Single crowns versus conventional fillings for the restoration of root‐filled teeth
Abstract
Background
Endodontic treatment involves removal of the dental pulp and its replacement by a root canal filling. Restoration of root filled teeth can be challenging due to structural differences between vital and non‐vital root‐filled teeth. Direct restoration involves placement of a restorative material e.g. amalgam or composite, directly into the tooth. Indirect restorations consist of cast metal or ceramic (porcelain) crowns. The choice of restoration depends on the amount of remaining tooth, and may influence durability and cost. The decision to use a post and core in addition to the crown is clinician driven. The comparative clinical performance of crowns or conventional fillings used to restore root‐filled teeth is unknown. This review updates the original, which was published in 2012.
Objectives
To assess the effects of restoration of endodontically treated teeth (with or without post and core) by crowns versus conventional filling materials.
Search methods
We searched the following databases: the Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE via OVID, EMBASE via OVID, CINAHL via EBSCO, LILACS via BIREME. We also searched the reference lists of articles and ongoing trials registries.There were no restrictions regarding language or date of publication. The search is up‐to‐date as of 26 March 2015.
Selection criteria
Randomised controlled trials (RCTs) or quasi‐randomised controlled trials in participants with permanent teeth that have undergone endodontic treatment. Single full coverage crowns compared with any type of filling materials for direct restoration or indirect partial restorations (e.g. inlays and onlays). Comparisons considered the type of post and core used (cast or prefabricated post), if any.
Data collection and analysis
Two review authors independently extracted data from the included trial and assessed its risk of bias. We carried out data analysis using the 'treatment as allocated' patient population, expressing estimates of intervention effect for dichotomous data as risk ratios, with 95% confidence intervals (CI).
Main results
We included one trial, which was judged to be at high risk of performance, detection and attrition bias. The 117 participants with a root‐filled, premolar tooth restored with a carbon fibre post, were randomised to either a full coverage metal‐ceramic crown or direct adhesive composite restoration. None experienced a catastrophic failure (i.e. when the restoration cannot be repaired), although only 104 teeth were included in the final, three‐year assessment. There was no clear difference between the crown and composite group and the composite only group for non‐catastrophic failures of the restoration (1/54 versus 3/53; RR 0.33; 95% CI 0.04 to 3.05) or failures of the post (2/54 versus 1/53; RR 1.96; 95% CI 0.18 to 21.01) at three years. The quality of the evidence for these outcomes is very low. There was no evidence available for any of our secondary outcomes: patient satisfaction and quality of life, incidence or recurrence of caries, periodontal health status, and costs.
Authors' conclusions
There is insufficient evidence to assess the effects of crowns compared to conventional fillings for the restoration of root‐filled teeth. Until more evidence becomes available, clinicians should continue to base decisions about how to restore root‐filled teeth on their own clinical experience, whilst taking into consideration the individual circumstances and preferences of their patients.
PICOs
Plain language summary
Single crowns or routine fillings for the restoration of root‐filled teeth
Review question
This review (an update of the original published in 2012) has been conducted to assess whether there is a difference in the effects of restoration of root‐filled teeth (with or without post and core) by indirect restorations (commonly crowns, inlays, or onlays) compared to conventional filling materials placed directly into the tooth.
Background
Root filling is a fairly routine dental procedure in which the injured or dead nerve of a tooth is removed and replaced by a root canal filling. However, the restoration of root‐filled teeth can be quite challenging as these teeth tend to be weaker than healthy ones. A dentist may use crowns (restorations made outside of the mouth and then cemented into place) or conventional fillings (direct filling with materials such as amalgam or composite/plastic resin). Although crowns may help to protect root‐filled teeth by covering them, conventional fillings demand less in terms of time, costs and removal of tooth structure.
Study characteristics
We searched the medical literature until 26 March 2015. This review includes one study with 117 participants in which a tooth (117 premolars) received a carbon fibre post, and was restored with either a fused porcelain to metal crown or a routine white filling. The study was of short duration (three years), included a relatively small number of participants, and was assessed to be at a high risk of bias due to missing results for people who dropped out of the study.
Key results
The evidence produced from one study concluded that none of the 117 root‐filled premolars experienced a catastrophic failure (i.e. one that cannot be repaired) after three years, although only 104 teeth were included in the final, three‐year assessment. The study concluded there was no difference between treatments for the risk of non‐catastrophic failure. There was no evidence available for any of our secondary outcomes: patient satisfaction and quality of life, incidence or recurrence of decay, periodontal health status, and costs.
Quality of the evidence
The quality of the evidence is very low. As there is only a single study, which is at high risk of bias, there is insufficient reliable evidence to determine whether single crowns are better than routine fillings. Future research should aim to provide more reliable information that can help clinicians to decide on appropriate treatment whilst taking into consideration the individual circumstances and preferences of their patients.
Authors' conclusions
Summary of findings
| Single crowns compared with conventional fillings for restoring root‐filled teeth | ||||||
| Patient or population: people with a permanent tooth that has undergone endodontic treatment Settings: private dental practice in Italy Intervention: composite filling with post covered with full‐coverage metal‐ceramic crown (and oral hygiene instruction) Comparison: composite filling with post (and oral hygiene instruction) | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of Participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Conventional filling | Single crown | |||||
| Catastrophic failure of restoration | 0 | 0 | 117 | ⊕⊝⊝⊝ | ||
| Non‐catastrophic failure of the restoration (3 years) | 57 per 1000 | 19 per 1000 | RR 0.33 (0.04 to 3.05) | 117 | ⊕⊝⊝⊝ | |
| Non‐catastrophic failure of post (3 years) | 19 per 1000 | 37 per 1000 | RR 1.96 (0.18 to 21.01) | 117 | ⊕⊝⊝⊝ | |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1. Downgraded one level for limitations in study design (high risk of attrition bias), one level for imprecision (one small study with wide confidence intervals) and one level for indirectness. | ||||||
Background
Description of the condition
Root filling, or endodontic treatment, is a fairly routine dental procedure in which the dental pulp (nerve) is removed and replaced by a root canal filling. It is usually indicated when there has been irreversible inflammation or necrosis (death) of the pulp, consequent to caries or trauma (Heydecke 2002). Root filling and subsequent restoration represents a cost‐effective option when it is compared with tooth extraction followed by implant placement (Pennington 2009).
However, the restoration of root‐filled teeth can be quite challenging due to the structural differences between vital and non‐vital root‐filled teeth. Root canal preparation, prior to completion of the restoration, involves a process of accessing and shaping of the root canal that can ultimately lead to weakening of the tooth (Sornkul 1992). Dentin, the main constituent of dental roots, becomes more brittle after removal of the pulp (Gutmann 1992). Other noticeable changes that occur after root filling are those associated with the appearance of root‐filled teeth. Altered light refraction and any remains of the pulp or filling material retained in the coronal portion of anterior teeth can cause darkening of the tooth (Cohen 2006).
Description of the intervention
Two methods, direct and indirect, can be used for the functional and aesthetic restoration of root‐filled teeth.
The direct approach is through conventional techniques, in which the dentist places a restorative material such as amalgam or composite directly into the tooth. Conventional fillings usually need a single clinical appointment, are generally simpler to achieve than the indirect method, and have good survival characteristics (Bjertness 1990; Da Rosa Rodolpho 2006).
Indirect restorations (i.e. crowns) are fabricated with materials such as cast metal or ceramics (porcelain). According to their classical indication, single crowns can restore proportionately larger amounts of missing dentin and enamel than other approaches (Cohen 2006). However, the need for impressions and associated laboratory work to complete the final restoration may add considerably to the overall costs.
Regardless of the approach used, a post may also be required in the root canal to provide better retention for conventional fillings or crowns (Bolla 2007).
How the intervention might work
Root‐filled teeth should be fully restored for a variety of reasons: to avoid recontamination of the root canal, to replace missing dental tissues (thus restoring function), and to strengthen the tooth (Vârlan 2009). The restoration of root‐filled teeth by crowns can improve their ability to withstand bite forces, and thereby increase their survival (Aquilino 2002). However, such restorations demand the removal of a large amount of structure from teeth that are already compromised (Pierrisnard 2002). Conventional fillings may be clinically acceptable where there is sufficient tooth structure to retain the restorative material, or in situations where less destructive preparations are used in conjunction with adhesive restorations (Hemmings 2000). The preservation of healthy tooth structure is critical for the survival of conventional fillings. However, in the case of root‐filled teeth, it has been reported that conventional composite fillings and crowns achieve the same success rate at three years (Mannocci 2002).
Current endodontic thinking proposes that there are four stages to root canal treatment: cleaning, shaping, obturation, and finally coronal restoration. A well adapted coronal restoration aims to prevent micro‐leakage and subsequent bacterial ingress and contamination of the root canal complex. This would apply to either single crowns or conventional fillings so long as the reconstruction was classified as satisfactory in its ability to seal the crown of the tooth. A systematic review including 63 studies reported that periapical healing was improved by 10% to 18% when the quality of the coronal restoration was judged as satisfactory as opposed to unsatisfactory (Ng 2008).
The final outcome following coronal restoration after root canal treatment may only become apparent after a period of time. Root‐filled teeth covered with crowns have a greater long term survival rate (81% ± 12% after 10 years) than root‐filled teeth without crown coverage (63% ± 15% after 10 years; Stavropoulou 2007). For this reason, conventional direct resin fillings in root‐filled teeth with limited loss of tooth structure have been also described as temporary restorations.
If this treatment concept is valid, then it is conceivable that every root‐filled tooth could benefit from coverage with a crown.
Why it is important to do this review
The choice of restorative method for root‐filled teeth is critical for the preservation of the remaining structure, and may influence long‐term effectiveness. However, there is still uncertainty about the comparative clinical performance of crowns and conventional fillings used to restore root‐filled teeth. The results of this review may better inform clinical decision making in the choice of either of these interventions for different clinical situations.
Objectives
To assess the effects of restoration of endodontically treated teeth (with or without post and core) by crowns versus conventional filling materials.
Methods
Criteria for considering studies for this review
Types of studies
Randomised controlled trials (RCTs) or quasi‐randomised controlled trials. We considered parallel group trials, split‐mouth trials, cluster trials and randomised patient preference trials.
Types of participants
Participants of any age or gender who had permanent teeth that had undergone endodontic treatment.
Types of interventions
Single full coverage indirect crowns (e.g. metal, metal‐ceramic, and all‐ceramic crowns) or other indirect partial restorations (e.g. inlays and onlays) compared with any type of filling materials for direct restoration (e.g. amalgam and composite). Trials that evaluated different types of bridge retainers were not considered for inclusion.
Comparisons were considered according to the type of post and core used (cast or prefabricated post), if any. We excluded studies with differences between groups regarding the types of posts used (e.g. crown on cast post versus direct restoration on no post).
Types of outcome measures
Primary outcomes
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Catastrophic failure of the restored tooth or restoration leading directly to extraction (to include the reasons for failure ‐ endodontic complications, restoration failure, tooth fracture).
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Non‐catastrophic failure of the restoration requiring further treatment* categorised as i) failure of the restoration; ii) failure of the post.
Secondary outcomes
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Patient satisfaction and quality of life using any validated instrument.
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Incidence or recurrence of caries (assessed clinically or by radiographs).
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Periodontal health status.
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Costs for the use of different interventions (direct and indirect costs, e.g. the resources and time for the patient, dentist, and dental laboratory).
*Endpoints were analysed at the last follow‐up time point, up to a period of 10 years after randomisation.
Search methods for identification of studies
Electronic searches
In conjunction with the Cochrane Oral Health Group's Trials Search Co‐ordinator, we developed detailed search strategies for each database searched. These were based on the search strategy developed for MEDLINE (OVID) but revised appropriately for each database.
We searched the following databases, most recently in March 2015.
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MEDLINE via OVID (1948 to 26 March 2015) (Appendix 1)
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Cochrane Oral Health Group's Trials Register (Appendix 2) on 26 March 2015
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Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2012, Issue 1) (Appendix 3) on 26 March 2012
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EMBASE via OVID (1980 to 26 March 2015) (Appendix 4)
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CINAHL via EBSCO (1980 to 26 March 2015) (Appendix 5)
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LILACS via BIREME (1980 to 26 March 2015) (Appendix 6)
For the MEDLINE search, we ran the subject search with the Cochrane Highly Sensitive Search Strategy (CHSSS) for identifying randomised trials in MEDLINE: sensitivity maximising version (2008 revision), as referenced in Chapter 6.4.11.1 and detailed in box 6.4.c of theCochrane Handbook for Systematic Reviews of Interventions version 5.1.0 (updated March 2011) (Higgins 2011). The search of EMBASE was linked to the Cochrane Oral Health Group filters for identifying randomised controlled trials, and the search of LILACS was linked to the Brazilian Cochrane Center filter.
Ongoing trials
Review author Zbys Fedorowicz (ZB) searched the following databases to March 2015, using keywords and terms expected to identify ongoing relevant trials.
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The metaRegister of Controlled Trials on http://www.controlled‐trials.com/
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The US National Institutes of Health register on http://www.clinicaltrials.gov/
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The WHO portal on http://who.int/ictrp/en/
Language
There were no language restrictions in the searches but we did not retrieve any studies that were not in the English language.
Searching other resources
In the original review, we examined the reference lists of relevant articles and contacted the investigators of included studies by electronic mail to ask for details of additional published and unpublished trials. One of the review authors (Patrick Sequeira‐Byron (PSB)) handsearched the journals listed below, in accordance with the recommendations of the Cochrane Oral Health Group, up to March 2015.
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Caries Research (from 2003)
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Community Dentistry and Oral Epidemiology (from 2001)
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International Endodontic Journal (from 2005)
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International Journal of Prosthodontics (from 2003)
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Journal of Dental Research (from 2003)
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Journal of Endodontics (from 2007)
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Journal of Prosthetic Dentistry (from 2003)
Data collection and analysis
Selection of studies
In the update of this review, three authors (PSB, ZF, EA) independently assessed the abstracts of studies resulting from the searches; any disagreement between two authors on eligibility was resolved by a third review author.
In the original review, two review authors (PSB, ZF) independently assessed the abstracts of studies resulting from the searches. Full copies were obtained of all relevant and potentially relevant studies, i.e. those appearing to meet the inclusion criteria and those for which there were insufficient data in the title and abstract to make a clear decision. Two review authors independently assessed the full‐text papers; any disagreement on eligibility was resolved through discussion and consensus or, if necessary, by a third review author. All irrelevant records were excluded; the details and the reasons for their exclusion are noted in the Characteristics of excluded studies section of the review.
Data extraction and management
ZF entered study details into the Characteristics of included studies tables in RevMan 5.1 (RevMan 2014). Two review authors (Ben Carter (BC), ZF) independently extracted data in duplicate, and only included them if there was a consensus; any disagreements were resolved by consulting with a third review author (Raphael Freitas de Souza (RFS)).
The following details were extracted if reported.
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Trial methods: (a) method of allocation; (b) masking of participants, trialists and outcome assessors; (c) exclusion of participants after randomisation and proportion, and reasons for losses at follow‐up.
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Participants: (a) country of origin and study setting; (b) sample size; (c) age; (d) gender; (e) inclusion and exclusion criteria; (f) caries risk status of study groups; (g) characteristics of the restored teeth such as type and location in the mouth, and the state of remaining structures; (h) salivary flow; (i) periodontal status; (j) presence and intensity of parafunction (i.e. bruxism); (k) materials and techniques used for root filling; (l) time from root filling to restoration.
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Intervention: (a) type of restoration; (b) materials and techniques used; (c) type of post and core used, if any; (d) time of follow‐up.
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Control: (a) type of restoration; (b) materials and techniques used; (c) type of post and core used, if any; (d) time of follow‐up.
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Outcomes: (a) primary and secondary outcomes mentioned in the Types of outcome measures section of this review.
If stated, the sources of funding were recorded. If a sufficient number of studies assessing similar interventions are identified for inclusion in future updates of this review, we will use information of source of funding to help to assess heterogeneity and the external validity of any included trials.
Assessment of risk of bias in included studies
Two review authors (Mona Nasser (MN), ZF) independently assessed risk of bias in the selected trials using The Cochrane Collaboration's tool for assessing risk of bias as described in section 8.5 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). The judgments were compared and any inconsistencies in the assessments between the review authors were discussed and resolved.
The following domains were assessed as at a low, high or unclear risk of bias:
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sequence generation (selection bias);
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allocation concealment (selection bias);
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blinding of participants and personnel (performance bias);
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blinding of outcome assessors (detection bias);
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incomplete outcome data (attrition bias);
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selective outcome reporting (reporting bias);
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other bias.
We categorised and reported the overall risk of bias of the included study according to the following:
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low risk of bias (plausible bias unlikely to seriously alter the results) if all domains were assessed as at a low risk of bias;
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unclear risk of bias (plausible bias that raises some doubt about the results) if one or more domains were assessed as at an unclear risk of bias; or
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high risk of bias (plausible bias that seriously weakens confidence in the results) if one or more domains were assessed as at a high risk of bias.
Measures of treatment effect
We carried out data analysis using the 'treatment as allocated' patient population. For dichotomous data, we expressed the estimates of effect of an intervention as risk ratios (RR) together with their 95% confidence intervals (CI). Although neither time‐to‐event or continuous data were reported, in future updates, if data are available, these effect measures will be used to summarise the data for each group accordingly. For continuous outcomes, we will present mean differences and their 95% confidence intervals; time‐to‐event data will be evaluated based on hazard ratios. If summary statistics are not available from the reports, we will attempt to calculate hazard ratios by means of other statistics and survival curves (Parmar 1998).
Unit of analysis issues
Although no cluster‐randomised trials were identified, these would have been checked for unit of analysis errors based on the advice provided in section 16.3.4 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
Dealing with missing data
In studies where data were unclear or missing, we contacted the principal investigators. If missing data were unavailable, we would have followed the advice given in section 16.1.2 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), and if appropriate, sensitivity analyses would have been carried out to input the missing data:
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best‐worst case scenario: which is the best scenario for the composite + crown and worst scenario for the composite only group
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worst‐best case scenario: which is the best scenario for the composite‐only group and worst scenario for the composite + crown group.
As only one study was included, we did not undertake these sensitivity analyses but will do so in future updates if more studies are available.
Assessment of heterogeneity
The paucity of studies included in this review did not permit any assessment of heterogeneity but in future updates if further studies are included, the following methods will apply. We will assess clinical heterogeneity by examining the characteristics of the studies, the similarity between the types of participants, the interventions and the outcomes as specified in the criteria for included studies. We will assess statistical heterogeneity using a Chi² test and the I² statistic. The I² values expressed as percentages will be categorised as follows: 25% as low, 50% as moderate, and 75% as high (Higgins 2003).
Assessment of reporting biases
If a sufficient number of studies assessing similar interventions are identified for inclusion in future updates of this review, we will assess publication bias according to the recommendations on testing for funnel plot asymmetry as described in section 10.4.3.1 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). If asymmetry is identified, we will attempt to assess other possible causes, and explore these in the discussion if appropriate.
Data synthesis
If future updates include a sufficient number studies (more than two) investigating similar interventions, we will conduct data analysis in RevMan (RevMan 2014), and the following methods will apply. We will use the fixed‐effect model if appropriate. If there is heterogeneity between the studies, we will undertake a random‐effects meta‐analysis, but if the heterogeneity between the studies is significant, we will explore the data to explain why, and may not undertake a meta‐analysis at all (see section 9.5 of the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0 (Higgins 2011)). If sufficient data are available, we will calculate a pooled estimate of effect of specific interventions together with their corresponding 95% confidence intervals (CI).
Subgroup analysis and investigation of heterogeneity
If a sufficient number of studies are included in any update of this review, and we identify moderate, substantial or considerable heterogeneity (see Assessment of heterogeneity), we plan to carry out the following subgroup analyses according to: the type of post and core used for retention in the root canal (cast posts, preformed posts or none); the type of restored tooth; the location in the oral cavity: anterior and posterior teeth (categorised into bicuspids and molars); and the type of crown (metal‐ceramic, all metallic or all ceramic crown).
Sensitivity analysis
We had planned to carry out sensitivity analyses to assess the robustness of our review results, in particular, to repeat the analyses excluding studies with a high risk of bias (Egger 1997). If future studies report the reasons for failure, we will carry out further sensitivity analyses to assess each of the reasons for failure, i.e. marginal failure, wear, presence of fractures.
Summarising the findings
We created a 'Summary of findings' table for the primary outcomes of this review following GRADE methods (GRADE 2004) and using GRADEPro software (GRADEpro 2008). To assess the quality of the body of evidence as high, moderate, low or very low, we considered the overall risk of bias of the included studies, the directness of the evidence, the consistency of the results, the precision of the estimates, and the risk of publication bias.
Results
Description of studies
Results of the search
The original electronic searches in 2012 retrieved 1022 references to studies after de‐duplication, out of which, 1016 were clearly ineligible and were eliminated. We obtained full‐text copies of the remaining six studies and subjected them to further evaluation. We excluded all but one of these studies.
Through handsearching, we did not retrieve any additional studies over and above those that had already been identified in the electronic search, therefore, we did not re‐run these searches for this update. No studies in languages other than English were identified and our searches of the trial registries did not identify any ongoing trials. We also examined several other reviews for potentially eligible studies but did not find any. No cluster‐randomised trials (i.e. groups of individuals randomised to intervention or control), were identified for inclusion in this review.
The updated searches to 26 March 2015 retrieved 279 references to studies, all of which were rejected after examination of title and abstract.
For further details, see Figure 1.
Study flow diagram
Included studies
A single study is included in this review (Mannocci 2002).
Characteristics of the trial setting and investigators
This study was a randomised controlled trial of three years duration. It was conducted in a private practice setting in Italy. One investigator based in a single clinic carried out all the treatment.
Characteristics of the participants
A total of 117 (54 male, 63 female) participants with an age range of 35 to 55 (mean 48) years were enrolled in this study. Each participant provided a single premolar tooth to include 24 maxillary first premolars, 57 maxillary second premolars, 3 first, and 33 mandibular second premolars that required orthograde endodontic treatment. The teeth had Class II carious lesions that did not involve the cusps; had no more than 40% loss in periodontal attachment; were in occlusal function after restoration; and were not used as abutments for fixed or removable partial dentures.
Characteristics of the interventions
A single operator carried out the orthograde endodontic treatment and the final restoration of the tooth. The root canal was obturated with gutta percha and then received a carbon fibre post (Composipost; RTD, St Egreve, France ®), which was cemented in the canal with composite (C&B; BISCO, Itasca, Ill., USA ®). The teeth were then restored with a composite material using an adhesive technique (60 participants) or had a composite core and build‐up (Z100; 3M, St Paul, Minn., USA ®), and were subsequently prepared for full‐coverage metal‐ceramic crowns according to standard clinical procedures (57 participants). All participants received routine oral hygiene instruction, which was provided by a dental hygienist at subsequent follow‐up visits.
Characteristics of the outcomes measures
Clinical, radiographic, and photographic assessments of outcomes were carried out by two calibrated examiners, neither of whom were investigators, at several time points: immediately before restoration, immediately after restoration, and at one‐, two‐, and three‐year recall. The principal outcomes assessed were the success or failure of the restoration. Failures were categorised as root fracture, post fracture, post decementation, clinical or radiographic evidence of a marginal gap between tooth and restoration, or the presence of secondary caries at the margins of the restoration.
Excluded studies
A list of the five studies excluded from this review and the reasons for their exclusion are reported in the Characteristics of excluded studies table.
Risk of bias in included studies
Details of these assessments are available in the relevant section of the Characteristics of included studies table, and are also presented in the 'Risk of bias' summary (Figure 2). The summary assessment of risk of bias for the single study included in this review was high risk (plausible bias that seriously weakens confidence in the results), because of incomplete outcome data.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study
Allocation
The investigators randomised participants to interventions with the toss of a coin and therefore, the sequence generation was judged as being at a low risk of bias. However, as they did not report the method used to conceal the allocation sequence, the study was assessed as being at unclear risk of selection bias.
Blinding
Blinding of participants and personnel
The type of interventions considered in this study did not permit blinding of the participants or the trial investigators, which made it at a high risk of performance bias.
Blinding of outcome assessors
Neither the participants nor the investigators were the assessors for the study outcomes. Outcomes were assessed by two independent calibrated examiners but they were not blinded so we assessed the risk of detection bias as high.
Incomplete outcome data
Five out of 60 participants in the composite‐only group were lost to follow‐up at the one‐year recall. At the two‐year recall, 12/60 of the participants in the composite‐only group did not attend for follow‐up; the report was unclear if these included the five participants lost at the one‐year recall. At the three‐year recall, 10/60 (composite only) and 3/57 (composite and crown) participants were unavailable for assessment. The report did not provide sufficient information on the final disposition of these missing participants and their corresponding outcome data; therefore the study was judged to be at high risk of attrition bias.
Selective reporting
Although the data provided by the investigators were sparse, the published report included all expected outcomes, including those that were prespecified in the trial's methods section. Therefore, we gave a judgement of low risk of reporting bias.
Other potential sources of bias
Baseline measurements of caries, periodontal and endodontic outcomes were not measured, so we judged this domain as an unclear risk of bias.
Effects of interventions
See: Summary of findings for the main comparison
Two review authors (BC, ZF) analysed the data and reported them as specified in Chapter 9 of the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0 (Higgins 2011).
Primary outcomes
1. Catastrophic failure of the restored tooth or restoration leading directly to extraction
No teeth were reported to have been lost as a result of trauma or endodontic or periodontal problems over the three‐year study period, but because of the large losses to follow‐up, the data were incomplete and it was not possible to confirm the validity of these findings.
2. Non‐catastrophic failure of the restoration requiring further treatment
a) Failure of the restoration (marginal fit, wear, presence of fractures)
Failures of the restoration occurring during each of the three years of the study are reported in Additional Table 1 and the analysis of restoration failure in Analysis 1.1. There was one failure in the composite and crown group (out of 54 participants) and three in the composite‐only group (out of 53 participants) by the end of the study; the risk ratio (RR) was 0.33 (95% confidence interval (CI) 0.04 to 3.05; P value = 0.33). Restoration failure, as an outcome over the three‐year study period, should be viewed as unclear.
| Time point | Composite + crown | Composite only |
| From randomisation to the end of year 1 | 0/57 | 0/55 |
| From the start of year 2 to the end of year 2 | 1/57 | 2/48 |
| From the start of year 3 to the end of year 3 | 0/54 | 0/49 |
| From randomisation to the end of year 3 | 1/54 | 3/53 |
b) Post failure
The post failures occurring during each of the three years of the study are reported in Additional Table 2 and the analysis of post failure across the three years in Analysis 1.2. At the end of the study period, there were two post failures (from 54 participants) in the composite and crown group and one (from 53 participants) in the composite‐only group; the RR was 1.96 (95% CI 0.18 to 21.01, P value = 0.58). Therefore, there was no evidence to indicate a difference in post failure rate between the two intervention groups; however, in view of the considerable amount of missing data, these results should be viewed as inconclusive.
| Time point | Composite + crown | Composite only |
| From randomisation to the end of year 1 | 0/57 | 0/55 |
| From the start of year 2 to the end of year 2 | 2/57 | 1/48 |
| From the start of year 3 to the end of year 3 | 0/54 | 0/50 |
| From randomisation to the end of year 3 | 2/54 | 1/53 |
Secondary outcomes
1. Patient satisfaction and quality of life using any validated instrument
This outcome was not reported nor measured by the study.
2. Incidence or recurrence of caries (assessed clinically or by radiographs)
No data were reported nor measured by the study.
3. Periodontal health status
No data were reported nor measured by the study.
4. Costs for the use of different treatment interventions (direct and indirect costs e.g. resources and time for the patient, dentist, and dental laboratory)
No data were reported nor measured by the study.
Discussion
Summary of main results
None of the trial's 117 participants, each with a root‐filled, premolar tooth restored with a carbon fibre post and either a full coverage metal‐ceramic crown or a direct adhesive composite restoration experienced a catastrophic failure of the restoration. The trial concluded that at three years there was no difference between groups in the non‐catastrophic failure rates. Decementation of the post and marginal gap formation occurred in a small number of teeth. However, in view of missing outcome data, this trial was assessed to be at a high risk of bias and therefore, caution is advised in the interpretation of these results.
Overall completeness and applicability of evidence
This study was completed 13 years ago; although the investigators indicated that they planned to continue the study for an additional three years, there would appear to have been no follow‐up or indeed, any further randomised clinical trials investigating these comparisons. The single trial met the eligibility criteria for inclusion; however, the restrictions placed on enrolment of teeth with moderately sized carious lesions with no cuspal involvement may have contributed to an element of selection bias. Additional factors to consider were that only premolar teeth, which are more likely to have proportionately less salvageable tooth structure than molars, were included in the study. And although posts, which some clinicians consider can reinforce a restoration or in some instances might weaken a tooth root, were integral to the restoration of these premolars, this may be at variance with their clinical applicability in the restoration of some molar teeth. It also remains unclear to what extent this evidence, based on somewhat older materials, may be applicable to the types of new materials currently at the disposal of clinicians.
Consequently, the included study may have addressed a restricted version of the review question in terms of the 'population' under investigation and the interventions used.
Quality of the evidence
Limitations in study design
There were challenges in the design of this study due to the inability to satisfactorily blind investigators and outcomes assessors to the interventions, which is considered a valuable step in reducing bias. In addition, a clearer definition of survival and in particular, non‐catastrophic failure of the restorations, would have helped to limit the effects of subjectivity in the assessment of these outcomes. Missing data for losses to follow‐up and the final disposition of missing participants, in a study where failure was a key outcome, were additional indicators of a high likelihood of biased assessment of the intervention effect. Overall, therefore, the included study was at high risk of performance, detection and attrition bias.
Inconsistency
Only one trial provided data in this review, therefore this assessment was not applicable.
Indirectness of evidence
The report provided minimal demographic details of the participants, in particular those relating to their caries‐risk status, so it is difficult to assess if they are representative of the population at large. Some of these variables (such as caries prevalence and incidence, as well as periodontal, endodontic and prosthetic risk factors) represent potentially key factors in the survival and longevity of either restorative procedure, and may ultimately have an impact on the directness and applicability of the results of the review.
Significant loss of tooth structure is an indicator of the clinical necessity for a post and core to restore endodontically treated teeth. However, whilst all of the premolar teeth in this study received a post, the criteria for post requirement were inadequately defined, and it remains unclear how these might apply to other clinical situations, i.e. molar teeth, which are likely to have proportionately more residual coronal tooth structure.
Imprecision
The main objective of the single study included in this review was to investigate the comparative success or failure of two interventions; however, to adequately power such an equivalence (or non‐inferiority) study, a substantially larger number of participants and a longer follow‐up period would normally be required. Thus, although the investigators concluded that there was no difference in failure rate between the two interventions, in view of the absence of a sample‐size calculation, there is a degree of uncertainty if the study included a sufficiently large enough number of participants to detect a modest and statistically significant difference, if indeed there was one.
Publication bias
Every effort was made to identify additional published studies. Only one trial was included and therefore, it was not possible to undertake a funnel plot assessment of publication bias (Higgins 2011).
These criticisms were summarised in terms of an overall GRADE quality rating per outcome. We downgraded once for study design, once for imprecision, and once for indirectness, i.e. very low quality overall.
Potential biases in the review process
Although bias can never be totally eliminated, the comprehensive search for studies, and the authors' independent assessments of eligibility of studies for inclusion in this review and the extraction of data, minimised the potential for bias in the review process.
Agreements and disagreements with other studies or reviews
We are unaware of any recent systematic reviews on this topic but there have been several recent mini reviews and evidence‐based summaries (Basrani 2004; Evidence‐Based Review 2009), which largely agree with the conclusions in this systematic review that there is no clear evidence of a difference, but the available evidence is of very low quality. This is in contrast to an earlier retrospective analysis of a random sample of the dental charts of 280 patients who had undergone endodontic treatment, which reported that when tooth type and radiographic evidence of caries were controlled, root‐filled teeth that were not crowned were lost at a six times greater rate than teeth crowned after obturation (Aquilino 2002). The results of this retrospective study, whilst providing valuable information on a range of clinical variables, do not constitute reliable, high quality evidence for the effects of the interventions considered in this review.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study
Comparison 1 Composite + crown versus composite only, Outcome 1 All years, failure of the restoration (non‐catastrophic).
Comparison 1 Composite + crown versus composite only, Outcome 2 All years, failure of post (non‐catastrophic).
| Core elements | Issues to consider | Status of research for this review and recommendations for future research |
| Evidence (E) | What is the current state of evidence? | This systematic review identified one RCT, which addressed some of the main outcomes and provided very limited evidence for the comparative effectiveness of single crowns versus conventional fillings for the restoration of root‐filled teeth. The single included study was underpowered, of short duration and was judged to be at high risk of bias due to missing outcomes data |
| Population (P) | Diagnosis, disease stage, comorbidity, risk factor, sex, age, ethnic group, specific inclusion or exclusion criteria, clinical setting | Permanent teeth with adequate bony support; without previous endodontic treatment; with preserved cusp structure; in occlusal function; not used as abutment for fixed or removable partial dentures |
| Intervention (I) | Type, frequency, dose, duration, prognostic | Metal or metal‐ceramic full coverage crowns, adhesive composite core with or without post (cast or preformed) |
| Comparison (C) | Type, frequency, dose, duration, prognostic | Any type of filling materials for direct restoration (e.g. amalgam and composite), or indirect partial restorations (e.g. inlays and onlays) with or without post |
| Outcome (O) | Which clinical‐ or patient‐related outcomes will the researcher need to measure, improve, influence or accomplish? Which methods of measurement should be used? | USPHS evaluation methods for measuring clinical research performance of restorative materials (Bayne 2005). If anterior teeth are involved, outcomes should include participant assessed aesthetic appearance |
| Time stamp (T) | Date of literature search or recommendation | 26 March 2015 |
| Study type | What is the most appropriate study design to address the proposed question? | RCT: multicentre, adequately powered |
| RCT = randomised controlled trial; USPHS = US Public Health Service | ||
| Single crowns compared with conventional fillings for restoring root‐filled teeth | ||||||
| Patient or population: people with a permanent tooth that has undergone endodontic treatment Settings: private dental practice in Italy Intervention: composite filling with post covered with full‐coverage metal‐ceramic crown (and oral hygiene instruction) Comparison: composite filling with post (and oral hygiene instruction) | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of Participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Conventional filling | Single crown | |||||
| Catastrophic failure of restoration | 0 | 0 | 117 | ⊕⊝⊝⊝ | ||
| Non‐catastrophic failure of the restoration (3 years) | 57 per 1000 | 19 per 1000 | RR 0.33 (0.04 to 3.05) | 117 | ⊕⊝⊝⊝ | |
| Non‐catastrophic failure of post (3 years) | 19 per 1000 | 37 per 1000 | RR 1.96 (0.18 to 21.01) | 117 | ⊕⊝⊝⊝ | |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1. Downgraded one level for limitations in study design (high risk of attrition bias), one level for imprecision (one small study with wide confidence intervals) and one level for indirectness. | ||||||
| Time point | Composite + crown | Composite only |
| From randomisation to the end of year 1 | 0/57 | 0/55 |
| From the start of year 2 to the end of year 2 | 1/57 | 2/48 |
| From the start of year 3 to the end of year 3 | 0/54 | 0/49 |
| From randomisation to the end of year 3 | 1/54 | 3/53 |
| Time point | Composite + crown | Composite only |
| From randomisation to the end of year 1 | 0/57 | 0/55 |
| From the start of year 2 to the end of year 2 | 2/57 | 1/48 |
| From the start of year 3 to the end of year 3 | 0/54 | 0/50 |
| From randomisation to the end of year 3 | 2/54 | 1/53 |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 All years, failure of the restoration (non‐catastrophic) Show forest plot | 1 | Risk Ratio (M‐H, Fixed, 95% CI) | Subtotals only | |
| 2 All years, failure of post (non‐catastrophic) Show forest plot | 1 | Risk Ratio (M‐H, Fixed, 95% CI) | Subtotals only | |
