Hey, Firstly, Yellowish teeth could be due to many reasons please consult dentist and see what is the possible reason for yellowness. There are many treatment options available to chose for yellow teeth but all these can be suggested after seeing underlying cause. Secondly regarding scaling it's a myth. It will only remove surface deposits n not enamel, some sensitivity post scaling is common in initial first 24 hours especially when you are doing scaling after years. But if a patients follows all instructions given by dentist all symptoms subsides in 24-48 hours. ☺ Have a Healthy smile