Dental Alloys Properties

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Questions and Answers

What is the primary reason for documenting the use of dental alloys?

To comply with medical device regulations (correct)

To ensure the alloy's composition is known

To track the cost of the alloy

To compare with other dental materials

What is the purpose of taking metal shavings from intraoral restorations?

To analyze the alloy's composition (correct)

To evaluate the alloy's esthetics

To test the alloy's corrosion resistance

To determine the alloy's strength

What is the primary method of corrosion in dental alloys?

Mechanical wear and tear

Electrochemical reaction (correct)

Chemical reaction with saliva

Thermal decomposition

Why is corrosion of dental alloys a concern from a biocompatibility standpoint?

Because it releases elements that can affect surrounding tissues Signup and view all the answers

What is a common method for measuring corrosion in dental alloys?

Observing the alloy for surface deterioration Signup and view all the answers

What is the significance of identifying and quantifying released elements in dental alloys?

To assess the alloy's biocompatibility Signup and view all the answers

What is the purpose of EDX analysis in dental alloys?

To characterize the alloy's composition Signup and view all the answers

What is the accuracy of analyzing dental alloys using scanning microscopy and EDX?

±1% Signup and view all the answers

What is an alloy typically composed of?

Two or more metals or non-metals Signup and view all the answers

What is a characteristic of dental alloys?

They are composed of at least four metals Signup and view all the answers

Why has the composition of dental alloys evolved over time?

Due to the increase in price of gold and palladium Signup and view all the answers

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

The complexity and diversity of the alloys Signup and view all the answers

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

Over 25 elements Signup and view all the answers

What is the most common way to express the composition of dental alloys?

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

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

Because it better predicts the number of atoms available to be released Signup and view all the answers

What is a key difference between weight percentage and atomic percentage?

Weight percentage and atomic percentage may be substantially different from one another Signup and view all the answers

What is a necessary condition for an alloy to have adverse biological effects?

The alloy releases elements Signup and view all the answers

What influences the biological response to an alloy?

The biological effects of released elements, the quantities released, and the duration of tissue exposure Signup and view all the answers

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

The surface structure of the alloy Signup and view all the answers

What is true about elemental release and corrosion from alloys?

It occurs in all alloys, regardless of type or composition Signup and view all the answers

What influences the lability of an element?

The electronic structure of the element Signup and view all the answers

What is the primary consequence of thermal treatment on a ceramic alloy?

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

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

They increase the attachment between ceramic and alloy Signup and view all the answers

What can modify the lability of an element?

The presence of other elements around it Signup and view all the answers

What reduces the lability of copper in dental alloys?

The presence of palladium Signup and view all the answers

Why may exposed oxides at the crown margin increase the toxicity of the alloy?

Because they promote elemental release Signup and view all the answers

What reduces the lability of titanium?

The formation of TiO2 on the surface of titanium Signup and view all the answers

What is the consequence of recasting base metal alloys?

A significant increase in the release of elements and cytotoxicity Signup and view all the answers

What is the problem with placing a gold surface coating on a nickel-based or cobalt-based alloy?

It enhances corrosion Signup and view all the answers

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

Because of the significant problems with the integrity of the long-term bonds between coatings and the alloys Signup and view all the answers

What happens to the release of ions from alloys over time?

It decreases Signup and view all the answers

What is the effect of solders on dental alloys?

They increase the corrosion of dental alloys Signup and view all the answers

What is the primary factor influencing the accumulation of elements locally around dental alloys?

Rate of release of elements at the implantation site Signup and view all the answers

What is unique about the corrosion properties of brass in the mouth?

It is extremely corrosion-prone Signup and view all the answers

In which tissue have elevated copper levels been demonstrated in dogs adjacent to crowns composed of brass?

Gingival tissues Signup and view all the answers

What is the significance of the study on patients with inflamed gingiva adjacent to various dental alloys?

It showed that alloy components are present in gingiva and mucosa Signup and view all the answers

What is the general trend observed in the levels of alloy components in human gingival tissues adjacent to dental alloys?

The levels are generally low Signup and view all the answers

What is the main reason why elements released from nonamalgam dental alloys do not contribute significantly to the systemic body burden of elements?

The amounts released are far below those taken in as part of the diet Signup and view all the answers

What is the primary source of metal intake in the body?

Daily dietary intake Signup and view all the answers

What is the significance of Table 8.3 in the context of dental alloys?

It compares the amounts of elements released from dental alloys to daily dietary intake Signup and view all the answers

Study Notes

Basic Material Properties

An alloy is a mixture of two or more metals or non-metals (elements).
Dental alloys typically contain at least four metals and often six or eight different metals, making them metallurgically complex.
Alloy compositions are diverse and have evolved over the past 20 years, with many types of alloys emerging that were unknown just a few years ago.
Most dental alloys were previously based on gold, but today's alloys may be based on silver, gold, palladium, nickel, cobalt, or titanium.

Alloy Composition

The composition of dental alloys 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 is better for predicting the number of atoms available to be released.
The wt.% and at.% of an alloy may be substantially different from one another.

Analysis of Dental Alloys

Dental alloys are classified as medical devices, and their use must be documented by the dentist and laboratory technician.
Information about an alloy's composition is available in the literature or from manufacturers.
Metal shavings can be taken from intraoral restorations and analyzed using scanning microscopy and energy-dispersive x-ray (EDX) analysis to determine the alloy's composition.

Corrosion and Release of Elements

Corrosion is the primarily electrochemical process of alloys involving the ionization of elements that are released into the environment.
Elements that are initially uncharged lose electrons and become positively charged ions as they are released into solution.
Corrosion is a chemical property of an alloy that influences other properties, including esthetics and strength.
The release of elements from an alloy is necessary for an alloy to have adverse biological effects such as toxicity, allergy, or mutagenicity.
Factors that influence the corrosion of dental alloys 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 (gold coating, soldering)
- Time in service

Factors Influencing Element Release

The composition of an alloy is a fundamental factor that influences element release.
Certain elements, such as copper, zinc, and nickel, have higher tendencies to be released than elements such as gold and palladium.
The lability of an element may be substantially modified by other elements around it.
The phase structure of the alloy and thermal treatment can also influence element release.

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.

Nonimplanted Dental Alloys

Elements released from nonimplanted dental alloys may or may not gain access into the body.
There is some evidence that elements from dental crowns and other alloys gain access to local gingival tissues or the oral mucosa.
However, there is little evidence to demonstrate that elements released from nonamalgam dental alloys contribute significantly to the systemic body burden of elements.

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Description

Learn about the composition and properties of dental alloys, including their metallurgically complex nature and diverse compositions.