Step One. Identify the correct teeth. 

The next image taken is the molars 209 and 210. Highlighted on the dental chart and outlined in the picture below. 

Step Two. Placing the sensor.

Make a cradle to hold the sensor in place by placing some swabs below the 209 and 210 on top of the lower molars .

Hold the sensor with the forefinger and thumb and imagine the line between them extends along the sensor. This will help you position it correctly.

Place the sensor in the mouth with the mid-line of the sensor opposite the developmental grove of tooth 209. Make sure that the caudal aspect of 210 is aligned 1mm inside the edge of the sensor.

Step Three. Position the tube head opposite the sensor so that the beam covers the sensor.

Place the cone opposite the sensor. Make sure that the entire cone covers the sensor. 

See through cones make this easy as you can look through the cone to see the sensor and teeth.

Sometimes its necessary to retract the lips to see the sensor in the open mouth.

With a see through cone the wire from the sensor can be lined up with the central line of the cone to ensure the beam covers the whole of the sensor.

Step Four. Roll the tube head to the correct angle.

As the beam is already aligned with the sensor. Calculate the correct angle using the bisecting angle technique and roll the tube head up to the right position. 

Start by visualising the view from a rostral aspect.

Visualise a line that moves along the sensor from the outside left of the mouth inwards. This is the long side of the sensor. Marked in yellow.

Next visualise a line through the centre of the teeth from cusp of the crown to apex of the root. Marked in pink.

Bisect (half) the angle between the yellow sensor line and the pink tooth line. 

Marked in white.

The correct angle is then calculated as perpendicular (90 degrees to) the white line that bisects (half’s) the angle of the sensor line (yellow) and the tooth line (pink). Marked in green. 

 The tube head can then be rolled up to the correct angle.

Tube head rolled up to the correct angle.

Step Five. Tube head orientation to patient mid-line,

The standard orientation for 209 and 210 is 45 degrees caudal  to the mid-line.

Step Six. Radiation factors.

The standard factors with a digital sensor are as follows:

Patient SizeLocationKVMAS
<= 15 KgMaxillary Molars 209 and 210600.160
> 15 KgMaxillary Molars 209 and 210600.200