Novel Anterior Cranial Base Area for Voxel-Based Superimposition of Craniofacial CBCTs.

A standard method to assess changes in craniofacial morphology over time is through the superimposition of serial patient images. This study evaluated the reliability of a novel anterior cranial base reference area, principally including stable midline structures (EMACB) after an early age, and compared it to the total anterior cranial base (TACB) and an area including only midline structures (MACB). Fifteen pairs of pre-existing serial CBCT images acquired from growing patients were superimposed with all techniques by applying a best-fit registration algorithm of corresponding voxel intensities (Dolphin 3D software). The research outcomes were the reproducibility of each technique and the agreement between them in skeletal change detection, as well as their validity. The TACB and EMACB methods were valid, since the superimposed midline ACB structures consistently showed adequate overlap. They also presented perfect overall reproducibility (median error < 0.01 mm) and agreement (median difference < 0.01 mm). MACB showed reduced validity, higher errors, and a moderate agreement to the TACB. Thus, the EMACB method performed efficiently and mainly included the stable midline ACB structures during growth. Based on the technical, anatomical, and biological principles applied when superimposing serial 3D data to assess craniofacial changes, we recommend the EMACB method as the method of choice to fulfil this purpose

Reliability of Different Anterior Cranial Base Reference Areas for Voxel-Based Superimposition.

The study aimed to evaluate the reliability and reproducibility and compare the outcomes of two 3D voxel-based superimposition techniques for craniofacial CBCT images, using anterior cranial base areas of different extent as references. Fifteen preexisting pairs of serial CBCTs (initial age: 11.7 ± 0.6 years; interval: 1.7 ± 0.4 years) were superimposed on total anterior cranial base (TACB) or middle anterior cranial base (MACB) structures through the Dolphin 3D software. The overlap of the reference structures was assessed visually to indicate reliability. All superimpositions were repeated by the same investigator. Outcomes were compared to assess the agreement between the two methods. Reliability was perfect for the TACB and moderate for the MACB method (p = 0.044). Both areas showed good overall reproducibility, though in individual cases there were notable differences for MACB superimpositions, ranging from -1.84 to 1.64 mm (TACB range: -0.48 to 0.31 mm). The overall agreement in the detected T0/T1 changes was also good, though it was significantly reduced for individual measurements (median < 0.01 mm, IQR: 0.46 mm, range: -2.81 to 0.73 mm). In conclusion, the voxel-based superimposition on TACB was more reliable and showed higher reproducibility than the superimposition on MACB. Thus, the extended anterior cranial base area is recommended for the assessment of craniofacial changes

Valid 3D surface superimposition references to assess facial changes during growth.

Currently, the primary techniques applied for the assessment of facial changes over time utilize 2D images. However, this approach has important limitations related to the dimensional reduction and the accuracy of the used data. 3D facial photography has been recently introduced as a risk-free alternative that overcomes these limitations. However, the proper reference areas that should be used to superimpose serial 3D facial images of growing individuals are not yet known. Here, we tested various 3D facial photo superimposition reference areas and compared their outcomes to those of a standard anterior cranial base superimposition technique. We found that a small rectangular area on the forehead plus an area including the middle part of the nose and the lower wall of the orbital foramen provided comparable results to the standard technique and showed adequate reproducibility. Other reference areas that have been used so far in the literature were less reliable. Within the limitations of the study, a valid superimposition reference area for serial 3D facial images of growing individuals is suggested. The method has potential to greatly expand the possibilities of this highly informative, risk free, and easily obtained 3D tool for the assessment of facial changes in growing individuals

Facial asymmetry and midsagittal plane definition in 3D: A bias-free, automated method.

Symmetry is a fundamental biological concept in all living organisms. It is related to a variety of physical and social traits ranging from genetic background integrity and developmental stability to the perception of physical appearance. Within this context, the study of human facial asymmetry carries a unique significance. Here, we validated an efficient method to assess 3D facial surface symmetry by best-fit approximating the original surface to its mirrored one. Following this step, the midsagittal plane of the face was automatically defined at the midpoints of the contralateral corresponding vertices of the superimposed models and colour coded distance maps were constructed. The method was tested by two operators using facial models of different surface size. The results show that the midsagittal plane definition was highly reproducible (maximum error < 0.1 mm or°) and remained robust for different extents of the facial surface model. The symmetry assessments were valid (differences between corresponding bilateral measurement areas < 0.1 mm), highly reproducible (error < 0.01 mm), and were modified by the extent of the initial surface model. The present landmark-free, automated method to assess facial asymmetry and define the midsagittal plane of the face is accurate, objective, easily applicable, comprehensible and cost effective

Smile Reproducibility and Its Relationship to Self-Perceived Smile Attractiveness.

The reproducibility of facial expressions has been previously explored, however, there is no detailed information regarding the reproducibility of lip morphology forming a social smile. In this study, we recruited 93 young adults, aged 21-35 years old, who agreed to participate in two consecutive study visits four weeks apart. On each visit, they were asked to perform a social smile, which was captured on a 3D facial image acquired using the 3dMD camera system. Assessments of self-perceived smile attractiveness were also performed using a VAS scale. Lip morphology, including smile shape, was described using 62 landmarks and semi-landmarks. A Procrustes superimposition of each set of smiling configurations (first and second visit) was performed and the Euclidean distance between each landmark set was calculated. A linear regression model was used to test the association between smile consistency and self-perceived smile attractiveness. The results show that the average landmark distance between sessions did not exceed 1.5 mm, indicating high repeatability, and that females presented approximately 15% higher smile consistecy than males (p &lt; 0.05). There was no statistically significant association between smile consistency and self-perceived smile attractiveness (η2 = 0.015; p = 0.252), when controlling for the effect of sex and age

Third Molar Agenesis Is Associated with Facial Size.

Individuals with congenitally missing permanent teeth, other than third molars, present smaller craniofacial configurations compared to normal controls. However, it is not known if agenesis of third molars is part of the same mechanism. Therefore, this study assessed individuals with and without isolated third molar agenesis and tested the relation of this condition to the size of their facial configurations, using geometric morphometric methods. We show that the absence of one or more third molars is associated with a smaller maxilla, smaller mandible and a smaller overall facial configuration. The effect was larger as the number of missing third molars increased. For example, the size of the mandibular centroids in five 16-year-old females with no, one, two, three or four missing third molars showed a size reduction of approximately 2.5 mm per missing third molar. In addition, in cases with third molar agenesis in one jaw only, the effect was also evident on the opposite jaw. Our findings suggest that isolated third molar agenesis is part of a developmental mechanism resulting also in craniofacial size reduction. This might be the effect of an evolutionary process observed in humans, leading to fewer and smaller teeth, as well as smaller facial structures

Number of Teeth Is Related to Craniofacial Morphology in Humans.

One of the most common dental anomalies in humans is the congenital absence of teeth, referred to as tooth agenesis. The association of tooth agenesis to craniofacial morphology has been previously investigated but remains unclear. We investigated this association by applying geometric morphometric methods in a large sample of modern humans. In line with previous studies, we report here that a reduced teeth number is linked to a less convex profile, as well as to a shorter face. The effects were similar for males and females; they increased as the severity of the tooth agenesis increased and remained unaltered by the inclusion of third molars and of allometry in the analysis. Furthermore, in cases with tooth agenesis only in the maxilla, there was no detectable effect in mandibular shape, whereas maxillary shape was affected independently of the location of missing teeth. The robustness of the present sample along with the shape analysis and the statistical approach applied, allowed for thorough testing of various contributing factors regarding the presence but also the magnitude of effects. The present findings suggest a relationship between number of teeth and overall craniofacial development and have evolutionary implications

Supernumerary Tooth Patterns in Non-Syndromic White European Subjects.

Supernumerary teeth form at an incidence of about 3% in the population, with differences among races and various clinical consequences. Information on detailed patterns, and especially on white subjects, is scarce in the literature. Therefore, we aimed to investigate the patterns of non-syndromic permanent supernumerary teeth in a white European population. A record review was performed in different orthodontic clinics and identified 207 eligible individuals with 258 supernumerary teeth. Approximately 80% of the subjects had one supernumerary tooth, while 15% had two. Supernumerary tooth formation was more often evident in males (male/female: 1.65). However, there was no sexual dimorphism in its severity. The following pattern sequences, with decreasing prevalence order, were observed in the maxilla: 21 > 11 > 12 > 18 > 28 and in the mandible: 34 > 44 > 35 > 45 > 42. Supernumerary teeth were most often unilaterally present, without sexual dimorphism. In the maxilla, they were more often anteriorly present, whereas in the mandible, an opposite tendency was observed. Supernumerary teeth were consistently more often observed in the maxilla than in the mandible; 74% were impacted, 80% had normal orientation (13% horizontal, 7% inverted), and 53% had normal size. The present thorough supernumerary tooth pattern assessment enables a better understanding of this condition with clinical, developmental, and evolutionary implications

Associations of facial profile and occlusion in the Northern Finland Birth Cohort 1966

Abstract Since the very early years of the profession, orthodontists have been interested in evaluating the effect of orthodontics on facial appearance and determine the appropriate treatment approach for each patient. However, the current literature mostly examines growing individuals and young adults because, traditionally, they constitute the majority of orthodontic patients. Nevertheless, this paradigm has now changed, with older adults also seeking orthodontic care in order to improve the esthetics and proper function of their occlusion. Within this spectrum, this work studied a large middle-aged adult population (N=1964) to determine the characteristics of their facial profile and make associations to underlying occlusal relationships. The study population comprised individuals who are all members of the NFBC1966 and had returned for a follow up examination visit in 2012, on their 46th birth year. On the day of their follow up visit, a comprehensive clinical examination was performed, and diagnostic records were taken, including extraoral photographs. For the purpose of this investigation, the occlusal measurements and profile photographs were collected and analyzed. The association between overjet, overbite and facial profile were assessed with traditional soft tissue measurements on profile photographs. In addition, geometric morphometric analyses were used to explore the variability of facial profile in this middle-aged population. Finally, the previously applied geometric morphometric methods were also used to regress facial profile shape on overjet and overbite. The results showed that overjet and overbite were more related to measurements describing the sagittal position of the upper and lower lips. This was more evident in severe malocclusions. Profile shape variation was related mainly to the protuberance of the lips, the projection of the nose and chin prominence. The shape of the upper lip was mainly associated to overjet, while overbite was mostly associated to the lower lip and the mentolabial curvature. This work described the unique profile characteristics of a large, homogenous population of middle-aged adults and assessed the effect of overjet and overbite on the profile appearance. It is concluded that anterior occlusion plays an important role in profile shape variation in middle-aged adults and its effect on facial profile is predominantly related to the sagittal position of the upper lip.Tiivistelmä Kautta aikojen hampaiston oikomishoidon ammattilaisia on kiinnostanut tutkia oikomishoidon vaikutusta kasvojen piirteisiin ja siten päättää yksilöllisesti potilaalle soveltuvasta hoitovaihtoehdosta. Tutkimuksissa on käsitelty lähinnä kasvavia yksilöitä ja nuoria aikuisia, joista perinteisesti oikomishoitopotilaiden pääosa myös koostuu. Tilanne on kuitenkin muuttunut, sillä nykyisin myös vanhemmat ihmiset hakeutuvat oikomishoitoon parantaakseen estetiikkaa ja asianmukaista purennan toimintaa. Tässä työssä tutkittiin suuren keski-ikäisen aikuisväestön (N=1964) kasvojen profiilin erityispiirteitä ja niiden yhteyttä hampaiden purentasuhteisiin. Kaikki tutkittavat kuuluvat Pohjois-Suomen kohortti 1966 tutkimusprojektiin (NFBC1966) ja he ovat käyneet seurantatutkimuksessa 46-vuotiaana vuonna 2012. Seurantakäynnillä tehtiin kokonaisvaltainen kliininen tutkimus kirjauksineen sekä otettiin kasvovalokuvat. Tämän tutkimuksen yhteydessä purennan piirteet ja profiilivalokuvat analysoitiin. Horisontaalisen ja vertikaalisen ylipurennan suhde kasvojen profiiliin arvioitiin perinteisillä pehmytkudosmäärityksillä profiilivalokuvista. Lisäksi tutkittiin geometriaan perustuvalla morfometrisellä analyysillä kasvojen profiilin vaihtelua tässä keski-ikäisessä väestöryhmässä. Geometristä morfometria-menetelmää käytettiin myös, kun tarkasteltiin regressioanalyysillä kasvojen profiilin suhdetta horisontaaliseen ja vertikaaliseen ylipurentaan. Tulokset osoittivat, että horisontaalinen ja vertikaalinen ylipurenta liittyy läheisimmin tuloksiin, jotka kuvaavat ylä- ja alahuulen sagittaalista asemaa. Tämä oli ilmeisintä vakavammissa purentavirheissä. Tutkimustulosten mukaan kasvojen profiilin muodon vaihtelu liittyi pääosin huulten ulkonemaan, nenän kokoon ja leuan voimakkuuteen. Regressioanalyysin mukaan ylähuulen asema liittyy pääosin horisontaaliseen ylipurentaan, kun taas alahuuli liittyi voimakkaimmin mentolabiaaliseen kaarevuuteen. Tämä tutkimus kuvaa suuren keski-ikäisen aikuisväestön omaleimaisia kasvojen profiilin piirteitä ja arvioi horisontaalisen ja vertikaalisen ylipurennan ilmenemistä profiilissa. Yhteenvetona voidaan todeta, että etuhampaiden purentasuhteet vaikuttavat merkittävästi kasvojen profiilin vaihteluun ja tämä vaihtelu liittyy kasvojen profiilissa pääosin ylähuulen sagittaaliseen asemaan

Facial shape affects self-perceived facial attractiveness.

Facial appearance expresses numerous cues about physical qualities as well as psychosocial and personality traits. Attractive faces are recognized clearly when seen and are often viewed advantageously in professional, social and romantic relationships. On the other hand, self-perceived attractiveness is not well understood and has been mainly attributed to psychological and cognitive factors. Here we use 3-dimensional facial surface data of a large young adult population (n = 601) to thoroughly assess the effect of facial shape on self-perceived facial attractiveness. Our results show that facial shape had a measurable effect on self-perception of facial attractiveness in both sexes. In females, self-perceived facial attractiveness was linked to decreased facial width, fuller anterior part of the lower facial third and more pronounced middle forehead and root of the nose. Males favored a well-defined chin, flatter cheeks and zygomas, and more pronounced eyebrow ridges, nose and middle forehead. The findings of this study support the notion that self-perceived facial attractiveness is not only motivated by psychological traits, but objectively measured phenotypic traits also contribute significantly. The role of social stereotypes for facial attractiveness in modern society is also inferred and discussed