Bacterial Microleakage and Bone Loss in Internal Connection Dental Implants Based on the Type of Abutment Used in Zirconia Partial Fixed Prosthesis: in Vivo Study

This clinical trial aims to observe if there are differences in bacterial micro-filtration on interfaces and to evaluate if there are differences in the occurrence of peri-implant diseases and bone loss in fixed partial monolithic zirconia CAD/CAM implantsupported prostheses with and without abutment in patients at the Advanced Implant Prosthetics Clinic of the Complutense University of Madrid, of both sexes, over 18 years of age, whose treatment plan is based on the replacement of dental pieces with two fixed partial dentures on implants, in such a way that the study will be performed "split mouth" rehabilitating one of them with zirconia bridges on attachments with connection and others with Zirconia bridges with flat attachments or without connection. The main question it aims to answer is whether the not use of abutment influence bacterial micro-leakage and the development of peri-implant diseases and bone loss at that level in fixed partial monolithic zirconia CAD/CAM prothesis. Participants will: * Receive two fixed partial monolithic zirconia CAD/CAM prothesis, one will be attached to an abutment (control group) and the other not (test group) * Subsequently, control appointments of the fixed implant supported prosthesis treatment will be performed (1, 3,6, 12 and 24 months) and radiographies will be made with the parallelizing device attached by the silicone key. Researchers will compare fixed partial monolithic zirconia CAD/CAM implant-supported prostheses with and without abutment to see: * Differences in bacterial micro-leakage on interfaces. * Occurrence of peri-implant diseases and bone loss