The natural history of periodontal disease in humans: risk factors for tooth loss in caries-free subjects receiving no oral health care.

Aim: No long-term studies have reported on risk factors for tooth loss in subjects without home or professional dental care. The purpose of this report is to identify potential risk factors for tooth loss among male Sri Lankan tea labourers who participated in a 20-year investigation of the natural history of periodontal disease. Material and Methods: Data for this report were obtained from the 455 subjects who participated in multiple examinations over the 20-year period from 1970 to 1990. Analyses included data from interim examinations in 1971, 1973, 1977, 1982 and 1985. Oral health assessments included the following: (1) attachment levels in millimetres on all mesial and mesio-buccal surfaces, excluding third molars; (2) plaque index; (3) gingival index; (4) calculus index; (5) caries index; and (6) missing teeth. Other variables included age, history of smoking and betel nut use. Statistical analyses included descriptive statistics and multivariate repeated-measures modelling with generalized estimating equations. Results: Tooth loss was significantly dependent upon interactions between the mean attachment loss and betel nut use (Z=3.40; p=0.0007) and history of missing teeth (Z=-3.70; p=0.0002). The effect of attachment loss on tooth loss was increased in the presence of betel nut and diminished when teeth were already missing at baseline. Conclusion: History of missing teeth, betel nut use and increasing attachment loss were significant predictors of tooth loss over time. Betel nut use increased the effect of attachment loss on loss of teeth, while history of missing teeth diminished the effect of attachment loss on tooth loss.