Background While regular periodontal care is advocated to reduce tooth loss considerably among periodontitis patients, evidence from observational studies is often limited to small single-center studies. This study aims to quantify the effect of periodontal care on tooth extractions using comprehensive Danish register data.

Methods A nation-wide register-based cohort study was conducted, encompassing 40-year-old individuals with incident periodontitis in 2001, tracked through Danish registers until the end of 2021. Receiving any periodontal care was determined annually, and the number of non-surgical tooth extractions serving as the annually varying outcome. G-estimation of structural nested mean models adjusted for time-varying confounding and loss to follow-up were employed to estimate the average treatment effect of periodontal therapy on subsequent tooth extractions.

Results The study included 1,251 40-year-olds with incident periodontitis in 2001. The average follow-up from 2002 onwards was 19.1 years and amounted to 23,878 person-years. On average, participants received periodontal care in 12.1 years (SD 6.3) and lost an average of 1.4 teeth (SD 3.0). G-estimation showed that receiving periodontal therapy in a given year reduced the number of teeth extracted in the following year by 0.03 (95% CI: −0.05 to 0.00). The cumulative effect of receiving periodontal therapy for five consecutive years was associated with an average of 0.06 (95% CI: 0.03 to 0.11) less extracted teeth. This protective effect was observed regardless of the baseline severity of periodontitis.

Conclusions Periodontal therapy resulted in a modest reduction in tooth extractions. The effectiveness of periodontal therapy against tooth loss seems to be considerably smaller than anticipated by earlier studies.

The authors have declared no competing interest.

This work was partly supported by the Danish Rheumatism Association (Gigtforeningen) #R171-A5894.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This was a register-based study. The study was approved by the Danish Data Protection Agency.

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The data that support the findings of this study are available from Statistics Denmark. Restrictions apply to the availability of these data, which were used under license for this study.