Complication and failure rates of fixed
dental prostheses in patients treated for
periodontal disease
Urs Bra¨gger
Stefanie Hirt-Steiner
Natascha Schnell
Kurt Schmidlin
Giovanni E. Salvi
Bjarni Pjetursson
Giedre Matuliene
Marcel Zwahlen
Niklaus P. Lang
Authors’ affiliations:
Urs Bra¨gger, Stefanie Hirt-Steiner, Natascha Schnell,
Giovanni E. Salvi, Giedre Matuliene, School of Dental
Medicine, University of Bern, Bern, <st1:country-region>Switzerland
Kurt Schmidlin, Marcel Zwahlen, Institute of Social
and Preventive Medicine, University of Bern, Bern,
<st1:country-region>Switzerland
Bjarni Pjetursson, Faculty of Odontology, University of
<st1:country-region>Iceland, Reykjavik, <st1:country-region>Iceland
Niklaus P. Lang, Faculty of Dentistry, The University
of Hong Kong, Hong Kong, SAR <st1:country-region>China
Corresponding author:
Dr Prof. Urs Bra¨gger
School of Dental Medicine
University of Bern
Freiburgstrasse 7
3010 Bern
Switzerland
Tel.: t41 31 632 2541
Fax: t41 31 632 4931
e-mail: urs.braegger@zmk.unibe.ch
Key words: cantilever extensions, complications, dental implants, failures, FDP, fixed dental
prostheses, periodontitis, supportive periodontal therapy
Abstract
Objectives: To evaluate the biological and technical complication rates of fixed dental prostheses
(FDP) with end abutments or cantilever extensions on teeth (FDP-tt/cFDP-tt) on implants (FDP-ii/cFDPii)
and tooth-implant-supported (FDP-ti/cFDP-ti) in patients treated for chronic periodontitis.
Material and methods: From a cohort of 392 patients treated between 1978 and 2002 by graduate
students, 199 were re-examined in 2005. Of these, 84 patients had received ceramo-metal FDPs (six
groups).
Results: At the re-evaluation, the mean age of the patients was 62 years (36.2–83.4). One hundred and
seventy-five FDPs were seated (82 FDP-tt, 9 FDP-ii, 20 FDP-ti, 39 cFDP-tt, 15 cFDP-ii, 10 cFDP-ti). The
mean observation time was 11.3 years; 21 FDPs were lost, and 46 technical and 50 biological
complications occurred. Chances for the survival of the three groups of FDPs with end abutments were
very high (risk for failure 2.8%, 0%, 5.6%). The probability to remain without complications and/or
failure was 70.3%, 88.9% and 74.7% in FDPs with end abutments, but 49.8–25% only in FDPs with
extensions at 10 years.
Conclusions: In patients treated for chronic periodontitis and provided with ceramo-metal FDPs, high
survival rates, especially for FDPs with end abutments, can be expected. The incidence rates of any
negative events were increased drastically in the three groups with extension cFDPs (tt, ii, ti).
Strategic decisions in the choice of a particular FDP design and the choice of teeth/implants as
abutments appear to influence the risks for complications to be expected with fixed reconstruction. If
possible, extensions on tooth abutments should be avoided or used only after a cautious clinical
evaluation of all options.
Today, partially edentulous patients are increasingly
aware of their functional, esthetic and social
handicaps.
An epidemiologic survey of the prevalence of
reconstructions in various age cohorts of Swiss
citizens revealed that, in the younger age groups,
fixed dental prostheses (FDPs) were more frequent
compared with removable partial dentures.
Over the last decades, the prevalence of removable
partial or full denture wearers shifted to the
very old age groups in industrialized countries.
Hence, removable partial dentures seem to be
less accepted in some European societies (Zitzmann
et al. 2007).
As an alternative to extensive reconstructions
on, e.g., furcation-involved molar teeth or the
installation of dental implants placed in the
posterior area, the concept of a shortened
dental arch may be acceptable by most patients
(Ka¨yser 1981, 1994). A shortened dental
arch limited to the premolar occlusionmay result
in sufficient occlusal stability, chewing efficacy
and no increased risk for temporo-mandibular
disorders (Witter et al. 1994a,1994b, 2001,
2007). As long as all premolar regions and one
occluding pair of molars were present, practically
no complaints about the chewing efficacy were
reported (Sarita et al. 2003). In cases with severely
reduced dental arches with 0–2 pairs of
occluding premolars only, however, patients frequently
expressed severe complaints (Sarita et al.
2003).
Date:
Accepted 8 September 2010
To cite this article:
Bra¨gger U, Hirt-Steiner S, Schnell N, Schmidlin K, Salvi GE,
Pjetursson B, Matuliene G, Zwahlen M, Lang NP.
Complication and failure rates of fixed dental prostheses in
patients treated for periodontal disease.
Clin. Oral Impl. Res. 22, 2011; 70–77.
doi: 10.1111/j.1600-0501.2010.02095.x
70 c_ 2010 John Wiley & Sons A/S
Before the period in which implants became a
predictable treatment to add functional units in
free-end situations, fixed dental prostheses with
distal cantilever extensions were frequently incorporated.
Occasionally, FDPs with cantilever
extensions were also chosen in order to avoid
additional preparations of teeth adjacent to edentulous
spaces, i.e., in cases of intact crowns or
still acceptable existing reconstructions. Cantilever
extension FDPs, however, demonstrated increased
failure rates at 10 years compared with
conventional end-abutment fixed bridgework
(Pjetursson et al. 2004, Tan et al. 2004). Moreover,
at 5 years, higher technical complication
rates were reported (Ha¨mmerle et al. 2000; Pjetursson
et al. 2007).
The incorporation of fixed dental prostheses on
abutment teeth requires the preparation of a
dentinal core with or without prior root canal
treatment, with or without composite build-ups
that may or may not require the placement of
posts and cores.
The risks encountered with dental reconstructions
are related to the complexity and the
cumulative number of the interventions required
(Miyamoto et al. 2007; De Backer et al. 2007).
For single crowns on teeth, increased failure rates
were observed in the absence of a considerable
dentinal core (ferrule) and in cases with cast posts
and cores (Creugers et al. 2005; Schmidlin et al.
2010).
Since the late 1980s, treatment planning in
fixed prosthodontics has been revolutionized by
the possibility of incorporating implant-borne
reconstructions. Tissue-integrated implants now
serve as the basis for single crowns and may be
used strategically correctly distributed in edentulous
ridges to receive the fixed dental prostheses.
Guided bone regeneration in combination with
grafting procedures may be applied to predictably
create the necessary bone volume for a particular
implant site. Furthermore, the need for complex
pretreatment of abutment teeth with a doubtful
prognosis seems to become obsolete with implants
being chosen as abutments (Walton
2009a, 2009b).
Because of anatomical/surgical and strategic
prosthetic considerations, the FDP on implants
may include distal and/or mesial cantilever extensions.
In a situation with an abutment tooth
in need of a restoration and with a good prognosis
adjacent to an edentulous space, a mixed tooth–
implant-supported FDP may still be preferred.
Decision-making processes for treatment planning
are challenging in daily practice. Furthermore,
patients must be informed about potential
risks associated with various treatment concepts.
The expectations related to the longevity of
required reconstructions in younger age cohorts
are high due to the considerable costs involved,
especially for fixed dental prostheses on teeth or
implants (Petersson et al. 2006; Incici et al.
2009).
Choosing from available options of restorations,
the longevity and complication rates
should be considered in order to estimate the
complexity of maintenance service to be expected
(Bouchard et al. 2009).
A series of systematic reviews based on clinical
studies have collected the combined estimated
annual failure and complication rates and cumulative
risks at 5 and 10 years with reconstructions
on teeth or implants (Tan et al. 2004; Lulic et al.
2007; Pjetursson et al. 2007; Aglietta et al. 2009).
However, the data available to base decision
making for the preference of a particular reconstruction
for a particular patient are still sparse. In
the systematic reviews mentioned above, o100
reconstructions could actually be evaluated for
some patient cohorts with a detailed description
of all events observed over 5, 10 or even more
years.
Patients with risk factors such as a history of
periodontal disease, smoking (Heitz-Mayfield &
Huynh-Ba 2009) and bruxism (Salvi & Bra¨gger
2009) may demonstrate higher event rates of
failures and complications than patients without
such conditions. To what extent these conditions
may lead to increased and more complex maintenance
and repair service is of particular interest
to the clinician.
The purpose of this study was to evaluate
retrospectively the biological and technical failure
and complication rates with FDPs in partially
edentulous patients treated for chronic periodontitis.
Material and methods
Patient accrual
For this retrospective cohort study, patients with
chronic periodontitis who had been treated by
graduate students as a part of their educational
training at the Department of Periodontology and
Fixed Prosthodontics, University of Bern, during
the period 1978–2002 were recruited. The patient
cohort has been characterized recently. At
the first examination, the proportion of patients
with periodontitis defined as ‘‘patients with interproximal
probing attachment loss of 5mm in
30% of the teeth present’’ was 88.1%. If the
definition of probing attachment loss of 5mm at
two non-adjacent teeth was chosen, 97.5% of the
cases were advanced periodontitis patients (Matuliene
et al. 2008).
Comprehensive dental treatment
All patients had been treated according to a
comprehensive treatment protocol (Lang & Lo¨e
1993). In brief, following complete periodontal,
endodontic and cariologic as well as complete
radiographic examinations, a treatment plan was
established and discussed with the patient in a
case presentation. This was followed by oral
hygiene instructions and the performance of
cause-related initial periodontal therapy (i.e.,
scaling and root planing under local anesthesia).
After 6–8 weeks, a thorough evaluation of the
outcomes of initial therapy was performed. Subsequently,
periodontal surgery was performed if
indicated. The condition after periodontal therapy
in this patient cohort has been characterized
recently by Matuliene et al. (2008). Only 2.9% of
the remaining pocket depths were 44mm, 30%
of the patients had a full-mouth bleeding index
o10% and 45% within 10% and 25%.
Root canals of devital teeth in need of treatment
were filled with guttapercha and AH26 or
AHt. In case of severely reduced dentinal cores,
placement of an indirect cast post and core was
implemented. Implants were placed to avoid
preparation of intact and healthy teeth or to avoid
the replacement of still acceptable adjacent restorations.
Finally, prosthetic therapy using dental
implant or tooth supported FDPs or single unit
crowns was performed. The restorations consisted
of ceramo-metal reconstructions that
were cemented with zinc phosphate or glass
ionomer cement.
Following the completion of comprehensive
treatment, patients were enrolled in a supportive
periodontal therapy (SPT) program at the clinic of
the University of Bern or they were referred back
to private practitioners for SPT.
Clinical examination
From the 392 original cases treated and documented
according to the requirements for the
specialty board certification of the Swiss Federal
Office for Health, 199 could be recruited and reexamined
during the year 2005. The remaining
193 patients had either moved away from the
area, were too frail to participate at the re-examination
or were deceased.
At the re-examination, the patients first filled
out a questionnaire related to changes in general
health aspects, their experiences with the reconstructions
and the frequency of recall sessions
during the last years.
The clinical examination included the enumeration
of teeth, implants and reconstructions
as well as the type of reconstruction and the
number of replaced teeth per reconstruction. A
complete periodontal chart revealed the recession
and the probing pocket depths (PPD) in relation
to the cemento-enamel junction or implant
shoulder at six aspects of each tooth/implant.
The presence of BOPt or BOP_ sites was
Bra¨gger et al _ Failure and complication rates of FDP
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2010 John Wiley & Sons A/S 71 | Clin. Oral Impl. Res. 22, 2011 / 70–77
noted. Probing was performed by means of an
electronic device (Florida Probe Corporation,
Gainesville, FL, USA) with a standardized dimension
and force set at 0.15N. Abutment teeth
were tested for pulp vitality (CO2 test) and the
presence of carious lesions. Reconstructions and
implant components were examined carefully for
any mechanical and/or technical complications.
The radiographic examination included an
orthopantomogram as well as periapical intraoral
radiographs from the crowned teeth and/or implants.
Episodes of failures and/or complications were
derived from the patient charts in case the
patients remained as recall patients at the clinic
or from the questionnaires in case the patients
returned to private practice for maintenance care.
Evaluation of complications
The evaluation of biological complications included
caries at abutment teeth, loss of tooth
vitality, presence or absence of a periapical endodontic
lesion, periapical endodontic lesion and
caries, periodontitis (PPD _ 6mm) and BOPt,
periimplantitis (PPD _ 6mm; according to the
criteria defined in Karoussis et al. (2003)) and
BOPt, abscess formation, root fracture and/or
dentin core fracture if present.
The assessment of mechanical/technical complications
included the identification of loss of
retention, loosening of occlusal screws, ceramic
chipping, fracture of the framework and/or implant
abutment fracture (Salvi & Bra¨gger 2009).
A failure was defined as a biological, technical
or traumatic event leading to either the extraction
of the tooth or the explantation/loss of the
implant or the loss of the original FDP.
Classification of reconstructions
The FDPs were classified into six different categories:
FDPs with either end abutments or cantilever
extension FDPs on teeth (FDP-tt/cFDP-tt), FDPs
with either end implant abutments or cantilever
extensions on implants (FDP-ii/cFDP-ii) or connecting
teeth and implants (FDP-ti/cFDP-ti).
Statistical analysis
The null hypothesis postulated no difference in
the survival/success rates between the different
designs of FDPs.
The data collected were grouped according to
six categories: fixed dental prostheses with end
abutments or cantilever extensions on teeth
(FDP-tt/cFDP-tt), on implants (FDP-ii/cFDP-ii)
ormixed on teeth and implants (FDP-ti/cFDP-ti).
Descriptive statistics listed the number of
reconstructions incorporated as well as the number
of reconstructions with complications and
failures observed over 5 and 10 years and over
the entire observation period (events per 100
years of object-time).
The cumulative risk after 5 and 10 years of
observation was calculated by subtracting the
Kaplan–Meier survival function from 1. Event
rates per 100 years of object-time were calculated
by dividing the number of events by the total sum
of the time an object was under observation.
Event rates were calculated for complications
(biological and technical) and failures (biological,
technical and traumatic). The Kaplan–Meier
survival function was used to calculate the probability
of a reconstruction being free of any
complication (biological and technical) or failure
(biological, technical and traumatic). Poisson’s
regression was used to compare the six different
categories of bridges with respect to the incidence
rate of failures, and of failures and complications
by calculating the rate ratios for the first 10 years
and over the complete observation time. For
some patients, more than one reconstruction
was included in the analyses. By calculating
robust standard errors in the Poisson regressions,
this correlation was accounted for.
For event rates and for incidence rate ratios
(IRR), the estimates and 95 percent confidence
intervals were reported based on the assumption
that the number of events is Poisson’s distributed
for a given sumof observation time. The P-values
reported are two-sided. For the cumulative incidence,
95% confidence intervals are reported
based on those obtained from the Kaplan–Meier
estimates. All analyses were performed using
Stata Version 11 (Stata Corporation, College
Station, TX, USA).
Results
Patients
From the 199 patients re-examined, 84 patients
had received fixed dental prostheses. Fifty-one
were female and 33 were male patients.
The mean age of the patients at the re-evaluation
was 62 years (range 36.2–83.4 years).
FDPs
In these patients, 175 FDPs had been seated. As
indicated in Table 1, 82 were FDP-tt, 9 were
FDP-ii, 20 were FDP-ti, 39 were cFDP-tt, 15
were cFDP-ii and 10 were cFDP-ti (Table 1).
One hundred and eleven FDPs were reconstructions
with end abutments and 64 were
reconstructions with cantilever extensions.
One hundred and twenty-one FDPs were tooth
supported, 24 FDPs were implant supported and
30 FDPs were tooth–implant supported reconstructions.
5.14% of the reconstructions consisted of two
units, 34.86% were three-units, 28.57% fourunits
and 31.43% 5–14-unit FDPs.
Abutments
Three hundred and fifty-six teeth and 86 implants
were restored with FDPs. Over the entire
observation period, 33 (9.3%) abutment teeth in
14 patients and two (2.3%) implants in two
patients were lost.
Observation time
The mean observation time of all the 175 FDPs
was 11.31 years (range 2.29–26.42 years). The
mean observation time of FDPs and c-FDPs on
teeth was longer (12.1 and 13.66 years, respectively)
compared with FDPs and c-FDPs on implants
(7.43 and 8.21 years) and compared with
mixed FDPs and c-FDPs (8.13 and 10.04 years).
Failures of the reconstructions
From the 175 originally seated reconstructions,
24 (13.7%) resulted in a failure. Twenty-one
failures of the reconstructions were associated
with the loss of teeth or implants. One was a
complete loss of an FDP and two were partial
losses of the FDPs.
Complications observed over the entire
observation period
In Table 2, the frequencies of various technical
and biological complications occurring over the
observation period are listed including all the
events. Fifty-nine biological complications occurred
over the entire period (including all
events): 11 caries, three loss of vitality, 13 periodontitis,
nine peri-implantitis, 12 periapical lesions,
five fractures and six combined lesions.
Forty-six technical complications occurred
over the entire observation period (including all
events): 17 ceramic chippings, 24 loss of retention,
three fractures of prosthetic components
(abutments), one loose occlusal screw, one
‘‘crown fracture’’, one trauma and one combined
lesion.
In Table 3, the estimated annual rates of
complications and failures per 100 FDPs are
listed. These estimated rates were based on the
Table 1. Number of FDPs in each category
Number
of FDPs
Number
of c-FDPs
tt 82 39
ii 9 15
ti 20 10
tt, tooth supported; ii, implant supported; ti,
tooth–implant supported; FDP, fixed partial
denture on end abutments; c-FDP, fixed partial
denture with a cantilever extension.
Bra¨gger et al _ Failure and complication rates of FDP
72 | Clin. Oral Impl. Res. 22, 2011 / 70–77 c_ 2010 John Wiley & Sons A/S
actual number of observed events in the first 10
years. Within the first 10 years, 40 biologic and
30 technical complications and 14 failures occurred.
The estimated annual event rates for biological
complications per 100 reconstructions ranged
from 0 to 2 for FDP with end abutments and
from 4.6 to 6.1 for FDPs with cantilever extensions.
The estimated annual event rates for technical
complications per 100 reconstructions ranged
from 0.6 to 1.9 for FDPs with end abutments
and from 1.9 to 7.8 for FDPs with cantilever
extensions.
The estimated annual event rates for loss of the
reconstruction per 100 FDPs ranged from 0 to 0.7
for FDPs with end abutments and from 1.1 to 2.5
for FDPs with extensions.
In Table 4, the estimated cumulative risks of a
complication or a failure at 5 and 10 years of
observation are listed, grouped according to the
six types of FDPs.
The cumulative risk for loss (failure) for FDPtt/
ii/ti and c-FDP t-I was 0 at 5 years and for
FDP-ii at 10 years.
The cumulative risk for loss (failure) for c-
FDPs was considerably higher at 5 and 10 years,
respectively, ranging from 10% to 23.6%.
The cumulative risk for biological complications
was still low for most of the types of FDPs,
with the exception of cFDP-tt (18.4%) and cFDPti
(10%) at 5 years, but increased for most of the
reconstructions at 10 years, when FDP-ii still had
a 0% risk, and the risks for other FDPs with end
abutments were 18.8% and 17.8%, respectively.
In the group of FDPs with cantilever extensions,
the cumulative risk at 10 years reached values
ranging from 43.2% to 70.4%.
The cumulative risks for technical complications
ranged from 0% to 35.7% at 5 years and
from 9.1% to 65% at 10 years.
In Table 5, the probabilities for the FDPs of
remaining free from any complication/failure
over 5 and 10 years are listed.
Already at 5 years, the FDPs with cantilever
extensions had lower probabilities to remain
completely unaffected (60–80%) compared with
FDPs with end abutments (88.9–100%).
At 10 years, the probability of remaining free
from complications/failures ranged from 70.3%
to 88.9% for FDP with end abutments, but was
clearly reduced to 25% and 49.8% in the group
with cantilever extensions.
In Fig. 1, the decreases in the number of FDPs
free from complications and failures are depicted
for each category using the Kaplan–Meier survival
function.
In Table 6, the IRR of failures, and failures
combined with any complications are listed for
the six groups of FDPs. Only the first 10 years as
well as the entire observation period were considered.
The rates of events observed in the group FDPtt
were chosen as a reference. Compared with the
reference, the IRR were reduced in seven out of
eight comparisons, with the most favorable values
for the failure of FDP-ii.
The IRR, however, were increased in c-FDPs
in 12 out of 12 comparisons.
Discussion
This study was undertaken to evaluate the biological
and technical complication and failure
rates encountered with fixed dental prostheses
on teeth and implants in partially edentulous
patients who had been treated for advanced periodontitis.
As reported recently (Schmidlin et al. 2010), 64
out of 199 patients re-examined in this study had
received 168 single crowns on either a tooth with
a vital pulp (56), an endodontically treated tooth
(34), a tooth with a cast post and core (39) or an
implant (39). During a mean observation period
of 11.8 years, 19 single crowns were lost. All the
crowns were ceramo-metal crowns. In that respect,
the presence of severe loss of dentin requiring
the fabrication of a cast post and core resulted
in the highest rate of failures.
From the 199 patients who were re-examined,
84 had received FDPs. Altogether, 24 out of 175
reconstructions were lost after an observation
period of about 11 years (range 2.29–26.42). For
all the parameters assessed, a trend for more
frequent negative events was observed for FDPs
with cantilever extensions. The time in function
of the FDPs of the present study was considerable.
Titles of published reports often report
observation times reaching far beyond 10 years.
However, when the means and ranges of the
actual observation times are scrutinized, a more
realistic estimation of the exposure times of the
reconstructions is revealed. Thus, up to 18- or
Table 2. Complications
Event details Frequencies % Cumulative
Biological events
Root fracture 1 0.9 50.5
Caries and excessive bone loss 1 0.9 51.4
Periapical disease and caries 2 1.9 49.5
Loss of vitality 3 2.8 13.1
Caries and periodontitis 3 2.8 47.7
Periimplantitis 9 8.4 33.6
Caries 11 10.3 10.3
Periapical disease 12 11.2 44.9
Periodontitis 13 12.2 25.2
Technical Events
Loosening of occlusal screw 1 0.9 97.2
Fracture of a crown framework 1 0.9 98.1
Trauma 1 0.9 99
Ceramic chipping and crown framework fracture 1 0.9 100
Fracture of secondary part (component) 3 2.8 96.2
Abutment fracture 4 3.7 55.1
Ceramic chipping 17 15.9 71
Loss of retention 24 22.4 93.4
Total 107 100
Table 3. Estimated annual rate of complications and failures per 100 FDPs based on the number of
events observed in the first 10 years
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
Reconstructions seated 82 9 20 39 15 10
Biological complications
Number of events in the first 10 years 12 0 3 15 5 5
Annual event rate per 100 crowns 1.8 0 2 5 4.6 6.1
95% CI 1–3.1 0–6 0.6–6.3 3.3–7.6 1.9–11 3–12.5
Technical complications
Number of events in the first 10 years 11 1 1 6 6 5
Annual event rate per 100 crowns 1.7 1.9 0.6 1.9 7.8 7.4
95% CI 1–3 0.2–15 0.1–4.3 0.9–4 2.8–21.5 3.3–16.5
Failures
Number of events in the first 10 years 2 0 1 8 2 1
Annual event rate per 100 crowns 0.3 0 0.7 2.5 1.8 1.1
95% CI 0.1–1.1 0–6 0.1–4.8 1.4–4.5 0.5–7.4 0.2–7.8
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP, fixed partial denture with cantilever
extension; ii, implant supported; CI, confidence interval; ti, tooth–implant supported.
Bra¨gger et al _ Failure and complication rates of FDP
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2010 John Wiley & Sons A/S 73 | Clin. Oral Impl. Res. 22, 2011 / 70–77
20-year long-term results may actually be reduced
to a mean observation period of about 10
years (De Backer et al. 2006a, 2006b; Decock
et al. 1996).
The detailed event rates/risks observed with
the different designs of the FDPs of this study
will be compared with the findings from other
reports.
Survival/failure
The chances for survival of the FDP-tt over 5 and
10 years were very favorable for reconstructions
observed in the present report (risk for failure 0%
and 2.8%). Based on seven publications with
2088 FDP-tt exposed to 11,998 years, the estimated
chance for survival was 93.3% at 5 years.
Based on eight publications with 1218 FDP-tt
exposed for 10,446 years, the estimated chance
for survival at 10 years was 89.2% (Pjetursson et
al. 2007).
In the present report, the most favorable
chance for survival was demonstrated by the
FDP-ii (100%). This is superior to survival rates
of 95.2% at 5 years reported in a systematic
review based on 17 papers, with 1384 FDP-ii
exposed to 6989 years and 86.7% at 10 years
reported in only three papers with 219 FDP-ii
exposed to 1889 years (Pjetursson et al. 2007).
Although subject to speculation, the reason for
this favorable outcome in the present study may
be explained on the basis of a careful presurgical
risk evaluation consequently performed for implant
patients in this cohort. Likewise, the patients
receiving implants for combined tooth–
implant supported reconstructions yielded higher
survival rates after 5 and 10 years compared with
those of systematic reviews (0% failure at 5 years
and 5.6% failures at 10 years). In those, much
lower estimated values were reported (Pjetursson
et al. 2007). Based on six studies, 199 FDP-ti
were exposed to 976 years of function and had a
chance for survival of 95.5% at 5 years. For 10
years, this was significantly reduced to 77.8%.
Only 72 FDP-ti could be analyzed and were
exposed to 517 years (Pjetursson et al. 2007).
In the present report, cFDPs-tt with cantilever
extensions demonstrated higher risks for failures
(10% at 5 years and 23.6% at 10 years) compared
with FDPs-tt with end abutments. This difference
between the survival of the two categories is
in agreement with the recent systematic review
(Pjetursson et al. 2007). Based on six papers with
432 cFDP-tt exposed to 2112 years, the chance
for survival was 94.4% at 5 and reduced to
80.3% at 10 years (based on six papers with
239 cFDP-tt exposed for 2229 years (Pjetursson
et al. 2007).
The cumulative risk for the failure of cantilever
reconstructions on implant abutments (cFDP-ii)
reached 13.3% at 5 years and remained at 13.3%
at 10 years in the present report. In a recent
systematic review (Aglietta et al. 2009), five
clinical studies with 180 cFDP-ii were included
and yielded a cumulative chance of survival of
94.3% at 5 and 88.9% at 10 years, respectively.
Comparison of the results of the present evaluation
on 5- and 10-year survival of tooth- or
implant-supported cantilever reconstructions
with those of the systematic reviews (Pjetursson
et al. 2007; Aglietta et al. 2009) that covered the
entire dental literature reporting on a mean observation
period of at least 5 years reveals 4–8%
lower survival after 5 years and 2–4% lower
survival after 10 years. These differences appear
to be small and not significant and may not have
to be justified. Especially, the 10-year survival
rate for implant-supported cantilever reconstruc-
Table 4. Estimated cumulative risk and 95% confidence interval of biological and/or technical complications and/or failures (including trauma) of FDP over
5 and 10 years of observation
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
Reconstructions seated 82 9 20 39 15 10
Reconstructions with biological complications
Cumulative risk (%) after 5 years 95% CI 2.5 0 0 18.4 0 10
(0.6–9.5) (0–37) (0–17.6) (9.2–34.8) (0–24.7) (1.5–52.7)
Cumulative risk (%) after 10 years 95% CI 18.8 0 17.8 43.2 70.4 58
(11–31.1) (0–52.2) (6.1–45.7) (28.5–62) (30–84.1) (28.5–89.4)
Reconstructions with technical complications
Cumulative risk (%) after 5 years 95% CI 6.2 11.1 0 5.4 35.7 20
(2.6–14.2) (1.6–56.7) (0–17.6) (1.4–20.1) (16.7–65.7) (5.4–59.1)
Cumulative risk (%) after 10 years 95% CI 15.6 11.1 9.1 18.2 Not enough data 65
(8.9–26.8) (1.6–56.7) (1.3–49.2) (8.5–36.3) (31.8–94.4)
Reconstructions lost
Cumulative risk (%) after 5 years 95% CI 0 0 0 10.4 13.3 0
(0–4.8) (0–36.9) (0–17.6) (4–25.4) (3.5–43.6) (0–52.2)
Cumulative risk (%) after 10 years 95% CI 2.8 0 5.6 23.6 13.3 10
(0.7–10.7) (0–52.2) (0.8–33.4) (12.4–42.1) 3.5–43.6 1.5–52.7
Biological complications included: caries, loss of vitality, periodontitis or periimplantitis (pocket depth _ 6mm, BOPt), periapical radiolucent zone, root or tooth fracture
and abscess.
Technical complications included: porcelain fracture, loss of retention, implant fracture, crown fracture and loosening of the occlusal screws.
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP-tt, fixed partial denture with cantilever extensions on teeth; ii, implant supported; CI, confidence
interval; ti, tooth–implant supported.
Table 5. Probability for FDPs to remain without any biological or technical complication or failures over 5 and 10 years
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
Reconstructions seated 82 9 20 39 15 10
Free of any complications after 5 years (%) 91.4 88.9 100 79.4 60 80
95% CI (82.7–95.8) (43.3–98.4) (82.4–100) (63–89.1) (31.8–79.6) (40.9–94.6)
Free of any complications after 10 years (%) 70.3 88.9 74.7 49.8 Not enough data 25
95% CI (57.4–79.9) (43.3–98.4) (45.4–89.8) (32.4–64.9) (4.1–54.2)
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP-tt, fixed partial denture with cantilever extensions on teeth; ii, implant supported; CI, confidence
interval; ti, tooth–implant supported.
Bra¨gger et al _ Failure and complication rates of FDP
74 | Clin. Oral Impl. Res. 22, 2011 / 70–77 c_ 2010 John Wiley & Sons A/S
tions of 86.7% in the present study compares
well with that of 88.9% reported in the systematic
review (Aglietta et al. 2009).
Biological/technical complications
Based on the events observed over 10 years,
the parameter of annual event rate per 100
reconstructions per year was calculated for both
technical and biological complications. These
annual rates ranged from 0 to 2 for FDPs
with end abutments but, again, were much
higher in the cantilever reconstruction groups
(c-FDP), ranging from 5 to 6.1 annual events
per 100 reconstructions.
Consequently, the cumulative risk for biological
or technical complications at 5 and 10 years
resulted in considerable differences between the
groups of reconstructions. The IRR at 10 years
(and over the entire observation period) ranged
from 1.4 up to 8.66. Eventually, this resulted in
low probabilities for the reconstructions to
remain completely free of any complications/
failures at 10 years.
Pjetursson & Lang (2008) presented a concept
for prosthetic treatment planning on the basis of
scientific evidence and applied it to eight clinical
situations in which the preferred treatment option
for fixed reconstructions was propagated.
The results of systematic reviews formed one
base for this concept. However, single studies
were carefully analyzed as well, as systematic
reviews tend to pool data from diverse patient
populations, treatment concepts, dentists, technicians,
materials and designs of reconstructions
(Walton 2002).
By defining strict inclusion criteria and by
providing statistical analyses that consider different
observation periods, different numbers of
objects, confidence intervals, etc., some of the
weak aspects of ‘‘pooling’’ data may be reduced.
In addition, the process of analyzing data for
systematic reviews points to the fact that outcomes
are still not being reported in an internationally
accepted standardized way. Reporting
complications in detail will eventually lead to
improved quality of future reports (Karlsson
1989; Decock et al. 1996; Salvi & Bra¨gger 2009).
Moreover, in evaluating the literature for clinical
treatment planning, the effects of single
cohorts have to be analyzed. In a specialist clinic
for prosthodontics, a patient cohort (Group 1)
treated in the years from 1989 to 1993 was
compared with a patient cohort benefitting from
the options of implant-supported reconstructions
being treated from 1992 to 2001 (Group 2). A
significant shift in the survival of single crowns
and FDPs on teeth was observed (Walton 2009a,
2009b). In Group 1, the estimated survival of
FDPs was 77 _ 8% at 10 years, while the
survival rate in Group 2 reached 90 _ 6% (still
NS, Po0.05). Three-unit FDPs were surviving
up to 97 _ 2% in Group 2.
In Group 1, devital abutment teeth of FDPs
demonstrated a reduced survival (89 _ 3%)
compared with Group 2 (96 _ 2%) (w2,
Po0.05). In Group 2, the fracture rate and losses
due to progression of periodontal disease were
also less frequent.
Because of the introduction of implants, the
span length and complexity of the provided FDPs
on teeth and the use of biologically and structurally
compromised abutment teeth were reduced
in Group 2 (Walton 2009a, 2009b).
Tooth–implant-supported FDPs have been presented
as an acceptable treatment option (Bra¨gger
et al. 2001; Lang et al. 2004; Nickenig et al.
2008), although higher risks for failures and
complications have been observed (Bra¨gger et al.
2005; Pjetursson et al. 2007).
The results of the present study appear to
validate the recommendation of an acceptable
treatment option, as tooth–implant-supported
FDPs did not result in increased failure and
complication rates compared with the FDP-tt
and FDP-ii.
The obvious discrepancy of the results of the
present study for the 10-year data of combined
tooth–implant supported reconstructions with
those of a systematic review (Lang et al. 2004)
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25
Observation time (years)
FDP-tt FDP-ii FDP-ti
c-FDP-tt c-FDP-ii c-FDP-ti
Kaplan-Meier survival function
FDP Fixed partial denture on end abutments tt tooth-supported
c-FDP Fixed partial denture with cantilever
extension
ii implant-supported
ti tooth-implant supported
Fig. 1. Fixed dental prostheses (FDPs) free from complication or failure by type of FDP (Kaplan–Meier survival function).
Table 6. Incidence rate ratio and 95% confidence interval of failures incl. complications by type of FDP
in the first 10 years and over the entire observation period (univariable)
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
First 10 years
Failure I 0 2.33 8.66n 6.38 3.95
95% CI 0–59.9w 0.21–25.51 1.93–38.8 0.93–43.88 0.38–40.93
Failure and complications
combined
I 0.6 0.85 1.97n 3.76n 3.31n
95% CI 0.07–4.99 0.3–2.41 1.15–3.35 1.62–8.73 1.65–6.63
Complete observation time
Failure I 0 0.84 4.16n 2.42 1.41
95% CI 0–9.75w 0.1–6.91 1.89–9.42 0.52–11.24 0.18–10.83
Failure and complications
combined
I 0.97 0.85 1.77n 3.21n 2.64n
95% CI 0.26–3.57 0.35–2.08 1.08–2.91 1.44–7.16 1.28–5.44
nPo0.05 (from Poisson’s regression).
wFrom exact Poisson’s regression.
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP-tt, fixed partial denture with cantilever
extensions on teeth; ii, implant supported; CI, confidence interval; ti, tooth–implant supported.
Bra¨gger et al _ Failure and complication rates of FDP
c_
2010 John Wiley & Sons A/S 75 | Clin. Oral Impl. Res. 22, 2011 / 70–77
is striking (94.4% vs. 77.8%). Because of the fact
that the actual number of FDPs t-i from which
long-term data were available for analysis in the
systematic review was small, changes in the
recommendations for treatment planning may
be explained. Combining evidence from the literature
with clinical logic may be optimal for
presenting practical guidelines (Greenstein et al.
2009) to improve the chance for a successful
tooth–implant-supported FDP.
The most obvious finding of the present report
was the confirmation of ‘‘cantilever extensions’’
as a technical risk factor.
In a retrospective evaluation of cFDP-tt that
had been incorporated 5–16 years before a followup
examination, biological and/or technical problems
in one out of every five abutment tooth
were reported (Ha¨mmerle et al. 2000). The same
abutment tooth could have been affected by
biological and technical complications at the
same time. The most frequent biological complication
was the loss of pulp vitality in 10% of
originally vital abutment teeth. The most frequent
technical complication was the loss of
retention, which occurred in 12% of non-vital
and in 4% of vital abutment teeth.
Moreover, a list of failures/complications from
137 re-examined c-FDPs of 213 originally placed
restorations after a mean exposure time of 6 years
(range 2–18 years) was presented (Decock et al.
1996). The Kaplan–Meier survival reached 60%
at 12 years. Sixty percent of the failures were true
failures leading to the loss of the reconstructions,
while in 40%of the ‘‘failures’’, a restoration could
be placed, endodontic or periodontal therapy was
provided or the c-FDPs could be recemented.
When cFDP-tt were followed over longer observation
periods in the same clinic (De Backer et
al. 2007), the failures in c-FDPs on devital abutment
teeth occurred earlier and were more frequent
compared with c-FDPs on vital teeth.
In a systematic review on cantilever reconstructions
on teeth (Lang et al. 2004), the following
annual rates of technical and biological
complications were listed for cFDP-tt: 0.95 for
caries of abutments, 3.95 loss of vitality, 1.75
loss of retention, 0.61 veneer frame work fracture
and 0.72 chipping of ceramic or fracture.
On the other hand, another systematic review
on cantilever reconstructions on implants
(Aglietta et al. 2009) reported the following rates
for biological and technical complications for
cFDP-ii after 5 years of function:
Periimplantitis: 9.4% of cFDP-ii, 10.5% veneer
fractures (3.9–26.6%), 8.5% screw loosening
(3.9–17%), 5.7% loss of retention (1.9–
16.5%), 2.1% abutment fractures (0.9–5.1%)
and 1.5% implant fractures (0.2–8.5%).
Limitations
The data obtained from this cohort of patients
need to be interpreted with caution.
First of all, only a small number of reconstructions
could be observed in each group of FDPs.
Many different clinical situations and reconstruction
designs were pooled. There were more than
20 dentists and more than 10 different technical
laboratories involved in the fabrication of the
reconstructions and this was not considered in
the evaluation of the data.
With the statistical analyses applied by
choosing IRR (Table 6), a statistically significant
increased risk for failure and failure and/or any
complication was noted for the groups of reconstructions
with extensions.
This information and the comparison with
other data in the literature can only be of partial
value while choosing between several treatment
options in restoring a particular patient with
FDPs. It must be stressed that many other factors
must also be considered andmay even lead to the
preference of an FDP design, which was found to
be at a greater risk in this or in other reports.
Among these factors are the following: the
particular clinical anatomical situation, the
expertise of the clinician and the technician,
themanufacturing processes, the alternative risks
or chances of, i.e., augmentation procedures,
placing more implants and finally, economic
aspects.
It seems to be extremely strenuous to design a
clinical study that considers all these factors.
Nevertheless, clinicians should be motivated to
systematically collect and document all relevant
information at regular intervals, thereby providing
the basis for amoremeaningful interpretation
of the survival and success rates of the reconstructions
inserted.
Conclusions
In conclusion, patients treated for chronic
periodontitis and provided with ceramo-metal
FDPs yield high survival rates, especially for
FDPs with end abutments. The incidence
rates of any negative events were drastically
increased in the three groups with cantilever
extensions c-FDPs (tt, ii, ti).
Strategic decisions in the choice of a particular
FDP design and the choice of teeth/implants
as abutments appear to influence the risks
for complications to be expected with fixed
reconstruction. If possible, extensions based
on tooth abutments should be avoided or used
only after a cautious clinical evaluation of all
options.
Acknowledgements: This study has
been supported in part by the Clinical
Research Foundation (CRF) for the Promotion
of Oral Health, Brienz, Switzerland. The
competent clinical performance of the Dental
Assistants of the Clinic for Periodontology and
Fixed Prosthodontics, University of Berne is
gratefully acknowledged. Moreover, the
competent and reliable service provided by the
Dental Hygienists of the Clinic during long
years of patient maintenance is highly
recognized.
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Bra¨gger et al _ Failure and complication rates of FDP
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2010 John Wiley & Sons A/S 77 | Clin. Oral Impl. Res. 22, 2011 / 70–77
Complication and failure rates of fixed
dental prostheses in patients treated for
periodontal disease
Urs Bra¨gger
Stefanie Hirt-Steiner
Natascha Schnell
Kurt Schmidlin
Giovanni E. Salvi
Bjarni Pjetursson
Giedre Matuliene
Marcel Zwahlen
Niklaus P. Lang
Authors’ affiliations:
Urs Bra¨gger, Stefanie Hirt-Steiner, Natascha Schnell,
Giovanni E. Salvi, Giedre Matuliene, School of Dental
Medicine, University of Bern, Bern, <st1:country-region>Switzerland
Kurt Schmidlin, Marcel Zwahlen, Institute of Social
and Preventive Medicine, University of Bern, Bern,
<st1:country-region>Switzerland
Bjarni Pjetursson, Faculty of Odontology, University of
<st1:country-region>Iceland, Reykjavik, <st1:country-region>Iceland
Niklaus P. Lang, Faculty of Dentistry, The University
of Hong Kong, Hong Kong, SAR <st1:country-region>China
Corresponding author:
Dr Prof. Urs Bra¨gger
School of Dental Medicine
University of Bern
Freiburgstrasse 7
3010 Bern
Switzerland
Tel.: t41 31 632 2541
Fax: t41 31 632 4931
e-mail: urs.braegger@zmk.unibe.ch
Key words: cantilever extensions, complications, dental implants, failures, FDP, fixed dental
prostheses, periodontitis, supportive periodontal therapy
Abstract
Objectives: To evaluate the biological and technical complication rates of fixed dental prostheses
(FDP) with end abutments or cantilever extensions on teeth (FDP-tt/cFDP-tt) on implants (FDP-ii/cFDPii)
and tooth-implant-supported (FDP-ti/cFDP-ti) in patients treated for chronic periodontitis.
Material and methods: From a cohort of 392 patients treated between 1978 and 2002 by graduate
students, 199 were re-examined in 2005. Of these, 84 patients had received ceramo-metal FDPs (six
groups).
Results: At the re-evaluation, the mean age of the patients was 62 years (36.2–83.4). One hundred and
seventy-five FDPs were seated (82 FDP-tt, 9 FDP-ii, 20 FDP-ti, 39 cFDP-tt, 15 cFDP-ii, 10 cFDP-ti). The
mean observation time was 11.3 years; 21 FDPs were lost, and 46 technical and 50 biological
complications occurred. Chances for the survival of the three groups of FDPs with end abutments were
very high (risk for failure 2.8%, 0%, 5.6%). The probability to remain without complications and/or
failure was 70.3%, 88.9% and 74.7% in FDPs with end abutments, but 49.8–25% only in FDPs with
extensions at 10 years.
Conclusions: In patients treated for chronic periodontitis and provided with ceramo-metal FDPs, high
survival rates, especially for FDPs with end abutments, can be expected. The incidence rates of any
negative events were increased drastically in the three groups with extension cFDPs (tt, ii, ti).
Strategic decisions in the choice of a particular FDP design and the choice of teeth/implants as
abutments appear to influence the risks for complications to be expected with fixed reconstruction. If
possible, extensions on tooth abutments should be avoided or used only after a cautious clinical
evaluation of all options.
Today, partially edentulous patients are increasingly
aware of their functional, esthetic and social
handicaps.
An epidemiologic survey of the prevalence of
reconstructions in various age cohorts of Swiss
citizens revealed that, in the younger age groups,
fixed dental prostheses (FDPs) were more frequent
compared with removable partial dentures.
Over the last decades, the prevalence of removable
partial or full denture wearers shifted to the
very old age groups in industrialized countries.
Hence, removable partial dentures seem to be
less accepted in some European societies (Zitzmann
et al. 2007).
As an alternative to extensive reconstructions
on, e.g., furcation-involved molar teeth or the
installation of dental implants placed in the
posterior area, the concept of a shortened
dental arch may be acceptable by most patients
(Ka¨yser 1981, 1994). A shortened dental
arch limited to the premolar occlusionmay result
in sufficient occlusal stability, chewing efficacy
and no increased risk for temporo-mandibular
disorders (Witter et al. 1994a,1994b, 2001,
2007). As long as all premolar regions and one
occluding pair of molars were present, practically
no complaints about the chewing efficacy were
reported (Sarita et al. 2003). In cases with severely
reduced dental arches with 0–2 pairs of
occluding premolars only, however, patients frequently
expressed severe complaints (Sarita et al.
2003).
Date:
Accepted 8 September 2010
To cite this article:
Bra¨gger U, Hirt-Steiner S, Schnell N, Schmidlin K, Salvi GE,
Pjetursson B, Matuliene G, Zwahlen M, Lang NP.
Complication and failure rates of fixed dental prostheses in
patients treated for periodontal disease.
Clin. Oral Impl. Res. 22, 2011; 70–77.
doi: 10.1111/j.1600-0501.2010.02095.x
70 c_ 2010 John Wiley & Sons A/S
Before the period in which implants became a
predictable treatment to add functional units in
free-end situations, fixed dental prostheses with
distal cantilever extensions were frequently incorporated.
Occasionally, FDPs with cantilever
extensions were also chosen in order to avoid
additional preparations of teeth adjacent to edentulous
spaces, i.e., in cases of intact crowns or
still acceptable existing reconstructions. Cantilever
extension FDPs, however, demonstrated increased
failure rates at 10 years compared with
conventional end-abutment fixed bridgework
(Pjetursson et al. 2004, Tan et al. 2004). Moreover,
at 5 years, higher technical complication
rates were reported (Ha¨mmerle et al. 2000; Pjetursson
et al. 2007).
The incorporation of fixed dental prostheses on
abutment teeth requires the preparation of a
dentinal core with or without prior root canal
treatment, with or without composite build-ups
that may or may not require the placement of
posts and cores.
The risks encountered with dental reconstructions
are related to the complexity and the
cumulative number of the interventions required
(Miyamoto et al. 2007; De Backer et al. 2007).
For single crowns on teeth, increased failure rates
were observed in the absence of a considerable
dentinal core (ferrule) and in cases with cast posts
and cores (Creugers et al. 2005; Schmidlin et al.
2010).
Since the late 1980s, treatment planning in
fixed prosthodontics has been revolutionized by
the possibility of incorporating implant-borne
reconstructions. Tissue-integrated implants now
serve as the basis for single crowns and may be
used strategically correctly distributed in edentulous
ridges to receive the fixed dental prostheses.
Guided bone regeneration in combination with
grafting procedures may be applied to predictably
create the necessary bone volume for a particular
implant site. Furthermore, the need for complex
pretreatment of abutment teeth with a doubtful
prognosis seems to become obsolete with implants
being chosen as abutments (Walton
2009a, 2009b).
Because of anatomical/surgical and strategic
prosthetic considerations, the FDP on implants
may include distal and/or mesial cantilever extensions.
In a situation with an abutment tooth
in need of a restoration and with a good prognosis
adjacent to an edentulous space, a mixed tooth–
implant-supported FDP may still be preferred.
Decision-making processes for treatment planning
are challenging in daily practice. Furthermore,
patients must be informed about potential
risks associated with various treatment concepts.
The expectations related to the longevity of
required reconstructions in younger age cohorts
are high due to the considerable costs involved,
especially for fixed dental prostheses on teeth or
implants (Petersson et al. 2006; Incici et al.
2009).
Choosing from available options of restorations,
the longevity and complication rates
should be considered in order to estimate the
complexity of maintenance service to be expected
(Bouchard et al. 2009).
A series of systematic reviews based on clinical
studies have collected the combined estimated
annual failure and complication rates and cumulative
risks at 5 and 10 years with reconstructions
on teeth or implants (Tan et al. 2004; Lulic et al.
2007; Pjetursson et al. 2007; Aglietta et al. 2009).
However, the data available to base decision
making for the preference of a particular reconstruction
for a particular patient are still sparse. In
the systematic reviews mentioned above, o100
reconstructions could actually be evaluated for
some patient cohorts with a detailed description
of all events observed over 5, 10 or even more
years.
Patients with risk factors such as a history of
periodontal disease, smoking (Heitz-Mayfield &
Huynh-Ba 2009) and bruxism (Salvi & Bra¨gger
2009) may demonstrate higher event rates of
failures and complications than patients without
such conditions. To what extent these conditions
may lead to increased and more complex maintenance
and repair service is of particular interest
to the clinician.
The purpose of this study was to evaluate
retrospectively the biological and technical failure
and complication rates with FDPs in partially
edentulous patients treated for chronic periodontitis.
Material and methods
Patient accrual
For this retrospective cohort study, patients with
chronic periodontitis who had been treated by
graduate students as a part of their educational
training at the Department of Periodontology and
Fixed Prosthodontics, University of Bern, during
the period 1978–2002 were recruited. The patient
cohort has been characterized recently. At
the first examination, the proportion of patients
with periodontitis defined as ‘‘patients with interproximal
probing attachment loss of 5mm in
30% of the teeth present’’ was 88.1%. If the
definition of probing attachment loss of 5mm at
two non-adjacent teeth was chosen, 97.5% of the
cases were advanced periodontitis patients (Matuliene
et al. 2008).
Comprehensive dental treatment
All patients had been treated according to a
comprehensive treatment protocol (Lang & Lo¨e
1993). In brief, following complete periodontal,
endodontic and cariologic as well as complete
radiographic examinations, a treatment plan was
established and discussed with the patient in a
case presentation. This was followed by oral
hygiene instructions and the performance of
cause-related initial periodontal therapy (i.e.,
scaling and root planing under local anesthesia).
After 6–8 weeks, a thorough evaluation of the
outcomes of initial therapy was performed. Subsequently,
periodontal surgery was performed if
indicated. The condition after periodontal therapy
in this patient cohort has been characterized
recently by Matuliene et al. (2008). Only 2.9% of
the remaining pocket depths were 44mm, 30%
of the patients had a full-mouth bleeding index
o10% and 45% within 10% and 25%.
Root canals of devital teeth in need of treatment
were filled with guttapercha and AH26 or
AHt. In case of severely reduced dentinal cores,
placement of an indirect cast post and core was
implemented. Implants were placed to avoid
preparation of intact and healthy teeth or to avoid
the replacement of still acceptable adjacent restorations.
Finally, prosthetic therapy using dental
implant or tooth supported FDPs or single unit
crowns was performed. The restorations consisted
of ceramo-metal reconstructions that
were cemented with zinc phosphate or glass
ionomer cement.
Following the completion of comprehensive
treatment, patients were enrolled in a supportive
periodontal therapy (SPT) program at the clinic of
the University of Bern or they were referred back
to private practitioners for SPT.
Clinical examination
From the 392 original cases treated and documented
according to the requirements for the
specialty board certification of the Swiss Federal
Office for Health, 199 could be recruited and reexamined
during the year 2005. The remaining
193 patients had either moved away from the
area, were too frail to participate at the re-examination
or were deceased.
At the re-examination, the patients first filled
out a questionnaire related to changes in general
health aspects, their experiences with the reconstructions
and the frequency of recall sessions
during the last years.
The clinical examination included the enumeration
of teeth, implants and reconstructions
as well as the type of reconstruction and the
number of replaced teeth per reconstruction. A
complete periodontal chart revealed the recession
and the probing pocket depths (PPD) in relation
to the cemento-enamel junction or implant
shoulder at six aspects of each tooth/implant.
The presence of BOPt or BOP_ sites was
Bra¨gger et al _ Failure and complication rates of FDP
c_
2010 John Wiley & Sons A/S 71 | Clin. Oral Impl. Res. 22, 2011 / 70–77
noted. Probing was performed by means of an
electronic device (Florida Probe Corporation,
Gainesville, FL, USA) with a standardized dimension
and force set at 0.15N. Abutment teeth
were tested for pulp vitality (CO2 test) and the
presence of carious lesions. Reconstructions and
implant components were examined carefully for
any mechanical and/or technical complications.
The radiographic examination included an
orthopantomogram as well as periapical intraoral
radiographs from the crowned teeth and/or implants.
Episodes of failures and/or complications were
derived from the patient charts in case the
patients remained as recall patients at the clinic
or from the questionnaires in case the patients
returned to private practice for maintenance care.
Evaluation of complications
The evaluation of biological complications included
caries at abutment teeth, loss of tooth
vitality, presence or absence of a periapical endodontic
lesion, periapical endodontic lesion and
caries, periodontitis (PPD _ 6mm) and BOPt,
periimplantitis (PPD _ 6mm; according to the
criteria defined in Karoussis et al. (2003)) and
BOPt, abscess formation, root fracture and/or
dentin core fracture if present.
The assessment of mechanical/technical complications
included the identification of loss of
retention, loosening of occlusal screws, ceramic
chipping, fracture of the framework and/or implant
abutment fracture (Salvi & Bra¨gger 2009).
A failure was defined as a biological, technical
or traumatic event leading to either the extraction
of the tooth or the explantation/loss of the
implant or the loss of the original FDP.
Classification of reconstructions
The FDPs were classified into six different categories:
FDPs with either end abutments or cantilever
extension FDPs on teeth (FDP-tt/cFDP-tt), FDPs
with either end implant abutments or cantilever
extensions on implants (FDP-ii/cFDP-ii) or connecting
teeth and implants (FDP-ti/cFDP-ti).
Statistical analysis
The null hypothesis postulated no difference in
the survival/success rates between the different
designs of FDPs.
The data collected were grouped according to
six categories: fixed dental prostheses with end
abutments or cantilever extensions on teeth
(FDP-tt/cFDP-tt), on implants (FDP-ii/cFDP-ii)
ormixed on teeth and implants (FDP-ti/cFDP-ti).
Descriptive statistics listed the number of
reconstructions incorporated as well as the number
of reconstructions with complications and
failures observed over 5 and 10 years and over
the entire observation period (events per 100
years of object-time).
The cumulative risk after 5 and 10 years of
observation was calculated by subtracting the
Kaplan–Meier survival function from 1. Event
rates per 100 years of object-time were calculated
by dividing the number of events by the total sum
of the time an object was under observation.
Event rates were calculated for complications
(biological and technical) and failures (biological,
technical and traumatic). The Kaplan–Meier
survival function was used to calculate the probability
of a reconstruction being free of any
complication (biological and technical) or failure
(biological, technical and traumatic). Poisson’s
regression was used to compare the six different
categories of bridges with respect to the incidence
rate of failures, and of failures and complications
by calculating the rate ratios for the first 10 years
and over the complete observation time. For
some patients, more than one reconstruction
was included in the analyses. By calculating
robust standard errors in the Poisson regressions,
this correlation was accounted for.
For event rates and for incidence rate ratios
(IRR), the estimates and 95 percent confidence
intervals were reported based on the assumption
that the number of events is Poisson’s distributed
for a given sumof observation time. The P-values
reported are two-sided. For the cumulative incidence,
95% confidence intervals are reported
based on those obtained from the Kaplan–Meier
estimates. All analyses were performed using
Stata Version 11 (Stata Corporation, College
Station, TX, USA).
Results
Patients
From the 199 patients re-examined, 84 patients
had received fixed dental prostheses. Fifty-one
were female and 33 were male patients.
The mean age of the patients at the re-evaluation
was 62 years (range 36.2–83.4 years).
FDPs
In these patients, 175 FDPs had been seated. As
indicated in Table 1, 82 were FDP-tt, 9 were
FDP-ii, 20 were FDP-ti, 39 were cFDP-tt, 15
were cFDP-ii and 10 were cFDP-ti (Table 1).
One hundred and eleven FDPs were reconstructions
with end abutments and 64 were
reconstructions with cantilever extensions.
One hundred and twenty-one FDPs were tooth
supported, 24 FDPs were implant supported and
30 FDPs were tooth–implant supported reconstructions.
5.14% of the reconstructions consisted of two
units, 34.86% were three-units, 28.57% fourunits
and 31.43% 5–14-unit FDPs.
Abutments
Three hundred and fifty-six teeth and 86 implants
were restored with FDPs. Over the entire
observation period, 33 (9.3%) abutment teeth in
14 patients and two (2.3%) implants in two
patients were lost.
Observation time
The mean observation time of all the 175 FDPs
was 11.31 years (range 2.29–26.42 years). The
mean observation time of FDPs and c-FDPs on
teeth was longer (12.1 and 13.66 years, respectively)
compared with FDPs and c-FDPs on implants
(7.43 and 8.21 years) and compared with
mixed FDPs and c-FDPs (8.13 and 10.04 years).
Failures of the reconstructions
From the 175 originally seated reconstructions,
24 (13.7%) resulted in a failure. Twenty-one
failures of the reconstructions were associated
with the loss of teeth or implants. One was a
complete loss of an FDP and two were partial
losses of the FDPs.
Complications observed over the entire
observation period
In Table 2, the frequencies of various technical
and biological complications occurring over the
observation period are listed including all the
events. Fifty-nine biological complications occurred
over the entire period (including all
events): 11 caries, three loss of vitality, 13 periodontitis,
nine peri-implantitis, 12 periapical lesions,
five fractures and six combined lesions.
Forty-six technical complications occurred
over the entire observation period (including all
events): 17 ceramic chippings, 24 loss of retention,
three fractures of prosthetic components
(abutments), one loose occlusal screw, one
‘‘crown fracture’’, one trauma and one combined
lesion.
In Table 3, the estimated annual rates of
complications and failures per 100 FDPs are
listed. These estimated rates were based on the
Table 1. Number of FDPs in each category
Number
of FDPs
Number
of c-FDPs
tt 82 39
ii 9 15
ti 20 10
tt, tooth supported; ii, implant supported; ti,
tooth–implant supported; FDP, fixed partial
denture on end abutments; c-FDP, fixed partial
denture with a cantilever extension.
Bra¨gger et al _ Failure and complication rates of FDP
72 | Clin. Oral Impl. Res. 22, 2011 / 70–77 c_ 2010 John Wiley & Sons A/S
actual number of observed events in the first 10
years. Within the first 10 years, 40 biologic and
30 technical complications and 14 failures occurred.
The estimated annual event rates for biological
complications per 100 reconstructions ranged
from 0 to 2 for FDP with end abutments and
from 4.6 to 6.1 for FDPs with cantilever extensions.
The estimated annual event rates for technical
complications per 100 reconstructions ranged
from 0.6 to 1.9 for FDPs with end abutments
and from 1.9 to 7.8 for FDPs with cantilever
extensions.
The estimated annual event rates for loss of the
reconstruction per 100 FDPs ranged from 0 to 0.7
for FDPs with end abutments and from 1.1 to 2.5
for FDPs with extensions.
In Table 4, the estimated cumulative risks of a
complication or a failure at 5 and 10 years of
observation are listed, grouped according to the
six types of FDPs.
The cumulative risk for loss (failure) for FDPtt/
ii/ti and c-FDP t-I was 0 at 5 years and for
FDP-ii at 10 years.
The cumulative risk for loss (failure) for c-
FDPs was considerably higher at 5 and 10 years,
respectively, ranging from 10% to 23.6%.
The cumulative risk for biological complications
was still low for most of the types of FDPs,
with the exception of cFDP-tt (18.4%) and cFDPti
(10%) at 5 years, but increased for most of the
reconstructions at 10 years, when FDP-ii still had
a 0% risk, and the risks for other FDPs with end
abutments were 18.8% and 17.8%, respectively.
In the group of FDPs with cantilever extensions,
the cumulative risk at 10 years reached values
ranging from 43.2% to 70.4%.
The cumulative risks for technical complications
ranged from 0% to 35.7% at 5 years and
from 9.1% to 65% at 10 years.
In Table 5, the probabilities for the FDPs of
remaining free from any complication/failure
over 5 and 10 years are listed.
Already at 5 years, the FDPs with cantilever
extensions had lower probabilities to remain
completely unaffected (60–80%) compared with
FDPs with end abutments (88.9–100%).
At 10 years, the probability of remaining free
from complications/failures ranged from 70.3%
to 88.9% for FDP with end abutments, but was
clearly reduced to 25% and 49.8% in the group
with cantilever extensions.
In Fig. 1, the decreases in the number of FDPs
free from complications and failures are depicted
for each category using the Kaplan–Meier survival
function.
In Table 6, the IRR of failures, and failures
combined with any complications are listed for
the six groups of FDPs. Only the first 10 years as
well as the entire observation period were considered.
The rates of events observed in the group FDPtt
were chosen as a reference. Compared with the
reference, the IRR were reduced in seven out of
eight comparisons, with the most favorable values
for the failure of FDP-ii.
The IRR, however, were increased in c-FDPs
in 12 out of 12 comparisons.
Discussion
This study was undertaken to evaluate the biological
and technical complication and failure
rates encountered with fixed dental prostheses
on teeth and implants in partially edentulous
patients who had been treated for advanced periodontitis.
As reported recently (Schmidlin et al. 2010), 64
out of 199 patients re-examined in this study had
received 168 single crowns on either a tooth with
a vital pulp (56), an endodontically treated tooth
(34), a tooth with a cast post and core (39) or an
implant (39). During a mean observation period
of 11.8 years, 19 single crowns were lost. All the
crowns were ceramo-metal crowns. In that respect,
the presence of severe loss of dentin requiring
the fabrication of a cast post and core resulted
in the highest rate of failures.
From the 199 patients who were re-examined,
84 had received FDPs. Altogether, 24 out of 175
reconstructions were lost after an observation
period of about 11 years (range 2.29–26.42). For
all the parameters assessed, a trend for more
frequent negative events was observed for FDPs
with cantilever extensions. The time in function
of the FDPs of the present study was considerable.
Titles of published reports often report
observation times reaching far beyond 10 years.
However, when the means and ranges of the
actual observation times are scrutinized, a more
realistic estimation of the exposure times of the
reconstructions is revealed. Thus, up to 18- or
Table 2. Complications
Event details Frequencies % Cumulative
Biological events
Root fracture 1 0.9 50.5
Caries and excessive bone loss 1 0.9 51.4
Periapical disease and caries 2 1.9 49.5
Loss of vitality 3 2.8 13.1
Caries and periodontitis 3 2.8 47.7
Periimplantitis 9 8.4 33.6
Caries 11 10.3 10.3
Periapical disease 12 11.2 44.9
Periodontitis 13 12.2 25.2
Technical Events
Loosening of occlusal screw 1 0.9 97.2
Fracture of a crown framework 1 0.9 98.1
Trauma 1 0.9 99
Ceramic chipping and crown framework fracture 1 0.9 100
Fracture of secondary part (component) 3 2.8 96.2
Abutment fracture 4 3.7 55.1
Ceramic chipping 17 15.9 71
Loss of retention 24 22.4 93.4
Total 107 100
Table 3. Estimated annual rate of complications and failures per 100 FDPs based on the number of
events observed in the first 10 years
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
Reconstructions seated 82 9 20 39 15 10
Biological complications
Number of events in the first 10 years 12 0 3 15 5 5
Annual event rate per 100 crowns 1.8 0 2 5 4.6 6.1
95% CI 1–3.1 0–6 0.6–6.3 3.3–7.6 1.9–11 3–12.5
Technical complications
Number of events in the first 10 years 11 1 1 6 6 5
Annual event rate per 100 crowns 1.7 1.9 0.6 1.9 7.8 7.4
95% CI 1–3 0.2–15 0.1–4.3 0.9–4 2.8–21.5 3.3–16.5
Failures
Number of events in the first 10 years 2 0 1 8 2 1
Annual event rate per 100 crowns 0.3 0 0.7 2.5 1.8 1.1
95% CI 0.1–1.1 0–6 0.1–4.8 1.4–4.5 0.5–7.4 0.2–7.8
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP, fixed partial denture with cantilever
extension; ii, implant supported; CI, confidence interval; ti, tooth–implant supported.
Bra¨gger et al _ Failure and complication rates of FDP
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2010 John Wiley & Sons A/S 73 | Clin. Oral Impl. Res. 22, 2011 / 70–77
20-year long-term results may actually be reduced
to a mean observation period of about 10
years (De Backer et al. 2006a, 2006b; Decock
et al. 1996).
The detailed event rates/risks observed with
the different designs of the FDPs of this study
will be compared with the findings from other
reports.
Survival/failure
The chances for survival of the FDP-tt over 5 and
10 years were very favorable for reconstructions
observed in the present report (risk for failure 0%
and 2.8%). Based on seven publications with
2088 FDP-tt exposed to 11,998 years, the estimated
chance for survival was 93.3% at 5 years.
Based on eight publications with 1218 FDP-tt
exposed for 10,446 years, the estimated chance
for survival at 10 years was 89.2% (Pjetursson et
al. 2007).
In the present report, the most favorable
chance for survival was demonstrated by the
FDP-ii (100%). This is superior to survival rates
of 95.2% at 5 years reported in a systematic
review based on 17 papers, with 1384 FDP-ii
exposed to 6989 years and 86.7% at 10 years
reported in only three papers with 219 FDP-ii
exposed to 1889 years (Pjetursson et al. 2007).
Although subject to speculation, the reason for
this favorable outcome in the present study may
be explained on the basis of a careful presurgical
risk evaluation consequently performed for implant
patients in this cohort. Likewise, the patients
receiving implants for combined tooth–
implant supported reconstructions yielded higher
survival rates after 5 and 10 years compared with
those of systematic reviews (0% failure at 5 years
and 5.6% failures at 10 years). In those, much
lower estimated values were reported (Pjetursson
et al. 2007). Based on six studies, 199 FDP-ti
were exposed to 976 years of function and had a
chance for survival of 95.5% at 5 years. For 10
years, this was significantly reduced to 77.8%.
Only 72 FDP-ti could be analyzed and were
exposed to 517 years (Pjetursson et al. 2007).
In the present report, cFDPs-tt with cantilever
extensions demonstrated higher risks for failures
(10% at 5 years and 23.6% at 10 years) compared
with FDPs-tt with end abutments. This difference
between the survival of the two categories is
in agreement with the recent systematic review
(Pjetursson et al. 2007). Based on six papers with
432 cFDP-tt exposed to 2112 years, the chance
for survival was 94.4% at 5 and reduced to
80.3% at 10 years (based on six papers with
239 cFDP-tt exposed for 2229 years (Pjetursson
et al. 2007).
The cumulative risk for the failure of cantilever
reconstructions on implant abutments (cFDP-ii)
reached 13.3% at 5 years and remained at 13.3%
at 10 years in the present report. In a recent
systematic review (Aglietta et al. 2009), five
clinical studies with 180 cFDP-ii were included
and yielded a cumulative chance of survival of
94.3% at 5 and 88.9% at 10 years, respectively.
Comparison of the results of the present evaluation
on 5- and 10-year survival of tooth- or
implant-supported cantilever reconstructions
with those of the systematic reviews (Pjetursson
et al. 2007; Aglietta et al. 2009) that covered the
entire dental literature reporting on a mean observation
period of at least 5 years reveals 4–8%
lower survival after 5 years and 2–4% lower
survival after 10 years. These differences appear
to be small and not significant and may not have
to be justified. Especially, the 10-year survival
rate for implant-supported cantilever reconstruc-
Table 4. Estimated cumulative risk and 95% confidence interval of biological and/or technical complications and/or failures (including trauma) of FDP over
5 and 10 years of observation
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
Reconstructions seated 82 9 20 39 15 10
Reconstructions with biological complications
Cumulative risk (%) after 5 years 95% CI 2.5 0 0 18.4 0 10
(0.6–9.5) (0–37) (0–17.6) (9.2–34.8) (0–24.7) (1.5–52.7)
Cumulative risk (%) after 10 years 95% CI 18.8 0 17.8 43.2 70.4 58
(11–31.1) (0–52.2) (6.1–45.7) (28.5–62) (30–84.1) (28.5–89.4)
Reconstructions with technical complications
Cumulative risk (%) after 5 years 95% CI 6.2 11.1 0 5.4 35.7 20
(2.6–14.2) (1.6–56.7) (0–17.6) (1.4–20.1) (16.7–65.7) (5.4–59.1)
Cumulative risk (%) after 10 years 95% CI 15.6 11.1 9.1 18.2 Not enough data 65
(8.9–26.8) (1.6–56.7) (1.3–49.2) (8.5–36.3) (31.8–94.4)
Reconstructions lost
Cumulative risk (%) after 5 years 95% CI 0 0 0 10.4 13.3 0
(0–4.8) (0–36.9) (0–17.6) (4–25.4) (3.5–43.6) (0–52.2)
Cumulative risk (%) after 10 years 95% CI 2.8 0 5.6 23.6 13.3 10
(0.7–10.7) (0–52.2) (0.8–33.4) (12.4–42.1) 3.5–43.6 1.5–52.7
Biological complications included: caries, loss of vitality, periodontitis or periimplantitis (pocket depth _ 6mm, BOPt), periapical radiolucent zone, root or tooth fracture
and abscess.
Technical complications included: porcelain fracture, loss of retention, implant fracture, crown fracture and loosening of the occlusal screws.
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP-tt, fixed partial denture with cantilever extensions on teeth; ii, implant supported; CI, confidence
interval; ti, tooth–implant supported.
Table 5. Probability for FDPs to remain without any biological or technical complication or failures over 5 and 10 years
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
Reconstructions seated 82 9 20 39 15 10
Free of any complications after 5 years (%) 91.4 88.9 100 79.4 60 80
95% CI (82.7–95.8) (43.3–98.4) (82.4–100) (63–89.1) (31.8–79.6) (40.9–94.6)
Free of any complications after 10 years (%) 70.3 88.9 74.7 49.8 Not enough data 25
95% CI (57.4–79.9) (43.3–98.4) (45.4–89.8) (32.4–64.9) (4.1–54.2)
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP-tt, fixed partial denture with cantilever extensions on teeth; ii, implant supported; CI, confidence
interval; ti, tooth–implant supported.
Bra¨gger et al _ Failure and complication rates of FDP
74 | Clin. Oral Impl. Res. 22, 2011 / 70–77 c_ 2010 John Wiley & Sons A/S
tions of 86.7% in the present study compares
well with that of 88.9% reported in the systematic
review (Aglietta et al. 2009).
Biological/technical complications
Based on the events observed over 10 years,
the parameter of annual event rate per 100
reconstructions per year was calculated for both
technical and biological complications. These
annual rates ranged from 0 to 2 for FDPs
with end abutments but, again, were much
higher in the cantilever reconstruction groups
(c-FDP), ranging from 5 to 6.1 annual events
per 100 reconstructions.
Consequently, the cumulative risk for biological
or technical complications at 5 and 10 years
resulted in considerable differences between the
groups of reconstructions. The IRR at 10 years
(and over the entire observation period) ranged
from 1.4 up to 8.66. Eventually, this resulted in
low probabilities for the reconstructions to
remain completely free of any complications/
failures at 10 years.
Pjetursson & Lang (2008) presented a concept
for prosthetic treatment planning on the basis of
scientific evidence and applied it to eight clinical
situations in which the preferred treatment option
for fixed reconstructions was propagated.
The results of systematic reviews formed one
base for this concept. However, single studies
were carefully analyzed as well, as systematic
reviews tend to pool data from diverse patient
populations, treatment concepts, dentists, technicians,
materials and designs of reconstructions
(Walton 2002).
By defining strict inclusion criteria and by
providing statistical analyses that consider different
observation periods, different numbers of
objects, confidence intervals, etc., some of the
weak aspects of ‘‘pooling’’ data may be reduced.
In addition, the process of analyzing data for
systematic reviews points to the fact that outcomes
are still not being reported in an internationally
accepted standardized way. Reporting
complications in detail will eventually lead to
improved quality of future reports (Karlsson
1989; Decock et al. 1996; Salvi & Bra¨gger 2009).
Moreover, in evaluating the literature for clinical
treatment planning, the effects of single
cohorts have to be analyzed. In a specialist clinic
for prosthodontics, a patient cohort (Group 1)
treated in the years from 1989 to 1993 was
compared with a patient cohort benefitting from
the options of implant-supported reconstructions
being treated from 1992 to 2001 (Group 2). A
significant shift in the survival of single crowns
and FDPs on teeth was observed (Walton 2009a,
2009b). In Group 1, the estimated survival of
FDPs was 77 _ 8% at 10 years, while the
survival rate in Group 2 reached 90 _ 6% (still
NS, Po0.05). Three-unit FDPs were surviving
up to 97 _ 2% in Group 2.
In Group 1, devital abutment teeth of FDPs
demonstrated a reduced survival (89 _ 3%)
compared with Group 2 (96 _ 2%) (w2,
Po0.05). In Group 2, the fracture rate and losses
due to progression of periodontal disease were
also less frequent.
Because of the introduction of implants, the
span length and complexity of the provided FDPs
on teeth and the use of biologically and structurally
compromised abutment teeth were reduced
in Group 2 (Walton 2009a, 2009b).
Tooth–implant-supported FDPs have been presented
as an acceptable treatment option (Bra¨gger
et al. 2001; Lang et al. 2004; Nickenig et al.
2008), although higher risks for failures and
complications have been observed (Bra¨gger et al.
2005; Pjetursson et al. 2007).
The results of the present study appear to
validate the recommendation of an acceptable
treatment option, as tooth–implant-supported
FDPs did not result in increased failure and
complication rates compared with the FDP-tt
and FDP-ii.
The obvious discrepancy of the results of the
present study for the 10-year data of combined
tooth–implant supported reconstructions with
those of a systematic review (Lang et al. 2004)
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25
Observation time (years)
FDP-tt FDP-ii FDP-ti
c-FDP-tt c-FDP-ii c-FDP-ti
Kaplan-Meier survival function
FDP Fixed partial denture on end abutments tt tooth-supported
c-FDP Fixed partial denture with cantilever
extension
ii implant-supported
ti tooth-implant supported
Fig. 1. Fixed dental prostheses (FDPs) free from complication or failure by type of FDP (Kaplan–Meier survival function).
Table 6. Incidence rate ratio and 95% confidence interval of failures incl. complications by type of FDP
in the first 10 years and over the entire observation period (univariable)
FDP-tt FDP-ii FDP-ti c-FDP-tt c-FDP-ii c-FDP-ti
First 10 years
Failure I 0 2.33 8.66n 6.38 3.95
95% CI 0–59.9w 0.21–25.51 1.93–38.8 0.93–43.88 0.38–40.93
Failure and complications
combined
I 0.6 0.85 1.97n 3.76n 3.31n
95% CI 0.07–4.99 0.3–2.41 1.15–3.35 1.62–8.73 1.65–6.63
Complete observation time
Failure I 0 0.84 4.16n 2.42 1.41
95% CI 0–9.75w 0.1–6.91 1.89–9.42 0.52–11.24 0.18–10.83
Failure and complications
combined
I 0.97 0.85 1.77n 3.21n 2.64n
95% CI 0.26–3.57 0.35–2.08 1.08–2.91 1.44–7.16 1.28–5.44
nPo0.05 (from Poisson’s regression).
wFrom exact Poisson’s regression.
FDP, fixed partial denture on end abutments; tt, tooth supported; c-FDP-tt, fixed partial denture with cantilever
extensions on teeth; ii, implant supported; CI, confidence interval; ti, tooth–implant supported.
Bra¨gger et al _ Failure and complication rates of FDP
c_
2010 John Wiley & Sons A/S 75 | Clin. Oral Impl. Res. 22, 2011 / 70–77
is striking (94.4% vs. 77.8%). Because of the fact
that the actual number of FDPs t-i from which
long-term data were available for analysis in the
systematic review was small, changes in the
recommendations for treatment planning may
be explained. Combining evidence from the literature
with clinical logic may be optimal for
presenting practical guidelines (Greenstein et al.
2009) to improve the chance for a successful
tooth–implant-supported FDP.
The most obvious finding of the present report
was the confirmation of ‘‘cantilever extensions’’
as a technical risk factor.
In a retrospective evaluation of cFDP-tt that
had been incorporated 5–16 years before a followup
examination, biological and/or technical problems
in one out of every five abutment tooth
were reported (Ha¨mmerle et al. 2000). The same
abutment tooth could have been affected by
biological and technical complications at the
same time. The most frequent biological complication
was the loss of pulp vitality in 10% of
originally vital abutment teeth. The most frequent
technical complication was the loss of
retention, which occurred in 12% of non-vital
and in 4% of vital abutment teeth.
Moreover, a list of failures/complications from
137 re-examined c-FDPs of 213 originally placed
restorations after a mean exposure time of 6 years
(range 2–18 years) was presented (Decock et al.
1996). The Kaplan–Meier survival reached 60%
at 12 years. Sixty percent of the failures were true
failures leading to the loss of the reconstructions,
while in 40%of the ‘‘failures’’, a restoration could
be placed, endodontic or periodontal therapy was
provided or the c-FDPs could be recemented.
When cFDP-tt were followed over longer observation
periods in the same clinic (De Backer et
al. 2007), the failures in c-FDPs on devital abutment
teeth occurred earlier and were more frequent
compared with c-FDPs on vital teeth.
In a systematic review on cantilever reconstructions
on teeth (Lang et al. 2004), the following
annual rates of technical and biological
complications were listed for cFDP-tt: 0.95 for
caries of abutments, 3.95 loss of vitality, 1.75
loss of retention, 0.61 veneer frame work fracture
and 0.72 chipping of ceramic or fracture.
On the other hand, another systematic review
on cantilever reconstructions on implants
(Aglietta et al. 2009) reported the following rates
for biological and technical complications for
cFDP-ii after 5 years of function:
Periimplantitis: 9.4% of cFDP-ii, 10.5% veneer
fractures (3.9–26.6%), 8.5% screw loosening
(3.9–17%), 5.7% loss of retention (1.9–
16.5%), 2.1% abutment fractures (0.9–5.1%)
and 1.5% implant fractures (0.2–8.5%).
Limitations
The data obtained from this cohort of patients
need to be interpreted with caution.
First of all, only a small number of reconstructions
could be observed in each group of FDPs.
Many different clinical situations and reconstruction
designs were pooled. There were more than
20 dentists and more than 10 different technical
laboratories involved in the fabrication of the
reconstructions and this was not considered in
the evaluation of the data.
With the statistical analyses applied by
choosing IRR (Table 6), a statistically significant
increased risk for failure and failure and/or any
complication was noted for the groups of reconstructions
with extensions.
This information and the comparison with
other data in the literature can only be of partial
value while choosing between several treatment
options in restoring a particular patient with
FDPs. It must be stressed that many other factors
must also be considered andmay even lead to the
preference of an FDP design, which was found to
be at a greater risk in this or in other reports.
Among these factors are the following: the
particular clinical anatomical situation, the
expertise of the clinician and the technician,
themanufacturing processes, the alternative risks
or chances of, i.e., augmentation procedures,
placing more implants and finally, economic
aspects.
It seems to be extremely strenuous to design a
clinical study that considers all these factors.
Nevertheless, clinicians should be motivated to
systematically collect and document all relevant
information at regular intervals, thereby providing
the basis for amoremeaningful interpretation
of the survival and success rates of the reconstructions
inserted.
Conclusions
In conclusion, patients treated for chronic
periodontitis and provided with ceramo-metal
FDPs yield high survival rates, especially for
FDPs with end abutments. The incidence
rates of any negative events were drastically
increased in the three groups with cantilever
extensions c-FDPs (tt, ii, ti).
Strategic decisions in the choice of a particular
FDP design and the choice of teeth/implants
as abutments appear to influence the risks
for complications to be expected with fixed
reconstruction. If possible, extensions based
on tooth abutments should be avoided or used
only after a cautious clinical evaluation of all
options.
Acknowledgements: This study has
been supported in part by the Clinical
Research Foundation (CRF) for the Promotion
of Oral Health, Brienz, Switzerland. The
competent clinical performance of the Dental
Assistants of the Clinic for Periodontology and
Fixed Prosthodontics, University of Berne is
gratefully acknowledged. Moreover, the
competent and reliable service provided by the
Dental Hygienists of the Clinic during long
years of patient maintenance is highly
recognized.
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