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PubMed2004

Injection biomechanics of bone cements used in vertebroplasty.

The incidence of osteoporotic bone fractures is growing exponentially as the western population ages and as life expectancy increases. Vertebroplasty, where acrylic or calcium phosphate cement is injected into the weakened vertebrae to augment them, is an emerging procedure for treating spinal fragility fractures. However, cement injection is currently limited because there are no clear standards for a safe, reproducible and predictable procedure. The purpose of this paper is to examine the role that bone cements play in the underlying bio-mechanisms that affect the outcomes of cement injection. Our most important finding after combining clinical, laboratory and theoretical research is that the process of cement injection poses conflicting demands on bone cements. The cements are required to be more viscous and less viscous at the same time. The challenge therefore is to develop biomaterials, techniques and/or devices that can overcome or manage the conflicting demands on cement viscosity.

Biomechanical Phenomena↗
PubMedDate not supplied

The influence of fatigue loading on the quality of the cement layer and retention strength of carbon fiber post-resin composite core restorations.

Clinical studies have shown that endodontically treated teeth restored with short posts or deficient ferrules show a high failure risk. This study. evaluated the influence of fatigue loading on the quality of the cement layer between prefabricated quartz coated carbon fiber posts with restricted length and the root canal wall in maxillary pre-molars. Two adhesive resin composite cements, chemical-cured Panavia 21 (Group 1) and dual-cured RelyX-ARC (Group 2), and one resin-modified glass-ionomer cement, chemical-cured RelyX (Group 3), delta were selected for this study. Post- and-core restorations were made on single-rooted human maxillary premolars from which the coronal sections were removed at the level of the proximal cemento-enamel junction (CEJ). Following endodontic treatment, a post-and-core restoration with 6-mm post length was prepared for each tooth. The posts were directly cemented into the root canal and, after applying an adhesive (Clearfil Photo Bond), they were built up with a core build-up composite (Clearfil Photo Core). For each group (n=8), half of the specimens were exposed to fatigue loading (10(6) load cycles) almost perpendicular to the axial axis (85 degrees), while the other half were used as the control. Three parallel, transverse root sections, 1.5-mm thick, were cut from each specimen at the apical, medial and coronal location. These sections were examined by Scanning Electron Microscopy (SEM) to evaluate the integrity of the cement layer, while the retention strength of the cemented post sections was determined with the push-out test. The multivariate results of MANOVA showed that the condition main effect (fatigue or control) was not significant (p=0.059); the two other main effects, type of cement and section location, were significant (p=0.001 and p=0.008). For both the push-out strength and SEM evaluation of the cement layer integrity, the results significantly improved from RelyX to RelyX-ARC to Panavia 21 and also from apical to coronal.

Bicuspid↗
PubMed1991

[Non-cemented alloplasty of the hip joint].

The authors present a review of the contemporary problem of non-cemented alloplasty of the hip joint. They compare the advantages and disadvantages of cemented and non-cemented endoprostheses of the hip joint in relation to possible loosening and possible re-operation and with regard to the surgical technique. The negative action of bone cement is divided into two groups: 1. immediate effects which act on surrounding tissues and the patient's organism during operation. 2. late effects which involve abrasion and the phagocytic response to small cement fragments and the formation of osteoaggressive granulations. These late effects are demonstrated on histological material. The authors emphasize that non-cemented alloplasty has also some pitfalls which involve in particular higher demands on the accuracy of the surgical technique and, no doubt, more severe haemorrhage. The main advantages are according to the authors the elimination of negative effects of bone cement, in particular late effects. The authors tried to classify the contemporary spectrum of available non-cemented implants with regard to their design, materials and surface finish.

Bone Cements↗
PubMed1997

Effect of HEMA-containing dentin desensitizers on shear bond strength of a resin cement.

PURPOSE: To determine whether the use of two HEMA-containing dentin desensitizing agents [Health-Dent Desensitizer with fluoride (H) or Gluma Desensitizer (G)], when applied at simulated "cavity preparation" and "cementation" appointments, affects the bond strength of lab processed resin composite restorations cemented to dentin. MATERIALS AND METHODS: The occlusal surfaces of 70 teeth were ground flat to expose dentin and polished to 600 grit. Teeth were randomly assigned to seven groups (n = 10). The treatments were applied in two sessions in order to simulate cavity preparation and cementation appointments. Water (W) was applied as a control instead of a desensitizing agent. H or G were applied for 30 seconds with a rubbing motion (1) at preparation appointment (HW and GW), or (2) at cementation appointment, after etching (WH and WG), or (3) at both sessions (HH and GG). In the control group, water was applied at both sessions (WW). All-Bond 2 and Dual Cement were used according to manufacturers' instructions to cement pre-polymerized resin composite cylinders (4 mm diameter) to the dentin surfaces using a force of 1.0 MPa. Specimens were thermocycled 300x and tested in shear until failure. Data was analyzed using one-way ANOVA and Tukey's HSD test at alpha = 0.05. RESULTS: Mean bond strength and standard deviations are reported in MPa: GW = 7.4 +/- 6.0; WW = 7.7 +/- 5.8; HW = 8.2 +/- 4.3; WH = 10.8 +/- 6.2; GG = 13.5 +/- 6.0; HH = 13.8 +/- 7.1; WG = 19.9 +/- 8.8. There were no significant differences in bond strengths for GW, WW, HW, WH and GG. Shear bond strength for WG and HH was significantly higher than all groups except for GG. Results of this in vitro study indicate that the use of desensitizers at the preparation and/or cementation appointment does not interfere with bond strengths of resin cement to dentin.

Analysis of Variance↗
PubMed2000

Effects of abutment size and luting cement type on the uniaxial retention force of implant-supported crowns.

STATEMENT OF PROBLEM: The assumption that increasing the diameter of the abutment/crown components will provide greater resistance to crown loosening forces than standard-sized components has not been reported either with clinical trials or in the laboratory. PURPOSE: This study attempted to determine what effect abutment dimension and type of luting agent have on the retention of the prosthetic crown. METHODS AND MATERIAL: Test specimens consisted of standard, wide, and "experimental" CeraOne titanium abutments and matching CeraOne gold cylinders cemented with a zinc phosphate permanent or a zinc oxide eugenol provisional cement. The mean uniaxial force (Newtons) and the load (MPa) required to dislodge the cylinder from the abutment was determined. Statistical analysis of the sample data was performed using a 2-way analysis of variance test (alpha=.05). RESULTS: Mean uniaxial resistance force (Newtons) was significantly greater for zinc phosphate cement than for zinc oxide cement (P <. 001). Abutment size was a significant factor when permanent luting cement is used (P <.001). Retention strength per unit area (MPa) of the wide abutments was lower than the standard size and "experimental" abutments. CONCLUSION: Permanent luting cement produced uniaxial retention forces approximately 3 times greater than provisional cement. The increase in surface area provided by a wide abutment did not result in an improvement in retention strength over the standard abutment.

Analysis of Variance↗
PubMed1976

A comparative study of some dental cements used in orthodontics.

It is suggested that decalcification occurring beneath orthodontic bands is, among other factors, related to the tensile bond strength of the cement to the enamel surface, its marginal leakage at the enamel-cement interface, and its solubility and and disintegration. Under the laboratory conditions described in this study the composite cement exhibited the greatest tensile bond strength to both enamel and band material. The composite cement also displayed no marginal leakage at the enamel-cement interface and showed no solubility or disintegration under the experimental conditions. It could therefore be anticipated that, of the four cements evaluated in this study, the composite cement would have the greatest potential for eliminating pathologic enamel decalcification occurring beneath orthodontic bands.

Composite Resins↗
PubMed1997

Effect of provisional cements on the bond strength of various adhesive bonding systems on dentine.

Temporization of prepared teeth is needed for protection of the pulp and the restoration of the patients' aesthetic and functional needs. When zinc-oxyphosphate cement is used, eugenol-containing provisional cements are preferred because of their sedative effect to the pulp and because of their acceptable compressive strength. However, prior to definitive adhesive cementation with composite luting resins and dentine bonding agents the use of eugenol-containing provisional cements has to be considered critical because eugenol severely disturbs the polymerization of resinous materials. The purpose of this study was to compare shear bond strength values of various adhesive luting systems on dentine which had been in contact with various provisional cements prior to dentine bonding. The results show that the provisional cements which were used considerably decreased some of the bond strength values of the dentine bonding systems tested. Freegenol and Fermit, however, seem to have beneficial effects on the SBS values of Syntac and ART Bond. The only bonding system which produces acceptably high average SBS values with a eugenol-containing provisional cement was P-Bond.

Adhesives↗
PubMed1987

Thermal diffusivity of glass-ionomer cements.

Thermal diffusivity, a property related to the thermal insulative efficiency of a material, was measured in nine glass-ionomer cements and compared with results from a silicate and a polycarboxylate cement. Each cement was mixed at various powder-liquid ratios (P/L) and moulded into a rectangular prism of approximate dimensions 2 cm cube with a thermocouple embedded in it. The prism was immersed in a constant-temperature bath at 1 degree C, and the fall in temperature was observed over a period of three min. Except for the initial and later stages, the plot of the logarithmic difference between external and internal temperatures of each block of cement against time showed a straight line in accord with theoretical prediction. From the slope, the thermal diffusivity of the material was calculated. The values for the silicate, polycarboxylate, and glass-ionomer-metal (cermet) showed a marked rise with increasing P/L, whereas at higher P/L, glass ionomer cements showed gradual change, with values being only slightly higher than the thermal diffusivity of dentin. Glass-ionomer cements are good thermal insulators over a wide range of P/L, and close agreement between experimental and theoretical data shows that glass-ionomer cements are homogenous isotropic materials.

Dental Cements↗
PubMed1986

Acidity of glass ionomer cements during setting and its relation to pulp sensitivity.

Recent findings regarding pulp sensitivity to luting glass ionomer cements have aroused controversy as to the cause of the problem. Contributing factors may include chemical irritation from the material and leakage. The pH changes during setting were determined for three glass ionomer cements, a zinc phosphate cement, and a polycarboxylate cement. The data showed that the glass ionomer luting cements may show lower pH values for longer times than the other cements. This initial acidity, involving a prolonged period at pH below 3, coupled with cytotoxicity of other ingredients, may lead to damaging effects on the pulp when manipulation of the material and tooth preparation and cementation procedures are less than ideal.

Dental Cements↗
PubMed2000

Effect of temporary materials on bond strength of resin-modified glass-ionomer luting cements to teeth.

PURPOSE: To evaluate the effect of temporary materials on the bond strength of resin-modified glass-ionomer luting cements to teeth. MATERIALS AND METHODS: 240 freshly extracted bovine central incisors were ground to expose enamel and dentin surface. Fuji Lute and Vitremer Luting Cement were bonded to enamel and dentin surfaces after pretreatment for 1 week with (1) a eugenol-containing cement (Propac), (2) a eugenol-free cement (Freegenol Temporary Pack), (3) a polycarboxylate cement (HY-Bond Temporary Cement Hard), (4) a chemically cured temporary restorative resin (Plast Seal), and (5) a light-cured temporary restorative resin (Fermit). The flattened enamel and dentin surfaces were used as controls. After bonded specimens were stored in water at 37 degrees C for 24 hrs, the tensile bond strength was measured at a crosshead speed of 0.5 mm/min. The data were statistically analyzed by one-way ANOVA and Dunnett's Post-hoc Procedure (P < 0.05). RESULTS: Plast Seal had no adverse effect on the tensile bond strength of Fuji Lute on both enamel and dentin surfaces, while the other temporary materials revealed significant decrease in bond strength. In Vitremer Luting Cement, Propac, and Fermit, as well as Plast Seal demonstrated tensile bond strengths similar to the controls.

Analysis of Variance↗
PubMedDate not supplied

Effect of seating force, margin design, and cement on marginal seal and retention of complete metal crowns.

PURPOSE: The purpose of this study was to determine the marginal discrepancy and retention of silver-palladium crowns cemented with zinc phosphate (Phosphacap) and glass-ionomer cement (Fuji Cap 1) using different seating forces on preparations with various margin designs. MATERIALS AND METHODS: Crown preparations with three finish lines--chamfer, shoulder, and shoulder with a 45-degree bevel--were sequentially prepared on a dentoform premolar. A metal die for each of the three finish lines was constructed. Complete metal crowns were fabricated for each metal die using a silver-palladium alloy. Three different seating forces--25, 100, and 300 N--were used to load the crowns until initial set of the cement. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using a digimatic indicator. Retention was determined by measuring the tensile strength using the Lloyd universal testing machine. RESULTS: The higher seating forces produced better crown seating but had no significant effect on crown retention. The shoulder and shoulder with bevel finish lines provided better crown retention than the chamfer. Glass-ionomer cement provided greater crown retention than zinc phosphate cement. No significant correlation between marginal seating and crown retention was revealed using a Pearson analysis. CONCLUSION: Marginal seal was not influenced by either margin design or type of luting cement, but was improved with higher seating force. Crown retention was affected by the margin finish line and the luting agent.

Analysis of Variance↗
PubMedDate not supplied

Marginal adaptation and microleakage of Procera AllCeram crowns with four cements.

PURPOSE: This study investigated the effect of different cements on microleakage and marginal adaptation of porcelain crowns. MATERIALS AND METHODS: Eighty extracted molars were divided into two groups. Teeth in one group were prepared to receive Procera AllCeram crowns, whereas the other group was prepared to receive metal-ceramic crowns. Copings were made following standard techniques, and groups were divided for cementation with zinc phosphate, glass-ionomer, resin-modified glassionomer, or resin cement. Specimens were subjected to thermocycling prior to microleakage testing, then sectioned. Microleakage was scored using a five-point scale; marginal adaptation was assessed with a traveling microscope. RESULTS: A significant association was found between cement type and degree of microleakage. With zinc phosphate, 76% of Procera AllCeram and 90% of metal-ceramic copings exhibited extensive microleakage. With glass-ionomer, 49% of Procera AllCeram and 66% of metal-ceramic copings had 0 microleakage scores; with resin-modified glass-ionomer, 10% of Procera AllCeram and 84% of metal-ceramic copings had 0 microleakage scores. With resin cement, 34% of Procera AllCeram and 96% of metal-ceramic copings exhibited 0 microleakage. Procera AllCeram copings had a significantly larger mean marginal gap (54 microm) compared to metal ceramic (29 microm). CONCLUSION: In both types of crowns, the use of resin cement resulted in the highest percentage of 0 microleakage scores, whereas the zinc phosphate cement resulted in the highest percentage of extensive microleakage.

Aluminum Oxide↗
PubMed1993

Facial skeletal augmentation using hydroxyapatite cement.

This study investigates the use of a new calcium phosphate cement, which sets to solid, microporous hydroxyapatite, for facial bone augmentation. In six dogs, the supraorbital ridges were augmented bilaterally with this hydroxyapatite cement. On one side, the hydroxyapatite cement was placed directly onto the bone within a subperiosteal pocket. On the opposite side, the cement was contained within a collagen membrane tubule and then inserted into a subperiosteal pocket. The use of collagen tubules facilitated easy, precise placement of the cement. All implants maintained their original augmented height throughout the duration of the study. They were well tolerated without extrusion or migration, and there was no significant sustained inflammatory response. Histologic studies, performed at 3, 6, and 9 months revealed that when the cement was placed directly onto bone, progressive replacement of the implant by bone (osseointegration of the hydroxyapatite with the underlying bone) without a loss of volume was observed. In contrast, when the cement-collagen tubule combination was inserted, primarily a fibrous union was noted. Despite such fibrous union, the hydroxyapatite-collagen implant solidly bonded to the underlying bone, and no implant resorption was observed. Hydroxyapatite cement can be used successfully for the experimental augmentation of the craniofacial skeleton and may be applicable for such uses in humans.

Animals↗
PubMed1996

Resorption of, and bone formation from, new beta-tricalcium phosphate-monocalcium phosphate cements: an in vivo study.

Hard cylinders (4.7 x 10 mm) of two kinds of beta-tricalcium phosphate-monocalcium phosphate monohydrate-calcium sulfate hemihydrate (beta-TCP-MCPM-CSH) cements with and without beta-TCP granules (500-1000 microns) were implanted into holes drilled in rabbit femoral condyles for up to 16 weeks. Empty cavities were used as control. Cement resorption and new bone formation in the cylinders were evaluated with contact microradiography and quantified through an automatic image analysis system. At 4 weeks, both kinds of cement cylinders were surrounded by new bone. At 8 weeks, except for beta-TCP granules, both cement cylinders were almost completely resorbed and replaced by bone tissue. At 16 weeks the bone in the cavities of both cements recovered a trabecular pattern, but only the bone trabeculae in the initial cavity of the cement with beta-TCP granules became thick and mature. However, the cavities of the empty control were still empty and large. These results show that the beta-TCP-MCPM-CSH cements stimulate bone formation and are rapidly replaced by bone tissue. When added with nonresorbable beta-TCP granules, this cement maintains bone formation for a longer time.

Animals↗
PubMed1996

Static and fatigue properties of two new low-viscosity PMMA bone cements improved by vacuum mixing.

With the objectives of reducing toxicity and improving the mechanical properties of the prior Sulfix-6 cement, a new low-viscosity bone cement with a new catalyst (Sulfix-60), and a gentamycin containing cement (Allofix-G) were developed. Although static strength could be improved in comparison with the older Sulfix-6 cement, investigations regarding improved fatigue strength and the influence of vacuum mixing on the mechanical properties were missing. Dynamic weakness was the major disadvantage of the older Sulfix-6 cement. To investigate fatigue strength specimens of the new bone cements were tested with load guiding until breakage or 20 million cycles. In the three series, hand mixing, vacuum mixing, and vacuum mixing with additional pressurization were performed, respectively. Vacuum mixing led to increased fatigue stability from 6.3 to 9.1 MPa for Sulfix-60, and from 6.3 to 8.2 MPa for Allofix-G. Additional compression had no significant effect. A 200% increased fatigue strength was detectable in comparison with the older cement. In the four-point bending test, similar results were found. It could be proved that an increased polymerization rate achieved with the use of the new catalyst was responsible for the improved mechanical properties of the new bone cement Sulfix-60.

Bone Cements↗
PubMed1997

Examination of hydroxyapatite filled 4-META/MMA-TBB adhesive bone cement in vitro and in vivo environment.

Bone response to hydroxyapatite (HA) fillers in the cured-4-methacryloyloxye-thyl trimellitate anhydride (4-META)/methyl methacrylate (MMA)-tri-n-butyl borane (TBB) adhesive bone cement was examined mechanically and histologically. A two-component system, consisting of powder and liquid, was formulated. The liquid portion was 5% 4-META dissolved in MMA and TBB; the powder was composed of 50 wt% poly (MMA) (PMMA) and 50 wt% dense HA fillers. The results indicated that the tensile strength decreased with the increase of HA filler size. The bone-bonding behavior of the improved cement was examined by optical microscopy and scanning electron microscopy. Seventy-two implants in six dogs for up to 24 weeks showed 4-META cement filled with HA was stable in the cement-bone interface. Histologic examinations showed that the exposed HA particles at the surface of the cured cement were generally associated with intimate attachment to bone without fibrous tissue, as well as interdigitation of cement to bone. The results suggest the importance of HA fillers in inducing bone apposition that improves cement binding to bone for long-term stability, thereby complementing rapid initial bone fixation of the cement.

Animals↗
PubMed1997

Mechanical properties of acrylic bone cement containing PMMA-SiO2 hybrid sol-gel material.

An organic-inorganic hybrid material, poly(methyl methacrylate) (PMMA)-SiO2 (SiO2 content of 72 wt%), was prepared by incorporating PMMA structure units covalently into an SiO2 glass network via the sol-gel approach. The hybrid sol-gel material PMMA-SiO2 was subsequently used as the solid powder component of bone cement and its mechanical properties were evaluated. The effects of the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) on the properties of the sol-gel hybrid bone cement were also investigated. The influence of these components on the temperature rise during polymerization was discussed. It was found that the new bone cement containing PMMA-SiO2 hybrid sol-gel material had higher modulus than that of Simplex-P bone cement. The addition of TCP in the new bone cement increased the Young's modulus and the polymerization time; the inverse was observed for the tensile, bending, and compressive strengths, and the polymerization temperature. The addition of HEMA and EGDMA in the new bone cement had the opposite effect of TCP. The comparison between the new sol-gel bone cement and the commercial Simplex P bone cement was discussed.

Biocompatible Materials↗
PubMed1998

Biomechanical characterization of a biodegradable calcium phosphate hydraulic cement: a comparison with porous biphasic calcium phosphate ceramics.

Biomechanical properties of a biodegradable calcium phosphate hydraulic cement (CPHC) were tested with rabbits. The cement was composed of beta-tricalcium phosphate (beta-TCP), monocalcium phosphate monohydrate (MCPM), and calcium sulfate hemihydrate (CSH), beta-TCP-MCPM-CSH cement. Cylinders of 4.7 mm in diameter and 10 mm in length were put into bone cavities created in the distal epiphysis of femurs in rabbits. Cylinders of the same size of porous biphasic calcium phosphate ceramics (BCPC, 75% hydroxyapatite and 25% beta-TCP) were implanted as references. Two, 4, 12, and 16 weeks after the operation, the rabbits were sacrificed. Histomorphometry showed that the cement was resorbed, leaving only 7.67 +/- 1.81% of bone cavity after 12 weeks. Newly formed bone occupied 34.59 +/- 4.00% of the cavity. Cylindrical bone-material composites were cut out with a small dental burr. Compressive force was applied to the specimens and compressive strength, elastic modulus, and toughness were calculated. The same tests were performed on cylinders of normal bone from the same site, which served as controls. The compressive strength and the toughness of the cement-bone composite were higher than those of normal bone and porous ceramics 12 weeks after the operation (p < 0.05). At 16 weeks the compressive strength and the toughness returned to the normal bone values. The elastic modulus of the porous ceramic-bone composite was higher than the normal bone at 4, 12, and 16 weeks after surgery (p < 0.05). We found that the beta-TCP-MCPM-CSH cement is replaced by new bone and that the cement-new bone composite has similar or better mechanical properties than normal bone within 16 weeks. This study suggests the usefulness of a particular cement for filling bone defects or for temporary fixation of orthopedic implants.

Animals↗