Restorative Dentistry Braz Oral Res 2008;22(4):358-63358 Microhardness assessment of different commercial brands of resin composites with different degrees of translucence Abstract: Owing to improvements in its mechanical properties and to the availability of shade and translucence resources, resin composite has become one of the most widely used restorative materials in present day Dentistry. The aim of this study was to assess the relation between the surface hardness of seven different commercial brands of resin compos- ites (Charisma, Fill Magic, Master Fill, Natural Look, Opallis, Tetric Ceram, and Z250) and the different degrees of translucence (translucid, enamel and dentin). Vickers microhardness testing revealed significant differences among the groups. Z250 was the commercial brand that showed the best performance in the hardness test. When comparing the three groups assessed within the same brand, only Master Fill and Fill Magic presented statistically significant differences among all of the dif- ferent translucencies. Natural Look was the only one that showed no sig- nificant difference among any of the three groups. Charisma, Opallis, Tetric Ceram and Z250 showed significant differences among some of the tested groups. Based on the results found in this study, it was not pos- sible to establish a relation between translucence and the microhardness of the resin composites assessed. Depending on the material assessed, however, translucence variation did affect the microhardness values of the resin composites. Descriptors: Composite resins; Hardness; Color. Taciana Emília de Almeida Anfe(a) Taciana Marco Ferraz Caneppele(b) Carlos Martins Agra(c) Glauco Fioranelli Vieira(d) (a) Graduate Student, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil. (b) Graduate Student, School of Dentistry of São José dos Campos, São Paulo State University, São José dos Campos, SP, Brazil. (c) PhD in Restorative Dentistry; (d)Associate Professor – Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil. Restorative Dentistry Corresponding author: Taciana Emília de Almeida Anfe Av. Dr. Octávio da Silva Bastos, 4035 São João da Boa Vista - SP - Brazil CEP: 13874-651 E-mail: tacianfe@uol.com.br Received for publication on May 03, 2007 Accepted for publication on Oct 08, 2007 Anfe TEA, Caneppele TMF, Agra CM, Vieira GF Braz Oral Res 2008;22(4):358-63 359 Introduction Resin composite is one of the restorative materi- als most widely used in present day Dentistry. This is mainly due to three factors: the first one is adhesion to tooth structure, the second is the improvement in its mechanical properties and the third reason is the availability of shades and translucence options that provide almost unlimited possibilities for this mate- rial to imitate the tooth. Among the most studied mechanical properties are flexural resistance and hardness, because they approximate the forces involved in mastication and those supported by the material. Various authors have shown that these are related to the character- istics of the organic matrix, the percentage volume and the type of load. Tooth shade is given by the color and translucence of the tooth enamel and the color of dentin. With the purpose of increasingly imitating the dental pat- tern, highly translucent resins have been launched, and these are used in the incisal third of an anterior restoration, or to cover the last layer of a posterior reconstruction, which results in the material receiv- ing intense masticatory load. It is not stated in the literature whether, within one and the same com- mercial brand, translucent resin supports the same load as does resin for enamel and for dentin. The authors were interested in finding out wheth- er a resin composite of the same commercial brand is altered by the use of translucent composite for fin- ishing the restoration. The aim of this study was to assess the relation between the surface hardness of seven different commercial brands of resin compos- ites with different degrees of translucence. Material and Methods Seven different commercial brands of resin com- posites were tested. Of each brand, 3 shades were Chart 1 - Selected Microhybrid Resins. Resin Composites Organic Matrix Inorganic Load Volume of Load Weight of Load Shade Batch n. Charisma Heraeus-Kulzer (Wehrheim, Germany) BisGMA TEGDMA • • barium aluminum fluoride glass high/dispersed silicon dioxide • • 61% 78% Incisal B2 OB2 010039 010200 010202 Fill Magic Vigodent (Rio de Janeiro, RJ, Brazil) methacrylate monomers • pryogenic silicon barium and aluminum silicate • • – 80% Incisal B2 enamel B2 dentin 223/05 067/06 035/06 Master Fill Biodinâmica (Ibiporã, PR, Brazil) bisphenol A glycidyl methacrylate ethylene urethane dimethacrylate • • titanium dioxide iron oxide • • – 79% Incisal B2 OB2 953/04 022/06 1050/05 Natural Look DFL (Rio de Janeiro, RJ, Brazil) bisphenol A diglycidyl methacrylate bisphenol A diethoxy methacrylate triethylene glycol dimethacrylate • • • silanized barium crystals hydrophobic amorphous silica • • 58.5-59% 77-78% Incisal B2 enamel B2 dentin 06010169 06010141 06030531 Opallis FGM (Joinville, SC, Brazil) BisGMA BisEMA TEGDMA • • • barium glass aluminum silicate silica dioxide • • • 57-58% 77.5-79% T-yellow EB2 DB2 03APR06 19JUL06 24MAY06 Tetric Ceram Ivoclar Vivadent (Schaan, Liechtenstein) BisGMA urethane dimethacrylate triethylene glycol dimethacrylate • • • barium glass aluminum and barium fluorosilicate glass high/dispersed silicon dioxide mutual spheroid oxides • • • • 60% 79% T B2 enamel B2 dentin H36386 H34662 H30145 Z250 3M ESPE (St. Paul, MN, USA) BisGMA UDMA BisEMA • • • zirconia Silicon • • 60% 82% Incisal B2 UD 6LU 6WG 6AP Microhardness assessment of different commercial brands of resin composites with different degrees of translucence Braz Oral Res 2008;22(4):358-63360 selected (translucent, enamel B2 and dentin B2), making a total of 21 groups of resin samples with 5 test specimens for each group (Chart 1). For each of the selected resin composite samples, surface microhardness was assessed. Surface hardness test A Teflon matrix 5 mm in diameter and 2 mm in thickness was used to make the test specimens. A glass slide (used in optic microscopy) was placed on a flat surface, and on top of it, a polyester strip. The Teflon matrix was placed on the polyester strip and filled with resin composite, and on top of that, an- other polyester strip and another glass slide were set. Digital pressure on the glass slide guaranteed that a smooth flat surface was obtained. The resin compos- ite was light activated in the center of the sample for 40 seconds on each of its two surfaces through the glass slide (JetLite 4000 Plus, J. Morita USA Inc., Mason Irvine, CA, USA). Five specimens were made of each material. The specimens were then stored in distilled water at 37°C for 7 days. Microhardness measurements on each specimen were made with a Vickers tester (HMV 2000, Shi- madzu, Kyoto, Japan) with a load of 50 g for 45 s, using an objective of 50 X. On every test specimen, 5 measurements were made, avoiding the peripheral areas of the sample. Statistical analysis of the data obtained was per- formed. The non-parametric Kruskal-Wallis test (significance of 5%) was selected for the analysis be- cause the values did not meet the normality and ho- mogeneity requirements. The test revealed significant differences among the groups. The Mann-Whitney test (significance of 5%) was applied to determine which groups differed among them. The second step of the statistical analysis assessed whether there were differences among the 7 brands of resins. Grouping of the values revealed that they filled the homogene- ity and normality requirements, which enabled the ANOVA statistical test to be applied with a signifi- cance of 5%. The Scheffe test (significance of 5%) determined the differences among the groups. Results The 21 groups of samples were assessed to ver- ify whether there were significant differences. The Mann-Whitney test (significance of 5%) was applied to determine which groups differed among them. The consolidated results are shown in Table 1. In Table 1, it is possible to observe that, within the same commercial brand, only the Master Fill and Fill Magic presented statistically significant differences among the three groups tested (shades: translucent, enamel B2 and dentin B2). Natural Look was the only one that showed no significant differences among any of the groups. Charisma, Opallis, Tetric Ceram and Z250 showed significant differences among some of the tested groups. Com- parisons were also made among all the commercial brands assessed. However, there was no homogene- ity among the results found. Thus, the translucent Table 1 - Comparison of hardness values among groups considering the results obtained with the Mann-Whitney test. Resins Mean (VHN) Charisma I 68.49 (A) Charisma B2 61.57 (B) Charisma OB2 65.13 (A,B,C) Fill Magic I 54.76 (D) Fill Magic B2E 64.02 (A,B,C,E) Fill Magic B2D 67.32 (A,C,F) Master Fill I 47.76 (P) Master Fill B2 51.75 (G) Master Fill OB2 55.72 (D,H) Natural Look I 64.16 (A,B,C,F,I) Natural Look B2E 64.37 (A,B,C,E,I,J) Natural Look B2D 65.76 (A,C,E,F,I,J,K) Opallis T-Y 57.76 (D,H,L) Opallis EB2 62.52 (B,C,E,I,J,K,M) Opallis DB2 62.22 (B,E,I,M) Tetric Ceram T 57.4 (D,H,L,N) Tetric Ceram B2E 57.91 (L,N) Tetric Ceram B2D 50.59 (G) Z250 I 96.39 (O, Q) Z250 B2 94.06 (Q) Z250 UD 96.38 (O) Resin composites that did not present statistically significant differences are listed above with the same letter in brackets. Anfe TEA, Caneppele TMF, Agra CM, Vieira GF Braz Oral Res 2008;22(4):358-63 361 resin presented higher or lower hardness values, de- pending on the commercial brand in question. The second step of the statistical analysis as- sessed whether there were differences among the 7 brands of resins. Grouping of the values revealed that they filled the homogeneity and normality re- quirements, which enabled the ANOVA statistical test to be applied with a significance of 5%. The Scheffe test (significance of 5%) determined the dif- ferences among the groups. Graph 1 shows the val- ues obtained in the hardness test for the resin com- posites assessed. Discussion The mechanical properties of a resin composite, considering the material’s composition, are related to the polymeric matrix, the inorganic load and the bonding agent. The surface hardness of a composite is determined both by the matrix and the inorganic load, so it is important to assess the properties of these components. The factor addressed in this research was the relation between translucence and surface micro- hardness of resin composites. With an increasing demand for esthetics, by both professionals and pa- tients, companies have developed resin composites with options not only of shades, but with a large variation in translucence, in an endeavor to obtain more and more natural results. Nevertheless, pro- fessionals are concerned about whether this varia- tion in translucence affects the mechanical proper- ties of the material. It is known that the shade of a resin and the particle size of its load may affect both translucence and the dispersion of light, and conse- quently the polymerization depth of the composite,1 which may alter its hardness. Translucence, even more so than color, may be a limiting factor with regard to the polymerization depth of some resinous systems.1,2 Resins with a similar composition may present different hardness values due to their characteristics of being more or less translucent.3 A more translucent material allows better light transmission from the light polymerizer, which results in a higher degree of conversion and consequently higher hardness.4,5 The difference of hardness between bottom and top surfaces is small- er in the more translucent resin composites than in the less translucent materials.3,6 Light transmission through darker colors is diminished because of less translucence.7 In agreement with the data presented by Aguiar et al.7 (2005), in the present study, the observed sur- face microhardness values did not vary significantly as a function of the degree of translucence of the composites. Nevertheless, although there was no homogeneity in the results found, there were statis- tically significant differences in the surface micro- hardness results of some of the commercial brands when translucence was a variable. For the compos- ites Charisma, Opallis, Tetric Ceram and Z250, significant differences were observed among some of the resins with different degrees of translucence within the same commercial brand. The compos- ites Master Fill and Fill Magic presented signifi- cant differences among all the different translucen- cies assessed. Whereas the Natural Look resin was the only one that showed no significant differences among any of the different degrees of translucence (Table 1). The differences observed in the microhardness test results presented by composites of the same Graph 1 - Comparison of hardness values obtained for the different brands assessed. (Resin composites that did not present statistically significant differences are presented above with the same letter.) M ic ro ha rd ne ss (V H N ) 0 25 50 75 100 NL OP MF Char Resin Composites Tetr Fill M Z250 125 c c,d b d a d 64.7 60.8 51.7 64.7 55.3 62.03 e 95.61 Microhardness assessment of different commercial brands of resin composites with different degrees of translucence Braz Oral Res 2008;22(4):358-63362 commercial brand could be explained by an altera- tion in composition. The component responsible for the degree of resin translucence is the factor that would have an influence on this result. However, the authors do not know what really differs among the translucent resins for enamel and dentin. The ma- jority of manufacturers allege that what is altered is the quantity of inorganic load. But, in the pres- ent study, it was not possible to establish a direct parallel between the percentage of inorganic load and surface hardness. Thus, it is probable that the organic component of the resins plays a decisive role in this property. Many authors allege that the degree of translu- cence of a resin composite may interfere in adequate polymerization of the material.1,6,8 Nevertheless, ac- cording to the data found in the present research, whether or not a resin composite is translucent is not a determining factor in the surface hardness result. If this were so, translucent composites would present better results in the microhardness test. But in the present study, only the Charisma presented a higher hardness value for the incisal shade, in comparison with the resin samples within the same commercial brand. Among the other commercial brands, the incisal shade sample presented a lower (Fill Magic, Master Fill, Natural Look, Opallis) or intermedi- ate (Tetric Ceram and Z250) hardness value when compared to the enamel and dentin shades. Thus, the supposition that translucence would be a deter- minant factor in a resin composite’s microhardness was not confirmed. In the present study, the test specimens assessed were 2 mm in thickness. Although some authors1,2 have demonstrated that the hardness assessed at depth underwent alteration as a result of shade or translucence, Martins et al.9 (2002) and Santos et al.10 (2000) related that there was no difference in microhardness in the first 2 mm of resin composite depth as a result of change in shade. That is why the authors decided to assess surface hardness only. Moreover, in a resin composite restoration using the direct technique, the recommendation for attaining adequate polymerization is to work with increments of up to 2 mm. It is important to note that, in this study, the composite was cured through the polyes- ter strip and received no further surface treatment. Some studies11,12 relate that there is a resin-rich sur- face layer when the polymerization occurs through a polyester strip and it would result in a lower surface hardness. However, Park et al.13 (2000) related that after 6 days of the polymerization there is no differ- ence between polished and polyester strip-finished surfaces in Vickers microhardness. A resin composite’s hardness depends on how the organic matrix is formed,14 and on its density and structure. The polymeric matrix is formed through the conversion of the double carbon bonds of mono- mers into covalent links, forming polymeric chains. The degree of conversion of a resin composite de- pends on the type of monomer and the quantity of photoinitiators present, and has a direct influence on hardness. A greater degree of conversion is com- monly associated with a greater degree of hardness.15 Some researchers have related that the hardness test can be used as an indirect method for assess- ing the degree of conversion of resin composites: the greater the degree of conversion, the greater the hardness.16,17 Nevertheless, hardness values cannot be used to compare the degree of conversion among different composites, since the results depend large- ly on the composition of the material.8 The type of polymeric chain that is formed after polymerization affects hardness. The mechanical properties are de- pendent on the formation of crossed chains, which does not necessarily indicate the degree of conver- sion of a resin.18 Different monomers present particular charac- teristics and different properties. It is known that there are variations among monomers as regards hydrophilia, degree of conversion and capacity to form crossed chains during polymerization. Among the composites assessed there was little variation in the organic matrix composition. The exception was Z250 that had no TEGDMA in its composition. TEGDMA is a low-molecular-weight monomer, whereas UDMA and BisEMA have higher molecu- lar weights. All of them are dilutant monomers of BisGMA, present in all the resins assessed. Some authors affirmed that the quantity of load is directly related to surface hardness.16,17,19,20 The greater the percentage volume of the load, the high- Anfe TEA, Caneppele TMF, Agra CM, Vieira GF Braz Oral Res 2008;22(4):358-63 363 er the hardness.21 Nevertheless, in the present study the data found are contrary to this evidence and are in agreement with the results found by Mandikos et al.14 (2001). The greater hardness of Z250 cannot be explained by the high percentage volume of the load in this material. Charisma presents a higher per- centage volume (61%) and Tetric Ceram has a value equal to that of Z250 (60%). However, the hardness values presented by these two resin composites were significantly lower than those of resin Z250. The materials assessed differ both in their organ- ic and inorganic compositions, which makes it dif- ficult to compare the results among the tested com- mercial brands.15,17,20,22 Conclusion Based on the data found in the present study, it was not possible to establish a relation between translucence and the microhardness values of the res- in composites assessed. Depending on the material assessed, however, translucence variation did affect the microhardness values of the resin composites. References 1. Ferracane JL, Aday P, Matsumoto H, Marker VA. Relation- ship between shade and depth of cure for light-activated dental composite resins. Dent Mater. 1986;2(2):80-4. 2. Shortall AC. How light source and product shade influence cure depth for a contemporary composite. J Oral Rehabil. 2005;32(12):906-11. 3. Kawaguchi M, Fukushima T, Miyazaki K. 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