Radiopacity degree of Bulk Fill composite resinsABSTRACT
Objective: To verify and compare the radiopacity of four composite resins available in the national market and analyze their compliance with International Standards Organization 4049 guidelines.
Methods: Five specimens of each Bulk Fill composite resin were prepared, and radiographs were taken alongside an aluminum step wedge using a digital imaging system. The images were processed using software capable of measuring mean grey values (MGVs), which were then converted to millimeters of aluminum. Statistical analysis was performed (P 0.05).
Results: The four tested composite resins showed radiopacity values higher than those of enamel and dentin, standing out the Tetric N-Ceram- Ivoclar Vivadent (11.05 mmAl). All samples are in accord with the ISO 4049 radiopacity standard. The resin Opus Bulk Fill and Tetric N-Ceram were compared to each other, revealing statistically significant differences (p0,05).
Conclusion: All materials demonstrated radiopacity values higher than those of dentin and enamel. All samples are in accordance with the International Organization for Standardization 4049 guidelines. More studies should be conducted with the composite resins used in this study due to the limited research involving these specific resins.
Indexing terms
Composite resins; Diagnostic imaging; Dentistry, operative
RESUMO
Objetivo: Verificar e comparar a radiopacidade de 04 resinas compostas do mercado nacional, e analisar se estão no padrão Organização Internacional de Normalização 4049 de radiopacidade.
Métodos: Foram confeccionados 05 corpos de prova para cada resina composta Bulk Fill testada , que foram radiografados ao lado de uma cunha de degrau de alumínio com um sistema de imagem digital. As imagens foram submetidas a um software capaz medir a valores médios de cinza (MGVs), os quais foram convertidos em milímetros de alumínio. Os dados foram analisados estatisticamente (p0,05).
Resultados: As 04 resinas compostas testadas mostraram valores de radiopacidade notadamente maiores que o equivalente ao esmalte e dentina, destacando-se a Tetric N-Ceram- Ivoclar Vivadent (11,05 mmAl). Todas estão dentro do padrão ISO 4049 de radiopacidade. Ao compará-las entre si, houve diferença estatisticamente significativa entre os grupos de resinas Opus Bulk Fill e Tetric N-Ceram (p-valor 0,05).
Conclusão: Todos os materiais mostraram radiopacidade superior ao equivalente a dentina e esmaltes. Todas estão no padrão Organização Internacional de Normalização 4049. Mais pesquisas devem ser realizadas devido ao reduzido número de estudos realizados com as resinas compostas em questão.
Termos de indexação
Resinas compostas; Diagnóstico por imagem; Dentística operatória
INTRODUCTION
One of the main limitations of composite resins is related to their polymerization shrinkage. This inherent property of the material leads to stress forces at the tooth-restoration interface, a factor that can be addressed by using a specific and meticulous protocol for material insertion into the cavity, with the composite resin cured at a maximum thickness of 2mm [1].
This characteristic of contraction in conventional composite resins leads to restoration failures when the contraction forces exceed the adhesive strength, forming cracks that may result in secondary caries and cuspal flexure in stress-prone areas, for example. In order to address the polymerization shrinkage issue and the subsequent sensitive technique (incremental techniques), which makes the procedure more time-consuming and uncomfortable for the dentist and the patient, the bulk-fill resins or single fill resins have emerged in the market [2].
This resin can be classified based on its consistency as either flowable or regular. Its primary characteristic is the low degree of shrinkage after polymerization, allowing the use of these materials in layers of 4–5 mm. These modifications have increased their translucency, and the addition of alternative photoinitiators like Ivocerin® (derived from dibenzoyl germanium) (Ivoclar Vivadent) and TPO (mono-alkyl phosphine oxide) enables a shorter polymerization time [3]. Therefore, the C-factor and the incremental technique will not have prominence in that clinical protocol.
In addition to the physicochemical properties, a good material needs to be radiopaque to ensure accurate diagnosis when interpreting radiographic exams. The detection of pores, secondary caries around restorations, gaps, contacts with adjacent teeth, and margin defects are the possibilities provided by a radiopaque material [4]. In this context, the International Standards Organization (ISO) 4049 defines that the radiopacity of an ideal composite material should be equal to or greater than that of aluminum, at the same thickness, because the radiopacity of 1 millimeter of aluminum is equivalent, at the same thickness, to the radiopacity of 1 millimeter of dentin. On the other hand, enamel has radiopacity twice as high as the radiopacity of aluminum at the same thickness [5,6].
Therefore, the practicality and mechanical properties of this material are evident, being comparable to those of conventional options [7]. However, the slant of the degree of radiopacity should be verified, emphasizing the importance of this research, since the excess or absence of the value can cause misdiagnose.
METHODS
This is a research study with a quantitative and experimental approach. The resins composite tested were Group 1 - Aura Bulk Fill – SDI (SDI Limited, São Paulo, SP, Brazil), Group 2 - Filtek One Bulk Fill - 3M Brazil (3M Company, Sumaré, SP, Brazil), Group 3 - Opus Bulk Fill - FGM Dental Group (FGM Dental Group, Joinville, SC, Brazil), Group 4 - Tetric N-Ceram – Ivoclar Vivadent (Ivoclar Vivadent AG, Barueri, SP, Brazil) and were provided according to the manufacturers’ instructions. After manipulation, they were placed into acrylic molds with an internal diameter of 06 millimeters and a height of 01 millimeter, positioned on a smooth glass plate. After the material placement, another glass plate was used to compress the material and standardize the thickness of the specimens, which were then measured using a caliper. Five specimens were prepared for each tested bulk-fill composite resin. The plate was fabricated with standardized dimensions, precisely aligning with the size of the sensor (phosphor plate) integrated into the Kodak CS 7600 system (Carestream Health, Rochester, New York, USA), used for the acquisition of radiographic images. For this purpose, a Spectro 70X X-ray apparatus (Dabi Atlante, Ribeirão Preto, SP, Brazil), operating at 70 kVp and 8 mA, was utilized. The focus-to-object distance was 30 cm, and the exposure time was 0.2 seconds, as recommended by the manufacturer for digital phosphor plate radiography. A voltage stabilizer was incorporated to prevent energy fluctuations. Following the radiographic exposures, the sensor was inserted into the scanning device of the Kodak CS 7600 system. The acquired images were analyzed using the ImageJ software (NIH).
After importing the images into the Digora for Windows software version 2.5 (Orion Corporation Soredex, Helsinki, Finland), compact areas of the specimens were selected. This facilitated the determination of the density of various materials, enabling a comparison with the radiopacity of different thicknesses of the aluminum penetrometer to ascertain the optical density value for each sample. The provided equation for converting values into millimeters of aluminum, as presented by Sousa Filho et al. [8], is expressed as follows: A × B / 2 + mmAl (radiopacity in millimeters of aluminum), immediately below the material’s radiographic density (DRM).
A = the radiographic density of the material (DRM) minus the radiographic density of the increment of the aluminum penetrometer immediately below the DRM.
B = the radiographic density of the increment of the aluminum penetrometer immediately above DRM minus the radiographic density of the increment of the aluminum scale immediately below DRM.
2 = represents the increment of 2 millimeters between each step of aluminum.
The data were organized in the Microsoft Excel program for the initial descriptive analysis. Statistical calculations were performed using the R software (statistical and graphical programming language) and SPSS Statistics 25.0, with a significance level set at 5% (p-value < 0.05). The Kolmogorov-Smirnov test was conducted to assess the normality of the data (p-value = 0.25), followed by the Mann-Whitney test.
RESULTS
Brands, Manufacturers, LOT Numbers, and Inorganic Composition of the Bulk Fill Composite Resins Tested.
DISCUSSION
A pairwise comparison between the groups was conducted using the Mann-Whitney Test to determine statistically significant differences (p-value < 0.05), as illustrated in table 1. There was a statistically significant difference between the Opus Bulk Fill-FGM Group (FGM Dental Group, Joinville, SC, Brazil) [9] and Tetric N-Ceram-IVOCLAR VIVADENT (Ivoclar Vivadent AG, Barueri, SP, Brazil) [10] (p-value < 0.05). The addition of elements with a higher atomic number, such as barium (Z=56), zinc (Z=30), aluminum (Z=13), strontium (Z=38), zirconium (Z=40), silicon (Z=14), yttrium (Z=39), ytterbium (Z=70), and lanthanum (Z=57), to the material composition enhances its radiopacity. This is due to their increased capability to efficiently absorb X-rays [11]. Therefore, the significant statistical difference (p-value < 0.05) found can be explained by the inorganic composition, as shown in table 2, that provides radiopacity to these two materials.
The manufacturer of Opus Bulk Fill (FGM Dental Group, Joinville, SC, Brazil) declares the presence of silanized silicon dioxide (silica) in the inorganic particles, without specifying the percentage by weight and volume [9]. This chemical element has a low atomic number (Z=14) compared to the composition of Tetric N-Ceram-IVOCLAR VIVADENT (Ivoclar Vivadent AG, Barueri, SP, Brazil), where barium glass and ytterbium trifluoride are present (75-77% by weight or 53-55% by volume) [10], with atomic numbers 56 and 39, respectively [11].
After converting the optical densities to millimeters of aluminum, as illustrated in figure 1, an increasing order of radiopacity measurements was observed for the composite resins Opus Bulk Fill-FGM Group (FGM Dental Group, Joinville, SC, Brazil) [9] (8.73 mmAl), Aura Bulk Fill-SDI (SDI Limited, São Paulo, SP, Brazil) [12] (9.52 mmAl), Filtek One Bulk Fill-3M (3M Company, Sumaré, SP, Brazil) [13] (9.55 mmAl), and Tetric N-Ceram-Ivoclar Vivadent (Ivoclar Vivadent AG, Barueri, SP, Brazil) [10] (11.05 mmAl). In accordance with the International Organization for Standardization (ISO) 4049, the radiopacity of these materials should be equal to or greater than the same thickness of aluminum [5]. Therefore, all the composite resins in this study are standardized according to this norm, with Tetric N-Ceram-Ivoclar Vivadent (Ivoclar Vivadent AG, Barueri, SP, Brazil) [10] standing out with the highest radiopacity at 11.05 mmAl. It is possible to check in table 2 the inorganic composition of all composite resins in this research.
Therefore, in order to achieve radiopacity, the Tetric N-Ceram Bulk Fill resin (Ivoclar Vivadent AG, Barueri, SP, Brazil) incorporates into its inorganic matrix 75-77% by weight or 53-55% by volume of barium glass and ytterbium trifluoride (with atomic numbers Z of 56 and 70, respectively) [10].
In contrast, the Filtek One Bulk Fill-3M Brasil resin (3M Company, Sumaré, SP, Brazil), designed for the same purpose, incorporates a combination of non-agglomerated/non-aggregated silica (Z=14), non-agglomerated/non-aggregated zirconia (Z=40), clusters of zirconia and silica, and clusters of ytterbium trifluoride particles (Z=70), accounting for 76.5% by weight and 58.4% by volume [13]. Its radiopacity value is reported as 9.55 mmAl. The presence of this diverse array of compounds with elevated atomic numbers justifies the higher radiopacity measurements observed in both materials [11].
FGM Dental Group (Joinville, SC, Brazil) specifies in the Opus Bulk Fill resin’s instructions that only silanized silicon dioxide (silica) is present as radiopaque filler [10]. Silica has a relatively lower atomic number (Z=14) compared to other elements commonly added to the inorganic matrix to enhance X-ray absorption [11]. This information helps explain its lower radiopacity value in millimeters of aluminum (8.73 mmAl) compared to the other materials investigated in this study.
Finally, the Aura Bulk Fill resin from SDI Limited (São Paulo, SP, Brazil) exhibited an intermediate radiopacity value of 9.53 mmAl. The product documentation does not provide information about the inorganic compounds used to impart radiopacity to the material; only elements from the organic matrix are listed, including Acrylic monomers (6-46%), Diurethane dimethacrylate (6-46%), Triethylene glycol dimethacrylate (6-46%), and 2,2-bis[4-(2-methacryloxy) ethoxy)phenyl]propane (6-46%) [12]. No radiopacity studies for the Aura Bulk Fill resin (SDI Limited, São Paulo, SP, Brazil) were found, underscoring the significance of this study and the need for further research.
The results of this research showcased higher radiopacity values when compared to other studies on the same resins, such as the study conducted by Yaylaci et al. [11]. This divergence is likely attributed to variations in methodologies, such as the X-ray machine brand, voltage, electrical intensity, focus-film distance, sensor type, or even alterations in speed and resolution within the system. Limited studies on radiopacity for the resins analyzed in this research were found, emphasizing the significance of this study.
CONCLUSION
All materials exhibit radiopacity superior to that of dentin and enamel equivalents, providing assistance to clinicians during the radiographic examination of restorations. This will provide the detection of pores, secondary caries to the restoration, gaps, contacts with adjacent teeth, and margins defects of the restorations.
Furthermore, all the resins studied in this research are in conform to the ISO 4049 standard for radiopacity, which means that it should be equal to or greater than the equivalent thickness of aluminum. This compliance ensures safety, efficacy, and quality.
ACKNOWLEDGMENTS
The State University of Piauí is sincerely thanked for their support in this research through the undergraduate research program.
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How to cite this article: Nunes TSL, Falcão CAM, Silva DP, Ferraz MAAL, Magalhães WLE. Radiopacity degree of Bulk Fill composite resins. RGO, Rev Gaúch Odontol. 2024;72:e20240048. http://dx.doi.org/10.1590/1981-86372024004820240018
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Assistant editor:
Luciana Butini Oliveira
