First to classify malocclusion on structural basis?
Salzmann in 1950 was the first to classify on occlusion based on the underlying skeletal structures.
1. SKELETAL CLASS I
2. SKELETAL CLASS II
3. SKELETAL CLASS III
In 1899, Edward Angle classified malocclusion based on the mesial-distal relation of the teeth, dental arches and jaws.
Morton Katz (1992) shifted the focus from the molars, canines and incisors to the region of premolars for the purpose of classifying malocclusion.
KINGSLEY (1956)
Based on the nature of the habits, Kingsley (1956) classified habits as:

Functional oral habit - E.g. mouth breathing.
Muscular habits - Eg. tongue thrusting, cheek/lip biting.
Combined muscular habits - Eg. thumb and finger sucking.
Postural habits.
	Chin-propping
	
Face leaning on hand
Abnormal pillowing.



Ref: Textbook of orthodontics Gurkeerat Singh 2nd ed page no 175
Salzmann
Kingsley
Angle
Katz