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Complex Amalgam
Brett Steed
Complex Amalgam Preparation and Restoration
Brett Steed
ID: 47539077
Operative Dentistry 430
Dr. Gardner
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Complex Amalgam
Brett Steed
Complex Amalgam Preparation and Restoration
Complex Amalgam Preparation
As the complex amalgam restoration involves the replacement of a considerable
amount of tooth structure, it is extremely critical that the complex preparation be
performed extremely well with a great deal of thought regarding retention of the
restoration. There are a number of options available for use in the complex amalgam
restoration to increase retention and resistance. These include the use of pins, retention
grooves, proximal troughs, dovetails, and circumferential slots (Summitt, Robbins,
Hilton, & Schwartz, 2006). An appropriate combination of these options will maximize
the resistance and retention of the complex amalgam restoration, leading to greater long-
term success. Each of these retentive options as well as the general form of the complex
amalgam preparation must meet certain critical requirements in order to ensure the
success of the restoration. Although the criteria contain many of the same requirements as
that of the class II amalgam preparation, there are also additional requirements that are
needed for the success of the complex amalgam preparation and restoration. The
following is a discussion of these critical requirements.
Class II requirements
As the complex amalgam includes elements of the class II amalgam, the
requirements of the class II amalgam must be met in
the complex amalgam preparation. Open
interproximal contacts are required to ensures that
proper contouring of the interproximal area occurs
during carving of the restoration (Summitt, et al.,
2006). As amalgam restorations rely on mechanical
retention, the walls of the preparation must converge
occlusally. This allows for the mechanical retention
of the restoration (Summitt, et al., 2006). Converging walls
for retention
*This preparation has no adjacent teeth, so
opening the contact does not apply here. However
the walls of the preparation do converge occlusally
and therefore this preparation does meet this critical requirement.
In order to ensure that there is no unsupported
enamel it is critical to ensure that the preparation contains
90 cavosurface margins. If unsupported enamel remains,
there is a greater chance of fracture (Summit, et al., 2006).
Meeting these requirement will help to ensure greater
90 cavosurface margins
success of the complex amalgam restoration.
*This preparation does contain cavosurface
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Complex Amalgam
Brett Steed
margins that are 90 and therefore meets the critical requirement.
Buccal/Lingual Shelf
Often referred to as a peripheral step or a ledge, a buccal/lingual shelf may
increase the resistance of the complex amalgam
restoration (Robbins, Burgess, & Summitt, 1989).
Creating the buccal shelf parallel to the occlusal
surface ensures consistency in the thickness of the
restoration occlusally (Summitt, et al., 2006).
*Although the buccal shelf in this preparation
dips slightly gingival on the buccal surface, the entire
buccal shelf is parallel to the occlusal surface and
therefore meets the critical requirement.
Pulpal slot
The pulpal slot is usually in the area of the central groove to allow for adequate
tooth structure to remain in the periphery of the tooth to support the restoration and
provide as much strength as possible to the tooth
(Roberson, Heymann, & Swift, 2006). The pulpal slot
must be at least 0.5 mm in depth which we ensure by
Pulpal slot in
area of the
preparing the slot 1mm in depth (Roberson et al., 2006).
central The pulpal slot provides greater resistance and retention to
groove the restoration, but it must be of sufficient bulk and
mechanical lock to provide that strength. The 1 mm depth
ensures enough bulk to the restoration. As well as being 1
mm in depth, the pulpal slot must accommodate the
smallest condenser. This allows for sufficient condensing
of the amalgam and provides greater strength to the restoration by avoiding excess
mercury or voids in the restoration (Summitt, et al., 2006).
*The pulpal slot in this preparation is located in the area of the central groove.
There is sufficient tooth structure remaining between the slot and the periphery of the
tooth, which provides the tooth and the restoration with the strength it, needs.
Proximal trough
The proximal trough must butt up against the axial wall. This serves to leave
enough tooth structure between the cavosurface margin and the proximal wall to ensure
that there is sufficient strength to resistant fracture. Allowing as much sound tooth
structure as possible in this area will contribute to greater structural integrity of the tooth
(Sarret, 2005). Readings indicate that slots and troughs should be at least 0.5 mm in
depth, which is covered by our critical criteria of 1mm (Roberson, et al., 2006). Again
the trough must accommodate the smallest condenser to ensure proper condensing of the
amalgam restoration.
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Complex Amalgam
Brett Steed
Pin
When using a pin it must be placed parallel to the cavosurface. It must be place
just into dentin and also allow for the clearance of the smallest condenser. This ensures
that proper condensing of the amalgam can be achieved resulting in sufficient strength to
the restoration (Summitt, et al., 2006).
Retention grooves
When placing retention grooves they must be able to
accommodate the smallest condenser. Again this allows for
adequate condensing of the amalgam in the groove
providing the greatest strength to the restoration.
*The retentive groove in this preparation accepts the
smallest condenser and therefore meets the critical
requirement.
Retention groove
Discussion
I found the complex amalgam preparation the most enjoyable of all the
preparations. I enjoyed the fact that I was able to remove a considerable amount of tooth
structure with the hand piece, which at this stage in my career is still quite fun. I also
enjoy the freedom you have in designing an appropriate preparation as you have the
option of using a variety of resistance and retention techniques. Although I found this
preparation enjoyable it is also very difficult to produce accurate dimensions. I found it
difficult to maintain a small enough proximal box as to avoid proximity to the pulp while
still providing enough room to place the proximal trough. One key thing I discovered
with this is to ensure that you place the proximal box directly against the axial wall. This
will allow you to create a sufficient trough while preserving enough tooth structure
between the trough and the cavosurface while maintaining a sufficiently small proximal
box.
I also found it difficult to keep the buccal shelf thin enough as to avoid removing
excess tooth structure resulting in close proximity to the pulp chamber. One thing that
worked well for me was to begin very slowly at a lower power setting on the hand piece
(to avoid removing excess tooth structure too quickly) and work around the periphery of
the tooth until the width of the buccal shelf is only the width of the bur. Slight
modifications in vertical depth can then be made but this provides a good reference point
as to the horizontal depth of the buccal shelf and prevents me from removing too much
tooth structure.
Complex amalgam restoration
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Complex Amalgam
Brett Steed
As the complex amalgam restoration replaces a large amount of tooth structure it
is essential that the critical requirements for the restoration be met. The following is a
discussion of these critical requirements.
Mesial open Closed distal
contact contact
Closed contact
It is essential that a closed contact be
achieved in this restoration. A closed
contact ensures food compaction does not
occur leading to patient irritation, gingival
inflammation and secondary/recurrent caries
(Newman, Takei, Klokkevold, & Carranza,
2006).
*The mesial contact in this
restoration is not closed. It does not pass the
light test or the floss test. The distal contact is closed however but does demonstrate
correct interproximal contour.
Lingual height of contour is too
low
Buccal/Lingual height of contour
When carving and shaping the restoration it
is important to restore a correct height of contour
that is in proper alignment in the arch/quadrant
(Summitt, et al., 2006).
*The lingual height of contour in this
preparation is too low. When compared to the
lingual height of contour of the adjacent teeth in the
Therefore the restoration does not meet this critical requirement.
Buccal/Lingual cusps and central groove
The buccal/lingual cusps as well as the central
groove must be in proper alignment withinin the arch.
*The lingual cusps of this restoration are located in
line with the cusps of the adjacent teeth. The central groove
is much too wide in this preparation and does not exhibit
true anatomy. The cusps are in line, but the central groove
is too wide and therefore this restoration does not meet the
critical requirements.
Properly shaped marginal ridge
A properly shaped marginal ridge helps in
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Complex Amalgam
Brett Steed
preventing interproximal food impaction that could lead to gingival inflammation and
secondary caries (Newman, et al., 2006).
*The marginal ridges in this preparation are properly shaped and therefore meet
this critical requirement.
Lingual cusps are too low
Proper cusp height and in occlusion
All occlusal anatomy should be continuous
with features seen in the adjacent teeth to allow for
proper occlusion (Dos Santos, 2007).
*The lingual cusps in this preparation are
too low. They are not the same height as the
lingual cusps of the adjacent teeth and would
therefore not be in proper occlusion. The restoration does not meet this requirement.
No marginal voids and Smooth with no scratches
It is important that there are no marginal voids in the restoration and that the
surface is free of scratches and defects. Surface roughness and marginal voids provide an
environment for bacterial buildup leading to failure of the restoration (Newman, et al.,
2006).
*There are no marginal voids in this preparation and the preparation does meet
this requirement. The preparation is smooth with no scratches and meets this critical
requirement.
Discussion
I have found the complex amalgam restoration particularly difficult for a number
of reasons. The first few times that I attempted the restoration I found that I was not
condensing quickly enough. Therefore during carving of the restoration it would often
fracture. The fracture would generally occur somewhere in the middle of the bulk of
amalgam indicated the point where I began condensing fresh amalgam on amalgam that
had previously begun to set. I was able to overcome this by learning to condense much
quicker than I have in the past. Once you use the smallest condenser to condense the
amalgam in the slot, troughs, and boxes, you can place the amalgam rather quickly in the
remainder of the preparation and use the larger condenser to appropriately condense the
amalgam. This allows for the amalgam to be uniformly condensed before any of setting
begins to occur.
Another difficulty I have had is with closing the contact. I have found that I get
so caught up in condensing such a large surface that I forget to ensure that I have
sufficiently condensed towards the adjacent teeth, providing me with a tightly closed
contact. As evidence from the picture, I had yet to master this technique at the time the
photos were taken. Remembering to condense the amalgam in the proximal box
thoroughly, ensuring that I condense towards the adjacent tooth to build enough bulk into
the contact, should help me overcome this problem.
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Complex Amalgam
Brett Steed
The third difficulty I have had is ensuring that I place my central groove in the
proper location. With many of my early attempts I found myself misplacing the central
groove and then trying to correct it later on in the carving, resulting in an extremely wide
central groove. I have found that if I “sketch” in a line where I would like my central
groove to be (based on the grooves of the adjacent teeth in the arch) it provides me with a
reference point to work from. This way I always maintain the tip of the instrument at the
“sketched” line, which has helped keep the central groove in the proper location and of
proper dimensions.
The proper height of the cusps is also difficult to achieve. I found the by using
the larger matrix bands (with the extensions) I am able to place a sufficient amount of
amalgam within the matrix which provides me with adequate height for the cusps. This
is the first time that I have needed to use the larger matrix bands and I have found them to
be very appropriate in this situation.
References
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Complex Amalgam
Brett Steed
Dos Santos, Jose. (2007). Occlusion: Principles and Treatment. Illinois, Quintessence
Publishing.
Newman, M.G., Takei, H.H., Klokkevold, P.R., & Carranza, F.A. (2006). Carranza’s
Clinical Periodontology (10th ed.). St. Louis: Elsevier
Robbins, J.W., Burgess, J.O., & Summitt, J.B. Retention and resistance features for
complex amalgam restorations. Journal of the American Dental Association, 118,
437-442.
Roberson, T., Heymann, H., & Swift, E. (2006). Sturdevant’s Art and Science of
Operative Dentistry. St Louis, Mosby Inc.
Sarret, D.C. (2005). Clinical challenges and the relevance of materials testing for
posterior composite restoration. Dental Materials, 21 (1), 9-20.
Summitt, J. B., Robbins, J. W., Hilton, T.J., & Schwartz, R. S. (2006). Fundamentals of
Operative Dentistry: A Contemporary Approach. Hanover Park, Illinois:
Quintessence Publishing Co.
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