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Pattern of alveolar bone loss and reliability of measurements of the radiographic technique.

The purposes of this paper were to study the pattern of bone loss among different teeth at the individual level and to study the effect of using different aggregated units of analysis on measurement error. Bone loss was assessed in standardized periapical radiographs from 293 subjects (18-68 years), and the mean bone loss score for each tooth type was calculated. These were then correlated by means of factor analysis to study the bone loss pattern. Reliability (measurement error) was studied by the internal consistency and the test-retest methods. The pattern of bone loss showed a unidimensional pattern, indicating that any tooth will work equally well as a dependent variable for epidemiologic descriptive purposes. However, a more thorough analysis also showed a multidimensional pattern in terms of four dimensions, which correspond to four tooth groups: 'incisors', 'upper premolars', 'lower premolars', and 'molars'. The four dimensions accounted for 80% of the total variance. The multidimensional pattern may be important for the modeling of bone loss; thus different models may explain the four dimensions (indices) used as dependent variables. The reliability (internal consistency) of the four indices was satisfactory. By the test-retest method, reliability was higher when the more aggregated unit (the individual) was used.