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ORIGINALARBEIT
P. Rehmann, A. Weber, B. Wöstmann, P. Ferger1
Clinical evaluation of
teeth fitted with
telescope crowns
for retaining a
partial denture
In this retrospective longitudinal study the data of 554 telescopic dentures with 1758 abutment teeth, which were
fitted between 1995 and 2004 in the Department of Dental
Prosthetics at the Justus Liebig University Giessen, Germany, was assessed and the risk of abutment tooth loss was
evaluated. The influence of the patient’s sex, the vitality of
the abutment teeth, the number of abutment teeth per telescopic denture and the impact of a follow-up program
were taken into account in the analysis. The mean observation time was 5.3 ± 2.9 years. There was a 90 % survival
probability for all abutment teeth at 6.9 years. The most
common reason for extraction was tooth fracture. Men lost
abutment teeth at a significantly earlier stage than women.
Tooth loss occurred earlier in dentures with few abutment
teeth than in dentures retained on a larger number of abutment teeth. There was also abutment tooth loss at an earlier stage if the teeth had been fitted with a post and core
and if patients did not attend recall appointments. The overall risk of abutment tooth loss with a telescopic partial denture should, however, be assessed as low.
Keywords: longitudinal study, abutment tooth, telescopic
denture, survival rate
Klinische Bewährung von Zähnen, die zur Verankerung einer Teilprothese mit Teleskopkronen versorgt wurden*
Im Rahmen einer retrospektiven Longitudinalstudie wurden
die Daten von 554 Teleskopprothesen mit 1758 Pfeilerzähnen, die im Zeitraum von 1995–2004 in der Poliklinik für
Zahnärztliche Prothetik der Justus-Liebig-Universität Giessen eingegliedert wurden, ausgewertet und das Verlustrisiko der Pfeilerzähne evaluiert. Die Auswirkungen des Geschlechts der Patienten, des Vitalitätszustandes der Pfeilerzähne, der Pfeileranzahl pro Teleskopprothese und der Einfluss eines Nachsorgeprogramms fanden dabei Berücksichtigung. Die mittlere Beobachtungszeit betrug 5,3 ± 2,9
Jahre. Die 90 %ige Überlebenswahrscheinlichkeit aller Pfeilerzähne lag bei 6,9 Jahren. Der häufigste Extraktionsgrund
war eine Zahnfraktur. Männer verloren signifikant früher
Pfeilerzähne als Frauen. Bei Prothesen mit wenigen Pfeilern
kam es früher zum Zahnverlust, als wenn die Prothese auf
einer größeren Pfeileranzahl verankert wurde. Mit Stiftaufbauten versorgte Zähne und eine fehlende Nachsorge führten ebenso zu einem schnellerem Pfeilerverlust. Insgesamt
ist das Verlustrisiko der Pfeilerzähne einer teleskopverankerten Teilprothese jedoch als gering einzuschätzen.
Schlüsselwörter: Longitudinaluntersuchung, Pfeilerzahn,
Teleskop, Überlebensrate
1
Department of Dental Prosthetics (Director: Prof. Dr. P. Ferger), Justus Liebig University Giessen, Germany
* Die deutsche Version dieses Beitrages wurde bereits in der DZZ 12/2006 publiziert.
Deutsche Zahnärztliche Zeitschrift • 62 • 2007 • 2 • © Deutscher Ärzte-Verlag, Köln
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P. Rehmann et al.: Telescopic crowns
Number
Treatment of the abutment (n = 134)
66
70
60
50
40
30
20
10
0
40
22
6
t
en
tm
ea
r
t
al
can
ot
o
R
on
cti
tra
Ex
on
rti
se
t in
s
Po
l
wa
ne
e
r
st
Po
Type of abutment tooth treatment
Figure 1 Treatment of the abutment teeth.
Figure 2 Survival function of the abutment teeth, n=1758, Kaplan-Meier.
Dentures
Year 1
Number of
telescopic
dentures
527
Year 2
481
Year 3
437
Year 4
386
Year 5
331
After 5
years
151
Number of extractions
Frequency
Percent
0
501
90.4
1
42
7.6
2
10
1.8
4
1
0.2
Total
554
100
Table 1 Number of telescopic dentures included in the study.
Table 2 Number of extractions per denture.
1 • Introduction
The required procedures for fitting the telescopic dentures were completed by various dentists and students on clinical/prosthetic courses. 94.6 % of the dentures were retained
on the residual dentition exclusively by cylinder telescope
crowns. If all the residual teeth were included in the restoration, the design of the denture base was dentoalveolar. Additional retention for the remaining 5.4 % telescopic dentures (30
dentures) was provided by cast clasps on the molars.
The mean age of the patients at the time of fitting the
denture was 58 ± 11 years. The youngest patient was aged 21
and the oldest 84. The mean observation period was 5.3 ± 2.9
years. The number of telescopic dentures still under observation after a specific period following fitting of the denture is
included in Table 1. Each denture was regarded as a separate
case.
In addition to treatment data routinely documented, data
recorded as part of an ongoing recall program were analyzed.
After the dentures had been inserted, all patients were offered the opportunity of participating in the recall program.
57 % of the patients accepted this offer and attended at least
one recall appointment.
The acquired data was first recorded and managed using
Microsoft Excel and then analyzed using SPSS – Version 12.0.
Kaplan-Meier analysis was used to calculate the survival
probability of the abutment teeth. Loss of an abutment tooth
was defined as the outcome event (time in years). The observation intervals without an outcome event were censored at the
time of the patient’s last documented visit. The survival time
A telescopic denture is a type of partial denture that provides
the patient with a high degree of oral comfort [10]. This
aspect is, however, only one of the many advantages of a telescopic denture. If the denture is fabricated correctly, the telescopic denture should also have a positive impact on conservation of the abutment teeth. The rigid connection to the residual dentition leads to secondary splinting and integrated
tilt prevention with mainly axial loading of the teeth, so that
the abutment teeth are protected and any existing mobility
is reduced [1]. Consequently even teeth with an unpredictable prognosis can be used as abutment teeth.
This study examined the impact of incorporating a telescopic denture on abutment tooth loss. A very large number of 1758 abutment teeth were enclosed in the study to
evaluate the risk of losing teeth used for retaining a telescopic denture.
2 • Materials and methods
This retrospective study included all telescopic dentures retained on natural abutment teeth (n=554 dentures with 1758
abutment teeth) inserted during the period 1995–2004 in the
Department of Dental Prosthetics at the Justus Liebig University Giessen. Implant-borne dentures were not included in the
study. Cases were also excluded in which there was no assessable follow-up data after fitting the denture.
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Figure 3 Survival function of the abutment teeth, n=1758, Kaplan-Meier, based on the patient’s sex.
Figure 4 Survival function of the abutment teeth, n=1758, Kaplan-Meier, based on vitality and root post treatment.
was recorded as a mean (M). The survival time of the abutment teeth was also recorded according to subcategories (sex
of patient; vitality of the abutment teeth; number of abutment teeth per telescopic denture; impact of the recall program) and differences tested for significance using the logrank test (p=0.05). Subcategories involving less than ten cases
were not included due to the low significance.
after 7.5 years (M: 8.5 years; 95 % confidence interval: 8.4–8.7
years) (Fig. 3). After five years (eight years) men still retained
92.2 % (81.6 %) of their abutment teeth, while women still retained over 95.6 % (87.2 %) of their abutment teeth.
3 • Results
3.1 Survival probability of all abutment teeth
During the observation period 134 procedures were completed on 1758 abutment teeth. These procedures (Fig. 1) included root canal treatment, fitting posts, post renewals or extractions. Tooth extractions accounted for half (49.3 %) of all
abutment tooth treatment (n = 66 with 53 dentures), which
corresponded to 3.8 % of all the abutment teeth in 9.6 % of all
dentures. The number of extracted abutment teeth per denture is included in Table 2.
At the end of the observation period 96.2 % of the abutment teeth were still in situ.
The majority of abutment tooth extractions (47 %) were
necessary due to tooth fracture that excluded the possibility of preserving the tooth. Periodontal disease was responsible for 28.8 % of the extractions. The percentages for other causes of abutment tooth loss were comparatively low
(Tab. 3).
The 90 % survival probability of all 1758 abutment teeth
(Fig. 2) was 6.9 years (M: 9.5 years; 95 % confidence interval:
9.3–9.8 years). After five years 93.9 % of the teeth were still
in situ – after eight years the figure was still 84.5 %.
3.2 Survival probability of the abutment
teeth based on the patient’s sex
Men lost their abutment teeth significantly earlier (p < 0.05).
With men survival probability of the abutment teeth fell below 90 % (n=856 teeth) after 5.9 years (M: 9.4 years; 95 % confidence interval: 9.1–9.7 years) and with women (n = 902 teeth)
3.3 Survival probability of abutment teeth based on vitality
Vital abutment teeth (n = 1524) survived significantly longer (p < 0.001) than teeth that had been fitted with a post
system (n = 226). The 90 % survival probability of vital abutment teeth was 7.6 years (M: 9.8 years; 95 % confidence interval: 9.5–10.0 years), whereas for teeth fitted with a post
system it was 2.7 years (M: 7.6 years; 95% confidence interval: 7.0–8.2 years) (Fig. 4). The survival probability after five
and eight years with vital teeth was 96.2 % and 87.0 %, whereas abutment teeth fitted with posts only had a survival
probability of 78.4 % and 67.5 %
3.4 Survival probability of abutment teeth based on the number of abutment teeth
The survival probability for teeth in dentures with a larger
number of abutments tended to be higher than for teeth in
dentures with few abutments (Tab. 4) (not significant, p > 0.05).
3.5 Survival probability of abutment teeth based on recall participation
Abutment teeth (n = 753) of patients who did not participate
in the recall program were extracted at a significantly
(p < 0.001) earlier stage than abutment teeth provided with
professional aftercare (n = 1005). If the patient attended at least one recall appointment, the 90 % survival probability of
the abutment teeth was 7.8 years (M: 9.7 years; 95 % confidence interval: 9.5–10.0 years) compared with only 4.3 years
(M: 7.9 years; 95 % confidence interval: 7.3–8.5 years) in the
case of patients who did not attend any recall appointments.
After five years 94.9 % and 88.1 % and after eight years 89.0 %
and 53.9 % of the abutment teeth were still in situ (Fig. 5).
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Reason for abutment tooth
extraction
Number
Percent (%)
Fracture
31
47.0
Periodontal disease
19
28.8
Caries
4
6.1
Natural extraction
3
4.6
Other practice
2
3.0
Tumor surgery
2
3.0
Root perforation
2
3.0
Fistula formation
1
1.5
No documentation
2
3.0
Extraction
66
100
Figure 5 Survival function of the abutment teeth, n=1758, Kaplan-Meier, impact of recall visits.
Table 3 Reasons for extraction and number of extractions.
4 • Discussion
copic dentures than in men. Thus a higher extraction rate
would be expected in women than in men.
The significantly shorter survival time of abutment
teeth fitted with a post and core compared to vital abutment teeth, as reported with similar results in other studies [5, 13, 18], brings into question the incorporation of
non-vital abutment teeth in denture frameworks. They
should only be incorporated in cases in which keeping the
teeth at risk greatly improves retention of the denture and
also the oral comfort and ultimately the quality of life of
the patient [10].
Several studies examined the influence of the number of
abutment teeth per denture on the survival probability of the
abutment teeth [2, 8, 9, 12, 17, 19]. With the exception of Wenz
et al. [19], who only examined dentures retained on resilient
telescope crowns, all authors reported a positive correlation
between the number of abutment teeth and the functioning
period of the abutment teeth; this correlation tended to be reflected in the patient group in this study.
The data of this study verifies the correlation between
the survival probability of the abutment teeth and participation in a recall program. Abutment teeth of patients who
attended recall appointments to allow professional aftercare of their denture and denture-bearing area had a signifi-
The data recorded in this study for the survival time of the
abutment teeth and extraction rate concurs to a great extent
with the results of other studies [1, 2, 5, 6, 7, 8, 13, 14, 16].
Overall the extraction rate of the teeth fitted with a telescope crown should be assessed as low; this is based mainly on
the fact that a telescopic denture is generally regarded as a
form of treatment that allows teeth with an unpredictable
or even questionable prognosis (reduced periodontium
function) to be incorporated in the denture, as the denture
can be easily extended if extraction should prove necessary.
The survival time of abutment teeth with telescopic
dentures is very similar to that of teeth treated with partial
and full cast crowns [15] and there is no indication to date
that incorporation of a telescopic denture results in premature loss of abutment teeth.
Results relating to the influence of the patient’s sex on
survival probability are controversial. In contrast to the
data recorded in this study, Eisenburger et al. [2] did not find
that the sex of the patient had any significance. On the other hand, Stark and Schrenker [16] stated that there was a higher incidence of inflammation of the periodontium and
mobility of the abutment teeth in women fitted with teles-
Number of dentures
Number of abutment
teeth per denture
First extraction
(in years)
90% SP
(in years)
5-year SP (%)
8-year SP (%)
Mean (in years)
30
1
1.41
1.47
64.71
64.71
7.6
169
2
1.03
5.26
92.71
63.21
8.22
160
3
0.2
7.64
93.88
88.87
8.92
106
4
0.34
5.58
92.23
84.64
8.14
55
5
4.07
8.45
98.67
90.19
8.44
29
6
0.77
8.94
97.79
97.79
8.85
3
7
-
-
-
-
-
2
8
1.95
1.95
-
-
2.54
Table 4 Survival probability (SP) of abutment teeth of telescopic dentures with a varying number of abutments (- = value not attained).
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cantly longer survival rate (M: 9.7 years) than the abutment
teeth of patients who only attended the clinic when a problem occurred (M: 7.9 years). Problems with the abutment
teeth of these patients were often so far advanced at the
time of their visit to the clinic that the teeth could no longer be preserved. It should also be noted that discrepancies
between the fitting surface of the denture and the mucosa
is often unnoticed by the patient and can frequently only
be diagnosed by the dentist at a checkup [11]. Dentures that
lack this type of load compensation (= no contact between
the denture saddles and mucosa when the attachment is
fully seated) represent a high risk for the abutment teeth,
as this induces greater movement of the abutment teeth
and can result in tooth loosening or even fracture of the
tooth [3].
Apart from the primary criterion of high-quality treatment [4], an ongoing recall program is also an important
criterion with regard to the survival time of teeth fitted
with telescopic crowns for retaining a removable partial
denture.
WISSENSCHAFT • 103
9. Igarashi, Y., Goto, T.: Ten-year follow-up study of conical crown-retained dentures. Int J Prosthodont 10, 149-155 (1997)
10. Kothe, A., Balkenhol, M., Wickop, H., Wöstmann, B., Ferger, P.: Orale Gesundheit und Lebensqualität vor und nach prothetischer Versorgung. Dtsch
Zahnärztl Z 58, 603-605 (2003)
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Kugelknopfanker im stark reduzierten Gebiss. Dtsch Zahnärztl Z 38, 10111015 (1983)
12. Mock, F., Schrenker, H., Stark, H.K.: Eine klinische Langzeitstudie von Teleskopprothesen. Dtsch Zahnärztl Z 60, 148-153 (2005)
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16. Stark, H., Schrenker, H., Bewährung teleskopverankerter Prothesen – eine
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Planungsmaßnahmen im teilbezahnten Gebiss. Dtsch Zahnärztl Z 39, 844847 (1984)
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43, 525-529 (1988)
7. Heners, M., Walther, W.: Pfeilerverteilung und starre Verblockung – eine klinische Langzeitstudie. Dtsch Zahnärztl Z 43, 1122-1126 (1988)
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• Contact address:
Dr. Peter Rehmann
Poliklinik für Zahnärztliche Prothetik
(Leiter: Prof. Dr. P. Ferger)
Zentrum für ZMK
Justus-Liebig Universität Giessen
Schlangenzahl 14
D-35392 Giessen
E-mail: Peter.Rehmann@dentist.med.uni-giessen.de
Deutsche Zahnärztliche Zeitschrift • 62 • 2007 • 2