Piper nigrum (black pepper) has been used in traditional medicine systems, particularly in Ayurveda and some folk remedies, for a variety of oral health issues, including canker sores (aphthous ulcers). The traditional rationale is largely based on black pepper's purported antimicrobial and anti-inflammatory properties, and its ability to stimulate saliva production, which may aid in oral healing. In some traditional Indian home remedies, black pepper is mixed with other ingredients such as ghee or honey and applied topically to canker sores to reduce discomfort and promote healing.

However, there is little to no scientific validation for the efficacy of Piper nigrum in treating canker sores specifically. While some laboratory studies have demonstrated antimicrobial and anti-inflammatory actions of black pepper or its active compound piperine, these studies generally focus on systemic effects or other types of inflammation and infection, rather than aphthous ulcers. There are no high-quality clinical trials or controlled studies demonstrating its effectiveness for this specific oral condition.

In summary, the use of Piper nigrum for canker sores is primarily justified by tradition, with minimal supporting evidence from scientific research. The strength of evidence is therefore rated low (1 out of 5).