64_pag. 502-507. Considerations on Dental Implants ... - incdmtm

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<strong>Considerations</strong> on Dental Implants Fixation
Conf. Sorin Kostrakievici * , As. Mircea Iulian Nistor * , S.l. Doina Bucur * ,
Medic Cristian Dobreci ** ,
*Politehnica” University of Bucharest, ** University of Medicine and Pharmacy
ABSTRACT
<strong>Considerations</strong> on dental implants fixation
In the paper it is presented a testing bench and the tests done on the special fixing
screws of the upperstructure of the metalic dental implants.
Are expressed also conclusions on measurements and those resulting for the users
and producers.
INTRODUCTION
In the nowadays dental practice one of the frequently used prosthetic methods consists
in the use of metalic dental implants, also known as root implants (after NIH 1988). These
implants implies a threaded body (fig.1) which is inserted in the mandibular or maxilar bone.
On this artificially created „root”, after osseointegration is fixed, the upperstructure of
the thooth manufactured in the dental laboratory in conformity with the anatomical structure
of the dental element of the patient. The fixing element of the upperstructure is, in this case,
also a special screw of M1.8 or M2 thread (depending of the manufacturing company.
Fig.1 Root implant
A – implant with surface treated with Titanium plasma; B – implant with surface treated with
hydroxylapatite (TPS); C - implant with fine surface texture; D - implant with medium surface texture.
<strong>502</strong>

International Conference
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MECAHITECH’10
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Fig. 2 Upperstructure fixing screw
Root osseointegration needs 3 to 6 months, time during which its central threaded
chanel is loaded up with different substances. Taking into consideration other substances
used in the dental practice such as metronidazole gel, special dental adhesive,
clorehexidine, etc., during the processes of threading into and out of the screw has been
reported accidents by tearing it off which is a very serious case as the restoring of the
implants is in general compromised.
The objective of the paper has been to investigate the resistance of the fixing screw for
different working hypothesis.
Fig.3 Testing bench
1 - rack, 2 – moment transducer IMADA HTG2-2N (0…2Nm),
3 – IMADA interface, 4 – computer display, 5 – receiving part.
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International Conference
2nd International Conference on Innovations, Recent Trends and Challenges
in Mechatronics, Mechanical Engineering and New High-Tech Products
Development
MECAHITECH’10
Bucharest, 23-24 September 2010
2. The testing bench and procedure
In order to check the different types of screws it has been manufactured a receiving
part having 10 threaded seats (fig.2, position 5) from which five are M1.8 and five M2. The
receivinf part is mounted on the rotating plate 1 of the testing bench. Above the plate is
postioned the moment transducer 2 which is connected to the computer 4. By the rotation of
the plate the special screw is treaded into the receiving part 5. The seats were treated initially
with blood, metronidazole gel, special dental adhesive, clorhexidrine and the first seat was
dried. The maximum clamping moment used was of 350Nmm as in the manufacturer
documentation.
The tested special screws were measured with a pasameter SUHL –TGL 20250.
Table 1 Outer diameter deviation of the thread for the M2 screw
Numărul
probei
Dimensiune
nominală filet [mm]
1. M2 -0,022
2. M2 -0,020
3. M2 -0,095
4. M2 -0,092
5. M2 -0,021
Abaterea de la
dimensiunea nominală [mm]
Table 2 Outer diameter deviation of the thread of the M1.8 screw
Numărul
probei
Dimensiune
nominală filet [mm]
Abaterea de la
dimensiunea nominală [mm]
1. M1,8 -0,006
2. M1,8 +0,004
3. M1,8 +0,0015
4. M1,8 -0,0092
5. M1,8 +0,011
0.4
proba 1 uscata
proba 2 clorhexidrina
0.35
0.4
0.3
0.35
0.25
valoarea m o m entulu i
0.2
0.15
0.1
0.05
Series1
valoarea m om entu lui
0.3
0.25
0.2
0.15
0.1
Series1
0
0.05
1 123 245 367 489 611 733 855 977 1099 1221 1343 1465 1587 1709 1831 1953 2075 2197 2319
-0.05
frecventa de 50 Hz
0
-0.05
1 37 73 109 145 181 217 253 289 325 361 397 433 469 505 541 577 613 <strong>64</strong>9 685 721 757 793 829 865
frecventa 50 Hz
Fig. 4 Tightening screw M2, dry
Fig. 5 Tightening screw M2, with
clorhexidrine
504

International Conference
2nd International Conference on Innovations, Recent Trends and Challenges
in Mechatronics, Mechanical Engineering and New High-Tech Products
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MECAHITECH’10
Bucharest, 23-24 September 2010
proba 3 gel metronidazol
proba 4 adeziv
0.4
0.45
0.35
0.4
0.3
0.35
valo area m o m en tu lui
0.25
0.2
0.15
0.1
Series1
valo area m o m en tu lu i
0.3
0.25
0.2
0.15
0.1
Series1
0.05
0.05
0
-0.05
1 77 153 229 305 381 457 533 609 685 761 837 913 989 1065 1141 1217 1293 1369 1445
0
-0.05
1 21 41 61 81 101 121 141 161 181 201 221 241 261 281 301 321 341 361 381 401 421 441 461 481
frecventa de 50 Hz
frecventa de 50 Hz
Fig. 6 Tightening screw M2, metronidazole
gel
Fig. 7 Tightening screw M2,
with adhezive
proba 5 sange
proba 1 uscata
0.45
0.4
0.4
0.35
valo a re a m o m en tu lu i
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
1 154 307 460 613 766 919 1072 1225 1378 1531 1684 1837 1990 2143 2296 2449 2602 2755 2908
-0.05
-0.1
Series1
v a l o a re a m o m e n tu l u i
0.3
0.25
0.2
0.15
0.1
0.05
0
1 103 205 307 409 511 613 715 817 919 1021 1123 1225 1327 1429 1531 1633 1735 1837 1939
-0.05
Series1
frecventa de 50 Hz
frecventa de 50 Hz
Fig. 8 Tightening screw M2,
with blood
Fig. 9 Tightening screw M1,8,
dry
proba 2 clorhexidrina
proba 3 gel metronidazol
0.45
0.45
0.4
0.4
0.35
0.35
0.3
0.3
v a l o a r e a m o m e n tu l u i
0.25
0.2
0.15
0.1
0.05
Series1
v a l o a r e a m o m e n tu l u i
0.25
0.2
0.15
0.1
0.05
Series1
0
1 182 363 544 725 906 1087 1268 1449 1630 1811 1992 2173 2354 2535 2716 2897 3078 3259 3440
-0.05
0
1 197 393 589 785 981 1177 1373 1569 1765 1961 2157 2353 2549 2745 2941 3137 3333 3529 3725
-0.05
-0.1
-0.1
frecventa de 50 Hz
frecventa de 50 Hz
Fig. 9 Tightening screw M1,8, cu clorhexidrine
Fig. 10 Tightening screw M1,8, with
metronidazole
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Bucharest, 23-24 September 2010
proba 4 adeziv
proba 5 sange
0.5
0.5
0.4
0.4
0.3
0.3
valo area m o m en tu lu i
0.2
0.1
0
Series1
valo area m o m en tu lu i
0.2
0.1
0
Series1
1 259 517 775 1033 1291 1549 1807 2065 2323 2581 2839 3097 3355 3613 3871 4129 4387 4<strong>64</strong>5 4903 5161
1 268 535 802 1069 1336 1603 1870 2137 2404 2671 2938 3205 3472 3739 4006 4273 4540 4807 5074 5341
-0.1
-0.1
-0.2
-0.2
frecventa de 50 Hz
frecventa de 50 Hz
Fig. 11 Tightening screw M1,8, with
adhezive
Fig. 12 Tightening screw M1,8, with blood
proba 1 seria I maxim
proba 1 seria II maxim
0.8
0.6
0.7
0.6
0.5
0.5
0.4
valo area m o m entu lu i
0.4
0.3
0.2
0.1
0
1 329 657 985 1313 1<strong>64</strong>1 1969 2297 2625 2953 3281 3609 3937 4265 4593 4921 5249 5577 5905 6233 6561
-0.1
-0.2
Series1
valo area m o m entu lu i
0.3
0.2
0.1
0
1 315 629 943 1257 1571 1885 2199 2513 2827 3141 3455 3769 4083 4397 4711 <strong>502</strong>5 5339 5653 5967 6281
-0.1
Series1
-0.3
-0.2
frecventa de 50 Hz
frecventa de 50 Hz
Fig. 13 Tightening screw M2, dry, maximum Fig. 14 Tightening screw M2, dry, maximum
moment
moment
According to the known relationship of torque screw:
M t= Q[ d 2 /2 × tg ( α + φ´ ) + µ 1 × D m /2] (1)
where:
µ dry = 0,2, µ wet = 0,15, φ´dry = arctg 0,2 = 11,3099° , φ´wet = arctg 0,15 = 8,53°, α = 30°
it can be deduced the values of the tensile forces in the screw rods when they are
maximum stressed:
Q = 243,345 N for the M2 screw and Q´= 483,50 N for the M1,8 screw (2)
For the two screws the resulting efective tensile forces in the threaded ros are:
σ t = 4Q / π d 1 ² = 136,019 N/ mm² şi σ´t = 297,03 N/ mm². (3)
3. CONCLUSIONS
In none of the tests was observed breaking any screw rod no matter of the material
interposed between the screw and the receiving plate. Also have not noticed cracks in the
structure of materials.
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2nd International Conference on Innovations, Recent Trends and Challenges
in Mechatronics, Mechanical Engineering and New High-Tech Products
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MECAHITECH’10
Bucharest, 23-24 September 2010
The conclusion here is clear that the tightening of these bolts wrench to the
recommended value of 350 Nmm, there is no riskof breaking special screws. But producers
are required to verify possible structural failure of the materials these being the only ones
which could lead to accidental breakage of these screws.
Even if tightening the screws at a maximum, possibly manually created with the
special designed instruments for thightining in the dental office, the tensile stress values do
not exceed allowable values, which justifies once again the claim that in the absence of
structural defects breaking their material is excluded.
During interventions, while working with them it is indicated to use dynamometric keys in
order to eliminate any unpleasant event.
BIBLIOGRAPHY
[1]. Cranin A. Herman , Klein Michael , Simons Alan - „Atlas of Oral Implantology” 1993,
Thieme Medical Publishers , New York
[2]. Dumitriu Horia Traian - „Parodontologie”, EdiŃia a-IV-a, Editura ViaŃa Medicală
Românească 2006
[3]. Gehrke Peter, Brunner Jochen, Wolf Dietrich, Degidi Marco, Piattelli Adriano - „Ziconium
Implant Abutments: Fracture Strength and Influence of Cyclic Loading on Retaining-
Screw Loosening”, Quintessence International vol.37, nr.7, ianuarie 2006
[4]. Karl Matthias, Rosch Silke, Friedrich Greaf, Taylor D. Thomas, Heckmann M. Siegfried
„Strain Situation after Fixation of Three-Unit Ceramic Veneered Implant Superstructures”
, Implant Dentistry, Vol. 14, nr. 2, 2005
[5]. Kohal Ralf-J., Klaus Gerold, Strub Jorg R. - „Zirconia-Implant-Supported All-Ceramic
Crowns Withstand Long-Term Load: A Pilot Investigation”, Clinical Oral Implant
Research.17, 2006
[6]. Rosenstiel, Land, Fujimoto - „Contemporary Fixed Prosthodontics”, 3-rd Edition, Ed.
Mosby, 2002
[7]. ISO 14801/2003 Încercarea la oboseală a implantelor dentare.
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