Scientific Concepts and Nail Care Theory
Anatomy first
The nail unit includes the nail plate, nail bed, matrix, lunula, cuticle, eponychium, hyponychium, sidewalls (lateral folds) and free edge. The matrix is the living tissue that produces the plate; the lunula is the visible, whitish portion of the matrix at the base. The cuticle is the thin layer of dead tissue that sheds from the eponychium onto the plate; the eponychium is the living fold of skin. Questions love to swap these two terms.
Growth and composition
The plate is hardened keratin with very little lipid and roughly 18 percent water, which is why dehydration shows as peeling and why dehydrating products are used before acrylic or gel. Fingernails grow about 1/8 inch (3 mm) per month and replace in four to six months; toenails grow much more slowly and may take nine to twelve months or longer. Growth speeds up in summer, during pregnancy and in youth. Nail plate pH is slightly acidic, around 4.5 to 5.5.
Disorders versus diseases
Onycholysis, onychorrhexis, leukonychia, Beau lines, koilonychia and onychophagy are conditions a technician may recognize. Fungal infection, paronychia, Pseudomonas (green discoloration) and inflammation are outside your scope - do not diagnose or treat; refer and decline the service.
Chemistry in the service
Monomers join into polymers; catalysts and initiators start the reaction. Acid and non-acid primers, dehydrators and gel photoinitiators all appear on the exam.
Rule of thumb: any condition that is inflamed, painful, pus-filled, discolored beyond the plate, or accompanied by lifting is a refer-out - when in doubt, do not work on it.