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# Clinical attachment level/loss (CAL) or level/loss of attachment (LOA)

Clinical attachment level/loss (CAL) or level/loss of attachment (LOA) – measured in mm as distance from the CEJ to the gingival margin (GM). LOA provides an estimation of the true periodontal support and is used for monitoring changes in periodontal support over time. CAL is easily measured when CEJ is exposed/visible. CAL can also be calculated following the formula CAL (mm)=PD (mm)+GR (mm).

CAL can’t be negative “-“.

For example:

If PPD = 6mm & GR= 3mm

LOA (CAL)= PPD (mm)+GR (mm) = 6mm + 3mm = 9mm

## LOA or CAL Instructions

#### Please refer to the diagrams for calculation of CAL in different clinical situations.

Depending on the position/level of the gingival margin CAL will be calculated as follows:

1. Gingival margin is apical to the CEJ – when gingival margin is apical to CEJ “true recession” then

LOA = PPD + GR, as shown in diagram below.

1. Gingival margin is at the level of CEJ and the CEJ is just visible.

We assume that recession is 0mm and calculate LOA following the equation below.

LOA =PPD + 0 mm

In this clinical situation LOA = PPD

1. Gingival margin is in its normal/natural position up to 3mm coronal to the CEJ.

LOA is calculated by deducting 3mm from the probing depth (PPD).

LOA = PPD -3mm

1. Gingival margin is significantly coronal to the CEJ due to enlargement.

In this clinical situation as GR is negative, we must deduct it from PPD to calculate LOA.

LOA = PPD + (-GR)

LOA = PPD – GR

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