Table 7. Mean image-quality scores with standard deviation in parentheses for each projection and collimation level.

Exposure	Projection	Minimum	Medium	Maximum	p-value
Fixed exposure
	OM	17.78 (2.56)	14.88 (2.9)	13.93 (2.8)	<0.0001a,b
	OM 30	16.95 (2.30)	16.52 (2.27)	16.55 (2.58)	<0.0001a,b,c
	Lateral	16.25 (2.47)	15.98 (2.24)	13.83 (2.88)	<0.0001b,c
Variable exposure
	OM	17.37 (2.79)	12.95 (2.6)	11.13 (2.8)	<0.0001a,b,c
	OM 30	17.17 (2.65)	14.32 (2.21)	13.92 (2.87)	<0.0001a,b
	Lateral	15.87 (2.32)	15.23 (2.27)	13.55 (2.7)	<0.0001b,c

OM, occipitomental; OM 30, occipitomental with 30° caudal beam angle.

p-values are shown wherever there is a significant difference between collimation levels.

^aMinimum was different to medium.

^bMinimum was different to maximum.

^cMedium was different to maximum.