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At least 595 records · Page 33Linked to original sources
PubMed2006

Genotoxicity and cytotoxicity of glass ionomer cements on Chinese hamster ovary (CHO) cells.

Glass ionomer cements are widely used in dentistry as restorative materials and adhesives for composite restorations. However, the results of genotoxicity studies using these materials are inconclusive in literature. The goal of this study was to examine the genotoxic and cytotoxic potential of three different glass ionomer cements available commercially (Ketac Cem, Ketac Molar and Vitrebond) by the single cell gel (comet) assay and trypan blue exclusion test, respectively. For this, such materials were exposed to Chinese hamster ovary (CHO) cells in vitro for 1 h at 37( composite function)C. Data were assessed by Kruskall-Wallis nonparametric test. The results showed that the powder from Ketac Molar displayed genotoxicity only in the maximum concentration evaluated (100 microg/mL). In the same way, the liquid from Vitrebond at 0.1% dilution caused an increase of DNA injury. Significant differences (P<0.05) in cytotoxicity provoked by all powders tested of glass ionomer cements were observed for exposure at 1,000 microg/mL concentration. With respect to liquids of glass ionomer cements evaluated, the major toxic effect on cell viability was produced at 10%, beginning at the dilution of 0.5% for Vitrebond. Taken together, we conclude that some components of glass ionomer cements show both genotoxic and cytotoxic effects.

Animals↗
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↗
PubMed1989

Load transfer of posts and cores to roots through cements.

This study evaluated differences in load transfer when cast posts are fixed to roots with different cements. Cast posts and cores were cemented with 40 endodontically prepared teeth by using four different cement mediums. The load exerted on the root surface through the post was evaluated using a strain gauge. The increased flexure after cementation was statistically analyzed. In conclusion, there was load transfer from post to root structure when posts were cemented, but no difference was found between cementation mediums.

Cementation↗
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↗
PubMed1992

Microleakage of new crown and fixed partial denture luting agents.

This study measured the in vitro microleakage of conventional and new FPD luting agents. Standardized preparations were made on 42 freshly extracted premolars. Facial and lingual chamfer margins were placed in enamel, mesial and distal in dentin and cementum, and castings were made in Rexillium III alloy and were then cemented with a standardized technique. Six groups of seven samples were tested, (1) polycarboxylate, (2) zinc phosphate, (3) glass ionomer, (4) Den-Mat Thin Film cement, (5) Panavia Ex, and (6) Den-Mat Thin Film cement with Tenure. The ranking of groups for stain ingress was from the greatest (1) to the least (6). A one-way analysis of variance and Tukey-Student range analysis revealed significantly similar groups, p less than 0.05:(1,2,3,4) (5,6).

Adhesives↗
PubMed1992

Comparison of the shear bond strength of a titanium composite resin material with dentinal bonding agents versus glass ionomer cements.

This study compared the in vitro shear bond strength of an autopolymerizing composite resin system (CR) (Ti-Core) with two third-generation dentinal bonding agents (DBA) (Tenure and Scotchbond 2) to glass ionomer cements (GIC) (Ketac-Silver, GC Miracle Mix, and Ketac-Cem). The experiment was divided in five groups. The shear bond strengths were evaluated on a universal testing apparatus at three different intervals; 15 minutes, 24 hours, and 7 days. Statistically, (two-way analysis of variance), the shear bond strengths from the greatest to least were: Ti-Core CR with Tenure DBA > Ti-Core CR with Scotchbond 2 DBA > Ketac-Silver GIC, GC Miracle Mix GIC > Ketac-Cem GIC. There were no differences in shear bond strengths according to time, and no interactions between groups and time. The shear bond strengths for Tenure DBA with Ti-Core CR were two and a half to three times greater than the silver-filled glass ionomers, Ketac-Silver GIC and GC Miracle Mix GIC. Tenure DBA with Ti-Core CR also had consistently greater shear bond strengths than Scotchbond 2 DBA with Ti-Core CR, and this trend is in agreement with similar research.

Cermet Cements↗
PubMed1993

Effect of adhesive luting agents on the marginal seating of cast restorations.

This study determined the effect of new adhesive luting agents on the marginal seating of cast restorations. Standardized preparations were completed on freshly extracted premolars, impressions were made, and complete metal veneer crowns were cast with a base metal alloy. The castings were placed on their respective teeth and the extent of marginal opening was recorded. They were then assigned to a luting agent group: glass ionomer cement (GI), polycarboxylate cement (PC), microfilled BIS-GMA composite resin with NPG-GMA/PMDM dentinal bonding agent (GMA + NPG), microfilled BIS-GMA/phosphate ester composite resin (GMA/PE), or zinc phosphate cement (ZP). The castings were cemented and marginal openings remeasured. ANOVA revealed that the cement groups were similar before cementation (p 0.35) but were different after cementation (p < 0.0001). Tukey's multiple comparisons test identified statistically similar groups that were different from other groups and ranked them from lesser to greater marginal opening: (GI, ZP, PC) (GMA/PE, GMA + NPG).

Adhesives↗
PubMed1994

Luting cement-metal surface physicochemical interactions on film thickness.

Low film thickness is critical to the clinical success of cemented castings. This study investigated the effect of luting agent-metal physico-chemical surface interactions on film thicknesses of representative luting agents. Control group luting agents were placed between two glass plates, as described by American Dental Association specifications 8, 61, and 66, and test group luting agents were positioned between glass and metal plates. The materials selected were zinc phosphate cement, polycarboxylate cement, glass ionomer cement, glass ionomer-composite resin hybrid cement and a resinous cement, with a type III gold alloy, a noble metal ceramic alloy, and a base metal ceramic alloy. A two-way analysis of variance and follow-up tests were done. The effects of the type of metal surface, type of cement, and their statistical interaction significantly affected film thickness (p < 0.0001). The type of cement had a greater affect on film thickness than the type of metal. A glass ionomer cement produced lower overall film thicknesses than other cement types, and a noble metal ceramic alloy created lower overall film thicknesses than other types of metal. American Dental Association specifications for cement film thickness did not accurately reflect normal cement use.

American Dental Association↗
PubMed1994

Retention of posts cemented with various dentinal bonding cements.

This investigation evaluated the retention of preformed posts with four different cements: C & B Metabond, Panavia, All-Bond 2, and Ketac-Cem. Sixty intact maxillary canines were selected for the study. The clinical crowns were removed and endodontic therapy done on each root, which was then prepared to receive prefabricated posts. The 60 samples were divided into four groups of 15, and the posts in each group were cemented with one of the four cements. The roots were mounted in acrylic resin blocks and the posts were separated from the canals with an Instron testing machine. Analysis of the forces needed to dislodge the posts with analysis of variance and Student-Newman-Keuls test disclosed that C & B Metabond cement was the most retentive (p < 0.05). No difference in retention was recorded between Ketac-Cem and Panavia cements. All-Bond 2 cement was the least retentive of cements.

Analysis of Variance↗
PubMed1994

Diametral tensile strength and bonding to dentin of type I glass ionomer cements.

This study evaluated the diametral tensile strength of type I glass ionomer cements and measured their tensile and shear bond strengths to dentin with and without conditioning. Four brands of glass ionomer cement and one brand of zinc phosphate cement were tested. Disks of each cement type were prepared and the 7-day diametral compression test for tension was conducted. The shear and tensile tests, with and without 10% polyacrylic acid dentin conditioning, were performed with an Instron testing machine. Two additional groups, one for each bond test, were prepared and conditioned with 90% trichloracetic acid. No significant differences of the diametral strength were found among the various glass ionomer cements. The comparison of means suggests that, except for trichloracetic acid dentin pretreatment, the conditioning is an effective promoter of shear strength and has no significant effect (p < 0.01) on the tensile bond strength. However, trichloracetic acid was found to be a most effective dentin conditioner for both shear and tensile bond strengths (p < 0.01).

Acid Etching, Dental↗
PubMed1993

Strength of a dental glass-ceramic after surface coating.

Clinical evidence suggests that using a resin luting agent rather than a traditional cement reduces the fracture incidence of glass-ceramic crowns. There is some evidence from stress analysis and fractography to indicate that fracture failure is typically initiated from their internal surface. The objective of this study was to determine if surface treatments and cement coatings of the fracture-initiating surface affected fracture stresses of ceramic discs in vitro. Glass-ceramic discs were cast, crystallized, and given various treatments. The discs were fractured with a ball-on-ring of balls biaxial fixture in air. The maximum stresses at the ceramic-coating interface were calculated using the bi-layer material equations. ANOVA and Tukey's multiple range test revealed that resin coating the fracture-initiating surface increased the biaxial fracture strength of the glass-ceramic discs by 33%. The effect was not reduced by short-term water storage. Etching alone did not significantly alter strength. The results suggest that crack-bridging is the most likely mechanism for the strengthening. Selecting techniques and materials that are likely to enhance crack-bridging may be a practical method of improving the performance of ceramic dental restorations.

Acid Etching, Dental↗