| Abstract|| |
Aim: To determine the surface roughness of esthetic restorative materials after finishing and polishing.
Materials and Methods: All 60 specimens were divided into four groups. Group I: Nanocomposite, Z 350 XT (3M ESPE, USA); Group II: Microhybrid composite, Z 250 (3M ESPE, USA); Group III: Compomer, Dyract XP (LD Caulk/Dentsply, USA); and Group IV: Resin modified glass ionomer cement (GIC), Fuji II LC (GC, Japan). Each group was again divided into three subgroups. Subgroup A: Sof-Lex (3M ESPE); Subgroup B: Super-Snap Rainbow finishing and polishing kit (Shofu INC, Japan); and Subgroup C: Control Mylar strip. Surface roughness was determined by Perthen Perthometer S6P profilometer.
Result: Filtek Z350 XT showed minimum surface roughness followed by Filtek Z250, Dyract XT and Fuji II LC. Super-Snap exhibited less surface roughness than Sof-Lex polishing systems.
Statistical Analysis: One-way analysis of variance (ANOVA) followed by multiple post hoc comparisons using least square difference method and unpaired t-test was used.
Conclusion: Filtek Z350 XT with Mylar strip exhibited least surface roughness.
Keywords: Composite; finishing; glass ionomer cement; polishing; surface roughness
|How to cite this article:|
Rai R, Gupta R. In vitro evaluation of the effect of two finishing and polishing systems on four esthetic restorative materials. J Conserv Dent 2013;16:564-7
|How to cite this URL:|
Rai R, Gupta R. In vitro evaluation of the effect of two finishing and polishing systems on four esthetic restorative materials. J Conserv Dent [serial online] 2013 [cited 2019 Nov 13];16:564-7. Available from: http://www.jcd.org.in/text.asp?2013/16/6/564/120946
| Introduction|| |
Achieving favorable esthetics in a tooth colored restoration is critical. Unpolished restorations increase the coefficient of friction and as a result may increase the rate of wear. Moreover rougher surfaces contribute to staining, plaque accumulation, gingival irritation, and recurrent caries. 
The demand for esthetic restorative material has increased substantially in recent years. On extreme ends of the continuum of direct tooth colored restorative materials are conventional glass ionomer cement (GIC) and resin composites. Glass ionomer cements have numerous desirable properties including fluoride release, adhesion to dentin and enamel, similar thermal expansion to dentin, and low solubility in oral fluids when set. , On the other hand composite restorations have better color stability, good adhesion to tooth structure, less porosity, and good strength.  Different composite materials have different surface characteristics which affect the longevity of the restoration. , A highly polished surface is difficult to achieve due to different amount of filler particles, their particle size and difference in hardness between filler particles and the matrix of resin composite. 
Recently, nanofilled composites have been introduced which consists of nanofillers. They have increased wear resistance and enhanced polishability due to reduced interstitial spacing between filler particles. , It can be used in all areas of mouth and provide smooth surface and mechanical properties suitable for high stress bearing areas.
In restorative procedures, surface characteristics such as roughness determine the clinical quality and behavior of restorative materials. Several articles have reported the effect of various polishing systems on surface roughness. ,,,, Most have indicated that none of the various polishing sequences could reproduce the surface smoothness initially created by a Mylar strip. However, the correct anatomic contour of the restoration is rarely achieved by using only a Mylar strip. 
Different methods can be used for finishing and polishing of the restorations.  Studies have reported no appreciable difference in plaque accumulation between surfaces polished by methods that resulted in average surface roughness (Ra) values within a 0.70-1.4 mm range.  However, there is a lack of consensus as to which material and technique provides the smoothest surfaces for composite. 
Filtek Z350 XT, a nanofilled composite has emerged as a new esthetic restorative material. Long-term conclusive studies on the behavior of compomer and glass ionomer cement during finishing and polishing are fewer.  Thus, the purpose of this investigation was to determine the surface roughness of different esthetic restorative materials (Filtek Z350XT, Filtek Z250, Dyract XP, Fuji II LC) after finishing and polishing with different kits (Sof-Lexfu Finishing and Polishing Kit and Super-Snap Rainbow Kit).
| Materials and Methods|| |
Sixty sample discs of four esthetic restorative materials were prepared to measure the surface roughness using profilometer. All the specimens were divided into four groups each consisting of 15 discs each.
Each group was further divided into three subgroups containing five specimens each. According to different polishing techniques the subgroups was:
- Group I (n = 15) - Nanocomposite-Z 350 XT (3M ESPE, St Paul, USA)
- Group II (n = 15) - Microhybrid composite-Z 250 (3M ESPE, St Paul, USA)
- Group III (n = 15) - Compomer-Dyract XP (LD Caulk/Dentsply, Milford, DE, USA)
- Group IV (n = 15) - Resin modified GIC-Fuji II LC (GC, Tokyo, Japan)
Subgroup A - Sof-Lex Finishing and Polishing Kit (3M ESPE, St Paul, USA)
Subgroup B - Super-Snap Rainbow Finishing and Polishing Kit (Shofu INC., Kyoto, Japan)
Subgroup C - Negative control Mylar strip.
All the specimens were prepared using standardized cylindrical molds with dimensions 10 × 2 mm. The mold was placed on a glass slab, which was covered with a transparent Mylar strip. The restorative material was placed directly into the mold in one increment using Teflon-coated hand instrument. The material was covered with another transparent Mylar strip on the top of the filled mold. A glass slide was placed against the top surface of transparent Mylar strip and pressed with light pressure to expel excess material from the mold. Quartz tungsten halogen activation light unit (API, India) was used to cure each specimen for 20 s. The intensity of curing light, that is, 1000 mW/cm 2 was always checked prior to curing of each specimen with an in-built radiometer.
The tip of light cure unit was in contact with the glass slide to keep a standard distance between the light cure unit and the specimen as 1 mm. The specimens were finished/polished with graded series (coarse, medium, fine, and extra fine) of Sof-Lex and Shofu rainbow discs. Finishing/polishing was carried out at 10,000 rpm for coarse and medium discs and 30,000 rpm for fine and extra fine discs as per manufacturer's instructions in planar motion. Discs once used were discarded. After each polishing step all the specimens were thoroughly rinsed with water and air-dried before next step until final polishing. For control subgroup, specimens were cured against Mylar strip only.
All the specimens were stored in light proof black container for 24 h at 37°C and 95 ± 5% relative humidity so as to simulate clinical conditions. The specimens were washed. Surface roughness was determined by Perthen Perthometer S6P profilometer. It was characterized by the height parameter, Ra (mm). Three measurements passing through the center of the specimen were performed and the average was obtained.
The results were tabulated and subjected to statistical analysis. The analysis was carried out with Statistical Package for Social Sciences (SPSS) software version 13. One-way analysis of variance (ANOVA) with post hoc analysis (least square difference) was applied to check significance among the various groups. Unpaired t-test was applied to evaluate significance among groups with respect to finishing systems. P-value < 0.05 was considered as statistically significant level.
| Results|| |
The results showed that among the materials, surface roughness was found to be in the following order: Filtek Z350 XT < Filtek Z250 < Dyract XT < Fuji II LC. This difference in surface roughness was statistically significant (P < 0.0001) in all the four experimental groups. Comparison of different polishing kits showed that there was a statistically significant difference (P < 0.0001) in surface roughness between all the subgroups. Super-Snap exhibited less surface roughness than Sof-Lex finishing kit. It was also revealed that best surface smoothness was obtained by Mylar strip [Table 1] and [Table 2].
|Table 2: One-way analysis of variance (ANOVA) amongst groups I, II, III, and IV for surface roughness|
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| Discussion|| |
The continuous development of esthetically acceptable adhesive restorative material has made a variety of tooth colored materials available for clinical use. Recent composites based on nanoparticle filler technology have been developed which can be used in esthetic as well as stress bearing areas. ,
The literature reveals that both the type of restorative material as well as the finishing and polishing protocol influence the surface geometry of esthetic restorations. ,,
In the present study, on comparing the mean surface roughness, it was found that all subgroups of Group I had less surface roughness as compared to corresponding subgroups of Group II which was statistically significant (P < 0.05). This may be attributed to their small particle size. The average particle size of primary filler in nanocomposite and microhybridis in nanometer and micrometer range, respectively. Due to this small size of filler particles the wear of the restoration does not create a rough surface. These results are supported by Lu et al., who also reported better surface smoothness of nanocomposites.  But these results are in contrary to Mitra et al., who reported similar surface roughness with nanoparticle resin Z350 XT and microhybrid resin Z 250.  They explained these findings as although the above mentioned two restorative materials are differently classified with regard to composition, the inorganic matrices of the resins are similar.
All the subgroups of Groups I and II showed less surface roughness than corresponding subgroups of Group III. Group III, that is, Dyract XT is a compomer which exhibits a closer chemical relationship to composite resin but gives different results on finishing and polishing. These results are also supported by Al-Fawaz and Awilya, who also reported less surface roughness with composite resin as compared to Hytac which is a compomer. 
On comparing the mean surface roughness of subgroups of Group IV, that is, glass ionomer cement to the corresponding subgroups of Groups I, II and III; the glass ionomer cement specimens showed more surface roughness. This can be explained due to incorporation of voids during mixing of cement. These results are supported by Neme et al., who also observed greater surface roughness in resin modified GIC as compared to hybrid composite. 
On comparing the mean surface roughness of all the groups of Subgroups A (Sof-Lex), B (Super-Snap), and C (Mylar strip); the results showed that the surface roughness was found in the following order: Sof-Lex > Super-Snap > Mylar strip.
The Mylar strip provided maximum surface smoothness. This can be explained due to presence of resin rich layer on the surface which is eliminated during finishing and polishing procedures leading to rougher surface. 
The Sof-Lex and Super-Snap aluminum oxide discs provide adequate surface smoothness as these discs do not displace the composite fillers. The filler in nanocomposite is so small that their stiffness is reduced and oxide discs are best recommended because their malleability promotes a homogenous abrasion of the fillers and the resin matrix.
The results showed that Super-Snap polishing kit produces decreased surface roughness as compared to Sof-Lex polishing kit. These results are supported by Barbosa et al., who observed smoother surfaces by Super-Snap system as compared to Sof-Lex system suggesting a better ability of Super-Snap discs to remove the scratches left by diamond burs. ,
Differences in the roughness after finishing and polishing techniques may be ascribed to distinct patterns of particle size and their arrangement within the resin matrix. For a finishing system to be rendered effective, the cutting particles must be harder than the filler particles; otherwise the abrasive medium may abrade the softer matrix only. This may paradoxically result in higher surface roughness. Therefore, the effectiveness of finishing and polishing procedures on restorative material surface may be more critical. 
Therefore within the limitations of this study it can be concluded that:
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.
- Filtek Z350 XT showed the minimum surface roughness amongst the experimental groups for all the polishing systems tested followed by Filtek Z250, Dyract XT, and Fuji II LC.
- Mylar strip exhibited least surface roughness followed by Super-Snap and Sof-Lex polishing system.
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Department of Conservative Dentistry and Endodontics, Institute of Dental Studies and Technologies, Modinagar, Uttar Pradesh - 201 201
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]