## 3 Results and Discussion
### Overdentures (OVD)  
Patients can clean at home overdenture prostheses more easily than a fixed full-arch; however, the presence of fixed prosthetic components can harbor plaque and calculus. Hence, hygiene should be performed every 3 or 4 months on the basis of the evaluation of clinical parameters and patient compliance. Extraordinary maintenance should be performed only in presence of clinical signs of inflammation (Figure 5).  
Other important and specific clinical factors have to be taken into consideration. For instance, the prevalence of peri-implantitis in patients with implants in augmented sites is more variable and less predictable compared with the prevalence in patients with implants in pristine sites [40; 41; 42; 43; 44]. There are differences in bone loss during the spontaneous progression period between pristine and augmented: the size and vertical dimension of the peri-implantitis lesion were larger at augmented than at pristine sites and the findings  
Figure 4: **Fixed full-arch prosthesis** on short and zygomatic implants: ordinary hygiene every 3 months and extraordinary every 6 months or in case of BOP+.  
Figure 3: **Fixed partial prosthesis** on implants in regenerated bone: ordinary hygiene every 3 months and extraordinary every 12 months or in case of BOP+.  
seemed to be confirmed by clinical data, which showed a faster and worsening progression of peri-implantitis in augmented bone [45].  
In patients with severely atrophic maxillae, zygomatic implants represent an alternative to conventional bone augmentation with the advantage of a fast functional rehabilitation [27; 28]. However, according to the literature, this kind of prosthetic rehabilitation is associated with an increased risk of mucositis [28]. The presence of false prosthetic gingiva, often related to zygomatic, tilted, and pterygoid implants, can favor plaque accumulation and retention.  
Nowadays short implants (defined as \(\leq\)6 mm long) are used as an alternative to reconstructive bone surgeries due to their up-to-date reliable results [26; 27; 46; 47; 48]. Despite of stable peri-implant marginal bone levels, short implants require a special attention in order to avoid marginal bone loss.  
For all of these patients with unfavorable clinical conditions, ordinary hygiene should be performed every 4 months for single crowns and every 3 months in all the other rehabilitations (Table 1, Figure 6). Especially in these kinds of rehabilitations, special attention should be given to the extraordinary hygiene removing the prosthesis and using the extra-oral magnetic cleaner.  
However, all the limitations of a communication should be taken into consideration: the lack of a control group and of a sample size calculation, and the absence of a statistical analysis and of a rigorous study design. For this reason, we strongly suggest for future research studies to confirm these results.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Types of Implant Prosthetic** & **ORDINARY** & **EXTRAORDINARY** \\
**Rehabilitations** & **Hygiene (Months)** & **Hygiene (Months)** \\ \hline Single crown & 6/4 * & BOP+ \\ \hline Fixed partial prosthesis & 4/3 * & 12/BOP+ \\ \hline Fixed full-arch & 4/3 * & 6/BOP+ \\ \hline Overdentures & 4/3 * & BOP+ \\ \hline \hline \end{tabular}  
* Patient compliance
* history of periodontitis
* augmented bone
* short implants (\(\leq\)6 mm long)
* zygomatic/pterygoid/tilted implants
* complex prosthesis with false gingiva. BOP: bleeding on probing.  
\end{table}
Table 1: Ordinary and extraordinary hygienic maintenance in different implant prosthetic scenarios.  
Figure 5: **Overdenture** (OVD) prosthesis on short implants: ordinary hygiene every 3 months and extraordinary only in case of BOP+.