Andre´ Bu¨chter Load-related implant reaction of mini ... · porary use of the native dentition...

Load-related implant reaction of mini-implants used for orthodontic anchorage

Andre BuchterDirk WiechmannStefan KoerdtHans Peter WiesmannJosef PiffkoUlrich Meyer

Authors’ affiliations:Andre Buchter, Stefan Koerdt, Hans PeterWiesmann, Josef Piffko, Ulrich Meyer, Departmentof Cranio-Maxillofacial Surgery, University ofMunster, Munster, GermanyDirk Wiechmann, Orthodontic Department,Medical School Hanover, Germany

Correspondence to:Dr Andre BuchterDepartment of Cranio-Maxillofacial SurgeryUniversity of MunsterWaldeyerstra�e 30D-48129 MunsterGermanyTel.: þ49 251 834 7013Fax: þ49 251 834 7020e-mail: [email protected]

Key words: anchorage, implant stability, orthodontic tooth movement, osseointegration

Abstract: The purpose of this study was to determine the clinical and biomechanical

outcome of two different titanium mini-implant systems activated with different load

regimens. A total of 200 mini-implants (102 Abso Anchors and 98 Dual Tops) were placed

in the mandible of eight Gottinger minipigs. Two implants each were immediately loaded

in opposite direction by various forces (100, 300 or 500 cN) through tension coils.

Additionally, three different distances between the neck of the implant and the bone rim

(1, 2 and 3 mm) were used. The different load protocols were chosen to evaluate the load-

related implant performance. The load was provided by superelastic tension coils, which are

known to develop a virtually constant force. Non-loaded implants were used as a reference.

Following an experimental loading period of 22 and 70 days half of the minipigs were

sacrificed, and implant containing bone specimens evaluated for clinical performance and

implant stability. Implant loosing was found to be statistically dependent on the tip

moment (TM) at the bone rim. Clinical implant loosing were only present when load

exceeded 900 cN mm. No movement of implants through the bone was found in the

experimental groups, for any applied loads. Over the two experimental periods the non-

loaded implants of one type of implant had a higher stability than those of the loaded

implants. Dual Tops implants revealed a slightly higher removal torque compared with

Abso Anchors implants. Based on the results of this study, immediate loading of mini-

implants can be performed without loss of stability when the load-related biomechanics do

not exceed an upper limit of TM at the bone rim.

The number of adult patients requiring

orthodontic therapy has undergone a

marked increase in recent decades (Bauer

& Diedrich 1990). However adults fre-

quently present pathologic findings like

periodontal and endodontic diseases, dys-

function of the mandibular joint, and early

loss of teeth (Diedrich 2000). As the tem-

porary use of the native dentition for ortho-

dontic anchorage is frequently limited, and

extraoral appliances are rejected for aes-

thetic reasons, an alternative approach

based on stable and cooperation-indepen-

dent anchorage is needed (Fritz et al. 2003).

Numerous studies have shown that con-

ventional osseointegrated implants are sui-

table for orthodontic loading and offer

stable anchorage for orthodontic purposes

(Gray et al. 1983; Roberts et al. 1994;

Odmann et al. 1988; Smalley et al. 1988;

Wehrbein & Diedrich 1993). Wehrbein &

Diedrich (1993) moreover reported that the

application of orthodontic forces positively

affects the peri-implant bone situation of

osseointegrated implants. In additional stu-

dies, Wehrbein (1994) and Wehrbein et al.

(1999) evaluated the quantity of minera-

lized bone in the vicinity of the implantCopyright r Blackwell Munksgaard 2005

Date:Accepted 29 September 2004

To cite this article:Buchter A, Wiechmann D, Koerdt S, Wiesmann HP,Piffko J, Meyer U. Load-related implant reaction ofmini-implants used for orthodontic anchorage.Clin. Oral Impl. Res. 16, 2005; 473–479doi: 10.1111/j.1600-0501.2005.01149.x

473

surface and found that osseous adaptation

mechanisms during orthodontic loading

resulted in increased implant stability.

Mini-implants with a small diameter

were developed to ease the surgical inser-

tion procedure and to allow anchorage at

different positions of the alveolar bone.

Both clinical and experimental studies

have demonstrated that these implants

were basically able to provide sufficient

and stable anchorage for tooth movement

during the entire time period of orthodontic

therapy. Whereas dental implants have

high long-term success rates at about 90–

95% (Adell et al. 1981; Albrektsson et al.

1981), mini-implants failed to reach these

high success rates despite the shorter usage

period. Besides infection-dependent im-

plant failure, factors that decrease implant

success are related to interrelated biome-

chanical parameters such as implant de-

sign, bone quality and extent and time of

loading (Orenstein et al. 1998; Miyawaki

et al. 2003). Whereas titanium screws have

mainly been evaluated as orthodontic an-

chorage systems in clinical trials (Park

2001), less is known about the factors

affecting implant stability in respect to

load-related biomechanics. Recent reports

on mini-implant anchors used in clinical

studies (Park 2001; Sawa et al. 2001)

demonstrated a high number of failures.

Thus, standard clinical protocols for a bio-

mechanical by related insertion and loading

scheme are not present.

The objective of the present study was

therefore to investigate the stability of two

mini-implant systems under immediately

applied continuous orthodontic loading.

Different loads as well as various insertion

situations, mimicking the clinical situa-

tion, were used to gain insight into an

optimised application of these anchor

systems.

Material and methods

Implant designs

Screw-shaped titanium mini-implants

with a length of 10 mm and a diameter

of 1.1 mm (Abso Anchors, Dentos. Inc.,

Taegu, Seoul, Korea) and 1.6 mm (Dual

Tops, Jeil Medical Corporation, Korea)

were used in this study (Fig. 1).

Experimental animals and mini-implants

Eight male Gottinger minipigs, 14–16

months of age and with an average body

weight of 35 kg, were used. A total of 200

implants (102 Abso Anchors and 98 Dual

Tops) were placed in the mandible of

Gottinger minipigs (Fig. 2). In accordance

with the experimental design, two treat-

ment groups were tested in each animal

(Table 1). The study was approved by the

Animal Ethics Committee of the Univer-

sity of Munster under the reference num-

ber G4/2004.

Surgical procedure

All surgery was performed under sterile

conditions in a veterinary operating thea-

tre. The animals were sedated with an

intramuscular injection of ketamine

(10 mg/kg), atropine (0.06 mg/kg) and

stresnil (0.03 mg/kg). In the areas exposed

to surgery 4 ml of local anaesthesia (2%

lidocaine with 12.5mg/ml epinephrine,

xylocain/adrenalines, Astra, Wedel, Ger-

many) was injected. The left and right

mandible was exposed by skin incisions

via fascial-periosteal flaps (Fig. 3). There-

after, the implants were placed in the

caudal part of the mandible, using spiral

drills according to the standard protocol of

the manufacturer.

Two corresponding implants were in-

serted by prefabricated distance holders in

a standard distance of 17 mm (Fig. 3) at

various insertion depths (Fig. 4), leading to

force applications at different (1, 2 and

3 mm) distances from the crestal bone

(Table 1). After insertion the screws were

immediately loaded with transverse forces.

The load was provided by Sentalloys

(GAC, Grafelfing, Germany) superelastic

tension coil springs (Fig. 5), which develop

a virtually constant force of 100, 300 or

500 cN (Table 1). The tension coil springs

were protected against soft tissue ingrowth

Fig. 1. Screw-shaped titanium mini-implants with a

length of 10 mm and a diameter of 1.1 mm (Abso

Anchors) left and 1.6 mm (Dual Tops) right.

Fig. 2. Minipig with placed mini-implants in the

mandible.

Table 1. Experimental design

Minipigs 8Implants 192þ 8 fracturedSacrifice (days) 22 70Implant type Abso Anchors/Dual Tops Dual Tops/Abso Anchors

Implants 96 960 cN, 1 mm lever arm Group: LT 0 8 � 8 � 8 � 8 �100 cN, 1 mm lever arm Group: LT 1 8 � 8 � 8 � 8 �300 cN, 1 mm lever arm Group: LT 2 8 � 8 � 8 � 8 �500 cN, 1 mm lever arm Group: LT 3 8 � 8 � 8 � 8 �300 cN, 2 mm lever arm Group: LT 4 8 � 8 � 8 � 8 �300 cN, 3 mm lever arm Group: LT 5 8 � 8 � 8 � 8 �

LT, loading type.

Buchter et al . Use of mini-implants in orthodontic anchorage

474 | Clin. Oral Impl. Res. 16, 2005 / 473–479

by small latex tubes. Screws without load-

ing served as control. Six different groups

(loading types¼LT, Table 1) were evalu-

ated: 0 cN, 1 mm lever arm (LT 0); 100 cN,

1 mm lever arm (LT 1); 300 cN, 1 mm

lever arm (LT 2); 500 cN, 1 mm lever arm

(LT 3); 300 cN, 2 mm lever arm (LT 4) and

300 cN, 3 mm lever arm (LT 5). The tip

moment (TM) at the bone rim is calculated

by the formula: TM¼ force � lever arm.

After coil application the skin and the

fascia periosteum were closed in separate

layers with single resorbable sutures (Vi-

cryls4-0, Ethicon, Norderstedt, Ger-

many). Perioperatively, an antibiotic was

administered subcutaneously (2.5 ml benzyl-

penicillin/dihydrostreptomycin, Tardomy-

cels, BayerVital, Leverkusen, Germany),

every 48 h for 7 days.

Clinical follow-up

The animals were inspected after the first

few postoperative days for signs of wound

dehiscence or infection and weekly there-

after to assess general health. Loading per-

iods of 22 and 70 days were used for half of

the implants. At days 22 and 70 animals

were sacrificed with an overdose of T61

given intravenously. Following euthanasia,

mandibular block specimens containing

the two corresponding implants and sur-

rounding tissues were dissected from all of

the animals. The samples were sectioned

by a saw to remove unnecessary portions of

bone and soft tissue. Implants were con-

trolled for signs of material failure, clinical

mobility, peri-implant infection and im-

plant distance was measured.

Removal torque testing

The removal torque test was performed by

applying a counter-clockwise rotation of

the implant about its axis at a rate of

0.11/s according to the experimental set

up of Li et al. (2002) (Fig. 6). For each

implant the torque rotation curve was

recorded. The removal torque was defined

as the maximum torque (N mm) on the

curve.

Statistical analysis

Mean values and standard deviations were

calculated for removal torque testing. Be-

tween both groups descriptive statistic was

used, because of the different implant geo-

metry. Multiple comparisons between

groups were performed using two-way ana-

lysis of variance and t-tests. Difference was

considered significant when Po0.05. All

calculations were performed through the

use of SPSS for Windows (SPSS Inc.,

Chicago, IL, USA).

Results

Clinical observation

During the insertion process six Abso An-

chors and two Dual Tops implants frac-

tured the caudal of the head and were not

included in the study; new implants were

inserted. All other implants were clinically

immobile after insertion. Implants were

monocortically inserted in the mandibular

bone. The animals recovered well after

surgery and no signs of infection were

noted at any time during the observation

period. All together five tension coils were

lost (two Abso Anchors LT 4 (one after 22

and one after 70 days); two Abso Anchors

LT 5 (22 days); one LT 3 (22 days) (Tables 2

and 3) and one Dual Tops LT 5 (22 days).

Three of the Abso Anchors implants

showed a little tip in the direction of the

applied force, so that the tension coils

slipped from the implants head. The reason

for the loss of the two tension coils is

unknown. All other implants, without

the five loosening implants, showed a

good stability at a clinical level. None of

the implants was found to have moved

through the bone. One Dual Tops, one

Abso Anchors LT 5 (22 days) and three

Abso Anchors LT 5 (70 days) showed an

implant bending in the upper part of the

screws accompanied by peri-implant

bone loss and slight signs of inflammation

(Table 4).

Removal torque

During the removal torque test one Abso

Anchors and one Dual Tops implants (22

days) fractured the caudal of the head. Over

the experimental periods the Dual Tops

(22 (without LT 3) and 70 days) and Abso

Anchors (22 days) reference implants of

both groups revealed a significantly higher

implant/bone stability than those of the

loaded implants (Tables 5 and 6). Dual

Tops implants revealed a higher mean

removal torque value compared with

Fig. 3. Prefabricated distance holder for two corre-

sponding implants.

Fig. 4. Various insertion depths by prefabricated

distance holder.

Fig. 5. Loaded implants with transverse force by

superelastic tension coil springs.

Fig. 6. Removal torque test.



Abso Anchors implants. As the implant

geometry differed between both implants,

removal torque testing was not statistically

compared between these two groups. The

results of the torque testing increased for

Abso Anchors implants stability over

time (significantly at LT 3). Whereas

Dual Tops implants showed no increase

in implant stability during the experiment.

Implant stability in terms of resistance

towards torsion forces were not statistically

dependent from the applied TMs.

Discussion

Whereas conventional or modified oral

implants have been shown to successfully

serve as anchorage for orthodontic appli-

ances (Wehrbein et al. 1996) mini-implants

failed to reach these high success rates.

When the high failure rates of mini-

implants are under evaluation two main

factors have to be considered. The biome-

chanical loading of peri-implant bone as

well as the time schedule of loading, have

been shown to have a major impact on the

peri-implant bone healing (Meyer et al.

2004) and can be assumed to determine

the clinical fate of mini-implants. A mono-

cortical mandibular anchorage system as

well as a load application in magnitudes of

orthodontic practice was therefore used in

the present study to gain insight into an

optimised clinical loading protocol.

Two main findings can be demonstrated

through our experimental approach. First,

implant failure is directly related to the

tipping moment (TM) at the bone rim.

Second, by reducing the main TM under

a threshold of 900 cN mm (300 cN and

3 mm lever arm) mini-implants can be

loaded immediately without impairment

of implant stability and implant success

rates. In most of the long-term clinical

studies implant failures have been attribu-

ted to overloading or excessive loading

when no peri-implantitis phenomena

were present. Most of the implants losses

were considered to be the result of exces-

sive strains and stresses at the bone/

implant interface (Adell et al. 1981). The

present study shows that all the implants

installed into mandibular bone were suc-

cessfully loaded and remained stable

throughout the entire duration of the study,

when tipping forces were not higher then

900 cN mm. This finding is in agreement

with earlier studies (Roberts et al. 1989,

1994) demonstrating that implants re-

mained stable when subjected to tip forces

ranging from 100 to 300 cN. Studies by

Isidor (1996, 1997) revealed that excessive

lateral loading of conventional osseointe-

grated implants, a loading regimen that

was also used in our experimental set up

(900 cN mm), resulted in a high risk for the

loss of osseointegration. The fact that the

degree of loading has a direct influence on

the stability of implants confirms the

superior influence of loads generated by

function. A number of in vitro studies,

including finite-element analysis (FEA),

have reported stress concentrations to oc-

cur in the marginal peri-implant bone after

lateral or oblique load application (Borchers

& Reichart 1983; Soltesz & Siegele 1984;

Mihalko et al. 1992). FEA clearly demon-

strate that the local strain distribution had

a significant impact on the biological activ-

ity of the adjacent bone tissue (Meyer et al.

2001a). FEA calculations of Isidor (1997)

revealed that not all forces may be tolerated

by the crestal bone on a long-term basis.

High strain values above 6700 mstrain re-

sulted in peri-implant bone resorption and

a negative balance between bone apposition

Table 2. Clinical results after 22 days

Implants types Dual Tops Abso Anchors

Tensioncoil lost

Implantloosening

Implant fracture/removal torque

Tensioncoil lost

Implantloosening


0 cN, 1 mm neck/bone distance100 cN, 1 mm distance to the bone300 cN, 1 mm neck/bone distance500 cN, 1 mm neck/bone distance 1300 cN, 2 mm neck/bone distance 1 1300 cN, 3 mm neck/bone distance 1 1 2 1 1

Table 3. Clinical results after 70 days

Implants types Dual Tops Abso Anchors

Tensioncoil lost

Implantloosening


Tensioncoil lost

Implantloosening


0 cN, 1 mm neck/bone distance100 cN, 1 mm distance to the bone300 cN, 1 mm neck/bone distance500 cN, 1 mm neck/bone distance300 cN, 2 mm neck/bone distance 1300 cN, 3 mm neck/bone distance 3

Table 4. Implants loosening in relation totip moment (TM) [TM (N mm)¼ force(N) � lever arm (mm)]

0

1

2

3

4

Imp

lan

t lo

ose

nin

g (

n)

100cNmm

500cNmm

900cNmm

Abso Anchor

Dual Top



and bone resorption (Isidor 1997), confirm-

ing the hypothesis posted by Frost (1998) as

well as the findings of several authors, who

reported adaptation mechanisms to a win-

dow of physiological loading (Meyer et al.

1999a). This is also in agreement with

observations made by Hoshaw et al.

(1994), who reported that high stress con-

centration may cause marginal bone re-

sorption around implants in a load model

(Meyer et al. 2001b; Buchter et al. 2005).

Some studies using static load models con-

firm our results that low mechanical load is

not accompanied by marginal bone defects

and impaired bone mineralization (Meyer

et al. 2001a). This, in turn, means that

mini-implants could serve as anchorage for

orthodontic force systems when loads do

not exceed a tolerable strain level. It is

important to note that the amount of

stresses and strains are dependent on the

geometry of the screw as well as on the

mechanical properties of the implant and

bone. As we have not performed an FEA

analysis in our investigation, strain and

stress values in peri-implant bone cannot

directly be correlated to implant instabil-

ities and loss rate in our study. The finding

of differences in implant stability between

implants systems may be based in the

differences in implant geometry influen-

cing the strain and stress distribution in

peri-implant bone (Buchter et al. 2004).

The results of the present study confirm

that implants can be immediately loaded

by continuous forces. While it has been

stated in some studies that immediate or

early loading of oral implants impedes

successful osseointegration (Sagara et al.

1993), recent studies suggest that immedi-

ate loading can be performed under defined

conditions (Meyer et al. 1999a, 1999b,

2004). Different investigations have indi-

cated that although premature loading has

been interpreted as inducing fibrous tissue

interposition, immediate loading per se is

not responsible for fibrous encapsulation. It

is the excess of micromotions during the

healing phase that interferes with bone

repair (Szmukler-Moncler et al. 1998). Ex-

perimental observations suggest that mi-

cromotions do not systematically lead to

fibrous tissue interposition and that toler-

ance to micromotion is design and load

dependent. The effect of a continuous lat-

eral or oblique load on the peri-implant

bone has been described in in vitro experi-

ments, also using FEA (Soltesz & Siegele

1984; Mihalko et al. 1992). As these mod-

els reveal that under conditions of a direct

bone/implant contact and moderate load

applications, marginal strains are lower

than the upper limit of tolerable bone

strains, immediate loading seems to be

possible without impairment of implant

stability. Furthermore, experimental stu-

dies have not generally been able to de-

monstrate implant loosening induced by

orthodontic load (Wehrbein et al. 1997;

Akin-Nergiz et al. 1998) even when these

loads were applied immediately. Addition-

ally, a number of clinical studies have

confirmed a positive effect of orthodontic

loading on the stability of titanium screw

implants, as well as the effects on peri-

implant bone (Roberts et al. 1994; Wehr-

bein et al. 1993, 1997; Hurzeler et al.

1998). The clinical view that loaded mini-

implants showed no movement through

the bone is confirmed by the present study.

Whereas this study was of short duration

and, hence, possible long-term effects on

implant stability were not elucidated, it

must be stressed that most of the load

Table 5. Removal torque values (N mm), Abso Anchors

Treatment group Loadingtype (LT)

Days 22 AbsoAnchors (N mm)

Days 70 AbsoAnchors (N mm)

Changewithin group

Change days22 vs. 70

Reference, 1 mm distance neck/bone 0 31 � 1.41 29.85 � 1.48 � 1.15 � 1.53 P¼ 0.482100 cN, 1 mm distance neck/bone 1 11.15 � 1.33 38.25 � 11.99 27.1 � 11.99 P¼ 0.109300 cN, 1 mm distance neck/bone 2 15.35 � 6.54 41.75 � 6.53 26.4 � 6.83 P¼ 0.23500 cN, 1 mm distance neck/bone 3 13.95 � 4.08 33 � 141 19.05 � 4.1 P¼ 0.018300 cN, 2 mm distance neck/bone 4 15.5 � 4.18 30.15 � 10.86 14.65 � 11.06 P¼ 0.233300 cN, 3 mm distance neck/bone 5 15.05 � 4.24 15.25 � 1.25 0.2 � 2.46 P¼ 0.938Change reference vs. 100 cN, 1 mm distance P¼ 0.001 P¼ 0.535Change reference vs. 300 cN, 1 mm distance P¼ 0.003 P¼ 0.165Change reference vs. 500 cN, 1 mm distance P¼ 0.024 P¼ 0.12Change reference vs. 300 cN, 2 mm distance P¼ 0.004 P¼ 0.98Change reference vs. 300 cN, 3 mm distance P¼ 0.0043 P¼ 0.001

Table 6. Removal torque values (N mm), Dual Tops

Treatment group Loadingtype (LT)

Days 22 DualTops (N mm)

Days 70 DualTops (N mm)

Change withingroup

Change days22 vs. 70

Reference, 1 mm distance neck/bone 0 109 � 2.08 111.05 � 3.05 2.05 � 2.08 P¼ 0.363100 cN, 1 mm distance neck/bone 1 76.25 � 3.8 73.9 � 6.49 � 2.35 � 7.53 P¼ 0.765300 cN, 1 mm distance neck/bone 2 72.75 � 5.28 55.6 � 5.32 � 17.15 � 7.5 P¼ 0.062500 cN, 1 mm distance neck/bone 3 82.3 � 15.72 52.05 � 6.89 � 30.25 � 17.17 P¼ 1.29300 cN, 2 mm distance neck/bone 4 42.95 � 5.09 55.15 � 7.41 12.2 � 6.3 P¼ 0.101300 cN, 3 mm distance neck/bone 5 60.15 � 5.87 59.95 � 18.1 � 0.2 � 19.59 P¼ 0.992Change reference vs. 100 cN, 1 mm distance P¼ 0.001 P¼ 0.002Change reference vs. 300 cN, 1 mm distance P¼ 0.003 P¼ 0.004Change reference vs. 500 cN, 1 mm distance P¼ 0.143 P¼ 0.01Change reference vs. 300 cN, 2 mm distance P¼ 0.001 P¼ 0.001Change reference vs. 300 cN, 3 mm distance P¼ 0.002 P¼ 0.0797



application are time limited in clinical

orthodontic practice.

We used in the surgical procedures a

closed-flap technique differs from the clin-

ical procedure in which no closed flap is

used. Depending on the localization the

miniscrews are either through attached

gingiva or the screw head is covered again

with mucosa letting only the wire or oil

spring penetrate the mucosa. In any case

there is an increased infection risk com-

pared with a closed-flap technique thus in

turn increasing the risk for screw failure.

To eliminate this infection risk, we used in

our study the closed-flap technique. Clin-

ical randomised prospective studies will be

necessary to investigate the implant loss

rate.

In conclusion the present study indicate

that a moderate static, lateral loading of

mini-implants with forces typically used

for orthodontic movement, does not impair

implant stability. It may be assumed that

above a defined threshold marginal bone

strains cannot be tolerated by the bone

tissue, leading to implant loosening.

Resume

Le but de cette etude a ete de determiner ce qui se

passait cliniquement et biomecaniquement au ni-

veau de deux systemes de mini-implants en titane

actives par differents regimes de mise en charge.

Deux cents mini-implants (102 Abso Anchors et 98

Dual Tops) ont ete places dans la mandibule de huit

mini-porcs de Gottinger. Deux implants chacun ont

ete immediatement mis en charge dans une direc-

tion opposee avec des forces variables (100 cN,

300 cN ou 500 cN) par des ressorts de tension. De

plus trois distances differentes entre l’epaulement de

l’implant et le rebord osseux (1, 2, 3 mm) ont ete

utilises. Les differents protocoles de mise en charge

ont ete choisis pour evaluer la performance implan-

taire vis-a-vis de la mise en charge. Cette charge

etait produite par des ressorts de tension super-

elastiques connues pour developper une force

quasi-constante. Des implants sans charge ont servi

de controle. Suivant une periode de mise en charge

de 22 et 70 jours la moitie des mini-porcs ont ete

euthanasies et les specimens comprenant l’os et

l’implant evalues pour leur performance clinique et

leur stabilite implantaire. La mobilite implantaire a

ete reconnue comme statisquement dependante du

moment de l’extremite au niveau du bord osseux. La

mobilite implantaire clinique a seulement ete re-

ncontree lorsque la charge depassait 900 cN mm.

Aucun mouvement des implants n’a ete trouvee

dans le groupe experimental pour aucune des forces

appliquees. Durant les deux periodes experimentales

les implants non-charges d’un type d’implant avai-

ent une stabilite superieure a celle des implants

charges. Les implants Dual Tops avaient une force

de torsion d’enlevement un peu plus importante que

les implants Abso Anchors. La mise en charge

immediate de mini-implants peut etre effectuee sans

perte de stabilite lorsque la charge en relation avec la

biomecanique n’excede pas une limite superieure du

moment de l’extremite au niveau du bord osseux.

Zusammenfassung

Belastungsbedingte Reaktionen von Mini-Implan-

taten, welche fur orthodontische Verankerungen

verwendet werden

Es war das Ziel dieser Studie, die klinische und

biomechanische Reaktion bei zwei verschiedenen

Titan Mini-Implantat-Systemen, welche verschie-

denen Belastungen ausgesetzt wurden, zu bestim-

men. Insgesamt wurden 200 Mini-Implantate (102

Abso Anchors und 98 Dual Tops) in die Unterkie-

fer von 8 Gottinger Minipigs eingesetzt. Immer zwei

Implantate wurden jeweils sofort in entgegen gesetz-

ter Richtung mit unterschiedlichen Kraften

(100 cN, 300 cN oder 500 cN) durch Zugfedern

belastet. Zusatzlich wurden drei verschiedene Ab-

stande zwischen dem Hals des Implantats und der

Knochenkante (1 mm, 2 mm, 3 mm) verwendet.

Die unterschiedlichen Belastungsprotokolle wurden

ausgewahlt, um die belastungsbedingte Implanta-

treaktion auszuwerten. Die Belastung wurde mit

superelastischen Zugfedern durchgefuhrt, welche

dafur bekannt sind, dass sie eine relativ konstante

Kraft entwickeln. Unbelastete Implantate dienten

als Kontrolle. Nach einer experimentellen Belas-

tungsdauer von 22 und 70 Tagen wurde je die Halfte

der Minipigs geopfert. An Knochenpraparaten mit

Implantaten wurde die klinische Reaktion und die

Stabilitat der Implantate ausgewertet. Es wurde

entdeckt, dass die Lockerung von Implantaten sta-

tistisch signifikant abhangig vom Kippmoment auf

Hohe der Knochenkante war. Eine klinische Lock-

erung von Implantaten trat nur auf, wenn die Belas-

tung 900 cN mm uberstieg. Bei den experimentellen

Gruppen konnte mit den applizierten Kraften keine

Bewegung der Implantate durch den Knochen aus-

gelost werden. Ueber die zwei Abschnitte des Ex-

periments wiesen die nicht belasteten Implantate

eines Typs eine grossere Stabilitat als die belasteten

Implantate auf. Die Dual Tops Implantate zeigten

leicht hohere Ausdrehmomente als die Abso An-

chors Implantate. Aufgrund der Resultate dieser

Studie kann eine Sofortbelastung von Mini-Implan-

taten ohne Stabilitatsverlust durchgefuhrt werden,

sofern durch die Belastung die obere Grenze eines

Kippmoments auf Hohe der Knochenkante nicht

uberschreitet.

Resumen

El proposito de este estudio fue determinar los

resultados clınicos y biomecanicos de dos sistemas

diferentes de mini-implantes de titanio activados

con diferentes regimenes de carga. Se colocaron un

total de 200 mini-implantes (102 Abso Anchors y

98 Dual Tops) en la mandıbula de 8 minicerdos

Gottinger. Se cargaron dos implantes inmediata-

mente en direcciones opuestas con varias fuerzas

(100 cN, 300 cN o 500 cN) a traves de resortes de

tension. Se usaron, adicionalmente, tres distancias

diferentes entre el cuello del implante y el reborde

oseo (1 mm, 2 mm, 3 mm). Los diferentes protocolos

de carga se eligieron para evaluar el rendimiento

relacionado con la carga. La carga se suministro por

medio de resortes de tension superelasticos, conoci-

dos por desarrollar una fuerza virtualmente con-

stante. Los implantes no cargados se usaron como

referencia. Tras un periodo experimental de carga de

22 y 70 dıas la mitad de los minicerdos se sacrifi-

caron, y se evaluaron los implantes conteniendo

especımenes oseos para el rendimiento clınico y

estabilidad de los implantes. El aflojamiento del

implante se encontro que era estadısticamente de-

pendiente de la punta del momento en el reborde

oseo. El aflojamiento clınico del implante solo se

presento cuando la carga excedio los 900 cN mm.

No se encontro movimiento de los implantes a

traves del hueso en los grupos experimentales, en

ninguna de las cargas aplicadas. A lo largo de los dos

periodos experimentales los implantes sin carga de

un tipo de implante tuvieron una mayor estabilidad

que aquellos de los implantes cargados. Los im-

plantes Dual Tops necesitaron un mayor torque

de remocion en comparacion con los implantes Abso

Anchors. Basandose en los resultados de este estu-

dio, la carga inmediata se puede llevar a cabo sin

perdida de estabilidad cuando la biomecanica rela-

cionada con la carga no supere un lımite superior de

la punta del momento en el reborde oseo.



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