Dental implants have shown a high success rate for rehabilitation of edentulous patients if certain conditions are met during treatment. Nevertheless, the risk of failure remains difficult to predict. The achievement of osseointegration depends on many factors, such as a suitable host, biocompatible materials, careful surgery, and an appropriate healing time [1].

The primary stability comes from the mechanical anchorage between the bone tissue and the pitch region of the implant immediately after implantation. The secondary stability comes from the formation of new vital bone, which replaces the gap between the local bone and the implant surface and replaces the necrotic bone.

The external morphology of the dental implant is a factor which leads to the mechanical engagement of the implant with the bone. Three-thread-design dental implants consist of three different thread designs. The first design is the micro-thread, or supra-fine thread, which is on the coronal third of the implant fixture and is attached to the cortical bone. These small, fine threads are designed for force distribution, an increase in the bone-implant contact area and a decrease in the force concentration at the abutment-implant connection area. The second design is the reverse buttress thread, which is on the middle third of the implant fixture. This design increases the retention between the implant and spongy bone and produces resistance to compressive force. The third design, the condensed thread, is located at the apical third of the implant fixture. The thinness at the beginning of this thread and an increase in thickness along the implant fixture are designed for the soft spongy bone condensability [2].

Osseointegration, a continuous process, represents the coupling of the osteoclast and osteoblast activity for bone repair, formation, and adaptation to function [3, 4]. Implant-bone integration is separated into three phenomena. The first phenomenon is distance osteogenesis. Distance osteogenesis means that bone formation takes place from the local bone toward the implant surface. This event is anticipated to happen in cortical bone healing [5]. The second phenomenon is contact osteogenesis, in which bone formation takes place from the implant surface toward the local bone. This osteogenesis consists of the early phase of osteogenic cell migration, osteoconduction, and de novo bone formation. The de novo bone formation at a solid surface has four stages. The first stage is secretion of the two noncollagenous proteins, osteopontin, and bone sialoprotein. The second stage is calcium phosphate nucleation, which consists of the calcium binding at the calcium binding sites of these proteins. The third stage is the crystal growth phase. The last stage of de novo bone formation is derived from collagen production and subsequent collagen mineralization. Finally, bone remodeling is the third phenomenon of implant-bone integration [6].