Reliability of Ashley Howes analysis in evaluating expansion potential: a cone beam computed tomography study.

Objectives: In recent times orthodontic treatment trends has swung towards non -extraction treatment. The Ashley Howes analysis evaluates the possibility of expansion based on the apical base. The transversal arch expansion potential of the mandibular arch also plays a role when considering maxillary expansion and should not be disregarded. Although, meant for both maxillary and mandibular arches, the subsequent focus of the analysis had mostly been in the maxillary arch. The aim of this study was to correlate the Ashley Howes analysis with buccal bone thickness at different vertical levels, tooth inclination and apical base width at the region of first premolars measured on CBCT images in both maxillary and mandibular arches.

Materials and methods: This retrospective study design evaluated pretreatment maxillary and mandibular study models and CBCTs of 84 patient records selected for the study. Based on the Ashley Howes analysis they were categorized into Group I (expansion not possible) and Group II (Expansion possible). The independent t-test was used for intergroup comparisons of CBCT parameters and Pearson correlation test was used to assess the relationship between expansion potential and CBCT parameters.

Results: In both maxillary and mandibular arches, Group II was characterized by greater buccal bone thickness at all vertical levels, greater apical base width and less premolar inclination when compared to groups without expansion potential although these differences were not statistically significant except for the mandibular apical base width. Although correlation between expansion potential and buccal bone thickness was not statistically significant in both the arches, it showed a positive correlation to apical base width and a negative correlation with premolar inclination in the mandibular arch.

Conclusion: The Ashley Howes analysis appears to reflect the relevant differences between extraction and non-extraction cases particularly in the mandibular arch.

Clinical relevance: Ashley Howes analysis could still be an effective tool in evaluating expansion potential and should be performed in both maxillary and mandibular arches.