PD PEDIATRIC DENTISTRY
PREFABRICATED CROWNS
PRACTICAL TRAINING
SUBJECT
ZLDL a0922c
PRACTICE
Vacational practice assigned to the 4th year of Dentistry is required.
OBJECTIVE
After termination of the practical
training the students will be
familiar with theoretical basis
and practical skills necessary for
treatment of primary dentition
by prefabricated crowns.
KNOWLEDGE
Knowledge necessary for the enrolment of the subject is given in
corresponding prerequisites.
TARGET GROUP
Students of the 5th year,
Dentistry
OUTCOMES
Students are familiar with working procedures essential for the
treatment of the primary dentition with prefabricated stainless steel
crowns and are able to treat the children in the clinical part of the
subject: Paediatric dentistry.
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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PREFABRICATED CROWNS
Treatment of teeth in primary and in permanent dentitions
using procedures of fixed prosthetics is very difficult and is chosen only
in cases of heavily destructed teeth by dental caries or in case of
anomalies in the hard dental tissues structure. Many factors make the
treatment in children by crowns difficult. Above all the difficult
cooperation with a small child, the time-consuming procedure which
desires proper tooth grinding, impression of both the treated and
antagonal jaws and taking of wax bite record. Enamel layer and dentinal
core of primary teeth are very thin, and the dental pulp cavity is
extensive. In permanent teeth, the enamel thickness does not differ
from that of adults, but the dentin layer is very thin and dental pulp
cavity large, especially in teeth with developing (open) apices.
Introduction of prefabricated crown technique is therefore great
progress in pedodontics treatment possibilities. They are produced
from stainless steel or nickel-chromium for distal teeth of primary
dentition. The crowns are produced in five to seven sizes for each tooth
of primary dentition and for the first molar of the permanent dentition.
They are adapted and cemented on the slightly grinded tooth in one visit
so that remaining clinical and laboratory procedures are not necessary.
Minimal tooth grinding is enabled by very thin layer of the metal used
for the crown (0.2 mm). The prefabricated crown is owing to its
thickness very flexible so that it can easily be adapted in the gingival
area and it can get over small irregularities in the preparation. The
crown should reach approximately 1-1,5 mm below the gingival margin
(into the sulcus). Retention of the crown is increased by cingulum; the
crown should snap over it. The metallic prefabricated crowns are not
esthetical that is why they cannot be used for the frontal region.
Recently, new types of crowns aesthetically acceptable appeared on the
market both for frontal and distal parts of dentitions. The preparation
for these crowns, demands, however, greater removal of hard tissues,
that is why the teeth devitalisation in the frontal region with following
endodontic treatment is often necessary.
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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TYPES OF PREFABRICATED CROWNS
There are many types of prefabricated crowns on the market at
the present time. The differences among them are not only in the
material used for their fabrication, but also in the way of their fastening
on the prepared tooth crown.
CLASSIFICATION ACCORDING THE MATERIAL USED
 All metallic crown (stainless steel, nickel-chromium, aluminium,
tin based crown)
 Stainless steel crown with facing (veneer)
 Resinous/composite crown
 Stainless steel crown
 Ceramics
CLASSIFICATION ACCORDING TO THE KIND OF FIXATION TO THE
TOOTH
 Cementation using luting cements
Zinc oxide phosphate, Zinc oxide eugenol, Polykarboxylate,
Glassionomer
 Bonded
resin based
composite based
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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INDICATION
RECONSTRUCTION OF THE CLINICAL CROWN
 in primary molars with extensive caries which cannot be
restored with the filling therapy
 in permanent molars with extensive caries which cannot be
successfully treated with the filling therapy ( long lasting
provisory treatment)
 in primary teeth with developmental anomalies of the enamel
 in permanent molars with developmental anomalies of the
enamel (e.g. molar-incisor hypomineralization – MIH).
 in primary molars after pulpotomy
 in genetically conditioned developmental anomalies of dental
hard tissues (amelogenesis imperfekta hereditaria,
dentinogenesis imperfekta hereditaria).
 in fractures of tooth crowns
 in caries localized on the mesial surface of the first primary
molars (high risk of the dental pulp exposure during cavity
preparation – high horns of the dental pulp)
 in children with the high risk of caries.
 in teeth with expressive attrition, abrasion or resorptions.
 in teeth with cervical demineralisations (particularly circular).
 in case of unsuccessful filling therapy (more tooth surfaces
involved)
 impossibility to maintain the dry field isolation
PART OT THE FIXED SPACE- MAINTAINERS
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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CONTRAINDICATION
 primary tooth before shedding (more than ½ of the radix
resorbed, expected exfoliation in 6-12 months).
 clinical or X-ray findings of pathological changes in the dental
pulp or in the periodontal tissue
WORKING PROCEDURE
FIG. 1
 occlusal reduction by 1,0
– 1,5 mm maintaining
the cuspal inclines of the
crown
 burs: fissure bur,
diamond plated fissure
bur, tapered bur,
diamond plated tapered
bur
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 2
 approximal reduction
 nearly vertical walls to
the long axis of the
tooth, slight
convergence in an
occlusal direction - 10o
maximally
 thin diamond tapered
bur
 gingival margin –
feather-edge finish line,
no shoulder, no chamfer
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 3
 in some cases, reduction
of buccal and lingual
surfaces is either
unnecessary or very
minimal
 reduction of large buccal
bulge (first primary
molar)
 thin diamond tapered
bur
Notes:
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 4.A
 buccal view of the lower
right quadrant
FIG. 4.B
 buccal view – occlusal
reduction, no shoulder,
no chamfer, featheredge
preparation
FIG. 5.A-B
 approximal view:
A) before preparation
B) after preparation
Buccal and linqual convexity is
maintained
A) B)
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 6A-B
 the same attitude for
young permanent
molars
A) B)
FIG. 7.A
 width of the space
available is measured
and proper size of crown
is selected (Boley gauge)
 before preparation
FIG. 7.B
 after preparation (trial
and error)
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 8
Reduction of the crown height:
 trimming with scissors
crown margin minimally
1mm beneath the free
gingival margin
If gingiva blanches – the crown is
too long
FIG. 9.A-B
Margin contouring :
A) primary molar
B) permanent molar
Gingival edges – crown
contouring-pliers, Johnsons
pliers, curved beak pliers.
A) B)
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 10.A-B-C
Crown contouring.
 crown-crimping pliers
may also be used for
crown contouring
 points of contact – ball
and socket pliers
 band stretching pliers
FIG. 11
 crown margins are
finished and polished –
feather edge
A)
B) C)
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 12
 falsely adapter crown
margin (margin
supragingivally), does
not reach below the
gingival margin
FIG. 13
 correctly adapted crown
margin (margin
subgingivally)
FIG. 14
Crown adaptation:
 crown is placed first
lingually, turned over
the occlusal surface
buccally under slight
pressure
 crown is then pressed
down
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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FIG. 15
Mistakes on crown adaptation:
 a ledge formation
prevents proper seating
the crown
 extensive preparation
results in crown tilting
 over extent of the crown
- too subgingivally
 crown is short
FIG. 16
Set of burs for tooth preparation
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PREFABRICATED CROWNS
PRACTICAL TRAINING
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Notes:
FIG. 17
Set of instruments for tooth
grinding