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AIM: The aim of this study was to compare clinical and radiographic outcomes of dental implants with different neck characteristics. METHODS: A protocol-oriented search aimed at the question: "In patients subjected to tooth replacement with screw-type dental implants does the modification of the implant neck macro- or microgeometry contribute to the improvement of survival rates and maintenance of the peri-implant marginal bone levels?" Primary outcomes were survival and marginal bone level (MBL) changes evaluated on randomized controlled trials with >10 participants and follow-up >1 year. Risk of bias was evaluated using the Cochrane Collaboration's tool. The review follows the PRISMA statement. RESULTS: Forty-three studies compared: (a) One- versus two-piece implants (N = 7); (b) Two-piece implants with different neck characteristics (machined and rough collars, microthreads, LASER microtexturing) (N = 21); (c) Two-piece implants with macrogeometry modifications (tapering, back-tapering, and scalloping) (N = 6). One- and two-piece implants showed similar survival (RR = 0.45, 95% CI: 0.12, 1.66, p = 0.23) and MBL changes (WMD = 0.09 mm, 95% CI: -0.27, 0.45, p = 0.64) at 1-year post-loading. Machined collar implants have higher risk of early failure than rough collar implants (RR = 3.96, 95% CI: 1.12, 13.93, p = 0.03) and 0.43 mm higher bone resorption (95% CI: 0.0, 0.86, p = 0.05). Microthreads (WMD = 0.07 mm, 95% CI: -0.01, 0.15, p = 0.10) and LASER microtexturing (WMD = 0.15 mm, 95% CI: -0.35, 0.65, p = 0.56) do not reduce bone resorption. Scalloped implants have 1.26 mm higher resorption (95% CI: 0.72, 2.00, p < 0.001). CONCLUSIONS: One- and two-piece implants have similar survival and MBL changes. Rough collar implants have lower MBL changes than machined collar implants. Additional modifications to rough collars are irrelevant.
Messias et al. (Thu,) studied this question.