Clinical Evaluation of Two Types of Cores for Support of Metal-Ceramic Full-Coverage Crowns on Endodontically Treated Premolars

Clinical Evaluation of Two Types of Cores for Support of Metal-Ceramic Full-Coverage Crowns on Endodontically Treated Premolars
Sameer Quraeshi*, Fazal Ghani**, Yawar Ali Abidi***, Saqib Rashid****, Ahsan Iqbal*****, Huda Shiraz******

* Assistant Professor, Fixed Prosthodontics Unit, Department of Prosthodontics, Fatima Jinnah Dental College & Hospital Karachi.
** Head of Department of Prosthodontics, Khyber College of Dentistry, University Campus, Peshawar 25120(Pakistan).
*** Head Department of Operative Dentistry, Dr. Ishrat-ul-Ibad Khan Institute of Oral Health Sciences (DIIKIOHS) Dow University of Health Sciences, Karachi.
**** Head Department of Operative Dentistry, Fatima Jinnah Dental College & Hospital, Karachi.
***** Lecturer, Department of Periodontology, Fatima Jinnah Dental College & Hospital Karachi.
****** Lecturer, Department of Prosthodontics, Fatima Jinnah Dental College & Hospital, Karachi.
Correspondence: “Dr. Fazal Ghani ”

How to CITE:

J Pak Dent Assoc 2011;20(1): 05-09


Premolars having smaller dimensions when exhibit structural-compromise require specific restorative and endodontic considerations. This study reports the efficacy of two core-buildup techniques for supporting artificial crowns on endo-treated structurally compromized premolars.


This study was conducted in Fixed Prosthodontics Department, Fatima Jinnah Dental Hospital, Karachi (Pakistan). Treatment-outcome scores based on clinical and radiographic examination, for endodontically treated premolar teeth restored with either a titanium post-resin-core or Nayyar-core supporting metal-ceramic crowns were recorded. These were recorded in 202 patients, during January 2008 November 2009, through follow-up of the restorations at 1, 2 and 3 months post-restoration periods. Data included the recording of patients’ age, tooth location, the extent of structural-deficit, the type of restoration. Using 5 determinants of treatment-outcome for the restored teeth, individual and mean scores for teeth were recorded. The score for each of the 5 determinants of treatment outcome was either 0 or 1 thus giving a total score ranging from 0 to 5. A higher score-value indicated poorer treatment outcome. Scores were compared and analyzed statistically using descriptive statistics and Chi-square test .


Patients had mean age 37.3 + 11.7 years. Teeth with Nayyar-core supported crowns was done in 128 (65.3%) cases as compared to post-resin-core supported crowns in 74 (34.7%) cases. Association between tooth structure loss and restoration type was statistically significant (P-value < 0.05). All teeth restored with Nayyar-core had > 1 wall remaining as compared to having 1 or 2 remaining walls in teeth restored with post-resin-core-crowns. At each follow-up examination, there was no significant difference between the mean outcome scores for teeth restored with Nayyar-core or post-resin-core.


Irrespective of the varying tooth-structure deficit, both types of cores proved effective in supporting artificial crowns during the follow-up period.


Endo-treated-teeth, Post-resin-core build-up, Nayyar-core, Corono-radicular amalgam core, Treatment-outcome.


The quality of endodontic therapy as well as the type of subsequent prosthodontic reconstruction are the two key determinants of a successful treatment for a severely structurally compromized tooth with pulpal insult.1 After endodontic treatment, teeth tend to dry out over time.2 Also such teeth exhibit relatively decreased resistance to fracture as compared to vital teeth.3 This extent of decrease in resistance to fracture is mainly a function of the severity of the tooth structure

compromise.4 Reinforcement of root-treated teeth with posts has been the treatment of choice to most clinicians when the tooth is badly broken down and even for teeth with one or two walls remaining.5 However, it has been stated that after placement, a post poses a higher risk of weakening the tooth rather than strengthening it and that its use eventually prone the tooth to vertical root-fracture. The likely reason for this has been attributed to the often needed removal of dentine as a root canal preparation measure for placing the post.6

The most obvious purpose of post incorporation is to preserve the core in a tooth exhibiting extensive coronal structure deficit. Preparation of a post space adds a certain degree of threat to a restoration procedure. Procedural accidents in the form of perforation are possible. The placement of posts also increases the odds of vertical root fracture and treatment failure, especially if an over-sized post channel is prepared. It has been suggested that posts should only be used when other methods for the support and retention of the core are not in hand.7 In this time of increased economic and professional accountability, variations in the utilization of posts to improve the retention of crowns or other restorations on endodontically treated teeth may be no longer necessary, 8 especially in patients having lower socio-economic profiles.8

Many procedures and techniques, for providing good internal support and retention for cores on such teeth, have been suggested and used. However, all of them are based on personal preference and clinical experience with no research evidence for superiority of one over the other. This has left the clinician with great confusion as to what constitutes adequate structural support, dowel length, the type of material or the appropriateness of the restoration. To some amalgam has remained the material of choice for placing an intra-corono-radicular restoration in such teeth.9

The use of amalgam usually specifies that retentive dentinal pins be used within the root canals or in areas surrounding them.10 However, the use of dentinal pins have the disadvantage of causing friction lock that produces fracture lines within dentine.11 To obviate this problem,

Nayyar et al suggested a technique using an amalgam dowel-core. In this technique, retention for the amalgam-core is derived from the remaining pulp chamber and the prepared canals by extending amalgam to these areas.9

They described this as a coronal-radicular dowel and core technique for root-treated multi-rooted teeth. The amalgam is condensed 2 to 4 mm into each canal, pulp chamber and into the coronal portion of the tooth. The set amalgam in the root canal and pulp chamber is to offer resistance to horizontal and vertical forces exerted on the restoration.

The mesio-distal and bucco-lingual dimension of a premolar tooth is relatively smaller than that of a molar tooth. To perform a core-build-up on such a small tooth is sometimes difficult. Furthermore, all endo-treated teeth do not require posts. It has also yet to be known whether a corono-radicular restoration not utilizing an endo-post could survive during tooth preparation for crown due to the deficient residual dentine. Dealing with patients having unsatisfactory socio-economic status by including the use of post in the treatment plan will certainly add up to their misery by raising the cost of treatment. This would be of particular concern for those already unable to afford the cost of root canal treatment and subsequent crown placement on it. Premolar teeth occupy important location in the arch with significant functional importance but have smaller dimensions require specific restorative considerations during and after endodontic therapy. The aim of this clinical follow-up study is to report treatment outcome achieved with either of the two suggested restorative options i.e. post-resin-core build-up or Nayyar-core build-up in endo-treated premolar teeth supporting metal-ceramic full-coverage artificial crowns.


Approval of the hospital Ethical Committee for conduction of the study, as well as patients informed consents were obtained. A total of 202 patients, presenting premolar teeth with indication for endodontic treatment because of pulp involvement due to advanced caries or trauma, were included in the study. After receiving endodontic treatment, the coronal structure deficit was restored with either the Nayya-core or the conventional post-resin-core. In both cases, GP points were first removed, from the coronal portion of the root canals, with the help of a piezo reamer. For placement of the Nayyar-core, the technique described by Nayyar et al was used.9 In brief, this involved the removal of the gutta percha points (Fuji IX GP, Fuji Corporation Japan) from the coronal end of the root canals but leaving up to 4mm gutta percha (GP) in the apical part of the root canals to provide a hermetic apical seal. The amalgam was then packed in the coronal part of the canals with a small condenser / endodontic plugger to facilitate the radicular extension for the amalgam that is to be condensed in the coronal portion of the tooth.

Subsequently, and following the routine technique, the existing pulp chamber of the tooth was also packed with amalgam to restore the lost aspects and contours of the tooth crown. Thus a corono-radicular amalgam core as proposed by Nayyar et al.9 Whereas for the placement of post-resin-core, the coronal parts root canals were cleaned of GP while leaving 4mm in their apical portions to maintain apical seal. Subsequently, using a Parapost drill, the corresponding canals were prepared to receive titanium parallel-sided posts that were cemented with glass-ionomer luting cement (GC America Inc, USA). The coronal contours of teeth were built-up in composite resin.

Finally, after placement of the Nayyar-core and the post-resin-core, teeth were prepared for placement of metal-ceramic / ceramo-metal / porcelain-fused-to-metal crowns and upon fabrication, were cemented on teeth. The collected data belonged to patients having received the mentioned treatments between January 2008 and November 2009 at the Fixed Prosthodontics Unit of the Department of Prosthodontics, Fatima Jinnah Dental College and Hospital Karachi, Pakistan. A pre-structured data collection sheet was used to record data related to the restoration of the teeth. Tooth structure related parameters included; tooth number, core-buildup type, material used, and tooth-structure-deficit. The treatment outcome related to each type of restorations placed in the premolar teeth of each subject were evaluated over a period of 3-months during 3 follow-up visits each one a month apart. For this to do at each of the follow-up visits, the treatment outcome was evaluated by scores obtained through 5 determinants of treatment outcome. These determinants included the recording of the periodontal pocket probing depth (PPD) of the restored tooth, (0 when PPD up to 2 mm and 1 when PPD > 2mm), bleeding on probing (BOP) of the restored tooth (0 when BOP not occurring upon placement of a blunt probe in the gingival crevice and 1 when BOP occurring), the recording of crown movement / dislodgment as felt through fingers on pressing it (0 when not present and 1 when present) and recording of radiographic evidence (peri-apical radiographic view) of the extent of adaptation of the core material to the tooth (0 when well-adapted and 1 when not) and history of event fracture of the core material (0 when no and 1 when yes). Thus for each restoration the corresponding individual score based on these 5 determinants of treatment outcome was calculated as well as the mean scores for each type of restoration among all patients in the category. The maximum possible adverse score for each restoration was set as 5 on the basis of the maximum adverse score of 1 for each of the 5 outcome determinants of the restoration. A higher score meant relatively poorer treatment outcome.

Using the SPSS version 16 statistical soft-ware, descriptive and analytical statistics were performed for

the data. Chi-square and t-tests were applied to data to see the significance of the association between the categorical variables of the type of restoration and the various variables related to the treated teeth.


There were 202 patients having a mean age of 37.3 + 11.7 years. Details of the distribution of the coronal structure deficit and restoration type are shown in Table 1. Nayyar-core was provided in 65.3% cases as compared to post-resin core in 34.7% cases. Inspection of the data in Table 1, show that the association, between tooth structure loss and restoration type was, statistically significant (P-value < 0.05). Nayyar-core was preferred in 128 teeth where more than one wall was remaining as compared to post-resin-core in 74 teeth that exhibited maximal structural compromise (only one or two walls remaining).

The data relating to restoration type and tooth number is shown in Table 2. Most commonly restored tooth was 45 (18.3%). Inspection of the data in Table 2, show that the association between restoration type and tooth number was found to be significant (P-value = 0.05). Tooth number 45 was the most preferred tooth for Nayyar-core buildup in amalgam (n = 26) whereas the maxillary first premolar was the tooth most restored with post-resin-core buildup (n = 15).

at each of the three follow-up examinations. It can be seen that on the first follow up visit (one-month after core restoration and placement of artificial crown on the tooth) no significant difference was noted between teeth restored with Nayyar-core (n = 85) exhibiting a mean score of 1.24 on a scale ranging from 0 to 5. In contrast, teeth with the post-resin-core (n = 62) exhibited a mean score of 1.33 on a scale ranging from 0 to 5. During the second follow-up visit (2-months post restoration stage) 82 cases of Nayyar-core exhibited a mean score value of 1.25 on a scale ranging from 0 to 5. On the other hand in the post-resin-core buildup cases (n = 59) the mean score value recorded was1.33. The difference between the mean score values for either type of build-up work for the support of the crown was insignificant. At the 3-months follow-up visit, 84 cases of Nayyar core exhibited a mean score value of 1.27 on a scale of 0 to 5. Post-resin-core cases reported were 59 with a mean value of 1.33

There was no significant difference between the teeth restored with Nayyar-core or post-resin-core. None of the teeth restored with the test cores and crowns exhibited poor adaptation of the core material to the tooth-structure, or fracture of the tooth or fracture of core material or material loss and degradation.


Appropriate prosthetic reconstruction is of paramount importance to the success of the root filled teeth along with good root canal treatment.1 It is a fact that placing a post in a root-treated-tooth would pose extra risks to the fracture of the tooth itself. 6 However, at the same time, the superiority or otherwise of the Nayyar core is also unclear. Therefore, proper understanding and knowing about the restorative techniques that could ensure the longevity of an already weakened tooth would prove beneficial for the dentist as well as the patient. This study made an attempt to provide new knowledge regarding the clinical efficacy of these restorative modalities for restoring the lost coronal structure of endo-treated teeth before placing crowns on them. It was determined whether placing a conventional post-core or a corono-radicular amalgam restoration (Nayyar-core) was preferable for endodontically treated premolars exhibiting structural deficit in the mesio-occlusal (MO), disto-occlusal (DO) or mesio-occluso-distal (MOD) aspects or even more extensive structural compromise than these.

While several factors influence, including those related to patients, local intra-oral condition and skills and experience of clinical and technical personnel, the outcome of treatment in such teeth, few were chosen to evaluate these restorations during a 3-months follow-up period. In this regard, the present work could act as a starting point for extensive research work to provide valid information. A limitation of the study is that all restorations were provided either by senior consultants or under their supervision in a specialist department and thus the finding may not reflect a kind of performance of such restorations placed in a general practice setting.

The results of the present study, however, show that premolar teeth with smaller mesio-distal and bucco-lingual dimension after endodontic treatment and restoration of their lost structure in aspects such as MO, DO, or even MOD with thin walls remaining do not essentially require the use of the traditional post-core restoration approach as is the daily common and routine practice.5 Rather Nayyar-core build-up would be beneficial. In all cases, both the core types as well as the material used remained intact not only during tooth preparation for crown but also did not suffer or caused any problems during the follow-up period. Despite this positive and useful finding, this study suggests further investigations of the appropriateness of other restorative options aiming at preventing damage to tooth-structure during placement of the restoration. This will ensure preventing the early loss of premolar teeth having strategically important location in the arch .


Within the limitations of the study it can be concluded that the placement of Nayyar-core is a preferred restoration for teeth with structural deficit confined to MO, DO or MOD aspects of the tooth. While Post-resin-core buildup could prove useful for teeth with maximum tooth loss and thin remaining dentin provided some form of ferrule was available. Mandibular premolar was the tooth most restored with Nayyar core. On follow up visits no significant difference was found in the teeth restored with pre-fabricated titanium post-resin-core build-up or with Nayyar-core. Each type core build up remained effective and intact during the period of observation of this study.


We would like to thank Dr. Hasan Mehdi, Department of Oral and Maxillofacial Surgery Fatima Jinnah Dental College, Hospital, Karachi, for his help in statistical analysis. .


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