A Triple-blinded Non-inferiority Multicentre Randomized Controlled Trial Comparing Hybrid and Fully Etched Implants.Part 1. Implant Stability.

This is a randomized triple-blinded, parallel-arm (1:1) controlled clinical trial with 6 months follow-up. Implants will be placed in 16 private practices. 128 patients will be randomly allocated to the test (hybrid implants)(64) and control (fully etched implants)(64) groups following stratified randomization in such a way that an equal number of patients in the test and in the control group will be enrolled in each study centre. The following individuals will be blinded as follows: 1) patients involved in the study will not be aware of the implants that are receiving; 2) surgeons: after the screening examination clinicians will choose the implant dimension but they will not be aware of the surface characteristic of the implant they are going to place until the implant socket is prepared; 3) the data collector/outcome assessor: of the implant stability will not be aware of the group allocation; 4) the statistician will not be aware of the group allocation. Treatment allocation will be concealed by using opaque sealed boxes and opened immediately before the implant placement (after implant socket preparation). At least 2 hours before the surgery all patients will be given antibiotic prophylaxis of 2g of amoxicillin (600mg of clindamycin for patients that allergic to penicillin). All implants (more than one implant per patient might be included) will be placed by 16 experienced surgeons in their respective clinic following according to the instruction provided by the manufacturer. The apicocoronal position of the implants will be equicrestal (i.e. the most coronal part of the machined collar is at the level of the alveolar ridge) or subcrestal (≤1 mm). In the test group and control group hybrid implants and fully etched implants (Volution, IRES®, Switzerland) will be placed. After surgery, in order to control discomfort and swelling, 600 mg ibuprofen every 8 hours if needed will be given. All subjects will be prescribed 0.12% chlorhexidine mouth rinse twice daily for 7 days. Immediately after the implant placement (Tpl) and at two months (T2) the implant stability will be measured using magnetic RFA (OsstellTM Mentor AB, Gothenburg, Sweden) by a trained clinician not involved in the study. The transducer will be screwed manually and RFA measurement were made both in the mesio-distal (MD) and bucco-lingual (BL) direction by keeping the device perpendicular at a distance between 2-4 mm and at least 3mm far away from the soft tissues. The peak insertion torque will be also registered. All implants will be submerged. Implants with ISQ values < 60 at the revaluation (T2) will undergo further measurements after 1 month till the 6th month after their placement. If at any timepoint (T2, T3, T4, T5, T6) the implant reaches a sufficient (stability ≥60) it will be considered stable till the end of the study, hence, no further ISQ assessment will be carried out and the prosthesis will be delivered (TL).

Continuous variables will be expressed as mean and standard deviation, whereas the absolute and relative frequency will be calculated for categorical variables. Regarding continuous variables, differences between groups will be tested by parametric or non-parametric test after testing the normal distribution of the data (Shapiro-Wilk test). For categorical variables chi-squared test (or Fisher test) will be adopted.