Download Stainless steel crown Preformed metal crowns (PMCs)

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Stainless steel crown
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Preformed metal crowns for primary and
permanent molar teeth: review of the
literature
The use of stainless steel crowns
報告者:R2 王俊翔
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Preformed metal crowns for primary
and permanent molar teeth: review
of the literature
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Ros C. Randall, PhD, MPhil, BChD
Pediatric Dentistry Vol.24 No.5 September/October 2002
Pediatric Restorative Dentistry Consensus Conference
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indications for use
placement techniques
Risks
Longevity
cost effectiveness
utilization
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Indications for use—primary
molar teeth
Preformed metal crowns (PMCs)
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PMCs for primary molar teeth were first
described in 1950 by Engel
The morphology of a primary molar tooth
differs significantly from its permanent
successor :
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greatest convexity at the cervical third of the
crown
The enamel and dentin are much thinner than
in the permanent tooth
pulp is large with prominent pulp horns
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after pulp therapy
for restorations of multisurface caries and
for patients at high caries risk
primary teeth with developmental defects
where an amalgam is likely to fail
fractured teeth
teeth with extensive wear
abutment for space maintainer
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Indications for use—permanent
molar teeth
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Pinkenon suggested that indications for
placement of a PMC should include child
patients who are unlikely to attend regular
recall appointment
teeth approaching exfoliation within 6 to
12 months should not be fitted with a PMC
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interim restoration of a broken-down or
traumarized tooth until construction of a
permanent restoration can be carried out
financial considerations
teeth with developmental defects
restoration of a permanent molar which
requires full coverage but is only partially
erupted
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Primary molar tooth preparation
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Placement procedures for primary
molar crowns
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placement of wooden wedges
occlusal surface: reduced by about 1.5 mm ,
maintaining its occlusal contour
Proximally: avoid the creation of ledges or steps
at the gingival finishing, slightly below the
gingivae
Lastly, ensure that all line angles are rounded
Effective local anesthesia of the tooth under
preparation is generally recommended
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Duggal and Curzon recommended trying the
selected crown for size before carrying out any
lingual or buccal reduction.
To obtain retention, the crown must seat
subgingivallyt to a depth of about 1 mm and a
degree of gingival blanching seems to be
inevitable
A crown that is high in the occlusion (1-1.5 mm)
is acceptable, as it is considered that primary
teeth can spontaneously adjust for this amount of
occlusal discrepancy over a week
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Selection of crown size
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restore the contact areas and occlusal
alignment of the prepared tooth.
trial and error
measuring the mesiodistal dimension of
the tooth space with dividers
measure the dimension of the contralateral
tooth
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Selection of crown size
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Crown modification
A correctly fitting crown should snap or
click into place at try-in
More and Pink recommended a bite-wing
radiograph at the crown try-in stage to
check for any margin overextension in the
interproximal area
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Crown trimming can be carried out with
crown scissors or an abrasive wheel
After trimming, the crown must be crimped
to regain its retentive contour
Once these adjustments are completed, the
crown margins should be thinned and
smoothed, final polishing being done with
a rubber wheel
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Cementation
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need a generous mix of cement to
adequately fill the crown space prior to
seating
it is recommended that the crown be first
seared over the lingual or buccal wall and
rolled over onto the opposite wall
Once seated onto the prepared tooth, the
crown should be maintained under pressure
while the cement sets
Placement procedures for
permanent molar crowns
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Occlusion:
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Unlike the primary molar crowns, those for
permanent teeth cannot be left in hyperocclusion
When a caries lesion has extended subgingivally,
the original tooth morphology should be restored
with either a bonded composite resin or an
amalgam restoration before commencing the
crown preparation. It is not recommended to
utilize only cement in these areas.
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Resin-modified glass ionomer (RMGI)
cement has been recommended as the
preferred material for cementation of
permanent molar PMCs
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Risks
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Periodontal concerns
Periodontal concerns
Nickel allergy
Esthetics
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A well-adapted crown margin facilitates good
oral hygiene and healthy gingivae, but gingivitis
can occur if the crown margins are inadequately
contoured or if residues of set cement remain in
contact with the gingival sulcus
Good- to moderate-fitting crowns seem to
produce minimal gingival problems or plaque
accumulation
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Periodontal concerns
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Nickel allergy
Patients in need of PMCs are likely to be
at a moderate-to-high risk for caries, with a
tendency to accumulate plaque and
marginal debris.
A preventive regime including oral hygiene
instruction should be routinely included
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The nickel content in the formulation
nickel-chromium crowns was around 70%,
greater than that of contemporary stainless
steel crowns, which contain 9%-12%
nickel, similar to that of many orthodontic
bands and wires
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Esthetics
Nickel allergy
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1992, Hensten-Petersen:
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The incidence of adverse reactions attributed
to orthodontic treatment is estimated as 1 in
100
1998,Janson et al.:
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concluded that orthodontic treatment utilizing
conventional Stainless Steel appliances does
not, in general, initiate or aggravate a nickel
hypersensitivity reaction
A well-known method of improving the
appearance of metal crowns is to cut a
window in the buccal wall of the cemented
crown and to restore this with composite
resin
Carrel and Tanzilli evaluated a veneering
resin for both anterior and posterior crowns:
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only 32% of the veneered crowns were intact
at 1 year, 41% having debonded and 27%
being partially retained
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Longevity of preformed metal
crowns
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From Table 1, the average failure races are
around 4 times greater for amalgam
compared with PMCs over approximately 5
years
concluding that preformed crowns are
superior to Class II amalgam restorations
for multisurface cavities in primary molars
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Cost effectiveness and utilization of
preformed crowns
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Taking a hypothetical group of 100 Class II
amalgam restorations and 100 PMCs in
primary molars, with failure rates of 26%
and 7%
PMCs ($91), Class II amalgam ($55)
55 x 26 = 2.2 x(9.1x7)
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Result
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Dentists spend approximately 50%- 60% of
their time replacing restorations
Use of a well-fining PMC, where
appropriate, could be expected to last the
lifetime of the primary tooth
PMCs are superior to amalgam restorations
for multisurface cavities in primary molar
teeth
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preformed metal crown (PMC)
The use of stainless steel
crowns
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N. Sue Scale, DOS, MSD
Pediatric Dentistry Vol.24 No.5 September/October 2002
Pediatric Restorative Dentistry Consensus Conference
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more commonly known in the United
States as the stainless steel crown (SSC)
extremely durable
relatively inexpensive
subject to minimal technique sensitivity
during placement
offers the advantage of full coronal
coverage
main disadvantage: appearance
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Caries risk factors
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This paper discusses these factors
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Caries risk factors
restoration longevity
cost effectiveness
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A very important consideration in
treatment decisions for the primary and
mixed dentition is the future caries
potential of the child
the best indicator for an individual's risk
for future caries is his or her previous
carious experience
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Their caries risk indicators for the child at
high risk include:
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dmfs
the development of 2 or more lesions in 1
year
numerous white-spot lesions
high titers of Streptococcus mutans
low socioeconomic strata
a history of a high frequency of sugar
consumption
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Another factor that must be considered in
deciding risk-based treatment options for
carious lesions is the ability to recall the
patient on a timely basis
the patient that is not likely to keep recall
appointments is definitely at higher risk for
the sequelae to progression of caries, failed
restorations and new/recurrent caries
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Randall,2002
„ literature review of studies compared the
longevity of SSCs with Class II amalgam
restorations
„ The follow-up time ranged from 2 years to
10 years (mean: 5 years)
„ The failure rate of Class II amalgams
ranged from 2 to 7 times that of SSCs
(mean: 4 times )
„ SSCs are superior to Class II amalgam
restorations for multisurface cavities in
primary molars
Restoration longevity
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The average life expectancy of Class II
amalgams in all studies was approximately
2 years.
when the restoration is expected/needed to
last longer than 2 years, or when the patient
is younger than 6, best practice would be to
choose an SSC in multisurface restorations
of molars, in young children.
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Cost effectiveness
Randall,2002
„ literature review of 5 clinical investigations
comparing the failure races of SSCs with
multisurface amalgam restorations to calculate
replacement costs for the 2 types of restorations
„ The follow-up time ranged from 2 years to 10
years (mean: 5 years)
„ The failure rate of Class II amalgams ranged from
2 to 7 times that of SSCs (mean: 4 times )
„ PMCs ($91), Class II amalgam ($55)
„ (55 x 4) /9.1= 2.4
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The most important function of the primary
molars is to maintain space for the
permanent successors
Unless these broken/lost restorations are
followed and replaced, many of these
children will need orthodontics to regain
lost space and accommodate the permanent
teeth. Thus the expense incurred goes far
beyond merely the cost to replace the
restoration.
Children who require general anesthesia:
„ aggressive use of SSCs is suggested based
on their longevity and the protection their
full coverage provides from future caries
„ may lengthen the time between the need for
such costly and risky procedures
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conclusion
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Poor children experience more caries
initially and are at greater risk for recurrent
decay because they are less likely to use
preventive services and keep recall
appointments
Children with maxillary anterior caries
have significantly greater risk to develop
buccal/lingual and proximal surface caries.
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Children who experience approximal caries
in the primary dentition will continue to
experience approximal caries to a greater
extent in the mixed dentition, regardless of
socioecomonic status and recall status
The SSC is superior in durability and
longevity to the Class II amalgam in
primary teeth
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Dental rehabilitation under general
anesthesia is expensive and places the child
at increased risk for morbidity or mortality.
A primary tooth with 2 or more surfaces
involved may receive stainless steel crowns
if the tooth is anticipated to exfoliate in 2
or more years
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Recommendations
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Children at high risk exhibiting anterior
tooth decay and/or molar caries may be
treated with stainless steel crowns to
protect the remaining at-risk tooth surfaces
Children with extensive decay, large
lesions or multiple surface lesions in
primary molars should be treated with
stainless steel crowns
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Recommendations
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Strong consideration should be given to the
use of stainless steel crowns in children
who require general anesthesia
Thanks for your attention!
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Developmental defects of teeth
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Amelogenesis imperfecta
dentinogenesis imperfecta
The rapid loss of tooth tissue results in early
wear and loss of occlusal height, and can cause
sensitivity in some individuals.
PMCs are considered to be the treatment of
choice for primary molar and permanent first
molar
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