Titanium implant and control abutment (negative control implant and abutment). Dental sites that potentially qualify for dental implant rehabilitation will be randomly assigned to either the test group (zirconia implants) or the control group (titanium implants). Also, G3-coated and control (non-coated) abutments will be equally distributed on test and control implants, to discriminate between peri-implantitis prevention due to the G3-coating or due to the specific implant characteristics. This is a split-mouth study so that each participant can act as his or her own control and to allow between and within group comparisons.

Zirconia implant and titanium implant for histological and histomorphometric evaluation.

This study will be performed in the area of the wisdom teeth (a "non useful" site that will not interfere with the rest of the study or with the patient's life), so it can only be performed in patients who no longer have these teeth. The procedure will match the procedures described for Groups A-B-C-D. Group E implants will only remain in the mouth for 2 months, after which they will be removed for further analysis. The removal of these implants, for the patient, has exactly the same implications as a normal molar extraction.

Test and control interventions correspond to those usually applied in dental implantology. The "two-step protocol" will be followed. Local anesthesia will be applied. A flap will be raised to perform a progressive perforation with a gradual increase of the orifice and a profuse irrigation until the bone preparation adapts perfectly to the implant. Implants will wear a closure cap and will be covered within the gingival flap during osseointegration (eight weeks), after which they will be exposed to evaluate secondary stability and to place the abutment, for which local crestal anesthesia will be applied. To expose the closure cap, a tissue punch will generally be used. Once placed, the abutments will not be removed from the implants. All abutments will be covered with a PEEK healing cap during prosthesis fabrication. Finally, the implants will be rehabilitated with fixed prostheses according to the needs of each patient. A follow-up period of 1 year is expected.

Test and control interventions correspond to those usually applied in dental implantology. The "two-step protocol" will be followed. Local anesthesia will be applied. A flap will be raised to perform a progressive perforation with a gradual increase of the orifice and a profuse irrigation until the bone preparation adapts perfectly to the implant. Implants will wear a closure cap and will be covered within the gingival flap during osseointegration (eight weeks), after which they will be exposed to evaluate secondary stability and to place the abutment, for which local crestal anesthesia will be applied. To expose the closure cap, a tissue punch will generally be used. Once placed, the abutments will not be removed from the implants. All abutments will be covered with a PEEK healing cap during prosthesis fabrication. Finally, the implants will be rehabilitated with fixed prostheses according to the needs of each patient. A follow-up period of 1 year is expected.

Test and control interventions correspond to those usually applied in dental implantology. The "two-step protocol" will be followed. Local anesthesia will be applied. A flap will be raised to perform a progressive perforation with a gradual increase of the orifice and a profuse irrigation until the bone preparation adapts perfectly to the implant. Implants will wear a closure cap and will be covered within the gingival flap during osseointegration (eight weeks), after which they will be exposed to evaluate secondary stability and to place the abutment, for which local crestal anesthesia will be applied. To expose the closure cap, a tissue punch will generally be used. Once placed, the abutments will not be removed from the implants. All abutments will be covered with a PEEK healing cap during prosthesis fabrication. Finally, the implants will be rehabilitated with fixed prostheses according to the needs of each patient. A follow-up period of 1 year is expected.

6 implants (3 tests and 3 controls) will be used to evaluate and compare osseointegration, via histological and histomorphometrical analysis, in the area of the wisdom teeth ("non useful" sites that will not interfere with the rest of the study or the patient's life) - it can only be performed in patients who no longer have these teeth. The procedure will match that described for Groups A-B-C-D. In this case, implants will only remain in the mouth for 2 months, after which they will be removed for analysis. The extraction will be performed with local anesthesia. A flap will be raised to expose the implant and, using a trephine bur (1 mm wider than the implant diameter), a bone cylinder containing the implant will be extracted. The resulting bone defect and regeneration process will be similar to those following a normal molar extraction. The flap will be sutured and primary curing is expected. A new implantation will not be carried out since in this area it is totally unnecessary.

Assessment of peri-implant inflammation sign: bleeding on probing (BOP).

Assessment of gingival alteration sign: gingival clinical attachment level (CAL). Peri-implantitis is defined as bone loss around implants, so crestal bone loss will be assessed using the gold standard parallel X-Ray technique to evaluate any changes in bone to implant contact (BIC) at both mesial and distal aspects of all implants.

Assessment of crestal bone loss. Peri-implantitis is defined as bone loss around implants, so crestal bone loss will be assessed using the gold standard parallel X-Ray technique to evaluate any changes in bone to implant contact (BIC) at both mesial and distal aspects of all implants.