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U L F A TU L F A T

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INTRODUCTION TO CHEMISTRY INTRODUCTION TO CHEMISTRY

OF DENTAL MATERIALSOF DENTAL MATERIALS INTRODUCTION TO CHEMISTRY INTRODUCTION TO CHEMISTRY

OF DENTAL MATERIALSOF DENTAL MATERIALS DR. YAWAR HAYAT KHANDR. YAWAR HAYAT KHAN

BDS, M.Sc. (London)BDS, M.Sc. (London)

Assistant Professor/ Head of Assistant Professor/ Head of Department (Dental Materials)Department (Dental Materials)

Islamic International Medical College (Dental Islamic International Medical College (Dental Section)Section)

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Topics/ LecturesTopics/ LecturesTopics/ LecturesTopics/ Lectures1.1. General Introduction to DentistryGeneral Introduction to Dentistry

2.2. Introduction to Dental MaterialsIntroduction to Dental Materials

3.3. Physical properties of materials:Physical properties of materials: Characterisation of solid surfacesCharacterisation of solid surfaces Adsorption, absorption, and sorptionAdsorption, absorption, and sorption Surface tension, wetting, capillary riseSurface tension, wetting, capillary rise Forces involved in Denture retentionForces involved in Denture retention

4.4. Thermal, Electrical and other related properties of Thermal, Electrical and other related properties of dental materialsdental materials

5.5. Mechanical properties i.e. stress, stain, stress/ strain Mechanical properties i.e. stress, stain, stress/ strain relationship and other related properties.relationship and other related properties.

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Topics/ LecturesTopics/ LecturesTopics/ LecturesTopics/ Lectures6.6. Classification of dental materials on their basis of Classification of dental materials on their basis of

chemistry e.g., example Polymers, Ceramics, Metals, Alloy chemistry e.g., example Polymers, Ceramics, Metals, Alloy and Composites.and Composites.

7.7. Impression materials in all respects and duplicating Impression materials in all respects and duplicating materials.materials.

8.8. Adhesion: Enamel and Dentine bonding agents and Adhesion: Enamel and Dentine bonding agents and bonding system.bonding system.

9.9. Dental Cements.Dental Cements. Zinc Phosphate Cement.Zinc Phosphate Cement. Zinc Oxide/ Eugenol, Modified Zinc Oxide/ Eugenol, Zinc Oxide/ Eugenol, Modified Zinc Oxide/ Eugenol,

Ethoxy Benzoic Acid Cement, Zinc Polycarboxylate, Ethoxy Benzoic Acid Cement, Zinc Polycarboxylate, Zinc Polyacrylate Cement, Silico Phosphate Cement.Zinc Polyacrylate Cement, Silico Phosphate Cement.

Glass Ionomer Cement and Hybrid Ionomer CementGlass Ionomer Cement and Hybrid Ionomer Cement Compomers, Cavity Varnish, Cavity Liners, Calcium Compomers, Cavity Varnish, Cavity Liners, Calcium

Hydroxide and Gutta purcha.Hydroxide and Gutta purcha.

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Topics/ LecturesTopics/ LecturesTopics/ LecturesTopics/ Lectures

10.10. Composite Restorative Materials and properties Composite Restorative Materials and properties of compositesof composites

11.11. Dental amalgam Dental amalgam

12.12. Abrasion and polishing materialsAbrasion and polishing materials

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Science of Dental Materials is an applied basic science dealing with the physical, chemical, biological properties and interaction with oral tissues of the materials used in clinical dentistry

This subject also deals with the manipulative techniques, applications and uses of dental materials

Every dental procedure requires the use of materials so a variety of materials are available which requires proper selection and evaluation

Subject is approached with the view of determining: Chemical nature of material Physical & mechanical functions Manipulative techniques Applications Biological considerations

To conclude it is relevant to say that the subject of dental materials is a basic science in itself with its own tenets and principles

Introduction to Dental MaterialsIntroduction to Dental MaterialsIntroduction to Dental MaterialsIntroduction to Dental Materials

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AIM OF THE SUBJECTAIM OF THE SUBJECT Since dentistry is considered both as an art and science

subject therefore, the aim of science of dental materials is to stress upon the principles involved in the use of dental materials. The main requirements for dental materials in general are as under: Why materials react and behave as they do? What manipulative techniques are used? How variation in techniques effect their properties? What is the effect of material on its environment? What is the nature of the interface between the synthetic material

and oral tissues? What is the effect of oral environment on the material? What is the appearance of materials? What other properties are important? Is the material easy and convenient to use?

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HISTORICAL BACKGROUNDHISTORICAL BACKGROUND Early History

Related to Phoenicians, Greeks & Romans Gold is one of the oldest materials used (prosthetic dental

purposes for at least 2500 years) Medieval & Early Modern Period

Dental historians doubt that beginning of Christian era to 1500 AD was a “DARK AGE” of inactivity

Shift of practice from prosthetic restoration to restoration of carious teeth which were filled with alum, honey and other substances during the period of 1050 – 1122 AD (Al Razi)

First book to treat dentistry independently was written in German in 1548 AD by Walter Herman Ryff

Beginning of Dental Science 1600 – 1840 AD

Period of Mechanical Improvement 1840 – 1900 AD

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HISTORICAL BACKGROUNDHISTORICAL BACKGROUND

Advances Since 1900 AD Establishment of Dental institutes Establishment of standard organizations

• American Dental Association (ADA)• National Bureau of Standards

Future Development in Biomaterials Specific Stress on bio-compatibility of

materials

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DENTAL MATERIALSDENTAL MATERIALS

Requirements of Materials Selection of Materials Handling of Materials Evaluation of Materials Application of Materials Classification of Materials

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REQUIREMENTSREQUIREMENTSof Materialsof Materials

Why materials react and behave as they do?What manipulative techniques are used?How variation in techniques effect their properties?What is the effect of material on its environment?What is the nature of the interface between the synthetic

material and oral tissues?What is the effect of oral environment on the material?What is the appearance of materials?What other properties are important?Is the material easy and convenient to use?

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SELECTIONSELECTIONof Materialsof Materials

Since variety of materials are available, so they require proper selection

Good selection leads to success of restoration

Selection is subjected to the need and type of restoration

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HANDLINGHANDLINGof materialsof materials

Direct materials (filling materials)

Indirect materials (impression materials)

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EVALUATIONEVALUATIONof Materialsof Materials

Proper evaluation & testing of the material is required before application

It is emphasized that most manufacturers of dental materials should operate appropriate quality assurance programs so that the materials are thoroughly tested and evaluated before release into the market

Steps for evaluation: Standard specification Laboratory evaluation Clinical trials

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Criteria for Selection

Analysis of problem

Consideration of requirement

Consideration of available material &

their properties

Choice of material

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Standard Specification Many standard specification tests of both national & international

standards are available which effectively maintained quality level of most of the dental materials

Laboratory Evaluations Certain lab tests some of which are used in standard specifications,

can be used to indicate the suitability of materials For e.g., simple solubility test can indicate the stability of a

material in aqueous media – a very important property for filling materials

The methods used to evaluate materials in lab give results which can be correlated with the clinical experiences

Clinical trials Ultimate test is clinical trial although lab tests provides suitable

information and useful data regarding materials Many materials provides good results in laboratory, but found

lacking when subjected to clinical use Majority of manufacturers perform clinical trials on materials in

cooperation with a hospital or university before finally releasing a product

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APPLICATIONAPPLICATIONof Materialsof Materials

Varies from material to material

Also depends upon the requirement and oral conditions

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CLASSIFICATIONCLASSIFICATIONOF MATERIALSOF MATERIALS

CeramicsMetalsPolymersComposites

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They are simple or complex combinations of metallic or non-metallic elements of periodic table

Characteristically they are hard & abrasive

Examples are Alumina, Tungsten Carbide & Silica

CERAMICSCERAMICS

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Metals are usually: Hard Lustrous Dense Good conductors of heat & electricity Ductile & malleable

They are electropositive i.e., they give positive ions in solutions

Of over 100 elements in the PERIODIC table, some 68 are metals

METALSMETALS

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Metals can occur either as pure elements, or in compounds with other elements in ores. For example:

Gold occurs as pure metal Silver occurs as pure metal Copper seldom occurs as pure metal

Metals can be produced by the following methods Thermal methods Hydrometallurgical methods Thermo-electrolytic methods

METALSMETALS

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Polymers are long-chain molecules consisting of many repeating units. A monomer is the smallest repeating unit in the polymer chain.

Polymers are prepared from monomers and the process is known as polymerization.

They are classified as natural materials and synthetic materials

Natural materials include proteins, polysaccharides (agar, alginate & starch), polyisoprenes (gutta percha and rubber), polynucleic acids (DNA & RNA)

POLYMERSPOLYMERS

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Synthetic materials includes polythene, nylon and bakelite

Organic compounds found in fossil fuels, as gas, oil, coal. Other natural polymers are wood pulp & cotton (cellulose), nucleic acids & collagen (structural building blocks of all living things)

Polymers have; Low melting points Fairly soft & not stiff Can be synthetically

produced

POLYMERSPOLYMERS

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Are combinations of basic ceramic, metallic & polymeric materials

Composites are prepared to improve properties of individual components & enhance their clinical service

Examples are Ceramic – metallic composites ----- Tungsten Carbide – Cobalt burs

COMPOSITESCOMPOSITES

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Materials in useMaterials in use

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