Aim: This study was designed to develop a three-dimensionally integrated model of CBCT craniofacial and dental cast data without any markers in skeletal Class III patients for the ultimate purpose of evaluating soft tissue changes after mandibular setback surgery, and to examine the accuracy of this model.
Materials and methods: The subjects comprised five skeletal Class III female patients who had undergone BSSRO at the average age of 20 years and 6 months.
The materials consisted of CBCT data of the craniofacial hard and soft tissues converted from DICOM format, scanned facial soft tissue data and dental casts of the patients. Facial soft tissue data, which were taken in the condition of exposed gingiva with a cheek retractor, and dental cast data were recorded by two kinds of optimal scanners. These data and lateral cephalometric digital data were taken before orthognathic surgery.
To apply the construction system previously reported, we constructed a craniofacial three-dimensional model by superimposing common regions of each data using Polygon Editing Tool software. First, we superimposed the scanned facial data with exposed gingiva on the CBCT soft tissue data registered at the common regions of the forehead and nose. Then, we superimposed the 3D dental cast data on the previously combined CBCT and scanned facial data by registering at the common frontal gingival region. After cropping each data, we merged the CBCT and dental cast data, and constructed the craniofacial soft and hard tissue three-dimensional integrated model. To examine the precision of this construction, we set three given points on each model. The points were the lower right and left canine cusps, and the lower right central incisal margin.
To examine the repeatability of this model, on the model of case 1, we measured the distance between the ordinary point of the measuring section to each point on CBCT hard tissue data and on dental cast data three times at one-week intervals, and calculated the mean value and standard deviation of the distance between these two positions of each point. To examine the accuracy of integration, we measured the distance between the ordinary point of the measuring section to each point on CBCT hard tissue data and on dental cast data on the models of case 1 to 5, and calculated the mean value and standard deviation of the distance between these two positions of each point.
Results: The mean value of the distance between the positions of each point was less than 0.3mm, and the standard deviation was less than 0.1mm.
Conclusion: The present integrated model of CBCT craniofacial soft and hard tissue data and dental cast data is a simple, low-invasive and highly-accurate method.
