Use of narrow-diameter implants in totally edentulous patients: a systematic review

Background: the objective of the present review was to evaluate the rehabilitation of edentulous patients through removable and fixed full arch dentures supported by narrow implants with a diameter from 2,5 mm to 3,5 mm. Methods: a systematic literature search with predetermined inclusion criteria was performed using the PubMed, cochrane library and google Scholar database to find rel- evant articles on clinical studies published in english language up to March 2017. the preliminary assessment of patients, intervention, comparison and outcome (Pico process ) was used to define the search strategy. Were included in the study randomized clinical trials, retrospective or prospective cohort studies involving implants with diameter 2.5 mm to 3.5 mm placed in edentulous patients. Follow up duration of at least 6 months following implant placement was required. Data were extracted by three review authors using data collection forms. Data collected were used to calculate the estimated survival rate at five years (%) with a standard Poisson regression analy- sis. For each study the estimated marginal bone loss (MBl) at 5 years was calculated by dividing the MBl reported by years of follow-up and multiplying for five. Results: eight clinical studies on rehabilitations supported by narrow diameter implants were identified. all studies were referred to over-dentures, with an average survival rate of 96%. No studies with sound data on full arch rehabilitations were found. overall, 368 patients received 825 implants. the identified narrow diameter implants were comprised between 2.5 and 3.3 mm. Follow-up ranged from 6 months to 7.6 years. only three of the eight studies reported the implant success rate, with the following values: 100% to 12 months follow-up, 52.3% to 7.6 years follow-up and 94% to five years follow-up. reported survival rates ranged from 84.7% to 100%. the estimated survival rate after five years(%) varied between 86.19% and 98.82%, derived from Poisson regression analysis. after normalization of the results, a weighted average was obtained with a confidence interval of 95% for survival with a value of 95. 4%± 4.3. all studies reported the bone level changes at the end of each follow-up. Mean MBl ranged from 0.48 mm to 2.45 mm with a follow-up ranged from 6 months to 7.6 years. Only two studies assessed the patient satisfaction with NDi, by questionnaires based on visual analogue scales (VaS) at 6 months and one year, respectively. in both studies the overall patient’s satisfaction was high (score>60). coNclUSioNS: clinical data, from this systematic review, suggest that NDis (2.5mm-3.3mm) represent an alternative treatment option to bone augmentation procedures, in the rehabilitation of edentulous jaw with limited width. the weighted average of the estimated survival rate at 5 years was similar to regular diameter implants. the average MBl value after five years was 1.39 mm similar to those reported for standard implants. Patient satisfaction was generally higher when compared with studies analyzing bone graft- ing, but the evidence was limited. Moreover the quality and level of evidence was limited in general and with a high risk of bias, so caution is advised when interpreting these data. Further studies are required to determine predictability and possible applicability for SDis also in supported fixed full- arch restorations.