Abstract
The decision is not always straightforward as to which orthognathic procedure is best for a good aesthetic result; three-dimensional imaging has brought new insight into this topic. The aim of this prospective study was to verify objectively whether postoperative changes occur within those regions not directly affected by surgical movements of the underlying jaw bones. The study included 83 young adults with skeletal class III deformities. They were classified into three groups according to the type of surgery: bilateral sagittal split osteotomy set-back of the mandible (BSSO), Le Fort I advancement of the maxilla, or a combination of both. Pre- and postoperative optical scans were registered as regional best-fits on the areas of the foreheads and both orbits. The shell to shell differences were measured and the average distances between the observed regions were calculated. As expected, changes were greatest in the regions where the underlying bones had been moved, but regardless of the operation performed, changes were found over the whole face. Changes in the nose, cheek, and upper lip regions in the BSSO group and in the lower lip and chin region in the Le Fort I group confirmed the concept of the facial soft tissue mask acting as one unit.
The skeletal class III dentofacial (SCIII) deformity, the most commonly treated orthognathic disorder in Slovenian orthognathic patients of Caucasian ancestry, is usually recognized easily during physical examination. However, numerous other diagnostic procedures are usually performed to determine the exact subtype of deformity. In addition to physical examination, photogrammetry, plaster casts, and lateral cephalogram imaging are the diagnostic procedures. Cephalometric analysis is probably still the best way to approach the definitions of phenotypes within the class III population, although three-dimensional (3D) analysis will undoubtedly play a greater role in the future. With all the diagnostic procedures completed and all the characteristics of the disorder specified, the decision is made as to the type of operation needed in order to achieve a stable normal occlusion, as the functional condition, and harmonious facial aesthetics, the main component of which comprises the facial soft tissues. The growing importance of aesthetic outcomes from surgery has switched the focus to the adaptation of the soft tissue to skeletal changes.
Orthognathic surgery, in conjunction with orthodontic treatment, is usually required for the correction of SCIII in adults. A number of surgical techniques can be used for the treatment of SCIII deformities such as mandibular setback, maxillary advancement, or a combination of both. The variability in the appearance of the soft tissue surface is of importance when choosing the surgical approach. Sometimes the decision as to the type of operation that is the treatment of choice for the best aesthetic result is completely clear, but in many cases there are dilemmas. Photogrammetry and lateral cephalometric analysis have been used numerous times for diagnostic and evaluation purposes but lack the third dimensionality. Computed tomography (CT), three-dimensional (3D) imaging by 3D laser, and optical surface scans have been used to assess facial surfaces. Radiation exposure still exists even after lowering the radiation dosage with the use of cone beam CT (CBCT). Surface scans without radiation only provide information about the surface and not about the underlying hard tissues; however they do have clear benefits, including accurate measurements of facial morphology and the changes associated with treatment. Method error depends on the technique used, but has been shown to be less than 0.5 mm in the systems most frequently used. The major limitation has been the inability to register images over time because of different head positions and different head sizes. We have already used this technology to determine our ethnically conditioned average face and to determine the characteristics of SCIII facial appearance.
In order to properly predict the final treatment result, a clearer vision is needed of the results of every operation, and treatment evaluation is the tool that shows this.
The objective of the present prospective study was to examine how different types of surgical procedure influence facial soft tissue changes after the surgical correction of SCIII deformity. Pre- and postoperative 3D images were captured (used to obtain facial contours) and regional analysis done to assess changes due to the operations, with appreciation of the fact that 3D registration can be based on stable surfaces instead of landmarks. We also used the 3D images to verify whether changes occurred within regions indirectly affected by surgical movements of the underlying jaw.
Materials and methods
The study included 83 young Slovene adults (45 females of average age 25 ± 9 years, and 38 males of average age 23 ± 6 years). For inclusion, patients had to have an SCIII deformity, defined using Wits appraisal as less than −2, and other cephalometric criteria. Exclusion criteria were post-traumatic deformities, greater asymmetries, syndromes, and clefts. These patients were classified into three groups according to the type of surgery carried out. The first group ( n = 45) consisted of patients who underwent bilateral sagittal split osteotomy of the mandible and setback (BSSO), the second group ( n = 10) consisted of patients who underwent Le Fort I osteotomy and advancement of the maxilla (Le Fort I), and the third group ( n = 28) comprised patients who underwent both of these procedures (BIMAX). The sex, age, weight, and height of patients in the three treatment groups are presented in Table 1 . All the operations were performed by the same surgeon. This study did not influence the clinical treatment protocols and was approved by the Slovenian National Medical Ethics Committee. Written informed consent for participation was obtained from the patients.
