TECHNICAL FIELD

Invention; is related to the surface preparation methods that increase connection and the adhesion quality of implant with the bone and periodontal tissues.

PRIOR ART

Dental implants are apparatuses that replace lost teeth, and are inserted into the bone to provide support fixed and removable prosthesis. Nowadays it is the best treatment alternative that can be applied in case of the loss of natural teeth.

Although dental implants are placed into the alveolar bone, three types of cells in the implant tissue interface are involved. These are; epithelial cells in the peri-implant epithelial, fibroblasts in the connective tissues and osteoblasts in the bone. Dental implants are also in contact with the dental plaque that leads to inflammation of the periimplant tissues in the oral cavity. Increasing the adhesion of soft tissue cells to the implant surface is an important method for preventing degeneration of peri-implant soft tissue.

Performing different surface engineering applications on implant surfaces, it has been tried to increase the quality of connection and adhesion of implant to the the bone and periodontal tissues. The more effective topography and surface roughness in the preparation of the implant surface is, the more important the cleaning and passivation of the surface is.

Researchers in previous studies have concluded that the long-term prognosis of implants depends not only on the quality of osseointegration but also implant abutments or the quality of mucosal closure between the implant gingiva.

While creating a surface topography using laser application in preparation of the implant surface, effluent does not occur on the surface and biocompatibility is maintained. Together with developments in laser applications technology, desired surface properties (roughness, preparation the surface topography in a neat and controlled way, surface energy, surface cleaning) can be created optionally.

The basic advantage of roughening with laser is that the required topography can be created in a single step causing no harmful effluent in a controlled manner.

Classification of the implants by surface properties;

1 ) Rough-surfaced implants,

2) Processed surfaced implants,

a) Polished surfaced implants,

b) Sandblasted and roughened surfaced implants,

c) Etched surfaced implants,

d) Sandblasted and etched surfaced implants,

e) Laser roughened surfaced implants,

f) Porous surfaced implants,

g) Porous sintered surfaced implants,

3) Coated surfaced implants:

a) Plasma spray coated surfaced implants,

b) Ceramic coated surfaced implants,

c) Tricalcium phosphate (TCP) coated surfaced implants, d) Hydroxyapatite (HA) coated surfaced implants

4) Combined implants.

As the surface morphology of the implant is as important as the design in osseointegration and the behavior of peri-implant tissues, the implant surfaces should be roughened.

The benefits of roughening:

1 ) Surface expands, distribution of power becomes more balanced. Since the force applied to a unit area will be reduced, the stress concentrated in the bone around the implant is distributed significantly.

2) Micro-mechanical retention of the implant increases; this is important for primary stabilization. 3) In particular, it increases the resistance of the implant against rotation and pulling forces.

4) Bone and peri-implant tissues penetrate and hold better to the rough surfaces. Thus, only by changing the topography of the material surface, the material gains superior properties.

If the roughness is greater than Ι ΟΟμιη, macroporosity is formed, if it is between Ι ΟΟμιη and nm, microporosity will be created. Micro roughness increases the adhesion of the implant to the bone which cannot only be explained by the mechanical interlocking, and it induces matrix deposition and mineralization by influencing cellular functions. That is, cells are sensitive to the surface microstructure and they use these structures for orientation and migration. Moreover, microtopography plays a role in differentiation of mesenchymal cells into fibroblasts, chondroblasts or osteoblasts. Although the ideal size of roughness vary according to the quality of the bone and the load applied on the implant, it is determined to be approximately 1 .0-1 .5 μιη. This is only formed by aluminum oxide between 25-75μιη (AI2O3) particles if sandblasting method is used. Although larger particles create more roughness, it does not affect bone respond in a positive way and does not increase the implant-bone contact. All these show that bone cells love grooving areas of and they respond surface roughness with steoid matrix deposition and mineralization. While bone cells recognize 1 .0-1 .5μιη roughness and adjust their cellular functions according to it, they perceive larger surface roughness as if it was flat.

Morphological irregularities at the nanometer level affect the biological response. If the oxide layer on the surface is thickened, metal surface turns the amorphous state containing non-crystalline oxide into a polycrystalline surface with a crystalline layer. This surface has a porosity in the nanometer level. Thick oxide layer improves the bone response in the the first week of implantation, but this difference loses its significance in the following weeks.

The outermost molecular layers of the biomaterial are important. The chemical properties of them direct the tissue response. For example; not titanium itself but the titanium surface oxide (TiO) layer formed spontaneously on the surface is what gives it a good biomaterial property. In this case, bone adheres titanium (Ti) surface firmly with passive growth (adaptive osseointegration).

The characteristic of implant surface plays a determining role in creating a connection between the implant and bone and soft tissues.

It has been known that tissues are not in contact with the implant material itself but the oxide layer on the outermost surface of the implant.

Changing the surface energy, surface passivation, the changes on the surface composition are physicochemical methods. Positively or negatively charged surfaces are known to have directed bone formation.

Animal experiments with rotation tests with rough surfaces and polished ones have revealed that the rough surfaces are resistant to the higher torque values. However, a very small part of the rough areas was found to have been filled with bone in these experiments.

Implant surface roughness, has a significant effect on the cellular behavior of the host tissues. For example, titanium (Ti) changes surface topography of cell attachment, orientation, spreading, proliferation, differentiation and secretion of the protein. Particularly, the roughness of the titanium (Ti) surface induces the production of bone-related extracellular matrix proteins especially made by integrin subunits and human osteoblasts.

Laser Roughened Surfaces

In the roughening of Titanium (Ti) implant surfaces, various lasers such as Nd: Yag laser, Diode pumped solid laser, CO2 laser, Fiber lasers are employed. The implants prepared with this new technique which has entered usage in recent years show superior properties when compared to the other implants prepared with other methods.

In one study, the effects of laser-treated titanium surfaces on the human gingival fibroblasts (HGF) viability, proliferation and adhesion were investigated. In this study where polished and sandblasted titanium (Ti) discs were applied as the control group, HGF adhesion was found more successful in the surfaces underwent laser. The results have shown that modified titanium (Ti) surfaces have not affected the viability of HGF. Significant differences have not been determined between the groups underwent different laser applications. Clinical studies have shown that more bone formation has occurred around the implant surfaces underwent laser. It was reported that it might be due to the fact that laser process improved bioavailability on the implant surfaces.

Biohorizons firm claims that bone loss is less on the surface which they called Laser-Lok compared to the traditional implants. It has been reported that while Laser-Lok prevents downward epithelial growth and maintains the coronal level, it forms the physical connective tissue attachment for the predetermined region on the implant.

What is Laser?

There are basically two methods of laser interaction with the material. The first method is processing material with continuous beam. The basic principle here is that spot heating and melting the material. This is a long- standing and well-known technique applied. What is new with the method is that the material is processed with short pulses. During this process, instantly a very high power is created and multi-photon interactions that do not take place under normal conditions become strong. The material is processed by not melting or decomposing but by the creation of a plasma environment in a short time and breaking the molecular bonds. When the laser is used very quickly, it does not make an impact on the outside of the material except the small operation area where the beam is focused, and thus, much more controlled process is carried out. Operating Principles of Laser

Laser usage parameters vary depending on the intended use. In the laser activity; the power of laser light, wavelength, pulse duration, time of administration are important according to the physical properties of the material applied. Any change in one of these factors changes the result of the laser treatment.

Osseointegration

Branemark investigated the issue in more details when he realized strict adaptation between titanium and bone during an experiment to examine revascularization in rabbit tibia with vital microscopy in 1955. Branemark et al (1985) called this phenomenon "osseointegration" and described it as "direct contact between titanium implant with living bone tissue observed with a light microscope magnification". The same researchers later strengthened this phenomenon by definition "the direct structural and functional connection between the living bone and the implant surface under load".

After Brenemark's osseintegration definition, other researchers have made various descriptions. It has been reported that Alberktsson have described osseointegration as "direct functional and structural link between living bone and load-bearing implant surface".

Osseointegration starts with the adhesion of the tissue products such as proteoglycans and glycosaminoglycans to the oxide layer, and the adhesion of the collagen bundles against them. Soft Tissue Interface

In contrast to the natural teeth, implants contain no periodontal ligament and gingival sulcus. Epithelium was found to be firmly adapted in the neck of the implant in the absence of dental plaque the in case of low level of inflammation.

Gingival sulcus around the implant epithelium is composed of keratinized epithelial cells. It is turning to combination epithelium increasingly towards apical epithelium. Combination epithelium consists of basal cell layer made up of basal cells connected by desmosomes.

A hemidesmosal combination has been observed in the transmucosal extension of the implant into the mouth or abutment surface.

There is a periosteum directly surrounding the neck of an osseointegrated implant, and the implant is supported with a well differentiated bone. If an inflammation occurs in periimplant membrane, the inflammation does not spread to the bone surface as the periosteum acts as a barrier against inflammation. In a study that examined the relationship between gingivitis and bone resorption around the implant, the "periosteal barrier mechanism" idea has been proposed. Researchers have found no association between pocket depth and bone resorption, or pocket depth and periodontitis in this study. Results revealed the existence of entirely different mechanisms around the osseointegrated implants when the inflammation caused by plaque was considered. However, there is a strong relationship between the plaque accumulated in the osseointegrated implant and gingivitis, and plaque control is very important as in the natural dentition.

Fibroblasts Adhesion to Implant Surface (Fibrointegration)

Adhesion; cellular behaviors such as morphological changes and functional changes and proliferation are greatly influenced by the surface characteristics such as hydrophilicity, roughness, texture and morphology. In the extensive research of soft tissue response to the oral implant surface, the implementation process on the surface of the implant materials has been found to affect significantly the attachment of epithelial cells beside oral fibroblasts. In addition, surface modification is required to inhibit the adhesion of oral bacteria to these titanium implants exposed to the oral cavity. Moreover, these modified surfaces should be resistant to mechanical abrasion such as brushing and professional cleaning. Therefore, the role of fibroblast adhesion to various surface properties and biological performance of different implant materials are very important in order to assess systematically.

Guillem-Martin et al (2013) studied the fibroblast adhesion and activation on the titanium surface prepared as micro with machine. In conclusion, they have reported that employing micro-corrugated surfaces rather than polished surfaces may improve implant integration in the gingival area, and micro-corrugated surfaces have enhanced early fibroblast adhesion and activation which is critical for forming a biological valve and ultimately improves tissue integration.

Fibroblasts are the cells found primarily in the loose connective tissue and their roles in wound repair mechanisms are important. Sticking to the adjacent sub-cells instead of the material, fibroblasts cause fibrous encapsulation.

Periimplantitis

The presence of bacteria on the implant surface may cause peri- implant mucositis and, if left untreated, this inflammation can lead to progressive destruction of the supporting alveolar bone surrounding the implant called periimplantitis. Therefore, removal of bacterial plaque biofilm is a prerequisite for the peri-implant infection treatment.

Today, pathological changes confined to the soft tissues surrounding the implant is described as periimplant mucositis; the destruction of soft and hard tissue observed around the implant, the pathological changes that can be observed clinically and radiographically are defined as periimplantitis.

BRIEF DESCRIPTION OF THE INVENTION

The invention relates to the methods of creating geometrical shapes using lasers which increase the adhesion quality of cells on the implant surface.

By creating a biological closure through the adherence of fibroblasts in the neck of the implant, the access of the bacteria to the implant surface should be prevented. Although increasing the surface roughnes has been considered to improve adhesion of fibroblasts in the previous studies, this state creates a convenient area for oral bacteria adhesion in the periimplant area, and will increase the resorption of the implant in the long term. Roughness in the control group was not created but the surface was prepared with machine. Control group yielded better results than the other groups due to cell cohesion and covering the surface with the fibroblast cells. Considering that adhesion of bacteria on smooth surfaces will be less, the smooth surfaces in the neck of the implant will provide long-term benefits in terms of periimplantitis.

The depth of the pits formed through laser can be controlled by the laser power, and the desired surface roughness values can be formed easily on the implant surface. When we consider the number of living cells adhered on the surface created using a fiber laser, the current type of laser, with the methods we put forward, we have determined significant differences. These methods are; triple Crosshatch, double Crosshatch, lining up the circles forming the intersection clusters, and surface topography created by processing a small circle in a larger circle. DETAILED DESCRIPTION OF THE INVENTION

The preparation of the implant surface with laser is more advantageous compared to other methods. It is possible to prepare surface topography as desired, particularly by making changes in the laser parameters. Using pulsed laser, a laser beam creates a dimple proportional to the beam diameter on the implant surface. The resulting energy can also provide micro and nano roughness appropriate for fibroblasts and osteoblasts adhesion to the implant surface. Especially laser beam's creating nano roughness provides a very great advantage in cells adhesion. The ridges will appear between the pits formed with laser beam on the implant surface. The cells are placed back into the pits, but cell extensions cannot exceed the ridges around the pits. It is important to increase the the implant surface covering rate of the cells. In order to prevent the formation of ridges around the pits and cells to cover the whole surface, the pits formed should somewhat overlap each other. Thus, the ridge between the two pits is reduced. Each pit must enter a little into the adjacent pits. Ridges still remain in some areas in such a work. Cross scanning with laser will enable to destruct the ridges. Laser beam is applied to the ridges that have remained in the cross hatch. Nanoroughness and micro roughness are created on the surface. Thus, all ridges that prevent cells completely from coating the surface are destroyed.

A pit formed on the implant surface depending on the beam diameter is usually in the form of a semicircle. The energy is not in equal intensity in every region of the beam. In order to obtain desired microroughness and nanoroughness on the entire surface, using a third laser beam in the second line will provide the roughness with effective control of the entire surface. Changing the diameter of the laser beam, changing the laser type, laser wavelength and power, changing the frequency and scanning speed will alter the impact of laser on the surface. The diameter of the pit (wooblediameter) formed on the implant surface altering with direct proportion to the beam diameter is very effective to form the desired geometry. Making roughness in pits created by a large beam diameters and again on the ridges by smaller beam diameters will be invaluable for the cells to cover the entire surface and to leave no place on the surface of the implant that is not contacted with cells. The implant surface preparation steps of our subject invention are as follows:

In order to prepare the surface in the first type;

^■ Forming a pit on the implant surface with at least one laser,

^■ Forming a second pit to intersect the created pit

^■ Increasing the cell adhesion surfaces with a small laser implementation on the ridge between two pits.

In order to prepare the surface in the second type;

^■ Forming a pit on the implant surface by a laser with large diameter,

^■ Forming pits by a laser with small diameter in the large created pit intersecting with each other,

^■ In addition, increasing the cell adhesion surfaces through a third laser with a shorter beam diameter application on the ridges remained between the pits with smaller diameters in the larger pits.

In order to prepare the surface in the third type;

^■ Scanning the implant surface with at least one laser

^■ Increasing the cell adhesion surfaces by scanning at least once intersecting in the different direction and angles from the first scanning

^■ In addition, each of the first and later scannings can be performed with different beam diameters.