## 4 Discussion
At the six-month follow-up, CRC was achieved in 52% in the CAF alone group and 37% in the CAF/CTG group. Although, there was a decrease in the percentage of CRC in the CAF alone and an increase in the CAF/CTG group after 12 months, 37% and 45%, respectively, and after 5 years, 35% and 52%, respectively. The authors also noted that the apical relapse of gingival margin was statistically significantly higher in the CAF alone group, which was explained by the lower keratinized gingival tissue thickness due to the lack of use of a connective tissue graft, similar to other studies [38]. Comparing the use of autogenous connective tissue and a substitute for CTG in covering gingival recessions, [PERSON] et al. [46] observed statistically greater increase in keratinized tissue width (baseline--2.4 mm, after 6 months 4.1 \(\pm\) 0.8 mm) in the CTG group than in the ADMA group (baseline--2.9 mm after 6 months 3.5 mm). [PERSON] et al. [47] underlined in a long-term 12-year study of MAGRs treatment with the use of an autogenous connective tissue substitute--Acellular Dermal Matrix and CAF or tunnel technique, a significant recurrence of gingival recession between 6 months and 12 years after the treatment. According to the authors, the factors determining the stability of results were KTW \(\geq\) 2 mm and GT \(\geq\) 1.2 mm at the 6 months period. Multiple adjacent 48 Miller class I gingival recessions with a GT less than 0.8 mm were covered using the CAF/ADM and CAF alone method. The average GT value in the treated MAGRs sites with complete root coverage was more than or equal to 1.3 mm. The values for ARC and CRC after 12 months were 94.84% and 83.33% in the CAF/ADM group, 74.99% and 50.00% in the CAF alone group, respectively. The increase in gingival thickness during the 12 months observation period was 0.69 mm, from 0.75 mm to 1.41 mm for the CAF/ADM group, namely the percentage of gingival thickness increase (GTI) was equal 88.00%. For the CAF group GT increase was 0.07 mm from 0.71 mm to 0.77 mm, namely the percentage of GTI was equal 8.45% and the intergroup difference was statistically significant. In the [PERSON] et al. study [38], evaluating the efficacy of MAGRs coverage procedures using the CAF method with and without the use of a connective tissue graft, GT at baseline was 0.73 mm in the CAF/CTG group and after 12 months 1.39 mm, i.e., an increase of gingival thickness of about 90.41% was achieved. In our study, at baseline the mean value for GT, measured in the center of the keratinized tissue (BGT\({}_{1}\)) in the test group was 1.04 mm and for the control group was 1.11 mm and after two years 1.79 mm and 1.51 mm respectively and therefore GT increase was 42.15 \(\pm\) 14.65% in the test and 26.63% in the control group. The mean AG value for the test group at baseline was 1.33 mm and for the control group 1.51 mm, after 24 months they increased to 3.69 mm and 3.87 mm respectively. Despite the demonstrated lower percentage of GTI, GT values greater than 1.5 mm and well over 3 mm width of attached gingiva may contribute to the long-term stability of the clinical results obtained. In order to determine the gingival thickness most of the authors apply the invasive bone sounding method using an endodontic file or periodontal probe together with a caliper [27; 28; 31; 37; 40; 43; 44]. The measuring point is located either 1.5 mm mid-buccally from the gingival margin [28; 38; 43] or 3 mm from the gingival margin [40; 44] or in the center of the keratinized tissue and marked as GT1 and 2 mm apically from the mucoginigival junction marked as GT2 [27; 37]. Within this study during each observation stage, apart from GT1 and GT2, another measurement point was determined given the absence of attached gingiva, located 2 mm apical from the clinical attachment level. According to [PERSON] et al. [48], the presence of vestibular keratinized gingiva with the thickness of at least 1.2 mm gives the possibility to raise a mucosal flap, which after repositioning guarantees complete gingival recession coverage without the need of a CTG.