This unconscionable gaming of the welfare system — and abuse of taxpayers’ funds — hit home recently with the sentencing of a Chelmsford dentist for his role in a $550,000 Medicaid fraud scheme. U.S. District Court Judge Margaret Guzman earlier this month ordered Dr. Scott Cale, 68, to serve 18 months in prison — less than the three years sought by prosecutors — and one year of supervised release after he pleaded guilty in April to his willful participation in committing health-care fraud.