How did the tooth devitalise in the absence of caries?

Teeth devitalise due to a variety of reasons, though caries is the main factor. Another reason for a tooth devitalising includes thermal injury to the pulp, which can occur from cavity preparation. The LL6 was restored with a PFM crown, which is a less conservative preparation than an all‐metal crown. The rates of pulp death over a 10‐year period vary depending on the level of preparation, but studies have found this can be as high as 15–20% for PFM crowns. The rates of pulp death decrease where less tooth reduction is undertaken. All teeth planned for an extracoronal restoration should undergo sensibility testing before treatment to limit complications of undertaking endodontic access through a crown. The most common forms of sensibility testing include the use of EPT or temperature testing. Historically ethyl chloride has been widely used to cold test teeth for vitality. However, this is now being replaced with refrigerant sprays such as Endo‐Ice and Endo‐Frost, which can reach much lower temperatures at −26 and −50 °C, respectively. These lower temperatures allow for more accurate sensibility testing, particularly where a crown is present.

How is furcation involvement classified and how does it affect prognosis?

Furcations are present on all multi‐rooted teeth and it is imperative that they are explored during a periodontal assessment with a suitably designed probe, such as a Naber’s probe. The level of furcation involvement is classified based on how far the probe penetrates:

• Grade I involves the probe being inserted up to a third of the furcation width.
• Grade II has the probe going further than a third of the furcation width, but it does not go all the way through.
• Grade III occurs where the probe can be inserted the full width of the furcation through to the other side.

The presence of a furcation indicates a significant loss of supporting attachment and would be seen in Stage III and IV of periodontitis, which require more complex management. In such cases the prognosis is reduced due to the loss of bone support and the increased likelihood of mobility.

What are the anatomical connections between the dental pulp and the periodontium?

The anatomical connections between the dental pulp and the periodontium are illustrated in Figure 1.8.2. The following features provide a pathway for endodontic‐periodontal communication that can lead to combined lesions:

• Apical foramen
• Lateral or accessory canals
• Dentinal tubules
• Perforations
• Fractures
• Resorption

What are the classifications for endodontic‐periodontal lesions?

Prior to the introduction of the 2017 Classification, the most widely used system for the classification of endodontic‐periodontal infections was Simon’s (1972). This is still the most used classification system among endodontists, but relies specifically on the chronology of the disease process, with limited information about the clinical picture in relation to the lesion. The classification of endo‐periodontal lesions is much broader since the introduction of the 2017 Periodontal Classification. Endo‐periodontal lesions fall into two broad categories under the 2017 Periodontal Classification system: where there is root damage, and where there is not. Root damage can occur in the form of fractures, perforations and resorption and, when evident, will reduce the prognosis of any proposed treatment due to the added complications of such pathology. Where an endo‐periodontal lesion exists with the absence of any obvious root damage, it is further separated based on whether the patient has a known history of periodontal disease or not. A patient with active periodontal disease will have a reduced prognosis due to the reduced bony support commonly seen in such patients. A grading system is used thereafter, but its parameters are the same regardless of whether the patient has periodontal disease or not (Table 1.8.1). The grading is as follows: