Teeth deprived of vital pulp and the possibility of restoration are a source of various research and a subject of numerous articles. In their practice, clinicians have often confirmed that a tooth after root canal treatment is less durable and more prone to fracture than a non-treated tooth. Thus, an optimal solution which protects other tissues from possible complications is looked for. Reasons for the deterioration of mechanical properties of tooth after canal treatment are connected inter alia with weakening of other structures as a result of loss of tooth hard tissues (1). Loss of two marginal ridges during cavity preparation leads to the reduction of tooth durability by 63% yet performance of only an endodontic access in a healthy and non-treated tooth results in its weakening by only 5% (2). Protection and maintenance of hard tissues at least 1 cm above the neck of a tooth – a so called ferrule effect which boosts tooth’s resistance to fracture – is also crucial (3). Furthermore, physical changes in dentine connected with its dehydration contribute to tooth fracture – dehydrated dentine becomes fragile due to a loss of 14% of its original durability and prioreception, which results in the lack of control over generated strengths (1, 2). Therefore, a proper restoration of a tooth after canal treatment conditions a further therapeutical effect. When choosing a type of tooth restoration, it is important to consider the following factors: an amount of the remaining tooth structures, location of a tooth in a dental arch, generated occlusive forces and an aesthetic aspect (4, 5). Until recently, a method of choice was restoration with posts and crowns (6). It was only when adhesive techniques were introduced that a bonding strength (microretention) could be applied without a necessity to provide mechanical retention for further restoration (macroretention) (7, 8). It is in accordance with a modern concept of a minimally invasive technique which is targeted at the lowest interference with a tooth structure and maintenance of a maximal amount of other tissues (9). Neumann created a classification of dental cavities treated endodontically and a therapeutical concept (10). Having taken this scheme into account, a clinical situation in which performance of an endocrown or a post should be considered are cavities in which one tooth wall or none of them are preserved. An endocrown is a monolithic and adhesively bonded restoration (11). It is owing to the possibility of microretention that an endocrown became an alternative in prosthetic treatment of teeth after canal treatment. It allows for tooth reconstruction without application of a post (12).

First of all, height of an occlusive surface of a minimum 2 mm must be reduced in order to obtain an optimal amount of space for an endocrown. Tooth walls thinner than 2 mm should be reduced. A preparation ridge ought to be located supragingivally. In some clinical situations, it is possible to place a preparation ridge subgingially, however, inclination between supragingival and subgingival preparation may not exceed 60°. A tooth chamber should be prepared in such a manner that eliminated all arches and a depth of the chamber ought to be at least 3 mm. Additional retention may be provided by removal of gutta-percha from a canal at the depth of maximum 2 mm. Such prepared tooth ought to be polished with a fine-grain bur (11). Despite guidelines on tooth preparation, literature provides cases when teeth, which did not follow these criteria, were successfully reconstructed with endocrowns. In their article, Biacchi et al. present the first case of a first mandibular molar with a significant loss of tooth structures, a fractured buccal wall, wide yet not sufficiently deep chamber and a preserved lingual wall. Although a preparation ridge did not cover enamel in its whole range, the tooth was reconstructed with an endocrown made of ceramics strengthened with leucite. After 3 years, the case was still airtight and periodontium – healthy (7). Whilst planning medical treatment, it is important to consider the guidelines. Yet, as shown above, in some cases not all criteria must be met in order to disqualify a tooth. Clinician’s experience is crucial in the selection of a procedure.

Endocrowns have been the most widely used in non-vital molars. According to numerous authors, among all groups of teeth, it is molars that provide the best conditions for the sustenance of such a restoration (11-14). Anatomy of these teeth also allows for mechanical retention by anchoring in a pulp chamber owing to its size and root canals orifices (13). Moreover, due to molars width, strength arms applied onto cusps are higher than in narrower pre-molars. As a result, prying forces are lighter in case of morals (14).

Lin et al. assessed the risk of failure in reconstruction of pre-molars after canal treatment with endocrowns and crowns. According to the results, a risk of failure is similar in both cases. Thus, it may be assumed that in proper occlusion conditions, an endocrown may be applied in the restoration of pre-molars (8). However, these teeth have got a smaller area of adhesive bonding and a higher crown, which is unfavourable for their mechanical properties (12, 13). Furthermore, an operating force is larger, as it was already mentioned. Pre-molars may also be influenced by additional strengths in case of group function, which must be taken into consideration when planning treatment (5). According to most of the authors, pre-molars should be provided with restoration in order to minimise the risk of possible complications (5, 13). However, no clear agreement has been reached in this subject. An endocrown is also an alternative – and even a method of choice – in reconstruction of teeth with low crowns (where there is no place for classic reconstruction with a post and a crown) and for teeth with short roots and obliterated canals, where no restoration can be done (7).