Variation in the shape and position of the internal nasal floor relative to the lower border of the piriform aperture in the genus Homo has been described as having three primary shape configurations: level, sloped, or depressed. The high frequency of depressed nasal floors among Neandertals relative to other fossil and extant groups (>80%) had originally led to the idea that nasal floor depression was related to an overall enlarged nasal capsule - an adaptive feature that would have been under selection among Neandertals living in cold, glacial climates. For a variety of reasons, subsequent research has found little empirical or theoretical support for this adaptive idea. Recent research on extant humans has also demonstrated that nasal floor shape variation, unlike many other midfacial traits, does not arise until well after birth, with nasal floor depression (when it occurs) appearing at the earliest around 3.0 years of age. Furthermore, nasal floor depression was also shown to correspond with a vertically expanded premaxillary region. Thus, it was hypothesized that nasal floor depression might be related to variation in key developmental and morphological aspects of the anterior maxillary dentition. This study metrically quantifies nasal floor topography for the first time in order to more objectively examine patterns of shape variation and to test explicit hypotheses regarding potential causative factors for nasal floor variation. The variables examined include anterior tooth dimensions, dental developmental rate, aspects of midfacial shape, overall facial size, and patterns of premaxillary/post-maxillary integration. It was found that among these, only dental developmental rate was clearly correlated with internal nasal floor shape. This result indicates that aspects of anterior dental development may indeed be a causative factor in the development of nasal floor shape variation. The existing visual discrete coding system for nasal floor topography was also evaluated in light of the new, quantitative data produced by this study as well as a critical comparison of the consistency of nasal floor topography definitions used previously in the literature. While it is suggested that quantitative data are preferable to qualitative data for this trait when possible, limitations in research methods for collecting quantitative data on osteological and fossil collections remain difficult to overcome. Thus a new, two-category presence/absence based system for describing nasal floor shape is proposed.

Objectives: Symmetry is essential for computer-aided surgical (CAS) procedures in oral and maxillofacial surgery (OMFS). A critical step for successful CAS is mirroring the unaffected side to create a template for the virtual reconstruction of the injured anatomical structure. The aim was to identify specific anatomical landmarks of the midfacial skeleton, to evaluate the symmetry in a group of the real-world Central European population, and to use these landmarks to assess midfacial symmetry in CT scans. - Material and methods: The retrospective cross-sectional study defined landmarks of the midface’s bony contour using viscerocranial CT data. The distances of the skeletal landmarks (e.g., the frontozygomatic suture and temporozygomatic suture) of the left and right sides from the midline were measured and statistically compared. Midfacial symmetry for reference points was defined as a difference within 0 mm and their mean difference plus one standard deviation. - Results: We examined a total of 101 CT scans. 75% of our population shows symmetrical proportions of the midface. The means of the differences for the left and right sides ranged from 0.8 to 1.3 mm, averaging 1.1 ± 0.2 mm for all skeletal landmarks. The standard deviations ranged from 0.6 to 1.4 mm, with a computed mean of 0.9 ± 0.3 mm. - Conclusion: We established a methodology to assess the symmetry of the bony midface. If the determined differences were equal to or lower than 2.5 mm in the mentioned midfacial skeletal landmarks, then the symmetry of the bony midface was considered present, and symmetry-based methods for CAS procedures are applicable. - Clinical relevance: Many CAS procedures require facial symmetry. We provide an easy-to-apply method to probe for symmetry of the midface. The method may be used for population-based research, to check for proper reduction of fractures after reposition or to screen for symmetry prior to CAS planning.

In dieser Arbeit wurde ein Arbeitsablauf entwickelt, um ein möglichst realistisches, biomechanisches Modell eines menschlichen Schädelknochens anhand eines Patienten-CT Datensatzes zu erstellen. Mit diesem Modell konnten Experimente aus der Literatur realistisch nachgestellt und anschließend der Mechanismus einer Orbitawandfraktur genauer untersucht werden. Es konnte gezeigt werden, dass das entwickelte Schädelmodell als Alternative für experimentelle biomechanische Untersuchungen verwendet werden kann. Somit sind eine Vielzahl parametrischer biomechanischer Studien möglich, ohne dabei auf Humanpräparate angewiesen zu sein.

In dieser Arbeit wurde ein Arbeitsablauf entwickelt, um ein möglichst realistisches, biomechanisches Modell eines menschlichen Schädelknochens anhand eines Patienten-CT Datensatzes zu erstellen. Mit diesem Modell konnten Experimente aus der Literatur realistisch nachgestellt und anschließend der Mechanismus einer Orbitawandfraktur genauer untersucht werden. Es konnte gezeigt werden, dass das entwickelte Schädelmodell als Alternative für experimentelle biomechanische Untersuchungen verwendet werden kann. Somit sind eine Vielzahl parametrischer biomechanischer Studien möglich, ohne dabei auf Humanpräparate angewiesen zu sein.