Beauty and esthetics play an essential role in planning and implementation of orthognathic surgery. The objective is not only to transfer the bite into a neutral and stable occlusion, but also to create an overall esthetic and appealing appearance of the patient (1, 2). But how is esthetics defined and how can it be measured? How and to what extent should the dental arches be displaced in order to achieve not only a proper occlusal result but also an equally favorable esthetic appearance of the patient's face? In the frontal view of the face, parallelism of the bi-pupillary line and the occlusal plane as well as symmetry of the facial halves certainly play an essential role (3–5). Canut et al. describe that the “beauty of the human face”, however, depends primarily on a balance of the three prominent facial features nose, lips and chin (6). Reuther even refers to these features as the “facial esthetic triad” and thus gives them a decisive importance in facial analysis prior to orthognathic surgery (7). Brons-Mulié's soft tissue analysis, which can be performed on both cephalometric radiographs and profile photographs of the head, precisely analyzes these structures in the vertical and sagittal dimensions of the face (8). Facial harmony is achieved if the proportions of the anatomical structures to each other approximately correspond to the golden ratio (8). Since the nose as well as the lips and the chin can be strongly influenced by orthognathic surgery, the aim of the surgical procedure should be to bring these facial components into a condition of facial harmony as far as possible (8). Although in the end esthetics is always the result of a subjective assessment, achieving the proportions of facial harmony ultimately leads to a comprehensible, objective esthetics, based on the reproducible mathematical procedure of the Brons-Mulié analysis (8–10). Thus, it can be applied as an auxiliary tool to plan a harmonious facial profile in orthognathic surgery, as described by Freihofer et al. and Mooren (9, 10). Gu et al. were able to show that the lateral attractiveness of the face correlates well with frontal attractiveness. Thus, in case of a harmonious facial profile also good frontal esthetics can be expected (11). In addition, Brons-Mulié analysis can also be applied postoperatively to assess and to improve the quality of surgical results.

The question arises how often facial harmony can be achieved or at least be improved in the context of orthognathic surgery. Furthermore, the question arises if the Brons-Mulié analysis is suitable as a decision-making tool in preoperative surgical simulation.

A total of 160 patients treated with orthognathic surgery between February 2002 and February 2014 were analyzed in this retrospective study. 99 patients (62%) were female and 61 patients (38%) were male. Age at the time of surgery ranged from 13 to 61 years with a median of 23 years. 64 patients (40%) were treated for Class II malocclusion and 92 patients (57.5%) for Class III malocclusion. The remaining patients underwent surgery due to a frontal open bite in Class I occlusion. 123 of 160 patients (76.9%) underwent bimaxillary surgery, 24 patients (15%) underwent bi-sagittal split osteotomy of the mandible, and 13 patients underwent Le Fort 1 osteotomy (8.1%).

A careful planning procedure is essential to ensure favorable surgical outcome in orthognatic surgery (12). It should not only lead to a stable occlusion, but also to a functionally and esthetically acceptable overall result (2, 9, 10, 12, 15). Steenen reported that correction of a disharmonious face is at least as important to patients as oral function recovery (16). Brucoli et al. pointed out that the creation of harmonious facial aesthetics can have a positive effect on patients' compliance and psychological status (17), and Wang et al. also reported positive effects of orthognathic surgery on patients' psychological well-being (18). This further emphasizes the enormous importance of facial esthetics in orthognathic surgery.

The esthetic appearance of the face depends on symmetry, averageness and the proportions of different parts of the face to each other (5, 9). Furthermore, it is evident that lateral attractiveness of the face correlates well with frontal attractiveness (11). Since orthognathic surgery can have a significant impact on facial profile in both, the vertical and sagittal dimension of the face, Freihofer and Mooren recommended defining an aimed-at profile line prior to orthognathic surgery, to which the postoperative result on the patient should approximate as closely as possible (9). But they were also able to show that free artistic drawing of such an aimed-at profile leads to strong variations even among experts and that the result therefore depends highly on individual preferences (9). Thus, Freihofer and Mooren recommend the use of the Brons-Mulié analysis to determine an aimed-at profile as objectively as possible in order to achieve reproducible and attractive postoperative soft tissue esthetics (9, 10).

With the concept of facial harmony, the Brons-Mulie analysis offers a simple tool for assessing facial esthetics, which can be used in addition to standard cephalometric analysis in the planning procedure prior to orthognathic surgery (8). In the vertical dimension the analysis offers a valuable supplement which allows a direct assessment of the vertical facial height. In the sagittal dimension the tool provides an evaluation of the soft tissue pogonion which in contrast to cephalometric analysis is independent of the angulation of the anterior cranial base (8). Further, the tool complements standard cephalometric analysis with an assessment of the lip position.

In the present study, a preoperative Brons-Mulié analysis was carried out preoperatively for all 160 patients in order to achieve an approximately harmonious profile line by performing orthognathic surgery. The outcome was assessed with a second postoperative Brons-Mulié analysis of the face. Data of this work show that despite preoperative application of the Brons-Mulie analysis as a decision-making tool, postoperative facial harmony in the vertical and sagittal dimension is not easy to achieve in every case. Table 1 and Figure 1 show that only the vertical dimension and the lower lip inclination could be markedly improved by 20% and 27%, respectively. In contrast, the Mandibula inclination could only be improved by 6% and the upper lip inclination even showed a slight deterioration of 7%. This could be due to the fact that the Brons-Mulié analysis can indeed visualize preoperative problems, but cannot determine exactly how many millimeters or degrees must be corrected in order to achieve the normal range of values. Furthermore, it is usually not possible to change a single parameter without influencing other parameters. For example, an elongated chin cannot be moved arbitrarily far cranially at the expense of the gingival smile line. Thus, sometimes values outside the normal range have to be accepted during planning and surgery.

Nevertheless, by objectifying esthetic problems and limitations for surgical movements, the Brons-Mulié method can help to favorably influence planning and surgical outcome. For example, in case of a low Mandibula inclination in class II patients, there is clear evidence that surgical advancement of the chin results in a better esthetic outcome (19–22). In the case of a severe chin retraction, the Brons-Mulié analysis can help to change a surgical plan from a pure mandibular advancement to a bimaxillary procedure. Using bimaxillary surgery, the chin can be moved further anteriorly, also by rotating the bimaxillary block around a transversal axis (23). Thus, an esthetically more favorable result can be achieved in many cases (24). Another example is the long face constellation with an increased mandibular inclination, which can be typically seen in Class III patients (25). In such cases, Brons-Mulié analysis may indicate the need to perform a bimaxillary procedure with a rotation of the bimaxillary block and a moderate setback of the mandible instead of a pure advancement of the maxilla, which even leads to an esthetically more favorable result of the facial profile (26, 27).

But the Brons-Mulié analysis is not only suitable as a decision-making tool. Using Fisher's exact test (Table 2) and logistic regression analysis (Tables 3, 4 and Figure 3) it was possible to show that certain initial conditions were obviously more difficult to correct by orthognathic surgery than others.

Table 3 shows that patients with an Angle Class III could often not be corrected sufficiently in the vertical dimension, while Class II patients often could not be treated successfully in the sagittal dimension with respect to the Mandibula inclination. Looking at the results of the logistic regression analysis, it becomes apparent that a preoperative long face constellation (Table 4: Success vertical/Pre-op. vertical: LF) and a preoperatively reduced Mandibula inclination (Table 4: Success MI/Pre-op. MI: L) had a significant influence on success. Odds ratio for both preoperative conditions was only 0.11, meaning that these constellations could only be corrected into the normal range with a significantly reduced probability. Thus, one constellation that was difficult to correct was the typical class III patient with a characteristic long face situation due to his progeny. Since bimaxillary surgery is often performed in anterior and caudal direction to protect the upper airway (28) and at the same time impaction of the jaws against the cranial base is complex and rather rarely performed, it becomes clear that it is difficult to sufficiently reduce an overly long lower face within the scope of bimaxillary surgery alone (Figure 4). The same applies to a constellation of a too low mandibula inclination. Although the pogonion can be brought much further anteriorly by bimaxillary surgery, in many cases it cannot be brought forward enough to ensure that the Mandibula inclination actually reaches the normal range (Figure 5). Both problems can be solved by an additional genioplasty (29), which can be performed as a bone reducing procedure in case of long face situations in Class III patients and as a bone augmenting procedure in Class II patients with decreased Mandibula inclination (30, 31). Genioplasty can be performed either simultaneous to bimaxillary surgery or during the clinical course after 6 months (32). In the latter case, it is again useful to perform a further Brons-Mulié analysis to assess the chin.

Brons-Mulié analysis provides a simple tool for esthetic assessment of the facial soft tissue profile in addition to standard cephalometric analysis, which can be useful prior to orthognathic surgery. The postoperative application of the Brons-Mulié analysis can help to assess the quality of outcome and to identify possible planning deficits in orthognathic surgery. Often, a chin correction is an excellent additional procedure to fulfil remaining facial treatment objective after correction of the dentoskeletal mal-relation.