BioDigital Orthodontics Management of skeletal deformities with orthognathic surgery-fusion model: part 1

Drs. Rohit C.L. Sachdeva, Takao Kubota, and Jun Uechi discuss the application of suresmile® in conjunction with orthodontic treatment and orthognathic surgery

Introduction
The versatility of using suresmile® technology based upon the principles of BioDigital Orthodontics in managing various orthodontic malocclusions has been described in previous articles.1-15
In this article and the next, the application of suresmile in planning, designing, and achieving controlled and predictable outcomes for patients requiring correction of their skeletal deformities with the aid of orthodontic and orthognathic surgery is discussed.

Care planning with suresmile
suresmile software provides the clinician the flexibility of planning care that is soft tissue, hard tissue, or dental driven. In other words, any of these craniofacial dental components may be used in singular or in tandem to develop the orthognathic surgical treatment objectives. (Currently, suresmile does not offer an approach to animate the integumental profile changes in response to hard tissue or dental changes. Dolphin 3D software (Dolphin Imaging & Management Solutions, Chatsworth, California) maybe used in conjunction with suresmile to demonstrate soft tissue changes.

Skeletal and dental movements can be simulated with suresmile software providing the doctor has a cone beam computed tomography (CBCT) image taken using a certified suresmile imaging system (Figure 1A). Currently, four systems are certified for use with suresmile: namely, i-CAT® Next Generation, i-CAT®, i-CAT® FLX (Imaging Sciences International, Hatfield, Pennsylvania), and Kodak® CS 9300 (Carestream Dental LLC, Atlanta, Georgia). This obviates the necessity of using the “fusion” technique to relate the dental models to the skeletal structures. However, if the doctor prefers the “fusion” technique, he/she may plan the surgery and then transfer the coordinates to the suresmile software to design the dental movements and the surgical archwires (Figure 1B). In case the doctor does not have access to 3D images of the craniofacial complex, he/she can scan the dentition intraorally and plan surgical movements by using 2D cephalometric-driven surgical treatment objectives and then applying the displacement values to simulate the movements of the 3D suresmile VDM (Virtual Diagnostic Model) or VTM (Virtual Therapeutic Model) (Figure 1C). The doctor should note the coordinate transformation from a 2D simulation to a 3D may not be as accurate but nevertheless provides for a reasonable alternative to planning customized care for a patient requiring orthognathic surgery.

Customized therapeutics with suresmile
suresmile software can be used to design many different types of archwires to suit the stage of treatment, i.e., pre-surgical or post-surgical, active, or passive. The design of the archwires is driven by the nature of the plan. Table 1 provides a summary of the various types of archwires that may be fabricated to achieve the planned results.

Patient R.S.
Patient R.S. presented at 25 years old with a Class 3 skeletal malocclusion and chief complaint of “I do not like my appearance and especially the protrusion of my lower jaw.”

Both 2D and 3D initial diagnostic records of the patient were taken. The initial photographs, cephalometric records, and analysis are shown in Figures 2A-2C. The suresmile Virtual Diagnostic Model (VDM) is shown in Figure 2D. In addition, a 3D CAT scan image at 1 mm resolution of the patient was taken with the ProSpeed F II (General Electric Systems, Milwaukee, Wisconsin) high-resolution medical CT scanner. The patient was bonded, and an intraoral therapeutic scan with the brackets on was taken of the patient (Figures 3A-3B).

The “fusion” technique was used to merge the intraoral Virtual Therapeutic Model (VTM) to the CBCT scan to create an accurate representation of the dentition with respect to the craniofacial complex (Figure 4). Note: Details of the preparation of the “fusion” technique have been described elsewhere.16, 17
Initially, a 2D Surgical Treatment Objective (STO) with a mandibular setback using BSSO was planned using the planning software that was created as a personalized program using C++ software (Figures 5A-5B). Note a surgical-first approach to treatment was planned for this patient. To allow for the post-surgical decompensation of the lower incisors, the mandibular setback was increased. Displacement values derived from the 2D STO were used as a guideline to design the surgical movements on the 3D-fused model (Figure 6). The surgical planning software used for this procedure was Rapidform 2006 (INUS Technology, Inc., Seoul, South Korea).18

Since the patient was planned for a surgery-first procedure, suresmile precision archwires were designed in advance of the planned surgery with the hope that they would be inserted immediately post-surgery to control Orthodontic Tooth Movement (OTM).

To enable the design of the suresmile
precision archwires, the displacement coordinates from the fusion model were first used to simulate the mandibular setback on the Virtual Therapeutic Model (VTM) (Figures 7-8). Next, the decompensation of the lower incisors and the coordination of the archwidth were planned on the VTM (Figure 9).
The surgical splint was designed by using the software Rapidform 2006 (INUS Technology, Inc., Seoul, South Korea),18 and the splint was printed using stereolithography (STL). Since the material is not biocompatible, a 3D impression of the splint was taken and poured in acrylic to create the biocompatible splint (Figure 10).

Just prior to surgery, standard 018″ and .016″ SE NiTi (GAC International, Bohemia, New York) wires were installed. Figure 11 shows patient R.S. 1-week post-surgery. The initial wires were maintained for 4 weeks to achieve alignment in the upper arch and decompensation in the lower arch. Check light Class 3 elastics were also used. At the 4-week appointment, the wires were replaced with standard 19 x 25 and 16 x 22 SE NiTi in the maxillary and mandibular arch, respectively (Figure 12). An .036″ transpalatal arch (TPA) was inserted to ensure stability of the maxillary arch, and light Class 3 elastics continued.
Six weeks later, suresmile precision archwires were inserted upper 19 x 25 SE NiTi, and 16 x 22 CuNiTi were inserted (Figure 13).

Twelve weeks post-surgery, the upper arch was replaced with a 19 x 25 suresmile Elgiloy archwire and the lower arch with a 19 x 25 CuNiTi suresmile. 17 x 25 TMA tip-back springs were placed in the lower arch to augment the leveling of the arch (Figure 14).

Twenty-one weeks post-surgery, the lower archwire was replaced with a 19 x 25 suresmile precision archwire and check triangular elastics continued (Figure 15).

Figure 16 shows the patient at the 25-week appointment
The patient was debonded 3 weeks later. Figure 17A shows the final extraoral and intraoral images. The final pano and ceph and the superimposition of the initial, the plan, and the final are shown in Figures 17B-17C.

The 3D Virtual Final Model (VFM) is shown in Figure 18A. Also, note the superimposition of the VFM to the VTS (Virtual Target Setup) demonstrates that the treatment outcome closely matches the plan (Figures 18A-18C). The total treatment time for this patient was 28 weeks.
A summary of the various steps in executing treatment for patient R.S. is shown in Table 2.

Conclusions
Patient R.S. was treated with a surgery-first approach and using the “fusion” technique with suresmile to plan and design customized care. The “fusion” technique was used to reconstruct the dental component of the craniofacial complex to allow for planning with suresmile because the CBCT scanner was not available on-site. With a CBCT scanner (certified by suresmile) the necessity of using the “fusion” technique could have been circumvented and the entire plan designed with suresmile software tools. In addition, the number of archwires used in the treatment of the patient could have been reduced especially with regard to stiffer alloys such as Elgiloy®.

Acknowledgments
For contributing to the surgical management of this patient, the authors wish to thank Dr. Takanori Shibata, Professor of Health Sciences University of Hokkaido, Japan. We also wish to thank Dr. Sharan Aranha and Arjun Sachdeva for all their hard work in helping us prepare this manuscript for publication.