## 4 Discussion  
The purpose of the study was to illustrate two surgical techniques by evaluating the clinical efficacy in terms of peri-implant mucosal gains in patients with unitary PSTD in the esthetic zone. Figure 5: (**A**): Appearance of the final restoration. (**B**): Radiographic image 5 months after definitive restoration. (**C**): Postoperative intraoral view. (**D**): Clinical view at 4 months of follow-up. \begin{table}
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PSTDs are an increasingly common finding due to the continuing demand for dental implants in the esthetic zone. For anatomical reasons, it is common to place implants with excessive vestibular angulation, with thin or even absent vestibular cortex, covered with a thin gingival phenotype and with a reduced amount of keratinized mucosa. This, taken together, would pose a risk of developing PSTD with consequent exposure of the implant surface [23; 35; 36]. Recent systematic reviews and consensus publications report that, on tooth, there are predictable techniques for coverage of the denuded root surface, with or without using CTG [37; 38; 39]. However, for implants (PSTD), some techniques to achieve coverage of the exposed implant surface have been described, but are limited to animal testing, clinical cases, or case series focused on shallow recessions [40; 41; 42]. Future work should address studies on the predictability of these techniques in a healthier research design. To date, among the most studied treatment options for the treatment of PSTD, the coronal advancement flap plus a CTG (in mild defects <2 mm) stands out [43]. A disadvantage of this technique is the use of vertical releasing incisions that significantly compromise the vascularization of the tissues, in addition to the esthetic risk due to the possible appearance of scars and the coronal displacement of the mucoginyal line [24; 44; 45]. To avoid these side effects, from the 1980s to the present time, in gingival recession defects and periodontal reconstructive surgeries, different flap designs have been developed that avoid or minimize the number of vertical or horizontal releasing incisions on the vestibular side, with or without the use of CTG, in order to maximize tissue preservation [31; 46; 47; 48; 49; 50; 51; 52; 53]. However, for the treatment of PSTD in unfavorable anatomical conditions (thin phenotype, dental implant malposition), there are no therapeutic protocols with sufficient scientific evidence to ensure complete coverage of peri-implant soft tissue dehiscence and comprehensive reconstruction of the papilla. The surgical approach of the present clinical case of PSTD is inspired by the work of [PERSON] et al. [31] who, in 2014, published a series of 15 cases of gingival recessions in the mandibular anterior area with a follow-up of up to two years after a bilaminar technique of only one horizontal incision in the bottom of the vestibule. The results showed an average root coverage of 90.6% \(\pm\) 16.8%. For the first surgical approach, the apical approach technique (horizontal incision in the bottom of the vestibule) was chosen because of its respect for the papillae and the ability to coronally reposition the vestibular flap. In addition, vertical releasing incisions are avoided with this technique, which reduces the appearance of unsightly visible scars and, as a consequence, increases the vascular supply to the flap. At 6 months after maturation, a gain of keratinized mucosa both in thickness and width around the implant 1.2 was achieved. For the second surgical approach, the palatal sliding flap published by [PERSON] [32] in 1995 and later modified by [PERSON] et al. [44] was chosen. This approach proposed advancing the palatal tissue coronally by means of partial thickness preparations at different depths.