Bond strength of cements to nickel-chromium and silver-palladium alloys

The bonding of zinc phosphate, polycarboxylate, and reinforced ZOE cements to nickel-chromium and silver-palladium alloys was measured by cementing flat surfaces of the metals together. Polycarboxylate cement produced higher bond strengths than the other two cements to both metals. Polycarboxylate cement bonded better to nickel-chromium alloys than to a silver-palladium alloy. Zinc phosphate and reinforced ZOE cements had similar bond strengths except for Biobond, to which zinc phosphate cement provided higher bond strength. Polycarboxylate cement failed cohesively to both types of metals, and zinc phosphate and reinforced ZOE cements failed adhesively.     

Inhibition of human pulpal gelatinases (MMP-2 and MMP-9) by zinc oxide cements

The interaction between metal ions and the oral environment is a major subject matter in dental research. Matrix metalloproteinases (MMPs) have been implicated in several pathological and physiological processes such as, periodontal tissue destruction, root caries, dentin calcification and pulpal inflammation. The aim of this work was to test the effect of zinc released from zinc oxide-eugenol (ZOE) cements, on the activity of the major pulpal gelatinolytic MMPs. Pulpal explants were cultured overnight in Dulbecco's Modified Eagle Medium and the activity of secreted enzymes was analysed by gelatin zymography in buffer conditioned with diverse ZOE cements. Phenanthroline, a zinc chelator, was used to revert the inhibition of MMPs caused by zinc. The major gelatinolytic proteinases present in the conditioned media were characterized as MMP-2 and MMP-9 by immunoprecipitation. All ZOE cements inhibited MMPs activity, whereas phenanthroline could partially revert the inhibition caused by plain ZOE and Intermediate Restorative Material (IRM).     

Effect of cement selection and finishing technique on marginal opening of cast gold inlays

STATEMENT OF PROBLEM: The standard cement for partial-veneer cast gold restorations has been zinc phosphate. With increasing interest in using resin and resin-modified glass ionomer cements for this purpose, marginal adaptation with use of these newer cements must be assessed. PURPOSE: The purpose of this in vitro study was to determine if the marginal adaptation of cast gold inlays is comparable for 3 different luting agents and 3 finishing techniques. MATERIAL AND METHODS: Cast gold inlays were cemented into triangular preparations on the buccal surface of 45 extracted human molars. Three operators each used a different technique for finishing margins: finishing during cementation (FD), finishing before cementation (FB), and finishing before and during cementation (FBA). The 15 teeth for each operator were divided into 3 subgroups of 5 each to accommodate 3 cements: zinc phosphate (Fleck's zinc phosphate: ZP), resin-modified glass ionomer (RelyX Luting: RXL), and self-adhesive modified resin (RelyX Unicem: RXU). For all specimens, fine sandpaper disks followed by fine cuttle disks were used for finishing the castings. The marginal gap was measured using a Nikon measuring microscope at x50 magnification. Data were analyzed with a 1-way ANOVA for each cement (alpha=.05). RESULTS: There were significant differences among finishing techniques for each cement (P<.05). For ZP, the smallest mean marginal gaps were for FD (31 microm) and FBA (42 microm). For RXL, FBA produced the smallest gap (19 microm). For RXU, FB (23 microm) and FBA (22 microm) were optimal. CONCLUSIONS: Within the limitations of this in vitro study, the marginal gap attained with cementation of partial-veneer cast gold restorations with ZP (31 microm) can also be obtained using RXL or RXU. The techniques of FD or FBA are best used for ZP, whereas the FBA technique is best for RXL, and either FB or FBA is optimal for RXU. The FBA technique yielded a small gap; this was common to all 3 cements.     

The effects of height and surface roughness of abutments and the type of cement on bond strength of cement-retained implant restorations

Objectives: To evaluate the effects and interactions between cement type, abutment height and surface roughness on bond strength of cemented implant restorations. Materials and methods: One hundred and sixty metal copings were fabricated and divided into 16 groups of 10 samples each. Copings were cemented on 4 and 6 mm height Alfa‐Gate^® abutment, using four types of cements: zinc phosphate (ZNP), glass ionomer (GI), and zinc oxide eugenol (ZOE) with or without 15% vaseline. Copings were removed using a universal testing machine and bond strengths were recorded. All abutments were sandblasted with 50 μm aluminum oxide and the experiment was repeated. Results were analyzed using univariate analysis, Games–Howell, and Bonferroni's pairwise comparisons tests at P≤0.05. Results: Bond strengths were significantly different according to cement type, abutment height, and surface roughness (P=0.001). The cement ranking from highest to lowest was: ZNP>GI>ZOE>zinc oxide eugenol with 15% vaseline (ZOEV). An increasing abutment height showed a significant increase in bond strength for permanent cements only (P≤0.05). Sandblasting abutment surface significantly the increased bond strength for all cement except the ZOEV at 4 mm abutment, and for only ZOE and GI cements at the 6 mm abutment (P≤0.05). Conclusions: ZP was the strongest cement and required using one of the variables (height, surface roughness) for maximum bond strength. GI bond strength was increased by both variables but sandblasting was more effective. ZOE required using both variables to be as effective as some of the permanent cement subgroups. ZOEV was the weakest and bond strength was not improved by either variables. To cite this article:
Al Hamad KQ, Al Rashdan BA, Abu‐Sitta EH. The effects of height and surface roughness of abutments and the type of cement on bond strength of cement‐retained implant restorations.
Clin. Oral Impl. Res. 22 , 2011; 638–644
doi: 10.1111/j.1600‐0501.2010.02011.x     

疏水性氧化锌丁香油水门汀的实验研究

采用具有良好拒水性能的聚四氟乙烯（ＰＴＦＥ）改性普通氧化锌丁香油水门汀（ＺＯＥ），以降低其水中溶解率。表明在ＺＯＥ中加入适量的ＰＴＦＥ，能显著降低ＺＯＥ的水溶解率，并能改善其机械性能，提高韧性。     

In vitro bond strength of silica-coated metal posts in roots of teeth.

This study determined the in-vitro bond strength of abrasive-sprayed and silica-coated Ni-Cr-Be posts to roots of extracted teeth using three resin cements (Panavia EX [P], Super-Bond C&B [SB], Prisma Universal Bond 2-Dicor [PUB-D]) and zinc phosphate cement (ZP). There were no significant differences among bond strengths of resin cements (8.8 to 10.8 MPa) bonded to abrasive-sprayed posts, but the bonds were stronger than those obtained using zinc phosphate cement (4.4 MPa). With the silica-coated posts, Super-Bond C&B produced the highest bond strength (14.5 MPa), followed by PUB-D (10.9 MPa), P (7.5 MPa), and ZP (5.4 MPa).     

A comparison between zinc phosphate and glass ionomer cement in orthodontics

In the past orthodontic band cementation has relied heavily on mechanically retentive cements such as zinc phosphate luting agents. The clinical performance of a glass ionomer cement (GIC), a chemically retentive cement, was evaluated against a conventional zinc phosphate cement (ZP). The recementation values for ZP were significantly higher over a 2-year treatment period than those of GIC. Failures between cement and enamel, and cement and stainless steel were noted for the ZP. Glass ionomer cement had significantly better retentive strength to enamel than to band material. Moisture contamination does not appear to be a problem in orthodontic band cementation with glass ionomer cement.     

The in vitro biological evaluation of dental cements using elution and binding by bovine serum albumin (author's transl)]

In order to evaluate in vitro biological properties of dental cements sixteen different cements including zinc oxide eugenol (ZOE), EBA, resin, polycarboxylate, glass ionomer cement and calcium hydroxide base material were tested regarding elution and binding by bovine serum albumin (BSA). The persistency of elution over long time after subsequent transfer to fresh water was calculated at 210 nm absorbance with ultra violet spectrometer. Also the eluates obtained were analyzed by high performance liquid chromatograpy. The continuous leaching of eugenol from ZOE cement was observed. Binding of eluates from cement to BSA was evaluated spectrophotometrically by utilizing the competition with 2-(4' hydroxyphenylazo) benzoic acid (HABA). EBA cement showed the highest binding ability by BSA because of the leaching o-ethoxybenzoic acid from this cement. The relevance of protein and pulp toxicity is discussed.     

The effect of zinc oxide-eugenol on the shear bond strength of a commonly used bonding system

Abstract – It has been claimed that eugenol has a detrimental effect on resin composites and dentin bonding systems. The aim of the present study was to examine whether zinc oxide-eugenol (ZOE) cement would reduce the efficacy of a bonding system. Human third molars were selected for the study, and cylindrical posts of a resin composite (Z100) were bonded vertically to a standardized flat dentinal surface, prepared on the buccal surface of the teeth and treated with Scotchbond Multi-Purpose. The tooth surfaces involved were either freshly cut, or had been exposed to ZOE cement for 6 days, with and without a subsequent thorough cleansing with ethanol. The bond strength in shear was measured after 24 hours. The results showed that ZOE cement had no negative effect on the bond strength of the resin composite (Z100) to dentin when this bonding system was used. The mean shear bond value for the specimens covered with ZOE cement for 6 days was 28.1 MPa. For specimens covered with ZOE cement and cleansed with 96% ethanol, the mean shear bond value was 23.5 MPa. The corresponding value for the controls was 19.0 MPa. These findings suggested that eugenol-containing temporary filling materials may be used safely prior to inserting resin based restorative materials, when Scotchbond Multi-Purpose is employed as the bonding agent.     

A simple model for evaluating relative toxicity of root filling materials in cultures of human oral fibroblasts

Standardized test tubes filled with freshly mixed root filling materials (AH26, CRCS, N2, Kloroperka NO, ZOE cement and 2 experimental cements, ECI and ECII) were transferred into tissue culture flasks. Normal human oral fibroblasts were seeded in the flasks. Morphological cell changes were studied up to 15 days after seeding. The size of cell-free zones around the test tubes and the total cell number per culture flask were calculated after 5, 10 and 15 days. The findings showed N2 cement to be by far the most toxic material at all observation periods, whereas no toxic reactions could be seen in relation to tubes filled with Kloroperka NO. Compared with the 5-day observation period, some cell recovery was observed around test tubes with AH26 and ECII, whereas almost full cell recovery was found around test tubes with CRCS, ZOE and ECI. It was concluded that the present model, which allows long-term observations of human cellular reactions to dental materials, can be used as a simple and relatively cheap screening test for initial toxicity testing of dental materials.     

Cytotoxicity evaluation of zinc oxide-eugenol and non-eugenol cements using different fibroblast cell lines

Objectives: Despite being commonly used as temporary cements in dentistry, there is a lack of studies regarding the cytotoxicity of zinc oxide-eugenol (ZOE) and zinc oxide non-eugenol (ZONE) cements. In addition, cytotoxicity evaluation of the materials often involves animal-based cells. Therefore, in this study, a cytotoxicity evaluation of commercially available ZOE and ZONE cements was carried out using both animal and human-based cells. Materials and methods. The extraction or dilution of the extraction from four commercially available cements (two zinc oxide-eugenol and two zinc oxide non-eugenol) was tested for cytotoxicity, using three different cells and a water-soluble treatzolium salt assay. The results were confirmed using a confocal laser microscope following calcein AM and ethidium homodimer-1 staining. Results. The results showed that there was a significant difference in cell viability depending on which cell was used, even when the same material was tested. Generally, L929 showed relatively low cell viability with a low EC50 (effective concentration of extracts that caused 50% of cell viability compared to the control) value compared to both HGF-1 and hTERT-hNOF. Such results were also confirmed by a confocal laser microscope. Conclusions. Careful consideration on interpreting the results for cytotoxicity evaluation of ZOE and ZONE cements is needed when different cells are used.     

A simple model for evaluating relative toxicity of root filling materials in cultures of human oral fibroblasts

Abstract Standardized test tubes filled with freshly mixed root filling materials (AH26, CRCS, N2, Kloroperka NØ, ZOE cement and 2 experimental cements, ECI and ECII) were transferred into tissue culture flasks. Normal human oral fibroblasts were seeded in the flasks. Morphological cell changes were studied up to 15 days after seeding. The size of cell-free zones around the test tubes and the total cell number per culture flask were calculated after 5, 10 and 15 days. The findings showed N2 cement to be by far the most toxic material at all observation periods, whereas no toxic reactions could be seen in relation to tubes filled with Kloroperka NØ. Compared with the 5-clay observation period, some cell recovery was observed around test tubes with AH26 and ECII, whereas almost full cell recovery was found around test tubes with CRCS, ZOE and ECI. It was concluded that the present model, which allows long-term observations of human cellular reactions to dental materials, can be used as a simple and relatively cheap screening test for initial toxicity testing of dental materials.     

In vitro activity of zinc oxide-eugenol and glass ionomer cements on Candida albicans

The aim of this study was to evaluate in vitro the antimicrobial activity of glass ionomer (GIC) and zinc oxide-eugenol (ZOE) cements against Candida albicans. Standardized GIC and ZOE specimens were maintained in contact with C. albicans suspension (1 x 10(6) cells/ml) at 37 degrees C for 24 h, 48 h or 7 days. A control group without any testing cement was included. After the incubation period, aliquots of 0.1 ml were plated on Sabouraud's agar, and then the number of colonies was counted. The results were expressed as values of logarithms of colony-forming units per milliliter (log CFU/mL) and were analyzed statistically by Kruskal-Wallis ANOVA. After 48 h of incubation, the ZOE group presented no growth of C. albicans. GIC and control groups presented similar mean values at all tested periods. According to the results obtained, it could be concluded that, under the experimental conditions, ZOE cement was more effective in vitro against C. albicans than GIC.     

Zinc eugenolate crystals: SEM detection and characterization

Zinc oxide eugenol-based dental cements are not employed routinely as permanent luting materials because the reaction-product matrix is not a stable, high-strength phase. Difficulty in identifying zinc eugenolate product has prevented determination of the structure-property relationships for the matrix. In the current work zinc eugenolate was synthesized and carefully characterized by SEM techniques. That information was used as the basis for examination of clinically recovered ZOE products. Zinc eugenolate crystals were characterized as parallelepiped shapes with 20:4:1 length-to-width-to-thickness geometries. The crystals were observed in post-operatively collected ZOE B&T and Temp Bond cements as highly oriented and well-packed plates. The poor mechanical strength of the cements seemed to be associated with weaknesses of individual crystals and not with inadequate product formation, discontinuity, or poor crystal-packing hypotheses.     

Cytotoxicity of some dental cements in a cell culture system (author's transl)]

Four dental cements of zinc phosphate cement, polycarboxylate cement, zinc oxide-eugenol cement and epoxy resin cement have been tested by means of cell culture method using L strain cell. The cells were cultured with a test piece of the cements in the incubator of 37 degrees C. The test pieces of powder, liquid, un-set cement and set cement were prepared. Cell multiplication, medium pH and zone index in agar diffusion method were measured and also cell morphological changes were observed around the test piece. Test pieces of the four un-set cements showed cytotoxic action at 2 hours administration, although the cytotoxicity of their cements decreased after setting. pH 7.2 of the normal medium was changed to 4.6 with un-set zinc phosphate cement. The other cements affected slightly comparing with zinc phosphate cement. The largest zone index which indicates degree of cytotoxicity, were observed around the test piece of the liquid of zinc phosphate cement. In this study, a biocompatibility of four dental cements was investigated and the following results were obtained. 1. Zinc phosphate cement showed strong cytotoxic action under the un-set condition, and the cytotoxicity almost disappeared after setting. 2. Polycarboxylate cement showed weaker cytotoxic action than zinc phosphate cement. However the cytotoxicity did not disappear after setting. 3. Zinc oxide-eugenol cement showed cytotoxic action which was similar to polycarboxylate cement, but it was slightly stronger than that of polycarboxylate cement. 4. Epoxy resin cement showed the weakest cytotoxic action than other three cements under the un-set condition. The cytotoxicity of set epoxy resin cement was strong, followed by zinc oxide-eugenol cement.     

Time‐dependence of coronal seal of temporary materials used in endodontics

The aim of this in vitro study was to compare parametrically the coronal seal ability over different periods of times of four restorative materials used to seal the pulpal access cavity after endodontic treatment. One hundred and thirty‐five mandibular premolars were divided randomly into three time groups (1, 2 and 4 weeks), each of which was in turn divided into four subgroups. Each subgroup was restored using one of four restorative materials: Coltosol, glass ionomer cement (GIC), zinc phosphate (ZP) cement, or intermediate restorative material (IRM) cement. The root canals were prepared using the crown‐down technique, and obturated using lateral condensation. Following placement of the restorative material, the samples were incubated in distilled water at 37°C and were subjected to 50 thermocycles (0 ± 4, 56 ± 4C). After immersing in (2%) methylene blue dye for 24 h, teeth were longitudinally sectioned and examined under a stereomicroscope. The results showed that Coltosol and GIC cement were significantly superior in sealing ability to ZP and IRM cements (P < 0.05). There was no significant difference between GIC cement and Coltosol. Both Coltosol and GIC after 1 week were significantly better than 4 weeks. There was no significant difference in the seal ability at different time periods when ZP and IRM cements were used.     

Interim luting agents, composite core surface hardness and retention of interim and final restorations

This study compared the effects of ZOE interim cement on the retention of interim acrylic and final cast crowns (cemented with zinc phosphate) over cores of current conventional and hybrid composite resin formulae, and a non-eugenol interim cement (NOG) and a calcium hydroxide liner (CaOH2) on interim and final retention values over hybrid cores. Results were compared to retention of cast crowns over amalgam cores. Retention was measured with an Instron Testing Machine. Location of cement failure during separation was recorded. Surface hardness of each group was compared. Retention of cast crowns cemented with zinc phosphate over amalgam cores was significantly higher than that of any of the resin core groups (ANOVA, P less than 0.05, Sheffe Contrast). There was no significant difference in final casting retention cemented over hybrid or conventional resin cores exposed to ZOE (13.625 vs 14.125 Kg). Final casting retention differences were not significant between the three interim cement groups. Final retention of all groups exposed to an interim luting agent were significantly less than the composite control groups. The use of CaOH, as an interim luting agent for acrylic crowns over hybrid cores compared to ZOE or NOG, should afford significantly greater retention with no adverse effect on the retention of the final casting. While the surface hardness of both types of composite resin was adversely affected by exposure to interim luting agents as compared to controls, there was no correlation between final casting retention values and surface hardness of polished composite. The interim cements invariably failed at the interim acrylic crown interface while the zinc phosphate cement failed at the core interface.     

Acidity of conventional luting cements and their diffusion through bovine dentine

AIM: To examine the changes in pH of luting cements and acid diffusion of luting cements through bovine dentine using a pH-imaging microscope (SCHEM-100; Horiba Ltd, Kyoto, Japan). METHODOLOGY: The pH of the surface of three conventional luting cements, glass-ionomer, zinc phosphate and zinc polycarboxylate was measured with SCHEM-100 for 1 month. The acid diffusion from the three luting cements through bovine dentine was investigated by measuring pH changes during the application of each luting cement on the bovine dentine surface. Coronal bovine dentine disks were prepared to thicknesses of 0.50 and 0.25 mm. Each luting cement was placed on the labial dentine surface, and the pH change of the pulpal surface was observed every 3 min for 30 min with SCHEM-100. RESULTS: Glass-ionomer showed the lowest pH values for longer times. Neutralization proceeded furthest in zinc polycarboxylate. The 0.5-mm-thick dentine disks showed no pH change on the pulpal side with all the three cements. The 0.25-mm-thick disks revealed evidence of acid diffusion on the pulpal side of the cemented dentine and significantly lower pH when cemented with glass-ionomer and zinc phosphate than with zinc polycarboxylates. CONCLUSIONS: This study demonstrated that glass-ionomer exhibited a lower setting pH than zinc phosphate and zinc polycarboxylate, and acid diffusions from glass-ionomer and zinc phosphate cements were observed when placed on 0.25-mm-thick dentine disks.     

Crowns cemented on crown preparations lacking geometric resistance form. Part II: effect of cement.

PURPOSE: This study evaluated the effect of different cements on resistance to dislodgment of crowns cemented on preparations lacking geometric resistance form. MATERIALS AND METHODS: A preparation that offered no geometric resistance form, with 20 degrees total occlusal convergence (TOC), 0.9 mm wide shoulder finish line, and a 2.5 mm axial wall height was created on an ivorine tooth using a milling machine. Ten metal test specimen die replicas and 10 standardized metal crowns with recipient sites for the application of external forces through a universal testing machine were fabricated. The crowns were cemented on the dies under 5 and 10 kg external loads, the marginal openings measured, loaded to dislodgment, and cleaned of cement. The process was repeated using zinc oxide and eugenol (ZOE), zinc phosphate (ZPh), resin modified glass ionomer (RMGI), and composite resin (CR) cements. RESULTS: Marginal openings under 5 kg cementation loads were 74.63 (+/-15.04) for ZOE, 75.98 (+/-18.20) microm for ZPh, 98.58 (+/-22.62) microm for RMGI, and 105.82 (+/-20.07) microm for CR cements respectively; under 10 kg cementation loads they were 57.62 (+/-15.86) microm, 59.55 (+/-15.41) microm, 95.00 (+/-19.52) microm, 101.30 (+/-12.52) microm respectively. Oblique dislodgment forces, measured with a Universal testing machine, were 40.18 (+/- 6.76) N for ZOE, 215.65 (+/-45.79) N for ZPh, 165.43 (+/-19.53) N for RMGI, and 181.54 (+/-30.75) N for CR respectively when crowns were cemented under 5 kg loads. The corresponding values for 10 kg loads were 38.62 (+/-4.19), 274.86 (+/-54.22), 139.70 (+/-21.71), and 160.40 (+/-21.21) respectively. Only zinc phosphate cement produced statistically enhanced resistance when crowns were cemented under 10 kg force (p value = 0.035). CONCLUSIONS: Under the conditions of the present study only crowns cemented with zinc phosphate displayed increased resistance to dislodgment on preparations lacking resistance form.     

Pulpal response in rhesus monkeys to cementation agents and cleaners.

The purpose of these studies was to compare pulpal inflammatory responses induced by cementation of precision amalgam inlays with zinc phosphate cement, with and without a Hydroxyline liner, Durelon cement, and ZOE controls. Hydraulic force was induced by the inlay insertion procedure. Cavilax, water, and polyacrylic acid were compared with ZOE controls. Both studies also used untreated teeth for comparison. The use of zinc phosphate luting cement in the 48-hour inlay study was the only condition provoking moderate to severe responses. Zinc phosphate cement over Hydroxyline liner and Durelon cement in the study of inlays and Cavilax cleaner, water, and polyacrylic acid in the study of cleaners showed mild responses comparable to the ZOE control in the 48-hour and in the 45-day periods.