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PubMed2001

Effects of ceramic component on cephalexin release from bioactive bone cement consisting of Bis-GMA/TEGDMA resin and bioactive glass ceramics.

The purpose of this study was to elucidate the effect of amount of ceramic cement powder on drug release from bioactive bone cement. The associated bone-bonding strength was also investigated. The bioactive bone cement under investigation consisted of bisphenol-alpha-glycidyl methacrylate (Bis-GMA), triethylene-glycol dimethacrylate (TEGDMA) resin and a combination of apatite- and wollastonite-containing glass-ceramic (A-W GC) powder. A-W GC powder (50%, 70% and 80% w/w) containing 5% cephalexin (CEX) powder hardened within 5 min after mixing with Bis-GMA/TEGDMA resin. The compressive strength of the cement with or without drug increased with increasing the amount of ceramic powder. The compressive strength of the 80% ceramic cement without the incorporation of cephalexin was 194 MPa. This compressive strength was about 3 times higher than that for polymethylmethacrylate cement. After the cement was implanted in the proximal metaphysis of the tibiae of male rabbits, the failure load for the cement was found to increase with increasing of the amount of ceramic powder. This finding suggested that the cement formed a bonding with bone. In vitro CEX release from bioactive bone cement pellets in a simulated body fluid at pH 7.25 and 37 degrees C continued for more than 2 weeks. Drug release profile followed the Higuchi equation initially, but not at later stages. The drug release rate increased with increasing amount of ceramic powder in the mixture. Since the pore volume of the cement increased with increasing of amount of ceramic powder, the drug diffused in the pores between the ceramics particle and polymer matrix. As hydroxyapatite precipitated on the cement surface, the drug release rate decreased, as observed at the later release stage. These results suggest that varying the amount of ceramic powder in the cement system could control the drug release rate from bioactive bone cement.

Absorbable Implants↗
PubMed2006

Bonding of dual-curing resin cements to dentin.

PURPOSE: The purpose of the study was three-fold: 1) to determine the strength of the bond between a number of dual-curing resin cements and dentin treated with corresponding adhesive systems, 2) to determine the effect on bond strength of not light curing the cements, and 3) to investigate whether application of a solution of sodium sulfinate or ascorbic acid would increase the bond strength in the cases where the manufacturer's version of an adhesive system resulted in low bond strength with chemically cured cement, ie, cement cured without light. MATERIALS AND METHODS: The adhesive systems comprised 5 simplified systems (Adper Scotchbond 1 XT, ED Primer II, Excite DSC, OptiBond Solo Plus, and Prime and Bond NT), and as controls, two three-step etch and rinse systems (Adper Scotchbond Multi-Purpose Plus and Gluma Solid Bond). The corresponding dual-curing resin cements were RelyX ARC, Panavia F 2.0, Variolink II, Nexus 2, Calibra, RelyX ARC, and 2Bond2. The cements were either light and chemically cured or only chemically cured. The adhesive systems were used as recommended by the manufacturers, which for some systems involved inclusion of a so-called activator or catalyst when used with chemically cured cement. Sodium sulfinate and ascorbic acid were applied as a 1% ethanol solution. The bond strengths were measured in shear after storing specimens for 24 h in 37 degree C water. RESULTS: When the dual-curing resin cements had been both light and chemically cured, the bond strengths increased in this order: Gluma Solid Bond < ED Primer II < Prime and Bond NT < Adper Scotchbond Multi-Purpose Plus < Excite DSC < Adper Scotchbond 1 XT < OptiBond Solo Plus. Omission of light curing of the cements decreased the bond strengths with OptiBond Solo Plus and Prime and Bond NT. The use of activator in conjunction with OptiBond Solo Plus and Prime and Bond NT increased the bond strength to chemically cured cement, but not to the level obtained when the cement was both light and chemically cured. The use of the catalyst of Adper Scotchbond Multi-Purpose Plus did not increase the bond strength with chemically cured cement. Pretreatment with a solution of sodium sulfinate or ascorbic acid increased the bond strength with chemically cured cement in the case of OptiBond Solo Plus, whereas only the solution of sodium sulfinate was effective with Prime and Bond NT. CONCLUSION: Clinicians should be aware that in situations where a dual-curing resin cement cannot be light cured, some adhesive systems suffer a loss of efficacy, even when respective activators are used. Pretreatment with a 1% ethanol solution of sodium sulfinate may restore much of the lost bond strength.

Ascorbic Acid↗
PubMed1990

Survival of crowns and bridges related to luting cements.

The longevity of 782 items of crown and bridgework was investigated in a retrospective study. The effect of different cement lutes was assessed for periods varying from 70 to 89 months using a survival analysis technique. The analysis of all types of restoration showed slightly better survival figures for restorations cemented with polycarboxylate but were not statistically significant when compared with those cemented with glass-ionomer. However, those cemented with polycarboxylate were significantly more successful than zinc phosphate. The restorations cemented with glass-ionomer showed no statistically significant improvement in survival rate compared with those cemented with zinc phosphate. Restorations cemented with zinc/oxide eugenol reinforced EBA cement had the lowest survival rate of the four cement types. Analysis of the survival of crowns alone showed the same ranking of the cements compared with all restorations. Comparison of bridges, ranked those cemented with glass-ionomer above those cemented with polycarboxylate, but not statistically different. Posts cemented with phosphate were ranked first and lasted significantly longer than those cemented with glass-ionomer.

Crowns↗
PubMed1992

Retentive strength, disintegration, and marginal quality of luting cements.

This study evaluated the retention of complete crowns by using five different methods of cementation. Complete crowns were prepared with standardized dimensions on extracted human molars. Metal crowns were cast with a high noble gold ceramic alloy and were cemented with zinc phosphate cement, glass ionomer cement, composite resin cement, composite resin cement with a dentinal bonding agent, and adhesive resin cement. The retention was measured by subjecting the specimens to tensile load until fracture occurred. The disintegration was measured according to American Dental Association Specification No. 8, and the condition of the cements at the margins of crowns was analyzed by use of a scanning electron microscope. Kruskal-Wallis one-way analysis of variance revealed statistically significant differences between the mean retentive strengths. The retention of the zinc phosphate and the glass ionomer groups was significantly different from that of the adhesive resin group. The retention of the adhesive resin cement was 65% greater than the retention of the composite resin and the composite resin/dentinal bonding agent group, but the Mann-Whitney Wilcoxon rank sum test did not depict this difference as significant. The mean +/- SD of the disintegration for the zinc phosphate, the glass ionomer cement, and the composite resin cement was 0.025 +/- 0.013, 0.023 +/- 0.011, and 0.017 +/- 0.001, respectively. The scanning electron microscope analysis of the margins revealed that the composite resin cement was almost intact, the zinc phosphate was subjected to limited disintegration, and the glass ionomer displayed the worst marginal integrity.

Adhesives↗
PubMedDate not supplied

Mechanical properties of luting cements after water storage.

This study determined the effect of water storage on flexural strength (FS) and compressive strength (CS) of 12 luting cements from different material classes. In addition, the influence of the curing method on the mechanical properties was investigated. The materials examined were two zinc phosphate cements (Harvard cement and Fleck's zinc cement), two glass ionomer cements (Fuji I and Ketac-Cem), three resin-modified glass ionomer cements (Fuji Plus, Fuji Cem and RelyX Luting), four resin cements (RelyX ARC, Panavia F, Variolink II and Compolute) and one self-adhesive universal resin cement (RelyX Unicem). The samples were prepared and tested according to ISO specifications. Specimens for FS and CS were loaded to fracture at a constant crosshead speed of 1 mm/minute. The mechanical properties were measured after the materials were stored in distilled water at a temperature of 37.0 +/- 1.0 degrees C for 24 hours and 150 days after mixing. In a one-way ANOVA, multiple mean value comparisons using Duncan's multiple comparison tests were performed. Resin cements had the highest flexural and compressive strengths, followed by self-adhesive universal resin cement. These materials were statistically stronger than resin-modified glass ionomer cements, glass ionomer cements and zinc phosphate cements.

Analysis of Variance↗
PubMed1995

Measurement of hydrostatic pressures during simulated post cementation.

Tooth sensitivity and fracture after cementation of posts for endodontically treated teeth have been a problem. This investigation developed an in vitro method of measuring intraradicular hydrostatic pressures created during simulated post cementation. The testing apparatus consisted of a pressure transducer and brush recorder connected to precision milled post spaces in a Plexiglas block. Cast post and cores were fabricated and cemented with three different luting agents: resinous cement, glass ionomer cement, and zinc phosphate cement. Mean hydrostatic pressures (psi) recorded during post cementation were zinc phosphate cement, 22.67; resinous cement, 19.77; and glass ionomer cement, 17.66. Zinc phosphate cement created substantially greater hydrostatic pressures than either the resinous or glass ionomer cements. This in vitro system was capable of discriminating intraradicular hydrostatic pressures among different classes of luting agents.

Analysis of Variance↗
PubMed2001

In vitro microleakage of luting cements and crown foundation material.

STATEMENT OF PROBLEM: Microleakage is a concern for the long-term prognosis of a cemented crown and foundation. PURPOSE: The aims of this investigation were, first, to evaluate microleakage of zinc phosphate cement and resin-reinforced glass ionomer cement under ideal (dry) versus contaminated (wet) conditions, and second, to compare 3 foundations under both ideal and contaminated conditions. MATERIAL AND METHODS: One hundred forty extracted molar teeth were cleaned and mounted. Tooth preparations for complete veneer cast crowns were completed with a chamfer finish line. A mesial surface class II cavity preparation 4 mm wide buccolingually and 2 mm deep was made in each tooth. Seven restorative groups were formed: amalgam/cavity varnish, amalgam/dentinal bonding agent, and composite/dentinal bonding agent, each with dry and contaminated groups, and a seventh group of class II cavity preparations without foundations. Finish lines for crown margins were refined 1.5 mm gingival to the restoration. Artificial crowns were cast in type III gold. Treatment groups were divided into 4 cement groups: dry and contaminated zinc phosphate cement and dry and contaminated resin-reinforced glass ionomer cement. The specimens were thermocycled and immersed in erythrosine B solution for 24 hours. Subsequently, they were rinsed, and their coronal portions were embedded in clear resin. Teeth were sectioned mesiodistally, and standard photomicrographs were made. The microleakage of each restoration and crown was measured. RESULTS: The least foundation microleakage was recorded for amalgam/dentinal bonding agents (ideal group) and composite/dentinal bonding agents (ideal group). The most microleakage was observed within the group without a foundation. In cement groups, the control and experiment sides were evaluated separately but displayed the same order of finding. The least leakage was recorded with resin-reinforced glass ionomer cement (ideal group); the most microleakage was noted with zinc phosphate cement (ideal group). An interaction was demonstrated on the experimental side between cements and the foundations (P=.0001). CONCLUSION: Within the experimental conditions of this study, less microleakage was recorded with resin-reinforced glass ionomer cement (ideal or contaminated) than with zinc phosphate cement (ideal or contaminated). There also was less microleakage evident with a foundation of silver amalgam or composite when a dentinal bonding agent was used under ideal conditions.

Analysis of Variance↗
PubMed2000

Predictions of cement microfracture under crowns using 3D-FEA.

PURPOSE: The objective of this research study was to test the effects of (1) crown margin type, (2) cement type, (3) cement thickness, (4) loading direction, and (5) loading magnitude on stress levels and distributions within luting cement that might lead to cement microfracture using three-dimensional Finite Element Analysis techniques. MATERIALS AND METHODS: Thirty-two three-dimensional computer models, as well as models for standards, were generated for a mandibular first premolar. Crown preparations exhibited shoulder or chamfer margin configurations, and zinc phosphate, zinc polycarboxylate, glass ionomer, and resin cements were used in thicknesses of 25 or 100 microm. Modeled crowns were loaded axially or obliquely at 10 and 100 MPa. Areas and levels of stress concentrations within the cement were determined. RESULTS: Stresses in the cement were low for all situations except 100 MPa oblique stressing. Stresses at the margins of crowns with chamfer marginal configuration were higher than those with shoulder margins. Stresses under oblique stressing were 10 to 150 times higher than under axial stressing. Except for Zn phosphate cement, cement thickness minimally affected stress levels and distributions. Greater stresses were found in cements with the greater Young's modulus. CONCLUSIONS: Although the chamfer margin design could lead to greater stresses near the margins that places the cement at risk for microfracture and possible crown failure, glass-ionomer and composite resin cements have more favorable mechanical properties for resisting microfracture.

Bicuspid↗
PubMed2004

An ex vivo evaluation of resin-modified glass polyalkenoates and polyacid-modified composite resins as orthodontic band cements.

OBJECTIVES: The objective of this ex vivo study was to assess the use of resin-modified glass polyalkenoates and polyacid-modified composite resins, as orthodontic band cements. MATERIALS AND METHOD: Plain stainless steel bands were cemented to 350 human extracted third molar teeth using 1 of 7 different cements. Following complete cement cure, half of each sample group was exposed to mechanical stress in a ball mill. Stressed and unstressed samples were tested in tension and the stress at which initial cement failure recorded. The mode of failure was recorded using an adhesive remnant evaluation. RESULTS: The mean band retention stresses offered by the cements studied ranged from 0.96 to 1.56 MPa. Fuji Ortho provided the highest mean band retention stress in "stressed" (1.56 MPa) and "unstressed" (1.45 MPa) states. Exposure to mechanical stress did not appear to significantly influence band retention or mode of cement failure for most cements. Fuji Ortho cement recorded the highest Weibull modulus for all cements tested. Virtually all samples failed at either the cement/enamel or cement band interface. CONCLUSIONS: Significant differences in band displacement stress values and mode of failure were demonstrated between the cements studied. However, generic comparisons were difficult to make.

Acrylic Resins↗
PubMed2004

Influence of cement type on the marginal adaptation of all-ceramic MOD inlays.

OBJECTIVE: The aim of this study was to investigate the in-vitro marginal adaptation of all-ceramic class II inlays which were luted with conventional multi-stage pre-treatment cements and one new type of cement, which requires no conditioning. METHODS: The marginal adaptation of 56 all-ceramic inlays was determined with scanning electron microscopy and microleakage tests. The marginal integrity of each tooth was evaluated at cement-dentin and cement-enamel junctions, with regard to the transitions between tooth-cement and cement-inlay. The inlays were luted on human molars with two resin cements, one compomer, one resin modified glass-ionomer and one new resin cement in accordance with the manufacture's recommended pre-treatment. Light- and chemical-curing modifications were investigated. All tests were performed after thermal cycling and mechanical loading (TCML). RESULTS: For the resin cements and the new material the marginal integrity was higher than 90% before and after TCML. The marginal adaptation was between 55-80% for the resin modified glass-ionomer and lower than 20% for the compomer. The microleakage was lower than 20% for all cements, only the compomer showed values up to 100% penetration. SIGNIFICANCE: The difference in marginal integrity between the new universal resin cement without any tooth pre-treatment and conventional resin cements after total-etching, priming and bonding was not significant. Resin GIC may be used with restrictions and compomer cement should not be used with all-ceramic class II inlay restorations.

Compomers↗
PubMed1999

Pilot study on the early shear strength of porcelain-dentin bonding using dual-cure cements.

STATEMENT OF PROBLEM: One of the most critical steps of the porcelain restoration technique is cementation. Mechanical stress before the resin cement reaches a certain degree of polymerization can displace or even fracture the restoration. Dual-cure materials are intended to be more effective at early stages of polymerization because they contain both photoinitiator and components for chemically activated reaction. PURPOSE: This study evaluated the early shear strength of bonding between porcelain and dentin, using dual-cure cements. MATERIAL AND METHODS: Sixty nonrestored human molars and premolars were randomly divided in 12 groups. The dual-cure cements tested were Porcelite and Dual. A chemically activated cement was also tested (C&B luting composite). Ceramic pieces, 3 mm high, were etched with hydrofluoric acid, silane-coated, and then bonded to flat dentin surfaces with each of the cements, associated with Optibond adhesive system. Photoactivation was made by using a light unit with 450 mW/cm2. The specimens were stored in water at 37 degrees C. Testing times were 10, 30, 90 minutes, and 7 days (referred to as maximum strength). RESULTS: Both Porcelite and Dual dual-cure cements show statistically similar shear strength for the same time interval. The chemically activated material showed statistically lower values when compared with both dual-cure cements, regardless of the time interval. Results at 7 days were much higher than those obtained at 90 minutes for the 3 cements tested. CONCLUSIONS: Both dual-cure cements tested presented similar results. The bond strength of dual-cure cements to dentin was higher at all time intervals than that obtained for chemically activated material. The high values for the coefficient of variation confirmed the technique-sensitive nature of the porcelain/dentin bonding procedure. Although dual-cure cements reach higher bonding strength values faster than the chemically activated material, it is not recommended to stress the bonding until 90 minutes after cementation, because the strength at that time is much lower than the maximum.

Acid Etching, Dental↗
PubMedDate not supplied

Deformation of restoration and fracture of luting cement film.

OBJECTIVES: Functional occlusal loading can generate complicated stresses in the luting cement film between a restoration and its abutment. Such stresses may lead to cement fractures, which can promote cement dissolution and induce clinical problems. The purpose of this study is to determine the function of the cement film under loading, and to clarify the relationship between the deformation of the restoration and the cement fractures. METHODS: Eccentric loads were applied onto model extension bridges which were cemented on brass dies with zinc phosphate cement. Strain measurements were recorded using of a strain gauge method, ultimate strength by tensile tests, leakage by dye penetration tests and cement fractures by ultrasonic microscopic analyses. Additionally, the bridges which were just seated on their dies without cementation were loaded, and strain measurements were recorded. RESULTS: The cases for linear strain increment with loading showed high tensile strength and minimal dye penetration. The cases with non-linear strain behavior showed low tensile strength and considerable dye penetration. However, no fracture was observed in the occlusal cement film in both cases. The cement fracture first occurred at the opposite marginal region to the loading side. CONCLUSIONS: One of the significant functions of the cement film is diminishing the deformation of restorations during loading. The deformation of the restoration affects initiation and propagation of the cement fracture considerably.

Alloys↗
PubMed2006

Optimizing resin cement removal around esthetic crown margins.

OBJECTIVE: To quantify luting cement at the crown-tooth interface of esthetic crowns fabricated using four different techniques and two methods of excess cement removal. MATERIAL AND METHODS: Four methods of crown fabrication were used: the feldspathic porcelain and platinum foil technique, the feldspathic porcelain and refractory die technique, the resin composite crown and CAD/CAM technique, and the feldspathic porcelain crown and CAD/CAM technique. Half of the cemented crowns were allocated to Group A: removal of excess cement by flicking-off with a plastic instrument 3 min after initial polymerization, or Group B: removal of excess cement using a wiping action with cotton pellets. Morphologic measurements, using non-destructive digital profilometry, were made of the volume of excess cement (mm(3)), mean maximum and mean depth of excess cement (microm), and surface area of excess cement (mm(2)). RESULTS: ANOVA and Duncan post-hoc tests revealed no statistical differences (p<0.05) between the four types of crown fabrication with respect to volume and mean depth of retained luting cement. There was a significantly greater volume, mean depth, and mean maximum depth of luting cement retained using the "flick off" method compared to the cotton pellet "wiping" method for excess cement removal, but no statistical differences in mean surface area between the two methods. CONCLUSIONS: Following removal of excess luting cement, as judged clinically, using two methods, subclinical amounts of cement remained adherent to the tooth surface of all specimens at the crown-tooth interface.

Analysis of Variance↗
PubMed1997

Hip screw augmentation with an in situ-setting calcium phosphate cement: an in vitro biomechanical analysis.

OBJECTIVES/HYPOTHESIS: This study was performed to determine whether a new, in situ-setting calcium phosphate cement would have sufficient mechanical integrity to reinforce compression screw fixation of unstable intertrochanteric fractures. We compared the cut-out resistance of screws augmented with calcium phosphate cement to the cut-out resistance of screws augmented with polymethylmethacrylate (PMMA). We used PMMA as the standard for comparison because it is currently used clinically. Our hypothesis was that initial fixation strength with PMMA and calcium phosphate cement augmentation would not be significantly different from one another. STUDY DESIGN: Cut-out testing of compression hip screws in paired human cadaveric proximal femurs was performed before and after augmentation with PMMA or calcium phosphate cement. Bilateral testing was performed to allow pairwise comparisons of the materials used for augmentation, and repeated testing was done to provide an internal control for the effects of bone quality. The initial fixation of screws augmented with calcium phosphate cement was compared with that of screws augmented with PMMA. METHODS: Ten paired human femurs (mean age, 75 +/- 9.2 years) were implanted with Richards AMBI compression hip screws. Basicervical osteotomies were then performed, yielding isolated proximal fragments for mechanical testing. Preaugmentation cut-out tests were performed under displacement control, with cut-out continuing to five millimeters at two millimeters per second. The screws were then removed, and the screw tracks were filled with 2.0 cubic centimeters of PMMA (one side) or calcium phosphate cement (contralateral side). After augmentation, the screws were reinserted and the cements were allowed to harden for twenty-four hours. Postaugmentation testing followed the protocols for preaugmentation testing, and the initial fixation strength of screws augmented with calcium phosphate cement was compared with the initial fixation strength of screws augmented with PMMA using a two-way repeated measures analysis of variance. RESULTS: The cut-out behavior of screws augmented with calcium phosphate cement was not significantly different from the cut-out behavior of screws augmented with PMMA. With calcium phosphate cement, yield strength increased by 15.8 percent (from 1,354 +/- 632 newtons to 1,568 +/- 320 newtons); with PMMA, the yield strength increased by 26.8 percent (from 1,477 +/- 526 newtons to 1,834 +/- 225 newtons). However, only the increase with PMMA augmentation was significant at p < 0.05). The energy to yield increased significantly (41 percent, p < 0.05) with both types of augmentation (from 2,399 +/- 1,186 newton-millimeters to 3,378 +/- 857 newton-millimeters for calcium phosphate cement, and from 2,635 +/- 1,113 newton-millimeters to 3,741 +/- 426 newton-millimeters for PMMA), whereas the stiffness increased only slightly with PMMA augmentation (6.2 percent, from 481 +/- 180 newtons per millimeter to 511 +/- 92 newtons per millimeter) and fell slightly with calcium phosphate cement augmentation (10 percent, from 457 +/- 201 newtons per millimeter to 411 +/- 663 newtons per millimeter). CONCLUSIONS: The in situ-setting calcium phosphate cement investigated in this study compared favorably with PMMA in a single-cycle cut-out test of augmented compression hip screws in senile trabecular bone. Our results suggest that these materials may have promise as substitutes for PMMA in the salvage of compression hip screw fixation in elderly osteopenic patients with complex intertrochanteric fractures and that further study of their use in this application is warranted.

Aged↗
PubMedDate not supplied

Adhesion of orthodontic cements to human enamel.

The tensile bonding characteristics of five orthodontic cements to etched human enamel with and without a silane primer after storage for 1, 7, and 30 days in artificial saliva at 37 C were compared. The scatter of the data was probably due to the wide variation of surface morphology of etched human enamel. Cement L, a composite resin cement, was significantly stronger than the other cements tested. Cement D, a polycarboxylate cement, was significantly the weakest cement tested. Cements U, O, and N-B were of relatively equal bond strengths. Of the direct-bonding systems commercially available, the N-B system had the fastest setting time. The silane primer used in the research decreased the bond strength of cement O; however, it significantly increased the bond strength of cement L. Storage in artificial saliva at 37 C for 30 days decreased the mean bond strengths of most of the orthodontic cements with and without a silane primer. The exceptions were cement N-B without a silane primer and cements O and D with silane primer.

Composite Resins↗
PubMed2002

[Air permeable diaphyseal obturators: efficacity of femoral cementing and prevention of associated cardiovascular disorders].

PURPOSE OF THE STUDY: Insertion of cement plugs into the femoral shaft has become an essential part of total hip arthroplasty procedures. The goal is to achieve secure cementing of the femoral component, but the pressure induced can cause serious problems. The purpose of this study was to determine the effect of a flexible bioabsorbable cement restrictor with decompression valves on cementing efficacy and to determine the effect of inserting the restrictor then the cement plug into the femoral shaft on respiratory functions. MATERIAL AND METHODS: The restrictor was implanted in 108 patients undergoing first-intention total hip arthroplasty. The canal was prepared and calibrated before inserting the restrictor at a depth estimated at preoperative planning to be 10 to 20 mm below the tip of the femoral stem. The efficacy of the restrictor was assessed using radiographic criteria for the quality of the cement sheath and its position relative to the femoral stem. Oxygen saturation of arterial blood and end-expiration PCO2 were measured at first incision, at insertion of the restrictor, at insertion of the cement plug, and at insertion of the femoral stem. RESULTS: The relative position of the restrictor was measured on postoperative x-rays at less than 20 mm in 75% of the patients, at 20-40 mm in 13% and at more than 40 mm in 12%. No cement leakage through the restrictor was identified on postoperative x-rays. The quality of the cement sheath was satisfactory in 71% of the patients (77 procedures), fair in 20% (22 procedures) and poor in 8% (9 procedures). For a first group of patients operated on under spinal anesthesia and optional oxygen delivered with a face mask, there was no significant difference in arterial blood oxygen saturation before the procedure and during the four explored operative times. Conversely, in a second group of patients who had general anesthesia without oxygen enrichment of the initial oxygen-nitrogen protoxide gas mixture, arterial blood oxygen saturation during the four operative times was statistically different from the preoperative value. The same observation was made for end-expiratory PCO2. DISCUSSION: The retrictor's decompression valves did not allow cement leakage beyond the restrictor. The risk of restrictor migration after insertion and after the increased pressure due to cement plug insertion was not increased and was found to be less than rates reported in the literature. In the patients who had general anesthesia, blood gases showed a minimal, but significant, decrease during the operative times susceptible to induce increased intramedullary pressure. In patients who had a non-cemented acetabular insert, use of the pressure-valve cement restrictor appeared to stabilize these parameters.

Absorbable Implants↗
PubMed1997

Influence of temperature and vacuum mixing on bone cement properties.

To analyze the influence of varying viscosity and mixing temperature (22 degrees C and 6 degrees C) on macro- and microporosity, density, and compressive strength in vacuum mixed bone cement, high, medium, and low viscosity cement were mixed in 2 vacuum mixing systems and compared with bowl mixing at atmospheric pressure. At 22 degrees C, vacuum mixing significantly reduced void volume to less than approximately 3 per mill. The reduction was most pronounced in low viscosity cement. Microporosity also was reduced in all cements by vacuum mixing and to highest degree in low viscosity cement. At 6 degrees C the reduction of micropores was more pronounced in high viscosity cement. In medium and especially low viscosity cement, the prechilling gave an increased number of micropores. Cement density also was significantly reduced in low viscosity cement at 6 degrees C. Vacuum mixing significantly increased compressive strength by approximately 15% in all cement types (30 days). The temperature did not significantly influence compressive strength, but low viscosity cement generally was stronger when mixed at 22 degrees C. It is concluded that vacuum mixing improves cement quality. However, the temperature influences the final result; in particular, low viscosity cement should not be mixed after prechilling to 6 degrees C.

Biophysical Phenomena↗
PubMed1992

Seating and retention of complete crowns with a new adhesive resin cement.

The retentive property of cast gold complete crowns cemented with an adhesive resin cement (Panavia Ex) was compared with retention of crowns cemented with zinc phosphate cement (Flecks) and the conventional resin cement (Comspan). The effect of these agents on seating of crowns also was evaluated. Panavia cement exhibited the highest retentive strength, with values almost twice those obtained with zinc phosphate cement. However, the difference in mean retention values of crowns cemented with Comspan cement or with zinc phosphate cement was not statistically significant. Both resin cements used in this study provided better seating of crowns than did zinc phosphate cement.

Adhesives↗