Cluster Phenomenon In Implantology

Introduction: Several studies on dental implants report a low failure rate. Most of these failures take place in a small number of patients. The occurrence of several failed implants in the same patient has been called cluster effect. Aim: To study the cluster cases in the patients attended at the Department of Oral and Maxillofacial Surgery of the University Clinic of Navarre (Spain), between: January 2006 - March 2009. Methodology: A table was designed to register cases of patients treated with dental implants that failed. A case was considered as cluster when there were at least three failed implants (one more implant than the average number of failures in patients with implant loss). Clusters cases were compared with general failures under the following variables: immediate implant placement after extraction, previous periodontal disease, periapical infection at the implant placement, patients under antidepressing treatment, necessity of bone graft and/or maxillary sinus lift, time elapsed between implant placement and the implant failure, and repetitive failures in the same patients. Results: 586 patients were attended with 2608 placed implants. Of 134 patients with failures, 12 were identified as cluster; 59 of 247 failed implants, failed in cluster form. Whereas the average quantity of failures in cluster patients was 4,91 aproximately 5 implants per patient; in patients without cluster, the average quantity of failures was 1,54. Additionally, 24 % of the failures took place in 12 patients. Conclusions: In the studied group, there seem to be a relation between clusters cases and the immediate implant placement after extractions, patients under antidepressing treatment, need of bone graft and previous periodontitis.