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Dental bases and liners

Restorative Dentistry
Forth Year

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Dental bases and liners

  1. 1. Dental Base and Liners Dr Rasha Alsheikh B.D.S., M.S.D KFU
  2. 2. Irritants Decay. Cavity preparation procedure. Restorative materials used. Leakage and Secondary caries lesions. ... !"#$%&'%#()*%+
  3. 3. Pulp Reaction to Irritation Healthy Reparative Reaction. Unhealthy Reparative Reaction. Destructive reaction.
  4. 4. Objective To prevent further irritation of the dento-pulpal tissues as well as to improve the defensive capability of the dento-pulpal tissues. Serve as a barrier against thermal changes, chemicals (irritants within the material), leakage (bacterial byproducts).
  5. 5. Condition of the tooth to be restored. configuration of cavity preparation, amount of the remaining dentin thickness (RDT). type of restoration to be used. Considerations
  6. 6. Classification Varnishes Liners Sub bases High strength bases Resin in a solvent Calcium hydroxide Calcium hydroxide, Zinc oxide-eugenol, Glass Ionomers. Glass ionomers, Resin- modified glass ionomers, Re-inforsed zinc oxide- eugenol, Zinc phosphate, Zinc polycarboxilate
  7. 7. Requirement: 1.should be capable an impervious layer on cut vital dentin, with thickness not compromising the bulk of the overlying restoration or its mechanical properties. 2.biologically compatible dento/pulpal tissues. 3.chemically compatible with both the dento/ pulpal tissues and the restoration.
  8. 8. 4.the material should not discolor neither the restoration nor the tooth. 5.should harden quick enough to allow subsequent insertion of the restoration. 6.should withstand (without change in shape or location) the condensation forces involve with the placement of the over laying restoration.
  9. 9. 7. stabilize or further diminish dentin permeability. 8.easily manipulated during preparation or insertion.
  10. 10. Thermal Properties ZOE , GI, Calcium Hydroxide, Z Polycarboxilate falls within the range of recognized insulators. minimal thickness 0.75mm
  11. 11. Protection against chemical insults Calcium hydroxide and ZOE provide an effective barriers against the penetration of irritants. GIC and Z-polycarboxilate can also be used as chemical insulators. Z-phosphate acidity is a concern.
  12. 12. The ability to with stand the occlusal stresses and to support the restoration is affected by the modulus of elasticity. Strength must be developed quickly. Low solubility. Physical properties
  13. 13. Fluid and water absorption: the more porous the material the greater will be the chance for fluid uptake. Calcium hydroxide is the most soluble followed by ZOE then ZPC. GIC least soluble. Coefficient of thermal expansion, ZOE is the closest to the tooth structure. viscosity: calcium hydroxide followed by ZOE had the highest flow. ZPC the highest viscosity.
  14. 14. Pulp Reaction Zinc Oxide-Eugenol: • the least irritant to the pulp • when placed within an effective depth + healthy pulp = reparative reaction. • when in direct contact with the pulp: - healthy and sound pulp slight inflammation will take place that might remain confined or may progress to involve all the pulp or may exacerbate to acute inflammation.
  15. 15. - if placed in direct contact with acute inflamed pulp the acute inflammation will subside then chronic inflammation takes place, further prognosis is similar to the healthy pulp exposure.
  16. 16. Calcium hydroxide: • it can be irritant • if placed at 100 micron or more healthy reparative reaction will occur. • if placed at less than 100 micron an unhealthy reparative reaction occur.
  17. 17. • if placed in contact with the pulp tissue: - if healthy pulp, pulp will deposit organic matrix which will mineralize within 4-6 weeks. - if degenerative pulp, the degeneration will convert to calcific degeneration, RCT is indicated before complete obliteration of the pulp space.
  18. 18. Zinc phosphate: • the most irritant base used: - acidity during setting (PH 3-4 at first) can be reduced by increasing the P/L ratio. - Microleakage as its soluble. - exothermic reaction.
  19. 19. • at 2.5 mm depth ZP can induce healthy reparative reaction. • at 1.5-2 mm depth an unhealthy reparative reaction will occur. • at depth < 1.5 mm there will be distraction in the pulp tissue.
  20. 20. Zinc polycarboxilate: • minimally irritating: - exothermic reaction - porosity - acidity (less than Zp)
  21. 21. • at 1 mm depth healthy reparative reaction occur. • at depth < 1 mm unhealthy reparative reaction or further distruction can take place. • when come in contact with the pulp distractive reaction occurs.
  22. 22. LINERS: relatively thin layers of material used primarily to provide a barrier to protect the dentin from residual reactants diffusing out of the restoration or from the oral fluids that may penetrate the tooth/restoration interface. They provide electrical insulation, some thermal protection. Terminology
  23. 23. some materials can provide pulpal treatment. indicated in with the pulpally extended metallic restorations that are not well bonded to tooth structure and not insulating ( amalgam, cast gold and other indirect restorations).
  24. 24. BASE: applied in thicker layers to provide thermal protection for the pulp and to supplement mechanical support for the restoration by distributing local stresses from the restoration to the underlying dentin. provide support during condensation of amalgam in case of thin dentin layer remaining.
  25. 25. Varnishes: A natural gum (copal), rosin, or synthetic resin dissolved in organic solvent. thin film Reduce leakage around the margins and walls of the cavity, prevent penetration of corrosive products of amalgam into dentin. Not to be used under composite restorations(interfere with the setting reaction) or glass ionomer restorations (prevent fluoride release).
  26. 26. Varnish is applied using a small cotton pledget. imageCache/Product/200
  27. 27. Liners: Dispersed calcium hydroxide in aqueous or resin carrier solution. Calcium hydroxide formation of reparative dentin PH = 11 only on dentin.
  28. 28. Glass-Ionomer Liners Faster setting Flow Contain hydroxidyl methacrylate no conditioning required Powder/Liquid Light cured GIC serve as an intermediate bonding material between dentin/composite restoration
  29. 29. Bases Thicker protective layers of cement that are placed under restorations, encouraging the recovery of the pulp and to protect the pulp from further insults.
  30. 30. Zinc Oxide- Eugenol Contain eugenol oil sedative effect. Powder/liquid or two pastes. Setting reaction mainly wetting of the ZO particles by the oil, chelating reaction follow. Retard penetration of acids and reduce any possible discomfort. !"#$%%&#'()*+,-.-/0*-)+(12%,-.-#0*-)%3(//(45% 6!&/7%8%80%9&16:-60;#('<!0*1)+#42%=>?#@A 9&16:-60;#('<!0*1)+#42B
  31. 31. Thin layer little thermal insolation. Strength and modulus of elasticity are low. Used in less stress bearing area, but can withstand the application of restorations. High strength base is often placed over. contra indicated under composite restorations( interfere with the setting reaction)
  33. 33. !!!"#$%&'"(%)*+%,-"./01
  34. 34. Calcium Hydroxide Cement Used for direct & indirect pulp caping beneath composite restorations. Two pasts, the reaction result in the formation of amorphous calcium disalicylate. Contain radiopaque fillers. Light cured product Urethane dimethacrylate & calcium hydroxide + low- viscosity monomer.
  35. 35. LOW COMPRESSIVE STRENGTH GREAT SOLUBILITY Thin layer little thermal insolation. Stimulate the formation of reparative dentin. Setting time 2 to 7 min
  36. 36. Zinc Phosphate Water based cement. Powder/Liquid: powder oxide mixed (ZO & MO) & sol. of phosphoric acid. Exothermic reaction hydrated amorphous network of z-phosphate surrounds incompletely dissolved particles. Setting time 5-9 min.
  37. 37. Fast setting High mechanical properties. Low acidity of the set cement. low solubility. Mixing over a large area in a cold slab. high acidity (pulp irritation)
  38. 38. Zinc Polycarboxilate Water based cement Powder/liquid: ZO/ viscous sol. of polyacrylic acis forms amorphous network of Z- polyacrylate surrounding the unreacted ZO particles. Not as strong as the Z-phosphate but less irritating to the pulp.
  39. 39. Moderate viscosity, moderate strength. Bond to enamel, mildly acidic. Histologic reaction similar to ZO- euginol. Short working time 3 min. Mix over a small area with a stiff spatula.
  40. 40. Glass Ionomer Cements Water based cement. Powder/Liquid or pre-packed capsules: powder (flouroaluminosilicate) liquid(aquas solution of polycarboxilate acid) slow acid base reaction result in the formation of amorphous silicate network surrounding the unreacted particles. chelating effect on tooth surface resulting in bonding to enamel and dentin.
  42. 42. Type I: Cementation of indirect restoration and orthodontic brackets. Type II: Restoring areas near the gingival tissue ( class V) Type III: used as liner and dental bonding agent.
  43. 43. Resin Modified GIC Were introduced to over come the problim of water sensitivity of GIC. and to improve the mechanical properties of GIC. powder/liquid: powder (flouroaluminosilicate), liquid (aquas solution of polycarboxilate acid modified with pendant methacrylate group, HEMA)
  44. 44. liner base cement advantage Limitation varnish X low cost long history of use washes out at the margin Calcium hydroxide x x tepm. low cost long history of use most effective zinc oxide eugenol x x x antibacterial long history of use sealing ability unable to withstand condensation forces zinc polycarbixilate x x long history of use thickness may inhibit the seating of cast glass ionomer x x fluoride release moisture sensitive resin x x strength sensetive
  45. 45. Temporary Filling: Maintain the position of the prepared tooth. Seal, insulate the preparation and protect the margins. Establish proper vertical dimension. Aid in diagnosis and treatment planning. Aid to evaluate candidate for esthetic replacement.
  46. 46. Function: Protection of the dentin-pulp organ. Sedation of the irritated pulp. Restoration & protection of  normal occlusion by preventing over eruption and tilting of teeth. Protection of periodontium. Restoration of tooth
  47. 47. Have enough strength and retention to withstand forces to which it will be subjected. Easily handled, contoured, polished and removed. Dimensionally stable. Short setting time. Doesn’t interfere chemically with
  48. 48. Types of Temporary Direct PR Intra coronal Prefabricated Indirect PR Extra coronal
  49. 49. Temporary Fillings: GI RMGI Z Ph ZOE Reinforced ZOE Non E-ZO Z-polycarboxilate Resin Acrylic Polycarbonate Cellulose acetate Aluminum
  50. 50. ANY QUESTION?