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PubMedDate not supplied

An animal model for interface tissue formation in cemented hip replacements.

OBJECTIVE: To create a model in sheep for investigation of early changes related to the formation of an interface membrane in hip prosthesis. STUDY DESIGN: Experimental study. ANIMALS: Twenty-four female adult Swiss Alpine sheep. METHODS: Sheep were divided into 2 groups of 12 for unilateral cemented total hip arthroplasty. In Group I, the prosthesis was fixed with retrograde cement gun injection to achieve a complete cement mantle, whereas in Group II a primary cement mantle defect was produced. Groups I and II were further divided into 2 sub-groups with study end points of 2 and 8.5 months after surgery. Radiographs were evaluated postoperatively and at euthanasia for migration of the femoral component and bone resorption. Histologic sections were evaluated semiquantitatively for changes in cell types and numbers, and bone reactions; and quantitatively for size of interface membrane and new bone formation. RESULTS: Radiographically, there tended to be an increase in bone resorption and periosteal bone formation throughout the femoral shaft in Group II compared with Group I, but this was only statistically significant at the region of the femoral neck (R5) at both time periods (P<.05). Semiquantitative histologic evaluation revealed significant increases (P<.05) in cellularity, numbers of fibroblasts, giant cells, macrophages, and mononuclear cells, in Group II primarily at 2 months after surgery. This was also true for interface membrane formation and bone remodeling. Quantitative data showed an increased in the size of the interface membrane and area of bone formation at 8.5 months in Group II. CONCLUSIONS: The cement defect model offered controlled and repeatable production of an interface membrane. The results suggest that a primary cement mantle defect could be a possible trigger for implant instability, eliciting a cascade of biomechanical and molecular events in bone tissue leading to aseptic loosening. CLINICAL RELEVANCE: The results show the effect of defects in the cement mantle in promoting interface membrane formation. Long-term and biochemical studies are required to evaluate the relevance of this interface membrane formation.

Animals↗
PubMed1999

A 2-year clinical study of two glass ionomer cements used in the atraumatic restorative treatment (ART) technique.

The purpose of the study was to evaluate, in a clinical study over 2 years, the deterioration of two glass ionomer cements used with the atraumatic restorative treatment (ART) technique or approach. Fifty-five Fuji IX and 45 ChemFil Superior restorations were placed randomly in 23 adult patients, mainly in small occlusal preparations in molar teeth. The restorations were placed in a dental hospital by one dentist using the ART technique. Photographs, radiographs and replicas were obtained at baseline and subsequent recalls. Both cements were easy to mix and place, but the radiolucency of ChemFil Superior was a disadvantage. Both cements also showed early high losses of sealant and restorative material. After 2 years, 34.5% of the sealants appeared to be completely lost, with caries recorded in 5.3% of the exposed fissures. In some instances, these small lesions may have been present, but not detected clinically, at the time of sealing. Restoration failures of 7.0% were from wear and fracture of the cements and recurrent caries. Mean cumulative wear was 83.1 microm for Fuji IX and 104.0 microm for ChemFil Superior, which was not statistically significant. The cements became darker after their placement to more closely match the restored teeth, but there were few exact matches. There was no surface staining and only minor marginal discrepancies and staining associated with the restorations. Although the short-term clinical performance of the two glass ionomer cements was reasonable, the materials require further improvements in their mechanical properties, to reduce sealant losses and wear. The cements evaluated appear suitable for restricted use only, in posterior teeth.

Adult↗
PubMedDate not supplied

The use and handling of acrylic bone cement in Danish orthopaedic departments.

In order to evaluate the use and handling of acrylic bone cement, questionnaire were presented to all Danish orthopaedic departments in 1987 and again in 1992. Marked improvements in the environmental safety precautions for handling of bone cement had taken place during the 5-year period. In 1992, the intraoperative handling and use of bone cement is thus generally considered safe. Further improvements are still to be advocated in some departments. The exposure to methylmethacrylate monomer (MMA) vapour during the cementation procedures should be eliminated by local punctual field suction or change to a bone cement with a lower content of monomer (MMA/n-decylmethacrylate/isobornylmethylacrylate bone cement). Unnecessary manual contact with the cement should be avoided, and if contact is necessary, special protective gloves (butyl rubber gloves or 4H-gloves) should be used in addition to ordinary surgical gloves.

Air Pollutants, Occupational↗
PubMed1990

The effect of etching on a number of glass ionomer cements.

In view of the continuing interest in the use of glass ionomer cements as a dentine substitute or base under composite resins, further investigations were carried out on the effects of the length of time of etching of the surface of the cement prior to the placement of the resin. A number of cements are available on the Australian market which are advocated for use in this technique. Each of them was subjected to etching for periods of 15, 30, 45, or 60 seconds and then stored in water for one week. Examination under a dissecting microscope and a scanning electron microscope revealed some variation in results between the different cements. It would appear that not all those materials presently marketed for this purpose are entirely suitable. Whilst 15 seconds is the preferred time for most cements, some require times up to 60 seconds to achieve the best result. Also, some of the cements showed signs of cracking, expansion and distortion after they had been stored in water for one week to allow for maturation before being prepared for viewing under the SEM. It is suggested that this group of cements is not suitable for the 'sandwich' technique.

Acid Etching, Dental↗
PubMed1983

Evaluation of bone cement failure criteria with applications to the acetabular region.

A Strain energy density (SED) criterion based on a fracture mechanics approach was used to assess the possible failure of acetabular bone cement after total hip replacement. Stress distributions in the cement at the bone-cement interface were calculated using two-dimensional finite element analyses. The results indicate that increasing the thickness of bone cement reduces the risk of cement fracture. The addition of a metal backing to the polyethylene cup and retention of the subchondral bone further reduces the risk of failure. The SED criterion was found to predict the same critical regions as zones of possible cement failure as the von Mises' criterion. Although either criterion can be used for predicting failure in this acetabular analysis both criteria are excessively conservative in predicting failure in regions where high principal compressive stresses are present. Further development of cement failure criteria are indicated.

Acetabulum↗
PubMed2006

Surface and chemical properties of surface-modified UHMWPE powder and mechanical and thermal properties of its impregnated PMMA bone cement, IV: effect of MMA/accelerator on the surface modification of UHMWPE powder.

In our previous study, we manufactured a reinforced poly(methylmethacrylate) (PMMA) bone cement with 3 wt% of the surface-modified ultra high molecular weight polyethylene (UHMWPE) powder to improve its poor mechanical and thermal properties resulting from unreacted methylmethacrylate (MMA), the generation of bubble and shrinkage, and high curing temperature. In the present study, the effect of ratios of MMA and N,N'-dimethyl-p-toluidine (DMPT) solutions in redox polymerization system was investigated for the surface modification of UHMWPE powder. We characterized physical and chemical properties of surface-modified UHMWPE powder and reinforced bone cements by a scanning electron microscope, ultimate tensile strength (UTS) and curing temperature (Tmax). It was found that UTSs (41.3-51.3 MPa) of the reinforced PMMA bone cements were similar to those (44.5 MPa) of conventional PMMA bone cement (control), as well as significantly higher (P < 0.05) than those (33.8 MPa) of 3 wt% unmodified UHMWPE powder-impregnated bone cement. In particular, the UTS of redox polymerization system using MMA/DMPT solution was better than that of radical system using MMA/xylene solution. Also, Tmax of the reinforced PMMA bone cements decreased from 103 to 72-84 degrees C. From these results, we confirmed that the surface-modified UHMWPE powder can be used as reinforcing agent to improve the mechanical and thermal properties of conventional PMMA bone cement.

Biomechanical Phenomena↗
PubMed1984

Cements containing syringic acid esters -- o-ethoxybenzoic acid and zinc oxide.

Fissure caries is reduced when syringic acid is incorporated into a cariogenic diet of rats. It was therefore of interest to synthesize n-hexyl and 2-ethylhexyl syringate and to evaluate the properties of cements with these compounds as ingredients. Liquids containing the esters dissolved in o-ethoxybenzoic acid (EBA) - when mixed with powders made up from zinc oxide, aluminum oxide, and hydrogenated rosin - hardened in from four to nine min. Properties of the cements were determined, when possible, according to ANSI/ADA specification tests. Depending on the powder-liquid ratio employed, we obtained compositions with varying physical properties desirable for different dental applications. The syringate cements, compared with the commonly used ZOE materials, have improved compressive and tensile strength, lower water solubility, do not inhibit polymerization, and are compatible with acrylic monomers. These cements pass, and mostly greatly exceed, the requirements for ZOE-type restorative materials. They also bond significantly to resins, composites, and non-precious metals. The bond strength is somewhat less than that of n-hexyl vanillate-EBA cement, but greatly exceeds the adhesion to various substrates of ZOE luting agents. Cements containing n-hexyl syringate were somewhat brittle. Best results were obtained with liquid compositions containing 5% 2-ethylhexyl syringate, 7% n-hexyl vanillate, and 88% EBA, which yielded non-brittle materials. These cements, because of the syringate ingredient, may possess caries-reducing properties. Thus, perhaps in conjunction with fluoride additives, they would be useful as insulating bases, pulp capping agents, root canal sealers, soft tissue packs, or intermediate restoratives.

Chemical Phenomena↗
PubMed1994

An investigation into the pressure transmitted to the pulp chamber on crown cementation: a laboratory study.

Pressure changes in the pulp chamber resulting from crown cementation have not been previously quantified. An experiment was designed to investigate the effect of smear layer removal on the peak pressure transmitted to the pulp chamber with crown cementation. Ten matched pairs of single-rooted premolar teeth were collected from adolescents and prepared for full-coverage crowns. The pulp tissue from each tooth was removed. One tooth from each pair had the smear layer removed with the application of 37% phosphoric acid for 30 s. The null hypothesis states that the removal of the dentinal smear layer will not change pressure in the pulp chamber resulting from the cementation. Before cementation, a hydrostatic head of pressure was used to perfuse the tooth, and the perfusion rate was recorded. Crowns were cemented with zinc phosphate cement with a seating force of 100 N. The mean peak pressures recorded were 85 Pa (SE 12 Pa) with the smear layer intact, and 194 Pa (SE 49 Pa) when the dentin was etched. The difference in the peak pressures transmitted to the pulp chamber with the two groups was significant (p < or = 0.05). A significant negative correlation was found between dentin thickness and the peak pressure transmitted to the pulp chamber (r = -0.5531, p < or = 0.01). We have shown that the pressure transmission to the pulp chamber during crown cementation can be measured. Since smear layer removal significantly influences the peak pressure, it is concluded that the pressure detected is at least partially dependent on the fluid flow through the dentin.

Acid Etching, Dental↗
PubMed1995

Factors affecting the adherence energy of experimental resin cements bonded to a nickel-chromium alloy.

Reliable adherence of resin-based cements is of prime importance for the longevity of cemented restorations. The present study investigated whether a relationship exists between adherence energy to a metal substrate and the degree of cross-linking and wetting characteristics of resin-based luting agents. The adherence energies between a sand-blasted metal surface and a series of experimental resin cements were measured by means of the wedge test. The degree of cross-linking was calculated from the monomer composition of the resin cements. The measured wetting characteristics were work of adhesion and surface tension, and their dispersive and polar components. Adherence energy varied between 22 and 81 J/m2 and was influenced by the nature of the resin cements: Those with a low degree of cross-linking resulted in high adherence values. Furthermore, resin cements whose monomers were relatively polar gave rise to high adherence values. Although other metals may not behave in exactly the same way, these results may help in the formulation of new, more retentive resin cements.

Acrylamides↗
PubMed2003

Use of a screw-syringe injector for cement delivery during kyphoplasty: technical report.

OBJECTIVE: Percutaneous kyphoplasty is postulated to have several advantages over percutaneous vertebroplasty for the treatment of vertebral compression fractures and is gaining increased popularity. However, cement delivery with the KyphX kit (Kyphon, Inc., Santa Clara, CA), the only commercially available device for percutaneous kyphoplasty, is relatively problematic. This kit uses a series of "bone filler device" (BFD) tubes. Each BFD must be loaded manually with cement, which is then injected into the kyphoplasty cavity by manually depressing an inner stylet. The high profile of the BFD cannulas and their stylets requires frequent repositioning of the image intensifier tube and table. Because each accommodates only a small volume, the BFDs must be exchanged frequently. This delivery method also places the operator's hands directly in the field of radiation. We sought to overcome these limitations. METHODS: Dissatisfied with the shortcomings of the BFDs, we substituted the EZflow screw-syringe injector (Parallax Medical, Mountain View, CA) we use to deliver cement during conventional percutaneous vertebroplasty. This amalgam of the KyphX kit and the screw-syringe injector has been used for kyphoplasty treatment of 26 thoracolumbar compression fractures in 17 patients. RESULTS: The screw-syringe injector allows controlled volumetric delivery of large boluses of high-viscosity cement without having to refill the reservoir. It minimizes radiation exposure and does not require repositioning of the x-ray tubes. It may theoretically allow decompression should cement extrusion occur. Also, it delivers cement to the interstices of bony trabeculae outside the kyphoplasty cavity, thus combining the mechanical benefits of percutaneous kyphoplasty and percutaneous vertebroplasty. CONCLUSION: The use of a screw-syringe injector has several merits over the customary means of cement delivery during kyphoplasty.

Bone Cements↗
PubMed2004

A procedure and criterion for bone cement fracture toughness tests.

Nowadays, two procedures, based on the recommendation of two American standards (ASTM E399 and ASTM D5045), are used to determine the fracture toughness, KIc, of bone cement. However, there is a lack of knowledge about the equivalence of the two testing methods applied to bone cement. Additionally, in spite of the recommendation of several authors to introduce a rejection criterion for specimens based on the size of defects found in the fracture surface, no data are available about the effect of porosity within the material on the KIc of bone cement. The aims of this study were to verify whether the KIc values calculated for bone cement using the two procedures are comparable and whether macroporosity within the tested samples affects the KIc value of bone cement, and, if so, to establish a rejection criterion for specimen selection. Samples of pure polymethyl methacrylate (PMMA) were tested by both procedures. Additionally, samples showing defects (macroporosity) of different sizes and located in different positions within the specimen were tested. The KIc value determined following the ASTM E399 procedure was 13 per cent lower than that calculated following the ASTM D5045 procedure. In the first series a lower data scatter was observed. Also, the presence of macroporosity on the fracture surface of the specimen affected the KIc value of bone cement. Therefore, the mechanical behaviour of samples was affected by defects within the material. Since it is possible to mould specimens without macroporosity, it seems recommendable to reject specimens with macroporosity on the fracture surface before calculating the KIc value of bone cement.

Bone Cements↗
PubMed1982

The sustained release of antimicrobial drugs from bone cement. An appraisal of laboratory investigations and their significance.

The release of gentamicin sulphate, sodium fusidate and diethanolamine fusidate from Palacos and CMW cements was studied using elution and serial plate transfer tests. Further tests were made to assay the drug remaining in the cement after antibacterial activity could no longer be detected by the above methods, to detect the sustained slow release of the residual drug, and to ascertain the mechanism of release. The results confirmed that the release of gentamicin sulphate could be detected for longer from Palacos cement than from CMW cement, but the opposite was true for sodium fusidate. Little difference was found in the case of diethanolamine fusidate. Comparison of elution and serial plate transfer tests, and of results of elution in buffers of different pH, demonstrated that the test method employed had a significant effect on the results, and the omission of details of methodology from some publications made comparison and evaluation of results difficult. Varying quantities of residual drug were found in cement from which antibacterial activity could no longer be demonstrated; further tests for sustained, slow release showed that the antibiotic did not remain fixed in the cement but was released at a rate too slow to be detected in the elution and serial plate transfer tests. It is concluded that antibiotics are released from the cement by a process of diffusion, but tests to determine the mechanism of diffusion were unhelpful. The theory of diffusion of drugs through solid matrices, and the clinical implications of the experimental findings, are discussed.

Acrylic Resins↗
PubMed2001

Cardiac output during hemiarthroplasty of the hip. A prospective, controlled trial of cemented and uncemented prostheses.

In a prospective, controlled study, we measured the effect on cardiac output of the introduction of methylmethacrylate during hemiarthroplasty for displaced fractures of the femoral neck. We treated 20 elderly patients who were similar in age, height, weight and preoperative left ventricular function with either cemented or uncemented hemiarthroplasty. Using a transoesophageal Doppler probe, we measured cardiac output before incision and at six stages of the procedure: during the surgical approach, reaming and lavage of the femoral canal, the introduction of cement, the insertion of the prosthesis, and in reduction and closure. We found that before the cement was introduced, there was no difference in stroke volume or cardiac output (p > 0.25). Cementation produced a transient but significant reduction in cardiac output of 33% (p < 0.01) and a reduction in stroke volume of 44% (p < 0.02). The introduction of cement did not affect the heart rate or mean arterial pressure. There was no significant difference in cardiac function on insertion of the prosthesis. Standard non-invasive haemodynamic monitoring did not detect the cardiovascular changes which may account for the sudden deaths that sometimes occur during cemented hemiarthroplasty. The fall in stroke volume and cardiac output may be caused by embolism occurring during cementation, but there was no similar fall during reaming or insertion of the prosthesis.

Aged↗
PubMed2006

Uncompromised quality of the cement mantle in Exeter femoral components implanted through a minimally-invasive direct anterior approach. A prospective, randomised cadaver study.

A complete cement mantle is important for the longevity of a total hip replacement. In the minimally-invasive direct anterior approach used at the Innsbruck University hospital, the femoral component has to be inserted into the femoral canal by an angulated movement. In a cadaver study, the quality and the extent of the cement mantle surrounding 13 Exeter femoral components implanted straight through a standard anterolateral transgluteal approach were compared with those of 13 similar femoral components implanted in an angulated fashion through a direct anterior approach. A third-generation cementing technique was used. The inner and outer contours of the cement mantles was traced from CT scans and the thickness and cross-sectional area determined. In no case was the cement mantle incomplete. The total mean thickness of the cement mantle was 3.62 mm (95% confidence interval 3.59 to 3.65). The mean thickness in the group using the minimally-invasive approach was 0.16 mm less than that in the anterolateral group. The distribution of the thickness was similar in the two groups. The mean thickness was less on the anteromedial and anterolateral aspect than on the posterior aspect of the femur. There is no evidence that the angulated introduction of Exeter femoral components in the direct anterior approach in cadavers compromises the quality, extent or thickness of the cement mantle.

Arthroplasty, Replacement, Hip↗
PubMed1976

Modulus of elasticity and strength properties of dental cements.

The modulus of elasticity of commercial dental cements was determined by an optical strain gauge method. Values of compressive and tensile strengths also were measured. Of the cements of primary consistency tested, a noneugenol zinc oxide cement had the lowest mechanical properties. A zinc phosphate cement had the highest value of compressive strength and modulus, but a zinc polyacrylate cement had the highest tensile strength. A zinc polyacrylate cement base had the highest tensile strength, but a zinc phosphate cement base had the highest compressive strength and modulus of elasticity. A calcium hydroxide liner had higher mechanical properties than an unmodified ZOE liner.

Dental Cements↗
PubMed2006

Screw vs cement-implant-retained restorations: an experimental study in the beagle. Part 2. Immunohistochemical evaluation of the peri-implant tissues.

Crestal bone loss has been reported to occur around dental implants. Even if the causes of this bone loss are not completely understood, the presence of a microgap between implant and abutment with a possible contamination of the internal portion of the implants has been suggested. The aim of this study was to see if there were differences in the vascular endothelial growth factor (VEGF) expression, microvessel density (MVD), proliferative activity (MIB-1), and inflammatory infiltrate in the soft tissues around implants with screwed and cemented abutments. Sandblasted and acid-etched implants were inserted in the mandibles of 6 Beagle dogs. Ten 3.5- x 10-mm root-form implants were inserted in each mandible. A total of 60 implants (30 with screwed abutments and 30 with cemented abutments) were used. After 12 months, all the bridges were removed and all abutments were checked for mobility. A total of 8 loosened screws (27%) were found in the screwed abutments, whereas no loosening was observed in cemented abutments. A gingival biopsy was performed in 8 implants with cemented abutments, in 8 implants with screwed abutments, and in 8 implants with unscrewed abutments. No statistically significant differences were found in the inflammatory infiltrate and in the MIB-1 among the different groups. No statistically significant difference was found in the MVD between screwed and cemented abutments (P = .2111), whereas there was a statistically significant difference in MVD between screwed and unscrewed abutments (P = .0277) and between cemented and unscrewed abutments (P = .0431). A low intensity of VEGF was prevalent in screwed and in cemented abutments, whereas a high intensity of VEGF was prevalent in unscrewed abutments. These facts could be explained by the effects induced, in the abutments that underwent a screw loosening, by the presence of bacteria inside the hollow portion of the implants or by enhanced reparative processes.

Acid Etching, Dental↗
PubMed1998

Hydroxyapatite cement implant for regeneration of periodontal osseous defects in humans.

A newly developed calcium phosphate cement used to promote bone regeneration in craniofacial defects was examined to determine its potential for treatment of periodontal osseous defects. Sixteen patients with moderate to severe periodontal disease and 2 bilaterally similar vertical bony defects received initial therapy including scaling and root planing followed by treatment with either calcium phosphate cement, flap curettage (F/C) or debridement plus demineralized freeze-dried bone allograft (DFDBA). Standardized radiographs were exposed at baseline and 12 months postsurgery for computer assisted densitometric image analysis (CADIA). The extent of the bony defect was determined during initial and 12 month re-entry surgery. Within 6 months of implant placement, 11 of 16 patients treated with calcium phosphate cement exfoliated all or most of the implant through the gingival sulcus. At all 16 test sites, a narrow radiolucent gap formed by 1 month postsurgery at the initially tight visual interface between the radiopaque calcium phosphate cement and the walls of the bony defect. Mean probing depth reduction and clinical attachment gain at sites treated with calcium phosphate cement were 1.6 mm and 1.3 mm, respectively at 1 year. Minimal bony defect fill was accompanied by mean crestal resorption of 1.4 mm. Alveolar crestal resorption at sites with calcium phosphate cement was statistically significant (P=0.001). These findings contrasted with the more favorable outcomes for controls treated with DFDBA or F/C. DFDBA sites exhibited probing depth reduction of 3.1 mm, clinical attachment gain of 2.9 mm, and defect fill of 2.4 mm. Respective clinical changes at F/C sites were 2.4 mm, 1.4 mm, and 1.1 mm. CADIA revealed clinically significant trends between the three treatment modalities at various areas-of-interest. Based on the findings of this study, there is no rationale available to support the use of hydroxyapatite cement implant in its current formulation for the treatment of vertical intrabony periodontal defects.

Absorptiometry, Photon↗
PubMed1994

The results of improved cementing techniques for total hip arthroplasty in patients less than fifty years old. A ten-year follow-up study.

Thirty-six patients (forty-two hips) in whom so-called second-generation cementing techniques, such as medullary lavage, use of an intramedullary cement plug, hand-mixing of the cement, and use of a cement gun to deliver the cement in a doughy state in a retrograde fashion, had been used for a primary total hip arthroplasty were evaluated at an average of eleven years (range, ten to fifteen years) after the operation. All of the patients had been less than fifty years old at the time of the operation. Thirty-one patients were evaluated by clinical and radiographic examinations and five, by a telephone interview. Twelve components (ten acetabular components [24 per cent] and two femoral components [5 per cent]) in ten hips had been revised for aseptic loosening. An additional five acetabular components (12 per cent) and five femoral components were definitely loose according to radiographic criteria. Three of these femoral components were polished stems that were considered loose only because of the presence of a radiolucent line, 0.5, one, and two millimeters wide, at the prosthesis-cement interface in zone 1 of Gruen et al. The other two loose stems were in patients who were receiving renal dialysis. These findings demonstrate excellent fixation of the femoral component but continued problems with fixation of the acetabular component despite the use of improved cementing techniques.

Activities of Daily Living↗