The Effect of Concave Healing Abutment on Soft Tissue Healing

Standard clinical and radiographic examination will assess the need for implant therapy, the number of implants and the rehabilitation type. The pre-operative skeletal data will be observed with a 3D cone-beam computed tomographic examination (Cranex 3D, Soredex, Tuusula, Finland). On implantation day just before surgery, an initial intra-oral scan (TRIOS3, 3Shape, Copenhagen, Denmark) will be taken (IOS#0) to provide the baseline of the soft tissue outline. The surgical procedure will involve a crestal incision with 2 lateral discharge incisions; a full flap will be raised and the periosteum will be carefully separated from the cortical bone. The implant osteotomy will be prepared by executing the drilling sequence recommended by the manufacturer according to bone density; the final single-use drill that comes with each implant will be implemented on top of the drills when relevant. SEVEN (MIS) Ø 4.2 mm implants with an internal hex connection of appropriate length will be placed according to a 1-stage surgical protocol. They will receive a Ø 4.8 x 6 mm wide abutment, either straight or concave, according to the randomization. To anticipate early bone loss the implants will be seated slightly in a subcrestal position. For single crown rehabilitations, a coin randomization will be performed to determine the abutment type, straight or concave; for plural restorations, randomization will start from the most distal implant. Height of all healing abutments will be 6 mm because this item provides the largest available mismatch concavity, 0.6 mm, compared to the straight abutment. After implant and abutment placement, the flap and periosteum will be reclined and sutured with single discontinued sutures around the abutments without tension. The patients will receive antibiotics (875/125 mg of Amoxicillin/Clavulanic acid, 3/d for 7 days; in case of penicillin allergy, 300 mg of Clindamycin every 6 h for 7 days) and analgesic anti-inflammatory treatment (600 mg Ibuprofen 3/d); rinsing with Chlorhexidine (0.12%) (Dentaid® PerioAid 0.12%) will be prescribed 2/d for 2 weeks. Sutures will be removed after 10 days (Cacaci et al., 2021). After a transmucosal soft tissue healing period of 6-8 weeks, the healed sites will be scanned (IOS#1).