Dental implants have an extremely high rate of success. However, there are differences of success rates between the lower and upper jaws. According to studies, lower jaw implants have a 95% rate of success and only 90% for the upper jaw. The reason for this being that the upper jaw is less dense compared to the lower jaw.
The remaining 5% or 10% failures are due to various reasons. The most often cited reason is the failure for the implant in the osseointegration process. If the tooth was placed in the wrong position, the implants might break, the implant may get loose, or worse get infected.