Functions and ideal properties of a sealer - year 2 essay

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.