Root end filling

Elimination of the infected pulp space by extraction of the tooth almost always results in healing of periapical lesions [1,2]. As early as the 1880s, attempts were made to remove the offending segment of the tooth and leave the remaining portion for function [3,4]. Even in those days, the necessity of thoroughly cleaning, disinfecting, and filling of the pulp space before surgery was understood [5]. When the operator was unable to reach the apex of the root satisfactorily, the root canal was filled and the root was resected to the level where the filling ended [6]. Complete regeneration of periapical tissues in such cases was demonstrated histologically as early as 1930 [6]. In light of contemporary knowledge, one may conclude that many surgical procedures performed contemporaneously with root filling may have been unnecessary, since root canal treatment by itself may have resulted in success [7–13]. Techniques commonly referred to as ‘‘retrograde filling,’’ ‘‘retrofill,’’ or ‘‘retroseal’’ (ie, the preparation of a root-end cavity and insertion of a root-end filling in the prepared cavity while leaving the main portion of the root canal space untreated and unfilled) began to appear in the literature in the mid-twentieth century [8,14]. The advocates of these techniques presuppose that root canal treatment or retreatment [15,16] via the coronal access is not feasible (eg, when a retentive post is present) and that the root-end filling function is to establish a barrier between the infected root canal and periapical tissues. Experiments in conventional root canal treatment have clearly shown that, despite thorough instrumentation and liberal use of antiseptic irrigation, a bacteria-free root canal cannot predictably be prepared, and any microorganisms left in the root canal are likely to proliferate. An intervisit antimicrobial medication is thus necessary to control the root canal infection [17–19]. After elimination of microorganisms from the root canal and root canal filling, resolution of periapical lesions is likely to occur, and it is shown that a residual periapical lesion is indeed a rare occurrence [20–23]. In periapical surgery, no antimicrobial irrigation or intervisit root canal medication is allowed for obvious reasons, and despite recent advances in surgical techniques and root-end preparation armamentaria [24–26], complete elimination of bacteria from the pulp space via the apical access is highly improbable. In fact, a recent clinical study showed that long after periapical surgery and root-end filling, viable bacteria may persist in the canals, constituting a potential risk of recurrence of periapical pathosis [27]. The sole reliance on root-end fillings, which are notoriously leaky [28], is probably responsible for a large number of periapical surgery failures [29,30]. The apical part of the root is often curved, contains accessory canals and ramifications, and is difficult to clean, disinfect, and fill through the coronal access cavity. Thus, by removing the apical part of the root, the infected root canal space may be eliminated. The apex of the root is resected, conventionally in an angle with the long axis of the root, to form a bevel facing the operator. The bevel is made to facilitate access, improve visualization of the root canal cross-section, help to diagnose fracture lines, and to facilitate preparation of a root-end cavity [31]. The angle of the bevel should be kept to a minimum because it is shown that an increase in the angle of the bevel increases the number of patent dentinal tubules [32] and may intensify apical microleakage [33].