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Residual stresses at the stem-cement interface of an idealized cemented hip stem.

During the operation of total hip arthroplasty, when the cement polymerizes between the stem implant and the bone, residual stresses are generated in the cement. The purpose of this study was to determine whether including residual stresses at the stem-cement interface of cemented hip implants affected the cement stress distributions due to externally applied loads. An idealized cemented hip implant subjected to bending was numerically investigated for an early post-operative situation. The finite element analysis was three-dimensional and used non-linear contact elements to represent the debonded stem-cement interface. The results showed that the inclusion of the residual stresses at the interface had up to a 4-fold increase in the von Mises cement stresses compared to the case without residual stresses.

Bone Cements↗

Comparative laboratory investigation of dual-cured vs. conventional glass ionomer cements for band cementation.

This laboratory study compared the mean tensile bond strength, mode of band failure, and survival time of orthodontic bands cemented with dual-cured cement or conventional glass ionomer cement. Survival time was assessed following application of mechanical stress in a ball mill. Mean tensile bond strength was significantly higher for bands cemented with the dual-cured cement (p < 0.01), and mean survival time was significantly greater. Bands cemented with glass ionomer failed mainly at the cement/band interface. The results suggest that dual-cured cement is superior to glass ionomer for band cementation.

Chi-Square Distribution↗

The effect of different cement insertion techniques on the bone-cement interface.

Since the introduction of cemented total hip arthroplasty, the method of cement usage has evolved through several generations. These changes may have been responsible for an improvement in femoral component longevity. The nature of the bone-cement interface in first-generation cementing techniques has been described, but the bone-cement interface in more recent cementing techniques has not. This article describes the bone-cement interface after 2 different cementing techniques in a canine total hip arthroplasty model.

Animals↗

The effective minimum cement thickness of zinc phosphate cement for luted non-precious crowns.

Non-precious metal crowns were prepared for natural teeth which were ground to a taper angle of 5 degrees. The movement of the crowns on teeth during repeated try-on seating was measured with a micrometer. Increasing the applied load from 2 to 10 kg resulted in an average crown movement of 63 micron. For most samples this movement continued when try-on was repeated. Casting irregularities were found to create furrows on some regions of the axial tooth surface during try-on seating. The diameter of the ADA specification consistency disk for zinc phosphate cement was found to depend strongly on the P:L ratio and the ambient temperature. The castings were cemented with zinc phosphate cement of controlled consistency. Cementation with a load of 10 kg gave rise to an average crown elevation of 54 micron and a range of measurements between -8 and 113 micron. The effective minimum cement thickness corresponding to this average was calculated to be 4.7 micron. Small negative values of elevation were attributed to deepening of tooth furrows during cementation. An analysis is given of data from the literature, relevant to the cement flow and irregularities in cement thickness.

Cementation↗

Improvement in the tensile bond strength between resin cement and dentin surfaces after temporary cement application.

PURPOSE: The aim of this study was to evaluate the efficacy of three tooth conditioners in restoring the reduced bond strength between resin cement and teeth resulting from remaining temporary cement. MATERIALS AND METHODS: Ethyl dihydrogen phosphate, methacryloxyethyl dihydrogen phosphate, and 2-methacryloxyethyl hydrogen maleate were evaluated as conditioners. After eliminating the temporary cement with a curette from the bovine dentin surface, the conditioners were applied onto the surface of the specimen and a resin cement was adhered. Stepwise scanning electron microscopic observation and tensile bond strength measurement were carried out. RESULTS: Granular substances were present on the dentin surface even when the temporary cement was carefully eliminated with a curette. When primer and resin cement were applied on this surface without conditioner application, no resin tag or hybrid layer was observed and the mean bonding strength between tooth and adhesive resin cement was 1.8 MPa. In contrast, resin tag and hybrid layer were observed after primer and resin cement application when the dentinal surface was treated with conditioner. Mean tensile bone strength values increased to 6.2 MPa for specimens treated with 20% methacryloxyethyl dihydrogen phosphate for 60 seconds. CONCLUSION: The authors recommend methacryloxyethyl dihydrogen phosphate as it provides high tensile bond strength values and requires no additional rinse step.

Analysis of Variance↗

Bond strength of permanent cements in cementing cast to crown different core build-up materials.

The purpose of this laboratory investigation was to evaluate the bond strength of permanent cement (Duo-cement Kit, Meron, Durelon) to commonly used core build-up materials (President, Dyract AP, Ionofil, Vitremer). Sixty specimens (five of each product) were fabricated as a canine core build- up. Full crown castings were made to fit each core specimen. Full crown castings were cemented to core samples and stored at 37 degrees C and 100% humidity for 10 days. After storage, the bond strength was measured with a Haunsfield tensometer in tensile mode at a crosshead speed of 5 mm/min. Statistical evaluation was performed with univariate analysis of variance (P<0.001). The cement types affected the bond strength of full crown castings to core materials (F: 14.80; P<0.001). The interaction between the cement and core materials was significant (F: 3.69; P<0.01). According to the Duncan's test it was found that the values of Duo-cement were statistically different from the other cements.

Analysis of Variance↗

Repair of segmental bone defects using bioactive bone cement: comparison with PMMA bone cement.

We developed a bioactive bone cement (BABC) that consists of apatite and wollastonite containing glass ceramic (AW-GC) powder and bisphenol-A-glycidyl dimethacrylate (Bis-GMA) based resin. In the present study, the effectiveness of the BABC for repair of segmental bone defects under load-bearing conditions was examined using a rabbit tibia model. Polymethylmethacrylate (PMMA) bone cement was used as a control. A 15-mm length of bone was resected from the middle of the shaft of the tibia, and the tibia was fixed by two Kirschner wires. The defects were replaced by cement. Each cement was used in 12 rabbits; six rabbits were sacrificed at 12 and 25 weeks after surgery, and the tibia containing the bone cement was excised and tension tested. At both the intervals studied, the failure loads of the BABC were significantly higher than those of the PMMA cement. The BABC was in direct contact with bone, whereas soft tissue was observed between the cement and bone in all PMMA cement specimens. Results indicated that the BABC was useful as a bone substitute under load-bearing conditions.

Animals↗

Cemented titanium stems show high migration: transprosthetic drainage system has no advantage over third-generation cementation technique.

INTRODUCTION: A newly developed cemented titanium stem with excellent laboratory results using a transprosthetic drainage system (TDS) was clinically tried for the first time. Prognostic radiographic methods including migration measurement and clinical investigation were performed for up to 7 years. MATERIALS AND METHODS: Twenty-two patients prospectively and consecutively received total hip replacement using a cemented titanium stem and a threaded Zweymüller cup. Ten stems (CPS) were cemented conventionally with a third-generation cementation technique. In 12 stems (TRIOS) a TDS was used to enhance cement mantle quality. Design of cup and stem was similar in all cases. RESULTS: More than 50% of all stems showed considerable subsidence (>1 mm at 2 years and >2.5 mm at 5 years) and progressive radiolucent lines ( >1 mm at 2 years). Two patients of the TRIOS group had to be revised at 7 years postoperatively. No significant differences were found in radiological parameters (migration, stem subsidence, tilting, occurrence of radiolucent lines) and clinical outcome between the two cementation techniques. All parameters indicate an unfavourable long-term survival. Use of a TDS did not show any significant advantages over the conventional cementation technique. CONCLUSION: It can be concluded that cementing titanium stems of this design cannot be recommended.

Aged↗

The glass polyphosphonate cement: a novel glass-ionomer cement based on poly(vinyl phosphonic acid).

This paper outlines research which aimed to develop a new type of Glass-ionomer cement, the glass polyphosphonate cement. The glass polyalkenoate cement, a form of Glass-ionomer cement, is now widely used in dentistry and is based on the reaction between an ion-leachable aluminosilicate glass and an aqueous solution of poly(acrylic acid) or its copolymers. The new cements described in this paper employ a novel polymer, poly(vinyl phosphonic acid), PVPA, as the acidic component. This is a much stronger acid than those used in the glass polyalkenoate cement, and various means must be employed to moderate the reaction in order to obtain a viable cement. These cements show a number of important differences in performance in comparison with PAA-based systems and these differences are discussed in the paper.

Fluorocarbon Polymers↗

Four-angle radiographic assessment of cement mantle thickness in cemented total hip arthroplasty.

In this study, the cement mantle thickness of 57 hips undergoing primary cemented total hip arthroplasty (THA) were investigated with 4 angle radiographs. All surgeries were performed with a standardized posterolateral surgical approach. In addition to conventional anteroposterior and lateral radiographs, obturator oblique and iliac oblique radiographs were taken. In the evaluation of the cementing grade on the anteroposterior radiograph, the incidence of hips with thin cement mantles was 25%. In evaluating the cementing grade on the anteroposterior and lateral radiographs, we found an incidence of hips with thin cement mantles of 37%. From the evaluations with 4 angle radiographs, 10 hips were additionally assigned as being of a poor cementing grade (Mulroy's grade C-2). Thin cement mantles were mainly seen on the iliac oblique radiographs.

Adult↗

Effects of distal cement voids on cement stress in total hip arthroplasty.

The purpose of this study was to determine whether voids in the distal cement mantle created during total hip arthroplasty increase cement stress at the distal tip of the femoral component. Using a three-dimensional finite element model of an idealized, cylindrical femoral shaft with implanted prosthesis, peak von Mises stress in the cement mantle was evaluated for five different air-bubble configurations and two cement mantle thicknesses, 2 mm and 5 mm. Results indicated that voids in the cement mantle increased peak cement stress at the medial tip of the prosthesis by 2% to 57%, with greater increases in stress being evident with larger bubble sizes. On the average, peak stresses were 53% greater in the models with the thinner cement mantle. Clinicians are encouraged to use a thicker cement mantle and to avoid bubble formation during total hip arthroplasty.

Arthroplasty, Replacement, Knee↗

Liquid gentamicin in bone cement: a laboratory study of a potentially more cost-effective cement spacer.

BACKGROUND: Liquid gentamicin is approved by the Food and Drug Administration, is readily available, and is much less costly than tobramycin, the more commonly used antibiotic in cement spacers. The purpose of the present study was to test the mechanical properties, elution characteristics, and antibacterial activity of liquid gentamicin in an acrylic bone cement spacer. METHODS: Standardized specimens consisting of Palacos cement combined with liquid gentamicin, powdered tobramycin, or no antibiotic were fashioned, and the three groups were tested with regard to compressive and tensile strength, elution characteristics (with use of radioimmunoassays), and antibacterial activity (with use of bioassays). RESULTS: The ultimate compression strength decreased by 49% (from 64.65 +/- 3.89 MPa to 32.96 +/- 3.33 MPa) and the ultimate tension strength decreased by 46% (from 35.85 +/- 2.97 MPa to 19.20 +/- 0.36 MPa) when the specimens containing 480 mg of liquid gentamicin were compared with the controls. The addition of tobramycin had no significant effect compared with the controls. The majority of gentamicin was released from the cement during the initial twenty-four hours (mean concentration, 26.4 mcg/mL). The mean concentrations at three and six weeks were 4.15 and 0.65 mcg/mL, respectively. The bioassays confirmed the bactericidal activity of the gentamicin released from the cement. CONCLUSIONS: Liquid gentamicin in bone cement is potent and bactericidal. Although the mechanical properties of the cement are significantly diminished by the addition of liquid gentamicin, the temporary nature of the cement spacer makes its use potentially worthwhile given the substantial cost savings to the hospital and the patient.

Anti-Bacterial Agents↗

Cardiopulmonary function and pulmonary microemboli during arthroplasty using cemented or non-cemented components. The role of intramedullary pressure.

An experimental model was designed to investigate the role of intramedullary pressure on cardiopulmonary function and pulmonary pathology during arthroplasty using cemented and non-cemented components. Twenty-four dogs were divided randomly into three groups: a group that received a non-cemented implant in which low intramedullary pressure was generated, a group that received a cemented implant, and one that received bone wax and an implant; high intramedullary pressures were generated in the latter two groups. Bone wax was used to generate high intramedullary pressures without the use of bone cement. In the group with the non-cemented implant, few pulmonary microemboli and no significant cardiorespiratory changes were found. In the groups that received bone wax and an implant or the cemented implant, there were many pulmonary microemboli and significant cardiorespiratory changes, including decreased arterial oxygen tension, increased pulmonary arterial pressure, and increased intrapulmonary shunt fraction. There was no evidence that methylmethacrylate monomer was responsible for the cardiorespiratory changes in the group with the cemented implant.

Animals↗

Movement of resin cement components through acid-treated dentin during crown cementation in vitro.

This study examined the hypothesis that components of crown cements may be forced through acid-treated dentin during cementation. Freshly extracted, human third molar teeth were prepared to accept full crowns. Roots were removed to allow irrigation of the pulp chamber with saline before, during, and after crown placement with resin dentin bond and resin composite cement. Saline samples were collected and analyzed by high performance liquid chromatography to identify and quantify resin components arriving in the pulp space. Two components of the bond-cement system used were identified in the pulp space samples immediately after crown cementation. These were 2-hydroxyethylmethacrylate and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane. The amounts of these components in the pulp space decreased when the bonding agent was cured prior to crown placement. The results of this study supported the hypothesis that crown cementing components may flow through acid-treated dentin during crown cementation.

Adolescent↗

In vitro study of endodontic post cementation protocols that use resin cements.

STATEMENT OF PROBLEM: Sodium hypochlorite (NaOCl) may alter resin bond strength by deproteination of demineralized dentin collagen. PURPOSE: To analyze the effect of NaOCl treatment on bond adhesion and tensile strength of different post cementation protocols in vitro. MATERIAL AND METHODS: The periconductual dentin of 120 single-rooted, caries-free, unrestored human teeth was etched with 37% orthophosphoric acid. The teeth in Group I (60) were left untreated, and the teeth in Group II (60) were treated with 10% NaOCl. Four post-cementation protocols were examined (15 teeth in each) for Groups I and II: ED Primer dentin adhesive + Panavia 21 Ex; ED Primer dentin adhesive + Dual Cement; Panavia 21 Ex; and Dual Cement. For each condition, resin tags, hybrid layers over the periconductual dentin and post surface, were analyzed by scanning electron microscopy (SEM). Specimens were loaded with a uniaxial tensile force using an electromechanical testing machine until cement failure. Bond adhesion and tensile strength with different protocols were examined statistically using multiple analysis of variance at a significance level of alpha<.05. RESULTS: SEM revealed morphologic differences; Group II exhibited cylindrical, solid tags and Group I, tapered, hollow tags. Uniaxial tensile strength tests showed that in Group I, Panavia 21 Ex cement was strongest, whereas in Group II, this protocol was the weakest and Dual Cement with adhesive was the strongest. In Group II, Panavia 21 Ex diminished the tensile bond strength; however, combination with dentin adhesive increased it. CONCLUSION: Within the limitations of this study, NaOCl treatment did not significantly alter tensile bond strength, but when combined with the dentin adhesive ED Primer, a significant rise in strength resulted. A positive relationship existed between increased tag numbers and higher tensile bond strength.

Adhesiveness↗

A comparison between zinc polycarboxylate and glass ionomer cement in the orthodontic band cementation.

Fixed orthodontic appliances have been held responsible for demineralization and caries since the time they were first introduced. Zinc polycarboxylate and glass ionomer cements are the primary materials used in band cementing. In this study, we evaluated the re-cementing frequencies, enamel demineralization and the degree of cement remains of the bands cemented with glass ionomer and zinc polycarboxylate cements. We have concluded that given the retentive properties and enamel decalcification degree, the glass ionomer cements are to be preferred by the orthodontist.

Cementation↗

Three-year comparison of fired ceramic inlays cemented with composite resin or glass ionomer cement.

Ceramic inlays offer a good alternative to posterior composites, which still show a high polymerization shrinkage. The thin cement layer will reduce the total amount of shrinkage and probably result in a better marginal adaptation and decreased marginal leakage. Fired feldspathic ceramic inlays cemented with either a glass ionomer cement or a dual-cured composite resin luting cement were compared intraindividually. During a 3-year period 118 inlays, 59 in each group, were examined. Eleven inlays were evaluated as non-acceptable during the period: two (3.4%) in the composite resin group and nine (15.3%) in the glass ionomer cement group. In the composite group one inlay fractured partially and one inlay was replaced because of postoperative sensitivity. In the glass ionomer group four inlays were totally lost, and partial fractures occurred in five inlays. In the fractured glass ionomer cemented inlays the cement was still in place in the cavities. Eight patients reported post-operative sensitivity. No secondary caries was detected around the inlays even though 46% of the patients were considered high caries risk patients.

Adult↗

[Does temporary cementing have an effect on the bond strength of definitively cemented crowns?].

To establish whether or not temporary cementing with zinc oxide-eugenol (ZOE) cement affects the bond strength of the subsequent zinc phosphate cement, 60 standardized metal blocks with cylindrical drill holes were produced. 50 specimens were coated with ZOE cement and subjected to different cleansing techniques (mechanical, with alcohol or organic solvent, soap, Al2O3) in groups of ten. After examination of the cleansed surfaces under the light microscope, amalgam cylinders manufactured according to a standardized procedure were cemented into the cavities using zinc phosphate cement and pressed out. Only the Al2O3 jet-cleaned surfaces were free of ZOE cement residues. With high statistical significance the knock-through test revealed lower bonding strength values for the specimens cleaned either with alcohol or organic solvents.

Aluminum Oxide↗