Eiendomspronomen

Dette er læreren min.
eller
Dette er min lærer.
Hun tenker på mora si.
eller
Hun tenker på sin mor.
These sentences are just the same. Så dum, ikke sant? The only difference is that, when the "substantiv" comes first the "eiendomspronomen", it is required to use "bestemt" within the subtantiv. (e.g. læreren min). The vise-versa is min lærer.
And maybe, you are thinking, what are these sin and si.
English:
I can brush her teeth. But she can brush her teeth.
Norsk:
Jeg kan pusse hennes tenner. Men hun kan pusse hennes tenner.
The first sentence is just fine but with the second sentence, it is totally WRONG. This should be the right way.
Jeg kan pusse hennes tenner. Men hun kan pusse sine tenner.
Did you see the difference or maybe you are thinking what is this sine again? If you are translating from english to norsk. Then you are wrong!!! How can I explain this. Maybe it will be clear if I will lay a table for these norwegian pronouns.

Subjektpronomen	Objektpronomen	Refleksivpronomen	Eiendomspronomen
Jeg	meg	meg	min, mitt, mi; mine
Du	deg	deg	din, ditt, di; dine
Han	ham	seg	sin, sitt, si; sine; hans
Hun	henne	seg	sin, sitt, si; sine; hennes
Vi	oss	oss	vår, vårt; våre
Dere	dere	dere	deres
De	dem	seg	si, sitt, si; sine; deres

Eiendomspronomen marked blue can't be used as refleksiveiendomspronomen.
Conclusion: Ohhh man, is it still confusing? Me too. Ok. Check han, hun and De. They are the third persons of pronouns. Rule in refleksivpronomen is different together with refleksiveiendomspronomen. Maybe it is better if I will lay a couple of examples.
The following examples are from one of my classmates. I wanna thank her for these examples. I hope these will be great examples.
Jeg har en nabo. Han har kona. Han liker ikke sin kone. Men han liker kona mi.
Jeg har en nabo. Han har konen. Han liker ikke kona si. Men han liker min kone.
These 2 examples are just the same. Check the differences of those in blue.
Mine, dine, sine and våre are plurals or in norsk, flertall.
Example:
De har 3 barn. De elsker barna sine. Vi liker barna deres også.
Du har en datter. Du elsker dattera di. Vi liker din datter også.
De har en datter. De elsker sin datter. Vi liker dattera deres også.
Based with the examples above, the following sentences below are wrong:
De har 3 barn. De elsker barna deres. Vi liker barna deres også.
De har en datter. De elsker deres datter. Vi liker dattera deres også.

I am hoping these make all clear. I am also confused, so don't worry. As I've said, we will get used with them. Good luck....