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PubMed1999

Fracture toughness of conventional, resin-modified glass-ionomer and composite luting cements.

OBJECTIVES: This study was conducted to determine if significant differences existed between the fracture toughness of three types of luting cement, and, if the method of mixing conventional glass-ionomer luting cements, hand-mixed or mechanically mixed, influenced the value obtained. METHODS: Three types of luting cement were investigated: conventional glass-ionomer cement (two handmixed and two capsulated cements, KetacCem, Fuji I and KetacCem Maxicap, Fuji Cap I), a resin-modified glass-ionomer cement (Vitremer Luting Cement) and a resin composite cement (Scotchbond Resin Cement). Eleven specimens of each of the six cements were fabricated to determine the plane strain fracture toughness using the chevron notch short rod technique. After seven days the specimens were loaded in a water bath, at a crosshead speed of 4 microns/s and the fracture toughness values calculated. RESULTS: ANOVA indicated significant differences between the cements (p < 0.0001) and each cement was compared with all others using Fishers PSLD test (p < 0.05). The rank order of results from highest fracture toughness value to lowest (mean +/- s.d.) was Scotchbond Resin Cement (1.31 +/- 0.17), Vitremer Luting Cement (1.08 +/- 0.1), Fuji Cap I (0.37 +/- 0.04), KetacCem Maxicap (0.37 +/- 0.05), Fuji I (0.34 +/- 0.04), KetacCem (0.27 +/- 0.03). SIGNIFICANCE: Of the cements tested, the resin composite cement is most likely to resist clinical failure by cement cohesive failure.

Analysis of Variance↗
PubMed2000

Tensile bond strength of resin-modified glass-ionomer cement to microabraded and silica-coated or tin-plated high noble ceramic alloy.

PURPOSE: The purpose of this study was to evaluate the influence of alloy surface microabrasion, silica coating, or microabrasion plus tin plating on the tensile bond strengths between a resin-modified glass-ionomer luting cement and a high-noble alloy. Bond strength between the microabraded alloy specimens and conventional glass-ionomer cement or resin cement were included for comparison. MATERIALS AND METHODS: One hundred twenty uniform size, disk-shaped specimens were cast in a noble metal alloy and divided into 6 groups (n = 10 pairs/group). The metal surfaces of the specimens in each group were treated and cemented as follows. Group 1: No surface treatment (as cast, control), cemented with a resin-modified glass-ionomer cement. Group 2: Microabrasion with 50-microm aluminum oxide particles, resin-modified glass-ionomer cement. Group 3: A laboratory microabrasion and silica coating system, resin-modified glass-ionomer cement. Group 4: Microabrasion and tin-plating, resin-modified glass-ionomer cement. Group 5: Microabrasion only, conventional glass-ionomer cement. Group 6: Microabrasion and tin-plating, conventional resin cement. The uniaxial tensile bond strength for each specimen pair was determined using an Instron Universal Testing Machine (Instron Corp, Canton, MA). Results were analyzed using a one-way analysis of variance (alpha = 0.05) and a Tukey post-hoc analysis. RESULTS: Mean bond strength: Group 1: 3.6 (+/- 1.5) MPa. Group 2: 4.2 (+/-0.5) MPa. Group 3: 6.7 (+/- 0.9) MPa. Group 4: 10.6 (+/- 1.8) MPa. Group 5: 1.1 (+/- 0.4) MPa. Group 6: 14.6 (+/- 2.3) MPa. Group 6 was significantly stronger than Group 4. The bond strength of specimens cemented with the resin-modified glass-ionomer cement using microabrasion and tin-plating (Group 4) was significantly stronger than all other groups except the resin cement with microabrasion and tin-plating (Group 6). CONCLUSION: Microabraded and tin-plated alloy specimens luted with the resin-modified glass-ionomer cement resulted in the greatest mean tensile strengths for the resin-modified glass-ionomer cement groups. This strength was 73% of the mean tensile strength of microabraded specimens luted with resin cement.

Aluminum Oxide↗
PubMed2005

Confocal laser scanning microscopic observations of secondary caries inhibition around different types of luting cements.

PURPOSE: To analyze in vitro artificial secondary caries inhibition around conventional luting cements and resin cements using a confocal laser-scanning microscope (CLSM). METHODS: Box shape cavities (approximately 3 mm long, 4 mm wide, and 1.5 mm deep) were prepared in bovine root dentin. One of five cements: Elite Cement 100 (EL) zinc phosphate cement, HY-Bond Carbo Cement (CA) polycarboxylate cement, Fuji I (FI) glass-ionomer cement, Fuji Luting (FL) GIC-based resin cement and Panavia F (PA) fluoride-releasing resin cement, was placed in the cavity. After polishing, the center of the cement surface was covered with an adhesive to preserve the original cement solubility. The specimens were stored in distilled water at 37 degrees C for 1 week, and stored in an artificial demineralizing solution for 3.5 days. Following this, each specimen was sectioned into two halves, trimmed, and polished. Thickness of inhibition zone, depth of outer lesion and cement solubility around each cement were determined by a CLSM. RESULTS: Inhibition zones were not seen in EL and CA, while they were found in FI, FL and PA. The depths of the outer lesions of CA and FI were significantly lower than those of EL, FL and PA (P< 0.05). The highest and the second-highest cement solubility were obtained in EL and CA, respectively. FI and FL indicated significantly lower cement solubility than EL and CA. PA tended to show the lowest cement solubility.

Analysis of Variance↗
PubMed2007

Cement restrictor function below the femoral isthmus.

Cement restrictors rely on achieving an interference fit with the wall of the medullary canal. Depending on the design of the cement restrictor, the intramedullary fit may be compromised as the femur starts to widen distally. Three different designs of cement restrictor were identified; universal, press-fit, and expandable. We determined which design of cement restrictor could resist the greatest pressures in a closed column of cement. Additionally, we recorded leakage of cement past the restrictor. We reamed synthetic femora to recreate the normal distal flare of the femur below the femoral isthmus. After inserting the cement restrictor, low-viscosity cement was gradually pressurized using an electronically controlled pneumatic ram. We then simultaneously recorded cement pressure above the cement restrictor and displacement of the cement restrictor. There was variation in the performance of the cement restrictors. The expandable cement restrictors resisted the greatest pressures. The resorbable expandable (REX Cement Stop) and press-fit cement restrictors reliably prevented cement leakage. The press-fit and universal restrictors failed at low pressures when deployed below the isthmus. The choice of cement restrictor may need to be modified if preoperative templating indicates the restrictor will sit below the femoral isthmus.

Arthroplasty, Replacement, Hip↗
PubMed1998

In-vitro solubility of three types of resin and conventional luting cements.

The solubility of resin luting cement remains unknown although the use of resin luting cement for routine cementation of restorations has increased. The purpose of this in-vitro study was to compare the solubilities of three resin cements currently in clinical use with three brands of conventional luting agents. The three resin luting cements, All-Bond C&B (AB, Bisco) Panavia 21 (P21, Kuraray), and Super-Bond C&B (SB, Sun-Medical), and the three conventional luting agents, Elite Cement 100 (EC, zinc phosphate cement, GC), HY-Bond Carbo-plus Cement (HCP, polycarboxylate cement, Shofu), and Fuji I (FI, glass-ionomer cement, GC) were used in this study. A modification of the ADA specification test was adopted to evaluate the solubilities of luting cements. The two types of media (distilled water and pH 4.0 lactic acid solution) in which specimens were stored for 30 days were prepared. The four luting cements, EC, FI, AB, and P21, were more soluble in lactic acid solution than in distilled water. Resin luting cements were markedly less soluble than conventional luting agents when placed in fresh lactic acid solution (0.001 mol/L) at pH 4.0 every 24 h over a 30-day period. The solubility rates of luting cements could be fitted to mathematical expressions which indicated that the solubilities increased linearly or logarithmically with immersion period. Fixed prosthodontic restorations cemented with resin luting cement may be capable of withstanding long-term clinical use compared with conventional luting agents.

American Dental Association↗
PubMed1977

Toxicity of some dental cements in a cell culture system.

A cell culture method has been used to study the effect of zinc phosphate cement (De Trey's Zinc Zement Improved), zinc silicophosphate cement (Fluoro-Thin) and polycarboxylate cement (Durelon) on animal cells. Disks (20 x 1 mm) of the materials were placed in the center of plastic Petri dishes and subsequently incubated with human epithelial cells. Cell multiplication, medium pH and the release of cement constituents were measured. All three cements exhibited a cytotoxic effect, which was most pronounced in the cultures with zinc silicophosphate cement and polycarboxylate cement. The results also indicated that cell growth on the surface of the disks is a more sensitive indicator of cytotoxicity than cell growth around the disks. pH of the medium was only slightly affected in cultures with polycarboxylate cement, whereas a decrease was found in cultures with zinc phosphate cement and especially with zinc silicophosphate cement. A rapid release of phosphate was found in cultures with zinc silicophosphate cement. Zinc was released into the medium from disks of zinc phosphate cement, zinc silicophosphate cement and polycarboxylate cement--exceeding the toxicity level for the present cell line after 24 h. In cultures with zinc silicophosphate cement and polycarboxylate cement the release of fluoride reached toxic levels within the same time interval.

Cell Division↗
PubMed1997

Influence of tooth surface roughness and type of cement on retention of complete cast crowns.

STATEMENT OF PROBLEM: Bond strength of luting cements to dentin is a critical consideration for success of cast restorations. PURPOSE OF STUDY: This study determined the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of respective cemented restorations. MATERIAL AND METHODS: Ninety artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a milling machine on extracted human teeth. Diamond, tungsten carbide finishing, and cross-cut carbide burs of similar shape were used. The crowns in each group were randomly subdivided into three subgroups of 10 for the three luting cements selected for this study: zinc phosphate cement (Fleck's), glass ionomer cement (Ketac-Cem), and adhesive resin cement (Panavia-EX). Retention was evaluated by measuring the tensile load required to dislodge the artificial crowns from tooth preparations with an Instron testing machine. RESULTS: Analysis of forces with parametric analysis of variance and Tukey's Studentized Range (HSD) disclosed a statistically significant difference for both luting cement and finishing burs (p < 0.001). A statistically significant interaction effect (p < 0.001) was also found. The greatest retention value (372.9 N) was for tooth preparations refined with carbide burs and cemented with Panavia-EX cement. However, the least retention value (201.6 N) was for tooth preparations completed with finishing burs and luted with zinc phosphate cement. CONCLUSIONS: Significant differences were found among all three cements for finishing burs. However, there was a difference only between Panavia-EX cement and the other two cements for tungsten carbide burs. For diamond rotary instruments, zinc phosphate cement was significantly different from glass ionomer and Panavia-EX cements.

Analysis of Variance↗
PubMed2002

Modelling debonded stem-cement interface for hip implants: effect of residual stresses.

OBJECTIVE: To assess the effect of the residual stresses due to cement curing on the load transfer of cemented hip implants. DESIGN: The load transfer at the stem-cement interface of an idealized hip stem surrounded by cortical bone was investigated using a three-dimensional finite element analysis. A debonded stem-cement interface was considered to simulate a highly polished stem in contact with cement; Coulomb friction at the stem-cement interface was considered. BACKGROUND: Numerical analyses on the load transfer of cemented hip implants do not include residual stresses due to cement curing at the stem-cement interface. METHODS: The magnitude of the residual stresses was determined experimentally. In the finite element model, non-linear contact elements modelled the debonded stem-cement interface. In particular, the compressive radial residual stresses that are generated at the interface, due to the cement expansion during curing, were treated similar to a press-fit problem. RESULTS: The cement stress distributions were affected by the magnitude of the residual stresses. Failing to include residual stresses underestimated the cement stresses at the interface, mainly affecting the radial and hoop stresses. The load was transferred from the stem to the cement more uniformly along the interface once residual stresses were included. CONCLUSIONS: Because there is no chemical bond at the interface between the stem and cement, the interface resistance depends on friction thus radial residual compressive stresses developed by the cement curing play a direct role. RELEVANCE: Implant loosening of cemented hip implants is one of the major causes of late failure of the arthroplasty. The load is transferred from the stem to the bone primarily across the interfaces, consequently modelling accurately the interface is essential in predicting the load transfer.

Biomechanical Phenomena↗
PubMed1996

Monitoring the integrity of the cement-metal interface of total joint components in vitro using acoustic emission and ultrasound.

Debonding of the cement-metal interface of cemented femoral components of total hip arthroplasty has been shown from clinical and autopsy material to be a common occurrence. Experimentally, debonding has been shown to increase markedly the strains in the adjacent cement mantle. Studies of autopsy-retrieved specimens demonstrate that debonding of the cement-metal interface is a key initiating event in loosening of cemented femoral components of total hip arthroplasty. However, both the radiographic and autopsy evidence of cement-metal interfacial debonding exist after the fact, that is, after debonding has occurred. The lack of prospective data showing that debonding does indeed occur under physiologic loading and occurs prior to other forms of failure of fixation leaves uncertain the issue of debonding and its role in initiating loosening of cemented femoral components. Knowing when, where, and to what extent the cement-metal interface debonds is critical information in understanding the process of loosening of cemented femoral components. Such information would contribute to improving the durability of stems and improving cementing techniques. In this study, the two nondestructive techniques of acoustic emission and ultrasonic evaluation of the cement-metal interface of cemented femoral stems of total hip arthroplasty were combined to investigate when, where, and to what extent cement-metal debonding occurred in vitro in simulated femurs loaded physiologically in fatigue in simulated single-leg stance. Debonding of the cement-metal interface of a cemented femoral component in this model was both an initiating event and a major mechanism of compromise of the cement-metal interface. Additional acoustic emission signals arose from cracks that developed in the cement.

Acoustics↗
PubMed1999

Demineralizing effect of dental cements on human dentin.

OBJECTIVE: This study was undertaken to verify the hypothesis that dentin surfaces are demineralized during placement of four kinds of chemically setting cements (zinc phosphate cement, luting glass-ionomer cement, restorative glass-ionomer cement, and zinc polycarboxylate cement). METHOD AND MATERIALS: Sixty cemented dentin disks were observed under scanning electron microscopy and with confocal laser scanning microscopy after use of an argon-ion etching technique. To determine the surface effects of the cements, 30 dentin surfaces were treated with 1 of 6 freshly mixed cements (5 per group) for 60 seconds. The disks were subjected to rinsing with a water spray and ultrasonic washing prior to scanning electron microscopic observation. RESULTS: Observation of cemented dentin specimens revealed that the dentin was not completely demineralized at the interface formed by the cement and dentin and that the extent and depth of demineralization along the interface tended to be nonuniform. Zinc phosphate cement caused the greatest demineralization of dentin, followed by luting glass-ionomer cement. The extent of demineralization with restorative glass-ionomer cement or zinc polycarboxylate cement was less discernible. Confocal laser scanning microscopy generally confirmed scanning electron microscopic observations and revealed that most of the specimens showed close adaptation of the cements to the dentin surfaces. CONCLUSION: Acid-containing cements have self-etching properties that are effective, to various degrees, in removing the smear layer and promoting close adaptation to dentin surfaces.

Acid Etching, Dental↗
PubMed2000

The influence of luting cement on the probabilities of survival and modes of failure of cast full-coverage crowns.

OBJECTIVES: This study compares the probabilities of survival and modes of failure of cast full-coverage crowns bonded with five cements when subjected to tensile pull-off testing. METHODS: Five groups of 25 sound human premolar teeth were prepared for full-coverage crowns, impressions recorded and customized castings fabricated in Ni-Cr-Mb bonding alloy. The cements tested were zinc phosphate, a hand-mixed and capsulated conventional glass-ionomer cement, a resin-modified glass-ionomer cement and a resin composite luting cement. The cemented crowns were stored in water at 37 degrees C for 24 h prior to application of a tensile pull-off force at a strain rate of 10 mm/min. The loads at failure were ranked and modelled by derived Weibull functions each describing the probability of a given specimen failing under a given load. Non-parametric statistical analysis was also applied to the results. RESULTS: There were no significant differences between the loads at failure of zinc phosphate cement, the hand-mixed or the capsulated glass-ionomer cements. The resin-modified glass-ionomer cement and the resin composite cement failed at significantly higher loads than the other three cements, but were not significantly different from each other. The Weibull modulus ranking for each cement from highest to lowest was resin composite = zinc phosphate, resin-modified glass-ionomer, hand-mixed conventional glass-ionomer and capsulated conventional glass-ionomer cement. SIGNIFICANCE: Weibull analysis allows dentists to compare the probability of survival of a crown bonded with different cements at a chosen load giving an indication of cement reliability.

Adhesiveness↗
PubMed1995

Retention of orthodontic bands with three different cements.

In 1878, zinc phosphate cement was introduced as a dental material and used to cement orthodontic bands. The prevalence of enamel decalcification beneath orthodontic bands has indicated the need for a fluoride-releasing orthodontic luting cement. The purpose of this study was to compare the retentive bond strengths of orthodontic bands cemented individually with zinc polycarboxylate, glass ionomer and zinc phosphate cement adhesives. Forty-eight extracted human molar teeth were embedded in resin blocks and each was randomly assigned to one of the three cement groups. Adapted bands were cemented by using hand pressure and a band seater. The cemented teeth were then put in synthetic saliva at 37 degrees C for twenty-four hours. The force required to fracture the cement bond was used as a measure of cement retention. Using an Instron universal testing machine, a tensile load was applied to each cemented band. The Kruskal-Wallis one-way analysis of variance test revealed no significant differences (p > 0.05) among the retentive strengths of the three cements. Both the zinc polycarboxylate and the glass ionomer cements tested were found to be suitable as orthodontic luting agents. In addition, the ability to bond to enamel and stainless steel and to leach fluoride make the glass ionomer cement an ideal orthodontic cement.

Analysis of Variance↗
PubMed2006

Strontium-containing hydroxyapatite bioactive bone cement in revision hip arthroplasty.

Clinical outcome of cemented implants to revision total hip replacement (THR) is not as satisfactory as primary THR, due to the loss of bone stock and normal trabecular pattern. This study evaluated a bioactive bone cement, strontium-containing hydroxyapatite (Sr-HA) bone cement, in a goat revision hip hemi-arthroplasty model, and compared outcomes with polymethylmethacrylate (PMMA) bone cement. Nine months after operation, significantly higher bonding strength was found in the Sr-HA group (3.36+/-1.84 MPa) than in the PMMA bone cement group (1.23+/-0.73 MPa). After detached from the femoral component, the surface of PMMA bone cement mantle was shown relatively smooth, whereas the surface of the Sr-HA bioactive bone cement mantle was uneven, by SEM observation. EDX analysis detected little calcium and no phosphorus on the surface of PMMA bone cement mantle, while high content of calcium (14.03%) and phosphorus (10.37%) was found on the surface of the Sr-HA bone cement mantle. Even higher content of calcium (17.37%) and phosphorus (10.84%) were detected in the concave area. Intimate contact between Sr-HA bioactive bone cement and bone was demonstrated by histological and SEM observation. New bone bonded to the surface of Sr-HA cement and grew along its surface. However, fibrous tissue was observed between PMMA bone cement and bone. The results showed good bioactivity of Sr-HA bioactive bone cement in this revision hip replacement model using goats. This in vivo study also suggested that Sr-HA bioactive bone cement was superior to PMMA bone cement in terms of bone-bonding strength. Use of bioactive bone cement may be a possible solution overcoming problems associated with the use of PMMA bone cement in revision hip replacement.

Animals↗
PubMed2003

An in vivo and ex vivo study to evaluate the use of a glass polyphosphonate cement in orthodontic banding.

The purpose of this study was to examine the effectiveness of a new glass polyphosphonate cement (Diamond) for orthodontic banding. Thirty-one subjects underwent in vivo testing to compare the failure rate of bands cemented using the test cement and bands cemented using a conventional glass polyalkenoate cement (Ketac-Cem) over a 6-month period at the beginning of active appliance therapy. In an ex vivo experiment 60 extracted teeth were banded using either the test cement or a glass polyalkenoate cement, and subjected to a debanding force using a Lloyd universal testing machine until failure. In the in vivo study the overall proportion of failure of the bands cemented with each cement was identical at 0.048. However, in the ex vivo study the probability of failure for the glass polyphosphonate cement was significantly higher than for the glass polyalkenoate cement, and the force to deband the glass polyalkenoate cement was greater than that of the glass polyphosphonate cement. In the clinical setting the new glass polyphosphonate cement performed as well as a conventional glass polyalkenoate cement, and these results suggest that it could be used as an alternative cement for orthodontic banding. The results of the ex vivo test bring into question the usefulness of this laboratory test as an indicator of clinical performance.

Dental Bonding↗
PubMed2006

Femoral cementing techniques: current trends in the UK.

INTRODUCTION: The results of a survey conducted amongst hip surgeons in Great Britain on the use of bone cement and femoral cementing techniques are reported. MATERIALS AND METHODS: A postal questionnaire was sent out to the members of the British Orthopaedic Association for their opinion on cement usage and femoral cementing techniques in primary hip arthroplasty. RESULTS: A majority of surgeons use high viscosity cement (82%) and cement containing antibiotics (77%). Almost a fifth of the respondents were unaware of the place of storage of the cement and of the ambient theatre temperature. Over two-thirds experienced inconsistencies in the handling of cement and attributed this to inconsistent theatre temperature (40%) and storage temperature (14%). A majority of the surgeons followed the 'modern' femoral cementing technique of vacuum mixing (94%), plugging the femoral canal (98%), pulsed lavage (87%), retrograde cement introduction (95%), use of stem centralisers (62%) and cement pressurisation. Four-fifths of the surgeons used time as a guide for cement and stem insertion rather than consistency of the cement. CONCLUSIONS: Though most of the surgeons follow contemporary cementing techniques, it appears that inconsistency of the working properties of the cement is a major impediment. Many surgeons are also unaware of the variables that can influence polymerisation and working time of the cement.

Anti-Bacterial Agents↗
PubMedDate not supplied

The effect of film thickness and surface texture on the resistance of cemented extracoronal restorations to lateral fatigue loading.

PURPOSE: The aim of the present study was to assess the effect of cement-film thickness and surface texture (roughness) on the resistance of cemented crowns to dynamic lateral loading. MATERIALS AND METHODS: Crown and abutment analogues were cemented using zinc-oxide-eugenol, zinc-phosphate, glass-ionomer, and composite cements. The space left for the cement lute was 0.02, 0.05, 0.1, 0.2, and 0.5 mm. The 3 degrees of surface texture subjected to investigation were (1) polished with up to 4,000-grit paper, (2) sanded using a 1,000-grit paper, and (3) sandblasted with 50-micron aluminum oxide. Testing was conducted according to the staircase procedure. The specimens were subjected to rotational fatigue loading until the cement bond failed or the components reached 1,000,000 stress cycles. RESULTS: The results showed that the relation between cement thickness and resistance to dynamic lateral loading is hyperbolic. For the zinc-oxide-eugenol, the zinc-phosphate, and the glass-ionomer cements increasing surface texture had a moderate effect. For composite cement, sandblasting doubled the resistance to dynamic lateral loading. For both parameters tested (cement thickness and surface texture), the ascending order of resistance was: zinc-oxide-eugenol, zinc-phosphate, and glass-ionomer cements. Crowns cemented with composite cement presented the highest resistance to dynamic lateral loading. CONCLUSION: Within the confines of the present experimental design, it is concluded that (1) decreasing the width of the cement layer increases the resistance to dynamic lateral loading, and (2) texturing the surface of the abutment and the restorations as after sandblasting increases the resistance to dynamic lateral loading.

Cementation↗
PubMed1997

Bioactive bone cement: comparison of AW-GC filler with hydroxyapatite and beta-TCP fillers on mechanical and biological properties.

Three types of bioactive bone cement (designated AWC, HAC, and TCPC), each consisting of bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin and a bioactive filler of apatite and wollastonite containing glass-ceramic (AW-GC), sintered hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder were made in order to evaluate the influence of the bioactive filler on the mechanical and biological properties of bone cement. The proportion of filler added to the cements was 70% w/w. The compressive, bending, and tensile strengths and the fracture toughness of AWC were higher than HAC and TCPC under wet conditions. The cements were evaluated in vivo by packing them into the intramedullary canals of rat tibiae. An affinity index that equalled the length of bone in direct apposition to the cement was calculated for each cement and expressed as a percentage of the total length of the cement surface. Histological examination of rat tibiae up to 8 weeks after implantation revealed that AWC had higher bioactivity than HAC and TCPC. New bone had formed along the AWC surface within 2 weeks, and at 4 weeks newly formed bone surrounded the cement surface almost completely. In HAC- and TCPC-implanted tibiae, immature bone had formed directly toward but not along the cement surface at 2 weeks. Observation of cement-bone interfaces showed that AWC had bonded to the bone via a so-called "Ca-P-rich layer"; the cement-bone interface remained stable, and the width of the CA-P-rich layer became thicker with time. On the other hand, in HAC- and TCPC-implanted tibiae, the cement surface fillers were surrounded by new bone and were absorbed gradually to become bone matrix. The cement-bone interfaces went inside the cement with time. Our results indicate that stronger interstitial bonding between the inorganic filler and the organic matrix resin in AWC lead to higher mechanical properties; results also indicate that the more stable cement-bone interface and higher bioactivity of AWC are due to early and uniform apatite formation on the cement surface.

Animals↗
PubMed1998

Bioactive bone cement: effect of the amount of glass-ceramic powder on bone-bonding strength.

We examined the influence of the proportion of glass-ceramic powder in a bioactive bone cement of our formula on the bone-bonding ability of cement. Changes in cement bonding with time also were examined. The bioactive bone cement consisted of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW-GC powder) and bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin. AW-GC powder was added to the cement as 0%, 30%, 50%, 70%, and 80% w/w. Rectangular plates (2 x 10 x 15 mm) of each cement with polished surfaces were implanted into the proximal metaphysis of the tibiae of male rabbits, and the failure load was measured by detaching tests 10 and 25 weeks after implantation. The failure loads of each cement were 0% = 0.03, 30% = 1.52, 50% = 2.67, 70% = 3.56, and 80% = 5.59 kg at 10 weeks, and 0% = 0.05, 30% = 1.68, 50% = 2.77, 70% = 3.80, and 80% = 6.37 kg at 25 weeks. Observation of the cement-bone interface revealed that all bioactive bone cements (30%-80%) formed direct contact with bone whereas intervening fibrous tissue was observed in all specimens of the 0% group. By scanning electron microscopy, all bioactive bone cements (30%-80% groups) showed direct contact with bone at the cement-bone interface. In the 0% group, direct contact with bone at the cement-bone interface was not observed. By electron-probe microanalysis, a Ca-P-rich layer was not detected at the cement-bone interfaces of the 30%-70% bioactive bone cements, but in some samples of the 80% cement specimens a thin Ca-P-rich layer (3 microns thick) was observed at the interface at 10 and 25 weeks after implantation. These results show that all of the bioactive bone cements tested had the ability to bond to bone and to function as bioactive composites of ceramics and polymers.

Animals↗