The evaluation of external and internal implant/abutment connections

1
The evaluation of external and internal
implant/abutment connections
2

• Introduction
• Implant/abutment connection
• External connection
• Internal connection
• -Advantage
• -Disadvantage
• Selection of external/internal connection

3
Introduction

• Long-term success of dental implants
• - biologic factor, surgical procedure,
  restorative principles
• Aesthetics, simplification of Tx.

4
Implant/abutment connection

• Primary determinants of
• Joint stability
• Joint strength
• Locational rotational stability
• gt Prosthetic stability
• ( Paul P. Binon 2000)

5
Implant/abutment connection

• Original Branemark protocol
• Fully edentulous pts. With fixed prosthesis
• Coupling mech. For implant placement
• - 0.7mm-tall external hexagon
• - Only rotational torque transferring mechanism
  during the surgical placement
• - not antirotational device for partial
  edentulous pts.

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External connection

• External hex-0.7mm standard hexagon
• interchangeable in regular size platform

7
External connection-Advantages

• Long term follow up data
• Extensive use
• Broad number of prescribed clinical application
• Level of complication efforts to find solution

8
External connection- Disadvantages

• Screw loosening
• Mechanical failure
• 0.7 mm ext hex 60-80Ncm antirotational
  resistance -gt hex height and width ?, tightening
  of fixture mount screw, pretapping for hard bone
• Difficulty of abutment connection- short hex
• Rotational misfit

9
External connection-Screw loosening

• Jemt (1991), Becker and Becker (1995)
• 40 screw loosening
• (ext.connection single tooth restoration)
• Levine (1999)
• 3.6-5.3 screw loosening(conical implant
  abutment connection.)
• Most often in sigle-tooth implant, molars

10
External connection-Screw loosening

• Short,narrow ext. geometry
• - limited engagement, short fulcrum point

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External connection-Screw loosening
????? cantilever? ???? ??? ? ? fulcrum? ???? ????
????? ? ?? ? ???? ?? screw? ????? ?? hex? ???
?? ?? ? ?? ??? screw? ?? ???? screw loosening?
Force transfer mechanism In ext. hex system
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External connection-Screw loosening

• Implant diameter hex height?
• ?screw loosening?

• ???? ??? ????
• ??? bending moment(F1 x C1)
• ???? ??? bending
  moment(F2 x D1)
• D1? ? F2?
• ? ??? ???? ?? ????? screw? ???? ?? ????? screw
  loosening?

13
External connection-Screw loosening

• Compensated by
• Changing ext. hexagon - 1.2mm hex
• Changing type of screw
• Pan(flat) head seat, long stem length, 6 thread
  depth design gtmax. preload min. friction
  interference
• Gold alloy screw, TorqTite (Teflon coating),
  Gold-Tite(pure gold coating) gt min. galling
  (adhesive wear)
• Specific torque application
• Precision of the fit over the hex

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External connection-Rotational misfit

• Freedom of fit- permits horizontal rotational
  movement to accommodate fitting error(Gyllenram
  F. 1994)
• White(1993) horizontal fitting error ? screw
  deformation on tightening

Between implant hexagonal extension abutment
counterpart
15
External connection-Rotational misfit

• Binon(1995)- 13? ext. hex implant test
• machining specification ??
• Rotational freedom-min 4?, Max 10.1?
• Binon(1996)-?? ???? ?? ??? rotational freedom ??
• Binon(1996)- 5???? rotational freedom? rapid
  screw loosening
• 1.5 taper on hex, microstop on abutment
  hexagonal corner

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Internal connection

• New interface design
• - To improve connection stability throughout
  function placement
• - To simplify the armamentarium necessary for
  the clinician to complete the restoration

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Internal connection

• Friction fit
• 8?taper(ITI, Avana, 3i TG, Ankylos)
• 11?taper(Astra)
• 2?Taper Rounded channel(Bicon)
• Morse taper 6?, 8?(ITI, Swissplus, Implantium)
• Passive fit
• Internal hex(octa.Paragon)
• Trichannel(Replace Select, Camlog)
• Cam cylinder(Frialit-2)

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Internal connection
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Internal connection- Advantages

• Screw loosening?
• Convenience of abutment connection
• Reduced vertical height platform for restorative
  components more esthetic
• Distribution of lateral loading deep within
  implant, wall engagement with the implant that
  buffer vibration, potential for microbial seal

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Internal connection- Screw loosening
?Cantilever? ???? ???? -Ext. hex ???? ?? screw?
????? ?? -int. con ?? screw? ???? ??? ?? ????
??? ???? ?? ??? ?? ???? ??? ????? ?? ?screw??
??? ?? ???? loosening? ?? ???? ??
21
Internal connection- Screw loosening
??? ??? ??? Internal lever arm? ??? ???? ???
???? ?? ?? ???? ??? ??? apex?? ???? ?? ????
???? ??? ?????? ???? ? ? ?? ???? ??? ??? ????
?????, screw loosening?
22
Internal connection-Low profile
????? head top?????(0.2mm) crown margin? ????? ??
metal showing ??
23
Internal connection-Internal hexagon(Paragon)

• Slip-fit internal hexagon
• friction fit
• longer hex(1.5mm)
• 1?taper male part
• lead-in bevel
• 3.5mm narrow configuration ??? ?? ???? ???(7? ???
  65.2 in Mn, 43.5 in Mx , De Bruyn 1999)

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Internal connectionInternal cylinder
hex(Frialit-2)

• Abutment screw? body?? 5mm ??
• Mechanical test good strength, minimal
  rotation, superior screw stability, resistance to
  loosening, excellent machining tolerance(Binon
  1999)

• Hex 60 indexing?? rotational resistance ??
• Cylinder lateral load resistance, resistance to
  joint opening, protection of abutment screw, high
  strength value

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Internal connectionCylinder cam/ Deep cam tube

• Camlog(Altatec)tube-in- tube connection, Deep
  cylinder(5.4mm,upper lower internal thread),
  symmetric trichannel(1.2mm depth, 0.5 1.7??)
• ??, ?? ??? ??, ?????
• Replace Select(Nobel Biocare)
• excellent lateral stability,easy seating

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Internal connection-Cone screw tapered connection

• 8? Morse taper(ITI, 3i TG, Avana)
• tapered abutment post nonthreaded shaft
• Internal tapered connection rationale
  mechanically locking friction fit, stable,
  self-locking interface
• Short-profile octa abutment/ straight post
• Sutter(1993) the ability of the conical portion
  of interface to absorb vibration functional
  load
• ? no load to apical screw
• 11?taper(Astra, Implantium)

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Internal connection-Cone screw tapered connection

• Morse taper type

ITI 3i TG Ankylos
Astra
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Internal connectionTrue Morse tapered connection

• Bicon(Boston, MA)
• without any threaded component
• 1? to 2?tapered post fits into smooth mirror
  image shaft
• Dry clean abutment post implant shaft to secure
  the frictional resistance fit/ optimal resistance
  to dislodgement

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An in vitro evaluation of the strength of an
internal conical interface compared to a butt
joint interface in implant design(Norton MR. COIR
1997)

• Resistance to bending force

Biconical (Astra )
Standard butt joint (Branemark)
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Material Methods

• Astra (3.515, uniabutment, 8Ncm), Nobel
  biocare(3.7515, 7mm abutment, 15 Ncm)
• Test1 resistance to 3-point bending at the
  fixture-abutment interface
• Test2 resistance to 3-point bending at the
  abutment-bridge cylinder interface
• 4mm from interface edge / Repeated 6times
• 0.3mm permanent plastic deformation

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Results
Test1. 3-point bending performance at
fixture-abutment interface joint Astra 1315 Nmm
/ Bra 645 Nmm moment Test2. Abutment-bridge
cylinder interface joint Astra 994Nmm / Bra
725Nmm moment ?Internal conical interface?
??????? bending force? ?? ???? ????? ???? ????
???? ?? ? ??
32
In vitro evaluation of strength of the conical
implant-to-abutment joint in two commercially
available implant system(Norton MR. JPD 2000)

• ITI(8?taper), Astra(11?taper) conical joint?
  resistance to bending moment
• 3-point bending test
• 0.3mm permanent plastic deformation
• - Astra(4.511) 4176Nmm/ ITI(4.114) 2526Nmm
• ???? system ?? ????? ???? ??? ??? ????? ?? ?? ???

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Mechanics of the implant-abutment connection An
8-degree taper compared to a butt joint
connection( Merz IJOMI 2000)

• Understanding of 8-degree Morse taper/ butt joint
  mechanics
• 12-mm ITI solid screw implant with 6-degree 7mm
  height abutment
• 3-dimensional non-linear finite element model

34
Merz (2000)-Results
35Ncm tightening Morse taper symmetric, low
stress Butt joint Higher stress, clinically
acceptable
30 degree off-axis loading of 380N Morse
taperconical joint?? thread ??, Supporting
effect Butt jointtension side? stress ?,
abutment separated
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Merz (2000)-Conclusion

• Butt joint Only axial preload of abutment screw?
  stability of connection
• - No lock? not absorb any lateral loading
• Taper connection form lock friction ? lateral
  loading resistance
• - reducing the load on the screw
• - stable rotation- free connection

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Comparision of strength and failure mode of seven
implant systems an vitro test (Mollersten JPD
1997)

• The influence of joint depth on resistanace to
  bending forces
• 7 implant system, 10 samples

Astra, ITI, Frialit-2, Impla-Med, Nobelpharma
Estheticone, IMZ titanium abutment, IMZ connector
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Mollersten (1997)

• Universal testing machine, compressive load
  0.1mm/s, perpendicular to long axis
• Depth of failed joint? failure force?? ????? ????
  ??
• Deep joint(IMZ Ti abut, Frialit-2)?? ?? ??

38
A vitro study of retained screw stability by
various connection designs between fixture and
abutment in implant dentistry(Jae-Sik Yang, JKAP
2004)

• 5???? ????, ???, ????? ??? connection system? ??
  screw loosening? ??
• 10?? ?? ??????
• 3Hz ??, ?? 200N, 7400? ????? ??????

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Jae-Sik Yang(2004)- Results

• ?? ???
• Ex1(94.88) ltIn4ltIn3ltIn2ltIn1(115.77)
• ???? ???
• In4(79.00)ltEx1ltIn3ltIn2ltIn1(94.63)
• ?? ???? ???? ?? ???? cone screw?? beveled hex??
  ?? ???, ?????? ???? ???? ???? cone screw ?? ?? ??
  ?? ?????.

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Internal connection- Disadvantages

• Expensive, ??? ??
• Screw type multiple implant ??? UCLA abutment ???
  ? ??
• - ????? ??? ???? ??? abutment? ?? ??? ??? ??
  path of insertion? ??? ?
• Screw type? ?? ??? screw loosening ???? external
  ? ??? ??

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Internal connection- Disadvantages
?Screw type trausmucosal abutment? gold cylinder
???? ? ? ???? misfit (between gold cylinder
transmucosal abutment) ?gold screw loosening
Gold cylinder
Misfit
Transmucosal abutment
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Selection of external/internal connection
system- Single implant

• internal connection screw loosening ??? ??
• external connection ????
• - MD, BL width ???, Wide implant, zero degree
  rotation abutment, gold abutment
  screw(30-35Ncm),SCRP, Occlusal adjustment

43
Selection of connection system-Multiple implant

• Screw-retained type
• external type??
• internal type?? ??? transmucosal abutment?????
  misfit? ?? gold screw loosening? ???? ??
• ?? ???? ???? external type? ? ???

44
Selection of connection system-Multiple implant

• Cement-retained type
• - Screw loosening ?? internal type? ??
• abutment? passive?? ???? ???? abutment? passive??
  ????? internal ?? external?? ???? passive fit ??
  ? ???? misfit? ?? screw loosening? ???? ??

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Selection of connection system-Multiple implant

• ?????? cantilever?? overloading
• ????? external type ?? screw? load? ???? ???
  loosening? ?? ??
• Internal type ??? ???? ?? fixture ??? ????? screw
  loosening? ??
• ? ?? ?????? external ????? screw loosening? ?
  ???? ??
• 3? ?? ????? splinting, cantilever ???,
  overload? ??? ??

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Conclusion