Different types of internal implant–abutment connections, namely hexagon and conical, have been used for implant restoration. However, data regarding the benefits of these internal connections in terms of clinical outcomes are scarce. Accordingly, the aim of this study was to compare radiographic marginal bone loss (RMBL) and associated implant complications between implants with internal hexagon (IH) connections and those with internal conical (IC) connections. Forty-nine patients with 98 implants (two per patient) placed in the posterior mandible were recruited. All implants were inserted in pairs in solid D2 bone according to a randomized sequence; the first patient received an IH connection implant on the mesial side while the second patient received an IC connection implant on the mesial side. Each patient received one implant with an IH connection and one with an IC connection, placed side-by-side. Four months after placement, all implants were loaded with single screw-retained ceramic restorations with internal hexagon or conical connections. RMBL and complications, including implant/prosthesis failure, were recorded at the time of implant loading (baseline) and 6, 12, and 36 months after loading. The results revealed no significant between-group differences in RMBL (P = .74), gingival bleeding on probing (P = .29), and complications (P = .32). Thus, the type of internal implant–abutment connection did not affect clinical outcomes, including RMBL and implant/prosthesis failure. Future studies should additionally evaluate long-term prosthesis-related complications such as screw loosening and fracture between the two types of internal connections.

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