Glass Ionomer: Bases and Liners

why is deep dentin clinically significant

deep dentin is:

- porous

- susceptible to desiccation

- poor bonding substrate

what does deep dentin fail to protect against

- heat from rotary instruments

- toxic restorative materials

- thermal changes

- mechanical forces

- galvanic shock

- bacteria/toxins

- poor bonding conditions

deep dentin = biologically _____ + _____ weak

vulnerable, structurally

goals of liners/bases

- cover deep dentin

- reduce tubular fluid flow

provide:

- thermal barrier

- physical barrier

- improve bonding env.

protect pulp from:

- bacteria

- toxins

dental liner is defined by _____ of material

thickness

*most important consideration for pulpal protection... thickness of remaining dentin when choosing liners and/or base*

what is a liner

thin film or coating/layer (< 0.5 mm)

applied to exposed dentin

protects pulp from chemical and bacterial insult

where is a liner placed

ONLY deepest areas of cavity prep:

- pulpal floor

- axial wall

when is a liner indicated

when prep is ~0.5 mm from pulp

most important factor for pulpal protection

remaining dentin thickness (RDT)

ex. of liners

calcium hydroxide

mineral trioxide aggregate (MTA-endo use, direct pulp cap)

glass ionomer

function of a dentin bonding agent (DBA)

seals dentinal tubules

prevents bacterial invasion

how is DBA used under composite

MANDATORY

acts as a bonding agent

how is DBA used under amalgam

optional

no etch

functions like a liner → reduces sensitivity

is etch required with dentin bonding agent

may require total etch, selective etch, or no etch technique when use as a bonding agent

what are the functions of calcium hydroxide (Dycal)

chemical barrier

antimicrobial (direct & indirect pulp capping)

stimulates reparative tertiary dentin (atubular)

what type of dentin does CaOH form

reparative (atubular) dentin

NOT reactionary

when is CaOH use indicated

deep cavities near pulp

must mix base and catalyst prior to placement

major disadvantage of CaOH

low compressive strength

material is brittle, weak under pressure, and unable to withstand the heavy forces of condensation when placing permanent restorations like amalgam

acts as a "low-strength base," requiring a stronger base (such as glass ionomer) to be placed over it to support the restoration

why must CaOH be covered

dissolves easily

cannot withstand forces

what covers CaOH

base (Not secondary liner for amalgam)

- thermal protection

base or secondary liner for composite

- done prior to etching and bonding

what is a base

thicker layer ( >0.5 to ~3 mm)

applied to exposed dentin

what is the only difference between liner and base

thickness

base

protects pulp from thermal insult in deep cavity preps

protects CaOH from dissolution

prep is 0.5 - 1.5 mm from pulp... what is done when RDT = 0.5-1.5 mm?

usually:

- base (RGMI)

- no CaOH unless very deep

amalgam:

- base as thermal insulator

- helps with retentive and resistance forms

composite:

- base is not necessary

*RGMI helps achieve better bond since deep dentin is not ideal bond*

functions of a base

- thermal protection

- protect CaOH

- mechanical support

- restore ideal prep form

- resist compressive forces (of mastication)

- block out undercuts for indirect restorations

ex. of bases

glass ionomer

compomers

zinc phosphate cement

carboxylate cement

zinc oxide eugenol

what are compomers

polyacid-modified composite resin

key properties of compomer

properties of both composite and glass ionomer

- require DBA

- high strenght

- low fluoride ( < 10% of GI)

- light cured (polymerization reaction)

- less soluble than GI

- less esthetic than composite

why are compomers not commonly used

poor physical properties

less esthetic than composite

key features of Zinc Oxide/ Eugenol (IRM)

low strength

sedative effect of eugenol = advantage

Zinc Oxide/ Eugenol used...

under amalgam (low stress areas)

ex. axial walls

issues with Zinc Oxide Eugenol

interferes with composite polymerization reactions of bonded restoration (ex. composite)

glass ionomers can be used as ____ or secondary liner (thin amount placed over primary liner; ex. over _______ and under composite

base, CaOH

what are glass ionomers used for

base

secondary liner

sometimes final restoration

key properties of glass ionomer

chemical bond to tooth (predictable bonds to enamel & dentin)

fluoride release + recharge

less esthetic & polishable than composite (exception EQUIA Forte)

can be pure or ______ glass ionomer (Ketac-Fil, EQUIA Fil) or resin ____ _____ ____ (RMGI) (Photac-Fil, Vitrebond)

conventional, modified glass inomer

pure or conventional glass ionmer

- acid/base reaciton

- aluminosilicate glass + polyacrylic acid ( w small ammounts of itaconic and tartaric acids)

- highest fluoride release

- lowest wear resistance & lowest strength

*new generations show marked improvement in strength and resistance ex. EquiaForte*

resin modified glass ionomer (RMGI)

- acid/base + polymerization (light activated) reaciton

- resin particles incorporated with glass ionomer

- less technique sensitive

- improved handling

- better physical properties

glass ionomer powder

SiO2 = 29.0%

Al2O3 = 16.6%

CaF2 = 34.3%

Na3AlF6 = 5%

AlF3 = 5.3%

AlPO4 = 9.8%

Calcium fluoroaluminosilicate glass

glass ionomer liquid

polymer acids:

- polyacrylic acid

- itaconic acid

- tartaric acid

glass ionomer setting reactoin

acid- base reaction between liquid (l) and powder (p)

polyacrylic acid (l) + aluminosilicate glass (p)

how do glass ionomers bond to tooth

chelation (chemically) to enamel and dentin

chelation reaction between carboxyl groups of polyacrylic acid and calcoum of hydroxyapatite crystals

carboxyl groups bind Ca2+ in hydroxyapatite

glass ionomer

reaction: acid- base

low strength

high fluoride

poor esthetics

low wear resistance

RMGI

reaction: acid-base + polymerization

moderate strength

moderate fluoride

better esthetics than GI

composite

reaction: polymerization (same with compomer)

high strength

no fluoride

best esthetics

high wear resistance

does composite or GI have higher wear resistance

composite

which material has best fluoride? highest strenght?

fluoride = glass ionomer

strength = composite > RMGI > GI

visual of fluoride releasing

fluoride recharging

process where dental materials absorb fluoride from external sources—such as toothpaste, mouthwash, or professional gels—and subsequently release it over time

tooth surface pre-treatment

- apply conditioner (polyacrylic acid) for 10 sec.

- rinse with water

- air dry

- avoid overdrying and any contamination

why use polyacrylic acid conditioner

removes smear layer without opening dentinal tubules & removing smear plugs

base and liners....

extend ideal prep to remove decay

prep is ready to receive liner & base

CaOH placement clinical steps--- mixing CaOH

equal parts base + catalyst

use cement spatula

DO NOT mix with placement instrument

* CaOH2 = Life = Dycal... true diff. between liners and base is only thickness*

place small, equal amounts of both pasts (____ and ____) on the oil repellant pad

catalyst, base

mix the two spates with a ____ ____, do not mix with the placement instrument

cement spatula

mix until a smooth, ____ colored mixture is obtained

uniformly

liner placement technique

small amount of mixed past on the ball tip of placing instrument

place only in deep portion of cavity prep.:

- pulpal floor

- axial wall

thin layer (on dentin closest to pulp)

wipe of the instrument before adding each ____ so that the material doesn't stick to the instrument

increment

important rules of liner placement

- placed only on pulpal floor & axial wall (class II) of prep

- allow to harden before placing base

- remove any liner that has spread onto walls

bases/secondary liners

types of bases:

- EQUIA-Forte: self curing glass ionomer materia

- polyacrylic acid used before placement

ex. of secondary liner:

- Vitrebond: light curing resin modified glass ionomer material

- polyacrylic acid used before placement

where is conditioner placed (removal of dentin smear layer & improves GI bond strength)

around liner where GI will be placed... GI will bond to tooth structure

NOT on liner

steps:

- dispense form bottle onto a pad & apply with disposable applicator peripheral to liner

- rinse with water

- dry with 2-3 short bursts of air

- surface will appear matte

capsule activation steps of EQUIA Forte (base placement)

1. shake or tap capsule to loosen powder

2. activate by pushing plunger (hold for 2 secs)

- make sure it is flush with main body

- fully pressed to avoid incorrect mixing

3. set into amalgamator & mix for 10 secs

EQUIA-Forte mixing

mix in amalgamator

set at 10 seconds on rabbit speed

visual of activated capsule in the amalgamator/mixer

place _____ in syringe; extend the dispensing tube

capsule

placement of base

- extrude small amount of "test" material from capsule using syringe

- carry material to prep using a "plastic" instrument or Dycal

- condense once placed in prep.

EQUIA says to place directly due to its ___ ____ capabilities

bulk flow

base in prep ready for condensing visual

condensing base

- keep base away from walls

extent of base:

- amalgam: placed to block out undercuts & to keep amalgam 2 mm from pulp as thermal insulator

-composite: used as secondary liner btwn CaOH and composite

(protect CaOH from being washed away)

important notes for base placement

prep is ready for permanent restoration when:

- no excess material is on pulpal floor

- no base material is on walls of prep

maintain 2 mm from pulp (amalgam)

EQUIA will self cure in 2.5 mins

properties of RMGI Vitrebond

- reduces shrinkage

- strong dentin bond

- radioopaque

- light cure (20 secs)

- ease of dispense/placement similar to CaOH

use of RMGI Vitrebond

secondary liner/base

CAN'T be used as a final restorative material

Vitrebond Plus Light-Cure Glass Ionomer Liner/Base

visual

visual internal tooth tissues

preoperative to 12 months post op progression

EQUIA Forte

glass hybrid with superior wear resistance and flexural strength

suitable for certain low compressive force areas

why is EQUIA Forte special ( new GI materials; advanced)

- high strength

- wear resistant

- resistant to acid erosion

- non sticky and packable

- no shrinkage

- high fluoride release & recharge capability

- better esthetics

- can be final restoration

available in 8 shades

clinical application of EQUIA Forte

- tooth prep

- pulp capping = CaOH beneath

- anatomical matrix system for class II

- rinse cavity prep w water

- blot dry with cotton pellet (do not desiccate... surface should appear moist)

restorative steps/tehcnique EQUIA Forte

- remove from mixer & load into GC capsule applier III

- 2 clicks to prime the capsule then syringe

- within 10 secs of mixing, extrude mixture directly into prep.

- form preliminary contour

moist dentin (no dessication)

working time ~ 1:15 mins from start of mixing at 23

avoid moisture contamination first 2.5 min

*higher temps will shorten working time*

class V material selection

use composite in esthetic zones

use GI:

- poor isolation

- high caries risk

- NCCLs

if isolation is a concern in class V restoration, probably use _______ ____ because significantly less sensitive to moisture than composite resin

glass ionomer

(GI exhibits chemical bond & natural adhesion to tooth structure)

material of choice for NCCL

esthetics not primary focus

consider glass ionomer when faced with the following situations

- decrease salivary function = high caries risk

- decrease patient motivation

- inability for proper home care

- increased difficult in isolation

- increased difficult in performing op. procedure bc pt physical or medical problems

finishing and polish GI

- check for smooth margins (sub gingival as well)

- place final EQUIA coat after etching perimeter of restoration w 35-37% phophoric acid for 30 secs

- light cure Equia coat = only when used as final restoration

- coat protects GI during the crucial first 24 hrs & makes restoration smooth and shiny (more esthetic)

when do you light cure EQUIA coat

only when it is used as a final restoration material

amalgam summary

moderate caries removal:

- base as thermal insulation

- no liner

deep caries removal:

- CaOH liner

- base as thermal insulator

any depth prep... can use DBA to seal dentinal tubules

(not required, but would apply DBA right before amalgam)

liners and secondary liners composite summary

deep caries removal:

- CaOH as liner

- GI as secondary liner

what must be placed before composite

DBA (always)

follow guidelines for particular DBA technique (our clinic uses selective etch)

what is selective caries removal

leave soft dentin over pulp to avoid exposure

aka indirect pulp cap

must start with asymptomatic vital tooth

benefits of selective caries removal

- maintains vitality of pulp by preventing pulp exposure

- apply minimally invasive (MI) techniques

- decrease financial burden on pt.

- restore tooth health

steps of SCR

- remove surrounding caries

- leave soft dentin at pulp (or leathery... only to avoid exposure)

- cover with CaOH

- cover with GI

- seal restoration ( no trauma or bacteria contamination)

covering soft dentin with CaOH in SCR

produces reparative dentin 6-8 weeks

seen radiographically in 10-12 weeks

favorable prognosis conditions for direct pulp cap

- asymptomatic tooth

- small exposure (< 0.5 mm)

- controlled bleeding

- clean field (rubber dam)

- minimal trauma, little desiccation of tooth occurred, no aspiration of blood into dentin (dentin blushing)

treat exposure with CaOH to form reparative dentin

important concepts

Liner vs Base = THICKNESS ONLY

CaOH:

-stimulates reparative dentin

-MUST be covered

GI:

- chemical bond (chelation)

deep dentin:

-poor bonding → use RMGI

composite:

-ALWAYS needs DBA

amalgam:

-needs thermal insulation (base)