This week I have a case of some very large mandibular third molars. The right mandibular third molar appears as if it’s two molars stuck together. This is due to gemination or twinning. Gemination is when a single developing tooth germ attempts to divide but is unable to completely divide resulting in one massively large tooth. With gemination there is an overall tooth count of 16 in the associated arch. This is not to be confused with fusion (which also results in a massively large tooth) but will only have 15 teeth present in the associated arch. In this case it appears that there is also gemination of the left mandibular third molar as well.
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First of all I really wanna thank you for all of this… really useful information & your effort is highly appreciated.
My question about this case is:
Sometimes fusion occurs with supernumerary tooth, in such case we can’t rely on the number of teeth to distinguish between fusion and gemination… any clue?
I’m glad you’re finding my site useful.
As for whether to consider gemination versus fusion with a supernumerary tooth, both are valid differentials. When I only have one radiograph and no information about the history of the patient I will put gemination as my first differential. The other could be included as well. This is a great question and one that I get every year by students when going over gemination versus fusion. thanks for asking.
I hope this is helpful for you.