Dental composite resin is an increasingly reliable, low-cost and minimally invasive treatment for the restoration of function and aesthetics to both anterior and posterior areas of the mouth. With the phasing down of dental amalgam, composites have become one of the most widely used materials to restore tooth structure lost through trauma, caries or other diseases, and can also be used as cements for crowns and veneers.[i] As restorative bonding materials, composites can successfully replace biological tissue in both appearance and function. At least half of posterior direct restoration placements now rely on composite materials.[ii]
Composite resins are often considered the best option for direct restorations when an aesthetic outcome is needed. The human tooth is a polychromatic structure and its colour is a result of the light interaction with enamel, dentin, and pulp. Many modern composite materials can now seamlessly mimic the colour, translucency, fluorescence, opalescence, and gloss of natural teeth.[iii]
Resin composite materials can be divided into categories based on their particle size and shape. For example, microfilled composite is made of colloidal silica with a particle size of 0.4 µm. This type of composite has high polishability, but has a low mechanical load, making it inadvisable for load-bearing situations.[iv] Hybrid filler contains particles of varied sizes. Resins with hybrid filler have reduced thermal expansion and higher mechanical strength. However, a larger volume of diluent monomer controlling viscosity can result in shrinkage. Nanofilled composite is filled with nanocluster units that act as a single unit. It has high mechanical strength, high wear-resistance, and is easily polished.[v]
Microhybrid composites are considered universal materials and may be applied in both anterior and posterior teeth, combining the resistance properties of hybrid composites with the polishing characteristics of microfilled composites.[vi] Hybrid, microfilled and nanofilled composites are currently among the most commonly-used materials for posterior restorations.[vii]
How do you solve the problem of polymerisation shrinkage and stress?
The durability of materials used in composites has advanced greatly over the last decade, and the use of resin composite – especially as a posterior restorative material – has markedly increased as a result. Nowadays, survival rates of direct composite resin exceed those of amalgam and they also present less risk of tooth or restoration fracture and cracking.[viii]
However, the average composite resin restorative material shrinks approximately 2-6%,[ix] in a process known as polymerisation shrinkage, and this can result in breakdown of the adhesive bonds, leading to restoration failure.[x] The polymerization shrinkage of composite resins occurs following the conversion of monomer molecules to a polymer structure through the replacement of van der Waals spaces with covalent bonds, leading to a decreased free volume.[xi]
Layering techniques were introduced to manage polymerisation stress. Application of composite in 2mm increments can also result in much more natural layering of colour and translucency.[xii] Using a composite system which offers a wide range of shades and translucencies, including an opaque shade, will enable clinicians to more accurately mimic the appearance of natural dental structures. Practitioners should use opaque shades to mimic dentine, followed by translucent shades to replicate layers of enamel. In doing so, this will accurately imitate the appearance of neighbouring teeth.[xiii] However, the process requires skill to ensure aesthetic results, and takes time. There is a risk of air being trapped between layers, which compromises the overall integrity of the restoration.[xiv]
The snowplough method of application was introduced to relieve shrinkage stress and improve the overall integrity of the restoration, while reducing the risk of the formation of air pockets. In this technique, a small amount of flowable composite is applied and not light-cured. In tests, this method has been found to be effective for posterior restorations in terms of cure and porosity, significantly reducing microleakage.[xv]
Restorative brilliance
BRILLIANT EverGlow® Flow from COLTENE offers low viscosity with high stability – making it extremely versatile to use. Its high-quality characteristics ensure polishability and gloss retention, along with a shade assortment including Duo Shades and three translucency levels. BRILLIANT EverGlow® Flow delivers a controlled flow for focussed work, whilst the low viscosity of the material provides optimal wetting, ideal for cavity linings and small fillings.
There is every indication that resin-based composite will continue to evolve as a solution for restoring dental function and aesthetics. Exciting new materials are continuously developing, to offer the means to restore tooth structure and appearance for patients who have experienced damage to teeth due to trauma, caries or other diseases.
For more on COLTENE, visit www.coltene.com,
email info.uk@coltene.com or call 0800 254 5115
Author: Nicolas Coomber, COLTENE National Account & Marketing Manager
[i] Li Wu Zheng, Jing Yi Wang, Ru Qing Yu, Biomaterials in Dentistry, Editor(s): Roger Narayan, Encyclopedia of Biomedical Engineering, Elsevier, 2019, Pages 278-288, ISBN 9780128051443, https://doi.org/10.1016/B978-0-12-801238-3.11033-5.
[ii] Cramer NB, Stansbury JW, Bowman CN. Recent advances and developments in composite dental restorative materials. J Dent Res. 2011 Apr;90(4):402-16. doi: 10.1177/0022034510381263. Epub 2010 Oct 5. PMID: 20924063; PMCID: PMC3144137.
[iii] Batista GR, Borges AB, Zanatta RF, Pucci CR, Torres CRG. Esthetical Properties of Single-Shade and Multishade Composites in Posterior Teeth. Int J Dent. 2023 Sep 12;2023:7783321. doi: 10.1155/2023/7783321. PMID: 37731956; PMCID: PMC10508992.
[iv] Bonsor SJ (2013). A clinical guide to applied dental materials. Pearson, Gavin J. Amsterdam: Elsevier/Churchill Livingstone. pp. 73–75. ISBN 978-0-7020-3158-8. OCLC 824491168.
[v] Bonsor SJ (2013). A clinical guide to applied dental materials. Pearson, Gavin J. Amsterdam: Elsevier/Churchill Livingstone. pp. 73–75. ISBN 978-0-7020-3158-8. OCLC 824491168.
[vi] Demarco FF, Baldissera RA, Madruga FC, Simões RC, Lund RG, Correa MB, Cenci MS. Anterior composite restorations in clinical practice: findings from a survey with general dental practitioners. J Appl Oral Sci. 2013 Nov-Dec;21(6):497-504. doi: 10.1590/1679-775720130013. PMID: 24473714; PMCID: PMC3891272.
[vii] Azeem RA, Sureshbabu NM. Clinical performance of direct versus indirect composite restorations in posterior teeth: A systematic review. J Conserv Dent. 2018 Jan-Feb;21(1):2-9. doi: 10.4103/JCD.JCD_213_16. PMID: 29628639; PMCID: PMC5852929.
[viii] Sethi A, Makkar S, Sidharth K, Kaur T, Sandhu SS, Joseph AK. Evaluation of the Flexural Strength of Submicron Hybrid Composite using Different Fabrication Methods: An in vitro Study. J Contemp Dent Pract. 2018 Feb 1;19(2):205-209. doi: 10.5005/jp-journals-10024-2237. PMID: 29422471.
[ix] chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://apps.dtic.mil/sti/tr/pdf/AD1013161.pdf
[x] Borouziniat A, Khaki H, Majidinia S. Retrospective evaluation of the clinical performance of direct composite restorations using the snow-plow technique: Up to 4 years follow-up. J Clin Exp Dent. 2019 Nov 1;11(11):e964-e968. doi: 10.4317/jced.55639. PMID: 31700568; PMCID: PMC6825734.
[xi] Abbasi M, Moradi Z, Mirzaei M, Kharazifard MJ, Rezaei S. Polymerization Shrinkage of Five Bulk-Fill Composite Resins in Comparison with a Conventional Composite Resin. J Dent (Tehran). 2018 Nov;15(6):365-374. PMID: 30842797; PMCID: PMC6399456.
[xii] Al Ghamdi Z. Layering Technique of Resin Composite Method for Direct Anterior Teeth Restorations: A New Appraisal. Saudi J Oral Dent Res, 8(7): 219-222. July 2023. DOI: 10.36348/sjodr.2023.v08i07.003
[xiii] Singer, Lamia, Ahmed Fouda, and Christoph Bourauel. “Biomimetic approaches and materials in restorative and regenerative dentistry.” BMC Oral Health 23.1 (2023): 105.
[xiv] Angelo Putignano, Vincenzo Tosco, Riccardo Monterubbianesi, Flavia Vitiello, Maria Laura Gatto, Michele Furlani, Alessandra Giuliani, Giovanna Orsini. Comparison of three different bulk-filling techniques for restoring class II cavities: CT, SEM-EDS combined analyses for margins and internal fit assessments. Journal of the Mechanical Behavior of Biomedical Materials. Volume 124. 2021. 104812. ISSN 1751-6161. https://doi.org/10.1016/j.jmbbm.2021.104812.
[xv] chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://apps.dtic.mil/sti/tr/pdf/AD1013161.pdf
