Mam
It's a myth that scaling causes loosening of teeth. Sometimes patients are having heavy deposits(calculus) on their teeth because of which there is bone loss and teeth are held together by support of calculus.
After scaling when calculus is removed people feel loosening of teeth which were earlier supported by calculus.
Next Steps
Get blood
sugar levels of your dad checked. Increased blood sugar levels are also one reason for loosening of teeth.
There are also few cases in which patients experience loosening of teeth post recovery from Covid 19, if such is the case of yours please visit a Dentist.
Health Tips
Ask your dad to do lukewarm salt water gargle three to four times a day.
Hope it helps.