Endodontic-periodontal lesions have been classified by various authors according to the primary cause of disease. A typical classification, based on the primary disease with a secondary effect, is as follows:

a) Primary endodontic lesion with drainage through the periodontal ligament - a deep narrow probing defect is noted on just one aspect of the tooth root.This is usually a draining sinus originating from an infected root canal system. 

b) Primary endodontic lesion with secondary periodontal involvement - there is a more extensive periodontal pocket which has occurred as a result of the drainage from the infected canal. Long-term existence of the defect has resulted in deposits of plaque and calculus in the pocket with subsequent advancement of the periodontal disease. 

c) Primary periodontal lesion - the periodontal disease has gradually spread along the root surface towards the apex. The pulp may remain vital but may show some degenerative changes over time. 

d) Primary periodontal lesion with secondary endodontic involvement - progression of the periodontal disease and the pocket leads to pulpal involvement via either a lateral canal foramen or the main apical foramen. The pulp subsequently becomes necrotic and infected. 

e) Combined endodontic-periodontal lesion - the tooth has a pulpless, infected root canal system and a co-existing periodontal defect.

A simpler classification would be to define any situation with both endodontic and periodontal diseases as being a "combined endodontic-periodontal lesion". An attempt should be made to identify the primary cause of a combined lesion but this may not always be possible. In such cases, it is not essential to determine which disease entity occurred first as the treatment will involve both endodontic and periodontal management. If only one of the problems was treated, then it would be expected that the lesion would not heal adequately. It is generally advisable to treat both tissues concurrently in order to create the most favourable environment for healing.

Diagnostic Methods

Initially a detailed medical and dental history must be obtained from the patient. The patient's description of any signs or symptoms will usually lead the clinician to a provisional diagnosis. A full periodontal and endodontic examination must then be carried out to confirm the diagnosis and to identify or exclude any other diseases that may be present. 

The clinical examination should include inspection of the gingival and mucosal tissues, periodontal probing, palpation, mobility testing, percussion, pulp sensibility testing, occlusal assessment, biting tests and a radiographic examination. 

Periodontal probing is essential to identify and determine the depth of periodontal pockets and the degree of loss of attachment. Periodontal probing should be carried out for the entire dentition, not just the tooth involved. Any suppuration or bleeding on probing should be noted. 

Pulp testing should be carried out with both carbon dioxide (dry ice) and an electric pulp tester (heat testing is of limited diagnostic use unless the patient complains of heat sensitivity). Pulp tests used in conjunction with thorough clinical and radiographic examinations will give an indication of the clinical status of the pulp - that is, it is usually possible to determine whether there is a reversible pulpitis, irreversible pulpitis, necrotic pulp, or a pulpless, infected root canal system. 

Radiographs are an essential tool to the diagnosis of any endodontic or periodontal condition. Long-cone parallel radiographs should be taken in order to check for loss of crestal bone, presence of periapical or lateral radiolucencies, presence and depth of previous restorations, presence of previous root canal fillings, root fractures, or any other pathology or abnormalities. The radiographic examination findings should be recorded on the patient's record card. 

An adequate diagnosis should include a comment about the current status of both the endodontium and the periodontium. A tooth showing signs of both endodontic and periodontal diseases should be classified as having a "combined endodontic- periodontal lesion". The primary cause of this combined lesion may be obvious in some cases but not in others. Furthermore, in some cases, the lesions may be unrelated and this should be also be noted.

 Treatment

Treatment of combined endodontic-periodontal lesions should follow the same general principles for treatment of these entities as though they were separate lesions. That is, the periodontal disease should be treated by routine scaling, root planing, oral hygiene instructions and follow-up maintenance therapy, including surgery in some cases. Diseased pulp tissue or infected root canals should be treated by cleaning, shaping, medicating and filling of the root canal system.

Most teeth with combined endodontic-periodontal lesions will have an infected root canal system. Therefore the endodontic treatment should be carried out over multiple visits and in conjunction with the periodontal treatment. This will provide an opportunity for antibacterial intra-canal medicaments to be placed in order to predictably eliminate bacteria from the root canal system. 

Medicaments such as Ledermix paste and calcium hydroxide pastes have been recommended as routine intra-canal medicaments. Ledermix paste is an ideal medicament to be used as an initial dressing particularly if the patient presents with symptoms. However the antibacterial spectrum of Ledermix paste, against the most commonly found endodontic bacteria, has been reported to be somewhat limited whereas calcium hydroxide has been reported to be the most predictable antibacterial medicament for endodontic microbes. Therefore, calcium hydroxide should be used in the root canals of all infected teeth at some stage prior to the placement of the final root canal filling. Calcium hydroxide can either be used alone as a dressing or in combination with Ledermix paste (as a 50:50 mixture).

In teeth with previous restorations, the pulpal disease is very likely to be associated with, or caused by, recurrent caries or marginal microleakage and bacterial contamination of the pulp space - these problems must be eliminated if the endodontic treatment is to succeed. Therefore all previous restorations should be removed prior to commencement of the endodontic treatment and the tooth should then be assessed to determine whether it is suitable for further restoration if the endodontic and periodontal treatment is successful.

It is important to ensure that a tooth undergoing endodontic treatment is adequately temporised to ensure that the coronal cavity is sealed and that there are no periodontal consequences from the temporary restoration (such as overhangs, inadequate contour, food packing, inability to clean, etc). In some cases it may be necessary to place a stainless steel orthodontic band in order to stabilise the remaining tooth structure and/or retain the temporary restoration. The use of a reinforced glass ionomer material, such as Ketac Silver, is ideal in these situations in posterior teeth as it will provide an adequate long-term temporary restoration with minimal periodontal effects. A tooth-coloured glass ionomer or composite resin can be used in anterior teeth.
 

The use of multiple appointments for endodontic treatment is convenient for the treatment of combined endodontic-periodontal lesions as it allows time for the initial non-surgical periodontal treatment to be carried out before continuing with the final root canal filling. The response of the patient and the tissues can be determined and the prognosis can be reassessed before any further treatment is contemplated. The periodontal tissues should be monitored for at least three months prior to considering any further treatment. During this reassessment time, the root canals can be left with either calcium hydroxide or a calcium hydroxide/Ledermix mixture in the canals. 

The placement of medicaments in the root canals during this reassessment phase also allows adequate time for the medicament to diffuse through the radicular dentine in order to kill any remaining microbes - such medicaments require at least 3-4 weeks to achieve a predictable concentration within the peripheral (or outer) layers of the dentine. There may also be sore minor beneficial effects from the medicaments in helping to promote healing within the periodontal ligament, as dentine and cementum have been shown to be permeable to such medicaments.

If the initial phase of treatment does not result in adequate improvement of the periodontal tissues, then the tooth should be considered for further periodontal treatment, including surgery. Flap surgery may be chosen in order to gain adequate access to the entire root surface for root planing and debridement. Following this external cleaning of the root surface, the tissues should be monitored to determine the healing response. Again during this phase of treatment, the root canals should be left with an intra-canal dressing for a period of at least four to six weeks. Then, if the tissues show initial signs of healing, the root canal filling should be completed and an adequate coronal restoration placed. The case should then still be monitored, both periodontally (initially at three monthly intervals), and endodontically (initially after six months) in order to determine whether there has been periodontal and periapical healing.

The presence of a combined endodontic-periodontal lesion will always result in a compromised situation following treatment. Even with apparently successful treatment, the tooth will still be compromised as there is likely to be some gingival recession and loss of periodontal attachment and bone support. It is of utmost importance that the patient maintains good oral hygiene and obtains regular professional care for this region.

Acknowledgment: Dr Paul Abbott, Senior Lecturer in Endodontics, the University of Western Australia. 

This material has been compiled with the assistance of Dr Louise Brown, Lecturer in Periodontics at the University of Melbourne. 

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