Transverse dimensions of dental arches in subjects with Class II malocclusion in the early mixed dentition.

The purpose of this study was to analyze the transverse dentoalveolar features of subjects with Class II Division 1 malocclusion in mixed dentition when compared to subjects with normal occlusion.The study was performed on 192 randomly selected subjects in the early mixed dentition. According to sagittal skeletal and occlusal features the sample was divided into two groups: 88 subjects (53 females and 35 males) with Class II skeletal disharmony and Class II, division 1 malocclusion (Class II Group, mean age 8 years and 10 months±11 months) and 104 subjects (66 females e 38 males) with dentoskeletal Class I relationships (Class I Group, mean age 9±1years). The Class II group was further divided into two subgroups (maxillary protrusion group and mandibular retrusion group) on the basis of the skeletal characteristics. Intermolar and intercanine distances were measured on dental casts in both arches and posterior and anterior transversal discrepancy (PTID and ATID) were calculated.Subjects with Class II malocclusion showed a significantly greater negative PTID (-2.1mm) which was associated with a significantly reduced maxillary width with respect to the Class I group (-2.2mm). The Class II group showed also a significantly greater negative ATID (-1.4mm) when compared to the Class I group. Subjects with mandibular retrusion showed a significantly greater reduction both in the maxillary intercanine width (-1.7mm). and in the maxillary intermolar width (-2.7mm) with respect to the Class I group. Subjects with maxillary protrusion presented with a significantly greater constriction at the maxillary intermolar width (-1.7mm) when compared to the Class I group.Class II malocclusion with mandibular retrusion is associated with a significant constriction of the maxillary arch with reduced intercanine and intermolar widths. When Class II malocclusion is due to a maxillary protrusion the constriction at the maxillary arch is limited to the intermolar width.