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PubMed1996

Intercalary replacement of canine femora using a new bioactive bone cement.

We have developed a bioactive bone cement (BA cement) consisting of Bis-GMA resin and bioactive glass powder. It has high compressive and tensile strengths, a low curing temperature and its bioactivity allows it to bond directly with bone. We operated on the 18 femora of nine mongrel dogs for intercalary replacement of part of the bone by a metal prosthesis using either PMMA cement or BA cement for fixation. Three dogs were killed at each of 4, 12 and 26 weeks after surgery for the evaluation of fixation strength by a push-out test and for histological examination by Giemsa surface staining and SEM. Fixation strengths with PMMA cement at 4, 12 and 26 weeks after surgery were 46.8 +/- 18.9, 50.0 +/- 24.7, and 58.2 +/- 28.9 kgf (mean +/-sD), respectively. Those with BA cement were 56.8 +/- 26.1, 67.2 +/- 19.2, and 72.8 +/- 22.2 kgf, respectively. Fibrous tissue intervened between bone and PMMA cement but BA cement had bonded directly to bone at 12 and 26 weeks. This suggests that BA cement will be useful in providing long-lasting fixation of implants to bone under weight-bearing conditions.

Animals↗
PubMed1996

[Mechanical properties of new low viscosity bone cements--can be improved by vacuum mixing].

With the objective of improving mechanical properties by using a new catalyst, a new bone cement (Sulfix-60) and a new low-viscosity cement with added gentamycin (Allofix-G) were developed. Dynamic weakness was the major disadvantage of the older Sulfix-6 cement, especially in comparison with high-viscosity bone cement. Although static strength could be improved, investigations into improved fatigue strength and the effect of vacuum-mixing on the static and fatigue strength had yet to be carried out. To investigate fatigue stability specimens of the new bone cements were tested using loads under wet conditions until breakage or 20 million cycles. In a first series the cement was hand-mixed in a second series vacuum-mixed alone, and in a third series vacuum-mixed under pressure. Additionally, the ultimate static bending strength was investigated using the standard four-point bending test for the three series of bone cement. Vacuum-mixing brought about an improvement in the dynamic strength of Sulfix-60 from 6.3 MPa, to 9.1 MPa and for Allofix-G from 6.3 MPa to 8.2 MPa; additional pressure brought no further improvement. A 200% increased fatigue stability was detectable in comparison with the older cement. The ultimate bending strength was also significantly improved by vacuum-mixing for both bone cements.

Biomechanical Phenomena↗
PubMed1996

Subsidence of THA stems due to acrylic cement creep is extremely sensitive to interface friction.

Acrylic cement, used to fixate total hip arthroplasty (THA), creeps under dynamic and static loading conditions. As a result, THA stems which are debonded from the cement, may gradually subside, depending on their shape and surface roughness. The purpose of this study was to evaluate the relationship among dynamic load, creep characteristics, interface friction, and subsidence patterns. A laboratory model consisting of a metal tapered cone, surrounded by a cement mantle, was developed. The cone was gradually compressed in the cement by a dynamic, sinusoidal axial force, cycling between 0 and 7 kN for 1.7 million cycles at a frequency of 1 Hz. Subsidence and cement strain were monitored. Two tapers were tested in this way. The relationships among subsidence, creep properties and interface friction were evaluated from a finite element (FE) model, used to simulate the experiments. In this model, the creep properties obtained in dynamic and static, tension and compression experiments measured earlier, were used. The subsidence patterns of both tapers were similar, but one subsided more than the other (380 vs 630 microns). Both subsided stepwise instead of continuous, with a frequency much smaller than that of the applied load. The characteristics of the subsidence and cement-strain patterns could be reproduced by the FE model, but not with great numerical precision. The stepwise subsidence could be explained by slip-stick mechanisms at the interface starting distally and gradually working towards proximal. Variations in friction from 0.25 to 0.50 reduced the total subsidence and the step frequency by about 50%. It was concluded that FE-models used to simulate the mechanical endurance characteristics of THA reconstructions, extended to incorporate cement creep, produce realistic results. These results showed that prosthetic subsidence under dynamic loads occurs due to cement creep. The extent of the subsidence is extremely sensitive to interface friction, hence to small variations in surface roughness and cement constitution. This may explain the relatively large variation of in vivo prosthetic subsidence rates reported in the literature.

Acrylic Resins↗
PubMed1996

Reinforcement of PMMA bone cement with a continuous wire coil--a 3D finite element study.

The changes in the mechanical response of a bone cement reinforcement, comprised of a continuous stainless steel coil imbedded within the PMMA bone cement matrix surrounding the distal tip of the total hip arthroplasty, was investigated. To achieve this, a 3D finite element model depicting two and one half rotations of the coil imbedded within the cement at the distal tip was constructed. Ideally, the wire coil should reduce the radial, and to a greater extent, the hoop stresses developing within the cement and at the cement-stem interface. As a means of comparison, a control model of only bone cement was also built. For the radial stresses, the control had about 4.5 times the compressive stress of the reinforced models (0.039 (+/-0.00065) MPa vs. 0.0087 (+/-0.0012) MPa) at the cement-stem interface. The tensile hoop stresses were also 4.5 times higher (4.272 (+/-0.0147) MPa and 0.95 (+/-0.0052) MPa) for the control than for the reinforced models. This indicates that the wire coil reinforcement is effective in reducing the cement mantle's radial and, more importantly, the hoop stresses which may lead to the failure of both the cement and the implant as a whole.

Bone Cements↗
PubMed1994

The effect of eugenol containing and non-eugenol temporary cements on the resin-enamel bond.

This study was undertaken to compare the effect of eugenol containing and non-eugenol temporary cements on the bond strength of three brands of luting cements to enamel. Flat enamel surfaces were prepared on 90 surgically removed, unerupted, human third molar teeth. The teeth were randomly divided into three groups of thirty. The flat enamel surfaces in two of the groups were treated with either a eugenol containing or non-eugenol temporary cement and the third group was left untreated. The teeth were stored in water for 7 days and the cements then removed and all surfaces etched. The teeth were divided into 9 sub-groups of 10 each and one of the three resin cements was then bonded to each sub-group. The relevant shear bond strengths were determined after 7 days. The results indicated that prior use of a eugenol containing temporary cement reduced the resin cement-enamel bond strengths. No differences were found between the bonds achieved by the three brands. It was concluded that eugenol containing temporary cements should not be used prior to bonding with resin luting cements.

Analysis of Variance↗
PubMed1990

[A technic for cementing orthodontic bands; SEM research on the enamel and filling damages and a protective wax technic to avoid them].

Damage of enamel and filling margins occurs during the removal of zinc phosphate cement with hooks and scalers after band cementation. This was revealed by scanning electron microscopy in different stages of the study in vitro and in vivo. When glass ionomer cement was used, and although the surplus cement was wiped off still being plastic, it could not be avoided that cement was wiped into the fissures and stuck to the slopes of the cusps. A protection of the occlusal surface with wax as described in this study is helpful for both using glass ionomer and zinc phosphate cement. Contamination of the occlusal surface with cement is avoided, and the isolating effect reduces the necessity to scratch off cement surplus.

Cementation↗
PubMed1984

Effect of the dentin smeared layer on tensile strength of cemented posts.

The tensile strengths for post lengths of 4 and 7 mm were compared in vitro with 3 different cementing media. In one group, the post preparation was rinsed with 5.25% NaOCl and in the other with 17% EDTA followed by 5.25% NaOCl. The EDTA-NaOCl flush had a profound effect when unfilled resin was used to cement the posts. A 4 mm post cemented with resin in the EDTA-NaOCl group was one and one-half times as retentive as a 7 mm post cemented with zinc phosphate and twice as strong as the 7 mm post with polycarboxylate cement. The 7 mm post cemented with the resin after the EDTA-NaOCl rinse was twice as resistant to displacement as the 7 mm post cemented with zinc phosphate and three times stronger than the polycarboxylate cement.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1992

Retentive properties of threaded split-shaft posts with titanium-reinforced composite cement.

The retention of posts in tooth roots is vital to the success of the restoration. This study compared the retention of posts of various sizes and diameters cemented with a titanium-reinforced composite cement with that of posts previously reported cemented with zinc phosphate cement. Four groups made up of 10 samples each were used and retention values were compared using a universal testing machine. Two-way analysis of variance and the Newman-Keuls multiple range comparison test were performed. Larger diameter posts cemented with titanium cement had better retention than similar posts cemented with zinc phosphate cement. The statistical increase in retention for the larger size posts is probably the result of the deeper channels (threads) in the dentin and the higher cohesive strength for the titanium-reinforced composite resin.

Composite Resins↗
PubMed1988

Glass ionomer cements in orthodontics--an update.

Because conventional bands continue to be used in clinical orthodontics, it is essential to evaluate new dental cements to establish their suitability as a cementing medium for orthodontic bands. This study was undertaken to determine the failure rate of bands cemented with a glass ionomer cement to premolar and molar teeth. The sample consisted of 100 consecutively completed cases. Stainless steel bands were cemented to premolar and molar teeth (799) with a glass ionomer cement (Ketac-Cem). The failure rate for the bands was 1.9%. This is significantly lower than the 5.1% recorded for bands cemented with a polycarboxylate cement reported in a previous study.

Child↗
PubMed2003

Fluoride release from orthodontic cements-effect of specimen surface area and depth.

OBJECTIVE: The aims of this in vitro study were firstly to compare fluoride release from a disc model of two orthodontic cements with various surfaces varnished, reducing the surface area by 25, 50 and 75%; secondly, to measure the fluoride release from previously exhausted discs of the same cements following removal of various depths of surface material. METHODS: Forty discs of each cement, Fuji Ortho LC and Ultra Band-Lok, (6mm diameter by 3mm) were divided into two groups of 20 discs each. For each material, the first group was divided further into four groups of five discs, one group acting as control, while the other three groups were varnished reducing the surface area by 25, 50 and 75%, respectively. The second group was exhausted initially over a 60 day pre-experimental period and was subsequently divided into four groups of five discs, one group acting as control. The other three groups had material ground from one of the flat surfaces, to depths of 10, 100 or 1000 microm, to reveal a fresh surface. In both studies, the discs were immersed either daily (up to day 20) or twice weekly (up to day 60) in fresh 2ml aliquots of deionised water. The fluoride concentration in the deionised water was measured at the end of the experimental period. RESULTS: For each cement, the relationship between the cumulative fluoride release and the percentage of the surface covered was clearly non linear at both 5 and 60 days. Fuji Ortho LC proved to release significantly greater amounts of fluoride at both 5 days and 60 days compared with Ultra Band-Lok. The results for Ultra Band-Lok were also significant when compared to the control group, but significantly less fluoride was released when compared with Fuji Ortho LC. When comparing the 25 and 50% covered discs, the amount of fluoride released was not significantly different for both cements. Furthermore, the relationship between fluoride release and depth was clearly non linear for both cements. CONCLUSIONS: For the materials tested in this study, reducing the surface area of the discs did not reduce the cumulative fluoride release in a linear fashion. In addition, the previously exhausted discs began to release fluoride again, but this fell to concentrations similar to the control discs after the initial 5-day period for both cements. This suggests that further traces of previously unreleased fluoride had become available from the subsurface of these cements. The pattern of fluoride release was similar for all models tested.

Acrylic Resins↗
PubMed1999

Laboratory evaluation of a compomer and a resin-modified glass ionomer cement for orthodontic bonding.

The mean shear debonding force of stainless steel orthodontic brackets with microetched bases bonded with either a compomer or a resin-modified glass ionomer cement was assessed. In addition, the amount of cement remaining on the enamel surface following bracket removal was evaluated. Finally, survival time of orthodontic brackets bonded with these materials was assessed following simulated mechanical stress in a ball mill. Debonding force and survival time data were compared with those obtained for brackets bonded with a chemically cured resin adhesive, a light-cured resin adhesive, and a conventional glass ionomer cement. There were no significant differences in mean shear debonding force of brackets bonded with the compomer, resin-modified glass ionomer, chemically cured resin adhesive, or the light-cured resin adhesive. Brackets bonded with a conventional glass ionomer cement had a significantly lower mean shear debonding force than that recorded for the other materials. The Adhesive Remnant Index (ARI) mode score indicated that significantly less cement remained on the enamel following debonding of brackets cemented with resin-modified or conventional glass ionomers compared with other adhesives. The median survival time for brackets cemented with the compomer, resin-modified glass ionomer, chemically cured resin, or light-cured resin were significantly longer than for brackets cemented with conventional glass ionomer. The compomer and the resin-modified glass ionomer adhesive appear to offer viable alternatives to the more commonly used resin adhesives for bracket bonding.

Acid Etching, Dental↗
PubMed2002

Fracture mechanics analysis of the dentine-luting cement interface.

The objectives of this study were to determine the fracture toughness of adhesive interfaces between dentine and clinically relevant, thin layers of dental luting cements. Cements tested included a conventional glass-ionomer, F (Fuji 1), a resin-modified glass-ionomer, FP (Fuji Plus) and a compomer cement, D (DyractCem). Ten miniature short-bar chevron notch specimens were manufactured for each cement, each comprising a 40 microm thick chevron of lute, between two 1.5 mm thick blocks of bovine dentine, encased in resin composite. The interfacial K(IC) results (MN/m3/2) were median (range): F; 0.152 (0.14-0.16), FP; 0.306 (0.27-0.37), D; 0.351 (0.31-0.37). Non-parametric statistical analysis showed that the fracture toughness of F was significantly lower (p <0.05) than those of FP or D, and all were significantly lower than values for monolithic cement specimens. Scanning electron microscopy of the specimens suggested crack propagation along the interface. However, energy dispersive X-ray analysis indicated that failure was cohesive within the cement. It is concluded that the fracture toughness of luting cement was lowered by cement-dentine interactions.

Animals↗
PubMedDate not supplied

Fracture resistance and marginal adaptation of conventionally cemented fiber-reinforced composite three-unit FPDs.

PURPOSE: This in vitro study investigated the marginal adaptation and fracture resistance of three-unit fiber-reinforced composite fixed partial dentures (FPD) luted with two different resin-modified glass-ionomers. MATERIALS AND METHODS: A total of 48 FPDs were constructed from the glass fiber-reinforced materials FibreKor/Sculpture, Vectris/Targis, or the polyethylene fiber system BelleGlass/Connect (n = 16 for each brand). The reconstructions were conventionally luted on human molars using resin-modified ProTecCEM or Fuji Plus and then exposed to thermocycling and mechanical loading. RESULTS: During thermocycling and mechanical loading, cementation failed in seven of eight FibreKor or BelleGlass FPDs and in one of eight Vectris/Targis FPDs luted with ProTecCEM. All Fuji Plus-cemented FPDs showed no signs of damage or cementation loss. The fracture resistance of the remaining FPDs was as follows: Vectris/Targis-ProTecCem 1,361 +/- 360 N, Vectis/Targis-Fuji Plus 923 +/- 207 N, BelleGlass/Connect 940 +/- 155 N, and FibreKor/Sculpture 524 +/- 202 N. The marginal adaptation of the cement-tooth interface deteriorated by 13% to 21% for all reconstructions after stress application, which was not statistically significant. The crown-cement interface had a significantly greater marginal gap only with the combination of FibreKor and Fuji Plus after stress simulation (change 33%). CONCLUSION: Conventional cementation of fiber-reinforced FPDs can lead to cementation loss. The marginal adaptation and fracture resistance deteriorated in comparison to adhesively cemented reconstructions.

Cementation↗
PubMed2005

Monkey pulpal response to an MMA-based resin cement as adhesive luting for indirect restorations.

PURPOSE: The objective of this study was to evaluate the pulpal response to a newly-developed MMA resin cement (MultiBond, Tokuyama) when used for adhesively luting composite resin inlays. MATERIALS AND METHODS: Cervical cavities were prepared in monkey teeth. The teeth were randomly divided into 3 groups. In the experimental group, a self-etching primer and a resin cement were applied to the cavities, and then hybrid composite inlays (Estenia, Kuraray) were inserted using freshly mixed resin cement. In the other groups, a zinc oxide/eugenol cement (Eugedain, Showa Yakuhin Kakou) or a glass-ionomer cement (Fuji II, GC) was used to fill the cavity. The teeth were then extracted after 3, 30, and 90 days, fixed in 10% buffered formalin solution, and prepared using routine histological techniques. Five-mum-thick sections were stained with hematoxylin and eosin, or Brown & Brenn gram stain for bacterial observation. Histopathological reactions in the pulp tissue and bacterial penetration along the cavity walls were assessed using a standardized score. RESULTS: No serious inflammatory reactions in the pulp, such as necrosis or abscess formation, were observed in any of the experimental periods, except for 1 case after 30 days, in which a pulpal exposure was suspected. Disarrangement of the odontoblast layer and deposition of reparative dentin were the major reactions observed in this specimen. No bacterial penetration along the cavity walls was detected. The monkey pulpal response and in vivo sealing ability of the MMA resin cement in combination with the self-etching primer was considered as good as that of the glass-ionomer cement. CONCLUSION: The new MMA resin cement showed acceptable biological compatibility to the monkey pulp when used to adhesively lute composite resin inlays.

Acrylic Resins↗
PubMed2006

Fracture resistance of teeth restored with 2 different post-and-core designs fixed with 2 different luting cements: an in vitro study. Part II.

OBJECTIVE: The purpose of this in vitro study was to investigate fracture resistance in teeth restored with cast posts and cores with and without ferrule and using 2 different luting cements. METHOD AND MATERIALS: Forty intact extracted maxillary premolars were endodontically treated after their crowns were removed 2 mm from the cementoenamel junction. Specimens were embedded in acrylic resin blocks, in aluminum cylinders, 2.00 mm apical to the cementoenamel junction. Twenty specimens were ferruled. Within this group, half of the posts and cores were cemented with zinc phosphate cement, while the other half were cemented with resin cement. The same procedures were followed for the nonferruled group. The posts and cores were cast in gold alloy. Specimens were placed in a universal testing machine, and loads were applied at an angle of 45 degrees and a rate of 1 mm/min until the teeth fractured. Analysis of variance and Tukey tests were used for statistical analysis; level of significance was established at 5%. RESULTS: There was no association between type of cement and cervical ferrule; ferruled specimens showed greater resistance than nonferruled ones, regardless of the cement used. CONCLUSION: A 2-mm cervical ferrule improves fracture resistance of restored teeth, but the type of luting cement used does not seem to affect resistance.

Analysis of Variance↗
PubMed1991

Luting cements: a review and comparison.

The paper discusses strength, retention, film thickness, working time, solubility, early sensitivity to water, biocompatibility and handling properties of zinc phosphate, polycarboxylate and glass ionomer cements. Zinc phosphate cement has acceptable strength, working time and biological properties. It is easy to handle, even when mixing large quantities. Polycarboxylate cement has less strength, different flow properties and a shorter working time, but excellent biocompatibility. The polycarboxylate cement is an alternative where pulp reactions are expected to occur and the load on the restoration during mastication is limited. Glass ionomer cement has the highest strength and retentive properties and a low solubility. It is difficult to spatulate, the working time is short, and contact with water during setting is critical for the quality of the surface layer of the material. The biological properties of glass ionomer cements are similar to those of zinc phosphate cements. It is an alternative to zinc phosphate cement where normal retention is impossible to obtain.

Glass Ionomer Cements↗
PubMed1995

Wear resistance of resin cements.

PURPOSE: To evaluate the in vitro wear resistance of four resin cements and a glass ionomer cement using a three-body wear test. MATERIALS AND METHODS: Each cement was evaluated as a direct restorative material as well as in conjunction with an inlay. All restorations were placed into cylindrical shaped cavity preparations generated on the flattened occlusal surface of human extracted molars. The bulk wear resistance of a cement was determined when tested as a direct restorative material. RESULTS: The wear resistance of all cements was greater when tested in conjunction with a resin composite inlay restoration. Although wear of a cement is dependent upon the method of testing, it was greater when combined with a less wear resistant resin composite inlay material. All of the cement materials used in this study exhibited less wear resistance than the resin composite inlays with which they were used. This in vitro wear testing system can be used as a screening test for the cement materials before a clinical study.

Analysis of Variance↗
PubMed1996

A sticky problem: the Xenopus cement gland as a paradigm for anteroposterior patterning.

The cement gland is a mucus-secreting organ found at the extreme anterior of frog embryos. It attaches the embryo to a solid support before swimming and feeding begin, and also serves a related sensory function that stops the embryo from moving once it is attached. Cement gland is an extremely useful anterior marker, whose study continues to yield fundamental information concerning vertebrate axial patterning. Cement gland arises from the outer layer of the embryonic ectoderm and, in Xenopus, forms a cone of columnar epithelium. It is the first ectodermal organ to differentiate, beginning to do so by late gastrula. A battery of genes expressed in the developing and mature cement gland serve as useful markers. Cement gland development can be influenced by both stimulatory and inhibitory cell interactions. Stimulatory signals arise from the anterior neural plate, head endoderm, and the dorsal mesoderm. Inhibitory signals are present in the posterior dorsal mesoderm and in ventral ectoderm and mesoderm. Further, signalling between the ectodermal layers may restrict cement gland differentiation to the outer ectodermal cells. Several secreted molecules are able to induce or repress cement gland formation: these include noggin, follistatin, hedgehog, chordin, retinoic acid, embryonic fibroblast growth factor (eFGF), Bone Morphogenetic Protein-4 (BMP-4), and Xwnt-8. Several of these factors alter expression of the homeodomain gene Xotx2, which may be a transcriptional activator of cement gland differentiation genes. The significance of the cell interactions and factors described in positioning cement gland at the front of the embryo is explored.

Animals↗