Smoking effects on root coverage outcomes between 3 and 12 months: A prospective cohort study

BACKGROUND: This study aimed to evaluate the impact of smoking on root coverage outcomes, comparing healing responses at 3-12 months following coronally advanced flap with a connective tissue graft (CAF+CTG). METHODS: This prospective cohort study included 27 participants (13 smokers, 14 non-smokers) who required root coverage for a single Cairo Type 1 defect. Smoking status was biochemically verified (salivary cotinine). Clinical parameters, including recession depth and width, keratinized tissue width, and percentage of root coverage, were assessed at baseline, 3 months, and 12 months postoperatively. Statistical analysis employed both parametric and non-parametric tests to assess intra- and inter-group differences. RESULTS: Compared with 3 months, both groups demonstrated increases in recession depth and decreases in percentage root coverage at 12 months. Median (interquartile range) recession depth increased from 1.0 (0.0-1.0) mm at 3 months to 1.0 (1.0-2.0) mm at 12 months in smokers, and from 0.0 (0.0-0.8) mm to 0.5 (0.0-1.0) mm in non-smokers. Root coverage percentage was significantly higher in non-smokers at 12 months, with 87.5% achieving root coverage compared with 66.6% in smokers (p = 0.024). Keratinized tissue width increased at 12 months, compared with 3 months, in both groups, from 5.08 ± 1.21 (mean ± SD) to 5.36 ± 1.80 mm and from 5.64 ± 1.59 to 5.77 ± 1.25 mm in smokers and non-smokers, respectively. CONCLUSIONS: The negative impact of smoking on CAF+CTG outcomes became statistically detectable at 12 months postoperatively, a finding underscoring the need to consider smoking status when treatment planning and discussing expectations with patients. PLAIN LANGUAGE SUMMARY: This study explored how smoking affects healing after a common gum surgery used to cover exposed tooth roots. We followed two groups of patients, smokers and non-smokers, for 1 year after they received the same treatment, which involved repositioning the gum and adding a tissue graft from the palate. At first, both groups showed good early healing, but differences emerged over time. By 12 months, smokers showed more return of gum recession and achieved less complete root coverage than non-smokers. Although most non-smokers maintained full coverage of the treated tooth, this was true for far fewer smokers. Both groups did show some healthy growth of the firm gum tissue around the tooth, but this did not offset the long-term disadvantage seen in smokers. These findings suggest that the harmful effects of smoking may not be obvious in the early months after surgery but become clearer as healing continues. Understanding this gradual difference can help dentists to guide patients more effectively, especially those who smoke, by setting realistic expectations and highlighting how smoking may limit the long-term success of treatment.