Table 2 Categorisation criteria of intraoral images

Upper and lower teeth 2 ~ 2

Straight, Horizontal

Image contains upper and lower center incisors and lateral incisors, a few contain children’s upper and lower incisors.

Upper and lower teeth 3 ~ 5

Straight

Image contains upper and lower canines, first premolars and second premolars.

Upper and lower teeth 4 ~ 6

Straight, Horizontal

Image contains upper and lower first premolars, second premolars and first molars.

Upper and lower teeth 6 ~ 8

Straight, Horizontal

Image contains the upper and lower first molars, second molars and the third molars (wisdom teeth).

BW: Left and right sides

Horizontal

The adult image includes the upper and lower first premolars, second premolars, first molars and the second molars. The child image includes the upper and lower canines(3), first molars(4) and the second molars(5) .

VBW

Left and right front

Straight

The adult image includes the upper and lower first premolars, second premolars and a few of the first molars. The child image includes the upper and lower first molars(4) and second molars(5).

VBW

Left and right behind

Straight

Image contains the upper and lower first molars and second molars; a few contain second premolars.

Occlusal

Upper and lower

Straight, Horizontal

Image contains adult and children Upper and lower front teeth.

Pediatric upper (52 ~ 62) and lower (72 ~ 82) arch images

Straight, Horizontal

Image contains upper and lower center incisors and lateral incisors. A few contain adult upper and lower center incisors and lateral incisors.

Pediatric upper (53 ~ 16, 63 ~ 26) and lower (73 ~ 36, 83 ~ 46) images

Straight, Horizontal

The image includes upper and lower canines(3), first molars(4) and the second molars(5). A few include adult upper and lower canines, first premolars, second premolars and the first molars(6).