## 2 Materials and Methods  
### Patient Selection  
The present study is a single-blind, parallel, randomized, controlled prospective clinical trial, the protocol of which was reviewed and approved by the local University/Hospital ethical committee (N4078) and recorded in public registry of clinical trials (www.clinicaltrials.gov, URL accessed on 27 December 2023--NCT06182670). The study was conducted according to the principles of Helsinki Declaration (as revised in Fortaleza 2013), following CONSORT (Consolidated Standards of Reporting Trials) guidelines. Patients were recruited from April 2021 to May 2023 at the Section of Periodontics, School of Dentistry, Department of Surgical Specialties, Radiological Science, and Public Health of the University of Brescia. The study flowchart is reported in Figure 1. \begin{table}
\begin{tabular}{c c c c} \hline
**Factor** & **Effect on Bone Levels** & **Influence of Soft Tissues** & **Reference** \\  & & **Bioptype** & **[PERSON] et al., 2015 [18]** \\ \hline Subcrestal vs. Bone level implants & Average \textless{1 mm of bone loss for both placements} & In the presence of thin, soft tissues, subcrestal placement should be preferred. & [PERSON] et al., 2019 [2] \\  & Comparable bone loss: mean mesial (m) bone loss was 1.41 (\(\pm\)1.65 mm) and 1.84 (\(\pm\)1.49 mm) for subcrestal and bone level, respectively, and mean distal (d) bone loss was 1.34 (\(\pm\)1.60 mm) and 1.73 (\(\pm\)1.31 mm). & Subcrestal implants show better bone levels in case of thin, soft tissues. & [PERSON] et al., 2018 [13] \\  & Implants placed 1 or 2 mm subcrestally show comparable bone remodeling (0.49 \(\pm\) 0.32 mm and 0.46 \(\pm\) 0.35 mm, respectively) & [PERSON] et al., 2023 [14] \\  & & Deeper subcrestal placement is advised in thin biotypes, as they exhibit higher mean marginal bone loss. & [PERSON] et al., 2022 [15] \\  & & & \\  & & & \\  & Less bone loss observed around conical connection implants in both human and animal models & Better soft tissue esthetics with internal hexagon. & [PERSON] et al., 2014 [27] \\ \hline  & Less marginal bone loss observed for platform switching vs. & [PERSON] et al., 2014 [27] \\  & algorithm matching & especially in case of larger mismatch & [PERSON] et al., 2019 [28] \\ \hline One-time abutment (OTA) vs. & Implants restored with an OTA speeded abutment removal & Implants restored with an OTA speeded abutment removal & Implants restored with an OTA speeded abutment removal & [PERSON] et al., 2017 [20] \\  & No difference in peri-implant bone loss observed & [PERSON] et al., 2020 [23] \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of the surgical and design implant factors, the relationship with the biotype, and their observed influence on the implant site. Patients needing a single tooth replacement in the upper and lower posterior areas (premolar and molar) by means of an implant-fixed rehabilitation were included in the present study. The implant site was assessed for bone volume and space based on the following requirements: 1.5 mm of residual buccal and lingual bone around the selected implant diameter, a minimum bone height of 10.5 mm in order to place an implant with a minimum length of 7.5 mm, and at least 1.5 mm of bone between the fixture and the adjacent tooth. Patients with systemic diseases; history of radiation therapy in the head and neck region; current treatment with steroids; neurological or psychiatric impairments that could interfere with good oral hygiene; immuno-compromised status, including infection with human immunodeficiency virus; severe clenching or bruxism; smokers (more than 10 cigarettes per day); drug or alcohol abuse; and inadequate compliance were excluded. All included patients gave their written consent after being informed in detail about the objectives of the study. Before treatment, patients were clinically and radiographically evaluated. An orthopantomography and peri-apical radiographs were used as a first-level exam to evaluate the bone quantity before implant placement.