4. • Pulp is a specialized connective tissue that occupies the pulp chamber.
• It comprises of nerve ,vessels, lymph channels .
• The restoration and maintenance of dental health through adequate restorative
treatment in order to protect pulp function is the main purpose of restorative
dentistry.
5. WHAT IS PULPAL IRRITATION ?
• The dental pulp is characterized as a connective tissue and as such
it is not considered an external tissue, yet its exposure to external
stimuli is constant.
• This is due to a number of factors including the permeability of
attrited or disrupted enamel as well as that of physiologic dentin
and cementum.
7. VARIOUS TYPES OF IRRITANTS :
• Microbial irritation
• Mechanical irritation
• Thermal irritation
• Chemical irritation
• Radiant irritation
8. • MICROBIAL IRRITATION:
Caused by bacteria or other micro-organisms.
It can be in the form of coronal ingress i.e. dental caries and crown
fractures; radicular ingress i.e. root caries; retrograde infection.
9. • MECHANICAL IRRITATION:
It can be caused by :
- Operative procedures
- Occlusal trauma
- Deep periodontal curettage
- Orthodontic movement
10. THERMAL IRRITATION:
• Heat from cavity preparation
• Heat conduction by fillings
• Frictional heat during polishing
11. •CHEMICAL IRRITATION
Caused due to :
- Various filling materials
- Various medicaments used for dehydration and desensitizing dentin.
- Dentin sterilizing agents such as phenol, silver nitrate, eugenol etc.
12. • RADIATION IRRITATION
Caused by X-RAY radiation, LASER beam, uptake of radium containing
water cause radiation irritation.
15. 1) It should stimulate reparative dentin formation.
2) It should maintain the pulp vitality.
3) It should release fluoride to prevent secondary caries.
4) It should be bactericidal or bacteriostatic.
5) It should adhere to restorative material.
6) It should resist forces during restoration placement and during the life of
restoration.
7) It should be radiopaque.
20. • Cavity liners are relatively thin layers of materials used to provide barrier
to protect the pulp and dentin from residual reactants diffusing out of
a restoration and/or oral fluids, which may penetrate leaky tooth –
restoration interface.
• Provide pulp protection –
o Chemical protection
o Electrical protection
o Thermal protection
o Mechanical protection
21. • May provide thermal and electrical insulation.
• Need for liners is greatest with metallic restorations that are not well
bonded with the tooth structure like amalgam, while composite
and resin modified GIC do not require liners as they bond to the tooth.
- Unless the cavity is very close to the pulp and pulpal medication is
needed.
22. 1. Thin film liners : (1-50 µm)
A. Solution liners (2-5 µm)
They are solutions of natural resins and gums in a suitable solvent,
of which thin coating is applied over surfaces of cavity preparations
before placement of restorations.
E.g. – Cavity Varnish.
24. • INTRODUCTION
Cavity varnish is a solution of one or more resins which when applied
onto the cavity walls, evaporates, leaving a thin resin film, that
serves as a barrier between the restoration and the dentinal tubules.
25. • APPLICATIONS
Reduces microleakage around margins of newly placed amalgam restorations
Reduces passage of irritants into the dentinal tubules from overlying restoration/base
Prevent penetration of corrosion products into the dentinal tubules in amalgam restorations
As a surface coating over certain restorations to protect them from dehydration or contact with oral fluids
Applied on metallic restorations as a temporary protection against galvanic shock
When electrosurgery is to be done adjacent to metal restorations, varnish is applied over metallic restorations,
serving as a temporary electrical insulator
26. • SUPPLIED AS
Liquid in dark coloured bottles
Commercial names - Harvard lac, Chem varnish, Secura, Fuji Varnish(GC),
Copal -F etc.
27. •COMPOSITION
a. Natural gum - Copal, rosin or synthetic resin
b. Organic solvent -Alcohol, acetone or ether
c. Medicinal agents - Chlorbutanol, thymol or eugenol
-Some varnishes also contain fluorides
28. • PROPERTIES
- Varnishes neither possess mechanical strength nor provide thermal insulation
because of thin film thickness.
- The film thickness ranges from 2 - 5 µm.
- The solubility of cavity varnish is low; they are virtually insoluble in water.
29. • MANIPULATION
The varnish may be applied using a brush, wire loop or small pledget of
cotton.
Several thin layers are applied.
Each layer is allowed to dry before applying the next one.
When the first layer dries, small pin-holes develop. These voids are filled
by succeeding varnish applications. Two coats of varnish are recommended.
Objective -To attain a uniform and continuous coating.
30. • PRECAUTIONS
- Varnish solutions must be tightly capped immediately after use to prevent
loss of solvent by evaporation.
- It should be applied in thin consistency. Viscous varnish does not wet the
cavity walls properly. It should be thinned by an appropriate solvent.
- Excess varnish should not be left on the margins of the restorations as it
prevents proper finishing of the margins of the restorations.
31. • CONTRAINDICATIONS
* Composite resins - The solvent in the varnish may react with the resin.
* Glass ionomer cement - Varnish eliminates the potential for adhesion, if
applied between GIC and cavity.
* When therapeutic action is expected from the overlying cement then
varnish is not applied.
Eg. – Zinc oxide eugenol and calcium hydroxide.
32. B. Suspension liners ( 20-35 µm)
Suspension of calcium hydroxide in an organic liquid such as methyl
ethyl ketone or ethyl alcohol. Acrylic polymer beads or barium sulphate
mono-fluorophosphate.
They are soluble hence cannot be applied at the margins of restoration.
33. 2. Thick film liners or cement liners ( 200-1000 µm)
-Thicker liners that are selected primarily for pulpal medication and thermal
protection are identified as cement liners.
In deepest portion of the preparation or when a microscopic pulpal
exposure is suspected, it is more important to encourage dentin
bridge formation by using calcium hydroxide composition.
E.g. – Calcium hydroxide.
35. Calcium hydroxide was introduced into dentistry by Herman in the year 1920 as a pulp
capping agent. Many because of its ability to stimulate reparative dentine formation and
also because of its antimicrobial properties.
• Available as :
a. Powder form – which can be made into paste using either aqueous /viscous /oil
based liquids.
39. • Manipulation
For mixing two pastes, use either calcium hydroxide applicator or spoon
excavator.
Mix with a stirring motion until you get a uniform colour.
Mixing should not take more than 10-15 seconds.
Then clean your instrument with gauze and place it on the tooth surface.
40.
41. • Properties
a. Working and Setting properties –
Working time – 1-2 min
The mixed material have a setting time that is 2-3 min.
Moisture reduces setting time and the material sets within few seconds
of being placed in the cavity.
42. • Consistency
The mixed cement has low viscosity, due to which it is difficult to apply
it to the cavities in thick section.
• Solubility
The set cement has high solubility in water.
When it is exposed to oral environment it dissolves. This limits its use to a
small areas requiring pulp protection.
It is mandatory to remove the liners from the margins/ walls of the cavity
as calcium hydroxide dissolves in oral fluids causing microleakage.
43. • Mechanical properties
Compressive strength – 20 MPa ( Sufficient to withstand condensation
pressures of amalgam)
Tensile strength – 1-2 Mpa
• Biological properties
In case of an exposed pulp, calcium hydroxide is used as a pulp-capping
agent.
Free calcium hydroxide has high anti-bacterial properties.
44. It is sufficiently biocompatible to be placed adjacent to the pulp.
The freshly mixed cement has a pH of 11-12.
The alkaline environment created by the cement initiates the reparative/
secondary dentin formation.
Thermal insulation
45. • Other form of calcium hydroxide used for endodontic purposes
As an intra-canal dressing or root canal sealer.
(Retarders added to increase working time)
Used in endodontic purpose because –
- Effective anti-bacterial properties
- Non – irritant to apical tissues
- Associated with stimulation of hard tissue repair in the apical foramen.
46. • Applications
- As cavity liners in deep cavities and beneath silicate and resin based
cements.
- As a cavity base
- For root canal sealer and intracanal dressing.
- Direct and indirect pulp capping agent.
- Sterilization of infected canal
- Apexification and apexogenesis
47.
48. Disadvantages of calcium hyroxide
• Low compressive and tensile strength.
• Associated with primary tooth resorption.
• Marginal failure with amalgam condensation.
• Does not adhere to dentin or resin restoration.
49. • Other cements used as a thick cement liner –
a. Zinc oxide eugenol cement ( Contra-indicated beneath composites)
b. Resin modified glass ionomer cement
c. Flowable composite
51. • Bases are materials, most commonly cements, that are used in thicker zinc
dimensions beneath permanent restorations to provide for mechanical,
chemical and thermal protection to the pulp.
E.g. – Zinc phosphate, zinc polycarboxylate, GIC and resin modified GIC.
• The thickness of a base should be 1-2 mm.
52. • According to their strength, bases are classified as :
A. High strength bases
- Zinc phosphate cement
- Zinc oxide eugenol cement (Modified – Type III)
- Zinc polycarboxylate cement
- Resin Modified GIC
B. Low strength bases
- Calcium hydroxide (Dycal)
- Calcium hydroxide ( Light cure)
- Zinc oxide eugenol cement ( Type IV)
53. • Factors for clinical considerations for usage of a pulp protecting agent –
- Remaining dentin thickness
- Design of the cavity
- Adhesive property of the material
- Proximity of the pulp to the floor of the cavity
- Type of restorative material used
54. • Clinical considerations
a. For shallow preparation ( > 2mm of RDT)
In shallow tooth excavation, pulp protection other than chemical
protection is not necessary.
- For amalgam restoration : Two thin coats of varnish, a single coat of
dentin sealer/ dentin bonding system and then restoration with
amalgam.
- For composite restoration : Preparation is treated with bonding
system ( etched, primed, coated bonding agent) and then restored.
55. b. For moderately deep preparation ( 0.5-2 mm of RDT)
- For amalgam restoration : Some extension of the preparation toward
the pulp so that a region includes less than ideal dentin protection.
Application of base only at that site using light cured resin modified GIC.
- Traditionally, zinc phosphate and zinc polycarboxylate cement were
preferred bases under amalgam restorations.
- Composite restoration : Zinc oxide eugenol is contra-indicated due to its
potential to inhibit polymerization of layers of bonding agent. RM GIC is
indicated if base is indicated.
56. c. For very deep preparation ( < 0.5 mm RDT)
- If RDT is small or pulp exposure is a potential problem then calcium
hydroxide is used to stimulate reparative dentin. Thickness of 0.5-1mm
is applied and sufficient for near or actual pulp exposure.
- If extensive dentin is lost because of caries and tooth excavation extends
close to the pulp a light cured resin modified GIC is applied over already
placed calcium hydroxide.
- The sealer or bonding agent is not applied until after the base is in place.
59. • These are therapeutic materials placed in the deep portion of the cavity
preparation.
• They should be covered with supporting base as they have low strength.
• In deep cavities, therefore a commonly used technique is to apply
thin sub-base of calcium hydroxide and then build up the base of the
cavity with cement bases prior to restoration.
60.
61. REFERENCES
• Art and science of operative dentistry by Sturdevant ( South Asian edition)
• Phillips’ Science of Dental Materials ( 11th Edition ) by Kenneth J. Anusavice
• Dental materials ( Clinical applications) by Pankaj Datta
• Basic dental materials by John J. Manappallil
