Which of the following type of fissure is not self cleansable?
MORPHOLOGY OF PIT & FISSURES
Nagano (1961) described following principal types of fissures, based on the alphabetical description of shape:

V – Type (34%)
U – Type (14%)
I – Type (19%)
IK – Type (26%)
Inverted Y – Type (7%)
I
IK
Inverted Y
All of the above