Purpose: The purpose of this in silico study was to determine appropriate implant treatment planning using three implant diameters and four different superstructures in enlarged mandibular first molar areas. Materials and Methods: A mandibular bone block was constructed, and four configurations using three implants (2.9 × 10 mm, 4.1 × 10 mm, and 4.8 × 10 mm) were created for the first molar area. The four superstructures were designed as one large crown for a widediameter implant, a crown with a cantilever for a wide-diameter implant, two splinted crowns of one standard-diameter and one narrow-diameter implant, and two separate crowns of one standard-diameter and one narrow-diameter implant. Vertical loads of 200 N and oblique loads of 100 N were applied to various predetermined spots on the occlusal surfaces of these superstructures. Principal and von Mises stresses were analyzed on both the cortical bone and implant structures. Results: Stresses were intensified in the cortical bone around the implant neck and implant-abutment interface. The highest compressive (36.97 MPa) and von Mises (265.71 MPa) stress values were noted in the model with standardand narrow-diameter implants supporting two separate crowns. The lowest compressive (15.86 MPa) and von Mises (16.36 MPa) stress values were observed in the model with a distally positioned wide-diameter implant supporting the crown with a cantilever. Conclusion: In an enlarged first molar area, a configuration with a wide-diameter implant near the second molar and a cantilevered crown might distribute stresses more favorably than other configurations. Keywords: crown, dental implant, finite element analysis, mandible, molar