Dental Alloys

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Questions and Answers

What is the minimum number of metals or non-metals that an alloy typically contains in dentistry?

Eight

Two

Six

Four (correct)

What is the primary reason for the evolution of alloy composition in dentistry over the past 20 years?

Development of new dental applications

Rise in prices of gold and palladium (correct)

Advancements in metallurgy

Increased demand for dental alloys

How many elements from the periodic table are used in today's dental alloys?

Over 30 elements

Over 25 elements (correct)

Over 15 elements

Over 20 elements

What is the most common way of expressing an alloy's composition in dentistry?

Weight percentage (wt.%) Signup and view all the answers

Why is atomic percentage a better predictor of an alloy's biological properties?

It better predicts the number of atoms available to be released and affect vital tissues Signup and view all the answers

What is the primary challenge in understanding the biocompatibility of dental alloys?

All of the above Signup and view all the answers

What is the relationship between the weight percentage and atomic percentage of an alloy?

They may be substantially different from one another Signup and view all the answers

What is the key factor in understanding the biological properties of dental alloys?

The atomic composition of the alloy Signup and view all the answers

What is the release of elements from an alloy necessary for?

Toxicity, allergy, and mutagenicity Signup and view all the answers

What is the primary factor that influences the corrosion of dental alloys?

Composition of the alloy Signup and view all the answers

Which of the following elements has a lower tendency to be released from an alloy?

Gold Signup and view all the answers

What is the term for the tendency of an element to be released from an alloy?

Lability Signup and view all the answers

What can reduce the lability of copper in dental alloys?

Palladium Signup and view all the answers

What is the result of the formation of TiO2 on the surface of titanium?

Reduced lability of titanium Signup and view all the answers

Why do different alloys have varying levels of corrosion and elemental release?

Due to differences in composition Signup and view all the answers

What is the relationship between the corrosion of an alloy and its biological effects?

Corrosion is necessary but not sufficient for an alloy to have adverse biological effects Signup and view all the answers

What is the main reason for the difference between wt.% and at.% in the gold-based alloy?

Because of the presence of other elements with different atomic weights Signup and view all the answers

What is the significance of phase structure in an alloy?

It determines the corrosion properties and biocompatibility of the alloy Signup and view all the answers

What is the percentage of titanium in the Ti6Al4V alloy by wt.%

81% Signup and view all the answers

What is the characteristic of a single-phase alloy?

It has a homogeneous structure Signup and view all the answers

What is the result of the interaction between the biological environment and the phase structure of an alloy?

It determines which element will be released and how the body will respond to the alloy Signup and view all the answers

What is the main difference between a single-phase alloy and a multiple-phase alloy?

The structure of the alloy Signup and view all the answers

What is the purpose of examining the phase structure of an alloy at the microscopic level?

To determine the presence of different phases in the alloy Signup and view all the answers

What is the significance of the atomic weights of the component elements in an alloy?

It determines the difference between wt.% and at.% Signup and view all the answers

What is the primary concern associated with the presence of multiple phases in alloys?

Increased risk of element release due to electrochemical corrosion Signup and view all the answers

How does surface roughness affect element release from alloys?

It increases element release by exposing more atoms to the external environment Signup and view all the answers

What is the effect of reduced pH on the corrosion of certain alloys?

It increases corrosion, particularly in nickel-based alloys Signup and view all the answers

What is the characteristic of corrosion in crevices, gaps, and pits?

It is higher due to the creation of local microenvironments Signup and view all the answers

What is unique about the surface composition of dental alloys?

It can be significantly different from the bulk composition Signup and view all the answers

What was observed about the surface composition of a certain gold alloy?

It was significantly lower in gold content than the bulk Signup and view all the answers

What was the effect of copper's prevalence at the surface of a gold alloy on its release into a biological medium?

It increased copper release due to copper's high lability Signup and view all the answers

What was observed about the release of palladium from a silver-palladium alloy into a biological medium?

It demonstrated a low tendency to be released Signup and view all the answers

What is the effect of thermal treatment on the structure of a ceramic alloy?

2-3.5 fold increase in the release of copper and zinc Signup and view all the answers

What is the role of metal oxides generated during the firing process?

Increase the attachment between ceramic and alloy Signup and view all the answers

What is the consequence of exposed oxides at the crown margin?

Increase in gingivitis Signup and view all the answers

What is the effect of recasting of base metal alloys on the release of elements?

Significant increase in the release of elements Signup and view all the answers

What is the consequence of the juxtaposition of different alloys in permanent contact?

Increase in corrosion Signup and view all the answers

Why should gold surface coating of nickel-based or cobalt-based alloys be discouraged?

Because it increases the corrosion of the alloy Signup and view all the answers

What is the effect of time on the release of ions from alloys?

The release of ions decreases with time Signup and view all the answers

What is the recommendation for solders or alloy combinations in dental applications?

Use only those solders or alloy combinations that have a low tendency for corrosion Signup and view all the answers

Study Notes

Alloys in Dentistry

An alloy is a mixture of two or more metals or non-metals (elements) and is metallurgically complex.
Dental alloys usually contain at least four metals, and often six or eight different metals.
Alloy compositions are diverse, and more than 25 elements in the periodic table are used in today's dental alloys.

Understanding Alloy Composition

Alloy composition can be expressed in two ways: weight percentage (wt.%) or atomic percentage (at.%).
Weight percentage is the most common way to describe an alloy's composition, but atomic percentage better predicts the number of atoms available to be released and affect vital tissues.
The weight percentage and atomic percentage of an alloy may be substantially different from one another.

Phases in Alloys

Phases are areas within an alloy that have essentially the same composition.
Single-phase alloys have a similar composition throughout their structure.
Multiple-phase alloys have areas that differ in composition, which can affect their corrosion properties and biocompatibility.

Corrosion and Biocompatibility

The corrosion of an alloy is critical to its biocompatibility because the release of elements from the alloy is necessary for an alloy to have adverse biological effects.
The biological response to an alloy depends on the biological effects of released elements, the quantities released, and the duration of tissue exposure.
Factors that influence corrosion include:
- Composition of the alloy (particularly at the surface)
- Phase structure of the alloy
- Surface structure (roughness, presence of oxides)
- Crevices, pits
- Thermal treatment/history
- Combinations of alloys
- Time in service

Elemental Release and Corrosion

Elemental release and corrosion occur from all alloys, regardless of type or composition.
The amount of corrosion and elemental release may vary dramatically among alloys.
Elements like copper, zinc, and nickel have higher tendencies to be released than elements like gold and palladium.
The lability of an element may be substantially modified by other elements around it.
Phase structure and surface characteristics can influence element release.

Surface Characteristics and Oral Environment

Surface roughness tends to increase elemental release because rough surfaces have high surface areas that expose more atoms to the external environment.
The oral environment near the alloy, such as reduced pH, can increase corrosion.
Corrosion is particularly high in crevices, gaps, and pits, and in the local environment of the gingival sulcus.

Thermal Treatment and Alloy Combinations

Thermal treatment, such as firing of a ceramic alloy, may cause an alteration of the structure within the alloy.
Metal oxides generated during the firing process can increase the attachment between ceramic and alloy, but may also promote elemental release and increase toxicity.
The juxtaposition of different alloys may increase corrosion when they are in permanent contact.

Clinical Practice Advice

Gold surface coating of nickel-based or cobalt-based alloys should be discouraged because the combination of the alloys and their permanent contact may enhance corrosion rather than retard it.
Only those solders or alloy combinations should be used that have a low tendency for corrosion.

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Description

This quiz covers the basics of dental alloys, including their composition and properties. It explains what alloys are, their metallurgically complex nature, and the diversity of alloy compositions.