LINERS & BASES.ppt vvv.vvvvvvvvvvvvvvvvv

Nsns usus u s jhjje isisu jsjsjss kshshsg kskshssu gdhduid kdhdhd ks sjaijaj sisosi sjushss is dd.

1. LINERS & BASES
DR.AFSHEEN ALI KHAN

2. INTRODUCTION
•Liners & bases are the materials placed between
the dentin & restoration to provide pulpal
protection.
•Liners & bases should provide:
–Chemical protection
–Electrical protection
–Thermal protection
–Pulpal medication
–Mechanical protection

4. CLASSIFICATION
THIN FILM LINERS
1-50 micron
BASES
1-2 mm
SOLUTION LINERS
2-5 micron
SUSPENSION LINERS
20-25 micron
THICK FILM LINERS
200-1000 micron
LINERS

5. LINERS
•These are volatile suspensions or dispersions
that are applied to the tooth surface in a
relatively thin film.
•Primarily used to provide a barrier to protect the
dentin from residual reactants diffusing out of a
restoration &/or oral fluids that penetrate leaky
tooth restoration interface.
•Also provide initial electrical insulation, thermal
protection & some pulpal treatment.
•Especially required for pulpally extended metallic
restorations.

7. Solution liners (2-5um thick)
•Solution liners are volatile non-aqueous solvents
of copal or any other resin which when applied
to the tooth structure evaporates to leave a thin
film.
•Resin content is intentionally low to produce a thin
film on drying which is flexible & dries rapidly.
•Most solvent loss occurs in 8-10 seconds.
•A thin film of 2-5 micron is formed over the smear
layer.
•Due to moisture in the smear layer & hydrophobic
nature of varnishes, a single coat covers only 55%
of the surface.

8. Contd.
•A second coat is recommended to produce sealing
of 80-85% of the surface.
•These varnishes prevent penetration of materials
into the dentin & therefore prevent micro leakage.
•Also helpful in reducing post-operative sensitivity.
•Therefore, their use is especially recommended in
deep preparations with any restorative or
cementing material containing acid.

9. SOLUTION LINERS
•2-5 micron in thickness.
•Why we use it?
Tooth preparation with rotary instruments generates
cutting debris, some of which is compacted
unavoidably into a layer on the surface called smear
layer.
•Smear layer produces some degree of tubule
sealing, although it is 25-30% porous.
•This layer is weak & results in slow long term
diffusion at the tooth restoration interface.
•To prevent this, solution liners (varnishes) are used.

10. CONTRAINDICATIONS
•Not recommended under:
• composites because solvent in the varnish can
react with or soften the resin component in the
composite, adversely affecting polymerization.
•GIC: eliminates potential for adhesion
•When therapeutic action is expected from the
overlying cement e.g ZOE and CA(OH)2

12. Contd.
•Varnishes are no longer recommended, instead
sealers are recommended under non-bonded
restorations & bonding system for bonded
restorations.

14. SUSPENSION LINERS
•20-25 micron in thickness.
•These are aqueous solution of resin in which
particles are suspended instead of dissolved.
•Dry more slowly & produce thicker films.

15. THICK FILM LINERS
•Also known as cement liners.
•Applied in thickness of 200-1000 micron.
•Usually supplied as two components which are
mixed together, initiating a setting reaction.
•Should allow sufficient time for mixing followed
by rapid setting so that material can be placed into
the cavity.
•Should be opaque so that they can be easily seen
on radiographs.

16. FUNCTIONS OF LINERS
•To provide protective seal on the exposed dentin
surface esp. isolating metallic restorations from
electrical circuits.
•To provide thermal insulation which is
proportional to the thickness of insulating
material.
•Pulpal medication which is provided by:
–Relief of pulpal inflammation
–Facilitation of dentin bridge formation.

17. Contd.
•Eugenol
–Para-substituted phenolic compound.
–Used to alleviate discomfort resulting from mild to
moderate inflammation.
–Produces palliative/ obtundent action on the pulp
when used in very low concentrations.
•Calcium hydroxide
–Stimulates reparative dentin formation in low
concentrations.
–Undergoes chemical setting reaction. but allows
minor amounts of calcium hydroxide release to
produce desired effect.

18. •Degrade over time to an extent that it no longer
provides mechanical support to the overlying
restoration.
•To start reaction, some calcium hydroxide must be
dissociated by moisture from air or from moist
dental surfaces.
•Eugenol & calcium hydroxide should not be
incorporated into the same formulation because
eugenol chelates with Ca ions producing a massive
exothermic reaction.
•Ca(OH) must be placed only on floor of cavity not
walls because”
•A) it affects adhesion
•B) moisture removal of CaOH gap

21. BASES
•Cements that are used in thicker dimensions
beneath permanent restorations to provide
mechanical, chemical & thermal protection to the
pulp.
•Examples are zinc phosphate, zinc oxide eugenol
& glass ionomer cement.
•Produced by mixing dental cements at higher than
normal powder to liquid ratio.
•Provides increased compressive strength &
decreased concentration of potentially irritating
liquids.

24. Contd.
•Previously, in a deep preparation, a calcium
hydroxide liner is placed followed by base.
•This is followed by varnish & then amalgam
restoration.
•Currently, light cured calcium hydroxide & GIC
are being used to both line & base relatively deep
preparations.
•Historical use of traditional liners, bases &
varnishes has become obsolete as more focus is
directed on the use of various bonding agents to
provide sealing of dentinal tubules.

26. COMMERCIAL EXAMPLESCOMMERCIAL EXAMPLES
of Varnishes, Liners and Basesof Varnishes, Liners and Bases

27. PULPAL PROTECTION
PROCEDURES

28. •Indications for use
–To treat or prevent hypersensitivity.
–Used instead of a varnish.
–Seal the dentinal tubules.
–Ideal for use under all indirect restorations.
•Mechanism of action
–Glutaraldehyde acts by blocking the dentinal
tubules, therefore preventing fluid flow &
decreasing sensitivity.
DENTIN SEALER

29. •Application Process
–Do not allow to contact soft tissues (HEMA
and glutaraldehyde).
–Apply the dentin sealer with the cotton-tipped
applicator.
–Apply over all areas of the exposed dentin.
Contd.

30. Thank you