The month of Ramadan, Muslims in all over the world are required for fast. Muslims understand the command of Allah is, in order to be a servant devoted.
God says
يايها الذين امنوا كتب عليکم الصيام کما كتب على الذين من قبلکم لعلكم تتقون
"Oh those who believe! Required on you fast as required on people before you that you cautious," (Surat. Inter alia-baqarah 2: paragraph 183)
When the fasting, body condition will change, such as changes physiology (related to the body composition and organ function), Hematology (related to the blood and liquid), and biochemistry blood (related to the electrolyte body). We call it as "the physiology of fasting."
One of the effects due to a person's fast that changes organ function form of the mouth. In the mouth, production glands saliva permanent working to prevent the mouth of dry. This causes the possibility of bad breath on the people who are fast. Bad breath people fast does not good. When kissed others definitely not preferred.
But bad breath people fasting, in the hereafter the future will be replaced by Allah with the smell of oil misk. My God.
From Abu hurairah, the Messenger of Allah SWT bersabda,
لخلوف فم الصائم أطيب عند الله تعالى من ريح المسك
"really bad breath people fasting more fragrant Allah than the smell of oil misk." (HR. Bukhari no. 1894 and Muslim no. 1151)
Then, any question: allow people to fast using toothpaste during to refresh the mouth? Actually, rubbing teeth not thing to cancel the fast?
However, to note is that toothpaste or water until swallowed into the mouth. It turns out siwak or brush your teeth is something good thing. The Prophet like siwak and Allah ridho with people who siwak.
Based on the word of the Prophet sallallaahu 'alaihi wasallam, "cleansing his teeth it clean mouth and bring keridlaan God." (HR. Inter alia-nasai with Sanad shahih of aisyah radliyallahu' anha).
The Prophet sallallaahu 'alaihi wasallam also said, "if only will not burdensome umatkaku, definitely I tell them cleansing his teeth on each prayer." (Muttafaq' alaih) and include prayer dzuhur and ASR; both after Sun slip. (Adapted from fatwa-fatwa Shaikh Abdul Aziz bin bazzrahimahullah and Sheikh Mohammed bin Salih Inter alia-uthaymeen)
Siwak is the name a Wood used to rub teeth. Another word, siwak is rubbing / cleaning teeth with Wood or the like to eliminate the yellow and dirt teeth, and also to clean the mouth.
Sayid sabiq rahimahullah said, "better if used to brushing your teeth are Wood wine from the country hijaz, because of the properties: the strengthening of gum, avoid toothache, easier of digestion, and launched urination. However, the Sunnah this can be obtained with everything can eliminate the yellow teeth and clean mouth, such as toothbrush, and the like. "(Fiqh Sunnah, I / 45). And this opinion also selected by the authors shohih fiqh Sunnah. Wallahu a'lam.
So, when there are people who asked allow rubbing teeth at the time to fast? Then the answer is OK.
Read also : Can I cool the Body While Fasting?