Study improves technique that uses 3D virtual representation for diagnosis and treatment of dentofacial deformities
Doctoral thesis developed by researcher Rodrigo Mologni Gonçalves dos Santos, defended at the Faculty of Electrical and Computer Engineering (FEEC) at Unicamp, offers four contributions to the improvement of the technique that uses 3D virtual representation for diagnosis and treatment planning of deformities dentofacials. The work, which was supervised by Professor José Mario De Martino and co-supervised by Professor Luis Augusto Passeri, from the Department of Surgery of the Faculty of Medical Sciences (FCM), resulted in several articles published in international scientific periods, in addition to a request for patent registration.
According to Rodrigo Santos, the conventional method of preparing orthognathic surgery, an aesthetic-functional intervention that aims to correct deformities of the facial bones and teeth, is carried out by hand, which takes a lot of the surgeon's time and makes the procedure more expensive. 3D virtual planning emerged to overcome these difficulties. “Our purpose was to contribute to the improvement and dissemination of this technology, the prospects of which are that it will replace the conventional method in the near future”, explains the author of the thesis.
Professor Passeri notes that although he has to work with the three-dimensionality of the skull and face, for a long time the surgeon did (and still does) planning the surgery in a two-dimensional way. “We used radiography as a basis, which is a flat structure. We even tried to obtain three-dimensional information, taking a frontal and a lateral x-ray, but obviously we were unable to generate truly three-dimensional values. With the 3D model of the skull, we now have more precise data, which allows us to plan the surgery in greater detail”, he considers.
Of the four contributions offered by the study, according to Professor De Martino, the most important was the one that automated the main stage of virtual surgical planning in 3D, in which the maxillary bone segments are repositioned in the skull. “The method created is capable of automatically correcting the most common dentofacial problems treated by orthognathic surgery, which involve skeletal malocclusion [problem with the fit of the lower and upper teeth], facial asymmetry and jaw discrepancy”, says Rodrigo Santos.
In the 3D virtual method, the surgeon has computer support, but planning still does not occur automatically. From the 3D representation of the skull, the professional clicks, drags and manually positions the bony parts, as if he were remodeling the skull. The objective is to make the set as close as possible to a pre-established standard, based on studies of the craniofacial characteristics of men and women and different ethnic groups. It turns out that this procedure can generate some distortion, since the values of the bone measurements change as the bone parts are moved.
Simply put, what Rodrigo Santos did to overcome this difficulty was to develop a computational method that identifies the most appropriate positions for the maxilla, the body of the mandible and the chin in the skull, minimizing the difference between the patient's measurements. and standard measurements. “The algorithm makes the moves automatically, interactively, until it finds the best solution. In the tests we carried out, this difference was less than one millimeter, which is perfect clinically”, reports the author of the thesis.
According to Professor De Martino, the proof of concept was very successful, demonstrating that the method is capable of contributing to the planning of surgeries aimed at correcting dentofacial problems. The technology was the subject of a patent application in Brazil. “It is an important initiative, but I think it is also necessary to seek intellectual protection outside the country”, observes the professor, who hopes that the tool can be licensed in the future, which would bring benefits mainly to patients.
Other contributions
In addition to this important contribution to the planning of orthognathic surgery, the research reached three other relevant results, which also offer more refined resources for preparing the intervention. The first of these refers to the positioning of the head. In the conventional method, once the image is generated, it is not possible to change this position. In the 3D virtual environment there is no such limitation. “In addition, the head can be placed in a certain position with greater precision, as the surgeon can visualize the patient’s skull”, observes Rodrigo Santos.
Another advance is related to cephalometric analysis [study of the dimensions of the skull and face], which leaves the two-dimensional plane and migrates to the three-dimensional. With this, truly three-dimensional values are generated, which avoids the loss of information resulting from the two-dimensionality of the radiography, used in the conventional method. “Without a doubt, this increases the accuracy of surgical planning, including because it preserves the three-dimensional geometry of the bone structures”, assesses Professor Passeri.
The last contribution of the work was the proposal of new cephalometric standards for adult Brazilians of European descent, based on computed tomography images, a technique that produces a craniofacial image that is more accurate and reliable than radiography. The latter generates distortions in the shape and size of the skull, in addition to not distinguishing the overlap and consequent hiding of bones. “We created these standards based on images from the Radiology Area of the Faculty of Dentistry of Piracicaba (FOP), access to which was only possible thanks to the collaboration of Professor Francisco Haiter Neto”, explains Rodrigo Santos.
In the analyzes he carried out, the researcher found that there are significant differences between men and women. According to him, male and female skulls are proportional, but men's jaws are larger. “We defined the measurements taking into account the difference in density between bones and teeth, which allows for a more precise identification of these elements”, says Rodrigo Santos, who received a scholarship granted by the Coordination for the Improvement of Higher Education Personnel (Capes) , funding agency of the Ministry of Education.
According to Professor Passeri, around 5% of Brazilians are recommended to undergo orthognathic surgery, which represents 10 million people, a contingent similar to the population of Portugal. “As we simplify the procedure, we expand access to this type of treatment”, he understands. The intervention, adds the specialist, is recommended for people with deformities in the facial bones and teeth that cause speech, respiratory, chewing and swallowing problems, among others. Both Professor Passeri and Professor De Martino highlight the importance of the work being conducted in a multidisciplinary way. “This is the type of study that requires the use of knowledge generated by more than one area. We had to learn from each other to arrive at the solutions we were looking for, which was very enriching for everyone”, points out De Martino.
Publications
- SANTOS, RMG; DE MARTINO, JM; HAITER NETO, F.; PASSERI, LA Influence of different setups of the Frankfort horizontal plane on 3-dimensional cephalometric measurements. American Journal of Orthodontics and Dentofacial Orthopedics, v. 152, no. 2, p. 242–249, Aug. 2017. DOI: 10.1016/j.ajodo.2009.08.026.
- UNICAMP. JM De Martino; RMG Santos; LA Passeri. Method for automatic repositioning of maxillary bone segments in three-dimensional virtual planning. BR n. 10.2017.004146-8, 2 Mar. 2017.
- SANTOS, RMG; DE MARTINO, JM; PASSERI, LA; ATTUX, RRF; HAITER NETO, F. Automatic repositioning of jaw segments for three-dimensional virtual treatment planning of orthognathic surgery. Journal of Cranio-Maxillo-Facial Surgery, v. 45, no. 9, p. 1399–1407, Sept. 2017. DOI: 10.1016/j.jcms.2017.06.017.
- SANTOS, RMG; DE MARTINO, JM; HAITER NETO, F.; PASSERI, LA Cone beam computed tomography-based cephalometric norms for Brazilian adults. International Journal of Oral and Maxillofacial Surgery, v. 47, no. 1, p. 64–71, Jan. 2018. DOI: 10.1016/j.ijom.2017.06.030.
- SANTOS, RMG; DE MARTINO, JM; HAITER NETO, F.; PASSERI, LA Cone-beam computed tomography-based three-dimensional McNamara cephalometric analysis. Journal of Craniofacial Surgery, 2018. DOI: 10.1097/SCS.0000000000004248. Pre-published.
