ABSTRACT
The development of metal implants and, particularly in the field of the dental ones, innovator methods are needed to allow the progress of new processes and materials with a higher osseointegration speed, so that a best implant-bone bond can be achieved in all type of patients, even for those who have problems to use dental implants due to have a reduced bone regeneration. 
Titanium and some of its alloys are materials admitted as biocompatible and their use is wide spread in the manufacture of dental implants. Nevertheless, some patients need times longer than the desirable to complete osseointegration. So, to reduce the time requires in this type of surgery as well as to widen the range of possible patients has a great clinical relevance. 
An innovating and incipient method to solve the above mentioned problems consist of the development of new osteoinductor coatings which will improve the properties of dental metallic implants. 
The aim of this Thesis Dissertation is focused on the development of new coatings with ostinductor properties to be used in metallic dental implants, the aim is to reduce integration times. On top of that, a new property is added to the coating to get better results such as the capacity to drug release when the situation requires it; avoiding on the one hand, infections or inflammatory process and on the other hand, to take medicaments by any means. 
To reach those goals a new organic-inorganic hybrid coating got through the sol-gel route is proposed. The grounds, that underlies in the carried out processes, is to get that the contact between metal implant and alive tissue is done through a degradable material which promotes the cell adhesion and proliferation, and the subsequent mineralization process. 
To get the best coating selection for this specific application a new protocol has been developed. The procedure consists of an integral study in which four silicon precursors were pre-selected: the tetraethyl-orthosilicate (TEOS), the methyl-trimethoxysilane (MTMOS), the vynil-triethoxysilane (VTES) and the 3-glycidoxypropil-trimethoxysilane (GPTMS). From those precursors new organic-inorganic hybrid coatings have been designed to meet all the requirements. A complete physical-chemical characterization was done in all the coatings obtained. In vitro testes were carried out in order to obtain the hydrolytic degradation of the films. Besides this, a model drug (procaine) was added into the hybrid network, with the aim of design coatings with the property to slow and control drug release. Cytotoxicity essay and human osteoblast cell proliferation were done to determine the biological behavior of the coatings.   
After the results got in the first stage of this Doctoral Dissertation, a vynil-triethoxysilane was selected as reference precursor. In the following stage, this study has been centered in the characterization and study of the behavior in vitro of two kinds of coatings. One of them have been prepared from mixtures of vynil-triethoxysilane and tetraethyl-orthosilicate (VTES: TEOS) and the other from mixtures of vynil-triethoxysilane and 3-glycidoxypropil-trimethoxysilane (VTES: GPTMS), with the aim to get new materials of physical-chemical and biological interest. 
At this level, during investigation, the following four aspects have been taken into account: 
(1) The physical-chemical, mechanical and anticorrosive properties. 
(2) Evaluation of the hydrolytic degradation. 
(3) Analysis of the drug release. 
(4) Evaluation of the osseinductuion of the coatings through essays of  mesenchymal stem cells proliferation and osteogenic differentiation of cultured onto the coatings. 
The results obtained along these study have shown that the coatings based on VTES:TEOS are hydrophilic and hydrolytic degradable. If these properties are important, those obtained from VTES:GPTMS coatings are also important. Thanks to the active character of the epoxy groups of these coatings, a better chemical bond with proteins and peptides is achieved. Nevertheless, after measuring and optimizing the obtained results at this stage of the study, it has been selected the coating based on the VTES:GPTMS, specially the formulation with a 20%wt VTES and a 80%wt of GPTMS (2V: 8G). 
With the elected coating a study in depth to optimize its final properties has been done. To start with, bioactive particles have been introduced with the aim of improving the osteointegración of implants. On the other hand, along the essays done, it has been possible to vary the cross-linking density of the coatings in a control and repetitive way, in order to have a higher control on the degradation time and the possible drug and active molecules release. The study has been based on the variation of the cure conditions, to do that, the network state has been analyzed using infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). 
Finally, with the control of the times and cure temperatures, new coatings have been achieved with cross-linking rates designed to the required measure.  Therefore to get networks with low or high bond density to control the degradation properties and drug release of the coatings obtained as required.