# Long-Term Stability of Er:YAG Laser Non-Surgical Periodontial Treatment
## 3 Results  
The participants of the present study are between 30 and 62 years old (46.87 \(\pm\) 8.49 years); 23.1% are male and 76.9% are female. Table 1 presents the data on changes in PPD and the comparison between both treatment groups from the initial examination up to one year after the therapy. After hand instrumentation, a statistically significant reduction in PPD is obtained in the first and third months (\(p\) < 0.05) (Table 1). Between the third and sixth month, there is a slight increase in the PPD (0.36 mm), and between the sixth and twelfth month the deepening of the pockets averaged 0.91 mm, which is statistically significant (\(p\) = 0.04). The overall mean reduction in this clinical indicator for the control group one year after therapy is 1.55 mm. In the group treated with the Er:YAG laser, the most pronounced reduction in pocket depth is observed in the period from the initial study to the first month--from 4.58 mm to 3.15 mm (\(p\) = 0.00) (Table 1). The reduction lasted until the sixth month, and between the sixth and twelfth month of treatment there is a slight deepening of the pocket by 0.05 mm (\(p\) > 0.05). One year after Er:YAG laser treatment of the periodontal pockets, a statistically significant (\(p\) = 0.00) reduction in the depth of the pockets from 4.58 mm to 2.88 mm is found. Table 2 presents the dynamic changes in GR for both therapeutic approaches. Twelve months after treatment, the increase in recession in both study groups is statistically significant compared to the initially measured values (\(p\) = 0.00). The CAL in the control group demonstrates a statistically significant decrease by the third month (\(p\) < 0.05), decreasing from 4.66 mm in the baseline to 3.56 mm in the first month and 3.10 mm in the third month after treatment (Table 3). The total gain of clinical attachment up to the third month after manual instrumentation is on average 1.54 mm. In the sixth month, there is a slight increase compared to the third month (0.03 mm), which has no significant difference (\(p\) = 0.511). However, between the sixth and twelfth month after mechanical therapy, a loss of clinical attachment of 0.11 mm is observed, which is \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Laser Group**} & \multicolumn{4}{c}{**Control Group**} \\ \cline{2-13}
**PPD** & **N** & \(\mathbf{\bar{x}}\) & **S\({}_{\mathbf{X}}\)** & \
\begin{tabular}{c} **Mean** \\ **Diff.** \\ \end{tabular} & **t** & \(p\)**-Value** & **N** & \(\mathbf{\bar{x}}\) & **S\({}_{\mathbf{X}}\)** &
\begin{tabular}{c} **Mean** \\ **Diff.** \\ \end{tabular} & **t** & \(p\)**-Value** \\ \hline PPD—baseline & 572 & 4.58 & 0.69 & & & 527 & 4.59 & 0.68 & & 1.23 & 27.79 & _0.00_ \\ PPD—1 month & 572 & 3.15 & 1.08 & & & 527 & 3.36 & 1.09 & & & & & \\ \hline PPD—1 month & 572 & 3.15 & 1.08 & & & 3.15 & 7.035 & _0.00_ & & 527 & 3.36 & 1.09 & & & & \\ PPD—3 months & 572 & 2.84 & 1.05 & & & 527 & 2.91 & 1.15 & & & & & & \\ PPD—6 months & 572 & 2.83 & 1.06 & & & 0.02 & 0.522 & 0.60 & & 527 & 2.95 & 1.07 & & & & & \\ PPD—6 months & 572 & 2.83 & 1.06 & & & & 0.05 & & 527 & 2.95 & 1.07 & & & & & \\ PPD—12 months & 572 & 2.88 & 0.99 & & & & 1.371 & & 0.17 & & & & & & & \\ \hline PPD—baseline & 572 & 4.58 & 0.69 & & & & 527 & 4.59 & 0.68 & & & & & & & \\ PPD—12 months & 572 & 2.88 & 0.99 & & & & 527 & 3.04 & 1.01 & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dynamic changes in pocket depth after Er:YAG laser (laser group) and conventional instrumentation (control group). statistically significant (\(p\) = 0.015). At the end of the observed period (1 year after therapy), a clinical attachment gain of 1.41 mm is reported compared to the initially measured values before treatment with hand instruments, which is statistically significant (\(p\) < 0.001). A statistically significant decrease in the CAL is observed up to the third month in the laser group as well (\(p\) < 0.05).