Sealers are used between dentine surfaces and core materials to seal the space, between core and filling materials in lateral condensation techniques, to seal complex canal anatomical irregularities such as lateral canals and dentinal tubules, to lubricate and facilitate seating of the master cone and provide antimicrobial properties within the final obturation material. Traditionally desirable characteristics were to adhere to dentine and the core material as well as to have adequate cohesive strength. Newer-generation sealers are being engineered to improve their ability to penetrate into dentinal tubules and bond to, instead of just adhering to, both the dentine and core material surfaces. Although no sealer meets all the properties of Grossman’s ideal sealer (Table 7.1), there are many sealers available that are clinically acceptable and widely used.

The materials are produced in a powder and liquid form (e.g. Roth Root Canal cement, Roth International Ltd., Chicago, USA) or a two-paste preparation (e.g. Tubli-Seal Kerr, Orange, USA). The components of the powder, consisting of zinc oxide, bismuth subcarbonate, barium sulphate and sodium borate, are mixed with the eugenol to form the sealer. These sealers are radiopaque (due to the addition of silver, bismuth and barium), antimicrobial and toxic to vital tissues. The setting reaction of the sealer is due to the formation of zinc eugenolate crystals embedded with zinc oxide. Free eugenol is present as the material sets, decreasing over setting time and is responsible for most of the cytotoxicity when unset. Setting time and working time are dependent on the proportion of bismuth subcarbonate to sodium borate and are affected by temperature and humidity. Paraformaldehyde was added to the controversial N2 paste and in Endomethasone for added antibacterial activity.

AH Plus (Dentsply Detrey, GmbH, Konstanz, Germany) is an epoxy resin-based sealer, which was produced as an alternative to its predecessor AH26 that released formaldehyde during the setting reaction. AH Plus exhibits acceptable biocompatibility, dimensional stability and insolubility.

Epiphany (Pentron Clinical Technologies, Wallingford, Conn.) consists of a dual cured sealer based on BisGMA, UDMA (urethane dimethacrylate) and hydrophilic methacrylates with radiopaque fillers that can coat the dentinal walls. Prior to application of the sealer, a primer must be applied to the dentine surface after a chelator such as EDTA has removed the smear layer. The sealer may then form a secondary monoblock bonding effectively to both dentines via the primer and with a chemical integration with the core material (Resilon).

EndoREZ is a hydrophilic UMDA resin capable of flowing into dentinal tubules with good biocompatibility. The sealer is used in combination with resin-coated gutta-percha points allowing the possibility of dual curing with both dentine and core material even in the presence of moisture.

Russian Red sealer is a variant of the phenol-formaldehyde resin, which sets very hard resulting in an insoluble mass within the root canal system. The sealer is strongly antibacterial and on setting results in shrinkage that leaves a reddish hue in the surrounding tooth structure. This type of paste filling is not advocated and can be very difficult to retreat.

Sealapex (SybronEndo, Orange, USA) and Apexit (Ivoclar Vivadent, Schaan, Liechtenstein) are well-known sealers based on calcium hydroxide that when used in conjunction with gutta-percha core material provides biocompatibility with the possible advantage of bioactivity of calcium hydroxide when placed adjacent to vital tissue. However, for this to occur, calcium hydroxide must dissociate into calcium and hydroxyl ions requiring the sealer to break down or dissolve compromising the seal. Questions remain regarding the long-term stability of these sealers.

Roekoseal (Coltene Whaledent, Altstätten, Switzerland) is a polydimethylsiloxane-based root canal sealer that polymerises with minimal shrinkage and shows good biocompatibility. The material is mixed with auto-mix tips similar to impression materials producing a white fluid paste that has low viscosity to flow within the root canal system. GuttaFlow (Coltene Whaledent Ltd., Sussex, UK) is a cold gutta-percha filling system that utilises a silicone matrix and powdered gutta-percha that is triturated before carriage to the canal on either a gutta-percha cone or by passive injection using a plastic cannula.

Ketac Endo (3M ESPE, St. Paul, MN, USA) is an adhesive root canal sealer with good biocompatibility and claims of root reinforcement due to adhesion to dentine. These sealers have been found to be more soluble and less antimicrobial with in vitro findings of leakage and disintegration over time. Due to its potential chemical bonding with dentine, issues about insolubility when using traditional gutta-percha solvents potentially make retreatment difficult.

A new category of root canal sealers based on MTA such as iRoot SP (Innovative BioCeramix, Vancouver, Canada) has been introduced in an attempt to address the inherent problems with existing sealers and biocompatibility particularly when extruded beyond the confines of the root canal. Calcium silicate sealers include some of the same hydraulic compounds found in Portland cement including tricalcium silicate and dicalcium silicate powder that reacts with water to form a highly alkaline cement (pH 12) to create a rigid matrix of calcium silicate hydrates and calcium hydroxide. When these sealers set, the dimensional change is less than 0.1 % expansion, which helps create a barrier that has superior sealing ability. The combination of a hydrophilic sealer that is biocompatible with excellent dimensional stability seems ideal, particularly with the potential of obturation materials coming into contact with fluid either apically or coronally potentially salvaging a compromised seal.

Traditional gutta-percha points or cones are produced in the beta phase and contains a mixture of zinc oxide, gutta-percha, radiopacifiers and plasticisers. Cones are manufactured as standardised 0.02 taper ISO cones and non-standardised 0.04, 0.06, 0.10 and 0.12 taper with specified tips or feathered tips according to manufacturing brand. Accessory points are also available from various manufacturers sized according to specified matched spreaders (e.g. SybronEndo system, SybronEndo, Orange, USA – XF, FF, MF, F, FM and M) (see Fig. 7.4).

An important characteristic of gutta-percha and of clinical importance is the fact that when it is exposed to air and light over time it becomes more brittle. Storage of gutta-percha in a refrigerator extends the shelf life of the material.

Gutta-percha is unable to provide a hermetic seal on its own and requires the use of an appropriate sealer. Gutta-percha is often applied to the canal using either a lateral condensing and/or vertical condensing force using spreader or pluggers to ensure adaptation occurs within the anatomical intricacies of the root canal system.

Cones can be sterilised chair side by immersion in sodium hypochlorite solution for 1 min. Gutta-percha is easily dissolvable by organic solvents such as chloroform, halothane or xylene making retreatment possible. The biocompatibility of gutta-percha has been tested thoroughly using cytotoxic, implantation, mutagenicity and usage tests.

Resilon, a new, synthetic resin-based polycaprolactone polymer has been developed as a gutta-percha substitute to be used with Epiphany, a new resin sealer in an attempt to form an adhesive bond at the interface of the synthetic polymer-based core material, the canal wall and the sealer, otherwise known as a secondary ‘monoblock’. It is manufactured in standardised ISO sizes and shapes, conforms to the configuration of the various nickel-titanium rotary instruments and is available in pellet form for injection devices. The manufacturer states that its handling properties are similar to those of gutta-percha, and therefore it can be used with any obturation technique. Resilon contains polymers of polyester, bioactive glass and radiopaque fillers (bismuth oxychloride and barium sulphate) with a filler content of approximately 65 %. It can be softened with heat or dissolved with solvents like chloroform.

Like traditional dentine bonding systems, etching and priming of the dentine surface is required to achieve a chemical bond. The root canal system must first be rinsed with 17 % ethylene-diamine-tetra-acetic acid (EDTA) to remove the smear layer. The Epiphany, a self-etch primer, is then applied to the canal and Resilon core material used to fill the root canal system. Light curing for 40 s will cure the coronal 2 mm of the canal, and self-curing of the remainder of the canal will occur within 15–30 min. This creates a secondary ‘monoblock’ in which the Resilon bonds to the Epiphany sealer, which in turn bonds to the dentine wall.

The ability of Resilon to effectively bond to tooth structure and thereby preventing leakage has been unproven to date. The reality of achieving an adhesive ‘monoblock’ in the apical portion of the canal is unpredictable with current available materials. The literature also suggests that Resilon is not stiff enough to strengthen residual root structure. Concerns remain regarding the biocompatibility and cytotoxicity of the Epiphany sealer. Evidence-based randomised controlled trials are lacking comparing Resilon to current gold standard gutta-percha techniques that have a proven track record at this time.

Another strategy to achieve an intra-canal monoblock utilising traditional gutta-percha was to chemically bind or mechanically impregnate a coating over the surface of gutta-percha cones creating a similar chemistry to the sealer. Ultradent Corporation has surface coated their gutta-percha cones with a resin (functional methacrylate groups) in attempt to create a bond between the canal wall, the core material and sealer (hydrophilic self-priming methacrylate-resin based) (Ultradent, South Jordan, Utah). A bond is formed when the resin sealer (EndoREZ) contacts the resin-coated gutta-percha cone creating a hypothetical tertiary ‘monoblock’ within the root canal system with three adhesive interfaces (dentine-sealer, sealer-coating and coating-gutta-percha).

Since the inception of the cement material generally known by its trade name ‘Mineral Trioxide Aggregate’ in 1993 by Torabinejad, it has found many applications in dentistry including direct pulp capping, pulpotomy, root-end filling, apexification and apexogenesis, treatment of horizontal root fractures, repair of internal and external resorption defects, perforation repair and obturation of the root canal system. It is a hydraulic cement (e.g. sets and is stable under water) relying primarily on a hydration reaction for setting to occur. Apical barriers are important for the obturation of canals with immature roots with large open apices. Traditional techniques employed have been to use chloroform customization of gutta-percha that can result in extrusion with either long-term biocompatibility issues or the need for surgical revision. Alternative barriers to prevent extrusion of material have included the use of calcium hydroxide, dentine plugs and hydroxyapatite, which permit obturation, whilst minimising potential extrusion of material beyond the confines of the canal. Calcium hydroxide apical barriers are often time-consuming repeated treatments that have been associated with the potential of root fractures when used for prolonged periods of time. Placement of an apical barrier and immediate obturation is an alternative to apexification using MTA. The material is compacted into the apical portion of the root canal and allowed to set. Gutta-percha is then compacted against this apical barrier without risk of extrusion. The technique is quick, reliable and clinically successful, eliminating the need for numerous visits and possible recontamination during traditional calcium hydroxide-based apexification procedures. It is worth noting that when a root canal system is fully obturated with MTA, re-entry for retreatment or the ability to create a post space can be very difficult using ultrasonic or rotary nickel-titanium instruments due to the inherent hardness and strength of the material.

Silver points were historically introduced as root canal obturation materials that were easily placed due to their inherent rigidity. However, their inability to three-dimensionally flow and conform to irregularly shaped root canal systems permitted leakage and the potential for corrosion. Corrosion by-products can cause irreversible staining and the potential for cytotoxicity inducing persistent periapical inflammation. Other potential shortcomings including complications encountered during apical surgery and the difficulties when needing to create a post space have made these materials redundant, particularly in the face of modern techniques and improved materials that are available today (Fig. 7.5).

A master cone corresponding to the final instrumentation size and length of the canal is coated with sealer, inserted into the canal, laterally compacted with spreaders and filled with additional accessory cones (see Figs. 7.6, 7.7 and 7.8). This technique has been the ‘gold standard’ to which other techniques have been compared. Lateral cold condensation has the advantage of excellent length control and can be accomplished with any of the acceptable sealers. The disadvantage of this technique is that it may not fill canal irregularities as well as the warm vertical compaction technique. The technique is as follows:

Solvents such as chloroform, eucalyptol or halothane are used to soften the outer surface of the cone as if making an impression of the apical portion of the canal. The canal must be wet with sodium hypochlorite solution prior to ‘impression’ taking to ensure that the gutta-percha master cone does not stick to the canal walls. The chloroform cone-dipped master gutta-percha cone is then removed from the canal and allowed to dry for 1 min to ensure that all solvent has evaporated and shrinkage is minimal. The cone is reinserted into the canal ensuring it follows the same path of insertion as withdrawal previously. The cone must be coated with sealer and laterally condensed with spreaders and accessory cones (same as cold lateral compaction) (Fig. 7.9).

Ultrasonics has also been advocated for obturation of the root canal system using a warm lateral condensation technique. Lateral condensation can be used by alternating heat after the placement of an accessory gutta-percha cone. Heat is transferred to the gutta-percha using an ultrasonically vibrated K-file, which softens the mass of gutta-percha allowing penetration of the finger spreader and matched accessory cone. This technique allows for better condensation and homogeneity of both sealer and gutta-percha (see Figs. 7.10, 7.11, 7.12 and 7.13).