The functions and ideal properties of an Endodontic sealer Dr Jatan Kothari In endodontic treatment, the primary aims of obturation are in essence to wholly remove, prevent the growth of and entomb remaining bacteria. The best root filling materials and techniques would be those that accomplish this goal with a 100% success rate, however as of yet no single approach can unequivocally boast superior evidence of healing success (Whitworth, 2005). Root canals obturated with gutta percha and sealer represents the lateral condensation technique for root filling: a method that tightly fills the canal three-dimensionally without using chemicals or heat to soften the gutta percha (Tronstad, 2003). Alongside the primary aims of an obturation method, this combination of materials is used to prevent the shrinkage problems of softened gutta percha. In this essay we will compare and contrast these materials based on their advantages and disadvantages i.e. how well they adhere to Grossmans’ ideal properties of a sealer. Some properties may not be listed or discussed as they are present in all the sealers listed, or is not characteristically significant in terms of distinguishing between materials e.g. only calcium hydroxide and MTA are listed as being difficult to remove so ‘easy/easier to remove’ has not been stated for the other materials; and radiopacity: all materials have a statistically greater radiopacity as compared to dentin. (Department of Endodontics, 2009) The role of a sealer: (Tomson, et al., 2014) • Seal the space between the obturating core material and the internal root surface • Fill the space between the core and accessory filling materials in lateral condensation • Seal the irregularities of the complex canal anatomy e.g. lateral canals and tubules • Lubricate and facilitate seating of the core and accessory filling material • Deliver antibacterial properties to the obturation system A sealer is more important than the core obturating material (used to occupy space) and works to form a bacteria-tight seal of the canal (Walton & Torabinejad, 2002). The materials used in sealers are poor at obturating the canal solely due to physical property inadequacies including shrinkage and difficult in removal so must be used in conjunction with a core material. Some of the most commonly used sealers are based on Zinc Oxide Eugenol, Calcium Hydroxide, Resin, MTA, Glass Ionomer, Calcium Silicate, and Silicone. These materials and others aim to fulfil a criteria outlined by Grossman (see table); however no sealer exhibits all of the properties and their use is based on compromise of a few. Ideal sealer properties (Grossman, 1988) Exhibits tackiness when mixed to provide good adhesion between it and the canal wall when set Establishes a hermetic seal Radiopaque, so that it can be seen on a radiograph Very fine powder, so that it can mix easily with liquid No shrinkage on setting No staining of tooth structure Bacteriostatic, or at least does not encourage bacterial growth Exhibits a slow set Insoluble in tissue fluids Tissue tolerant; that is, non-irritating to periradicular tissue Soluble in a common solvent if it is necessary to remove the root canal filling Zinc Oxide-Eugenol (Tomson, et al., 2014) Advantages: • Powder and liquid set very slowly • Exhibit antimicrobial properties Disadvantages: • Resorb if extruded into the periapical tissues • Exhibits toxicity when placed directly on vital tissues • Shrink slightly on setting • Slightly soluble • Stains dentine (Walton & Torabinejad, 2002) Calcium Hydroxide (Ca(OH)2 (Athanassiadis, et al., 2007) Advantages: • Highly antibacterial ➢ Biologically, through the release of hydroxyl ions, a highly alkaline and therefore hostile environment for microorganisms is formed which damages cytoplasmic membranes, suppresses enzyme activity and inhibits DNA replication; in addition Ca(OH)2 inactivates the lipopolysaccharide endotoxin required by gram-negative bacteria to maintain cell wall integrity. ➢ Physically, it kills remaining microorganisms by withholding substrates for growth and limiting space for multiplication • Biocompatible: non irritating to periradicular tissue and exhibits low solubility • Able to encourage periapical hard tissue healing around teeth with infected canals • Inhibits root resorption and stimulation of periapical healing after trauma • Do not shrink Disadvantages: • Low solubility and diffusibility of Ca(OH)2 make it difficult to raise the pH high enough to kill certain bacteria e.g. E.Faecalis • Lack of physical sturdiness means thorough condensation of gutta percha is important to minimize the risk of root filling loosening (Orstavik 2005) • Difficulties in removal from canal walls. Both incomplete removal and subsequent resorption of material in the apical third are reported and attributed to the failure of root canal treatment (Riccuci & Langeland, 1997) Resin (Tomson, et al., 2014) Encompass a few types of composites including epoxy and methyl methacrylate. Epoxy resins: Advantages: • Antimicrobial action, • Adhesion, • Long working time, • Ease of mixing • Very good sealability • Dimensionally stable Disadvantages: • Releases formaldehyde which causes dentine staining • Relatively insoluble in solvents • Exhibits some toxicity when unset • Displays solubility to oral fluids Methyl methacrylate: Hydrophilic sealer that exhibits good wetting, biocompatibility and is able to penetrate dentinal tubules MTA (Mineral Trioxide Aggregate) (Rawtiya et al, 2013) Advantages: • Highly biocompatible and stimulate mineralisation • Hard tissue inductive by encouraging differentiation and migration of hard tissue producing cells • Antimicrobial • Form hydroxyapatite on MTA surface and produce a biological seal • Higher adhesiveness to dentine than conventional Zinc Oxide Eugenol cements • Forms Ca(OH)2 • Provides an effective seal against dentine and cementum and promotes biological repair through regeneration of periodontal ligament • Not sensitive to moisture and blood contamination Disadvantages: • Staining through release of ferrous ions • Long setting time of 2 hours 45 minutes and a working time of less than 4 minutes • Compressive strength inadequate • No solvent can fully dissolve MTA • Improper handling properties Glass Ionomer (Tomson, et al., 2014) Adheres to dentine and provides and adequate apical and coronal seal. Its hardness makes it insoluble and more difficult to remove for any correction or retreatment. Also exhibits less antibacterial activity than zinc oxide Eugenol and Ca(OH)2 based sealers. Calcium silicate (Tomson, et al., 2014) Relatively new material in comparison to other sealers; it displays excellent sealing properties and biocompatibility. Silicone (Tomson, et al., 2014) Another relatively new material; it has low viscosity to flow within root canal system, demonstrates limited shrinkage and is biocompatible to the periradicular tissues. Discussion Clinical evidence suggests that sealer choice may not have a decisive impact on outcome. Slow setting sealer cements are generally preferred, which will allow adequate lubrication for accessory point insertion and accommodate revision and consolidation of the fill if voids are detected on intermediate radiographs (Whitworth, 2005). Hence the prolonged used of Zinc Oxide Eugenol as a sealer From this observation and a brief description of the contemporary sealers available, we can determine that there is unlikely to be a statistically significant difference with each sealer in terms of its efficacy in obturation. All provide characteristically unique and advantageous properties whilst also demonstrating some failure. Use of sealer is therefore down to personal choice and apparent success of the material. References Tronstad, L., 2003. Clinical Endodontics A Textbook. 2nd ed. Oslo: Thieme. Whitworth J. Methods of filling root canals: principles and practices. Endodontic Topics 2005:12:2-24 Grossman L: Endodontics. 11 ed. Philadelphia, Lea & Febiger, 1988 Tomson, R., Polycarpou, N. & Tomson, P., 2014. Contemporary obturation of the root canal system. British Dental Journal, 216(6), pp. 315-323. Walton, R. E. & Torabinejad, M., 2002. Principles and Practices of Endodontics. 3rd ed. Philadelphia: W.B. Saunders Company. Athanassiadis, B., Abbott, P. & Walsh, L., 2007. The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics. Australian Dental Journal Supplement, Volume 52, pp. 64-82. Ricucci D, Langeland K. Incomplete calcium hydroxide removal from the root canal:a case report. Int Endod J 1997;30:418 –21. Orstavik D. Materials used for root canal obturation: technical, biological and clinical testing. Endodontic Topics 2005:12:25-38 Rawtiya M, Verma K, Singh S, Munuga S, Khan S. MTA-based Root Canal Sealers. J Orofac Res 2013;3(1):16-21 Department of Endodontics, Hacettepe University, Faculty of Dentistry, Ankara, Turkey. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology (Impact Factor: 1.5). 08/2009; 108(3):e135-40. DOI:10.1016/j.tripleo.2009.04.016