Dentin boning agents /certified fixed orthodontic courses by Indian dental academy


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Dentin boning agents /certified fixed orthodontic courses by Indian dental academy

  1. 1. DENTIN BONDING AGENTS INDIAN DENTAL ACADEMY Leader in Continuing Dental Education  
  2. 2.  ADHESION- The mechanism that bonds two materials in intimate contact across an interface - Davidson (1996). Types of adhesion 1. Physical Bonding 2. Chemical Bonding 3. Mechanical Bonding 1. PHYSICAL BONDING Physical bonding involves Vander walls forces or other electrostatic interactions that are relatively weak. It may be the only type of bonding if surfaces are smooth and chemically dissimilar. 2. CHEMICAL BONDING Chemical bonding involves bonds between atoms formed across the interface from the adhesive to the adherend. Because the materials are often dissimilar, the extent to which this bonding is possible is limited and the overall contribution to bond strength is normally quite low.  3. MECHANICAL BONDINGMechanical bonding is the result of an interface that involves undercuts and other irregularities that produce interlocking of the materials. 
  3. 3.  CHEMICAL ADHESION Primary atomic bonds may be of three different types: 1) Ionic, 2) Covalent, and 3) Metallic. Ionic Bonds These primary bonds are of simple chemical type, resulting from the mutual attraction of positive and negative charges. The classic example being sodium chloride (Na+Cl-). Because the sodium atom contains one valance electron in its outer shell and the chlorine atom has 7 electrons in its outer shell, the transfer of the sodium valance electron to the chlorine atom results in the stable compound Νa+Cl−. Covalent Bonds In many chemical compounds, adjacent atoms share two valance electrons. The hydrogen molecule, H 2 is an example of covalent bonding. The single valence electron in each hydrogen atom is shared with the other combining atom, and the valence shells become stable.   Metallic Bonds Certain atoms of a few crystals like gold can easily donate electrons from their shell and form a gas of free electrons. The contribution of free electrons to this could results in the formation of positive ions that can be neutralized by acquiring new valence electrons from adjacent atoms.
  4. 4.  Inter atomic Secondary Bonds In contrast with primary bonds, secondary bonds do not share electrons. Instead, variation among molecules or atomic groups induces polar forces that attract these molecules. a. Hydrogen Bonding In water molecule one oxygen atom is attached to two hydrogen atoms. These bonds are covalent because the oxygen and hydrogen atom share their electrons. As a consequence, electrons do not shield the protons of the hydrogen atoms pointing away from the oxygen atom efficiently. Thus the proton side of the water molecule becomes positively charged. On the opposite side of the water molecule, the electrons that fill the outer orbit of the oxygen provide a negative charge. When water molecule mingles with other molecules the hydrogen portion of one molecule is attracted to the oxygen portion of its neighboring molecule, and hydrogen bridges are formed.   Vander Walls Forces Normally the electrons of the atoms are distributed equally around the nucleus and produce an electrostatic field around the atom. However this field may fluctuate so that its charge becomes momentarily positive and negative. A fluctuating dipole is thus created that will attract other similar dipoles. Such inter atomic forces are quite weak.
  5. 5. ENAMEL ADHESION Buonocore- first proposed chemically treating enamel with acid solutions in 1955. -H3PO4 creates micro-porosities in the enamel surface and enables bonding of resin to this surface via micro mechanical retention. Application time- 15 seconds The first bonding agents marketed for this technique were unfilled BISPHENOL A GLYCIDYL DIMETHACRYLATE (BIS GMA) resins. Enamel etching results in three different micro morphologic patterns. Type 1: The most common type involves preferential removal of the enamel prism cores, the prism peripheries remaining intact. Type 2: Etching pattern is the opposite of type 1 involving preferential removal of the peripheries with the cores being left intact. Type 3: Etching pattern contains areas, which resembles both type 1 and type 2 along with some distinct areas where the pattern of etching appears to be unrelated to the enamel prism morphology.
  6. 6.  Gwinnett and Buonocore -use of lower acid concentrations to prevent the formation of precipitates that could interfere with adhesion. Application of 50% phosphoric acid for 60 seconds -monocalcium phosphate monohydrate precipitate that can be rinsed off. concentrations below 27% may create a dicalcium phosphate monohydrate precipitate that cannot be easily removed and, consequently, may interface with adhesion. Other acids -maleic acid, citric acid, nitric acid and oxalic acid
  7. 7. HYBRID LAYER HYBRID LAYER: (“adhesion interface”, “resin-dentin inter-diffusion zone”, inter penetration zone). is a “transitional zone of resin reinforced dentin sandwiched between cured resin and the unaltered dentinal substrate” (Nakabayashi 1982). essential mechanism of adhesion -micro- mechanical & generated by monomer impregnation of the exposed collagen of demineralized superficial dentin.
  8. 8. REQUIREMENTS OF A DENTIN BONDING AGENTBond strength: Biocompatibility of the material:Long-term durability of the bond:.Polymerization’s shrinkage:
  9. 9.  Adhesive forces operating across an interface depends on several factors.    Clinical factors affecting adhesion Factors affecting adhesion to mineralized tissue . Clinical Factors Affecting Adhesion Salivary and or blood contamination Moisture Contamination From Hand-piece. Oil contamination of hand piece of Air Syringe Surface roughness of tooth surfaces Mechanical undercuts in tooth preparations Fluoride contents of teeth
  10. 10.  Presence of plaque, calculus, extrinsic stains / debris Presence of bases or liners on prepared teeth Tooth dehydration. Constituents of temporary cements
  11. 11. FACTORS AFFECTING ADHESION TO MINERALIZED  I. Factors related to theTISSUES adherent 1. Physicochemical properties of dentin that complicate dentin adhesion 2. The dentin smear layer and dentin permeability. 3. Transformed dentin surface structure due to physiological and pathological processes.   II. Factors Related to The Restorative Resins i. Physical properties of adhesives. ii. Polymerization contraction of restorative resins. iii. Young’s modulus of elasticity. iv. Initial polymerization site v. The relaxation of contraction stress by hygroscopic expansion. vi. Thermal expansion coefficient and thermal conductivity. vii. Transmission of stress across the composite dentin interface.
  12. 12. CLASSIFICATION ACCORDING TO GENERATIONS  FIRST GENERATION DENTIN BONDING AGENTS  -Buonocore 1956  a glycerophosphoric acid dimethacrylate – containing resin would bond to acid etched dentin.  bond -due to the interaction of this bifunctional resin molecule with the calcium ions of hydroxyapatitie, but immersion in water would greatly reduce this bond. Nine years later Bowen tried using N-Phenyl glycine and glycidyl methacrylate (NPG-GMA), which is a bifunctional molecule or coupling agent. This molecule had one end bonding to the dentin while the other bonds to the composite resin. The bond strengths of these system was however 1-3 Mpa. The NPG-GMA also bonded to the dentin by chelation with calcium on the tooth surface.
  13. 13. Materials1.Glycerophosphoricacid dimethacrylate. 2. Cyanocrylate 3. N-Phenyl Glycine – Glycidyl Methacrylate Eg., CERVIDENT No commercial products are available from this generation. Intraoral hydrolysis of GPDM, polymerization problems of Cyanocrylate and instability of NPG- GMA precluded their use. DISADVANTAGES: 1. Poor bond to dentin familiar amalgam type retentive cavities 2. Used only for small class III and class V restorations where there was adequate enamel to which to bond. 3. Postoperative sensitivity in attempted posterior occlusal restorations.
  14. 14. SECOND GENERATION DENTIN BONDING AGENTS 1970- halo phosphorous esters of unfilled resins bisphenol-A glycidyl methacrylate (Bis-GMA), hydroxyethyl methacrylate (HEMA). bonded to dentin by an ionic bond to calcium by chloro phosphate groups. These were weak bonds but were an improvement over the first generation systems.
  15. 15.  MATERIALS a. Clearfil – A reaction product of 2 – HEMA and a phenyl phosphate ester. (Phenyl – p) was utilized. 1 – 3 Mpa. b. Scotch Bond – Halo phosphorous ester of BIS – GMA. 1 –3 Mpa. c. Prisma Universal Bond – 6.5 to 7.0 Mpa. d,. Dentin Adhesit – An adhesive system that utilizes a isocyanate onomer and 5% NaOcl as a conditioner – solubilize the dentin collagen.  DISADVANTAGES 1. Weak bond to dentin 2. Mechanical retention form was still necessary since bond strength alone was inadequate. 3. Margins on dentin were problematic since the low dentinal bond strengths permitted extensive marginal microleakage. 4.Restoration failure occurred most commonly due to hydrolytic decomposition.
  16. 16. THIRD GENERATION DENTIN BONDING AGENTS Acid etching of the dentin partially removes or modifies the smear layer Acid opens the dentin tubules partially and increases their permeability acid must be rinsed completely before application of the primer. The primer -hydrophilic resin monomers like hydroxyethyl trimellitate anhydride and bisphenol dimethacrylate (BDPM). The primers contain a hydrophilic group that infiltrates the dentin and the hydrophobic group that adheres to the resin. The dentin primers usually used in these third generation systems may be 6% phosphate penta-acrylate (PENTA); 30 percent HEMA and 64% ethanol. After the application of the primer the unfilled resin adhesive is applied. In most of these systems, the phosphate primer modifies the smear layer by softening it after penetration and it cures forming a hard surface. The adhesive is then applied attaching the cured primer to the composite resin. However bonding was not very successful because the resins did not penetrate the smear layer and the smear layer was very weak.
  17. 17. - XR bonding system - Gluma bonding system - Tenure dentin bonding system - 4 META - Phenyl-P - Mirage bond Super bond
  18. 18. FOURTH GENERATION DENTIN BONDING AGENTS complete removal of the smear layer
  19. 19. FIFTH GENERATION DENTIN BONDING AGENTS reducing the bonding steps The fifth generation consists of two different types of adhesive materials. - The so called “one bottle system”. - Self etching primer bonding systems. Indications: • Direct composite restoration. • Indirect bonding. • Root desensitization
  20. 20.  Chemistry: • HEMA, BisGMA, dimethacrylates, and patented polyalkenoic acid copolymer. • Technique: • Etch enamel and dentin for 15 seconds. • Using a fully saturated brush tip, apply 2 consecutive coats of Single Bond. • Dry for 2-5 seconds. Light-Cure for 10 seconds Water and ethanol
  21. 21. SIXTH GENERATION DENTIN BONDINGAGENTS proper bond to enamel and dentin used only one solution. 1. Compartment 1 : Containing methacrylate phosphoric acid esters, photo initiators and stabilizers. 2. Compartment 2 : contains water, complex fluoride and stabilizers. 3. Compartment 3 has a micro brush.
  22. 22. CLASSIFICATIONS OFMODERN ADHESIVES   Classified based on number of clinical application steps and interaction with tooth substrate.  1. Total etch adhesives [E + P,A] a) Two step etch adhesives [E + P + A] b) Three step etch adhesives2. Self etch adhesives [E + P, A] a) Two step self etch adhesives [E + P + A] = [C,P,A] b) One Step self etch adhesives