This paper reports on a cohort study that evaluate the short-term healing response following periodontal flap debridement surgery in patients with moderate to advanced periodontal disease.

The cohort design is appropriate to address the research question. Exposure was defined as current cigarette smoking of at least 10 cigarettes per day. Occasional smokers were excluded. Whether or not former smokers were part of the group of nonsmokers is not stated. The surgeons performed standardised periodontal surgery and were blinded for exposure status. The outcome measures were assessed in a blinded fashion after nonsurgical periodontal therapy (baseline) and 6 months after flap debridement surgery (FDS). Evaluated outcome measures included mean PD, mean CAL, mean recession depth, and mean proportions of sites with residual PD of 3 mm and CAL gain of 2 mm. A primary endpoint was not specified. Overall, treatment and periodontal evaluation of patients was well designed. Figure 1

Figure 1.
figure 1

Frequency of sites showing probing depth reduction to values ≤3 mm at 6 months after surgery, according to presurgery probing depth.

The main problem with the study design and/or the report is that the selection criteria for the cohort remain ambiguous. Was this a single or multicentre study? Were consecutive patients enrolled? What were the periodontal inclusion criteria, ie, how was the need for FDS determined? What is the racial/ethnic composition of the study cohort? There is a striking difference between the smoking prevalence in males (74%) and females (27%). Although adjustments for gender were performed, other potentially important confounders were not considered in the analysis, eg particularly surgeon or race/ethnicity.

It is uncertain if and in what direction such adjustments would have changed the estimates. Even if no bias by these or unmeasured confounders was assumed, however, it is not clear to which populations these results could be generalised. We believe that only larger clinical studies allowing adjustments for multiple covariates could contribute new evidence to the area.

Practice point

  • This study suggests a negative effect of smoking on gingival surgery but larger studies/reviews are necessary to clarify the real effect.