In Vivo studies of longevity of internal bleaching

Brown 1965

• 7.5% discoloured after 1–5 years

• 46.3% some colour regression

• Howell 1981

  • 50% colour regression by 1 year

• Feiglin 1987

  • 55% discoloured over 6 years

• Holmstrup et al 1988

  • 20% discoloured by 3 years