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PubMed1991

Risk factors for cement eczema.

Risk factors for cement eczema were studied among workers employed in the Danish construction industry. 2 cohorts exposed to cement containing different concentrations of water-soluble chromate were examined. A statistically significant decrease in the number of workers with allergic cement eczema was found in the cohort exposed to cement with the lower water-soluble chromate concentration. Allergic cement eczema was found to have a greater extent of involvement than irritant cement eczema. A 3rd cohort was followed to evaluate individual risk factors. The degree of exposure to wet cement seems to have a certain, though not statistically significant, effect on the risk of developing irritant cement eczema. Individual preventive measures, such as the use of gloves and creams, did not seem to reduce the development of irritant cement eczema.

Chromates↗

PubMed1997

Identification of otx2 target genes and restrictions in ectodermal competence during Xenopus cement gland formation.

The homeobox gene otx2 is a key regulator of positional identity in vertebrates, however its downstream target genes and mechanism of action are not known. We have analyzed otx2 function during formation of the Xenopus cement gland, an organ that expresses otx2. The cement gland forms at early neurula from extreme anterior ectoderm and corresponds to the chin primordium of mammals. Previous studies (Blitz, I. and Cho, K. (1995) Development 121, 993-1004; Pannese, M., Polo, C., Andreazzoli, M., Vignali, R., Kablar, B., Barsacchi, G. and Boncinelli, E. (1995) Development 121, 707-720) showed that misexpressed otx2 could activate cement gland formation. However, it was not clear whether this was a direct effect of otx2 or a secondary consequence of other tissues induced by otx2. In this study we ask whether otx2 activity is spatially and temporally restricted in the ectoderm and whether cement gland-specific genes are direct targets of otx2. In order to control the timing of otx2 activity, we constructed a dexamethasone-inducible otx2 protein (otx2-GR) by fusion with the ligand-binding domain of the glucocorticoid receptor. We conclude first, that regionally restricted factors regulate otx2 activity since otx2-GR is able to activate the cement gland markers XCG and XAG only in ventrolateral ectoderm, and never in the neural plate. Second, we show that temporal responsiveness of the ectoderm to otx2-GR is limited, beginning only at mid-gastrula but continuing as late as tailbud stages. Third, we show that otx2-GR activates expression of the cement gland differentiation marker XCG in the absence of protein synthesis, identifying a direct target of otx2. otx2-GR can also activate expression of the endogenous otx2 gene, defining an autoregulatory loop. Fourth, we show that otx2-GR is sufficient to overcome the inhibitory effects of retinoic acid on cement gland formation, indicating that this effect is caused by failure to express otx2. Corroboratively, we show that otx2 autoactivation is prevented by retinoic acid. Together, these findings suggest that otx2 directly controls cement gland differentiation, and that spatial and temporal modulation of otx2 activity limits cement gland formation to the front of the embryo.

Animals↗

PubMed2004

Propagation of fatigue cracks in acrylic bone cements containing different radiopaque agents.

In this work three iodine-containing monomers were proposed as new radiopaque agents for acrylic bone cements. In previous studies the addition of iodine-containing methacrylate monomers provided a statistically significant increase in tensile stress, fracture toughness and ductility, with respect to the barium sulphate (BaSO4)-containing cement. However, since fatigue resistance is one of the main properties required to ensure a good long-term performance of permanent prostheses, it is important to compare the fatigue properties of these new bone cement formulations with the radiolucent and BaSO4-containing bone cements. Because the acrylic cements have initial cracks, fatigue crack propagation studies were performed. It can be observed that these acrylic cements followed the Paris-Erdogan model. The results showed that the addition of some organic radiopacifiers (DISMA, TIBMA) increased the fatigue crack propagation resistance as compared to the radiolucent cement, being similar to the BaSO4-containing cement. The radiolucent cement showed a low crack propagation resistance.

Complex Mixtures↗

PubMed1980

[Biological and histological changes induced by cement dust].

In animal experiments pneumoconiogenic properties of metallurgic and Portland cement dust, produced in Poland, were investigated. Experimental pneumoconiosis was developed by intratracheal single administration, to white rats, of 50 mg of dust suspended in 0.6 ml of NaCl physiological solution. The control groups were composed of animals to whom intratracheally physiological NaCl solution, TiO2 dust and two quartz dusts of varying fibrogenic properties--weak and mild, were administered. The content of crystalline silica, as determined chemically, was approx. 3% in both cement samples. X-ray diffraction did not show any content of crystalline phases in the cements, TiO2 dust contained rutile, whereas both quartz dusts contained about 100% alpha-quartz. After 3 months the animals were sacrificed. Wet lungs weight and hydroxyproline content in lungs were determined. In addition, mediastinal nodes and lungs were examined histologically. Cement dust was found to exhibit weak fibrogenic properties, not different significantly from fibrogenic properties of inert TiO2. Nevertheless increases in fibrogenic effect of cement dusts were significantly higher as compared to the control group (geometric mean hydroxyproline content in the control group was 2.52 +/- 0.06 mg, 4.50 +/- 0.09 in the Portland cement and 4.88 +/- 0.06 in metallurgic cement. Histological changes in lungs, due to cement effect are not progressive, expressing merely inflammatory reaction to dust. Nevertheless despite weak fibrogenic properties the cement dust provokes lesions of macrophages in lungs.

Animals↗

PubMed1978

A method for assessing the clinical solubility and disintegration of luting cements.

A test was designed for evaluating the distintegration of cementing agents in the oral cavity. The cements were placed in small holes located in the proximal surfaces of cast gold restorations so that the materials were not subject to abrasion. Each cement was placed in one hole located occlusally and one located gingivally. Four commercial cements of four different types (zinc phosphate, zinc silicophosphate, polycarboxylate, and EBA-Alumina zinc oxide/eugenol) were tested in 15 patients, and differences were observed in the deterioration rates of the different cements over the 6 month period. The disintegration rate of a given cement was the same in the gingival and occlusal positions. No correlation was observed between the clinical data on loss of material and the solubility of the cements as measured by conventional in vitro tests.

Aluminum↗

PubMed1978

Clinical evaluation of cement solubility.

This study evaluated a method of comparing the in vivo solubility of permanent luting cements. The cements were carried in crypts placed in complete dentures. A vented cover allowed for free access of fluids. Nine cements were evaluated, and cement loss was measured at 6 months. The glass ionomer (at two powder-liquid ratios) and silicophosphate cements demonstrated an approximately equal amount of solubility, which was less than for the other cements tested. The results of this study are in fairly close agreement with two previously published studies on the clinical solubility of cements.

Acrylic Resins↗

PubMed1998

Characterization of the development of elasticity in dental luting cements.

OBJECTIVES: The development of elasticity of dental luting cements was investigated as an indicator of working and setting time. METHOD: A displacement rheometer was used to monitor the development of elasticity. Three luting cements were examined. RESULTS: The initial onset of elasticity in the glass-ionomer and polycarboxylate cements did approximate the manufacturer's quoted working times. The onset of elasticity did not appear to define a clinically useful working time for the zinc phosphate cement. CONCLUSIONS: The development of elasticity in luting cements as a measure of working time was not universally relevant. The demonstration of the presence of elasticity in some cements may have consequences for cementation and all ceramic crown systems.

Cementation↗

PubMed2004

An investigation of pH changes of various cements.

OBJECTIVE: In this study, the time-related pH changes that occur in cements having different structures were observed. METHOD AND MATERIALS: Eight cements consisting of four permanent and four temporary cements were used. The materials were prepared according to manufacturers' instructions. The materials were used in 0.100 +/- 0.02-g increments, with the purpose of standardizing the effect of massive differences. The 80 total specimens, including 10 from each cement type, were prepared, and the pH value of the distilled water was measured at 3,10,30,60, and 120 minutes, and then again 24 hours later. RESULTS: Analysis of variance showed the relation between the kind of cement and its pH change during the course of the study was statistically significant. CONCLUSION: Though temporary cements indicated neutral pH from the beginning of the study, the acidity of the other cements changed with time and took values approximate to neutral pH within 24 hours.

Dental Cements↗

PubMed1993

A new bioactive bone cement consisting of BIS-GMA resin and bioactive glass powder.

We have developed a bioactive bone cement consisting of silane-treated CaO-SiO 2-P 2O 5-CaF 2 glass powder as the filling particles and bisphenol-a-glycidyl methacrylate (BIS-GMA) diluted with triethylene-glycol dimethacrylate (TEGDMA) as the organic matrix. Histological examination demonstrated direct bonding between the cement and bone along the circumference of the cement at 4 weeks after implantation in rat tibia. The compressive strength and toughness of the cement were two and four times greater than those of polymethylmethacrylate (PMMA) cement, respectively. The inflammatory reaction of the skin caused by the new cement was not as intense as that for PMMA 3 days after subcutaneous implantation. This new cement may be applicable as a bioactive bone cement with high mechanical strength.

Animals↗

PubMed1976

Adhesion of polycarboxylate cements to dental casting alloys.

The adhesive strengths of four commercial polycarboxylate cements to five dental casting alloys were compared with the strength of a conventional zinc phosphate cement. The following results were obtained. (1) The polycarboxylate cements showed adhesion that was four to 12 times greater than that of the zinc phosphate cement to all alloys tested. (2) The adhesive strength of the polycarboxylate cements was greater to the chemically active substitute alloys, such as the copper, nickel-chromium, and silver-tin-zinc alloys. The adhesion of the polycarboxylate cements to the chemically stable gold and silver-palladium alloys was not as great, but was four to six times that of the zinc phosphate cement. (3) The difference in adhesive strength between the brands of polycarboxylate cement was generally slight or statistically insignificant.

Acrylates↗

PubMed1989

Effects of etching time on surface morphology and adhesion of a posterior resin to glass-ionomer cement.

This study examined the effects of etching time on surface morphology and adhesion of posterior composite resin to glass-ionomer cement. Three glass-ionomer cements and four etch times were studied. Bond shear strength results revealed significant differences by both cement and etch time. Glass-ionomer surfaces etched for 30 seconds produced the strongest bond to resin. Ketac-Silver cement provided greater shear resistance than either Ketac-Bond cement or GC lining cement. Scanning electron microscopy revealed greater surface roughness for etched versus unetched glass ionomer. However, no subsurface differences were noted with increased etch times. These findings indicate that 30 seconds is the optimal etch time for glass-ionomer cement and that Ketac-Silver cement provides the strongest bond to resin of any of the materials tested. Etched glass-ionomer subsurfaces did not reveal marked differentiation in morphology, suggesting that an alternative method is necessary to detect these differences.

Acid Etching, Dental↗

PubMed1992

Adhesive properties of modified glass-ionomer cements.

The incorporation of water-soluble polymers and/or vinyl monomers into glass-ionomer cements can yield toughened "hybrid cement-composites". This study compared a commercial water-hardening glass-ionomer cement and seven experimental hybrids in their bonding to both dentin and Silar composite. The cements were sanded and phosphoric-acid-etched or left with an unaltered matrix-formed surface when adhesion to composite was tested. The seven hybrids included: 15% 2-hydroxyethyl methacrylate (HEMA) with appropriate initiators/activators, 29% HEMA, 27% HEMA + 0.5% polyacrylic acid (PAA), 0.5% PAA, 1.5% PAA, 2.5% polyvinyl alcohol, and 2.5% gelatin. Acceptable bond strengths to applied composite and to dentin were observed for most of the modified hybrid cements. There were higher bond strengths with composite when the hybrids were left unetched. Bonding of some unetched, HEMA-containing cements achieved bond strengths (29% HEMA, 10.09 MPa) significantly higher than those of the unmodified cement (4.92 MPa). Resin-modified cements may promote better bonding by improved interaction and compatibility with the resin component of the composite.

Acid Etching, Dental↗

PubMed1993

Fluoride release from light-activated glass ionomer restorative cements.

Fluoride release from four light-activated glass ionomer cements, including newly developed restorative cements, was evaluated and compared with four conventional acid-base glass ionomer cements. There was no significant difference between the group of light-activated cements and the group of conventional cements, and light-activated cements were found to have a potential for releasing fluoride equivalent to that of conventional cements. The amount and rate of release varied among cements. It may be affected not only by the formation of complex fluoride compounds and their interaction with polyacrylic acid but also by the type and amount of resin used for the photochemical polymerization reaction.

Acrylic Resins↗

PubMed1991

Glass-ionomer cements in orthopaedic surgery: design of laboratory tests.

Recently, interest has been shown in the use of Glass-ionomer cement as a bone cement in orthopaedic surgery. This paper discusses the determination of working time, setting time and compressive strength for an experimental Glass-ionomer [GI] and the existing poly(methyl methacrylate) [PMMA] cement. Conventional test methods and some novel techniques are explored. Suggestions are made for new techniques which will allow the comparison of different types of cement. The effect of different storage media on cement stability has shown that both cements show a degree of instability dependent on the medium used. The properties reported for the GI cement suggest that it has the potential to be a new bone cement.

Bone Cements↗

PubMed2006

Microleakage of porcelain veneer restorations bonded to enamel and dentin with a new self-adhesive resin-based dental cement.

UNLABELLED: Cementation technique of bonded ceramic restorations is a time-consuming and technique-sensitive procedure critical to long-term success. OBJECTIVE: Evaluate the performance of a self-adhesive, modified-resin dental cement (Rely-X UniCem, 3M-ESPE) for the cementation of ceramic veneer restorations without previous conditioning of the tooth surface, and in combination with a one-bottle adhesive and a self-etching adhesive. METHODS: Thirty-six premolars received a veneer preparation that extended into dentin. Leucite-reinforced pressed glass ceramic (Empress 1) veneers were cemented following manufacturers' instructions, according to the following treatment groups (n=9): (1) Variolink-Excite Ivoclar-Vivadent (V+E control), (2) Unicem+Single Bond 3M-ESPE (U+SB), (3) Unicem+Adper Prompt L-Pop 3M-ESPE (U+AP), (4) Unicem 3M-ESPE (U). After 24h storage at 37 degrees C, teeth were thermocycled (2000 cycles) at 5 and 55 degrees C, immersed in ammoniacal silver nitrate for 24h, placed in a developer solution overnight and sectioned using a slow-speed saw. Three 1mm longitudinal sections were obtained from each tooth and evaluated for leakage with a microscope (1x to 4x). Imaging software was used to measure stain penetration along the dentin and enamel surfaces. RESULTS: ANOVA with SNK (alpha=0.05) revealed that on dentin, U had significantly less leakage than U+SB and U+AP, but no different than V+E; on enamel U had leakage values that were significantly greater than the groups with adhesives. SIGNIFICANCE: The self-adhesive cement U gave low leakage on dentin that was comparable to the cement that employed an adhesive for sealing dentin, whereas this cement benefits from use of an adhesive when cementing to enamel.

Acid Etching, Dental↗

PubMed2006

Osteochondral graft fixation using a bioresorbable bone cement.

Multiple osteochondral grafts can be used to resurface large joint defects in both humans and horses. In humans, immediate postoperative weight bearing can be prevented, however in the equine, it is unavoidable. Early weight bearing can create detrimental graft micromotion. The aim of this study was to investigate the role of a bioresorbable cement in improving the initial stability of multiple osteochondral graft repairs of large subchondral cystic lesions in the horse. Configurations employed for filling a 20mm diameter cylindrical defect included: (A) twelve 4.5mm diameter grafts with cement, (B) five 6.5mm diameter grafts with cement, (C) four each of 4.5mm and 6.5mm grafts with cement and (D) cement only. Intact bone slices (E) were also tested. Push-out tests were used to quantify construct to host sidewall interface fixation. Configuration (A) proved clinically impractical (n=3). Configurations (B) (n=6), and (C) (n=4) had statistically similar interface stiffnesses and failure stresses (43+/-8 and 30+/-12 MPa and 0.96+/-0.1 and 1.2+/-0.3 Mpa, respectively) suggesting that they are equally susceptible to interface movement in the immediate postoperative period. By way of comparison, defects filled only with cement had an average stiffness of 53+/-7MPa and failure stress of 1.8+/-0.3 MPa (n=6) while the intact femoral condyle demonstrated a stiffness of 108+/-7 MPa and failure stress of 18+/-0.4 MPa (n=6). Cement augmentation improved immediate postoperative stability of multiple osteochondral graft constructs over uncemented constructs, although in all cases the observed moduli of elasticity and yield stress values were lower than those observed for cement only and intact bone test specimens. (all numbers are mean+/-SEM).

Absorbable Implants↗

PubMed2004

Early cementing does not increase debond energy of grit blasted interfaces.

A fracture mechanics based approach was used to determine the debond energy or fracture toughness of the stem-cement interface for a variety of conditions. The goals of the study were to determine if early cementing of stems increased the debond energy of grit blasted stem-cement interfaces and if debond energy was dependent on mold type. Early (2 min) and late (6 min) times of cementation were considered for two different grit blasted surface finishes (16 and 60 grit, Ra=5.7 or 2.3 microm). Specimen fabrication was performed using a relatively simple, unconstrained rectangular mold and a mold that more closely simulated in vivo conditions. The rectangular mold was used with all components at room temperature whereas the in vivo simulated mold had a body that resembled the femoral canal in shape and was warmed to body temperature. Early cementing did not increase the debond energy using the in vivo simulated mold. Extensive porosity was found at the interface, and porosity had a strong negative effect on debond energy. When the simpler, rectangular mold was used, early cementing did result in higher debond energies, but few voids were found at the interface. It appears that porosity at the interface was the major factor affecting the debond energy. The results from this study do not support the concept that improved stem-cement interface strength can be obtained by application of the cement while it is in a low viscosity state.

Adhesiveness↗

PubMed2003

Comparative in vitro study on the long term performance of cemented hip stems: validation of a protocol to discriminate between "good" and "bad" designs.

The long-term clinical success of cemented hip stems is influenced both by the implant design, and by the surgical procedure. A methodology is proposed for discriminating between implant designs with different clinical outcomes. The protocol was designed with industrial pre-clinical validation in mind. Two cemented stem types were tested, one (Lubinus SPII) having good and the other (Müller Curved) having poor clinical outcomes. Three implants for each type were subjected to a mechanical in vitro test of one million loading cycles. Each cycle reproduced the load components of stair climbing. Interface shear micromotion was measured during the test in the direction of rotation and along the stem axis. The stem roughness before and after the test was compared. After the test, the cement mantles were retrieved and inspected through dye penetrants to detect evidences of micro-damage. For each specimen, the events of the loosening process were examined, based on the in vitro data available, so as to analyze the whole failure mechanism. The protocol developed was sensitive to the implant design, with significantly different results being found for the two stem types, both in terms of stem-cement micromotions, surface roughness alteration, and cement mantle damage. The information yielded by the three different investigation techniques was consistent for each of the two groups of specimens tested, allowing a better understanding of the failure process. In vitro inducible micromotion and permanent migration measurements, together with cement-stem interface fretting damage and cement fatigue damage, can help predicting the clinical performance of cemented stems.

Bone Cements↗