Amalgam Creeps and Marginal Breakdown

For Dental Materials Topic: Amalgam

1. CREEPS AND
MARGINAL
DETERIORATION
AMALGAM
Presented by Villanueva, Justin and Limonar, Shane

2. CREEPCREEPCREEP
it is defined as the time-
dependent plastic strain of a
material under static load or
constant stress.

3. CREEPCREEPCREEP
Other Factors that causes creeps of amalgam
It arises from the continued setting expansion of the
amalgam, the formation of corrosion products,
mastication, or from the thermal expansion of the
amalgam during ingestion of hot foods.

4. CREEPCREEPCREEP

5. conventional alloy - low copper
amalgam 2.5 % creep
High performance alloy - High
copper amalgam 0.2 % creep
CREEPCREEPCREEP
According to ADA Specification
no. 1 Creep should be below 3%
Influence of
Microstructure on creeps

6. CREEPCREEPCREEP

7. Instrument has been built in a
solid aluminum block containing
two amalgam specimen test
stations where the temperature
of 37 degrees celsius is prescisely
controlled with a digital
microprocessor controller and a
designated creep test, weight is
applied onto the specimens.
Determining
Creep

CREEPCREEPCREEP

8. CREEPCREEPCREEP
Clinical significance of creep :
Creep causes the
amalgam to flow
such that the
unsupported
amalgam protrudes
out from the margin
of the cavity
Those unsupported
edges are weak and
may further weaken
by corrosion
This causes ditch
around the margins
of amalgam
restoration

9. MARGINALMARGINALMARGINAL
DETERIORATIONDETERIORATIONDETERIORATION

10. Referred to as “Marginal breakdown”,
“ditching”, and “crevice formation”.
Regardless of the type of amalgam,
marginal fracture increases with
time
“Marginal breakdown”,
ditching crevice formation

11. IT IS THE GRADUAL
FRACTURE OF THE
PERIMETER OR
MARGIN OF A
DENTAL AMALGAM
FILLING, WHICH
LEADS TO THE
FORMATION OF
GAPS BETWEEN
THE AMALGAM
AND THE TOOTH.
DENTMAT

12. Excess amalgam, left lying over the occlusal or
proximal surface should be carved correctly
The angle of the carvo-surface margin should be
greater than 70º and the cavity should be
designed to allow for this.
On completion of packing, burnish the margins
both before and after carving to improve
marginal adaptation.
CLINICAL TECHNIQUES TO PREVENT
MARGINAL BREAKDOWN

13. THE ABSENCE OF THE
CORROSION-
SUSCEPTIBLE PHASE
IN THE
MICROSTRUCTURE OF
HIGH-COPPER
AMALGAMS IS
ASSUMED TO BE
THE PRINCIPAL
FACTOR RESPONSIBLE
FOR THE SUPERIOR
RESISTANCE OF
THESE ALLOYS TO
MARGINAL
BREAKDOWN..
DENTMAT

14. marginal breakdown with alloys having creep
values below 1%, restorations made from higher-
creep alloys generally experience greater
marginal breakdown than do restorations of
lower-creep
alloys.

15. THE PRECISE
MECHANISM OF
MARGINAL
BREAKDOWN AND
SPECIFIC
PROPERTIES ARE NOT
COMPLETELY
UNDERSTOOD.
HOWEVER, IT IS
ADVISABLE TO SELECT
ALLOYS THAT
INHERENTLY HAVE
LOW CREEP AND
POSSESS EXCELLENT
RESISTANCE TO
CORROSION.
DENTMAT

16. https://pubmed.ncbi.nlm.nih.gov/3855901/
https://www.slideshare.net/achillies88/strength-and-creep-of-dental-
amalgam-3837449
https://youtu.be/o_n-v7HVrt4
REFERENCE:

17. thank you for
listening!