Hello,
It seems that the white line you are talking about is Linea Alba.
Linea alba is a horizontal white streak or line in buccal mucosa in level with occlusion.
It has no potential for malignancy/cancer.
Leukoplakia is a white plaque or patch that cannot be characterised clinically or pathologically as any other disease.
It is is usually associated with habits like tobacco chewing,aricanut, smoking.
No signs of leukoplakia in your case.
Next Steps
Complete oral examination.
Health Tips
Please Correlate clinically.