Adapting Häävikko’s dental age for the assessment of Italian children: use of LMS and other models based on smoothing splines

The expression ''dental age'' (DA) denotes the mean age at which a given stage of dental development is achieved in a population chosen as calibrator. The rhythm at which the maturation occurs is a characteristic of a given population in a given period. When DA is determined on subjects of a population different from the calibrator, the shape of the relationship of DA to chronological age (CA) must be empirically determined to trace reference charts for DA that properly apply to this population. The aim of this study is to show how the DA determined in a calibration set (Häävikko''s DA) can be adapted to apply to another population (Italian children), by means of CA-dependent smooth functions of the location, scale and shape of DA distribution. A set of 492 good quality panoramic films taken on healthy Italian children aged 5.5-14.5 years was analysed. The techniques under comparison produced quite similar curves: a parsimonious (4 e.d.f.) and rather satisfactory smoothing spline was found for median, but not for scale and shape indices: so the meaning of SDS values derived from these adjusted reference charts may result doubtful. Among the software products considered here, LMS program was found to be particularly user friendly, since allows the user to visually control the effect of changing the number of e.d.f. on the pattern of DA reference charts.