The order of caries susceptibility of primary teeth is:

Caries susceptibility of primary teeth (in descending order) 2nd molar > 1st molar > canine > lateral incisor > central incisor Caries susceptibility of permanent teeth (in descending order) 1st molar > 2nd molar > Max. 2nd PM > Max. 1st PM & Mand. 2nd PM > Max. central & lateral incisor > Max. canine & Mand. 1st PM > Mand. Central & lateral incisor > Mand. canine Surfaces involved in descending order (in primary teeth)  Occlusal > molar interproximal > incisor interproximal. (Proximal surfaces were affected more in first than in second primary molars).