Judy Fan-Hsu DDS, FAGD
There is insufficient evidence to support or refute the effectiveness of conventional fillings over crowns for the restoration of endodontically treated teeth.
In endodontically treated premolars, is there a difference in failure rates when restored with conventional resin filling materials compared to crowns?
The authors conducted a comprehensive search of literature up to February 13, 2012, of six electronic databases and hand searched seven dental journals as well as searches of ongoing trials (concluded on February 12, 2012). The authors included randomized clinical trials (RCT) and quasi-randomized clinical trials written in English for their searches. Other inclusion criteria involved studies with at least three years in duration, participants of any age or gender having single previously untreated permanent premolars requiring endodontic treatment. Two independent observers conducted the selection of studies. Any disagreement was resolved by discussion and consensus or by a third reviewer. Risks of bias
were well presented as a quality assessment of included studies. Primary outcome measures include catastrophic and non-catastrophic failures of restored tooth, restoration, or post. Secondary outcome measures are patient satisfaction, recurrent caries, periodontal health, cost, and endpoint follow-up evaluations up to 10 years.
Only one RCT study was included, 117 participants with root filled premolars restored with a carbon fiber post, randomized to receive either a full coverage metal-ceramic crown or direct adhesive composite restoration. At three years follow up, there were no differences between the two groups in non-catastrophic restoration failure rates, risk ratio (RR) was 0.34 (95% confidence interval
0.04 to 3.16; p=0.34). The RR for post failure was 1.96 (95% CI
0.18 to 21.01, p=0.58). The systematic review
authors assessed the risk of bias
to be high, due to missing outcome data.
There is insufficient evidence to support or refute the effectiveness of conventional fillings over crowns for restorations of endodontically treated pre-molars based on this one study.
Source of Funding:
None specified (generated by Cochrane Oral Health Group).
Importance and Context:
This research question is important because deciding the restoration for an endodontically treated tooth is very commonly encountered in dental practices. Currently crowns are considered the restoration of choice for endodontically treated teeth (1). Although endodontically treated teeth have been extensively studied, the treatment planning and materials to restore them remains controversial (2). This SR attempted to identify studies that met the high standard of methodological rigor expected in Cochrane Reviews. No more recent SRs or RCTs were identified using the same key words and strategy as this SR through May 2015.
Strengths and Weaknesses of the Systematic Review:
This SR had a fundamental flaw in that it was based on a poorly constructed clinical question. It attempted to answer a complex question that has many determinants including the number of surfaces, opposing arches, and condition of the tooth, for example. The study had an acceptable search strategy, although there was no mention that grey literature was searched. The inclusion and exclusion criteria were clearly stated. Conflict of interest was not stated. Another major weakness is that the authors found only one study that randomized between crowns and composite, so the authors could not pool the results of multiple studies.
Strengths and Weaknesses of the Evidence:
The evidence consisted of a single RCT. This RCT had few participants (n=107), was of short duration (3 years) and a power analysis was not presented, adding to the uncertainty whether the sample size was sufficient to detect a significant difference between treatments. It also had a very specific, non-standard clinical treatment prior to randomization, thus limiting the generalizability of the results to clinical scenarios. The specific treatment was that, contrary to typical clinical practice; each premolar (all had cusps intact) that needed endodontic therapy received a post prior to randomization to a crown or filling. Many clinicians in this case would not place a post in the access cavity and, instead, would simply proceed to a restoration, because the placement of a post is to retain a core buildup for a crown and therefore is not necessary when a composite restoration is placed or the tooth has not yet been prepared for a crown. The study did not mention the assessment of the amount of tooth structure left after the root canal treatment, which is usually the criteria to decide whether to crown the tooth versus restore the tooth with a filling. The RCT was also weakened by the possibility of biased outcomes, because of inconsistent timing of post-op assessment. It also had a high risk of bias
due to missing data, skewing the findings toward participants with bad outcomes who are more likely to return for follow-up. Both the investigators and independent assessors were not masked
Implications for Dental Practice:
The restorative choice after root canal therapy is critical for preservation of tooth structure, which affects the long-term function of the tooth (3) and overall dentition (4). Crowns have been considered the restoration of choice for endodontically-treated teeth (1). This review concludes that there is no evidence for a difference between restoring with crown or a conventional restoration, but a degree of uncertainty exists. Further well-designed, high quality RCTs are needed to address the specific clinical factors affecting the prognosis of the chosen restoration. Until more evidence becomes available, clinicians should continue to make their best decisions based upon many factors, which may include: remaining tooth structure, occlusion, masticatory force, parafunctional habits, materials available, cost, operator clinical experience, and patient preferences.
(1). Cohen S, Hargreaves KM. Pathways of the Pulp. 9th Edition. St. Louis: Mosby, 2009.
(2) Faria AC, Rodrigues RC, de Almeida Antunes RP, de Mattos Mda G, Ribeiro RF. Endodontically treated teeth: Characteristics and considerations to restore them, J of Prosthodontic Research, 2011, April, 55: 2, pp. 69–74.
(3) Fedorowicz Z, Carter B, de Souza RF, de Andrada Lima Chaves C, Nasser M, Sequeira-Byron P , Single crowns versus conventional fillings for the restoration of root filled teeth. Cochrane Database Systematic Review, 2012 May 16;5:CD009109.
(4) Varlan C, Dimitriu B, Bodnar D, Suciu I, Current opinions concerning the restoration of endodontically treated teeth: basic principles. Journal of Medicine and Life 2009;2(2):165-72.