dental materials - unit 1

properties of dental materials

Define dental materials

The study of materials that are applied in dentistry for the fabrication of Dental Appliances and Tooth Restorations

A DENTAL APPPLIANCE is a device used to _______. What are some examples?

Provide function

• Examples: dentures, braces, retainers

What are TOOTH RESTORATIONS used for? What are some examples?

Restore or replace tooth structure to original state

• Examples: Crowns, bridges, amalgam, composite, indirect restorations

What are the uses of Dental Materials?

1. Replace/restore tooth structure lost through trauma or caries

2. Prevent the invasion of caries

3. Replace soft and hard tissue

4. Take impressions of existing conditions or teeth prepared for a prosthetic device

5. Finish and polish restorations or prosthesis

Dental Materials have a criteria to be approved by the CDA. What is part of the criteria? (5)

1. Can’t be poisonous or harmful to the body

2. Not harmful or irritating to the tissues of the oal cavity

3. Must help protect the tooth and oral tissues

4. Must resemble natural teeth as closely as possible

5. Easily formed and placed in the mouth for restorations

What are the properties of Dental Materials?

1. Mechanical properties

2. Thermal change and conductivity

3. Electrical properties

4. Corrosive properties

5. Solubility

6. Application properties

7. Hardness, Ductility and Malleability

8. Retentive properties

What is the meaning of Mechanical properties?

Response to force (strength and flexibility)

What is the biting/chewing force on molars? (in lbs) - Mechanical properties

170lbs

What is the meaning of Thermal change and conductivity?

Thermal Change: change in temperature

Thermal Conductivity: Rate of heat flow

• *metal conducts heat/cold so a base is used to protect the pulp nerve

What is Galvanism? - Electrical properties

An electrical current contacting between two dissimilar metals

• In the mouth: saliva (electrolyte) + 2 dissimilar metals = electric current

• (can create corrosion)

What is Galvanic Shock?

Pain experienced when 2 dissimilar metals contact each other

What is corrosion?

A chemical reaction that occurs within a metal when exposed to corrosive factors (temperature, humidity, and saline)

What is tarnish?

Surface discoloration or change in the finish of metal

What is solubility?

Rate at which a material dissolves in fluid

Define absorption

Ability of a material to take in fluid

Define adsorption

Concentration of molecules on a surface

What are Application properties in dental materials? (4)

1. Flow - allows material to be adapted easily

2. Adhesion - ability to stick

3. Wettability - ability of a liquid to spread

4. Viscosity - (high = thick consistency || low = thin consistency)

What is the meaning of Hardness, Ductility and Malleability?

• Strength

• Stretchability

• Ability to be flattened/shaped

What is Proportional Limit?

point just before a material becomes permenently deformed and the shape is permanently changed

What is the meaning of Retentive properties?

Ability to hold dental materials in the tooth

What are the three methods of achieving adhesion? (3)

1. mechanical retention - drilling to make undercuts to lock material in place

2. physical retention - luting using cements

3. chemical retention - bond

What are 5 factors that affect the manipulation of dental materials?

1. manipulation time - amount of time mixing material

2. setting time - time for material to harden

3. moisture

4. temperature

5. consistency - primary/luting or secondary

Define Force - (Stress & Strain)

Any push or pull upon matter

Define Stress - (Stress & Strain)

Reaction within a material to externally applied force

Define Strain - (Stress & Strain)

A change produced within a material in result to stress

Define Compressive force

occurs when materials are compressed

Define Compressive stress

amount of pressure applied to cause a material to break

Define Compressive strain

changes resulting from compressive stresses

Define Tensile Stress

occurs when two forces are applied in opposite directions

Define Tensile strain

the amount of force necessary to pull a material apart

Define Shear Stress

when equal or opposite forces are applied against opposite planes

Define Shear strain

the point at which a material is destroyed through the action of two portions sliding over each other

Thermal changes in the mouth are of major concern for two reasons:

1. Contraction and expansion

2. The need to protect the pulp from thermal shock

What is Microleakage? What causes it? Why is it bad?

The separation of material and tooth structure

• Caused by a difference in expansion between the dental material and the tooth

• Creates an opening for caries activity to begin

Define Percolation. What does it lead to?

The in and out flow of fluids, debris, and microorganisms

• Leads to: Sensitivity, tooth loss, recurrent decay, pulp damage