## 4 Discussion
Fifty-four patients with 74 implants (39 TL, 35 BL) underwent subgingival debridement. After 6 months, both groups showed similar prevalence and significant improvements in clinical parameters. However, the complete resolution of PM was not achieved in either group, with comparable changes in bleeding upon probing observed for both implant types [29]. This may have been due to similarities in manufacturing control and surface treatment, which likely influenced the biological response more than mechanical failure. The present investigation supports the findings of [PERSON] et al., 2024 [30], which suggested that abutments in a TL group were particularly sensitive to preload changes compared to those in a BL group. Their study showed that variations in the preload significantly affected stress distribution in both implants and screws. It is important to note that the present analysis focused on single-unit implant restoration. Other studies [31] have also simulated the replacement of a premolar with an implant-supported cantilever prosthesis, showing that implant type influences fracture load. Their results indicate that Bone-Level implants limit catastrophic failures to restoration, whereas Tissue-Level implants are more prone to deformation in the transmucosal portion, complicating repairs. This aligns with our findings that stress is higher at the neck of the implant in TL implants. This outcome is also reflected in a case report [32], where a patient with a Tissue-Level implant (right maxillary first molar) placed ten years prior experienced crown movement. A panoramic radiograph revealed a fractured abutment screw. After removing the screw fragment, a new restoration was placed, but two years later, both the screw and implant fractured, requiring surgical removal. The authors emphasized that prevention is key to avoiding implant failure, recommending the use of wide-diameter implants placed centrally in the occlusion, particularly in the posterior area. The present authors echo and support this recommendation, suggesting that implants with thicker walls may help reduce stress during loading. In the present simulation, while rough contact models were used for simplicity, they can also be considered a limitation because they oversimplify the physical interaction between implant-abutment surfaces. They typically assume a perfect, frictional connection between the surfaces without considering real-world complexities like sliding, varying friction, microscopic surface deformations, contaminants, saliva, and other aspects present in implant-supported restoration. Another study limitation is that the residual stress due to tightening was not directly simulated. Additionally, the absence of dynamic loading and fatigue considerations limits the understanding of the implant's behavior under real-world conditions. In summary, the simulated model showed that the Tissue-Level implants had a shorter screw nearby the cervical area than the Bone-Level implants. As it bent during force incidence, higher stress levels closer to the cervical area could be observed. Additionally, it is important to observe that the axial wall from the Tissue-Level implants was thinner than that from the Bone-Level implants. The combination of the thinner wall and smaller screw probably increased the stress on the Tissue-Level implants during oblique load incidence, an effect that can be exacerbated when an abutment-implant connection is not ideal.