|Year : 2015 | Volume
| Issue : 4 | Page : 141-145
Need of a new classification for post and core failure
Sougaijam Vijay Singh1, Anil Chandra2
1 Department of Conservative Dentistry and Endodontics, DAV Centenary Dental College and Hospital, Yamunanagar, Haryana, India
2 Department of Operative Dentistry, King George Medical College and Hospital, Lucknow, Uttar Pradesh, India
|Date of Web Publication||27-Nov-2015|
Sougaijam Vijay Singh
Department of Conservative Dentistry and Endodontics, DAV Centenary Dental College and Hospital, Yamunanagar - 135 001, Haryana
Source of Support: None, Conflict of Interest: None
Introduction: Since many years, post has been commonly used to provide adequate support and retention for the restoration of endodontically treated teeth. Although it is successful, several cases of failure have been reported. Various classifications of teeth for post and core were given in the past. However, classification on the basis of failure of post and core has not yet been described. Methods: Electronic search on PubMed and a hand search were performed to identify relevant literature, which were thoroughly screened before the articles were included in the study. Results: Based on the search, various classifications related to post and core had been given by many authors; however, it was observed that certain aspects of the classification regarding the failure of post and core were not yet included. Therefore, the manuscript is an attempt to emphasize the need to develop a classification system for the failure of post and core. Conclusion: The new classification on failure of teeth restored with post and core has been proposed by the authors as Type I, Type II, Type III, and Type IV depending upon the type of failure. The new classification aims at better understanding the failure of post and core and can be a valuable tool during epidemiological surveys.
Keywords: Classification, core, failure, post
|How to cite this article:|
Singh SV, Chandra A. Need of a new classification for post and core failure. Dent Hypotheses 2015;6:141-5
| Introduction|| |
The success of endodontically treated tooth depends on its restoration; this is because of loss of coronal tooth structure as well as the radicular dentin and impaired normal protective reflexes due to the reduced level of proprioception in such teeth.  The changes that accompany root canal therapy and the thickness of the residual walls and cusps determine the selection of the restorative materials and procedures for endodontically treated teeth. ,,,,
Important factors of the treatment plan to be considered for a severely damaged tooth , are the evaluation of importance of the tooth for occlusion or aesthetics, the amount of remaining tooth structure after removal of all caries and old restorations, canal configuration, and the ability to control plaque and eliminate periodontal infection.
Post and core has been successfully used to provide adequate support and retention; however, several cases of failure of post and core have been reported.
Several classifications related to post and core have been given by several authors but till date there is no literature on the classification of failure of post and core. Therefore, a classification on failure post and core is needed and has been proposed by the authors. It is important that the recording, treatment plan, and communication for the tooth to be restored with post and core are easy and simple for the clinician and researchers. The manuscript is an attempt to develop a classification system for the failure of post and core that is simple to score and describes the condition in detail without utilizing much time.
| Methods|| |
A literature survey was performed of the database of PubMed to identify all the articles published between January 1970 and August 2015 using the following key phrase: "post core restoration in endodontics" (titles selected = 509). During the electronic search and hand search, the reviewers observed no documentation on the classification of failure of post and core. Therefore, an electronic search was carried again on "failure of post and core" (PubMed = 290) and "classification of failure of post and core" (PubMed = 19), resulting in 818 titles of the articles searched.
The selection criteria were limited to articles in English; articles that were not in English were excluded from the study. Out of 818 titles of the search, 39 search articles were included in the study [Figure 1]; however, before finalizing the list of the excluded articles the reviewer discussed each of the excluded articles and resolved any remaining uncertainties of the article status. Titles, abstracts, and full text of all the articles were analyzed by two examiners for the meta-analysis portion. On the basis of the search, various classifications were given by many researchers.
| Results|| |
Clinical protocol for diagnosing extensively damaged teeth criteria given by Esteves and Corressia  assessed the following: Ferrule effect, root and crown length relation, and endodontic condition under criterion 1 - ferrule effect, criterion 2 - crown to root length relationship, and criterion 3 - endodontic condition. According to the criteria, they classified the endodontic damage teeth under Class I, Class II, and Class III.
Classification was also given according to the remaining tooth structure. The classification describes five classes, depending on the number of remaining axial cavity walls. 
Class I - Access preparation with all the remaining four axial cavity walls.
Class II - With three remaining walls (loss of one cavity wall), also known as mesioocclusal or the distoocclusal cavity.
Class III - With two remaining cavity walls also known as mesial-occlusal-distal (MOD) cavity.
Class IV - With one remaining wall, in most cases buccal or lingual.
Class V - With no cavity wall remaining (decoronated tooth).
Another classification was based on the number of primary canals in endodontically treated teeth where the teeth were divided into three groups.  Class I refers to one canal, Class II refers to two canals, and Class III refers to three canals. Each class was further subdivided on the basis of the percentage of remaining tooth structure as complete (C), partial (P), no clinical crown (N). The remaining tooth structure is evaluated by the least of two percentages.
First percentage - The remaining coronal tooth height following tooth preparation.
Second percentage - The horizontal, cross section measurement in the gingival half of the remaining coronal tooth structure following root canal treatment and preparation. The smallest percentage measured within the gingival half is taken into consideration:
- Complete clinical crown (C) is between 66% and 100%.
- Partial clinical crown (P) is between 33% and 66%.
- No clinical crown (N) is 0% to 33% of the tooth structure.
The two percentages are combined to present accurate classification of the tooth.
A classification has also been presented by Kurrer  on the pulpless teeth requiring post and core based on the amount and retentive capacity of tooth that will provide the resistance and retention.
A tooth restorability index  was formulated to assess retention and resistance of the remaining structure on the crown. A numerical value is used to observe the predictability of the tooth to be restored. The tooth was equally divided into six sections - two buccal, two proximal, and two lingual areas. The amount of coronal dentine for each sextant above the finishing line of the preparation was observed and a scoring system of 0-3 was given to each section.
Unfortunately, even though many classifications were given, the classification based on the failure of post and core of endodontically treated teeth have not been included by any author. In view of the above fact, there is a need of the new classification on the basis of failure of post and core.
| Discussion|| |
Whenever there is an extensive loss of coronal tooth structure, a post is given to retain a core in a tooth. , However, preparation of a post space has certain disadvantage such as perforation in the apical portion or lateral areas of the root (strip perforation). Moreover, there is an increased chance of root fracture after the placement of posts  and treatment failure,  especially when post channel preparation is oversized.  The shear strength and toughness were found to be significantly lower when compared to the vital dentin  and less effort was required to fracture the dentin because of more mature collagen intermolecular crosslinks.  Studies have shown a decrease in the fracture resistance of endodontically treated teeth after post and core placement or the failure to increase the fracture resistance of endodontically treated teeth with post and core. ,,,,,,,,,
Hussey and Killough  have also observed that 24% of general dentists feel that the teeth are strengthened by post placement but clinical and laboratory data  indicated that the main purpose of the post is retention of core to provide a crown or prosthesis and not to strengthen the teeth.
Various studies ,,,,, provided clinical data on post and core failure [Table 1]. According to Ingle,  the average percentage of failure of post and core from 10 studies were 9% and the most common cause of post and core failure was loosening of post ,,,,, as shown in [Figure 1]. The other causes of failure were root fracture, ,,,,,,,,, caries, , abscess,  bent or fracture of the post [Figure 2], and root perforations [Figure 3].
However, there is limited literature on the classification of the failure of post and core. In view of the above fact and the need of a classification for failure of post and core, the authors have proposed a classification with Type I, Type II, Type III, and Type IV as shown in [Table 2]. The classification system mentioned is comprehensive, uncomplicated, easy to use, and less time-consuming.
|Table 2: Proposed classification of tooth according to the type of post and core failure|
Click here to view
| Conclusion|| |
Although there is sufficient literature on the failure of post and core, there is no literature on the classification of failure on post and core. Therefore, a classification on the failure of post and core has been proposed on the evidence present in the recent literature, the post and core cases that came to the outpatient department of the hospital, and cases that were treated by the authors. The classification is simple to understand and can be a good tool for use during epidemiological surveys and also clinical studies.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]