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PubMed1998

Basic studies on hydroxy apatite cement: I. Setting reaction.

Self-setting cements, alpha D-Cement and alpha DT-Cement, were prepared. They consisted of only the calcium phosphates alpha-TCP, TTCP and DCPA. These cements reacted and hardened in a moist environment at 37 degrees C. The powder X-ray diffraction patterns were taken to examine the conversion of their reactions as a function of time. The cements reacted and produced hydroxyapatite. The optimum powder/liquid ratio of alpha D-Cement was 2.0 and that of alpha DT-Cement was 1.8. The initial setting time of alpha D-Cement was 87.5 m and that of alpha DT-Cement was 107.5 m. The component and the product of these cements are calcium phosphates which are the putative minerals in teeth and bones. Therefore, these cements are useful for oral surgery as bone-filling materials.

Bone Substitutes↗
PubMed1996

Cement augmentation of intertrochanteric fracture fixation: a cadaver comparison of 2 techniques.

We evaluated 2 techniques of cement augmentation to enhance fixation of intertrochanteric hip fractures. 4 fixation groups with 6 cadaver femurs in each group were compared: stainless steel lag screw and side plate with and without cement augmentation and a titanium alloy expandable dome plunger and side plate with and without cement augmentation. Gauges were used to establish the mechanical behavior of intact and then fractured femurs to simple uniaxial loads. Subsequent loading to failure allowed determination of maximum fixation strengths and modes of failure. Cement augmentation of each device increased its load to failure. There was no significant difference between the cemented lag screw and the uncemented dome plunger groups with average loads to failure of 4.0 x 10(3) N. The greatest average load to failure was in the cemented dome plunger group (5.6 x 10(3) N) with the lowest in the uncemented sliding hip screw group (3.6 x 10(3) N). Device cut-out as a cause of failure occurred mostly in the uncemented lag screw group. Sliding was enhanced by those methods that increased the fixation surface area within the femoral head, unless cement encroached in the region of the barrel-screw junction. Strain analysis showed that the dome plunger unloaded the bone at the calcar, regardless of cement augmentation, while the sliding hip screw allowed for compressive stresses in this area. Proper cement augmentation increases load to failure and minimizes nail cut-out for both devices studied. However, the dome plunger, a device with a large fixation area in the femoral head, was equally effective and eliminated potential cement encroachment. Failure of intertrochanteric fracture fixation in osteoporotic bone may be minimized by an appropriate choice of device or cement augmentation.

Bone Cements↗
PubMed2001

Stiffness optimisation of cement and stem materials in total hip replacement.

It is acknowledged that bone resorption and fatigue fracture of cement in total hip replacement may cause feature problems. The solution is frequently sought associated with the stiffness of cement and stem. The purpose of this paper is firstly to describe the effect of changes in modulus of elasticity of the cement material for the implanted prosthesis on the fatigue notch factor (Kf). The paper further describes a method of numerical optimisation to determine the optimal stiffness characteristics of cement and stem materials, which minimises the probability of fatigue fracture of cement at all interfaces with the stem and the bone, while limiting the amount of bone resorbed. The parameters describing the elastic moduli of cement and stem were considered as design variables. The method was applied to an equivalent 2D finite element model of femoral hip replacement in combination with an optimisation procedure using the ANSYS program. The results of the first study suggest that lower modulus of elasticity of cement material decreases Kf in the cement at all interfaces and proximal bone while higher values increase Kf. For the second aim, Young's moduli of about 0.6 and 22 GPa are optimal for cement and stem materials, respectively. These characteristics decreased the probability of fatigue fracture of cement at all interfaces with the stem and the bone as a result of decreasing Kf in cement at all interfaces, while limiting the amount of bone resorbed as a result of increasing Kf in the proximal bone.

Algorithms↗
PubMed2002

Clinical evaluation of two adhesive composite cements for the suppression of dentinal cold sensitivity.

STATEMENT OF PROBLEMS: Postoperative cold sensitivity after the cementation of indirect restorations with composite cements has been reported frequently but not scientifically documented. PURPOSE: This controlled clinical study was designed to simulate the dentin/composite cement interface immediately after cementation of a cast restoration. The desensitizing capabilities of a composite cement that contains a self-etching, dual-polymerizing resin adhesive system were compared with those of a composite cement that use phosphoric acid etching followed by a single-bottle, light-activated primer/resin-based adhesive. MATERIAL AND METHODS: The hypersensitive root surfaces of selected teeth were randomized to receive 1 of 3 treatments: coating with a self-etching adhesive (Linkmax) and its respective cement, coating with a conventionally etched adhesive (RelyX ARC) and its cement, or no treatment (negative control). The sample size was 22. Dentin sensitivity was ascertained with an accurate cold testing device that slowly decreased in temperature. Tooth sensitivity was measured both immediately and at 7 days after placement. Two-way analysis of variance and Fisher's least significant difference test (P<.05) were used to determine whether significant differences existed as a function of treatment type or time. RESULTS: Immediately after placement, the self-etching adhesive and its respective cement resulted in more suppression of cold sensitivity than no treatment (control); with Linkmax treatment, the temperature at which teeth responded was reduced by 8.4 degrees C. The conventionally etched adhesive and its cement reduced the temperature at which teeth responded by 9.4 degrees C. After 1 week, these temperature reductions were 7.0 degrees C and 4.3 degrees C, respectively. Untreated controls at the 2 intervals showed a mean decrease in sensitivity to cold of 3.6 degrees C and 4.1 degrees C. Statistical analysis showed type of composite cement to be a significant factor. CONCLUSION: Within the limitations of this study and in comparison to untreated control teeth, Linkmax treatment resulted in a significant reduction in tooth root sensitivity over 1 week (P=.02), whereas RelyX ARC did not (P=.066).

Acid Etching, Dental↗
PubMed1992

Experimental hydroxyapatite cement cranioplasty.

Hydroxyapatite cement is a calcium phosphate-based material that when mixed with water forms a dense paste that sets within 15 minutes and isothermically converts in vivo to a microporous hydroxyapatite implant. This cement was used to reconstruct bilateral 2.5-cm-diameter full-thickness critical-sized parietal skull defects in six cats. One side was reconstructed with 100 percent hydroxyapatite cement, and the other with a mixture of 50 percent hydroxyapatite cement and 50 percent ground autogenous bone by weight. These animals were sacrificed at 6 and 12 months after implantation. Positive and negative controls also were prepared. The anatomic contour of the soft tissue overlying all hydroxyapatite cement implants was well maintained, there were no wound infections or structural failures, and the implants were well tolerated histologically. None of the negative (unreconstructed) control defects was completely filled with repair bone, and all positive (methyl methacrylate) controls demonstrated foreign-body giant-cell formation and fibrous encapsulation of the implants. Examination of decalcified and undecalcified sections revealed progressive but variable replacement of the cement by new bone and soft tissue without a change in the shape or volume of the hydroxyapatite cement-reconstructed areas. New bone comprised 77.3 and 64.7 percent of the tissue replacing the hydroxyapatite cement and hydroxyapatite cement-bone implants, respectively. Replacement of the hydroxyapatite cement implants by new bone is postulated to occur by a combination of osteoconduction and implant resorption. These results indicate that further experimental research leading to the possible application of hydroxyapatite cement for full-thickness calvarial defect reconstruction in humans is warranted.

Animals↗
PubMed2003

[Morphologic evaluation of adhesive/resin cement system and fiber post: a sem investigation].

AIM: The purpose of the present paper is to carry out an SEM investigation into the adhesive cementation of quartz fibre posts in canals treated with endodontic cements containing or not containing eugenol. METHODS: Sixteen selected tooth roots were subdivided into 4 groups and prepared with the step-back technique. Group A, without canal filling and with a cemented post, was the control group; in groups B and C, the canals were closed with guttapercha, endomethasone C and eugenol, those of group D with guttapercha and AH Plus without eugenol. The canals were prepared so as to be able to take D.T. light-posts irrigated with water (group C with ethyl alcohol) mordanted with orthophosphoric acid after applying 2 layers of photopolymerised ONE-STEP; 2 layers of ONE-STEP were applied to the post. DUO-LINK cement was positioned in the canal after inserting the post, removing excess resin and photopolymerising. The samples were prepared for SEM observation. RESULTS: Group A: the apical portion shows the post absorbed into the cement and resin tags; group B: porosity is noted between cement and post, the hybrid layer does not present tissue penetration of the dentin resin; group C: bullae can be seen between cement and post surface and between hybrid layer and cement; group D: there is relative continuity between post surface, cementing resin, hybrid layer and underlying dentin. CONCLUSION: The study has shown that eugenol interferes with the formation of the hybrid layer, the pictures relative to the resinous cement appeared different depending on whether the canal was treated with cement containing or not containing eugenol.

Dental Implants↗
PubMed1990

[The utilization of glass ionomer sealing cements].

In order to fix the reconstructive work, a luting cement is used. The main task of this cement is to retain the restoration on the tooth and to fill and seal the gap between them. The first glass ionomer luting cement came on the market in 1978. In the beginning, the cement did not perform as expected: high solubility, high viscosity and hypersensitivity, even followed by pulp death, were reported. The glass ionomer luting cement compares now favourably with the traditional non-adhesive cements. Nevertheless, the zinc phosphate cement is still the most commonly used cementing agent in the dental private practice. Studies have shown that the problems of hypersensitivity after the use of glass ionomer luting cements are more dentist related than material related. This article explains how to use the glass ionomer luting cements in order to achieve a successful cementation.

Dental Restoration, Permanent↗
PubMed1990

Histomorphological studies of the long-term skeletal responses to well fixed cemented femoral components.

Thirteen femora that were obtained at autopsy from patients in whom a cemented total hip replacement had been implanted from forty months to 17.5 years earlier were evaluated radiographically and morphologically. All of the patients had been functioning well, and only one of the prostheses showed radiographic evidence of loosening. Serial sections of the proximal portion of the femur that enclosed the femoral component of the prosthesis showed that the host bone was intimately and directly apposed to the cement, and fibrous tissue intervened only rarely. The bone-remodeling processes had created a dense shell of substantial new bone around the cement-mantle that resembled a new cortex, attached to the outer cortex by new trabecular struts. Evidence of ingrowth of bone from this dense shell of bone into the undulating surface of the cement was found in many areas. In the adjacent femoral cortex, there was substantial osteoporosis and cortical thinning. The cement-bone interface was intact and excellent throughout, despite the presence of fractures within the cement-mantle and de-bonding at the cement-prosthesis interface in some specimens. The cemented femoral components were well tolerated by the skeleton over a long period of use, and fibrous tissue had rarely formed at the femoral cement-bone interface of these well fixed and clinically successful prostheses. The cement-mantle was well supported by extensive medullary bone-remodeling and formation of a dense shell of new bone. The internal bone-remodeling helped to maintain the cemented femoral components over time and did not cause loosening of the prosthesis.

Adult↗
PubMed1989

[Influence of thermal cycling on the adhesive strength of adhesive resin cement].

The purpose of this study was to examine the influences of thermal cycling on the adhesive strength of the adhesive resin cements. Four kinds of adhesive resin cements, which belonged to the commercial composite resin inlay products, were used for the study. They were CR Inlay Cement, Duo Cement, Dual Cement and P-30 diluted with Enamel Bond. The shear adhesive strengths to tooth substance and composite resin inlay were measured. Adhesive strength to etched enamel : CR Inlay Cement showed the highest values of 274 kg/cm2 after immersion in water at 37 degrees C for 24 hours and 230 kg/cm2 after 300 thermal cycles at 4 degrees C for 3 min and at 60 degrees C for 3 min. Adhesive strength to etched dentin : P-30 diluted with Enamel Bond showed the highest values of 64 kg/cm2 after 24-hour immersion in water, and 63 kg/cm2 after 300 thermal cycles. Adhesive strength to composite resin inlay : CR Inlay Cement showed the highest values of 310 kg/cm2 after 24-hour immersion in water, 306 kg/cm2 after 300 thermal cycles, and 297 kg/cm2 after 1000 thermal cycles. Adhesive resin cements other than CR Inlay Cement, showed a decrease in adhesive strengths to tooth substance and composite resin inlay after thermal cycling. Especially, Dual Cement and Duo Cement showed considerable decreases.

Adhesiveness↗
PubMed1988

Shrinkage of centrifuged cement.

Two postulated mechanisms for the failure of prosthetic implants secured with bone cement are: failure of the cement itself, and loosening at the bone/cement interface. Failure rate with cement can be reduced by increasing the strength of the cement, and loosening can be reduced by minimizing cement shrinkage during polymerization. This paper shows that centrifuging cement to reduce porosity (and presumably increase strength) results in a substantial increase in cement shrinkage over uncentrifuged cement. A second set of experiments demonstrated that pressurization of cement to four atmospheres during polymerization resulted in tensile strengths comparable with those reported for centrifuged cement. Thus, the use of uncentrifuged bone cement, pressurized during polymerization, should minimize implant failure rates.

Atmospheric Pressure↗
PubMed1998

Cemented femoral stem performance. Effects of proximal bonding, geometry, and neck length.

The effects of proximal bonding, distal stem geometry, and femoral neck length on cement and interface stresses were determined to understand better their role in clinical performance. The effects of stem design were compared with the effects of environmental variables, patient weight, and patient activity. Finite element models were used to determine peak cement and interface stresses, and an experimental layout was used to separate design and environmental effects. Bonding reduced cement mantle stresses by 35% to 60%, to levels below the cement fatigue strength. A flat sided implant provided more torsional resistance, reducing shear stresses at the proximal cement-prosthesis interface by 22% to 73% with respect to a distal round implant. Neck length had minimal effects on stresses compared with bonding or implant geometry. Cement-bone interface stresses were more sensitive to patient activity than to the design variables. Therefore, claims that a strong cement and prosthesis bond may be harmful to the bone-cement interface are unjustified based on these results. The best combination of design variables was a proximally bonded, flat sided implant with neck length left to the surgeon's discretion. This combination was most effective at protecting the cement mantle and prosthesis interface and perhaps the cement-bone interface by minimizing stresses associated with cement debris generation.

Activities of Daily Living↗
PubMed2000

Fracture toughness of resin-based luting cements.

STATEMENT OF PROBLEM: The introduction of resin-modified glass ionomer cements has expanded the choices of luting cements available to the clinician; however, few independent studies are available on the fracture toughness of the currently available resin-modified glass ionomer luting agents compared with the composite cements. PURPOSE: This investigation evaluated the relative fracture toughness (K(IC)) of 3 composite luting cements (Panavia 21, Enforce, and C&B Metabond), 3 resin-modified glass ionomer luting cements (Advance, Vitremer Luting, and Fuji Duet), and a conventional glass ionomer luting cement (Ketac-Cem) at 24-hour and 7-day storage times. MATERIAL AND METHODS: K(IC) was determined by preparing minicompact test specimens (n = 8) with introduced precracks. Specimens were stored in distilled water at 37 degrees C + 2 degrees C until testing. Testing was performed on an Instron testing machine at a displacement rate of 0.5 mm/min. RESULTS: ANOVA (P <.001) and REGW Multiple Range Test (P <.05) demonstrated significant differences among several of the cements tested. The mean fracture toughness values of C&B Metabond at 24 hours and Enforce at both 24 hours and 7 days were significantly greater than use any of the other cements tested. CONCLUSION: The resin-modified glass ionomer cements exhibited improved fracture toughness when compared with the conventional glass ionomer; however, they were still inferior to Enforce and C&B Metabond composite cements.

Analysis of Variance↗
PubMed1991

Effect of aging on temporary cement retention in vitro.

Retention of restorations cemented with temporary cement varies. Some cements are adhesive and others are weak in retention. In addition, cement retention may vary over time. This study determined (1) the retentive properties of four temporary cements, and (2) the effects of aging on temporary cement retention. Cylindrical amalgam cores and mated stainless steel retainers with a 0.05 mm cement space were used in the study. Cores were cemented into the retainers and stored in 100% humidity at 37 degrees C until tested. Retention was measured by applying a compressive force to the cores through a rod in an Instron machine. Half the samples were tested after 1 week and half were tested after 6 weeks. The results indicate a significant difference in retentive value among the four cements, including a significant decrease in retention for one cement over the 6-week aging period.

Cementation↗
PubMed2002

Hardness and in vitro wear of a novel ceramic restorative cement.

The aim of the present work was to compare a new ceramic restorative cement for posterior restorations, DoxaDent, with other types of tooth-colored materials for direct use as regards hardness and in vitro wear. Four hybrid resin composites, one polyacid-modified resin composite, one resin-modified glass ionomer cement, one conventional glass ionomer cement, one zinc phosphate cement, an experimental version as well as the marketed version of the ceramic restorative cement, were investigated. Hardness of the materials was tested with the Wallace indentation tester and wear was tested with the ACTA wear machine. All tests were carried out on 2-wk-old specimens. DoxaDent was as hard as the zinc phosphate cement and the hardest resin composite. The ceramic restorative cement wore significantly more than the resin composites, the same as the zinc phosphate cement, and less than the glass ionomer cements. No correlation between hardness and wear was found. It can be concluded that the ceramic restorative cement is a rather hard material but with a relatively low wear resistance.

Aluminum Compounds↗
PubMed2005

An investigation into the use of two polyacid-modified composite resins (compomers) and a resin-modified glass poly(alkenoate) cement used to retain orthodontic bands.

The aim of this investigation was to determine the effectiveness of a conventional glass poly(alkenoate) cement (Intact) and newer polyacid-modified composite resin cements (Transbond Plus and Ultra Band-Lok) to retain orthodontic bands. In the in vitro part of this study, stainless steel bands were cemented to 240 extracted third molar teeth in three test groups comprising Intact, Transbond Plus and Ultra Band-Lok. The force to deband (N) for all three cements was recorded using an Instron universal testing machine after the following observation periods: 20 minutes and 3, 6 and 12 months. The results indicated that all three cements increased their median force to deband after 12 months. Of the two compomers, Transbondtrade mark Plus demonstrated the highest median force to deband at all four time intervals. In the in vivo part of the study, 30 patients participated in a randomized cross-mouth clinical trial where the molar bands were cemented in place using either Intact or Transbond Plus. Ultra Band-Lok was not used in the clinical part of the study. The results showed there to be no clinically significant difference in band failure rates between the two cements. When patients were asked to score each for taste, there was a significant difference, with the glass poly(alkenoate) cement (Intact) being more acceptable than the polyacid-modified composite Transbond Plus (P < 0.001). No significant differences were observed in the in vitro median force to deband or in vivo band failure rates between the glass poly(alkenoate) cement and the polyacid-modified composite resins. The choice of cementing agent can therefore be made on patient factors, e.g. taste, or operator factors, e.g. ease of handling, cost and shelf life.

Cementation↗
PubMed1994

The effect of delayed placement of capsulated cements on crown seating.

The effect of delayed seating of a crown onto a die was determined when using capsulated zinc phosphate and glass ionomer cements. The space between the crown and the die was varied up to 60 microns, and the commencement of seating was from 30 to 210 seconds after mixing ended. The zinc phosphate cement gave gradually increasing seating discrepancies with time, but providing 45 microns of space was present, the crown could be well seated up to 3 minutes after mixing. It is argued that this cement is particularly suitable for cementing burnishable inlays. The glass ionomer cement permitted reduced seating discrepancies compared with zinc phosphate cement when 45 microns of space was present, but gave poor results when the seating was delayed more than three minutes. The capsulated cements were clean and quick to use, and it is recommended that if there is a delay in seating, a new mix of cement should be prepared rather than attempting to complete cementation with an obviously setting cement.

Cementation↗
PubMed1989

[A study on adhesive strength of cyanoacrylate dental adhesive, 'F.H. Cement'--thermal-cycled effects].

This study investigated the adhesive strength of cyanoacrylate dental adhesive, 'F.H cement' after being thermal-cycled in order to certify its stability in water. The adhesive strength was compared using Zinc phosphate cement, Glass ionomer cement, Dental adhesive resin and F.H cement when an ivory die and a cast crown were adhered by these different cements. Results of the study indicated the following: 1. The adhesive strength after being thermal-cycled indicated that F.H cement had a greater strength than the other cements (Zinc phosphate cement and Glass ionomer cement) and was equal to that of the Dental adhesive resin. 2. F.H cement was also found to be the strongest in adhesive strength when different tapers were used.

Cyanoacrylates↗
PubMed1992

The effect of early water contact on glass-ionomer cements.

The purpose of this study was to observe the effect of immersion in water at 3, 5, 7, and 10 minutes after mixing on the surface of three regular and one light-curing glass-ionomer cements by measuring penetration of a methylene blue solution. Early solubility of these cements was also measured and compared with that of a zinc phosphate and a polycarboxylate cement. A blue-stained zone was observed in all glass-ionomer cements, but an inner, opaque zone was observed in only two of the regular glass-ionomer cements. Extending the time between start of mixing and immersion in water decreased the width of both zones in all cements and markedly lowered the loss of substance from the surface of regular glass-ionomer cements. However, time after mixing had no or only a limited effect on the loss of substance from the light-curing glass-ionomer cement, the zinc phosphate cement, or the polycarboxylate cement.

Glass Ionomer Cements↗