What problems occur most when using local anaesthetics in mouth care?

Numbness: Local anesthetics are used to temporarily block pain at the injection site, but they can spread to nearby structures as well. Dental anesthetics can cause difficulty with speech, eating, and occasionally eyelid drooping. Furthermore, numbness of the mouth can make one more prone to tongue, lip, or cheek biting, so it's important to remain aware of that possibility.

Injected Local Anes: Allergic reaction to local; reaction to Epinephrine with injected local anesthetic causing heart rate acceleration and sudden feelings of stress; ineffective numbing despite drug infiltration; infection from flawed injection sterile technique or poor patient pre-existing immune system or poor post procedure oral care; post injection nerve damage causing persistent oral numbness or pain are a few.