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Microleakage of various composite resin systems
Abstract
The object of this study was to compare the microleakage between various composite resin systems of multistep, one-bottle, and self-etching systems using electrical conductivity. After making class V cavities ( around CEJ), they were bulk filled with three kinds of resins of A3. Teeth were storaged in a saline solution for one day, after then, they were finished and polished using Sof-Lex system. Another stress of thermocycling was made for 500 times from with each dwelling time of 10 seconds. Electrical conductivity (microamphere, ) was checked four times: before and after cavity preparation, after filing, after thermocycling. One-way ANOVA and 95% Scheffe Post Hoc test was used for checking any statistical difference among groups. Another 95% Paired Samples T-test was also used for estimating any significant difference within group after cavity filling or thermocycling. The results were as follows: 1 Every specimen showed various range of microleakage after filing. There was, however, no difference between composite resin systems. 2. All composite resin systems showed marked increase in microleakage with a thermocycling (p
The purpose of this study was to evaluate the effect of a new resin monomer on the microleakage of composite resin restorations. By adding new methoxylated Bis-GMA (Bis-M-GMA, 2,2-bis[4-(2-methoxy-3-methacryloyloxy propoxy) phenyl] propane) having low viscosity, the content of TEGDMA which has adverse effects on polymerization shrinkage might be decreased. As a result, microleakage might be improved. cavities with occlusal margins in enamel and gingival margins in dentin were prepared on buccal and lingual surfaces of 40 extracted human premolars. Prepared teeth were randomly divided into four groups and restored with Clearfil SE bond (Kuraray, Japan) and one of experimental composite resins; EX1, Experimental composite resin1 (Bis-M-GMA/TEGDMA = 95/5 wt%, 40 mm nanofillers); EX2, Experimental composite resin2 (Bis-M-GMA/TEGDMA = 95/5 wt%, 20 mm nanofillers); EX3, Experimental composite resin3 (Bis-GMA/TEGDMA = 70/30 wt%, 40 nm nanofillers); and Filtek Z250 (3M ESPE, USA) was filed as a control group. The restored teeth were thermocycled, and immersed in 2% methylene blue solution for 24 hours. The teeth were sectioned buccolingually with a low speed diamond saw and evaluated for microleakage under stereomicroscope. The data were statistically analyzed by Pearson Chi-Square test and Fisher Exact test (p = 0.05). The microleakage scores seen at the enamel margin were significantly lower than those of dentin margin (p = 0.007). There were no significant differences among the composite resins in the microleakage scores within each margin (p > 0.05). Bis-M-GMA, a new resin monomer having low viscosity, might in part replace high viscous Bis-CMA and might improve the quality of composite resin.
To evaluate microleakage of Class V resin-based composites (RBC) bonded with two self-etching dentin adhesive systems. Class V cavities were restored with either one or three increments of RBC to determine whether the restorative method affected microleakage.
60 extracted human premolars and molars were randomly assigned to 6 groups for bonding with Clearfil Liner Bond 2V or Etch & Prime 3.0 or Prime & Bond NT. The latter, using a total-etch technique, was used as a control. Cavities were cut in both the buccal and lingual surfaces. Half of each preparation was in enamel and half was in cementum/dentin. The teeth were thermocycled and the restorations examined microscopically for leakage using Procion Brilliant Red as a marker. SEM microphotographs were prepared from dye-labeled and non dye-labeled areas to illustrate the micromorphology of the systems.
None of the groups showed microleakage at the enamel margins. All groups showed microleakage at the gingival margins. At the gingival margin, there was no significant difference between the groups irrespective of the bonding material (Kruskal-Wallis: ANOVA P=0.2113). No significant difference was observed with each material when the bulk filling (one increment) technique was compared with the three-increment technique. SEM showed that the self-etching materials produced a shallower depth of etch, and a less abundant resin tag complex than the material using a separate phosphoric acid gel. In dye-labeled areas, debonding was predominantly cohesive in resin.
Gingival margin microleakage is not prevented by either restoring cavities with self-etching materials of the control using a total-etch technique.
The electrical conductivity readings of extracted human teeth were taken: prior to placement of pit and fissure sealants; immediately after placement of the pit and fissure sealants; 2 weeks after immersion of the specimens in distilled water at 37°C; and after 7200 strokes on a toothbrushing machine. The specimens were then immersed in dye for 24 h, sectioned and evaluated for evidence of dye penetration.
The electrical conductivity readings were then compared to dye penetration results to determine if a correlation existed.
A positive correlation existed between the electrical conductivity readings and dye penetration. Threshold values of electrical conductivity existed (which varied for each sealant)—readings above these threshold values indicated sealant failure or leakage.
The possibility of using electrical conductivity as a diagnostic tool is definitely worthy of further research—particularly its potential as an in vivo method of assessing leakage.
This study compared microleakage patterns for glass-ionomer-cement-based resin systems with and without a separating agent placed between the glass ionomer and resin. Results indicated significant leakage (100%) at the dentin glass-ionomer interface for specimens without a separating agent. Those with a separating agent showed almost no leakage between the dentin and glass ionomer (10%) and some leakage at the resin/glass ionomer interface (40%). These results suggest that the forces of polymerization shrinkage are stronger than the chemical bond between glass-ionomer cement and dentin. This bond fails during resin polymerization, eliminating any supplementary retention gained through chemical adhesion to dentin and opening a pathway for microleakage.
The use of adhesive resin composites for restoration of Class V lesions often results in cervical marginal gap formation due to polymerization contraction. In this laboratory study, flexible linings applied between the bonding agent and the bulk restorative appeared to preserve the marginal integrity of Class V restorations during curing. Measurements of the polymerization contraction stress showed 20 to 50% relief due to various flexible intermediate materials. Apparently, reduction of the total stiffness by application of an intermediate layer can render the total restoration sufficiently flexible to compensate for that part of the stress that would otherwise exceed the bond strength.
Two standardized V-shaped cavities were prepared at the cementoenamel junction of buccal and lingual surfaces of each of 45 extracted premolars (total 90 cavities). Nine combinations of bonding agents (Bondlite, Cervident, Clearfil, Heliobond, Pyrofil, Scotchbond, Concise) with restorative materials (Command, Ultrafine, Cervident, Silux, Heliosit, Pyrofil, Ketac-fil, Concise) were randomly assigned to the cavities. After thermocycling, dye penetration and sectioning of the teeth, the degree of penetration in the cavity walls was assessed. All combinations showed some degree of leakage. In all cases significantly more leakage was found in gingival (dentin or cementum) walls than in occlusal (enamel) walls. For enamel walls combinations of Bondlite with Command ultrafine and Pyrofil newbond with Pyrofil were superior; for dentin or cementum walls the combination of Clearfil newbond with Silux gave the least leakage.
Although much has been accomplished during recent years, it is apparent that a great deal remains to be done for a more comprehensive understanding of the microleakage phenomenon. The techniques used in the past have contributed to a better understanding of the subject. Perhaps the future of microleakage study lies in the development of new techniques, the reapplication of old techniques, or the combination of several that have been reviewed. Use of the electron microprobe or the scanning electron microscope may provide answers to many remaining questions.