recorded a highly significant posterior displacement of the disc relative to the condyle ( p < 0.01) in both treatment groups, with mean sagittal angular reductions from 21.2° ± 9.3° to 1.8° ± 0.2° (a mean change of −19.4° ± 9.1°) in the Twin-Block group, and from 15.5° ± 11.6° to −0.9° ± 0.5° (a mean change of −16.4° ± 11.0°) in the Bionator group [ 39 ].
Arat et al., using a different analytical approach (measuring medial, anterior, and posterior angles relative to the condylar midline), identified slight angular variations, noting an increase in the medial angle of the disc from 56.30° ± 2.72° to 61.57° ± 4.47°, although these configurational adaptations were interpreted as physiological and did not reach statistical significance [ 37 ].
Similarly, spatial repositioning was detected by Elfeky et al., who used CBCT landmarks to demonstrate mildly significant dimensional alterations in the relationship between the most superior aspect of the mandibular fossa and specific cranial reference planes (e.g., Frankfort Horizontal plane, p = 0.019) following Twin Block therapy [ 40 ].
They reported a slight trend toward posterior disc positioning, which they attributed to differences in data acquisition between pre- and post-treatment assessments: at 6 months, in both groups (control and treated), the disc appeared to have shifted to a more posterior position, approaching the ideal “12 o’clock” reference.