Can Dental composite bonding be placed over previous bonding?

I recently had bonding done to my lateral incisors to make them appear longer. After one day, one side split in half leaving half resin on my teeth. I went back to my dentist to get it fixed and instead of filing off the leftover resin, he just re-bonded the whole tooth over the previous resin. Three days later, the new bonding fell off leaving the old resin to remain again. Should he have taken off the old resin?