Background: Dental implants that are 2.0 mm in diameter or smaller (mini-implant, small diameter implant) have been advocated as an acceptable alternative to conventional diameter implants (3.0-5.0 mm diameter) for definitive oral restoration. Studies indicate that under normal intra-oral loads, the pattern of force transmitted to supporting crestal bone increases in inverse proportion to the implant diameter. For conventional diameter implants, these stresses were not predicted to exceed physiologic limits. However, none of the available studies investigates implant diameters less than 3.0 mm. Extrapolation of the data suggests that further reduction of implant diameter would induce greater crestal bone stress, possibly beyond physiologic limits. Objectives: A finite element analysis (FEA) study was designed to ascertain if reduction of implant diameter to 1.8 m would, (1) increase cervical bone stress and (2) result in non-physiologic stress in the investing bone. Materials and Methods: A finite element model of a 1.8 mm Χ 12 mm titanium implant was produced through micro computed tomography scanner (Scanco, Switzerland, FEA elements = 144,194. FEA nodes = 162,784). Results: Crestal bone stresses increased as predicted and Von Mises stresses (an average of 300 MPa) exceed the trabecular and cortical bone yield stress of 100 MPa and 33 MPa respectively. Conclusion: The results indicate that, for implants of 1.8 mm diameter, normal occlusal forces can induce stresses that are destructive to investing bone.