One of the most frequent causes of tooth loss is vertical root fracture, which occurs primarily, although not exclusively, in association with root canal treatment. Vertical root fractures tend to develop slowly and often go unnoticed until clinical signs and symptoms occur, by which time extraction may be the only possible treatment. Apical surgery, also known as endodontic microsurgery, has proved to be a successful modality for treating persistent or recurrent endodontic infection, but it may jeopardize the long-term prognosis in teeth that have already undergone endodontic therapy.
To determine the frequency of vertical root fractures in teeth treated with apical surgery, von Arx et al from the University of Bern, Switzerland, conducted a retrospective study of 864 patients who had been treated with apical surgery over a 20-year period. All surgeries had been performed by the same surgeon in a dedicated surgical room, under local anesthesia and using a surgical microscope. Follow-up took place at 1, 5 and 10 years after surgery; all teeth in this study had at minimum a follow-up of 1 year. Vertical root fractures were identified in extracted or surgically removed teeth.
The overall rate of vertical root fracture after apical surgery in these teeth was 4%. Thirty-three percent of the vertical root fractures occurred in mandibular first molars; slightly more than one-quarter occurred in maxillary second premolars. Fractures occurred most frequently in the mesial root of mandibular molars. Vertical root fractures occurred in <1% of treated maxillary anterior teeth; fractures in mandibular premolars were also rare. No significant difference in the incidence of vertical root fracture was found between men and women or between primary and repeated apical surgery. The percentage of vertical root fracture rose as the patient’s age increased, but the increase did not achieve statistical significance. Two-thirds of the vertical root fractures occurred within the first year after apical surgery.
Previous studies have shown that maxillary premolars and mandibular molars (especially the mesial root of mandibular first molars) are at the highest risk for vertical root fractures, a conclusion this study supports. Those studies also demonstrated that endodontic retreatment significantly increased the number of cracked and fractured roots. The most important takeaway from this study is its finding that vertical root fractures are infrequent following treatment with apical surgery or resurgery.