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PubMed1995

Biomechanical assessment of a new adhesive bone cement for otologic surgery.

The adhesion of metallic prostheses to bone is a major problem in otologic surgery. Conventional bone cements lack significant adhesive strength, which predisposes the cemented prosthesis to loosening. The advent of surgically implantable hearing devices is one example where an adhesive cement to secure metal to bone would be useful. The biomechanical properties of a new cement, 4-META/MMA-TBB opaque resin, were evaluated in an animal model. The cement is composed of 4-methacryloyloxyethyl trimellitate anhydride (4-META) and methyl methacrylate (MMA) as monomers and tri-n-butyl borane (TBB) as an initiator. Titanium disks were cemented to the tibias of rabbits, which were sacrificed at 0 and 90 days. Tensile and shear bond strengths between bone and metal were tested at both times. The mean baseline tensile and shear bond strengths were 8.92 MPa and 11.96 MPa, respectively. Adhesive failure occurred at the bone-cement interface. The decrease in bond strength at 90 days was minimal. Thus, 4-META/MMA-TBB cement is a promising new metal-to-bone adhesive that may be useful for the surgical fixation of metallic prostheses in otologic surgery.

Adhesives↗
PubMed1996

The effect of methotrexate-loaded bone cement on local destruction by the VX2 tumour.

Previous studies have shown that the activity of the cytostatic drug methotrexate (MTX) embedded in acrylic cement is not affected by thermal changes in the cement. MTX is slowly released from the cement for several months and remains biologically active throughout this period. Our aim was to determine whether MTX embedded in cement would control the local growth of a tumour. In 15 rabbits we injected 0.1 ml of VX2 tumour suspension into the proximal tibia. At 3, 5, 7, 10 and 14 days three animals were killed and the tibiae removed and examined histologically. With increasing growth of the VX2 carcinoma there was increased bone destruction and a rise in the numbers of osteoclasts, but after 14 days the numbers of osteoclasts had decreased. We then injected VX2 into the tibiae of another 45 rabbits. After 5 days most of the tumour was curetted out and the defect filled with cement containing either 0 g, 0.1 g, 0.5 g, 1.0 g or 2.0 g MTX/40 g cement. The rabbits were divided into three groups and killed at 3, 7 or 10 days after implantation of cement. The number of osteoclasts and the amount of bone destruction were measured in each tibia. In all three groups bone destruction and osteoclast proliferation were markedly decreased with higher doses of MTX, but bone destruction was not eliminated. Our findings show that in the higher doses used, which were not toxic to the animal, MTX-embedded cement may be of value in minimising the amount of tumour-induced osteolysis and may be a useful adjunct in the surgical management of pathological fractures.

Animals↗
PubMed1996

The Nicolas Andry award: comparative results of cemented and cementless total hip arthroplasty.

A prospective randomized clinical trial comparing cemented to cementless total hip arthroplasty has been ongoing at the author's institution since 1987. All parameters assessed showed that there was no statistically significant difference in any of the health related quality of life measures used when patients with cement were compared with patients without cement at any of the followup periods as many as 4 years later. The improvement was dramatic and sustained. No components (cemented or cementless) have been revised to date (average, 4.8 years). A radiographic analysis showed probable loosening of the cemented socket in 24% and presumed minimal pelvic osteolysis in 8%. The cementless sockets showed a greater frequency and severity of pelvic osteolysis (14%). The cemented femoral component was judged to be possibly loose in 10%; however, none were considered probably loose. The patients who had cementless femoral components were doing extremely well with the components showing very little subsidence or proximal stress protection noted. Osteolysis on the femoral side was not seen in any of the cementless stems. Total hip replacement gives comparable clinical results when health related quality of life measures are analyzed; however, metal backed cemented acetabular components have a high rate of radiographic failure. Short-term stability of a non-cemented porous coated titanium stem, however, gave excellent clinical and radiographic results.

Aged↗
PubMed1997

Radiographic analysis of a cemented titanium alloy femoral component.

Proximal femoral cortical bone remodeling was evaluated radiographically about a 1 piece cemented titanium alloy femoral prosthesis implanted with modern cement techniques and was compared with one described previously in which early cement techniques and a stainless steel stem were used. Two hundred twenty-six total hip replacements (196 patients) were observed for an average of 6.3 years (range, 5-10 years). Analysis of all hips revealed that the ratio of cortical thickness to that of the overall femoral bone diameter did not change significantly about the periprosthetic bone throughout the length of the study. Cortical hypertrophy and atrophy occurred at rates similar to those seen with the early cement techniques. Distal fusiform cortical hypertrophy and the formation of osteosclerotic (reactive) lines at the bone cement interface occurred at approximately half the rate using modern cement techniques. In addition, cortical atrophy was associated with the formation of these reactive lines, the occurrence of osteolytic lesions, and progressive bone cement interface radiolucencies. Although periprosthetic cortical atrophy occurred at rates similar to those reported previously, important differences were noted between the findings of this study and the earlier study; these differences most likely were a result of cement technique or the prosthesis.

Aged↗
PubMedDate not supplied

The effect of pulpal fluid flow on tensile bond strength of a glass-ionomer cement: an in vivo and in vitro comparison.

Previous studies of the bonding capabilities of glass-ionomer cements have concentrated on the use of in vitro testing conditions. Since early moisture contamination appears to have adverse effects on the physical properties of glass-ionomer cements, and with the probability of pulpally derived dentinal fluid being present under in vivo conditions, the objective of this study was to compare in vivo tensile bond strength with in vitro tensile bond strength of a glass-ionomer cement to dentin utilizing the same teeth under similar test conditions. A glass-ionomer lining cement was placed on freshly exposed labial dentin of the maxillary incisor on 10 Rhesus monkeys. Immediately following placement, an orthodontic button was placed over the cement and left undisturbed for 1 hour. The teeth were then extracted and stored in 100% relative humidity for 23 hours. An Instron testing machine was used to register in kilograms the force required to cause tensile bond failure of the cement. Identical methodology was then used on the same teeth for in vitro testing. The concluding results indicate that a statistically significant difference (P < or = 0.05) exists between in vivo and in vitro tensile bond strengths of the glass-ionomer lining cement and that the bond failure was cohesive in character for all cases both in vivo and in vitro. These findings suggest that clinically, tensile bond strengths of glass-ionomer cements to cut dentin can be expected to be weaker in vital teeth than in devital teeth.

Animals↗
PubMed1997

[Temporary antibiotic-loaded cemented prosthesis for two-stage septic hip arthroplasty].

PURPOSE OF THE STUDY: During the excision period of a two-stage revision arthroplasty, the hip has a low function and an unacceptable leg length discrepancy. The goal of this study was to expose technical details in order to perform a simple articulated cement spacer which could be implanted during this period to improve hip function, to authorize partial weight bearing and to avoid leg length discrepancy. MATERIAL: This method was applied in three two-stage procedures justified because of particular immunodeficiency conditions: a 43 years old man who had bone marrow allograft and immunosuppressive therapy because of leukemia suffering of subacute septic hip arthritis; a 58 years old man suffering of diabetes and active C-hepatitis who had a septic loosening of a total hip arthroplasty (THA); a 76 years old woman suffering of diabetes who had a third septic loosening of THA. METHOD: The prosthesis was made of antibiotic-impregnated cement according to organisms antibiotic resistance. The prosthetic junction between head and diaphysis was reinforced with a tibial plate. Prosthetic shape was identical to the one of femoral broaches inserted in the femur after prosthetic and cement removal. The broach size was chosen when mechanical stability in the femur was obtained, and avoided leg length discrepancy after trials with cups. The tibial plate was bent in order to reinforce the junction with regard to the shape of the determined broach. Two doses of antibiotic-impregnated cement were mixed and molded with hands, then the plate was incorporated at the appropriate location, finally the broach was applied on this composite and cement in excess was removed before polymerisation. For prosthetic head, two options were available: to mold the cephalic zone of the cement at the patient acetabulum diameter with a soft aluminium cup previously molded in the acetabulum; to mold the cement cephalic zone with a trial cup in order to obtain a 22 or 28 ball. For this last option, a third dose of antibiotic-impregnated cement was prepared and placed in the acetabulum, a trial femoral head was applied in it to mold the location for the 22 or 28 prosthetic head. Before insertion, a collar was applied on the stem to prevent migration. Active mobilization was encouraged, and partial weight-bearing authorized. RESULTS: The mean range of hip flexion during period was 60 degrees. The patients were discharged approximatively 12 days after the first stage. Two patients had effective painless partial weight-bearing. The second stage was performed six weeks later on the average. The second procedure was easier than the second stage of a conventional two-stage procedure because of: easy and low hemorrhagic dissection authorized by the prosthesis; low difficulties with soft tissue tension as the prosthesis prevents leg length discrepancy; preservation of the articular space which prevents soft tissue sacrifice during the second stage. CONCLUSION: This simple technique is effective to prevent complications related to the excision period of a two-stage hip revision arthroplasty. Likewise, the economical aspect (short delay of hospitalisation, quick functional recovery) should be considered when compared with the excision period of a conventional two-stage procedure.

Adult↗
PubMedDate not supplied

Radiopacity of dual-cured and chemical-cured resin-based cements.

PURPOSE: The objective of this study was to determine radiopacity values of a group of resin-based cements and to compare them to those of enamel and dentin. MATERIALS AND METHODS: Three specimens 2.5 mm thick were prepared from each of 18 cements (nine chemical-cured and nine dual-cured). Three tooth sections 2.5 mm thick were cut from extracted molars. Specimens and tooth sections were divided into three matching groups. Following standard radiographic techniques, images of each group of specimens, along with an aluminum step wedge were obtained. Optical density readings for each material were determined with a transmission densitometer. Radiopacity values were subsequently calculated as equivalents of aluminum thickness. RESULTS: Analysis of variance indicated significant differences in radiopacity values among the materials (P < 0.0001). Four dual-cured cements (Variolink, Geristore, Enforce, and Nexus) had radiopacity values significantly greater than that of enamel, while two (Choice and Adherence) had radiopacity values similar to enamel. For the remaining three dual-cured cements, Duolink had a radiopacity value significantly lower than that of enamel but higher than that of dentin, while both Lute-It and Resinomer had values similar to dentin. For the chemical-cured cements, five materials had radiopacity values significantly higher than enamel (Sealbond, Advance, Scotchbond, Cement-It, and Dyract-Cem), while two had values significantly lower than enamel but higher than dentin (Biomer and Panavia 21). The remaining two cements had radiopacity values significantly lower than dentin. CONCLUSION: For a group of 18 resin-based cements, some had radiopacity values similar to or significantly lower than that of dentin.

Absorptiometry, Photon↗
PubMed1989

Glass-ionomer cement film thickness and working time.

Reports on film thickness for adhesive glass-ionomer cements have not been consistent, and confusion exists relative to proper working times. In this investigation, film thickness was measured over a range of times for three glass-ionomer cements by using a traditional ADA glass plate technique and a simulated clinical cementation technique with castings and dies. The cements were examined from 60 seconds to 255 seconds from the start of mix. Results indicated that the simulated clinical technique generally provided less film thickness. No significant differences in film thickness were found between the brands of cement through 240 seconds with film thickness ranging from 7.24 to 20.5 microns. Greater differences between the cements were observed with the ADA technique beyond 135 seconds from the time of mix. Relative to film thickness, working times would appear to be greater than previously reported for glass-ionomer cements.

Chemical Phenomena↗
PubMed1990

Effect of prolonged ultrasonic instrumentation on the retention of cemented cast crowns.

Occasionally the need arises to remove restorations that have been cemented. Several ultrasonic tips have been developed to aid in removing cemented restorations. Earlier studies of the effects of ultrasonic vibration reveal detrimental effects on amalgam surface and marginal integrity and, at short instrumentation periods (2.5 minutes) in vitro, no significant effect on the retention of cemented cast crowns. Twenty identically machined metal dies had nonprecious crowns waxed, cast, and fitted. Each casting was cemented twice with glass ionomer and zinc phosphate cement. Each cement was tested for the effects of vibration on retention. The cements were mixed according to manufacturer's specifications, placed under 5 kg load, then placed in 37 degrees C water and contained in a humidor. Retention was tested with a 4202 Instron machine to determine the forces needed to overcome retention. Retention ranged from a high of 125.36 kg for glass ionomer without vibration to a low of 19.11 kg for zinc phosphate vibrated for 12 minutes. The use of vibration is considered an advantageous adjunct to other cast restoration removal devices.

Cementation↗
PubMed1993

Change in pH during setting of polyelectrolyte dental cements.

The change in pH during setting has been studied for five different glass polyalkenoate (ionomer) cements and for two different zinc polycarboxylate cements using a flat-headed combination electrode on both the fresh cement and on a slurry of the set cement. The results show that the pH of the glass ionomers was slightly lower in the early stages of setting than was the pH of the zinc polycarboxylates and also that the pH of glass ionomers rises more slowly. For anhydrous cements (i.e. those formulated from dried polymer) pH was found to rise quicker than for hydrous cements (i.e. those prepared from aqueous solutions of polymer). Previous workers have assumed that anhydrous cements undergo slower rises in pH than hydrous ones. Our results clearly refute this assumption, and also suggest that the reported pulpal irritation associated with the use of anhydrous glass ionomers may be due to something other than low pH.

Acrylic Resins↗
PubMed2004

Shear bond strength of different types of luting cements to an aluminum oxide-reinforced glass ceramic core material.

OBJECTIVE: The aim of this study was to find the optimal choice of luting cement to Synthoceram, an aluminum oxide-reinforced glass ceramic material. The bond strength of five different commercial luting cements to the ceramic material was evaluated. The effect of surface treatments, etching, sandblasting, silanizing, and combinations of these treatments was also investigated. METHODS: Shear bond strength tests were performed using the ceramic material as substrate with each of the luting cements. Cements rods were prepared on pre-treated ceramic surfaces. The shear bond strength was determined 24 h after cementation. The effect of surface treatments: etching, sandblasting, and sandblasting followed by etching, respectively, on the morphology of the material, was investigated with SEM. RESULTS: The shear bond strength increases significantly from Ketac Cem, Rely X Luting, Fuji Plus, Panavia F to Xeno Cem. The surface treatments etching and/or sandblasting followed by silanization generally provide the highest bond strength values. SIGNIFICANCE: Based on the results of this study, the use of resin composite based cements is preferred for cementation of an all-ceramic restoration with an aluminum oxide-reinforced glass ceramic base. Surface treatment of etching and/or sandblasting followed by silanization is recommended.

Aluminum Oxide↗
PubMed2004

Effect of mixing method on the porosity of encapsulated glass ionomer cement.

OBJECTIVE: To observe cement specimens mixed by various methods non-destructively using microfocus computerized tomography (micro-CT) and to evaluate the effect of mixing method on porosity. METHOD: Five glass ionomer cements were used: two were hand-mixed and three were encapsulated. The latter were mixed either by shaking or rotating. Fifteen cylindrical specimens were prepared for each material by each mixing method and stored in distilled water at 37 degrees C until testing. The specimens were observed and analyzed using micro-CT. 201 sliced images were obtained horizontally along the length of the specimens. Three-dimensional reconstructions were made and the sizes, numbers and total volume ratio of bubbles in the specimens were calculated. RESULTS: Mixing method had a significant effect on porosity (P<0.05). For the luting/lining cement, mechanical mixing produced a significantly higher porosity (P<0.05). For the restorative cement, there were only small differences in porosity between specimens mixed by the two methods. More large bubbles were detected in specimens mixed mechanically than by hand for the fluid material. This suggested that for low-viscosity materials bubbles may combine until a certain viscosity is reached during setting. SIGNIFICANCE: The strength of glass ionomer cement is affected by incorporated porosity and this depends on the mixing method. For low-viscosity cements, hand-mixing is favored in order to reduce porosity and increase strength, but this is not generally applicable to high-viscosity cements.

Cementation↗
PubMed1978

Retention of endodontic dowels: effects of cement, dowel length, diameter, and design.

The retentive capacity of three preformed endodontic dowel designs was compared at two lengths and two diameters, with three different cements. The greatest single factor influencing retention of these devices was the design used. Of the types tested in this study, the most retentive were threaded, parallel-sided dowels screwed into tapped channels. Serrated, parallel-sided dowels cemented in matched cylindrical channels provided intermediate retention, and smooth-sided tapered posts were the least retentive. Another major factor in retention was the length of imbedment into dentin. An increase in dowel imbedment depth usually corresponded to increased retention. The effect of cement type was significant only with tapered dowels. Zinc phosphate cement was most retentive, carboxylate cement exhibited intermediate retention, and the epoxy cement was least retentive. For the other post designs, cement type had no significant effect on retentive capacity. Finally, variations in dowel diameter had no significant effect on retentive ability.

Crowns↗
PubMed1989

Maximum bond strength of dental luting cement to amalgam alloy.

Although dental amalgam is used frequently under artificial crowns for restoration of severely damaged teeth, there is little information available on the bond between luting cements and this alloy. This study was designed for determination of the strength of the bond between a dental amalgam alloy and three crown-luting cements. Cylinders of dental amalgam were joined in pairs, with use of a zinc-phosphate, a glass-ionomer, and an acrylic-adhesive resin cement. The tensile-fracture stress of 45 samples of each cement was measured with a universal testing machine, and subjected to a Weibull analysis. The fractured surfaces were examined under low magnification with use of a light microscope, and at low and high magnifications with use of a scanning electron microscope, for evaluation of the appearance of the fractured joints. The Weibull analysis demonstrated that the adhesive resin cement provided a stronger and more predictable bond than either the zinc-phosphate or the glass-ionomer cement. The appearance of the fractured surfaces gave no indication of the strength of the joints, a feature that is common to brittle materials. The results suggest that crowns placed on teeth offering a large amalgam-alloy surface could be retained more predictably with an adhesive resin cement.

Acrylic Resins↗
PubMed2005

Influence of temporary cement remnant and surface cleaning method on bond strength to dentin of a composite luting system.

The aim of the current study was to evaluate the influence of polycarboxylate temporary cement remaining on the dentin surface on the bond strength of a composite luting system. An acrylic resin plate was luted to bovine dentin with a polycarboxylate temporary cement (HY-Bond Temporary Cement Hard, HYB). The temporary cement was not used for the control groups. After removing the temporary cement with an excavator, dentin specimens were divided into five groups; 1) no subsequent treatment, 2) cleaning with a rotational brush (RTB), 3) cleaning with a rotational brush and non-fluoridated flour of pumice, 4) sweeping with an air scaler, and 5) treated with a sonic toothbrush. A silane-treated ceramic disk (IPS Empress) was bonded to each dentin specimen with a composite luting system (Panavia F). Shear testing results showed that the RTB groups exhibited the highest bond strength regardless of the use of temporary cement (P < 0.05). The use of a rotational brush with water coolant is recommended to achieve ideal bond strength between the Panavia F luting system and dentin to which HYB temporary cement was primarily applied.

Aluminum Silicates↗
PubMed1991

Discoloration of dental cements and composites in a sulfide solution.

In an early study the discoloration of certain hardened silicate cements, after exposure to an atmosphere of hydrogen sulfide (H2S) for 24 h at room temperature, was ascribed to the formation of dark-colored sulfides of base metal impurities (Paffenbarger et al. JADA 25,32,1938). A recent study noted that, in general, silicate and glass ionomer cements were more prone to color shifts than composites after exposure to H2S for 9 weeks (Sugawara, Ph. D. Thesis, Nihon Univ.). The aim of the present study was to devise a simple, aqueous sulfide exposure test for esthetic restorative materials. The general procedure was to expose specimen disks to a 0.1% (w/v) sodium sulfide solution, adjusted to pH 9, for 1-7 days at 37 degrees or 55 degrees C. The 55 degrees C-Na2S exposure was designed as an accelerated test. Materials studied included: 1 silicate and 2 silicophosphate cements of known lead content, a glass ionomer cement (FIIF), several commercial composites and an experimental, hydrophilic composite. Known amounts of base metal contaminants in the form of appropriate salt solutions were added to the liquid components of FIIF and the composites. Specimens exposed to distilled water under the same conditions served as controls. Exposure to the aqueous sulfide medium resulted in the following ranking in order of decreasing discoloration: Glass ionomer cement greater than silicophosphate cement greater than silicate cement greater than hydrophilic composite greater than hydrophobic composite. Generally, the results of the aq. Na2S test paralleled those obtained with H2S. The degree of discoloration is dependent on a number of factors: the nature, concentration and leachability of the metal impurities, and the hydrophilicity and permeability to sulfide of the esthetic restoratives.

Chlorides↗
PubMed1991

Biocompatibility of a glass ionomer luting agent. 2. Crown cementation.

In this experiment, 64 crown preparations were made in four primates. Final impressions, die fabrication, wax patterns and castings were achieved using conventional established clinical and laboratory techniques. Vented and unvented crowns were cemented with a glass ionomer cement (GI) and a zinc phosphate cement (ZOP). Some preparations were protected with calcium hydroxide liquid. On the same animals, in teeth not used for crowns, Class V cavities were prepared and GI and ZOP inserted by means of a pressure technique imitating hydraulic pressure generated during crown cementation. After periods of 5 and 60 days, the animals were sacrificed, the jaws dissected, fixed in formalin and prepared for histological evaluation. Of the 64 cemented crowns, one was unaccounted for. Of the unvented crowns with GI (5 days), vented crowns with GI (60 days), unvented crowns with ZOP (60 days), Class V with ZOP (5 days) and GI (60 days) with a remaining dentin thickness (RDT) of less than 1 mm, inflammatory responses of greater than or equal to 1 degree (on a scale 1-4 degrees) were observed. The use of liquid calcium hydroxide reduced the intensity of the reactions, in particular when small RDTs were present. It can be concluded that when RDTs of 1 mm or more were present, the cements in all groups were non-toxic. When it is estimated that the RDT is less than or equal to 1 mm, the use of a calcium hydroxide liner is recommended. Placement of luting agents in Class V preparations with pressure resulted in reactions resembling crown cementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1978

[Compressive strength and deformation of dental cements].

Several dental cements have been tested for compressive strength, modulus of elasticity and plastic strain at fracture. Sylindrical specimens (4 x 6 mm) were compressed to fracture with two different crosshead speeds (2 mm/min, 0.1 mm/min) at two temperatures (23 +/- 1 degrees C and 37 +/- 1 degrees C). The results showed that the zinc phosphate cement had relatively high strength and a very small elastic and plastic strain during compression. The luting type of glass-ionomer cements showed properties near to that of the zinc phosphate cement. The other cements had either lower strength or higher elastic and plastic deformation than the zinc phosphate cement. Several cements showed a marked reduction of the mechanical properties when tested at a low crosshead speed or at 37 degrees C.

Composite Resins↗