There are two types of dental implants, immediate and delayed dental implants;
Immediate Implants
Immediate Implants can be placed when the temporary crown that goes on top of the implant, or the denture that goes on top of the several implants, will not traumatize or overly stress the implant(s) during chewing function. What we have learned in the past few years is that if you have most of your teeth, and the temporary crown that goes on the implant is made just for esthetics but not to chew against the opposing tooth for several months, the implant can function without being damaged. The final crown will be placed usually within 3-5 months after the initial implant placement.
Immediate implants have also been used successfully on the lower arch when the lower arch has no teeth and the upper arch has a denture. There are many considerations for success including: density of the bone, length and width of the implant, the curve of the lower arch, how forceful the bite is, and also whether the patient grinds their teeth at night in their sleep. In addition, the overall medical status and age can also play a role. Taking all these into consideration, there are still a lot of people who are still candidates for immediate placement. This should be decided together with the dentist as well as the surgeon placing the implant(s).
It should be noted that statically, implants that are left for the normal healing period of 3-5 months before being subject to bite pressure run a higher percentage success rate.
Delayed Implants
Delayed Implants is the traditional method for placing implants. The dentist under local anesthesia raise the gum at the desired site, places the implant body but not the post, and then covers the top of the implant with the gum. He then waits 3 months in the lower jaw, or 5 months in the upper jaw. When that time has elapsed, using local anesthesia, he reopens the gum, removes the implant cover screw, replaces that with a taller screw called a healing collar. Two weeks he later replaces that with an abutment (also known as a post). He now places a temporary crown made of plastic. After 3 -4 weeks of chewing on this, impressions are taken of the post and sent to the laboratory. The laboratory will then make the final crown, which the dentist will try in, and let the patient wear, usually with an intermediate strength cement. This is done so that if the dentist has to get back into the implant, he can still remove the crown over it. This ability to get back into the underlying implant is important and in certain situations the dentist uses a screw retained crown for the same purpose. This also permits him to get re-entry into the underlying crown implant.
This is how the vast majority of implants are done for the patient.
Read more about dental implants here.