Sealing the deal in endodontics – obturation

endodonticsJohn Rhodes describes the rationale for obtaining a good seal during endodontic treatment by demonstrating two contrasting techniques for obturating the root canals once they have been prepared and disinfected.

I want to begin this article by determining what we are trying to achieve by obturation. All contemporary research points to infection control and disinfection of the root canals as the single most important determinant of endodontic success. The root canals must be thoroughly disinfected before obturating.

Preparation and the creation of a taper to the primary root canals aids disinfection and obturation by creating a natural resistance to flow apically as the diameter of the preparation decreases. This helps reduce the risk of extrusion of either irrigant or obturating material and sealer.

Once the canals are prepared and disinfected, obturation preserves the status quo by preventing entry of microorganisms by coronal microleakage and directly killing any microorganisms that may remain after disinfection.

It is important to note that you cannot expect the obturating material to disinfect or seal a poorly disinfected canal.

By ecologically denying nutrition, space and environmental conditions favourable for the establishment of harmful microbial communities, the balance is tipped in favour of a reduction in the inflammatory response and activation of healing pathways, including migration and stimulation of osteoblasts.

What technique is best?

In terms of treatment outcome, Kirkevang and Horsted-Bindslev (2002) found ‘no single approach can unequivocally boast superior evidence of healing success’, but this study did not include modern bioceramic sealer techniques.

Comparing cold lateral condensation with warm vertical, Peng et al (2007) again found no significant difference, but greater chance of overextension with warm gutta percha techniques.

So, as long as a hermetic or biological seal is achieved after thorough disinfection it does not seem to matter which technique is used.

Coronal/apical seal essential synergy for success

Sealing the case after preparation and disinfection does not stop at obturation of the root canals; for long-term success, it is also essential to provide good coronal seal.

Ray and Trope (1995) highlighted the importance of good coronal seal and established that the best outcome was provided by good obturation and good coronal seal.

Poor coronal seal will allow a microbial challenge to the seal provided by the obturating material, and a poorly obturated tooth will provide no barrier to coronal microleakage or recolonisation of the root canal.

A paradigm shift

There are basically two rationales for obturating the root canals.

Gutta percha techniques aim to obliterate the majority of the prepared canal with gutta percha, a thin film of sealer provides the interface between root filling material and the dentinal wall.

Gutta percha techniques include cold lateral condensation, warm vertical compaction or carrier-based systems.

Bioceramic sealers, perhaps more correctly called hydraulic calcium silicate-based sealers, are relatively new in endodontics but have shown excellent potential (Donnermeyer et al, 2019).

They also have bioactive properties, inducing biological healing (Giacomino et al, 2019).

There is a paradigm shift in technique with bioceramic sealers; here a single gutta percha cone acts as a spacer while the majority of the disinfected root canal system is obliterated with a bioactive sealer.

The sealer is delivered either in a pre-mixed syringe or as component parts that can be mixed in the surgery.

This method appears to have very promising results and early published research has shown success rates of 90% at 12 months using a single cone and Bioroot RCS (Zavattini et al, 2020)

Warm vertical compaction

Warm vertical compaction techniques are popular with endodontists; they provide a versatile and predictable means of obturating most cases efficiently.

With warm vertical compaction techniques, it is not uncommon to see lateral canals with puffs of sealer exiting the foramina on the final radiograph. While these may look interesting on the radiograph, there is no evidence that their presence improves the likely success rate.

Case one

Case one highlights a typical molar endodontic case obturated with a vertically compacted gutta percha technique (Figure 1).

It was unusual as there were six individual canals (Figures 2 and 3). The final result shows a good apical coronal seal with little extrusion of sealer apically (Figure 4).

  • Figure 1: Case one – the preoperative radiograph shows fine and moderately curved root canals in the mandibular right first molar. Periapical radiolucencies are present on both mesial and distal roots

Case two

The maxillary first molar in case two was extremely long. A vertical paralleling radiograph has been used to visualise the palatal root (Figures 5 and 6).

  • Figure 5: Case two – the preoperative radiograph shows the maxillary right first molar with caries and long, fine moderately curved canals

Warm vertical compaction technique

Cone fit

The preparation must be tapered with the narrowest diameter apically. This increases resistance to flow and prevents extrusion of sealer and gutta percha.

A pre-matched master cone is fitted with tugback in the root canal to the working length or sometimes 0.5mm short of working length.

Downpack

The master cone is introduced into the dried canal with a light coating of sealer (Figure 8). The cone is seared off at the level of the pulp floor and plugged with a cold plugger.

The heated plugger is then gently advanced apically until it is 5-7mm short of the working length.

It is allowed to cool for a few seconds before being removed with a burst of heat. This leaves a plug of gutta percha at the apex of the tooth and a void behind.

The apical cork of gutta percha is plugged with a cold plugger while it cools (Figure 9).

  • Figure 7: The plugger must fit passively to within 5-7mm of the working length

Back fill

The void that remains after the downpack is rapidly filled with thermoplasticised gutta percha to the level of the pulp floor and is then packed with a cold plugger (Figure 10).

  • Figure 10: Back filling

Single cone and Bioceramic sealer

Case three

This is a typical case sealed using Bioroot RCS (Septodont) and single cone gutta percha.

The preoperative radiograph shows a maxillary second molar restored with an amalgam restoration (Figure 12).

The tooth is necrotic and the root canals undoubtedly infected as there is periapical radiolucency around the apices of the roots.

The postoperative radiograph shows well sealed root canals (Figure 13).

Coronal seal is provided by a composite restoration that was placed immediately.

Coronal seal is extremely important; in this case, a composite restoration was placed after obturation (Figure 14).

  • Figure 12: Case three – preoperative radiograph shows a maxillary second molar restored with an amalgam restoration

Single cone and Bioceramic sealer technique

Cone fit

The preparation must be tapered with the narrowest diameter apically. This increases resistance to flow and prevents extrusion of sealer during obturation.

Bioceramic sealers are highly biocompatible and will not induce an inflammatory response.

A pre-matched master cone is fitted with tugback in the root canal to the working length or sometimes 0.5mm short (Figure 15).

Figure 15: The master cone is pre-measured and fitted with tugback

Sealer placement

Sealer can be injected into the prepared root canal, placed into the canal on a gutta percha cone, or introduced using a lentulo spiral filler (Figure 16).

Figure 16: Sealer can be injected into the root canals

Cone placement

The pre-fitted master cone is introduced slowly into the canal to the working length, seared off at the level of the pulp floor and plugged with a cold plugger (Figure 17).

Sometimes, a small amount of additional thermoplasticised gutta percha is required to cork the orifice of the root canal and prevent sealer being washed away when the access cavity is sealed.

Figure 17: The gutta percha is seared off at the level of the pulp floor and plugged with a cold plugger

Comparison of techniques

Both techniques are suitable for obturating endodontic cases successfully (Table 1).

Bioceramic (BC) single cone

Vertical compaction (VC)

Comments

Simple  technique

More complex

Requires a tapered preparation

Requires a tapered preparation

Canal predominantly filled with sealer

Canal predominantly filled with gutta percha

Little equipment required

Heated plugger, and backfill device

Pre-mixed sealer or mix in surgery as powder-liquid

Auto-mix sealer or powder-liquid

Sealers used with VC need to be heat tolerant

Bioactive properties

Resin-based sealers are not bioactive

BC sealers cannot be used for warm compaction

Don’t over-dry canals

BC sealers require water to set

Useful in long, narrow canals where pluggers may not reach deep enough

There may be anatomical situations that make VC more difficult; long thin roots, canals with severe curvature

If the heated plugger does not reach 5-7mm from WL then the apical part of the root canal is essentially filled with a single cone!

Work well in perforation repair cases as the sealer requires moist conditions to set

VC can be used in conjunction with a bioceramic cement in perforation repair cases

Good for cases with irregular internal morphology

Good for cases with irregular internal morphology

Good in immature root canals, bioactive properties useful for root closure

Must ensure a matrix apically in immature roots to prevent extrusion of sealer and gutta percha

Table 1: Comparison of techniques

Conclusion

Hydraulic calcium silicate cements have many uses in modern endodontics; they have excellent biocompatibility and bioactive properties.

The introduction of sealers made from these materials is an exciting and interesting development that appears from early research to have very good potential.


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This article was commissioned for Clinical Dentistry magazine. Sign up to receive the latest issue of Clinical Dentistry magazine at www.fmc.co.uk/shop/clinical-dentistry.

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