## 3 Results  
We carried out a retrospective controlled study establishing, as a control group, the implants treated with only OHLLT, a choice that is supported by extensive literature reporting successful treatments with this modality; the test group was represented by OHLLT + Er:YAG laser treatment. All peri-implant pockets were treated successfully with clinical signs of soft and hard tissue healing. In fact, at T\({}_{1}\), all implants showed the absence of suppuration and contemporary resolution of bleeding on probing (BOP). The percentage of bone loss was analyzed for each implant. Mean bone loss due to peri-implantitis at T\({}_{0}\) (before laser treatments) was 5.8 mm in the upper arch and 5.2 mm in the mandible, as detected from the preoperative periapical radiographs. The total amount of bone loss, considering both the upper and lower arch, was 5.6 mm (Table 1). Figure 5: Er:Yag ([PERSON], Doctor Smile) in action on bone surfaces (power: 3.2-3.8–4.4 W, frequency: 20 Hz, energy: 160–190–220 mJ, depending on bone density, from lower to higher, water: 70%, air: 80%). In the group of implants that received only OHLLT ([PERSON], Doctor Smile), we noticed at T1 a mean bone loss after treatment of 2.1 mm in the upper arch and 2.4 mm in the mandible, resulting in a total mean bone loss of 2.3 mm (Table 2). Implants that received OHLLT ([PERSON], Doctor Smile) + Er:YAG laser (Pluser, [PERSON]), at T1, showed a mean bone loss of 2.0 mm in the upper arch and 2.5 mm in the mandible, with a total mean bone loss of 2.3 mm (Table 3). The results showed no statistically significant differences between the two groups at \(p\) < 0.01 (\(p\) = 0.596). Statistical analysis revealed no significant difference in postoperative bone loss between the two groups. According to the Kolmogorov-Smirnov test, overall, the data followed a normal distribution (value of the K-S test statistic = 0.0912; \(p\) = 0.36112). Statistical analyses are presented in Tables 4 and 5. \begin{table}
\begin{tabular}{c c c c} \hline
**Implants** & **Upper** & **Lower** & **Total** \\ \hline Total amount & 126 & 84 & 210 \\ Preoperative bone loss & 5.8 mm & 5.2 mm & 5.6 mm \\ \hline \end{tabular}
\end{table} 
Table 1: Preoperative bone loss. \begin{table}
\begin{tabular}{c c c c} \hline
**OHLLT + Er:YAG Group** & **Upper** & **Lower** & **Total** \\ \hline Total amount & 54 & 34 & 88 \\ Postoperative bone loss & 2.1 mm & 2.4 mm & 2.3 mm \\ \hline \end{tabular}
\end{table} 
Table 2: Postoperative bone loss—OHLLT (Wiser, Doctor [PERSON]). \begin{table}
\begin{tabular}{c c c c} \hline
**OHLLT + Er:YAG** & **Upper** & **Lower** & **Total** \\ \hline Total amount & 72 & 50 & 122 \\ Postoperative bone loss & 2.0 mm & 2.5 mm & 2.3 mm \\ \hline \end{tabular}
\end{table} 
Table 3: Postoperative bone loss—OHLLT ([PERSON], Doctor [PERSON]) + Er:YAG ([PERSON], Doctor [PERSON]). \begin{table}
\begin{tabular}{c c c c} \hline
**OHLLT + Er:YAG** & **Upper** & **Lower** & **Total** \\ \hline Total amount & 72 & 50 & 122 \\ Postoperative bone loss & 2.0 mm & 2.5 mm & 2.3 mm \\ \hline \end{tabular}
\end{table} 
Table 3: Postoperative bone loss—OHLLT ([PERSON], Doctor [PERSON]) + Er:YAG ([PERSON], Doctor [PERSON]). \begin{table}
\begin{tabular}{c c c} \hline
**OHLLT + Er:YAG Group** & **OHLLT Group** & **\(p\) Value** \\ \hline
**BoP** & 2.45 \(\pm\) 0.38 & 2.46 \(\pm\) 0.42 & \textless{}0.0012 * \\
**P.S.** & 1.12 \(\pm\) 0.23 & 1.17 \(\pm\) 0.22 & \textless{}0.0015 * \\
**P.D.** & 5.58 \(\pm\) 0.19 & 5.61 \(\pm\) 0.21 & \textless{}0.0015 * \\ \hline \end{tabular}
\end{table} 
Table 4: Peri-implant parameters among test group (OHLLT + Er:Yag) and control group (OHLLT), pretreatment.