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PubMed1996

IR and NMR analyses of hardening and maturation of glass-ionomer cement.

It has been reported that the silicate phase as well as the cross-linking of the polycarboxylic acid by aluminum and calcium ions played an important role in the hardening of glass-ionomer cement. The objective of this study was to investigate the structural change during hardening of the cements by means of infrared (IR) spectroscopy and solid-state nuclear magnetic resonance (NMR) spectroscopy and to confirm the role of the silica phase in the hardening of the cement. For that purpose, we measured the change in compressive strength of an experimental glass-ionomer cement, two commercial glass-ionomer cements, and a polycarboxylate cement and carried out 29Si and 27Al NMR analyses of the cement samples after the strength measurement. In the IR spectra during hardening, a characteristic band of the silicate network around 1000 cm-1 shifted toward high frequency with time. The spectrum after hardening was similar to that for a hydrated amorphous silica structure. The 27Al NMR analysis showed that Al3+ ion was tetrahedrally coordinated by oxygen in the original glass, but a part of the Al3+ ion was octahedrally coordinated after hardening to form Al polyacrylate gel. The chemical shift of Si in the 29Si NMR spectra also changed during hardening. The variation in the chemical shift reflected the structural change in the silicate network. The initial increase in compressive strength of the cement was mainly caused by polycarboxylate gel formation. However, it was concluded that the reconstruction of the silicate network contributed to the increase in strength with time during the period after the gelation by cross-linking was completed.

Compressive Strength↗
PubMed2001

Mixing systems and the effects of vacuum mixing on bone cement.

The aim of a good cement mix is to produce bone cement that has the best mechanical properties possible in order that it can carry out its load transfer role successfully over the lifetime of the implant. The data presented shows that vacuum mixing reduces the cement porosity, which results in improved strength, and resistance to creep deformation and fatigue failure in the bone cement. It seems, however, that eliminating a high degree or all of the cement porosity may be detrimental because it leads to greater shrinkage and cracking in the material. A moderate vacuum level will improve the mechanical properties, but reduce the risk of thermal shrinkage and cracking which is seen at higher vacuum levels. In addition, the mixer design has a significant influence on the quality of the cement produced, affecting porosity, unmixed powder and subsequently the mechanical properties of the material. In the next issue we will be concluding this series of articles by covering the importance of temperature and its effects on the phases of the cement polymerisation process. Bone cement training courses are being run within hospitals by Summit Medical as part of our commitment to enhancing the skills of the perioperative practitioner and to ensuring the best long-term outcome for the patient.

Biomechanical Phenomena↗
PubMed2001

Temperature and its effect on bone cement.

Bone cement mixing is often seen as a simple procedure, but the skill of the perioperative practitioner in mixing the cement may ultimately be the difference between the success and failure of a hip or knee joint replacement. Klaus-Dieter Kühn (2000) states: 'The nurses (together with the surgeon) have enormous influence on the quality of the cement dough produced; in the end, this will considerably influence the clinical long-term result of a cemented hip, acetabulum or cemented knee.' (Bone Cements). This process doesn't happen by default. It is the result of good education, supported by sound evidence and backed up by practical experience. This series of articles has explained every aspect of cement management, covering technique, temperature, timing, mixing equipment, the importance of reproducible cement quality and health and safety issues.

Bone Cements↗
PubMed2003

The use of bone cement induces an increase in serum astroglial S-100B protein in patients undergoing total knee arthroplasty.

UNLABELLED: Cerebral microemboli can occur during arthroplasty with the use of bone cement. Astroglial S-100B protein is a sensitive marker of cerebral damage. Therefore, we designed this study to determine the effect of bone cement on the brain by investigating serum levels of S-100B protein in patients undergoing bone surgery with or without bone cement. Fourteen patients undergoing knee arthroplasty (n = 7) or reamed intramedullary nailing for tibial fracture (n = 7) requiring a pneumatic tourniquet were enrolled in this study. Bone cement containing polymethyl methacrylate and methyl methacrylate was used for every patient undergoing knee arthroplasty. Serum samples were obtained from venous blood before the induction of general anesthesia, 15 min after deflation of a pneumatic tourniquet, and 3 days after the operation. The serum level of S-100B protein was significantly increased 15 min after a pneumatic tourniquet deflation in the knee arthroplasty group compared with the tibial fracture group (0.41 and 0.08 ng/mL, respectively; P < 0.05). In all patients studied, no neurological abnormalities were noted in the postoperative period. These results suggest that, in patients undergoing knee arthroplasty, bone cement may transiently induce astroglial injury, although it does not alter neurological outcome. IMPLICATIONS: Serum S-100B protein was significantly increased 15 min after a pneumatic tourniquet deflation in patients undergoing knee arthroplasty with bone cement, but not in those undergoing reamed intramedullary nailing for tibial fracture without bone cement. These results suggest that bone cement may transiently induce astroglial injury.

Aged↗
PubMed1998

Bioactive bone cements.

Poly(methylmethacrylate) (PMMA) bone cement, used to fix implants into the bone, produces good surgical results if used correctly. However, prostheses do eventually become loose and the breakdown of the cement mantle is a factor in this failure. Limitations of PMMA cement, which lead to problems with the fixation of the implant, include its mechanical characteristics and its influence upon surrounding bone, associated with the polymerization reaction. A bioactive bone cement is particularly designed to produce a better interface between the cement and bone. However, an improvement in mechanical properties, especially fatigue, creep and fracture toughness, are an added necessary requirement to increase the lifetime of a cemented implant. The development of a bioactive cement has been conducted mainly in two ways; firstly, to improve existing PMMA cement by the addition of various bioactive agents and secondly, to design an alternative matrix for the bioactive material to be combined with. The most promising investigations which have been conducted, along with their relative benefits and drawbacks, are discussed.

Biocompatible Materials↗
PubMed1992

The press-fit Kinemax knee arthroplasty. High failure rate of non-cemented implants.

We report the results of 75 consecutive primary press-fit Kinemax arthroplasties with an average follow-up of 14 months (three to 28). We reviewed 26 cemented and 49 non-cemented tibial components implanted into 72 patients (30 men and 42 women, median age 70 years). At the latest follow-up the overall evaluation (Hospital for Special Surgery knee rating scale) for cemented cases was excellent in 54%, good in 42% and poor in 4%. No cemented prosthesis loosened. Of the non-cemented cases 55% were excellent, 23% good, and 2% fair. Ten tibial implants (20%) loosened and required revision. Residual pain marred the result in 24% of the non-cemented prostheses and in 4% of the cemented group. We do not recommend the press-fit, smooth-surfaced Kinemax prosthesis for non-cemented use.

Adult↗
PubMed1997

Antibiotic prophylaxis in total hip arthroplasty. Review of 10,905 primary cemented total hip replacements reported to the Norwegian arthroplasty register, 1987 to 1995.

We have assessed the effect of different regimes of antibiotic prophylaxis on the survival of total hip implants, comparing antibiotics administered both systemically and in the bone cement, systemically only, in the bone cement only and with no antibiotics given. We studied 10,905 primary cemented total hip replacements, performed for osteoarthritis of the hip and reported to the Norwegian arthroplasty register between 1987 and 1995. Cox-estimated failure-rate ratios (FRR) are presented with adjustment for gender, age, the brand of cement, the prosthesis, the type of operating theatre and the operating time. For revisions performed for infection (39 operations), the lowest rate of revision was found among patients receiving antibiotic-containing cement plus systemic antibiotics (n = 5804). The revision rate for the 4586 patients receiving systemic antibiotics only was 4.3 times greater (95% CI 1.7 to 11.0, p = 0.001); in 239 with antibiotics in the bone cement only it was 6.3 times greater (CI 1.6 to 25.0, p = 0.003); and in the 276 who did not receive antibiotics it was by 11.5 times greater (CI 2.1 to 63.0, p = 0.002). Adjustment for the total amount of systemic antibiotic administered did not change the results. We also observed an increased revision rate for aseptic loosening (109 operations) comparing the systemic-only (FRR = 1.8, CI 1.1 to 2.9, p = 0.01) and the cement-only regimes (FRR = 2.6, CI 1.2 to 5.9, p = 0.02) with the combined dosage. Our findings show that systemic antibiotics combined with antibiotic-containing bone cement led to fewer revisions than the other methods.

Antibiotic Prophylaxis↗
PubMed1994

The cement mantle in total hip arthroplasty. Analysis of long-term radiographic results.

The correlation between the thickness of the cement mantle, the medullary canal fill, and the orientation of the stem and the long-term radiographic outcome of 836 cemented femoral components in patients who had a primary total hip replacement was assessed with use of survival analysis over a twenty-one-year follow-up period. The femoral stems of hips that had a two to five-millimeter-thick cement mantle in the proximal medial region had a better outcome than stems implanted with a thicker or thinner cement mantle. Stems in femora with less than two millimeters of proximal medial cancellous bone had a better outcome than stems in femora with thicker cancellous bone. Stems that filled more than half of the medullary canal had better radiographic results than those that filled half or less. Progressive loosening, fracture of the cement, and radiolucent lines at the stem-cement or bone-cement interfaces were more likely to develop in stems that were oriented in more than 5 degrees of varus than in those in neutral or valgus. The noted correlations were true whether the stem was made of titanium alloy or of stainless steel. The results of this study emphasize the importance of careful preoperative planning in total hip arthroplasty done with cement and provide guidelines for the selection of the shape, size, and position of the stem.

Bone Cements↗
PubMed1995

Revision hip arthroplasty with the use of cement and impaction grafting. Histological analysis of four cases.

The findings of radiographic studies have suggested that the cementing of an implant with a polished tapered stem into a bed of impacted bone allograft may provide adequate function of the joint and may restore bone in the proximal part of the femur. However, radiographs of hips with cancellous bone graft adjacent to cement are difficult to interpret, and the viability of impacted bone graft that is adjacent to cement and its capability for remodeling are unclear. To evaluate this interface further, we obtained biopsy specimens from the proximal part of the femur at the time of removal of trochanteric wires from four patients eleven to twenty-seven months after revision hip arthroplasty with cement and impaction grafting. Three relatively ill defined zones were identified histologically: an inner zone consisting of bone cement, fibrous tissue, and partially necrotic trabeculae with evidence of bone-remodeling; a middle zone consisting of viable trabecular bone and probable formation of so-called neocortex with fewer particles of bone cement; and an outer zone consisting of viable cortex. Fibrous tissue was present around some of the incorporating fragments of bone graft, but no continuous fibrous membrane was seen. Particles of cement were identified, but no polyethylene debris was visible on examination with light microscopy. The results demonstrated remodeling of bone and at least partial restoration of bone stock in the proximal part of the femur after revision arthroplasty with cement and impaction grafting.

Aged↗
PubMed1995

The effect of the type of cement on early revision of Charnley total hip prostheses. A review of eight thousand five hundred and seventy-nine primary arthroplasties from the Norwegian Arthroplasty Register.

We studied the survival of 8579 Charnley prostheses, in 7922 patients, according to the different types of cement that had been used. All of the patients had had a primary total hip replacement for primary coxarthrosis. The mean duration of follow-up was 3.2 years (range, zero to 6.4 years). The data were collected from the national Norwegian Arthroplasty Register. The duration of survival was defined as the time to revision due to aseptic loosening. The Kaplan-Meier estimate of survival at 5.5 years for the 1226 femoral components that had been implanted with low-viscosity cement was 94.1 per cent (95 per cent confidence interval, 92.1 to 96.2 per cent), compared with 98.1 per cent (95 per cent confidence interval, 97.5 to 98.6 per cent) for the 6589 components that had been implanted with high-viscosity cement (p < 0.0001). The remaining 764 femoral components had been implanted with Boneloc cement, which was classified as neither high nor low-viscosity, and these components were considered as a separate group in the analyses. The Boneloc cement had been used for only three years, and the two-year survival rate of these prostheses was 95.5 per cent (p < 0.0001). The cement contained an antibiotic in 2801 (42 per cent of the hips in which the femoral component had been implanted with high-viscosity cement, compared with only thirty (2 per cent) of those in which it had been implanted with low-viscosity cement.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed1997

Measurement of polyethylene wear in acetabular components inserted with and without cement. A randomized trial.

We measured the three-dimensional wear of polyethylene after total hip arthroplasty with a titanium metal-backed Mallory-Head prosthesis that was inserted with cement in sixty-nine patients (sixty-nine hips) and with a press-fit titanium metal-backed Mallory-Head prosthesis that was inserted without cement in seventy patients (seventy hips). A modular titanium femoral head was used in all of the hips. The patients in the present study were part of a larger double-blind randomized trial comparing the result of total hip arthroplasty performed with cement with that of the same procedure performed without cement in 250 patients. The criterion for inclusion in the study of polyethylene wear was a minimum duration of follow-up of four years, which was met by 148 patients. As adequate radiographs for digitization were not available for nine patients, 139 patients were included in the present study. The age of the patient, the postoperative Harris hip score, the diameter of the femoral head, the thickness of the liner in the polar region of the acetabular component, and the duration of follow-up were similar for the two groups. The mean rate of volumetric wear of the polyethylene was significantly greater in the prostheses that had been inserted without cement than in those that had been inserted with cement (155.1 cubic millimeters per year compared with 98.5 cubic millimeters per year; p = 0.000008). Thirty-four (49 per cent) of the seventy hips in which the prosthesis had been inserted without cement had evidence of osteolysis on radiographs, compared with twelve (17 per cent) of the sixty-nine hips in the other group (p = 0.0002). Osteolysis was associated with an increased rate of polyethylene wear only in the hips in which the prosthesis had been inserted without cement.

Acetabulum↗
PubMed1999

The fate of stable cemented acetabular components retained during revision of a femoral component of a total hip arthroplasty.

BACKGROUND: The decision as to whether to revise or retain a well fixed cemented acetabular component during revision of a femoral component is especially difficult; the rate of loosening of cemented acetabular components is high, whereas that of porous-coated acetabular components inserted during revision is low. However, removal of a well fixed cemented acetabular component can result in increased operative morbidity and cost and in loss of acetabular bone. Data that can be used to predict the long-term survival of retained well fixed cemented acetabular components are therefore needed. METHODS: We studied the five to thirteen-year clinical and radiographic results in a group of twenty-six consecutive patients in whom a well fixed cemented acetabular component had been retained during revision of a femoral component. Typical demographic data on the patients and information about the components were recorded, and the cemented acetabular components were graded as A through F, according to the system of Ranawat et al., at the time of the femoral revision. The average duration of follow-up was 8.4 years (range, 5.0 to 12.7 years). No patient was lost to follow-up. RESULTS: Four acetabular components (15 percent) had progressive radiolucency (at forty-eight, forty-eight, fifty-nine, and seventy-five months after the femoral revision) and were considered radiographically loose despite not being associated with symptoms. All four components were graded as either E or F at the time that they were retained during the femoral revision; radiographic loosening was significantly related to these two grades (p < 0.01). No acetabular component with a grade of A, B, C, or D loosened. The components that loosened had been in vivo for a relatively shorter, as opposed to longer, duration before the femoral revision compared with the components that did not loosen (p < 0.05). CONCLUSIONS: Retention of the well fixed cemented acetabular components was associated with good clinical results but with a 15 percent rate of loosening. Revision of a cemented acetabular component solely on the basis of the duration that it was in vivo or whether a previous revision had been done does not appear to be warranted. Our findings suggest that acetabular components with a grade of A, B, C, or D at the time of a femoral revision may be retained, as these components continued to function at the time of the five to thirteen-year follow-up in the current study.

Acetabulum↗
PubMed1996

Flexure strength of resin-modified glass ionomer cements and their bond strength to dental composites.

The flexure strength of three resin-modified glass ionomer cements and one conventional glass ionomer cement and their bond strength to dental composites were studied by measuring the three-point bending and the shear strengths. The bond strengths between the dental composite and the resin-modified glass ionomer cements were dependent on the curing modes. Resin-modified glass ionomer cements bonded significantly more strongly to cured dental composites than dental composites bonded to cured resin-modified glass ionomer cements. However, the dental composites showed a significantly stronger bonding to the resin-modified glass ionomer cements than to the cured conventional glass ionomer cement, to which the dental composite did not adhere without acid etching. The flexure strengths of the resin-modified glass ionomer cements were significantly improved compared with the conventional one but were still significantly lower than that of the dental composites.

Acid Etching, Dental↗
PubMed1983

A comparison of the mechanical properties of Simplex, Zimmer, and Zimmer low viscosity bone cements.

Many different methods have been used to compare polymethylmethacrylate bone cements. In this paper the three currently available cements were compared in regard to dough and set times, heat of polymerization, compressive, tensile, 3 and 4 point bending strengths, fracture toughness, flexural modulus, void density distribution, and viscosity. Methods used were ASTM designated for bone cement or plastics in general whenever possible. Significant differences in set and dough times and heat of polymerization were noted. All cements were equal in compressive, tensile, and fracture toughness testing; Zimmer Regular Cement was significantly weaker (p less than 0.001) in flexural testing and had a significantly (p less than 0.001) decreased modulus of elasticity when compared to LVC and Simplex Cements. Void density distributions were not significantly different. Viscosity was shown to vary between these cements as well. This data was analysed both to determine differences between various brands of cement and to assess the relevance to clinical use and failure modes in vivo of these different means of testing.

Bone Cements↗
PubMed1997

Intramedullary, antibiotic-loaded cemented, massive allografts for skeletal reconstruction. 26 cases compared with 19 uncemented allografts.

We compared the outcomes of 26 intramedullary cemented massive allografts with 19 allografts without cementation; all allografts were used for reconstruction after excision of bone sarcomas. In the cementation group, 12 allografts were used as osteochondral grafts (proximal humerus 4, proximal tibia 4, and distal femur 4), 7 as intercalary diaphyseal allografts of the femur, and 7 for a knee arthrodesis. In the uncemented allografts, 3 allografts were used as osteochondral grafts (proximal humerus 2, proximal tibia 1), 2 as intercalary diaphyseal allograft of the femur, and 14 for a knee arthrodesis. The average length of follow-up was 40 (25-60) months. 14 of 26 cemented allografts had an excellent (osteotomy line: not visible) or good (fusion > or = 75% of the cortical thickness) healing of the junction site. Infection developed in 1 allograft. Fracture occurred in 4 of 12 cemented osteochondral allografts due to a subchondral collapse (all in the proximal tibia). Fractures at the junction site in the lower extremity developed in 4 of 22 cemented allografts. In 19 allografts without cementation, 11 had excellent or good healing of the junction. Late infection developed in 4 allografts, fracture of the allograft in 3 cases, and junction fracture in 3 of 17 patients with reconstruction of the lower extremity. Intramedullary graft cementation seems to reduce the fracture and infection rates.

Adolescent↗
PubMed1999

Influence of filler content and gap dimension on wear resistance of resin composite luting cements around a CAD/CAM ceramic inlay restoration.

We investigated the influence of filler content and gap dimension on the wear resistance of composite luting cement around CAD/CAM ceramic inlay restorations. Experimental hybrid dual-cured composite luting cements containing 60, 70, 72, 74 and 80 wt% of silanated barium-silica fillers were used for cementing CAD/CAM ceramic inlay into the cavity. The specimens involving inlay-cement-tooth interfaces were subjected to a three-body wear test. The relation between the interfacial gap dimension and wear loss was also investigated using 60, 70 and 80 wt% filled cements. The cements containing more than 70 wt% filler presented significantly higher wear resistance than 60 wt% filled cement. There was a positive linear relationship between gap dimension and wear loss, and the inclination of the regression line decreased with increasing filler content. These results indicated that the higher filler content of the cement increased the wear resistance and this desirable influence appeared more remarkably in the wider horizontal gap dimension.

Analysis of Variance↗
PubMed1996

[Effects of smeared layer on luting strength of dental cements].

Effects of smeared layer on the bond strength between dentin and dental cements were evaluated. Four surface conditions (No treatment, K-etchant, Dentin conditioner and EDTA) were prepared on the ground dentin of bovine frontal teeth. A copper tube was fixed and filled with a dental cement (zinc-phosphate cement or glass-polyalkenoate cement). A hook was embedded in the tube, with or without 1 MPa load during cementation. The bond strength was measured by a tensile test using a universal testing machine. No treatment had the largest bond strength of zinc-phosphate cement with or without load. No treatment, Dentin conditioner and EDTA had large bond strengths of glass-polyalkenoate cement with or without load; the bond strength of K-etchant was small without load and comparable to those of other surface conditions when load was applied. These results suggested that the bond strength of three surface conditions was not stronger than that of no treatment. Therefore, the elimination of smeared layer was concluded to have no advantage for increasing the bond strength between dentin and dental cements.

Animals↗
PubMed1999

Effect of two variables on the fatigue performance of acrylic bone cement: mixing method and viscosity.

The goal of the present work was to establish the relative influence of one exogenous variable versus one endogenous variable on the fully-reversed tension-compression fatigue performance of bone cement. The method used to mix the cement constituents was the exogenous variable, while the viscosity of the mixed cement dough was the endogenous variable. Two commercial cement formulations (Palacos R and Osteopal) and two cement mixing methods (hand mixing and vacuum mixing) were used. It was found that for a given mixing method, cement viscosity exerts a marginal influence on fatigue performance. On the other hand, for a given cement formulation, vacuum mixing led to a statistically significant improvement in fatigue performance. The present results demonstrate the superior influence of mixing method over cement viscosity.

Acrylates↗