Trisha E. O`Hehir, RDH
When we collect clinical data on a patient, inevitably measurements are taken for pocket depths or attachment levels. In either case, the question can be asked: Where does the tip of the probe actually stop? Does it stop at the coronal edge of the epithelial attachment, or the apical edge of the epithelial attachment, which would actually be the coronal edge of the connective tissue attachment? Or, does it in fact pass through the epithelial attachment and into the connective tissue?
By now, you might be asking yourself, does it really matter? After all, the epithelial attachment is only roughly one millimeter? Does one millimeter really make that much difference?
In our day-to-day practice, I don`t think it makes much difference. In fact, getting both dentist and dental hygienist to arrive at measurements within two millimeters is considered calibrated. But, it is an interesting histologic question, especially for researchers, since some studies make conclusions based on probing measurements of less than one millimeter.
Where the probe stops
Research has shown us that where the probe stops is different in health than in disease. In the presence of periodontal inflammation, the probe tip is likely to pass painlessly through the epithelial attachment and into the connective tissue. In health, however, the probe tip may stop at the coronal edge of the epithelial attachment. Therefore, conclusions we draw from our therapy should take into consideration this fact.
To better understand this concept, we must look back several decades. Prior to 1921, probing was thought to penetrate to the connective tissue, as it was felt there was no epithelial attachment. In 1921, the theory of an organic epithelial attachment was introduced by Dr. Gottlieb. He concluded that routine probing could not penetrate this attachment without causing pain. Dr. Orban concurred with this finding in 1929, when he demonstrated that attempted separation of the epithelial attachment from the enamel surface resulted in tearing of both epithelial and connective tissues.
This theory was challenged in 1952 by Dr. Waerhaug, who was able to insert a steel blade into the sulcus of a dog, passing through the epithelial attachment and ending at the coronal aspect of the connective tissue attachment, using only seven grams of force.
A variety of both animal and human studies followed, using various tools in an attempt to demonstrate the potential for probe penetration. In addition to probes and steel blades, cellulose acetate strips, cavit, self-curing acrylic, and even gas particles were used. With more pressure, penetration of the connective tissue was always evident. With enough pressure, the probe reached the bone. It was also shown that the curvature of the tooth affected the direction the probe tip followed. Extremely convex teeth prevented the probe from following into the curvature of the tooth, directing the tip into adjacent epithelial tissue instead.
These early histologic studies demonstrated a stronger bond between the tooth surface and the epithelial cells than between the cells themselves. In untreated periodontal cases, the probe easily penetrated between epithelial cells rather than between the tooth surface and the epithelial attachment.
Later, it was concluded that a false equation had been followed, that of equating the clinical sulcus with the histologic sulcus. Since the probe, in some cases, can penetrate the connective tissue, the clinical sulcus measurement may actually extend into the connective tissue attachment, while the histologic sulcus is considered to be the distance from the gingival margin to the coronal aspect of the epithelial attachment.
Researchers in 1976 compared clinical sulcus measurements to histologic measurements, using probe markings taken before and after extraction of both periodontally healthy and periodontally diseased teeth. Two research teams that year concluded that routine gentle probing of untreated periodontal pockets resulted in penetration of the epithelial attachment and measurements extending into the connective tissue attachment. Inflammation associated with untreated periodontal disease explains the ease with which the probe penetrated the epithelium, providing a deeper clinical measurement than histologic measurement. Based on their findings, Dr. Listgarten and his research team concluded that the junctional epithelium averaged 1.3 millimeters.
As clinicians, it may seem obscure and unimportant, but this information provides us with the histologic facts associated with pocket measurements taken in both diseased and healthy sites. When measurements are reduced after debridement therapy, several aspects should be considered. First, of course, there will be some shrinkage of the marginal tissue resulting from elimination of the inflammation. There will also be healing of the epithelial attachment, changing the spot where the probe tip stops, and therefore contributing to the shallower measurements. When measuring the success of your periodontal therapy, keep this obscure fact tucked in the back of your mind. Our knowledge of histology adds to our understanding of the disease process and of our clinical success.
References available upon request.
Trisha E. O`Hehir, RDH, is a senior consulting editor of RDH. She also is editor of Perio Reports, a newsletter for dental professionals that addresses periodontics.