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PubMed2005

The outcome of various cements in combination with titanium reconstruction plates after segmental resection of the mandible.

We report on 82 patients who had segmental resection of the mandible and immediate reconstruction with titanium plates, which were supplemented by polymethylmethacrylate cement (n=32), glass ionomer cement (n=27), silicone (n=9), or nothing (n=14). The mean (S.D.) follow-up time was 92 (26) months. Six months after operation, 27 (46%) of the plates with polymethylmethacrylate cement or glass ionomer cement were removed. During the same time period, four (28%) of the plates were removed in the group with no additional material and two (22%) in the group that had silicone. There was a significant difference in survival time of the metal between the group with silicone and the group with glass ionomer cement (p=0.014, log rank). Although silicone performed slightly better than the reconstruction plate on its own, we doubt whether any cement is necessary.

Aluminum Silicates↗
PubMed2005

The influence of surface treatment and luting cement on in vitro behavior of two-unit cantilever resin-bonded bridges.

OBJECTIVES: The purpose of this study was to find the optimal combination of surface pretreatment and luting cement for two-unit CoCr cantilever resin-bonded bridges. METHODS: Tensile peel, load and torque strength tests were performed using flat ground bovine teeth as substrate, four different commercially available luting cements, and CoCr beams as simulated cantilever resin-bonded bridges. The CoCr beams were pretreated with sandblasting or Rocatec. Tensile peel, load and torque strengths were determined 72h after cementation. The effects of sandblasting and Rocatec pretreatments on the morphology of the CoCr surface was investigated with SEM and EDAX analysis. RESULTS: The average strengths of the three tests showed that Rely X ARC, Resiment and Panavia were the same and significantly lower than UniFix. Rocatec showed a significantly higher average bond strength than sandblasting considering all tests. The peel test, which showed the lowest failure values, is clinically the most relevant test. This test showed that only UniFix as luting cement with sandblasting as pretreatment generates a significantly higher bond strength compared with the other cements and pretreatments. SIGNIFICANCE: Based on the results of this study the use of Unifix with sandblasting as metal surface pretreatment, is preferred for cementation of two-unit CoCr cantilever resin-bonded bridges.

Aluminum Oxide↗
PubMed2003

Early cement damage around a femoral stem is concentrated at the cement/bone interface.

This study aimed to improve understanding of the mechanical aspects of cemented implant loosening. After aggressive fatigue loading of stem/cement/femur constructs, micro-cracks and stem/bone micro-motions were quantified to answer three research questions: Are cracks preferentially associated with the stem/cement interface, the cement/bone interface or voids? Is cement damage dependent on axial position? Does cement damage correlate with micro-motion between the stem and the bone? Eight Charnley Cobra stems were implanted in cadaveric femora. Six stem/cement/femur constructs were subjected to "stair-climbing" loads for 300 kcycles at 2Hz. Loads were normalized by construct stiffness to avoid fracture. Two additional constructs were not loaded. Transverse sections were cut at 10mm intervals, stained with a fluorescent dye penetrant and examined using epi-fluorescence stereomicroscopy. Crack lengths and cement areas were recorded for 9 sections per specimen. Crack length-density was calculated by dividing summed crack length by cement mantle area. To isolate the effect of loading, length-density data were offset by the baseline length-density measured in the non-loaded specimens. Significantly more cracks were associated with the interdigitated area (35.1%+/-11.6%) and the cement/bone interface (31.0%+/-6.2%) than with the stem/cement interface (11.0%+/-5.2%) or voids (6.1%+/-4.8%) (p<0.05). Load-induced micro-crack length-density was significantly dependent on axial position, increasing proximally (p<0.001). Micro-motions were small, all stems rotated internally. Cement damage did not correlate with micro-motion.

Aged↗
PubMed1999

Microdamage accumulation in the cement layer of hip replacements under flexural loading.

Mechanical fatigue of bone cement leading to damage accumulation is implicated in the loosening of cemented hip components. Even though cracks have been identified in autopsy-retrieved mantles, damage accumulation by continuous growth and increase in number of microcracks has not yet been demonstrated experimentally. To determine just how damage accumulation occurs in the cement layer of a hip replacement, a physical model of the joint was used in an experimental study. The model regenerates the stress pattern found in the cement layers whilst at the same time allowing visualisation of microcrack initiation and growth. In this way the gradual process of damage accumulation can be determined. Six specimens were tested to 5 million cycles and a total of 1373 cracks were observed. It was found that, under the flexural loading allowed by the model, the majority of cracks come from pores in the bulk cement and not from the interfaces. Furthermore, the lateral and medial sides have statistically different damage accumulation behaviours, and pre-load cracks significantly accelerate the damage accumulation process. The experimental results confirm that damage accumulation commences early on in the loading history and that it is continuously increasing with load in the form of crack initiation and crack propagation. The results highlight the importance of replicating the loading and restraint conditions of clinical cement mantles when endeavouring to accurately model the damage accumulation process.

Aluminum↗
PubMed1996

Shear bond strengths of three resin cements used with three adhesive primers for metal.

This study compared the durability and shear bond strengths of combinations of three adhesive primers and three resin cements bonded to silver-palladium-copper-gold (Ag-Pd-Cu-Au) and cobalt-chromium (Co-Cr) alloys. The adhesive luting cements Imperva Dual, Panavia 21, and Super-Bond C&B and the adhesive primers Metal Primer material, V-Primer material, and Cesead Opaque Primer material were used. The application of Metal Primer material was effective in improving the shear bond strengths between each of the three resin cements and Ag-Pd-Cu-Au alloy compared with nonprimed specimens. Co-Cr alloy primed with Cesead Opaque Primer, followed by cementation with Imperva Dual or Super-Bond C&B luting cements yielded the strongest shear bond strengths after 50,000 thermocycles, and Panavia 21 cement did not reveal any significant differences in bond strengths between nonprimed specimens and those primed with Cesead Opaque Primer at all thermocycles.

Adhesives↗
PubMed2004

Marginal and flexural integrity of three classes of luting cement, with early finishing and water storage.

OBJECTIVES: The aims of this investigation were to clarify the effects of finishing-time and 24 h water-storage on mechanical properties and marginal adaptation to dentin of seven modern luting cements, representing three chemical types. METHODS: Bistite II, Chemiace II, Compolute, XenoCem, PermaCem, Fuji Cem and Fuji Plus were investigated with specimen sub-groups (N=10) for each property measured. The principal series of experiments was conducted in dentin cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, the maximum marginal gap width and the opposing width (if any) per cavity were measured microscopically, and summed. Then the overall sum of gap-widths (per group; N=10) was calculated. Marginal gaps were similarly measured in Teflon cavities, together with shear-bond-strengths to dentin and early flexural strengths, moduli and swelling data. RESULTS: For specimen-sets polished immediately after setting, summed marginal gaps of 23-121 microm were observed, for all luting cements except Compolute. A significantly different (p<0.05) result of either no gap or 6-28 microm summed gap-widths occurred in specimens polished after 24 h. For all materials, their shear-bond-strengths, flexural strength and moduli significantly increased after 24 h storage. SIGNIFICANCE: The marginal behavior can be interpreted in terms of the contributions of bonding, shrinkage, swelling and compliance of components, along with compositional features of the cements. With these types of cement it is generally inadvisable to polish the interfacial luting surface immediately after cementing. The polishing procedures should be carried out not less than 24 h later. One resin-cement was able to withstand immediate finishing.

Bicuspid↗
PubMed2001

Evaluating acrylic and glass-ionomer cement strength using the biaxial flexure test.

Frequently, bone cement strengths are evaluated from uniaxial tests, such as three- or four-point flexure. Measurement of material strength in this manner may not provide an accurate characterisation of a bone cements true load-bearing capacity. In most orthopaedic applications, there exists a state of biaxial stress and so biaxial strength information is most useful. To address this issue, the biaxial flexure strength of two polymethylmethacrylate orthopaedic (PMMA) bone cements and two glass-ionomer dental cements have been determined. The biaxial strength of orthopaedic bone cements have been compared to the three-point bending strength. Furthermore, the calculated theoretical biaxial strength was compared with a value of biaxial strength utilising the finite element method. For all materials tested the calculated biaxial strength is significantly greater than the three-point bending strength. The biaxial test offers several advantages over three-point bending because it critically explores surface flaws--as it does not matter in which orientation the crack lies. However, it does minimise the volume or surface area investigated and also the edge effect. The difference in strength calculated for the two testing methods can be explained quantitatively in terms of the volume of material under stress. This work has demonstrated that the biaxial flexure test can be used for the testing of orthopaedic bone cements.

Acrylic Resins↗
PubMed2002

Experimental studies on a new bioactive material: HAIonomer cements.

The lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents has resulted in the development of glass ionomer cements (GICs) for biomedical applications. In order to improve biocompatibility and biomechanically match GICs to bone, hydroxyapatite-ionomer (HAIonomer) hybrid cements were developed. Ultra-fine hydroxyapatite (HA) powders were produced using a new induction spraying technique that utilizes a radio-frequency source to spheriodize an atomized suspension containing HA crystallites. The spheriodized particulates were then held at 800 degrees C for 4 h in a carbolite furnace using a heating and cooling rate of 25 degrees C/min to obtain almost fully crystalline HA powders. The heat-treated particles were characterized and introduced into a commercial glass ionomer cement. 4 (H4), 12 (H12) and 28 (H28) vol% of fluoroalumino silicate were substituted by crystalline HA particles that were dispersed using a high-speed dispersion technique. The HAIonomer cements were subjected to hardness, compressive and diametral tensile strength testing based upon BS6039:1981. The storage time were extended to one week to investigate the effects of cement maturation on mechanical properties. Commercially available capsulated GIC (GC) and GIC at maximum powder:liquid ratio (GM) served as comparisons. Results were analyzed using factorial ANOVA/Scheffe's post-hoc tests and independent samples t-test at significance level 0.05. The effect of time on hardness was material dependent. With the exception of H12, a significant increase in hardness was observed for all materials at one week. A significant increase in compressive strength was, however, observed for H12 over time. At 1 day and 1 week, the hardness of H28 was significantly lower than for GM, H4, and H12. No significant difference in compression and diametral tensile strengths were observed between materials at both time intervals. Results show that HAIonomers is a promising material, which possess good mechanical properties. Potential uses of this new material include bone cements and performed implants for hard tissue replacement in the field of otological, oral-maxillofacial and orthopedic surgery.

Biocompatible Materials↗
PubMed2003

Theoretical and experimental model to describe the injection of a polymethylmethacrylate cement into a porous structure.

A theoretical approach was used to determine the distribution of a poly(methylmethacrylate) cement after its injection into a porous structure. The predictions of the model were then compared to experimental results obtained by injecting a polymethylmethacrylate cement into an open-porous ceramic filter. The goal was to define a model that could predict what factors affect the risk of cement extravasation and hence how the risk of cement extravasation can be minimized. The calculations were based on two important rheological laws: the law of Hagen-Poiseuille and the law of Darcy. The law of Hagen-Poiseuille describes the flow of a fluid in a cylindrical tube. The law of Darcy describes the flow of a fluid through a porous media. The model predicted that the extravasation risk was decreased when the cement viscosity, the bone pore size, the bone permeability and the bone porosity were increased, and when the diameter of the extravasation path and the viscosity of the marrow were decreased. Experimentally, the effect of the marrow viscosity and extravasation path could be evidenced. Therefore, the model was believed to be an adequate approximation of the experimental behavior. In conclusion, the experimental results demonstrated that the model was adequate and that the best practical way to decrease the risk of extravasation is to increase the cement viscosity.

Bone Cements↗
PubMed2003

Toughness, bonding and fluoride-release properties of hydroxyapatite-added glass ionomer cement.

Improving the mechanical strength of glass ionomer cement while preserving its favorable clinical properties such as fluoride release, bonding to tooth structure and biocompatibility is desirable. In this study, hydroxyapatite was incorporated into chemically setting glass ionomer cement and its effect on the fracture toughness, bonding to dentin and fluoride release was identified. Commercial glass ionomer cement (Fuji IX GP((R)) ) was the control and base material. Eight weight percent of hydroxyapatite was added into the glass ionomer powder. Specimens were fabricated and the fracture toughness, shear bond strength and eluted fluoride ion concentration were measured. Adding hydroxyapatite into the glass ionomer cement led to significantly higher fracture toughness after 15min and 24h from mixing. The hydroxyapatite-added cement also exhibited bond strength to dentin similar to that of the control from 15min to 56 days and consistent fluoride release for 13 weeks. SEM findings showed a cohesive type of fracture in the material for all specimens in both groups. These results indicate that hydroxyapatite-added glass ionomer cement has a potential as a reliable restorative material with improved fracture toughness, long-term bonding to dentin and unimpeded ability of sustained fluoride release.

Biocompatible Materials↗
PubMed1996

Factors contributing to the temperature rise during polymerization of resin-modified glass-ionomer cements.

Part of the setting reaction of a resin-modified glass-ionomer cement (RMGIC) is a photoinitiated polymerization. As a result of the polymerization exotherm, the temperature of the cement may rise during setting. This study investigated the temperature rise for two liner/base- and two restorative-type RMGICs. The effects of factors such as specimen thickness, exposure time and environment temperature were investigated. The thermal diffusivity of the cements was also evaluated. Temperatures were measured using a thermocouple embedded in the centre of 6-mm diameter specimen discs of 1, 2, or 3 mm thickness. The exposure times used to cure the specimens varied from 15 to 60 s. The test were carried out at either 25 or 37 degrees C. The temperature rises attributable to the polymerization reaction ranged from 11 to 26 degrees C for the liner/base cements and from 8 to 17 degrees C for the restorative cements. Increasing the specimen thickness reduced the temperature rise only when inadequate exposure times were used. Raising the environmental temperature resulted in a smaller temperature rise. The thermal diffusivities were determined from cylindrical specimens. These ranged from 1.9 x 10(-3) to 2.5 x 10(-3) cm2 s-1, the lining cements showing lower values than the restorative materials.

Chemical Phenomena↗
PubMedDate not supplied

Polymerization contraction stress in dual-cure cements and its effect on interfacial integrity of bonded inlays.

OBJECTIVES: To compare the polymerization contraction stress of resin cements in dual-cure and self-cure modes, and verify its effect on microleakage and gap formation in class I cavities restored with porcelain inlays. METHODS: Dual-cure cements (Calibra, Choice and RelyX ARC) were monitored for contraction stress during 30 min in the tensilometer, in the presence or absence of photo-activation. Microleakage was evaluated in porcelain inlays bonded to cavities prepared in bovine incisors, combining the same adhesive (One-Step) with each of the cements in both activation modes. Epoxy replicas of the sectioned specimens were analyzed in the SEM to determine the percentage of discontinuous margins. RESULTS: The stress developed in dual-cure mode was higher than in self-cure mode for all cements. In self-cure mode, no significant difference in stress was found among materials. Choice and RelyX ARC showed higher microleakage in dual-cure mode than in self-cure mode. Calibra did not show a significant difference in microleakage between activation modes. Contraction gap results showed wide variations, and no significant differences were detected among the groups. Gaps occurred more often in dentin, with an overall average of 22 +/- 17.5%. CONCLUSIONS: The higher stress generated in dual-cure cements subjected to photo-activation may lead to higher marginal leakage. In the confinement condition represented by the class I inlay, even the lower contraction stress of the cements in self-cure mode had enough magnitude to disrupt the bonding to dentin.

Animals↗
PubMed2000

Hip arthroplasty with a collared straight cobalt-chrome femoral stem using second-generation cementing technique: a 10-year-average follow-up study.

Clinical and radiographic results of 116 patients who had undergone 132 hip arthroplasties at our institution from 1983 to 1988 with a collared cemented straight cobalt-chrome femoral stem using second-generation cementing technique were reviewed. Twenty hips in 20 patients who were part of the original cohort were lost to follow-up. Mean age at the time of surgery was 68.2 years. Mean radiographic follow-up was 9.6 years with a minimum follow-up of 5 years. Ten-year survivorship of the component was 96.5% with revision considered as an endpoint and 94.2% with either revision or radiographic loosening considered the endpoint. Three implants (2.3%) were revised for aseptic loosening at a mean of 8.1 years after implantation. One implant (0.8%) was revised for septic loosening at 10.5 years after surgery. Of the implants not revised, 1 showed evidence of circumferential bone-cement radiolucencies, and 1 had radiolucencies at the implant-cement interface. Five of the surviving femoral components (5.0%) showed focal areas of cystic osteolysis, and proximal femoral bone resorption under the collar was seen in 32 patients (31.7%). There were no cases of cement fracture or stem subsidence. The biomechanical and material properties of this stem combined with second-generation cementing technique look promising for long-term survivorship.

Aged↗
PubMed1999

Posterior distal cement extrusion during primary total hip arthroplasty: a cause for concern?

Manually operated injection systems are routinely used to deliver polymethyl methacrylate during cemented femoral component primary total hip arthroplasty (THA). The goal of cement delivery is to achieve sufficient intrusion of cement into the trabecular bone of the prepared femur so that the femoral component is securely bonded to the femur. We have observed posterior distal cement extrusion (PDCE), which appears to be secondary to too-successful pressurization. We sought to quantify and offer a possible explanation for this phenomenon. Eight patients with PDCE were identified, with an estimated incidence range of 0.90%, to 1.6% of primary cemented femoral component THA. All occurred in female patients of small stature. Endosteal canal diameters were also small, averaging 11 mm, 10 cm from the lesser trochanter. The PDCE occurred at an average distance of 9.8 cm from the midpoint of the lesser trochanter, and was most easily visualized on the lateral radiograph where it resided in the posterior soft tissues. Examination of 49 human femora showed 1 or more vascular channels in the posterior aspect of the femur in all specimens. The most proximal vascular channel averaged 10.1 cm distal to the lesser trochanter and had an average lumen diameter of 1 mm. The vascular channel contained an artery and 2 veins by histologic examination. We postulate that PDCE represents the escape of low-viscosity cement out of the vascular channel, and laboratory simulation supports this possibility. Because this finding has not previously been reported, we hoped that other centers will look closely for this phenomenon.

Aged↗
PubMed1998

In vitro study of 24-hour and 30-day shear bond strengths of three resin-glass ionomer cements used to bond orthodontic brackets.

Interest in using composite resin-glass ionomer hybrid cements as orthodontic bracket adhesives has grown because of their potential for fluoride release. The purpose of this pilot study was to compare shear bond strengths of three resin-glass ionomer cements (Advance, Fuji Duet, Fuji Ortho LC) used as bracket adhesives with a composite resin 24 hours and 30 days after bonding. The amount of adhesive remaining on the debonded enamel surface was scored for each adhesive. Mesh-backed stainless-steel brackets were bonded to 100 extracted human premolars, which were stored in artificial saliva at 37 degrees C until being tested to failure in a testing machine. The hybrid cements, with one exception, had bond strengths similar to those of the composite resin at 24 hours and 30 days. Fuji Ortho LC had significantly lower bond strengths (ANOVA p < or = 0.05) than the other adhesives at 24 hours and 30 days when it was bonded to unetched, water-moistened enamel. Adhesive-remnant scores were similar for all cements, except for cement Fuji Ortho LC when it was bonded to unetched enamel. The resin-glass ionomer cements we tested appear to have bond strengths suitable for routine use as orthodontic bracket-bonding adhesives.

Acid Etching, Dental↗
PubMed2003

Suction technique to improve cement penetration under the tibial component in total knee arthroplasty.

Improving the longevity and reliability of cemented total knee arthroplasty remains an important part of orthopaedic research. This paper examines the recently described method of preparation of the cancellous surface of the tibia using suction cannulae in the proximal tibia and stem recess during pulsatile lavage and component fixation. The technique provides a surface clear of debris, fat, blood and marrow, and prevents backflow of blood. A retrospective analysis of post-operative radiographs shows significant improvement in the penetration of cement into the tibial plateau, and improved cement profile towards the periphery. Techniques of stem cementation are also compared, and it is recommended that for this particular design implant, cement should be applied into the cut stem recess in the tibia rather than to the stem of the implant itself. This technique of preparation of the cut surface of the tibia is a simple and, to-date, complication-free method of reliably providing satisfactory cement penetration during total knee arthroplasty.

Aged↗
PubMed1998

Comparison of conventional and resin-modified glass-ionomer luting cements in the retention of post-crowns by fatigue loading.

Fatigue testing may be used for in vitro evaluation of luting cements, allowing comparison of materials under controlled conditions. It is recognized that glass-ionomer cements are materials which are susceptible to microcracking, even during curing prior to load application, and their failure can be related to crack propagation. The aim of this study was to compare the retention of post-crowns cemented with conventional and resin-modified glass-ionomer cements, the latter having significantly greater fracture toughness, under cyclic loads which are representative of physiological service. A custom-designed fatigue machine was used for three tests each comprising 18 specimens in a modified randomized complete block programme. Correlation of load amplitude to endurance was low, as expected from static test experience, but cement comparison was made through Kaplan-Meier survival and cumulative hazard functions. Differences in the performance of the cements were indicated, but were not statistically significant in this study, although analysis by Cox's proportional hazards model indicated that significance may be gained by a larger study.

Acrylic Resins↗
PubMed2003

Effect of design of pre-fabricated posts and post heads on the retention of various cements and core materials.

The retention of new Para Post (PP) rounded undercut post head (PP-XT) was compared with the conventional flattened head (PP-P), using amalgam Dentacore and Synergy composite as core materials. The retention of the posts PP (passive serrated), PP-P (passive serrated with venting channels), PP-XP (passive, raised diamond-style pattern) and PP-XT (threaded on the coronal portion, and passive, raised diamond-shaped pattern on the apical portion), cemented with zinc phosphate cement (ZPC) or Duo Cement to extracted teeth, was evaluated. Tensile strength plots were recorded using an Instron instrument, while pulling the post and core in opposite directions. The following conclusions were drawn from this study: (i) The round undercut PP-XT head was more retentive than the PP-P head with both core materials. (ii) Amalgam was more retentive than Synergy with both head designs. (iii) PP-XT was the most retentive post to extracted tooth canals and PP-XP was the least retentive with either ZPC or Duo Cement. Post retention with (iv) ZPC in decreasing order of magnitude: PP-XT > PP-P > PP > PP-XP; and with Duo Cement: PP-XT > PP > PP-P > PP-XP - ZPC exhibited the highest retention of cemented posts.

Bisphenol A-Glycidyl Methacrylate↗