Bradley Tucek was sent home from the dentist with Panadol, despite telling family he was in "agony".
Four days later he was found dead.
The 33-year-old, from North Sydney, visited the dentist on July 14 and was told he had an infection.
He was given antibiotics, painkillers and was booked in for another appointment to remove the tooth.
Tucek was found dead by concerned colleagues on Monday, July 18, but police believe he died on the Saturday.
A post-mortem examination will take place to determine how he died, but his family said he was in a "great deal of pain and suffering" before his death.
His sister, Ally Valentine, spoke of her family's pain following Tucek's sudden death.
"Our lives were ripped into a billion pieces this week with the devastating news our dearly loved son, brother, brother-in-law, uncle, grandson, cousin, nephew and friend passed away suddenly and unexpectedly," she wrote on a GoFundMe page set up to raise money to fly his body to Perth.
"We are hurting so much and have a logistical nightmare ahead of us over the coming weeks.
"The circumstances of Brad's death are heart-wrenching. Brad lived by himself in Sydney, while his parents and sister live in Perth.
"He spent much of the pandemic alone due to border closures and working from home.
"Last week he fell ill with a toothache and was sent home from a dentist with antibiotics and an inadequate level of painkillers.
"Brad endured a great deal of pain and suffering before dying alone in his home, on his kitchen floor.
"We are utterly devastated by this and don't want Brad to be alone any longer.
"We want answers as to how a simple toothache can lead to a devastating loss of life."