The complication of the natural tooth adjacent to the distal end implant has frequently been reported. The vertical root fracture occurred in heavily restored teeth near the implant, especially in Kennedy’s Class I and Class II edentulous area. Previous studies suggested that the occlusion design of the implant may cause overload in the adjacent tooth. This cross-sectional study aimed to compare the relative occlusal force between the implant in the distal end and the tooth adjacent to the implant in maximum intercuspation. Patients with implant restoration replacing teeth in free end space adjacent to natural tooth were recalled. The occlusion is examined as a shim stock passes through the occluded tooth in heavy or light bites. The heavy bite or a light bite with shim stock that cannot pull through is HB1 or LB1. If the shim stock can pull through it is considered HB0 or LB0. The implant is classified into 3 groups, HB1LB0, HB1LB1, and HB0LB0. The T-scan was used to determine the relative occlusal force of the implant and adjacent tooth in each group. A total of 20 patients with 45 implants were recalled and examined. The mean duration of the overall functional implant is 3.35 years. The occlusion type of implant with HB1LB1 is 4.44%, HB1LB0 77.77%, and HB0LB0 17.77%. There was a significant different between relative occlusal force of HB0LB0 implant group (M = 1.94, SD = 2.36) and adjacent teeth (M = 11.64, SD = 7.54); p = 0.025. The relative occlusal force of the distal end implant and the adjacent mesial tooth was a statistically significant difference in maximum intercuspation of the HB0LB0 group. Further prospective control or randomized control study should be conducted to find the cause-relationship between the occlusion of the implant distal end and failure of the adjacent tooth to prevent harming both the implant and the adjacent natural tooth.