The ultimate goal of periodontal therapy is to restore periodontal tis
sues lost through disease or trauma. The most predictable way to accom
plish this goal is by guided tissue regeneration (GTR). The principle
of GTR is to give preference to certain cells to repopulate the wound
area to form a new attachment apparatus. Clinically this is accomplish
ed by placing a barrier over the defect thereby excluding gingival tis
sues from the wound during early healing. The first generation of GTR
barriers were non-resorbable which implies that they have to be remove
d in a second surgical procedure. Resorbable barriers have recently be
en introduced, changing GTR into a single-step procedure. Periodontal
defects that will predictably benefit from GTR therapy are intrabony,
furcation class II and gingival recession defects. This paper reviews
the scientific evidence of what can be achieved by GTR procedures for
various periodontal defects as well as factors of importance to increa
se the predictability of a successful treatment outcome.