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Composite resins, a challenge in dental restoration

Dra. Adriana Garzón
Odontóloga. Pontificia Universidad Javeriana

Introduction

Over time, composite resins have evolved in the dental industry in order to find solutions to the daily challenges we face in the dental office[1], such as finding a good material strength, finding a resemblance to the natural color of the tooth or eliminating post-operative sensitivity with a product that is biocompatible with the tooth structure.

This has made research in biomaterials grow, and nanotechnology, which is the understanding and use of matter on an atomic and molecular scale for industrial purposes, is being used. This makes it feasible to further reduce the size of the filler particles, making it possible to obtain manometric magnitudes.[2] Nanoparticles do not reflect light because of their size; light waves pass through them without reflecting on them. Thus, when added to composites, they do not alter their opacity or translucency. Nanoparticles do not behave as solids but as liquids, as they are transparent and behave in this way, they could not be used as filler material, therefore they are accompanied with larger particles between 0.7 microns, which act as support, give viscosity to the material, color, opacity and radiopacity to this type of resins.

Nanohybrid resins that offer high translucency, similar to microfiller resins, while maintaining their physical properties and wear resistance equivalent to hybrid resins. They have applications both upstream and downstream. The incorporation of the filler particles within the matrix significantly improves its mechanical properties. The smaller the size and percentage of the filler particles, the lower the elastic modulus.[4][5]

Although the characteristics of composite resins are key in the restoration, the preservation of the dentin-pulp complex and the reintegration of an injured pulp to its normal function are the biological premises that should govern all operative maneuvers,[5] so the operator should not only be clear about the composite with which to restore but also the demineralizer and/or adhesive that will allow the integrity of the tooth to be restored in its entirety

Zafira Light Curing Composite® a material designed to detail.

This product is a light-curing nanohybrid resin for the restoration of anterior and posterior teeth. Its formula is based on the combination of different methacrylate monomers, silane agents and inorganic fillers with radiopaque characteristics and a particle size distribution ranging from 40 nm to 2.0 µm, with a total filler content of more than 78% by weight. This composite has been developed with “Nano Smart Position – NSP” technology, so its nanoparticles have been placed in the interstices of the larger particles by means of an industrial process, generating a product with physical, mechanical and esthetic properties suitable for dental restoration, in addition to excellent handling.

Without neglecting any aspect, Zafira Light Curing Composite® allows to stratify the color has shades enamel, dentin, incisal, bleach, opacifier to give naturalness to the restoration, because the color stability of the composite resin is an important property that influences its clinical longevity, the teeth of the anterosuperior sector must remain without visible changes after having been restored for considerable periods of time.[6]

As well as esthetics, composite resins should be evaluated in tests of compressive strength, tensile strength, elastic modulus and others.

The behavior of the polymeric material against compressive stresses are highly representative in the posterior sector during jaw closure and masticatory movements, the values of the materials are similar to those of enamel + dentin, which is ideal for its behavior in the oral cavity. Zafira Light Curing Composite® has a compressive strength in enamel equal to 62.2 ± 23.8(MPa). In dentin equal to 193.7 ± 30.6(MPa). [7]

The elastic modulus is useful to know the elastic behavior or deformation of the material against stress, a fundamental point to correlate with the stress dissipation capacity during mastication and the behavior against shrinkage stress generated during polymerization at the adhesive interface. Zafira Light Curing Composite® showed an enamel result equal to 1338.2(MPa). On Dentin equal to 1653.7(MPa). [8]

Adhesive system of maximum biocompatibility, strength and durability.

It is not only necessary to have a composite with optimum characteristics, it is also important to be careful with the adhesive to be used.

In the new bonding agents, such as Zafira Bond® , the incorporation of nanofillers with a layer thickness of 10 microns increases the penetration of the resin monomers and the thickness of the hybrid layer, improving the mechanical properties of the bonding systems between the dental structure and the restoration. [9,10]

Zafira Bond® combines etchant, primer and adhesive in one bottle. It is a water- and ethanol-based bonding agent that bonds to dentin and enamel. The prior use of an etchant is optional on both enamel and dentin substrates, therefore, the adhesive can be used in three modes:

self-etching, selective etching or total etching (enamel and dentin).

This adhesive system contains 10-MDP (methacryloyloxydihydrogen phosphate), a molecular structure that improves the resistance to biodegradation of the adhesive interface based on the formation of multiple nano-layers of Ca salts that, together with the molecule on the dentin, protect the collagen fibers from hydrolysis. These nano-layers would explain the high stability of the bond and its physical strength, proven in clinical and laboratory studies, and the improvement in longevity. This phenomenon occurs with slightly higher pH acids than traditional ones, so selective pre-etch of the enamel is recommended. [11]

The clinical steps of application of these adhesives are crucial to the resulting bond interface.[12]

Tissue conditioning, a professional's decision

To restore a dental element using adhesive systems, in addition to achieving good adhesion between the restorative biomaterials and dental enamel, adhesion of the latter to the dentin substrate is essential.[13] The total etching technique has been proposed as a starting point for various improvements in the protocols and adhesive systems designed for this purpose.

Based on the total etching technique, various improvements in the protocols and adhesive systems designed for this purpose have been proposed. This has generated new possibilities for adhesive restorations, including favorable results in endodontically treated teeth, with innumerable advantages over traditional non-adhesive materials [14].

Zafira Etchant Gel® is a water-based etchant containing 37% phosphoric acid to condition the enamel and dentin structure, according to the instructions and indications for use.

that accompany the different dental bonding systems. Its strength is mainly based on its thixotropic power which allows to control the tissue to be demineralized under the technique chosen by the professional.

Bibliografía
  1. Rodríguez, G., Douglas, R., Pereira, S. (2008). Evolución y tendencias actuales en resinas compuestas. Act Odont Venez; 46(3): 381-92.
  2. Calza, T.; Carranza Astrada, A. C. & Bonnin, C. E. La nanotecnología aplicada al desarrollo de resinas compuestas y sistemas adhesivos a esmalte y dentina. Reporte de un caso clínico. Methodo Investig. Apl. Cienc. Biol., 3(3), 2018. Disponible en:
    https://methodo.ucc.edu.ar/index.php/methodo/article/view/82.
  3. Christiani, Juan José, Acevedo, Edgardo Daniel, & Rocha, María Teresa. (2023). Estabilidad de Color de Tres Resinas Nanohíbridas en Relación al Tipo Pulido Realizado. International journal of odontostomatology, 17(1), 64-69. https://dx.doi.org/10.4067/S0718-381X2023000100064
  4. Fernandes, M. S.; Rodrigues, M. A. P.; Penha-Junior, T.; Bresciani, E.; Toma, S. H.; Araki, K.; Medeiros, I. S. & Dutra-Correa, M. Influência da adição de nanopartículas de prata a um sistema adesivo e de diferentes métodos de envelhecimento, sobre a cor da resina composta. Braz. Oral Res., 33 Supl. 2:262, 2019
  5. Paz Pumpido, F. (2005). Biocompatibilidad de los adhesivos dentinarios. Avances en Odontoestomatología, 21(1), 339-345. Recuperado en 12 de diciembre de 2023, de http://scielo.isciii.es/scielo.php?script=sci_arttext&pid=S0213-12852005000100002&lng=es&tlng=es.
  6. Urquía-Morales, C.; Brasca, N.; Girardi, M.; Bonnin, C.; Ríos, A.; Girardi, I.; Chávez-Lozada, J. & Delgado, A. Influence of surface sealants on microleakage in composite restorations. Int. J. Odontostomat., 11(4):467-73, 2017.
  7. Baldión Elorza Paula A Pruebas de resistencia tensil diametral de tres materiales de resina compuesta. Pruebas Laboratorio de materiales y ciencias básicas (LIMACIB) Facultad de Odontología Universidad Nacional de Colombia. Recuperado en 12 de diciembre de 2023, de https://zafiranewstetic.com/category/estudios/
  8. Baldión Elorza Paula A. Pruebas de microdureza de tres materiales de resina compuesta. Pruebas Laboratorio de materiales y ciencias básicas (LIMACIB) Facultad de Odontología Universidad Nacional de Colombia. Recuperado en 12 de diciembre de 2023, de https://zafiranewstetic.com/category/estudios/
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  10. Kasraei SH, Atai M, Khamverdi Z, Khalegh Nejad S. Effect of nanofiller addition to an experimental dentin adhesive on microtensile bond strength to human dentin. J Dent (Tehran). 2009;6(2):91-96.
  11. Moncada, Gustavo, García Fonseca, Renata, de Oliveira, Osmir B, Fernández, Eduardo, Martín, Javier, & Vildósola, Patricio. (2014). Rol del 10-metacriloxidecilfosfato dihidrogenado en el cambio de paradigma de los sistemas adhesivos integrados en la dentina. Revista clínica de periodoncia, implantología y rehabilitación oral, 7(3), 194-199. https://dx.doi.org/10.1016/j.piro.2014.09.008
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