Quintessence international
Five-year clinical follow-up of prefabricated precision attachments: A comparison of uniand bilateral removable dental prostheses Johannes Schmitt, DMD 1 /Manfred Wichmann, PhD, DMD 2 / Stephan Eitner, PhD, DMD 3 /Jörg Hamel, DMD 4 / Stefan Holst, PhD, DMD 3
Objcvs: To evaluate the clinical long-term success of prefabricated precision attachments in retaining uni- or bilateral removable dental prostheses. Mo Mrs: Twenty-three patients with uni- or bilateral shortened dental arches received removable dental prostheses attached to the residual dentition with two types of precision attachments. Rss: After 5 years, 70% of bilateral and 25% of unilateral removable dental prostheses remained clinically functional. The most frequent cause of clinical failure was fracture of the abutment teeth for bilateral partial dentures and irreversible wear of the precision attachment for unilateral prostheses. Oral hygiene status significantly improved, and the mean pocket depth of the abutment teeth did not increase after 5 years. Cocso: Removable partial denture prostheses, retained bilaterally with precision attachments,
are a reliable treatment modality without negative long-term effects on periodontal health, whereas unilateral removable dental prostheses cannot be recommended because of high clinical failure rates. (Quintessence Int 2011;42:413–418)
Ky ors: distal free end, precision attachment, removable dental prosthesis, unilateral
A shortened dental arch or distal free-end
teeth adjacent to treated or untreated pos-
situation is defined as a dentition with
terior-bounded edentulous spaces, teeth
intact anterior teeth and a reduction of
restored with fixed dental prostheses had a
occluding pairs of posterior teeth that affect
10-year survival estimate of 92% compared
the
Restorative
with spaces that remained untreated (81%
solutions include fixed tooth- or implant-
survival of adjacent teeth). However, the
retained restorations and removable dental
application of removable dental prostheses
prostheses. A removable dental prosthesis
resulted in only a 56% survival rate.2
premolars
and
molars.
1
can be retained by clasps or extracoronal
The advantages of using attachment-
attachments or be designed as an over-
retained removable dental prostheses are
denture retained by telescopic copings.
improved esthetics, readjustable retention
When evaluating the long-term survival of
force, and a reduced incidence of secondary caries that is often observed with claspretained dentures.3
1
Assistant
Proessor,
Dental
Clinic
2,
Department
o
Prosthodontics, University Clinic Erlangen, Erlangen, Germany. 2
While some clinical
studies of precision attachment–retained removable dental prostheses report good
Dean and Clinical Director, Dental Clinic 2, Department o
results with 80% of the prostheses function-
Prosthodontics, University Clinic Erlangen, Erlangen, Germany.
ing properly after a 3-year period,4 other
Associate
studies observed failure rates of 35% to
3
Proessor,
Dental
Clinic
2,
Department
o
Prosthodontics, University Clinic Erlangen, Erlangen, Germany. 4
Private Practice, Karlsruhe, Germany.
Correspondence: Dr
Johannes Schmitt, Dental Clinic 2,
Department o Prosthodontics,
University Clinic Erlangen,
Glueckstr 11, 91054 Erlangen, Germany. Email: johannes.
[email protected]
40% after 5 years and only a 30.1% clinical survival rate after 8 years. 5 In longitudinal studies, the lack of success of extracoronal attachments was attributed primarily to biologic and secondly to technical factors.6,7
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MethOd and MateRialS Patients presenting with uni- or bilateral shortened dental arches were informed of the study and gave their written consent. The study protocol was approved by the local ethical committee (IRB no. 2783). A total of 23 patients participated in the study in 2000 and 2001 and received a total of 20 bilaterally retained removable dental prostheses and eight unilaterally retained removable
dental
prostheses
retained
by precision attachments (Swiss Mini-SG System, Cendres & Meteaux). The Mini-SG system is a prefabricated precision attachment system based on
Fig 1 Removable dental prostheses or Kennedy Class II occlusion. Unilateral prosthesis or Kennedy Class II with splinted teeth (mandibular central and lateral incisors and right canine and frst premolar). The inset image shows the emale part o the Mini-SG attachment with spring bolt and activation screw.
one universal male and several different female components. For all Kennedy Class II situations, splinting of abutment teeth was performed. In addition, bracing arm constructions were planned (Fig 1). In Kennedy Class I cases, splinting of abutment teeth was carried out for all but three dentures (Fig 2). For Kennedy Class I bilateral situations, extracoronal attachments with interchangeable plastic inserts that are adjustable with
To achieve long-term clinical success with
an activation screw or by replacing the
precision attachments, at least two abut-
insert itself were used, whereas the uni-
ment teeth should be splinted,
lateral removable dental prostheses were
8
and a
number of technical improvements have
anchored with spring bolt attachments.
been developed in recent years. These
The first examination was conducted
include adjustable retentive forces with set
2 weeks after the prosthesis was inserted
screws and interchangeable plastic inserts
(baseline).
that allow for easy recovery of retention and
performed annually for 3 years and after 5
eliminate problems associated with wear of
years of clinical function. To evaluate oral
components.
hygiene status and gingival inflammation,
Follow-up
examinations
were
Despite the number of studies of preci-
Plaque Index (PI) and Gingival Index (GI)
sion attachments available, no data are avail-
scores were assessed.9,10 Periodontal prob-
able comparing the clinical performance
ing depths were measured at six locations
and success of precision attachments in
near each abutment tooth. Data analysis
uni- or bilateral edentulous situations. The
consisted of descriptive statistics and the
rationale of the present prospective clinical
Wilcoxon test for paired data ( P ≤ .05).
investigation was to assess the long-term outcome of unilaterally retained removable dental prostheses or bilaterally retained removable dental prostheses with regard to
ReSultS
their technical and biologic complications. It
was
bilaterally
Prostheses survival rates after 3 and 5 years
prostheses
of clinical function are shown in Table 1. For
would positively affect long-term stability
bilaterally retained removable dental pros-
and longevity of the prosthesis, whereas
theses, the most common complication and
unilaterally retained removable dental pros-
cause for prosthesis failure was fracture
thesis retention would be more susceptible
of abutment teeth, whereas for unilaterally
to technical complications.
retained removable dental prostheses, irre-
retained
hypothesized removable
that
dental
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Fig 2 Removable dental prostheses or Kennedy Class I occlusion. Bilateral prosthesis or Kennedey Class I, and the unsplinted single abutment teeth (maxillary right frst premolar and let canine). The inset image shows the emale part o the Mini-SG attachment with the plastic insert and activation screw.
table 1
Prosheses survival raes Class i: Blaeral dsal exensons (baselne, n = 20)
Class ii: unlaeral dsal exensons (baselne, n = 8)
3
80.0%
62.5%
5
70.0%
25.0%
Year
table 2
Fig 3 Irreversible mechanical wear on the male attachment part. The inset image shows a new male attachment part.
Reasons for proshesis failure Class i: Blaeral dsal exensons (toal no. of aachmens = 43)
Class ii: unlaeral dsal exensons (toal no. of aachmens = 8)
Irreversible mechanical wear of attachment
—
4
Fracture of abutment splinting
—
1
Fracture of abutment tooth
4
1
Caries
2
—
versible mechanical wear of the male part
For bilaterally retained removable dental
of the attachment occurred (Table 2 and Fig
prostheses, the attachment retention force
3). Four nonsplinted abutment teeth (two
could usually be restored with screw activa-
vital, one endodontically treated) fractured
tion, but exchange of the plastic insert was
in the bilateral group.
necessary in one-third of all attachments
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table 3
technical complicaions occurring during he 5-year observaion period Class i: Blaeral dsal exensons (toal no. of aachmens = 43)
Class ii: unlaeral dsal exensons (toal no. of aachmens = 8)
Attachment screw activation
20
3
Change of plastic insert
17
—
Irreversible mechanical wear of attachment
—
4
Fracture of ceramic veneering
—
3
1
1
Decementation
during the 5-year observation period. In four
removable dental prosthesis design without
clinical cases, the male part of the spring bolt
reciprocation elements in patients with a
attachment for the Kennedy Class II situations
reduced vertical dimension may put this
showed irreversible mechanical wear after 4
type of restoration at risk for failures.
years of clinical function, and the restoration had to be replaced (Table 3).
In vitro investigations showed that these attachments tend to introduce significantly
The mean probing depth values ranged
more stress at the terminal abutment tooth
from 2.1 to 3.1 mm for the abutment teeth
compared with clasp-retained dentures.14
after 5 years and did not increase com-
With the use of the extracoronal attach-
pared with baseline values (.023 ≤
.850).
ment systems, fracture of unsplinted abut-
Data for PI and sulcus bleeding index (SBI)
P ≤
ment teeth or caries on splinted abutments
showed a statistically significant decrease
can lead to irreversible prosthesis failure.
(P < .001) and dropped to 52.1% and
Therefore, use of the extracoronal attachment
50.2%, respectively, in both groups after 5
system requires at least two splinted, vital,
years.
and periodontally healthy abutment teeth.8,13 The survival rate for the unilaterally retained removable dental prostheses was 25.0% after 5 years; using the miniaturized
diSCuSSiOn
attachment system for this indication is highly questionable. An in vitro investigation
The observed survival rate of precision
demonstrated that movement of the abut-
attachment–retained bilateral removable
ment tooth and denture base of unilaterally
dental prostheses was comparable to the
stabilized dentures is significantly greater
reported survival rates of clasp-retained
than with the bilateral design.15 Jin et al rec-
removable dental prosthesis after 5 years,
ommended positioning occlusal contacts
but inferior to the 95.1% survival rate report-
exactly on top of the crest of the alveolar
ed
den-
ridge and not extending the restorations
Despite the vitality of the teeth,
distally to the first molar.15 The observed
three of the observed abutment tooth frac-
destructive and irreversible wear of the
tures, all of which led to failure of bilateral
miniaturized male attachment part and the
dentures, occurred on nonsplinted attach-
fracture of a vital and splinted abutment
ments and are in accordance with data
tooth in the present investigation is a strong
reported in the literature.13 Thus, the low
indicator of prosthesis movement during
survival rate of 70% after 5 years refers par-
clinical function. It can be assumed that the
tially to nonsplinted abutment teeth, which
design of a unilaterally retained removable
created a lack of uniformity in the bilater-
dental prosthesis without crossarch stabi-
ally retained removable dental prosthesis
lization and extended cantilever lengths
group. Nonsplinted abutment teeth with a
creates significant stress on the fixed dental
for
tures.
telescopic
11,12
crown–retained
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prosthesis. The additional lack of control on the lateral and vertical forces on both the removable and fixed dental prosthesis may be the primary reason for the observed technical failures. As suggested by other authors, bilateral
aCKnOwledgMentS The authors express their gratitude to cian Erwin Schütz or his outstanding and excellent technical expertise during cal teamwork. The study was supported Meteaux.
dental technicollaboration years o cliniby Cendres &
stabilization should be recommended for Kennedy Class II situations if removable dental prostheses are used.15–17 A remarkable finding of this study was the need to
RefeRenCeS
change the plastic insert in the female part of the bilaterally retained removable dental prosthesis attachments, confirming previous in vitro findings that showed only negligible amounts of wear on plastic female inserts in comparison with metal-alloy matrix and patrix components.18
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