Author: Dr. Syed Mukhtar, Dr. Ashok Kumar, Dr. Shioraz Siddiqui.
Dr.Z.A. Dental College, A.M.U, ALIGARH.

 

Abstract:
Recent advances in endodontics and increased patient awareness has resulted in the increased demand of endodontic treatment. But unfortunately not all treatment results in predictable success and in various cases the disease continues even after the primary endodontic treatment (Post Treatment Disease). Endodontic retreatment may offer the patient a second chance to save a root-treated tooth that would otherwise be destined for extraction. This paper discusses the various issues with non-surgical endodontic retreatment and also describes the success of non-surgical endodontic retreatment in achieving healing of persistent periapical lesions.

Introduction:
The results of endodontic treatment are influenced by a number of biological and technical factors like diagnosis, root canal morphology, root canal instrumentation and obturation, and complications during the treatment. A considerable number of cases suffer from “post treatment disease” after primary endodontic treatment. Post-treatment disease (apical periodontitis associated with root canal-treated teeth) is primarily caused by infection of the root canal system. The affected teeth can be treated either by retreatment (orthograde) or by apical surgery (retrograde).Endodontic retreatment is a procedure performed on a tooth that diagnostically demonstrates incomplete treatment, yet the actual conditions require further endodontic treatment to achieve successful results.¹ These two approaches differ significantly in rationale-  “retreatment is an attempt to eliminate root canal microorganisms”, whereas  “surgery is an attempt to confine the microorganisms within the canal”. The main benefit of retreatment, therefore, is better curtailment of the root canal infection. Being limited in this regard, surgery is a compromise unless microorganisms are assumed to be harbored periapically, retreatment is unfeasible or restricted, or a retreatment attempt has failed.

Case Reports:

Case report #1:
A 28 yr male patient reported with tenderness in tooth no. 35. There was a history of previous endodontic treatment done some 6 months back. On radiographic examination the treated tooth revealed poorly obturated canal & periapical radiographic changes (fig.1a). After the discussion of the problem with the patient an informed consent was obtained and a joint decision for retreatment was taken.

Access was gained with round diamond burs and then previous canal filling was removed with the help of xylene based gutta-percha solvent (CARVENE, Dentpro, India.) and headstroem files (H-files). The canals were thoroughly irrigated with 3% sodium hypochlorite, working length was determined (fig.1b) & then canal preparation was done with k-files with a step-back technique. In between the treatment appointments an interim dressing of calcium hydroxide points was given as an intracanal medicament. On subsequent appointments when the patient became asymptomatic the tooth was scheduled for obturation. Before obturation the canals were irrigated with a final rinse of EDTA to remove the smear layer. The canals were then obturated with laterally condensed gutta-percha & zinc oxide - eugenol based sealer (fig.1c). The tooth was restored with porcelain fused to metal full crown restoration.  After 6 months follow up the tooth is absolutely asymptomatic and radiographic evaluation shows signs of periapical healing (fig. 1d).

Pre-Operative Radiograph	Ubturation removed & working length	Post obturation	At 6 month follow up

Case report #2:
A 23 yr female patient reported with tenderness in tooth no. 37. There was a history of previous endodontic treatment done some 1 year back. On radiographic examination the treated tooth revealed poorly obturated canasl & periapical radiolucency at the root apex (fig. 2a). An informed consent was obtained and the decision for non-surgical retreatment was taken. After gaining the access previous obturation material was removed with the help of xylene based gutta-percha solvent (CARVENE, Dentpro, India.) and H-files. Working length was determined (fig. 2b) and then biomechanical preparation was done with the help of manual stainless steel k-files used in a step back manner. As the tooth exhibited a C-shaped canal anatomy, final finishing of the canal walls was done with H-files used in a circumferential filing motion. The tooth was obturated (fig. 2c) with thermoplasticised gutta-percha system obtura-II (Obtura Spartan, Fenton, MO). As the tooth had a week coronal structure so cast metal post and core was fabricated and the tooth was finally restored with porcelain fused to metal crown. At 1 year follow up the patient is absolutely asymptomatic  and the periapical lesion is almost completely healed (fig. 2d).

Pre-Operative Radiograph	Ubturation removed & working length	Post obturation	At 6 month follow up

Discussion:
The success rate for root canal treatment carried out with currently accepted principles should be high. Indeed, published figures of between 70 and 95% have been quoted in studies using samples derived from teaching hospitals. However, there is marked variation in the ability of operators to achieve successful results. Obviously, there is a contradiction between what is achievable and what is actually achieved.

Root canal treatment usually fails when treatment falls short of acceptable standards.² The reason many teeth do not respond to root canal treatment is because of procedural errors that prevent the control and prevention of intracanal endodontic infection.³ Undoubtedly, the major factors associated with endodontic failure are the persistence of microbial infection in the root canal system and/or the periradicular area.⁴

Causes of failure include: incomplete obturation, root perforation, external root resorption, coexistent periodontal-periradicular lesions, grossly overfilled or
overextended canals, canals left unfilled, developing apical cysts, adjacent pulpless teeth, inadvertently removed silver points, broken instruments, unfilled accessory canals, constant trauma, and nasal floor perforation.⁵ Recent literature has additionally suggested coronal leakage of bacteria or endotoxin as potential causes of endodontic treatment failure.^16-8

When root canal treatment fails there are three possible ways of dealing with the problem:

• Root canal retreatment
• Root end surgery
• Extraction

Assuming that persistent intraradicular infection is the most common cause of failure, it is worthwhile retreating failed teeth prior to surgery or extraction in order to exclude such a possibility.⁹

Indications of Retreatment:

Endodontic Retreatment can be considered when:

• Persistent pain or symptoms develop in a tooth that has received root canal treatment
• The existing root canal treatment is deficient technically
• There have been procedural errors
• A new coronal restoration (such as a crown) is planned on a tooth with a technically deficient root canal filling or in the presence of non-resolving periapical radiolucencies

Unique Considerations for Endodontic Retreatment:

• Retreatment and initial root canal treatment share similar biologic principles and objectives. However, the following are unique to retreatment:
• An extensive restoration may have to be sacrificed and remade.
• Retreatment may be performed to prevent potential disease.
• Morphologic alterations resulting from the previous treatment may present unusual technical and therapeutic challenges.
• Root filling and possibly restorative materials be removed from the canals.
• The healing rate is generally slower than that after initial treatment, because of greater difficulty in eliminating the infection.
• Patients may be more apprehensive than with the "routine" initial treatment; effective communication is required

Re-treatment planning must include a careful evaluation of periapical condition, so that a decision can be made among non-surgical (orthograde) re-treatment, surgical (retrograde) procedure or tooth extraction.¹⁰ Clinicians should evaluate previously treated teeth and judge success by the standards of patient comfort, healthy periodontium, and absence of radiographic pathology. At times, certain teeth exhibit inadequate treatment based on present day criteria, but fulfill the definition of success, such teeth must be watched carefully but must be considered for retreatment if new dentistry is planned. The various factors that should be considered when choosing between retreatment versus other options are; the strategic value of the tooth, periodontal evaluation, restorative evaluation, patient expectations and finally the chairtime & cost of the procedure.

Conclusion:
With available current evidence in support of the non-surgical retreatment many of the teeth with existing post treatment disease can be managed non invasively with retreatment rather than going for the surgical approach.It has been shown that high success rates can be achieved for root canal retreatment, especially when failure of the existing root treatment was due to technical inadequacy.

References:

1. AAE’s Glossary of Contemporary Terminology for Endodontics.
2. Siqueira, J. F. (2001), Aetiology of root canal treatment failure: why well-treated teeth can fail. International Endodontic Journal, 34: 1–10. doi: 10.1046/j.1365-2591.2001.00396.x.
3. Molander A, Reit C, Dahlén G, Kvist T (1998) Microbiological status of root-filled teeth with apical periodontitis.  International Endodontic Journal 31, 1–7.
4. Ingle JI, Bakland LK. Endodontics. 4th ed. Philadelphia: Lea & Febiger, 1994:32–3.
5. Madison S, Wilcox LR. An evaluation of coronal microleakage in endodontically treated teeth. Part III. In vivo study. J Endod 1988;14:455–8.
6. Torabinejad M, Ung B, Kettering JD. In vitro bacterial penetration of coronally unsealed endodontically treated teeth. J Endod 1990; 16:566–9.
7. Alves J, Walton R, Drake D. Coronal leakage: endotoxin penetration from mixed bacterial communities through obturated, post-prepared root canals. J Endod 1998;24:587–91.
8. Ricucci D, Gro¨ ndahl K, Bergenholtz G. Periapical status of root-filled teeth exposed to the oral environment by loss of restoration or caries. oral surg Oral Med Oral Pathol Oral Radio Endod 2000;90:354–9.
9. Ruddle Clifford J, Nonsurgical endodontic retreatment: issues influencing treatment. Dentistry Today February 1998.
10. Wright WE: Prosthetic management of the periodontally compromised dentition, J Calif Dent Assoc 17:9, pp. 55-60,1989.