The aim of this study was to assess intra-arch mandibular dimensional changes that
may occur during mouth opening using cone beam-computed tomography (CBCT). Fifteen
patients in need of any type of treatment whose execution considered a pre- and post-CBCT
assessment consented and were enrolled. CBCTs were taken with the following settings:
90 kV, 8 mA, field of view (FOV) 140 by 100 mm (height and diameter), Voxel size 0.25
mm (high resolution). The pre-CBCT was executed in the maximum mandibular opening
(MO), while the post-CBCT was in the maximum intercuspation (MI). A thermoplastic
stent with radiopaque fiducial markers (steel ball bearings) was fabricated for each
patient. Measurements were made using radiographic markers between contralateral canines
and contralateral first molars and between ipsilateral canines and first molars on
both sides. Paired t-tests were performed to evaluate the difference between open
and closed positions on these four measurements. In the MO position were registered
a significative tightening of the mandible at the canine (-0.49 mm, SD 0.54 mm; p
< 0.001) and molar points (-0.81 mm, SD 0.63 mm; p < 0.001) and a significative shortening
of the mandible on the right (-0.84 mm, SD 0.80 mm; p < 0.001) and left sides (-0.87
mm, SD 0.49 mm; p < 0.001). Within the study limitations, mandibular flexure determined
a significant shortening and tightening between maximum intercuspation to maximum
opening positions. Mandibular dimensional changes should be considered in light of
other patient factors in the treatment planning of implant positioning and long-span
complete arch implant-supported fixed prostheses in order to avoid technical complications.