To crown or not to crown: an evidence based guide

How do you restore root filled teeth? When should you crown and when shouldn't you? What are the rates of failure? Do you have the evidence to back you up?

Root filled teeth are usually restored with direct, intracoronal restorations such as amalgam or resin based composites, or indirect fabricated cast restorations such as a crown or onlay, sometimes supported by a post and core.

Crowns have been thought to be more superior than direct restorations but are more expensive, take more clinical time and can be quite destructive to tooth tissue. The majority of litigations in dentistry are comprised of restorative and prosthetic malpractice, usually involving overtreatment! (Lopez-Nicolas et al. 2011)

Many guidelines have been developed to aid clinicians decide the best option for restoring teeth but none have been widely adapted. Furthermore, many of these have been associated with poor methodology and lack of evidence based protocols.

Wouldn’t it be nice if we have a systematic review of randomised control trials and observational studies to inform new protocols? This is exactly what Afrashtehfar, Ahmadi, Emami, & Tamimi did in 2017!

So what did they find?

The main risk factor for restorative failure was deemed to be remaining coronal tooth structure. Based on their findings, they suggest the following:

less than 1 wall remainingTeeth with <1 remaining wall

A crown with post that has a complete ferrule is the best option here, but still caries a failure rate of 0-35% at 6 years! When no ferrule is available they recommend the healing forceps and an implant.

1 wall remainingTeeth with 1 remaining wall

A post retained crown is the best recommendation. These were associated with lower failure rates that crowns without posts or even post retained direct restorations.

2 walls remainingTeeth with 2 remaining walls

Crowned teeth without posts had a higher failure rate than post retained crowns. It seems that only 2 walls are insufficient to provide a good coronal scaffold to maintain crowns without catastrophic failure.

3 walls remainingTeeth with 3 remaining walls

Intracoronal restorations like amalgams and composites had a higher failure rate (~10%) than a crown (0-5.6%). Studies suggest a post is not needed when 3 remaining walls are present.

4 walls remainingTeeth with four remaining walls

The systematic review did not find enough evidence of cases where only direct restorations were used. But when crowns were used, there was 0% failure in 6 years with teeth with 4 remaining walls.

Be critical

There are 2 main points that one should bear in mind when reading this review:

  1. The followup times were limited to 3-10yrs only! As clinicians we generally hope to quote better success rates than this!
  2. The review excluded other extra-coronal restorations like onlays which some say, are a better alternative that full crowns in many cases due to being less destructive.

Read the full text of the article by clicking on the link in the references.


References

Lopez-Nicolas M, Falcon M, Perez-Carceles MD, Osuna E, Luna A (2011) The role of a professional dental organization in the resolution of malpractice claims the professional dentist college in the region of Murcia (Spain). Medicine and Law 30, 55–63. Afrashtehfar_et_al-2017-International_Endodontic_Journal (1)

Afrashtehfar, K. I., Ahmadi, M., Emami, E., & Tamimi, F. (2017). Failure of single-unit restorations on root filled posterior teeth : a systematic review, 951–966. https://doi.org/10.1111/iej.12723

 

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