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Trapezoidal thread profile

Thommen implants use thread designs optimized to their intended applications. The thread designs of the cylindrical implants and conical-cylindrical implants are therefore slightly different. The cylindrical implants, SPI®ELEMENT, SPI®ONETIME, and SPI®DIRECT, have a trapezoidal thread profile designed in accordance with ISO 9268. The thread pitch is a constant 1.0 mm. This thread design ensures an even transmission of occlusal loads in soft and dense bone. The constant thread pitch and depth combine to promote maximum primary stability.

Asymmetrical thread profile

The conical-cylindrical implant, SPI®CONTACT, has an asymmetrical thread profile designed in accordance with ISO 5835. This thread profile provides optimal dispersion of vertical loads given the reduced length of the cylindrical section compared with the other implant models. The thread pitch of the SPI®CONTACT is a constant 0.8 mm. The tighter thread pitch promotes primary stability by increasing the overall thread surface area that extends into the bone. This is an important consideration with this implant again because of the reduced length of the cylindrical section. As an added advantage, the tighter thread pitch allows more precise vertical positioning of the implant. The thread depth of the SPI®CONTACT is constant from the apical end to a level 1.5 mm below the machined collar. Here, the thread depth is reduced somewhat and the thread profile is "flattened" in order to contact the cortical bone gently and over a broader surface area. This minimizes the possibility of excessive bone compression.

Self-tapping design

Thommen implants are all self-tapping. This simplifies and expedites the surgical procedure as no additional thread-tapping step is required. The selftapping design also promotes close adaptation between implant threads and bone for optimal primary stability. The self-tapping grooves are incorporated into the implant body starting just above the domed apical end. They extend only as far coronally (approximately three or four threads) as is necessary to ensure efficient and stable implant insertion. SPI®CONTACT has only three self-tapping grooves. This is because the conical-cylindrical design requires a wider osteotomy, meaning that the self-tapping grooves normally do not come into contact with dense cortical bone.

Microsurface

The "microsurface" of the implant refers to the topography and characteristics of the modified endosseous surface. Thommen implants all feature a sandblasted/acid-etched endosseous surface. This surface modification technology, which is now widely considered an industry standard, has been employed with Thommen Implant System since 1999, and with their predecessor since 1988. This represents over twenty years' experience with the sandblast/acid-etch protocol.

1988-1998: Sandblasted, acid-etched, anodized 1999-2004: Sandblasted, acid-etched 2005: Sandblasted, thermal acid-etched

The clinical benefits of the sandblast/acid-etch protocol are very well documented: in short, it encourages more rapid osseointegration of the implant, and thus shortens the healing time for the patient. This means that the patient receives the final prosthesis, and therefore restoration of oral function and esthetics, faster. The sandblast/acid-etch technology, as used with Thommen implants, has undergone a number of evolutionary steps, as shown above.

Looking at the current process in more detail, the following refinements were introduced in 2005. The sandblasting process was further optimized by the introduction of automatic sandblasting equipment, which further increased the onsistency and reproducibility of the surface roughness ¹.

The sandblasting parameters were fine-tuned to achieve a surface roughness value of S_a between 1.0 and 2.0 µm which is known in oral implantology to promote optimal clinical performance ². The acid-etching process was also optimized to create a hydrophilic surface which is known to accelerate the healing process by promoting the activity of osteoblasts, the bone-forming cells that play a key role in the integration of implants into bone ³.

¹ Cochran DL, Buser D, ten Bruggenkate CM, Weingart D, Taylor TM, Bernard JP, Peters F, Simpson JP.; Clin Oral Implants Res. 2002;13(2):144-53 Bornstein MM, Lussi A, Schmid B, Belser UC, Buser D.; Int J Oral Maxillofac Implants. 2003;18(5):659-66 Bornstein MM. Schmid B. Belser UC. Lussi A. Buser D.: Clin. Oral Impl. 2005;16(6):631-38 Szmukler-Moncler S, Testori T, Bernard JP.; J Biomed Mater Res B Appl Biomater. 2004 Apr 15; 69(1):46-57

² Albrektsson T, Wennerberg A.; Int J Prosthodont. 2004 Sep-Oct;17(5):536-43

³ Lossdorfer S, Schwartz Z, Wang L, Lohmann CH, Turner JD, Wieland M, Cochran DL, Boyan BD.; J Biomed Mater Res. 2004 Sep 1;70A(3):361-9

Design process

Thommen Implant System components are all designed by Thommen Medical with the highest attention paid to safety, reliability and handling simplicity. Our Research & Development (R&D) team is fullye quipped with the latest 3D CAD design software systems and comprehensive in-house testing facilities. The central goal of our R&D department is to combine the input we receive from our advisors and the market with engineering innovation to create and introduce the ideal clinical solutions rapidly.

Finite Element Analysis

One of the tools which speeds the development process is our extensive use of Finite Element Analysis in close collaboration with external partners. Finite Element Analysis allows us to perform stress and strain analysis on a computer model, without having to physically produce prototypes. Once a narrow set of design attributes is isolated, prototypes can be produced and tested in our in-house facility. The result is a faster development cycle and an earlier solution to the needs of the clinician.

Internal testing

Thommen implants and abutments undergo rigorous testing, under the guidelines of ISO and other applicable standards, to ensure they meet or exceed design-required strength and precision specifications. The illustration shows a -hydropulser - test apparatus used to simulate occlusal loading of implants, abutments and abutment screws. Components are subjected to loads far in excess of what would normally be encountered in the patient's mouth. By performing the majority of such testing at our own facility, we are able to monitor and control the test conditions very closely and analyze the results rapidly.

Development partners

Thommen Medical also works closely with world-class organizations such as the Robert Mathys Foundation and the Zurich University of Applied Sciences Winterthur, who offer extensive resources for materials research, design testing and evaluation.

Material characteristics

Thommen Implant System components are manufactured using materials selected to provide an ideal combination of strength, stability and biocompatibility.

Titanium
Thommen implants and abutments are manufactured using Grade 4 Commercially Pure Titanium (norm: ASTM F67 / ISO 5832-2). While being somewhat more difficult to process, this grade provides the highest strength and durability characteristics among the commercially pure titanium grades, making it ideal for the major Thommen Implant System components. The superior biocompatibility offered by commercially pure titanium (of all grades) in comparison with titanium alloys, also makes it the natural choice for implants and abutments.

Titanium alloy
Thommen abutment screws, which are subjected to high levels of stress, are manufactured out of a special high-strength titanium alloy, Ti-6Al-7Nb (norm: ISO 5832-11). This alloy was developed in response to concerns about adverse tissue reaction with Vanadium (as contained in the still-common Ti-6Al-4V alloy). It is widely used in orthopedic devices and shows excellent strength and biocompatibility characteristics.

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