caracteristicas cono morse

Review Article
Performance of conical abutment (Morse Taper) connection implants:
A systematic review
Christian M. Schmitt,1 Getulio Nogueira-Filho,2 Howard C. Tenenbaum,3 Jim Yuan Lai,3
€ ring,1,2 Jo
€ rg Nonhoff4
Carlos Brito,2 Hendrik Do
1
Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Erlangen, Germany
Department of Preventive Dentistry, University of Toronto, Toronto, Ontario, Canada
3
Department of Periodontology, University of Toronto, Toronto, Ontario, Canada
4
Clinical Research DENTSPLY Friadent, Mannheim, Germany
2
Received 7 January 2013; revised 20 February 2013; accepted 20 February 2013
Published online 9 May 2013 in Wiley Online Library (wileyonlinelibrary.com). 10.1002/jbm.a.34709
Abstract: In this systematic review, we aimed to compare
conical versus nonconical implant–abutment connection systems in terms of their in vitro and in vivo performances. An
electronic search was performed using PubMed, Embase,
and Medline databases with the logical operators: “dental
implant” AND “dental abutment” AND (“conical” OR “taper”
OR “cone”). Names of the most common conical implant–
abutment connection systems were used as additional key
words to detect further data. The search was limited to
articles published up to November 2012. Recent publications
were also searched manually in order to find any relevant
studies that might have been missed using the search criteria
noted above. Fifty-two studies met the inclusion criteria and
were included in this systematic review. As the data and
methods, as well as types of implants used was so heterogeneous, this mitigated against the performance of meta-analysis. In vitro studies indicated that conical and nonconical
abutments showed sufficient resistance to maximal bending
forces and fatigue loading. However, conical abutments
showed superiority in terms of seal performance, microgap
formation, torque maintenance, and abutment stability. In
vivo studies (human and animal) indicated that conical and
nonconical systems are comparable in terms of implant success and survival rates with less marginal bone loss around
conical connection implants in most cases. This review indicates that implant systems using a conical implant–abutment
connection, provides better results in terms of abutment fit,
stability, and seal performance. These design features could
lead to improvements over time versus nonconical connecC 2013 Wiley Periodicals, Inc. J Biomed Mater Res
tion systems. V
Part A: 102A: 552–574, 2014.
Key Words: systematic review, dental implant, dental abutment, Morse Taper, implant–abutment connection
€ ring H, Nonhoff J. 2014. Performance of
How to cite this article: Schmitt CM, Nogueira-Filho G, Tenenbaum HC, Lai JY, Brito C, Do
conical abutment (Morse Taper) connection implants: A systematic review. J Biomed Mater Res Part A 2014:102A:552–574.
INTRODUCTION
Implant systems differ in terms of the geometry of the
implant–abutment interface with particular differences
between both conical and nonconical connection systems
(indexed external or internal connections). The implant–
abutment connection represents the weakest point of dental
endosseous implant fixtures, as it must resist maximal and
permanent masticatory forces as well as penetration by
bacteria.
The formation of a marginal gap between the implant
and abutment might lead to increased loss of marginal bone
because of the penetration of bacteria into the implant–
abutment interface (i.e., compared to an implant without a
gap that permits bacterial invasion). It has been claimed
that with conical implant–abutment attachment systems,
this is not as much of a risk as the gap is much smaller
with less leakage at the implant–abutment interface,1,2 thus
retarding or preventing bacterial colonization. However, it
must be recognized that as of now, there are no endosseous
dental implant systems that can provide a complete seal at
the implant–abutment interface1,3,4 and so this is still an important clinical issue.
Regarding the mechanical properties of implant connections, it has been assumed that different abutment connections might provide greater resistance to displacement that
is caused by excessive occlusal forces.5 In this regard it has
Correspondence to: C. M. Schmitt; e-mail: [email protected]
Contract grant sponsor: Bavarian Association for Scientific Dentistry, Germany (VfwZ)
552
C 2013 WILEY PERIODICALS, INC.
V
REVIEW ARTICLE
been speculated that this displacement will increase stress/
strain on the endosseous implant thus promoting the acceleration of marginal bone loss.6,7 Clearly then, there is need
for improvements in the connection systems currently in
use but at this time it is unknown as to whether one connection system currently available, might be superior to
others. This review was undertaken to determine whether
there is any evidence to support the superiority of any connection system over the other. Based on previous claims, it
was decided to focus more specifically on the performance
of conical (Morse Taper) implant–abutment connection systems and to compare them with each other and to implant
systems with nonconical interfaces and to determine
whether there might be improved clinical outcomes with
one of these systems.
MATERIAL AND METHODS
This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and MetaAnalyses statement, the recommendations of the Cochrane
Handbook for Systematic Reviews and known literature
guidelines writing a systematic review.8–11 Several articles
related to the in vitro and in vivo performance of conical
implant–abutment connection systems were reviewed. The
central review questions were as follows:
1. Do implant systems with a conical (Morse Taper)
implant–abutment connection compared to nonconical
implant–abutment connection systems in vitro show better performances in terms of implant–abutment seal and
under mechanical stress/loading?
2. Does the use of a conical (Morse Taper) implant–abutment connection system compared to a nonconical
implant–abutment connection system result in less marginal bone level changes and higher implant survival
rates?
Inclusion and exclusion criteria
Studies were included according to the following general
inclusion criteria:
1. Publication in an international peer-reviewed journal.
2. Study published in English.
3. Publication not older than 15 years.
Additional inclusion criteria for in vitro studies:
1. Only comparative studies with a minimum number of
two groups, with one related to the use of a conical
(Morse Taper) implant–abutment connection and the
other related to the use of another conical or nonconical
implant–abutment connection system.
2. Studies investigating implant–abutment seal, particularly
microgap formation and bacterial leakage.
3. Studies investigating the performance of the implant–
abutment unit under loading conditions in vitro;
especially preload/torque loss, load fatigue performance/
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH A | FEB 2014 VOL 102A, ISSUE 2
resistance, bending moment/maximal load resistance and
strain/stress distribution in and around the implant–
abutment interface with respect to the implant–abutment
configuration.
Additional inclusion criteria for in vivo studies:
1. Only comparative studies (animal and human trials),
with a minimum number of two groups, with one related
to the use of a conical (Morse Taper) and the other to a
nonconical implant–abutment connection system.
2. In cases of clinical trials only prospective clinical comparative studies with a minimum follow-up of 12
months.
3. Studies investigating marginal bone level changes and
implant survival rates.
Publications not meeting all mentioned inclusion criteria, using analytical formulas only, or dealing with case
reports, case series, abstracts, letters, and narrative reviews
were excluded from this systematic review. In the presence
of duplicate publications, only the study with the most inclusive data was selected.
Search strategy
The following electronic databases were searched:
1. The Cochrane Library (up to November, 15th, 2012):
a. CDSR (Cochran Database of Systematic Review),
b. The Cochrane Central Register of Controlled Trials
(CENTRAL),
c. The Cochran Review Groups.
2. MEDLINE (up to November, 15th, 2012).
3. EMBASE (up to November, 15th, 2012).
Electronic search was carried out using the logical operators: (“dental implant”) AND (“dental abutment”) AND
[(“taper”) OR (“cone”) OR (“conical”)]. In order to detect
additional trials dealing with conical implant–abutment systems, the databases were searched for major implant systems with a conical implant–abutment connection,
including: ITI/ Straumann Dental Implant System (Straumann AG, CH-Basel/ Straumann GmbH, Freiburg, SwitzerR (Dentsply FRIADENT GmbH, Mannheim,
land), AnkylosV
Germany), BICON Dental Implants (BICON Europe, Sohren,
Germany), AstraTech Implant System (AstraTech GmbH, Elz
R (Camlog GmbH, Wimsheim, Germany),
Germany), ConelogV
R (NobelBiocare Ag, Sweden), AlphatecV
R BONINobelActiveV
R DUOtex (Henry Schein Dental Depot GmbH,
tex, AlphatecV
Langen, Germany), Neoss Implant System (Neoss GmbH,
K€
oln Germany), Neodent Titamax CM, Neodent Alvim II Plus
IC (Neodent, Curitiba, Parana, Brazil), and TS Implant System (Osstem Implants GmbH, Eschborn Germany). Therefore
the name of the system, respectively, the manufacturer was
used as a logical operator and combined with the keywords
as follows: (“dental implant”) AND (“dental abutment”) AND
(“name of the system” OR “name of the manufacturer”).
In addition a hand search was carried out for the last
six months in the following journals: Journal of Clinical
553
Periodontology, Journal of Dental Research, Clinical Oral
Implants Research, Clinical Implant Dentistry and Related
Research, Journal of Periodontology, Journal of Periodontal
Research, The International Journal of Oral & Maxillofacial
Implants, Journal of Cranio and Maxillofacial Surgery,
Implant Dentistry, International Journal of Prosthodontics,
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology
and Endodontology, The International journal of Periodontics & Restorative Dentistry, The Journal of the American
Dental Association, The Journal of Prosthetic Dentistry,
American Journal of Dentistry, Journal of Esthetic and Restorative Dentistry, Quintessence International, Periodontology 2000, British Journal of Oral and Maxillofacial Surgery,
Journal of Oral and Maxillofacial Surgery, Journal of Cranio
Maxillofacial Surgery, Journal of Canadian Dental Association, and Journal of Oral Implantology.
The search and screening process was carried out by two
independent examiners (CS, GN) to minimize the potential
for reviewer biases. After electronic search all titles, key
words and abstracts were screened. Irrelevant studies or
studies not meeting the inclusion criteria were excluded. All
full texts of the remaining articles were acquired for the second screening. The references of all selected publications
were additionally checked for further relevant data. In cases
of missing or insufficient data the corresponding authors
were contacted via e-mail. After detailed full text examination
and agreement between examiners further articles were
excluded. All remaining studies were included in this systematic review. The references were managed with specific bibliR , NY).
ographic software (EndNoteX4, ThomsonReutersV
Data extraction
Data extractions were performed independently by the two
reviewers (CS, GN) using data extraction tables. In cases of
disagreements, the data were double checked with the original data. The following data were extracted from the
selected articles: (1) authors, (2) title, (3) year of publication, (4) journal name, (5) implant–abutment connection,
(6) implant system, (7) number of implants per group, (8)
study design, (9) primary objective, (10) secondary objectives, (11) methods, and (12) results.
RESULTS
The initial electronic literature search identified 468 publications (Fig. 1). Hand search did not provide any additional
studies. Review of all titles, key words, and abstracts led to
the exclusion of 345 studies, which left 123 studies for full
text screening. After full text evaluation, 52 articles were
excluded, as they did not fulfill inclusion criteria. Reference
screening revealed eight additional studies. A total of 79
studies were analyzed in detail for potential inclusion in the
review. Twenty-seven additional studies were excluded for
the following reasons: eight studies did not include a comparable control group with another conical or nonconical
implant–abutment connection system,12–19 two studies used
implant and abutment replicas as a control group,20,21 three
studies used analytical formulas only,22–24 three studies did
554
SCHMITT ET AL.
FIGURE 1. Study selection process. [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com.]
not investigate a conical implant–abutment connection, five
studies did not meet primary objectives,25–29 one study had
a follow-up of only 6 months,30 one study had a retrospective design,31 and four in vivo studies used implants with
machined surfaces.32–35
The remaining 52 studies were included in the review.
Thirteen out of 52 studies dealt with implant–abutment seal
performance, particularly focusing on bacterial colonization,
saliva leakage, endotoxin ingress as well as overall microleakage based on dye penetration. Thirty studies concentrated on stress and loading performance/resistance of the
implant–abutment unit. Nine studies were carried out in
vivo, and there were five animal and four clinical (i.e.,
human) trials. Regarding the secondary outcome of some in
vitro studies, there was overlap between groups.2,3,5,36,37 If
applicable and meeting the inclusion criteria, a double
assessment was conducted concerning the secondary outcome.2,3,5,36,37 The study characteristics and outcomes for in
vitro studies are detailed in Tables I and II, and for in vivo
studies in Tables III and IV.
In vitro
Seal performance. Eight trials studied the bacterial leakage
of the implant–abutment interface.1,3,4,36,38–41 Following
PERFORMANCE OF CONICAL IMPLANT–ABUTMENT CONNECTION SYSTEMS
System
# Samples
Pr. Objective
10 per group, 5 According to the
recommendaper bacterial
tion of the
species
manufacturer
P. aeruginosa, A.
actinomycetemcomitans
N.a.
S. aureus
P. aeruginosa (PS), A.
actinomycetemcomitans
(AA)
Human saliva
Used Bacteria/
Dyes
N.a.
N.a.
Sec.
Objectives
20 per system Titamax II Plus 20 Bacterial leakage Bacterial leakage
Teixeira et al., Internal cone, Titamax CM,
Ncm, Titamax
into the implant- from the
2011
internal hex
Titamax II Plus (10 per
CM 32 Ncm,
abutment
implant-abutexperiment)
(Neodent)
(recommended
interface
ment interface
by the
manufacturer)
Bacterial leakage
from the
implant-abutment interface
Bacterial leakage
from the
implant–abutment interface
According to the Saliva leakage
recommendainto the implant–
tion of the man- abutment
ufacturer (20
interface under
Ncm)
loaded and
unloaded
conditions
Insertion torque
Ankylos (Dents- 10 per system According to the
ply Friadent),
recommendaReplace Select
tion of the
(Nobel Biomanufacturer
care), Bone
System
Internal cone, Universal II HI
internal hex
and CM,
(Implacil De
Bortoli)
Morse taper,
SIN, Sistema de 20 per group,
internal and
Implante
10 loaded
external hex
Nacional
and 10
unloaded
Connection
Assenza et al., Internal cone,
2011
internal trilobed,
cemented
Tripodi et al.,
2012
Nascimento
et al., 2012
Author/ Year
SEAL PERFORMANCE
TABLE I. Seal Performance
Result
Implant abutment Contamination:
connection and
External hex:
incubation in
Loaded 10 out
human saliva.
of 10, unloaded
Detecting saliva
3 out of 10 Interleakage. Half of
nal hex: Loaded
the specimens:
10 out of 10,
Cycling with 120 unloaded 4 out
N, 500,000
of 10, Morse
cycles at 1.8 Hz
taper: Loaded 9
out of 10,
unloaded 1 out
of 10
Bacterial inocula- For PS inoculation of the
tion: 2 out of 5
implant and
in the conical
abutment congroup and 2 out
nection and
of 5 in the interdetecting bactenal hex group,
rial leakage
for AA: 0 out of
five in the conical and 3 out of
5 in the internal
hex group
Bacterial inocula- Bacterial leakage:
internal conical
tion of the
1 out of 10, inimplant and
ternal trilobed 6
abutment conout of 10,
nection, and
cemented 0 out
measuring bacof 10
terial leakage
1. Bacterial con- Into: Conical 70%
tamination
and internal hex
before and 2. af- 100% leakage.
ter implant-abut- From: Conical
ment connec77.7% and intertion, incubation
nal hex 100%
and colony
leakage
growth
calculation
Method
System
Aloise et al.,
2010
# Samples
Insertion torque
Pr. Objective
Sec.
Objectives
Used Bacteria/
Dyes
Internal cone, Bicon Implant
10 per system Ankylos 25 Ncm, Bacterial leakage N.a.
internal cone System
Bicon tapped,
from the
(Bicon), Anky(recommended
implant-abutlos (Dentsply
by the
ment interface.
Friadent)
manufacturer)
S. sanguinis
11 per system Morse Taper 1: 35 Bacterial leakage Preload loss after S. sanguinis
(6 with and 5 Ncm, Morse
into the implant
thermal cycling
without
Taper 2 and
abutment interand mechanical
loading)
external hexago- face subjected
fatigue
nal: 15 Ncm,
to thermal cy(recommended
cling and meby the
chanical fatigue.
manufacturer)
Internal cone, Ankylos (Dents- 14 per system Ankylos 25 Ncm, Bacterial leakage Torque value loss E. coli
four groove
ply Friadent),
Bone level 35
into the implant- after loading
internal cone Bone level (ITI
Ncm, (recomabutment interStraumann)
mended by the
face during
manufacturer)
loading
Connection
Ricomini Filho Internal cone 1 Not mentioned
et al., 2010
(one piece),
internal cone
2 (two
pieces),
external hex,
locking taper
Koutouzis
et al., 2011
Author/ Year
SEAL PERFORMANCE
TABLE I. Continued
Result
Implant abutment Ankylos: 1 out of
connection,
14, mean CFUs
loading in E.
14.07652.56,
coli medium,
torque increase
disconnection
(2.8563.23
measuring loos- Ncm), Bone
ening torque,
level (ITI): 12
incubation and
out of 14, mean
measuring CFUs CFUs
184.646242.32,
torque decrease
(-5.0062.77
Ncm)
Connection, ther- Bacterial leakage
mal cycling and
after loading:
mechanical faMorse Taper 1
tigue testing,
(67%), Morse
sterilization and
Taper 2 (50%),
contamination
external hexagoto bacterial menal (0%), locking
dium, detorque
taper (60%) Premeasurements
load loss after
and SEM
cycling: Morse
analysis
Taper 1
(12.5%), Morse
Taper 2
(-23.3%), external hexagonal
(-23.1%).
Inoculation S. san- Bactarial leakage:
Ankylos 20%,
guinis, connectBicon 20%.
ing abutment
and implant,
incubation and
proof of bacterial presence or
absence
Method
Internal cone Ankylos (Dents(2x), external ply Friadent),
OsseoSpeed
flat, internal
(Astratech),
flat
Standard ITI
(ITI Straumann, Nobel
Replace
Tapered
Groovy (Nobel
Biocare)
Internal cone, Ankylos and
manipulated
manipulated
internal
Ankylos
cone, tri(Dentsply Friachannel indent), Nobel
ternal
Replace Select
connection
(Nobel
Biocare)
Baixe et al.,
2010
Tesmer et al.,
2009
System
Internal cone, OsseoSpeed
internal cone (AstraTech),
Ankylos
(Dentsply
Friadent)
Connection
Harder et al.,
2010
Author/ Year
SEAL PERFORMANCE
TABLE I. Continued
According to the
recommendation of the
manufacturer
Insertion torque
Molecular leakage N.a.
of endotoxin
along the
implant abutment interface
Pr. Objective
Sec.
Objectives
Used Bacteria/
Dyes
Method
Result
LPS of Salmonella enterica Inoculation of
Endotoxin detecimplant with
tion in both
LPS, connection groups after 5
to abutment and minutes. Signifiincubation, encant less endodotoxin detectoxin concentration and
tion (mean) for
measuring conOsseoSpeed
centration over
units over the
time (168h)
whole examination period
Longitudinal cut- The mean micro5 per system
Nobel 35 Ncm, ITI Microgap between Microgap compar- N.a.
gap was larger
ting and scaning titanium and
implant and
15 Ncm, Astra
for flat-to-flat
ning electron
zirconia
abutment
25 Ncm, Ankyinterface sysmicroscopy
abutments
los 15 Ncm (rectems compared
ommended by
to conical interthe
face systems,
manufacturer)
zirconia abutments showed
smaller microgaps than titanium abutments
10 per system Ankylos and
Bacterial invasion N.a.
A. actinomycetemcomitas, Implant abutment Bacterial contamimanipulated
into the implant
P. gingivalis
connection, con- nation Ankylos:
Ankylos 25
abutment
tamination with
(Aa 3/10, Pg 0/
Ncm, Nobel
interface
bacterial solu10, median
Replace Select
tion (Aa and
CFUs; Aa 0, Pg
35 Ncm, (recomPg), disconnec0), Nobel
mended by the
tion, incubation
Replace select:
manufacturer)
and detecting
(Aa 9/10, Pg 9/
bacterial
10, CFUs; Aa
contamination
24.5, Pg 12),
manipulated
Ankylos: (Aa 10/
10, Pg 10/10,
CFUs; Aa 81, Pg
55)
8 per system
# Samples
Insertion torque
Gross et al.,
1999
Internal cone OsseoSpeed
10 per system According to the
(3x), div.
(Astratech),
recommendaexternal flat
Ankylos, Friation of the
manufacturer
(7x), flat
lit-2, IMZ
1internal
(Dentsply Friacone, flat 1
dent), Bonefit
internal siliconical and
con washer
synOcta (ITI
Straumann),
Branemark
(Nobel Biocare), Semados (Bego
Semados),
HaTi (Ledermann), Calcitek Implants
# Samples
Jansen et al.,
1997
System
Internal cone, Standard SLA
5 per system
According to the
trilobed inter- implant (ITI,
recommendanal, internal
Straumann),
tion of the
hex
Replace Select
manufacturer
(Nobel Biocare), Intralock short collar implant
(Intra-lock Int.)
Internal cone, ITI (Straumann), 3 per system (1 10 Ncm, 20 Ncm
external hex
3i, CeraOne
per torque
and according
(2x), spline
and Steri-Oss
group)
to the recomconnection
(Nobel Biomendation of
care), Spline
the
(Sulzer
manufacturer
Calcitek),
Connection
Coelho et al.,
2008
Author/ Year
SEAL PERFORMANCE
TABLE I. Continued
N.a.
Dye leakage over
time
Used Bacteria/
Dyes
Gentian violet dye
Toluidin Blue dye
Bacterial seal from Microgap between E. coli
implant- abutimplant and
ment interface
abutment
N.a.
Sec.
Objectives
Sealing capability
of implant
system
Pr. Objective
Result
Contamination of Total release after
implant inter144h: ITI 55%,
face, connection Intra-lock 22%
to abutment and and Replace
measuring dye
Select 100%.
leakage over
time with spectrophotometric
analysis
Contamination of Leakage increased
implant interin all systems
face, connection over time with
to abutment and no significant
measuring dye
differences after
leakage over
80 minutes,
time with specleakage
trophotometric
decreased siganalysis
nificantly as
tightening torque increased to
recommended
values
Bacterial inocula- All systems
tion of the inner showed bactepart of the
rial leakage of
implant, abutthe implant
ment connecabutment intertion, cultivation
face after 5
and detection of days, the micro
bacterial leakage gap was less
over time (14
than 10 mm in
days), microgap all systems, condetection with
ical connection
SEM
systems showed
the smallest
micro gap
Method
Connection
System
Conexao Implant
Systems (Conexao Sistemas
de Protese)
Branemark
CeraOne (Nobel
Biocare), 3i
Osseotite-STA
(3i, Biomet),
Replace SelectEasy (Nobel
Biocare),
Lifecore Starge1-COC (LC
Lifecore
Biomedical)
Internal cone,
internal hex,
external hex
External hex,
external hex,
cam tube, Internal cone
Ribeiro et al.,
2011
Quek et al.,
2008
Load fatigue performance/ resistance
Seetoh et al.,
Internal cone,
Ankylos (Dentsply
2011
internal hex1
Friadent), Lifecone, internal
core PrimaConfour groove1
nex (Keystone
cone
Dental), Bone
Level (ITI
Straumann)
Author/ Year
STRESS/LOADING PERFORMANCE
TABLE II. Stress/Loading Performance
15 per system, (5
per group: recommended torque and -20%
and 120% Ncm)
30 per system
10 per system, 5
per group (titanium (Ti) and
zirconia (Zr)
abutments)
# Samples
Branemark 28 Ncm,
3i 32 Ncm,
Replace Select 35
Ncm, Lifecore 30
Ncm (recommended by the
manufacturer and
-20%/ 120%)
30 Ncm
According to the
recommendation
of the
manufacturer
Insertion torque
Sec. Objectives
Load fatigue perform- Effect of decreasance/ resistance of
ing/ increasing
different implanttightening torabutment connecque values
tion systems and
about 20%
region and mode
of failure
Load fatigue perform- Determine the failance/ resistance of
ure mode and
three implant- abutregion
ment connection
systems
Load fatigue perform- Fatigue performance/ resistance of
ance of Ti and
different implantZr abutments
abutment connecand determine
tion systems
failure mode
and region
Pr. Objective
Fatigue loading
until failure or
maximal cycles
(5 3 106 cycles).
Examination of
the fracture
region and
surface with
SEM
Fatigue loading
and calculating
of the F50 value
(at which 50%
of the samples
failed and 50%
ran out), stereomicroscopy and
SEM analysis of
fracture region
Fatigue loading
until failure of
the implant
abutment
specimens or
maximal cycles
(10 Hz, 5 3 106
cycles). SEM
analysis of
fracture region
Method
No significant difference between the
Ti abutments tested
for the three systems. Straumann
Zr abutments
showed significant
better load fatigue
resistance than
Ankylos and PrimaConnex implantsabutment systems.
External hexagonal:
F50, 53.567.8 N,
internal conical:
F50, 4462.49 N, internal hexagonal:
F50, 4563.40 N. In
24 out of 30 cases
fracture region was
observed in the
threaded part of
the abutment.
No statistical significant differences in
the number of
cycles to failure
between the four
systems when recommended torque
values were used;
failure location is
system specific and
always occurs at
the weakest point
of the implant abutment connection.
Result
System
ITI Solid and SynOcta implants
(ITI Straumann)
Branemark (Nobel
Biocare), ITI
Solid screw (ITI
Straumann)
ITI Standard (S)
and synOcta (O)
implants (ITI
Straumann) 1
Solid (S) and
synOcta (O)
abutments (ITI
Straumann)
Connection
Internal cone,
internal octagon
Internal cone,
external hex
Internal cone, internal octagon
Author/ Year
Cehreli et al.,
2004
Khraisat et al.,
2002
Perriard et al.,
2002
STRESS/LOADING PERFORMANCE
TABLE II. Continued
20 specimens for
O-O, 10 for O-S
and 10 for S-S
combination
(AbutmentImplant)
7
8
# Samples
Sec. Objectives
Load fatigue perform- Mode and region
ance/ resistance of
of failure
two different
implant- abutment
connection systems
Load fatigue perform- Fracture mode
and region,
ance/ resistance of
peak stresses in
different ITI
the implantimplant-abutment
abutment
connections
connection
40 Ncm
Load fatigue perform- Tightening torque
ance/resistance of
loss after
different implantloading
abutment connection systems
Pr. Objective
Branemark 32 Ncm,
ITI 35 Ncm (recommended by
the manufacturer)
35 Ncm (recommended by the
manufacturer)
Insertion torque
Result
Fatigue loading
Solid abutments
(500,000 cycles,
showed significant
Periotest value
higher RTVs than
(PTVs) measuresynOcta abutments,
ments after evboth implant abutery 100,000
ment connections
cycles), after tershowed comparamination reble high fatigue
moval torque
resistances
value (RTV)
measurement
Fatigue loading
ITI solid screw: no
until failure of
failures, Branethe implant
mark: fracture
abutment specibetween 1,778,023
mens or maxiand 1,733,526
mal cycles
cycles (significant
(1,800,000
difference); fraccycles), fracture
tures occurred
surface analysis
between the
with SEM
threaded and
unthreaded parts of
the abutments
Implant abutment S-O connection more
connection and
resistant to force
fatigue loading
application; S-O
(step procedure,
combination supeand calculating
rior to O-O and SF50), FEM detectS; S-S- and O-O
comparable; in
ing stress peaks
cases of fracture no
in implant-abutpreferential locament
tion detectable in
connection
all three groups;
stresses in the
implant-abutment
interface: O-O more
stresses than S-O
and S-S
Method
Connection
System
OsseSpeed (Astratech), Branemark (Nobel
Biocare)
Internal cone,
external hex
Norton et al.,
1997
Tightening/ loosening torque, cold welding
Osstem Implant
Park et al.,
Internal cone, inSystems (US II,
2010
ternal cone1
SS II, GS II)
external colar,
external hex
OsseoSpeed (1-piece Uni-abutment St and 2piece Profileabutment ST)
(Astratech)
Internal cone, internal hex1
cone
Norton et al.,
2000
Bending moment/ maximal load resistance
Coppede et al., Internal cone, inAlvim II Plus
2009
ternal hex
implants with
internal hex (IH)
and with internal cone (IC)
(Neodent
Implants)
Norton et al.,
Internal cone, inOsseoSpeed
2000
ternal cone
(Astratech),
standard ITI (ITI
Straumann)
Author/ Year
STRESS/LOADING PERFORMANCE
TABLE II. Continued
10 per system, 5
per group (titanium and tungsten carbide
carbon coated
titanium
abutments)
6
6
30 Ncm
Compression force
tightening abutment to implant
and screw removal
torque before and
after cycling
Astra 8 Ncm, Brane- Resistance to bendmark 20 Ncm
ing moment/ maxi(recommended by
mal fatigue
the manufacturer)
resistance
1-piece abutment 15 Resistance to bendNcm, 2-piece
ing moment/ maxiabutment 25 Ncm
mal fatigue
(recommended by
resistance
the manufacturer)
Astra 25 Ncm, ITI 35 Resistance to bendNcm (recoming moment/ maximended by the
mal fatigue
manufacturer)
resistance
6
Pr. Objective
IH implants 10 Ncm, Resistance to bendIC implants 20
ing moment/ maxiNcm (recommal fatigue
mended by the
resistance
manufacturer)
Insertion torque
10
# Samples
N.a.
N.a.
N.a.
N.a.
N.a.
Sec. Objectives
Astra: Mean Pb 4176
Nmm, mean Mb
5507 Nmm, significant higher bending moments at
plastic deformation
and failure than ITI:
Mean Pb 2526
Nmm, mean Mb
3269 Nmm
Astra (1-piece): Mean
Pb 4176 Nmm,
mean Mb 5507
Nmm; Astra (2-piece): Mean Pb 4049
Nmm, mean Mb
6281 Nmm, no statistical significant
differences
Astra: Mean Pb 1315
Nmm, mean Mb
2030 Nmm; Branemark: Mean Pb
mean 645 Nmm ,
mean Mb 1262
Nmm , significant
difference between
systems
IC: 90.58 6 6.72 kgf
(MDF), no fracture,
IH: 83.876 4.94 kgf
(MDF), 79.8664.77
kgf (FF), significant
difference for MDF
Result
Measuring comAll systems showed
pression force
preload loss after
and tightening
initial tightening.
and removal torExternal hexagonal
que before and
connection showed
after loading
significantly higher
(106 cycles).
preload loss after
loading than the
two conical
connections
3 point bending
test until failure
or maximum
load, measuring
plastic bending
moment (Pb)
and maximal
bending
moment (Mb)
3 point bending
test until failure
or maximum
load, measuring
plastic bending
moment (Pb)
and maximal
bending
moment (Mb)
Maximal loading
until failure,
measuring maximal deformation force (MDF)
and fracture
force (FF)
3 point bending
test until failure
or maximum
load, measuring
plastic bending
moment (Pb)
and maximal
bending
moment (Mb)
Method
System
Alvim CM
implants and
Universal abutment CM oneand two-piece
(Neodent)
OsseoSpeed
(Astratech), BioLok (Bio-Lok),
Branemark (Nobel Biocare),
Screw-vent
(Zimmer Dental)
Standard and synOcta ITI (ITI
Straumann)
Connection
Internal cone, internal cone
Internal cone,
external hex
(2x), internal
hex1 cone
Internal cone, internal octagon
Author/ Year
Richiardi
Copedde
et al., 2009
Piermatti et al.,
2006
Ding et al.,
2003
STRESS/LOADING PERFORMANCE
TABLE II. Continued
12 ITI standard, 24
synOcta (12
with solid and
12 with synOcta
abutment)
10
34 per implantabutment system, 17 per
group (loading
and no loading)
# Samples
35 Ncm (recommended by the
manufacturer)
32 Ncm
20 Ncm solid abutment, 10 Ncm
two-piece abutment (recommended by the
manufacturer)
Insertion torque
Repeated torque/
reverse torque values of each system
and implant-abutment combination
Removal torque in
combination with
loading
Effect of loading on
the abutment removal torque
Pr. Objective
Method
Result
Effect of repeated Measuring reLoading increased reinsertion/ removal torque afmoval torque; two
moval cycles on
ter repeated
piece system had
the abutment reinsertion/ reto be removed in
moval torque
moval and after
two steps with torloading (1,325
que gain of the seccycles), SEM
ond piece after
loading (cold welding); increasing
number of abutment insertion/removal decreased
removal torque
values
N.a.
Off axis loading of Astra showed significant higher torque
the specimens
loss than other sysand recording
tems under loading
removal torque
conditions, screw
every 250.000
design seems so
cycles up to 106
cycles
be an important
factor influencing
the loosing torque
Maximal failure
Measuring
Initial removal torque
load
repeated in/ out
of solid abutments
torque values
combined with
and maximal
standard and synbending
Octa implants were
moment, SEM
significantly higher
than the initial torque removal of the
synOcta implant1
abutment, solid
abutments with
both implant types
showed significant
higher load
resistance
Sec. Objectives
Saidin et al.,
2012
Internal cone, trilobe, internal
hex, internal
octagon
N.a. (simulation)
Stress/ strain distribution
Yamanishi
External hex, inter- N.a. (simulation)
et al., 2012
nal cone, internal straight
Astratech (diame- 5 for Astra, 4 for
ters 3.5 and 5.0),
ITI
standard ITI (ITI
Straumann)
Internal cone, internal cone, internal cone
Norton et al.,
1999
N.a.
N.a.
3
Weiss et al.,
2000
# Samples
System
Standard ITI (ITI
Straumann),
SpectraClone
(Alpha Bio),
Spline, Integral
and Omnitek
(Calcitek), SteriOss, Branemark
(Nobel Biocare)
Connection
Internal cone (2x),
external hex
(3x), internal octagon, flat rim
Author/ Year
STRESS/LOADING PERFORMANCE
TABLE II. Continued
Insertion torque
Pr. Objective
Comparison of torque
loss as a result of
multiple consecutive closures within
and between the
systems
N.a.
N.a.
Effect of implantabutment connection on micromotion and abutment
stress distribution
Effect of implant
abutment design
on abutment micromovement,
implant- abutment
interface and periimplant stress
distribution
Group 1: low torque Torque loss after dif(4-50 Ncm),
ferent tightening
Group 2: high tortorques in wet and
que (100- 300
dry environment
Ncm)
for different
implant-abutment
connections
According to the
recommendation
of the
manufacturer
Method
Result
Fenite element
analysis method
(FEM), simulating an oblique
load
Fenite element
analysis method
(FEM), simulating axial and
oblique loads
N.a.
External hex connection: Largest
amount of abutment movement,
higher labial bone
stresses; Internal
conical: Lowest
abutment movement and low labial
peri-coronal bone
stresses
Stress concentrates
at vertices of nonconical abutments;
conical abutments
showed more uniformly distributed
stresses; internal
hex connection
showed the greatest stresses, followed by internal
conical, octagonal
and the trilobed
connection.
200 repeated con- Significant higher
secutive closing/
maintaining torque
opening cycles
values in either
and measuring
conical frictional
the torque
elements or intervalues
locking lines, removal torque
declined for all systems progressively
up to 200 c/o cycles
Measuring differAll combination
ent tightening
showed comparaand the resultble removal toring removal torques in wet and
ques in wet and
dry environments;
dry
cold welding did
environments
not occur between
20 and 40 Ncm;
surface area of
interface seems to
influence torque
loss
N.a.
N.a.
N.a.
Sec. Objectives
3
N.a.
Conexao Implant
System (Conexao Systemas
de Protese)
Neodent Implant
System
Internal cone, internal hex,
external hex
Internal cone, internal hex,
external hex
Nishioka et al.,
2011
Pessoa et al.,
2010
# Samples
5
System
Internal hex, exter- Conexao Implant
nal hex, internal
System (Conoctagon 1cone,
exao Systemas
internal cone,
de Protese), ITI
internal locking
(Straumann),
taper
Bicon
Connection
Pellizzer et al.,
2011
Author/ Year
STRESS/LOADING PERFORMANCE
TABLE II. Continued
N.a.
According to the
recommendation
of the
manufacturer
According to the
recommendation
of the
manufacturer
Insertion torque
N.a.
Sec. Objectives
Stress/ strain in periimplant bone and
influence on abutment and implant
stability (before
and after
osseointegration)
Influence of connection type on
bone-to-implant
relative displacement and
abutment
microgap
Strain/ stress distribu- Effect of implanttion around
abutment conimplants
nection and
implant fixture
alignment
Strain/ stress distribution around
implants
Pr. Objective
Result
Photoelastic analy- Axial load: Greatest
sis under vertistress concentracal and oblique
tion in the cervical
loading
and apical thirds.
Oblique load: At
the implant apex
and in the cervical
adjacent to the
load direction. Internal octagon1
cone presented the
lowest stress concentrations, external hex exhibited
the greatest
stresses.
Strain gauge
Statistically signifianalysis
cant difference
comparing the
implant- abutment
connections, Morse
Taper and internal
hexagon did not
reduce strain
around implants,
no statistical significance in the placement configuration
Conical connection
Fenite element
showed a signifianalysis method
cant higher abut(FEM), simulatment stability, the
ing non-axial
smallest microgap
loading for immediate loaded
and the lowest
and osseointestress in the abutgrated implants
ment screw; marginal bone stresses
were comparable
for the simulation
of immediate
placed implants
and lower for
Morse Taper connection implants after
osseointegration
Method
Neodent Implant
System
Frialit-2, Ankylos
(Dentsply
Friadent)
synOcta, Monoblock ITI (ITI
Straumann),
Bicon Implants
(Bicon), OsseoSpeed
(AstraTech)
Frialit-2 (Dentsply
Friadent), Bicon,
standard ITI
Straumann
Internal cone, internal hex,
external hex,
one-piece
implant
Internal cone, internal hex
Internal cone, internal cone, internal cone,
one-piece
implant
Internal cone, internal hex, internal cone
Bernardes
et al., 2009
Quaresma
et al., 2008
Akca et al.,
2008
Lin et al., 2007
System
Connection
Author/ Year
STRESS/LOADING PERFORMANCE
TABLE II. Continued
N.a.
2 per system
N.a.
4
# Samples
N.a.
Not mentioned
N.a.
Not mentioned
Insertion torque
Force transmission in
the peri-implant
bone region of
implants with different conical
implant-abutment
connections
Strain/ stress distribution around
implants influenced
by implant-abutment connection
Strain/ stress distribution in the prosthesis, abutment,
implant and surrounding alveolar
bone under different loading
conditions
Peri-implant stress
fields generated
from four different
implant-abutment
interfaces
Pr. Objective
N.a.
N.a.
N.a.
N.a.
Sec. Objectives
Result
No significant difference under centered axial loading,
smallest periimplant stress field
for internal hexagonal connection
under off-center
loads; Internaltaper interfaces
presented intermediate results
Fenite element
Conical abutment
analysis method
showed lower
(FEM), simulatstresses on alveolar
ing different verbone and prothesis
tical occlusal
and higher stresses
forces
on abutment. Internal hexagonal abutment showed
higher bone
stresses and lower
abutment stresses
The internal conePhotoelastic and
implants showed
strain-gauge
similar interface
analysis under
force transfer charvertical and
acteristics that
oblique forces
resemble a one-piece implant system
Fenite element
Internal conical conanalysis method
nection performed
better as a force(FEM), simulattransmission meching different ocanism than other
clusal loads
systems, conical
systems showed
lower interface and
marginal bone
stresses than internal hexagonal connection system
Photoelastic strain
analysis under
different vertical
center and offcenter loading
conditions
Method
Branemark (Nobel
Biocare), ITI
solid, synOcta
(ITI Straumann)
ITI and hypothetical butt joint ITI
(ITI Straumann)
Internal cone,
external hex, internal octagon
Internal cone,
external hex
Internal cone,
external flat top
Alkan et al.,
2004
Merz et al.,
2000
Hansson et al.,
2000
Kitagawa et al., Internal cone,
2005
external hex
ITI Straumann,
Astratech, Branemark (Nobel
Biocare)
Internal cone, internal cone,
external hex
Cehreli et al.,
2004
Ankylos (Dentsply
Friadent), Branemark (Nobel
Biocare)
N.a. (simulation)
System
Connection
Author/ Year
STRESS/LOADING PERFORMANCE
TABLE II. Continued
N.a.
N.a.
N.a.
N.a.
2 per system
# Samples
Ankylos 20 Ncm,
Branemark 32
Ncm (recommended by the
manufacturer)
N.a.
Simulated with torque of 35 Ncm
according to the
recommendation
of the
manufacturer
Simulated
according to the
manufacturers
recommendations
Not mentioned
Insertion torque
Dynamic behavior
(screw loosening)
of different
implant-abutment
connections
Stress distribution
around implants
with conical and
external flat
implant abutment
connections
Mechanics of two different implantabutment
connections
Stress distribution of
preloaded dental
implant screws in
different implantabutment joint systems under simulated occlusal
forces
Force transfer characteristics of different
implant abutment
connections
Pr. Objective
N.a.
N.a.
N.a.
N.a.
N.a.
Sec. Objectives
Result
Fenite element
analysis method
(FEM) comparing the movement of the
taper-and external type-joint
model
The external typejoint model showed
rotation movement,
the taper type-joint
showed no
movement
Strains around Branemark implants were
lower than around
Astra and ITI
implants particularly under vertical
loads
3-dimensional fen- In all systems maxiite element analmum stress was
ysis method
examined between
(FEM), 3 simuthe shank and first
lating occlusal
thread of the abutloads (horizonment; stress
tal, vertical,
increased in all sysoblique)
tems under loading
conditions
Fenite elment
Significant higher
analysis method
stress in the butt
(FEM), simulatjoint connection
ing vertical and
tightening the abutdifferent off-axis
ment to the
loads
implant, taper connection compensated high forces,
butt joint showed
more stress in the
implant abutment
connection
Significant decrease
Fenite element
in the peak boneanalysis method
implant interfacial
(FEM), simushear stress in conlated axial
ical implant abutloading
ment connections,
external flat top
showed high marginal peri-implant
stress peaks, conical system showed
lower marginal
stress peaks
Photoelastic and
strain gauge
analysis with
vertical and
oblique load
application
Method
Astratech,
Branemark
(Nobel Biocare)
Astratech, Branemark (Nobel
Biocare)
Astratech,
Branemark
(Nobel Biocare)
Internal cone,
external hex
Berglundh
et al., 2005
Abrahamsson Internal cone,
et al., 1998
external hex
Abrahamsson Internal cone,
et al., 1996
external hex
Beagle dog
Beagel dos
Beagle dog
Ankylos (Dentsply Mongrel
Friadent), Branedog
mark (Nobel
Biocare)
Internal cone,
external hex
Weng et al.,
2011b
Animal
model
Ankylos (Dentsply Mongrel
Friadent), Branedog
mark (Nobel
Biocare)
System
Internal cone,
external hex
Connection
Weng et al.,
2011a
Author/Year
ANIMAL STUDIES
TABLE III. Animal Studies
5
5
6
8
6
# Animals
Healing
10 implants per
system
9 implants per
system
24 implants per
system
submerged
submerged
submerged
4 groups a 8
submerged
implants (conical equicrestal
and subcrestal,
external hexagonal crestal and
subcrestal)
4 groups a 6
nonsubmerged
implants (conical equicrestal
and subcrestal,
external hexagonal crestal and
subcrestal)
# Implants
No
No
Yes
No
No
Loading
Histological
observation
N.a.
N.a.
Secondary
objective
Histological obser- Soft tissue
vation periresponse
implant tissue,
around
marginal bone
implants to
loss
plaque
formation
Histological obser- Soft tissue
vation periaround
implant tissue,
implants
marginal bone
loss
Radiographical
marginal bone
loss
Radiographical
marginal bone
loss
Radiographical
marginal bone
loss
Primary
objective
Marginal bone
loss: Astratech
0.5760.44 mm,
Branemark
0.6260.12 mm
Marginal bone
loss Conical:
equicrestal
(0.6860.59 mm),
subcrestal
(0.7660.49 mm)
External: equicrestal
(1.3260.49 mm),
subcrestal
(1.8860.81mm)
Marginal bone
loss Conical:
equicrestal
(0.4860.66 mm),
subcrestal
(0.7960.93 mm)
External: equicrestal
(0.6960.43mm),
subcrestal
(1.5660.53 mm)
Marginal bone
loss: Astratech
0.0960.16 mm,
Branemark
0.7760.42 mm
Marginal bone
loss: Astratech
0.6460.44 mm,
Branemark
0.6460.72 mm
Results
568
SCHMITT ET AL.
PERFORMANCE OF CONICAL IMPLANT–ABUTMENT CONNECTION SYSTEMS
Connection
45
177
24 month
12 month
Ankylos (Dents- CT
ply Friadent),
Seven Sweden and
Martina
Implants
Nobel Active
RCT
(NA) internal
multicenter
and
study
external, Nobel Replace
(NR,
Nobel
Biocare)
Internal
cone,
external
hex
Internal
cone,
external
cone
external
trilobe
Crespi
et al.,
2009
Kielbassa
et al.,
2009
26
40
# Patients
24 month
12 month
Follow-up
Astratech, Bra- CT
nemark (Nobel Biocare),
ITI
(Straumann)
RCT
Study Design
Internal
cone,
external
hex
Samo Smiler
Implants,
Biospark
System
Bilhan
et al.,
2010
Pieri et al., Internal
2011
cone,
internal
hex
Author/
Year
HUMAN STUDIES
TABLE IV. Human Studies
Placed
Healing
Loading
Objective
Results
immediately nonsubmerged immediately Clinical and Marginal bone
radioloss: Conical
graphical
0.260.17
outcome
mm, internal
(marginal
hex
bone
0.5160.24
loss),
mm Implant
implant
success: Consuccess
ical 94.7%,
internal hex
100%
42 (Astra), 36
delayed
submerged
delayed
Soft tissue, Marginal bone
(Branemark),
marginal
loss: Astra29 (ITI)
bone loss,
tech 0.6660.1
implant
mm, ITI
survival
0.860.1 mm,
Branemark
1.160.1 mm,
Implant survival: all
100%
34 (Branemark), Immediately nonsubmerged Immediately Marginal
Marginal bone
30 (Ankylos)
bone loss,
loss: Conical
implant
0.7360.52
survival
mm, external
hexagonal
0.7860.45
mm Implant
survival:
both 100%
117 (internal
delayed
nonsubmerged immediately Marginal
Implant surNA), 82
bone loss
vival: Internal
(external
and soft
NA 96.6%,
NA), 126
tissue
external NA
(NR)
behavior,
96.3%, NR
implant
97.6% Marsurvival
ginal bone
rate
loss: Internal
NA
0.9561.37
mm, external
NA
0.6460.97
mm, NR
0.6361.18
mm
40 (20 per
group)
# Implants
REVIEW ARTICLE
bacterial species were used: Escherichia coli, Aggregatibacter
actinomycetemcomitans (Aa), Porphyrmonas gingivalis (Pg),
Streptococcus sanguinis (Ss), Pseudemonas aeruginosa (Pa),
and Streptococcus aureus (Sa). One study examined microbacterial endotoxin leakage from the implant–abutment
interface using lipopolysaccharides (LPS) from Salmonella
enterica (Se).42 Only Nascimento et al. examined human saliva leakage of the implant–abutment interface.43 Outcome
of included studies showed that 100% seal of the implant–
abutment interface to the outside could not be achieved
regardless of the implant–abutment connection used.4,38,39
Even if an abutment was tightened to an implant under
sterile conditions, bacterial invasion into the interface was
still demonstrated in most cases (Table I).1,40
Only one study demonstrated 100% bacterial seal using
the Ankylos implant–abutment unit to ingress/colonization
with Pg. However, when another organism, Aa, was tested it
was demonstrated that this particular bacterial species
could still penetrate into the AnkylosV implant–abutment
interface.1 Bacterial leakage was also shown in all implant–
abutment connection systems under loading in vitro.36 In
contrast, Ricomini Filho et al. reported no leakage at all
when testing the external hex implant–abutment connection
system using Ss.3
Two studies evaluated the implant–abutment seal using
dyes (toluidine blue and gentian violet) by measuring particle absorption with spectrophotometric analysis.28,44 Coelho
et al. documented significantly lower dye leakage with the
Morse Taper and internal hexagonal connection as compared to the tri-lobed internal connection system. Leakage
was recorded in all systems and decreased significantly as
tightening torque was increased to the values recommended
by the manufacturers.28
In summary: the performance of the seal was (1) different in every implant system in vitro regardless of the connection, and (2) there appeared to be significantly less
bacterial contamination in implant systems using a pure
conical implant–abutment connection as compared to other
connection systems.1,4,36,40,41 However, although conical
implant–abutment connection systems were able to reduce
bacterial contamination significantly, they were still unable
to prevent leakage of microbial endotoxin into the seal/gap
area.42 Nascimnento et al. showed siginficant less human saliva penetration to the implant–abutment interface in conical conncetion systems.43
Microgaps were detected in all systems with the scanning electron microscope (SEM), but were generally less
than 10 mm for all connections tested in this manner.39 The
mean microgap was significantly larger for flat-to-flat interface systems compared to conical interface systems.45 Using
finite element analysis (FEM),46 Merz et al. documented the
formation of a microgap for external hexagonal connection
systems on the tension side of the implant under oblique or
horizontal loading simulation. Pessoa et al. also demonstrated microgap formation on tension sides for internal
hexagonal and external hexagonal connection systems. Conical implant–abutment systems did not appear to develop
microgaps.2,37
R
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH A | FEB 2014 VOL 102A, ISSUE 2
Stress/load performance. All studies dealing with stress or
loading performance of the implant–abutment unit were
included in this part of the review. Depending on the primary outcome, the studies were summarized under the following subtopics: (1) load/fatigue performance, respectively,
and resistance. There were six studies in this category,47–52
(2) bending moment/ maximal load resistance (4 studies53–
56
, (3) preload loss (tightening/ loosening torque) and cold
welding, consisting of six studies,57–62 and (4) stress and
strain distribution in and around the implant–abutment
interface, consisting of 14 studies.2,5–7,37,63–71 Regarding the
secondary objectives, there was an overlapping between the
four subtopics in few studies. The studies were assessed for
both objectives if applicable and meeting the inclusion criteria (Table II).
Load fatigue performance/ resistance. In the investigation
of load fatigue performance, specifically resistance of the
different implant–abutment connection systems, five trials
studied the mode of abutment failure using stereomicroscopy or SEM.47–52
Although primary outcomes were different in the studies, they all focused on the issue of load fatigue performance/resistance. In relation to this Seetoh et al., Quek et al.,
and Khraisat et al. measured the fatigue loading of the
specimens until failure or to a maximum number of cycles
(5 3 106, 5 3 106 and 1.8 3 106 cycles).47,49,51 Cehreli
et al. tested implant–abutment performance using a maxiR
mum number of 500,000 cycles and used the PeriotestV
R Values (PTVs)
system to measure the so-called PeriotestV
over 100,000 cycles of loading/unloading. Ribeiro et al. and
Perriard et al. calculated the F50 value at which 50% of the
samples failed and 50% run out.48,50,52 Cehreli et al. were
unable to demonstrate failure of either the Morse Taper or
the internal octagonal attachments used for implant–abutment connections, even after 500,000 loading/unloading
cycles. There was a trend towards increased values for PTV
for both implant–abutment connection designs and there
was no significant difference between either connection systems in this regard.50 After the application of 1.8 3 106 to
5 3 106 cycles, several failures occurred.47,49,51 Khraisat
et al. reported a significant difference between the Morse
Taper (ITI Straumann) and external hexagonal connection
system (Branemark), in that no fractures were noted for the
Morse Taper group while the mean fracture rate for the
external hexagonal groups was somewhere between 1733
and 1778 cycles.51 After 5 3 106 maximum cycles, there
were no statistically significant differences relating to fatigue resistance for the various abutment systems and this
was also not altered by different manufacturer-recommended tightening torques.47,49 When focusing on the F50
value, Ribeiro et al. demonstrated superior fatigue resistance for external hexagonal implant–abutment systems (F50:
53.5 6 7.8 N), with no statistically significant differences
between the conical (F50: 44 6 2.49 N) and internal hexagonal (F50: 45 6 3.40 N) interfaces.48 Failure of the abutments
was system-dependent and occurred primarily in the region
of the weakest point, the screws, respectively, the threaded
569
parts, or between the threaded or unthreaded parts of the
abutments.48,49,51
Bending moment/ maximal load resistance. All four trials
focused on bending moment/maximal load resistance of the
implant–abutment connection used similar methods.53–56
Coppede et al. measured maximum deformation force
(MDF) and fracture force (FF) of the specimens under a
compressive load delivered at 45! from the vertical (500
gkf load cell with 1 mm/min dislocation) for internal conical (one-piece) and internal hexagonal (two-piece) implant–
abutment connection systems.53 Higher MDF values were
demonstrated for the internal conical implant–abutment
connection (90.58 6 6.72 kgf) as compared to the internal
hexagonal connection with a two-piece abutment (83.72 6
4.94 kgf). Fractures only occurred in the internal hexagonal
group at the weakest point; the threaded part of the screw.
No fractures were detected in the abutments or implants.53
Norton et al. studied the resistance of different internal conical implant–abutment connections and systems (ITI and
Astratech with solid abutments), an external hexagonal connection (Branemark, Nobel Biocare) and an internal hexagonal connection with cone and a two-piece abutment
(Astratech).54–56 The findings were published in three
papers where comparable loading approaches were used.
High load tests were run with increasing force and at a constant velocity of 1 mm/min until the applied load caused a
failure of the unit or maximal load was achieved.
Plastic bending (PB) and maximal bending (Mb) moments
were measured and compared between systems and connections. The internal conical implant–abutment connection with
R ) and the internal hexagonal
a one-piece abutment (AstratechV
R)
connection with cone and a two-piece abutment (AstratechV
had the highest resistance to bending forces. No statistically
significant differences were observed for any of the parameters studied in any of the implant systems.55 In comparing different internal conical one-piece abutment systems
R and ITIV
R ) it was shown that there was signifi(AstratechV
R
cantly higher resistance to bending forces for the AstratechV
implant–abutment connection system54 as compared to the
R ), with an
ITI system. The Branemark system (Nobel BiocareV
external hexagonal connection demonstrated the least resistance (Norton 1997) to bending. Another study62 also documented significantly higher resistance to bending forces for
systems using internal conical implant–abutment connections
in comparison to those using internal octagonal connections.62
Tightening/loosening torque and cold welding. Six trials
studied changes in preload, specifically tightening torque
loss or gain of the implant–abutment system.57–62 The principle objectives were to assess the changes in torque after
initial tightening and how this was influenced by the following: (1) Increased/decreased initial tightening torque,60 (2)
Repeated tightening and removal cycles,58,59,62 and (3) Fatigue loading.57,58,61 Two investigations addressed seal performance, whereas others were focused on stress/load
performance, particularly dealing with load fatigue performance of the implant–abutment unit.3,36,50 Ricomini Filho
570
SCHMITT ET AL.
et al. and Park et al. documented torque loss following initial tightening of the abutment to the implant but without
loading, and this was done with several internal conical and
external hexagonal implant–abutment connections.3,57
Ding et al. showed that there was initial loss of torque
after tightening; however, this loss was significantly less in
the internal conical group in comparison to the internal octagonal group.62 As well, Norton et al. documented no cold
welding measuring on the removal torque for ITI and Astratech Morse Taper implant–abutment connection systems
with applied torque values between 20 and 40 Ncm. Higher
insertion torque values (>100 Ncm) increased the rate of
cold welding, but also the rate of fractures.60 The environment (dry and wet) did not influence these outcomes.60 Torque loss was also measured as a result of multiple
consecutive closures using different implant–abutment connections. It was shown that when tightening and removal
cycles were increased in number, there were concomitant
reductions in the torque forces required for removal of the
abutment.58,59 Using this approach, Weiss et al. documented
significantly higher maintenance of torque values for both
conical frictional or interlocking elements.59
The effect of loading on torque required for abutment
removal was studied. This demonstrated that internal conical implant–abutment connection systems had significantly
less torque loss compared to internal octagonal connection
systems3 as well as external hexagonal57 connection systems. It was also shown that loading can cause cold welding
to occur between the implant and abutment in conical systems.3,36,58 Alternatively, it was shown that there was more
loss of torque in the conical connection group compared to
the external hexagonal or internal hexagonal groups after
cycling.61 However, they concluded that the design of the
connection was not a significant factor in loss of torque but,
rather, the screw design such that the use of a screw with a
thick stem and a journal provided the least loss of torque
after several cycles or tightening and loosening.
Stress/strain distribution. Fourteen studies dealt with
stress/strain distribution around dental implants and
implant–abutment interfaces. Stress transmission from the
implant–abutment interface to peri-implant bone was
detected using FEM.6,7,37,63,71 Similar data were shown
using photoelastic and strain gauge analysis.65–68,70 FEM
was also used to examine peaks of stress distribution at the
implant–abutment interface.
Four trials evaluated the stresses that occur in the periimplant and interface regions (implant–bone interface)6,7,37,63 and three evaluated only interface stresses, and
others tried to mimic occlusal loading and assessed the
stresses at three interfaces.2,64,69 One study from the load
fatigue performance/resistance subgroup also investigated
the effects of the addition of more force to the implant–
abutment interface, but this was more or less a secondary
research objective.52 Of the papers included here for analysis it was found that only two looked at the influence of the
implant–abutment joint design on abutment screw loosening using FEM (which of course would lead to movement at
PERFORMANCE OF CONICAL IMPLANT–ABUTMENT CONNECTION SYSTEMS
REVIEW ARTICLE
the abutment–implant interface).5,69 When photoelastic
strain gauge analysis was used to assess peri-implant
stresses under different loading conditions, it was demonstrated that internal conical connections did not reduce
stresses around implants compared with internal or external hexagonal connections.67,68
Cehreli et al. showed that the strain around Brånemark
implants with an external hexagonal connection was lower
than around ITI and Astratech implants with an internal conical connection, particularly under vertical loads.65 However,
the force distribution around the implants systems was similar
and it was concluded that the implant–abutment mating
design is not the decisive factor affecting stress and strain
magnitudes in a bone model.65 Comparing several conical
implant–abutment connection systems (ITI, Bicon, Astratech)
with a one piece ITI implant revealed that internal-conical connection implants have similar force transfer characteristics
than one-piece implants and the connection may not be the decisive factor influencing stress distribution around implants.66
Pessoa et al. documented lower marginal peri-implant bone
stresses around an internal conical connection implant compared with internal and external hexagonal connection
implants for osseointegrated implants using FEM.37
Also Quaresma et al. showed lower stresses in bone in
the conical group compared to the internal hexagonal
group.6 Additionally, Lin et al. and Hansson et al. reported
that conical implant–abutment connection systems performed better as a force transmission system than internal
hexagonal and external flat top systems. This resulted in
reduced peak stresses and force transmission to the marginal and apical peri-implant bone regions.7,63 Concerning
stress distribution at the implant–abutment interface, several groups documented higher stresses when external hexagonal implant–abutment connection systems were used as
compared to when internal conical and internal hexagonal
connection systems were utilized.2,37 Additionally, with the
use of conical-connection systems there was even more stability of the abutment, also with the smallest microgap in
comparison to external and internal hexagonal connection
systems.2,5,37,71 Rotational abutment movements and microgap formation were shown most often with implant systems
using the external hexagonal connection system.2,5
In vivo
Animal studies. This part of the review included five studies. Weng at al. compared radiographic marginal bone level
changes around conical and nonconical implant–abutment
connection systems for submerged and nonsubmerged
implants. Marginal bone level changes were statistically significant, with less bone loss around conical connections of
submerged and nonsubmerged implants.72,73 Berglundh
et al. documented similar outcomes for submerged healing
implants.74 Other included studies reported either comparable or less nonsignificant marginal bone loss around conical
connection implants (Table III).75,76
Human studies. The included studies differ in terms of
their implant placement and loading protocols. Two studies
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH A | FEB 2014 VOL 102A, ISSUE 2
documented implant success and bone level changes around
immediately placed and loaded conical and nonconical
implant–abutment connection implants.77,78 Further studies
followed delayed implant placement protocols with submerged or nonsubmerged healing and delayed or immediate
loading protocols.79,80 Regarding implant survival and success rates of included data revealed that conical and nonconical implant–abutment connection systems do not differ
statistically. However, three studies documented less marginal bone level changes for conical connection systems,
two out of these with a significant difference.77,78,80 Only
one study documented higher marginal bone losses around
conical implant–abutment connection systems compared to
nonconical ones (Table IV).79
DISCUSSION
This review found some relevant in vitro and in vivo evidence for the use of conical implant–abutment connection
system as it seems superior to nonconical connection systems. Reviewing the current literature concerning the performance of conical implant–abutment connection systems
revealed a large number of comparative studies dealing
with in vitro investigations. However, only few studies compared conical with nonconical connection implants in vivo.
In vitro data revealed that most systems have a gap
smaller than 10 mm.39,45 The smallest gap among all connections showed the Astra implants followed by the Ankylos
implants that have conical interface geometry.39,45 Therefore, the conical interface geometry seemed to provide a
better fit, but may not completely eliminate the gap
between the implant and abutment. One may say that a
more import factor is the abutment performance under mechanical stress as abutment movement promotes gap
enlargement and bacterial penetration. Whether this has
any clinical impact remains questionable.
For conical connection systems no rotational abutment
movement or microgap enlargement was detected under
vertical and oblique occlusal loading.2,5,37,71 External and internal hexagonal connection systems were more susceptible
to abutment micromovements.2,5,37,71 Another factor for
long-term implant–abutment stability may have the maintenance of torque value between implant and abutment after
tightening. Obviously this can prevent abutment screw loosening or movement and also microgap formation. All tested
connection systems showed torque loss after initial
tightening.53,57,62
Mechanical stress showed impact on torque values. In
most cases, conical systems showed either higher resistance
to torque loss or resulted in cold welding between implant
and abutment.3,36,53,57 No cold welding was reported for
systems without cone. Multiple consecutive closing and removal cycles showed impact on torque loss for all connection systems.59,62 With the increasing number of cycles the
torque value decreased significantly.59,62 Before final insertion of the superstructure, the number of cycles should be
minimized in order to avoid further torque loss.
All factors promoting the formation of a microgap
between implant and abutment may compromise seal
571
performance. As demonstrated, an absolute overall bacterial
seal between implant and abutment cannot be achieved.
However, most of the results indicate a statistically higher
bacterial seal for conical implant–abutment connections systems.1,4,36,40,41 In order to keep bacterial penetration as low
as possible, conical connection systems with small microgaps and resistance against abutment movement should be
favored. Abutments should be tightened to the implants
according to the manufacturer’s recommendations.
To guarantee long-term implant success, the number of
mechanical complications under loading must be minimized.
The implant–abutment connection may well be regarded as a
key point to success. The region and mode of abutment fracture also seems to be system specific but quite comparable
between systems. It was documented that fractures usually
occur at the weakest point of the construction.48,49,51 It should
be recognized then, that it is not only the geometry of the
implant–abutment interface that might influence abutment
fracture resistance, but other components and design factors
as well. These could include the number of components (onepiece or two-piece abutment connections), screw-length and
diameter; thread design, material as well as contact area. Outcomes of this review suggest that the literature is inconclusive
as to what connection is superior insofar as resistance of fracture of the fixture is concerned after loading. Studies that
investigated the effects of maximal bending forces on implant
systems suggested that implants with a conical implant/abutment connection system were more resistant to fracture than
other designs.53–55,60 This was particularly noteworthy with
respect to the one- piece conical abutment connection, which
provided greater deformation and fracture resistance to the
implant–abutment assembly under oblique compressive loading when compared to internal hexagonal and external hexagonal connection systems.53,56
High stress peaks at the implant–abutment interface,
particularly the abutment screw, may also explain how
some systems fracture or fail. Given these data it would
appear that the geometry of the interface might have an important impact on stress distribution and peak stress formation in and around implants, and effects that transcends
mere positioning of the implant and even the condition of
the bone into which the fixture has been placed.7 Studies
included in this review clearly showed that there were significantly lower stress values in the implant–abutment interface of conical implant systems as compared to external
hexagonal connections.2,37,64 However, the stresses were not
critical for all connections under loading simulation.
Despite the comments above, some authors have concluded that the implant–abutment mating design is not a
decisive factor insofar as the effects this might have on the
magnitudes of stress and strain bone. In relation to this, for
example, it has also been suggested that the diameter of the
implant could play an important role insofar as resistance
to fracture or failure of integration is concerned.64,65
Regarding study characteristics of the clinical studies
(animal and human) included in this review it was found
that many different experimental approaches were utilized,
particularly in the implant placement and loading
572
SCHMITT ET AL.
protocols.77–80 Such variation makes it difficult, albeit not
impossible to compare the outcomes of the different investigations to one another. Loss of marginal bone loss was
observed for all implant systems regardless of whether the
implants had been placed using a submerged or nonsubmerged placement protocol. Similarly the placement of immediate or delayed implants (including early or late
loading) had no effect on the loss of marginal bone. However, when marginal bone loss was assessed for implants
with conical connection systems versus those with nonconical connection systems, it was shown that there was less
bone loss about the former in most cases.72,73,75,77,80
Nevertheless, given the state of the literature in this area
it must still be recognized that there are probably several
factors that might work in concert or singly that influence
marginal heights of bone. However, at the very least it
would appear that the conical implant connection system
is more favorable insofar as maintenance of marginal bone
is concerned.
CONCLUSION
Within the limitations of the present review the following
conclusions were drawn:
In vitro
" No connection has a 100% bacterial seal. However, evidence showed that conical connection systems seem to
be superior in terms of bacterial seal.
" Conical implant–abutment connection systems seem more
resistant to abutment movement and microgap enlargement under loading. Internal and external hexagonal connection systems seem inferior in terms of abutment
movement and microgap formation.
" Conical connection systems have higher torque loss resistance than other systems.
" Conical connection systems have high resistance to fatigue loading and maximum bending.
" Conical connection systems seem to have lower abutment
screw stresses than external hexagonal connection systems and are comparable to internal hexagonal systems.
The cone compensates high stresses and protects the
screw from overloading.
" The implant–abutment interface geometry seems to be an
influencing factor for stress and strain transmission
around the implant.
In vivo
" Conical and nonconical connection systems are comparable in terms of implant success and survival.
" In most cases conical connection systems seem to produce a lower marginal bone loss.
ACKNOWLEDGMENTS
The first author was supported by grants from the Bavarian
Association for Scientific Dentistry, Germany (VfwZ) and
Dentsply Friadent. The authors declare that there is no conflict
of interest associated with this systematic literature review.
PERFORMANCE OF CONICAL IMPLANT–ABUTMENT CONNECTION SYSTEMS
REVIEW ARTICLE
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PERFORMANCE OF CONICAL IMPLANT–ABUTMENT CONNECTION SYSTEMS