Hi...Brushing twice a day is a good habit...Yellow lining around teeth suggests plaque and calculus deposition between your teeth and gums... Plaque is basically thin layer deposited around teeth because of action of bacteria on food which can be easily removed with brushing, but due to inability to reach certain areas during brushing or less saliva or crowded teeth, it calcifies over a period of time which is called calculus and requires professional help to remove it... Bleeding gums, foul breath, yellow teeth are its symptoms... You can visit dentist for oral examination and get a scaling and cleaning of teeth done... Hope this will help... Feel free to ask any further queries...

The yellow line is tartar and plaque deposit that cannot be removed by brushing. Sometimes brush is not able to reach some surfaces of teeth especially between two adjacent teeth and along gum line. This causes tartar formation. You need to visit Dentist to get cleaning (Scaling ) done to remove tartar. After that you can prevent this from re occuring by proper toothbrushing. Your Dentist will show you the right technique to brush effectively.