The aim of the present prospective study was to investigate after a 2-year of follow-up any influence of the surgical technique, manual or digitally guided, on peri-implant marginal bone levels stability in implants placed 1 mm sub-crestally.

Patients were treated by means of platform-switched implants provided with a 5 degrees internal conical connection and supporting single screw-retained fixed crowns. Marginal bone level (MBL) measured at prosthesis installation (t0) at 1 (t1), 2 (t2) and at 3 years of follow-up visit (t3) were considered. MBL change from t0 to t3 was investigated. The distance between the implant neck and the first radiographically detected bone to implant contact was considered to evaluate the bone loss. Two groups were considered: Test Group (GD) for implant sites treated with a digitally guided surgery procedure. Control Group (FH) for implants surgically placed without digitally guided surgery, respectively. All the procedures were performed by an experienced operator. Additionally, for both groups MBL changes were correlated to different supra-crestal soft tissue height (STH) amounts: less than 3 and ≥ 3 millimeters, respectively. Peri-implant soft tissue parameters such as probing depth (PPD), modified Sulcus Bleeding Index (mBI) and modified Plaque Index (mPI), were assessed for all the restorations included.

Inclusion Criteria:

• absence of mandibular and/or maxillary atrophy; presence of partial edentulism of at least one pair of elements and adequate amount of bone tissue to be able to insert an implant, i.e., a minimum amount of residual bone of 5 mm in thickness and 10 mm in height; presence of an antagonistic element with respect to the tooth to be rehabilitated.

Exclusion Criteria:

• patients presenting with a clinical history of systemic diseases and metabolic deficits, presence or previous leukocyte dysfunction/deficiency, blood disorders, hemophilia, dicoumarolic drug therapy, treatment of prolonged steroid therapy, history of neoplasms resulting in chemotherapy and/or radiation therapy in the head and neck district, history of chronic renal problems, chronic liver disease, bone metabolism disorders, uncontrolled endocrine disorders, and ongoing pregnancy and/or lactation. presence of local inflammation such as untreated periodontitis, bruxism condition or clenching habit, habitual oral infections, mucosal disorders (erosive lichen planus), oral lesions (ulcers, malignant lesions), inadequate oral hygiene, and poor compliance.