One of the desirable features for a satisfactory restoration is smooth surface finish. ¹ , ² High-quality finishing and polishing of dental restorations are important aspects of critical clinical restorative procedures that enhance both esthetics and longevity of restored teeth. ³ , ⁴ , ⁵ Surface roughness due to improper finishing/polishing of dental restorations can result in excessive plaque accumulation, gingival irritation, increased surface staining, and poor esthetics of restored teeth that could potentially lead to demineralization of enamel, possible recurrent caries, and periodontal problems. ⁶ , ⁷ , ⁸ , ⁹ Furthermore, patient consciousness of restorations with possible irritations to tongue, lips, and cheeks is matter of concern. Therefore, smoothness of restorations is of utmost importance for its success.

Among the wide variety of finishing and polishing devices that are available in the market to the clinician, silicon carbide-coated or aluminum oxide-coated abrasive discs, impregnated rubber or silicone discs and wheels, mutifluted tungsten carbide finishing burs, and hard bonded-surface coated ceramic diamond rotary instruments are most commonly used to finish and polish dental restoratives. ¹ , ⁵ , ¹⁰ , ¹¹ Each of these instruments or devices leaves the surface of various restorative materials with varying degrees of surface roughness.

The effectiveness of finishing/polishing procedures on restorative surfaces is an important consideration in restorative processes. As finishing/polishing procedures are usually conducted immediately postpolymerization, this prematurity can make the restorative material more susceptible to effects of heat generation. Delayed finishing/polishing may make the restorative material less susceptible to negative effects of heat generation. ¹² , ¹³ , ¹⁴ Thus, it becomes important to determine which finishing/polishing system and finishing/polishing time offer best results for esthetic restorative materials in clinical practice.

The study aimed to evaluate the efficacy of various finishing and polishing systems using various procedures on surface roughness of esthetic restorative materials and also to evaluate the effect of immediate or delayed finishing/polishing procedures on surface roughness of esthetic restorative materials.

A well-finished restoration with less adhesive properties contributes not only to better esthetics but also reduces the development of secondary caries and periodontal disease. Thus, we must remain cognizant of the right polishing system and timing for each material to obtain optimum results.

Materials used in the study

In this experimental in vitro study, silorane-based composite, methacrylate-based composite, compomer, and glass ionomer cement were evaluated for surface roughness Table 1.{Table 1}

The samples were represented as follows:

Silorane-based composites (SBC)

Specimen preparation

All specimen preparation was done by a single operator, to reduce variability. Specimens were prepared using Brass molds (10 mm diameter × 2 mm thickness). The mold was sandwiched between transparent matrix strips. The uncured composites were inserted into the mold and intentionally overfilled. Light pressure was applied to expel excess material from the mold. Each specimen was light cured (CICADA dental LED curing light radiometer, Foshan CICADA Dental Instruments Co, Ltd, China) through the top and bottom for the duration recommended by the manufacturers. The intensity (200–400 mW/cm ²) of the light-curing unit was checked before each sample run using a radiometer. The set cylindrical specimens were separated from the mold. The specimens were stored at 100% relative humidity at 37°C for 24 h.

Experimental design

Eighty specimens of each restorative material were fabricated (n = 10). The matrix strip formed surface was used as a baseline for all tests. Twenty specimens were finished and polished immediately using four finishing and polishing procedures and the remaining twenty specimens were finished and polished after a week Figure 1. Specimens were examined for obvious voids, labeled on the bottom and randomly separated into four treatment groups. Figure 1

Expermental design

Data were statistically analyzed by t-test (for each material and time period) and one-way ANOVA followed by Tukey's post hoc (for finishing and polishing agents). The data were expressed as mean ± SD P < 0.05 was considered as significant.

Analysis of time period irrespective of finishing and polishing system showed that Ra values were greater (P < 0.05) in delayed polishing in GIC > MBC > SBC > DAP, suggesting immediate polishing is better. Within the materials, when immediate and delayed polishing was compared to baseline readings, polishing was better (less Ra value) in DAP < SBC < MBC < GIC in immediate; whereas in delayed polishing, the order was SBC < MBC < DAP < GIC. Among the materials, SBC had the least Ra values indicating the smoothest surface among all materials, followed by MBC, DAP, and GIC Figure 2and Figure 3. Comparison of polishing and finishing systems irrespective of materials showed that Ra values were lower (P > 0.05) in diamond + Astropol combination followed by tunsten + soflex, tungsten + Astropol whereas as diamond + soflex had the greatest Ra values indicating that diamond and soflex combinations should be least used during the finishing and polishing of composites Figure 2and Figure 4. Figure 2

Comparison of roughness with materials and finishing/polishing systems (μm).

The finishing and polishing techniques employed for the tooth-colored dental restorative materials improves its longevity and aesthetic appearance of the material. ¹⁵ Polishing is complicated by the heterogeneous nature of these dental materials, i.e., hard filler particles embedded in a relatively soft matrix. Some other factors affecting the polishability of resin restorations are filler content, particle size, polishing medium, and polishing technique. ¹⁶ , ¹⁷ In this study, Surtronic 3 + was used to evaluate the surface roughness values (Ra) and the results were statistically analyzed using one-way ANOVA with Tukey's post hoc.

The time for finishing and polishing is an important factor to be considered because it has an effect on the surface roughness of esthetic restorative materials. In this study, irrespective of polishing system used, both GIC and MBC showed increased roughness values at both the immediate (24 h) and delayed (1 week) period as compared to the baseline value. Among the polishing materials, DAP and SBC demonstrated least Ra values within 24 h (immediate) followed by MBC and GIC while the Ra values after a 1 week (delayed) showed SBC and MBC created the least surface roughness followed by DAP and GIC.

Therefore, based on the results of this study, the surface roughness of the materials when finished/polished was measured immediate (24 h) showed the least Ra values when compared to delayed (1 week). These results were supported by Venturini et al. ¹⁴ that immediate polishing did not produce a negative impact on the surface roughness, hardness and microleakage of a microfilled (Filtek A110) and a hybrid (Filtek Z250) resin composite compared to delayed polishing. Cenci et al. ¹⁸ recommended immediate polishing since this procedure reduces the number of clinical sessions. Several other authors also have proposed a 24-h delay for finishing procedures, ¹⁹ , ²⁰ which supports the result obtained in this study, but most clinicians perform finishing/polishing procedures immediately after restoration placement.

However, the system used for finishing and polishing also should be taken into consideration. The types of finishing/polishing systems and abrasives might have an influence on the surface roughness of the materials. Despite carefully placing the matrixes during esthetic restoration, removal of excess material or recontouring of restorations is often clinically necessary. For proper contouring anatomically structured teeth, diamond and carbide burs are necessary. ¹ Finishing diamonds were best suited for gross removal and contouring because of their high cutting efficiency oncomposite surfaces while carbide finishing burs would be best suited for smoothing and finishing as a result of their low cutting efficiency. ²¹ , ²²

In this study, extra-fine diamond burs and 30-fluted tungsten carbide burs were used to finish the surface of the restorations and following these procedures soflex discs (in Groups I and III) and Astropol and Astrobrush (in Groups II and IV) were used to polish the restorations. When different polishing systems were used irrespective of materials, the surface roughness (Ra) values varied from high to least in the order when diamond bur-soflex disc, tungsten carbide bur-Astropol and Astrobrush, tungsten carbide bur-soflex disc, and diamond bur-Astropol and Astrobrush.

According to the results obtained in this study, the surface finish was good when diamond bur–Astropol and Astrobrush was used. Other investigator have shown that Super-snap abrasive discs produced a smoother surface than Astropol and Astrobrush silicone polishers for all the materials, ¹⁹ the results would be valid clinically for readily accessible and flat surfaces, i. e., not for all areas in the mouth. Therefore, silicone polishers are necessary for posterior areas and for concave and convex surfaces. ¹⁹

After finishing and polishing of esthetic materials with different techniques, the remaining roughness may be attributed to distinct patterns of particle size and their arrangement within the resin matrix. For a finishing system to be rendered effective, the cutting particles should be harder than the filler particles; otherwise, the abrasive medium may abrade the softer matrix only. This may result in higher surface roughness. Therefore, the effectiveness of finishing and polishing procedures on restorative material surface may be more critical. ²³ , ²⁴ Further research is required to assess the other mechanical properties of these esthetic restorative materials. Additional in vivo and in vitro studies are desirable to further substantiate the findings of this study.

Under the limitations of this in vitro study, it might be concluded that: (i) SBC showed least Ra values followed by < MBC < DAP < GIC, (ii) immediate (24 h) finishing/polishing of materials is better than delayed, and (iii) among all the polishing system used diamond bur–Astropol and Astrobrush showed good surface finish.

Acknowledgment

This study was supported by Indian Council of Medical Research under the Short Term Research Scholarships (STS 2014), research proposal no: 2014-05757.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or nonfinancial in this article.