Periodontium Regeneration and Development

Connective Tissue and Periodontal Cells

• Connective tissue, PDL, bone, and cementum are derived from undifferentiated connective tissue cells.
• These cells develop into fibroblasts, osteoblasts, and cementoblasts.

Regeneration of the Periodontium

• Regeneration is a continuous physiologic process under normal conditions.
• New cells and tissues are formed to replace mature and dead cells.
• This process is termed "wear and tear repair".

Regeneration during Destructive Periodontal Disease

• Gingival and periodontal diseases are chronic inflammatory conditions that involve healing processes.
• Bacteria and bacterial products prevent healing from proceeding to completion.
• When bacterial plaque is removed, the inherent regenerative capacity of tissues is established.

Repair and Healing

• Repair is the restoration of the continuity of the diseased marginal gingiva.
• It involves the reestablishment of a normal gingival sulcus at the same level as the base of a preexisting pocket.
• This process is called "healing by scar".
• Bone loss is arrested with mobilization of epithelial and connective tissue cells into the damaged area.

New Attachment and Reattachment

• New attachment is the embedding of new PDL fibers into new cementum and attachment of epithelium to a tooth surface.
• Reattachment is not the correct term, as new fibers are formed and attach to new cementum.
• Reattachment refers to repair in areas of the root not previously exposed to pockets.

Animal Studies

• Animal studies can be used to evaluate periodontal regeneration and new attachment.
• This method involves extraction of the examined tooth with its periodontium after successful treatment.

Reconstructive Surgical Techniques

• Reconstructive techniques can be subdivided into three major therapeutic approaches:
  • Non-bone graft-associated
  • Graft-associated
  • Biologic mediator-associated
• Clinicians often combine these approaches in clinical practice.

Non-Graft-Associated Reconstructive Procedures

• These procedures aim to achieve new attachment or periodontal bone regeneration.
• GTR (Guided Tissue Regeneration) is the main procedure used in clinical practice.
• Laser-assisted new attachment procedure (LANAP) may also result in new attachment and regeneration.

Guided Tissue Regeneration (GTR)

• GTR is used to prevent epithelial migration along the cemental wall of the pocket.
• It maintains space for clot stabilization.
• GTR involves placing barriers (membranes) to cover the bone and periodontal ligament, excluding the epithelium and gingival connective tissue.

Principles of Non-Graft New Attachment

• Complete removal of all irritants with or without exposure of the area with a flap.
• Occlusal adjustment may be indicated if there is trauma from occlusion.
• The possible outcomes of therapy depend on which cells populate the area first:
  • Epithelial cells: long junctional epithelium
  • Gingival connective tissue cells: fibers parallel to the tooth surface and remodeling of the alveolar bone
  • Bone cells: root resorption and ankylosis
  • Periodontal ligament cells: new formation of cementum and PDL (new attachment)

Evaluation of New Attachment and Bone Regeneration

• Clinical methods: comparison of pre and post treatment records of pocket probing, attachment level, gingival indices, and alveolar bone level.
• Radiographic methods: standardized technique is needed for reproducible positioning of the film and the tube.
• Surgical re-entry: evaluation can be performed by taking repeated impressions.
• Histologic methods: type of attachment can be determined only by histologic analysis of tissue blocks obtained from the healed area.