Transcript Lecture 1 Introduction to Dental materials

Dental Materials
Restorations, Luting and Pulp
Therapy
Introduction
Restorations :
A restoration is a material which substitutes
the missing tooth structure and restores the
form and function of the tooth
Types of Restorations
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Temporary, intermediate and
permanent
Direct and indirect
Esthetic and non-esthetic
Temporary Restorations
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when ?
Time ?
Treatment to the pulp
Disadvantage:
sensitivity
microleakage
zinc oxide eugenol ( ZOE )
Intermediate Restorations
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particularly used in pedodontics
Conventional zinc-eugenol cements are
deficient in toughness. They have
inadequate strength and abrasion
resistance
. As a result, polymer reinforced cement
(IRM) is used.
Requirements of a Temporary Filling Material
1. Should have adequate strength to last a
few weeks, but weak enough to be
dislodged easily.
2. Should be easy to insert and remove.
3. Should have adequate seal.
4.Should have antibacterial properties.
5. Should have a beneficial effect (pain relief,
healing, etc.) on the pulp.
6. Should have cariostatic properties.
Permanent Restoration
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any material that is expected to last
much longer than the temporary and
intermediate restorations.
Ex.: direct filling gold, amalgam ,
composite resins, glass ionomer cement,
silicate cement , as well as porcelain,
composite and cast metal inlays and
onlays.
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The length of time :
Amalgam
--------- composite
Direct and Indirect Restorations
Esthetic and Nonesthetic
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An esthetic material is obviously
something which is pleasing to an
individual. Gold !!
- Today an esthetic material implies any
material that is capable of reproducing
the color and appearance of a natural
tooth.
LUTING ( Cementation )
Cementation is the process by which
crowns, restorations and other devices
are fixed or attached to tooth structure
using an intermediate material called
cement.
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Types
Temporary cementation
Permanent cementation
Temporary Cementation
-Temporary bridges
- should have some soothing effect on the
pulp of the freshly prepared vital tooth
An example of such a temporary bonding
cement is a zinc oxide eugenol based
cement
Permanent Cementation
a) strong
b) insoluble in oral fluids.
c) be advantageous if it had some
chemical bonding to the tooth
structure.
d) It should be fluid enough to flow .
Ex. zinc phosphate cement, glass
ionomer cement, resin cement,
polycarboxylate cement
PULP CAPPING
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Pulp capping is a process of placing a
specialized agent in contact with or in close
proximity to the pulp with the intention of
encouraging formation of new dentin
(secondary dentin) and promote the healing
of the pulp.
Criteria for Pulp Capping
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The pulp should be healthy and uninfected.
The area of exposure should be no more
than 0.5 mm.
Following exposure the dentist should
make all attempts to immediately isolate
the tooth and prevent contamination.
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Types of Pulp Capping :
1) Direct pulp capping
2) Indirect pulp capping
Direct Pulp Capping
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Such a situation is often encountered
during :
– deep carious lesions
– Traumatic fractures of the tooth
– Iatrogenic exposure during cavity
preparation
– Iatrogenic exposure during crown
preparation.
Indirect Pulp Capping
Secondary dentin formation can be
induced even when the pulp is not
exposed but is near exposure. When
the calcium hydroxide is placed in the
region of the near exposure, it can still
induce new dentin formation through
the remaining thin dentinal wall.
Indications of indirect pulp capping :
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Deep carious lesions close to the
pulp.
During excessive crown preparation
the pulp is often visible through the
remaining dentin as a pinkish or
reddish spot or area.
Similar near exposures may be seen
in cases of traumatic tooth fracture.
CEMENT BASE
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is a layer of cement placed beneath a
permanent restoration to encourage
recovery of the injured pulp and to protect it
against numerous types of insults .
The type of insults depends upon the
particular restorative material. It may be
thermal or chemical. The base serves as
replacement or substitute for the protective
dentin, that has been destroyed by caries or
cavity preparation
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A) High Strength Bases :These are used
to provide thermal protection & mechanical
support for the restoration.
Ex.: zinc phosphate, zinc polycarboxylate,
glass ionomer and reinforced ZOE cements.
B) Low Strength Bases : have minimum
strength and low rigidity. Their main
function is to act as a barrier to irritating
chemicals and to provide therapeutic benefit
to the pulp. Ex: calcium hydroxide and zinc
oxide eugenol.
Properties of Dental Cements
Thermal Properties :
important sp. When metallic R. Is
used.
- Thickness at least 0.75 mm
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Protection Against Chemical
Insults
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Serve as barrier
Calcium hydroxide and zinc oxideeugenol are most effective for this
especially in deep (close to the pulp)
cavities.
Polycarboxylate and glass ionomer
bases are also used as chemical
barriers in more moderate cavities
Therapeutic Effect
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Some bases are used for their
therapeutic benefit to the pulp. For
example, calcium hydroxide acts as a
pulp capping agent and promotes the
formation of secondary dentin. Zinc
oxide-eugenol has an sedative effect
on the pulp.
Strength :
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the cement base should develop
sufficient strength rapidly, in order to
allow early condensation of amalgam.
The minimum strength requirement of
a base between 0.5 and 1.2 mPa.
The cement base must have
sufficient strength to:
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Withstand the forces of condensation .
Withstand fracture or distortion under
masticatory stresses .
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The base is selected according to:
1)Design of the cavity
2) Type of permanent restorative
material used.
3) Proximity of the pulp to the cavity
walls .
Cavity Liner
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Is a dentine sealer that is less than 0.5
mm thick and is able to promote the
health of the pulp by adhesion to the
tooth structure or by antibacterial
action .
Liners And Varnish
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Liners and varnishes are agents in a
volatile solvent which when applied to
a surface evaporates leaving behind a
thin film. This film acts as a barrier
which has different functions
depending on the circumstance and
the location where it is applied