DEPT. OF CONSERVATIVE DENTISTRY

& ENDODONTICS 2 May 2023

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CAVITY LINERS AND BASES

Presented by-Dr NISHANT KHURANAPG Student

Guided By:- Dr M.P. Singh&Dr Hemant Chourasia

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CONTENTS• Introduction• Causes of pulpal pain• Objectives for pulpal protection• Classification of Intermediary bases• Ideal requirements of intermediary bases• Solution liners (varnish)• Suspension liners • Cement liners• Cement base• References

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INTRODUCTION

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STEPS OF TOOTH PREPARTIONINITIAL TOOTH PREPARTION STAGE

• STEP 1:- OUTLINE FORM & INTIAL DEPTH

• STEP 2:- PRIMARY RESISTANCE FORM

• STEP 3:- RETENSION FORM• STEP 4:- CONVENIENCE FORM

FINAL TOOTH PREPATION STAGE

• STEP 5:- REMOVAL OF ANY REMAINING INFECTED DENTIN OR OLD RESTORATIVE MATERIAL

• STEP 6:- PULP PROTECTION• STEP 7:- 2ND RESISTANCE &

RETENTION FORM• STEP 8:- PROCEDURES FOR

FINISHING EXTERNAL WALLS• STEP 9:- FINAL FINISHING

9 STEPS WITH 1 GOAL

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PULP PROTECTORS:- LINER, BASES & VARNISH

Main reason for using a liner or base is to protect the pulp or to aid pulpal recovery or both.

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Q WHY DOES A TOOTH ACHE ??

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• the pulp communicates with the fluid inside the dentinal tubules , and if there is disturbance in the dentinal fluid it can be sensed by the pulp as pain

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• Pulp Protection requires consideration of:-1. Sealing the smear layer2. Chemical protection3. Electrical protection4. Thermal protection5. Mechanical protection6. Pulpal medication

OBJECTIVES OF PULPAL PROTECTION

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SEALING THE SMEAR LAYERS• Tooth preparation with rotary

instruments generates cutting debris, some of which is compacted unavoidably into a layer on the cut surface. This layer of material is called SMEAR LAYER & is typical of any cut surface, dentine or otherwise.

• Its 25-30% porous & can not prevent Slow Long Term Diffusion

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PULP PROTECTION AGAINST

Thermal insult

Electrical insult

Chemical iritant

Mechanical protection

Pulpal medication

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RELATION BETWEEN DENTIN PERMEABILITY & PULP PROTECTION

• Dentin permeability increase as remaining dentin thickness decrease towards the pulp.

• Factors which influence the need for pulp protection - depth of the cavity - location of walls & floor relative to the pulp horns - surface condition of dentin.

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CLASSIFICATION OF INTERMEDIARY BASES

According to Marzouk 1. Varnishes 2. Liners 3. Sub base 4. Bases• According to Sturdevant 1. Liners:-- Thin a) Solution liners (varnish 2-5

µm) b) Suspension liners (20-25

µm) - Thick – cement liners 2. Bases

• According to Charbeneau 1. Cavity varnish 2. Intermediary bases (liners) 3. Cement bases.

• According to Schwartz 1. Cavity sealers - varnish - resin bonding agents 2. Liners 3. Bases.

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IDEAL REQUIRMENTS• The material should create an impervious layer.• Biologically & Chemically compatible.• Should not discolor tooth or restorative material.• Should harden quickly.• Should withstand the condensation forces.• Should stabilize or diminish dentin permeability.• Should be easily manipulated.

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CAVITY LINERSDefinition: Anusavice – Thin layer of cement such as calcium hydroxide suspension in an

aqueous or resin carrier used for protection of the pulp.

Sturdevant – Thin layers of material used primarily to provide a barrier to protect the dentin from residual reactants diffusing out of a restoration or oral fluids (or both) that may penetrate leaky tooth restoration interfaces.

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• Liners can be classified on the basis of their film thickness into:- Thin film liners

a) Solution liners (varnish 2-5 µm or 0.002- 0.005mm)

b) Suspension liners (20-25 µm or 0.02-0.025mm)

- Thicker film liners cement liners(200-1000 µm or 0.2 to 1 mm)

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VARNISHES (SOLUTION LINERS)• Def:- Any liner based on non-aqueous solvents that rely on evaporation

for hardening is designated as a solution liner(or Varnish).

• Copal or natural resin dissolved in non-aqueous volatile solvent, (ether, alcohol and acetone) upon drying it will produce a thin film layer.

• ADVANTAGES:- flexible – dry rapidly.

• On the other hand, thick films tend to trap solvent during drying and become brittle.

[2-5 µm]

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COPALITE VARNISH OCCLUDING DENTINAL TUBULES

[Courtesy of SC Bayne, school of dentistry, University of Michigan, Ann Arbor, MI]

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VARNISH [COPALITE] Composition Natural gum – copal resin Synthetic resin – nitrated

cellulose Solvents Medicinal agents –

chlorobutanol, thymol & eugenol.

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FUNCTIONS• Prevents microleakage.• Reduces post-operative sensitivity.• Prevents penetration of toxic materials.• Does not act as an insulator. Properties: Neither possess mechanical strength nor provide thermal insulation.

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INDICATIONS: - Enamel & dentin walls –

reduce the penetration of oral fluids around metallic restorations.

- Over metallic restoration – reduce post-operative sensitivity

- Dentinal walls – minimize penetration of acid from zinc phosphate cements.

CONTRAINDICATIONS: 1-Under silicate cement → as it blocks the

transfer of fluoride ions from silicate cement to tooth.

2-Under glass ionomer cement and polycarboxylate cement as it prevents or decrease their adhesiveness to tooth structure.

3-Under resinous restorations as acrylic resin and composite → as the residual monomer will dissolve the varnish destroying the integrity of the varnish film, which will be of no value to be used.

4-In moderately deep and deep cavities → as it does not provide thermal insulation property.

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METHOD OF APPLICATION• Dry the cavity• Soak a small cotton pellet with varnish• Squeeze at one corner of cavity without moving it• Soak it again and squeeze it again at another corner of cavity, do it till a continuous film is formed over cavity walls• Dry it for 2 to 3 min• Usually 3 applications are sufficient• Also applied with camel brush• Thickness 2 -5 microns

COPAL- F• Protective varnish containing 5% Sodium Fluoride

based on Copal gum for insulating exposed dentine and providing thermal barrier.

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CERVITEC® PLUS-  IVOCLAR VIVADENT N.A.

-Chlorhexidine Varnish-Protect exposed root surfaces-Treat of open dentin tubules-1% chlorhexidine and 1% thymol in a homogenous solution-Colorless, transparent clear varnish-Provides optimum esthetics in the anterior part of the mouth

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CAVITYSHIELD™ 5% NAF VARNISH - 3M ESPE COMPANY

• Bubblegum flavor• Enhanced asepsis

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SUSPENSION LINERS• Def:- Liners based on water have many of the

constituents suspended instead of dissolved & are called suspension liners.

• Ca(0H)2 or zinc oxide in a synthetic resin• Water solvent based; H2O soluble• 10-25 µm film; Used to line only the dentin

[20-25 µm]

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Solution Liner/Varnish-Organic solvent based

-H2O insoluble

-2-5 µm

-Used to line cavity up over cavosurface margins

- They are flexible and dry rapidly

Suspension liner-Water Solvent based

-H2O soluble

-20 – 25 µm

-Used to line only the dentine

- Dry more slowly and produce thicker film

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CEMENT LINERS• Def:- Thicker liners that are selected primarly for pupal medication &

thermal protection are sometimes identified as cement liner.

[200-1000 µm = 0.2-1mm]

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FUNCTIONS:1. Primary purpose protective seal of exposed dentin surface. 2. Electrical insulation (with newly placed amalgam restoration) from the electrical circuts with restorations in adjacent teeth. 3. Thermal insulation with metallic restoration

4. Pulpal medication

COMPOSITION:- Suspension of calcium hydroxide

- methyl ethyl ketone or ethyl alcohol

- Methyl cellulose – thickening agent

- acrylic polymer beads or barium sulfate

- Calcium mono-fluoro-phosphate.

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ZINC OXIDE LINER- Used in moderately deep cavities.

- Palliative or obtundant effect

- Not used under composite restorations.

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CALCIUM HYDROXIDE LINER- Forms reparative dentin

- Used under composite restorations

- In deep cavities

- In exposures or suspected exposures.

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MANIPULATION OF CA(OH)2

Sqeeze equal parts of Ca(OH)2 paste, mix homogenously

Make a bead and carry with applicator, allow it to flow on the surface of concavity created by caries and dry for 2-3 min

If in Powder form carry with tweezer and repeat till it occupies required dimensions

If in suspension form-Injectible ,Drop it on the site indicated

Thickness-1-50microns for solution liners and suspension liners 20-25 microns

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Calcium hydroxide

Glass ionomer Reinforced ZOE

Components Paste with Ca(OH)2,LC resin & polyphenols

Powder(Al-silicate)liquid(polyalkenoate acid,LC resin)

Paste (with ZnO) paste (with eugenol)

Thermal conductivity

Insulator insulator Insulator

Solubility 0.3-0.5% high 0.08%(low) modest

Compressive strength

138 Mpa 128 Mpa 71 Mpa

Elastic modulus 588 Mpa 1820 Mpa -----

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CAVITY BASES• Definition:-Anusavice – Layer of insulating, sometimes medicated,

cement, placed in the deep portion of the preparation to protect pulp tissue from thermal & chemical injury.

Marzouk – Insulating materials that can be used directly on certain areas of the dentinal parts of the preparation.

Sturdevants- Bases(1 to 2 mm) are used to provide thermal protection for the pulp and to supplement mechanical support for the restoration by distributing local stresses from the restoration across the underlying dentin surface.

[1-2mm]

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• TYPES - High Strength Bases Provide thermal protection for pulp & mechanical

support for the restoration. Eg:Zn phosphate,Zn poly carboxylate,Glass ionomer,RMGI

-Low Strength Bases Have min strength & rigidity, Act as a barrier to

irritating chemicals and to provide therapeutic effect to pulp.

eg: Ca Hydroxide, ZnOE

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HISTORICAL BACKGROUND:• Before 1960’s Zn phosphate cement

Reinforced ZnO/E

• 1970 polycarboxylate cement• 1985-1994 GlC• Light Cured GIC & compomers chemical adhesion, Good mechanical properties, fluoride release, command setting and rapid achievement of strength.

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Zinc polycarboxylate

ZOE Calcium hydroxide

GIC

CompositionAnd setting Reaction

P-Zinc oxide, L-(phosphoric acid)

P- Zinc oxide liquid(polyacrylic acid)

P-zinc oxideL- eugenol

Base pasteCatalyst paste

P, F-Al-Si glassL- polyacrylic acid

p/L ratio 1.4 g/0.5 ml

1.5/1 6/1 by weight 1/1 3/1 by weight

Setting time 2.5-8 min 6-9 min 4- 10 min 2.5- 5.5 min 3- 5 min

Compressive strength

104 Mpa 55- 67 Mpa 4- 55 Mpa 10-27 Mpa 128 Mpa

Diametral tensile strength

5.5 Mpa Slightly higher than ZnPO4

0.3- 5.3 Mpa 1 Mpa 6.6 Mpa

ModulOfElastcty

13.7 Gpa 2.4 -4.4GpaNot brittle as ZnPO4

0.2- 5.4 Gpa

0.37 Gpa …..

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GENERAL APPLICATIONS1. Thermal and chemical insulation

2. Temporary restorations – Zn OE

3. Intermediate restorations – IRM

4. Permanent restorations – GIC

5. Temporary Luting – Type I ZOE

6. Permanent Luting – GIC, ZnP, Zn Poly Carb

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SUMMARY OF PULP PROTECTION PROCEDURES

Shallow Excavation[RDT > 2mm]

Moderate Excavation[RDT 0.5 - 2mm]

Deep Excavation[RDT < 0.5mm]

Amalgam -/-/Sealer -/base/sealer Dycal/base/sealer

Composite -/-/DBS -/-/DBS Dycal/-/DBS

Gold inlays & onlays

-/-/cement -/base/cement Dycal/base/cement

Ceramics -/-/DBS, CC -/-/DBS, CC Dycal/-/DBS, CC

(Medicament / Liner / Sealer)

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SCHEMATIC DIAGRAM FOR AMALGAM RESTORATION

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REFERENCES• Philps’ science of dental materials – 11th edition• Basic Dental Materials- Mannapallil• Restorative dental materials – Craig • Sturdevant’s art & science of operative dentistry – 5th

edition• Operative dentistry – Marzouk

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