Astanga Hrudaya
विधुरे मातृकाश्चाष्टौ षोडशेति परित्यजेत्। हन्वोः षोडश, तासां द्वे सन्धिबन्धनकर्मणी॥२७॥
two vidhura, and eight matraka should be avoided in the hanu (lower Jaw) there are sixteen; of them, the two which binds the joints (of the lower jaw with the skull, should not be cut)
english translation