# A Novel, Minimally Invasive Method to Retrieve Failed Dental Implants in Elderly Patients
## 2 Materials and Methods  
This study followed a retrospective cohort design. More specifically, a sample of patients treated in a private dental clinic (Santiago, Chile) had their data reviewed after receiving an indication for implant removal. The following study was approved by the ethics committee of the Eastern Metropolitan Health Service (SSMO) of Santiago (Chile), and performed following the principles outlined in the Declaration of Helsinki. Since this study was based on data from patient forms, no research-specific consent form was applied. However, all patients had read and signed a consent form before dental treatment, agreeing with the possible confidential use of their clinical forms for research. Consent for clinical care was sought after notifying patients about implant failure, proposed treatment procedures, and risks/benefits. The study included all 150 patients treated between 2017 and 2020, wherein 199 implants were considered as failed. A dentist with 15 years of experience in oral implantology examined the patients and decided on implant removal based on biological, mechanical, or iatrogenic causes. Removal was indicated as part of the treatment plan. Among patients with an indication for implant removal, we included only independent elderly adults (60 years or more). Participants had a pretreatment history of osseointegrated implants exposed to the oral environment. Moreover, inclusion depended on having implants with at least one of the three conditions: (1) horizontal bone loss observed through routine oral radiographs, greater than the first three threads of the implant and associated with signs of peri-implant inflammation; (2) implants without the possibility of predictable prosthetic rehabilitation or with possible aesthetic implications, and (3) defective retention system, i.e., damaged hexagon, deformed internal thread or fractured abutment screw with no possibility of removal. Furthermore, the exclusion criteria were (1) radiographic image compatible with lack of osseointegration, (2) implant mobility, and (3) implants with pain to percussion test. Retrieval of all implants was initiated by using a reverse torque implant removal toolkit (Neo Fixture Remover, Neobiotech, Seoul, Korea; Figure 1), without the requirement of raising a flap. Implant retrieval begins by inserting a torqued stem at 40-80 Ncm into the internal implant thread, followed by the attachment of an implant extractor device (Figure 1A), which is screwed to the initial stem in the opposite direction. When both devices were assembled, counter-torque is performed using a torque ratchet (Figure 1B), at which the removal device is firmly fixed to the implant. In turn, removal occurs consequently to reverse torque oscillating between 100 and 500 Ncm (Figure 1C,D). Traditional trephination took place whenever implant removal was not viable by the previous technique. In those cases, a flap was raised to expose the failed implant. In turn, peri-implant osteotomy was performed by using a trephine of the same diameter as the implants (Figure 2A). Those cases counted as failed use of the reverse torque system (Figure 2B). Data collected from patient forms for this study included: (1) implant location, by arch (maxilla/mandible) and region (anterior/posterior); (2) cause of failure, classified as iatrogenic (wrong location or impossibility to be rehabilitated), biological (peri-implantitis with poor prognosis in the short/medium term), and mechanical (fractured implant or damaged internal connection); (3) implant connection, external/internal, and (4) removal torque (Ncm). Regarding sample size, this study used a convenience sample corresponding to all potentially eligible patients of the study clinic. That clinic has used the tested implant removal equipment since its clearance for patient use in Chile in 2017. Statistical analysis was performed using SPSS version 22.0 (SPSS Inc, Chicago, IL, USA) with a significance level of 0.05. The Shapiro-Wilk test was used to evaluate data distribution.