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03 Apr 2017

By Maciej Zarow, Walter Devoto et al

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[Case study] Reconstructing endodontically treated posterior teeth

Current status of endodontically treated teeth

Restoration of endodontically treated teeth represents a challenge for the practitioner, because it requires profound knowledge not only of restorative dentistry, but of endodontics and periodontics as well. The main reason for loss of endodontically treated teeth is their bad reconstruction. Unfortunately, the clinical concepts regarding the restoration of root canal treated teeth are not clear and often based on conjecture due to a lack of sound empirical data. The diversity of published opinions is confusing and may lead to less-than-optimal treatment selections. There is also an emerging debate about whether a post is necessary. The purpose of the present article is to organize this topic in evidence-based principles and provide dental practitioners with clear guidelines about restorative therapy for premolar and molar teeth.

 

Download the free eBook "Reconstructing endodontically treated posterior teeth - with or without post?"

 

Clinical application

 

A 36-year-old patient came to the surgery complaining of pressure pain on tooth 16. The tooth had been provisionally restored while on holiday after the partial loss of a restoration in silver amalgam (Fig 1).

The radiograph (Fig 2) showed a periapical transparency and it was decided that an endodontic intervention was needed on the tooth in question. It was decided that the inappropriate amalgam restoration on tooth 15 would be eliminated as well and two restorations would be applied in composite. For the teeth in question, the final treatment decision fell on an indirect composite restoration, a partial onlay, and an inlay.

 

Fig 1.png

Fig 2.png

 

 

 

 

 

 

 

 

 

 

 

 

 


Fig 1 and 2
Initial clinical image and radiograph: the pulpal necrosis, confirmed by the vitality test, can be clearly seen.

 

When rebuilding one or more cusps with the need to optimize the form, the contact points, and occlusion, and if there is more than one restoration in the same hemi-arch, indirect restoration is chosen. This means two short appointments, rather than one long one, but it does give excellent results.

Currently, composite offers diverse advantages. The ability to modify and correct, simple and rapid lab work, as well as better conversion than when the composite is cured during chair time. Once the restorations are removed, the secondary caries are accurately cleaned in order to be able to carefully evaluate the quantity and quality of the sound residual tissue (Fig 3).

Tooth 16 had a completely integral distal and vestibular wall of adequate thickness, while the palatine wall appeared intact on its distal cusp, but rather thin (> 1.5 mm) in its mesial component. It was possible to treat this tooth as a vital element, proceeding parallel to the restoration on tooth 15 without using a post.

Next, adhesive phase (ClearfilTM Protect Bond, Kuraray, Okayama, Japan) was applied and a build-up in composite materials was constructed in order to optimize the dimensions of the inlay, which was subsequently prepared to seal the tubules of vital tooth 15. The material (Enamel plus HFO, Micerium, Avegno, Italy) was then applied in thin layers so as to reduce the danger of the restoration contracting on the healthy residual walls (Fig 4).

Once the restoration had been built up with layers of composite, a little glycerine could be applied and polymerized again for 1 minute so that there was a good film surface to work on with the preparation burs (Fig 5).

 

Fig 3.png

Fig 3 Once the tooth has been treated post-endodontically and after the cavity has been thoroughly cleaned, the healthy residual tissue can be assessed and decisions made on the most appropriate restoration technique.

 

 

Fig 4.png

Fig 4 The composite restoration is built up very gradually in order to reduce curing shrinkage that causes stress to the walls.

 

Fig 5.png

Fig 5 Once the build-up has been completed, the final layer is cured with glycerine for protection.

 

Then, the build-up was optimized by leaving at least 2 mm of space for the inlay by reducing the mesial-palatine cusp, which was to be completely reconstructed in composite. After applying 000 retraction cord (UltrapakĀ®, Ultradent, South Jordan, UT, USA), an impression was then taken (Fig 6) with precision material (ImpregumTM and PermadyneTM, 3M ESPE, St Paul, MN, USA).

The impression was sent to the laboratory where, in only a few days, the two inlays could be manufactured using the same material which had been applied as a base for the restoration (Fig 7).

 

Fig 6.png

Fig 6 The preparation is now complete and the retractor threads are positioned for a precision impression.

 

Fig 7.png

Fig 7 The composite inlays are ready for adhesive cementing.

 

The third appointment involved the cementing of the inlays and this is ideally done with the same light-curing composite which was used both for the build-up and for the inlays. It was then possible to remove the excess material and activate the light curing at the earliest convenience.

It is crucial, if this form of luting is used, to optimize the forms and dimension of the build-up and ask the technicians to use an abundant layer of wax on the bottom and wall of the plaster model (not on the margins!) before beginning the stratification of the inlay. This gap will be filled by the lightcuring composite, which will have been heated in order to render it more fluid. Pre-formed matrixes were used (Sectional Matrix System, KerrHawe, Bioggio, Switzerland) during all of the adhesive and cementing stages (Fig 8). In this way, the neighbouring teeth are protected from any excess material which would be difficult to remove when cementing the contiguous element. It is recommended to never cement the two teeth at the same time (Fig 9).

The inlay was locked in by exposing it for a few seconds to the LED lamp before checking to see if there was any excess bonding or composite material. Once it has been ensured that all excess material has been removed, the curing lamp can be activated for 6 minutes, making sure to apply the lamp on all surfaces possible.

It is at this point that the finishing and polishing stages can be completed with rubbers, diamond paste, and shining material (Shiny System, Micerium). The results achieved 6 months on can be seen in the check-up photograph (Fig 10). In the bitewing radiograph, the different radiopacities of the composites used can be appreciated (Fig 11).

 

Fig 8.png

Fig 8 A pre-formed transparent matrix (KerrHawe) is positioned in order to protect the adjoining cavity during the cementing phase of one of the inlays.

 

Fig 9.png

Fig 9 Once the first inlay has been cemented, any excess material is carefully eliminated. The interproximal can then be finished and the second inlay begun.

 

Fig 10.png

Fig 10 The finished case. Please note the high level of functional and esthetic integration.

 

 Fig 11 a.png

Fig 11 b.png

Fig 11 (a and b) The final radiographs show the healing and precision of the inlays: the different radio-transparencies of the materials utilized are clearly shown and this helps to understand the thickness of the build-up, the dentin, and the enamels used.

 

 Fig 12.png

Fig 13.png

Figs 12 and 13 The initial case: the pain that the patient was complaining of may have been caused by more than one element on the same hemi-arch.

 

Conclusions and guidelines for practitioners

As a result of the present review and the authorsā€™ clinical experience, several conclusions and guidelines for practitioners can be drawn.

  • In the case of endodontically treated molars, if adequate coronal dentin is present and the pulp chamber provides adequate retention for a core build-up, no additional fiber post reinforcement is needed.

  • A fiber post should be used during reconstruction of endodontically treated molars in the case where there is an absence of coronal dentin. During core build-up reconstruction, especially when no post is applied, special care has to be focused on achieving the best possible adhesion to the dentin through:

 

  • Rubber dam isolation
  • Removing gutta-percha remnants from the orifice of the root canals
  • Perfect cleaning of the dentinal surface
  • Adequate application of the bonding system
  • Adequate light-curing of the bonding system and resin composite
  • Incremental placement of the composite to reduce polymerization shrinkage and achieve satisfactory marginal adaptation.
  • During the restoration of endodontically treated premolars, use of a fiber post is recommended for the length at least equal to the length of the crown.
  • Fiber post placement or composite core build-up restoration should be performed immediately after endodontic treatment whenever possible.

 

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