morphometric measurements were performed on
digital stereophotogrammetric images, and facial soft
tissue asymmetry quantified. Data were obtained
longitudinally and compared to those obtained in
healthy, control subjects.
2. Materials and methods
The facial soft tissues of a 20-year-old man were
imaged by using the VECTRA M3 3D Imaging System
(Canfield Scientific, Fairfield, NJ, USA). The instrument is
a stereophotogrammetric unit made up of three pods.
In each pod, there are two cameras that photograph
the subject’s face from different points of view (Fig. 1).
A previous calibration permits to obtain the metrical
data of the facial surface (from ear to ear, from trichion
to neck) in a few milliseconds. Files can be exported
and elaborated with proprietary and custom software.
In particular, the Mirror® Vectra Software (Canfield
Scientific, Fairfield, NJ, USA) was used in the present
investigation [4].
The patient had a diagnosis of skeletal Class III
dysmorphism and was a candidate for a surgical
intervention of bimaxillary osteotomy. The patient was
analysed in 4 different stages (preoperative, at the end of
orthodontic treatment, and postoperatively 6, 12 and 24
months after surgery). On each occasion, he was imaged
while seating with a natural relaxed expression (closed
lips, teeth in slight contact).
A group of 23 subjects were selected from the
Laboratory archive to form the control group (13 females
and 10 males, mean age 26, SD 6.8 years); they all had
a diagnosis of dentoskeletal Class I and no history of
traumas or alterations in the facial bones. Acquisitions
were obtained after the patients’ written informed
consent and did not involve any invasive, painful or
dangerous procedure. All procedures were performed as
previously described in the literature [12,13]. In brief, on
each facial image, a set of 50 anthropometric landmarks
were identified and digitized. Afterwards, following the
protocol validated by Codari et al. [3], the anterior part of
the face was delimitated by the following 10 landmarks:
trichion (tr); right and left frontotemporal (ft); right and
left zygion (zy); right and left tragion (t); right and left
gonion (go); gnathion (gn) (Fig. 2).
Each half-face was split into three thirds (upper, middle
and lower part); the mid facial plane of maximum
symmetry was automatically obtained, and the two
facial halves superimposed. The software automatically
calculated the Root Mean Square (RMS) distance values
among the two facial halves separately for each facial
third, thus providing a set of symmetry values. The
lower the value, the higher the symmetry. Ideally, very
symmetrical areas should have an RMS value of 0.
To assess the longitudinal modifications, the preopera-
tive image was superimposed on those obtained at 6, 12
and 24 months after the intervention, and RMS values
obtained. The software also produced colorimetric maps
which highlight the modifications in an intuitive way.
The same procedures were followed for the subjects of
the control group, and descriptive statistics (mean, SD)
were obtained for regional facial asymmetry and used to
calculate z-scores (Patient value minus reference mean
value divided by reference SD). The smaller the z-score,
the similar the patient is to the control group.
IRB Approval
Stomatology Edu Journal
Figure 1. VECTRA M3 3D Imaging System (Canfield Scientific, Fairfield, NJ,
USA): the three pods that surround the subject can be seen.
SOFT-TISSUE FACIAL ASYMMETRY BEFORE AND AFTER ORTHOGNATHIC SURGERY:
APPLICATION OF A NEW 3D PROTOCOL
Figure 2. Landmarks used for symmetry analysis. (Written consent for the
publication of this image was obtained).
The work described was carried out in accordance with
The Code of Ethics of the World Medical Association
(Declaration of Helsinki). Informed consent was obtained
from all patients, and their privacy rights observed. Ethi-
cal approval was given by University ethics review board.
3. Results
Table 1 illustrates the time-related variations in facial
asymmetry in the analysed patient. A trend of improve-
ment in his facial symmetry was observed during the
follow-up examinations.
With regards to the lower third of the face, the RMS value
obtained from the overlap of the pre-surgical images
of the two hemifaces was 1.2 mm; this value decreased
in the subsequent acquisitions made after 6, 12 and 24
months. A reduction in the RMS values was also found in
the middle and upper facial thirds.
When the facial asymmetry of the patient was compared
to that of healthy, reference subjects using z-scores, a
trend of improvement was seen after surgery (Fig. 3). The
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