Concepts

dental implant surfaces – physicochemical properties, biological performance, and method’s adopted by SDI

Introduction
Pure titanium and titanium alloys are well established standard materials in dental implants. Because of their favorable combination of mechanical strength, chemical stability, and Biocompatibility. Integration of titanium implants with the Surrounding bone is critical for successful bone regeneration and healing of dental implant. The concept of osteointegration was discovered by Branemark and his co-worker and, has had a dramatic influence on clinical treatment of oral implants. The first generation of successfully used clinical titanium implants, which were machined with a smooth surface texture, now Approach 50 years in clinical use. Since then, implant surfaces have long been recognized to Play an important role in molecular interactions, cellular response and osteointegration, and Scientists all over the world have developed the second generation implants with surfaces Which can accelerate and improve the implant osteointegration. These second generation of clinically used implants underwent .

• Mechanical blasting
• Coupled or not
• With acid etch
• Bioactive coatings
• Anodized
• Laser modified surfaces

The main objective for the development of implant surface modifications is to promote Osteointegration, with faster and stronger bone formation. This will likely confer better Stability during the healing process, which, preferentially, will improve the clinical Performance in the area of poor bone quality and quantity.

Furthermore, such promotion may, in turn, accelerate the bone healing and thereby allowing immediate or early loading Protocols. Recently growing micro and Nano- technology is rapidly advancing surface engineering in implant dentistry. Such advances in surface engineering technologies have resulted in more complicated surface properties from micro- and nanometer scales, including the morphology, chemistry, crystal structure, physical, and mechanical properties.

Such surfaces, intentionally modified with respect to microscale and nanoscale features, may represent a next generation of oral implant systems if possible to transfer to complex three-dimensional geometries. Hitherto, micro- and Nano-fabricated surfaces have not reached the clinical evidence stage.

However, it is not known whether the improved bone response is due to surface roughness or the surface Composition.

Furthermore, somewhat surprisingly, there is yet not enough hard evidence (Randomized clinical trials) to tell whether the second generation of the implants has a better Clinical performance than the machined implants used earlier.

Nevertheless, experimental Evidence from in vitro and in vivo studies strongly suggests that some types of surface Modifications promote a more rapid bone formation than machined surfaces. It has been proposed that increasing osteo conductivity by these surface design strategies is Related to the altered implant topography resulting in enhanced osteoblast and pre osteoblast Adhesion, thereby leading to accelerated bone formation.

However, it is well known that titanium implantation in bone results in contact of the titanium surface with complex environment including blood components and other Cells, not only the osteogenic ones. Recently, it has been shown that changes in the physicochemical Properties of the titanium results in significant modulation of cell recruitment, Adhesion, inflammation and bone remodeling activities in addition to regulation on bone Formation response.

These different methods for implant surface modification may lead to different and unique Surface properties that might affect the host-to-implant response. This chapter reviews the state of art of development in dental implant surfaces and current Trends in surface modifications that aim to accelerate the osteointegration of dental Implants. The above article contains an overview of the most popular surface textures, adopted by SDI, chemical modifications including Nano-surface design based on nanoscale modification of the implant surface, but also briefly describe the interface biology of oral implants.

Surface roughness of titanium implants

Surface roughness has been identified as an important parameter for implants and its Capacity for being anchored in bone tissue. There exist a variety of different manufacturing Methods to increase the surface roughness of the implant, where the most commonly used are:

• Machining
• Sandblasting
• Acid etching
• Anodic oxidation
• Laser modification

Or a Combination of these. Further, commercially available implants have been categorized According to the roughness value
(Sa) into 4 groups:

• Smooth (Sa < 0.5 μm)
• Minimally rough (Sa = 0.5-1.0 μm)
• Moderately rough (Sa = 1.0-2.0 μm)
• Rough (Sa > 2.0 μm)

The Sa value represents the mean height of peaks and pits of the Surface, while another important parameter is Sdr, which represents the developed surface Area compared to a perfect flat area. With a larger surface area a larger contact to the bone
Tissue could be obtained.

There exists another 50 some direct or combined surface roughness Parameters, however It is unknown to what extent these are Important. For Sa measurements different factors will affect the out coming result as the type of equipment used, the area
of analysis, the filtering process of the raw data, the cut-off Values as well as where on the implant the measurements are
performed.

To obtain more comparable values in the literature guidelines for measurements have been published further, it
is important to acknowledge that the surface chemistry and surface phase composition of the implant surface will change by altering the surface roughness.

Machined surface

The first generation of Osseo integrated implants had a relatively smooth machined surface (Brenemark et al. 1969). The machined implant surface is solely turned and considered to be Minimally rough (Figure 1). Different roughness values have been published using different Measuring techniques. Moreover, manufacturing tools, bulk material, lubricant and Machining speed will influence the resulting surface topography. Typical Sa values for Machined surfaces are 0.3-1.0 μm. The surface oxide consists of a 2-10 nm thick mostly Amorphous layer of TiO2 (Lausmaa, 1996).

Depending on the sterilization method the oxide Layer could be crystallized into rutile structure (Jarmar et al., 2008). Further,
the thickness And temperature is important on the phase composition. The bone responses to machined surfaces have been extensively evaluated in different animal models as well as clinical trials. The machined surface was the first used surface in clinical Dental applications and has excellent long time followup.

Further, other extra oral applications with bone anchored implants use machined Implants, such as bone anchored
hearing aids and bone anchored Amputations prosthesis For major limbs as legs and arms. The healing around the implant
is characterized by an increase in bone-implant contact Starting at the implantation while the biomechanical stability slightly
decrease over the first Weeks, possible due to inflammation and bone remodeling, and being fully recovered after 4 Weeks in
rat tibia (Branemark et al., 1997).

Endosteal down growth of bone tissue covering The implant threads occurs in the marrow cavity and reach up to 70% bone implant contact After 16 weeks in rat tibia which could be compared to clinically stable oral implants Retrieved up to 16 year after implantation where the bone-implant contact was measured to 56-85% (Sennerby et al., 1991). 85 % bone-implant contact was observed for a clinically Stable bone anchored amputations prosthesis retrieved after 11 years.

Further, in the latter study it was shown that hydroxyapatite forms directly at the implant Surface shown in high-resolution transmission electron microscopy (TEM).