INTRODUCTION Introduction of composite restorative materials in the 1960s marked the beginning of modern cosmetic dentistry by combining the principles of esthetics and tooth conservation. Smooth, highly polished restorations are more esthetically appealing and less susceptible to plaque accumulation and extrinsic discoloration and they also exhibit improved mechanical properties.1 Early studies have shown that the smoothest surface of a resin restoration is attained when the resin is polymerized against an appropriate matrix strip. When a matrix is not used, polymerization of outer layer is inhibited, resulting in a surface layer rich in organic binder with stick and soft consistency. In either case, removal of that outermost resin by trimming and nishing procedures would lead to producing a harder, more wear resistant, and, hence, a more aesthetically stable surface.2 The primary goal of nishing is to obtain a restoration with good contour, occlusion, healthy embrasure forms and a smooth surface. Tight margins of the restorations should blend aesthetically into the tooth's natural contours.2 The resin matrix and the ller particles of composite resins do not abrade to the same degree due to different hardnesses. For instance, craters are often formed around hard quartz particles of conventional composite resins after polishing. As consequence, irregularities appear on the surface of the restorations. The ller content of the composite resin also affects roughness, as microlled composite resins show smoother surfaces than hybrid composite resins. Similarly, the resin matrix composition may also play a role in the nal smoothness of the restoration.3The nishing and polishing procedure involves some fundamental principles that allow us to better understand its application in dentistry.4 A variety of instruments are commonly used for nishing and polishing tooth-colored restorative materials including; carbide and diamond nishing burs, abrasive impregnated rigid points, impregnated rubber cups and points, aluminium oxide coated abrasive discs, abrasive strips, and polishing pastes.5 Each of these instruments or devices remove the oxygen inhibited layer of resin but leave the surface of restorative materials with varying degrees of surface roughness. Thus it is important to understand which type of surface-nishing treatments would signicantly affect the surface irregularities of different composite resin restorations. The present study evaluated the effect of various nishing and polishing procedures on the surface roughness of nanolled composite and the effectiveness of surface sealant application after nishing and polishing procedure of tested composite. MATERIAL AND METHOD The resin composites used in this study were Z- 350(nanolled) of shade A3,60 Cylindrical blocks of light- cured resin composite, 6mm in diameter and 3mm in depth, were prepared in a stainless steel mould. The stainless steel mould was placed on a glass slab and the composite was inserted in each cavity in a single increment using a resin packing plastic instrument. Flash was removed and material was nished ush with the top of the mold surface. A Mylar Strip & glass slide was placed on the mould and the specimen discs were light cured from both the sides for 40seconds as instructed using a Quartz-Tungsten-Halogen (QTH) unit. The tip of the curing light was placed on the glass slide perpendicular to the specimen surface to standardize the distance between the light source and the specimen. All specimens were stored in distilled water at 370C for 24 hours in an incubator (Incubator (DBK BOD, Model - DTC 96, Innovative Bacteriological Incubator). The 60 samples of composite resin were then randomly divided into 3 subgroups, as listed in . A Mylar Strip group of 20 specimens of both the materials received no polishing treatment after being cured. The remaining 40 specimens were surfaced with a Diamond nishing bur in a rotary motion, for 15 seconds with water coolant, to simulate initial nishing of the restorative material. The three nishing and polishing system used in this study were Shofu nishing and polishing kit, Sof-Lex composite nishing and polishing kit (3M), Mylar Strips (Unident). shows the complete description of these systems. 20 samples of each of the two composite resins were nished and polished with the Sof-Lex system and Shofu polishing system as specied by the manufacturer. To measure the surface roughness of the specimens a prolometer was used. Three measurements in different directions were recorded for the ten EFFECT OF THREE FINISHING AND POLISHING SYSTEMS ON THE SURFACE OF NANOFILLED COMPOSITE RESIN. A NOVEL RESEARCH APPROACH Original Research Paper Dr. Konark B.D.S(HONS), M.D.S, Senior lecturer, Department of conservative dentistry and endodontics, Patna Dental College and hospital. X 101GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS Dentistry Background: The aims of this study were to evaluate the effectiveness of three nishing and polishing systems on the surface of nanolled composite, and to evaluate the effect of the surface sealant application (prime & bond) on the surface roughness after nishing and polishing procedures of tested composite. Material and Method: A total of 60 composite discs of dimension 6 x 3 mm (6mm in diameter x 3mm in thickness) were made using a custom made stainless steel mould and then randomly divided into 3 subgroups for nishing and polishing by three different methods; Sof-Lex, Shofu and Mylar strip. The average surface roughness (Ra, �m) of all specimens was measured with aprolometer. A surface sealant was then applied to all the treated specimens, according to manufacturer's instructions and the average roughness was measured again. Result: Statistically signicant difference was observed in surface roughness values before and after sealant application when nished and polished with shofu system. The lowest roughness values, before and after sealant application, was obtained when cured under a Mylar strip and the highest values were obtained when treated with Shofu. Conclusion: The Mylar strips gave lowest Ra values followed by Sof-Lex followed by Shofu and the surface sealant improved the surface texture of tested specimens drastically. ABSTRACT KEYWORDS : Nanolled composite; Mylar strips; Sof-Lex and Shofu nishing and polishing system. Dr. Anju Singh* B.D.S, M.D.S, Assistant Professor, Department of Dentistry, Nalanda Medical College and Hospital. *Corresponding Author VOLUME-8, ISSUE-9, SEPTEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra 102 X GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS specimens in each group, the mean Ra value was determined for each specimen, and mean Ra for each group then was determined. Then surface sealant (prime & bond) was applied to all treated specimens and the average roughness (Ra) was measured. The results were analyzed statistically by ANOVA F, paired and unpaired 't' test. RESULT The surface roughness values of the tested composite nished and polished with three different systems before and after sealant application have been mentioned. Statistically signicant difference was observed in surface roughness values before and after sealant application when nished and polished with Shofu system. The lowest roughness values, before and after sealant application, was obtained when cured under a Mylar strip and the highest values were obtained when treated with Shofu. with ANOVA F, comparing Ra values with different nishing and polishing systems for Z350. The difference is statistically signicant before (p value 0.04) and even after (p value 0.005) sealant application. DISCUSSION Many signicant advances have been made since then with regards to improving the properties of earlier resin based restorative materials. These resin materials have progressed from macrolls to microlls and from hybrid to microhybrids, and new materials such as packable and nanolled composites have been introduced to the dental market. Each type of composite resin has certain advantages and limitations.6 Nanolled composite have been produced with nanolled technology and formulated with nanomerand nanocluster ller particles. This combination reduces the interstitial spacing of ller particles and, therefore, provides increased ller loading, better physical properties and superior polish and gloss retention.2 The mechanism in mechanical nishing and polishing using abrasive particles are part of triobiology, the discipline associated with material science, physics, chemistry and surface engineering. Finishing in dentistry refers to the steps of gross contouring of the restoration to obtain desired anatomy while polishing refers to the reduction and smoothening of the surface roughness and scratches created by the nishing instruments in the process of gross reduction and initial polishing.4 Dentists have always been encouraged to take time and effort to adequately nish and polish restorations. The clinical and scientic reasons for careful nishing and polishing have been to remove excess ash and rene the margins of the restoration, to reduce the risk of fracture, since a rough surface may be more likely to fracture, to reduce surface imperfections, hence reducing surface area and thus reducing the risk of surface breakdown and corrosion. The other reasons are to produce a smooth surface less likely to retain plaque, to improve oral function of mastication since food slides more easily over polished tooth surfaces, to produce smooth surfaces that facilitate oral hygiene procedures with access to all surfaces, marginal areas and interproximal areas through normal tooth brushing and use of dental oss, to produce smooth restoration contacts leading to less wear on opposing and adjacent teeth and to produce a more aesthetic restoration for the patient.4 It has been reported that the colour measuring geometry inuenced the colour measurement of composite resins with different surface roughness. If the surface conguration has a matte nish there would be an excessive amount of light reected at the surface level and a reduction of light transmission through the material. Surface texture controls the degree or scattering or the reection of the light striking on the natural tooth or restorative material. For this reason clinicians experience problems in establishing harmony of the shade, obtained with the original shade that was selected using a shade guide especially after nishing and polishing procedures.3 All abrasive nishing and polishing devices fall into one of three categories as coated abrasive, bonded abrasive or loose abrasives. A fourth classication includes cutting instruments such as uted or multiuted tungsten carbide nishing burs. Coated abrasive are nishing devices usually in the form of a paper, Mylar strip or some other polymeric backing, wherein the abrasive particles are distributed on the surface of backing or some other symmetric matrix design. Aluminum oxide constitutes the most commonly used abrasives compound on coated abrasives discs with silicon carbide. Bonded abrasives are devices in which the abrasive particles or media are uniformly dispersed throughout the device matrix. The device is usually an elastomeric material such as rubber or silicone compound but can also be rigid or nonelastic in nature. The last groups classied under abrasive devices are loose abrasives. With respect to use in dentistry loose abrasive polishing pastes contain a ne particle size distribution of either aluminium oxide or diamond particles dispersed in a water soluble vehicle such as glycerine.4 Various motions may be critical to the development of optimal surface smoothness. A rotary motion, a planar motion and a reciprocating motion can be employed to polish the surface of resin based material. In rotary motion the axis of rotation is parallel to the surface being smoothened. The planar motion is a rotational movement with the axis of the rotation of the abrasive device perpendicular to the surface being smoothened. Reciprocating motion is employed when a nishing strip is pulled back and forth over a surface. The results obtained by Fruit and others (1996) comparing different polishing motions showed that for all possible combination of the materials and abrasive grits, the planar motion achieved the lowest average roughness values.7 In our study, the specimens polished with planar motion (Sof-Lex disks) gave lower surface roughness values than the specimens polished with rotary motion (Shofu). Several studies stated that the large particles embedded in Sof-Lex disks tend to rip through the surface of resin composite and, when used with certain hybrid composites, tend to cut and abrade ller particles and resin matrix equally, resulting in a smooth surface.7 For a composite nishing system to be effective the cutting particles (abrasive) must be relatively harder than the ller materials, otherwise the polishing agent will only remove a soft resin matrix and leave the ller particles protruding from the surface. The hardness of aluminium oxide is signicantly higher than silicon dioxide, and generally, higher than most ller materials used in composite formulations.5The trend of Sof- Lex discs is to provide a slightly smoother surface with the aluminium oxide abrasive on rigid matrix as this has the ability to atten the ller particles and abrade the softer resin matrix at an equal rate. In the literature, the most common methods used to assess the effectiveness of nishing and polishing instruments include: Visual evaluation, Scanning electron microscopy and Prolometric analysis. We used Prolometric analysis to evaluate the surface nish of different composites with different polishing systems. There are two advantages with the mechanical prolometer method used in our study. First the prolometer gives a quantitative aspect through the calculation of (Ra) which cannot be obtained with SEM, and secondly, it enables the sample surface to be studied more precisely, as the stylus sweeps the sample surface detecting tiny variation.3 In this and other studies Mylar strips formed the smoothest surface in all the composite groups tested. The surface obtained with a Mylar strip is perfectly smooth and it is rich in resin organic binder. Therefore removal of outermost resin by nishing-polishing procedures would tend to produce a harder more wear resistant layer hence an aesthetically stable surface.4 Despite VOLUME-8, ISSUE-9, SEPTEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra careful placement of matrices, removal of excess material and recontouring of restorations is often clinically necessary. This requires some degree of nishing and polishing that will violate the smoothness obtained with a matrix.1-5,8 However even after accomplishing appropriate nishing and polishing technique the surface of all resin composites exhibit micro irregularities that inherently lead to material wear, deterioration and marginal inltration resulting mainly from the abrasive processes to which the restoration is subjected in the oral environment. In an attempt to overcome this problem, using a thin layer of low viscosity resin over polymerized composite restoration has been investigated. This approach is assumed to provide a more uniform, regular surface, thereby, enhancing surface smoothness. Although the properties of the latest resin composites have been optimized, indeed, there is still lack of study reporting whether or not the surface integrity of these materials may be enhanced by the use of low viscosity surface sealant. A sufcient ly lowviscosi ty res in agent wi th proper characteristics and formulation, even though not specically developed for such purpose, could be successfully used as a surface sealant. Various Studies have suggested coating polymerized resin composite with adhesive agent or ssure sealant.9Rebonding of composite restoration with unlled resin has been recommended for penetration of the sub- surface microcracks and interfacial gaps generated during nishing and polishing procedures.10 In our study surface sealing with Prime and Bond (Dentsply), had a positive effect on surface roughness. The results of this study are in accordance with the results of studies by CYG Takuchi, EHG Lara, 20039 and Nuray Attar 2007.2 CONCLUSION The nanocomposite resin tested in this study (Z350), Mylar strip provided the smoothest surfaces followed by Sof-Lex followed by Shofu. REFERENCES 1. Türkün LS, Türkün M. The effect of one-step polishing system on the surface roughness of three esthetic resin composite materials. Oper Dent 2004;29(2):203-11. 2. Endo T, Finger WJ, Kanehira M, Utterodt A, Komatsu M. Surface texture and roughness of polished nanolled and nanohybrid resin composites. Dent Mater J 2010 Mar;29(2):213-23. 3. Sarac D, Sarac YS, Kulunk S, Ural C, Kulunk T. The effect of polishing techniques on the surface roughness and color change of composite resins. J Prosthet Dent 2006;96(1):33-40. 4. Jefferies SR. Abrasive nishing and polishing in restorative dentistry: a state- of-the-art review. Dent Clin North Am 2007;51(2):379-97. 5. Ruyter IE. Composites - characterization of composite lling materials: reactor response. Adv Dent Res 1988;2(1):122-9. 6. Attar N. The effect of nishing and polishing procedures on the surface roughness of composite resin materials. J Contemp Dent Pract 2007;8(1):27-35 7. Lu H, Roeder LB, Powers JM. Effect of polishing systems on the surface roughness of microhybrid composites. J Esthet Restor Dent. 2003;15(5):297- 303. 8. Uctasli MB, Arisu HD, Omurlu H, Eliguzeloglu E, Ozcan S, Ergun G. The effect of different nishing and polishing systems on the surface roughness of different composite restorative materials. J Contemp Dent Pract 2007;8(2):89-96. 9. Neme AL, Frazier KB, Roeder LB, Debner TL. AL Neme, KB Frazier, LB Roeder, TL Debner. Effect of prophylactic polishing protocols on the surface roughness of esthetic restorative materials. Oper Dent 2002;27(1):50-8. 10. Hoelscher DC, Neme AM, Pink FE, Hughes PJ. The effect of three nishing systems on four esthetic restorative materials. Operative Dentistry, 1998,23,36-42. Oper Dent 1998;23(1):36-42. X 103GJRA - GLOBAL JOURNAL FOR RESEARCH ANALYSIS VOLUME-8, ISSUE-9, SEPTEMBER-2019 • PRINT ISSN No. 2277 - 8160 • DOI : 10.36106/gjra