In Genesis 49:12, "teeth whiter than milk" signify the Celestial Spiritual [milk] in the Lord's Natural [teeth], where Judah is here representing the Lord. (Arcana Coelestia 2184-2185).

In Psalms 3:7; 37:12, 58:6; Matthew 8:12, teeth signify the lowest natural things in man: in the genuine sense, their truths, in the opposite sense, their falsities. So the gnashing of teeth signifies the collision of falsities with truths. (Arcana Coelestia 4424[3])

In Exodus 21:27, this signifies truth in the natural, here the ultimate, which is the sensuous. (Arcana Coelestia 9062)

The tooth signifies the corporeal proprium, which is the lowest degree of man. (Arcana Coelestia 10283[12])

'Teeth,' as in Genesis 49:12, in the genuine sense, signify the natural level of life. Any hard part of the body, like bones and cartilage, corresponds to the truths and goods of the lowest natural level. 'Teeth' signify the outer edges of the life of the natural self, or the sensory level. There is a natural sensory will, and a natural sensory understanding. When the sensory levels are separated from the interior of the mind, their supposed truths are really mere falsities, and do violence to truths and destroy them. This situation appears in many passages, because sensory people do not see any truth in its own light, but engage in reasoning and altercations about everything... These altercations are heard in the hells as the gnashing of teeth. Viewed in itself, this is the collision of falsity and truth. This is the meaning of 'gnashing of teeth' in Matthew 8:12, 13:42, 50, 22:13, 24:51, 25:30, and Luke 13:28.

(Odkazy: Apocalypse Revealed 435)

4424. What the Lord's words quoted above embody in the internal sense becomes clear without explanation, for at this point the Lord uses comparisons rather than representatives and meaningful signs. Only the meaning of the words of the final verse has to be stated - 'He will cut him off and assign him his part with the hypocrites, where there is wailing and gnashing of teeth'.

He will cut him off means separation and removal from goods and truths, for people who have a knowledge of what is good and true, as those within the Church do, but who lead a life of evil are said to be cut off when that knowledge is removed from them; for in the next life their knowledge of good and truth is separated from them and they are restricted to evils and derivative falsities also. The reason why this takes place is so that they do not communicate with heaven through their knowledge of good and truth and with hell through their evil and consequent falsity, and thereby are left hanging between the two. A further reason is so that they do not profane goods and truths, as happens when these are mixed together with falsities and evils. The same is also meant by the Lord's words addressed to the one who hid his talent in the earth,

Take the talent from him and give it to him who has ten talents, for to everyone who has, it will be given, so that he may have in abundance; but from him who has not, even what he has will be taken away. Matthew 25:28-29.

And what the Lord says elsewhere has the same meaning - Matthew 13:12; also Mark 4:25, and Luke 8:18.

[2] And assign him his part with the hypocrites means that his lot, meant by 'part', lies with those who outwardly give the appearance of knowing the truth so far as doctrine is concerned, and of cherishing good so far as life is concerned, but who inwardly have no belief at all in truth nor any desire at all for good, who are 'the hypocrites'. People like this have become 'cut off' in the sense described here. Consequently when external things are taken away from these people, as happens to all in the next life, they are seen to be what they are like internally - people devoid of faith and charity. Yet they have pretended to have these, so that, capturing the attention of others, they could earn themselves positions of importance, monetary gain, and reputation. Within the Church that has become ruined virtually everyone is like this, for they have things that are external but none that are internal. Hence the interior aspects of those people are engulfed in the deluge described immediately above in 4423.

[3] Where there will be wailing and gnashing of teeth means their state in the next life, 'wailing' that state as regards evils, and 'gnashing of teeth' that state as regards falsities, for 'teeth' in the Word means lowest natural things - in the genuine sense truths going with these, and in the contrary sense falsities going with them. Teeth also correspond to those things. For these reasons 'the gnashing of teeth' means the clash of falsities and truths. People immersed in wholly natural things and governed by ideas resulting from sensory illusions, believing nothing which they do not see by means of these, are said to be where there is 'the gnashing of teeth', and in the next life seem to themselves to be there when they draw conclusions about the truths of faith on the basis of their own illusions. A Church in which good and truth have been brought to ruin teems with people such as these. The same is meant again in other places by the gnashing of teeth, as in Matthew,

The sons of the kingdom will be thrown into outer darkness, where there will be wailing and gnashing of teeth. Matthew 8:12.

'The sons of the kingdom' means those within the ruined Church.

'Darkness' means falsities, 4418, for they are in darkness when surrounded by the dark cloud mentioned above. 'The gnashing of teeth' means the clash of falsities with truths there. The same matter occurs in other places, such as Matthew 13:42, 50; 22:13; 25:30; and Luke 13:28.