## 3 Discussion  
Loss of occlusal support can impair the masticatory performance and change the neuromuscular pattern of the jaw during masticatory activity [16; 17]. When the posterior molars are missing for a long time, interim restorations are required to establish a new vertical dimension of occlusion and to give the joint and neuromuscular system the time to adapt [18]. In particular, the long-term use of interim restorations during implant treatment has been recommended [19]. In this clinical report, the interim restorations were fabricated using the CAD-CAM method, and used for 3 months to allow the settling of the abutment to the implant and stabilization of the temporomandibular joint and neuromuscular system. Afterward, the crown design was modified in accordance with the newly established vertical dimension with digital techniques, and then converted to monolithic zirconia using the milling method. The use of CAD allowed the application of modifications according to functional and aesthetic demands [20]. Image replacement of the abutments using the image superimposition technique enhanced the marginal fit of the definitive restorations. The workflow is also applicable to prefabricated abutments and different types of retention systems, such as screw-or cement-retained prosthesis.  
Long-term use of interim restorations is necessary during the course of treatment using oral implants or in situations involving comprehensive occlusal reconstruction [19; 20]. Since the introduction of computer-aided design and computer-aided manufacturing (CAD-CAM) to dentistry by [PERSON] et al. [21], CAD-CAM has become an alternative to the conventional methods used for fabricating fixed interim restorations [22]. [PERSON] et al. [23] demonstrated that CAD-CAM poly (methyl methacrylate)-based interim crowns had a superior marginal fit and a uniform internal gap compared to manually fabricated crowns. [PERSON] et al. [24] reported that CAD-CAM interim crowns had higher surface hardness and wear resistance. [PERSON] et al. [25] showed high flexural strength in CAD-CAM interim polymers than in the bis-acrylate composite resin and conventional acrylic resin. [PERSON] et al. [20] mentioned the use of CAD-CAM-fabricated high-density interim restorations enabled predictable and easier results in the prolonged pretreatment phase.  
Even though this digital method can overcome the challenge of occlusal changes in the initial period after the delivery of restorations, a reliable connection between the implant and abutment should be confirmed to decrease the axial displacement of the abutment under functional loading [10; 12; 26]. The implant screw must be tightened with adequate torque to achieve the optimum preload [12; 27; 28]. In the present study, the abutment screw was retigitened when the interim restoration was removed for taking the second impression, three months after the abutment connection. This additional retigitening would be beneficial to compensate for the loss of vertical position of restoration caused by settling in actual clinical practice. Although the use of dental implants to restore edentulous sites is recognized as  
Figure 5: Follow-up image 8 months after the end of the treatment.  
a verified treatment modality, a longitudinal outcome study [29] reported the incidence of early and late infectious postoperative complications that could lead to treatment failure, including the loss of vertical dimension. Thus, careful clinical and paraclinical examinations on postoperative infection are also needed for the maintenance of oral function.  
The limitation of this workflow is that the types of prostheses for which the described digital techniques can be applied are limited to the monolithic zirconia because the prostheses are mainly designed using computer software. Further comprehensive clinical studies on diverse dedulous patients are required to validate the effects of this digital technique.