The 23-year-old's wedding to the hockey player on August 14 this year could have been spoilt if she didn't have her pretty smile.
In an upcoming Ellen DeGeneres show, the Lizzie McGuire star told the US host: 'The beginning part of the day I lost my tooth.
'Tooth fell out in my hand, thank god I didn't swallow it - not good for a bride on her wedding day.'
The star added: 'I bit into a bagel, I was sitting on the bed with my mum and my sister and they're like 'You're an idiot, you did not. Come on!''
The star explained how the incident had happened at around 11am but she didn't have to begin getting ready for another three hours, although she still got upset.
She said: 'I started laughing at myself and then I really burst into tears.'
However, her wedding planner, Mindy Weiss, came to the rescue.
Duff added: 'Mindy's sister's husband's best friend is a top dentist in Montecito and she called him up.'