Tobias K. Boehm (December 26, 2025)
Periodontal probe inside a pocket in an area with gum recession. “CEJ” stands for cemento-enamel junction and marks the end of the white enamel portion of a tooth, or the beginning of the darker-colored root surface. (Dr. Boehm)
Clinical attachment levels (abbreviated as “CAL”) are almost never measured and recorded in a dental office, but may be recorded by a periodontal specialist. If they are recorded, it looks like a double row of numbers, one for probing depths and one for the clinical attachment levels as I have done here for two consecutive visits in an old paper chart:
Example of a paper-based periodontal chart with probing depths (line 1 and 3) and clinical attachment levels (line 2 and 4) (Dr. Boehm)
Electronic charts may automatically record clinical attachment levels by simply adding probing depths (as explained in this article) and gum recession measurements. However, this often artificially inflated clinial attachment levels as the default gum recession level is assumed as zero by these programs. Consequently, the clinical attachment level by default in those programs is the same as probing depth, which is incorrect and useless for treatment decisions.
What is measured here?
Measuring clinical attachment level (CAL) with a periodontal probe. CEJ stands for cemento-enamel junction and is the place where the enamel and root surface of a tooth meet. Sulcus base means the floor of a gum pocket if there is no gum disease. Clinical attachment level is the distance from the CEJ to floor of the pocket or sulcus, and in this example would be 5 mm based on the markings of the probe. (Dr. Boehm)
The concept of clinical attachment level is simple: It simply measures how far down along the root surface the base of a pocket is relative to the crown of a tooth. In absence of gum disease, gum tissue attaches to a tooth just where the crown of a tooth ends. The crown of a tooth ends where the enamel part of a tooth ends, and where the root surface begins.
The advantage of this measurement is that the position where the crown or enamel end on a tooth does not change once a tooth is formed, unless something (i.e. a cavity, a dentist) removes this part of a tooth. So, there is a fixed position that should never change in the life of an individual that damage from gum disease can be measured against.
If the is gum recession exposing the root surface, this becomes easy to measure as shown here:
Here, the tip of the probe sits on the floor of the pocket, and the position of the CEJ on the probe is the clinical attachment level, so 5 mm in this example as in this type of periodontal probe the bottom end of the wide black band marks 5 mm length.
However, measuring clinical attachment level in most circumstances requires two steps as the CEJ is usually covered by gum tissue, as shown here:
So, the steps are to identify the CEJ first by feeling for it, and then advancing the probe further into the pocket until it reaches the floor of the gum pocket. The amount by which the probe advances further into the gum pocket from the CEJ is the clinical attachment level or CAL measurement.
So, while in principle this measurement is easy to understand, it is hard to measure as it requires two steps. Moreover, the CEJ sometimes is hard to find, may be destroyed by cavities or covered by fillings. Sometimes the CEJ is not formed well, or discolored enamel disguises it. In other situations, tooth wear and injuries can alter the CEJ over time. Measuring also takes a similar amount as measuring probing depths.
Since measuring clinical attachment level and recording takes additional effort and time with little effect on typical treatment planning, most dental teams do not bother with it.
So, if hardly anyone bothers measuring this and automated recording is often wrong, why does clinical attachment level matter?
What do the numbers mean?
While routine measuring and recording clinical attachment levels is almost never done, they are important for periodontal diagnosis and treatment decisions. Clinical attachment level is the critical measure for defining and diagnosing gum diseases (1). At the most basic, clinical attachment level numbers mean the following:
- 0 mm CAL: No attachment loss. There is no exposed root surface. Absence of periodontitis.
- 1+ mm CAL: Attachment loss present. Root surface is exposed. Periodontitis may be present.
Generally, the worse CAL, the worse the periodontal condition. Clinical attachment level equals loss of attachment, or loss of tooth supporting tissue. Periodontitis is staged by the amount of clinical attachment loss, and graded by the amount of attachment loss over time. Generally, CAL measurements of 5 mm or more suggest severe periodontal disease which leads to tooth loss.
Typically, if attachment loss is associated with deep probing depths, bleeding on probing and signs of microbial infection (i.e. plaque, tartar buildups, pus), clinical attachment loss leads to a diagnosis of periodontitis, a type of gum disease that causes tooth loss.
Attachment loss does not always indicate presence of periodontitis as attachment loss can still be present after succesful treatment of periodontitis. Attachment loss can be associated with chronic injury from abnormal chewing habits or mouth piercings. Attachment loss can also be seen in areas of gum recession that result from tooth position, orthodontic treatment and other injuries.
A clinical attachment level of zero does not rule out periodontal disease as minor gum disease such as gingivitis can still be present. That is why periodontal exams look at other measures such as probing depths and bleeding on probing.
Even though clinical attachment level is critical to diagnosing periodontal disease, recording a full set of clinical attachment levels is usually not needed for diagnosing periodontal disease, treatment planning or insurance reimbursement. A dentist simply has identify presence or absence of attachment loss for diagnosing periodontitis, and can estimate severity based on clinical impression and radiographic appearance. Typically, periodontal bone loss seen on radiographs correlates with attachment loss, and the worst affected site usually determines periodontal diagnosis. For insurance purposes, probing depths and radiographs usually are sufficient to provide the evidence a dentist needs to support the dentist’s diagnosis and treatment decision.
Even though radiographs and probing depths can be substitute measures for clinical attachment loss in most circumstances, it is well known that clinical attachment loss precedes radiographic bone loss by about 6 months (2). This matters for early detection and treatment periodontitis where dentists can identify attachment loss when there may not be any noticeable bone loss on radiographs. In those cases, deep cleaning (“scaling and root planing”) may be enough to stop periodontitis and prevent the need for surgery.
Alternative Measures
Clinical attachment level is also referred to as “attachment level” or “CAL”.
Attachment loss refers to the amount of lost attachment over time. The clinical attachment level represents attachment loss experienced over the entire lifetime of an individual (i.e. CAL = attachment loss). Sometimes, attachment loss may mean the amount of attachment loss within a shorter time period, as seen by the increase in CAL between seen over a year of treatment (or some over time period).
Relative attachment level (“RAL”) is a measurement sometimes used in research, or used when the cemento-enamel junction is not available as a landmark. In this case, a dentist or researcher will measure the distance from a different landmark (i.e. cusp tip, border of a crown, or the edge of plastic mold that fits over the teeth) to the base of a pocket. RAL and CAL will correlate, but be different by some fixed distance amount depending on the landmark position relative to the CEJ.
Bone level or “Radiographic bone level” (RBL) correlates with clinical attachment level, and measures the distance form the CEJ to the nearest jaw bone (“alveolar bone”) on radiographs. Typically, the bone level is about 2 mm greater than clinical attachment level as this is the average thickness of the soft tissue attachment that sits above the bone.
How does clinical attachment level affect my gum treatment?
While dentists may not purposefully measure and record clinical attachment levels, clinical attachment levels do matter for treatment decisions. Since presence or absence of clinical attachment loss distinguishes the two most common gum diseases, gingivitis and periodontitis, this also determines treatment:
- No attachment loss: Regular tooth cleanings (“prophylaxis”) will likely be recommended. Typically, the interval between cleanings is 6 to 12 months.
- Attachment loss present: Dentists will either recommend deep cleanings (“scaling and root planing”) to treat active disease, or “periodontal maintenance” once the gum disease is treated an controlled. Since insurance may not cover “periodontal maintenance”, dentists may decide to bill the more complex cleanings needed as “prophylaxis” even though more effort is needed. Typically, for individuals with attachment loss, visits for preventive gum disease treatment are more frequent, usually about every 3 to 4 months.
Dentists will also consider attachment levels when deciding whether to remove teeth. Typically, teeth with clinical attachment levels of 5 mm or greater have an increased risk for tooth loss. When clinical attachment level approaches the end of a tooth root at about 10 mm or more, teeth tend to become noticeably loose. Therefore, dentists may decide to remove teeth with severe attachment loss in order to focus on saving teeth with less attachment loss.
What conditions cause clinical attachment loss?
The most common cause of clinical attachment loss is periodontitis. Other conditions that can be associated with attachment loss include:
- Chronic injury (from destructive habits, aggressive brushing, piercings, chewing habits)
- Non-carious cervical lesions (wedge-shaped or smooth areas of tooth structure loss at the neck of teeth not caused by cavities)
- Orthodontic treatment
- Abnormally positioned teeth
- Tooth fractures
- Fillings, crowns, bridges, root canal treatment (sometimes as result handling the gum tissue during treatment)
- Loss of adjacent teeth
How should probing clinical attachment levels change during treatment?
Typically, periodontal treatment arrests periodontal disease, and clinical attachment levels will stay the same once periodontal disease is eliminated. Clinical attachment levels may improve after scaling and root planing as the gum tissue tightens up around teeth and probing depths improve. This can be temporary, or it can cycle up and down over time with the degree of control on gum disease.
Some periodontal treatments such as lasers, guided tissue regeneration, bone grafting and biologics may achieve true improvement (“gain”) in clinical attachment levels by regenerating lost attachment. While it may be difficult to tell clinically whether improvement of clinical attachment level is simply the effect of increased resistance to probing from tighter gum tissue, or regrowth of lost tooth attachment, this has been demonstrated in research studies.
When should clinical attachment levels be measured?
Dentists will look for clinical attachment loss when suspecting significant periodontal disease. In practice, dentists will rarely record clinical attachment levels as part of routine periodontal charting.
Is there a clinical attachment level on implants?
No. Dental implants do not attach to gums and bone the same way teeth do. Instead, bone grows directly onto implant surfaces and gum tissue will form a weak gasket-like seal near the location where a denture, crown or bridge attaches to the dental implant. The closest variable to attachment level for dental implants is bone level. Dentists will look periodically how close the jaw bone attaches to the connection point for implant-supported crowns, bridges or dentures. For healthy implants, this should be close (2 mm or less) to the connecting part of the dental implant (“platform”).
Why does clinical attachment loss develop?
In gum disease, changes in the microbial flora around teeth cause inflammation in the gums. Inflammation in the gums leads to tissue swelling, and the tissue swelling creates a deeper space between teeth and gums, resulting in deeper pockets. In addition, inflammation damages the gum tissue attachment to teeth, allowing for deeper penetration of periodontal probes into the tissue, resulting in clinical attachment level measurements. As time goes on, microbes invade the damaged tissue attachment, causing the gum tissue to further separate from the tooth and the base of the pocket to become deeper, resulting in worsening clinical attachment level. On average, untreated gum disease causes a loss of about 0.1 mm of attachment per year (3). Eventually, the continued attachment loss reaches the end of the tooth root, at which point the tooth falls out (if it has not been removed or lost earlier).
About the author:
Tobias K. Boehm, DDS, PhD, MBA, PC, DABP, DICOI, FGDIA is the founder of The Dental Institute, executive director at The Defeating Epilepsy Foundation and a professor at Western University of Health Sciences where he teaches and practices a periodontal specialist.
References:
(1) Caton, J.G. et al (2018). A new classification scheme for periodontal and peri-implant diseases and conditions – Introduction and key changes from the 1999 classification. J Clin Periodontol 2018:45:45S(Suppl 20):S1-S8. https://onlinelibrary.wiley.com/doi/pdf/10.1111/jcpe.12935?msockid=105b374f85bd65a700b022fa842f643f
(2) Goodson JM, Haffajee AD, Socransky SS. The relationship between attachment level loss and alveolar bone loss. J Clin Periodontol. 1984 May;11(5):348-59. doi: 10.1111/j.1600-051x.1984.tb01331.x. PMID: 6585374.
(3) Needleman I, Garcia R, Gkranias N, Kirkwood KL, Kocher T, Iorio AD, Moreno F, Petrie A. Mean annual attachment, bone level, and tooth loss: A systematic review. J Periodontol. 2018 Jun;89 Suppl 1:S120-S139. doi: 10.1002/JPER.17-0062. PMID: 29926956.