###### Abstract  
The study reviewed the state of the art of the clinical use of a convergent-neck-designed Prama implant. This implant was introduced approximately 10 years ago and was characterized by a specific and unique convergent neck with a microtextured surface (UTM surface) and Zirconium Titanium (ZirTi) implant body surface. The neck design was developed to adopt the biologically oriented preparation technique (BOPT). A critical analysis of the published clinical studies and an evaluation of the adopted clinical protocols were performed. A total of forty-six articles were eligible to be reviewed. Only sixteen clinical studies reported clinical outcomes on Prama implants, and nine of these were selected having the longest follow-up from different research groups. The clinical follow-up/duration of the studies ranged from 12 months to 6 years. The initially proposed protocols explored neck supracreal-transmucosal placement and gained interest due to its minimally invasive concept and the ability to proceed without a pre-prosthesis second surgery. The following investigations dedicated attention to the subrestal or equicrestal implant placement with the conventional flap approach. The clinical studies characterized by the transmucosal exposed neck approach reported high survival rates with a stable bone morphology and reduced bone loss during the follow-up. Further recent implementations included the introduction of different convergent neck heights that need to be evaluated. The use of intraoral scanner technologies and digital workflow resulted in a simpler methodology with control of the marginal crown morphology. The studies support the concept that the hard tissue parameters (such as marginal bone level, MBL) and soft tissue parameters (such as pink esthetic score, PES) were stable or improved during the follow-up. Definitive crowns, designed with low invasiveness for soft tissues, were possible thanks to the morphology of the neck. The clinical studies support the use of the Prama implant with the different neck positions, demonstrating hard tissue preservation and optimal esthetic results in the first years following insertion. However, the current body of evidence is not robust enough to draw definitive conclusions, especially in the long term, and further high-quality research (long-term randomized trials) is required to consolidate these early observations. convergent neck implants; flapless technique; two-piece implant; MBL; esthetic results; dental implants; digital intraoral scanners +
Footnote †: journal: Applied Sciences  
10 Years of Convergent Neck Implants: A Systematic Review of Clinical Outcomes, Initial Original Concepts, and Changes in Surgical and Prosthetic Protocols  
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tion of the neck, its configuration, and the consequent effectiveness on mucosal healing and on the prosthetic procedures (i.e., intraoral scan 3D impression) [1; 2; 3; 4]. A two-piece implant, characterized by a 2.8 mm convergent neck with a microtextured surface, was developed and proposed in 2014. The implant enabled tailored insertion (supracrestal level, crestal level, or subrestal level) depending on several clinical protocols or clinical situations. Additionally, the implant neck was conceived to comply with the biologically oriented preparation technique (BOPT) concepts [5]. The technique involves a vertically prepared prosthodonic protocol without a distinct finish line, enabling the mucosa to adapt to the prosthetic profile determined by the crown. Consequently, by adjusting the crown contours, clinicians can manage and modify the peri-implant soft tissues [5]. Recently, histological studies on animals demonstrated the stable morphology of bone tissues around implants with the neck designed following the BOPT [6] and following the same preparation concepts of teeth prepared using a prosthetic preparation with no finishing line [7]. The neck surface has been analyzed by both morphological [8] and histological studies [6; 9].