The aim of this review was to assess the long-term outcomes of restorations supported by implants and natural teeth with regard to complications associated with implants, teeth, and restorations, as well as the influence on these parameters of the connector type used. A net-based search in PubMed was combined with a manual search. Clinical studies, reviews, and biomechanical studies were included. Information on survival rate, complication rate, incidence of tooth intrusion, and, where applicable, type of connector used, was retrieved from the clinical studies. Force distribution and types of connectors used were retrieved from the biomechanical study. A summary of outcomes was retrieved from the reviews. A total of 25 articles were selected for inclusion in this review, including clinical studies (15), biomechanical studies (7), and reviews (3). Implant success rates ranged from 79.5%–100%. Tooth complications occurred in 5.4%–11.8% of cases. Complications in the suprastructure were observed in 5%–90% of cases. Tooth intrusion presented in a total of 0%–66% of all cases, more often in cases with nonrigid connection (0%–66%) than in cases with rigid connection (0%–44%). Biomechanical studies show a large difference in stress distribution and in dependence on the type of connector used, with most studies demonstrating that nonrigid connectors drastically reduce stress on the suprastructure while increasing forces on supporting teeth and implants. Long-term success rates for tooth-implant connections are lower than for solely implant-supported restorations with regard to prognosis for teeth, implants, and suprastructure. Use of rigid connectors leads to more favorable clinical outcomes in terms of long-term stability, occurrence of complications, and tooth intrusion.

Introduction

During past decades, implant treatment emerged as a widely accepted treatment modality with a reported long-term success rate greater than 90% for the treatment of both partially and completely edentulous patients.1 However, the combined use of teeth and implants as anchors for prosthetic restorations remains a controversial issue.

Although implants become osseointegrated and thus have a rigid connection to supporting bone, teeth are supported by the periodontal ligament, allowing for physiologic mobility that leads to displacement of the crown of 50–200 µ if forces of 0.1 N are applied.2 Implants, on the other hand, demonstrate maximum displacement of 10 µ.3 A different behavior for masticatory forces results, leading to excessive load on the restoration, the abutments, and the implant. Complications such as fracture of mechanical parts and a higher incidence of caries at the crown margin and tooth intrusion have been described.4 The use of both rigid and nonrigid connectors of different designs has been suggested to minimize these effects.4,5 

Although the literature evaluating long-term treatment outcomes of solely implant-supported suprastructures is abundant, only limited data are available on the combined use of implants and natural teeth. The purpose of this review is to evaluate the long-term success rates of combined implant-tooth–supported fixed partial dentures, as well as the influence of the connector type and the biological force distribution.

Materials and Methods

A net-based search on PubMed using the terms “tooth AND implant AND connection,” “tooth AND implant AND connected,” “tooth AND implant,” and “implants AND tooth AND fixed partial denture” was performed and was combined with a manual search, which was based on the references of selected articles. Clinical studies, reviews, and biomechanical studies were included. The review was limited to publications in English.

Information on survival rate, complication rate, incidence of tooth intrusion, and, where applicable, types of connectors used, was retrieved from the clinical studies. Force distribution and types of connector used were retrieved from the biomechanical study. A summary of outcomes was retrieved from the reviews. A meta-analysis was not performed.

Results

A total of 25 articles were selected to be included in this review. Articles were classified as follows: clinical studies (15; Table 1), biomechanical studies (7; Table 2), and reviews (3; Table 3). A subclassification was made according to the use of rigid vs nonrigid connectors and studies in which no differentiation between the 2 was made. Publication dates ranged from 1995–2009, and observation time ranged from 3–10 years.

Table 1.

Clinical studies*

Clinical studies*
Clinical studies*
Table 1.

Continued

Continued
Continued
Table 2.

Reviews

Reviews
Reviews
Table 3.

Biomechanical studies

Biomechanical studies
Biomechanical studies

Survival or success rates of implants ranged from 79.5%–100%. Tooth complications, including tooth fracture, caries, endodontic and periodontal problems, and other complications, occurred in 5.4%–11.8% of cases. Complications of the suprastructure, such as fracture, abfracture of veneers, and so forth, were observed in 5%–90% of cases. Intrusion was present in a total of 0%–66% of all cases and was more frequent in cases with nonrigid connection (0%–66%) vs cases with rigid connection (0%–44%).

Most biomechanical studies show that the use of nonrigid connectors drastically reduces stress on the suprastructure but increases forces on supporting teeth and implants. The use of rigid connectors drastically increases the forces on bone surrounding teeth and implants.

Discussion

Although the combined use of teeth and implants to support prosthetic restorations has been repeatedly suggested for many years, only limited data are available on the long-term success of this treatment approach. A wide range of success rates has been reported.

An argument has been made that different reactions to forces between implants and natural teeth may have a negative impact on treatment outcomes, and the use of nonrigid connectors has been suggested.6 However, biomechanical studies demonstrate that a shift of force distribution from the suprastructure to the supporting teeth occurs when nonrigid connectors are used.712 Although clinical data suggest a lower incidence rate of complications involving the suprastructure and implants, a higher incidence of tooth intrusion is observed when nonrigid connectors are used. This seems to be independent of the specific design of the nonrigid connector.1315 The use of rigid connectors increases the amount of bone loss observed around implants, although no major differences in implant survival rates have been noted.16,17 

The wide variety of outcomes may be due to the fact that the incidence of tooth intrusion and other complications increases over time, with more complications presenting after the 3 year time point. Therefore, studies of shorter duration demonstrate better clinical outcomes.

A prospective evaluation revealed an incidence of intrusion of 66% in the nonrigid group vs 44% in the rigid group over 5 years.14 These numbers are significantly higher than those reported in other studies, possibly because the design of the study allowed evaluation of even minor levels of intrusion. In the same study, tooth loss due to root fracture was reported with the use of both rigid and nonrigid connectors. An overall higher rate of complications was reported in the nonrigid group.

Nickening et al18 reported a higher incidence of technical complications when nonrigid connectors were used. This contrasts with the findings of other clinical studies and with the findings of biomechanical studies indicating higher stresses on the suprastructure when rigid connectors are used.

A factor that should be taken into consideration is the amount of periodontal support provided for abutment teeth. Decreased periodontal support on the abutment teeth increases forces on the remaining supporting bone and on the implant.9 In the same study, it was demonstrated that the use of a rigid connector increases forces on the restoration and on the implant but decreases forces on the bone.

In most clinical studies, a slightly greater amount of bone loss was observed around implants in implant-tooth–supported restorations as compared with those that were entirely implant supported. However, no influence of this finding on short-term implant survival rate was reported. Use of an internal hexagon implant abutment connection increases denture stability while increasing stresses in the abutment; this suggests that the use of an external abutment is favorable in these cases.12 

The combination of teeth and implants to support restorations yields a lower long-term success rate than the use of implants alone. If use of this combination cannot be avoided, then the use of rigid connectors with only periodontally nonimpaired teeth yields higher success rates.

Conclusions

  • Only limited long-term clinical data exist.

  • Biomechanical models have their limitations with regard to the clinical application of retrieved findings.

  • Tooth-implant connections have higher failure and complication rates compared with tooth-tooth/implant-implant–supported restorations.

  • Despite the more favorable force distribution of nonrigid connectors observed in biomechanical models, rigid connections achieve better outcomes with regard to long-term stability, complications, and tooth intrusion. However, greater marginal bone loss around implants is observed when this type of connector is used.

  • The combination of teeth and implants to support restorations yields a lower long-term success rate than the use of implants alone.

References

References
1.
Albrektsson
T
,
Dahl
E
,
Enbom
L
,
et al.
Osseointegrated oral implants: a Swedish multicenter study of 8139 consecutively inserted Nobelpharma implants
.
J Periodontol
.
1988
;
59
:
287
296
.
2.
Muhlemann
HR
.
Physiologic and pathologic dental mobility
.
SSO Schweiz Monatsschr Zahnheilkd
.
1951
;
61
:
53
63
.
3.
Cohen
SR
,
Orenstein
JH
.
The use of attachments in combination implant and natural tooth fixed partial dentures: a technical report
.
Int J Oral Maxillofac Implants
.
1994
;
9
:
230
234
.
4.
Lang
NP
,
Pjetursson
BE
,
Tan
K
,
Brägger
U
,
Egger
M
,
Zwahlen
M
.
A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years
.
Clin Oral Implants Res
.
2004
;
15
:
643
653
.
5.
Lang
NP
,
Pjetursson
BE
,
Tan
K
,
Brägger
U
,
Egger
M
,
Zwahlen
M
.
A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. II. Combined tooth-implant-supported FPDs
.
Clin Oral Implants Res
.
2004
;
15
:
643
653
.
6.
Schlumberger
TL
,
Bowley
JF
,
Maze
GI
.
Intrusion phenomenon in combination tooth-implant restorations: a review of the literature
.
J Prosthet Dent
.
1998
;
80
:
199
203
.
7.
Nishimura
RD
,
Ochiai
KT
,
Caputo
AA
,
Jeong
CM
.
Photoelastic stress analysis of load transfer to implants and natural teeth comparing rigid and semirigid connectors
.
J Prosthet Dent
.
1999
;
81
:
696
703
.
8.
Ormianer
Z
,
Brosh
T
,
Laufer
BZ
,
Shifman
A
.
Strains recorded in a combined tooth-implant restoration: an in vivo study
.
Implant Dent
.
2005
;
14
:
58
62
.
9.
Lin
CL
,
Wang
JC
,
Kuo
YC
.
Numerical simulation on the biomechanical interactions of tooth/implant-supported system under various occlusal forces with rigid/non-rigid connections
.
J Biomech
.
2006
;
39
:
453
463
.
10.
Lin
CL
,
Chang
SH
,
Wang
JC
,
Chang
WJ
.
Mechanical interactions of an implant/tooth-supported system under different periodontal supports and number of splinted teeth with rigid and non-rigid connections
.
J Dent
.
2006
;
34
:
682
691
.
11.
Lin
CL
,
Wang
JC
,
Chang
WJ
.
Biomechanical interactions in tooth-implant-supported fixed partial dentures with variations in the number of splinted teeth and connector type: a finite element analysis
.
Clin Oral Implants Res
.
2008
;
19
:
107
117
.
12.
da Silva
EF
,
Pellizzer
EP
,
Quinelli Mazaro
JV
,
Garcia Júnior
IR
.
Influence of the connector and implant design on the implant-tooth-connected prostheses
.
Clin Implant Dent Relat Res
.
2010
;
12
:
254
262
.
13.
Lindh
T
,
Dahlgren
S
,
Gunnarsson
K
,
et al.
Tooth-implant supported fixed prostheses: a retrospective multicenter study
.
Int J Prosthodont
.
2001
;
14
:
321
328
.
14.
Block
MS
,
Lirette
D
,
Gardiner
D
,
et al.
Prospective evaluation of implants connected to teeth
.
Int J Oral Maxillofac Implants
.
2002
;
17
:
473
487
.
15.
Cordaro
L
,
Ercoli
C
,
Rossini
C
,
Torsello
F
,
Feng
C
.
Retrospective evaluation of complete-arch fixed partial dentures connecting teeth and implant abutments in patients with normal and reduced periodontal support
.
J Prosthet Dent
.
2005
;
94
:
313
320
.
16.
Naert
IE
,
Duyck
JA
,
Hosny
MM
,
Van Steenberghe
D
.
Freestanding and tooth-implant connected prostheses in the treatment of partially edentulous patients. Part I. An up to 15-years clinical evaluation
.
Clin Oral Implants Res
.
2001
;
12
:
237
244
.
17.
Naert
IE
,
Duyck
JA
,
Hosny
MM
,
Quirynen
M
,
van Steenberghe
D
.
Freestanding and tooth-implant connected prostheses in the treatment of partially edentulous patients. Part II. An up to 15-years radiographic evaluation
.
Clin Oral Implants Res
.
2001
;
12
:
245
251
.
18.
Nickenig
HJ
,
Schäfer
C
,
Spiekermann
H
.
Survival and complication rates of combined tooth-implant-supported fixed partial dentures
.
Clin Oral Implants Res
.
2006
;
17
:
506
511
.
19.
Mau
J
,
Behneke
A
,
Behneke
N
,
et al.
Randomized multicenter comparison of two coatings of intramobile cylinder implants in 313 partially edentulous mandibles followed up for 5 years
.
Clin Oral Implants Res
.
2002
;
13
:
477
487
.
20.
Kindberg
H
,
Gunne
J
,
Kronström
M
.
Tooth- and implant-supported prostheses: a retrospective clinical follow-up up to 8 years
.
Int J Prosthodont
.
2001
;
14
:
575
581
.
21.
Lindh
T
,
Gunne
J
,
Tillberg
A
,
Molin
M
.
A meta-analysis of implants in partial edentulism
.
Clin Oral Implants Res
.
1998
;
9
:
80
90
.
22.
Brägger
U
,
Aeschlimann
S
,
Bürgin
W
,
Hämmerle
CH
,
Lang
NP
.
Biological and technical complications and failures with fixed partial dentures (FPD) on implants and teeth after four to five years of function
.
Clin Oral Implants Res
.
2001
;
12
:
26
34
.
23.
Hosny
M
,
Duyck
J
,
van Steenberghe
D
,
Naert
I
.
Within-subject comparison between connected and nonconnected tooth-to-implant fixed partial prostheses: up to 14-year follow-up study
.
Int J Prosthodont
.
2000
;
13
:
340
346
.
24.
Gunne
J
,
Astrand
P
,
Lindh
T
,
Borg
K
,
Olsson
M
.
Tooth-implant and implant supported fixed partial dentures: a 10-year report
.
Int J Prosthodont
.
1999
;
12
:
216
221
.
25.
Garcia
LT
,
Oesterle
LJ
.
Natural tooth intrusion phenomenon with implants: a survey
.
Int J Oral Maxillofac Implants
.
1998
;
13
:
227
231
.
26.
Fartash
B
,
Arvidson
K
.
Long-term evaluation of single crystal sapphire implants as abutments in fixed prosthodontics
.
Clin Oral Implants Res
.
1997
;
8
:
58
67
.
27.
Steflik
DE
,
Koth
DL
,
Robinson
FG
,
et al.
Prospective investigation of the single-crystal sapphire endosteal dental implant in humans: ten-year results
.
J Oral Implantol
.
1995
;
21
:
8
18
.
28.
Hita-Carrillo
C
,
Hernandez-Aliaga
M
,
Calvo-Guirado
JL
.
Tooth-implant connection: a bibliographic review
.
Med Oral Patol Oral Cir Bucal
.
2010
;
15
:
e387
e394
.
29.
Lindh
T
.
Should we extract teeth to avoid tooth-implant combinations
?
J Oral Rehabil
.
2008
;
35
(
suppl 1
):
44
54
.
30.
Maezawa
N
,
Shiota
M
,
Kasugai
S
,
Wakabayashi
N
.
Three-dimensional stress analysis of tooth/implant-retained long-span fixed dentures
.
Int J Oral Maxillofac Implants
.
2007
;
22
:
710
718
.