Polymethylmethacrylate Based Bone Cement Research Articles

Effects of polymethyl methacrylate-based bone cement graft for treating excessive gingival display and its dimensional facial changes: 12-Month clinical study

Objectiveto present a 12-month follow-up with photographic and tomographic analyses of the effect of polymethyl methacrylate-based bone cement graft (PMMA) in gingival exposure (GE) in patients with excessive gingival display (EGD). MethodsTwelve patients with EGD were included. The PMMA was surgically placed. A frontal and lateral photograph protocol was performed at baseline (T0), 3 (T3), 6 (T6), and 12 months (T12) post-operatively. Soft tissue cone-beam computed tomography (ST-CBCT) was performed at T0 and T12. Measures included GE, length of the lip vermilion (LLV), lip shape (LS), nose width (NW), filter width (FW), nasolabial angle (NAS) while smiling, and nasolabial angle at rest (NAR). The height, thickness, and volume of the cement graft were also measured in the ST-CBCT. The comparisons were performed by Kruskal-Wallis test at 5 % of significance (p < 0.05). ResultsThe height, thickness, and volume of the PMMA were respectively 12.84 ± 1.59 mm, 3.83 ± 0.53, and 1532.02 ± 532.52 mm3. PMMA significantly decreased GE from 8.33 ± 1.25 mm (T0) to 6.60 ± 0.93 mm (T12) (p < 0.01). NAR was 98.34 ± 9.28° at T0 and increased to 105.13 ± 7.33° at T12; however, the angle value was not statistically different (p = 0.08). LLV, LS, NW, FW, and NAS did not exhibit statistical differences between the baseline and follow-up periods. ConclusionsPMMA significantly decreased GE in a 12-month follow-up without influencing adjacent soft tissue anatomical structures.

Computational Study on Interfacial Interactions between Polymethyl Methacrylate-Based Bone Cement and Hydroxyapatite in Nanoscale

Polymethyl methacrylate (PMMA)-based bone cement (BC) is a key material in joint replacement surgery that transfers external forces from the implant to the bone while allowing their robust binding. To quantitatively evaluate the effect of polymerization on the thermomechanical properties of the BC and on the interaction characteristics with the bone ceramic hydroxyapatite (HAp), molecular dynamics simulations were performed. The mechanical stiffness of the BC material under external loading increased gradually with the crosslinking reaction occurrence, indicating increasing load transfer between the constituent molecules. In addition, as the individual Methyl Methacrylate (MMA) segments were interconnected in the system, the freedom of the molecular network was largely suppressed, resulting in more thermally stable structures. Furthermore, the pull-out tests using HAp/BC bilayer models under different constraints (BC at 40% and 85%) revealed the cohesive characteristics of the BC with the bone scaffold in molecular detail. The stiffness and the fracture energy increased by 32% and 98%, respectively, with the crosslink density increasing.

Evaluation of the effects of chitosan/multiwalled carbon nanotubes composite on physical, mechanical and biological properties of polymethyl methacrylate-based bone cements

ABSTRACTBecause of some undesirable properties of polymethyl methacrylate(PMMA) bone cement, it is necessary to adopt a new strategy to improve its function. In this study, after preparing of chitosan (CS) powder and CS/multiwalled carbon nanotubes (MWCNTs) composite powder, they were added to the PMMA bone cement in different percentages with homogeneous distribution. The results showed that by adding CS/MWCNTs to the PMMA, injectability and setting time were increased and maximum temperature and contact angle were decreased, significantly. Mechanical tests showed that by adding 25 wt. % of CS/MWCNTs to the PMMA, the compressive and bending strength were increased, significantly. According to the results obtained from the bioactivity and cellular activity test, by adding 25 wt. % of CS/MWCNTs to the PMMA, apatite like deposition and extra cellular matrix formation were increased, significantly. Accordingly, 25 wt. % PMMA-CS/MWCNTs composite can create a new approach to improve commercial bone cements.

Effect of Incorporation of Lanthanum and Cerium-doped Hydroxyapatite on Acrylic Bone Cement Produced from Phosphogypsum Waste

This study demonstrates the utilization of phosphogypsum waste for preparation of hydroxyapatite, lanthanum-doped hydroxyapatite and cerium-doped hydroxyapatite. Three concentrations of doping for each rare earth elements were prepared (0.25, 0.5, 0.75 weight %( respectively to be used as nanoparticles fillers additive to enhance the antibacterial activity, mechanical properties and bioactivity of conventional polymethyl methacrylate based bone cements. The prepared nanoparticles fillers are incorporated manually in 20 weight % to conventional polymethyl methacrylate bone cement to achieve polymethyl methacrylate cement composites. The results revealed that cerium-doped in 0.5 weight % with hydroxyapatite / polymethyl methacrylate cement composite permits remarkable increase in antibacterial activity against Staphylococcus aureus, while preserving a reasonably adequate compressive strength, and showed much higher calcium and phosphorus ions release (P-value ≤ 0.05). Within limitation of this study, the results are indicating the opportunity of the innovative bone cement for dental and orthopedic applications.

Antimicrobial peptides prevent bacterial biofilm formation on the surface of polymethylmethacrylate bone cement

Antibiotic-loaded polymethylmethacrylate-based bone cement has been implemented in orthopaedics to cope with implant-related infections associated with the formation of bacterial biofilms. In the context of emerging bacterial resistance to current antibiotics, we examined the efficacy of short antimicrobial peptide-loaded bone cement in inhibiting bacterial adhesion and consequent biofilm formation on its surface. The ability of α-helical antimicrobial peptides composed of 12 amino acid residues to prevent bacterial biofilm [methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli] formation on the surface of model implants made from polymethylmethacrylate-based bone cement was evaluated by colony-forming unit (c.f.u.) counting of bacteria released by sonication from the biofilms formed on their surfaces. The biofilms on model implant surfaces were also visualized by light microscopy after staining with tetrazolium dye (MTT) and by scanning electron microscopy. When incorporated in the implants, these peptides caused a mean reduction in the number of bacterial cells attached to implants' surfaces (by five orders of magnitude), and 88 % of these implants showed no bacterial adhesion after being exposed to growth media containing various bacteria. The results showed that the antibiofilm activity of these peptides was comparable to that of the antibiotics, but the peptides exhibited broader specificity than the antibiotics. Given the rapid development of antibiotic resistance, antimicrobial peptides show promise as a substitute for antibiotics for loading into bone cements.

Experimental investigations of the aerated polymethylmethacrylate-based vertebral cement flow in capillaries.

Introduction:A constant growth in the population suffering from osteoporotic vertebral weakening is observed. As a result, vertebroplasty procedures become more and more common. Unfortunately, they may be associated with several complications occurring during bone cement injection, including its leakage or overheating of tissues. Despite several experimental studies, there is a lack of data related to random aeration of the bone cement. Therefore, the main objective of the following investigations was to emphasize that random aeration of the bone cement, and, consequently, a compressibility factor, could not be treated as a negligible factor during the vertebroplasty procedure and had to be taken into account in the development of the mathematical model.Materials and methods:A special test rig to reproduce the vertebroplasty procedure was designed and built. The authors conducted numerous experiments on polymethylmethacrylate-based bone cement flows, analyzing different flow conditions, such as volume flow rate and flow channel diameter. Time periods of the flow front between characteristic sections and pressures (differential and gauge) were measured.Results:All investigations revealed that bone cements mixed in special mixing kits were characterized by a random level of aeration which led to varied flow parameters. Comparing the experimental results with the theoretical values of the continuity equation, the highest difference in the flow duration reached 140%.Discussion:It has been proven that the aeration of the bone cement alters the flow dynamics. Therefore, much more data are required for statistical analysis to validate a mathematical model of the bone cement flow.

In vitro Growth Pattern of Primary Human Osteoblasts on Calcium Phosphate- and Polymethylmethacrylate-Based Bone Cement

Background/Purpose: Polymethylmethacrylate (PMMA) and calcium phosphate (Ca-P) cements are widely used for arthroplasty surgery and augmentation of bone defects. However, aseptic implant loosening in absence of wear-induced osteolysis indicates an unfavourable interaction between the cement surface and human osteoblasts. Our underlying hypothesis is that cement surfaces directly modify cell viability, proliferation rate, and cell differentiation. Methods: To test this hypothesis, we examined primary human osteoblasts harvested from six individuals. These cells were pooled and subsequently seeded directly on cement pellets prepared from Palacos® R, Palacos® R+G, and Norian® Drillable cements. After incubation for 24 and 72 h, cell viability, proliferation rate, apoptosis rate, and cell differentiation were analysed. Results: Upon cultivation of human osteoblasts on cement surfaces, we observed a significantly reduced cell viability and DNA content compared to the control. Analysis of the apoptosis rate revealed an increase for cells on Palacos R and Norian Drillable, but a significant decrease on Palacos R+G compared to the control. Regarding osteogenic differentiation, significantly lower values of alkaline phosphatase enzyme activity were identified for all cement surfaces after 24 and 72 h compared to cultivation on tissue culture plastic, serving as control. Conclusions: In summary, these data suggest a limited biocompatibility of both PMMA and Ca-P cements, necessitating further research to reduce unfavourable cell-cement interactions and consequently extend implant survival.

In vivo evaluation of bioactive PMMA-based bone cement with unchanged mechanical properties in a load-bearing model on rabbits.

Polymethylmethacrylate-based bone cements are widely used for fixation of joint replacements. To improve the long-term outcome, bioactive bone cements are aspired to advance the bone-cement interface. This study evaluated the in vivo properties of a new polymethylmethacrylate-based bioactive bone cement with addition of amphiphilic phosphorylated 2-hydroxyethylmethacrylate. Previous in vitro studies confirmed bioactive properties in cell culture, as well as unchanged mechanical properties are tests according to ISO 5833:2002.Three different variations of the cement (polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate, polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate + CaCl2 and polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate + CaCl2 + Na2CO3) were compared to conventional polymethylmethacrylate cement. To evaluate the properties under load-bearing conditions, a spacer prosthesis was implanted into the femoral diaphysis of 24 rabbits. Additionally, a cement plug was installed into the proximal tibia. After three months, polished sections with Giemsa surface staining were prepared. The bioactivity was determined using the bone affinity index.The sections showed a good osseointegration of the bioactive bone cement without cement cracks under load-bearing conditions. Regarding the bone affinity index, the bioactive bone cement revealed a significantly higher value in the proximal tibia (25.9-37.7%) and around the spacer prosthesis (36.8-58.9%) compared to the conventional polymethylmethacrylate cement (12.8-17.0%).The results confirm the in vivo bioactivity of this bone cement. The absence of cement cracks indicates a sufficient mechanical stability to fix prostheses with this bioactive cement, but for a final assessment long-term tests are necessary.

Acrylic cement formulations modified with calcium deficient apatite nanoparticles for orthopaedic applications

Polymethyl methacrylate-based bone cements are used worldwide by the orthopaedic surgeons to secure joint implants with the skeleton. However, the clinical use of this cement is accompanied by complications such as exothermic heat produced during the polymerization reaction, lack of bone bonding ability and shrinkage to name a few. In the present work, the effect of incorporation of calcium-deficient hydroxyapatite nanoparticles on the properties of a commercially available orthopaedic bone cement matrix has been investigated. Initial and final setting time of the cement has been found to decrease with calcium-deficient hydroxyapatite nanoparticles addition. The exothermic heat dissipation during the polymerization has been found to significantly decrease with the calcium-deficient hydroxyapatite nanoparticle incorporation in the bone cement. Contact angle study revealed that with the increasing percentage of calcium-deficient hydroxyapatite nanoparticle, the composite cement becomes more hydrophilic. In vitro biomineralization study confirmed the bioactivity of the nanocomposite bone cement with the formation of primary and secondary apatite on the cement surface. Present study suggests that the incorporation of calcium-deficient hydroxyapatite nanoparticle into the orthopaedic bone cements could help to overcome some of the shortcomings of the orthopaedic cement.

Complication of Polymethylmethacrylate Bone Cement in the Mandible

Polymethylmethacrylate bone cements have been widely used in orthopedic surgery as well as in maxillofacial area. Despite the advantages, it is well known that acrylic bone cements may cause bone or soft tissue necrosis because of the properties of its components and polymerization. This clinical report presents an extensive necrosis of the mandible after the use of the acrylic bone cement to fill the cyst cavity. The purpose of this article was to alert the clinicians about the complications that may occur after the use of the polymethylmethacrylate-based bone cements.

Theoretical prediction and experimental determination of the effect of mold characteristics on temperature and monomer conversion fraction profiles during polymerization of a PMMA-based bone cement.

The present work is concerned with applications of a kinetic model for free-radical polymerization of a polymethylmethacrylate-based bone cement. Autocatalytic behavior at the first part of the reaction as well as a diffusion control phenomenon near vitrification are described by the model. Comparison of theoretical computations with experimental measurements for the temperature evolution during batch casting demonstrated the capacity of the proposed model to represent the kinetic behavior of the polymerization reaction. Temperature evolution and monomer conversion were simulated for the cure of the cement in molds made of different materials. The maximum monomer conversion fraction was markedly influenced by the physical properties of the mold material. The unreacted monomer acts as a plasticizer that influences the mechanical behavior of the cement. Hence, the same cement formulation cured in molds of different materials may result in different mechanical response because of the differences in the amounts of residual monomer. Standardization of the mold type to prepare specimens for the mechanical characterization of bone cements is recommended. Theoretical prediction of temperature evolution during hip replacement indicated that for cement thickness lower than 6 mm the peak temperature at the bone-cement interface was below the limit stated for thermal injury (50 degrees C for more than 1 min). The use of thin cement layers is recommended to diminish the risk of thermal injury; however, it is accompanied by an increase in the amount of unreacted monomer present in the cured material.

Ultrasonic characterization of the curing process of hydroxyapatite‐modified bone cement

Ultrasonic parameters such as velocity of sound and broad-band ultrasonic attenuation (BUA) are sensitive to changes in the viscoelastic properties of a material. Bone cement undergoes changes is these properties as it cures. By monitoring the propagation of ultrasonic pulses through a sample of curing bone cement, the curing reaction of polymethylmethacrylate-based (PMMA) bone cement was investigated for hydroxyapatite (HA) concentrations of 0, 10, and 30% (by weight). As the material hardens, the velocity of sound increases by 70%. BUA shows a large peak at the midpoint of the velocity transition. These data are used to compare the cure time and cure duration for PMMA bone cement mixed with hydroxyapatite particles. Measurements of the final sound velocity and BUA were also performed to investigate the mechanical properties of the fully cured cement, and to compare to compression testing data. This is the first time the curing process of bone cement has been investigated as a function of hydroxyapatite concentration. Results indicate that the cure time is not significantly affected by the addition of HA particles, and that both velocity of sound and BUA are sensitive to the curing process. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 56: 593–599, 2001

Ultrasonic characterization of the curing process of hydroxyapatite-modified bone cement.

Ultrasonic parameters such as velocity of sound and broad-band ultrasonic attenuation (BUA) are sensitive to changes in the viscoelastic properties of a material. Bone cement undergoes changes is these properties as it cures. By monitoring the propagation of ultrasonic pulses through a sample of curing bone cement, the curing reaction of polymethylmethacrylate-based (PMMA) bone cement was investigated for hydroxyapatite (HA) concentrations of 0, 10, and 30% (by weight). As the material hardens, the velocity of sound increases by 70%. BUA shows a large peak at the midpoint of the velocity transition. These data are used to compare the cure time and cure duration for PMMA bone cement mixed with hydroxyapatite particles. Measurements of the final sound velocity and BUA were also performed to investigate the mechanical properties of the fully cured cement, and to compare to compression testing data. This is the first time the curing process of bone cement has been investigated as a function of hydroxyapatite concentration. Results indicate that the cure time is not significantly affected by the addition of HA particles, and that both velocity of sound and BUA are sensitive to the curing process.

Bioactive polymethyl methacrylate-based bone cement: Comparison of glass beads, apatite- and wollastonite-containing glass–ceramic, and hydroxyapatite fillers on mechanical and biological properties

A new bioactive bone cement (designated GBC) consisting of polymethyl methacrylate (PMMA) as an organic matrix and bioactive glass beads as an inorganic filler has been developed. The bioactive beads, consisting of MgO-CaO-SiO2-P2O5-CaF2 glass, have been newly designed, and a novel PMMA powder was selected. The purpose of the present study was to compare this new bone cement GBC's mechanical properties in vitro and its osteoconductivity in vivo with cements consisting of the same matrix as GBC and either apatite- and wollastonite-containing glass–ceramic (AW-GC) powder (designated AWC) or sintered hydroxyapatite (HA) powder (HAC). Each filler added to the cements amounted to 70 wt %. The bending strength of GBC was significantly higher than that of AWC and HAC (p < 0.0001). Cements were packed into intramedullar canals of rat tibiae in order to evaluate osteoconductivity as determined by an affinity index. Rats were sacrificed at 2, 4, and 8 weeks after operation. An affinity index, which equaled the length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface, was calculated for each cement. At each time interval studied, GBC showed a significantly higher affinity index than AWC or HAC up to 8 weeks after implantation (p < 0.03). The value for GBC increased significantly with time up to 8 weeks (p < 0.006). The handling property of GBC was comparable with that of PMMA bone cement. Our study revealed that the higher osteoconductivity of GBC was due to the higher bioactivity of the bioactive glass beads at the cement surface and the lower solubility of the new PMMA powder to MMA monomer. In addition, it was found that the smaller spherical shape and glassy phase of the glass beads gave GBC strong enough mechanical properties to be useful under weight-bearing conditions. GBC shows promise as an alternative with improved properties to the conventionally used PMMA bone cement. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 51, 258–272, 2000.

Polymethylmethacrylate-based bone cement modified with hydroxyapatite

A commercial acrylic bone cement was modified by the incorporation of different weight fractions of polycrystalline hydroxyapatite (HA), and the modified formulation was investigated. The influence of the filler proportion on the flow characteristics and the mechanical behavior of the resultant composite was evaluated. The residual monomer present in the cured materials was measured by gas chromatography. The comparison of the residual monomer present in the cements with and without reinforcement demonstrated that the degree of polymerization was not affected by the addition of HA. Porosity morphology was analyzed by optical and scanning electron microscopy. Image examination revealed that the porosity and the pore size of the hardened cement increased with an increasing amount of particulate filler. Flexural, compressive, and fracture properties of the cement with varying amounts of HA reinforcement were measured. It was found that up to 15 wt% HA could be added for increases in flexural modulus and fracture toughness. HA acts as a rigid filler that enhances fracture resistance and flexural modulus. Our results show that the workability of the modified formulation limited the incorporation of the ceramic filler to a maximum value of 15 wt%. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 150–158, 1999

Polymethylmethacrylate-based bone cement modified with hydroxyapatite.

A commercial acrylic bone cement was modified by the incorporation of different weight fractions of polycrystalline hydroxyapatite (HA), and the modified formulation was investigated. The influence of the filler proportion on the flow characteristics and the mechanical behavior of the resultant composite was evaluated. The residual monomer present in the cured materials was measured by gas chromatography. The comparison of the residual monomer present in the cements with and without reinforcement demonstrated that the degree of polymerization was not affected by the addition of HA. Porosity morphology was analyzed by optical and scanning electron microscopy. Image examination revealed that the porosity and the pore size of the hardened cement increased with an increasing amount of particulate filler. Flexural, compressive, and fracture properties of the cement with varying amounts of HA reinforcement were measured. It was found that up to 15 wt% HA could be added for increases in flexural modulus and fracture toughness. HA acts as a rigid filler that enhances fracture resistance and flexural modulus. Our results show that the workability of the modified formulation limited the incorporation of the ceramic filler to a maximum value of 15 wt%.