## 4 Discussion  
In our study, which involved 91 implants and had a mean follow-up period of 24 months, the absence of progressive bone loss around the implants was observed at a rate of 96.7% at the implant level and 96.5% at the patient level when considering all types of surgical treatment combined with implantoplasty. In the subgroup that underwent reconstructive surgical modalities, a 100% absence of progressive bone loss rate was achieved at both the implant level and patient level. For the subgroup treated with apically repositioned flap, a rate of 92.9% absence of progressive bone loss was observed at the implant level, while it reached 98.2% at the patient level. In the subgroup that underwent a combination of flap apicalisation and reconstructive surgery, an absence of progressive bone loss rate of 98% was achieved at the implant level and 98.2% at the patient level. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Reconstructive** & **Apically Repositioned Flap** & **Combined** & **Total** \\ \hline Failure (implant) & 0 & 2 & 1 & 3 \\ Failure (patient) & 0 & 1 & 1 & 2 \\ Absence of marginal bone loss & & & & \\ rate (implant level) & & & & \\ Absence of marginal bone loss & & & & \\ rate (patient level-) & & & & \\ \hline \hline  & The rate was 100\% in the class I lesions sub-group treated by REC. The rate was 92.9% in the class II lesion sub-group treated by ARP. The rate was 98% in the class III lesion sub-group treated by COM. & \\ \end{tabular}
\end{table} 
Table 2: Peri-implant failure and absence of marginal bone loss rate. Figure 8: Percentage of implant or patient showing absence of progressive bone loss. REC: reconstructive, ARP: apically repositioned flap, COM: combined. The main criticism of our study is that the implantoplasty procedure can diffuse titanium particles into the tissue surrounding the peri-implant lesion. However, in biopsies of peri-implant inflammatory lesions, titanium particles are frequently found [30]. According to [PERSON] et al., titanium, in small quantities, has no influence on the tissue but can cause inflammation if its concentration increases [31]. To minimise these side effects caused by titanium particles, we rinsed the surgical site thoroughly and used a strong surgical suction close to the drill. The advantages of our study lie in the large number of subjects (57), which to our knowledge is the largest number of patients evaluated in this respect. The large number of implants (91) evaluated is also an advantage in a case series. Only one study ([PERSON] et al.) [32] evaluated more implants (135) but on a smaller number of patients (43). All other studies evaluated fewer patients and fewer implants ([PERSON] et al. [33], [PERSON] et al. [34; 35], [PERSON] et al. [36], [PERSON] et al. [37], [PERSON] et al. [38], [PERSON] et al. [39], [PERSON] et al. [40; 41], [PERSON] et al. [42], [PERSON] et al. [43], [PERSON] et al. [44], [PERSON] et al. [45], [PERSON] et al. [46]). Our study was based on routine clinical practice and gives an insight into the results that can be expected in a routine peri-implantitis treatment activity. Our mean follow up was 2 years, the same as [PERSON] et al. [38] and [PERSON] et al. [32], whereas in many studies the follow up was only one year ([PERSON] et al. [37], [PERSON] et al. [42], [PERSON] et al. [44], [PERSON] et al. [39]) or less (6 months, [PERSON] et al. [33]). This may be a disadvantage of our study as this follow up should be increased to more than 3 years, as did [PERSON] et al. [34; 35], [PERSON] et al. [36], and [PERSON] et al. [40], or even more (9 years, [PERSON] et al. [46]) to know the long-term effects of the treatment. Due to heterogeneity in study designs, patient characteristics, materials used (the use or not of membranes and different types of bone grafts/bone substitutes), evaluation methods, and follow-up duration, comparisons with previous studies were difficult. First, some studies have used other associated criteria to assess the success rate after surgical treatment of a peri-implant lesion.