New Jersey officials are investigating a dentist after a 3-year-old boy died in his care while restrained and under local anesthetic for a routine cavity-filling procedure. The dentist was still on probation after the death of a 6-year-old girl in 2004. Dr. Patrick Bamgboye, 64, is cooperating with authorities, an attorney for his employer, Dental Health Associates, told The Star-Ledger newspaper of Newark for a story yesterday. It’s too early in the investigation to assert blame, attorney Harry Levin said.