MECAHITECH 1 Bucharest, 23-24 September 21 Considerations 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 Considerations 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. 52
MECAHITECH 1 Bucharest, 23-24 September 21 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 ( 2Nm), 3 IMADA interface, 4 computer display, 5 receiving part. 53
MECAHITECH 1 Bucharest, 23-24 September 21 2. The testing bench and procedure In order to check the different types of screws it has been manufactured a receiving part having 1 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 35Nmm as in the manufacturer documentation. The tested special screws were measured with a pasameter SUHL TGL 225. Table 1 Outer diameter deviation of the thread for the M2 screw Numărul probei Dimensiune nominală filet [mm] 1. M2 -,22 2. M2 -,2 3. M2 -,95 4. M2 -,92 5. M2 -,21 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 -,6 2. M1,8 +,4 3. M1,8 +,15 4. M1,8 -,92 5. M1,8 +,11 proba 1 uscata proba 2 clorhexidrina 5 5 5 5.5 valoarea m om entului 5 5.5 1 123 245 367 489 611 733 855 977 199 1221 1343 1465 1587 179 1831 1953 275 2197 2319 -.5 frecventa de 5 Hz -.5 1 37 73 19 145 181 217 253 289 325 361 397 433 469 55 541 577 613 649 685 721 757 793 829 865 frecventa 5 Hz Fig. 4 Tightening screw M2, dry Fig. 5 Tightening screw M2, with clorhexidrine 54
MECAHITECH 1 Bucharest, 23-24 September 21 proba 3 gel metronidazol proba 4 adeziv 5 5 5 5 5 valo area m o m en tu lu i 5 5.5.5 -.5 1 77 153 229 35 381 457 533 69 685 761 837 913 989 165 1141 1217 1293 1369 1445 -.5 1 21 41 61 81 11 121 141 161 181 21 221 241 261 281 31 321 341 361 381 41 421 441 461 481 frecventa de 5 Hz frecventa de 5 Hz Fig. 6 Tightening screw M2, metronidazole gel Fig. 7 Tightening screw M2, with adhezive proba 5 sange proba 1 uscata 5 5 valo a re a m o m en tu lu i 5 5 5.5 1 154 37 46 613 766 919 172 1225 1378 1531 1684 1837 199 2143 2296 2449 262 2755 298 -.5 - valo a re a m o m en tu lu i 5 5.5 1 13 25 37 49 511 613 715 817 919 121 1123 1225 1327 1429 1531 1633 1735 1837 1939 -.5 frecventa de 5 Hz frecventa de 5 Hz Fig. 8 Tightening screw M2, with blood Fig. 9 Tightening screw M1,8, dry proba 2 clorhexidrina proba 3 gel metronidazol 5 5 5 5 v alo are a m o m e n tu lu i 5 5.5 v alo are a m o m e n tu lu i 5 5.5 1 182 363 544 725 96 187 1268 1449 163 1811 1992 2173 2354 2535 2716 2897 378 3259 344 -.5 1 197 393 589 785 981 1177 1373 1569 1765 1961 2157 2353 2549 2745 2941 3137 3333 3529 3725 -.5 - - frecventa de 5 Hz frecventa de 5 Hz Fig. 9 Tightening screw M1,8, cu clorhexidrine Fig. 1 Tightening screw M1,8, with metronidazole 55
MECAHITECH 1 Bucharest, 23-24 September 21 proba 4 adeziv proba 5 sange.5.5 valo area m o m en tu lu i 1 259 517 775 133 1291 1549 187 265 2323 2581 2839 397 3355 3613 3871 4129 4387 4645 493 5161 1 268 535 82 169 1336 163 187 2137 244 2671 2938 325 3472 3739 46 4273 454 487 574 5341 - - - - frecventa de 5 Hz frecventa de 5 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.8.6.7.6.5.5 1 329 657 985 1313 1641 1969 2297 2625 2953 3281 369 3937 4265 4593 4921 5249 5577 595 6233 6561 - - 1 315 629 943 1257 1571 1885 2199 2513 2827 3141 3455 3769 483 4397 4711 525 5339 5653 5967 6281 - - - frecventa de 5 Hz frecventa de 5 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 =,2, µ wet =,15, φ dry = arctg,2 = 11,399, φ wet = arctg,15 = 8,53, α = 3 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 = 483,5 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 = 136,19 N/ mm² şi σ t = 297,3 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. 56
MECAHITECH 1 Bucharest, 23-24 September 21 The conclusion here is clear that the tightening of these bolts wrench to the recommended value of 35 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 26 [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 26 [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, 25 [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, 26 [6]. Rosenstiel, Land, Fujimoto - Contemporary Fixed Prosthodontics, 3-rd Edition, Ed. Mosby, 22 [7]. ISO 1481/23 Încercarea la oboseală a implantelor dentare. 57