Amalgam Class I Restoration Explained

In this lecture I explain in step-by-step fashion the basics of amalgam class I restoration. a photo guide is attached to the guide to aid in better understanding of the topic

1. Amalgam

Class I Preparation

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2. Overview

Class | cavity is routinely restored with
composite restoration, but it also can be done
with amalgam.

Why to choose amalgam?
a Strength
= Longevity
= Ease of use
= Clinically proven success

= And it is the only restorative material that its
external surface improve over time.

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3. e e
Indications
Amalgam is indicated in the following situations:

= when the defect is not in area of esthetic importance
= moderate to large defect

= in area with heavy occlusal contact

= Or in tooth that will serve as an abutment for

removable partial denture

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4. Amalgam preparation
We will classify amalgam class | into three types:

= Conservative Class |
= Extensive Class |

= Oclusolingual, and oclusofacial class I

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5. Conservative Class I

in this type, the cavity is not that deep, and relatively

away from the pulp

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6. Clinical Steps

wie.

After providing anesthesia, isolation is 8 by rubber dam

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(most preferably), but isolation with cotton roll is also
acceptable in conservative class | cavity.
The purpose of isolation is to keep dry field, and avoid

annoyances (saliva, tongue, frequent spitting)

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7. Tooth Preparation

Tooth preparation will be divided into two steps for the

purpose of clearification: intial tooth preparation, and final
tooth preparation

| Tooth Preparation |

I

Initial Preparation | Final Preparation

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8. Clinical Steps

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Before starting, keep in mind:

= Avoid cutting into cusp, because of two reasons, first, it save
more tooth structure, and second, to avoid exposing pulp
horns which lies beneath the cusps.

= Keep the width of your preparation as conservative as
possible.

= Try your best to avoid cutting marginal ridge, avoid
cutting and weakening tooth structure as much as possible.

= If two cavities have a wall of 0.5 mm between them or Less,
then it is better to join them together, to form one cavity.

= Extend your preparation to follow carious enamel and dentin

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9. Clinical Steps

= Most of our preparation is done with bur 245, it is highly
recommended. It has a length of 3 mm and diameter of 0.8 mm.
Keep these numbers in mind. If you are using another bur, it is
recommended to measure its length and diameter with a ruler
to guide you through the preparation.

= The advantage of using bur 245 is that it increase the retention
form, because it has convergent shape. It also has round end,
which result in slightly rounded line angles, which is highly
advantageous.

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10. = Convergent sides
= Rounded ends

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11. Clinical Steps

= Preparation begin by inserting the bur into the most carious
pit, using bur 245 at high-speed with water coolant.

# The bur should be kept parallel to the Long axis of the tooth
while preparing Il

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12. Clinical Steps

= Tip: Never insert the bur into the cavity if it is not rotating. The
bur should be rotating when it is applied to the tooth and
should not stop rotating until it is removed completely from
the tooth

= The depth of bur insertion is 1.5 — 2 mm which is half the bur
254 (for unfamiliar burs, measure them!). The preparation depth
of 1.5-2 mm will result in pulpal floor on dentin. Always make
your cavity floor on dentin and never on enameL

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13. Clinical Steps

= While you are on the same pit, include any fissures that are
radiating from the pit.

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14. Clinical Steps

= While cutting, if there is risk of damaging the marginal ridge,
tilt the bur outward for 10 degrees to follow the direction of
enamel rods and cut without risking the marginal ridge.

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15. Clinical Steps
Initial Preparation.

= The bur depth and orientation is maintained while moving
the bur to the other pit through the central fissure.

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16. Clinical Steps

Initial Preparation
= Tip: the outline of the preparation should be smooth with
gently flowing curves

sharp curves: avoid

smooth curves

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17. Clinical Steps

= Tip: The bur should extend proximally (to include all caries
without damaging the marginal ridges) and facially and
lingually to include carious defect but as conservatively as
possible. The smaller the width of preparation, the stronger
the restoration will become.

# Eventually, Our preparation will have an ideal depth of
1.5-2 mm. Even if there is caries on the floor, do not extend
your preparation more than that. Remaining caries will be
removed during the final preparation stage.

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18. Clinical Steps

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The final tooth preparation stage includes:

= Removal of remaining defective enamel and infected dentin
on the pulpal floor

= Pulp Protection with Liner or base or both, if needed

a Finishing of external wall

= And cleaning the prepared cavity

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19. Clinical Steps

Final Preparation

= If there is caries Left in the pulpal floor it should be removed
with Large round carbide bur. Cutting should be stopped when
hard dentin is felt. All caries should be removed at this stage,
and the non-infected area around caries should be Left without
cutting. This produce a shape similar to picture below:

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20. Final Preparation

Peripheral
seat

|

peripheral
seat

Wi Section of

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21. Final Preparation

= When the cavity is deep, a thin Layer of resin-modified glass
ionomer cement is placed in the deepest portion of cavity only.
It protect the pulp from thermal stimuli, produce fluoride, and
strong enough to withstand the force of condensation.

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22. Clinical Steps

CRA WS | a U

= Tip: Cavosurface bevel (a usual step in composite restoration)
is contraindicated in amalgam preparation.

99%

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23. Clinical Steps

Final Preparation

= After setting of GIC, the cavity is cleaned from debris using
cotton pellet moistened with water. Never dehydrate
(over-dry) the dentin, because it Lead to non-vital dentinal

tubules.

m After completing conservative cavity preparation, the next
rational step is to place amalgam, right? ... Well, true.
But certain scientific criteria should be followed rather than
filling the hole with amalgam blindfolded!

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24. Clinical Steps
Desensitizer Placement

= (Optional) dentin desensitizer is placed in the preparation
before amalgam condensation. Desensitizer produce lamellar
plugs in the dentinal tubules. These plugs reduce sensitivity of
dentin.

N

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25. Clinical Steps

¡and Condensation
= Amalgam is placed into the prepared cavity using amalgam
carrier.

= Amalgam is added incrementally and each addition is
condensed well before we add another mix.
= A large condenser is used first to condense amalgam then a

smaller one is used, this reduce the mercury content and
exposed it to outside.

= The cavity should be over-filled with amalgam to allow better
carving.

= Some clinicians prefer to use burnisher and strokes it
mesiodistally and faciolingually over the condensed amalgam.
It is called pre-carve burnishing

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26. Clinical Steps

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27. Clinical Steps

‘Carving and Finishing

= Carving is done immediately after condensation.

= The dentist should have in his mind an image of the desired
tooth anatomy.

= The carving instrument is placed on the un-prepared tooth
surface and moved across the preparation margin.

= The operator should not tend to carve deep occlusal grooves
in the restoration, because these groove cause chipping of
amalgam and weaken the restoration.

= The mesial and distal fossae in posterior teeth should be
carved slightly Lower than the adjacent marginal ridges.

= After completion, Amalgam should reflect the correct anatomy
of the tooth.

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28. Clinical Steps
‘Carving and Finishing

= Amalgam that is under-carved should be further carved.
Amalgam restoration that is over-carved should be replaced.

= After completion of carving, a small burnisher is used to
polish amalgam surface.

= Finally a cotton is wiped on the restoration to give a little bit
of shine.

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29. Clinical Steps

Additional Steps
= Next, the occlusion of the restoration should be checked with

articulating papers and smoothed. High spots can result in
severe pain for the patient, and lead to apical periodontitis.

= Patient is instructed to bite on the articulating paper over the
tooth, and asked to occlude gently, and to move the teeth
laterally, Any high spot will be seen as colored spot.

= Colored spot with a silver dot in the center indicate very high
contact and should be smoothed. little colored spot is normal
and require no further manipulation.

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30. Clinical Steps

= Polishing is an esthetic step that could be done after 24 hours
from the placement of restoration, because complete
crystallization of amalgam require time.

The purpose of polishing is:

= To complete the carving

= Refine the anatomy, contour and marginal integrity of
restoration

= Enhance surface texture of restoration

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31. Clinical Steps
Polishing

= The first step is to use either a white alumina stone or green

stone to correct small irregularities in restoration. it should be
placed at 90 degree to the margins

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32. = After that, a round finishing bur ( bur NO. 4 or 6) is used to
resurface the restoration.

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33. Clinical Steps
Polishing

= After that an abrasive system is used to add further esthetic
quality and polishing to the restoration. A course of coarse-grit,
medium-grit, and fine-grit abrasive rubber points are used for
this purpose, Starting with the coarse-grit and ending with
fine-grit. The polishing step should performed at low speed
handpiece with water coolant to prevent over-heating the
restoration and further thermal injury to the pulp.

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34. Clinical Steps

= The final restoration will have a shiny surface. If after all these
steps the restoration is not shiny, redo the steps of polishing.

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35. Extensive Class I

Caries is considered extensive if the distance between
infected dentin and the pulp is less than 1 mm, or when

the caries has extended into the cusp.

= Rubber dam placement is highly recommended. If operator
accidentally exposed the pulp, pulp capping will have more
successful outcome if rubber dam were used. In addition,
rubber dam provide dry field and prevent contamination of
working field.

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36. Extensive Class I

Initial Preparation

= Same principles applied in conservative class | preparation
are applied here.

= All infected dentin and caries should be excavated to the
depth of 1.5-2 mm. Follow the caries, and get a flat floor

= If caries is extending into cusps, bur should be tilted inward
for 10 degree to minimize cutting of cusp structure.

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37. Extensive Class I

Final Preparation

= During this stage, the remaining infected dentin is removed
as described previously for conservative class | preparation.

= For deep excavations where remaining dentin is very close to
the pulp (Less than 0.5 mm), a thin Layer of calcium hydroxide
is placed over deepest area, and sealed with RMGI. The
purpose of placement of RMGI is that it can withstand the
condensation force, while calcium hydroxide is brittle.

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38. Extensive Class I

Restoration Stage |

= After placement of liner (calcium hydroxide) and base (RMGI),
dentin desensitizer is used. Then, amalgam is placed,
condensed and carved in the same way described previously
for conservative class | restoration.

= Finishing and polishing has been described earlier.

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39. Other Forms of Class I Preparation

= Maxillary molars sometimes exhibits caries on the lingual
fissure that connects with distal oblique ridge and distal pit
on the occlusal surface.

= Mandibular molars sometimes exhibit caries on the facial
fissure that extend from the facial cusp ridge.

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40. OclusoLingual Class I

u After establishment of Local anesthesia, rubber dam
placement Is highly recommended. Isolation with cotton roll
and high-volume suction is also acceptable

= The Bur 245 is inserted into the distal pit.

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41. OclusoLingual Class I

= The long axis of the bur should be parallel to the Long axis
of the tooth, and should remain parallel throughout
preparation procedure.

= The bur is positioned so that it cut more mesially than

distally (70:30 ratio), to avoid weakening the small
distolingual cusp.

= The depth of preparation should be maintained at 1-5-2 mm
into the dentin.

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42. OclusoLingual Class I

= The bur then moved to the lingual surface to remove
remaining caries on the lingual fissure.

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43. OclusoLingual Class I

= The bur is slightly inclined to follow the anatomy and
contour of the tooth.

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44. OclusoLingual Class I

= After completing initial preparation, Bur 245 is used to refine
distoaxial and mesioaxial line angles. This will result in round
line angles which minimize stress on tooth structure.

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45. OclusoLingual Class I

u If needed, distoaxial and mesioaxial grooves are made into
the axial wall of preparation to provide additional retention.

= The final preparation is accomplished by removal of
remaining caries on the pulpal and axial walls using round
bur with slow speed

= Deep spots are coated with Liner or base (or both).

= The tooth is then cleaned from debris, and washed with
cotton moistened with water.

= Then air spray is used to remove excessive moisture from
working field. Care should be taken not to dehydrate the
dentin, as this Lead to damaging of odontoblasts.

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46. OclusoLingual Class I

= Desensitizer is placed onto freshly prepared dentin.

= For this type of preparation, there is a special technique for
placement of matrix. It is called Barton Matrix.

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47. OclusoLingual Class I

= First, Tofflemire matrix is placed around the tooth

= Then, a piece of band is positioned between the tooth surface
and already positioned band

= The piece should be placed more gingivally to secure it firmly
in the position

= Around wedge is coated with heat-softened material (e.g.,
green stick compound) and placed between the Tofflemire
band and the cut piece of band.

= While the material is still soft, a burnisher is used to press the
material gingivally, to secure the matrix piece and get optimal
contour. (Refer to previous photo for clearification)

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48. OclusoLingual Class I

= Amalgam is mixed and placed into the prepared tooth surface
and condensed with Larger condenser first, then a smaller one.

= The cavity should be over-filled

= Lingual amalgam is placed first, Care should be taking during
condensation not to break the already placed Lingual
amalgam

= If fracture occur and the amalgam has set, remove all the
amalgam and start again.

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49. OclusoLingual Class I

= The carving and polishing procedure has been described
eariler

Final result:

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50. OclusoFacial Class I

= Mandibular molars sometimes exhibit caries on the facial
fissure that extend from the facial cusp ridge.

= The preparation and restoration of such caries is similar to
that discussed to Occlusolingual Class I restoration, although
it is usually restored with composite resin.

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51. Reference

Art and Science
of Operative
Dentistry

16th edition

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*
ArtanaScience
OPERATIVE DENTISTRY

urdev: Art

E) @lraqiDental

52. THANK YOU
+ EB

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