Purpose: Control over marginal bone loss (MBL) and its progression is critical for preserving peri-implant tissue health. A moderate MBL over the first year has conventionally been associated with clinical success. However, different implants are associated with distinct amounts of MBL during their first functional year. Therefore, this study evaluated the MBL in pristine maxillary bone around implants with different types of implant-abutment connections and sought to determine the effect of other clinical factors on this tissue response. Materials and Methods: Two hundred forty-six implants were placed in 101 patients with a mean age of 54.43 years. The MBL around two different types of implants (internal versus external prosthetic connection) was evaluated at 6 and 18 months after loading. Different variables were recorded to analyze their influence on radiographic parameters using a complex samples general linear model. Results: At 18 months, MBL ranged from 0 to 3.56 mm; less than 1 mm was lost around 46.3% (mesial) and 40.2% (distal) of the implants, while no bone was lost around 19.5% (mesial) and 19.9% (distal). The MBL was significantly higher around external than internal connections (0.714 vs 0.516 mm/year, respectively). Age, smoking habit, and connection type were directly related to mesial and distal MBL at 6 and 18 months postloading. Conclusion: Implant design is a key factor in peri-implant MBL. Age and smoking also play major roles in maintaining the stability of peri-implant bone. Schlagwörter: dental implant, dental implant design, dental prosthesis, implant-abutment connection, implant-abutment interface, marginal bone