Reconstructive Osseous Surgery Question And Answers

Reconstructive Osseous Surgery Question And Answers

Question 1. Write on bone grafts and their classification.
Answer:

The regeneration of periodontal tissue and in particular alveolar bone is an important goal of all periodontal therapy.

Classification Of Bone Grafts

• Based on the mechanism of healing, bone grafts may be classified into osteoconductive, osteoinductive, and osteogenic. All autografts, allografts, and alloplastic fall into one of more of these categories.

Read And Learn More: Periodontology Important Question And Answers

1. Osteogenic grafts: These are grafted in which there are viable cells- osteoblasts that can themselves be involved in the new bone formation process.
2. Osteoinductive grafts:
   • They do not have viable cells but have proteins that can induce the neighboring/surrounding cells to differentiate into osteoblasts and then form new bone.
   • The usual inductive proteins are the BMPs that are made available in allografts that have been demineralized –DFDBA.
3. Osteoconductive grafts: They act as space filers; contain neither viable cells nor inductive proteins that influence new bone formation. All traditional alloplastic and xenografts act in this manner.

• On the basis of nature and origin bone grafts can be classified into four types.

1. Xenografts: The donor of the graft is from a species different from the host.
2. Allografts: The donor is of the same species but with different genes.
3. Autografts: The graft is a transplant from one area to another in the same individual.
4. Alloplasts: A non-bone graft consisting of inert synthetic material.

Autogenous Grafts:

• It may be obtained from intraoral or extraoral sites. Intraoral sites include symphysis, maxillary tuberosity, edentulous ridges, or healing extraction sockets.
• The obtained bone may be in the form of chips, bone blend, osseous coagulum or bone swaging may be done. The preferred extraoral site is the iliac crest.

Allografts: They are obtained from cadaver sources. Available in two forms-FDBA and DFDBA.

• Xenografts: They are mostly obtained from calf bone, kiel bone, etc.
• Alloplastic
  1. Hydroxyapatite
  2. B-Tricalcium phosphate.

Question 2. Discuss the role of bone grafts in periodontal therapy.
Answer:

• The application of bone grafts in regenerative therapy is largely restricted to vertical osseous defects and furcation areas.
• These grafts have not been predictably able to achieve any evidence for regeneration in horizontal bone loss.
• Among the various grafts, autografts are thought to be the gold standard as they have osteogenic, inductive, and conductive properties.
• However, the need for a second surgical site and its attendant postoperative morbidity, and the limited volume of grafts available are its potential drawbacks.
• Allografts have the advantage of greater availability, and inductive action if used in the form of DFDBA.
• However, the amount of available BMP is influenced by a number of factors such as donor age, systemic condition, and processing procedure and therefore there is a batch-to-batch variation and lack of uniformity in the graft performance.
• Xenografts and alloplastic have unlimited availability, are easily manageable, and are economically affordable.
• They are however limited by their biological ineffectiveness due to inert filer effect. They are now being used as carriers for more inductive bioactive materials.
• Periodontal regeneration as a goal is a presumed endpoint in therapy that has proved elusive so far even with the advent of many graft materials, predictable and complete regeneration is yet to be achieved.
• Consequently, a number of newer graft materials have become available commercially to achieve this endpoint. Some of the newer trends in this regard are discussed below.

Question 3. Discuss the biomimetic agents used in periodontal therapy.
Answer:

These are agents that have evolved on the principle that regeneration of periodontal tissues should occur in a manner that closely resembles the events that occur during tooth formation.

Enamel Matrix Derivative

• Formation of cementum is thought to be deeply influenced by the enamel matrix proteins such as Amelogenin that are thought to be able to induce differentiation of undifferentiated cells of the dental follicle to cementoblasts.
• Threfore, these proteins were postulated to play a role in regenerative therapy. Commercially available agents are derived from tooth buds of porcine origin and have been extensively used in regenerative periodontal therapy in vertical defects, furcation defects and also in root coverage procedures.

Growth Factor Incorporated Grafts: Recently, bone replacement grafts have been made available that have incorporated BMP and PDGF-BB into filer materials such as tricalcium phosphate (TCP) and collagen sponges and encouraging results have been reported. Long-term results are still awaited.

Platelet Rich Plasma (PRP) and Platelet Rich Fibrin (PRF)

• Autologous platelet concentrates such as PRP have the advantage that endogenous growth factors are made available in the normal form and concentrated to many times in a 10 mL volume of blood.
• The TGF and PDGF present in plasma are capable of regenerating bone by their effect on differentiating osteoblasts.

Question 4. Describe guided tissue regeneration and its rationale.
Answer:

Introduction and Historical Perspective

• Guided tissue regeneration (GTR) is the procedure in which a barrier (membrane) is utilized to exclude the gingival epithelium and connective tissues from occupying the periodontal wound site.
• It has been shown to result in regeneration of the lost periodontal tissues.
• This hypothesis was originated by Melcher in 1976, who suggested that the type of cells which repopulate the wound defect after periodontal surgery determines the nature of attachment that will form.
• It was further established by Karring, Nyman et al in 1982 who demonstrated new attachment following surgical treatment.
• So the provision to exclude specific tissues, i.e. the gingival epithelium and connective tissue cells during the healing phase of a periodontal defect wound had resulted in the development of devices, commonly known as barrier membranes.

The Rationale of GTR

• The concept of GTR evolved primarily from a better understanding of wound healing following periodontal therapy.
• Healing after conventional periodontal therapy occurs primarily by the formation of long junctional epithelium, which might not be as stable as the original periodontium and does not represent true regeneration.
• This kind of healing is primarily the result of epithelial invasion of the healing periodontal wound.
• During the process of wound healing several cell populations have access to the wound, but the rate of cell migration results only in selective cell re-population of the healing wound.
• Among the cell populations that find access, histological evaluations have established
  the presence of cementoblasts, osteoblasts, fibroblasts, and epithelial cells.
• The rate of cell migration of epithelial cells ensures that these cells form the larger constituent of cells that re-populate the healing wound with the final result that a junctional epithelial attachment is formed.
• Experimental studies have shown that the use of barriers to restrict epithelial invasion can result in a replication of periodontal structure in content, volume, and function.
• Such barriers need to be restrictive to connective tissue and osseous cell sources as well while allowing cells from the periodontal ligament to re-populate the healing wound.
• The periodontal ligament is able to contribute cell lines available in connective tissue and bone and hence the regeneration potential of fibroblasts and osteoblasts is unaffected.
• Hence the use of such barriers as an adjunct to conventional periodontal therapy has resulted in a better end point of success in terms of periodontal regeneration.

Question 5. What are the design criteria for GTR membranes?
Answer:

The design criteria for GTR devices are as follows:

1. Biocompatibility
2. Cell exclusion
3. Space maintenance
4. Tissue integration
5. Ease of use
6. Cost effectiveness
7. Biological activity.

Question 6. Discuss the classification of GTR membranes.
Answer:

1. Generation: Nonresorbable
2. Generation: Bioresorbable: Natural or synthetic
3. Generation: Bioabsorbable with biological mediators, viz growth factors and polypeptides.

Non-resorbable Materials: The earliest developed GTR barriers were primarily non-resorbable. While they were extremely successful in producing the right treatment outcomes, the necessity of a second surgical sitting for the removal of the barrier was considered a disadvantage.

Examples of non-resorbable materials include:

1. Expanded polytetrafluoroethylene: E-PTFE (Gore-Tex)
2. Dense polytetrafloroethylene: (Tef Gen).

Resorbable Materials: Examples of resorbable materials that have been used in GTR techniques in the past include the following

1. Collagen, for example, Biomend, BioGide.
2. Polyglactin 910, for example, Vicryl mesh.
3. Polylactic acid-citric acid ester, example: Guidor.
4. Polylactic acid, for example, Resolut.
5. Lamellar bone mesh, for example, Lambone.
6. Atrisorb.

• The principal advantage of resorbable materials is the elimination of a second surgical sitting for removal of the membrane. However as discussed earlier, the biochemistry of bio-degradation and the elimination of metabolic end products is a key issue.
• Generally, collagen membranes have been far more successful than polymer membranes and the chemical and physical treatment of collagen has resulted in a biocompatible product with well-controlled resorption rates.

Question 7. What are the indications of GTR?
Answer:

The guided tissue regeneration technique finds excellent application with predictable results in the following periodontal indications:

• Intrabony periodontal osseous defects
• Class 2 Furcation defects
• Class 1 and Class 2 gingival recession.

Question 8. Describe the procedure of GTR.
Answer:

Step 1: Adequate local anesthesia is administered.

Step 2: A full-thickness mucoperiosteal flap is raised extending at least by one normal tooth on either lateral side of the defect undergoing treatment.

Step 3: The flip is also raised to a sufficient apical extent keeping in mind the size of the GTR barrier and its extension by at least 4–5 mms beyond the defect in all directions.

Step 4: An appropriate membrane shape is chosen and trimmed to suit the configuration of the defect.

Step 5: The membrane is then carefully placed and positioned around the defect with appropriate sutures around the tooth.

Step 6: The mucoperiosteal flap is sutured in a manner so as to completely cover the membrane.

Step 7:

• Postoperative instructions include an antibacterial mouth rinse and the prescription of an antibiotic regimen may be considered. Suture removal may be performed after 7–14 days.
• Removal of the membrane is necessary after a period of 12–18 weeks if a non-resorbable barrier is used.

Question 9. Write a note on guided bone regeneration.
Answer:

• Bone augmentation using GTR principles is known as guide bone regeneration (GBR) and has found extensive applications in implant dentistry. It has been used widely to resolve ridge defects.
• The membranes used for this procedure are more cross-linked and take a longer time for resorption than membranes used for GTR.

Conclusion

• Collagen membranes have been proven to significantly enhance periodontal regeneration.
  However, none of the available materials till date, has shown a complete or true regeneration.
• Bio-material research has offered newer and better materials continually and there is no doubt that the GTR technique will go beyond being limited to regenerative therapy.
• The delivery of growth factors and other polypeptides to the periodontal wound defect to accelerate healing is seen as the future in GTR.