Advances in Dental Research, Vol 13, 162-169, Copyright © 1999 by International & American Associations for Dental Research
Two-stage implant systems
M. E. Fritz
Emory University School of Medicine, Department of Surgery, 954 Gatewood Road, Atlanta, Georgia 30322, USA.
Since the advent of osseointegration approximately 20 years ago, there has
been a great deal of scientific data developed on two-stage integrated
implant systems. Although these implants were originally designed primarily
for fixed prostheses in the mandibular arch, they have been used in
partially dentate patients, in patients needing overdentures, and in
single-tooth restorations. In addition, this implant system has been placed
in extraction sites, in bone-grafted areas, and in maxillary sinus
elevations. Often, the documentation of these procedures has lagged. In
addition, most of the reports use survival criteria to describe results,
often providing overly optimistic data. It can be said that the literature
describes a true adhesion of the epithelium to the implant similar to
adhesion to teeth, that two-stage implants appear to have direct contact
somewhere between 50% and 70% of the implant surface, that the microbial
flora of the two-stage implant system closely resembles that of the natural
tooth, and that the microbiology of periodontitis appears to be closely
related to peri-implantitis. In evaluations of the data from implant
placement in all of the above-noted situations by means of meta-analysis,
it appears that there is a strong case that two-stage dental implants are
successful, usually showing a confidence interval of over 90%. It also
appears that the mandibular implants are more successful than maxillary
implants. Studies also show that overdenture therapy is valid, and that
single-tooth implants and implants placed in partially dentate mouths have
a success rate that is quite good, although not quite as high as in the
fully edentulous dentition. It would also appear that the potential causes
of failure in the two-stage dental implant systems are peri-implantitis,
placement of implants in poor-quality bone, and improper loading of
implants. There are now data addressing modifications of the implant
surface to alter the percentage of osseointegration. New types of
reinforcements for dental implants and the use of growth factors to augment
bone regeneration so that implants can be placed more easily are now being
actively investigated.
