Bone Regeneration And Grafting Question And Answers

Reconstructive Osseous Surgery

Question 1. Write short note on root surface conditioner.
Answer. Several substances have been used to condition the root surface, for attachment of new connective tissue fiber.

Various agents used as root surface conditioner are:

• Chemical treatment of root surfaces
  • Acid etching, i.e. citric acid and tetracycline
  • Detergents, i.e. cetylpyridinium chloride and sodium N-lauroylsarcosine
  • Chelating agent, i.e. EDTA
  • Enzymes
  • Attachment proteins, i.e. fibronectin and growth factors
• Mechanical
• Laser

Read And Learn More: Periodontics Question And Answers

Citric Acid

• It is used at pH of 1 for 2-3 minutes on root surface, after surgical debridement it produces a surface demineralization, which in turn induces cementogenesis and attachment of collagen fibers.
• It removes the smear layer, and may open dentinal tubules, thus allowing cementum to form within these tubules and produces cementum pins. This could be associated with accelerated cementogenesis.
• Epithelium does not migrate apically because of the accelerated healing either by connective tissue attachment or a collagen adhesion may occur before epithelium migrates.
• Citric acid may demineralize small bits of residual calculus, disinfect the root surface and aid in removing endotoxins.

EDTA

• It is used at concentration of 24% and at pH 7.
• EDTA exposes collagen fibers of dentine matrix, which leads to the adhesion of blood clot to the root surface and favors migration of fibroblasts.
• It improves clot organization, retard epithelium down growth and enhances clinical attachment gain.
• It has advantage over citric acid as it acts at neutral pH while citric acid acts at acidic pH and necrotizes surrounding periodontal tissue.

Fibronectin

• It acts as adhesive for attachment of fibroblast on root surfaces.
• It promotes connective tissue attachment and regeneration of bone.
• It prevents separation of flap and favor hemostasis.
• Prevents migration and proliferation of epithelial cells.

Tetracycline

• Remove smear layer and exposes dentinal tubules.
• Enhances attachment and spreading of fibroblasts on root surfaces.
• Decreases epithelial cell attachment.
• Reduces gingival collagenolytic activity by inhibiting neutrophil collagenases.

Growth Factors

• Various growth factors used are platelet derived growth factor, insulin like growth factor, fibroblast growth factor.
• These are the naturally occurring polypeptide molecules which are secreted by macrophages, endothelial cells, fibroblasts and platelets which regulate events in periodontal wound healing.
• They undergo regulation of connective tissue cell migration as well as proliferation of periodontal ligament cells, differentiation of osteoblasts and cementoblasts and production of extracellular matrix proteins for periodontal regeneration.

Question 2. Describe bone grafts in periodontics.
Or
Write short note on bone graft in periodontics.
Or
Write short note on bone replacement graft.
Or
Write short answer on bone graft.
Or
Write short note on bone grafts.
Or
Define and classify bone grafts write in detail the different types of bone grafts used in periodontics.
Answer.

Graft

It is a viable tissue/organ that after removal from donor site is implanted/transplanted within the host tissue, which is then repaired, restored and remodeled.

Bone Graft Material

An ideal bone graft material should have biologic acceptability, predictability, clinical feasibility, minimal postoperative hazards, minimal postoperative squeal and good patient acceptance.

Classification of Bone Graft Materials

Depending on sources

• Nonvital bone graft
  • Allograft (human bone): Freeze dried bone allograft
  • Xenograft: Anorganic bovine bone
• Vital bone graft
  • Intraoral: Osseous coagulum, bone blend, bone harvested from extraction site
  • Extraoral: Iliac crest graft

According to Naser (1999)

• Human bone
  • Autogenous grafts
    • Extraoral
    • Intraoral
  • Allografts
    • Fresh frozen bone
    • Freeze dried bone allograft
    • Decalcified freeze dried bone allograft
• Bone substitutes
  • Xenografts
    • Bovine-derived hydroxyapatite
    • Coralline calcium carbonate
  • Alloplasts
  • Absorbable
    • Nonsintered hydroxyapatite
    • α- and β-tricalcium phosphate
    • Calcium sulfate
  • Non absorbable
    • Bioglass
    • HTR polymer

According to the mode of action:

• Osteogenic: New bone is formed by bone forming cells contained in the graft
• Osteoinductive: Bone formation is induced in the surrounding soft tissues immediately adjacent to the graft.
• Osteoconductive: Grafted material does not contribute to new bone formation but serves as scaffold for bone formation originating from adjacent host bone.

Autografts

Intraoral site

• Osseous coagulum:

This technique uses small particles of donor bone, hence it provides additional surface area for the interaction of cellular and vascular elements.

• Sources:
  • Lingual ridge on the mandible, exostosis, tori, edentulous ridges, bone distal to the terminal tooth.
  • In this technique a bur is used in the donor site to reduce it to small particles which when coated with blood becomes coagulum and is placed in the defect.
• Bone blend:
  • In this technique bone is removed from the pre-determined site with chisels or rongeur forceps, placed in the autoclaved plastic capsule with a few drops of saliva, and triturated for sixty seconds to a workable plastic like mass and is packed into the bony defect.
• Bone swaging:
  • This technique requires presence of an edentulous area adjacent to the defect from which the bone is pushed into contact with root surface without fracturing the bone at its base.

Extraoral Site

• Iliac autografts/extraoral hip marrow: The use of iliac cancellous bone marrow has shown good result in bony defects with varying number of wall and furcation defects.Disadvantage: Additional surgical trauma.

Allografts

• Allograft is the tissue transfer between individuals of same species but of non – identical genetic composition.
• Allografts were utilized in an attempt to stimulate bone formation in the intrabony defects to avoid additional surgical insult which is associated with the use of autogenous grafts.
• There are two types of allografts used clinically i.e.
  • Freeze dried bone graft: It is an osteoconductive material which has varying results.
  • Demineralized freeze dried bone grafts: Demineralization process exposes the components of bone matrix which are known as bone morphogenic protein e.g. osteogenin which is a bone inductive protein isolated from extracellular matrix of human bones. So it is an osteoinductive material.

Xenografts

• Recently, an inorganic, bovine derived bone marrow under the brand name Bio-Oss is successfully used for both periodontal defects and implant surgery. It is the porous bone mineral matrix from bovine cancellous or cortical bone.
• Bio-Oss is biocompatible with adjacent tissue, eliciting no systemic immune response.
• Periodontally Bio-Oss is used as a graft material which is covered by resorbable membrane. The membrane prevents migration of fibroblasts and connective tissue into the pores between granules of the graft.
• Since allografts are foreign to organism so they have potential to prove an immune reaction.

Corel Derived Materials

They are of two types i.e. natural coral and coral derived porous HA. Both of these are biocompatible.

Alloplasts/Non-bone Graft Material

• Non-bone graft materials have also been used for restoration of periodontium.
• Some of them are sclera, dura, cartilage, plaster of Paris, ceramics and coral derived materials
• All alloplastic materials are conducive in nature

Bioactive Glass

It consists of sodium and calcium salts, phosphates and silicon dioxide with particle size ranging from 90 to 170 µm or 300 to 355 µm.

Question 3. Discuss regenerative/reconstructive osseous surgery in management of osseous defects following periodontium.
Answer. The following reconstructive surgical techniques have been proposed:

• Nongraft associated new attachment.
• Graft associated new attachment.
• Combination of both.

Nongraft Associated New Attachment

Various techniques of non graft associated new attachment are:

• Removal of junctional and pocket epithelium: This method include:
  • Curettage: Only 50% of junctional or pocket epithelium can be removed
  • Chemical agents: Most commonly used drugs are sodium sulfide, phenol, camphor, sodium hypochlorite and antiformin. Main disadvantage is depth of action is not controlled
  • Ultrasonic methods: Due to lack of clinician’s tactile sense while using this method it is again unsuccessful.
  • Surgical methods:
• Prevention of epithelial migration:
  • Eliminating junctional and pocket epithelium may not be sufficient because the epithelium from the excised margin may rapidly proliferate apically to become interposed between the healing connective tissue and cementum. It is done by guided tissue regeneration (GTR)Concept of GTR is based on the assumption that periodontal ligament cells have potential for regeneration of attachment apparatus to tooth.
• Process of GTR offers possibility of producing new attachment in teeth with advanced periodontal destruction.
• In this technique matrix proteins and growth factors show promising results.
• This technique involves the placement of barrier membrane which bridges the space between the alveolar crest and cervical portion of tooth, thus preventing apical migration of epithelial cells from surgical flap in defective space and facilitating repopulation by cells of periodontal ligament.
• Two types of GTR membrane are used, i.e.
  • Degradable membranes: For example, collagen, polylactic acid, vicryl and Guidor membrane.
  • Nondegradable membranes: For example, Millipore, teflone membrane, Gore-tex periodontal material.
• Procedure of placement of membrane
  • Step 1: Raise a full thickness flap, extending a minimum of two teeth anteriorly and one tooth distally, to the tooth being treated.
  • Step 2: Debride the osseous defect and plane the root surface.
  • Step 3: Trim the membrane according to the size of the area being treated. The membrane should be extended approximately
  • Step 4: Suture the membrane around the tooth with a sling suture.
  • Step 5: The flap is positioned back to its original position or slightly coronal to it and is sutured using interrupted sutures. The membrane should cover completely, in case of nondegradable membrane, after 5 weeks of the operation; it should be removed with a gentle tug.
• Clot stabilization, wound protection and space creation.
  • Successful results gained with graft materials, barrier membranes and coronally displaced flaps have been attributed to the fact that all of these protect the wound and create a space for undisturbed and stable maturation of the clot. So this suggests that preservation of the root surface, that is, a fibrin clot interface prevents apical migration of the gingival epithelium and allows for connective tissue attachment during the early wound healing period.

Root Biomodification

Several substances have been used to condition the root surface, for attachment of new connective tissue fiber. These include citric acid, fibronectin and tetracycline. They are used in root biomodification/root surface preparation.

Citric Acid

When used with pH 1 for 2-3 minutes on root surface, after surgical debridement it produces a surface demineralization, which intern induces cementogenesis and attachment of collagen fibers.

Action of Citric Acid

• It removes the smear layer, and may open dentinal tubules, thus allowing cementum to form with in these tubules and produces cementum pins. This could be associated with accelerated cementogenesis.
• Epithelium does not migrate apically because of the accelerated healing either by connective tissue attachment or a collagen adhesion may occur before epithelium migrates.
• Citric acid may demineralize small bits of residual calculus, disinfect the root surface and acid in removing endotoxins.

Technique

• Raise full thickness flap.
• Perform thorough root planing.
• Apply cotton pellets soaked in citric acid pH 1 for 2-3 minutes.
• Remove and irrigate root surface profusely with water.
• Replace the flap and suture.

Fibronectin

• It acts as adhesive for attachment of fibroblast on root surfaces.
• It promotes connective tissue attachment and regeneration of bone.
• It prevents separation of flap and favor hemostasis.
• Prevents migration and proliferation of epithelial cells.

Tetracycline

• Remove smear layer and exposes dentinal tubules.
• Enhances attachment and spreading of fibroblasts on root surfaces.
• Decreases epithelial cell attachment.
• Reduces gingival collagenolytic activity by inhibiting neutrophil collagenases.

Graft Associated New Attachment

• Autograft: Tissue transfer from one position to new position in same individual.
• Allograft: Tissue transfer between individuals of same species but with nonidentical genes.
• Xenograft: Donor of graft is from the species different from the host.
• Alloplastic graft: Graft of inert synthetic material which is sometimes known as implant material.

Question 4. Define periodontal flap give its classification and discuss treatment modalities for three, walled osseous defects in detail.
Or
Write short answer on classification of periodontal flap.
Or
Discuss guided tissue regeneration (GTR).
Answer. Periodontal flap is a section of gingiva and/or mucosa surgically elevated from underlying tissues to provide visibility and access to bone and root surface.

Classification of Flap

According to thickness of flap/bone exposure after flap reflection:

• Full thickness/mucoperiosteal flap: All the soft tissues including periosteum are elevated.
• Partial thickness/mucosal flap/split thickness flap: Reflection of only the epithelium and a layer of underlying connective tissue.

According to the placement of flap after surgery:

• Nondisplaced flap: Flap is returned and suture back to its original position.
• Displaced flap: Flap is repositioned coronal, apical or lateral to its original position.

According to design of flap/Management of the papilla:

• Conventional flap: Splitting the papilla into facial half and lingual/palatal half, e.g. modified Widman flap, undisplaced flap, apically displaced flap.
• Papilla preservation flap: Entire papilla is incorporated into one of the flaps.

Treatment Modalities of Three-walled Osseous Defect

Three-wall defect—Three walls are present in defect. It can be treated by nongraft associated new attachment procedures.

Question 5. Write short note on guided tissue regeneration.
Or
Discuss guided tissue regeneration (GTR).
Answer. Concept of guided tissue regeneration is based on the assumption that periodontal ligament cells have potential for regeneration of attachment apparatus to tooth.

• Process of guided tissue regeneration offers possibility of producing new attachment in teeth with advanced periodontal destruction.
• In this technique matrix proteins and growth factors show promising results.
• This technique involves the placement of barrier membrane which bridges the space between the alveolar crest and cervical portion of tooth, thus preventing apical migration of epithelial cells from surgical flap in defective space and facilitating repopulation by cells of periodontal ligament.

Types of GTR

• Two types of guided tissue regeneration membrane are used, i.e.
  • Degradable membranes: For example, Collagen, polylactic acid, vicryl and Guidor membrane.
  • Nondegradable membranes: E.g. Millipore, teflon membrane, Gore-Tax periodontal material.

Procedure of Placing Guided Tissue Regeneration Membrane

• Step 1: Raise a full thickness flap, extending a minimum of two teeth anteriorly and one tooth distally, to the tooth being treated.
• Step 2: Debride the osseous defect and plane the root surface.
• Step 3: Trim the membrane according to the size of the area being treated. The membrane should be extended approximately
• Step 4: Suture the membrane around the tooth with a sling suture.
• Step 5: The flap is positioned back to its original position or slightly coronal to it and is sutured using interrupted sutures. The membrane should cover completely, in case of nondegradable membrane, after 5 weeks of the operation; it should be removed with a gentle tug.

Guided Tissue Regeneration Indications

• Narrow or three wall intrabony defects
• In circumferential defects
• In class 2 furcation defects
• Recession defects

Guided Tissue Regeneration Contraindications

• Medical conditions contraindicating surgery.
• Infection at defect site.
• Poor oral hygiene
• Patients with smoking
• Tooth mobility greater than 1 mm
• Defect less than 4mm deep
• Width of gingiva at defect site is less than 1 mm
• Thickness of attached gingiva less than 5 mm
• Furcation with short root trunks
• In generalized horizontal bone loss
• In advanced lesions with little remaining support
• In multiple defects

Question 6. Write short note on root conditioning.
Answer. It is a process which aims at obtaining new attachment by conditioning the root surface with the help of agents known as root conditioners or root surface conditioners or root biomodifiers.

Root Conditioning can be Done with Help of Following

• Chemical treatment of root surfaces
  • Acid etching by citric acid and tetracycline
  • Detergents, i.e. Cetylpyridinium chloride and sodium N-lauroylsarcosine
  • Chelating agents, i.e. EDTA
  • Enzymes
  • Attachment proteins, i.e. Fibronectin and growth factors.
• Mechanical
• LASER.

Citric acid

• It is used at pH of 1 for 2–3 minutes on root surface, after surgical debridement it produces a surface demineralization, which in turn induces cementogenesis and attachment of collagen fibers.
• It removes the smear layer, and may open dentinal tubules, thus allowing cementum to form within these tubules and produces cementum pins. This could be associated with accelerated cementogenesis.
• Epithelium does not migrate apically because of the accelerated healing either by connective tissue attachment or a collagen adhesion may occur before epithelium migrates.
• Citric acid may demineralize small bits of residual calculus, disinfect the root surface and aid in removing endotoxins.

Tetracycline

• It removes the smear layer and exposes the dentinal tubules.
• It enhances the attachment and spreading of fibroblast on the root surfaces.
• It decreases the epithelial cell attachment.

EDTA

• It is used at a concentration of 24% and at pH 7.
• It exposes the collagen fibers of the dentine matrix, which facilitates the adhesion of blood clot to the root surface, and thereby favors the migration of fibroblasts.
• It improves clot organization, retards epithelium downgrowth and enhances clinical attachment gain.

Growth Factors

• Naturally occurring polypeptide molecules secreted by macrophages, endothelial cells. fibroblasts, and platelets that regulate events in periodontal wound healing.
• They regulate connective tissue cells migration and proliferation of periodontal ligament cells, differentiation of osteoblasts and cementoblasts and production of extracellular matrix proteins for periodontal regeneration.

Enamel Matrix Proteins

• Enamel matrix proteins are isolated from developing porcine teeth.
• Promote periodontal regeneration by mimicking events that take place during development of the periodontal tissues.
• Enhance PDL cell attachment

Fibronectin

• Acts as adhesive for the attachment of fibroblast on the root surfaces.
• It promotes the connective tissue attachment and helps in bone regeneration.
• Prevents the separation of flap and favors the hemostasis.

Question 7. Write short note on Osseoinduction.
Answer. It is also known as osteoinduction.

It involves the new bone formation via stimulation of osteoprogenitors from the defect to differentiate into osteoblasts and begin forming new bone.

• At the time of remodeling the osteoinductive materials are contributory to the formation of bone.
• Most commonly used osteoinductive materials in implant dentistry are bone allografts and bone autografts.
• Bone autografts are transferred from one position to another in same individual. Autogenous bone is the best as it has both osteogenetic and osteoinductive properties. These grafts are resorbed and replaced by the viable bone.
• Allografts are the grafts which are transferred between genetically dissimilar members of same species. Allografts are demineralized freeze dried bone allograft or freeze dried bone allograft.

Question 8. Write short note on resorbable membrane.
Answer. Resorbable membranes are also known as biodegradable membranes.

• Resorbable membranes consists of Osseoquest marketed on name of Gore-Tex which is a combination of polyglycolic acid, polylactic acid and trimethylene carbonate which resorbs in 6 to 14 months.
• Bioguide marketed on name of Osteohealth is a bilayered porcine derived collagen membrane.
• Atrisorb marketed on name of block drug is a polylactic acid gel.
• Biomend marketed on name of calcitech which is a bovine achillies tendon collagen which resorbes in 4 to 18 weeks.
• Out of all the resorbable membranes bioguide is easy to use and is preferable.
• Use of resorbable membranes is combined with autogenous bone from adjacent areas or other graft materials and root biomodifiers.

Question 9. Classify bone grafts. Write in detail about allograft.
Answer.

Allograft

• Allograft is also known as homograft.
• Allograft is the tissue transfer between individuals of same species but of non-identical genetic composition.
• Allografts were utilized in an attempt to stimulate bone formation in the intrabony defects to avoid additional surgical insult which is associated with the use of autogenous grafts.
• Bone allografts are commercially available from tissue banks.
• Bone allografts are obtained from cortical bone within 12 hours of the death of the donor, defatted, cut in pieces, washed in absolute alcohol, and deep-frozen. The material may then be demineralized, subsequently ground and sieved to a particle size of 250 to 750 μm, and freeze-dried.
• Finally, it is vacuum-sealed in glass vials.
• Numerous steps are also taken to eliminate viral infectivity. These include exclusion of donors from known high-risk groups and various tests on the cadaver tissues to exclude individuals with any type of infection or malignant disease. The material is then treated with chemical agents or strong acids to inactivate the virus, if still present.

Types of Allografts

There are two types of allografts used clinically i.e.

• Freeze dried bone graft
• Demineralized freeze dried bone grafts
  • Freeze Dried Bone Graft
    • It is considered to be the osteoconductive material.
    • It is radiopaque
    • It can be broken down by the way of foreign body reaction.
    • This is primary indicated in bone augmentation which is associated with the implant treatment.
  • Demineralized Freeze Dried Bone Graft
    • It is considered to be the osteoinductive material.
    • According to the laboratory studies demineralized freeze dried bone graft is considered to be have high osteogenic potential as compared to Freeze Dried Bone Graft and so it is preferred.
    • It is more of radiolucent material.
    • It is rapidly resorbed.
    • It is primarily indicated in the periodontal disease associated with the natural tooth. As it shows prominent probing depth reduction, attachment level gain and osseous regeneration.
    • Combination of demineralized freeze dried bone graft and guided tissue regeneration is very successful as a treatment method.
    • Limitations of the use of demineralized freeze dried bone graft include the possible, although remote, potential of disease transfer from the cadaver.

Question 10. Write short answer on autograft.
Answer. Autograft is the bone obtained from the same individual.

• Autograft is also known as autogenous bone graft.
• Grafts are transferred from one position to another within the same individual. Autogenous bone, is certainly the best since it has both osteogenetic and osteoinductive potential.
• Its availability is nevertheless limited, and its use generally results in additional inconvenience for the patient.
• They are resorbed and replaced by few viable bone. Autogenous bone grafts can be harvested from intraoral or extraoral sites and can be cortical bone or cancellous bone.

Site for Obtaining Autogenous Grafts

The various sites for procuring autogenous bone grafts are as follows:

• Intraoral sites: Healing extraction wounds, edentulous ridges, exostosis, lingual ridge on the mandible, bone distal to the terminal tooth, lingual surface of the mandible at least 5 mm from the roots, maxillary tuberosity and mandibular retromolar area.
• Extraoral sites: Iliac autografts-posterior iliac crest. Problems associated with iliac autografts are postoperative infection, exfoliation, sequestration, varying rates of healing, root resorption and rapid recurrence of the defect. Root resorption is very common with fresh iliac. It has been observed clinically that frequent curettage of the resorbed area, particularly in the crestal areas of newly forming bone, often reverses the process. Due to the morbidity associated with donor site anti root resorption, the iliac crest marrow grafts are not used now in regenerative periodontal therapy.

Various Autografts

Osseous Coagulum

• This is a mixture of bone dust obtained by grounding cortical bone and blood.
• Round carbide bur revolving at 25,000 to 30,000 rpm is used within the surgical site to reduce donor bone to small particles, which is then coated with the patient’s blood to make coagulum.

Autograft Advantages

• It is a rapid technique.
• Complements osseous resective procedures that may be required at surgical site.
• Its particle size provides additional surface area for interaction between cellular and vascular elements.

Autograft Disadvantages

• Cannot be used in larger defects because of inability to procure adequate material.
• Poor surgical visibility is present.
• Relatively low predictability.
• Inability to use aspiration during accumulation of coagulum.
• Fluidity of the material makes it difficult to transfer coagulum to the defect.

Autograft Bone Swaging

• Piece of bone is incompletely detached from its base by a chisel and swung into a neighboring bone defect with some of its blood supply maintained.
• It is the technique which requires existence of an edentulous area adjacent to the defect.
• It represents a contiguous or pedicle bony autograft utilizing the principle of greenstick fracture of long bones.

Bone Blend

It involves removing bone (cortical, cancellous or both) from accessible intraoral do not site by chisel or rongeur forcep, placing it in sterile plastic amalgam capsule with pestle and then triturating.