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Patient initial facial and intraoral photos.
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A digital methodology is described by showing the treatment of a patient that presented a Class III malocclusion (Figures 1 and 2).
Initial records of the patient. (A) Lateral headfilm. (B) Cephalometric tracing. (C) Panoramic radiograph.
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A digital methodology is described by showing the treatment of a patient that presented a Class III malocclusion (Figures 1 and 2). The position and inclination of MSE appliance were changed from the initial default setting, taking into consideration the following parameters: bone thickness at the level of the four micro-implants (BT), appliance distance from palatal mucosa (DM), minimum micro-implant length for bicortical engagement (ML) and guiding bar interference (GBI) with palatal mucosa, as shown in Figure 7 and Table 2.
STL files of CBCT and dental arches. (A) before alignment. (B) After alignment.
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Then, the CBCT and dental arches STL files were aligned at first manually by overlapping three landmarks and then globally with Geomagic Studio 12 software (3D Systems, Morrisville, Carolina del Nord, USA) as shown in Figure 3. The combined model of CBCT and dental arches was imported in Rhinoceros (v. 6) software (Robert McNeel & Associates, Seattle, Washington USA).
Determination of reference planes and axes on the maxilla. (A) Skeletal landmarks utilized: point on oral aspect of midpalatal suture at the level of second premolars (MS5) and second molars (MS7), most posterior point of vomer (VP), most lateral point of the zygomatic process of the maxilla on the right (ZR) and left side (LZ). (B) Midsagittal plane (MP), in blue, passing through MS5, MS7, and VP. (C) Horizontal palatal plane (HPP), in light blue, perpendicular to MP and passing through MS5 and MS7. (D) Center of Maxilla (CM) point, defined by the intersection of the projection of the bizygomatic line (ZR'-ZL') to HPP and posterior part of midpalatal suture (MS5-MS7 line). (E) CM point as the origin of the x, y, z coordinate system of the maxilla.
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The first plane is the Midsagittal Plane (MP), passing through the points Midpalatal Suture 5 (MS5), Midpalatal Suture 7 (MS7), and Vomer Posterior (VP) (Figure 4A and B). On this plane, the intersection between the projection of the BZL and the midpalatal suture (MS4-MS7 line) is named the Center of Maxilla (CM) point (Figure 4D). The MSE position can be modified by moving the CA along the x, y, z axes of the maxilla (Figure 4E), while the MSE inclination can be modified by changing the appliance Yaw, Pitch and Roll (Figure 6B).
Setting of MSE in the maxilla in the initial default position. (A) Virtual model of MSE appliance with 4 micro-implants; the center of the appliance (CA), the light blue dot, is computed as the midpoint of the center of 4 micro-implant slots (yellow dots) and is set as the origin of MSE coordinate system. (B) MSE located in the initial default position in the maxilla, in which the CA point is coincident with the center of maxilla (CM) point, and the MSE x', y,' z' coordinate system is aligned with the maxilla x, y, z system.
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The virtual model of the MSE appliance was designed using Rhinoceros software (Figure 5A).
(A) User interface developed with Rhinoceros software, with which the inclination (Yaw, Pitch, and Roll) and position (dx, dy, dz) of MSE appliance can be changed to optimize the bone thickness (BT) at the level of the 4 micro-implants identified with numbers 1-4, the appliance distance from the palatal mucosa (DM), the micro-implant length required to obtain bicortical engagement (ML) and the guiding bar interference (GBI). (B) yaw, pitch, roll, and reference axes for MSE.
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A user interface has been developed (Figure 6A), with which the position and inclination of the MSE appliance can be changed from its initial default setting. The MSE position can be modified by moving the CA along the x, y, z axes of the maxilla (Figure 4E), while the MSE inclination can be modified by changing the appliance Yaw, Pitch and Roll (Figure 6B). The parameters' last values are displayed in Figure 6A.
Parameters analyzed during the digital planning of MSE position and inclination: minimum micro-implant length required to obtain bicortical anchorage (ML), appliance distance from palatal mucosa (DM), bone thickness at the level of the micro-implant insertion sites (BT), guiding bar interference (GBI) with palatal mucosa. (A) sagittal section. (B) coronal section.
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The position and inclination of MSE appliance were changed from the initial default setting, taking into consideration the following parameters: bone thickness at the level of the four micro-implants (BT), appliance distance from palatal mucosa (DM), minimum micro-implant length for bicortical engagement (ML) and guiding bar interference (GBI) with palatal mucosa, as shown in Figure 7 and Table 2.
Lab work for MSE. (A) Virtual model with the final position of MSE after digital planning. (B) Digital design of positioning guide. (C) Fixation of the MSE appliance in the positioning guide with steel ligatures. (D) Positioning of the MSE appliance on the dental stone model by means of the resin guide for bending and welding of MSE arms.
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A final position and inclination of MSE were identified for the patient (Figure 8A). Then, a 3D positioning guide was designed on top of the virtual model of dental arches with final MSE position (Figure 8B), the virtual guide was 3D printed with Grey resin (Formlabs, Somerville, USA), the MSE appliance was inserted into the resin positioning guide and secured with steel-ligature (Figure 8C), and finally, the guide and the appliance were placed on the stone model for the bending and welding of the appliance arms to the molar bands (Figure 8D).
(A) Finalized MSE appliance on the dental stone model. (B) MSE appliance after placement in the patient oral cavity. (C) Intraoral picture after maxillary expansion.
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The finalized appliance (Figure 9A) was cemented in the patient oral cavity, and subsequently, 4 micro-implants 11 mm long were inserted through the appliance slots into the palatal bone (Figure 9B). MSE activation consisted of 2 turns in the morning and two turns in the evening (0.13 mm expansion per turn) until an inter-incisal diastema appeared and then two turns in the evening until expansion completion (Figure 9C); the total appliance activation was 4 mm.
Patient wearing the facemask. (A) Frontal view. (B) Lateral view.
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A force of 16 ounces was applied bilaterally, by means of 2 elastics with a diameter of 3/8' attached to the intra-oral hooks (Figure 10).