Transcript Dental cements

Dental cements
‫أحمد عبد العزيز الحسين‬
‫أخصائي تركيبات سنيه في وزارة الصحة األردنية‬
‫محاضر غير متفرغ في جامعة العلوم والتكنولوجيا األردنية‬
Ahmad Abdul Aziz Alhussien
Prosthodontist at M.O.H
Part time lecturer at J.U.S.T
BSc , MSc, Jor. Board/ prosthodontics
Uses of dental cements
• Pulpal protection (liners, bases, varnishes)
• Luting cementation (crowns, inlays, onlays
veneers)
• Restorations (temporary and permanent)
• Surgical dressing (e.g. periodontal surgery)
Cavity varnish
• a thin layer placed on the floor and wall of the
cavity to seal dentinal tubules and minimize
microleakage.
• Composition:
– Natural resin (copal)
– Synthetic resin dissolved in solvent such as alcohol
or chloroform.
Cavity varnish
Application method:
– The varnish is applied in a thin layer
– The solvent evaporates within 5 –15 seconds
– A second layer is applied
The resin component protects pulp by:
– Sealing dentinal tubules
– Reducing microleakage
– Reduce staining
Dispensing and clinical considerations
• 2 bottles:
– Varnish: 90% solvent, 10% resin (copal)
– Solvent to dilute varnish if solvent evaporates
• The lid should be kept tightly closed
• Varnishes have been largely replaced by
bonding agents since varnishes wash out
quickly
Liners/low strength base
Calcium hydroxide
 Clinical uses:
– Liner to protect pulp
– Direct and indirect pulp capping
 Dispensing:
• 2 paste system “Self-cured”
– Base: Calcium phosphate, calcium tungstate, Zinc
oxide, Glycol salicylate
– Catalyst: Calcium hydroxide, zinc oxide, zinc stearate
in ethylene toluene sulfonamide
• Light cured cement: UDMA + Ca hydroxide +
barium sulfate filler and low viscosity monomer
Liners/low strength base
Calcium hydroxide
• Set cement is calcium disalicylate
• Properties:
– Has an alkaline Ph 9-11(stimulates dentine
formation)
– Setting time: 2-7 minutes
– Weak compressive strength
– Thermal insulator
– High solubility
Liners/low strength base
ZnO/Eugenol
• Uses:
– Pulpal protection in deep cavities
• Properties:
– Weak
– Sedative effect
– Little thermal insulation
High strength base (>0.5mm)
• Function:
– Insulator
– Support for restoration
• Materials used:
– GIC
– Resin modified-GIC
– Polymer reinforced ZnO/E
• Properties required for high strength bases:
– High strength that develop quickly
– Low thermal conductivity
– Moderate elastic modulus
Luting cements
• Desirable features:
– Good wettability
– Good flow
– Thin film thickness: 25 µm or less to fill the space
between tooth structure and restoration.
Restorations
• Permanent: cements are rarely used as
restorations due to:
– Low strength
– Low wear resistance
– High solubility
• The exception is GIC, used for class V cavities
and primary teeth.
Zinc oxide eugenol temporary filling
Dental cements
ZnO cements
Glass ionomer cements
Resin cements
Compomer cements
Hybrid ionomers
Zinc phosphate
Zinc polycarboxylate
Zinc oxide eugenol
• Advantages:
1. Wide variety of uses
2. Sedative to the pulp
3. Easily manipulated
• Disadvantages
1. Low strength
2. High solubility
3. Not used under composite resin
Zinc oxide eugenol
• Some are resin or EBA reinforced
• New products are eugenol free “cavit”
• Properties:
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Sedative effect on pulp and antibacterial
Biocompatible .. irritant if in direct contact with pulp
Eugenol interferes with setting of resin
Moderate strength
Retention is mechanical
Water and temperature increase accelerate setting
Zinc phosphate
• Used to be used as a permanent luting agent
• Composition:
– Powder: zinc oxide
– Liquid: phosphoric acid and water buffered by Al +
Zn to slow setting
• Setting reaction: 5-9 minutes, exothermic,
controlled by incremental incorporation of
powder into liquid. Cement is porous.
Zinc phosphate
• Properties
– Initial acidity with pH of 4.2, becomes neutral
after 48 hours.
– Retentive by mechanical retention sandblasting of
crowns or inlays
– Similar strength to GIC, high CS, low tensile
strength.
– Low solubility once set
– Fast setting
– Moisture adversely affects cement
Zinc phosphate
• Manipulation
• Powder is dispensed and divided into 4-6
portions
• Liquid is dispensed according to manufacturer
• Mixing is gradual at 15 seconds intervals for
60-120seconds
• Large strokes over a large area
Zinc polycarboxylate
• Uses:
– High strength base
– Final cementation of indirect restorations
• Composition:
– Powder: zinc oxide
– Liquid: polyacrylic acid
• Properties:
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Lower compressive strength than other cements
Mild acidity
Higher viscosity when mixed but reasonable flow
Liquid should not be dispensed before needed, to
avoid water evaporation and viscosity
– Retention is chemical and mechanical
– To increase working time use a cold slab
• Manipulation: powder liquid systems, 90% of
powder added first then the rest is mixed with
liquid to adjust consistency
Glass ionomer cements
Composition
• Main components are:
– Glass
– Polyacid
– Water
– Tartaric acid
• Different types and combinations of polyacid
and glass create different versions of GIC
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Glass
Three main components:
Silica SiO2
Alumina Al2O3
Calcium fluoride CaF2
In addition to sodium and aluminium fluorides,
and calcium or aluminum phosphates.
• Components are fused at high temperatures,
shock cooled then ground to a powder. Particle
size depends on application
 Liquid
• Liquid: co-polymers of polyacrylic acid and water
• E.g. of copolymers used:
• Acrylic acid and itaconic acid
• Acrylic acid and maleic acid
 Viscosity of the liquid depends on molecular
weight and polyacid concentration.
 Tartaric acid influences working ad setting time
 DISPENSING
• 2 bottle system hand mixed:
o Powder
o Liquid
• Anhydrous cement: powder (glass and freeze
dried polyacid) and distilled water
• Capsules (pre-measured powder and liquid)
mixed using a triturator (mixer). Easy to use, GIC
is directly dispensed into cavity, eliminate errors
from manual mixing.
Acid base reaction. Three overlapping steps:
• Dissolution
• Gelation
• Hardening
Glass ionomer cements
 Composition and reaction explained previously
 Uses:
• low/high strength bases (in deep cavities use
calcium hydroxide instead)
• Luting agents
• Core build up
• Restorative material (e.g. class V)
• Manipulation
Resin modified-GIC
Uses:
• Permanent cementation of crowns and
bridges
• Core build up
• Liners
• Bonding of orthodontic brackets
Resin modified-GIC
 Properties:
• Fluoride release
• Low solubility once set
• Early low pH then increases
• High fracture toughness but lower than resin
cements
• Problem of water sorption (contraindicated for
all-ceramic restorations, may cause cracking due
to expansion)
• Manipulation: capsules, powder liquid systems
Resin-based cements
• They are modified composites … Microfill or
microhybrid
• Properties:
– Insoluble and high wear resistant
– Good esthetic under all-ceramic crowns
– Bonded by etching and bonding, sandblasting of internal
surface of restoration
• Setting:
– Chemical cure
– Light cure
– Dual cure: most versatile
Compomer cements
• Composition:
– Powder: fluorosilicate glass, sodium fluoride, selfcured and light-cured initiators
– Liquid: polymerized-methacrylate-carboxylic acid
monomer, water, acrylate-phosphate monomer,
diacrylate monomer
• Properties:
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Fluoride release
low solubility
high bond strength
high fracture toughness and strength