Triangular Versus Circular Implant Neck Design and Their Effect on Marginal Bone Loss: a Systematic Review.

OBJECTIVES: This literature review evaluates the differences between triangular and circular neck designs and their influences on marginal bone remodelling as well as peri-implant hard and soft tissue health. The primary aim was to compare implant survival and hard-tissue outcomes (peri-implant bone level, implant stability quotient and insertion torque). The secondary aim was to compare soft-tissue outcomes (probing depth, bleeding on probing, plaque index and full-mouth plaque score). MATERIAL AND METHODS: The literature review followed PRISMA statement and used a PICOS-based focus question. An extensive search was conducted in MEDLINE (PubMed), Embase, Cochrane Library and Web of Science for studies published between December 1, 2015, and December 1, 2025. Inclusion criteria focused on human adult clinical studies, triangular vs circular neck implants, ≥ 3 months follow-up, and reporting at least one relevant clinical/radiographic parameter. Study risk of bias was assessed using the Joanna Briggs Institute Checklists. RESULTS: From 2999 identified records, 5 studies were included, comprising a total of 86 patients with follow-up ranging from 3 to 60 months. All studies compared triangular and circular neck implants. Implant survival was 100% in all studies. No significant differences were found in insertion torque, implant stability quotient and soft-tissue parameters. Two studies reported significantly lower (P ≤ 0.05) peri-implant bone level with triangular neck implants, while others found no significant differences. CONCLUSIONS: The results indicate that triangular and circular implant neck designs demonstrate comparable clinical performance, with no clear differences in implant survival, insertion torque, implant stability quotient, and in soft-tissue outcomes. Peri-implant bone level may be lower with triangular neck implants in some settings, but findings are inconsistent across studies and limited.