LECTURE 1 BY HEAD OF DEPARTMENT DR RASHID

LECTURE 1 BY HEAD OF DEPARTMENT DR RASHID HASSAN ASSISTANT PROFESSOR SCIENCE OF DENTAL MATERIALS DEPARTMENT RAWAL INSTITUTE OF HEALTH SCIENCES RAWAL COLLEGE OF DENTISTRY ISLAMABAD 1

INTRODUCTION TO DENTAL MATERIALS AND INSTRUMENTS 2

Science Of Dental Materials l Is defined as, “The Study of composition and properties of dental materials and the manner in which they interact with the environment in which they are placed”. 3

Oral Environment l Very demanding. l There can be 1. 2. 3. Temperature variations. p. H Variations in Masticatory forces. 4

Temperature Variations l l Normal temperature of oral cavity (32℃ to 37℃). On intake of a cold/hot food or drink temperature range increases (0℃ to 70℃). 5

p. H Variations l p. H of saliva is neutral (7. 0) l On intake of acidic fruit juices or alkaline medicaments, p. H may vary from 2. 0 to 11. 0. 6

Variations in Masticatory Forces l l l Muscles of Mastication apply forces to the dentition. Masticatory forces vary from tooth to tooth. Average force applied by the tooth increases from anteriors to posteriors. Tooth Second molar First molar Average force (N) 800 390 Bicuspids 288 Cuspids 208 Incisors 155 7

IDEAL PROPERTIES OF A DENTAL MATERIAL Biocompatible. l Binds permanently with the tooth structure. l Esthetically acceptable. l Exhibit properties similar to the tooth structure. l Initiate tissue repair and regeneration. l 8

DENTAL MATERIALS l l 1. 2. 3. 4. Ultimate goal: Improve and maintain the quality of life of a dental patient. All dental materials fall under 4 main groups: Polymers. Metals. Ceramics. Composites. 9

POLYMERS l Chemical compound consisting of large organic molecules formed by the union of many smaller monomer units is called a “POLYMER” l Chemical reaction in which low molecular weight monomers are converted into high molecular weight polymer chains “POLYMERIZATION” 10

METALS l “An opaque lustrous chemical substance that is a good conductor of heat and electricity, and when polished is a good reflector of light”. The Metals Handbook (1992) 11

CERAMICS l “An inorganic compound with non metallic properties, typically composed of metallic (or semimetallic) and non metallic elements. ” 12

COMPOSITES l “A material formed from two distinct phases is called a composite material” l Two distinct phases can be easily separated on microscopic scale. l Final properties are either superior or intermediate to the individual constituents. 13

CLASSIFICATION OF DENTAL MATERIALS 14

CLASSIFICATION OF DENTAL MATERIALS Dental materials can be classified as: 1. Preventive dental materials. 2. Restorative dental materials. a) b) 3. 4. Direct restorative dental materials. Indirect restorative dental materials. Auxiliary dental materials. Temporary restorative dental materials. 15

1. PREVENTIVE DENTAL MATERIALS l l l Basic aim is to provide resistance to the progression of an active carious lesion. Carious lesion cause the demineralization of the dental enamel. These include: a) Chemotherapeutic agents like Dentifrices, Mouthwashes and cavity varnishes. b) Pit and fissure sealants. c) Floride releasing cements. 16

1. PREVENTIVE DENTAL MATERIALS Preventive dental materials can also serve as Restorative materials. l Can be either, 1) Short time periods. 2) Moderately long time period. 3) Longest time periods. l 17

2. RESTORATIVE DENTAL MATERIALS l l 1. 2. 3. 4. 5. 6. 7. 8. Help to repair or replace defected tooth structure. These include: Amalgam. Bonding agents. Resin based composites. Compomers. Ceramics. Liners. Cement bases. Dental polymers. 18

Types of Restorative dental materials a) l l Direct restorative materials: Used intraorally. fabricate restorations / prosthetic devices directly on the teeth or tissues. Indirect restorative materials: Used extraorally. Formed indirectly over a cast or models. 19

3. AUXILIARY DENTAL MATERIALS l l 1. 2. 3. 4. 5. 6. Materials used in the process of fabricating dental prosthesis. These include: Impression materials. Dental waxes. Gypsum casts and model materials. Finishing and polishing abrasives. Acrylic resins for impressions. Acid etching solutions. 20

4. TEMPORARY RESTORATIVE DENTAL MATERIALS l l l 1. 2. 3. 4. Sub category of restorative materials. Intended to be used to restore the tooth temporarily. These include: Orthodontic wires. Cements used as temporary liners. Cements used as temporary filling materials. Acrylic resins used for inlays, onlays, crowns and fixed partial dentures. 21

SELECTION OF DENTAL MATERIALS 22

SELECTION OF DENTAL MATERIALS 1. 2. 3. 4. Analysis of the problem. Consideration of the requirements. Consideration of the available materials and their properties. Choice of a suitable material. 23

1. Analysis of the problem l Basic and very important step. l Incorrect analysis may lead to wrong treatment plan. l Poor prognosis and failure of treatment. e. g. Selection of a filling material. 24

2. Consideration of the requirements l Enlist the requirements that a material must meet. l Requirements of a material are dependent upon the situation. 25

3. Consideration of the available materials and their properties Clear concept about the properties. l In case of immediate problem, Must choose from the materials in hand. l Dentist must be up to date with the advancements. Thorough comparison of Properties of the available materials with requirements. l 26

4. Choice of a suitable material l 1. 2. 3. Final step. Narrowing the range of choice. Factors: Availability. Ease of handling. Cost effectiveness. 27

QUESTIONS? ? ? 28