Comparison of unilateral chewing movements vs. dental guidance through the dental guidance ratio.

STATEMENT OF PROBLEM: Limited knowledge exists about the interaction between dental morphology and mandibular excursive movements. PURPOSE: This study evaluated dental guidance in lateral excursive movement and its relationship to jaw motion in unilateral chewing. MATERIAL AND METHODS: Three-dimensional mandibular movement paths (in lateral guiding movements and in the final part of a monolateral chewing stroke) were collected with automated infrared motion analysis in 22 subjects with complete, permanent dentitions. On 2 traces selected from the recorded movements, the angular values projected in all planes of space obtained from 2 lines tangent to a point at a distance of 2.5 mm from maximum intercuspation were used to calculate a canine and a molar dental guidance ratio (DGR). Descriptive statistics were computed for the DGRs in the 3 spatial planes. RESULTS: Assuming masticatory movements of any given subject are restricted or guided by dental anatomy, a value below 100% of the DGR was expected. This was true for the frontal plane only, with mean values of approximately 80% (working-side movements, canines, and molars) and approximately 60% (nonworking-side movements for both molars and canines). In the horizontal and sagittal planes, mean values between 102% and 137% were found. CONCLUSION: Within the limitations of this study, masticatory movement was within the physical borders dictated by dental anatomy in the frontal plane only.

Harmonic analysis of facial profiles: a 10-year evaluation.

A 10-year longitudinal evaluation was performed of the morphology of soft tissue facial profiles of 14 healthy adults (8 female and 6 male; mean age at the second evaluation, 34 years). Standardized left-side photographs were taken of each subject, and facial profiles were traced between trichion and cervical point. The line joining the 2 landmarks was set as the baseline, and each outline was automatically digitized and mathematically reconstructed by a 20-harmonic elliptic Fourier series expansion. Shape modifications were quantified by calculating the morphologic distance between the Fourier reconstruction of each facial profile in the 2 examinations. The area enclosed in each facial outline was automatically computed, and the difference between the soft tissue areas obtained in the 2 examinations was calculated. On average, significant longitudinal differences were found in both men and women for shape differences (P < 0.05), while size variations were significant only in men. While the 10-year increase in size was significantly (P < 0.01) larger in men than in women, no sex-related differences were found for shape modifications. Between the third and the fourth decades of life, both men and women experience some modifications in their facial soft tissues. While shape changes in both sexes, size changes are particularly evident in men and less manifest in women, who show greater variability in the amount of change that takes place.

Morphometry of the orbital region: a soft-tissue study from adolescence to mid-adulthood.

The objective of this study was to gain information about normal sex-related linear and angular dimensions of the orbital region; left-right symmetry; and growth changes between adolescence and mid-adulthood. The three-dimensional coordinates of several soft-tissue landmarks on the orbits and face were obtained by an electromagnetic digitizer in 40 male and 33 female adolescents aged 12 to 15 years, 73 female and 89 male young adults aged 19 to 30 years, and 41 male and 38 female adults aged 31 to 56 years. From the landmarks-binocular and intercanthal widths; paired height and inclination of the orbit relative to both the true horizontal (head in natural head position) and Frankfurt plane; length and inclination of the eye fissure; and the orbital height to eye fissure length ratio were calculated and averaged for age and sex. Comparisons were performed by factorial analysis of variance. Both the linear dimensions and the angular values were significantly larger in male subjects than in female subjects of corresponding age (p < 0.05). A significant effect of age was found (p < 0.05): while the linear distances and the orbital height-to-length ratio were greater in older people of the same sex, the inclination of the eye fissure decreased as a function of age. Both orbital inclinations were larger in the young adult group than in the adolescent and middle-aged groups. On average, the paired measurements were symmetrical, with similar values within each sex and age group. Data collected in this investigation could serve as a database for the quantitative description of human orbital morphology during normal adolescent and adult growth.

Restorative and orthodontic treatment of maxillary peg incisors: a clinical report.

This clinical report describes a combination treatment approach to an esthetic defect that resulted from diastemata and peg-shaped lateral incisors. Minor tooth movement was achieved through the use of a removable orthodontic appliance and orthodontic rubber band, and full-coverage PFM crowns were placed on the lateral incisors. These complementary orthodontic and restorative procedures successfully corrected the defect.

Normal growth and development of the lips: a 3-dimensional study from 6 years to adulthood using a geometric model.

A 3-dimensional computerised 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 provide reference data for selected dimensions of lips (linear distances and ratios, vermilion area, volume); (2) to quantify the relevant growth changes; and (3) to evaluate sex differences in growth patterns. The 3-dimensional coordinates of 6 soft-tissue landmarks on the lips were obtained by an optoelectronic instrument in a mixed longitudinal and cross-sectional study (2023 examinations in 1348 healthy subjects between 6 y of age and young adulthood). From the landmarks, several linear distances (mouth width, total vermilion height, total lip height, upper lip height), the vermilion height-to-mouth width ratio, some areas (vermilion of the upper lip, vermilion of the lower lip, total vermilion) and volumes (upper lip volume, lower lip volume, total lip volume) were calculated and averaged for age and sex. Male values were compared with female values by means of Student's t test. Within each age group all lip dimensions (distances, areas, volumes) were significantly larger in boys than in girls (P < 0.05), with some exceptions in the first age groups and coinciding with the earlier female growth spurt, whereas the vermilion height-to-mouth width ratio did not show a corresponding sexual dimorphism. Linear distances in girls had almost reached adult dimensions in the 13-14 y age group, while in boys a large increase was still to occur. The attainment of adult dimensions was faster in the upper than in the lower lip, especially in girls. The method used in the present investigation allowed the noninvasive evaluation of a large sample of nonpatient subjects, leading to the definition of 3-dimensional normative data. Data collected in the present study could represent a data base for the quantitative description of human lip morphology from childhood to young adulthood.

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 Student's 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.

The effects of a single intercuspal interference on electromyographic characteristics of human masticatory muscles during maximal voluntary teeth clenching.

In 13 healthy subjects (eight men and five women, mean age, 22 years), an aluminum intercuspal interference (height, 0.25 mm) was placed on the maxillary right first premolar to study its effect on the contractile symmetry of the right and left masseter and anterior temporalis muscles when measured through a Percentage Overlapping Coefficient (POC), derived from surface electromyographic recordings of maximum voluntary teeth clenching. Additionally, and to estimate the potential of the experimental intercuspal interference to induce lateral displacement of the mandible, a Torque Coefficient (TC) was derived from surface electromyographic recordings. The conclusion was that the experimental occlusal interference gave rise to asymmetric contractile activity in the studied mandibular elevator muscles as well as a potential to displace the mandible in a lateral direction.

A three-dimensional computerized mesh diagram analysis and its application in soft tissue facial morphometry.

A modified computerized mesh diagram analysis that allows rapid and independent quantifications of soft tissue facial size and shape in the three-dimensional space is presented. Normal references are provided, and the application of the method is also exemplified by the analysis of two maxillofacial surgical patients. The Three-Dimensional Facial Morphometry method has been used for the collection of the x, y, z coordinates of 22 soft tissue landmarks in 50 men and 50 women (all healthy young white adults). The method detects the three-dimensional coordinates of retroreflective, wireless markers positioned on selected facial landmarks with two charge-coupled device cameras, working in the infrared field. The midpoint between the right and left tragus landmarks served as the origin of the coordinate axes, and the landmark coordinates were rotated, setting the intercantheal line horizontal on both the frontal and the horizontal planes, and the Camper's plane inclined at -7.5 degrees on the sagittal plane. A standardized mesh of equidistant horizontal (dimension: half the upper face width), vertical (half the vertical projection of upper face height), and anteroposterior (half the horizontal projection of upper face depth) lines was consequently constructed. The lattice was replicated on the entire face and comprised 84 parallelepipeds. Both male and female reference meshes had a harmonious and symmetric appearance, with gender differences in facial size but not in facial shape. The standard normal reference was superimposed on the patient's tracing, and the global (size plus shape) difference was then evaluated by the calculation of the relevant displacement vectors for each soft tissue landmark. A global difference factor was calculated as the sum of the modules of all the displacement vectors. Consequently, a size normalization was performed, and the shape difference (size-standardized) was then evaluated by the calculation of new relevant displacement vectors for each landmark, as well as a shape--global difference vectors.

Quantitative description of the morphology of the human palate by a mathematical equation.

OBJECTIVE: To derive a three-dimensional mathematical description of normal human hard tissue palatal size and shape. METHODS: The maxillary dental casts of 30 adolescents free from respiratory problems, who had a complete (28 teeth) permanent sound dentition with normal occlusion, were studied. The x, y, z coordinates of several standardized palatal and dental landmarks were obtained with a computerized three-dimensional digitizer. Palatal landmarks were used to derive a mathematical equation of palatal shape in the frontal and sagittal planes. Palatal width, length, frontal and sagittal heights, and sagittal slope, as well as dental arch transverse and anteroposterior dimensions, were computed. RESULTS: Neither the size nor the shape of the palate was significantly influenced by gender. Only the intercanine distance was larger (p < .025) in males than in females. CONCLUSIONS: Data collected in the present investigation could represent a first database for the quantitative description of normal human palatal morphology in subjects with a complete permanent dentition.

Craniofacial growth: a three-dimensional soft-tissue study from 6 years to adulthood.

Normal facial growth and development was analyzed through indirect anthropometry in a mixed longitudinal and cross-sectional investigation; 2,023 examinations were performed on 1,156 healthy Caucasian children and adolescents between 6 and 17 years of age and on 191 young adults. Three-dimensional coordinates of 22 facial landmarks were collected with the Three-Dimensional Facial Morphometry method by automated infrared photogrammetry. Selected three-dimensional parameters (linear distances, angles, and a ratio), describing facial height, width, depth, and convexity on the horizontal plane, were calculated and averaged for age and sex. Within each age group, most linear distances were significantly larger in males than in females, with some exceptions in the 11 to 12 age group, where female growth velocity showed a spurt. In females of the 14 to 15 age group the face had almost completed growth; in males of the same age group, a large increase was still to occur to attain adult values. The sexual dimorphism of the parameters calculated did not appear in the different parts of the face to the same extent: a large part of male facial preponderance occurred in the lower third of face. From 6 years of age to adulthood, the soft-tissues in the facial lower third increased by about 23% (males) and 17% (females), in the middle third by about 18% (males) and 13% (females), and in the upper third by about 16% (males) and 9% (females). The male vs. female comparisons within each age group suggested a sexual dimorphism in the timing of soft-tissue facial growth, but an overall similar attainment of different adult dimensions.

Facial volume changes during normal human growth and development.

BACKGROUND: To describe normal soft tissue growth and development of the human face through volume changes and to assess the presence of sexual dimorphism. METHODS: Facial landmark identifications (2,023) were performed on 1,347 healthy Caucasian children and adolescents, ages 6-18 yr, and young adults, ages 19-32 yr. Three-dimensional coordinates of 22 facial landmarks were collected by automated infrared photogrammetry. Facial volumes and selected linear distances and ratios were calculated and averaged for age and sex. RESULTS: Whereas in females in the 14-15 age group, the face had almost completed its growth relative to the adult group, in males a large increase was still to occur, in general agreement with previous reports on craniofacial growth, which suggested a strong tendency in males for growth to continue for several years beyond that seen in females. The male vs. female comparison reflected the different growth patterns. On average, within each age group volumes were significantly larger in males than in females, with some exceptions in the 11-12 age group, where female growth velocity showed a spurt. Sexual dimorphism in facial volume did not appear in different parts of the face to the same extent: a large part of male facial volume preponderance occurred in the lower third of the face. CONCLUSIONS: From 6 yr of age to adulthood, facial soft tissues increased their volumes by >40%, with different growth patterns in boys and girls.

Three-dimensional study of growth and development of the nose.

OBJECTIVE: The aim of this study was to describe normal nasal growth in a large sample of boys and girls from 6 to 14 years of age, to compare nasal development at 14 years of age with its adult dimensions, and to evaluate differences in growth patterns between males and females. DESIGN: Growth and development of the nose were analyzed through the three-dimensional facial morphometry method. One thousand thirteen examinations were performed on 402 children between 6 and 14 years of age and on 101 adults. Three-dimensional coordinates of five nasal landmarks were collected. Eleven parameters including nasal volume and external surface were calculated and averaged for age and sex. RESULTS: Volume, surface, and linear distances were larger in males than in females, with the exception of the 11-to-12 age group, where a sharp female growth spurt was present. In males, the growth spurt was broader, and continued to 13 years of age at a nearly steady rate. Statistically significant gender differences could be found both in the adult group and before the adolescent growth spurt. CONCLUSIONS: Our findings are in general agreement with previous reports on craniofacial growth, which suggested a strong tendency in males for growth to continue for several years beyond that seen in females.

A three-dimensional non-invasive study of head flexion and extension in young non-patient subjects.

Head flexion and extension movements near the natural head position (NHP) were analysed for the location of the mean instantaneous centre of rotation (ICR). Forty-six healthy young adults (30 women and 16 men) with sound dentitions, free from cranio-cervical disorders, performed habitual movements that were automatically detected and measured by an infrared three-dimensional motion analyser. ICR and curvature radius were calculated for each movement and subject. In both extension and flexion, ICR position changed during the motion. The movement was symmetrical in all subjects. No gender or flexion/extension differences were found for both ICR position and relevant curvature radius. On average, ICR relative to NHP soft-tissue nasion was located at about 150% of the soft-tissue nasion-right tragus distance, with an angle of about 220 degrees relative to the true horizontal. Results suggest that head flexion or extension is always performed with a combination of rotation (atlanto-occipital joint) and translation (cervical spine) even in the first degrees of motion. Moreover, NHP at rest seems to be some degree more flexed and anterior than head position during movements. These relative positions and their muscular determinants could also influence mandibular posture at rest and during functional movements.

Soft tissue facial morphology related to headform: a three-dimensional quantitative analysis in childhood.

The object of this investigation was to determine whether children of the same age with different headforms differ in their three-dimensional soft-tissue facial characteristics. The three-dimensional coordinates of 22 standardized facial landmarks were automatically collected in a sample of 70 boys and 71 girls age 11 to 13 years attending a junior high school. From the collected landmarks, several three-dimensional facial angles, linear distances, linear distance ratios, and volumes were calculated. For each subject the cephalic index (maximal head breadth/ maximal head length x 100) was computed and three groups of measurements for each sex were obtained (dolicho-, meso- and brachycephalic). A two-way factorial analysis of variance compared the effects of sex and headform, and the interaction sex x headform. On average, boys had significantly (P < or = 0.05) longer and wider faces than girls, with a larger lower third facial volume relative to middle third facial volume. A significant (P < or = 0.05) effect of headform over facial morphology was found for all angles with a prevalent axial orientation. Conversely, no effect was demonstrated for angles with a sagittal orientation, nor for any other considered parameters. For each sex, the dolichocephalic children had smaller values than the brachycephalic children (i.e., more convex faces in the left-right direction), while the mesocephalic children had intermediate values. No sex x headform interactions were found. Results confirm that a different headform (skull) is associated with a different three-dimensional facial morphology (combined effect of skull and soft tissues), but without size differences.

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.

Three-dimensional facial morphometry and conventional cephalometrics: a correlation study.

The purpose of this study was to compare the correlation between three-dimensional soft tissue measurements obtained with three-dimensional digital infrared photogrammetry and two-dimensional data obtained with conventional cephalometry. Facial morphometry was investigated in a group of 20 healthy young men using both systems on each subject. From the lateral radiographs, conventional two-dimensional cephalometric hard and soft tissue data were calculated, while three-dimensional linear and angular soft tissue measurements were computed from the infrared photogrammetry. The correlations between the two sets of measurements were calculated. Three-dimensional soft tissue measurements correlated to cephalometric data primarily contained information useful for esthetic analysis. The soft tissue infrared measurements also allowed evaluation of the general hard tissue situation. Since the soft tissue measurements are calculated with a noninvasive system, they could be computed more frequently during treatment and be used to supplement pretreatment and posttreatment radiographs.

Fourier analysis of human soft tissue facial shape: sex differences in normal adults.

Sexual dimorphism in human facial form involves both size and shape variations of the soft tissue structures. These variations are conventionally appreciated using linear and angular measurements, as well as ratios, taken from photographs or radiographs. Unfortunately this metric approach provides adequate quantitative information about size only, eluding the problems of shape definition. Mathematical methods such as the Fourier series allow a correct quantitative analysis of shape and of its changes. A method for the reconstruction of outlines starting from selected landmarks and for their Fourier analysis has been developed, and applied to analyse sex differences in shape of the soft tissue facial contour in a group of healthy young adults. When standardised for size, no sex differences were found between both cosine and sine coefficients of the Fourier series expansion. This shape similarity was largely overwhelmed by the very evident size differences and it could be measured only using the proper mathematical methods.