Survival rate and clinico-radiographic parameters around narrow-diameter dental implants for fixed dental prostheses in the posterior regions: A systematic review

Narrow-diameter dental implants (NDDIs) are suggested to be a reliable alternative to bone augmentation techniques, but evidence regarding the feasibility of NDDIs in the posterior area is limited. This review investigated the survival rates of NDDIs, as well as peri-implant clinical and radiographic parameters for a fixed dental prosthesis in posterior regions compared to standard-diameter dental implants (SDDIs). One investigator performed an electronic search of the English literature in the Web of Science, PubMed, Scopus, and EMBASE databases until December 2020. The focused question was: "Do narrow diameter dental implants restoring fixed dental prosthesis demonstrate more alveolar bone loss as compared to standard diameter dental implants in posterior maxillary and mandibular regions?" The 9 studies selected for this review assessed a total of 498 patients (250 males, 206 females, aged 19-86 years), 725 NDDIs and 260 SDDIs were placed. The mean follow-up duration was 71 months (range: 12-176 months). A high survival rate of NDDIs was noticed (i.e., 97.37% [range: 94.7-100%]). The mean probing depth and bleeding on probing scores ranged between 3.67 mm and 3.12 mm, and 10% and 33.42%, respectively. However, the only study reporting plaque index (PI) demonstrated a mean PI score of 1.39. The majority of the studies reported mean marginal bone loss scores below 1.0 mm. In conclusion, NDDIs appear to be a feasible treatment option in patients requiring fixed dental prosthesis in posterior regions since they exhibit comparable survival rates to SDDIs, as well as a clinically acceptable peri-implant clinical and radiographic tissue response.