Calculating a PHI score

June 1, 2004
A "prophylaxis" is a preventive procedure designed to keep periodontally healthy people healthy. According to this definition, our prophy patients should have no pockets and no bleeding, right?

by Trisha O'Hehir

A "prophylaxis" is a preventive procedure designed to keep periodontally healthy people healthy. According to this definition, our prophy patients should have no pockets and no bleeding, right? Nice idea, but when was the last time you had a full schedule of people with no probing scores deeper than three millimeters and no bleeding points? Four millimeter pockets with bleeding now seem to be the norm rather than the exception. Even our patients think bleeding is normal. Gingival bleeding allows bacteria and toxins to travel from the mouth to other parts of the body, contributing to the perio-systemic link we now hear so much about. Pockets and bleeding are becoming more important in this discussion.

Many people today know their blood pressure numbers, blood sugar scores, and cholesterol levels. They should know their periodontal health score as well. Lots of periodontal indices are used in research, but very few are used in practice.

For many years we calculated plaque scores for patients using the Plaque Control Record. It wasn't as successful as we had hoped in involving people in their oral health condition because plaque is not an accurate measure of disease activity or level. There were patients with lots of plaque but little or no disease. Others worked hard and had little or no visible plaque, but had active disease. It just didn't seem fair that it didn't connect to disease levels.

Periodontal charting data reveals actual disease levels, but patients have a hard time understanding the numbers on the chart. We need a composite number that reflects patients' periodontal health status.

The easiest system for this is the Periodontal Health Index (PHI). This is the number of pockets over the number of bleeding points. The ideal score is 0/0. It's hard to get excited about a few fours and bleeding, but totals have a different impact. To calculate a patient's PHI, count the number of pockets recorded and the number of bleeding points. For example, 24/38 takes on a different meaning when the goal is 0/0, and the patient has a few fours and bleeding in the posterior. While 24/38 is not the worst score, it puts things into perspective for both the hygienist and the patient.

The worst possible score in a mouth of 28 teeth is 168/168. This means that six surfaces of each of the 28 teeth have a pocket depth of at least four millimeters, as well as bleeding upon probing. Hopefully, you don't have any patients like this!

Most pockets begin between the teeth, so the majority of pockets and bleeding occur in the interproximal areas. This focuses the bleeding and pocket depth scores on four surfaces of each tooth. If the second number of the index — the bleeding score — is over 100, the patient is ignoring interproximal plaque control or using an improper technique. If all 28 teeth have interproximal bleeding associated with them, the potential bleeding score is 112 (28 x 4 = 112).

Facial surfaces generally have fewer bleeding points or pockets than interproximal sites because people are more likely to brush those surfaces and skip interproximal areas. Since the lingual surfaces receive the least attention during brushing, more bleeding points and pockets are usually seen on lingual rather than facial surfaces.

You can calculate the range of scores for any patient if you know the number of teeth they have. Simply multiply the number of teeth by four to calculate the number of interproximal surfaces, or by six for the total number of surfaces measured. Patients with periodontal disease often start with scores of 25/100 to 85/140 or more.

The numbers drop dramatically after therapy. Patients enjoy seeing the numbers change, and it's gratifying to see the positive effects of your therapy. Not all the healing takes place in the first couple of months of non-surgical therapy. Continued healing can be measured during the months following treatment. A few areas may need more instrumentation, and oral hygiene may need refining.

By the second or third maintenance visit after therapy, scores are often well below 10/10.

If someone in the office is assisting you with periodontal charting by writing down the numbers, the patient is aware of the range of numbers and where bleeding points are noted. This is especially true if you explain the process before you begin. Knowing the range of numbers and having a general idea where they occur in the mouth does not have the same impact that the total score does. A few fours and some bleeding don't sound too bad. A PHI score of 37/85 is what puts it into perspective. These figures reflect the number of infected areas in the mouth that need to be treated. This score provides the basis for your treatment plan and case presentation.

One of my patients who is an engineer actually calculated his expected rate of healing by comparing his baseline score with his first score after instrumentation. He mathematically calculated the next three scores. He was pleased when he achieved exactly what he expected at the next visit. The following visit he missed his predicted score by just a few numbers and was sure he hadn't done enough interproximal cleaning. The PHI motivated this man.

I recently received a curious call from a dentist who wanted to know what kind of charting I was doing. He was playing tennis with one of my patients who told him his perio score was 3/5, and asked the dentist what his score was! My patient was proud of his score because he'd reduced it from 86/122. The dentist didn't know his own PHI, and didn't know how to calculate it, so he called me. After we talked, he changed his charting system to calculate a PHI for each patient, and now he knows his own PHI!

With perio scores, competition grows between family members. Rather than asking about a hygiene visit, their first question is, "What was your score today?" It's fun to see patients get excited about their improvement and take an active part in their treatment. It helps them understand the situation and connects them to their oral health the same way blood pressure, blood sugar, and cholesterol scores do.

Your dentist employer will also like the PHI score because it provides a snapshot picture of the periodontal charting. He or she doesn't have to look at all 168 probing scores. The PHI score provides the bottom line. That score, along with your description of the case and plans for treatment, provide a complete picture. It eliminates the problem of a busy dentist rushing in to do an exam, checking for caries, ignoring the charting which indicates periodontal disease, and simply saying the tissues look fine. Providing the dentist with the PHI score gives concise information that ties into your proposed treatment.

You don't need a particular periodontal charting form to calculate the PHI. Simply count the number of probing scores over three millimeters and the total number of bleeding points, and you have the score. One charting form does provide a space for calculating and recording the PHI score. The Perio-Data™ charting form includes a monitoring section to record the number of pockets in each sextant according to category: 4mm, 5-7mm, and 8+mm. Bleeding points are also tallied for each sextant. The numbers are then totaled for the mouth and the PHI score is recorded. Perhaps computer programs will include this unique Perio-Data feature ( in the future.

I predict that people will soon keep track of their PHI scores just as they do their blood pressure numbers, blood sugar scores, and cholesterol levels. This tells patients how many infected sites they need to treat. Improvement in the PHI score documents the success of treatment and the patient's efforts in controlling disease. It's a win/win tool for you, the dentist and the patient.

Trisha E. O'Hehir, RDH, BS, is a senior consulting editor of RDH. She is also an international speaker, author, instrument designer, inventor, and oral health detective. Her Web sites are and She can be reached at (800) 374-4290 or at [email protected].