SPI®System Implant/ Abutment ConnectionStart with a Solid Connection

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SPI®System Implant/Abutment Connection

The implant/abutment connection lies

at the heart of any implant system. At

the present time there are more than

twenty different implant/abutment

connections on the market, some of

which meet the various requirements

better than others. This paper presents

an overview of how divergent

requirements for an implant/abutment

connection can be combined to

provide a superior esthetic solution

without compromising long-term

reliability.

The requirements for an optimal

implant/abutment connection can be

summarized as follows:

· Minimum platform height for optimal

prosthetic flexibility

· Accurate transfer of the implant

position to the master model

· Precise rotational orientation for

single-tooth restorations

· Maximum mechanical stability

· Optimal fatigue resistance

· Minimized microgap

· Overload protection

The SPI®System implant/abutment

connection was developed more than

twenty years ago and has proved itself

decisively in the meantime. The implant/

abutment connection of the SPI®System

was one of the first to have an internal

hexagon. Internal connections have a

great advantage over external connec-

tions in that they allow a longer engaging

surface while reducing the platform

height of the implant, which allows

more flexibility in designing the emer-

gence profile of the final restoration.

The internal hexagon of the

SPI®System is manufactured with

the highest precision and allows an

extremely accurate transfer of the

implant position to the master model,

which in turn ensures a perfect fit for

the prosthesis. The internal hexagon

also provides precise rotational

orientation and stability for single-tooth

implant restorations thanks to the

large, indexed contact surfaces1.

A unique feature of the SPI®System

implant/abutment connection is the

reinforcement collar on the implant

platform. This carries the bulk of

Start with a Solid Connection

3

2

1

non-axial forces and gives optimal

mechanical stability to the implant/

abutment connection. Further, the

reinforcement collar helps to isolate the

abutment screw from lateral forces

which could otherwise contribute to

screw loosening.

Fig. 1:

SPI®System implant/abutment

connection:

1 Reinforcement collar

· optimal mechanical stability

· focused compression for minimal

microgap

2 Internal hexagon

· minimal height for prosthetic flexibility

· rotational stability for single-tooth

implant restorations

· accurate impression transfer

3 FEM-optimized wall dimensions

· optimal fatigue resistance

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Finally, the reinforcement collar focuses

the contact area between the implant

and abutment, so that there

is higher surface compression in the

critical perimeter area of the connec-

tion with comparatively modest torque

used on the abutment screw. This

minimizes the microgap between the

implant and abutment which in turn

reduces the occurrence of bacterial

contamination2.

In determining the design of an internal

connection, particular attention has to

be paid to the strength of the implant

walls: they must be able to withstand

significant torque loads placed on the

connection during surgical insertion as

well as strong occlusal forces without

fear of deformation or fracture. For this

reason, the dimensions of the

SPI®System implant/abutment connec-

tion were calculated and optimized

using the finite element method, and

thoroughly tested on our in-house hy-

dropulser equipment to ensure optimal

strength and fatigue resistance.

All SPI®System components are

subjected to strict testing in ac-

cordance with ISO 14801. This dictates

dynamic strength testing parameters

of 2 million loading cycles at a frequency

of 2 Hz in a saline solution with a tem-

perature of 37º C (to replicate the oral

cavity).

In the FEM images, the color scale

indicates the level of stress – with blue

the lowest and red the highest. During

the design optimization process,

modifications are made and tested

until the ideal distribution of stress –

and hence strength – is obtained.

Fig. 2:

Design optimization with FEM analysis

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Fig. 3:

Test set-up for implants and prosthetic

parts according to ISO 14801

Fig. 4:

In-house laboratory for fatigue testing

Fatigue testing (ISO 14801)

10 mm

Specimen holder

PMMA

Implant

Normal bone level(no bone resorption)

Abutment

Gold coping

Simulated crown

F

5 mm

Load F [N] Runout 2 3 106 cycles

F30º

Specimen holder

PMMA

Implant

Abutment

Gold copingSimulated crown

Load rod

11 mm 8 mm

3 mm

Bone resorption

Runoutload

Lo

ad

F [

N]

3 3

1 3

Test conditionsFrequency 2 HzRunouts 2 3 106 cyclesEnvironment 0.9 % NaCI/37º C

�

The SPI® abutment screw

Fig. 5:

1 Small screw head

narrow screw channel/better

esthetics

2 Conical screw seat

to prevent loosening of the screw

3 Reduced diameter shaft

for optimal fatigue resistance

Predesigned breakage point

for overload protection

The abutment screw plays a central

role for the mechanical strength and

optimal fatigue resistance of the

SPI®System implant/abutment connec-

tion. To begin, let us summarize the

requirements of an ideal abutment

screw:

· Minimal head diameter

· No loosening

· Optimal fatigue resistance

· Overload protection

· Excellent pick-up and carrying ability

The abutment screw of the SPI®System

has a small screw head – with a diameter

of 1.6 mm respectively 1.9 mm com-

pared with more typical diameters of

2.2 mm to 2.6 mm. The small screw

head is possible because it does not

need to withstand the higher clamping

forces which other designs may require

(typically 35 Ncm) and it is protected

from non-axial loads by the reinforce-

ment collar discussed previously. The

small screw head allows SPI®System

abutments to be produced with a nar-

rower screw channel and thicker walls.

This in turn gives the dental technician

more freedom for prosthetic design and

fabrication for a strong and esthetic result.

One typical complication of implant/

abutment connections is that the

screw may loosen3,4. This is caused by

non-axial forces that may lead to rela-

tive motions between screw head and

abutment5. The abutment screw of the

SPI®System has a conical screw seat

(conical angle of 60°) that precludes

such relative lateral motions and mini-

mizes the risk of the screw becoming

loose. The same concept has been

used for decades in the car industry to

keep wheel lug nuts tight. Tests on the

hydropulser equipment have shown

that after 2 million load cycles no

Fig. 6:

Wheel of a car with the same concept

of a conical screw seat

change in the abutment screw’s

tightening torque could be observed.

The abutment screw utilizes a proven

reduced diameter shaft (anti-fatigue

shaft)6, a common component in engi-

neering that is used in the design of

connections that are subject to strong

dynamic loads7. An anti-fatigue shaft

screw differs from a normal screw in

that the shaft is subject to deformation

when exposed to tension and acts like

a spring. Tightening the abutment

screw imparts a calculated amount of

tension (“pre-load”) on the shaft which

compresses the abutment onto the

implant to generate a stable connec-

tion. The appropriate pre-load of the

abutment screw is attained by the

application of the correct tightening

torque. With the SPI®System, for the

reasons described above, the required

torque is lower than that used with

many implant systems available. It is

important not to exceed the specified

torque, because this places excessive

pre-load on the shaft and actually pre-

vents it from functioning properly.

1

3

2

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In addition to its physical design,

optimal fatigue properties of the

SPI®System abutment screw are

ensured by the use of a high-strength

titanium alloy. The selected titanium

alloy has excellent biocompatibility and

is widely used in orthopedic devices8,9.

The SPI®System abutment screw also

serves as the pre-designed breakage

point for the implant/abutment con-

nection. This minimizes the risk of

damaging the implant should the pros-

thetic be exposed to an overload,

which may occur, for example during

an accident. Prosthetic components

may be repaired or replaced relatively

easily, but it is critical that the implant

be protected in such an event. The op-

timal breakage point was determined

through careful FEM analysis and

thorough testing on the hydropulser

equipment.

Finally, convenient and safe handling is

an important design requirement for an

abutment screw. The SPI®System abut-

ment screw satisfies this requirement

with its unique 4-lobe head design.

The 4-lobe head is specially tapered to

allow easy and secure pick-up of both

abutment screw sizes using a single

screwdriver. Further, the 4-lobe head

is more resistant to deformation than

a comparably sized hexagon.

Conclusion

The SPI®System implant/abutment

connection, combined with the

SPI®System abutment screw, offers an

ideal balance of reliability, safety and

esthetics.

· Minimum platform height and head

diameter for optimal prosthetic

flexibility and excellent esthetic

results.

· Tight tolerances and precise

production methods ensure an

extremely accurate transfer of the

implant position to the master model,

which in turn ensures a perfect fit for

the prosthesis.

· Internal hexagon provides precise

rotational orientation and stability for

single-tooth implant restorations

thanks to the large, indexed contact

surfaces.

· High surface compression in the

critical perimeter area of the

connection results in a minimal

microgap between the implant and

the abutment, which in turn reduces

the occurrence of bacterial contami-

nation.

· Optimal mechanical stability and

fatigue resistance thanks to a supe-

rior design and durable material.

· Built-in protection from screw loosen-

ing with proven design techniques.

· Easy and convenient handling.

With over twenty years of proven

results, the SPI®System implant/abut-

ment connection and abutment screw

is indeed a solid connection on which

to build a lasting, beautiful restoration.

ZusammenfassungIm vorliegenden Artikel wird die Funktion der

Implantat/Abutment-Verbindung des SPI®Systems

eingehend beschrieben.

Die Verbindung zwischen Implantat und Abutment

ist eines der wichtigsten Elemente eines Implantat-

systems. Es werden verschiedene Anforderungen

an die Funktion gestellt wie minimale Bauhöhe

für prothetische Flexibilität, präzise Passungen,

optimale Ermüdungsfestigkeit etc. Um eine

bestmögliche Lösung anzubieten, kommt beim

SPI®System eine Innenverbindung, ergänzt mit einem

Führungsring, zum Einsatz. Die Innenverbindung

ist mit einem Sechskant zur Rotationssicherung

ausgebildet und weist im Vergleich zur Aussenver-

bindung eine längere Führung des Abutments auf.

Diese Führung ist ausschlaggebend für die Stabilität.

Eine Besonderheit des SPI®Systems ist der

Führungsring: Dieser schützt die Abutmentschraube

vor nicht axialen Kräften und verhindert eine

Schraubenlockerung. Zusätzlich wird durch den

Führungsring die Auflagefläche zwischen Implantat

und Abutment reduziert, wodurch bei gleichem

Anzugsmoment eine höhere Flächenpressung und

somit eine bestmögliche Abdichtung gegen Körper-

flüssigkeiten ermöglicht wird.

Die SPI® Abutmentschraube hat einen kleinen

Schraubenkopf, damit ein dünner Schraubenkanal

ermöglicht wird. Dies ist für eine optimale ästhe-

tische Versorgung notwendig. Die optimalen

Eigenschaften gegen Ermüdung der Abutment-

schraube werden einerseits durch das Design einer

klassischen Dehnschaftschraube, wie sie im traditio-

nellen Maschinenbau für dynamisch hoch belastete

Verbindungen verwendet wird, andererseits durch

die Verwendung einer hochfesten Titanliegierung

ermöglicht.

Das SPI®System wurde mittels FEM-Berechnungen

optimiert und die Ermüdungsfestigkeit ausgiebig

getestet. Dabei wurde das System so ausgelegt,

dass im Falle einer Überbelastung, wie zum Beispiel

bei einem Unfall, die Abutmentschraube als

Sollbruchstelle agiert und somit das Implantat vor

einer Beschädigung schützt.

�

1 Binon PP. The Effect of Implant/Abutment Hexagonal Misfit on Screw Joint Stability. Journal of Prosthodontics Vol. 9, 1996; 149–160

2 Steinebrunner L, Worfart S, Bössmann K, Kern M. In Vitro Evaluation of Bacterial Leakage Along the Implant-Abutment Interface of Different Implant Systems.

JOMI Vol. 20, Number 6; 2005; 875–881

3 Jung RE, Pjetursson BE, Glauser R, Zembic A, Zwahlen M, Lang NP. A systematic review of the 5-year survival and complication rates of implant supported single

crowns. Clin. Oral Impl. Res.19, 2008; 119–130

4 Kreissl ME, Gerd T, Muche R, Heydecke G, Strub JR. Technical complications of implant-supported fixed partial dentures in partially edentulous cases after an

average observation period of 5 years. Clin. Oral Impl. Res. 18, 2007; 720–726

5 Schwarz MS. Mechanical complications of dental implants. Clin Oral Impl Res. 2000; 11 (Suppl.): 156–158

6 DIN 250-1: Bolted Connections with Reduced Shank; Survey, Range of Application and Examples of Installation. 1974–09

7 Köhler H, Jende S. Motorverschraubung. GWV Fachverlage GmbH, Lexikon Motorentechnik, Der Verbrennungsmotor von A bis Z; Wiesbaden 2004

8 ASTM F1295-05 Standard Specification for Wrought Titanium-6 Aluminum-7 Niobium Alloy for Surgical Implant Applications

9 ISO 5832 Wrought Titanium-6 Aluminum-7 Niobium Alloy; 1994-09-01

RésuméCet article donne une description détaillée de la

fonction de la liaison implant/abutment du système

SPI®. La liaison entre l’implant et l’abutment est un

des éléments les plus importants d’un système

d’implants. Différentes exigences sont posées à la

fonction, comme la hauteur minimale de construc-

tion pour la flexibilité prothétique, des adaptations

précises, une résistance à la fatigue optimale, etc.

Le système SPI® utilise une liaison intérieure associée

à une bague de guidage afin d’offrir la meilleure

solution possible. La liaison intérieure est formée

d‘un hexagone assurant la protection antirotati-

onnelle et présente, par rapport à la liaison

extérieure, un guidage plus long de l‘abutment.

Ce guidage est décisif pour la stabilité.

La bague de guidage est une particularité du

système SPI®: elle protège la vis d’abutment des

forces non axiales et empêche un desserrage de

la vis.

La bague de guidage réduit de plus la surface

d’appui entre l’implant et l’abutment, ce qui offre

une pression superficielle plus élevée avec le

même couple de serrage et donc une meilleure

étanchéification contre les liquides corporels.

La tête de la vis d’abutment SP® est petite, ce qui

permet d’obtenir un canal de vissage plus fin,

nécessaire pour un soin esthétique optimal. Les

caractéristiques de fatigue optimales de la vis

d’abutment sont dues d’une part à la conception

d’une vis à tige allégée classique, telle qu’utilisée

dans la construction mécanique traditionnelle pour

des liaisons soumises à de fortes charges, et d’autre

part à l’utilisation d’un alliage titane à résistance

élevée.

Le système SPI® a été optimisé par des calculs

par éléments finis et la résistance à la fatigue a été

largement testée. Le système a été conçu de sorte

que la vis d’abutment agisse en tant que point de

rupture en cas de surcharge, par exemple d’un

accident, et protège ainsi l’implant d’un dommage.

RiassuntoNel presente articolo viene illustrata in dettaglio la

funzione della connessione impianto/abutment del

sistema SPI®. La connessione tra l’impianto e

l’abutment è uno degli elementi più importanti di

un sistema implantare. Vengono richiesti diversi

requisiti alla funzione, come un’altezza minimale

per la flessibilità protesica, accoppiamenti precisi,

resistenza ottimale alla fatica ecc.

Per offrire la migliore soluzione possibile nel sistema

SPI® viene impiegata una connessione interna

integrata da un anello di guida. La connessione

interna è dotata di un esagono con funzione

antirotazionale e, rispetto alla connessione esterna,

presenta una guida dell‘abutment più lunga. Tale

guida è determinante per la stabilità.

Una particolarità del sistema SPI® è l’anello di guida:

questo protegge la vite per abutment dalle forze

non assiali e impedisce un allentamento della vite.

Inoltre l’anello di guida riduce la superficie di

appoggio tra impianto e abutment rendendo

possibile, a parità di coppia di serraggio, una pres-

sione superficiale più elevata e, di conseguenza, la

migliore tenuta possibile contro i liquidi corporei.

La vite per abutment SPI® presenta una testa di

piccole dimensioni, per ottenere un canale di

avvitamento più stretto. Ciò è necessario per una

ricostruzione ottimale dal punto di vista estetico. Le

proprietà ideali di resistenza alla fatica della vite per

abutment si devono da un lato al design di una

classica vite con gambo scaricato, del tipo tradizio-

nalmente impiegato nella costruzione di macchine

per connessioni soggette ad un carico elevato dal

punto di vista dinamico, dall’altra all’impiego di una

lega di titanio estremamente resistente.

Il sistema SPI® è stato ottimizzato grazie a calcoli

FEM e la resistenza alla fatica è stata ampiamente

testata. Il sistema è stato progettato in modo tale

che, in caso di sovraccarico, come ad esempio in

caso di incidente, la vite per abutment funge da

punto di rottura prestabilita proteggendo l’impianto

da eventuali danni.

ResumenEn el presente artículo se describe de forma detal-

lada la función de la unión implante/pilar del sistema

SPI®. La unión entre el implante y el pilar es uno de

los elementos más importantes de un sistema de

implantes y debe satisfacer diferentes requisitos,

como una altura de construcción mínima para

permitir flexibilidad protésica, además de unos ajus-

tes precisos, una resistencia a la fatiga óptima, etc.

Para poder ofrecer la mejor solución posible, en el

sistema SPI® se ha empleado una unión interior

complementada con un anillo guía. Dicha unión está

formada por un hexágono para bloquear la rotación

y, en comparación con la unión exterior, presenta

una guía del pilar más larga. Esta guía es determi-

nante para la estabilidad.

Una particularidad del sistema SPI® es el anillo guía:

este elemento protege el tornillo de pilar de las

fuerzas no axiales y evita que el tornillo se afloje.

Además, mediante el anillo guía se reduce la superfi-

cie de apoyo entre el implante y el pilar, de modo

que con un mismo apriete se permite una mayor

presión superficial además del mejor sellado posible

frente a los fluidos corporales.

El tornillo de pilar SPI® tiene una cabeza pequeña

que permite utilizar un canal más fino. Esta

característica es necesaria para una reconstrucción

estética óptima. Las propiedades de fatiga óptimas

del tornillo de pilar se consiguen, por un lado, gracias

al diseño de un tornillo de dilatación clásico —como

los empleados en la construcción tradicional de

maquinaria para uniones dinámicamente sometidas

a una elevada carga—, y, por otro, mediante el uso

de una aleación de titanio extraordinariamente

resistente.

El sistema SPI® ha sido optimizado mediante

cálculos por el método de elementos FEM y la

resistencia a la fatiga ha sido ampliamente probada.

En este sentido, el sistema ha sido concebido de

modo que, en caso de sobrecarga, como sucede

por ejemplo en un accidente, el tornillo del pilar

actúe como punto de rotura nominal para proteger

el implante contra los daños.

A SOLID PARTNER FOR SOLID IMPLANTS.www.thommenmedical.com

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