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Properties of Dental Materials

Lessons, visuals, quizzes, flashcards, and resources—organized in teaching order.

Thermal and Electrical Properties

Thermal and Electrochemical Dynamics in Dental Materials

Thermal Properties of Dental Materials

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COEFFICIENT OF THERMAL EXPANSION • Linear coefficient of thermal expansion: - a measure of how much it expands per unit length if heated one degree higher. - The change in length per unit length of the material for a 1°C change in temperature • LCTE= Fractional change in length/Change in temperature.

COEFFICIENT OF THERMAL EXPANSION • Linear coefficient of thermal expansion: - a measure of how much it expands per unit length if heated one degree higher. - The change in length per unit length of the material for a 1°C change in temperature • LCTE= Fractional change in length/Change in temperature.

The Linear Coefficient of Thermal Expansion (LCTE) measures how much a material expands per unit length when heated by one degree. Mathematically, it is defined as:

$\text{LCTE} = \frac{\text{Fractional change in length}}{\text{Change in temperature}}$

In the oral cavity, a significant mismatch in LCTE between the dental restorative material and the natural tooth structure can lead to microleakage, marginal gaps, and eventual restoration failure during thermal cycling.

Sources

COEFFICIENT OF THERMAL EXPANSION • Linear coefficient of thermal expansion: - a measure of how much it expands per unit length if heated one degree higher. - The change in length per unit length of the material for a 1°C change in temperature • LCTE= Fractional change in length/Change in temperature.

Thermal Conductivity represents the rate of heat flow through a material. For instance, gold exhibits high thermal conductivity, which can cause significant thermal sensitivity in patients if a protective base or liner is not used.

Thermal Diffusivity measures the speed with which a temperature change spreads through an object when one surface is heated. It is governed by density, specific heat, and thermal conductivity:

High density & high specific heat result in low thermal diffusivity, meaning temperature changes transmit very slowly.
Low heat capacity & high thermal conductivity result in high thermal diffusivity, causing rapid transmission of temperature changes.

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THERMAL CONDUCTIVITY • a.k.a. Coefficient of thermal conductivity • The rate of heat flow through a material. • Materials have different rates of conducting heat • Gold causes the most sensitivity

THERMAL CONDUCTIVITY • a.k.a. Coefficient of thermal conductivity • The rate of heat flow through a material. • Materials have different rates of conducting heat • Gold causes the most sensitivity

THERMAL DIFFUSIVITY - is a measure of the speed with which a temperature change will spread through an object when one surface is heated. - High density & high specific heat = low thermal diffusivity / very slow temperature change/ - Low heat capacity & high thermal conductivity = high diffusivity & temperature changes transmit rapidly..

THERMAL DIFFUSIVITY - is a measure of the speed with which a temperature change will spread through an object when one surface is heated. - High density & high specific heat = low thermal diffusivity / very slow temperature change/ - Low heat capacity & high thermal conductivity = high diffusivity & temperature changes transmit rapidly..

Electrochemical Phenomena: Galvanism, Tarnish, and Corrosion

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GALVANISM – Generation of electrical currents in mouth – Results from presence of dissimilar metals in mouth – Causes pain and tastes metallic Galvanic shock - Pain sensation caused by the electrical current generated when two dissimilar metals are brought into contact in the oral environment - Sudden short-circuit through the two alloys

GALVANISM – Generation of electrical currents in mouth – Results from presence of dissimilar metals in mouth – Causes pain and tastes metallic Galvanic shock - Pain sensation caused by the electrical current generated when two dissimilar metals are brought into contact in the oral environment - Sudden short-circuit through the two alloys

Galvanism is the generation of electrical currents in the mouth resulting from the presence of dissimilar metals. When two dissimilar metals come into contact in the oral environment, a sudden short-circuit occurs through the two alloys, producing a painful sensation known as galvanic shock and often causing a metallic taste.

Sources

GALVANISM – Generation of electrical currents in mouth – Results from presence of dissimilar metals in mouth – Causes pain and tastes metallic Galvanic shock - Pain sensation caused by the electrical current generated when two dissimilar metals are brought into contact in the oral environment - Sudden short-circuit through the two alloys

Metals in the oral cavity are also subject to surface and structural degradation:

Tarnish: A surface discoloration or slight loss of surface luster. It is a surface reaction of metals to components in saliva or foods, forming a thin oxidized film through reactions with sulfides, oxides, or chlorides.
Corrosion: A chemical or electrochemical process in which a solid (usually a metal) is attacked by an environmental agent, resulting in partial or complete dissolution. It is accelerated by the presence of dissimilar metals and leads to surface roughness and pitting.

Sources

TARNISH - is a surface discoloration on a metal or a slight loss or alteration of the surface finish or luster - reaction with a sulfide, oxide, chloride, or other chemical causes surface discoloration through formation of a thin oxidized film. - Surface reaction of metals to components in saliva or foods

TARNISH - is a surface discoloration on a metal or a slight loss or alteration of the surface finish or luster - reaction with a sulfide, oxide, chloride, or other chemical causes surface discoloration through formation of a thin oxidized film. - Surface reaction of metals to components in saliva or foods

CORROSION Chemical or electrochemical process in which a solid, usually a metal, is attacked by an environmental agent, resulting in partial or complete dissolution. – Results from presence of dissimilar metals – Roughness and pitting

CORROSION Chemical or electrochemical process in which a solid, usually a metal, is attacked by an environmental agent, resulting in partial or complete dissolution. – Results from presence of dissimilar metals – Roughness and pitting