I saw a very small dot on my same teeth using mobile camera several times but dentist say that there was no such things....does mobile camera view lack in precision?

Your post is a bit incoherent, but if your dentist says your teeth are fine, I'd go with their opinion rather than trying to diagnose carious lesions yourself.

If by mobile camera you mean a cell phone, it's not designed like a professional intra-oral camera. Your Dentist has 10,000 hours of Dental School education, multiple hundreds of hours of post-graduate education, and a lifetime of clinical experience. You have a choice following his/her advice, or seek a second opinion.