## 4 Discussion  
The aims of this retrospective cohort study were to compare the long term (>10 years) results of PS and PM dental implants in the upper anterior maxilla. Based on our results,  
Figure 4: Clinical photograph of an implant of the platform switching group with detailed description of parameters evaluated for the Pink and White Esthetic scores. PS implants showed statistically significant (\(p<0.05\)) lower MBL and PPD and higher PES values compared to PM implants. As for peri-implant diseases, no statistically significant differences were noted among the two groups, even if a lower prevalence was reported in the PS group. These results are in accordance with previously conducted systematic reviews on the topic: in a meta-analysis, [PERSON] et al. [33] concluded that PS implants show statistically significant lower MBL levels compared with PM implants. At the same time, a prosthetic workflow able to avoid any microdamage on the connective component may result in an increased stability of marginal bone levels, even in the long run [34]. Furthermore, according to [PERSON] et al. [35], significantly less MBL was detected in PS implants compared to PM-implant abutment configuration. Hence, several aspects must be taken into account, starting with patients' pre-existing clinical conditions, operators' experience [35], the micro and macro design of the implant neck [36], the interimplant distance [37] or the IAI positioning [38]. Precisely with regard to the IAI placement with respect to the bone crest, [PERSON] et al. [25] claimed that no statistically relevant differences were recorded for MBL. Both creally and subcrestally inserted implants, during a 12-month follow-up period, showed overlapping results. The two groups showed acceptable results [39, 40] for the two objective esthetic scores; however, statistically significantly better results were found out for PS implants for the PES score. Even [PERSON] et al. [41] reported higher PES values for PS implants without statistically significant differences. In the present study, the same expert operator inserted all dental implants which shared the same implant surface (SLA) and carried out the prosthetic treatment. In all cases, standard commercial abutments were used, with different gingival heights reflecting implant depth and position, and cement-retained single crowns or bridges were delivered to patients. The main limitations of this study are its retrospective nature and the limited sample enrolled; furthermore, radiographic and clinical analysis were conducted only at the latest follow-up visit, with no interim data on MBL or PPD progression. Several patients could not be enrolled in this study even if they had dental implants installed for more than 10 years due to the absence of a baseline periapical X-ray taken at the day of prostheses delivery, a procedure highly recommended to evaluate reproducible long-term evaluation of MBL [42, 43]. However, to the best of the authors' knowledge, this study presented the longest follow-up available in the literature (>10 years) with a standardization of surgical and prosthetic treatments. Both groups showed acceptable MBL levels after a minimum of 10 years of functional loading, ranging from 1.02 to 1.67 mm; however, PS implants exhibited lower peri-implant bone resorption and PPD values. Overall, 17.24% of dental implants at the patient level were affected by peri-implantitis and 32.76% by peri-implant mucositis, a result in accordance with [PERSON] et al. [44]. As for peri-implant diseases, our data, even if not statistically significant, are in accordance with previous studies [45], showing reduced rates of peri-implantitis for PS implants compared to PM implants. Recently, [PERSON] et al. [46] evaluated MBL progression using preclinical experimental peri-implantitis model with the same TL and BL implants used in this study. Based on their study, the severity of peri-implantitis was greater in PM implants compared to PS implants.