The mystery of recall intervals

March 1, 2003
In my first job, I completely messed up the recall system. Most of the patients were coming in every six months, some every three or four months.

By Trisha O'Hehir

In my first job, I completely messed up the recall system. Most of the patients were coming in every six months, some every three or four months. Future appointments were always made before the patient left the office. Now remember, this was back in the dark ages of dental hygiene — 1968 — maybe before you were even born!

I falsely believed that my worth and value as a hygienist was entirely related to the amount of calculus I removed. With that in mind, I wanted to be sure all my patients really got their money's worth from their "cleaning" appointments. If someone didn't have much calculus, I stretched out the recall, figuring they would have more calculus next time. If I didn't remove a lot of calculus, I didn't really do anything worth charging for — or so I thought. I used a simple formula, three months went to six, four months went to eight and six months went to 12.

It all seemed very logical to me, until six months later when the schedule was blank. Oops, I really messed up big time! Good thing I left that job after just a year, leaving the next hygienist to fix things. Sorry about that!

The goal of recalls should be disease prevention, not just filling an appointment book. What is the ideal interval to prevent disease? Is it three months, four months, six months or 12 months? Or maybe it's two weeks? Before you decide on the recall interval for your next patient, look at the research to see how well each one works, and then make a decision based on each individual's needs.

• Six months — The standard today is the six-month recall, set in stone by insurance companies. You don't need scientific evidence to prove that — just suggest three-month recalls and your patient will shriek, "But my insurance only covers two cleanings a year!" How many times a day do you hear that?

As a kid in northern Minnesota, I was expected to see the dentist once a year. Each September, I had to bring a card to school, signed by the dentist, proving my yearly check-up. A lot of good it did. Our family dentist didn't believe in restoring deciduous teeth, so all the kids in my family went to the dentist with tooth decay and came home with tooth decay, but we did get our cards signed!

It wasn't research that changed the yearly check-up to six months — it was Bucky Beaver. Ipana toothpaste commercials featured Bucky Beaver, telling us to "...use Ipana toothpaste and see the dentist twice a year." This seems to have replaced the previous tradition of yearly visits, especially for children.

Even though researchers didn't specifically study the six-month recall, the information can be found in aspects of other studies. Unfortunately, the evidence points out the ineffectiveness of six-month recalls.

A study done in Sweden evaluated two-week dental hygiene visits that were provided right in the schools. A dental hygiene clinic is part of the school layout in Sweden, which made it easy for the 100 test children to see the hygienist every two weeks for oral hygiene instructions, cleaning, and fluoride. A control group of 100 children saw their family dentist and hygienist at traditional intervals — probably every six or 12 months. After two years, most of the 100 kids seeing the hygienist every two weeks had no new decay and no gingivitis. This really was a success. However, a few kids were at greater risk for decay, and despite good care, that small subgroup developed 19 cavities.

As bad as that sounds, results were much worse for kids in the control group. Most of these kids experienced both decay and gingivitis — a total of 575 carious lesions! Would you agree with me that the "traditional recall interval" in this study was a complete failure?

How often do kids come into your office on a regular six-month recall with new decay? If that happens, something's wrong. I used to think that was normal. I was thrilled when they had fewer cavities than the time before. Some kids and adults even expect it. They don't ask "if" they have decay; they ask, "How many cavities do I have?"

This was a baffling question when I worked in Switzerland. Patient after patient would ask me — in German, of course — something about "blombes." I couldn't find that word in my German dictionary, so after hearing it repeatedly and just shrugging my shoulders and looking really stupid, I asked the assistant what "blombe" meant. "Oh, that's easy," she said, "blombe is a hole." All this time, patients were asking me how many holes they had in their teeth, convinced it was normal to have new "holes" each time they came in. They just wanted to know how many!

Just so you and I are "on the same page," new disease at each visit is a warning signal. Something's wrong. It may be that the bacterial infection — caries or periodontal disease — wasn't effectively treated in the first place, the interval is too long, or there are circumstances putting this person in an extremely high-risk category. Your detective work will uncover the answer.

• Three months — I find it so funny to read a research article that proudly states the subjects were all receiving regular perio maintenance every three months in the dental school clinic, and yet they all qualified for the study by having 5 millimeter pockets that bleed! In these cases, the three-month recall program isn't working; it's just cultivating disease for future research studies. Well, maybe it is successful — if having patients for research every year is the goal!

Before I thought about the ultimate goal of recalls, I was on the faculty of a couple of dental hygiene schools that managed to have the same perio patients for students to treat year after year. We never effectively stopped the disease process; we just kept treating it from year to year. There is an advantage to this of course — you always have a good pool of patients for next year's students to treat. If the disease is not effectively treated, your recall patients will have pockets and bleeding at every visit.

The evidence supporting the three-month recall comes primarily from retrospective. These studies look back at a practice and measure clinical outcomes of patients after many years on a three-month recall. These results are compared to the results of others in the practice who were not seen regularly. Those on a three-month recall lost fewer teeth and had better periodontal health than those who weren't seen regularly.

In a 15-year prospective study, test subjects were seen every two months for the first two years, and then every three months for the next four years. The goal was intensive oral hygiene instructions and repeated motivation. In contrast, the control group had 12-month recalls for six years. For ethical reasons, the control group was discontinued at that point, due to high levels of disease. The 12-month recall didn't work without the foundation of excellent oral hygiene skills. The study continued for nine more years. Recall intervals were determined individually, based on patient needs — 65 percent were seen once a year, 30 percent twice a year and 5 percent — those considered "risk subjects" — were recalled three to six times per year. During the 15 years, less than 1 percent of subjects developed high levels of tooth decay. Most of the subjects had low plaque levels, no pockets, and no gingivitis. This study points out the benefits of two-month recalls and the advantages of intensive oral hygiene instructions before extending the recall interval to three months or more.

No studies are available directly comparing two-month and three-month intervals. Three months is the traditional choice for perio patients, by default, rather than comparison to shorter intervals. We know a three-month interval doesn't work for everyone, as evidenced by the number of perio maintenance patients in dental school clinics who qualify for research studies because they have 5 millimeter pockets with bleeding. It may work for most people, so identify those at risk and offer them a shorter interval.

• Two weeks — There is research to support a two-week interval to reverse gingivitis or establish tissue health. In 1965, Dr. Harold Löe reported his research on experimental gingivitis in man, now considered a classic study. With no oral hygiene, people develop gingivitis in two weeks. Resuming oral hygiene reverses gingivitis. Many researchers use the two-week recall for several months after surgery, before moving to a longer recall interval.

For patients with active disease, the two-week interval can stop disease progression. This is really therapy, and not a recall to maintain health. It's an option for patients showing signs of active breakdown, those with a compromised immune system, or for those patients going through times of stress which interfere with their normal plaque control routine. A 15-minute appointment every two weeks may be just enough to get patients through a tough time. For example, it may be the answer for patients suffering from, for example, severe pregnancy gingivitis or accountants who smoke during tax season.

• Individualized intervals — Can we predict what the recall interval should be for individuals? Several studies measured bacterial re-growth following instrumentation and reported return to baseline levels at eight to 10 weeks. That's closer to two months, not three. Convincing patients to come in six times a year when they're used to six-month recalls presents quite a challenge. Maybe that's why so many clinicians opt for the three to four month recall. It's a compromise, but still better than six months.

The primary criteria suggested by researchers is history of past disease, suggesting that those with 2 millimeters of attachment loss should be considered at risk for further periodontal breakdown and therefore should be seen more often than people with no attachment loss. A specific interval is never stated.

Risk factors that will compromise healing or predispose people to disease progression are smoking, diabetes, poor oral hygiene, genetics, age, and medications that dry the mouth, No formula has yet been suggested or researched using risk factors to determine recall intervals. Perhaps one day we will have a dipstick test for the sulcus, providing the answer to this question. Until then, I suggest this basic rule — shorter is better. This is basically what you do now, but I think we feel compelled to save our patients money by stretching out the recall whenever we can. Just remember, patients should come in for recall visits healthy — no bleeding and no calculus. When that happens, your interval is perfect. You are indeed keeping healthy people healthy.

Trisha E. O'Hehir, RDH, BS, is a senior consulting editor of RDH. She also is an international speaker and editor of Perio Reports, a newsletter containing news about periodontics for dental professionals. The Web site for Perio Reports is She can be reached by phone at (800) 374-4290 and by e-mail at [email protected].

To review previously published articles in RDH or Dental Economics magazines, visit: or

Type in an author's name or keyword in the search function and then retrieve the desired article from the archives.