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PubMed1997

Antibiotic delivery system using bioactive bone cement consisting of Bis-GMA/TEGDMA resin and bioactive glass ceramics.

A novel drug delivery system containing cephalexin (CEX) as a model drug using a new bioactive bone cement consisting of 15% bisphenol-alpha-glycidyl methacrylate (Bis-GMA), 15% triethylene-glycol dimethacrylate (TEGDMA) resin and 70% apatite- and wollastonite-containing glass-ceramic (A-W GC) powder was investigated. A-W GC powder containing CEX powder hardened within 5 min after mixing with Bis-GMA/TEGDMA resin, and furthermore its compressive strength was expected to be higher than that of polymethylmethacrylate cement. In vitro CEX release from bioactive bone cement pellets in a simulated body fluid at pH 7.25 and 37 degrees C continued for more than 2 weeks. The drug release rate increased with increasing amount of CEX in the mixture. All of the drug release profiles followed the Higuchi equation at the initial stage, but not at later stages. As hydroxyapatite was precipitated out on the cement surface, the drug release rate decreased. These results suggest that the CEX release rate from bioactive bone cement could be controlled by varying the amount of drug in the cement system.

Biomechanical Phenomena↗
PubMed1999

Influence of glass composition on the properties of glass polyalkenoate cements. Part I: influence of aluminium to silicon ratio.

Hydrolysis of aluminium-oxygen-silicon bonds is thought to be the first step in the setting reaction of polyalkenoate cements and the aluminium to silicon ratio of the glass is widely believed to be a dominant factor determining cement properties. The properties of glass polyalkenoate cements based on the generic glass composition (6 + X)SiO2 x (4 - X)Al2O31.5P2O5 x 4CaOCaF2 with varying aluminium to silicon ratio were studied. Setting and working times of the cement pastes, compressive strength, un-notched fracture strength, Young's modulus, fracture toughness and toughness were evaluated for the cements. In contrast to previous studies the aluminium to silicon ratio was not found to influence the cement properties significantly. The high phosphorus content of the glasses studied is thought to reduce the influence of the aluminium to silicon ratio of the glass, as a result of phosphorus locally charge balancing four coordinate aluminium ions in the glass network, as well as providing an additional mechanism of degradation in the form of hydrolysable phosphorus-oxygen bonds.

Aluminum Compounds↗
PubMed2001

Shear bond strengths of three resin cements to dentine over 3 years in vitro.

OBJECTIVES: This study was conducted to evaluate the bond durability of three resin cements bonded to bovine dentine over a period of 3 years. METHODS: Ten bovine dentine specimens were tested for shear bond strengths with each of the following materials: Panavia 21, BISTITE resin cement, and MASA Bond (experimental resin cement) at 1 day, 6 months, 1 and 3 years after cementation of a composite rod. All specimens were stressed in shear at a crosshead speed of 1mm min(-1) until failure. The means of the bond strengths were compared statistically by two-way ANOVA and Fisher's PLSD test (P<0.05). The mode of failure was classified after fracture of the bonds by SEM observation. Results for the mode of fracture were analyzed using the Mann-Whitney U-test. RESULTS: The shear bond strengths (MPa+/-SD) for different times (1 day, 6 months, 1 and 3 years) were: Panavia 21 (15.2+/-3.6, 9.3+/-3.2, 8.5+/-2.1, 6.8+/-2.4), BISTITE (15.6+/-2.8, 11.0+/-1.4, 10.4+/-2.2, 9.0+/-2.7) and MASA Bond (29.6+/-9.5, 17.5+/-4.6, 19.6+/-4.5, 16.1+/-5.4). Panavia 21 and BISTITE strengths were significantly lower (P<0.05) at all times compared with MASA Bond, and 1 day strengths for all three materials were significantly higher (P<0.05) than 3 year strengths. Regarding the fracture modes after bond testing, there were statistical differences between the 1 day and the 1 year results for all cements (P<0.05). Although no Panavia 21 specimen showed complete cohesive failure in the demineralized dentine during the experiment, several BISTITE and MASA Bond specimens showed cohesive fracture in the demineralized dentine. For BISTITE, partially or complete demineralized dentine cohesive failures increased over time. CONCLUSIONS: The type of resin cement seemed to have an influence on the long-term durability of bonding to dentine.

Analysis of Variance↗
PubMed2002

The effect of ethanol on acrylic bone cement.

Prosthesis loosening is a major problem associated with the use of poly(methyl methacrylate) (PMMA) bone cement that may be related to a peri-implant vacuolisation commonly observed at bone-cement interface. Methyl methacrylate (MMA) monomer may be one of the cement components partly responsible for the mentioned vacuolisation due to a cytotoxic effect associated to this compound. Alcoholism has been related to bone necrosis in predisposed individuals. Furthermore, ethanol has been shown to clean material with adherent cement debris during cleaning procedure in laboratory. Consequently, we have decided to study whether ethanol will also be related to an increased liberation of MMA from the polymer matrix. 'In vitro' release studies using PMMA plates were conducted to access the role of ethanol on the liberation of the monomer. Contact angle measurements and surface tension estimation were also carried out in order to find a possible effect of ethanol on surface cement properties. Results suggest that ethanol, even in small quantities, enhances the leaching of the monomer from the polymer matrix, but does not considerably change the wettability properties of the cement surface.

Acrylic Resins↗
PubMed2000

In vitro release studies of methylmethacrylate liberation from acrylic cement powder.

Bone cement or polymethylmethacrylate (PMMA) is commonly used for anchoring cemented prosthesis to the bone. Cytotoxic effect of culture media exposed to PMMA powder may be related with long term problems associated with acrylic cement application, being the monomer (methylmethacrylate) one of the cement's component partly responsible for the cytotoxic effect. The present work reports the studies of monomer release from acrylic bone cement powder under different experimental conditions: setting time of PMMA (in solution and air) and different culture media composition. High-performance liquid chromatography was used for the determination of residual monomer. Mathematical models were applied to experimental dissolution data revealing that monomer release is lightly affected by the studied variables. The monomer release seems to be a surface phenomena, suggesting that the possible actions of monomer will mainly be due to the initial loss of non polymerized monomer rather than to further depolymerization of the already polymerized cement.

Bone Cements↗
PubMed2003

THA loading arising from increased femoral anteversion and offset may lead to critical cement stresses.

Aseptic loosening of artificial hip joints is believed to be influenced by the design and orientation of the implant. It is hypothesised that variations in implant anteversion and offset lead to changes in the loading of the proximal femur, causing critical conditions to both the bone and cement. The goal of this study was therefore to analyse the role of these parameters on loading, bone strains and cement stresses in total hip arthroplasty (THA). A validated musculo-skeletal model was used for the analysis of muscle and joint contact forces during walking and stair climbing. Two different anteversion angles (4 degrees vs. 24 degrees ) and prostheses offsets (standard vs. long) were analysed. The loads for each case were applied to a cemented THA finite element model. Generally, stair climbing caused higher bone strains and cement stresses (max. +25%) than walking. Variations in anteversion and offset caused changes in the loading environment, bone strain distribution and cement stresses. Compared to the standard THA configuration, cement stresses were raised by increasing anteversion (max. +52%), offset (max. +5%) and their combination (max. +67%). Femoral anteversion, offset and their combination may therefore lead to an increased risk of implant loosening. Analyses of implant survival should consider this as a limiting factor in THA longevity. In clinical practice, implant orientation, especially in regard to pre- and post-operative anteversion, should be considered to be more critical.

Arthroplasty, Replacement, Hip↗
PubMed2000

Negative pressure intrusion cementing technique for total knee arthroplasty.

Negative pressure intrusion (NPI) is an alternative cementing technique for the tibial baseplate of total knee arthroplasty that uses a suction cannula in the proximal tibia to remove excess fluids and fat before cementing. This technique was compared with standard third-generation positive pressure intrusion (PPI) techniques in an in vitro implantation and analysis of 6 pairs of cadaveric tibiae. Six matched pairs of fresh frozen tibiae were prepared by cutting the tibial surfaces, standard cleaning and surface drying, then performing PPI and NPI on 1 of each pair. No objective differences were noted on radiographs or direct cement depth measurement analysis. Scanning electron micrograph evaluation revealed that the PPI specimens had consistently more voids in the cement-bone composite, and the NPI specimens had consistently narrower empty spaces between bone and cement, resulting in tighter fill in NPI specimens. NPI was shown to enhance characteristics known to improve tensile and shear strength in cement-bone composites.

Adult↗
PubMed1990

Use of high-energy shock waves for bone cement removal.

The revision rate of total hip arthroplasty has increased dramatically over recent years, leading to different methods of extraction of the femoral cement mantle to reduce operative time and surgical risks. The use of high-energy shock waves produced by the Dornier HM.3 Lithotripter to interrupt the cement-bone interface and to reduce the material properties of the cement is investigated. Tests were conducted to measure the pull-out strength of cemented treated rods versus untreated rods, from the medullary canal of canine femurs. The treated femurs showed an average reduction in pull-out strength of 43%. An investigation involving the material properties of acrylic bone cement was also conducted. The properties tested were the compressive modulus of elasticity, the ultimate compressive strength, the ultimate tensile strength, and fracture toughness. The scanning electron microscope aided in determining whether microfractures in the cement resulted from the shock wave treatment. A theoretical study utilizing the finite element method was used to investigate areas of select shock wave treatment about the femoral prosthesis. Analysis of the results showed that the lithotripter treatment had no significant effect on the compressive properties but reduced the tensile properties and fracture toughness significantly. Scanning electron microscopy uncovered definite areas of induced microfractures not present in the control specimens. This study supports the concept of clinically noninvasive, preoperative shock wave treatment prior to total hip revision.

Animals↗
PubMed1993

Preventing distal voids during cementation of the femoral component in total hip arthroplasty.

Cement voids have been noted in close approximation to the unfilled hole in the distal end of the femoral prosthesis. These cement voids result from the displacement of cement by the expansion of air trapped in the distal prosthesis. Voids in the distal cement have been shown to lead to an increased incidence of cement failures. This potentially deleterious situation can easily be avoided by plugging the hole in the distal stem. This may be accomplished three ways: using a centralizer, using the plastic plug supplied with the prosthesis, or filling the hole with cement prior to implanting the prosthesis.

Cementation↗
PubMed1989

Comparison and optimization of three centrifugation systems for reducing porosity of Simplex P bone cement.

Simplex P bone cement was spun for 30, 60, and 120 seconds in three different centrifugation systems (I.E.C. HN-S II, I.E.C. clinical, and Johnson & Johnson) to determine whether differences among the three systems also produce differences in the improvement of the fatigue strength of the cement. The fatigue properties of the cement after centrifugation were also assessed when it was mixed with monomer that had been chilled to 0 degrees C. There were important and statistically significant differences in the fatigue life of Simplex P spun for the same duration in the different centrifuges. Simplex P prepared as recommended by the manufacturer had an average fatigue life of 15,143 cycles in the test system used. Optimum centrifugation among the techniques studied increased the fatigue life nearly fivefold, to the range of 71,000 cycles. Taking into account both the fatigue strength and the viscosity of the cement, the optimum centrifugation system for improving the fatigue life of Simplex P bone cement is the Miller cartridge containing two packs of cement spun in the IEC-HN-S II centrifuge. The authors recommend 30 seconds of centrifugation if the monomer is not chilled prior to mixing and 60 seconds if the monomer is chilled.

Bone Cements↗
PubMed1996

Early radiographic results comparing cemented and cementless total hip arthroplasty.

In a randomized clinical trial of cemented and cementless total hip arthroplasty, 147 patients (76 cemented, 71 cementless) have had a minimum 4-year clinical and radiographic follow-up evaluation. No revisions have been done in either group. Two cemented acetabular components were considered definitely loose and 18 were probably loose; 7 cemented stems were possibly loose at last follow-up examination. One cementless socket was considered unstable. Although cementless femoral component subsidence occurred in 10 cases, the sinkage always stabilized within 6 months, and no stem was considered unstable at last follow-up examination. Significant femoral bone resorption was rare, and so-called "spot welds" were uncommon using this titanium stem. Distal cortical hypertrophy was common, but the cause is uncertain. Osteolysis was seen around 10 cementless and 6 cemented sockets. A small area of lysis occurred in the proximal medial femoral neck in 15 cemented stems and 1 cementless stem. No cases of distal femoral lysis were seen in either group. Despite excellent clinical results with no difference between groups, the high rate of early radiographic failure of this metal-backed acetabulum should preclude its use. Osteolysis will continue to be a problem in both groups, and its prevention should remain the focus of future studies.

Acetabulum↗
PubMed1998

Acetabular reconstruction with impacted morselized cancellous allografts in cemented hip arthroplasty: a histological and biomechanical study on the goat.

Bone defects in total hip arthroplasty revision surgery can be restored with different types of bone graft. The use of impacted morselized allograft chips in combination with cement is the treatment of our choice. To establish the incorporation capacity of the grafts and mechanical stability of the implant, an animal model in the goat was developed. An acetabular defect was created and restored with morselized grafts and a cemented cup. Postoperative performance of the reconstruction was followed both histologically and biomechanically. Histology showed that consolidation of the graft with the host bone bed had occurred within 3 weeks. In the following period a front of vascular sprouts infiltrated the graft. Graft resorption, woven bone deposition, and subsequent remodeling resulted in a new trabecular structure. This structure contained only scarce remnants of the original dead graft material. At the graft-cement interface, graft resorption and new bone formation had resulted in areas of direct vital bone-cement contact. Locally, a soft tissue interface was present. After longer follow-up periods, progressive interface formation and loosening of the cups were found in most animals. Mechanical testing showed that the stability of the reconstruction increased during the first 12 postoperative weeks. Thereafter, the stability decreased, probably by soft-tissue interface formation at the graft cement interface. We conclude that cemented morselized allografts have a high capacity to incorporate. Initial cup stability is adequate to provoke graft incorporation with decreasing stability after the incorporation process has been completed.

Acetabulum↗
PubMed1999

The use of vancomycin and tobramycin in acrylic bone cement: biomechanical effects and elution kinetics for use in joint arthroplasty.

We examined the effects of vancomycin on the compressive strength and fatigue life of bone cement and the pharmacokinetics and antimicrobial activity against methicillin-resistant Staphylococcus aureus of vancomycin eluted from bone cement, both alone and in combination with tobramycin. Two cements, Palacos and Simplex, were tested. Three antibiotic preparations were tested: lyophilized vancomycin (vancomycin-L), vancomycin powder (vancomycin-P), and tobramycin powder (Lilly, Indianapolis, IN). Although antibiotics did not significantly affect compressive strength, the fatigue life of bone cement was significantly decreased with vancomycin. Thus, fatigue testing revealed effects on cement strength not apparent by compression testing. Vancomycin-P had a substantially less detrimental effect on fatigue strength than vancomycin-L. Vancomycin-P elutes less efficiently than tobramycin. Although relatively little vancomycin-P eluted from bone cement, it retained biologic activity.

Anti-Bacterial Agents↗
PubMed1999

Effect of stem stiffness and bone stiffness on bone remodeling in cemented total hip replacement.

The hypothesis in this study is that the stem stiffness-to-bone stiffness ratio influences the incidence and type of bone remodeling and fixation with cemented total hip arthroplasty. Ninety-one patients with 99 hips had cemented stems using 3 different anatomic porous replacement designs. The APR I and APR II titanium stems with proximal porous coating on the proximal one fourth of the stem were cemented into 49 and 35 patients. The APR II-C stem, which is a cobalt-chrome stem only for cemented fixation, was cemented into 15 patients. These 3 different stem designs were used to study different metals as well as different stem shapes. The average follow-up was 4.3 years (range, 2-10 years) with all hips having 2 years' follow-up and 42 hips at least 5 years' follow-up. Bone remodeling was measured as stress shielding, calcar resorption, and distal hypertrophy on anteroposterior and lateral radiographs of the hip. Stress shielding was measured by the 4 grades described by Engh. A stem stiffness-to-femoral bone stiffness ratio was calculated from the plain radiographs with the stem stiffness known from the manufacturer and the bone stiffness calculated using measurements of the outer and inner diameters of the femur. There was no statistical difference for bone remodeling and fixation between the 3 stem shapes or 2 metal types used in these hips. No stem was loose, and only 10 had radiolucent lines. Stress shielding was statistically related to stem stiffness but was more strongly related to the axial stiffness ratio, mediolateral bending stiffness ratio, anteroposterior stiffness ratio, and torsional stiffness ratio. Stress shielding grade 3 and 4 was present in 20% of hips with a torsional stiffness ratio < 0.33, in 38% of hips with a torsional stiffness ratio of 0.34 to 0.5, and in 70% of hips with a torsional stiffness ratio > 0.5. Five-year results showed no statistical change in stress shielding, calcar resorption, and distal hypertrophy from the 2-year observations. The stem stiffness-to-bone stiffness ratio influenced bone remodeling but not fixation of these cemented stems.

Adult↗
PubMed1995

A new light-cured glass ionomer cement that bonds brackets to teeth without etching in the presence of saliva.

Previous studies stress certain advantages of glass ionomer cements, for use in bonding orthodontic brackets to teeth. Failure rate, however, had been higher than with conventional procedures. A new light-cured glass ionomer cement exhibited all the necessary qualities needed to bond brackets, without any etching and in the presence of saliva. The tensile strength of this cement exhibited enough resistance to forces needed to move teeth. The debonding procedures were also completely undamaging to the underlying enamel surfaces. On removal of the appliances, no decalcification was observed on any teeth, because the cement releases fluoride. Both the time saved during a routine strap-up, plus the ease to both the operator and the patient, could make light-cured glass ionomer cement the ultimate choice for bonding techniques after many trials, this cement is now being routinely and successfully used on all patients.

Acid Etching, Dental↗
PubMed2004

Investigating the effects of bone cement, cyanoacrylate glue and marine mussel adhesive protein from Mytilus edulis on human osteoblasts and fibroblasts in vitro.

Bone cement is a widely used standard fixation substance in Orthopaedic Surgery. Cyanoacrylate glue is available for wound closure to supplement suturing. The mussel adhesive protein extracted from Mytilus edulis (Cell-Tak, BD Biosciences, Heidelberg, Germany) is an experimental fixation device used for in vitro purposes of cell adhesion. The aim of this study is to introduce a cell culture model investigating the effects of commonly applied and experimental glues on human fibroblasts and osteoblasts in vitro. Cells cultured without additives served as a control group. Microscopic examination was performed to evaluate the morphologic changes. An apoptosis test (Apo-Tag, Chemicon International, Temecula, CA, U. S. A.) was applied to determine the rate of natural cell death at the end of the study. It could be demonstrated that morphological changes in bone cement are different in fibroblasts and osteoblasts. Osteoblasts seem to grow on bone cement and develop an orderly formation. Fibroblasts grow in a confluent monolayer around bone cement but do not adhere to the cement itself. This is a desirable effect since most Orthopaedic applications aim at osteointegration as opposed to fibrous tissue overgrowth. Apoptosis attributed to bone cement is comparable to the respective natural rate of apoptosis. Cyanoacrylate glue and the mussel adhesive protein lead to an almost complete apoptosis in the investigated cells. Their routine application should be avoided. The developed cell culture model seems appropriate for performing further investigations.

Animals↗
PubMed1995

Histologic evaluation of tetracalcium phosphate-based cement as a direct pulp-capping agent.

Histologic healing processes were observed at 1, 3, 7, and 10 days after application with either tetracalcium phosphate cement or calcium hydroxide cement to the exposed pulp of the rat maxillary incisors. In teeth applied with calcium hydroxide cement, necrotic tissue was present beneath the cement before new hard tissue formed. In contrast, tetracalcium phosphate cement elicited a dentine bridge formation with no evidence of either intervening tissue necrosis or marked inflammation. Furthermore on ultrastructural examination the newly formed hard tissue was in direct contact with the material. This study suggests that 4CP cement possesses a biocompatible property, which indicates its potential for use as a direct pulp-capping agent.

Animals↗
PubMed1998

Preliminary evaluation of hydroxyapatite cement as an augmentation device in the edentulous atrophic canine mandible.

OBJECTIVE: The purpose of this study was to answer the following two questions: (1) Can hydroxyapatite cement in combination with demineralized freeze dried bone feasibly augment the dimension of an atrophic edentulous canine mandible? (2) What is the histologic fate of an augmentation graft composed of hydroxyapatite cement and demineralized freeze dried bone placed on the surface of an atrophic edentulous canine mandible? STUDY DESIGN: Each of four mixed-breed canines (weighing 50 to 60 pounds) underwent bilateral mandibular dental extraction (canine to second molar) and radical alveolectomy. After 4 months of healing, a bilateral subperiosteal mandibular augmentation graft was put into place, with hydroxyapatite cement/demineralized freeze dried bone on the surface of one hemimandible and porous granular hydroxyapatite and demineralized freeze dried bone on the surface of the other hemimandible. The animals were killed after functioning on a soft diet for 9 months, and the grafted hemimandibles were harvested. RESULTS: Both hydroxyapatite cement and granular hydroxyapatite grafts appeared to augment the edentulous atrophic canine mandible. On histologic exam, the hydroxyapatite cement grafts showed osteoconduction and subperiosteal and endosteal osteonal bone formation, whereas the granular hydroxyapatite grafts showed only osteoconduction. Neither graft material showed chronic or acute inflammation. CONCLUSION: Hydroxyapatite cement can function feasibly as a mandibular augmentation device. The histologic fate of hydroxyapatite cement is different from that of granular hydroxyapatite. It has a fate comparable to autograft or allograft cortical bone grafts.

Alveolar Ridge Augmentation↗