RESUMO
This study investigated the influence of different levels of exposure to smoking on periodontal healing for 12 mo after nonsurgical periodontal therapy and supportive periodontal care every third month. Eighty smokers willing to quit smoking and with periodontitis were included. Participants were offered an individualized voluntary smoking cessation program. Data collection included questionnaires and a full-mouth periodontal examination. Group-based trajectory modeling was used to model smoking trajectories over the follow-up. The effect of smoking trajectory on periodontal parameters over time was estimated with mixed effects modeling. Three smoking patterns were identified: light smokers/quitters (n = 46), moderate smokers (n = 17), and heavy smokers (n = 17). For the periodontal data, the first factor, moderate periodontitis, included the number of sites with clinical attachment levels (CALs) of 4, 5, 6, and 7 mm; periodontal pocket depths (PPDs) of 4, 5, and 6 mm; and bleeding on probing. The second factor, severe periodontitis, consisted of the number of sites with a CAL ≥8 mm and PPD ≥7 mm. Heavy smokers commenced with a higher average CAL of 1.1 mm and 10 more sites with severe periodontitis than light smokers/quitters. While light smokers/quitters and moderate smokers obtained an average improvement of 0.6-mm PPD and 0.7-mm CAL, respectively, heavy smokers experienced 0.5-mm attachment loss. Heavy smokers had only a 50% reduction in the number of sites with moderate periodontitis when compared with light smokers/quitters and moderate smokers. While most participants benefited from nonsurgical periodontal therapy with results affected in a dose-response manner, the therapy had no effect on severe periodontitis among heavy smokers. Smoking cessation should be part of periodontal therapy; otherwise, limited benefits would be observed among heavy smokers, hindering the effect of treatment.