Abstract:
A method for making an intraosseous dental implantations including the steps of supplying a layer of powder of a material designed to form the implantation and applying a laser sintering beam to said powder to form a layer of the implantation and repeating the two above operations several times by depositing each time a following layer of powder over the preceding one treated with the laser beam to form the implantation with the laser beam being applied to the powder layers so as to form cavities on a surface of the implantation designed to be colonized by the patient&#39;s bone.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a method for making intraosseous dental implantation structures with predefined surface geometry and implantation structure realized by said method.  
         [0003]     2. State of the Prior Art  
         [0004]     As known, in the partial or total edentulous dental implantations of various forms realized for example in titanium are used and are inserted in the bone to replace natural dental elements lost due to illness or trauma.  
         [0005]     Such implantations necessitate variable recovery times generally between three months in the mandible and six months in the upper jawbone so that the bone integration assuring retention in time of the implanted manufactured article takes place inside the bone.  
         [0006]     In the modern implantology context and more specifically ‘Tissue Engineering’ it its known that the surface of the implantation must have a certain degree of roughness in order to favor the healing process and thus obtain a faster and better bone integration of the implantation.  
         [0007]     In the known art, to obtain the rough surface, different methods have been proposed such as for example, the so-called ‘plasma spraying’, treatment with acids, sand blasting, or combinations of these last two techniques.  
         [0008]     The above-mentioned known methods however did not allow obtaining a surface porosity such as to stimulate a satisfactory bone integration, also bringing other not negligible inconveniences. For example, in the case of plasma spraying, there is the risk of considerable release of particles of the implantation covering. In the case of sand blasting, there is the possibility of having residual particles contaminating the surface of the article with sand. Similar inconveniences make necessary laborious and costly decontamination treatments of the implantations.  
         [0009]     It has also been proposed to form a porous covering by applying on the surface of the implantation a titanium powder mixed with a binder to then subject the piece to a high-temperature treatment during which the particles of powder are molten and remain adherent to the implantation.  
         [0010]     But this method does not allow obtaining characteristics of satisfactory porosity for rapid and effective bone integration since during the melting the powder particles can take on random forms giving origin to surface configurations unsuited to stimulating bone integration.  
         [0011]     Furthermore, the above method can involve the presence of traces polluting substances incorporated in the surface of the implantation due for example to residues of adhesive among the grains of titanium.  
         [0012]     The object of this invention is to make available a method for making an intraosseous implantation structure allowing the formation of surfaces of the implantation which would stimulate an intense angiogenetic activity while promoting the formation of the bone in shorter times than in implantations heretofore known.  
         [0013]     Within the framework of this object, a purpose of this invention is to realize an intraosseous implantation structure which would ensure better and more durable stability of the dental implantation integrated in the bone in the long period.  
         [0014]     Another purpose is to realize an intraosseous implantation structure which would allow a considerable increase in the contact surface with the bone and consequently better distribution of the masticatory forces from the implantation to the bone.  
         [0015]     The present intraosseous implantation structure also allows realizing a manufactured implantation article of customized dimensions based on the bone morphology of the individual patient.  
         [0016]     Another purpose of this invention is to realized an intraosseous implantation structure having better mechanical stability, that is greater resistance to the masticatory load forces.  
       SUMMARY OF THE INVENTION  
       [0017]     This and other purposes, which are better explained below, are achieved by using in accordance with this invention a method for making intraosseous dental implantations including the steps of supplying a layer of powder of a material intended to form the implantation and applying a sintering laser beam to said powder to form a layer of the implantation and repeating the two above operations several times by depositing each time a following layer of powder over the preceding one treated with the laser beam to form the implantation with the laser beam being applied to the powder layers so as to form cavities on the surface of the implantation designed to be colonized by the patient&#39;s bone.  
         [0018]     Again in accordance with this invention it was sought to make available a an intraosseous dental implantation structure with predetermined geometry surface characterized in that it includes a surface having micro and macro cavities of definite dimensions having osteogenetic effect with the implantation structure being realized by means of sintering in layers of metal or ceramic powders using a laser beam. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     Additional characteristics and advantages of the subject of this invention are clarified by an examination of the description of a preferred but not exclusive form of realization of this invention illustrated by way of non-limiting example applying said principles. In the drawings:  
         [0020]      FIG. 1  shows a cross-sectioned elevation view of the intraosseous dental implantation structure in accordance with this invention,  
         [0021]      FIG. 2  shows a cross section view in accordance with plane of cut II-II of  FIG. 1 ,  
         [0022]      FIG. 3  shows an elevation view of the intraosseous dental implantation structure in accordance with this invention, and  
         [0023]      FIG. 4  shows diagrammatically the manufacturing process of the implantation in accordance with this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     With particular reference to the numerical symbols of the above figures, the intraosseous implantation structure in accordance with this invention designated as a whole by reference number  1  includes a ‘biomimetic’ surface which has a particular geometrical conformation consisting of cavities having osteogenetic effect and designated as a whole by reference number  2 .  
         [0025]     The cavities  2  have a definite characteristic size between 70 and 800 microns with depth variable between 10 and 100 microns.  
         [0026]     Preferably the cavities  2  include micro and macro cavities. The micro-cavities have dimensions between 70 and 200 microns while the macro-cavities are between 200 and 800 microns.  
         [0027]     These cavities are capable of stimulating within them an intense angiogenetic activity while concentrating the bone growth factors—including Bone Morphogenetic Proteins (BMP)—to promote bone formation faster compared with the present which takes from 4 to 6 months.  
         [0028]     In addition, these cavities, once the bone has grown inside them, ensure better and longer stability over the long period to the dental implantation integrated in the bone. As a result from the biomechanical viewpoint there is a considerable increase in the contact surface with the bone and consequently better distribution of the masticatory forces between the implantation and the bone.  
         [0029]     From the biological viewpoint the cavities are decisive in promoting the formation of the bone faster than now.  
         [0030]     The implantation structure in accordance with this invention and especially the associated manufacturing method as explained below also allow realizing a custom-made implantation manufactured article for the patient starting from the performance of a TAC and its graphic refashioning and obtaining the three-dimensional model of the maxillaries.  
         [0031]     The implantation can be realized in a single piece fitted with the stump (not shown in the figure) already pre-angled to correct any disparallelisms between multiple implantations and/or natural dental elements.  
         [0032]     In cases where it is wished to proceed to immediate loading of the implantation after its insertion in the bone, on the manufactured article implanting in a single piece and with customized dimensions based on the bone morphology of the individual patient, a ceramic false set of teeth can be constructed in ceramic, resin or metal and ceramic (not shown in the figure).  
         [0033]     Obtaining the two above characteristics, implantation and stump in a single customized piece and preconstructed false set of teeth, can take place by using an innovative manufacturing method calling for realization of both the dental implantation and the false set of teeth by sintering of titanium or ceramic powders using a laser beam. It is understood that the manufacturing method can also be used for formation of the implantation without stump or preconstructed prosthesis.  
         [0034]     As shown diagrammatically in  FIG. 4  the implantation  1  can be realized using a productive unit  11  including a controlled-atmosphere chamber  12  in which the article is formed.  
         [0035]     The powder is deposited in layers ( FIG. 4  shows the just deposited last layer  18 ) on a vertically movable platform  14  along a cylinder  19 . Each time a layer of powder is deposited a laser device striker arm  13  generates a sintering laser beam directed towards the layer of powder just deposited so as to form a layer of the implantation. Grains of powder struck by the laser melt and immediately afterward solidify again to form part of the implantation. The platform  14  is moved downward by known movement means not shown in the figure as the article is formed.  
         [0036]     The laser beam is controlled so as to form the cavities  2  having osteogenetic effect on the outer surface of the implantation. The laser device  13  is controlled for this purpose by known control means  15  which can include a PC, where a three-dimensional model of the implantation which it is desired to realize is memorized and an appropriate controller capable of piloting the laser device  13  as a function of the data supplied by the PC on the model of the article.  
         [0037]      FIG. 4  shows part of the implantation during realization with reference  16  while  17  designates the powder which is not molten by the laser and which can be recovered for a subsequent manufacturing process.  
         [0038]     The layers deposited can have advantageously a thickness between 1 and 100 microns. The powder used in the process is a metal powder advantageously pure titanium powder or of grade 2, 4 medical or ceramic titanium.  
         [0039]     The grains of titanium powder can have nanometric dimensions. Preferably as shown in  FIG. 4  the layers of powder to be sintered are deposited in accordance with planes perpendicular to the extension of the implantation which has a generally elongated cylindrical or conical form.  
         [0040]     During the manufacturing process advantageously in the chamber  12  there is an inert gas (for example argon) so as to reduced to the minimum the chance that impurities might adhere to the surface of the implantation.  
         [0041]     It was surprisingly found that the use of laser sintering in the manufacturing process allows obtaining a surface porosity of the implantation with exceptionally good osteointegration properties and quite drastic reduction in the time necessary for healing.  
         [0042]     In addition, the manufacturing method in accordance with this invention allows obtaining a nearly decontaminated product directly.  
         [0043]     Indeed, when using known manufacturing techniques, the implantations have to then be subjected to costly and laborious decontamination processes aimed at cleaning the article of sandblasting residues, mechanical processing oils or other impurities as necessary.  
         [0044]     By realizing the implantation using a sintering beam in controlled atmosphere the surface of the article already has a high level of cleanliness. The product, at the most, can be subjected to a mere ultrasound treatment with distilled water or organic acids.  
         [0045]     Connection between the stump and the implantation where construction of the two parts is planned, separate stump and implantation, it is preferably of the pure conical type.  
         [0046]     Fastening of the stump (not shown) to the bone screw  1  is obtained by insertion of a shank thereof conformed in accordance with a Morse cone inside an axial cavity  4  with a corresponding conformation realized inside the bone screw. This cavity  4  has a troncoconical conformation with tapering toward the tip, or cylindrical.  
         [0047]     In this cavity the shank of the stump can by coupled by pressure for anchoring of the prosthesis. The stump, however, could also be applied by screwing to the implantation.  
         [0048]     The cavity  4  is characterized by having a hexagonal shape on the apical bottom  3  where the most spinal part and with the same shape as the stump is engaged. The shape of the bottom of the cavity  4  could however be triangular, square or octagonal.  
         [0049]     A variant of the bottom form of the cavity  4  of the implantation is to adopt a 5 or 6-point star design where the shank of the interchangeable stump of analogous form fits.  
         [0050]     The conical connection allows better mechanical stability, that is a better resistance to masticatory load forces.  
         [0051]     This connection also allows better biological stability and prevents passage of fluids and bacteria towards the inner parts of the implantation.  
         [0052]     In addition, the end hexagon or the 5 or 6-point star ensure correct positioning of the stump by also opposing rotational forces.  
         [0053]     To allow screwing or positioning of the implantation in the bone, the driver, which bears the implantation, is advantageously provided with an interfaceable hexagon or 6-point star portion which fits into the most apical part of the inner cavity of the hex-shaped implantation thus making possible application of the necessary force for positioning of the implantation in the bone.  
         [0054]     As shown in  FIGS. 1 and 3 , on the outer side surface of the implantation  1  a fraenum is formed which might involve about two-thirds of the length of the implantation.  
         [0055]     The third apical of the implantation can be solid and its outer surface have the macro cavity of a diameter or 70 to 800 microns. With the new sintering procedure it is possible to construct this part so that all the cavities are interconnected by micropores to constitute a network of intercommunicating cavities and pores allowing colonization by the bone.  
         [0056]     The surface of the coronal top two-thirds of the implantation has micro cavities 70 to 200 microns in diameter.  
         [0057]     The top edge at the neck level of the implantation is beveled and smooth with an angulation between 0° and 40°.  
         [0058]     It is noted that the interconnection micropores between the cavities could be formed at any point of the implantation  1  where there are cavities  2 .  
         [0059]     It is now clear that the preset purposes have been achieved.  
         [0060]     An intraosseous implantation structure characterized by having a surface with micro and macro cavities of definite sizes which induce formation of the bone is realized. It is this geometric drawing of the surface which produces the osteogenetic effect.  
         [0061]     The manufacturing method in accordance with this invention allows realizing a surface porosity provided with micro-cavities such as to lead to surprising and unexpected results form the osteointegration viewpoint.  
         [0062]     In addition, thanks to the method in accordance with this invention it is possible to exclude from the manufacturing process the laborious and costly decontamination treatments to which the implantations realized using known techniques had to be subjected.  
         [0063]     Naturally the above description of an embodiment applying the innovative principles of this invention is given by way of non-limiting example of said principles within the scope of the exclusive right claimed here.  
         [0064]     The intraosseous implantation structure in accordance with this invention can be realized to measure in a single piece with form, size and preangulations of the stump so as to allow customized adaptation to the requirements of the osseous formation of the individual patient.  
         [0065]     The structure is also characterized by a conical joint connection between the stump and the implantation. Naturally the materials used as well as and the dimensions can be any, depending on requirements and the state of the art.