Dentin Biomodification Question And Answers

Root Biomodification Question And Answers

• The periodontium consists of a cell and tissue complex organized spatially into the basic components of cementum, periodontal ligament, and alveolar bone. The challenge of regeneration is to reconstitute this complex onto a root surface that is the site of marginal periodontitis.
• Periodontitis produces substantial changes of the tooth root surface. The normal root is rich in collagen with extrinsic and intrinsic fibers that form a renewable connection to the adjacent alveolar bone.

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• Plaque-induced inflammation destroys these fibers allowing down growth of junctional epithelium. Thus the root surface becomes exposed to the periodontal pocket and the oral environment with loss of collagen.
• The root surface also becomes hypermineralized and loaded with bacterial toxins. Thus it becomes unsuitable for new connective tissue attachment necessary for periodontal regeneration.

Question 1. Describe the rationale and classification of root biomodification.
Answer:

Root bio modification refers to procedures performed on periodontally affected root surfaces in order to make it a hospitable substrate and encourage migration, attachment, and proliferation of periodontal connective tissue progenitor cells.

Root bio modification is classified as:

1. Mechanical bio modification: Scaling and root planing, laser
2. Chemical bio modification: EDTA, citric acid
3. Biochemical bio modification: Tetracycline
4. Biological bio modification: Enamel matrix derivatives, growth factors.

1. Mechanical Biomodification

• Mechanical bio modification involves scaling and root planing which is the most important step.
• This includes the removal of necrotic cementum as well as the removal of softened dentine. Although scaling and root planing is effective in removing bacterial deposits and endotoxins from the root surface, it results in the formation of a smear layer, a residue of highly calcified material laden with bacteria and its by-products.
• On the planed surface, this smear layer is considered to be a physical barrier that inhibits the formation of new connective tissue attachment.

2. Chemical Biomodification

• The biochemical approach to periodontal regeneration uses acid demineralization (citric acid, tetracycline HCL), ethylenediaminetetraacetic acid (EDTA), and protein activation (growth factors).
• The principle is that demineralization of the root surface will preferentially increase protein binding and promote fibroblast attachment while at the same time inducing epithelial exclusion by contact inhibition.
• Simultaneously, protein activation enhances specific cell proliferation, chemotaxis, and enhanced cellular attachment.

Question 2. What are the agents used for root bio-modification?
Answer:

Materials used for Chemical Biomodifiation

• Citric Acid
  • Topical application of citric acid (pH-1) demineralizes the root planed cementum and/or dentin to a depth of 1–5 µm, exposing the collagen fibrils of cementum and/or the dentin matrix.
  • This exposed collagen enhances the linkage between the firing in the blood clot and the demineralized root surface. This initial firin linkage to acid-conditioned root surfaces is apparently stable and seems to prevent apical migration of epithelium and promotes new connective tissue attachment.

Citric acid acts through one or more of the following mechanisms:

1. Demineralization of the root surface
2. Root detoxification
3. Removal of smear layer
4. Exposure of root collagen and opening of dentinal tubules
5. Initial clot stabilization
6. Enhanced fibroblast growth and stability.

• Tetracycline HCL
  • More recently, interest has been focused on the potential of tetracycline hydrochloride for conditioning the planed root surface. Similar to citric acid, an aqueous solution of tetracycline HCL demineralizes the root surface, removes the smear layer, and exposes the dentinal tubule (not as widely as in citric acid).
  • In addition to its demineralizing ability, tetracyclines have several other properties such as antimicrobial activity against periodontal pathogens, substantivity to root surfaces, collagenase inhibitory effect, anti-inflammatory effect, and ability to inhibit bone resorption.
  • All these properties would seem to make it more desirable for use as a root conditioner.
  • The recommended technique is similar to citric acid except that the application time of tetracycline HCL is 5 minutes because a saturated solution of tetracycline hydrochloride gives a pH between 2–3 only.
• Growth Factors
  • A growth factor is a general term used to denote a class of polypeptides that stimulate a wide variety of cellular events such as proliferation, chemotaxis, differentiation, and production of extracellular proteins. These factors are primarily produced by cells in the inflamed area (macrophages, endothelial cells, fibroblasts, platelets, etc.).
  • Factors include platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), basic fibroblast growth factor (FGF), and transforming growth factor (TGF) α and β. Growth factors could be used to control events such as the proliferation of fibroblasts and osteoblasts from the periodontal ligament during periodontal wound healing.
  • It has been found that PDGF and IGF interact synergistically to accelerate the regeneration of all components of the periodontium.
• Bone Morphogenic Proteins (BMPs): These are a group of 20–30 related proteins, are osteoinductive factors that may have the potential to stimulate mesenchymal cells to differentiate into bone-forming cells. The most commonly used are BMP-2 and BMP-3 (osteogenesis).
• Fibronectin: This is an extracellular matrix glycoprotein and it acts as a bridge between cells and the collagen matrix by its ability to act as a substratum for cell adhesion. Fibronectin promotes migration, adhesion, attachment, and synthetic ability of fibroblast.
• Laminins
  • These are a group of structurally related glycoproteins and they are a major non-collagenous protein component of the basement membrane. Laminins are highly interactive molecules that contribute to the network structure of the basement membrane through their interaction with type 4 collagen and other proteins.
  • The basement membrane regulates the cytoskeletal organization of cells and it can thus influence cell shape, gene expression, migration, and differentiation.
  • It has been established that both fibronectin and laminin are involved in the attachment of gingival fibroblasts to root surface. Thus there has been considerable interest in utilizing these agents to promote fibroblast attachment to root surfaces and establish new attachment.
• Enamel Matrix Proteins (EMPs)
  • These are produced by mesenchymal cells of the dental follicle when it gets exposed to the
  • Hertwig’s epithelial root sheath. EMPs stimulate undifferentiated mesenchymal cells to form cementoblasts. Among EMPs, amelogenins make up a large part and amelogenins with similar molecular structures have been found in many different mammalian species.
  • Placement of EMPs on a properly prepared tooth surface during surgery can result in significant regeneration of lost periodontal tissues.

Ethylene Diamine Tetra Acetic Acid (EDTA)

• Non-buffered EDTA had been used to remove the smear layer of its low ph. Recently, neutrally buffered EDTA (PrefGel®) has been used as a root conditioner in conjunction with the use of enamel matrix proteins. This removes the smear layer by acting as a chelating agent.
• The use of various factors for conditioning the root surface has been reported in the literature with varying results. However, a decision to incorporate these materials into regular surgical techniques is as yet pending.
• Specific techniques, such as Miller’s technique for the treatment of gingival recession and the use of enamel matrix proteins for periodontal regeneration, however, require the use of certain root conditioning agents. In these situations, limited success has been demonstrated and this justifies the adjunctive use of such conditioners in these techniques.