Longitudinal soft-tissue profile changes: a study of three analyses.

The purpose of this study is to describe the changes in six soft-tissue parameters that are commonly used by orthodontists in their diagnosis and treatment planning as well as in the evaluation of profile changes that occur with growth and orthodontic treatment. The parameters evaluated were two angles of facial convexity, the Holdaway soft-tissue angle, Merrifield's Z angle, and Rickett's esthetic line and lip relationships. The subjects of this study consisted of 20 males and 15 females for whom lateral cephalograms taken between the ages of 5 and 25 years were available. Descriptive statistics for the absolute and incremental changes are presented on a yearly basis between the ages of 5 and 17 years and at adulthood. Growth profile curves were constructed for each parameter, and regression equations were developed to describe the age-related changes in the six parameters for both males and females. The present findings indicated that the male and female growth profile curves were significantly different, except for the angle of facial convexity (excluding the nose) and Merrifield's Z angle. One of the conclusions that can be derived from this investigation is that the two angles of soft-tissue facial convexity, the Holdaway soft-tissue angle, and Merrifield's Z angle do not behave in a similar manner with age. Therefore, the clinician needs to use a number of soft-tissue parameters to better evaluate the soft-tissue profile. A limited number of cephalometric standards have been identified for each parameter. These standards can be used by the orthodontist as representative of the change between the age of 5 years and adulthood. This should enable the orthodontist to treat the patient to soft-tissue norms that are age- and sex-specific, rather than to an adult standard.