The mean marginal bone level was 0.94 mm below the neck of the implant at 1 month after restoration placement (T₁). The optimal position of the peri-implant bone after a maturation period should be at the same level as the neck of the implant. This means that part of the biological width of the present study, which is acting as a barrier, was in contact with the implant surface roughness and was therefore more prone to biofilm formation, soft tissue infection, and peri-implantitis. Apparently, the large gap between the socket wall and the regular diameter implant, notwithstanding the local augmentation procedure, did not fill completely during healing which led to a compromised bone level. The Checchi et al. [22] study also mentioned that the bone level at the commencement of loading was 0.43 mm apically of the implant neck, possibly confirming the idea that better initial bone levels are reached with wider implants.

The mean change of the marginal bone height during the 1-year follow-up was − 0.17 mm, which is very limited. The Tallarico et al. and Checchi et al. studies’ peri-implant bone loss [21, 22] was 0.23 mm and 0.68 mm respectively, from initial loading to the 1-year evaluation. Apparently, after the period of healing and maturation peri-implant, bone levels remain rather stable.

Zirconia restorations are presumed to be highly biocompatible and can potentially attach to soft-tissue. It is claimed that zirconia promotes the attachment of human gingival fibroblasts in vivo, which is desirable because it mimics tooth cementum’s ability to attach to gingiva, forming the junctional epithelium [25]. With respect to the evaluation items of the peri-implant soft tissues of the present study, the findings are consistent with a healthy status, confirming the high biocompatibility of the material. The limited probing depth (mean value of 1.9 mm at the 1-year evaluation) is possibly associated with the claimed soft-tissue attachment potential. An advantage of screw-retained restorations is the absence of a microgap at the interface of the crown and abutments and the absence of possible cement remnants in the area of the peri-implant soft tissues. The use of abutments with angulated screw channels could, as a consequence of its design, promote soft tissue health. In addition, the high patient compliance to the prescribed post-treatment oral hygiene instructions could have played an important role in the observed very healthy peri-implant soft tissues.