There are four types of bone in the human face and the length of treatment for placing and restoring implants with a "tooth" and crown depends on which type of bone the implant is placed in. Implants have to integrate with the surrounding bone before a tooth and crown is placed on it.

Type I bone is comparable to oak wood, which is very hard and dense. This type of bone has less blood supply than all of the rest of the types of bone. The blood supply is required for the bone to harden or calcify the bone next to the implant. Therefore, it takes approximately 5 months
for this type to integrate with an implant as opposed to 4 months for type II bone.

Type II bone is comparable to pine wood, which isn't as hard as type I. This type of bone usually takes 4 months to integrate with an implant. 

Type III bone is like balsa wood, which isn't as dense as type II. Since the density isn't as great as type II, it takes more time to "fill in" and integrate with an implant. 6 months time is suggested before loading an implant placed in this type of bone. Extended gradual loading of the implant can, however, improve the bone density. 

Type IV bone is comparable to styrofoam, which is the least dense of all of the bone types. This type takes the longest length of time to integrate with the implant after placement, which is usually 8 months. Additional implants should be placed to improve implant/bone loading distribution. Incremental loading of the implants over time will improve bone density. Bone grafting or augmentation of bone are often required. Bone expansion and or bone manipulation can improve initial implant fixation.