strength.

Acid Etching, Dental↗
PubMed1990

Optimization and comparison of three vacuum mixing systems for porosity reduction of Simplex P cement.

Simplex P bone cement was prepared in three commercially available vacuum mixing systems, the Enhancement Mixer, the Mixevac II High Vacuum System, and the Mitab Vacuum System, to determine the improvement in fatigue strength associated with porosity reduction of the cement in all three systems. The results of the fatigue tests of vacuum-mixed Simplex P were also compared to the fatigue strength of Simplex P prepared by centrifugation of the cement immediately after mixing. Vacuum mixing one pack of Simplex P per syringe in all three systems was not effective in complete removal of all the large voids from the cement. Fatigue failure occurred very early in those specimens containing the large voids. There was no significant difference in fatigue life between one pack of cement per syringe mixed under vacuum in the three systems and the control cement (no vacuum, uncentrifuged). Vacuum mixing two packs of cement per syringe was more effective than one pack per syringe, and all three systems significantly increased the cycles to failure of Simplex P over the control cement. However, the Enhancement and Mitab vacuum mixing systems still produced some very weak specimens in fatigue. Two packs of cement per syringe prepared in the Mixevac II vacuum mixing system were significantly stronger in fatigue than two packs mixed in either the Enhancement or Mitab vacuum system. The Mixevac II vacuum mixing system was the most effective technique of the three vacuum mixing systems tested. Centrifugation of one or two packs of Simplex P per syringe produced a more uniform cement that was free of large voids and thus eliminated the very weak specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Cements↗
PubMed1989

[Studies on physico-chemical properties of self-setting apatite cement].

A new dental cement was developed by use of tetracalcium phosphate monoxide (Te-CP) and dicalcium phosphate dihydrate (DCPD). When an equimolar mixture of the two calcium phosphates was mixed with diluted phosphoric acid, it hardened into a phase of hydroxyapatite (HAp) resembling the main inorganic phase of hard tissues. The present study was undertaken to investigate physico-chemical properties of this newly developed apatite cement and to evaluate its potential as dental cement to clinical application. The setting time was reduced in the presence of synthetic HAp, indicating added HAp to be an accelerator in the setting reaction. The pH of paste rapidly increased to a neutral range from initial solution acidity of about 2.0 and the subsequent setting reaction proceeded in a neutral and weak alkaline pH range. The hardened solid 4 hours after saturation was identified as single phase of apatite by X-ray diffraction. The HAp crystallinity of the set cement varied with the crystallinity of HAp added as setting accelerator. The wet compressive strength of the cement stored for one day in synthetic saliva at 37 degrees C increased to 400 kg/cm2 as added HAp crystallinity decreased. Moreover no disintegration took place when the cement was stored at 37 degrees C in synthetic saliva, which was undersaturated with respect to DCPD but well supersaturated for HAp. In clinical application to animals, no significant cleavage was observed between the hard tissues and the cement by SEM even three months after the cement paste was filled in the tooth cavity of monkeys. In the specimen prepared one week after implantation in the medullary canal of rats, no inflammatory cell appeared. The specimen prepared one month after implantation showed that the set cement was tightly contacted with newly formed bone. These findings strongly suggest that the newly developed self-setting apatite cement is useful as a pulp capping agents, root canal fillings and bone substitute.

Animals↗
PubMed1989

[Experimental observations on acrylic bone cement containing antitumor drugs].

By methods of human osteosarcoma cell culture in vitro, 3H-TdR isotope incorporation, gas chromatography and animal test, experimental observations were made on acrylic bone cement containing antitumor drugs. The results were as follows: 1. BLMA5, DACT, Ara-c, CDDP, and ADM were more thermostable. It is possible that these drugs can endure the polymerizing heat of bone cement. 2. The effective release of BLMA5, Ara-c and DACT from bone cement persisted over 2 months. 3. Scanning electron microscopy revealed that drug particles in the bone cement decreased or disappeared after immersion of the cement in tissue culture medium or implantation of it in animal bones. This shows that drug particles can be released from bone cement in vitro or in vivo 4. Animal experimental demonstrated that the bone cement containing BLMA5 or Ara-c had no effect on the healing of soft tissue, and the injury in local bone and bone marrow adjacent to the bone cement was slight and could recover in 4-8 weeks. 5. The release of residual monomer from polymerized bone cement continued as long as one month. Although the residual monomer inhibited the growth of tumor cells slightly during the early stage, it was far from being as effective as medicated bone cement.

Animals↗
PubMed1988

The effect of centrifugation on the fatigue life of bone cement in the presence of surface irregularities.

Reduction of the porosity of bone cement by centrifugation significantly improves the fatigue life of the cement when smooth, waisted specimens are tested. However, bone cement in vivo has surface irregularities at the interdigitation of the cement with the trabecular bone. The effect of centrifugation on the fatigue life of Simplex P in specimens containing surface irregularities was investigated by examining both composite specimens of trabecular bone and bone cement and specimens containing a sharp, circumferential notch. For the specimens with the sharp notch, the bone cement that had been centrifuged lasted significantly longer in fatigue (47,039 +/- 40,277 cycles) than the uncentrifuged specimens (3103 +/- 1950 cycles). Eleven of 15 uncentrifuged specimens broke at the location of a void, rather than the notch. In contrast, when the porosity was reduced by centrifugation, 13 of the 15 specimens broke at the notch. For the specimens that were a composite of bone cement and trabecular bone, the centrifuged specimens had a significant increase in fatigue life compared to the uncentrifuged specimens when tested at both 7 MPA (641,056 +/- 444,131 cycles vs. 237,969 +/- 124,153 cycles) and 15 MPA (8800 +/- 4673 cycles vs. 1534 +/- 719 cycles). Reduction of porosity in bone cement by centrifugation significantly extends its fatigue life even in the presence of trabecular bone or sharp surface notches as used in total joint replacements. These data support the concept that reduction of porosity of bone cement by centrifugation may extend the duration of fixation of the components in cemented total joint arthroplasties.

Animals↗