Table 2. Histological grading criteria for healing.

Grade	Features
Grade 1 (very light healing)	Necrotic epithelium
	No collagen fibers
	Low vascularity
	No granulation tissues
	Abscess formation
Grade 2 (moderate healing)	Epithelial proliferation in the margin of ulcer
	Moderate collagen fibers
	Moderate vascularity
	Onset of granulation tissue formation
Grade 3 (advanced healing)	Epithelium continuation
	Well-organized granulation tissue
	Abundant collagen and capillaries content
Grade 4 (well-organized healing)	Complete epithelialization
	Fibrous connective tissue
	Normal amount of capillaries
	Absence of granulation tissue