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PubMed1992

Effect of surface roughness and cement space on crown retention.

The effects of varying luting agent space and internal surface roughness with different types of cores and cements were studied. One hundred eighty amalgam and 180 composite cores were cemented into standardized stainless steel retainers. Cores and retainers were divided into 12 groups according to core type, core diameter, and retainer roughness. Each group was further subdivided according to cement, A: zinc phosphate (ZOP); B: resin; and C: glass ionomer cement (GIC). Subgroups were divided into thermal-cycled and nonthermal-cycled groups. Thermal cycling was at 5 degrees to 55 degrees C, repeated 500 times. Cores were separated from their retainers with a compression rod in an Instron testing machine at a crosshead speed of 0.02 cm/minute. Results were as follows: Amalgam cores were most retentive. Resin and ZOP cements were equally retentive with amalgam cores, but GIC was less retentive. Resin cores cemented with resin cement were more than twice as retentive than those cemented with ZOP or GIC cements. Retainers with rough internal surfaces were most retentive. A reduced cement space between core and retainer was most retentive. Thermal cycling reduced retention.

Analysis of Variance↗
PubMed1988

A comparison between zinc phosphate and glass ionomer cement in orthodontics.

In the past orthodontic band cementation has relied heavily on mechanically retentive cements such as zinc phosphate luting agents. The clinical performance of a glass ionomer cement (GIC), a chemically retentive cement, was evaluated against a conventional zinc phosphate cement (ZP). The recementation values for ZP were significantly higher over a 2-year treatment period than those of GIC. Failures between cement and enamel, and cement and stainless steel were noted for the ZP. Glass ionomer cement had significantly better retentive strength to enamel than to band material. Moisture contamination does not appear to be a problem in orthodontic band cementation with glass ionomer cement.

Cementation↗
PubMed1979

The recementation of orthodontic bands using different cements.

A clinical study on band failure rate was carried out on 5949 bands cemented to the teeth of 293 patients drawn from three orthodontic practices. The failure rate ranged from a minimum of 7% in a sample from a practice where bands were cemented with Durelon cement (Group 2) to a maximum of 19% in a sample from a practice where bands were cemented with oxyphosphate cements (Group 3). Comparison between the results of the two controlled prospective studies from one practice (Groups 1 and 2) indicated that the use of a commercially available polycarboxylate cement (Durelon) resulted in a lower failure rate than that experienced with an experimental formulation of polycarboxylate cement. The teeth on which cemented bands failed most frequently were the maxillary central incisors. Comparison of the band failure rates between different practices (Groups 2, 3 and 4) showed that patients in Groups 3 and 4 experienced a higher band failure rate than patients in Group 2, due possibly to different types of bands, cements, and cementing procedures of the different operators.

Adolescent↗
PubMed2003

Acidity of conventional luting cements and their diffusion through bovine dentine.

AIM: To examine the changes in pH of luting cements and acid diffusion of luting cements through bovine dentine using a pH-imaging microscope (SCHEM-100; Horiba Ltd, Kyoto, Japan). METHODOLOGY: The pH of the surface of three conventional luting cements, glass-ionomer, zinc phosphate and zinc polycarboxylate was measured with SCHEM-100 for 1 month. The acid diffusion from the three luting cements through bovine dentine was investigated by measuring pH changes during the application of each luting cement on the bovine dentine surface. Coronal bovine dentine disks were prepared to thicknesses of 0.50 and 0.25 mm. Each luting cement was placed on the labial dentine surface, and the pH change of the pulpal surface was observed every 3 min for 30 min with SCHEM-100. RESULTS: Glass-ionomer showed the lowest pH values for longer times. Neutralization proceeded furthest in zinc polycarboxylate. The 0.5-mm-thick dentine disks showed no pH change on the pulpal side with all the three cements. The 0.25-mm-thick disks revealed evidence of acid diffusion on the pulpal side of the cemented dentine and significantly lower pH when cemented with glass-ionomer and zinc phosphate than with zinc polycarboxylates. CONCLUSIONS: This study demonstrated that glass-ionomer exhibited a lower setting pH than zinc phosphate and zinc polycarboxylate, and acid diffusions from glass-ionomer and zinc phosphate cements were observed when placed on 0.25-mm-thick dentine disks.

Acids↗
PubMed2000

Bond strength of dual-cured resin cements to human teeth.

PURPOSE: This study evaluated the bond strength of four commercial resin luting cements to enamel and superficial dentin, using a second-generation laboratory composite. MATERIALS AND METHODS: Forty teeth were embedded in acrylic: 20 had superficial dentin exposed; 20 had enamel exposed. Each group was divided into four subgroups (n = 5) to be bonded with Variolink II, Dual Cement, 2-bond-2, and Permalute System, using an inverted, truncated cone of pre-cured Artglass that was placed over the resin cement with a load of 2 N for 2 seconds. Specimens were stored at 37 degrees C in 100% relative humidity for 24 hours before being tested for tensile bond strength (MPa). Data were analyzed using a two-way analysis of variance. Tukey-Kramer intervals for comparisons among resin cements and bonding substrates were calculated at a .05 significance level. RESULTS: Significant differences were found among resin cements. Variolink II had statistically higher bond strength values for both substrates than the rest of the cements evaluated. When bonding was to enamel, all failures were cohesive in the composite, and when bonding was to dentin, some adhesive failures occurred at the resin cement-dentin interface. Permalute System had higher bond strengths than 2-bond-2 and Dual Cement when bonded to enamel. CONCLUSIONS: Variolink II and Permalute had statistically different bond strengths to enamel and dentin. Variolink II showed statistically higher values for dentin bonding than the other cements. Use of Variolink II and Permalute resulted in statistically higher bond strengths than the other two cements.

Acrylates↗
PubMed1998

Evaluation of cytotoxicity of calcium phosphate cement consisting of alpha-tricalcium phosphate and dicalcium phosphate dihydrate.

A newly developed calcium phosphate cement, MM, was evaluated for tissue irritability by means of cell cultures. In this study, MM showed extensive mild cytotoxicity compared with other cements before setting. Inhibition of adhesion of L-929 cells was not observed after contact with MM for 24 hours. The influence of MM on colony formation was approximately the same as that of another calcium phosphate cement and less than that of a glass ionomer cement. Toxicity of MM after setting was compared with four cements; another calcium phosphate cement, glass ionomer cement, silicate cement and zinc oxide eugenol cement, but MM showed the least influence on cell morphology. Judging from these results, MM appears to be less cytotoxic than the cements in current use.

Animals↗
PubMed1989

[Changes in retention strength of luting cements by repeated loading].

The retention of crowns cemented on abutment tooth model was examined for three types of luting cements when compressive loads of 2.5 to 10.0 kg were repeatedly applied to the occlusal plane. The chamfer type Ni-Cr alloy crown and abutment tooth model were prepared, and their surfaces to be cemented were sandblasted with glass beads. Loads were applied 7,200 times a day for 1, 3, or 7-day period after cementing. The polycarboxylate and zinc phosphate cements showed higher crown retentions than glass ionomer cements. Although retention strength of glass ionomer cements was significantly increased by storing the cemented specimen in water for 7 days, repeated loading tended to decrease retention. In polycarboxylate cements and one brand of zinc phosphate cement employed, retention strengths were decreased when stored in water over 3 days. However, their highest levels were maintained or even positively impacted by repeated loading for 7 days.

Crowns↗
PubMed1989

[Study on clinical standard consistency of the luting cement].

Various properties of dental luting cement are influenced by powder/liquid ratio. The standard consistency of luting cement is determined in Japanese industrial standard and American dental association's specifications. However, it is not considered that a constant consistency is best for luting cement of all kinds. This study were performed on suitable consistency of individual cement with regard to bond strength and disintegration. Most suitable consistency was almost the same as standard consistency by the specification in the case of Zinc phosphate cement (GC's Elite cement 100). But, in the case of Polycarboxylate cement (Shofu's HY-Bond carbo cement) and Glass alkynoate cement (GC's Fuji ionomer Type I Liv), maximum bond strength can be obtained with a more powder/liquid ratio than standard consistency by the specification. Especially, Glass alkynoate cement shows this tendency strongly. Therefore, it must be manipulated quickly after mixing.

Dental Bonding↗
PubMed2000

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-SiO(2)-P(2)O(5)-CaF(2) 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.

Animals↗
PubMed2002

Interfacial tensile strength between polymethylmethacrylate-based bioactive bone cements and bone.

We have developed two types of polymethylmethacrylate (PMMA)-based bioactive bone cements containing bioactive glass beads (designated GBC) or apatite-wollastonite containing glass-ceramic powder (designated AWC) as the filler. A new method was used to evaluate the bone-cement interfacial strength of these bioactive bone cements. Two types of bioactive bone cements (GBC and AWC) and PMMA cement (CMW-1) were put in a frame attached to the smooth tibial metaphyseal cortex of the rabbit and polymerized in situ. The load required to detach the cement from the bone was measured at 4, 8, and 16 weeks after implantation. The interfacial tensile strength of GBC and AWC showed significantly higher values than PMMA cement from 4 weeks, and increased with time. For GBC, strength reached a maximum value of 12.39 +/- 1.79 kgf 16 weeks after implantation. Histological examination of rabbit tibiae up to 16 weeks demonstrated no intervening layer between the bioactive bone cements and the bone, whereas fibrous tissue was observed at the interface between the PMMA cement and the bone. From this study, we conclude that PMMA-based bioactive bone cements have a relatively higher adhesiveness at the interface than the conventionally used PMMA cement, showing potential as a promising alternative.

Animals↗
PubMed1983

Cement strain measurement surrounding loose and well-fixed femoral component stems.

Strain measurement within the cement surrounding stemmed total hip femoral components was accomplished using PMMA encapsulated and embedded strain gauges. Cement strain measurement associated with a well-bonded stem-cement interface and an unbonded stem-cement interface (i.e., loose prosthesis) was performed. The presence of a stem-cement bond was found to reduce proximal cement strain magnitudes while having little effect on distal cement strain magnitudes. The assurance of a stem-cement bond on only the proximal third of the interface was found to have an effect similar to that of a complete stem-cement bond. The results of this experimental investigation confirm the theoretical prediction that the stem-cement bond is important in maintaining the integrity of the cement mantle surrounding a stemmed femoral component.

Biomechanical Phenomena↗
PubMed2003

Tissue response to a newly developed calcium phosphate cement containing succinic acid and carboxymethyl-chitin.

We developed a new calcium phosphate cement containing succinic acid and carboxymethyl-chitin in the liquid component. In this study, the biocompatibility and osteoconductivity of this new cement were investigated. After mixing, cement in putty form was implanted immediately between the periosteum and parietal bone and in the subcutaneous tissues of rats. In control cement, distilled water was used instead of the liquid component. In addition to histological evaluations, analyses with X-ray diffraction and Fourier transform infrared were performed for the subcutaneously implanted cements. Histological examination showed slight inflammation around the new cement on the bone and in the subcutaneous tissue at 1 week after surgery. At 2 weeks, the cement was partially bound to the parietal bone. The extent of the surface of the new cement directly in contact with the bone increased with time, and most of the undersurface of the new cement bound to the host parietal bone by 8 weeks. Analysis by X-ray diffraction showed that the new cement in the subcutaneous tissue was transformed into hydroxyapatite by 8 weeks. These results indicate that this new calcium phosphate cement is useful as a bone substitute material.

Absorbable Implants↗
PubMed2006

Augmentation of implant purchase with bone cements: an in vitro study of injectability and dough distribution.

Vertebroplasty is widely used to treat (augment) osteoporotic fractures of the spine. This technique--with or without metallic implants--might have more widespread indications, if the mechanics of the injection and distribution of the cement dough through cannulated instruments and implants were better understood. This study was performed to investigate injectability of calcium phosphate and acrylic bone cements through implant prototypes, which featured different perforated sleeve designs. Using a custom-made capillary rheometer, the forces needed to inject 10 mL of the cement dough through standard cannulas were measured in the first series of experiments. In the second series, plastic sleeves were attached to the rheometer, simulating the implant. In both series, the dough was injected into ambient laboratory atmosphere, and in the second series, cement distribution was analyzed by means of an optical system. Injection of cement dough through the cannulas required forces between 50 and 400 N in the case of acrylic cements and between 40 and 500 N in case of the calcium phosphate cements. Using different sleeves did not have a significant influence on the distribution of the cement dough around the sleeve. The amount of cement dough injected was reduced when a perforated implant was attached to the cannula. More material was delivered through the proximal holes of the implant, leading to a V-shaped distribution of the cement dough. Among topics to be investigated in future studies is determination of the injectability of cement dough into trabecular bone or bone-like structures.

Biocompatible Materials↗
PubMed1984

Effect of cement pressure and bone strength on polymethylmethacrylate fixation.

The effect of the quality of the bone and of the cement pressurization magnitude and duration on the fixation achieved with polymethylmethacrylate (PMMA) bone cement is studied in vitro. Seventy-one cement-bone interface specimens, prepared under various conditions of pressurization of low-viscosity bone cement, are tested in tension. The load at failure and the maximum cement penetration are measured to assess the fixation achieved, and the quality of the bone is assessed by determining the compressive strength of each of the bone specimens. Statistical analysis of the data indicates that the pressure magnitude is the most influential of the factors considered in the cement penetration behavior and in the development of failure load capacity. The duration of the pressure does not appear to be a significant factor. The cement penetration is a decreasing function of the bone strength, reflecting a decrease in the porosity and an increase in the area fraction. Although not directly measured in these tests, these latter bone properties are indirectly measured by the bone compressive strength. The effect of increasing bone strength on the failure load is nonlinear. The development of adequate failure load capacity is the result of a balance between the cement penetration allowed by the porosity of the bone and the inherent strength of the cancellous bone itself. Weak bone, although adequately penetrated by cement, cannot provide strong fixation. Stronger, denser bone limits cement penetration, but pressurization enhances development of failure load capacity through more complete infusion and interlocking of the cement in the available pore space. The strength of the fixation achievable for any bone is limited by the intrinsic strength of the bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1988

Sustained pressurization of polymethylmethacrylate: a comparison of low- and moderate-viscosity bone cements.

There is at present great uncertainty relating to the fixation of joint implants. The deficiencies of acrylic bone cement are well documented, but the limitations of cementless fixation are as yet imcompletely identified. The purpose of this study was to investigate the potential of sustained external pressurization to improve the mechanical characteristics of conventional acrylic bone cement. The effect of serially increasing sustained pressurization of two commerically available acrylic bone cements (Simplex-P and LVC) was evaluated in human cadaver femora. A new method for determination of the shear strength of the bone-cement interface in place of the traditional pushout tests was used. In this model, there was a significant increase in the bone-cement interfacial shear strength with increasing pressure, but no difference in the shear strength was found between the two cements. At all pressure levels, the shear strength of the cement was greater than that previously reported. Increased cement penetration into the cortical bone was demonstrated with increasing pressure and low-viscosity cement, but the extent of cement penetration did not correlate with the shear strength of the bone-cement interface.

Adult↗
PubMed1997

Effects of stem length on mechanics of the femoral hip component after cemented revision.

Bone loss in the proximal femur at the time of revision hip arthroplasty for a failed primary cemented femoral component can substantially reduce the stability of the revision stem. Use of an extended-length femoral component has been suggested to aid in achieving long-term fixation; however, the optimal stem length is unknown. A three-dimensional finite element model of a Charnley-type revision femoral component in a sclerotic shell of cortical bone devoid of cancellous bone was developed, and five different stem lengths ranging from 140 to 273 mm were used. The interface between the sclerotic bone and cement mantle consisted of fibrous tissue. Distal to the sclerotic bone, bonding was allowed between the cement and bone. Relative motion between the cement and bone was reduced substantially when the stem extended beyond the original defect. Maximum principal stresses in the proximal cement mantle decreased from 7.7 to 5.5 MPa, but cement stresses near the distal tip increased from 7.9 to 10.7 MPa when the stem just bridged the defect. Further increases in stem length reduced the distal cement stresses. Increases beyond two femoral diameters had a minor effect on changes in relative motion, cement mantle stresses, and stresses across the cement-bone interface. The results suggest that a femoral component that extends beyond the area of cancellous bone defect by two femoral diameters will be most effective in minimizing stresses and motion that could be associated with clinical loosening of the cemented revision. A shorter stem that just bridges the cancellous bone defect left from the primary procedure may not provide adequate distal fixation due to high cement-bone shear stresses.

Biomechanical Phenomena↗
PubMed1979

The morphology of polymethylmethacrylate (PMMA) bone cement: surface structures and causes of their origin.

This study deals with the correlation between the polymerizing bone cement and the surrounding tissue. The surface structures of bone cements, polymerized in air, in tissue medium (in vitro) and in human bone during implantation were investigated and compared with the contours of the tissue of the implant bed. Basing on the dimensional differences it was differentiated between contours of 1st order and 2nd order: contours of 1st order are within the macroscopic range, contours of 2nd order within the microscopic range. The surface of bone cement polymerized in living human tissue differed essentially from samples polymerized under laboratory conditions. The differences are to be seen macroscopically in the coarse relief as well as microscopically in the shape and the connection of the superficial methylmethacrylate beads. Bone cements, polymerized in air show an ideal, even and closed surface. Bone cements, polymerized in tissue medium exhibit macroscopically some wrinkles, in the microscopic range their contours are either closed (samples prepolymerized at 22 degrees C) or partly open and partly closed (samples prepolymerized at 24 degrees C). The surface of bone cement implants, retrieved from human bones are characterized macroscopically by a marked wrinkled and papillary relief, microscopically by flattened beads, and most often by an irregular, rough and open surface with isolated beads giving almost the impression of a porous surface structure. The character of the surface of the bone cement originates from external, mechanical influences, from changes in the volume of the bone cement and from effects of the surrounding tissues. The surface of the bone cement implanted in human bone conforms exactly with the contour of the adjacent tissue; the tissue contour is infact a negative of the cement surface. The incomplete connection between the superficial PMMA beads seems to be of some practical value: In areas, where the PMMA beads are largely isolated, the mechanical stressability of the "polymer composite" is relatively low. Under high load, beads and bead-clusters may break off the surface. Shattering of bone cement implants possibly may start from such an open, porous surface area where PMMA beads are extensive isolated.

Acrylic Resins↗
PubMed1998

Femoral cementing techniques in total hip replacement.

Clinical studies have shown that second-generation femoral cementing techniques at total hip replacement result in a superior fixation of the femoral stem. In an effort to determine what benefits further developments in cementing techniques would provide, we compared the morphology of the cement mantles produced by traditional finger-packing and gun-insertion techniques. The porosity of the cement mantles was quantified using computerised image analysis. The finger-packing technique caused large air inclusions that resulted in large pores in the substance of the cement mantle, whereas the cement-gun technique did not result in any individual pore with an equivalent diameter greater than 3 mm. The mean porosity of cement mantles prepared using the finger-insertion technique was 8.3%, whereas the mean porosity in gun-prepared mantles was 1.7%. The use of a cement gun significantly reduced the porosity of femoral cement mantles (P = 0.02). Reduction of defects in the substance of the cement mantle may account for the increased survival of femoral prostheses inserted when second-generation techniques were used. Further reduction of the porosity of the cement mantle could not be expected to produce as dramatic a clinical improvement in prosthesis fixation.

Arthroplasty, Replacement, Hip↗