Assessment of orbital volume and morphological changes after rapid maxillary expansion performed with tooth-bone and bone-borne devices. A retrospective study using surface-to surface matching technique

Aim: The effects of RME not only involve dental arch width and maxillary vault area but also associated maxillofacial structures. Displacement can be observed at the level of the frontal, zygomatic, and parietal bones, supporting the contention that the zygomaticomaxillary sutures, can be influenced by maxillary expansion. It would seem reasonable to assume that the orbits also may be affected by RME orthopedic treatment. The aim of the present study was to 3-dimensionally evaluate and compare the volumetric and morphological changes of the orbital cavity after RME performed with tooth-borne (TB) and bone-borne (BB). Method: CBCT scans from previous published material (TB group=18 subjects, BB group=18 subjects) were included in the present study according to the following criteria: 1) age between 11 and 15 years, 2) CBCT scans of good quality taken prior to the placement of the maxillary expander (T1) and 6 months after its removal (T2), 3) no caries, dental restorations or endodontic therapy of the upper first molars and the first and second premolars, 4) no artifact, 5) absence of pulpal calcification, 6) no previous orthodontic treatment, 7) no systemic disease or usage of medication. Slicer 3D software was used to generate a mask including soft tissues of the orbital cavities and create 3D rendered models from T1 and T2 CBCT scans (.stl). The .stl file including both right and left orbits was imported into Mimics software in order to exactly separate and delimit the orbital volumes by using specific planes cut and landmarks. Finally, the obtained 3D rendered models of T1 and T2 were imported into Geomagic Software in order to perform super-imposition and surface deviation analysis. Volumetric data of right and left orbital cavity at T1 and T2 were also recorded and Student’s T test was preliminary used to assess difference in orbital volume changes between both sides. Student’s T test was used to compare the volumetric dimension of the orbits between T1 and T2 in each group as well as the difference in the volumetric dimension the orbits from T1 to T2 between TB and BB. Results: Data of left and right orbits were merged in both groups since no differences were found in volumetric changes between both side (p>0.05). TB and BB group showed no significant changes in orbital volume between T1 and T2 (TB=0,14 cm3, BB=0,18 cm3) ( p > 0.05). According to the surface deviation analysis, the percentage of matching between orbit T1 and T2 orbit models were respectively 88,5% for TB group and 89,7% for BB group ( range of tolerance 0,6 mm). Conclusions: RME therapy in both form, i.e. with toothborne and bone-borne expander, did not affect volumetric and morphological changes of orbital cavity.