Commentary

Historically, root canal treatment was performed over multiple visits. This was primarily to ensure ‘sterility’ of the root canal system prior to obturation and to allow enough operational time to achieve the mechanical and biological objectives of the treatment. Modern advances in the theory and practice in endodontics inform us, beyond any doubt, that the theory of sterility is not achievable clinically. Meanwhile, the development of innovative instruments and devices has increased the efficiency of treatment performance. Practitioners who believe that successful and painless root canal treatment can be accomplished in one visit and those who prefer multiple-visit procedures can all find a rationale in the literature.1, 2, 3

Our knowledge of the pathogenesis of these complications indicates that the causative factors of flare-ups comprise mechanical, chemical and/ or microbial injury to the periapical tissues.1 Indeed, most cases of flare-up occur as a result of acute periapical inflammation, secondary to intra-canal procedures. Regardless of the type of injury, the intensity of the inflammatory response is directly proportional to the intensity of the tissue injury, which results in a cascade of cellular and molecular events ending in the clinical scenario of flare-ups.

The heterogeneity encountered in the present systematic review reveals the enormous variables involved in trying to address the questions of the study. The conclusion is not surprising at all, then, considering the proposed mechanisms of pathogenesis of this patho-physiological phenomenon. One might assume that incidence of post-operative flare-ups following use of the traditional treatment approaches and armamentarium would be different from that with current approaches. For example, the use of rotary nickel–titanium files result in less debris extrusion to the periapical area compared with the step-back technique, and thus provokes fewer postoperative complications. Another variable is the technique, volume and concentration of intra-canal irrigation, which directly impact on the microbial load of the root canal system and elsewhere.

The results of this review highlight the need for well-controlled clinical research to establish the factors associated with successful implementation of single-visit treatment and re-treatments.