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PubMed2000

Shape optimization of metal backing for cemented acetabular cup.

Stresses are generated in implant materials and bone, and at their interfaces. These stresses may affect the structural properties of the implant/bone system, or bring it to failure at some time in the postoperative period. Due to these stresses, acetabular cup loosening becomes an important problem for long term survival of total hip arthroplasty. It was found that metal backing would tend to reduce stresses in the underlying acrylic cement and bone. Yet, recent studies of load transfer around acetabular cups have shown that metal backing generates higher stress peaks in cement at the cup edges, while generates lower stress peaks in bone at the central part of acetabulum (dome), thus the bone at the dome becomes more stress shielded. In this study a numerical shape optimization procedure in combination with an axisymmetric finite element model was used in order to optimize the shape of a stainless steel metal backing shell. The design was to minimize fatigue notch factor in cement along cement/bone and cement/metal backing interfaces in order to prevent failure of cement mantel and loosening of acetabular components, at the same time increasing fatigue notch factor in bone at the center of acetabulum to prevent stress shielding. The results of this study indicate that cemented acetabular cup designs can be improved by using metal backing shells of non-uniform thickness, thick at the dome and thin at edges. Fatigue notch factor in cement was reduced by 2.3% at cement/metal backing interface and increased by 1.3% in the central bone of acetabulum. Von Mises stresses in the cement edge were reduced by 17.8% and 19.3% along cement/bone and cement/metal backing interfaces, respectively. Thus the optimal design will reduce the possibility of fatigue fracture of cement and decrease the stress shielding effect and the likely incidence of bone resorption, whereby extend the expected life of the prostheses.

Acetabulum↗
PubMed2003

Cement pressurization after provisional repair of femoral cortical defects.

Cortical defects are common and problematic in cemented revision hip arthroplasty. Extruded cement can cause thermal injury, pain, and impingement. Decreased cement pressure limits bony interdigitation and leads to loosening. Historically, surgeons have used a finger to contain cement and improve pressure, and decrease porosity, but, with large or multiple defects, fingers are ineffective. Novel solutions--such as wrapping foil suture packaging or half a syringe barrel around the defects--have been previously published. In the study reported here, we used modern cementing techniques, continuous pressure monitoring, and porosity calculations to analyze the utility of the 3 provisional defect-fixation techniques. The foil and the hemisyringe worked as well as a finger (P > .05). All 3 techniques enhanced pressurization and maintained the porosity reduction. Although manually pressurizing cement and feeling resistance provide the surgeon with more tactile feedback, using the gun and a proximal adapter was more effective in improving pressure. Using these provisional defect-fixation techniques as well as a cement gun and proximal adapter can improve cement pressure and decrease porosity. These techniques are particularly useful with large or multiple cortical defects encountered in revision arthroplasty or total hip arthroplasty after open reduction.

Animals↗
PubMedDate not supplied

Clinical evaluation of marginal fit of a new experimental all-ceramic system before and after cementation.

PURPOSE: The purpose of this in vivo study was to evaluate the marginal fit of inlay and crown abutments for fixed partial dentures (FPD) made from a new all-ceramic material. MATERIALS AND METHODS: Sixteen patients were selected for the study. After abutment preparation, impressions were made and master dies were fabricated. FPDs were made with the experimental heat-pressed lithium-disilicate glass-ceramic following the manufacturer's recommendations. At random, one abutment of each FPD was chosen for evaluation (11 crown and 8 inlay abutments). Impressions of the restoration margins were taken before and after adhesive cementation. Replicas of the abutment margins were investigated by SEM. The marginal discrepancies were evaluated in sections of 200 microm. The highest value of each section was applied, and the mean of all sections of each replica was used for statistical analysis. RESULTS: The median of the marginal discrepancies before cementation was 96 microm for crowns and 89 microm for inlays. After adhesive cementation, the median increased for crowns to 130 microm and for inlays to 92 microm, a significant increase in the marginal discrepancies caused by cementation for crowns, but not for inlays. There were no significant differences between the discrepancies of crowns and inlays before or after cementation. CONCLUSION: The maximum marginal discrepancies found in this study were between 50 and 265 microm before cementation and between 70 and 285 microm after cementation, with no significant differences between the means for crowns and inlays. Adhesive cementation caused a significant increase of the marginal discrepancies for crown, but not inlay, abutments.

Cementation↗
PubMed2004

Vertebroplasty: cement leakage into the disc increases the risk of new fracture of adjacent vertebral body.

BACKGROUND AND PURPOSE: Patients successfully treated with vertebroplasty often return with new pain caused by a new vertebral body fracture. The new fractures often are adjacent to the vertebral bodies that were initially treated. In our clinical work, we have observed that cement leakage into the disk increases the risk of new fracture of the adjacent vertebral body. This study analyzed the risk of new fractures of adjacent vertebral bodies in relationship to cement leakage into the disk. METHODS: This study was based on 38 patients with painful compression fractures treated with vertebroplasty. Patients who returned with new pain after initial successful vertebroplasty were evaluated by repeat MR imaging. We analyzed the incidence of new fractures of adjacent vertebral bodies in relationship to cement leakage into the disk that had occurred during the initial vertebroplasty. RESULTS: Fourteen patients developed new fractures during the follow-up period. In 10 patients, the new fractures were associated with cement leakage into the disk, whereas four patients had new fractures that were not associated with cement leakage into the disk. This difference was statistically significant (P =.018). A detailed analysis showed that 58% of vertebral bodies adjacent to a disk with cement leakage fractured during the follow-up period compared with 12% of vertebral bodies adjacent to a disk without cement leakage (P <.0005). CONCLUSION: Leakage of cement into the disk during vertebroplasty increases the risk of a new fracture of adjacent vertebral bodies.

Aged↗
PubMed2004

Hardening of dual-cure resin cements and a resin composite restorative cured with QTH and LED curing units.

OBJECTIVE: The aim of this study was to determine the effects of light intensity and type of light unit (quartztungsten-halogen [QTH] or light-emitting diode [LED]) on the hardening of various resin cements and a resin composite restorative. METHODS: Disk specimens were prepared from 4 dual-cured resin cements (Variolink II, Calibra, Nexus 2 and RelyX ARC). Two QTH light-curing units (Visilux 2, at 550 mW/cm2, and Optilux 501, at 1,360 mW/cm2) and a LED unit (Elipar FreeLight, at 320 mW/cm2) were used for curing. Specimens were light-cured or dual-cured for 10, 30 or 40 seconds with 1 of the 3 light units (curing applied to upper surface only) and were tested 24 hours after curing. Additional cement specimens were self-cured and tested at 15, 30 and 60 minutes and at 24 hours. Testing consisted of measurement of Knoop hardness number (KHN) for each specimen. Six KHN values were obtained for the upper surface only of the various cement specimens in each test group. Disk specimens 2.5 mm thick were also prepared from a resin composite restorative (XRV Herculite). These were light-cured as above, and KHN measurements were obtained for both the upper and the lower surfaces. Mean KHNs were determined, and data were analyzed with analysis of variance. RESULTS: The groups were significantly different (p < 0.05). High-intensity light curing resulted in the highest KHN values for all materials with any of the 3 light-curing times. For the cements, LED light curing (with both dual-curing and light-curing modes) resulted in hardness values similar to those achieved with conventional QTH light curing, although there were some exceptions. However, both LED and conventional QTH light curing resulted in inferior hardening of lower surfaces of the XRV Herculite specimens at the 3 curing times. For all cements except Nexus 2, self-curing resulted in significantly lower hardness values than dual curing. The self-curing mechanism of Variolink II cement needed a longer time to activate than those of the other cements. CONCLUSIONS: High-intensity light curing and longer curing times resulted in the highest KHNs. The LED curing unit was associated with the lowest hardness values for lower surfaces of the resin composite restorative.

Analysis of Variance↗
PubMed1992

Pulp reactions to resin cements.

Several formulas of a resin-filled cement that successfully passed a series of laboratory tests were evaluated for their pulp reactions in primates. Their performance was compared to three controls: a positive control (silicate cement), a negative control (zinc oxide-eugenol) and a control group with the protection of calcium hydroxide. The chemical cure resin cement scored the lowest reactions for the 5-day evaluation. The intermediate and prolonged periods demonstrated no significant differences while average, acceptable responses were recorded. No resin cement formula scored as low as the negative control for the three time periods. Silicate cement, the positive control, scored the greatest inflammatory reaction of any material in the intermediate period, but this response was resolved after 60 days. When the resin cements were used with calcium hydroxide, the traditional reactions to calcium hydroxide were observed; an initial mild irritation that diminished with time and was completely resolved after 60 days. The resin cements, with or without the calcium hydroxide, compared favorably to the negative control IRM after 60 days. If the resin cements are appropriately applied, they are expected to be well tolerated by the human pulp. The microorganisms associated with microleakage (MLM) were minimal and there appeared to be no correlation between the MLM and pulp inflammation.

Analysis of Variance↗
PubMed2004

Effects of light intensity through resin inlays on the bond strength of dual-cured resin cement.

PURPOSE: To evaluate the influence of the light intensity, irradiation time, and thickness of the indirect restoration composite on the bond strength of dual-cured resin cement immediately after cementation, applying the resin coating technique. MATERIALS AND METHODS: Three hundred forty composite blocks as an adhesive surface and four thicknesses of indirect restoration composite disks were prepared. The surface of the composite blocks was coated with low-viscosity resin composite and immersed in water for 24 h. After immersion, dual-cured resin cement was applied to the resin-coated surface and the indirect restoration composite disks were placed on it. Light irradiation was performed through four thicknesses of indirect restoration composite disks with conventional halogen (40 s) and high intensity (10, 20, 40 s) light units. The specimens were stored in water at 37 degrees C for 10 min or 24 h, and the tensile bond test was performed. RESULTS: For the 1-mm composite thickness, there were no significant differences in the bond strengths between 10 min and 24 h after cementation with the four light curing methods. For the composite thicknesses of 3 or 4 mm, the bond strength 24 h after cementation was significantly higher than that at 10 min after cementation with conventional halogen (40 s) and high-intensity light units at 10 s and 20 s, but there was no significant difference with the high-intensity light unit applied for 40 s. CONCLUSION: The bond strength of dual-cured resin cement immediately after cementation could be greatly influenced by the irradiation time and the light intensity penetrating the indirect restoration composite.

Analysis of Variance↗
PubMed2006

Biomechanical properties of bone cement with addition of cefuroxime antibiotic.

Antibiotic-loaded bone cement has been used as prophylaxis against infection in total joint replacement surgery. Its effect on the mechanical strength of cement is a major concern as high dose of antibiotic was associated with a significant reduction in mechanical strength of bone cement. However, the cut-off antibiotic that weakens the mechanical strength of cement remains to be determined. This study was undertaken to observe the changes in the mechanical properties of bone cement with gradual increments of Cefuroxime antibiotic. Cefuroxime at different doses: 0, 1.5, 3.0 and 4.5gm were added to a packet of 40gm bone cement (Simplex P) and study samples were prepared by using third generation cementing technique. Mechanical impact, flexural and tensile strength were tested on each sample. Significant impact and tensile strength reduction were observed after addition of 4.5 gm of Cefuroxime. However, flexural strength was significantly reduced at a lower dose of 3.0 gm. The maximum dose of Cefuroxime to be safely added to 40mg Surgical Simplex P is 1.5gm when third generation cementing technique is used. Further study is needed to determine whether it is an effective dose as regards to microbiological parameters.

Anti-Bacterial Agents↗
PubMed1990

[Thermal diffusivity of dental cements].

Thermal insulative efficiency, is one of the desirable properties of the dental cements. In this study, the thermal diffusivity of three types of dental cements, were measured. Thermal diffusivity was determined by the following method. Two thermo-couples were used and connected to a chart record, the first was embedded in the cylindrical block of the cement specimen and the other in a mixing of ice and water (reference thermocouple). All them were set in a apparatus consisting of a double cooling bath. Calculation of thermal diffusivity were based on the curve provided of the record during cooling of the cement and a theoretical mathematic model. Values were ranged from 2,985 to 3,934 cm2.sec-1. ZOE cement exhibited the highest value, the glass-ionomers the lowest and the poly-carboxylates were average. The results showed that the thermal diffusivity of the cements is dependent from the type of the cement but the differences between them were not statistically significant. Additionally, the values obtained were about the same as the dentin, so the dental cements may consider as good thermal insulators.

Dental Cements↗
PubMed1989

The effects of surface configuration on the retentive properties of parallel-sided dowels cemented with a composite luting agent.

Factors which have effect on the retention of any dowel include the shape, length, diameter, and surface configuration of the dowel, the cementing medium, precision fitness and material, etc. The shape and surface configuration are the most important among all factors. Recent developments of the etching technique for cast metal has improved the bonding strength between base metal alloys and composite cement which offers a great opportunity for better retention of the dowel if its surface has been etched. In the past, because it has often been ignored that the bonding at the cement-dentin interface is weaker than that between the metal and cement, the true impact of surface configuration and cement thickness on the retention of dowels has never really been observed. In this study, plastic transparent rods were substituted for natural teeth to avoid anatomical variation and circular horizontal grooves were placed on the channel walls to strengthen the retention between the cement and the plastic rods. A total of 140 dowel samples were cast in Rexillium III and were divided into seven groups. The surfaces of the samples were treated differently by smoothing, sandblasting, chemical etching, electrolytic etching and serrating, and fixed into the channels of the plastic rods by cementation with composite resin. Immediately thereafter, the samples were submerged in 37 degrees C water for 7 days. Instron crosshead speed 1 mm/min was used in measuring the tensile forces required for extracting the dowels from the channels. Data were analyzed with the ANOVA method. Among the three factors known to have an effect on the retention being considered in this study, the circular horizontal groove proved to be the most influential, and surface configuration came next, while cement thickness was the least influential. Among the different surface configurations, the serrated dowels showed the best retention and were followed in order by etched and smooth or sandblasted dowels.

Biocompatible Materials↗
PubMed1986

The effect of centrifugation on the fracture properties of acrylic bone cements.

In this study, centrifugation did not alter the static or cyclic fracture properties of bone cement. Tests of fracture toughness and fatigue-crack propagation of centrifuged specimens of commercial cements (with and without antibiotic additions) demonstrated no significant difference from control values. Among the cements tested, Palacos (with and without antibiotic) was found to have a significantly higher fracture toughness than either Simplex or Zimmer. We attributed this difference in fracture toughness to the higher molecular weight measured for the Palacos cements. For the tested cements, only Simplex had a significantly greater volume contraction on setting due to centrifugation. The results of our study demonstrate that centrifugation of bone cement does not improve the cement's resistance to fracture in the presence of surface imperfections, such as those found at the bone-cement interface.

Bone Cements↗
PubMed1980

[Study on the setting reaction of the zinc phosphate dental cement (1). Effects of aluminum in liquid on setting reaction (author's transl)].

The liquid of zinc phosphate dental cement contains Al3+ and Zn2+, and these ions effect greatly on the setting reaction of the cement. When zinc oxide powder is mixed with this cement liquid, reaction products in the set cement are amorphous and not made sure by X-ray diffraction. Therefore the setting reaction of zinc phosphate cement is not certain. In this paper the effects of Al3+ on the setting reaction of cement are examined by X-ray diffraction, thermal analysis and infrared spectrum, and set cements are observed by SEM and microradiography. Judging from these results, it is conclude that Al3+ in the cement liquid precipitates amorphous aluminium phosphate due to change of pH of liquid when it is mixed with zinc oxide powder.

Aluminum↗
PubMed1981

[A study on the mechanical properties of bone cement (methylmethacrylate) and its strength alteration in vivo (author's transl)].

UNLABELLED: Bone cement (Methylmethacrylate) is now extensively used for the fixation of various endoprostheses in orthopaedic surgery. Although considerable number of works have been accumulated on the use of this material, relatively little is known about its basic characteristics such as inherent physical properties and the strength alteration in vivo. In recent years, loosening of the prosthesis has become one of the major problems, jeopardizing the use of the prosthesis in conjunction with the bone cement. The aim of this study is to investigate the mechanical properties of the commonly available bone cements and, particularly, to see any chronological deterioration of the material in vivo. METHODS: 1. For the study of the mechanical properties, dumbbell-shaped test pieces were made of three different types of commercially available bone cement (Surgical Simplex, CMW and Palacos R) and tested under tension load using Shimazu Autograph in a temperature and moisture controlled room (Experiment I). 2. The same test pieces (Surgical Simplex and CMW) were imbedded in the paravertebral muscle of rabbits for one, six and sixteen months and, then, tested in the same fashion as in Experiment I (Experiment II). 3. The fracture surface of the test piece after the tension load testing was examined under a scanning electron-microscope to find any changes before and after the imbedding (Experiment III). RESULTS: 1. The bone cement showed a viscoelastic behavior under the tension load in vitro. 2. The modulus of elasticity was the smallest in Palacos R which showed the greatest amount of viscoelastic deformation in vitro. 3. The longer was the imbedded period, the weaker was the tensile strength. The amount of viscoelastic deformation tended to decrease with time, which resulted in the decrease of the total amount of deformation. The modulus of elasticity was the smallest in the sixteen week group in both Surgical Simplex and CMW. 4. The scanning electromicroscopic studies failed to reveal any significant changes on the fracture surface after the imbedding. CONCLUSION: In view of this considerable strength alteration of the bone cement in vivo, the author considers this would be an important factor leading the prosthesis into loosening other than the hitherto proposed various factors such as chemical damage of the bone by the monomer, thermal bone necrosis by the polymerization heat and fatigue fracture of the bone adjacent to the bone cement. While the improved technique in the use of the bone cement is mandatory, the author stressed the importance of further research into the better material or method for the interface between the bone and the prosthesis.

Animals↗
PubMed1995

The femoral stent. Surgical technique for a new method of cementing the femoral component in the presence of a large cortical defect.

Modern cement technique consists of the use of porosity reduction of the cement, a femoral medullary canal plug, injection of the cement using a cement gun, centralization of the stem, and pressurization of the cement. The use of cement in femoral revision is increasing rapidly; however, when there is a major cortical defect, forming and pressurizing the cement column might appear impossible. We describe a surgical technique for sealing such defects with a custom-made, intraoperatively fashioned femoral stent that allows for temporary restoration of the cortical tube of the femur, and therefore full pressurization of the cement.

Bone Cements↗
PubMed1995

Prediction of the long-term durability of all-polyethylene cemented sockets.

A retrospective study was done to determine the correlation between the rate of aseptic loosening and the early radiographic appearance of the bone-cement interface of the acetabulum of primary cemented total hip prostheses. Two hundred thirty-six hips implanted with modern cement technique were studied during an average clinical and radiographic followup of 9 years. Early radiographs and the last available radiographs were studied by 3 independent observers, and the quality of the bone-cement interface was evaluated with a standardized scoring system. On the acetabular side, the authors noted 0.8% clinical failure, a 3% rate of radiographic migration, and a 3.4% rate of progressive global radiolucency. Only 2.2% of hips considered well fixed on the postoperative film were loose. Of the hips considered not well fixed, the rate of aseptic loosening was 14.4%. The authors conclude that (1) the state of the bone-cement interface as seen on the early postoperative radiograph can predict the longevity of a cemented socket with a high degree of probability, and that (2) cementation of an all-polyethylene socket using modern cement technique is an excellent method of fixation for patients 60 years of age and older with degenerative joint disease.

Bone Cements↗
PubMed1994

Bateman bipolar hemiarthroplasty for displaced intracapsular femoral neck fractures. Uncemented versus cemented.

Four hundred forty-seven patients with 451 displaced fractures of the femoral neck were treated with Bateman bipolar hemiarthroplasty (190 cemented and 261 uncemented) between 1985 and 1990 in the authors' institution. During a follow-up period of at least two years, the authors found less thigh pain (13% versus 46.2%) and higher Harris hip scores (86 versus 79) in the cemented group in comparison with the uncemented group. Radiographic examination showed less radiolucent zones and subsidence in the cemented group. Heterotopic ossification was more common in the cemented group. Despite the fact that the cemented group had longer operative times (average, 20 minutes) and more blood loss (average, 160 ml) during the operation, there was no significant difference in the early mortality rate observed between these two groups. The cemented prostheses provided better functional and radiographic results and fewer failures in the early stage. In addition, the cemented prostheses did not lead to more complications and higher mortality rates. Thus, for elderly patients who need early ambulation and functional recovery, the cemented Bateman bipolar prosthesis appears to be a better choice than the uncemented Bateman prosthesis.

Aged↗
PubMedDate not supplied

Radiopacity of resin-based inlay luting cements.

The radiopacity of a group of seven resin-based inlay luting cements in addition to two porcelain veneer cements was determined. Four inlay cements (Indirect Porcelain System Dentist Bonding Kit, Dicor MGC, Duo, and Twinlook) were found to have radiopacity values significantly greater than the radiopacity of enamel. Two other inlay cements (Dual and Porcelite Dual Cure) were found to have radiopacity values not significantly different from that of enamel, while All-Bond Crown and Bridge cement had a radiopacity value significantly lower than the radiopacity of dentin. For the two porcelain veneer cements examined, one material (Mirage Bond) had a radiopacity value significantly greater than that of enamel, while the other (G-Cera Porcelain Veneer Bonding System) had a radiopacity value significantly lower than that of dentin. It was concluded that only the materials that have radiopacity values greater than or equivalent to the radiopacity of enamel are suitable for use as inlay cements. For porcelain veneers, a relatively high radiopacity value of the cement is advantageous.

Analysis of Variance↗
PubMed1993

Cemented versus cementless total hip arthroplasty. A comparative study of equivalent patient populations.

Seventy-one cemented total hip arthroplasties (THAs) in 66 patients were compared with 70 cementless THAs in 61 patients. The cemented and cementless components were identical except for the presence of a porous proximal surface on the cementless component. The mean follow-up time was 4.3 years in the cemented group and 4.1 years in the cementless group, with a minimum follow-up of two years. Postoperative Charnley pain scores were identical for both groups, as was the incidence of limp. The final Charnley function score, however was significantly higher in the cementless group (5.6) than in the cemented group (5.1). One revision was performed in the cemented group, none in the cementless group. Complete demarcation of the bone-cement interface was presented in two cemented components and was associated with subsidence. Three cementless components had early subsidence, and two of these had complete radiopaque lines around the porous surface. None of these three patients, however, had unsatisfactory pain or function scores. The most important finding of this study is the equivalence of clinical results noted in both cemented and cementless THA as late as six years after operation.

Activities of Daily Living↗