REGENERATIVE OSSEOUS SURGERY

The ultimate goal of periodontal therapy is the complete restoration of the structure and function of diseased periodontal tissues. Regeneration of periodontium is considered to be an essential part of current mode of periodontal treatment approach.

INTRODUCTION

Therapeutic bone regeneration approaches uses the principles of osteogenesis, osteoconduction and osteoinduction.

Osteogenesis: The direct transfer of vital cells to the area that will regenerate new bone.

Osteoconduction: Embraces the principles of providing the space and a substratum for the cellular and biochemical events progressing to bone formation.

Osteoinduction: Embodies the principle of converting pluripotential , mesenchymal derived cells along the osteoblasts pathway with subsequent bone formation.

PRINCIPLES OF OSSEOUS REGENERATION

 Clinical methods: It consists of comparisons between pretreatment and

post treatment pocket probings and determination of clinical gingival findings. Probe can be used to determine pocket depth, attachment level and bone level.

 Radiographic methods: It allows assessment of the bone tissue adjacent to

the tooth. A comparative study of pretreatment bone level and post therapy bone fill with 12 month reentry bone measurement showed that linear radiographic analgesics significantly underestimates pretreatment bone loss and post treatment bone fall.

EVALUATION OF NEW ATTACHMENT AND PERIODONTAL RECONSTRUCTION

Recent radiographic evaluation methods are:

Substraction radiography

CADIA (Computer Assisted Densitometric Image Analysis)

 Surgical re-entry: Surgical reentry of a treated defect after a period of

healing can provide a good view of the state of the bone crest that can be compared with the view taken during the initial surgical intervention.

This method is very useful but has two shortcomings: It requires a frequently unnecessary second procedure and it does not show the type of attachment that exists.

 Histologic methods: Type of attachment can be determined by

histological analysis of tissue blocks.

 NON BONE GRAFT ASSOCIATED

PROCEDURES Removal of junctional and pocket epithelium Its presence interferes with the direct apposition of

connective tissue and cementum, thus limiting the height to which periodontal fibers can insert to the cementum. Methods to remove junctional and pocket epithelia are

Curettage: Use of ultrasonic methods, lasers, rotary abrasives.

Chemical agents: Sodium sulphide, phenol camphor, Antiformin and NaOCl.

Techniques: Recommended one

TECHNIQUES

 Prevention or impeding of epithelial migration:

Two methods: One consists of total removal of the interdental papilla

covering the defect and its replacement with a free autogenous graft obtained from palate.

Second approach is the use of coronally displaced flaps, which increase the distance between the epithelium and healing area.

 Clot stabilization, wound protection and space creation:

Some investigators have attributed the successful results reported with graft materials, barrier membranes and coronally displaced flaps to the fact that these techniques protect the wound and create a space for undistributed and stable maturation of the clot.

 Biomodification of the root surface:

Changes in the tooth wall offers periodontal pockets interfere with new attachment. Several substances have been used in attempts to better condition the root surface for attachment of new connective tissue fibers. They are:

Citric acid Fibronectin Tetracycline

Polypeptide growth factors Growth factors are polypeptide molecules released by cells

in the inflamed area that regulate events in wound healing. They regulate C.T migration and proliferation and synthesis of protein and other components of the extracellular matrix.

They are recreated by macrophages, endothelial cells, fibroblasts, platelets etc..

 

Enamel matrix proteins They are believed to favour periodontal regeneration.

Enamel matrix proteins that are derived from …..teeth with trade name ‘Emdogain’ can also be used for periodontal regeneration.

  

GUIDED TISSUE REGENERATION

GTR is the term used to define procedures wherein regeneration of lost periodontal structures is sought via selective cell and tissue reproduction of the periodontal wound (AAP 1992)

 

 DEFINITION

  The principle of GTR is based on exclusion of epithelial

and gingival connective tissue cells from the healing area by the use of a physical barrier that may allow (guide) periodontal ligament cells to repopulate the detached root surface where they can regenerate a new attachment or new attachment apparatus.

 PRINCIPLES OF GTR (Melcher hypothesis)

  First generation membranesThese are non absorbable membranes  Second generation membranesThese are bio absorbable or bio degradable

membranes.  Third generation membranesThese are first and second generation membranes

with adhesion molecules and growth factors.

 CLASSIFICATION OF GTR MEMBRANES 

 Bio absorbable membranes: Guidor Resolute Vicryl Atrisorb Biomend Perioguide Periogen Non absorbable membranes Silicon sheets Cellulose outate lab filters Millipore filters Polytetrafluroethylene (PTFE) membrane Rubber dam

  Bio compatible: it should not elicit an immune response

that interferes with healing Stabilization of the blood clot: it should stabilize the

blood clot as it acts as a reservoir of precursor cells required for regeneration.

Cell occlusiveness: it should act as barrier for certain cells that prevent regeneration.

Space maintenance: it should provide space for ingrowth of cells potential for regeneration from adjacent periodontal ligament.

Tissue regeneration Ease of use: it should be easy to trim and place in the

defect site Biological activity 

 IDEAL REQUISITES OF GTR MEMBRANES

  Step I: A full thickness of mucoperiosteal flap should

be reflected 2-3 mm beyond the defect. Vertical incision should be given where ever necessary.

  Step II: Debridement of osseous defect and curettage

of the inner surface of the flap.  Step III: Root planning followed by root conditioning of

the exposed root surfaces should be accomplished.  Step IV: Create fresh bleeding at the defect site to

allow progenitor cells to progress from bone to the site. 

PROCEDURE

Step V: The membrane should be trimmed so that it extends 2-3 mm beyond the margins of the defect in all directions. Trimming of the flap should also permit primary tension- free closure of the flap.

Step VI: The membrane should be adapted to the site and stabilized with the help of suture or tacks.

Step VII: Suture the site with silk suture to obtain tension free primary closure. Dressing may be considered to enhance patient comfort but it should not displace or collapse the graft.

Step VIII: Post operative instructions and antibiotics should be given.

Step IX: If non-re absorbable membrane is used, it should be removed after 4-6 weeks.

  It is a process which aims at obtaining new attachment by

conditioning the root surface with the help of agents known as root bio modifiers.

Root bio modification can be done with the help of the following:

  Chemical treatment of root surface Acid etching (Citric acid

and tetracycline) Detergents (cetylpyridinium chloride and Na N- lauroylsarcosine)

Chelating agents: ethylene diamine tetra acetic (EDTA)acid. Enzymes Attachment proteins (fibronectin and growth factors) Mechanical Lasers

ROOT BIOMODIFICATION

It is used at a pH of 1 for 2-5 minutes It removes smear layer of microcrystalline debris and eliminates

endo toxins and bacteria from root-planned surface. It exposes the dentinal tubules that appear wider with funnel

shaped orifices. An early fibrin leakage occurs to the exposed collagen fibers

which prevents the migration of epithelial cells on the treated root surfaces.

It accelerates healing and promotes formation of new attachment by enduring cementogenesis and attachment of collagen fibers.

CITRIC ACID:

It is used at concentration of 24% at pH 7. It exposes the collagen fibers of the dentine matrix. It improves clot organization, retards epithelium

growth and enhances clinical attachment gain. EDTA has advantage over citric acid as it acts at

neutral pH unlike citric acid that necrotizes the surrounding periodontal tissues.

EDTA:

It is a glycoprotein and acts as an adhesive for the attachment of fibroblast on root surfaces.

Promotes connective tissue attachment and bone regeneration

Prevents the separation of flap and favours hemostasis Prevents the migration and proliferation of epithelial

cells Commercially available: tissucol and tisseel

FIBRONECTIN:

TETRACYCLINE: It removes the smear layer and exposes

the dentinal tubule It decreases the epithelial cell attachment It also reduces the gingival collagenolytic

activity GROWTH FACTORS: Naturally occurring polypeptide molecules

secreted by macrophages, endothelial cells, fibroblasts and platelets.

They regulate C.T cell migration and proliferation of periodontal ligament cells, differentiation of osteoblasts and cementoblasts and production of extracelluar matrix proteins.

ENAMEL MATRIX PROTEIN  Enamel matrix proteins mainly

amelogenin are secreted by Hertwig epithelial root sheath during tooth development.

They induce a cellular cementum formation and therefore play a role in in periodontal regeneration.

It is osteopromotive not osteoinductive as it stimulates bone formation when combine with freeze dried bone allograft.

It promote cell spreading and bone cell attachment and differentiate immature bone cell into mature cell that form new bone.

It consists of proteins such as Amelogenin(90 %), Proline rich non Amelogenin, Tuftlin and tuft protein, serum protein, Ameloblastin, Amelin.

It is commercially available as Emdogain derived from developing procaine tooth approved by U.S Food & Drug Administration.

It is available as viscous gel.

PROCEDURE  Raise a flap for regenerative purpose. Remove all granulation tissue and tissue tags, exposing

the underlying bone and remove all root deposit by hand, Ultrasonic scaling or both.

Completely control bleeding within the defect. Demineralise the root surface with Citric acid pH 1. This

removes the smear layer and facilitates adherence of Emdogain.

Rinse the wound with saline and apply the gel to fully cover the exposed root surface. Avoid contamination with blood or saliva.

Close the wound with sutures. Perfect abutment of the flap is necessary.

GRAFTS

Bone grafting is a surgical procedure by which new bone or a replacement material is placed into spaces between or around broken bone (fractures) or defects to aid in healing.

DEFINITION:

Autograft: Extraoral – lip marrow Fresh Frozen  Intraoral Osseous coagulum Bone blend Tuberosity Extraction sites Continguous autografts

CLASSIFICATION:

Allograft DFDB allograft FDBA’s / Autogenous bone grafts (ABG’s) Freeze dried bone allografts  Xenografts Bovine anorganic cancellous bone Procine non antigenic collagen Alloplastic materials Reabsorb able – β- tricalcium phosphate Non absorbable- durapatite, hydroxyapatite [hard

tissue replacement]

Osteoinductive potential Predictability Accessability Availability – quantity Safety Biologic compactibility Immunologic acceptability Minimal sequelae Rapid vascularisation Minimal operative hazards

IDEAL REQUISITES OF BONE GRAFTS

BONE FROM INTRAORAL SITES  Osseous Coagulum: R. Eael Robinson described a technique using a

mixture of bone dust and blood that he termed “Osseous coagulum”. The technique uses small particles ground from cortical bone. The advantage of the particle size is that it provides additional surface area for the interaction of cellular and vascular elements.

Source of graft material – Lingual ridge of the mandible, exostoses, edentulous ridges, bone removed by osteoplasty or osteotectomy

AUTOGENOUS BONE GRAFTS

Technique: The bone is removed from the source with a carbide bur # 6 or #8, placed in a sterile dappen dish and used to fill the defect.

Advantages: Ease of obtaining bone from already exposed surgical site

Disadvantage: Low predictability and inability to procure adequate material for large defects.

Bone blend: To overcome the disadvantage of

osseous coagulum, the bone blend technique has been proposed. It uses an autoclaved plastic capsule and pestle. Bone is removed from a predetermined site, triturated in the capsule to a workable plastic like mass and packed into bony defects.

Cancellous bone marrow transplants: Cancellous bone can be obtained from the maxillary

tuberosity, edentulous areas and healing sockets. The maxillary tuberosity is also contains a good amount of cancellous bone.

Bone swagging: This technique requires 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. It is a different procedure.

BONE FROM EXTRA ORAL SITES:

Iliac autografts: The use of fresh or preserved iliac

cancellous marrow bone has been extensively investigated. However, because of problems associated with its use, the technique is no longer in use. Problems like post operative infection, exfoliation, sequestration etc.

Tissues transferred from one individual to another genetically dissimilar individual of the same species.

Undecalcified- freeze dried allograft

FDBA is considered as an osteo conductive material. It has reported that bone filling exceeding 50% and in 67% of the defects grafted with FDBA and in 78% of the defects grafted with FDBA plus autogenous bone. Have lesser osteogenic potential than DFDBA. FDBA mixed with autogenous bone is more effective. 

ALLOGRAFTS

FDBA, a material readily available from various bone banks, has been shown to be osteoconductive. when FDBA is combined with an ABG, it may become osteoinductive.

Sepe and colleague in 1978 showed that you can achieve a 50% or greater bone fill in various types of defects 60% of the time.

More recently Saundus and colleagues in 1983 showed that when FDBA is combined with ABG, there is an 80% chance of achieving 50% of greater bone fill in all defects.

Yukna & Sepe used a combination of tetracycline and FDBA in a 4:1 ratio in 62 defects and where able to achieve complete fill in 22 sides, greater than 50% in 39 sites and less than 50% in one site. These results appears to be better than those when FDBA is used alone.

Yukna & Vastardis in 2005 demonstrated histologically in vitro. FDBA to be significantly more osteoconductive and osteoinductive than DFDBA. They concluded that FDBA may stimulate earlier, more rapid and larger quantities of new bone formation than DFDBA.

FDBA, being readily available appears to be an ideal material for use as a biologic expander when ABG material is alone insufficient

Decalcified freeze dried bone allograft:

DFDBA is considered as an osteoinductive bone graft. Have higher osteogenic potential than FDBA. DFDBA in periodontal defects results in significant probing depth reduction, attachment Level gain and osseous regeneration. The combination of DFDBA nad GTR has also proved to be very successful. DFDBA provides more bone refill than FDBA. DFDBA grafts results in 2.5 to 3mm of bone fill which is less than autogenous bone.

 

Urist showed the inductive capabilities of DFDB. He and his colleagues isolated a bone morphogenic protein (BMP) that is capable of Osteogenic induction by inducing primordial cells to differentiate into osteoblasts.

Demineralization exposes the collagen matrix that harbors the inductive protein, thereby permitting greater inductibility, The ideal particle size is between 250 and 500 µm. This small size permits high inductive potential, easy resorption and replacement, increased surface area for primordial mesenchymal interaction.

Particles smaller than 250 µmare absorbed quickly and larger ones are inadequately used.

DFDBA meets all the criteria for ideal grafting material.

Availability Predictability Bio compactability Osteo inductivity Osteo conductivity Cost effectiveness Safety

Laurell and colleagues (1998), in meta analysis review of 21 trials (512 intra bony defects) found the following.

DFDBA significantly enhanced bone fill when combined with DFD without bone grafts.

The average fill was 1.2 mm for DFD and 2.3 mm for DFD + DFDBA, irrespective of defect configuration.

In comparing the percent of cases Defect of 4 -5 mm have a greater percent of bone

fill, bone coverage of deeper defect (greater than or equal to 6mm). Even though deeper defects have the potential for the largest amount of bone fill.

Currently an inorganic bovine derived bone marketed under the trade name Bio- Oss has been successfully used both for periodontal defects and in implant surgery. It is an osteoconductive porous bone mineral matrix from bovine cancellous or cortical bone. The organic components of the bone are removed but the trabular architecture and porosity is retained. The physical features permit clot stabilization and revascularization to allow for migration of osteoblasts, leading to osteogenesis. Bio- Oss is biocompatible with the adjacent tissues eliciting no systemic immune response.

XENOGRAFTS

Available sources: Bovine and Procine Different processing technique…. Biocompatible and

structurally similar Xenografts are osteoconductive. Readily available and almost entirely free of the risk of

disease transmisson.  Two types Bovine anorganic cancellous bone (BACB) Bio-Oss Biolgical apatite crystals –blocks/ granules Procine non – antigenic collagen (PNAC) Bio-Oss collagen Healthy pigs

Collagen – alkaline treatments- bilayer structure- eliminate risk of bacterial or viral contamination

Specific purification process… Antigenicity and Residual fat or protien

BIO-OSS

Natural, osteo conductive bone subsitute that promotes bone growth.

Consists of mineral portion of bovine bone, provides the body with matrix for the bone cell migration and integrated into the natural physiologic remodelling process.

Its natural bone mineral offers preidictable results which have been poven through years of clinical experience.

Bio- Oss : morpholology like human bone. 

BIO –OSS COLLAGEN

It consists of bio oss spongiosa granules(0.25-1 mm) and 10% highly purifieed procaine collagen.

It is highly porous, posessed a large internal surface area and functions as a scaffold for bony ingrowth.

The collagen component enables convenient handling and simple appplications but doesnot functions as a barrier

PEP - GEN 15

It is a procaine inoranic bone. It contains a synthetic 15 amino acid sequence

with stearic simillarities to the cell binding sites of type 1 collagen.

Pep gen P 15 uses a synthetic peptide that is irreversibly bounbd ot an inorganic bovine derived material , a natural substance simillar to that found in human bone.

It promotes attatchment of reparative cells from surrounding tissues and facillitates the biometric environment for bone growth

They are chemically diverse synthetic, inorganic, biocompatible and bioactive bone grafts substitutes that are supposed to promote bone healing through osteoconduction.

Various types: Hydroxyapatite Ceramics i) resorbable (β tricalcium phosphate) ii) non resorbable (bioactive glasses) Polymers

ALLOPLAST

Hydroxyapatite: Major inorganic component of bone Available in porous non resorbable, dense non

resorbable and resorbable forms Resorbability of hydroxyapatite is determined by the

temperature at which it is processed.

β tricalcium phosphate (β TCP) It is porous form of calcium phosphate It serves as a biological filter It is partially resorbable, first serving as a scaffold and

then is replaced by bone. It is superior to hydroxyapatite in stimulating bone

formation but inferior to bioglass in stimulating bone formation.

Bioactive glasses

Bioactive glasses are composed of CaO, NaO, SiO and P2O5. When bioactive glasses are exposed to tissue fluids, a layer of silica

gel and calcium phosphate is formed on the surface. The soluble silica gel layer promotes bone formation of osteoblasts

through extracellular bone matrix.

Polymers They are biocompactible microporous composites of

polymethylmethacetate, polyhydroxyethyl mathaacetate and Ca(OH)2. They are hydrophilic which enhances clotting and their negative

charged particles allow adherence to bone. They appear to serve as a scaffold for bone formation when it close

contact with alveolar bone.

The flap is extended atleast one tooth mesial and distal to the defect for exposure of atleast 2-3mm of surrounding sound bone. Vertical releasing incisions are optional.

Once the flap are reflected, there are three zones-Root surface,Soft

tissue and Bone are addressed.

ZONE-1: The root surface is meticulously scaled and root planned.

Scaling alone is not sufficient because it will not remove softened or necrotic cementum, bacterial endotoxins, remnants of junctional epithelium or residual calculus. Enamel finishing burs are often used to smooth the root surface. If thorough root preparation is not carried out,the root surface may not be amenable to cementogenesis are able to sustain the growth of fibroblast.

 

SURGICAL PROCEDURES FOR PLACEMENT OF BONE GRAFT:

ZONE 2: Soft tissue

With flaps reflected, large curettes are used against the bony surface to remove all granulation tissue and residual fibers attached to the bone. All fibers must be removed to open the marrow spaces and permit intimate contact between graft material and bone.

ZONE 3:BONE

Chronic wounds are often associated with a dense or sclerotic bone that is poorly vascularized and therefore less osteogenic than freshly created defects. For this reasons decortications is performed with round burs(NO 0.25-0.5)permitting rapid proliferation of granulation tissue with undifferentiated mesenchymal cells, rapid degeneration of bone and rapid anastomoses of graft and bone.

The graft material is placed in small increments and care is taken to pack each increment down adequately while moving excessive fluid.

Overfilling of graft will compensate for some loss of graft material but will make primary closure difficult.

The flap are reapproximated with digital pressure to cover the defect completely.

The vertical mattress or intrapapillary suturing is ideally recommended using monofilament. 

All grafting technique requires presurgical scaling, occlusal adjustment as needed and exposure of the defect with full thickness flap. The flap technique best suited for grafting purposes is the papilla preservation flap, because it provides complete coverage of interdental area after suturing. The use of antibiotics after the procedure is generally recommended.

The combination of barrier techniques with bone grafts and other methods has been suggested and procedures following these ideas proposed by several authors. The following technique has been described by Schallhorn and Mc Clain.

Perform a regenerative type flap. It reuisin has occurred and coronal flap positioning is required for membrane coverage periosteal separation is performed. 

Defect is debrided of all granular tissue and the root surface is planned to remove all reminants of plaque accretions and other root surface alterations.

  Odontoplasty or osteoplasty are performed if required for adequate

access to the defect including intraradicular or furcation fundus concavities and reduction of enamel projection.

COMBINED TECHNIQUES

The bone graft is prepared in a dapen dish, hydrating it with sterile saline or local anesthetic solution.

  Appropriate membrane is selected and trimmed to fit the

deserved position and placed on a sterile gauze.  The area is thoroughly cleansed and isolated and regenerative

site root surface is treated with cotton pellets soaked in citric acid pH 1-3 minutes taking care that the solution does not go beyond the root and bone surface.

  If a sclerotic bone surface exists in the graft site, intramarrow

penetration is performed with ¼ .  The ligament surface is “scrapped” with a periodontal probe to

remove any scar and stimulate bleeding.

The DFDBA is packed firmly in the defect using an overfill approach covering the root trunk and combination or confluent vertical dehiscence or horizontal osseous defects.

  The custom-fitted membrane is places over the graft and

secured as appropriate.  The area is rechecked to ensure that adequate graft

material remains in the described area and the flap is positioned to cover the membrane and recurred with nonabsorbable sutures.

  The periodontal dressing is passively applied over the

surgical area with surgical covering the sutures..

The future of periodontal regenerative techniques depends on the emergence of new products , which will lead to a predictable positive outcome when used in proper combination in select sites and patients…

CONCLUSION