Guided tissue regeneration

Guided tissue regeneration (GTR) is the use of barrier membranes to exclude the superficial gingival tissues from a healing periodontal surgical wound and thus promote wound repopulation by cells of the periodontal ligament which are able to regenerate the periodontium. The basic technique involves the placement of a thin membrane overlying the periodontal defect under the gingival flap during periodontal surgery. The membrane is secured in place, usually with an internal suture, and the flap is repositioned and sutured over the membrane (< ?xml:namespace prefix = "mbp" />Figures 12.1 and 12.2). Originally, membranes made of expanded PTFE fibres (GORE-TEX) were used. This material is very biocompatible, but the main disadvantage of its use is that a second surgical procedure is required 6 weeks after membrane placement in order to remove the material. Consequently, a range of resorbable membrane materials have been developed that are used in a similar way but do not require re-entry surgery at a later date. These include membranes of polylactate/polyglycolate polymers (similar to the material used for resorbable sutures) and membranes made from collagen obtained from animals, typically of bovine source.

Fig 12.1 Diagram of the principles of guided tissue regeneration. (A) Pocket formation and infrabony defect. (B) Flap raised surgically, and granulation tissue from infrabony defect removed. (C) Membrane placed over defect. (D) Flap replaced and sutured. Membrane forms a barrier to exclude gingival tissues from surgically debrided defect and promotes wound repopulation by cells migrating from the periodontal ligament and bone (arrows).

Fig 12.2 Membrane placed in defect during GTR surgery.

Graft materials

A wide range of graft materials have been described for placement in periodontal defects to promote periodontal regeneration. The types of graft are summarized in Table 12.1. The biological principle behind their use is that they act as a three-dimensional scaffold within the surgical defect to promote the in-growth of periodontal ligament and bone cells, ultimately resulting in resorption of the graft and replacement with healthy bone. In addition, theoretically, some of these materials have bioactive properties such as the presence of growth factors within the matrix that may further promote regeneration. However, the significance or superiority of this potential activity has not been convincingly demonstrated over and above the “osteoconductive” activity of the graft as a scaffold material. Histological studies of graft materials suggest that in some cases they are not completely resorbed but become merely encapsulated by fibrous tissue. Thus, there is debate about whether the radiographic appearance of bone regeneration seen with these methods is actually always equivalent to true periodontal regeneration. Nevertheless, the clinical improvements seen with grafting materials are similar to those of other regenerative techniques.

Table 12.1 Types of graft material for periodontal regeneration