Can we brush our teeth using a toothbrush and toothpaste while fasting?
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said:
As for the miswaak, it is permissible and there is no difference of opinion concerning that. But they differed as to whether it is makrooh after the sun has passed the meridian, and there are two well known views, both of which were narrated from Ahmad. But there is no shar’i evidence suggesting this to be makrooh which can be regarded as an exception from the general meaning of the texts about the miswaak. End quote from al-Fataawa al-Kubra (2/474).
Shaykh Ibn Baaz (may Allaah have mercy on him) was asked: What is the ruling on using toothpaste when fasting?
Cleaning the teeth with toothpaste does not break the fast as is the case with the miswaak. But one should be careful to avoid letting any of it reach his throat, but if that happens accidentally then he does not have to make up the fast. End quote from Majmoo’ Fataawa al-Shaykh Ibn Baaz (15/260).