Determining smoothness of polished microfilled composite resins

Profilometric analysis of two composite resins' surface repolished after tooth brush abrasion with three polishing systems

Aim:

To evaluate the effect of three polishing protocols that could be implemented at recall on the surface roughness of two direct esthetic restorative materials.

Materials and Methods:

Specimens (n = 40) measuring 8 mm (length) × 5 mm (width) × 4 mm (height) were fabricated in an acrylic mold using two light-cured resin-based materials (microfilled composite and microhybrid composite). After photopolymerization, all specimens were finished and polished with one of three polishing protocols (Enhance, One Gloss, and Sof-Lex polishing systems). The average surface roughness of each treated specimen was determined using 3D optical profilometer. Next all specimens were brushed 60,000 times with nylon bristles at 7200 rpm using crosshead brushing device with equal parts of toothpaste and water used as abrasive medium. The surface roughness of each specimen was measured after brushing followed by repolishing with one of three polishing protocols, and then, the final surface roughness values were determined.

Results:

The data were analyzed using one-way and two-factor analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD). Significant difference (P < 0.05) in surface roughness was observed. Simulated brushing following initial polishing procedure significantly roughened the surface of restorative material (P < 0.05).

Conclusion:

Polishing protocols can be used to restore a smooth surface on esthetic restorative materials following simulated tooth brushing.

Effect of finishing technique on the microleakage and surface texture of resin-modified glass ionomer restorative materials

PURPOSE

The purpose of this study was to evaluate the effects of wet and dry finishing/polishing procedures on the microleakage and surface texture of resin-modified glass ionomer (RMGI) restorative materials.

MATERIALS AND METHODS

Class V cavity preparations were made at the cemento-enamel junction (CEJ) on the buccal and lingual surface of 30 extracted human molars. The teeth were restored in three groups of 10 (20 preparations in each group) using Fuji II LC and Vitremer, both RMGIs, and Fuji II, a capsulated conventional glass ionomer cement (control). One restoration per tooth was finished/polished with copious applications of water and the other was finished/polished without water. All restorations were finished/polished using a sequence of four abrasive disks. Finishing/polishing was initiated according to manufacturers' instructions-immediately after light-curing Fuji II LC and Vitremer, and 15min after placement for Fuji II. The specimens were thermocycled and subjected to a silver nitrate leakage test. Each tooth was sectioned buccolingually and examined with an optical microscope at 40x to determine the extent of microleakage at enamel and dentin margins. The data were subjected to a non-parametric statistical analysis. To evaluate surface roughness after polishing, three disks each of Vitremer and Fuji II LC were fabricated in Teflon molds. One disk of each material was not finished/polished (control). The others were finished/polished using Sof-Lex abrasive disks. One specimen of each material was kept wet during all finishing/polishing procedures, while the other was kept dry. Atomic force microscopy was used to determine the average roughness (R(a)) of the specimens.

RESULTS

For each material, microleakage at the enamel margin was very slight. Leakage of the conventional glass ionomer Fuji II was severe at dentin margins. Statistical analysis indicated that both Vitremer and Fuji II LC had significantly less leakage than Fuji II, and that Vitremer had significantly less leakage than Fuji II LC (p<0.05). Leakage at enamel margins was significantly less than at dentin margins. Differences related to wet and dry polishing were not statistically significant. Profilometry data indicated that polished specimens were rougher than those cured against a Mylar strip. Wet polishing created greater surface roughness than dry polishing.

CONCLUSIONS

RMGIs rather than conventional glass ionomers should be used in Class V cavity sites to allow immediate finishing and to reduce the incidence of microleakage. Dry finishing of RMGIs with abrasive disks is recommended because it produces a smoother surface and does not contribute to microleakage. However, wet finishing of conventional glass ionomers is still recommended to avoid desiccation.

The surface finish of light-cured composite resin materials

A necessity for any dental restorative material is its ability to take and maintain a smooth surface finish. Composite resin restorative materials with fillers and matrix of differing hardness are difficult to finish and polish. The use of aluminum trioxide discs is a popular and acceptable method of finishing composite restorative materials where the material is accessible. Burs and stones are used for finishing and polishing inaccessible areas. This study was undertaken to compare the surface finish of composite resin restorative material when finished with white stones, superfine diamond burs and aluminum trioxide discs. The finished surface was measured with a profilometer and the roughness average value used to compare the surfaces. The aluminum trioxide discs gave the best and most consistent results. It was possible to attain similar results with the superfine diamond bur. However, the results were highly variable. None of the methods used achieved the smoothness of composite resin cured against a transparent matrix.

Effectiveness of reciprocal-action instrumentation for polishing composite resin: an in vitro study

This in vitro study investigates the use of reciprocal-action instrumentation for polishing composite resin restorative materials. Electron photomicrographs were made of surfaces of a microfilled and a hybrid composite resin restorative material polished by various reciprocal-action polishing procedures, including several types of polishing pastes used with nonabrasive plastic tips. The best polish on the microfilled composite resin restorative material tested was produced by ending with 3-mu diamond polishing paste. The best polish on the hybrid composite resin restorative material tested was produced by ending with 0.5-mu diamond polishing paste. The surfaces produced were comparable to those produced by polishing discs.

An evaluation of polishing agents for composite resins

After the gross reduction and fine finishing of a composite resin restoration, selecting a system to create the smoothest polish is difficult because high magnification is necessary to compare the surface roughness. The surfaces of four anterior and posterior composite resins were compared using a Mylar strip, an unfilled resin as a glaze, polishing with three rubber polishers, and three different manufacturers' series of disks. This study suggested that pairing a specific composite resin with a matching polishing system produced the smoothest surface. Because of the differences in the size, shape, number of filler particles, and the type of resin, one system was incapable of creating the smoothest surface for all composite resins.

The nature and effects of composite finishing pastes

Specimens of composite resins, contoured and finished with a series of microfine diamonds, were finished with a selection of commercially available composite finishing pastes. The resulting surfaces were examined using scanning electron microscopy (SEM) and surface profilometry. Samples of the pastes were investigated using SEM and energy dispersive X-ray spectroscopy. All the paste systems employed an abrasive of similar composition and particle size. The selection of finishing pastes produced marked improvements of the surfaces of the composite resins. The small differences measured between the performances of the four finishing pastes included in this study could not be corroborated by SEM evaluation. Therefore, within the limitations of this study, there was little evidence to suggest that any one paste system was superior to the others. The results of this study indicate that commercially available composite resin finishing pastes of the type investigated may be used to improve the surface of all types of contemporary composite resins and may be of particular value in finishing the concave surfaces of restorations of composite resins following contouring and finishing with microfine diamond burs.

Evaluation of surface finish of microfilled resins

Five microfilled resin restorative materials were evaluated for ease of polish and surface finish. Ease of finish was evaluated subjectively; surface smoothness with a profilometer. In addition, scanning electron microscope examinations were conducted to evaluate the structural composition of the microfills. No difference was found in ease of finish, but surface smoothness varied among the five products. The SEM evaluation revealed that four of the products had a heterogeneous composition while the fifth appeared to be a homogeneous microfill.

Finishing and polishing of composites

Four different methods for finishing and polishing the surfaces of two different composite materials were studied by measuring the roughness of specimens at different stages of the procedures. Method 1 consisted of four different Shofu SuperSnap discs. Method 2 included the Shofu Dura-White stone, the Shofu CompoSite point, and the Vivadent polisher for composite resins. In method 3 the four 3M Sof-Lex XT discs were used. Method 4 comprised a green stone, a carbide finishing bur, and the Vivadent polisher for composite. All four methods were completed by using Kerr Command Ultrafine Lustre Paste. The composites used were Silux and P30. After the initial finishing, all four methods gave significant effect when used on the Silux, but on the P30 only methods 2, 3, and 4 gave a significant improvement. However, the degree of effectiveness of the methods varied greatly.

Abrasion of acrylic veneers by simulated toothbrushing

The abrasion responses were tested on four acrylic veneer materials, K + B Plus, K + B 75, Isosit, and Ivocron. The studies were performed in two independent research laboratories. Two different brushing machines were used with an abrasive slurry. The results were used for comparing the degree of abrasion for the resin materials. Three analytical methods of measuring the degree of abrasive wear were used: surface profile measurement, microscopic evaluation, and measurement of loss of volume. Isosit showed the best abrasion resistance of the four materials tested.