Retreatment is common in endodontics. The purpose of this article was to classify the different clinical situations encountered in retreatment cases and relate them to the outcome after an observation period of 24 months. A total of 425 patients (452 teeth) from 451 patients, consecutively admitted for root-canal retreatment, were monitored during a 24-month period. All teeth (254 molars, 107 premolars, and 91 single-root anterior teeth) were divided into two major categories: teeth with modified anatomy from previous endodontic treatment (root-canal-morphology altered) and teeth in which no significant anatomical changes were made by the former endodontic treatment (root-canal-morphology respected). Although the overall success was 69.03%, the success in the root-canal-morphology-respected group was 86.8% and in the root-canal-morphology-altered group 47% (Mann-Whitney U test p < 0.0001). The clinical success of an endodontic retreatment seems to depend on whether alterations in the natural course of the root canals were caused by previous root-canal treatment.The orthograde retreatment of dental elements previously treated with the most varied techniques is a fairly common clinical practice, particularly for endodontic specialists. The need for retreatment has been frequently analyzed by using different points of view. In different European countries, epidemiological studies have shown an elevated number of teeth to be retreated resulting in periapical radiolucencies from poor root-canal therapies (1). Some authors have investigated the diagnostic process, general knowledge on retreatment procedures, and clinical behavior among dental students, general practitioners, and specialists.The decision making process should consider the many different variables, as clearly illustrated by Reit and Dahlen (2). Some authors have reported better clinical results with surgical procedures compared with orthograde retreatment (3), although others have reported similar clinical outcomes using both techniques with slight differences related only to the time element (4).In addition, only a few clinical trials have assessed orthograde retreatment efficacy, and most were conducted more than 10 yr ago. Bergenholtz et al. (5) reported a success rate of 78% in teeth with periapical pathologies and 94% in teeth without. Others, reviewing earlier literature on retreatment, reported a favorable outcome for greater than 66% of the study cases considered for the literature analysis (6). Allen et al. (7) obtained a favorable 65.6% outcome in a sample group of 667 subjects controlled after 6 months or more.On the contrary, other authors related their outcomes to microbiological problems to discriminate root-canal retreatment. Sundqvist et al. (8), for example, reported an overall success rate of 74% of 50 cases examined after retreatment. They found that the success rate in bacteria-free canals was almost 80%; whereas in teeth with particular bacteria species the outcome was significantly lower (66%). In a study by Sjogren et al. (9), sim...

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Surgical retreatment of teeth previously treated with surgery is a valid alternative to extraction. However, association with post-treatment disease was greater than after a primary surgical approach.

Single versus multiple visits for endodontic treatment of permanent teeth.