Dental Cements

Dental Cements

Dental Cements

Materials used in dentistry for various applications such as luting, temporary restorations, and endodontics.

Luting

The process of cementing or bonding dental restorations like crowns or bridges to the tooth structure.

Intermediate Restorative Materials

Materials like cavity varnishes, liners, and bases that act as a barrier between filling material and dentine.

Cement

A substance that binds and hardens independently, used to bind materials together in dentistry.

Barrier Materials

Substances that provide thermal, chemical, and electrical barriers between filling materials and dentine.

Thermal Insulation

Protection of the pulp from sudden temperature changes or rises caused by filling materials.

Chemical Barrier

Protection of the pulp from irritating chemicals.

Electrical Barrier

Prevention of pain caused by galvanic cells formed by different metallic restorations.

Setting Time

The time taken for a dental material to harden or set in the mouth environment.

calcium hydroxide cements

• 2 paste cement

• 1 contains 50% calcium hydroxide, 10% zinc oxide, 40% ethyl toluene sulphonamide

• 1 contains 40% butylene glycol disalicylate, titanium dioxide, calcium sulphate

• setting reaction is one chelation between ZnO and butylene glycol disalicylate

• freshly mixed cement has high pH - 12

• enhances formation of secondary dentine

calcium hydroxide cements properties

• compressive strength = low (rises over 24h and ranges between 9-26MPa)

• mainly used as sub-liner/pulp cap under zinc phosphate

calcium hydroxide: for direct pulp capping when pulp exposure is suspected

calcium hydroxide cements disadvantages

• high solubility

• but light cured equivalents have lower solubility and are therefore preferred

• has resin component in it allowing it to be cured

Mineral Trioxide Aggregate cements (MTA)

• MTA mixed with water hydrates to form calcium silicate hydrate and calcium hydroxide - so needs moisture to set

  • works well in oral environment

  • exhibits long setting time

• made up of hydrophilic particles that set in presence of water

• (two types) gray and white MTA - gray MTA has iron

• bioactive material

MTA composition

• tricalcium silicate

• dicalcium silicate

• tricalcium aluminate

• tetracalcium aluminoferrite

• calcium sulphate dihydrate

• bismuth oxide (radiopacifier)

MTA uses

• pulp capping

• root-end filling

• pulpotomy

• apexogenesis

• apical barrier formation in teeth with open apices

• repair of root perforations

shown to seal off pathways of communication between root canal system and surrounding tissues, significantly reducing bacterial migration

Biodentine composition

powder:

• 1- Tricalcium silicate = main material

• 2- Dicalcium silicate = second core material

• 3- Calcium carbonate

• iron oxide shade

• zirconium oxide = radiopacifier with trisilicate core

liquid phase:

• calcium chloride = accelerator

• water soluble polymer = water reducing agent

Is a calcium-silicate based material

Biodentine vs MTA

• biodentine = contains no tricalcium aluminate and no gypsum

• biodentine liquid phase contains calcium chloride = faster hydration

Biodentine characteristics

• setting time = 9-12 mins

  • (due to increase in particle size, addition of calcium chloride to liquid component)

• setting reaction = hydration of calcium-silicate phases

• setting products = calcium silicate hydrate & calcium hydroxide (carbonate)

• ability to release calcium when in solution and is source of hydroxyapatite in contact with synthetic tissue fluids

Biodentine uses

• treat damaged dentine (restorative and endodontic indications)

• used as dentine substitute under a composite for posterior restorations

• root perforations

• apexifications

• resorptions

• retrograde fillings

• pulp capping procedures

• dentine replacement

Properties of luting cements

• ease of manipulation

• low film thickness

• long working time with rapid setting at mouth temp

• low solubility in oral fluids

• adhesion to tooth structure and restorative

• adequate tensile and compressive strengths

• biocompatibility

• radiopacity

• anticariogenic properties

common setting reactions for cements

• chemical reaction (zinc phosphate)

• solvent evaporation (copal varnish in acetone)

• heat mediated: thermal (GP)

zinc phosphate cement composition

powder:

• ZnO

• 10% MgO, SiO2 and traces of Ba and Ca salts

liquid phase:

• 40~70% aqueous solution of o-phosphoric acid (H3PO4) and easter

• small amounts of Al and Zn acting as buffers

zinc phosphate cement setting reaction (equation)

ZnO + 2H3PO4 = Zn(H2PO4)2

ZnO + Zn(H2PO4)2 = Zn3(PO4)2 . 4H2O

Zinc Phosphate Cements

• A type of dental cement with a pH that rises from around 2 to 5.9 within 24 hours

• becomes nearly neutral after 48 hours.

• exothermic setting reaction

• typical mixing time of around 5 minutes

• setting time of around 15 minutes.

zinc phosphate cements variables

• high powder : liquid ratio accelerates the reaction

• moisture accelerates the reaction

• low temp retards (slows) reaction, thus mixing done on cool slab (not below the dew point)

• rapid addition of powder accelerates the reaction

Zinc Polycarboxylate Cements

• powder:

  • 90% ZnO

  • 10% MgO

• liquid:

  • aqueous solution of high molecular weight polyacrylic acid

• It forms zinc polyacrylate

• properties comparable to zinc phosphate

• is adhesive to tooth structure.

Zinc Oxide-Eugenol composition

liquid:

• eugenol 85%

• olive oil 15%

powder:

• 69% ZnO

• white rosin 29%

• zinc stearate 1%

• zinc acetate 0.7%

zinc oxide - eugenol

• zinc oxide + water = zinc hydroxide - this reacts with eugenol = zinc eugenolate

• zinc eugenolate can readily hydrolyse to fore free eugenol and zinc hydroxide

• pH = neutral

• natural bactericide

• eugenol = obtundent + mild pulp irritant

• eugenol acts as free radical sink, so should not be used with composites as inhibits polymerisation AND can cause discolouration of composite

• modified zinc-oxide eugenol cements available with resin component to improve compressive strength + decrease solubility

EBA Cement

• modified Zinc Oxide-Eugenol (ZOE) cement

• powder:

  • ZnO (60-75%)

  • fused quartz or alumina (20-35%)

  • hydrogenated rosin (6%)

• liquid:

  • eugenol (37%)

  • ethoxybenzoic acid (63%)

• It has lower solubility and higher strength than conventional ZOE.

Resin Cements

• Low-viscosity composite materials with filler distribution and initiator content adjusted for low film thickness and suitable working and setting times

• wide range of applications:

  • inlays

  • fixed bridges

  • ortho

• curing:

  • light-cured

  • self-cured

  • dual-cured

Bonding procedure includes pre-treatment of both tooth and restoration surfaces:

• Total etch (etch and rinse)

• Self-etch (acidic functional monomers)

Self-Adhesive Resin Cements

• Two-part materials

• dispensed in individual syringes OR dual-barrel syringe dispensers

• They are used for inlays and onlays.

• main constituents:

  • functional acidic monomers

  • di-methacrylate monomers (bis-GMA, UDMA, TEGDMA)

  • filler particles

  • activator-initiator systems

Root Canal Therapy (procedure)

• removal of pulp and all remnants,

• cleaning of canal and pulp chamber,

• sealing of the canal and pulp chamber to prevent infection to adjacent bone

• permanent restoration - to obturate pulp space of a tooth and restore tooth's function.

properties of RCT

• ability to seal completely

• retain seal

• bactericidal

• good biocompatibility with bone/tooth surface

• appropriate mechanical strength

• promote long term retention of sound dental support for functional crown

incomplete obturation of root canal system = failure

Root Fillings types

two types:

• rigid points

• plastic (cements, pastes or sealants)

• combo of two

rigid:

• metallic

• polymeric

plastic:

• ZnO-eugenol

• epoxy resins, GIC

• calcium hydroxide

Gutta Percha composition (solid material)

• Semi-plastic, structural isomer of natural rubber - Trans-poly(1,4 isoprene)

• properties differ from natural rubber- harder, lacks resilient, cannot be stretched reversibly

Polymeric cones of GP with other constituents such as ZnO, barium sulphate, plasticisers & pigments are also used

GP properties

• supplied as preformed points

• match the diameter and taper of reamers used for root fillings

• cones are used stacks or singly

• can also be used in form of rods - softened before use by heating/treating with solvents

• can be made to take up shape of apical tip of the root

• paste sealer used as GP not sufficiently flexible enough to take shape of root canal and seal completely against infection

GP - pros and cons

pros:

• reshaping and remolding possible - due to semi plastic nature

• biocompatible at root tip

• radiopaque

• removed and replaced of required

cons:

• lacks rigidity = placement is difficult

• root canal prep is critical - must be confined to prevent excess material being expressed beyond apex

• ages rapidly - becomes brittle

Amalgams

• used via orthograde or retrograde approaches

• orthograde = from crown of the tooth

• retrograde = directly into apex via surgical approach

• well tolerated by tissues

• build up of amalgam in oral mucosa = amalgam tattoos

amalgam - pros and cons

pros:

• inexpensive

• radiopaque

• long shelf life

• plastic on insertion with quick setting time

cons:

• difficult to condense in RC

• tends to be expressed beyond apex of tooth

• shows considerable leakage

sealants

• cytotoxic during setting

• biocompatible on setting

• dissolved and resorbed by vital tissue

• unsuitable for use alone

X4 types:

• ZnO-eugenol

• Epoxy resin

• GP dissolved in organic solvents, chloroform, eucalyptol

• cements

  • GIC

  • zinc polycarboxylates

  • calcium hydroxide

ZnO summary

• natural bactericide

• acts as acid in traces of water, reacting with base eugenol

• cement sets via neutralisation

• hydroxyapatite filled ZnO-eugenol is a way of improving biocompatibility

Epoxy resins summary

• contains epoxy ring - opens presence of molecules i.e amines

• traces of curing agents are needed

• diamines used as compared to more toxic amines used in industrial adhesives

• radiopacity by addition of calcium tungsgate and zirconium dioxide

• more than adequate working & setting time