Dental Amalgam Properties

Dental Amalgam Properties

Explain the physical properties of dental amalgam.
Answer:

ADA specification no. 1 for amalgam alloy lists three physical properties as a measure of the quality of amalgam, i.e. strength, dimensional change, creep, and flow.

Strength: The compressive strength of dental amalgam is strong but it is weak in tension and shear.

“What Are The Key Properties Of Dental Amalgam”

Compressive Strength:

• High-copper single compositional alloys have the highest compressive strength of 510 MPa. This value is obtained after 7 days.
• As 1-hour compressive strength is also important due to clinical significance, it is much less than half the final strength.

Properties Of Dental Amalgam Fillings

• Patients should be told not to use hard masticatory forces for 6 to 8 hours after restoration gets done, at this time 70 to 80% of total strength is achieved.
• Compressive strength is the least for the low-copper alloys both in 1 hour duration or 7 days duration.

“Role Of Compressive Strength In Dental Amalgam Performance”

The following are the compressive strengths of various amalgams:

“Best Ways To Understand Dental Amalgam Properties In Dentistry”

Tensile Strength:

• Amalgam cannot withstand high tensile or bending stresses and can fracture easily in improperly designed restorations.
• So the cavity should be designed so the restoration will receive minimal tension or shear forces.

Dental Amalgam Characteristics

• The tensile strength of both the low and high-copper amalgam ranges from 48 MPa to 64 MPa.

Dental Amalgam Separator

Following is the tensile strength of various amalgams:

“Importance Of Dental Amalgam Properties For Restorative Work”

Dimensional Change:

• As mercury gets combined with the amalgam it undergoes two dimensional changes, i.e. contraction and expansion.
• Excessive contraction can lead to microleakage, sensitivity, and secondary caries, while excessive expansion can produce pressure on the pulp and post-operative sensitivity and protrusion of restoration.

Amalgam Filling Performance

• As per ADA specifications no. 1, amalgam should neither contract nor expand more than 20 µm/cm when measured at 37°C between 5 minutes and 24 hours after the beginning of trituration.
• Expansion is more for low-copper than high-copper alloys.
• Modern amalgam shows net contraction, while old amalgam always shows expansion.

“Risk Factors For Failure Due To Poor Dental Amalgam Properties”

Creep And Flow:

• Creep is defined as time-dependent plastic deformation.
• A creep of dental amalgam is a slow progressive permanent deformation of set amalgam which occurs under static or dynamic loading over a period of time.
• High-copper alloys as compared to conventional silver tin alloys have low creep values.

Amalgam Material Properties

• It is mainly associated with low-copper amalgam.
• Low creep values lead to marginal deterioration while very high creep values result in the ditching of amalgam restoration.

Various Creep Values Of Amalgam Are:

“Early Signs Of Problems With Dental Amalgam Restorations”

Flow refers to the deformation which occurs during the setting of amalgam. The greater is the flow, the greater the chances of restoration failure