Virgilio F. Ferrario

Distance from symmetry : a three-dimensional evaluation of facial asymmetry

PURPOSE A new method for the quantification of facial asymmetry has been developed and applied to a group of 80 young, healthy, white adults with no craniofacial, dental, or mandibular disorders. The method calculates an asymmetry vector (distance from the symmetry) that allows both the quantification of the absolute degree of asymmetry and its three-dimensional direction and verse. METHODS For each subject, the three-dimensional coordinates of 16 standardized soft-tissue facial landmarks (trichion, nasion, pronasale, subnasale, B point, pogonion, eye lateral canthi, nasal ala, labial commissure, tragus, gonion) were automatically collected using a noninvasive instrument. The coordinates underwent a four-step analysis: 1) calculation of the plane of symmetry, the facial centers of gravity, and the asymmetry vector in each subject; 2) calculation of the mean absolute asymmetry in each sample; 3) calculation of the mean asymmetry vector (resultant vector) in the population; and 4) calculation of the separate contributions of the single facial structures to the facial asymmetry. RESULTS A certain degree of soft-tissue facial asymmetry was found both in the individuals and in the global population, and it was evident especially in the middle (tragus) and lower (gonion) thirds of the face. The right side of face was larger than the left side.

Active range of motion of the head and cervical spine: a three-dimensional investigation in healthy young adults.

Purpose. To define reference values for head–cervical range of motion (ROM) in healthy young adults, to assess the effect of sex, and to quantify the separate contribution of other body districts.

Preliminary Evaluation of an Electromagnetic Three-Dimensional Digitizer in Facial Anthropometry

OBJECTIVE In this investigation, the precision of a commercial three-dimensional digitizer in the detection of facial landmarks in human adults was assessed. METHODS Fifty landmarks were identified and marked on the faces of five men, on five women, and on a stone cast of the face of one man. For each subject, the three-dimensional coordinates of the landmarks were obtained twice using an electromagnetic three-dimensional digitizer, and the duplicate digitizations were superimposed using common orientations and centers of gravity. Metric differences between homologous landmarks were assessed, and Dahlbergs error was computed. RESULTS For both men and women, the error was 1.05% of the nasion-midtragion distance, while for the cast, it was 0.9%. When the duplicate digitizations were used to mathematically reconstruct the faces, and several distances, angles, volumes, and surfaces were computed, more than 80% of the measurements had coefficients of variation lower than 1%. CONCLUSIONS The digitizer can assess the coordinates of facial landmarks with sufficient precision, and reliable measurements can be obtained.

Three-dimensional analysis of active head and cervical spine range of motion: effect of age in healthy male subjects.

OBJECTIVE To assess the effect of age on active head-cervical range of motion in healthy men. DESIGN Three-dimensional cervical motion ranges and patterns were measured in 70 men. BACKGROUND The effect of age on cervical range of motion is still discussed. METHOD Twenty adolescent (mean age 16 year), 30 young adult (mean age 23 year), and 20 mid-aged (mean age 37 year) men performed maximal head and cervical spine flexion-extension, lateral bending, and axial rotation. Movements were detected using a digital optoelectronic instrument. Maximum head-cervical spine and thoracic motions were separated. RESULTS Flexion and extension were larger in the adolescents and young adults (130-132 degrees ) than in the mid-aged men (117 degrees ). Thoracic movement increased as a function of age. Lateral bending was symmetric, associated with head-cervical rotation and extension, and larger in adolescents (85 degrees ) than in young (77 degrees ) and mid-aged adults (79 degrees ). Axial rotation was symmetric, associated with flexion-extension and lateral bending, and similar in the three age groups (respectively, 160 degrees, 155 degrees, 153 degrees ). CONCLUSIONS Active head-cervical range of motion reduced between 15 and 45 years of age in men. Relevance The present data can be used as a reference for cervical range in motion in men between 15 and 45 years.

Calcification of the stylohyoid ligament: incidence and morphoquantitative evaluations.

To study the incidence of calcification of the stylohyoid ligament, 286 orthopantomographs were analyzed. All patients had no symptoms. The total incidence of calcification was noted to be high, at 84.4%. The number and the length of calcifications increased with age, and there was no relationship to sex or mandibular size. The phenomenon is often evident bilaterally. The variety of results reported in the references depends on different criteria in radiographic evaluation and in patient selection.

Occlusion and center of foot pressure variation: Is there a relationship?

The influences of head and body posture on the mandibular rest position, the range of functional movements, and the initial tooth contact have been documented. In this investigation, the modifications of the position of the center of foot pressure during natural standing were studied in 30 women. The subjects were divided into three groups: healthy women (control), women with an asymmetric (unilateral) Angle class II malocclusion, and women with temporomandibular disorders. Data were acquired in 30-second trials by use of a force plate that allowed a separate assessment of each foot while the subjects maintained different dental positions: rest position; centric occlusion; maximum clench; occlusion on two cotton rolls placed on the mandibular teeth distal to the canines; and maximum clench on two cotton rolls. Bivariate analysis was used to compute the mean values and relevant variability for the center of foot pressure location during each trial. The results demonstrated that the modifications of foot center of pressure were not influenced by temporomandibular disorders and asymmetric malocclusion or by different dental positions.

Age- and sex-related changes in the normal human ear.

The objective of this study was to supply information about: (1) normal sex-related dimensions of ears (linear distances and ratios, area); (2) left-right symmetry; and (3) growth changes between childhood and old age. The three-dimensional coordinates of several soft-tissue landmarks on the ears and face were obtained by a non-invasive, computerized electromagnetic digitizer in 497 male and 346 female healthy subjects aged 4-73 years. From the landmarks, paired ear width and length, the relevant ratios, ear areas and angles relative to the facial midline, as well as indices of left-right symmetry, were calculated, and averaged for age and sex. Comparisons were performed by factorial analysis of variance. All ear dimensions were significantly larger in men than in women (p<0.001). A significant effect of age was found (p<0.001), with larger values in older individuals. The ear width-to-length ratio and the sagittal angle of the auricle significantly decreased as a function of age (p<0.001) but without sex-related differences. On average, the three-dimensional position of ears was symmetric, with symmetry coefficients ranging between 92% and 96%. Asymmetry was found in the sagittal angle of the auricle (both sexes), in the ear width-to-length ratio and ear width (men only). Data collected in the present investigation could serve as a data base for the quantitative description of human ear morphology and position during normal growth, development and aging. Forensic applications (evaluations of traumas, craniofacial alterations, teratogenic-induced conditions, facial reconstruction, aging of living and dead persons, personal identification) may also benefit from age- and sex-based data banks.

Accuracy and Reproducibility of a 3-Dimensional Stereophotogrammetric Imaging System

PURPOSE To test the accuracy and reproducibility of a 3-dimensional (3D) stereophotogrammetric imaging system for measuring the facial soft tissues of healthy subjects. MATERIALS AND METHODS Three-dimensional soft tissue facial landmarks were obtained from the faces of 10 adult subjects, by use of a 3D stereophotogrammetric imaging system (Vectra; Canfield Scientific, Fairfield, NJ). Sixteen linear measurements were computed. Systematic and random errors between operators, calibration steps, and acquisitions were calculated. RESULTS No systematic errors were found for all performed tests (P > .05, paired t test). The method was repeatable, and random errors were always lower than 1 mm, except for the distance from cheilion to cheilion. Repeated sets of acquisition showed random errors up to 0.91 mm, without systematic biases. CONCLUSION The 3D stereophotogrammetric imaging system can assess the coordinates of facial landmarks with good precision and reproducibility. The method is fast and can obtain facial measurements with few errors.

Three-dimensional facial morphometric assessment of soft tissue changes after orthognathic surgery.

OBJECTIVE In this study, a 3-dimensional system with landmark representation of the soft tissue facial surface was applied for the evaluation of facial changes occurring after orthognathic surgery in 5 patients. STUDY DESIGN Standardized facial landmark acquisitions were performed before and 1 year after surgery (combined maxillary Le Fort I and sagittal mandibular osteotomies). The 3-dimensional coordinates of 22 facial soft tissue points were collected on each subject through use of a computerized noninvasive method and used to calculate a set of selected parameters. RESULTS Three-dimensional soft tissue analysis of patients was in general agreement with the type of surgery performed, with volumetric contraction of the lower facial third and expansion of the middle facial third. Moreover, negative effects of surgery were quantified (eg, an increase in alar base dimensions); the global asymmetry of facial soft tissues was increased by intervention, but asymmetry in the lower facial third was reduced. CONCLUSIONS The method used in this study proved useful as a complementary diagnostic aid, enabling quantitative evaluation of the final soft tissue results of surgery, which were proportional to those expected on the basis of the type of treatment and skeletal data.

Soft-tissue facial morphometry from 6 years to adulthood: a three-dimensional growth study using a new modeling.

A recently introduced three-dimensional computerized system with landmark representation of the soft-tissue facial surface allows noninvasive and fast quantitative study of facial growth. The aims of the present investigation were (1) to quantify growth changes in soft-tissue facial morphology, (2) to evaluate sex differences in growth patterns, and (3) to provide reference data for selected angular and linear measurements that could be of interest for the objective analysis of maxillofacial surgery or orthodontic patients. The three-dimensional coordinates of 22 standardized facial landmarks were automatically collected by automated infrared photogrammetry using the three-dimensional facial morphometry method in a mixed longitudinal and cross-sectional study, in which 2023 examinations were obtained in 1348 healthy nonpatient subjects between 6 years of age and young adulthood. Selected parameters (angles, linear distances, and ratios) were calculated and averaged for age and sex. Male values were compared with female values by means of Students t test. Within each age group, linear distances were significantly larger in boys than in girls (p < 0.05) with some exceptions coinciding with the earlier female growth spurt, whereas angular measurements did not show a corresponding sexual dimorphism. Linear distances in girls had almost reached adult dimensions in the 12-to-13-year-old age group, whereas in boys a large increase was still to occur. This was most evident in the middle third of the face, where both sexes showed almost the same dimension and amount of growth up to the age of 13, with significant differences afterward, boys being larger than girls. On the contrary, in the lower third of the face, significant differences occurred throughout the whole investigated period, boys being always larger than girls. The male versus female angular comparison reflected the differential timing in attainment of adult proportions. The three-dimensional facial morphometry method allowed the noninvasive evaluation of a large sample of nonpatient subjects, leading to the definition of three-dimensional normative data about facial soft tissues. The method could supplement more invasive radiographic evaluations, allowing frequent examinations of children and adolescents before and during treatment, as well as in the follow-up.