Biomechanical Outcomes of Tooth-Implant-Supported Fixed Partial Prostheses (FPPs) in Periodontally Healthy Patients using Root Shape Dental Implants
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
10.1515/bjdm-2017-0001
L SOCIETY
BALKAN JOURNAL OF DENTAL MEDICINE ISSN 2335-0245
CA
GI
LO
TO
STOMA
Biomechanical Outcomes of Tooth-Implant-Supported
Fixed Partial Prostheses (FPPs) in Periodontally
Healthy Patients using Root Shape Dental Implants
SUMMARY Argine Harutyunyan1, Argirios Pissiotis2
Background: Connecting an osseointegrated implant and a natural 1Postgraduate student, Yerevan State Medical
tooth is a treatment alternative for partially edentulous patients in some University after Mkhitar Heratsi (YSMU)
clinical situations. The main issue of a connected tooth-implant system is Armenia
2School of Dentistry
derived from the dissimilar mobility patterns of the osseointegrated fixtures
and natural abutments causing potential biomechanical problems within the Aristotle University of Thessaloniki
Thessaloniki, Greece
entire system. Purpose: The aim of this review was to multilaterally analyze
and discuss the main biomechanical factors that may question the reliability
of splinted tooth-implant system and the long-term success of fixed partial
prostheses (FPPs) supported by both teeth and implants with an emphasis
on the disparity of mobility of these two different abutments. Material and
methods: An electronic MEDLINE (PubMed) search supplemented by
manual searching was performed to retrieve relevant articles. An assessment
of the identified studies was performed, the most valuable articles were
selected and biomechanical outcomes of tooth-implant splinting system
were analyzed. Results: 3D FEM stress analyses and photoelastic studies
show uneven load distribution between the tooth and the implant and stress
concentration in the crestal bone around the implant neck when connected
to a natural tooth by FPPs. However, clinical studies demonstrate good
results for both the implants and FPPs supported by splinted implant-to-
tooth abutments. Conclusion: Connecting implants to natural teeth is not
a preferable treatment option because of possible inherent biomechanical
complications. Whenever possible, this treatment option should be avoided.
Keywords: Tooth-Implant Supported Prostheses, Natural Tooth, Osseointegrated Dental REVIEW PAPER (RP)
Implant, Occlusal Force, Finite Element Analysis, Rigid Connector, Non-Rigid Connector Balk J Dent Med, 2017; 21:1-11
Introduction considerably, and some of them are even contradictory.
Several studies demonstrate a good prognosis for implant-
The introduction of osseointegrated implants by tooth-supported FPPs2-8, others reveal considerable bone
Per-Ingvar Bränemark has had a revolutionary effect on loss, even loss of osseointegration and failure of FPPs
all fields of dentistry1. Dental implants were originally supported by natural teeth and endosseous implants.
developed for the treatment of complete edentulism. There are several biomechanical factors that may
However they are now widely used to treat partial jeopardize the entire prosthetic treatment and affect
edentulism, but the philosophy of this treatment concept, the long-term success of implant-tooth-supported
particularly regarding the connection of dental implants FPPs such as: a) differences in the mobility pattern
with natural teeth is still a big dilemma. The combined between natural teeth and osseointegrated implants, b)
use of implants and teeth appeared in the mid 1980s2. occlusal force pattern (that is the magnitude, duration,
Numerous studies and analyses have been performed since frequency, distribution and direction of the forces during
then, but the conclusions derived from these studies differ the function), c) characteristics of prosthesis (rigidity,2 Argine Harutyunyan, Argirios Pissiotis Balk J Dent Med, Vol 21, 2017
connector type (rigid, non-rigid), connector position( near the axial mobility of a connected tooth. They advocate
the tooth, near the implant), length of span, the features that a tooth rigidly connected to a single Bränemark
of materials of which the prosthesis is made etc.), d) implant will take an active part in supporting the axially
characteristics of the implant system (implant shape, applied forces of the prosthesis due to the resiliency of
length, diameter, surface macrostructure, implant-to- the implant screw joint and a momentary opening of the
abutment connection), e) characteristic of the bone around abutment-implant interface without any additional flexible
the teeth and the implants ( the quality and the quantity of element4.
the bone), f) number of connected teeth and implants2,14,27, Chapman and Kirsch21 recommend the use of an
29. All these factors determine the stress which affects the intra-mobile element (IME) which would increase the
bone around splinted implants and teeth. implant abutment compatibility with natural abutments.
The main issue regarding splinting implants with This would therefore allow rigid interconnection through
natural teeth is the difference of their mobility pattern the prosthesis21,22 . The question of whether additional
which could be considered as a biomechanical challenge implant-integrated resilient elements are necessary is still
for the entire splinted system11, 13, 14, 17, 20. controversial13.
Natural teeth with a sound periodontal ligament The second issue is the difference of tactile
have a mobility between 15-20µm (axial displacement) sensitivity threshold between implants and teeth which
and 150-200µm (horizontal displacement)10, while is 8,75 times higher for implants23. This significant
osseointegrated implants rigidly attached to the bone difference in mechanoperception may cause ineffective
have a mobility of less than 10µm11, which is due to a bite force control and stress concentration on the implant
combination of the bone elasticity and the flexibility of side of implant-tooth-supported FPPs.
the implant system (implant-prosthesis, implant-abutment, Other studies affirm that the load condition is the
prosthesis flexibility itself)12-14. Such a discrepancy main factor affecting stress distribution in different
between the mobility patterns causes lever arm overload components of implant-tooth-supported FPPs (bone,
forces on the stiffer abutment (implant) and may lead to prosthesis, fixture)14,15,24. Indeed, occlusal load duration,
several physiological, mechanical and biomechanical magnitude, distribution, frequency and the direction of the
problems (bone loss around the implants, abutment and forces during the function have a great influence on both
prosthesis screw loosening and fracture, prosthesis and the FPPs and the abutments. Decreasing occlusal loading
implant fracture, tooth intrusion) when implants are forces on the pontic area of the FPPs and directing these
rigidly connected to teeth. forces through the long axis of abutments significantly
To overcome the difference in mobility and the decrease the risk of unfavorable stresses within the
above mentioned problems non-rigid connector types prosthesis and the bone around the teeth and the implants.
have been proposed by different authors15-17. However, Data concerning the number of splinted teeth
there is no clear consensus regarding the effectiveness of and implants are also controversial4-6, 20,40 . In their
this type of connectors because of the potential clinical retrospective multicenter study, Lindh et al5 found out
hazard of natural tooth intrusion5. Several studies reported that intrusion of natural teeth (which is one of the main
no significant difference between rigid and non-rigid complications when connected with implants) was
connector types12, 18. most common in the prosthesis design with one implant
The position of the non-rigid connector in FPP is also connected to one tooth. Splinted natural teeth have less
an issue of discussion. It has been shown that placement mobility compared with the mobility of a single tooth,
of the non-rigid connector on the implant side rather thus making the whole unit mobility more comparable
than the tooth side of FPPs has both biomechanical and to that of the implants12, 25-27. On the other hand, some
technical advantages11, 19. It was also documented that authors insist that the addition of an extra tooth increases
the use of the patrix part of the non-rigid connector on the load on the implants rather than supports them17.
the implant site and the matrix part on the pontic site may Splinting more than one implant will increase their
be biomechanically efficient by reducing the potential resistance against occlusal loading forces and reduce
harmful cantilever forces and stress formation around the deflection of the prosthesis, thus reducing the risk of
the implant11. Lawrence et al 17 advocated modifying mechanical complications4,6,20. Load transfer to implants
the design of the conventional prosthesis (placing the and natural tooth changing the number of splinted
attachment near one of the abutments (tooth or implant)) implants were estimated by Nishimura et al16. They
and to extend the cantilevers from both sides of the performed quasi-3D testing, analyzed a photoelastic
abutments and join them with an internal attachment at the model and changed the number of splinted implants by
middle part of the prosthesis. They insist that using this removing of the abutment of the medial standing implant.
design will create less torque and stress on the implants The results showed higher apical stress concentration
without overloading the natural teeth. around the abutments when only one implant was splinted
Rangert et al 4, 20 showed that a single Bränemark with a tooth regardless of the type of the connector. When
implant has an inherent bending flexibility that matches forces were directed on the implant segment, the stressBalk J Dent Med, Vol 21, 2017 Tooth-Implant-Supported FPPs 3
concentration around the tooth and the implant were in peri-implant bone, the bone around natural teeth as
similar to that of a two-implant condition. However, well as within the prosthesis. Articles based on 2D
they concluded that a 13-mm implant as a posterior FEA and photoelastic stress analysis methods were
abutment may adequately support the 3-unit prosthesis excluded because of their limitations and drawbacks
rigidly connected to a tooth. Jemt et al9 performed a long- (lack of information and accuracy). One of the included
term follow-up study using Bränemark implants. They articles contained both 2D and 3D FEA methods28. Only
connected several implants to natural teeth and came to information from 3D FEA results was extracted.
the conclusion that 2-3 implants (at least) are adequate Studies, included implant-tooth-supported FPPs
to take the full load of the segment by themselves when in periodontally compromised patients were excluded.
splinted with natural teeth (the continuous prosthesis Case reports, publications based on patient records only,
stability rate was 98,7%). questionnaires or interviews were also excluded.
The aim of this study was to summarize the results
of the existent stress analysis studies (3D FEA and
photoelastic methods) and clinical studies and to discuss
the biomechanical outcomes of implant-tooth-supported Results
FPPs with an emphasis on the differences between tooth
and implant mobility patterns. It is known from literature that teeth have a certain
physiologic mobility within their respective alveolar
sockets. This physiological mobility is due to the presence
of a periodontal ligament (PDL) between the tooth and
Material and Methods the alveolar bone surrounding it. The PDL is composed of
intercellular ground substance (matrix), fibers (collagen,
An electronic MEDLINE (PubMed) search between oxytalan, elaunin), and cells with their neurovascular
1980 and 2015 was conducted to retrieve relevant supply. Tooth mobility is a direct function of the
articles. A further manual search from the bibliographies mechanical properties of the periodontal protein matrix
of the former articles was performed to include as many with its collagenous elements10. Tooth movement (TM)
references as possible. The search included English- when a horizontal force is applied to the crown may be
language articles published in the Dental Literature. divided into 3 phases: a) initial TM, b) intermediate TM,
The search terms used were : “tooth-implant c) terminal TM10.
connection”, “splinting”, “implant connected to a natural The initial (desmodontal) TM is explained by the
tooth”, “tooth intrusion”, “rigid connector”, “biomechanics”, special syndesmotic anchorage of the tooth in the alveolar
“load distribution”, “tooth-implant-supported fixed partial bone. Within this phase the resistance of the tooth against
prosthesis” and combinations of these terms. the force is very small. This phase corresponds with a
Manual searching was applied to the following first phase of readiness orientation and stretching of the
journals: Clinical Oral Implants Research, International PDL fibers without strain. The collagen fibers of PDL
Journal of Prosthodontics, Journal of Clinical have a wavy configuration in the relaxed state29 which
Periodontology, Journal of Prosthetic Dentistry, enables the tooth enable to move easily without any
Periodontology 2000, International Journal of Oral and resistance at the beginning of force application. This
Maxillofacial Implants. initial displacement of a natural abutment would cause
From a total of 1879 titles electronically identified stress concentration around a rigidly connected implant
from the initial search, 95 studies were selected for abutment before the two become comparable in their
potential inclusion (included by titles and abstracts). resiliencies.
63 studies were selected for full text evaluation (32 The degree of desmodontal TM depends on several
studies were excluded: cross-sectional, case reports, old factors: the width of the PDL, the shape of the root, the
implant technology), from which only 51 studies met the structure, disposition and interlacing of the collagen
inclusion criteria and final data extraction. Prospective fibers10.
and retrospective clinical studies, as well as randomized If the force is increased, the resistance of the tooth
controlled clinical trials (RCT) were included in this against that force will suddenly increase-in this state, the
paper. Inclusion criteria for clinical studies involved TM is at the limit between its initial and intermediate
patients with periodontally healthy teeth, root shape phase. In order to push the crown over a distance similar
endosseous osseointegrated dental implants and fixed to the phase of initial TM, greater forces are needed (100-
partial prostheses supported by both teeth and implants. 1500Gm). In this phase tooth movement occurs due to an
Studies based on 3D finite element analysis and elastic deformation of alveolar bone10.
photoelastic stress analysis were also included as these With an increase in force over 1500Gm pain is
methods are extremely useful and have become the main registered. During this phase the crown hardly moves
tools for numerically assessing stresses and deformations anymore in spite of a strong increase in applied force4 Argine Harutyunyan, Argirios Pissiotis Balk J Dent Med, Vol 21, 2017
(1500-1750Gm). Teeth with a healthy periodontium will In a free-standing implant-supported prosthesis,
show a narrow and sharply delimited zone of terminal force application to one portion is distributed to the
TM. For several seconds the tooth will not yield any nearest osseointegrated fixture-bone interface. The
movement. Lasting stress produces further movement force is concentrated at that interface and the amount
of the crown. A tooth with a sound PDL has horizontal of its distribution to the remaining implant(s) depends
and vertical mobility and the upper limit of physiologic on the flexibility of the surrounding bone, implant,
horizontal tooth mobility is greater than that of vertical abutment, retaining screws and prosthesis. The amount
mobility (150-200µm vs 15-20µm) 3,4,10. of deformation of the retaining screws (most flexible part
PDL damps the forces acting on a tooth. This of the system) are in the range of 100µm. Therefore, the
damping effect is not only due to collagen fibers, but also amount of force distribution to the remaining fixtures
due to the vascular system (blood and lymph vessels) and is much less than that found in natural teeth-supported
the interstitial fluid of PDL. Saul et al.30 performed an in FPPs (PDL can permit 500µm of movement)17. However,
vivo study on living and dead rats to find out the roles of the maximum load on each implant will be less than the
different component parts of PDL in the reduction of the applied complete occlusal force27.
oscillation amplitude of a tooth in its socket, when the In the case of the prosthesis supported by an implant
tooth has been subjected to intrusive force. They showed and a tooth, the latter does not carry a fair share of
that the extracellular and the intracellular fluid systems loading as the resilience of the tooth is higher than that
have a hydraulic damping effect and dissipate the force of the implant. When the force is applied at the tooth
acting on a tooth during an intrusion. side and/or in the middle part (pontic) of the FPPs, the
It can be concluded that due to the presence of the tooth dips into its alveolar socket causing bending of the
PDL the occlusal forces applied on the tooth are equally prosthesis. This creates a bending moment on the implant
distributed on the bone around the root. The natural tooth neck-bone interface, which means that only one part of
receives the impact energy and transfers it in to the end of the force is carried by the tooth while the other (main)
the root in the form of a stress wave31. Most of the energy part is transmitted through the implant into the bone.
is dissipated by the highly absorptive PDL. The magnitude of this bending moment is dependent on
An osseointegrated endosseus implant has a the tooth mobility and the flexibility of the prosthesis,
very close apposition to the bone. Besides, at the the implant and the bone4.On the other hand, forces
microscopic level there is a bone ingrowth to the macro- directly applied on the implant do not load the tooth and
and micropores of the implant surface. Such a close consequently, only the implant carries the complete load13.
contact allows for a direct transfer of stress from the Landgren & Laurell14 reported theoretical
implant to the surrounding bone without any relative calculations and showed that an implant-tooth-supported
movement between them and without any changes bridge functions as a cantilever only for a very short time.
in magnitude or duration as the PDL and related At the beginning of load application the FPPs is supported
mechanoreception is absent around an osseointegrated by the implant only. After the moment is increased to
implant27. An osseointegrated implant has only about a certain level (240Nm), the implant-abutment-crown
10µm displacement which is due to surrounding bone unit rapidly angles in the lateral direction with a certain
elasticity13. Because of the lack of micromovement most amplitude. They assumed that this deflection is sufficient
of the force distribution is concentrated at the crest of the for a tooth with a normal apical mobility to reach the
ridge32. Lateral forces are concentrated at the crestal area bottom of the socket, and when intruded further, the
of the alveolar ridge, vertical forces are concentrated at apical yield of the root is close to zero (as of an implant),
the crestal and apical parts of the bone17. even if large forces are applied. If plus the bending of
Because of the differences in the mobility pattern the beam, only 5-6N are needed to convert the bridge
between teeth and implants, occlusal forces applied on the from an implant-supported cantilever construction to a
FPPs supported by both implants and natural teeth will be bilateral construction (as the tooth touches the bottom of
distributed on the bone differently compared with solely the socket, it doesn’t move apically anymore and starts
teeth-supported and solely implant-supported FPPs. sharing the forces with an implant).
In solely teeth-supported FPPs situations the load The presence of the PDL provides not only
is equally distributed between both abutment teeth when physiologic tooth mobility, but also tactile sensitivity
force is applied at the middle of the bridge. If the force which plays an important role in the coordination of
is placed at the mesial or distal end of the FPPs the total masticator muscle activity and control of applied occlusal
load is carried by the mesial or distal abutment tooth, forces. No periodontal ligament receptors are available for
respectively13. However, Lawrence et al.17 note that tactile function if the tooth is replaced by an endosseous
if occlusal force is applied only on one abutment it will implant23. When the threshold of perception of teeth and
evoke a micro-movement of the other abutment and the implants are compared, higher values have been reported
periodontal fibers will distribute generated compression, for implants. Hämmerle et al.23 conducted an in vivo
tension and rotational forces on all teeth. study to determine the threshold of tactile perception ofBalk J Dent Med, Vol 21, 2017 Tooth-Implant-Supported FPPs 5
endosseous dental implants and to compare it with that of results showed that lateral forces significantly increased
natural teeth. Twenty-two healthy subjects with implants the stress values of implants, prostheses and the alveolar
of the ITI Dental Implant System were included in the bone compared with axial occlusal forces, regardless
study. A total of 34 implants were placed and served as of the bone quality. Maximum von Mises stress values
abutments for single tooth crowns (in function for a in the implant system (σI,max) and prosthesis (σP,max)
minimum of 1 year). An electronic measuring device demonstrated no significant differences between the
was used to determine the threshold values. The range bone qualities under the same loading condition, but the
of forces applied for calibration reached from 0,01N to maximal stress values for the alveolar bone (σAB,max)
10N (1-1000g, 1g represents 0,01N force). The obtained increased when the bone quality was reduced. The authors
values ranged from 13,2 to 189,4g (mean value of 100,6g) of the aforementioned study also showed that decreasing
for the implants and from 1,2 to 26,2g for the control the occlusal forces on the pontic area significantly
teeth (mean value of 11,3g).The mean threshold value decreased the values of σI,max, σP,max and σAB,max
for implants was 8,75 times higher than that for teeth. . Under axial forces the maximum stress concentrated
Thus, when a tooth with exquisite mechanoreception locations in the implant system were found at the contact
is connected to an implant with less mechanoreceptive butt-joint interface between the abutment and the implant,
sensitivity by FPPs, the magnitude of bite forces may the bottom of the internal hexagon joint of the abutment
increase when a patient bites on the implant side of the and threads of the abutment screws. Under the same
prosthesis. However, several studies have proved that the forces the maximum stress concentrated locations of
magnitude of bite forces in patients with osseointegrated σAB,max and σP,max were found at distal cervical areas
implants is comparable to that of patients with natural in the cortical bone and bottom of the mesial connector,
teeth33. Gunne et al34 in vivo measured vertical forces respectively. For the lateral loading condition the
and bending moments on 10 three-unit prostheses in corresponding locations of σI,max, σP,max and σAB,max
the posterior mandible of 5 patients (intra-individual were found at the contact butt-joint of the implant ,
measurement). All patients had a prosthesis supported
lingual cervical areas in the cortical bone and the lingual
by one implant and one tooth in the molar region on one
bonded region between the prosthesis and the abutments,
side (rigid connection) and a freestanding, two-implants-
respectively.
supported prosthesis on the other. The prostheses had been
In another study Lin et al tried to investigate the
worn for 5-6 years. The results showed no significant
biomechanical interactions in TISP by varying the
differences in functional load magnitudes related to
number of splinted teeth and connector types15. They
the abutment type. Akca et al35 performed a similar
constructed a 3D FEA FPPs model which contained one
study (in vivo) to evaluate maximal occlusal bite forces
Frialit-2 implant in the mandibular second molar region
(MOFs) and marginal bone level changes in patients
splinted to the first and second premolars. They came to
with tooth-implant-supported FPPs. They came to the
conclusion that even MOFs under functional loading the conclusion that load condition was the main factor
were higher for implants (mean: 353,61N) than for teeth affecting the stress developed in the implant, bone and
(mean: 275,48N). These increased functional loads are prostheses when comparing it with the connector type
far below an overloading of implants. In the same study, and the number of splinted teeth. The 3D FEA showed
radiographic measurements revealed a stable marginal reduced stress values in centric and lateral contact
bone level around the implants and a total marginal bone situations when the occlusal forces were decreased on
level improvement from the baseline to 24 months at the the pontic (26-69%). Under uniform multiple oblique
mesial site (mean:0,28±0,519mm) and at the distal site forces the σI,max were at the base of the internal hexagon
(mean:0,097±0,518mm), which shows that this splinted joint of the abutment and mesial butt-joint interface
system has a promising marginal bone level stability for between the abutment and the implant. The σAB,max
the implants. were concentrated on the lingual cervical areas in the
Several 3D finite element analyses have been cortical bone around the teeth and the implant side when
implemented to assess load distribution and stress the occlusal forces acted only on the premolar and on
concentration in TISP. Lin et al.24 analyzed the the prosthesis, respectively. Regarding the connector
biomechanics in a tooth-implant splinted system using type they came to the conclusion that using non-rigid
3D FEA with different occlusal forces for various bone connector increased the prosthesis stress more than 3,4-
qualities. They constructed a model which contained fold compared with the rigid connector. Depending on the
one Frialit-2 implant splinted to the mandibular second specific connector used, the σP,max were on the concave
premolar that was embedded in a simplified bony surface of the male component and bottom area for non-
segment. Four bone quality categories were established, rigid and rigid connectors, respectively. Regarding the
with the elastic parameters assigned to the bone values number of splinted teeth they found that this factor did
varying. The stress distribution in the splinting system not affect stress values either for the implant or for the
was observed under four different loading conditions. The alveolar bone or for the prosthesis.6 Argine Harutyunyan, Argirios Pissiotis Balk J Dent Med, Vol 21, 2017
Meniccuci et al.28 implemented 2D and 3D FEAs to removed, a 3-unit fixed restoration was simulated with a
assess the stress in the bone around an implant and a tooth pontic. In this type of model, when force was applied at
which are rigidly connected when a load is applied on the the load point T, stresses concentrated at the apical part of
tooth. Two different loading conditions were compared in the implant were twice as high as the 2-implant condition.
this study: an axially directed static load (10 seconds) and The highest stresses were observed at the second implant
a transitional load (5 miliseconds). The results of the 3D with the load applied at points 4 and 5. Low level stresses
FEA showed the stress concentration at the neck of both were produced within the distal part of the tooth because
the tooth and the implant when static load was applied. of its distal bending ability.
Under short term transitional forces the stress around both In the rigid connection scenario the results showed
abutments was much less (-50%) than that seen under the the following: for the 2-implant model, when the load
static loading. Thereby, they concluded that load duration was applied on the tooth abutment, similar apical stresses
has a greater influence on the amount of generated were generated around the tooth and the medial implant.
stresses in the bone around the implant rigidly connected Some low level responses were noted at the distal surface
to the tooth than load intensity, and that the static loads are of the medial implant and at the medial surface of the
more detrimental for the bone than the transitional loads. distal standing implant. As the forces were directed to the
They suggested that the main reason for these results were implant segment, stresses also transferred to the distal part
the visco-elastic properties of the PDL and the very short of the splinted system. The highest stresses were observed
load time which is removed before the loaded tooth starts around the distal implant along its distal surface and
to sink in its alveoli (before visco-elastic creep occurs). As at the apex when the load was applied at point 5 (which
a result the tooth reacts like a rigidly anchored abutment indicates the intrusion and distal bending of the implant).
sharing the load with the implant. Several in vivo studies have been performed by
Nishimura et al.16 conducted photoelastic stress different authors to investigate the biomechanics of
analysis to evaluate stress distribution in an implant- TISP10,20,23,30,34-37. Richter et al.36 presented data from
tooth splinted system using different types of connectors. their in vivo study in which 10 tooth-implant-supported
They fabricated a life-size photoelastic model of an adult FPPs in the mandible of 9 different patients were
human left mandible for quasi-3 dimensional testing. The examined while the intra-mobile elements (IME) of 3
edentulous area was extended distally from the second IMZ implants were replaced by a measuring device with
premolar. Two screw-type implants (3,75mm diameter, strain gauges. After the abutment screws were fixed, the
13mm length) were included into the model at the first measuring device was calibrated. The results showed
and second molars. Multiple restorations incorporating higher buccal than lingual directed stresses (only in 6 of
3 types of connections between the medial implant and 34 registrations). Measured lateral bending moments were
the natural tooth were fabricated: a) non-connection up to 25N×cm during occlusion and chewing.
(proximal contact only), b) rigid solder joint, c) non-rigid Another in vivo study was performed by Gunne and
connection. Vertical point loads were applied at 6 fixed Rangert20. They measured in vivo bite forces, implant
identified locations on the occlusal surface of the tooth- axial forces and bending moments on 5 patients with
implant restoration: T, over natural tooth, 1- medial to FPPs supported by a natural tooth and a single Bränemark
implants, 2-over medial implant, 3-inter-implant, 4- over implant rigidly connected to each other by a MacCollum
distal implant, 5- distal to implants. The results of the attachment and a locking screw. The patients were divided
non-connected model were as follows: loading directed into two groups according to the magnitude of the applied
on the tooth (point T) transferred low stress to the apices forces, a light-biting group and a hard-biting group. The
of both implants (the distal implant received a smaller results demonstrated mean forces of 12N and 95N for
amount of forces compared with the medial implant), light-biting and hard-biting groups, respectively. They
the highest stress intensity was seen apical to the natural also showed that in the light-biting group the tooth did not
tooth. Loadings directed on the implant areas (loading fully engage and the implant carried the major portion of
points 1-5) produced little or no discernible stress in the the applied bite force. For the hard-biting group, the tooth
apical areas of the tooth; the later was concentrated to the shared the load on an equal basis with the implant. They
distal parts close to the implants. Thus, when the load was reported bending moments of 3-5N×cm and 10-16N×cm
applied over each abutment, the highest stress intensity for the light- and hard-biting groups, respectively.
was seen apical to that abutment. The highest stress within As mentioned earlier the type of connector used
the structure was produced under loading on point 5. The is also an important biomechanical factor affecting
distal implant underwent intrusion and distal bending. stress distribution in the tooth-implant system. Several
Stress was concentrated at the distal crest and at the apex authors advocate the use of a rigid connection25, 28, 35, 38,
of that implant. 39, which assumes a stiff junction between component
Results of the non-rigid connection between the parts of the structure with no relative motion of one
abutments were similar to those of the non-connected part against another. The use of this type of connector
situation. When the abutment of the medial implant was reduces tooth intrusion incidence and transfers the loadBalk J Dent Med, Vol 21, 2017 Tooth-Implant-Supported FPPs 7
more evenly through the prosthesis, but as the tooth and bone quality. The maximum stress concentrations were
the implant have a different degree of mobility, more found in type IV bone (Lekholm and Zarb classification,
stress is concentrated around the implant which has been 1985) followed by type III, II and I. In a type I bone,
shown by the aforementioned as well as other FEA and the stress distribution is more uniform as the entire bone
photoelastic studies41,42. To overcome the disparity in block is compact and homogeneous. The results from
mobility of the different abutments, non-rigid connectors studies24 confirm that implants connected to teeth should
have been introduced. Indeed, a flexible prosthesis will be used with caution in softer (type IV) bone regions.
tend to redistribute the load between the abutments with 3D FEA is generally accepted as a very useful tool
unequal stiffness. With a flexible bridge the tendency to assess stress generation and mechanical responses of
for any applied load is to be primarily transmitted to simulated clinical situations. However, the constructed FE
the nearest abutment whether it is a natural tooth or an models are mathematical models of the real object and/
implant27. In this situation the exact point of applied or phenomenon. Hence, it is not possible to reproduce
occlusal force becomes a priority. The use of a non-rigid all the details of the real loading conditions, material
connector may be more efficient in terms of compensation properties and the geometries of the component parts
for the dissimilar mobility under axial loading forces only. (especially the geometry of the alveolar bone), and some
However, under lateral occlusal forces this compensation important parameters that influence the clinical outcomes
becomes insignificant. It should be mentioned that most of implant-tooth-supported FPPs may be overlooked.
of tooth intrusion cases in splinted systems were detected Such a parameter is the limitation of calculation of the
when non-rigid connectors were used 4,6,38. Hence, a host reaction to the stresses applied. Therefore the results
potential priority of one type of connector over another is derived from FEA only provide a general understanding
still unclear. of the biomechanical aspects of the splinting system and
To increase the compatibility of implants with need to be completed and validated by clinical studies.
teeth IMZ implants (Interpore-IMZ, Irvine, Calif.) were Several clinical studies3,7,9,25,51 and systematic
introduced with an intra-mobile element between the reviews25,38,44,45 have been implemented to find out the
implant and the prosthesis. Richter et al.36 used IMZ survival rates of implants and FPPs supported by implants
implants in in vivo and in vitro study to measure the and natural teeth.
bending moments on the implant caused by axial and Mau et al.51 have compared two different coatings
lateral forces. They fastened four different types of of intra-mobile cylinder implants (IMZ, Koch 1976) -
connecting devices: 1. IME, 2. an intra-mobile connector hydroxyapatite (HA) and titanium plasma-flame (TPF) –
(IMC), 3. a titanium metal IME and 4. a mobile test between patients with Kennedy Class I or II mandibular
device. The results were as following: the max bending partially edentulous arches in a randomized controlled
moment was 40% of the highest stress using a metal IME trial and estimated the cumulative success rates of the
(640Nmm), 25% with the IME (400Nmm), 15% with the implants after 5 years of follow-up period. All FPPs
IMC (240Nmm) and 14% for the test device (224Nmm). were supported by one natural tooth (first or second
Van Rossen et al.43 estimated the effectiveness premolar) and one implant placed in the molar region.
of stress-absorbing elements and their role in stress- The connection between the implants and the teeth was
absorption and stress-distribution in the cortical and rigid (screw-retained attachments). From all 313 admitted
trabecular bone around a tooth and an implant when patients 155 (49.5%) were randomized to HA-coated IMZ
connected to each other. In their FEA they proved that implants as test group and 158 (50.5%) patients were
using a stress-absorbing element with a low E-modulus randomized to TPF-coated IMZ implants as control group.
both damps and distributes the loading forces more The main criteria of comparison were the duration of no
uniformly in the bone surrounding the implant and integration deficiency (ID) and of no functional deficiency
the tooth. We can summarize that resilient elements (FD) of the implants after the placement of FPPs (the
improve the load distribution between two different authors defined ‘integration deficiency’ as implant loss,
abutments by decreasing implant stiffness, thus, making bone loss since the operation of at least 4 mm at the
the interconnection more compatible. Moreover, these medial or distal aspect, periotest value of at least 10,
shock-absorbing elements allow a rigid, yet retrievable manual mobility grade >0). The 5-year cumulative success
connection between teeth and implants22. It should be rates for no ID were 69.5% (95% CI, 58.3-80.7%) with
mentioned, however, that this design of implant-prosthesis HA and 82.2% (95% CI, 74.2-90.6%) with TPF.
connection has drawbacks, such as wear, fatigue and/ Naert et al.25 conducted a retrospective study to
or fracture, which requires a frequent replacement of the evaluate the success of the freestanding and tooth-implant
resilient component. connected FPPs up to 15 years of follow-up period. A total
Bone characteristics (quality and quantity) are one of of 668 Bränemark implants were placed in 246 patients. In
the most important issues to consider when planning an 123 patients, 339 implants were connected to 313 teeth by
implant-tooth treatment. It has been proved that stress in means of FPPs (test group). In another randomly selected
the bone surrounding the implant increases with reduced group of 123 patients, 329 implants were connected to8 Argine Harutyunyan, Argirios Pissiotis Balk J Dent Med, Vol 21, 2017
each other (control group). The mean follow-up period survival rates for FPPs were 90.4% (95% CI: 79.8-95.6%)
was 6.5 years (1.5-15y) for the test group and 6.2 years and 77.8% (95% CI: 66.4-85.7%), respectively. As it
(1.3-14.5y) for the control group. The cumulative implant may be seen from the results, the survival rates for both
success (based on the implant immobility and/or lack of implants and FPPs were lower for splinted implant-tooth-
the implant fractures after loading) in the test and control supported cases compared with solely implant-supported
groups were 94.9% and 98,4%, respectively. situations. Annual failure rates of implants in combined
Hosny et al.3 performed an intra-individual implant-tooth-supported FPPs (1.33%) were significantly
comparison in 18 partially edentulous patients up higher than those of implants in free-standing implant-
to 14-year (mean 6.5) follow-up time to assess the supported FPPs (0.51%).
outcome of FPPs supported by teeth and implants and
by freestanding implants only. The combined FPPs were
supported by 30 implants and 30 teeth (both rigid and
non-rigid connection), and the freestanding FPPs were Discussion
supported by 48 implants (Bränemark system). After
14 years of follow-up time the results were ‘excellent’: There are some clinical situations in which an
no implant failed and no mechanical failures of implant implant-tooth connection is unavoidable and the only
components (fracture, loosening) or superstructure was choice of treatment such as: a) an insufficient number of
detected. Therefore, they concluded that splinting teeth natural teeth or implants (when insertion of additional
with implants does not affect the long-term outcomes of implants is not possible because of systematic, local or
the implants and the marginal bone stability. However, financial limitations) to serve as sole abutments for FPP,
this study is limited by a small number of patients. b) additional support for periodontally compromised
Gunne et al.7 compared the outcomes of the FPPs teeth from stable implants, c) unfavorable location and
supported by implants only with FPPs supported by distribution of abutments (both teeth and implants),
splinted implants and teeth. 23 patients with Kennedy d) prosthetic versatility and retrievability46. Splinting
Class I dentitions in the mandible were included in the implants with natural teeth also has several advantages:
study. All patients were provided with implants ad modum proprioception from natural teeth, broadened treatment
Bränemark on each side posterior to the mandibular possibilities, better esthetic outcomes (retaining the
residual teeth. On one side the FPPs were supported natural tooth preserves the adjacent papillae), reduced
by two implants, and on the other side the FPPs were treatment cost, additional support for total load on
supported by one tooth and one implant. A total of 69 dentition etc. However, decision-making criteria for
implants were inserted and 46 FPPs were fabricated and rehabilitation of partially edentulous arches by splinting
followed-up up to 3 years. The authors showed interesting implants with natural teeth are still a dilemma. Clinical
results about fixture survival, FPPs survival and marginal studies (both prospective and retrospective) show good
bone loss when comparing solely implant-supported prognosis for combined implant-tooth-supported FPPs.
and implant-tooth-supported combination bridges. The Lindh et al.5 conducted a retrospective multicenter
survival rate of the implants was 88.4% and for both study which comprised 185 implants in 111 patients
types of FPPs it was the same. The survival rate of the from 6 different clinics in Sweden. The results showed
FPPs was higher in implant-tooth combinations than in a cumulative implant survival rate of 95.4% for up to 3
solely implant-supported FPPs (91.3% vs 82.6%). They years of follow-up. The frequent complications were loss
also observed lower mean marginal bone loss adjacent to of osseointegration (6/185), followed by peri-implant
the implants connected to the natural teeth than those that infections (4/185) and natural tooth intrusion (15% of the
were adjacent to the non-splinted implants. cases). Another retrospective study conducted by Hans
Pjetursson and Lang performed a 2-part meta- et al.6 evaluated clinical treatment outcomes of FPPs
analysis to find out the survival rates of implants and using different sizes and numbers of teeth and implants
FPPs after an observation period of 5 and 10 years for as abutments (follow-up up to 8 years). They presented a
free-standing implant-supported and implant-tooth- cumulative implant survival rate of 89.8% after 5 years of
supported FPPs. After 5 years of observation, the survival service. Jemt et al.9 performed another retrospective study
rates for implants were 95.4% (95% CI: 93.9-96.5%) and on 876 consecutively placed implants (Bränemark system)
90.1% (95%CI: 82.4-94.5%) in free-standing and implant- in a total of 244 patients treated and annually followed
tooth-supported situations, respectively. After 10 years at the Bränemark clinic (Gothenburg, Sweden) for up to
of observation the survival rates were 92.8% (95% CI: 20 years. The authors aimed to find out the results of the
90-94.8%) and 82.1% (95% CI: 55.8-93.6%), respectively. treatment of partially edentulousness by means of FPPs
After 5 years of function the survival rates for FPPs in supported by osseointegrated implants. From 876 implants
free-standing and implant-tooth-supported cases were 43 were connected to the adjacent teeth to support 12
96.6% (95% CI: 95.9-97.3%) and 94.1% (95%CI: 90.2- FPPs in total of 9 patients. The authors did not observe
96.5%), respectively. After 10 years of function the any significant problems associated with the connectionBalk J Dent Med, Vol 21, 2017 Tooth-Implant-Supported FPPs 9
of implants with teeth. However, they mentioned that problems that may jeopardize the longevity and
treatment involving a mechanical connection between successfulness of the complete treatment. Natural teeth
teeth and implants should be approached with caution. have a physiologic mobility due to the PDL, which
Although these and many other studies show is absent in osseointegrated dental implants. Hence,
successful treatment outcomes, two main complications connecting these two different abutments causes uneven
associated with splinting an implant with a natural tooth, load distribution between them, and as a result possible
which are bone loss around the implant and natural implant abutment overloading.
tooth intrusion, still question this treatment option. A decision should be based on well-considered
Tooth intrusion is one of the main problems when treatment planning, i.e. choosing periodontally healthy
connected to implants which can occur in up to 7.3% of teeth, planning the positions and number of inserted
the cases29. Several studies tried to explain the causes implants, directing occlusal forces through the long axis
of this phenomenon31,47, but till now there is no clear of abutments and performing a meticulous management of
answer. Some authors insist that the cause of intrusion the occlusion.
is multifactorial31,48,49. Some of the possible factors are: As we can see from the available studies there is
disuse atrophy, differential energy dissipation, impaired no definite opinion neither about the number of splinted
rebound memory, rachet effect, debris impaction, fixed implants and teeth, nor about the connector type, position
prosthesis flexure, mandibular flexure (only in mandible). and rigidity. Only one thing is clear: when connecting
It has been shown to occur mainly in teeth non-rigidly implants with teeth, the implants will always carry the
connected to implants4,6,38. However, this problem can greater part of the loading.
also occur with any other attachment type37,48. Several To give a definite answer to: “Is splinting an
authors showed a reversibility of tooth intrusion31,50 by osseointegrated implant with a natural tooth a reliable
disconnecting solder joints or other methods (occlusal treatment option?” further research and long-term studies
adjustment, changing the contours of coping sidewalls etc.). are needed.
Studies involving 3D FEA and photoelastic analyses,
in vivo and in vitro, prospective and retrospective studies
were included in this study. Differences in mobility and
tactile sensitivity of natural teeth and osseointegrated
References
implants were discussed, the main biomechanical factors
affecting the longevity and success rate of combined FPPs 1. Branemark PI, Hansson BO, Adell R, Breine U, Lindström
have been introduced, the survival rates of implants and J , Hallén O et al. Osseointegrated implants in the treatment
FPPs supported by solely implants and splinted implant- of the edentulous jaw. Experience from a 10-year period.
tooth abutments were compared in the current paper. Scand J Plast Reconstr Surg Suppl, 1977; 16:1-132.
Both short- and long-term clinical studies, retrospective 2. Ericsson I, Lekholm U, Bränemark PI, Lindhe J, Glantz PO,
and prospective studies and systematic reviews show Nyman S. A clinical evaluation of fixed-bridge restorations
acceptable results for implants and FPPs. However stress supported by the combination of teeth and osseointegrated
analysis methods (3D FEM and photoelastic) show more titanium implants. J Clin Periodontol, 1986; 13:307-312.
stress concentration around the implants and within the 3. Hosny M, Duyck J, Van Steenberghe D, Naert I. Within-
superstructure. subject comparison between connected and nonconnected
tooth-to-implant fixed partial prostheses: up to 14-year
The current paper contains certain restrictions, as the
follow-up study. Int J Prosthodont, 2000; 13:340-346.
other important biomechanical factors, such as implant 4. Rangert B, Gunne J, Sullivan DY. Mechanical aspects of a
characteristics (length, diameter, surface macrostructure), Branemark implant connected to a natural tooth: an in vitro
the proximity of the splinted teeth and implants to each study. Int J Oral Maxillofac Implants, 1991; 6:177-186.
other, material of prosthesis (type of alloy for metal 5. Lindh T, Dahlgren S, Gunnarsson K, Josefsson T, Nilson
framework, veneering material - acrylic, ceramic), H, Wilhelmsson P et al. Tooth-implant supported fixed
opposing construction type in antagonist jaw (fixed, prostheses: a retrospective multicenter study. Int J
partial or complete removable dentures) were not included Prosthodont, 2001; 14:321-328.
and discussed. 6. 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.
7. Gunne J, Astrand P, Ahlen K, Borg K, Olsson M. Implants
in partially edentulous patients. A longitudinal study of
Conclusion bridges supported by both implants and natural teeth. Clin
Oral Implants Res, 1992; 3:49-56.
There are several clinical situations in which a tooth- 8. Astrand P, Borg K, Gunne J, Olsson M. Combination of
to-implant connection seems to be the only treatment natural teeth and osseointegrated implants as prosthesis
option. However, planning this construction type the abutments: a 2-year longitudinal study. Int J Oral Maxillofac
practitioner should realize the potential biomechanical Implants, 1991; 6:305-312.10 Argine Harutyunyan, Argirios Pissiotis Balk J Dent Med, Vol 21, 2017
9. Jemt T, Leckholm U, Adell R. Osseointegrated implants in 26. Lanza MD, Seraidarian PI, Jancen WD, Stress analysis
the treatment of partially edentulous patients. A preliminary of a fixed implant-supported denture by the finite element
study on 876 consecutively placed fixtures. Int J Oral method (FEM) when varying the number of teeth used as
Maxillofac Implants, 1989; 4:211-217. abutments. J Appl Oral Sci, 2011; 19:655-661.
10. Mühleman HR. Periodontometry, a method for measuring 27. Skalak R. Aspects of biomechanical considerations. In:
tooth mobility. Oral Surg Oral Med Oral Pathol, 1951; Brånemark, P.- I., Zarb, G.A. & Albrektsson, T., eds.
4:1220-1233. Tissue-Integrated Prostheses: Osseointegration in Clinical
11. Cohen SR, Orenstein JH. The use of attachments in Dentistry. Chicago:Quintessence, 1985; pp: 117-128.
combination implant and natural-tooth fixed partial
28. Menicucci G, Mossolov A, Mozzati M, Lorenzetti M, Preti
dentures: a technical report. Int J Oral Maxillofac Implants,
G. Tooth-implant connection: some biomechanical aspects
1994; 9:230-234.
based on finite element analyses. Clin Oral Implants Res,
12. Naert I, Quirynen M, van Steenberghe D, Darius P. A six
2002; 13:334-341.
year prosthodontic study of 509 consecutively inserted
implants for the treatment of partial edentulism. J Prosthet 29. Michalakis KX, Calvani P, Hirayama. Biomechanical
Dent, 1992; 67:236-245. considerations on tooth-implant supported fixed partial
13. Richter EJ. Basic biomechanics of dental implants in dentures. J Dent Biomech, 2012; 3:1758736012462025. doi:
prosthetic dentistry. J Prosthet Dent, 1989; 61:602-609. 10.1177/1758736012462025.
14. Lundgren D, Laurell L. Biomechanical aspects of fixed 30. Bien SM. Hydrodynamic damping of tooth movement. J
bridgework supported by natural teeth and endosseous Dent Res, 1966; 45:907-914.
implants. Periodontol, 2000 1994; 4:23-40. 31. Sheets CG, Earthman JC. Tooth intrusion in implantassisted
15. Lin CL, Wang JC, Chang WJ. Biomechanical interactions prostheses. J Prosthet Dent, 1997; 77:39-45.
in tooth-implant supported fixed partial dentures with 32. Becker CM, Kaiser DA, Jones DJ. Guidelines for splinting
variations in the number of splinted teeth and connector implants. J Prosthet Dent, 2000; 84:210-214.
type: a finite element analysis. Clin Oral Implants Res, 33. Haraldson T and Carlsson GE. Bite force and oral function
2008; 19:107-117. in patients with osseointegrated oral implants. Scand J Dent
16. Nishimura RD, Ochiai KT, Caputo AA, Jeong CM. Res, 1977; 85:200-208.
Photoelastic stress analysis of load transfer to implants and 34. Gunne J, Rangert B, Glantz PO, Svensson A. Functional
natural teeth comparing rigid and semirigid connectors. J loads on freestanding and connected implants in three-unit
Prosthet Dent, 1999; 81:696-703. mandibular prostheses opposing complete dentures: an in
17. Weinberg LA. The biomechanics of force distribution
vivo study. Int J Oral Maxillofac Implants, 1997; 12:335-341.
in implant-supported prostheses. Int J Oral Maxillofac
35. Akca K, Uysal S, Cehreli MC. Implant–tooth-supported
Implants, 1993; 8:19-31.
fixed partial prostheses: correlations between in vivo
18. Misch CM, Ismail YH. Finite element stress analysis
of tooth-to-implant fixed partial denture designs. J occlusal bite forces and marginal bone reactions. Clin Oral
Prosthodont, 1993; 2:83-92. Implants Res, 2006; 17:331-336.
19. Chee WW, Mordohai N. Tooth-to-implant connection: a 36. Richter EJ, Spiekermann H, Jovanovic SA. Tooth-to-
systematic review of the literature and a case report utilizing implant fixed prostheses: biomechanics based on in vitro
a new connection design. Clin Implant Dent Relat Res, and in vivo measurements. In: Laney WR, Tolman DE, eds.
2010; 12:122-133. Tissue integration in oral, orthopaedic and maxillofacial
20. Rangert B, Gunne J, Glantz PO, Svensson A. Vertical load reconstruction. Chicago, IL: Quintessence Publishing Co.,
distribution on a three-unit prosthesis supported by a natural 1990, pp: 133-139.
tooth and a single Branemark implant. An in vivo study. 37. Ormianer Z, Brosh T, Laufer BZ, Shifman A. Strains
Clin Oral Implants Res, 1995; 6:40-46. Recorded in a Combined Tooth-Implant Restoration: An In
21. Chapman RJ, Kirsch A. Variations in occlusal forces Vivo Study. J Implant Dent, 2005; 14:58-62.
with a resilient internal implant shock absorber. Int J Oral 38. Lang NP, Pjetursson BE, Tan K, Bragger U, Egger M,
Maxillofac Implants, 1990; 5:369-374. Zwahlen M. A systematic review of the survival and
22. Kay HB. Free-Standing versus Implant-Tooth-Interconnected complication rates of fixed partial dentures (FPDs) after an
Restorations: Understanding the Prosthodontic Perspective. observation period of at least 5 years. II. Combined tooth
Int J Periodontics & Res Dent, 1993; 13:47-69. –implant-supported FPDs. Clin Oral Implants Res, 2004;
23. Hämmerle CHF, Wagner D, Brägger U, Lussi
15:643-653.
A, Karayiannis A , Joss A et al. Threshold of tactile
39. Greenstein G, Cavallaro J, Smith R, Tarnow D. Connecting
sensitivity perceived with dental endosseous implants and
Teeth to Implants: A Critical Review of the Literature and
natural teeth. Clin Oral Implants Res, 1995; 6:83-90.
24. Lin CL, Wang JC. Finite Element Analysis of Presentation of Practical Guidelines. Compend Contin Educ
Biomechanical Interactions of a Tooth-Implant Splinting Dent, 2009; 30:440-453.
System for Various Bone Qualities. Chang Chung Med J, 40. Guven S, Eratilla V. Evaluation of stress distributions in
2006; 29:143-153. peri-implant and periodontal bone tissues in 3- and 5-unit
25. Naert IE, Duyck JA, Hosny MM, Van Steenberghe D. tooth and implant-supported fixed zirconia restorations by
Freestanding and tooth-implant connected prostheses in the finite elements analysis. Eur J Dent, 2015; 9:329-339.
treatment of partially edentulous patients. Part I: an up to15- 41. Wnag JC, Huang SF, Lin CL. Biomechanical Responses of
years clinical evaluation. Clin Oral Implants Res, 2001; Endodontically Treated Tooth Implant–supported Prosthesis.
12:237-244. J Endod, 2010; 36:1688-1692.Balk J Dent Med, Vol 21, 2017 Tooth-Implant-Supported FPPs 11
42. Ozawa S, Caputo AA, Nishimura RD, Tanaka Y. Photoelastic 48. Rieder CE, Parel SM. A survey of natural tooth abutment
evaluation of load transfer to an implant connected to a intrusion with implant-connected fixed partial dentures. Int J
natural tooth under varying types of periodontal support. J Period & Res Dent, 1993; 13:335-347.
Prosthodont Res Pract, 2006; 5:129-136. 49. Schlumberger TL, Bowley JF, Maze GI. Intrusion
43. Van Rossen IP, Braak LH, de Putter C, de Groot K. Stress phenomenon in combination tooth-implant restorations: a
absorbing elements in dental implants. J Prosthet Dent, review of the literature. J Prosthet Dent, 1998; 80:199–203.
1990; 64:198–205. 50. Chee WW, Cho GC. A rationale for not connecting implants
44. Mamalis A, Markopoulou K, Kaloumenos K, Analitis A. to natural teeth. J Prosthodont, 1997; 6:7-10.
Splinting osseointegrated implants and natural teeth in 51. Mau J, Behneke A, Behneke N, Fritzmeier CU, Gomez
partially edentulous patients: a systematic review of the Roman G, d’Hoedt B et al. Randomized multicenter
literature. J Oral Implantol, 2012; 38:424-434. comparison of two coatings of intramobile cylinder implants
45. Pjetursson BE, Tan K, Lang NP, Bragger U, Egger M, in 313 partially edentulous mandibles followed up for 5
Zwahlen M. A systematic review of the survival and years. Clin Oral Implants Res, 2002; 13:477-487.
complication rates of fixed partial dentures (FPDs) after an
Received on June 29, 2016.
observation period of at least 5 years. I. Implant-supported Revised on September 29, 2016.
FPDs. Clin Oral Implants Res, 2004; 15:625–642. Accepted on October 12, 2016.
46. Laufer BZ, Gross M. Splinting osseointegrated implants
and natural teeth in rehabilitation of partially edentulous
patients. Part II: principles and applications. J Oral Rehabil, Correspondence:
1998; 25:69-80. Argine Harutyunyan
47. English CE. Biomechanical concerns with fixed partial 2 Koryun str, Yerevan 0025, Armenia
dentures involving implants. J Implant Dent, 1993; 2;221-242. E-mail: argineh@mail.ruYou can also read
