Purpose: To review the biologic rationale behind tissue/bone regeneration; describes the most common methods used to obtain regeneration,; and discusses the factors that influence regenerative success as well as challenges that still need to be overcome.
•The type of healing that occurs after conventional endodontic and periodontal therapy either repair or regeneration.
•Healing is critically dependent on the cell type that repopulates the wound first, thus the cells with the fastest migration rate tend to dominate the initial healing phase
•Epithelial cells migrate approximately 10 times faster than other periodontal cells, which is why periodontal therapy typically results in the formation of long junctional epithelium.
•Periodontal defects is mostly an open wound, whereas endodontic lesion is primarily a closed wound. This has resulted in a more favorable regeneration outcome for endodontic related defects.
Bone Replacement Grafts:
•Autogenous Grafts: are considered the gold standard bone replacement grafts.
•Allografts: most commonly used forms are FDBA and DFDBA. •Xenografts: most common animal sources are bovine and porcine. •Alloplasts: are the most commonly investigated grafting materials for periapical defects, positive results with respect to periodontal regeneration in periapical defects have been reported by using calcium sulfate.
•Occlusive barrier membranes are used to exclude epithelial cells and connective tissue fibroblasts from a periodontal wound.
•This allows other regenerative cells ( bone, PDL and cementobalsts ) to repopulate the area and promote periodontal regeneration in the area. •Barrier membranes can be divided into non-resorbable and bio-absorbable categories.
•Nonresorbable membranes: •Most commonly used material is the ePTFE membrane. •Recent studies showed that intrabony defects treated with ePTFE membrane can expect to undergo between 3 – 3.5 mm of bone fill. •One study compared the use of ePTFE membrane vs. no membrane in the treatment of periapical lesions after apical surgery, the results showed that defects treated with ePTFE membrane healed faster than controls. •Bioabsorbable Membranes:
•Most common material is collagen.
•Numerous studies have shown bioresorbable membranes to be effective at promoting regeneration in both endodontic and periodontal defects.
•The necessity of using a membrane to enhance GTR for endodontic applications is controversial.
Growth Factors/Cytokines/Host Modulating Agents:
•PRP growth factors including BMPs, PDGF, and EMD are the most commonly used agents.
•There is some debate as to the best treatment modality for obtaining regeneration.
•Some advocate the use of bone replacement grafts alone, other suggests that a membrane alone might be sufficient.
•A systematic review by Reynolds et al. demonstrated that in infrabony defects, bone replacement grafts increase bone level and educes crestal bone loss compared with open flap debridement.
•A recent Cochran database systematic review compared GTR with membranes alone and GTR and bone grafting with OFD, the author concluded that GTR with or without bone graft improved CAL gain and reduced pocket depths.
Factors That Affect Success:
Knowledge of the factors that can negatively affect regeneration outcomes and subsequent careful case selection can help to optimize successful regeneration attempts. Moreover, a critical need still exists for a therapy that can enhance the regeneration in a predictable fashion.