Periodontal Therapy and Tissue Regeneration

Guided Tissue Regeneration (GTR)

• The ultimate goal of periodontal therapy is to not only stop the progression of periodontal disease but also to restore the damaged supporting apparatus.

Periodontal Healing

• Regeneration: the growth and differentiation of new cells and intercellular substances to form new tissues, occurring by growth from the same type of tissue that has been destroyed or from its precursor.
• Regeneration in the periodontium:
  • Gingival epithelium is replaced by epithelium.
  • Connective tissue, PDL, bone, and cementum are derived from undifferentiated connective tissue cells that develop into fibroblasts, osteoblasts, and cementoblasts.

Regeneration under Normal Conditions

• Regeneration of the periodontium is a continuous physiologic process, where new cells and tissues continuously replace mature and dead cells, termed "wear and tear repair".

Regeneration during Destructive Periodontal Disease

• Most gingival and periodontal diseases are chronic inflammatory conditions, and regeneration is part of the healing process.
• Bacteria and bacterial products can prevent healing from proceeding to completion, but removing bacterial plaque and preventing its reformation allows the inherent regenerative capacity of tissues to establish.

Repair and New Attachment

• Repair: restoration of the continuity of the diseased marginal gingiva and re-establishment of a normal gingival sulcus at the same level as the base of a preexisting pocket, involving mobilization of epithelial and connective tissue cells with increased mitotic division.
• New attachment: the embedding of new PDL fibers into new cementum and attachment of epithelium to a tooth surface previously denuded by disease.

Reattachment and Epithelial Adaptation

• Reattachment: the reunion of the connective tissues with a root surface on which viable periodontal ligament tissue is present, used to describe the healing of areas of the root not previously exposed to pockets.
• Epithelial adaptation: close apposition of the gingival epithelium to the tooth surface without complete obliteration of the pocket, which may be as resistant to disease as true connective tissue attachments.

Regeneration of PDL and New Attachment

• Regeneration of PDL is the basis for new attachment because PDL provides continuity between the alveolar bone and cementum, and contains cells that can synthesize and remodel the 3 connective tissues of the alveolar part of the periodontium.

Possible Outcomes of Therapy

• During healing stages of a periodontal pocket, the area is invaded by cells from 4 different sources, modifying the final outcome of pocket healing:
  • Oral epithelium: results in a long junctional epithelium.
  • Gingival connective tissue: results in fibers parallel to the tooth surface and remodeling of the alveolar bone, with no attachment to the cementum (recurrence of pocket).
  • Bone: may result in root resorption and ankylosis.
  • Periodontal ligament: results in new formation of cementum and PDL (new attachment).