## 1 Introduction  
Severe dental caries, extensive tooth fracture, and severe periodontitis can result in impaired masticatory ability, and subsequent tooth loss is very debilitating in elderly people [1, 2, 3]. Replacement of the missing teeth with dental implants is a common treatment modality for restoring the masticatory ability [4, 5]. Restoring the posterior edentulous area with implant-supported restorations can not only significantly improve the patient's masticatory function [6], but also relieve the psychological stress by its chewing effect [7]. A patient-centered retrospective study reported that the oral health-related quality of life and overall treatment satisfaction were high in the implant-supported fixed dental restorations [8].  
Occlusional contact loss can occur after the delivery of implant-supported fixed dental prostheses. There are several possible reasons for the changes in occlusion following the prosthetic restoration of the posterior area. First, the prosthesis sinking phenomenon can be caused by the loading applied to the implant-abutment connection in clinical practice [9, 10]. The micro-roughness and irregularity of the surface at the connection of the implant and abutment can get flattened by the torque tightening, resulting in a reduced distance between the contacting surfaces [7]. Moreover, compressive force by long-term occlusal loading could generate plastic deformation of the interface of connection [11]. This settling phenomenon induces the axial displacement of the prosthesis [12]. The amount of settling of abutments to implants varies in all implant systems, and it has been reported that the implants with internal conical connection have higher settling values than those with external hexagonal connection [9; 12]. Mandibular dislocation was reported in partially edentulous patients without molar supports [13]. In the unilateral occlusal support, the loss of vertical support resulted in the upward movement of the mandible in the posterior region during clenching. Analysis of the movement amplitude showed a significant difference between the edentulous conditions of the posterior teeth [14]. Analysis of electromyographic activity also revealed that the unilateral occlusal support tended to cause a unilateral activity of the masticatory muscles [14]. The muscle activity caused larger compressive loading in the contralateral temporomandibular joint that was related to the movement of the mandible. A persistent loss of posterior support could be problematic. Repetitive loading on the joint could reset the three-dimensional positions of the condyle and mandible differently from the previous position with the posterior teeth. When the upward movement on the edentulous side is applied consistently, the mandible could be settled in the displaced position.  
Implant treatments involve a period of edentulous state for the healing of extraction site and osseointegration of the implants except for the concept of immediate placement and loading [15]. Thus, mandibular dislocation could be crucial in posterior edentulous patients who are planned to receive implant-supported fixed dental prostheses. After prosthesis delivery, the functional forces of the constrictor muscles are recovered that could induce changes in the mandible in the maximal intercuspal position. Thus, this resettling could be the cause of the loss of occlusal contact that occasionally occurs after the delivery of the implant-supported prostheses in the free-end edentulous cases. The present case demonstrates a strategic workflow for minimizing the initial occlusal contact loss of implant-supported fixed prostheses in the posterior region by using a computer-aided design and computer-aided manufacturing (CAD-CAM) interim prosthesis, further intraoral optical impression for registration of the newly established vertical dimension of occlusion, digital image matching technique, and computer design modification.