Assalamou Alaykom I heared one day in the TV one Cheykh saying that the prophet (peace and blessing be upon him). said " in the 10th day your baby birth take a piece of date (tamra) and massage his gum with it. In cha allah when he grow up he will have straight teeth whith no dental congestion. I would like to know if there are ahadith concerning this sunna. I leave you in peace. with best regards

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is a confirmed that the Prophet used to chew a date and then put it in the infant’s mouth as we clarified in Fatwa 82088. Some jurists stated that this can also be done with something sweet in the absence of dates.

However, the Prophetic narration does not state that this act is done on the 10th day as you mentioned. Rather, the Sunnah is to do this immediately upon birth. Indeed, the Prophet chewed a date and put it in the mouth ‘Abdullaah, the son of Abu Talhah when Anas took him to the Prophet when he was born. 

Moreover, An-Nawawi stated that the jurists agreed that it is desirable to chew a date and put it in the mouth of the baby when he is born.

Finally, the narration does not state that if this is done then the infant will grow to have straight teeth with no dental congestion.