Buffon and De Sciglio each missed Italy's 2-1 win over England on Saturday.
Buffon hurt his left ankle and knee a day before the England game, and De Sciglio had an injured left leg.
Italy next faces Costa Rica on Friday in Group D, then meets Uruguay four days later.
About 150 schoolchildren were invited to attend Tuesday's training session and posed for pictures with the Azzurri. Mario Balotelli was mobbed by kids seeking autographs.