Background and Aims: Dental crowding is considered a significant factor in the development of malocclusion. Identifying the factors contributing to its formation aids in selecting appropriate treatment strategies and achieving stable post-treatment results. Since the relationship between jaw base length and this factor remains unclear, the objective of this study was to investigate the association between the jaw base length and dental crowding in individuals with different skeletal patterns in the sagittal dimensio in north of Iran.
Materials and Methods: In this cross-sectional study, 42 individuals from each skeletal class (I, II, and III) were enrolled based on crowding of >4 mm and ≤4 mm, selected through census from all patients referred to the Orthodontic Department of Babol Dental School (Iran) between 2011 and 2025. These samples were examined for the association between jaw base length in each skeletal classification and dental crowding. Lateral cephalograms from before treatment were used to measure the jaw base length. T-tests, one-way ANOVA, and Bonferroni post hoc tests were employed to examine the desired associations, with a significance level of 0.05.
Results: A total of 126 patients (64.3% female) were evaluated. The relationship between jaw base length and crowding was not significant with respect to age, but it was reported as significant in females in the mandible (P=0.024). The present study indicated that the length of the maxillary and mandibular bases in the entire sample did not show a direct and significant correlation with the degree of dental crowding. However, subgroup analysis based on skeletal classes revealed significant differences in maxillary and mandibular base lengths between skeletal classes I, II, and III at both crowding levels (≤4 mm and >4 mm) (P=0.008, 0.011, and P<0.001, respectively). In the mandible, class III had the greatest length and class II had the shortest. In the maxilla, class III had the shortest length and class II had the greatest.
Conclusion: These findings suggest that sagittal skeletal patterns play a significant role in the dimensional changes of the jaws. Furthermore, in classes I and III, examining the mandibular base length is more important, as its reduction may be associated with more severe crowding. The maxillary and mandibular base lengths in the entire sample did not exhibit a direct and significant correlation with the severity of dental crowding. These variables were not significant with respect to age but were reported as significant in females in the mandible. Therefore, a single anatomical index like base length cannot solely predict the severity of crowding.
