Los Angeles, Aug 13 : Pop-icon Madonna doesn't really like her teeth as she thinks they are so "ugly". She shared that it is the reason she wears mouth grills to hide them. Regularly seen wearing jewellery over her gnashers, the 63-year-old pop superstar finally opened up about why she decided to change up her look with customised mouth bling - saying she worries her teeth don't look very nice, reports aceshowbiz.com. During an appearance on The Tonight Show Starring Jimmy Fallon, she showed off her latest grill piece, telling the host, 'I just got these new grills, and if I start lisping will you tell me?' Jimmy replied, "Ooh they're beautiful! I love them." The 'Material Girl' singer then went on to explain she had the new grills made as a special birthday present for herself as she prepares to turn 64 on August 16. She added: "They're my 'birthday grills'. It's almost my birthday, so I got myself a pair of grills." Madonna then told the host she has been wearing mouth jewellery for "decades" and explained the reason why she covers her teeth. She said: "People have a problem with my grills, I don't know why ... I just like the way it looks - it's mouth jewellery - and I have really ugly teeth." During the interview, Madonna continued to worry about whether her latest accessory was giving her a lisp and went on to take it out before the host stopped her. She said: "No, don't! Leave it, it looks cool!" /IANS