Do ALL 'double' teeth have two root canals? ?

In diagrams of teeth I note that 'single' teeth show a single root canal, and 'double' teeth two root canals, so do ALL 'double' teeth have two? I understand that 'double' teeth can have different patterns of root canals, e.g, '11' pattern, 'Y' pattern, 'H'... show more In diagrams of teeth I note that 'single' teeth show a single root canal, and 'double' teeth two root canals, so do ALL 'double' teeth have two?

I understand that 'double' teeth can have different patterns of root canals, e.g, '11' pattern, 'Y' pattern, 'H' pattern, and 'inverted Y' pattern, but do ALL doubles have two?
Update: Thanks uneyk and Dan W. It seems a littel more detail may be required. The tooth in question is the first double/premolar on the left top (starting from the front). The reason I ask is that I had a route canal treatment some years ago, and recently a further problem. My dentist 'expressed' surprise at... show more Thanks uneyk and Dan W. It seems a littel more detail may be required.
The tooth in question is the first double/premolar on the left top (starting from the front).
The reason I ask is that I had a route canal treatment some years ago, and recently a further problem. My dentist 'expressed' surprise at how rare two root canals were in this tooth, or perhaps some teeth.
I subsequently went to another dentist who advised that this particular tooth ALWAYS has two canals.
It may be a case of my dentist covering up for a lack of knowledge or poor work first time round by not treating both.
Further comment would be welcome.
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