6.1
Restoration of a Root‐Filled Tooth with a Fibre Post‐Retained Crown
Bhavin Bhuva, Francesco Mannocci, and Massimo Giovarruscio
Objectives
At the end of this case, the reader should know when a post may be used to restore a root‐filled tooth and appreciate the factors that influence the survival of compromised teeth restored with posts.
Introduction
A 37‐year‐old male patient presented, complaining of cold sensitivity and occasional throbbing pain associated with the upper left first premolar tooth.
Chief Complaint
The patient complained of pronounced and prolonged pain with cold foods and drinks. There was also spontaneous, poorly localised, lingering throbbing pain in the upper left premolar region.
Medical History
Unremarkable.
Dental History
The patient was an infrequent attender. He had seen an emergency dentist approximately one year previously, who had advised restoration of a carious tooth that had fractured. A temporary restoration had been placed but the patient failed to return for treatment.
Clinical Examination
Tooth UL4 was restored with a disto‐occlusal temporary dressing (Figure 6.1.1). The tooth was not tender to percussion, but gave a painful response to cold sensibility testing that lingered for several seconds. There were no periodontal probing depths greater than 3 mm associated with the tooth.
What does the radiograph reveal (Figure 6.1.2)?
- Extensive caries in the UL4 that appears to extend close to the pulp.
- Periodontal ligament space widening associated with the UL4.
- Tooth UL6 is root treated to a good standard and the associated periapical tissues appear healthy.
Diagnosis and Treatment Planning
A diagnosis of symptomatic irreversible pulpitis was made for tooth UL4.
The patient’s symptoms were due to inflammation of the pulp as a result of the deep caries. Although the caries had not breached the pulp proper, the bacterial insult associated with the carious lesion had caused the pulp to become irreversibly inflamed.
What are the treatment options for this tooth?
- No treatment.
- Root canal treatment (subject to restorability assessment) followed by cuspal coverage restoration.
- Extraction followed by replacement with (i) implant‐retained crown, (ii) conventional or resin‐bonded bridge, or (iii) removable partial denture.
Following discussion of the various treatment options, the patient decided to proceed with root canal treatment of tooth UL4. The patient was advised that, in the first instance, the residual sound tooth structure would need to be assessed following caries removal. Only following restorability assessment can it be established whether the tooth is restorable, and whether a post may be required to retain a core, prior to cuspal coverage restoration.
When and how should we assess restorability?
- Restorability assessment is a fundamental step of endodontic treatment that should be carried out at an early stage, in order to determine the feasibility of the treatment, as well as the restorative prognosis of the tooth.
- All existing restorations and caries should be removed so that the quality and quantity of the residual tooth structure can be assessed.
- Without removing the entire existing restoration, it is not possible to detect caries, marginal leakage or cracks, even when the restoration appears clinically and radiographically acceptable.
- Complete coronal disassembly will facilitate more conservative and appropriately directed access cavity preparation. Where feasible, the operator may also be able to use the existing cavity to direct the endodontic access to prevent further removal of tooth structure. This has been described as ‘restoratively driven’ or ‘caries‐driven’ access.
- The quantity and location of residual tooth structure will allow the operator to decide on the most appropriate method for restoring the tooth. It is at this stage, that the operator should plan the final restoration, so that all of the treatment steps can be carried out accordingly. The decision as to whether a post‐retained restoration is required cannot be made without assessment of the remaining tooth structure following coronal disassembly.
Treatment
Following local anaesthesia, dental dam isolation of tooth UL4 was performed. The disto‐occlusal caries was removed initially with a diamond bur under copious water spray. Caries removal was completed with a stainless steel rose‐head bur. The tooth was deemed to be restorable following assessment of the residual sound tooth structure. The buccal and palatal cusps were undermined by the caries, such that their residual thickness was considered insufficient to avoid fracture during function, particularly as the patient had group function on lateral excursive movements.
Endodontic access revealed a hyperaemic pulp, confirming the diagnosis of irreversible pulpitis. Two canals were located and root canal instrumentation was initiated. Copious irrigation with 3% sodium hypochlorite solution was performed throughout the procedure. The working lengths of the root canals were determined using an electronic apex locator.
Root canal preparation was carried out using stainless steel hand files to obtain a glide path, followed by preparation with nickel titanium rotary instruments. After completion of the preparation, the canals were rinsed with 17% ethylenediaminetetraacetic acid (EDTA) solution, in order to remove the smear layer created during root canal preparation. A master cone periapical radiograph was taken to verify the preparation of the canals (Figure 6.1.3). Final irrigation of the canals was completed with sodium hypochlorite, which was dynamically activated using a sonic device. The canals were dried with paper points and obturated with gutta percha and sealer, using a warm vertical condensation technique. Post spaces were left in both canals for subsequent core placement.
When is post retention necessary?
Posts are necessary when there is insufficient tooth structure to support the coronal restoration. In almost all cases where a post is required, the definitive restoration will involve the provision of an onlay or crown. The purpose of post placement in this case was to facilitate the retention of the core, as there was a large class II cavity and the residual axial walls were of insufficient thickness, and therefore strength, to prevent subsequent cusp fracture. The use of posts has been shown to be beneficial to restoration and tooth longevity in root‐filled premolar teeth with class II or greater defects. Further indications for a post may be when retreatment is performed and a post was used following the initial treatment, or where there is an anatomically wide canal and the residual dentine walls are thin (for example, an immature tooth).
What is meant by the ferrule effect?
The ferrule effect refers to a circumferential collar of cast metal or ceramic (provided by the cuspal coverage restoration), which encircles the near parallel walls of dentine, coronal to the margins of the cuspal coverage preparation (Figure 6.1.4).
The presence of an adequate ferrule effect is a critical factor for the retention of a cuspal coverage restoration. Posts do not reinforce root‐filled teeth and cannot retain the cuspal coverage restoration in the absence of a sufficient ferrule effect.
An adequate ferrule effect is also a significant factor in preventing root fracture of teeth restored with rigid posts and post decementation with fibre posts. In addition to the presence of an adequate ferrule effect, the longevity of root‐filled teeth has been increasingly shown to be determined by the overall volume of sound tooth structure, number of residual walls, tooth location and number or proximal contacts.
What are the advantages of placing the post immediately after endodontic treatment has been completed?
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