## 2 Materials and Methods
The reflection of the lingual flap can extend to the intrasulcular part of the second molar, and it is aimed at exposing the initial margin of the lingual zone (Figure 2F). The elevation proceeds from the retromolar area to the lingual zone; the retractor must maintain contact with the bone throughout all stages of detachment. Close contact with the bone surface allows for optimal flap elevation without tearing the periosteum, which is crucial to avoid complications. A key point is the change in the inclination of the bone from the buccal to the lingual area of the retromolar region. This important step is demonstrated clearly using a human jaw model (Figure 3). During buccal and retromolar elevation, the tip of the elevator is in close contact with the bone, and the concave inner portion of the elevator faces downward (Figure 3A-C). When transitioning to the lingual area, the tip of the elevator remains in close contact with the bone, but the concave inner portion of the elevator faces upward (Figure 3D-F). Step 4: Protection of the flap  
Protection of the flap is achieved by using the internal part of the retractor in contact with the bone, and a delicate reflection is performed either by the operator or the assistant,  
Figure 1: Anatomical dissection of retromolar area performed by students. RA: retromolar area; LS: lingual side; LN: lingual nerve. moving the distal part of the instrument from the vestibular to the lingual side. It is crucial to gently reflect and keep the internal tip of the retractor in contact with the lingual bone margin (Figure 4). Figure 3: Close contact of the retractor to the bone and the change from a vestibular to lingual inclination in the retromolar area. Note how during the buccal (**A**,**B**) and retromolar flap elevation (**C**), the concave inner portion of the elevator faces downward. When moving to the lingual area (**D**), the tip of the elevator stays in close contact with the bone, while the concave inner side of the elevator is oriented upwards (**D**–**F**). Figure 2: Design and reflection of a full-thickness flap to protect the lingual nerve. Design and reflection of a full-thickness flap to protect the lingual nerve. Design of a vestibular full-thickness flap (**A**); full-thickness elevation of the buccal flap (**B**–**D**); full-thickness elevation of the retromolar area and the initial portion of the lingual area (**E**); reflection of the lingual flap (**F**). Once the mucoperiosteal flaps were mobilized and protected, a round surgical bur was used to remove the bone and section the tooth depending on the position and inclination. Following tooth extraction, the socket underwent debridement, and primary wound closure was performed using gentle, non-traumatic sutures. Special attention was paid to avoid taking more than a 3 mm section from the lingual mucosa just distal to the lower second molar, preventing inadvertent entrapment of the lingual nerve by the suture. Every patient underwent a review on the initial postoperative day and, subsequently, one week after the surgery, coinciding with the removal of the sutures. During each postoperative visit, thorough examinations were conducted to assess any sensory nerve impairment of the inferior alveolar, lingual, or mylohyoid nerves. In the context of evaluating sensory nerve function in the lingual nerve, each participant was queried about any sensations of tingling or numbness in their tongue. To establish the presence or absence of sensory impairment in the lingual nerve, a more objective evaluation of nerve injury was conducted. This assessment adhered to the procedures outlined by [PERSON] and [PERSON] [26], as well as those employed by [PERSON] [17] and [PERSON] [27]. The assessment encompassed the following criteria:  
1. Light touch sensitivity;
2. Tactile discrimination ability;
3. Pain perception awareness;
4. Two-point discrimination while in motion.