Screw loosening remains a frequent complication with implant-supported prostheses. While clinical evidence suggests that posterior single implant crowns present a high rate of complications, whether the absence of interproximal contacts with adjacent natural teeth is a contributing factor to these complications remains unclear.

The purpose of this finite element analysis study was to evaluate the biomechanical behavior of single implant-supported crowns placed in the posterior mandible. Two variables were investigated: the impact of implant position (first molar versus second molar) and the nature of the interproximal contact with the adjacent teeth (mesial versus mesial and distal interproximal contacts).

Three mandibular models were constructed using microtomography: fully dentate (control), partially edentulous with a missing second molar replaced by a single implant-supported crown (mesial interproximal contact only), and partially edentulous with a missing first molar replaced by a single implant-supported crown (mesial and distal interproximal contacts). The finite element analysis simulated occlusal loading during masticatory function. Stress distribution was evaluated by using the von Mises stress criterion, with principal stress analysis for bone anisotropy. Model validation was performed against experimental tooth displacement data.

Implants with both interproximal contacts (first molar position) exhibited more evenly distributed stress and significantly lower stress concentrations on the implant neck compared with the implant with only a mesial interproximal contact (second molar position). The second molar position showed higher stress at the implant-abutment connection.

Implant positioning and the number of interproximal contacts significantly influenced stress distribution and prosthesis stability. Implants placed between natural teeth present a lower risk of screw loosening and enhanced long-term crown stability.