What is the CAL anyways? I like to remember the CAL as “Clinical Attachment LOSS”. The reason I like to think about it as “loss” and not “level”, is because you are calculating the attachment that is now missing. One key thing to know is that the CAL is always measured from a fixed point which is the part that the crown meets the root of the tooth, otherwise known as the CEJ (cementoenamel junction).
Knowing that you need to start from the CEJ, the rest is a breeze.
If there is recession present, meaning loss of gum tissue, then you will need to measure from the CEJ to the start of the gum line (not INTO the gum line).
Now insert the probe and measure the probing depth meaning the measurement from the gum line to the base of the pocket. You can read this by looking at the point of the probe that is visible just at the gum line.
Add these two numbers to get your CAL. An even easier way is just to put the probe to the base of the pocket and look at where the CEJ lands on the probe. This measurement will include the pocket and the recession.
Your CAL will be equal to the probing depth
You will need to get the full probing depth of the full pocket first even though there is inflammation.
Feel for the CEJ or blow air into the pocket to see the CEJ. Measure the distance from the CEJ up to the gum line. This will tell you how much tissue is overgrown over the CEJ.
Subtract the overgrown tissue from the probing depth to get the CAL.