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