Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
नवम्यां च न कुर्वीत कदाचिद्दंतधावनम् ।व्यतीपाते च संक्रांतावेकादश्यां च पर्वसु ॥ १४२ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 142.
... and the 9th, one should never clean the teeth. On vyatipata (a bad Sun and Moon yoga) and on sankranti (the Sun's entry into a sign); on the 11th and on parva (junction day) days ...
Simple meaning: Never clean the teeth with a twig on these days. Oil massage rules begin for bad yoga and sign-entry days.
अर्कभौमदिने षष्ठ्यां नाभ्यंगो वैधृतौ तथा ।
No oil massage on Sunday, Tuesday, the 6th or bad yoga days. Rules for amla bathing follow.
पुत्रहानिर्भवेत्तस्य त्रयोदश्यां धनक्षयः ।
Amla bathing on the 10th risks grief over a son; the 13th, wealth; the 2nd, both.
अमायां च नवम्यां च सप्तम्यां च कुलक्षयः ।
This may harm the family on a new moon, 9th or 7th. A full moon with the Moon by day is Anumati.