# Peri-Inplant Tissue Stability: A Series of Five Case Reports on an Innovative Implant Design
## 1 Introduction  
The long-term maintenance of dental implants depends on sustained osseointegration and many other factors such as local and systemic risk factors, prosthetic rehabilitation, implant positioning, and correct biofilm control [1, 2, 3]. In addition, the stability of the mucosal tissue around the implant not only serves as a barrier separating the oral environment from the implant's supporting bone structure but also plays a crucial role in protecting against microbial invasion and in the health of the peri-implant tissues [4]. The literature suggeststhat the absence or an inadequate quantity of the keratinized mucosa (KM) can negatively affect the patient's oral hygiene control [4; 5; 6; 7]. However, there is a growing amount of high-level evidence associating an inadequate KM quantity (<2 mm) with peri-implant mucositis. [PERSON] et al. related that a minimum quantity of 2 mm of KM was essential to minimize the incidence of peri-implant mucositis and future marginal bone loss [4]. Thus, maintaining the health and integrity of the epithelial lining and connective tissues above the peri-implant bone crest is vital to ensure long-term implant health and stability [8]. In this sense, several approaches have been suggested to improve the quality and stabilization of the soft tissues around implants, such as modifications in the micro and macro design of the trans-mucosal implant abutment or the coronal area of the implant. This can promote the formation of woven bone in the healing chambers and facilitate further morphological changes in the bone toward a haversian-like structure, which, over time, significantly improves its mechanical properties. As a result, the adjacent bone experiences minimal loading, preventing stress concentrations that could surpass the minimum effective strain needed for bone modeling and remodeling [9; 10; 11; 12; 13]. Other authors have shown that concave or convergent abutment designs attempt to increase the thickness of the peri-implant tissues [14]. The concave emergence profile of the implant design plays a significant role in promoting soft tissue growth and stability, in comparison to traditional designs [15], providing more space for fibroblast proliferation, tissue fixation, and reduced bone resorption [12]. Figure 1 schematically shows the proposed innovative design of the Collo implant. New dental implant designs that focus on increasing soft tissue stability and promoting optimal healing processes around dental implants may enhance the long-term success of implant-supported rehabilitation. However, as far as we know, there have been no reports in the literature of well-designed clinical studies on the development of dental implants that consider their interaction with bone tissue and the peri-implant mucosa. In the present five cases, 25 implants installed in the maxilla and mandible in end-tulous patients, which were monitored clinically and radiographically at times ranging from 0 to 38 months, were evaluated. For each implant, the marginal bone level (MBL) was measured immediately after the installation of the implant/prosthesis, six months later, and at the most recent evaluation of each patient. Thus, the main objective of this study was to evaluate the long-term effects of a novel dental implant design, specifically focused on improving the quality and stability of peri-implant soft tissues, on the health and success of dental implants in dedentulous patients. This study aimed to clinically and radiographically evaluate an implant with an innovative design (Collo implant), which presents a concave  
Figure 1: Schematic image of the innovative new design of the Collo implant inserted into the bone tissue. The figure provides a visual representation of how this novel implant design may contribute to the stability and sealing of peri-implant tissues, particularly highlighting the intricate details of the cervical portion of the implant.