Liners and bases

1. PULPAL
CONSIDERATIONS
Dr. Mahvesh Hasan
FCPS II TRAINEE
Dept of Operative Dentistry
DIKIOHS

2. Importance of remaining dentin
thickness
0.5 mm
1 mm
2 mm
Remaining
dentin
thickness
25 %
10 %
Minimal
or Nil
Effect of
toxic
substances

3. Causes of Pulpal Inflammation
Types of stimulus Examples of stimulus
Physical Thermal, electrical
Mechanical Handpiece,
traumatic occlusion
Chemical Dental
materials, Caries
Biologic Bacteria from saliva

4. Response to bacteria
Even early enamel caries lesions that extend less than one-
fourth of the way to the DEJ have been shown to induce a
slight pulpal reaction

5. Response to bacteria
• Reparative Dentin
• Reactionary Dentin
• Dentin Sclerosis

6. Response to bacteria

7. Marginal leakage

8. Response to instrumentation
Research has shown that 3% to 22% of
teeth with full coverage crowns require
endodontic therapy

9. Response to instrumentation
• The degree of pulpal reaction is dependant on the
amount of friction and dessication
• Frictional heat generated by tooth preparation can
result in burn lesions in the pulp and abscess
formation
• Dessication results in dentinal fluid being lost from
tubules
• Pressure has greater effect on temperature rise than
rotational speed

10. Clinical impact
• Preparation using low-speed rotary instrumentation
has been shown to be more traumatic to the pulp
than high-speed preparation.

11. Keys to minimizing adverse pulpal
reactions from rotary instrumentation
• Adequate air-water coolant spray
• Light pressure
• Sharp rotary cutting instruments
• Preservation of tooth structure

12. Hydrodynamic Theory
When a stimulus causes the slow fluid movement to
become more rapid, nerve endings in the pulp are
deformed , creating a response that is interpreted as
pain

13. Classification and types
• CAVITY SEALERS: Varnish, Adhesive sealers
• CAVITY LINERS: Glass ionomer, Calcium hydroxide
• Bases: - 1. Zinc phosphate cement.
2. Reinforced zinc oxide / eugenol
cement.
3. Zinc polycarboxylate cement.
4. Glass ionomer cement.

14. Cavity sealers
• Varnish
• Adhesive sealers
• Provide protective coating and barrier to leakage
• Coat all walls of the cavity
• Provide various degrees of seal

15. Varnish
• Material applied in thin film thickness usually 2 – 5
microns.
• It could be applied to all prepared cavities on both
enamel and dentin.
• Protective coating and Barrier to leakage
• Seals the dentinal tubules and reduces leakage
around a restoration.
• Provides no thermal
insulation

16. Varnish
Composition:
• Organic copal resin or synthetic gum dissolved in
solution of ether, chloroform or acetone.
• This solution evaporates rapidly after placement on
the tooth leaving a thin layer of semi-permeable
membrane.
• The thickness of this layer is 5 – 25 microns
depending on the type of the solvent and the
number of applications.

17. • Application process
o Applied with either a small disposable applicator or a cotton pellet.
o Thin coating of the varnish on the walls, floor, and margin of the cavity
preparation.
o Apply a second coat.

18. Adhesive sealers
• Provide sealing as well as bonding at the interface
between restoration and cavity preparation walls.

19. Concerns about use of adhesive
sealers under amalgam
• Barrier to corrosion products
• More technique sensitive than varnishes
• Expensive and time consuming
• Pooling of resin
• Incorporation into amalgam

20. Cavity Liners
• Dental liners provide a thin barrier (0.5 mm) that
protects the pulpal tissue and provide some type of
therapeutic benefit.
• Main function : Physical barrier and therapeutic
effect
• It does not function as thermal insulators.
• It is applied only to dentin.

21. Cavity liners
• Calcium Hydroxide
• GIC

22. Calcium Hydroxide
• Indications for use
o Protects the pulp from chemical irritation by its
sealing ability.
o Stimulates the production of reparative or secondary
dentin.
o Compatible with all types of restorative materials.
• Application process
o Placed only on dentin.
o Placed directly over the deepest portion of the
preparation.

24. • Disadvantages:
• Has no obtundant property.
• Not strong enough to provide reliable support for a
restoration under heavy occlusal stresses, so a
strong base material should be used to cover it.

25. Glass ionomer cement
• Composition:
• Powder: → Fine ionomer silicate glasses
(Alumino-silicate).
• Liquid: → Aqueous solution of copolymer of
polyacrylic acid.
• Recommended as liners under resin
composites to reduce microleakage

26. Advantages:
• Adhesive to tooth structure
• Anticariogenic: → Through the release of fluoride
ions, which will be up-taken by hydroxyapatite to
be changed into → Fluoro-hydroxyapatite, which is
more acid resistant.
• Semi-translucent color → when dealing with anterior
restorative material it will not affect the color of the
final restoration.

27. • Disadvantages:
• 1- Water sorption, leading to:
→ Leakage.
→ Discoloration.
→ Penetration of microorganisms.
• 2- Low wear or abrasion resistance: → So, when
used as a restoration, it should not be placed in
stress bearing areas.

28. Bases
• Insulation
• Bulk build up
• Blocking of undercuts

29. • Resin composite exhibits low thermal diffusivity that
a thermal insulating base should be unnecessary
• Insulating base for thermal protection should be
used under metallic restorations
• Thickness 0.5-0.75 mm