Introduction: Holdaway proposed a 1:1 ratio of NB-L1: NB-Pog as an ideal relationship between mandibular incisors (L1) and bony chin for white populations. When the Holdaway ratio is not 1:1, the Holdaway difference (NB-L1 - NB-Pog) provides a quantitative judgment regarding the L1 position relative to chin projection for diagnosis and treatment planning. Steiner incorporated the Holdaway ratio into his chevrons to create customized solutions for each patient. The desired L1 position in the 2nd set of predictions in his chevrons is derived by estimated NB-Pog in 2 or 3 years of treatment using the 1:1 ratio of NB-L1: NB-Pog. However, many studies have found that the ratios were not close to 1:1 for the samples with pleasing faces. The presentation aims to show 1) treatment changes of the Holdaway difference based on treatment outcome assessment on 52 skeletal Class I and 53 skeletal II Caucasian adolescents with 3 different vertical skeletal patterns (6 subgroups) and 2) clinical application using updated Holdaway difference guidelines.

Discussion: The skeletal Class II group showed significantly higher Holdaway difference values than the skeletal Class I group. The Holdaway difference increased as the skeletal vertical dimension became more divergent. The findings imply that each subgroup needs an individualized Holdaway difference to improve diagnosis and treatment planning accuracy when using the Steiner analysis and chevron: 1mm, 2mm, and 3mm for skeletal Class I hypo-, normo- and hyperdivergent patients respectively, and 3mm, 5mm, and 7mm for skeletal Class II hypo-, normo- and hyperdivergent patients respectively.

Conclusion: Maintaining initial Holdaway differences for those with skeletal hypo- and normodivergent patterns is suggested to induce favorable soft tissue profile changes in adolescent patients. Reducing Holdaway difference is essential for improving facial convexity in skeletal hyperdivergent growing patients