COMPARATIVE STUDY REGARDING THE EFFECT OF DIFFERENT FINISHING AND POLISHING SYSTEMS ON A BULK-FILL COMPOSITE RESIN SURFACE
compounds called adhesion-fragmentation monomers( AFM) that contributes to the release of polymerization stress while maintaining the physical properties of the newly created polymer chains. The organic component also contains DDDMA( 1,12-dodecanediol dimethacrylate) which provides low resin viscosity, decreasing exothermic reactions and polymerization shrinkage, and UDMA( urethane dimethacrylate), an increased molecular weight monomer, that reduces resin viscosity and polymerization shrinkage. The inorganic component of Filtek Bulk Fill Posterior Restorative consists in a combination of nonagglomerated / non-aggregated silica particles of 20 nm, non-agglomerated / non-aggregated zirconia particles with sizes ranging from 4 to 11 nm, respectively zirconia / silica clusters( containing 20 nm silica particles and 4 to 11 nm zirconia particles). The inorganic component also includes ytterbium trifluoride aggregate particles of 100 nm( YbF3), which have the role of increasing radiopacity of the material. The total inorganic phase loading is about 76.5 %( by weight), equivalent to 58.4 %( by volume). Details about composite resins type, producer and chemical composition are presented in Table 1. Twenty cylindrical samples 5 mm in diameter and 2 mm thick were made using plastic moulds The conformers were placed in tight contact with a celluloid matrix between two glass plates, in order to obtain a smooth, flat and a surface free of pores. The samples were lightcured for 40 s on both sides through glass plate to ensure complete polymerization of the material, using a light emitting diode light curing device( Optilight LD MAX – Gnatus) heaving a wavelength of 470 nm to 480 nm, a maximum power of 600 mW / cm 2 and providing a polymerization depth of up to 3 mm. After removing samples from moulds they were randomly divided into 4 groups. Samples from group 1( control), were not finished or polished and the samples in groups 2-4, were finished and polished using three different systems. In group 2, samples were firstly contoured and finished using tungsten carbide burs from Komet Dental / Gebr Brasseler GmbH & Co. KG, Germany in the following order: for the coarse finishing step( cut-off) the H135Q bur, batch 906561 was used and for ultra-fine finishing( contouring) the H135UF bur, batch 903481( ISO 500314166031014) was used. Each bur was used for 30 seconds, at 20,000 rpm and under continuous water cooling. Burs were driven in one direction, clockwise. Subsequent polishing was performed with a one-step polishing system Occlubrush( KerrHawe SA, Switzerland) made of polycarbonate fibers impregnated with silicon carbide particles. The small cup brushes were used at 5000 rpm, for 30 seconds and without polishing paste. In group 3, samples were contoured and finished using the H135Q and H135UF carbide burs( Komet Dental / Gebr Brasseler GmbH & Co. KG, Germany). The polishing was done with a two-step polishing system Sof-Lex( 3M ESPE). This system is made up of disposable spiral wheels for finishing( the beige one) and polishing( the white one). The lamellar discs are made of a thermoplastic elastomer impregnated with aluminium oxide particles. Each lamellar disk was used once for each sample, for 30 seconds, without paste or
Table 1. Details about tested material
Material / Manufacturer /
Type / Batch No./
Shade
Filtek Bulk Fill Universal
Restorative
3MESPE, St. Paul, MN,
USA
N720858 / A3
Matrix
bis-GMA, AUDM,
AFM, DDDMA UDMA,
TEGDMA, bis-
EMA( 6)
Chemical composition Filler Load: 76.5 wt % / 58.4 vol %
Type
Non-agglomerated / non-aggregated silica particles
Non-agglomerated / non-aggregated zirconia particles
Clusters of aggregated silica and zirconia particles Ytterbium trifluoride aggregate particles
Size
20 nm
4- 11 nm
100 nm
Bis-GMA: Bisphenol A diglycidyl ether dimethacrylate; AUDM: aromatic dimethacrylate; AFM: adhesion-fragmentation monomers; DDDMA: 1,12-dodecanediol dimethacrylate; UDMA: urethane dimethacrylate; TEGDMA: Triethyleneglycoldimethacrylate; bis EMA( 6): ethoxylated bisphenol-A dimethacrylate.
water cooling, at speed of 20,000 r. p. m. according to the manufacturer ' s specifications. In group 4, samples were contoured and finished using the H135Q and H135UF burs( Komet Dental / Gebr Brasseler GmbH & Co. KG, Germany). Subsequent polishing was performed with the multi-step Super Snap System( Shofu, Inc. Kyoto, Japan). This system consists of discs for contouring, finishing, polishing and superpolishing. The discs are manufactured without a metallic ring, do not expose the mandrel to the active surface, and they are impregnated with aluminium oxide powder of different grain size. For the present study, the purple finishing discs, the green polish and the pink ones for super-polish were used successively. Each abrasive disc was used once for each sample, without water spraying, without paste, for 30 seconds and the hand-piece was used at a speed of 10,000-20,000 rpm. Finally, the samples were cleaned from the debris by washing with distilled water and dried with air. Subsequently, they were subjected to qualitative surface evaluation using the scanning electron microscope VEGA II LSH TESCAN( Czech Republic) and to quantitative profilometric analysis using a profilometer Taylor Hobson-Surtronic 25( Ametek Inc, Berwyn, PA, USA). Ten traces were registered in different areas with a tip load of 0.75 mN, a tip diameter of 10 µ m, a trace length of 0.25 mm, a scanning speed of 0.5 mm / s and a cut-off length of 0.8 μm. The roughness parameters were calculated and the mean arithmetic deviation, Ra, of the assessed profile was used. The Kolmogorov-Smirnov normality test was used to determine the distribution of data in groups. ANOVA and Tukey post hoc statistical tests were used to compare the results in groups.
3. Results Some SEM surface images at different magnification with morphological aspects of Filtek Bulk Fill composite resin samples in groups 1-4 are presented in Fig. 1. In group 1 – Fig. 1a)( control samples), very rare micro-voids may be observed in small magnification( 500 ×), which can be inferred as arising from the sample preparation technique,
Original Article
Stomatology Edu Journal
93