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PubMed1997

Restoration of pedicle screw fixation with an in situ setting calcium phosphate cement.

STUDY DESIGN: Pedicle screws were pulled out of human cadaveric vertebrae before and after augmentation with polymethylmethacrylate or in situ-setting calcium phosphate cement. The fixation strength of screws augmented with calcium phosphate cement was compared with that of screws augmented with polymethylmethacrylate. OBJECTIVES: To determine whether a new in situ-setting calcium phosphate cement might be suitable for augmenting the fixation of pedicle screws. The principle objective was to compare the pull-out resistance of screws augmented with calcium phosphate cement with the pull-out behavior of screws augmented with polymethylmethacrylate. Polymethylmethacrylate augmentation was chosen as the standard because of its current clinical use. Five types of screws were tested to determine whether screw design had an effect on the efficacy of augmentation. SUMMARY OF BACKGROUND DATA: Although many factors affect the pull-out resistance of pedicle screws, a key determinant of their performance is the strength of their attachment to the spine. In elderly, osteopenic patients, the screw-bone interface is especially at risk for stripping during insertion or pull-out after surgery. In these patients, polymethylmethacrylate has been used to augment pedicle screw fixation, although its use is not without risk. In situ-setting calcium phosphate cements may provide an alternative to polymethylmethacrylate in this application. Like polymethylmethacrylate, calcium phosphate cements can be injected into the prepared screw hole. They have the added advantage of being resorbed and replaced during healing and normal bone remodeling. METHODS: Thirty human lower lumbar vertebrae (L3-L5) were implanted bilaterally with one of five types of pedicle screws (n = 6 for each screw type). The screws were pulled out 3.0 mm at 0.25 mm/sec with a servohydraulic materials testing machine. The 3.0-mm pull-out distance, which was slightly longer than one thread pitch, was designed to strip the screw-bone interface but to leave the pedicle otherwise intact. After the initial testing, the screws in each vertebrae were removed, and the screw tracks were filled with 2.0 cc of polymethylmethacrylate (one side) or calcium phosphate cement (contralateral side). After augmentation, the screws were reinserted, and the cements were allowed to harden for 24 hours. Postaugmentation testing followed the protocols for preaugmentation testing, and the pull-out resistance of screws augmented with calcium phosphate cement was compared with the pull-out resistance of screws augmented with polymethylmethacrylate. RESULTS: Mechanically, calcium phosphate cement compared favorably with polymethylmethacrylate for augmenting pedicle screws. Both restored the strength of the screw-bone interface: across all screw types, the average increase in pull-out strength was 147% with polymethylmethacrylate augmentation and 102% with calcium phosphate cement. There were no significant differences because of screw type with either type of augmentation. CONCLUSIONS: The in situ-setting calcium phosphate cement investigated in this study compared favorably with polymethylmethacrylate in a single-cycle, pull-out test of augmented pedicle screws in senile trabecular bone. With further evaluation, this cement may offer an alternative to polymethylmethacrylate for the enhancement of pedicle screw fixation clinically.

Bone Cements↗
PubMed2001

Charnley total hip arthroplasty with use of improved cementing techniques: a minimum twenty-year follow-up study.

BACKGROUND: In total hip arthroplasty, techniques for cementing the femoral component have changed over time. The purpose of the present study was to determine whether a cementing technique that includes use of a distal cement plug and retrograde filling of the femoral canal affects the fixation of the femoral component at a minimum of twenty years after the operation. METHODS: Between 1976 and 1978, the senior one of us (R.C.J.) performed 357 total hip arthroplasties with use of a Charnley flatback polished femoral stem and a contemporary cementing technique (insertion of a distal cement plug and retrograde filling of the femoral canal with cement) in 320 patients. The results after a minimum follow-up of twenty years were compared with those after 330 total hip arthroplasties performed, between 1970 and 1972, with the same femoral stem by the same surgeon with use of a hand-packing technique of cementing in 262 patients. The clinical and radiographic evaluation as well as the duration of follow-up were identical in the two groups. RESULTS: In the group managed with the contemporary cementing technique, six (1.8%) of the 336 hips that had not been lost to follow-up or revised because of infection or dislocation were revised because of aseptic loosening of the femoral component. Of the ninety-one hips in the eighty-two patients who were alive at a minimum of twenty years, five (5%) had a revision because of aseptic loosening of the femoral component. Only one hip was revised during the fifteen-to-twenty-year follow-up interval. (The revision was performed because of a fracture of the femoral component.) The rate of failure when radiographic signs of loosening were included was 4.8% (sixteen of 336 femoral components that had not been revised because of infection or dislocation) for the group managed with the contemporary cementing technique compared with 6.3% (twenty of 319 hips) in the group managed with the hand-packing technique; the difference was not significant (p = 0.40). Adequate filling of the femoral canal with cement was found to be associated with improved survival of the femoral component (p = 0.03). CONCLUSIONS: While no significant difference between the two cementing techniques could be identified, the ability to deliver adequate cement around the femoral component was more predictable with the contemporary cementing technique. In addition, the prevalence of loosening of the femoral component was low with use of either technique, a tribute to the Charnley flatback polished femoral component design.

Adult↗
PubMed2001

Long-term follow-up study of bioactive bone cement for repairing a segmental defect in a canine femur.

We report on a 7-year long-term follow-up study of a bioactive bone cement (BA cement) that was used to repair a segmental defect in a canine femur. Bilateral femoral segmental defects were repaired with metallic implants that were fixed to the femur using two kinds of bone cement. The BA cement used in this study consists of an apatite- and wollastonite-containing glass ceramic (AW-GC) with a bis-phenol-alpha-glycidyl methacrylate (bis-GMA)-based resin. The bone-cement interface was examined histologically. Previous short-term studies have shown that using BA cement for segmental replacement of the canine femur produced excellent biomechanical and histological results. The BA cement maintained the fixation of a metallic implant to the femur very well. In contrast, the PMMA cement did not maintain alignment under long-term weight-bearing conditions. The results of histological examinations showed direct bonding between the BA cement and bone, while an intervening soft tissue layer was observed at the bone-cement interface with the PMMA cement. The BA cement bonded to the bone through a Ca-P-rich reactive layer, which was twice as thick after 7 years than it was at 26 weeks. No adverse effects of BA cement were observed during the 7-year observation period.

Animals↗
PubMedDate not supplied

Comparison of 7 luting protocols and their effect on the retention and marginal leakage of a cement-retained dental implant restoration.

PURPOSE: To determine the cement bond strength and marginal leakage of castings cemented to implant abutments. MATERIALS AND METHODS: Fifty-six titanium abutments and castings were divided into 7 groups (n=8), 1 for each cement. Castings were cemented to abutments using 1 of 3 resin-based cements (RES, RES-B, and RES-B-P), a resin-modified glass ionomer (GI), a polycarboxylate cement (PCB), an acrylic urethane cement (UDM), or a zinc phosphate cement (ZP). Specimens were placed in 100% humidity at 37 degrees C for 24 hours. Specimens were subjected to compressive load cycling followed by thermal cycling; they were then immersed for 24 hours in 0.5% basic fuchsin. Castings were removed with an Instron universal testing machine with a crosshead speed of 0.125 cm/min. Leakage was visually graded from 0 (no leakage) to 2 (leakage extended beyond the lower half of the internal surface of the casting). Failure load (FL) was analyzed with analysis of variance and Scheffe's test (alpha = .05). Chi-square was used to analyze leakage (alpha = .05). RESULTS: Cements were categorized by FL into 4 statistically unique groups: (1) RES-B-P (351 N) and GI (337 N); (2) ZP (245 N) and RES-B (241 N); (3) PCB (107 N); and (4) RES (63 N) and UDM (55 N). Leakage was greater for the PCB group than for the other groups (7 of 8 specimens demonstrated leakage; P < .01). Three ZP specimens demonstrated leakage. UDM and RES each had 1 specimen with leakage. RES-B-P, RES-B, and GI showed no leakage. CONCLUSIONS: Luting agents designated by the manufacturer as provisional cements demonstrated lower resistance to removal, regardless of material type. Luting agents described by manufacturers as "permanent" differed in resistance, with resin cements being most resistant, followed by zinc phosphate and polycarboxylate cements. Provisional cements demonstrated leakage comparable to higher-strength materials.

Dental Cements↗
PubMed1990

Osteolysis in alloarthroplasty of the hip. The role of bone cement fragmentation.

Movement at the interface between bone and cement and fractures of the cement can cause fragmentation of the polymethylmethacrylate (PMMA) bone cement implant. In order to obtain further information about the effect of PMMA fragments on the surrounding tissue and the role of such particles in the development of bone resorption, the authors investigated 17 patients with cemented total hip endoprostheses showing osteolysis and implant loosening in the femoral shaft with (Group B) and without (Group A) involvement of the acetabulum. The roentgenographic follow-up examinations revealed an initially slow and later more rapid extension of the endosteal bone erosions, with a predilection for the tip of the stem, the lesser trochanter, and laterally for the middle of the stem. At revision surgery, tissue samples were taken from the joint capsule and the bone-cement interface, in particular from the osteolysis in the femoral shaft and the acetabulum. The tissue samples were processed for histology, microscopically examined, and semiquantitatively evaluated. The retrieved devices were also carefully inspected. Large foreign-body granulomas were found at the bone-cement interface and in the joint capsule. Histiocytes and foreign-body giant cells stored particles of PMMA and polyethylene, of which fragmented bone cement predominated. Granulomatous tissue invaded bone canals and marrow spaces and induced resorption of the surrounding bone. In four cases in Group A, tissue from the osteolysis contained only fragmented bone cement, demonstrating that PMMA particles alone may be responsible for triggering focal bone resorption. Osteolysis seems to begin at the site where disintegration of bone cement begins. In cases in which polyethylene particles were found in the tissue in addition to fragmented bone cement, wear from the ultrahigh molecular weight polyethylene socket has been increased by entrapment of PMMA particles between the joint surfaces. Thus, fragmentation of bone cement and abrasion of polyethylene enhance each other. Bone cement particles promote polyethylene wear, which in turn promotes granuloma formation, bone resorption, and subsequent bone cement disintegration.

Acetabulum↗
PubMed1998

Retention of parallel-sided titanium posts cemented with six luting agents: an in vitro study.

PURPOSE: This in vitro study compared the effectiveness of 6 luting systems on the retention of prefabricated titanium posts. MATERIAL AND METHODS: A total of 120 single-rooted teeth were sectioned at the cementoenamel junction and treated endodontically. Roots were mounted in copper cylinders, and prefabricated, parallel-sided titanium posts were cemented according to the manufacturer's instructions. Two resin-ionomer hybrid cements and 2 resin cements were tested with corresponding dentin bonding agents. A glass ionomer cement was also tested, and zinc-phosphate cement served as the control. Samples were tested in an Instron universal testing machine to catastrophic tensile failure. RESULTS: Advance cement with Prime and Bond systems was found to be statistically more retentive than all other groups tested (P < .05). Cement It with Bond It and Permalute with Permalute Primers A and B systems demonstrated significantly greater retention than Ketac Cem cement, Resinomer with One-Step system and zinc-phosphate cement (P < .05). There was no statistically significant difference among Ketac Cem cement, Resinomer with One-Step system, and zinc-phosphate cement.

Analysis of Variance↗
PubMed2006

In vitro evaluation of the retention of zirconia-based ceramic posts luted with glass ionomer and resin cements.

The retention of zirconia-based ceramic posts (CosmoPost system) luted with glass ionomer and resin cements was evaluated. Thirty-two extracted, caries-free, unrestored teeth were selected and stored in chlorhexidine and water solution. The teeth were endodontically treated and randomly assigned to two groups (n=16). Each tooth was decoronated and prepared to a depth of 10.0 mm from root surface to receive a 1.4 mm diameter zirconium dioxide post. Each group had posts cemented with either glass ionomer cement (Fuji I) or resin cement (Variolink II). The post/teeth specimens were embedded in resin blocks and subjected to tensile testing. The tensile force required to dislodge the cemented posts in a tensile testing machine was recorded. The mean stress values of both groups were analyzed for statistical differences using ANOVA and Student's t-test. Significance level was set at 5%. Mean peak forces at failure (N) and standard deviation for the tested cements were the following: Fuji I = 121.8 (+/-17.4) and Variolink II = 228.1 (+/-36.8). Posts luted with the resin cement presented statistically significant higher tensile bond strength than those retained with glass ionomer (p<0.05). It may be concluded that zirconia posts cemented with resin-based cement (Variolink II) failed at statistically significant higher values compared to those cemented with glass ionomer cement (Fuji I). Regardless of the cement type, the posts failed adhesively at the cement/post interface when subjected to a tensile force.

Acid Etching, Dental↗
PubMed2004

The effect of a resin-based sealer on crown retention for three types of cement.

STATEMENT OF PROBLEM: In an effort to control postoperative sensitivity, dentin sealers are being applied following crown preparation with little knowledge of how crown retention might be affected. A previous study demonstrated no adverse effect when using a glutaraldehyde-based sealer, and existing studies have shown conflicting results for resin-based products. PURPOSE: This study determined if a resin sealer applied to prepared dentin affected retention of cemented castings when using 3 common types of luting agents. MATERIAL AND METHODS: Extracted human molars (n=55) were prepared with a flat occlusal, 20-degree taper, and 4-mm axial length. The axial surface area of each preparation was determined and specimens were distributed equally among groups (n=11). A 2-step, single-bottle adhesive system (One Step) was used to seal dentin following tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer) specimens that required use of adhesive with cementation. Using ceramometal high noble alloy (Olympia), a casting was produced for each specimen and cemented with a seating force of 20 Kg using either zinc phosphate (Fleck's), glass ionomer (Ketac-Cem) or modified-resin cement (Resinomer) with the single-bottle adhesive. Castings were thermal cycled at 5 degrees C and 55 degrees C for 2500 cycles; then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with alpha=.05. The nature of failure was also recorded and the data analyzed with a chi-square test. RESULTS: Mean dislodgment stresses for unsealed and sealed conditions were 3.7 +/- 1.0 and 2.2 +/- 0.8 MPa for zinc phosphate; 2.7 +/- 1.2 and 4.2 +/- 0.9 MPa for glass ionomer, respectively (P<.001). Retentive stress of castings cemented with modified-resin cement was 6.4 +/- 1.7 MPa. With resin sealer in combination with zinc phosphate, cement resided totally on castings in 82% of the situations and was on both surfaces without sealer. The tooth failed before casting dislodgment in 9 of 11 specimens cemented with modified-resin cement. CONCLUSIONS: Resin sealer decreased casting retentive stress by 42% when used with zinc phosphate. However, sealer use resulted in 55% increased retention when used with glass ionomer. The modified-resin cement produced the highest mean dislodgment stress, nearly always exceeding the strength of the tooth.

Analysis of Variance↗
PubMed1998

Effects of eugenol and noneugenol endodontic sealer cements on post retention.

Resin cements are sometimes recommended to enhance the retention of posts in endodontically treated teeth. Many sealer cements used in endodontics contain eugenol, however, which has been shown to inhibit the polymerization of resins. The purpose of this study was to evaluate the effects of a eugenol and a noneugenol sealer cement on the retention of posts. Sixty extracted canines were divided equally into four groups. Each tooth received conventional endodontic therapy and was prepared to receive a post. Two sealer cements were used in obturation: one contained eugenol and one was eugenol-free. The posts were cemented with either zinc phosphate cement or resin cement. Each combination of sealer and post cement was tested for retention on an Instron testing machine. The type of sealer used had no effect on post retention with either cement. Post retention was significantly greater with the zinc phosphate cement than the resin cement.

Analysis of Variance↗
PubMed1995

Effect of dynamic loading methods on cement film thickness in vitro.

PURPOSE: Reduced cement flm thicknesses can improve crown seating and decrease marginal discrepancies. Improved marginal adaptation has the potential to reduce plaque accumulation, periodontal disease, and cement dissolution. Studies have indicated that dynamic seating methods can reduce seating discrepancies associated with zinc phosphate and resin cements. However, other types of cements and other dynamic techniques have not yet been studied or compared, nor has the mechanism for improved seating been fully explained. Therefore, the purpose of this study was to investigate the effect of a variety of loading methods on the film thicknesses of current types of crown and fixed partial denture cements compressed between glass plates. MATERIALS AND METHODS: This study investigated the effect of three dynamic loading methods on film thickness of six representative fixed prosthodontic cements. These included zinc phosphate, resin-modified glass ionomer, encapsulated glass ionomer, adhesive composite resin, composite resin, and polycarboxylate. The method was derived from American Dental Association specifications for cement film thickness. In control groups, the cements were placed between two glass glass plates and statically loaded with a 15-kg weight. The test groups were initially similarly loaded, and then for 30 seconds further subjected to simulated repeated patient opening and closing, vibrations from an electromallet, or an ultrasonic device. RESULTS: Mean film thicknesses ranged from 7.4 micrometers for polycarboxylate / ultrasound up to 40.3 micrometers for composite resin / static. Two-way analysis of variance revealed that the effects of material type and cementation method and their interaction all significantly affected film thickness (P < .0001). Multiple range analysis showed that dynamic methods were generally superior to static loading and that the ultrasonic method was the best overall. CONCLUSIONS: The different dynamic loading methods all significantly decreased cement film thicknesses between glass plates. The ultrasonic method was the most effective. The type of cement used also influenced film thickness. Composite resins were more affected than other materials.

Analysis of Variance↗
PubMed2004

[The effect of different fabrication methods and luting cements on post retention].

OBJECTIVE: This study was to compare the retention of posts fabricated by different methods and cemented with various cements in order to provide a guidance for clinical choice of post fabrication methods and luting cements. METHODS: Ninety human maxillary anterior teeth were sectioned by the cementoenamel junction and post-holes were prepared. All roots were embedded in the center of plastic cylinders and paralleled with the cylinder. All samples were divided into 9 groups randomly and equally. Posts fabricated with different methods were then cemented with different luting cements. Each sample was placed into a specialized jig and mounted on a tensile testing machine with crosshead speed of 5 mm/min. Constant tensile force was applied until the post was dislodged, and the tensile force required to dislodge the cemented post was recorded. RESULTS: The mean retention force of parapost and direct post demonstrated significantly higher than that of indirect post did (P < 0.05), but there was no significant difference between parapost and direct post(P > 0.05). The mean retention of parapost cement demonstrated significantly higher than that of ZPC and HY-Bond cement did (P < 0.05), but there was no significant difference between ZPC and HY-Bond cement (P > 0.05). CONCLUSION: Different fabrication methods and luting cements significantly affect the retention of posts; and there exists an interaction between different fabricating methods and luting cements.

Cementation↗
PubMedDate not supplied

Antibacterial properties of current orthodontic band cements.

PURPOSE: Manufacturers commonly provide information on the physical properties of dental materials, but information on their antibacterial properties is often missing. This study determined the antibacterial properties of four currently used orthodontic band cements against three different strains of Streptococcus mutans. METHODS: The cements utilized were Durelon, Ketac, Mizzy Zinc Phosphate, and Band-Lok, a recently introduced, resin-based, dual-cure glass ionomer cement. Disk diffusion assay methodology was used to test for zones of bacterial inhibition around cement samples. Zones of inhibition were measured in millimeters using an electronic caliper. In addition to cured cement plugs and freshly mixed cement samples, a new variation, in the form of a cement plug surrounding a stainless-steel band, was tested. Twelve combinations resulted from the four cement types and three forms. RESULTS: Of the variables studied, the mix forms of Durelon, Ketac, and Mizzy Zinc Phosphate cement showed the greatest bacterial inhibition (Kruskal-Wallis, P < 0.05). Among the cements tested, Mizzy Zinc Phosphate showed the largest zones of inhibition, with Durelon and Ketac having comparable zones of inhibition (Kruskal-Wallis, P < 0.05). Band-Lok did not exhibit an inhibitory effect against any of the three strains of S. mutans tested. CONCLUSION: A "containment effect" of no bacterial inhibition was observed in the cement samples surrounded by the stainless-steel band material.

Analysis of Variance↗
PubMedDate not supplied

Development of bioactive PMMA-based cement by modification with alkoxysilane and calcium salt.

Poly (methyl methacylate) (PMMA) bone cement is one of the popular bone-repairing materials for fixation of artificial hip joints. Significant problems on the PMMA bone cement are caused by loosening at the interface between bone and the cement, since the cement does not show bone-bonding, i.e. bioactivity. Development of PMMA bone cement capable of bone-bonding has been therefore long desired. The prerequisite for an artificial material to show bone-bonding is the formation of a biologically active bone-like apatite layer on its surface when implanted in the body. The same type of apatite formation can be observed on bioactive materials even in a simulated body fluid (Kokubo solution) with ion concentrations nearly equal to those of human blood plasma. Fundamental researches for bioactive glasses and glass-ceramics revealed that the apatite deposition is initiated by release of Ca2+ ions from the material into the body fluid, and by catalytic effect of Si-OH groups formed on the surface of the material. These findings lead an idea that novel bioactive cement can be designed by incorporation of Si-OH groups and Ca2+ ion into PMMA bone cement. In the present study, PMMA bone cement is modified with 20 mass % of various kinds of alkoxysilanes and calcium salts, and its apatite-forming ability was evaluated in Kokubo solution. The apatite formation was observed on the surface of the modified cements containing 20 mass % of CaCl2, irrespective of the kind of the examined alkoxysilane. On the other hand, the apatite formation was observed on the cement containing CaCl2, Ca(CH3COO)2 or Ca(OH)2, but not on the cement containing CaCO3 or beta-Ca3(PO4)2, even when the cement contains 3-methacryloxypropyltrimethoxysilane (MPS). The results indicate that modification with alkoxysilane and calcium salts showing high water-solubility is effective for providing PMMA bone cement with bioactivity.

Journal Article↗
PubMedDate not supplied

A more reliable method for incudostapedial rebridging ossiculoplasty: bone cement and wire.

Polymaleinate glass ionomer cement is a commercially available bone cement (Ketac Cem Radiopaque, ESPE, Germany) that can be used to reconstruct a discontinuity between the incus and the stapes. The popularity of bone cement in otologic surgery is increasing. If the missing part of the incus is too long, the results in the long term could be unsatisfying. Under such circumstances, a new method of incudostapediopexy that uses wire and involves remodeling of the long process of the incus with bone cement is introduced. A retrospective analysis of the outcomes of incudostapedial rebridging ossiculoplasty (ISRO) procedures carried out in 21 patients between June 1999 and September 2003 was performed. A total of 17 patients were treated with bone cement only; in 4 of these patients, hearing loss reoccurred within 6 months. The procedure was repeated in 2 of these patients using both bone cement and wire with satisfactory hearing results (air-bone gaps, 7.5 and 8.8 decibels hearing level [dB HL]) after 1 year. Four patients underwent ISRO wire and bone cement initially. The long-term results of these 6 "wire-and-cement" cases, which were followed for a mean of 21 months, were satisfactory (air-bone gap, 9.8 dB HL). The postoperative air-bone gap in the 15 patients who were treated by ISRO with bone cement only excluding the 2 reoperation cases was 12.1 dB HL. ISRO with bone cement is a cost-effective and safe procedure that yields good hearing results in selected cases. If the distance between eroded incus and stapes is too long to be reconstructed with bone cement alone, the surgeon should consider using wire with bone cement.

Adolescent↗
PubMed2006

Cementing techniques in hip resurfacing.

The subject of the cementing technique in hip resurfacing has been poorly studied to date. The hip resurfacing prosthesis is unique in the family of cemented prostheses because the cement mantle is blind (hidden underneath the implant) and is radiographically obscured. This presents an immediate challenge to the surgeon at the time of surgery, but also has a longer-term implication in terms of lack of post-operative clinical observation. This should be compared with total hip replacement or total knee replacement where the cement mantle can at least be partially observed both intra- and post-operatively. With this in mind, the objective of this review is, firstly, to understand the cement mantles typically achieved in current clinical practice and, secondly, to identify those factors affecting the cement mantle and to consolidate them into an improved and reproducible cementing technique. The outcome of this work shows that the low-viscosity technique can commonly lead to excessive cement penetration in the proximal femoral head and an incompletely seated component, whereas a more consistent controlled cement mantle can be achieved with a high-viscosity cementing technique. Consequently, it is recommended that a high-viscosity technique should be used to minimize the build-up of excessive cement, to reduce the temperature created by the exothermic polymerization, and to help to ensure correct seating of the prosthesis. A combination of these factors is potentially critical to the clinical success of some articular surface replacement (ASR) procedures. It is important to note that we specifically studied the DePuy ASR system; therefore only the general principles (and not the specifics) of the cementing technique may apply to other resurfacing prostheses, because of differences in internal geometry, clearance, and surgical technique.

Adhesiveness↗
PubMed2006

Finite element analysis of the long-term fixation strength of cemented ceramic cups.

Clinical studies have shown that adequate fixation of ceramic cups using bone cement is difficult to achieve. As the cement-ceramic bond strength is low, a satisfactory fixation strength requires a cup design that allows mechanical interlocking, although such a design will probably promote cement cracking and therefore cup loosening in the long term. An investigation has been carried out to establish whether a cemented ceramic cup can be designed in such a way that both a satisfactory initial fixation strength is obtained and cement cracking is reduced to levels found around PE cups functioning well in vivo. By means of finite element analysis, the fatigue loading of three geometrically different cemented acetabular cups, with ceramic and PE material properties, has been simulated, and the severity of the crack patterns produced in the cement has been analysed. Furthermore, the fixation strength has been analysed by simulating a pull-out test prior to and after fatigue testing. All ceramic cups produced much larger amounts of cement damage during fatigue testing than any PE cup, caused by stress concentrations in the cement that were attributable to the high stiffness of the ceramic. Even a completely smooth ceramic cup produced more damage than a sharp-grooved PE cup. Owing to the excessive cement cracking, the fixation strength of the ceramic cups dropped after fatigue loading. It is concluded that cemented ceramic cups have an increased risk of long-term mechanical failure by comparison with PE cups, and that a ceramic cup design that combines sufficient fixation strength with low cement failure may be difficult to achieve.

Acetabulum↗
PubMed1991

Effects of intra-core mechanical interlocks and cement type on full crown retention.

This study compared the retention of full cast crowns over cores of amalgam or a Bis-GMA composite resin when cemented with a Bis-GMA composite resin cement or a zinc phosphate cement. The surfaces of two groups of Bis-GMA composite cores were mechanically altered with a groove or dimples to provide physical retention; two other groups were either etched with 1.23% acidulated phosphate fluoride (APF) or exposed to a zinc oxide-eugenol interim luting agent before crown cementation. Control groups of unaltered composite or amalgam core served as comparison standards. The zinc phosphate cement provided significantly greater retention with the amalgam core than with any of the composite cores. The APF-treated composite cores had the least retention of any of the zinc phosphate cementations. Cementation failure over the composite cores was at the core surface. Crown retention over the control and dimpled-surface composite core with the resin cement was twice that with zinc phosphate, and significantly greater than retention of castings cemented with the resin cement over amalgam cores. Retention over amalgam cores was significantly greater with zinc phosphate cement than with the composite resin cement.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1997

Advanced cement technique improves fixation in elbow arthroplasty.

An in vitro study was conducted to assess the efficacy of advanced cementing techniques in the fixation of the humeral stem in elbow arthroplasty. Sixteen fresh frozen cadaveric distal humeri were prepared to accept an acrylic sham humeral stem. Conventional cementing technique using doughy cement manually inserted and packed was performed in 8 specimens. The advanced cementing technique, consisting of canal irrigation, brushing and drying with gauze, canal plugging, and low viscosity cement pressurization with a delivery system was performed in the other specimens. All humeri subsequently were sectioned into 10 mm thick sections, photographed, and digitized to quantify the perimeter and area of the stem, cement mantle, corticocancellous junction, and cement voids. The degree of cement filling, determined from the area fraction of cement to the total available area within the corticocancellous junction, was significantly greater in the advanced group compared with the conventional group. Mechanical assessment of the specimens consisted of a push out load to failure test of the cement mantle from bone. For all locations in the distal humerus, the failure load and failure stress in the advanced group was significantly greater than the conventional group. It is concluded that development of an effective cement restrictor and application of advanced cement techniques in vivo should improve the initial fixation of the humeral component and may decrease the incidence of aseptic loosening associated with elbow arthroplasty.

Biomechanical Phenomena↗