What to do when the teflon stops being non-stick?

Situation: electric skillet, multiple years old. Teflon surface, generally in good condition.

Made turkey spaghetti sauce the other night, and somehow some of the substance burnt onto the teflon surface. I have soaked the skillet in hot water, added dish cleanser, scraped (with plastic utensil), and there is still a good bit of residual burnt on crap.

Any wisdom on how to get that off, without utterly demolishing the skillet and removing the non-stick (ha ha) coating?

Does Teflon get tired?