Stephen Gaunt was related to the disabled victim, John Daly, 52 – who suffers from cerebral palsy and learning difficulties – and broke into his home, in Liverpool, to steal from him last May.
Gaunt, who was high on cocaine at the time of the attack, bit his victim’s fingers, using his teeth to rip off his rings, before snapping back his hand.
He also threatened to stab John if he refused to comply with his demands.
The 24-year-old – who has 21 convictions for 52 crimes – smirked in court as the judge handed down his sentence.
Judge Stephen Everett said: “You are a young man, who, having seen and heard you, is unlikely to change.
“If that is the case you will remain a significant risk to the public for a long time, possibly until you’re too old and infirm to carry out such acts of violence.
“Until you work on your whole approach to life, and until you receive a substantial amount of assistance, you will remain a danger to the public for many, many, many years. The reality is you will never be released until you prove you are no longer a danger to society.”
Police welcomed the sentence, with Detective Inspector Andy Milligan adding: “The victim in this case had tried to help Gaunt in the past but Gaunt betrayed and took advantage of him in the most shocking way.
“During the incident, Gaunt bent the victim’s fingers back and then stole a number of rings by literally gripping his teeth round them and pulling them off.
“The victim needed surgery on his hand and, months after the incident, he is still in constant pain. His ordeal has also left him nervous and he still describes himself as feeling ‘numb’ inside.”