Class I Amalgam Restoration

Uploaded by UMichDent on 29.05.2009

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This carious lesion requires a class I restoration. There is staining of the fissures and pits
that the explorer can penetrate and catch.
The tooth being worked on is a second molar. However it has been mounted in the first molar
position in this instance in order to facilitate access. This leaves an open distal contact.
The tooth is in contact with the opposing arch. As a guide for cavity preparation and
restoration, mark the centric stops with articulating paper by tapping the teeth together. These
blue marks show the supporting cusps on the bicuspids and molars. The centric stops are
compromises on the incline planes of the mesial buccal and also the distal lingual incline
of the molar.
The rubber dam has been applied to isolate the operating site. Note the floss and the
rubber dam clamp as a safety precaution. This particular preparation will be started with
a number two round bur. The bur align in two directions. First, perpendicular to the plane
across the tips of the buccal to lingual cusp. And second, a plane across the mesial to distal
marginal ridges. Remove the bur very slightly from contact while maintaining the established
alignment and start the bur rotating. This removal before activation of the bur tends
to prevent breakage of the flutes to the bur. Initial penetration is through enamel and
approximately one-half millimeter into dentin with extension into each of the carious fissures
and enamel faults carried out at that depth. The air-water spray is used as a coolant.
A sweeping motion of the bur is an effective method of round bur use.
This is a radiograph of the tooth being prepared. The superimposed number two round bur shows
the relationship of enamel thickness to the diameter of that bur and is an effective method
of measuring to help guide the depth of penetration.
This histological ground section shows dentinal tubules, enamel, dentinoenamal junction, and
the number two round bur at the dentinoenamel junction. This is the depth mentioned earlier,
approximately one-half millimeter into dentin.
In this particular tooth the cavity is approximately one and a half times the depth of the diameter
of the head. This depth was established by placing the bur head against the radiograph
of the tooth as was shown and using the bur as a measuring device. After completion of
initial outline forms switch to a straight fissure bur number 56 in this case. Maintain
the depth previously established when using the round bur. Align the bur and keep this
alignment during tooth tissue removal. Note the height of the cutting flutes you can see
above the surface of the preparation and use this height as a guide for maintenance of
pulpal floor depth. Widen the isthmus and lean the bur slightly into the buccal groove.
Lean the bur into the distal marginal ridge area to establish a full taper or divergence.
This also prevents undercutting the enamel rods and maintains a maximum bulk of dentin
under the remaining ridge. At the mesial, the bur is tipped in a similar manner with
the hand position adjusted for that area.
This histological section shows the relationship of the fissure bur to the direction of enamel
rods in the marginal ridge area.
This outline form, both internal and external, results in use of the straight fissure bur.
Notice that the width of the isthmus in the mesial section is nearly ideal. There is a
wider section than ideal into buccal groove area and also the distal isthmus because the
carious lesion in the floor has undermined the enamel.
In the lingual groove and central pit area there is a small whitish area of enamel still
present beneath the arrow.
This is not ideal and the cavity needs to be deepened slightly.
Using the same fissure bur at ultra speeds plane the floor lightly to remove the remaining
Refinement and retention are done using a slow speed handpiece and a straight fissure
bur. Use a two-handed approach with the fingers of the left hand steadying the head of the
handpiece. While refining the preparation; pulpal floors, walls, and margins, the bur
is slipped tight, is tipped slightly at the distal marginal ridge area in order to prevent
undermining the enamel rods. Lean the bur slightly toward the buccal wall and more exaggerated
into the buccal groove again because of the pattern of the enamel rods. The slow speed
handpiece should be run fairly rapidly with a light touch during this smoothing procedure
while proceeding completely around the preparation. Slow rotation may result in irregularity of
the wall outline.
This is the outline form after refinement. Again note the walls are smooth, the isthmus
is nearly ideal on the mesial but wide on the distal. Now that the external and internal
outline forms have been established, caries removal is carried out. Caries remain in the
distal and buccal areas.
The spoon excavator is used to remove gross soft caries. Notice the peeling effect when
doing this procedure on soft carious dentin.
After the gross caries have been removed with a spoon excavator and the remaining tooth
structure beneath feels fairly firm, check the soundness of the dentin with an explorer.
Take care during this procedure not to exert heavy force towards the pulp.
A large round bur is now used in a slow speed handpiece. In this particular case, a number
four round steel bur has been chosen to remove the remaining carries. It is operated at a
fairly slow speed using a brushing action with air used intermittently to blow away
the debris. Remove all the peripheral caries progressing toward the deeper center portion
of the carious lesion.
Cleanse the cavity with a small amount of water on a cotton pellet and dry it gently
with cotton or air.
Check this again with the explorer to make sure all caries have been removed and only
firm dentin remains.
After all caries are removed retention form is placed. In this case a straight fissure
bur is being used. Retention is placed by tipping slightly under the cuspal areas. Do
not place retention under the groove extensions or into the marginal ridge areas because this
would result in weakening of the tooth. Retention should not be excessive and cause undermining
of the enamel.
Cleanse preparation with water on a cotton pellet and again dry carefully.
Place the double-ended [west coast?] cement instrument into the preparation to get a general
idea of the amount of cement that will be needed. Since B&T is being used cavity varnish
is not required at this time.
Place the cement into the cavity. In this case it is placed in two increments, the buccal
and distal areas in which caries required removal of dentin beyond the ideal depth of
cavity preparation.
Coat the instrument with cement powder and adapt the cement into the pulpal floor area
that has been extended in the caries removal operation.
Clean the cement from the margins and from the retentive areas with a spoon excavator.
Be sure to remove the cement from all areas of retention.
This is the outline of the preparation and the outline of the base in the floor of the
preparation. Again note that the base covers only that area removed beyond the ideal depth.
Apply cavity varnish to the entire cavity preparation including the walls, floor, and
margins. Use a small wisp of cotton on an endodontic file to do this. Pretest the amalgam
pluggers in the preparation to make sure they will fit into all areas of the preparation.
In this case the condenser cannot reach the bottom of the floor of the mesial extension.
A smaller condenser or a [west coast?] plugger can be used.
Pre-try the carvers at this time also. A number 26 spoon is being used for this preparation.
Ride the spoon on the marginal area and not into the preparation itself.
Try the 5C carver, the discoid end being used here.
In use with the cleoid end of the 5C, note that the cleoid end should not extend further
than half-way across the preparation because that would remove amalgam from the opposite
margin. Place an increment of amalgam into the central area and begin condensation.
Condense with a firm, rocking motion.
As the deeper portion is filled progress to larger condensers when possible.
The preparation should be overfilled. Place the condenser at right angles to the tooth
surface to begin formation of the central groove and overpack the margins. Do not push
the amalgam back into the preparation but allow it to spill over the edges of the tooth.
Mercury-rich amalgam is removed during condensation by this overfilling.
Start carving with a number 26 spoon to remove the excess. Keep the spoon riding on the margins
and do not allow it to carve into the depths of the cavity.
Carefully carve around all the margins progressing around the preparation in an orderly manner.
Then use a 5C discoid end to define the margins.
Air may be used to remove the excess amalgam.
The cleoid end of the 5C carver is used to define the central groove, the lingual groove,
and also the buccal and supplemental grooves. The distal and central pits are also established
with this instrument. Again note the cleoid end should not extent further than half-way
across the preparation because that would remove amalgam from the opposite margin.
The rubber dam is removed. Check the occlusion by tapping the teeth together lightly. Examine
the restoration for burnished areas resulting from contact.
Areas that show any burnishing in this are slightly relieved with a 5C carver.
Check the occlusion again by tapping the teeth together gently with blue carbon paper. This
particular restoration has a very dark blue contact area which needs to be relieved slightly
since all the contact areas should have a uniform density of color from the carbon.
After making occlusal adjustment with the contacts, check the occlusion again. Press
the teeth more firmly together and check working and balancing excursions. In this case, there's
a very long slide that needs to be removed.
After the adjustments have been made check the occlusion again. Always be sure to include
working and balancing excursions.
The entire restoration is burnished using a conical burnisher or round ball burnisher
after the occlusion has been established. Accentuate the grooves and do not burnish
heavily in the centric stop areas.
A thorough burnishing will greatly minimize the time needed to complete the finishing
and polishing at a subsequent appointment. Finishing and polishing should take place
a minimum of 24 hours after placement of the restoration.
After a minimum of 24 hours, examine the restoration for areas of attrition which would indicate
high occlusion. Check the margins with a cow horn explorer with the tine held perpendicular
to the margins.
Check the occlusion with carbon paper including working and balancing excursions.
Note the centric stop area is still maintained.
A definite pattern should be followed during the finishing procedures working from coarser
to finer abrasives during the procedure.
With a slow speed handpiece start finishing by using a small round finishing bur to accentuate
the grooves. Operate the bur at a fairly rapid speed using a very light, brushing action.
Use the small round finishing bur only in the deep grooves and not across the broad
surfaces of the restoration.
Next use a small pear-shaped finishing bur to emphasize the grooves and to start widening
them. Move around the restoration in a definite pattern. When using a new, sharp finishing
bur it may be operated in reverse to prevent excessive amalgam removal.
Lastly, a large pear-shaped finishing bur is used with a light brushing action over
the rough surfaces of the restoration. Take care not to destroy the centric stop areas
by overfinishing with the burs.
Examine the restoration with an explorer over all the margins. A catch from tooth to filling
means excess filling material, a catch from filling to tooth means short or overfinished
margins. Areas that have a slight catch at the base of deep grooves are adjusted with
a thin flame-shaped bur. The bur is used in a back and forth motion level with the restoration.
Begin the polishing procedure with a slurry of XXX Silex and a black rubber cup.
Follow the contours of the restoration. Place the cup into the grooves and around the cusp
tips so as not to destroy the anatomy built into the restoration.
After polishing the entire restoration with Silex rinse the tooth thoroughly.
Place a clean, fresh rubber cup in the handpiece. A slurry of tin oxide is used for final polish.
If a fresh rubber cup is not used or the tooth not rinsed thoroughly the remaining particles
of Silex will scratch the final polish produced by the tin oxide. Follow the anatomy again
in the final polish.
When the polishing of tin oxide is complete rinse the tooth thoroughly.
Make a final check on the margins with the explorer.
And also make a final check with the occlusion with articulating paper.
This concludes the class I amalgam and would provide a patient many years of service.
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