Oral Health Group

Clinical Attachment Level – How to Calculate and Interpret this Important Measurement

October 1, 2013
by Peter C. Fritz, BSc, DDS, FRCD(C), PhD (Perio)

Periodontal probing continues to be a key element in the diagnosis of periodontal disease and this maneuver is performed hundreds of thousand times a day in dental offices across the world. However, a probing depth alone does not reveal the complete state of health of the area being measured. Clinicians need additional information about the health of the periodontal tissues that complement the probing data.

Probing depths are important, but if we rely exclusively on this parameter, the level of bone support for the tooth may be over — or under-estimated. Probing depths do not take into consideration gingival recession, overgrowth or changes of the marginal gingiva associated with tissue swelling.

It would be much more helpful to have a measurement of the dentogingival complex which, is the sum of all supracrestal soft tissue components and reflects the histomorphological aspect of the periodontium. This is measured by sounding of the alveolar bone, a dental maneuver performed with a periodontal probe under local anaesthesia utilizing increased probing pressure. In healthy natural teeth, the dentogingival complex measures approximately 3.0mm at both the buccal and lingual sites. Interdental sites measure 4.5-5.0mm due to the support provided to the interdental soft tissues by adjacent teeth. The clinical relevance of the dentoginigval complex (Dentogingival Complex Measurement — DGM) is much greater than a measure of periodontal attachment (a derived measurement combining probing depth and distance of the gingival margin relative to the CEJ) or biologic width, the latter that cannot be measured at chair side.

However, the limitation in routinely measuring the DGM is that the patient must be anesthetized to permit bone sounding and the repeated micro-wounding of the connective attachment may outweigh the benefit of elucidating the measurement. As such, the measurement of the DGM is generally reserved for pre-prosthetic surgery. Emerging dental technologies are promising in that this measurement could be achieved without micro-wounding.

Another measurement of the extent of the periodontal support that is often reported, but is occasionally misinterpreted is the clinical attachment level (CAL). This is the measurement of the position of the soft tissue in relation to the cemento-enamel junction (CEJ) that is a fixed point that does not change throughout life, albeit at times it is hard to visualize (e.g. in case of abfraction lesions or chemical root erosions). Two measurements are used to calculate the CAL: the probing depth and the distance from the gingival margin to the CEJ.

Where it gets confusing is that the gingival margin may be in one of three places:

1.  The CEJ may be coronal to the gingival margin. This is known as recession and is very simple to measure.

2.  The CEJ may be at the same level as the gingival margin.

3.  Occasionally, the gingival margin extends significantly over the CEJ making an accurate measurement quite difficult (Fig. 1).

Taken together, the probing depth plus the distance from the gingival margin to the CEJ comprises the clinical attachment level (Fig. 2).

Measuring the interdental clinical attachment level presents an additional challenge. The tissues on the buccal and lingual aspects of the teeth bulge outward to form the buccal and lingual papilla. The depression between the two papilla, often described as “saddle shaped,” is known as the interdental col. The size and shape of the interproximal contact area governs the shape and depth of the interdental col. Since the shape of the interdental papilla is determined by adjacent tooth surfaces, the interdental contact area and the interdental bone septum, the shape is not uniform throughout the mouth. The inteproximal contact area is most coronal point between the two central incisors and becomes progressively more apical towards the distal areas of the arch. As a result, the papillary height decreases from the anterior to posterior. Fortunately, no additional “correction factor” is required for the calculation of the interdental CAL, though it is clear that the height of the interdental tissues may be influenced through non-inflammatory (i.e. anatomical) changes in the contact area often altered by orthodontic tooth movement, interproximal restorations and other variation in the occlusion.

It has been suggested that clinical attachment level and clinical attachment loss be used synonymously. However, this can generate confusion. If clinical attachment loss is defined as the extent of the periodontal support that has been destroyed around a tooth, then, in health, one might assume that this should be expressed as zero millimeters. However, this is not the case.  Even with the recommended probing force of 0.2-0.25N (about 25 grams of pressure) the tip of the periodontal probe always penetrates into tissue that is below the sulcus (Fig. 3). In a patient with a healthy gingiva, the sulcus is histologically at a maximum of 0.5mm depth, but periodontal probing will routinely yield a measurement of between 2.0-3.0 mm.  With no recession, this would result in a clinical attachment level calculation of 2.0 minus 3.0 mm representing no loss of periodontal attachment (Fig. 4). As such, expressing this as clinical attachment loss is confusing, because, in reality, nothing has really been lost.  A better term to express attachment loss may be “true attachment loss” (Fig. 2). OH

Dr. Fritz is an Adjunct Professor in the Faculty of Applied Health Sciences at Brock University and is Staff Periodontist in the Niagara Health System. His private specialty practice is in Fonthill, Ontario. www.drpeterfritz.com

Oral Health welcomes this original article.

Additional Readings/References
—  Wolf, H.S., Ratietschak, K. and Hassell. M. Periodontology Color Atlas of Dental Medicine. 3rd ed. New York: Thiem; 2005.

— Nield-Gehrig J.S., Fundamentals of Periodontal Instrumentation. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2008.

— Zuhr, O., & Hurzeler, M.  Plastic Esthetic Periodontal and Implant Surgery.  1st ed. Chicago: Quintessence Publishing; 2012.