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PubMed1997

The effect of cementing procedures on retention of prefabricated metal posts.

Twelve prefabricated posts were cemented in extracted teeth with zinc phosphate cement, 14 with resin cement after the canals were acid etched and 14 with zinc phosphate cement after acid etching. After thermocycling, specimens were subjected to a straight-line tensile force. The posts cemented with resin cement had significantly higher tensile strength than those cemented with the two zinc phosphate cement treatments.

Acid Etching, Dental↗
PubMed1978

Adaption of luting cement to enamel, dentin and restorative material.

Thirty-two teeth with artificial crowns cemented with four different cements were sectioned and the cementing interfaces were studied by means of a replica technique. Scanning electronic microscopic examination of the replicas demonstrated that slits occurred in all specimens either at the cement/tooth interface, the cement/alloy interface or both. Differences between the various cements in width and length of the slits could not be assessed by this method, but marked variations in the localization of the slits were noted. A composite resin cement showed slits only at the cement/tooth interface. A zinc phosphate and an EBA cement showed slits at both interfaces whereas a polycarboxylate cement was the only cement which exhibited good adaption to enamel and dentin, leaving gaps at the cement/alloy interface.

Adhesiveness↗
PubMedDate not supplied

[Antimicrobial activity of orthodontic band cements].

The prevalence of enamel decalcification and caries beneath orthodontic bands, has indicated the need for a new enamel binding adhesive orthodontic cement. The purpose of this study was to evaluate the antimicrobial activity, in vitro, on Streptococcus mutans and Lactobacillus, acidophillus, of three materials used to cements the orthodontic bands. The cements studied were: Zinc phosphate cement, Glass-ionomer cement, and Policarboxylate cement. Thirty petri plates were seeded with S. mutans, and thirty with L. acidophillus; on each plate three pellet were placed, one of each cement studied. Petri plates were incubated under microaerophilic conditions at 37 C, and checked at 72 hrs. for Streptococcus, mutans, and four days for Lactobacillus acidophillus to evaluate the inhibition zone. The results were tabulated for each material. It was demonstrated that exists important variations in the antimicrobial properties of the materials studied, as in the microbial sensitivity to these cements.

Dental Cements↗
PubMed1984

Early erosion of dental cements.

The disintegration in water of various unset glass ionomer cements, a polycarboxylate and a zinc phosphate cement was measured gravimetrically after exposure of the cements to a constant water jet. The test gave reproducible results with significant variations between the various types and brands of cements. For zinc phosphate and polycarboxylate cements, no weight loss was observed in the period from 4 to 8 min after commencement of mixing. All the glass ionomer cements showed a significant loss of weight at 4 min and a somewhat reduced weight loss at 6 min after start of mixing. Two cements, a filling and a luting material, showed reduced weight when exposed to a water jet even 8 min after start of mixing. The early erosion as recorded in the present study conforms with the setting of the glass ionomer cements.

Chemical Phenomena↗
PubMed1981

[Retention of three different luting cements (author's transl)].

Employing zinc phosphate, polycarboxylate and glass ionomer cements, effect of cement layer thickness on retention of crowns at their axial wall was investigated. Stainless steel preparations and occlusally perforated crowns having taper angles of 2.9 and 5.7 degrees were cemented, regulating the thickness at the axial wall from 5 to 60 mu. These dies were stored in a 100% relative humidity atmosphere at room temperature or in distilled water. After 48 hr, retention was measured, applying the load vertically to occlusal preparation surface through a plunger (Fig. 1). Due to the inclusion of unreacted powder particles in the set structure of all three cements, evidence of a critical value was always shown in the cement thickness-retention relationship (Figs. 2, 3 and 4). When the cement thickness was reduced below the critical value, the retention increased remarkably and was not affected by the environment. Above the critical value, however, the retention of these cements was relatively small and affected considerably by the environment. By water immersion, the increase in the retention was found for the two polyacrylate, but not for the zinc phosphate. Correlation between retention and mechanical strengths of the three cements in the respective environments was indefinite.

Adhesiveness↗
PubMed1997

Properties of acrylic bone cement: state of the art review.

Acrylic bone cement occupies a distinctive place in the hierarchy of synthetic biomaterials, because it is the only material currently used for anchoring the prosthesis to the contiguous bone in a cemented arthroplasty. However, the cement is not without its drawbacks. The main one is the role that it has been postulated to play in the aseptic loosening and, hence, clinical life of the arthroplasty. In turn, this role is directly related to the mechanical properties of the cement, especially the resistance to fracture of the cement in the mantle at the cement-prosthesis interface or the cement-bone interface. The present work is a detailed critical review of the recent literature on the properties of bone cement that are considered germane to its use in the stated application. The relevant properties are identified and a case is made for including each of them. Compilations of the values of these properties, obtained under clearly identified conditions, are presented for the six commercial formulations of bone cement in current popular orthopedic use. The gaps and unresolved questions in the current data base, efforts that should be made to address these issues, and research directions are covered.

Acrylates↗
PubMed1999

Pressurization of bioactive bone cement in vitro.

We have developed a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW glass-ceramic powder), silica glass powder as an inorganic filler, and bisphenol-a-glycidyl methacrylate (bis-GMA) based resin as an organic matrix. The efficacy of this bioactive bone cement was investigated by evaluating its pressurization in a 5-mm hole and small pores using a simulated acetabular cavity. Two types of acetabular components were used (flanged and unflanged sockets) and a commercially available polymethylmethacrylate (PMMA) bone cement (CMW 1 Radiopaque Bone Cement) was selected as a comparative control. Bioactive bone cement exerted greater intrusion volume in 5-mm holes than PMMA bone cement in both the flanged and unflanged sockets 10 minutes after pressurization (p < 0.05). In the small pores the bioactive and PMMA bone cements exerted almost identical intrusion volumes in flanged and unflanged sockets 10 min after pressurization. The intrusion volume in the flanged socket 10 minutes after pressurization was greater than that in the unflanged socket in all groups (p < 0.05). These results show that bioactive bone cement intrudes deeper into anchor holes than PMMA bone cement.

Biocompatible Materials↗
PubMed2000

Evaluation of bioactive bone cement in canine total hip arthroplasty.

Total hip arthroplasties (THAs) were performed in beagle dogs using a bioactive bone cement (BABC) consisting of a silane-treated apatite- and wollastonite-containing glass-ceramic (AW glass-ceramic) powder and a silica glass powder as the filling particles and a bisphenol-A-glycidyl dimethacrylate-based resin (Bis-GMA-based resin) as the organic matrix. The outcomes were compared with the results of polymethylmethacrylate (PMMA) bone cement. The mechanical properties of the BABC were stronger than those of PMMA bone cement. The bonding strength of the BABC to bone in the dogs' femora increased with time and reached 3.7 MPa at 24 months after implantation whereas that of PMMA bone cement was 2.0 MPa (p < 0.05). Histological examination showed direct bonding between the BABC and the femoral bone for up to 24 months after implantation. However, with PMMA bone cement an intervening soft-tissue layer consistently was observed at the bone-cement interface. Direct bonding at the interface between the BABC and the bone through a calcium phosphorous layer 30 microm-thick was revealed by scanning electron microscopy. Femoral bone resorption was observed at 24 months after implantation in the BABC group, but it was not observed in the PMMA bone cement group. Direct bonding between BABC and the bone may have accelerated femoral bone resorption. Cement fractures of the BABC were observed on the acetabular side 24 months after implantation. Weak bonding between the BABC and an acetabular component made of ultrahigh molecular weight polyethylene (UHMWPE), relatively high elastic characteristics of BABC, and weakness of the calcium phosphorous layer formed on the surface of this cement seemed to lead to failure at 24 months on the acetabular side.

Animals↗
PubMed2000

A theoretical and experimental analysis of polymerization shrinkage of bone cement: A potential major source of porosity.

A theoretical basis for understanding polymerization shrinkage of bone cement is presented based on density changes in converting monomer to polymer. Also, an experimental method, based on dilatometry and the Archimedes' principle is presented for highly precise and accurate measurement of unconstrained volumetric shrinkage of bone cement. Furthermore, a theoretical and experimental analysis of polymerization shrinkage in a constrained deformational state is presented to demonstrate that porosity can develop due to shrinkage. Six bone-cement conditions (Simplex-Ptrade mark vacuum and hand mixed, Endurancetrade mark vacuum mixed, and three two-solution experimental bone cements with higher initial monomer levels) were tested for volumetric shrinkage. It was found that shrinkage varied statistically (p< or = 0.05) from 5.1% (hand-mixed Simplex-Ptrade mark) to 6.7% (vacuum-mixed Simplex-Ptrade mark) to 10.5% for a 0.6:1 (polymer g/monomer mL) two-solution bone cement. Shrinkage was highly correlated with initial monomer content (R(2) = 0.912) but with a lower than theoretically expected rate. This discrepancy was due to the presence of residual monomer after polymerization. Using previously determined residual monomer levels, the theoretic shrinkage analysis was shown to be predictive of the shrinkage results with some residual monomer left after polymerization. Polymerization of a two-solution bone cement in a constrained state resulted in pores developing with volumes predicted by the theory that they are the result of shrinkage. The results of this study show that shrinkage of bone cement under certain constrained conditions may result in the development of porosity at the implant-bone cement interface and elsewhere in the polymerizing cement mantle.

Animals↗
PubMed2001

Bioactive bone cement: Effect of silane treatment on mechanical properties and osteoconductivity.

A novel bioactive bone cement (GBC) was developed with newly designed bioactive MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) glass beads as the inorganic filler and high molecular weight poly(methyl methacrylate) as the organic matrix. The purpose of this study was to examine the relationship between the amount of the silane coupling agent (gamma-methacryloxy propyl trimethoxy silane) used to treat the glass beads and the mechanical and biological properties of the resultant bone cement. Serial changes in the cement over time were also investigated. Five different kinds of cement, in which the glass beads were treated with different amounts of the coupling agent, were prepared. The quantities of the coupling agent were 0 (control), 0.1, 0.2, 0.5, and 1.0% (w/w) of the glass beads, and the cements were designated GBCs0, GBCs0.1, GBCs0.2, GBCs0.5, and GBCs1.0, respectively. After soaking in water at 75 degrees C for 5 days, GBCs0.1 and GBCs0.2 had significantly higher bending strengths than the other cements. Each GBC was packed into intramedullar canals of rat tibiae to evaluate osteoconductivity, as determined by affinity indices. Rats were killed 4 and 8 weeks after the operation. The affinity index was calculated for each GBC and equaled the length of bone in direct contact with the cement and was expressed as a percentage of the total length of the cement surface. Histologically, new bone had formed along all of the GBC surfaces within 4 weeks. At each time interval, a decreasing trend in the affinity index of GBC was found as the amount of the coupling agent increased. At 8 weeks, no significant change in the affinity index occurred when the amount of the coupling agent increased from 0 to 0.2%, whereas a significant decrease in the affinity index was observed when the amount of the coupling agent increased from 0 to 0.5 or 1.0%. The affinity indices for all the GBCs increased significantly up to 8 weeks. When both the mechanical properties and osteoconductivity were taken into consideration, GBCs0.1 and GBCs0.2 were the best cements, and they showed excellent osteoconductivity and strong enough mechanical properties for clinical use.

Animals↗
PubMed2002

Characterization of new acrylic bone cements prepared with oleic acid derivatives.

Acrylic bone-cement formulations were prepared with the use of a new tertiary aromatic amine derived from oleic acid, and also by incorporating an acrylic monomer derived from the same acid with the aim of reducing the leaching of toxic residuals and improving mechanical properties. 4-N,N dimethylaminobenzyl oleate (DMAO) was used as an activator in the benzoyl-peroxide radical cold curing of polymethyl methacrylate. Cements that contained DMAO exhibited much lower polymerization exotherm values, ranging between 55 and 62 C, with a setting time around 16--17 min, depending on the amine/BPO molar ratio of the formulation. On curing a commercial bone cement, Palacosreg R with DMAO, a decrease of 20 C in peak temperature and an increase in setting time of 7 min were obtained, the curing parameters remaining well within limits permitted by the standards. In a second stage, partial substitution of MMA by oleyloxyethyl methacrylate (OMA) in the acrylic formulations was performed, the polymerization being initiated with the DMAO/BPO redox system. These formulations exhibited longer setting times and lower peak temperatures with respect to those based on PMMA. The glass transition temperature of the experimental cements were lower than that of PMMA cement because of the presence of long aliphatic chains of both activator and monomer in the cement matrix. Number average molecular weights of the cured cements were in the range of 1.2x10(5). PMMA cements cured with DMAO/BPO revealed a significant (p<0.001) increase in the strain to failure and a significant (p<0.001) decrease in Young's modulus in comparison to Palacosreg R, whereas ultimate tensile strength remained unchanged. When the monomer OMA was incorporated, low concentrations of OMA provided a significant increase in tensile strength and elastic modulus without impairing the strain to failure. The results demonstrate that the experimental cements based on DMAO and OMA have excellent promise for use as orthopaedic and/or dental grouting materials.

Acrylates↗
PubMed1989

Adhesive bone cement both to bone and metals: 4-META in MMA initiated with tri-n-butyl borane.

In order to develop a new bone cement which is expected to prevent loosening of a prosthesis by better adhesion, the cement composed of 4-methacryloyloxyethyl trimellitate anhydride (4-META) and methyl methacrylate (MMA) as monomers and tri-n-butyl borane (TBB) as an initiator was evaluated. The tensile bond strength between bone and metals adhered with 4-META/MMA-TBB cement was above 7 MPa. The values were higher than that with conventional bone cement (1 MPa) or MMA-TBB cement (2 MPa). Therefore, 4-META was effective for improving adhesion. When cohesive failure of the bone was observed with the scanning electron micrography after the tensile test, fracture occurred on the bone side below the interface between the bone and the 4-META/MMA-TBB cement. This result showed that the cement adhered tightly to both the bone and metals. Thus, it is concluded that the 4-META/MMA-TBB cement is useful as an adhesive bone cement.

Adhesiveness↗
PubMed1995

Bioactive bone cement: the effect of amounts of glass powder and histologic changes with time.

A study was conducted to examine the influence of the amount of glass powder added to a bioactive bone cement of our formula on its mechanical and biologic properties. Serial changes in the cement with time were also examined. The bioactive bone cement consisted of CaO-SiO2-P2O5-CaF2 glass powder and bisphenol-a-glycidyl methacrylate resin. Glass powder was added to the cement in 30, 50, 70, and 80% weight ratios. The compressive strengths of the resulting cements (171-239 MPa) were more than double that of polymethylmethacrylate cement (68 MPa). Histologic examination of rat tibiae bearing artificial defects packed with each bioactive cement showed direct bone contact 4 weeks after surgery. The cement with a higher percentage of glass powder showed better direct formation of bone around its periphery with a thicker reactive layer. Under scanning electron microscopic observation, the reactive layer showed increased levels of calcium and phosphorus. Examination of histologic changes up to 26 weeks showed progressive bone formation around the cement and no sign of biodegradation.

Animals↗
PubMed2003

Fatigue and fracture toughness of acrylic bone cements modified with long-chain amine activators.

The composition of acrylic bone cement has been identified as one of the important parameters affecting its mechanical properties and may, in turn, ultimately influence the longevity of a cemented arthroplasty. Our aim in this study was to determine the influence of change of one compositional variable, the activator, on the fatigue performance and fracture toughness of specimens of the fully cured cement. To that end, three sets of cements were prepared, containing either the conventional activator, 4-N,N dimethyl p-toluidine (DMPT), or novel ones that are tertiary amines based on long-chain fatty acids, that is, 4-N,N dimethylaminobenzyl oleate (DMAO) and 4-N,N dimethylaminobenzyl laurate (DMAL). In the fatigue tests, the specimens were subjected to tension-tension loading, and the results (number of cycles to failure, Nf) were analyzed using the linearized form of the three-parameter Weibull equation. The fracture toughness (KIc) tests were conducted with rectangular compact tension specimens. All fracture surfaces were subsequently examined with scanning electron microscopy. We found that the Weibull mean fatigue lives for specimens fabricated using the DMPT, DMAL, and DMAO containing cements were 272,823, 453,551, and 583,396 cycles, respectively. The corresponding values for KIc were 1.94 +/- 0.05, 2.06 +/- 0.09, and 2.00 +/- 0.07 MPa radical m, respectively. Statistical analyses showed that for both the DMAL- and DMAO-containing cements, the mean values of Nf were significantly higher compared to the corresponding value for the DMPT-containing cement (Mann-Whitney test; alpha < 0.10). This result is attributed to the higher molecular weights of the former cements compared to the latter. The same trend was found for the mean KIc values (Mann-Whitney test; alpha < 0.05), with the trend being explained in terms of the differences seen in the crack morphologies. These results thus demonstrate that these novel amines are viable alternatives to DMPT for incorporation into acrylic bone cement formulations in the future.

Amines↗
PubMed2004

Gentamicin release from two-solution and powder-liquid poly(methyl methacrylate)-based bone cements by using novel pH method.

The release of gentamicin as a function of time was measured for Palacos and two-solution bone cements by using a novel pH technique. The pH of an aqueous solution of gentamicin is a function of the gentamicin concentration and it decreases linearly over concentrations of 0.0-0.1 wt %. Therefore, a new, direct, and inexpensive in vitro technique was developed based on continuous readings of the pH in phosphate-buffered saline (PBS) at 37 degrees C to determine the release kinetics of gentamicin from poly(methyl methacrylate) (PMMA)-based bone cement. In addition, this method was used to compare the release profiles of Palacos R-40 bone cement with a two-solution bone cement developed in our laboratory and loaded with two different concentrations of gentamicin sulfate. Finally, the pH-based method was used to track the elution of gentamicin in both mixed and static conditions to determine the effect of mixing on the diffusion of gentamicin out of the cement. It was found that Palacos R-40 released 4.95 +/- 0.22 wt % of its gentamicin after 24 h in PBS solution. This data compares favorably with previously reported values of gentamicin elution from Palacos R-40, which ranged from 3 to 8 wt % of the total amount of incorporated gentamicin, depending on the size and the surface area of the samples. The results show that Palacos samples released 4.84 +/- 0.27 mg after 24 h, a two-solution cement loaded with an equivalent concentration of gentamicin sulfate released 3.81 +/- 0.52 mg, and two-solution cement loaded with twice the concentration of Palacos released 5.53 +/- 0.26 mg of gentamicin. A higher percentage of release was recorded from Palacos than from the two-solution bone cement, and the effect of PBS mixing conditions on the release kinetics was only significant in the early stages of release and not at 24 h. It was concluded that monitoring the pH is an effective technique to measure gentamicin release from PMMA-based bone cements in PBS solution.

Anti-Bacterial Agents↗
PubMed2004

Fracture toughness of steel-fiber-reinforced bone cement.

Fractures in the bone-cement mantle (polymethyl methacrylate) have been linked to the failure of cemented total joint prostheses. The heat generated by the curing bone cement has also been implicated in the necrosis of surrounding bone tissue, leading to loosening of the implants. The addition of reinforcements may improve the fracture properties of bone cement and decrease the peak temperatures during curing. This study investigates the changes in the fracture properties and the temperatures generated in the ASTM F451 tests by the addition of 316L stainless steel fibers to bone cement. The influence of filler volume fraction (5-15% by volume) and aspect ratios (19, 46, 57) on the fracture toughness of the acrylic bone cement was assessed. Increasing the volume fraction of the steel fibers resulted in significant increases in the fracture toughness of the steel-fiber-reinforced composite. Fracture-toughness increases of up to 2.63 times the control values were obtained with the use of steel-fiber reinforcements. No clear trend in the fracture toughness was discerned for increasing aspect ratios of the reinforcements. There is a decrease in the peak temperatures reached during the curing of the steel-fiber-reinforced bone cement, though the decrease is too small to be clinically relevant. Large increases in the fatigue life of acrylic bone cement were also obtained by the addition of steel fibers. These results indicate that the use of steel fibers may enhance the durability of cemented joint prostheses.

Biocompatible Materials↗
PubMed2005

Gentamicin-loaded bone cement with clindamycin or fusidic acid added: biofilm formation and antibiotic release.

The formation of staphylococcal biofilms on experimental bone cements, loaded with 0.5 or 1.0 g of active gentamicin and an additional equivalent amount of gentamicin, clindamycin, or fusidic acid was investigated. The biofilms were formed in a modified Robbins device over a 3-day time span and the influence of the additional antibiotics was quantified by expressing the number of colony forming units relative to the corresponding bone cement containing only gentamicin. Combinations of gentamicin with either fusidic acid or clindamycin reduced growth of clinical isolates of both gentamicin-sensitive Staphylococcus aureus and gentamicin-resistant coagulase-negative staphylococci to approximately 28%. To determine whether adding a second antibiotic has influence on the gentamicin release, cement blocks were placed in phosphate buffer and aliquots were taken at designated sampling intervals. The influence of the additional antibiotics was quantified by expressing the percentage released of the total amount of antibiotic incorporated in the different bone cements. After 3 days, all bone cements had released similar percentages of gentamicin, whereas more clindamycin and fusidic acid were released after doubling their concentration in the bone cements. In conclusion, bone cements loaded with combinations of gentamicin and clindamycin or fusidic acid are more effective in preventing biofilm formation than bone cements with gentamicin as a single drug. In addition, the presence of clindamycin or fusidic acid in gentamicin-loaded bone cement has no influence on the total gentamicin release.

Biofilms↗
PubMed2003

Fatigue testing and performance of acrylic bone-cement materials: state-of-the-art review.

Over the past three decades or so, a very large volume of literature has been generated on the impact of an assortment of variables on the fatigue lifetimes of a large number of acrylic bone-cement formulations. In the present article, this literature is examined critically to reveal areas of agreement, areas of disagreement, as well as a welter of underexplored and unexplored topics. For example, there is unanimity of support for the notion that an increase in the molecular weight of the powder constituents or the fully cured cement leads to an increase in the cement's fatigue life, whereas there is disagreement as to whether vacuum mixing the cement constituents leads to an increase in the fatigue life of the fully cured cement (relative to the hand-mixed counterpart). Among the underexplored topics is systematic study of the effect of test frequency on the fatigue results, whereas determination of the optimal concentration of the antibiotic in an antibiotic-loaded cement is an example of the unexplored topics. It is pointed out that resolving the controversies, addressing the underexplored topics, and filling the lacunae will allow comprehensive evaluations of acrylic bone-cement materials to be made. This enhanced body of knowledge will prove invaluable in the continued use of acrylic bone cement as the anchoring agent in cemented arthroplasties.

Animals↗