Pan Masala Stains and Shape of Teeth.

From what I comprehend, your teeth alignment may not be proper due to which your brushing is not effective even though you may be putting the effort. Maligned teeth lead to faster decay due to difficulty in cleaning and brushing properly and as a consequence stains and plaque develop faster. All of this results in destruction of teeth structure or loss of teeth. The line of treatment in your case would be correcting your teeth alignment first with braces naturally. Once corrected the results will be permanent and your teeth will be much more healthy in future. Also needless to say cessation of any habit such as smoking/ tobacco if any has to be stopped. You're best advised to visit a dentist for Better understanding of your problem and the treatment options. Cheers!!