Tooth loss at 22 years under periodontal maintenance (Hirschfeld, 1978)

Hirschfeld L, Wasserman B. "A Long-Term Survey of Tooth Loss in 600 Treated Periodontal Patients." Journal of Periodontology, 1978; 49(5):225-237.

Description

A question that keeps coming up in practice: does periodontal treatment really preserve teeth over the long run? Nearly 50 years later, this study remains one of the most cited references for answering it, thanks to an exceptionally long follow-up — an average of 22 years after active treatment.

Method

600 patients from a private periodontal practice, actively treated and then followed under maintenance, were re-examined an average of 22 years after the end of active treatment. The authors recorded the number of teeth lost to periodontal disease over that period, as well as the specific outcome of teeth deemed "of questionable prognosis" at the time of initial treatment (deep pockets, furcation involvement).

Results

Of the 600 patients: 300 (half) lost no teeth to periodontal disease during follow-up; 199 lost 1 to 3; 76 lost 4 to 9; and 25 patients ("extreme downhill") lost 10 to 23. Of 2,139 teeth originally classified as questionable prognosis, 666 were eventually lost — but 394 of those were concentrated among just one-sixth of patients (the worst-outcome subgroup), versus 272 losses spread across the remaining five-sixths. The same pattern held for teeth with furcation involvement.

Analysis

This is a retrospective study with no untreated control group (which would be ethically unthinkable today) — so it can't directly compare to the natural course without treatment. Its value comes from its rare follow-up length (22 years) and sample size. The most important finding isn't the overall average, but the highly uneven distribution: the vast majority of patients keep nearly all their teeth under regular periodontal maintenance, while a small subgroup accounts for most of the losses — a finding that redirected decades of subsequent research toward identifying individual risk factors (smoking, diabetes, compliance) rather than applying a uniform prognosis to all patients.

Conclusion

Under regular periodontal maintenance, tooth loss related to periodontal disease remains limited for the majority of patients — even for teeth initially classified as questionable prognosis. The real clinical challenge, then, isn't just initial treatment, but early identification of the high-risk subgroup, for whom closer follow-up meaningfully changes the long-term prognosis.