## 4 Discussion  
The present study evaluates the marginal bone modification around one-stage, platform-switched, internal conical connection implants positioned 2 mm sub-crestally or equi-crestally. The results show that the mean MBMs of the test and control groups were comparable with values of 0.61 mm and 0.52 mm, respectively, at 12 months of prosthetic function. This is due to the apical remodeling of the marginal bone level according to the initial soft tissue height, which was not considered in this paper as an indicator for the apical position of the implant. So, it is possible that thinner phenotypes were included in the test group, compared to the control group. However, following the distinction made by [PERSON] et al. [19] and [PERSON] et al. [15], all the MBMs in the control group equi-crestal implants developed as bone loss below the implant neck level, whilst the MBM in the test group was limited to the area above the implant neck, due to the 2 mm of sub-crestal depth of the planned fixture position. Therefore, MBMs in the test group resulted in zero bone loss. This leaves, on average, 1.5 mm of coronal marginal bone that protects the treated and threaded portion of the fixture, helping to prevent future biological and esthetic complications [2; 13; 14; 15]. In fact, in a recent 10-year prospective study, [PERSON] and colleagues [7] demonstrated that implants with Early BL >0.5 mm during the first year of function showed 5.43 times higher odds of future peri-implantitis development than implants with Early BL < 0.5 mm. Bone loss seems to have mostly occurred in the first 3 months after surgery for both groups, in agreement with other histological studies conducted on animals and humans [42; 43; 44]. Those studies also demonstrated that implant supra crestal soft tissues around implants then tend to stabilize after 8-12 weeks, achieving an average height of 3.6 mm height on average, which constitutes the new supracrestal tissue attachment. MBM seems to be a necessary step for the re-establishment of such a dimension [19]. As a consequence, mucosal thickness at the time of implant placement is a significant influencing factor on peri-implant marginal bone stability, and the soft tissue height seems to be inversely proportional to the early bone resorption. This is likely due to the necessary space for the formation of the aforementioned 3.6 mm of tissue height, which occurs at the expense of the bone [7; 9; 13; 16; 45; 46]. In the present study, a soft tissue thickness ranged between 1 and 4 mm, with 2 and 3 mm being the most frequent values. [PERSON] et al. [45] analyzed the bone loss around bone-level implants in patients with thin (<2 mm) and thick (>2 mm) soft tissue and found a mean bone loss of 1.17 mm in the first group at 12 months after restoration. Despite one-third of the patients in our control group showing an STH of 2 mm, none of the implants exceeded 0.75 mm of bone loss. This difference might be due to other factors, such as implant type and design. Our bone loss results are in line with the one obtained by [PERSON] et al. [16] and [PERSON] et al. [19], who measured 0.04 mm and 0.11 mm of bone loss, respectively, around sub-crestally placed platform-switched implants. [PERSON] et al. [19] also observed 0.33 mm of bone loss around equi-crestal implants, more than in the current study. However, they also performed a soft tissue augmentation procedure, which could have provided the extra space for the supracrestal tissue attachment re-establishment.