The influence of finishing time on the marginal seal of a resin-modified glass-ionomer and polyacid-modified resin composite

The Effect of Additional Finishing and Polishing Sequences on Hardness and Roughness of Two Different Dental Composites: An In Vitro Study

Aim:

The aim of this study was to evaluate the effect of additional finishing and polishing sequences on a new structural colored (Omnichroma) and a conventional dental composite (Estelite Sigma Quick).

Materials and Method:

Forty disk-shaped dental composite specimens were prepared from each dental composite and assigned to four groups in terms of additional finishing polishing sequences. Group 1: Mylar strip (control). Group 2: Abrasive disks. Group 3: After abrasive disks, application of a felt brush with abrasive paste. Group 4: After abrasive disks, application of a felt brush with abrasive paste. Then, a single-bottle adhesive was applied as a surface sealer. Hardness and surface roughness were measured using the Vickers hardness test and a profilometer, respectively. SEM images of one of each group were captured at 500x, 1500x, and 3500x magnifications. Two-way analysis of variance, Tukey HSD, and Shapiro–Wilk tests were used for the statistical analysis.

Results:

Mean hardness values differ in terms of finishing-polishing sequences ( P < .001), dental composites ( P < .001), and interaction of finishing-polishing sequences-dental composites ( P < .001). Mean roughness values differ in terms of finishing-polishing ( P = .002). The main effect of composites on roughness values was not found statistically significant ( P = .990). Also, there is no difference between the mean roughness values in terms of the interactions of finishing-polishing and composites ( P = .967).

Conclusion:

Finishing-polishing with abrasive disks and abrasive paste are important steps for these dental composites. However, the application of a single-bottle adhesive as a surface sealant on these composites decreases the hardness of the materials.

Review: Finishing and polishing procedures of (resin-modified) glass ionomers and compomers in paediatric dentistry

BACKGROUND

A smooth surface has a beneficial effect on the aesthetic quality and longevity of a dental restoration, as well as on its biocompatibility with oral tissues. In this review studies on glass-ionomer cements (GIC), resin-modified glass-ionomer cements (RM-GIC), and compomers or polyacid-modified resin composites (PAM-C) were assessed as these are currently used in paediatric dentistry.

METHOD

Medline databases (USA National Library of Medicine) was searched using WinSpirs and Pubmed. This search used a keyword filter including dental materials, polishing procedures, and instrumentation including influencing factors.

FINDINGS

Although the literature shows different commercially available tools it seems that the ideal polishing instrumentation in paediatric dentistry for GIC and compomers is not yet on the market. Furthermore, the constant development of dental materials and polishing products impose a need for continuous scientific research.

Evaluation of the surface hardness of composite resins before and after polishing at different times

PURPOSE

The aim of this study was to evaluate the surface hardness of six composite resins: Revolution, Natural Flow, Fill Magic Flow, Flow-it! (flowables), Silux Plus (microfilled) and Z100 (minifilled) before and after polishing at different times.

MATERIALS AND METHODS

For this purpose, 240 specimens (5mm diameter, 1.4mm high) were prepared. Vickers hardness was determined before and after polishing at different times: immediately, 24h, 7 and 21 days after preparation of the samples. Statistical analysis was performed by ANOVA and Tukey test.

RESULTS

There was no difference in the hardness of flowable resins, which had lower hardness than the minifilled resin. The minifilled resin showed the highest surface hardness as compared to the other materials (p<0.01). All materials exhibited higher hardness after polishing, being more evident after 7 days.

CONCLUSION

It may be concluded that, regardless of the composite resin, surface hardness was considerably increased when polishing was delayed and performed 1 week after preparation of the samples.

Evaluation of microleakage in human, bovine and swine enamels

The suitability of bovine and swine teeth has been evaluated when they are used as substitutes for extracted human teeth in varied researches. This study evaluated in vitro the marginal microleakage in human, bovine and swine enamel. Cubic cavities (2 x 2 x 2 mm³) were prepared in enamel blocks from human, swine and bovine teeth. The cavities were filled with composite resin and conventional glass-ionomer cement. All the samples were thermocycled for 1,000 cycles (5 ± 2°C - 55 ± 2°C) and immersed in 2% methylene blue solution for 12 hours. The microleakage was quantified by a spectrophotometric technique. The results were statistically analyzed using ANOVA and Tukey's test. The glass-ionomer cement presented significantly higher leakage means (µg/ml ± SD) than the composite resin for all substrates (0.0695 ± 0.01313 vs. 0.0471 ± 0.0163, p < 0.01). No significant differences were found between bovine and swine enamel (0.0668 ± 0.0246 vs. 0.0674 ± 0.0286); however, both presented statistically higher leakage means than human enamel (0.0407 ± 0.0195, p < 0.01). It was concluded that the microleakage pattern was affected by substrates, and that bovine and swine substrates allow higher marginal leakage than human substrates. The results indicate there should be precaution in the substitution of human substrate in laboratory studies of microleakage.