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SUMMARIES ANNUAL SESSION Application of 3D Imaging to Modern Orthodontics Presented by Dr. Lucia Cevidanes Summarized by Dr. William Finnegan, Northern Region Editor maxillary asymmetry. The final diagnosis of hemimandibular hypertrophy was really a tissue problem where the soft tissue on one side was thicker than the other side. T he concern about radiation and the cost of Cone Beam CT imagery has faded. A Cone Beam CT scan uses less radiation than a full orthodontic survey. The set-up cost of digital imaging is around $100,000, and the cost to install a Cone Beam CT unit will be $175,000 to $185,000. Treatment planning with 3D imaging will evaluate more factors than linear measurements, angles, goals of occlusion and facial esthetics. The fact that we can take a 3D image model and rotate it in any direction will help us with root positioning, impacted teeth, future of tooth eruption, asymmetries and craniofacial anomalies. Using the anterior surface of the cranial base for superimpositions we can more accurately evaluate growth and treatment response. • A young patient (four years old) was diagnosed with microfacial microsomia. The 3D image revealed that the patient did not have a joint on the right side with failure of vertical growth of the ramus. There were then four treatment choices: distraction osteogenisis, costochondrial graft, functional orthopedics or post-pubertal surgical reconstruction. • A 9.5-year-old patient was used to describe color mapping and segmentation. Using the whole structure of the cranial base or just the anterior cranial fossa for superimposition and masking different anatomic structures we can see changes that occur over a period of time to the anatomic structures that we are interested in using different colors for before, during and after images. • A patient was first seen at six to seven years of age. There was some question whether one was dealing with a case of hemifacial microsomia or mandibular fracture. The CT scan demonstrated that the asymmetry was probably caused by an early fracture where the ramus on one side was narrower and shorter than the normal side. The Cone Beam scan taken at nine years of age, after the use of a hybrid orthopedic appliance showed an improvement in the ramus height. • A patient with restricted mouth opening with treatment planned to have a cornoidectomy until a CT scan showed an early case of condylar fracture where the condyle grew around the articular eminence. The asymmetry could be diagnosed with a pan but the CT scan also showed that the condyle actually articulated with the zygomatic arch. • A diagnostic problem wherein a patient’s bite started to open during orthodontic treatment. The CT scan with a new visualization tool revealed that this was a case of rheumatoid arthritis. Dr. Cevidanes showed the following: 1. Failure of eruption: Cases where. . . • The Cone Beam CT scan showed that the failure of eruption of lower teeth was due to the teeth developing in the direction of the lingual cortical bone. Today these teeth would be erupted with implant screws. • Permanent lower bicuspids and cuspids were still unerupted at age 23 because the deciduous teeth had not exfoliated. The removal of deciduous teeth, including an abscessed deciduous cupsid, allowed all the permanent teeth to erupt normally. • A panorex view was used to place bone anchors, but the 3D image showed a supernumerary tooth behind the tooth of a premolar. • A small odontome was found attached to an impacted canine that was to be moved into the arch. 2. Asymmetries: Examples included cases where. . . • 22 A patient was diagnosed as having hemimandibular hypertrophy. A 3D image discovered that it was not a mandibular problem but a P C S O B U L L ET I N • S P R I N G 2 0 0 7 ANNUAL SESSION The 3D imaging can be useful in evaluating treatment responses to functional orthopedics, orthognathic surgery and growth of the face. The use of SNA-SNB-ANB measurements on lateral cephalograms are not adequate indicators of treatment response because they cannot show growth displacements as well as 3D imaging. The increase in the lower face height, for example, can camouflage an increase in mandibular length. Of course other factors affect treatment timing. The peak of growth velocity is important, but you may have to consider compliance, which might be more important before the peak. Functional appliances such as the Herbst and Frankel regulator 2 were investigated. The differences between these two appliances, of course, is that the Herbst is a tooth bone appliance and the Frankel completely tissue borne. In the Herbst appliance, you have to wonder how much influence growth will have in six months so that most of the change is tooth positioning with the lower anteriors being proclined. You also have to wonder about the statement that the Herbst will help correct anterior disk displacement. The results with the Frankel II regulator (completely tissue borne) showed that the disks were positioned correctly in the articular fossa. There was some growth in the lateral S P R I N G 2 0 0 7 • P C S O B U L L ET I N SUMMARIES surface of the ramus, in the superior surface of the condyles and in the inferior border of the mandible. These changes were significantly different from the untreated Cl II patients and the normal occlusion growth. Surgical changes with records taken before surgery, immediately post-surgery and one year post-surgery are recorded in 3D from superimpositions at the anterior cranial fossa. The color mapping with 3D imaging shows changes that happened pre-surgery immediately post-surgery and then six months to a year after surgery. Not only can you measure accurately the changes to the maxilla and mandible and the condylar position, but you can also see the soft tissue changes. These methods of identifying changes should also allow studies of long-term growth changes as well as preplanning with the surgeon where the surgical cuts will be and where the surgical segments can be precisely placed during surgery. This will be very important for patients with craniofacial anomalies that need complex surgery. Dr. Cevidanes specified that the topics that she has presented are not from research data but are only preliminary findings that should generate a lot of future investigation. ❖❖❖ 23