3D text dropping frame rate

I am using 3D text to show score.
whenever i get a callback to update score i update text
{
textMesh.text = score+“”;
}

this textMesh i already initialized in Start() as TextMesh using GetComponent().

when i commented this line, game was smooth, but after removing comment frame rate drops whenever i update score from 58 to 20;

Don’t update it each frame. It rebuilds the mesh making it slow.

And regarding score+“”:
score.ToString()