Developmental stage specific ANB reference values based on a longitudinal sample of untreated Caucasian subjects

Objectives: The study aimed to assess the longitudinal changes in the ANB angle before and after adolescence, and determine Class I normative values for childhood and adolescent Caucasian patients based on cervical vertebral maturation stages (CVMS) and gender. Setting and sample population: The sample included 71 (41 females and 30 males) untreated Caucasian subjects who took part in a growth study between 1959 and 1976. Materials and methods: Lateral cephalometric radiographs were analysed at CVMS1 (childhood) and again at CVMS4-5 (adulthood). A paired sample t-test was used to analyse ANB angle differences between the two time points. Subjects who were skeletally and dentally Class I at adulthood (51 subjects) had their radiographs at CVMS1 (childhood) and CVMS2-3 (adolescence) used to establish Caucasian normative values for those stages. Data were also analysed for gender and skeletal classification differences. Results: There was a statistically significant decrease in ANB value (2.3°) from CVMS1 to CVMS4-5 in the combined sample as well as the skeletal Class I and Class III groups (2.5° and 3.3° for Class I and Class III subjects, respectively). The reduction was smaller and not statistically significant in Class II individuals (1.5°). In Class I individuals, ANB values were 4.68° (SD:1.76°) at CVMS1, 2.86° (SD:1.18°) at CVMS2-3, and 2.13° (SD:0.99°) at CVMS4-5. No significant gender differences were found. Conclusions: Statistically significant decreases in the ANB angle can be expected between childhood and adulthood in Class I and Class III patients but not Class II untreated subjects. Adult normative values should not be used for children.