Chapter Six Checking & Verification
CHECKING AND VERIFICATION OF CROWNS
AND FIXED PROSTHESES
In fact, making any necessary corrections or modifications for each unit of a
bridge at an early stage saves troubles that we may be faced with after final
completion of the bridge. However, certain adjustments may be needed after
construction e.g. those factors related to registration of the mandibular positions.
Evaluation:
After removal of the temporary restoration, any remaining cement should be
removed from the prepared tooth surface with an explorer. The preparations are
rinsed with water and air spray, and after drying the area is inspected. All
residual cement should be removed because even a very small particle of
temporary cement can prevent a casting from seating completely. The completed
restoration is cleaned either ultrasonically or with a steam cleaner then
disinfected. Then we start trying in the restoration.
Crowns and fixed prosthesis should be checked from many aspects:
1. Seating.
2. Marginal integrity.
3. Retention and stability
4. Occlusion.
5. Contour alignment and occlusal anatomy.
6. Contour of the pontic and its relation to the mucosa of the alveolar ridge.
7. Connectors.
8. Esthetics
9. Radiographic checking.
1. Seating:
The restoration should be able to be seated with little frictional resistance.
Gentle occluding force should be sufficient to complete the seating. Any definite
resistance to seating should draw attention for determining the cause.
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Chapter Six Checking & Verification
Causes of resistance to complete seating:
(a) Excessive proximal contacts:
The location, size and tightness of proximal contacts should resemble those
of the natural teeth. The use of floss is a convenient method to compare the
contacts with adjacent teeth in the dentition. If the floss will not pass, the contact
is excessively tight, if it goes through easily, food impaction may result.
Most patients will give reliable information as to a tight proximal contact
when asked. They feel the restoration is pressing too hard on one or both of the
adjoining teeth provided a local anaesthesia has not been administered.
Excessive tightness in all-metallic restorations:
If a tight contact prevents the seating of an all-metal restoration, adjustments
are readily made with a rubber wheel. The satin finish produced helps identify
where binding occurs because a shiny spot will appear where adjustment is
necessary. A special quick drying marking liquid can be used to cover the contact
surface and on seating, the excessive contact area will be detected as the marking
layer will be scratched.
Excessive tightness in porcelain restorations:
A tight proximal contact in unglazed porcelain is easily adjusted with a
cylindrical stone. The area of contact can be identified with red pencil or thin
marking tape. After glazing, slight change in the contact may be observed
because of the pyroplastic surface flow that occurs during firing. If adjustment of
a glazed restoration is needed, it can be repolished with diamond impregnated
silicone points or diamond-polishing paste.
N.B.:
Deficient contact in all-metallic restorations: can usually be corrected by
soldering. Deficient porcelain restorations: a low fusing "add on" or correction
porcelain can be used.
(b) Presence of nodules on the fitting surface of the restoration:
A magnifying lens may be used to examine the fitting surface particularly at
the inner angles. Any nodules should be removed carefully.
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Chapter Six Checking & Verification
(c) Over extension of the gingival margin:
Error in die making and or wax pattern carving may result in over extending
gingival margins of the restoration causing resistance to complete seating. New
impressions are taken and new dies and working casts are made and construction
is completed to have a satisfactory end result.
(d) Tight casts:
Though the whole procedure of impression making, die construction, wax
pattern fabrication investing and casting, accuracy of the final restoration with no
dimensional changes was of prime importance. However, we may be faced with a
tight cast that cannot be seated completely. This can be dealt with by painting the
fitting surface of the restoration with a special quick drying marking liquid, then
trying to seat the restoration. The paint in the tight areas will be scratched due to
friction. If the area of interference is small and well defined, it can be reduced by
spot grinding. If the areas of interference are multiple or there is generalized
tightness, electro-stripping technique is used to remove a uniform thin layer from
the fitting surface.
(e) Faulty assembling and soldering.
(f) Lack of parallelism of abutment teeth.
2. Margin Integrity:
The completed restoration should go into place without binding of its
internal aspect against the occlusal surface or the axial walls of the tooth
preparation i.e. the best adaptation should be at the margins.
Several techniques have been used to detect where a casting binds against an
occlusal or axial wall; as disclosing waxes, air abrasion to form a matte finish
surface, powdered sprays and special elastomeric detection pastes.
3. Retention and Stability:
The restoration should have adequate retentive properties. It should be able
to be retained in position by tenso-frictional grip during initial seating.
Stability of bridge can be verified by placing one finger on one retainer and
see whether there is evidence of a rocking action on the other retainer. It should
not rock or rotate when force is applied.
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Chapter Six Checking & Verification
If instability is due to a small nodule, this can usually be corrected, however,
if it is due to distortion, a new casting will be necessary.
4. Occlusion:
It should be checked by the use of thin articulating paper which will leave a
mark on the high spots, or by using occlusal indicator wax. With this technique, a
thin sheet of wax is moulded over the restoration. The patient is then asked to
bite on it. Where the restoration shows through the wax is the point which needs
easing. It is important to check occlusion not only in centric, but also in the
lateral and protrusive excursions.
5. Contour, Alignment and Occlusal Anatomy:
Contour and alignment should be compared with the neighboring teeth and
similar teeth on the opposite side. Occlusal anatomy should represent the proper
anatomical form a compared with the similar natural tooth on the opposite side.
6. Contour of the pontic and its relation to the mucosa of the alveolar
ridge:
The relationship of the pontic to the ridge should be self-cleansing. Pressure
of the pontic against the ridge causes blanching of the mucosa. The pressure can
be verified by passing dental floss between the pontic and the ridge
antroposteriorly.
The pontic should have the correct contour that allows the food sweep over
the mucosa as massaging and stimulating action and not to impinge directly up
on it causing irritation and inflammation.
7. Connectors:
In case of rigid connectors: Checked for adequate strength and maintain the
correct interproximal relationship.
In case of non-rigid connectors: We have to be sure that they have adequate
retentive qualities and maintain the correct interproximal relationship.
8. Esthetics:
Crowns and fixed prostheses must be in harmony with the neighboring
natural teeth particularly the form, size, surface characterization and color match.
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Chapter Six Checking & Verification
9. Radiographic Checking:
This is to verify gingival adaptation and to make certain that no undetected
open margins exist inerproximally.
N.B.:
Meal ceramic restorations require a separate metal evaluation step, when the
margin integrity, stability, occlusion and substructure (coping) design are
evaluated.
During the subsequent bisque evaluation, the marginal integrity and stability are
reevaluated to determine whether any distortion has occurred during firing
proximal contours, stability and the color, texture and glaze also are evaluated.
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