**Core Concept**
The difficulty in periodontal surgery arises from anatomical considerations, particularly the relationship between the tooth and surrounding structures. The second molar is a multi-rooted tooth with a complex root anatomy, making it challenging to approach surgically.

**Why the Correct Answer is Right**
The second molar's distal aspect is particularly difficult to access due to the presence of the maxillary tuberosity, a bony prominence that forms the posterior boundary of the maxillary alveolar process. This limits the available space for surgical access and increases the risk of damaging surrounding structures such as the maxillary sinus. The proximity of the distal aspect of the second molar to the maxillary sinus also makes it a high-risk area for sinus exposure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while the maxillary canine is a prominent tooth, its proximity to the second molar is not the primary reason for difficulty in periodontal surgery in this area.

**Option B:** This option is incorrect because the anterior aspect of the second molar is not typically considered the most difficult to access in periodontal surgery.

**Option C:** This option is incorrect because while the second molar's mesial aspect is also challenging, the distal aspect is more difficult due to the reasons mentioned above.

**Clinical Pearl / High-Yield Fact**
When planning periodontal surgery for the second molar, it is essential to carefully evaluate the patient's anatomy, including the presence of a maxillary sinus, to minimize the risk of complications and ensure a successful outcome.

**Correct Answer:** C.