The Space Shuttle tiles were explicitly not ablative. However, there were problems with the fragility of the tiles, which meant that at least a few tiles needed

The Space Shuttle tiles were explicitly not ablative. However, there were problems with the fragility of the tiles, which meant that at least a few tiles needed to be replaced after almost every flight. There is some speculation that it would have been better to use ablative tiles, which would need to be replaced regularly but would be less susceptible to unexpected damage. https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protecti... I don't think that Elon has clarified yet whether or not the Starship tiles will be ablative, but keep in mind that Dragon currently uses a single-piece ablative heatshield which is theoretically good for several reuses.