# Subperiosteal Anchorage in Orthodontics: A Narrative Review
## 4 Discussion  
### Clinical Procedure and Survival Rates  
As its name suggests, the onplant does not sit in a bone cavity but on the surface of the palatal bone. Onplant devices require three surgical procedures: the first to place them, the second to expose the onplant's screw through the mucosa and the third to remove them. The onplant is placed under the periosteum on the posterior part of the hard palate during a \"tunneling\" procedure. A full-thickness mucoperiosteal incision must be made on the anterior part of the hard palate in order to place the onplant away from the incision; this aspect of the procedure is aimed at reducing soft tissue inflammation and creating the best condition for osseointegration [26]. The conditions for osseointegration, primary bone-to-onplant contact and avoidance of micro-motions are given by the midpalatal area and the thickness of the oral mucosa [17]; 10-12 weeks are needed for osseointegration. Patients are asked to wear a vacuum-formed stent to place pressure on the mucosa in order to maintain the correct position of the onplant. After the healing time, the implant is exposed with a punch, a healing screw is placed and after 1-2 weeks of healing the abutment is ready to be loaded, connecting it to the orthodontic or prosthetic device. A simple transfer impression technique of the abutment allows the fabrication of the orthodontic device. Finally, to remove the onplant, a portion of soft tissue overgrowth needs to be removed, which could cause postoperative discomfort for the patient. Most often the underlying bone shows a textured pattern that mirrors the textured undersurface of the onplant. Since invention, onplants have been little investigated. Few studies are available on the success or failure rate of subperiosteal implants, both in vivo on animals or in patients. A clinical study on humans, reported by [PERSON] and [PERSON], evaluated the success rate of Onplants as 82.8% in total, including only one failed onplant due to missing osseointegration [18]. In a previous pilot study, [PERSON] et al. reported a success rate of 87.5% [6]. An experimental test conducted by [PERSON] et al. on the implantation of Onplant in animal mandible resulted in a poor success rate of 33%. Due to these consid \begin{table}
\begin{tabular}{l l} \hline
**Authors (Year) [Reference]** & **Type of Study** \\ \hline [PERSON] and [PERSON] (1995) [9] & In vivo animal study \\ \hline [PERSON] and [PERSON] (2001) [10] & Case series \\ \hline [PERSON] et al. (2001) [11] & In vitro study \\ \hline [PERSON] et al. (2002) [7] & Case report \\ \hline [PERSON] et al. (2002) [12] & Case report \\ \hline [PERSON] et al. (2003) [13] & In vivo animal study \\ \hline [PERSON] et al. (2005) [14] & Case report \\ \hline [PERSON] et al. (2006) [6] & Pilot study \\ \hline [PERSON] et al. (2007) [15] & In vivo animal study \\ \hline [PERSON] et al. (2007) [16] & Randomized controlled trial \\ \hline [PERSON] et al. (2008) [17] & In vivo animal study \\ \hline [PERSON] and [PERSON] (2008) [18] & Randomized controlled trial \\ \hline [PERSON] et al. (2009) [19] & In vivo animal study \\ \hline [PERSON] et al. (2012) [20] & Randomized controlled trial \\ \hline [PERSON] et al. (2013) [21] & In vivo animal study \\ \hline [PERSON] et al. (2013) [22] & In vitro study \\ \hline [PERSON] et al. (2014) [23] & In vivo animal study \\ \hline [PERSON] et al. (2017) [24] & In vitro study \\ \hline [PERSON] et al. (2021) [25] & In vitro study \\ \hline \end{tabular}
\end{table} 
Table 1: Results of the database search based on the SPIDER tool. erations, a stable Onplant device position is an important predictive factor for successful osseointegration and the mandible does not represent a proper anatomical location for subperiosteal implants [17]. Also, [PERSON] et al. reported a loss rate of 20.8% with the implantation of subperiosteal implants in domestic pigs [23], while [PERSON] et al. reported a very high success rate of 95.8% during an experimental study on rabbit calvaria [15].