From: Results of a randomized controlled trial of level IIb preserving neck dissection in clinically node-negative squamous carcinoma of the oral cavity
Level
IIb preserving
Control
P value
Mean (n)
SD
Ia
3
1.4
3.1
2.1
0.88
Ib
5.5
2.9
4.7
2.6
0.459
IIa
7.6
8.4
7.1
7.5
0.84
IIb
–
6.1
4.9
III
4.3
3.3
5.7
3.8
0.29