Secondary pneumatization of the maxillary sinus in callitrichid primates: Insights from immunohistochemistry and bone cell distribution

Growth and microanatomy of the paranasal sinuses in two species of New World monkeys

Paranasal sinuses of living apes and humans grow with positive allometry, suggesting a novel mechanism for bone enlargement. Here, we examine the paranasal sinuses of the owl monkey (Aotus spp.) and a tamarin (Saguinus midas) across postnatal development. The prediction that paranasal sinuses grow disproportionately faster than the main nasal chamber is tested. We used diffusible iodine-based contrast-enhanced computed tomography and histology to study sinuses in eight Aotus and three tamarins ranging from newborn to adult ages. Sinuses were segmented at the mucosa-air cavity interface and measured in volume. All sinuses were lined by a ciliated respiratory epithelium, except for the ethmoid air cells in Aotus, which are lined in part by olfactory epithelium. An age comparison indicates that only the maxillary sinus and ethmoid air cells are present in newborns, and two additional sinuses (invading the orbitosphenoid and the frontal bone), do not appear until late infancy or later. Comparing newborns and adults, the main nasal airway is 10 times larger in the adult Aotus and ~ 6.5 times larger in adult Saguinus. In contrast, the maxillary sinus far exceeds this magnitude of difference: 24 times larger in the adult Aotus and 46 times larger in adult Saguinus. The frontal sinuses add significantly to total paranasal space volume in both species, but this growth is likely delayed until juvenile age. Results suggest ethmoid air cells expand the least. These results support our prediction that most paranasal sinuses have a distinctly higher growth rate compared to the main nasal chamber.

Human maxillary sinus size, shape, and surface area: Implications for structural and functional hypotheses

OBJECTIVES

Although research into human maxillary sinus (MS) morphology has overwhelmingly focused on sinus volume, other aspects of morphology (e.g., overall shape, mucosal surface area) factor prominently in hypotheses regarding MS form and function. Here, we investigate MS volume in conjunction with measures of MS shape and surface area in a large, diverse sample of modern humans. We test whether variation in MS volume is associated with predictable changes in MS shape (i.e., allometry) and investigate the influence of MS size-shape scaling on mucosal surface area dynamics.

MATERIALS AND METHODS

Measures of MS volume and surface area were obtained from computed tomographic (CT) scans of 162 modern human crania from three ancestral backgrounds-Equatorial Africa, Europe, and East Asia. 3D coordinate landmarks and linear measurements were also collected. Multivariate analyses were employed to test for associations between MS volume and other morphological variables.

RESULTS

Significant associations between MS volume and 3D shape were identified both across and within the subsamples. Variation in MS volume was found to predominantly relate to differences in MS height and width dimensions relative to MS length. This pattern of allometric scaling was found to differentially influence total mucosal surface area and the SAV ratio.

CONCLUSION

This study suggests that variation in MS volume is disproportionately mediated by MS width and height dimensions. This finding has implications for hypotheses which structurally link MS morphology to craniofacial ontogeny and those which suggest that MS morphology may perform adaptive physiological functions.

3D CT stereoscopic imaging: observations of the frontal and anterior ethmoid sinuses development from birth to early adulthood

Objective: Our objective is to provide observations demonstrated with 3Dimensional Computed x-ray Stereoscopic Imaging (3DCTSI) in the evaluation of the anterior ethmoid and frontal sinus development from birth to age 18. Methods: This is a retrospective evaluation of patient’s CT studies performed over a fifteen-year period, reported as normal studies, and included 53 patients (142 sides) from birth to age 18. Results: At birth, there are two spaces covered by folds, the uncinate and bulla lamellae. The spaces communicate with the Middle Meatus (MM) through the emerging ethmoid infundibulum (EI) and the retrobulbar recess space (RBRS). In the first month after birth, an expansile and breakdown developmental phase blend and continue throughout the growth into the teenage years. The 3D images reveal dark lamellar structures, on the surface of the medial lamina papyracea as well as bridging the broken spatial outlines. The dark lamellae represent the mucosal lamina propria, in unossified lamellae and are the origin of permanent spatial walls. From ages 4 to 18 years, initially, the frontal recess (FR) and later the MM penetrate into the cancellous frontal bone creating the frontal Sinus (FS), the frontal septum (FS), Inter-Frontal Sinus Septal Cell (IFSSC), as well as the Fronto-Ethmoidal and Frontal Bulla Spaces. Conclusion: 3DCTSI is the first intuitive imaging modality to reveal the microanatomical development of the anterior ethmoid and frontal sinus anatomy.

Changes in pneumatization of the maxillary air sinuses in Korean adults following biomimetic oral appliance therapy

Objective

For the treatment of obstructive sleep apnea in adults, mandibular advancement devices (MADs) are often used. Since adults with a prognathic mandibular phenotype are at risk of developing an unfavorable facial profile, midfacial development using biomimetic oral appliance therapy might provide a suitable alternative. However, the effect of this procedure on the maxillary air sinuses is unknown; therefore, changes in sinus pneumatization were investigated in this study.

Methods

After obtaining informed consent, 16 consecutive Korean adults with midfacial hypoplasia had 3D cone-beam (CB) CT scans taken, and biomimetic upper appliances (DNA appliance®, Vivos Therapeutics, Inc., USA) were constructed.

All subjects were instructed to wear the device 12–16 h/day. Each month, examination for the progress of midfacial development was recorded. Post-treatment, a follow-up 3D CBCT scan was undertaken with no device in the patient's mouth. Pre- and post-treatment linear and volumetric measurements were obtained using appropriate software, and compared statistically using t-tests.

Results

The mean age of the sample was 25.0 yrs ± 8.7. The mean treatment time was 15.5 mths ± 5.2. Post-treatment, the transpalatal bone width increased from 35.3 mm ± 3.0 to 38.5 mm ± 2.0 (P < 0.001); the maxillary air sinus volume on the left side increased from 18.8 cm³ ± 6.5 to 20.0 cm³ ± 6.0 (P < 0.05), and from 18.5 cm³ ± 5.7 to 19.7 cm³ ± 5.8 (P < 0.05) on the right side.

Conclusions

Biomimetic oral appliance therapy may be able to increase the maxillary air sinus volume in adults. In view of these preliminary findings, further studies on the effect of enhanced pneumatization on paranasal sinus function and sleep parameters are warranted.

Vertebral pneumaticity is correlated with serial variation in vertebral shape in storks

Birds and their ornithodiran ancestors are unique among vertebrates in exhibiting air-filled sinuses in their postcranial bones, a phenomenon called postcranial skeletal pneumaticity. The factors that account for serial and interspecific variation in postcranial skeletal pneumaticity are poorly understood, although body size, ecology, and bone biomechanics have all been implicated as influencing the extent to which pneumatizing epithelia invade the skeleton and induce bone resorption. Here, I use high-resolution computed-tomography to holistically quantify vertebral pneumaticity in members of the neognath family Ciconiidae (storks), with pneumaticity measured as the relative volume of internal air space. These data are used to describe serial variation in extent of pneumaticity and to assess whether and how pneumaticity varies with the size and shape of a vertebra. Pneumaticity increases dramatically from the middle of the neck onwards, contrary to previous predictions that cervical pneumaticity should decrease toward the thorax to maintain structural integrity as the mass and bending moments of the neck increase. Although the largest vertebrae sampled are also the most pneumatic, vertebral size cannot on its own account for serial or interspecific variation in extent of pneumaticity. Vertebral shape, as quantified by three-dimensional geometric morphometrics, is found to be significantly correlated with extent of pneumaticity, with elongate vertebrae being less pneumatic than craniocaudally short and dorsoventrally tall vertebrae. Considered together, the results of this study are consistent with the hypothesis that shape- and position-specific biomechanics influence the amount of bone loss that can be safely tolerated. These results have potentially important implications for the evolution of vertebral morphology in birds and their extinct relatives.

Fissures, folds, and scrolls: The ontogenetic basis for complexity of the nasal cavity in a fruit bat (Rousettus leschenaultii)

Mammalian nasal capsule development has been described in only a few cross-sectional age series, rendering it difficult to infer developmental mechanisms that influence adult morphology. Here we examined a sample of Leschenault's rousette fruit bats (Rousettus leschenaultii) ranging in age from embryonic to adult (n = 13). We examined serially sectioned coronal histological specimens and used micro-computed tomography scans to visualize morphology in two older specimens. We found that the development of the nasal capsule in Rousettus proceeds similarly to many previously described mammals, following a general theme in which the central (i.e., septal) region matures into capsular cartilage before peripheral regions, and rostral parts of the septum and paries nasi mature before caudal parts. The ossification of turbinals also generally follows a rostral to the caudal pattern. Our results suggest discrete mechanisms for increasing complexity of the nasal capsule, some of which are restricted to the late embryonic and early fetal timeframe, including fissuration and mesenchymal proliferation. During fetal and early postnatal ontogeny, appositional and interstitial chondral growth of cartilage modifies the capsular template. Postnatally, appositional bone growth and pneumatization render greater complexity to individual structures and spaces. Future studies that focus on the relative contribution of each mechanism during development may draw critical inferences how nasal morphology is reflective of, or deviates from the original fetal template. A comparison of other chiropterans to nasal development in Rousettus could reveal phylogenetic patterns (whether ancestral or derived) or the developmental basis for specializations relating to respiration, olfaction, or laryngeal echolocation.

Ontogeny of the human maxilla: a study of intra-population variability combining surface bone histology and geometric morphometrics

Bone modeling is the process by which bone grows in size and models its shape via the cellular activities of the osteoblasts and osteoclasts that respectively form and remove bone. The patterns of expression of these two activities, visible on bone surfaces, are poorly understood during facial ontogeny in Homo sapiens; this is due mainly to small sample sizes and a lack of quantitative data. Furthermore, how microscopic activities are related to the development of morphological features, like the uniquely human-canine fossa, has been rarely explored. We developed novel techniques for quantifying and visualizing variability in bone modeling patterns and applied these methods to the human maxilla to better understand its development at the micro- and macroscopic levels. We used a cross-sectional ontogenetic series of 47 skulls of known calendar age, ranging from birth to 12 years, from a population of European ancestry. Surface histology was employed to record and quantify formation and resorption on the maxilla, and digital maps representing each individual's bone modeling patterns were created. Semilandmark geometric morphometric (GM) methods and multivariate statistics were used to analyze facial growth. Our results demonstrate that surface histology and GM methods give complementary results, and can be used as an integrative approach in ontogenetic studies. The bone modeling patterns specific to our sample are expressed early in ontogeny, and fairly constant through time. Bone resorption varies in the size of its fields, but not in location. Consequently, absence of bone resorption in extinct species with small sample sizes should be interpreted with caution. At the macroscopic level, maxillary growth is predominant in the top half of the bone where bone formation is mostly present. Our results suggest that maxillary growth in humans is highly constrained from early stages in ontogeny, and morphological changes are likely driven by changes in osteoblastic and osteoclastic rates of expression rather than differences in the bone modeling patterns (i.e. changes in location of formation and resorption). Finally, the results of the micro- and macroscopic analyses suggest that the development of the canine fossa results from a combination of bone resorption and bone growth in the surrounding region.

The biomechanical significance of the frontal sinus in Kabwe 1 (Homo heidelbergensis)

Paranasal sinuses are highly variable among living and fossil hominins and their function(s) are poorly understood. It has been argued they serve no particular function and are biological 'spandrels' arising as a structural consequence of changes in associated bones and/or soft tissue structures. In contrast, others have suggested that sinuses have one or more functions, in olfaction, respiration, thermoregulation, nitric oxide production, voice resonance, reduction of skull weight, and craniofacial biomechanics. Here we assess the extent to which the very large frontal sinus of Kabwe 1 impacts on the mechanical performance of the craniofacial skeleton during biting. It may be that the browridge is large and the sinus has large trabecular struts traversing it to compensate for the effect of a large sinus on the ability of the face to resist forces arising from biting. Alternatively, the large sinus may have no impact and be sited where strains that arise from biting would be very low. If the former is true, then infilling of the sinus would be expected to increase the ability of the skeleton to resist biting loads, while removing the struts might have the opposite effect. To these ends, finite element models with hollowed and infilled variants of the original sinus were created and loaded to simulate different bites. The deformations arising due to loading were then compared among different models and bites by contrasting the strain vectors arising during identical biting tasks. It was found that the frontal bone experiences very low strains and that infilling or hollowing of the sinus has little effect on strains over the cranial surface, with small effects over the frontal bone. The material used to infill the sinus experienced very low strains. This is consistent with the idea that frontal sinus morphogenesis is influenced by the strain field experienced by this region such that it comes to lie entirely within a region of the cranium that would otherwise experience low strains. This has implications for understanding why sinuses vary among hominin fossils.

Zygomaticomaxillary Morphology and Maxillary Sinus Form and Function: How Spatial Constraints Influence Pneumatization Patterns among Modern Humans

Previous research has suggested that the maxillary sinuses may act as "zones of accommodation" for the nasal region, minimizing the impact of climatic-related changes in nasal cavity breadth on surrounding skeletal structures. However, a recent study among modern human crania has identified that, in addition to nasal cavity breadth, sinus morphology also tracks lateral facial form, especially anterior-posterior positioning of the zygomatics. Here, we expand upon this previous study to further investigate these covariation patterns by employing three samples with distinct combinations of nasal and zygomatic morphologies: Northern Asians (n = 28); sub-Saharan Africans (n = 30); and Europeans (n = 29). For each cranium, 30 landmarks were digitized from CT-rendered models and subsequently assigned to either a midfacial or maxillary sinus "block." Two block partial least squares (2B-PLS) analyses indicate that sinus morphology primarily reflects superior-inferior dimensions of the midface, rather than either nasal cavity breadth or zygomatic position. Specifically, individuals with relatively tall midfacial skeletons exhibit more inferiorly and laterally expanded sinuses compared to those with shorter midfaces. Further, separate across-group and within-group 2B-PLS analyses indicate that regional differences between samples primarily build upon a common pattern of midfacial and sinus covariation already present within each regional group. Allometry, while present, only explains a small portion of the midface-sinus covariation pattern. We conclude that previous findings of larger maxillary sinuses among cold-adapted individuals are not predominantly due to possession of relatively narrow nasal cavities, but to greater maxillary and zygomatic heights. Implications for sinus function and midfacial ontogeny are discussed. Anat Rec, 300:209-225, 2017. © 2016 Wiley Periodicals, Inc.

The hidden anatomy of paranasal sinuses reveals biogeographically distinct morphotypes in the nine-banded armadillo (Dasypus novemcinctus)

Background

With their Pan-American distribution, long-nosed armadillos (genus Dasypus) constitute an understudied model for Neotropical biogeography. This genus currently comprises seven recognized species, the nine-banded armadillo (D. novemcinctus) having the widest distribution ranging from Northern Argentina to the South-Eastern US. With their broad diversity of habitats, nine-banded armadillos provide a useful model to explore the effects of climatic and biogeographic events on morphological diversity at a continental scale.

Methods

Based on a sample of 136 skulls of Dasypus spp. belonging to six species, including 112 specimens identified as D. novemcinctus, we studied the diversity and pattern of variation of paranasal cavities, which were reconstructed virtually using µCT-scanning or observed through bone transparency.

Results

Our qualitative analyses of paranasal sinuses and recesses successfully retrieved a taxonomic differentiation between the traditional species D. kappleri, D. pilosus and D. novemcinctus but failed to recover diagnostic features between the disputed and morphologically similar D. septemcinctus and D. hybridus. Most interestingly, the high variation detected in our large sample of D. novemcinctus showed a clear geographical patterning, with the recognition of three well-separated morphotypes: one ranging from North and Central America and parts of northern South America west of the Andes, one distributed across the Amazonian Basin and central South America, and one restricted to the Guiana Shield.

Discussion

The question as to whether these paranasal morphotypes may represent previously unrecognized species is to be evaluated through a thorough revision of the Dasypus species complex integrating molecular and morphological data. Remarkably, our recognition of a distinct morphotype in the Guiana Shield area is congruent with the recent discovery of a divergent mitogenomic lineage in French Guiana. The inflation of the second medialmost pair of caudal frontal sinuses constitutes an unexpected morphological diagnostic feature for this potentially distinct species. Our results demonstrate the benefits of studying overlooked internal morphological structures in supposedly cryptic species revealed by molecular data. It also illustrates the under-exploited potential of the highly variable paranasal sinuses of armadillos for systematic studies.

Ontogeny and Microanatomy of the Nasal Turbinals in Lemuriformes

The nasal cavity of strepsirrhine primates (lemurs and lorises) has the most primitive arrangement of extant primates. In nocturnal species, the numerous turbinals of the ethmoid bear a large surface area of olfactory mucosa (OM). In this study, we examine turbinal development in four genera of diurnal or cathemeral lemuriformes. In addition, we examined an age series of each genus to detect whether structures bearing OM as opposed to respiratory mucosa (RM) develop differently, as has been observed in nocturnal strepsirrhines. In adults, the maxilloturbinal is covered by highly vascular respiratory mucosa throughout its entire length, with large sinusoidal vessels in the lamina propria; any parts of other turbinals that closely borders the maxilloturbinal has a similar mucosa. Posteriorly, the most vascular RM is restricted in the nasopharyngeal duct, which becomes partitioned from the dorsal olfactory region. A comparison of newborns to adults reveals that the first ethmoturbinal increases more in length in the parts that are covered with RM than OM, which supports the idea that ethmoturbinals can specialize in more than one function. Finally, we observe that the regions of turbinals that are ultimately covered with RM develop more accessory lamellae or additional surface area of existing scrolls compared to the regions covered with OM. Because such outgrowths of bone develop postnatally and without cartilaginous precursors, we hypothesize that the complexity of olfactory lamellae within the ethmoturbinal complex is primarily established at birth, while respiratory lamellae become elaborated due to the epigenetic influence of respiratory physiology. Anat Rec, 299:1492-1510, 2016. © 2016 Wiley Periodicals, Inc.

Bone-associated gene evolution and the origin of flight in birds

BACKGROUND

Bones have been subjected to considerable selective pressure throughout vertebrate evolution, such as occurred during the adaptations associated with the development of powered flight. Powered flight evolved independently in two extant clades of vertebrates, birds and bats. While this trait provided advantages such as in aerial foraging habits, escape from predators or long-distance travels, it also imposed great challenges, namely in the bone structure.

RESULTS

We performed comparative genomic analyses of 89 bone-associated genes from 47 avian genomes (including 45 new), 39 mammalian, and 20 reptilian genomes, and demonstrate that birds, after correcting for multiple testing, have an almost two-fold increase in the number of bone-associated genes with evidence of positive selection (~52.8 %) compared with mammals (~30.3 %). Most of the positive-selected genes in birds are linked with bone regulation and remodeling and thirteen have been linked with functional pathways relevant to powered flight, including bone metabolism, bone fusion, muscle development and hyperglycemia levels. Genes encoding proteins involved in bone resorption, such as TPP1, had a high number of sites under Darwinian selection in birds.

CONCLUSIONS

Patterns of positive selection observed in bird ossification genes suggest that there was a period of intense selective pressure to improve flight efficiency that was closely linked with constraints on body size.

Ontogeny of the Middle-Ear Air-Sinus System in Alligator mississippiensis (Archosauria: Crocodylia)

Modern crocodylians, including Alligator mississippiensis, have a greatly elaborated system of pneumatic sinuses invading the cranium. These sinuses invade nearly all the bones of the chondrocranium and several bony elements of the splanchnocranium, but patterns of postnatal paratympanic sinus development are poorly understood and documented. Much of crocodylomorph--indeed archosaurian--evolution is characterized by the evolution of various paratympanic air sinuses, the homologies of which are poorly understood due in large part to the fact that individual sinuses tend to become confluent in adults, obscuring underlying patterns. This study seeks to explore the ontogeny of these sinuses primarily to clarify the anatomical relations of the individual sinuses before they become confluent and thus to provide the foundation for later studies testing hypotheses of homology across extant and extinct Archosauria. Ontogeny was assessed using computed tomography in a sample of 13 specimens covering an almost 19-fold increase in head size. The paratympanic sinus system comprises two major inflations of evaginated pharyngeal epithelium: the pharyngotympanic sinus, which communicates with the pharynx via the lateral (true) Eustachian tubes and forms the cavum tympanicum proprium, and the median pharyngeal sinus, which communicates with the pharynx via the median pharyngeal tube. Each of these primary inflations gives rise to a number of secondary inflations that further invade the bones of the skull. The primary sinuses and secondary diverticula are well developed in perinatal individuals of Alligator, but during ontogeny the number and relative volumes of the secondary diverticula are reduced. In addition to describing the morphological ontogeny of this sinus system, we provide some preliminary exploratory analyses of sinus function and allometry, rejecting the hypothesis that changes in the volume of the paratympanic sinuses are simply an allometric function of braincase volume, but instead support the hypothesis that these changes may be a function of the acoustic properties of the middle ear.

Beyond the sniffer: frontal sinuses in Carnivora

Paranasal sinuses are some of the most poorly understood features of mammalian cranial anatomy. They are highly variable in presence and form among species, but their function is not well understood. The best-supported explanations for the function of sinuses is that they opportunistically fill mechanically unnecessary space, but that in some cases, sinuses in combination with the configuration of the frontal bone may improve skull performance by increasing skull strength and dissipating stresses more evenly. We used CT technology to investigate patterns in frontal sinus size and shape disparity among three families of carnivores: Canidae, Felidae, and Hyaenidae. We provide some of the first quantitative data on sinus morphology for these three families, and employ a novel method to quantify the relationship between three-dimensional sinus shape and skull shape. As expected, frontal sinus size and shape were more strongly correlated with frontal bone size and shape than with the morphology of the skull as a whole. However, sinus morphology was also related to allometric differences among families that are linked to biomechanical function. Our results support the hypothesis that frontal sinuses most often opportunistically fill space that is mechanically unnecessary, and they can facilitate cranial shape changes that reduce stress during feeding. Moreover, we suggest that the ability to form frontal sinuses allows species to modify skull function without compromising the performance of more functionally constrained regions such as the nasal chamber (heat/water conservation, olfaction), and braincase (housing the brain and sensory structures).

Tour of a labyrinth: exploring the vertebrate nose

This special issue of The Anatomical Record is the outcome of a symposium entitled "Inside the Vertebrate Nose: Evolution, Structure and Function." The skeletal framework of the nasal cavity is a complicated structure that often houses sinuses and comprises an internal skeleton of bone or cartilage that can vary greatly in architecture among species. The nose serves multiple functions, including olfaction and respiratory air-conditioning, and its morphology is constrained by evolution, development, and conflicting demands on cranial space, such as enlarged orbits. The nasal cavity of vertebrates has received much more attention in the last decade due to the emergence of nondestructive methods that allow improved visualization of the internal anatomy of the skull, such as high-resolution x-ray computed tomography and magnetic resonance imaging. The 17 articles included here represent a broad range of investigators, from paleontologists to engineers, who approach the nose from different perspectives. Key topics include the evolution and development of the nose, its comparative anatomy and function, and airflow through the nasal cavity of individual species. In addition, this special issue includes review articles on anatomical reduction of the olfactory apparatus in both cetaceans and primates (the vomeronasal system), as well as the molecular biology of olfaction in vertebrates. Together these articles provide an expansive summary of our current understanding of vertebrate nasal anatomy and function. In this introduction, we provide background information and an overview of each of the three primary topics, and place each article within the context of previous research and the major challenges that lie ahead.

Minor contributions of the maxillary sinus to the air-conditioning performance in macaque monkeys

The nasal passages mainly adjust the temperature and humidity of inhaled air to reach the alveolar condition required in the lungs. By contrast to most other non-human primates, macaque monkeys are distributed widely among tropical, temperate and subarctic regions, and thus some species need to condition the inhaled air in cool and dry ambient atmospheric areas. The internal nasal anatomy is believed to have undergone adaptive modifications to improve the air-conditioning performance. Furthermore, the maxillary sinus (MS), an accessory hollow communicating with the nasal cavity, is found in macaques, whereas it is absent in most other extant Old World monkeys, including savanna monkeys. In this study, we used computational fluid dynamics simulations to simulate the airflow and heat and water exchange over the mucosal surface in the nasal passage. Using the topology models of the nasal cavity with and without the MS, we demonstrated that the MS makes little contribution to the airflow pattern and the air-conditioning performance within the nasal cavity in macaques. Instead, the inhaled air is conditioned well in the anterior portion of the nasal cavity before reaching the MS in both macaques and savanna monkeys. These findings suggest that the evolutionary modifications and coetaneous variations in the nasal anatomy are rather independent of transitions and variations in the climate and atmospheric environment found in the habitats of macaques.

Repeated loss of frontal sinuses in arctoid carnivorans

Many mammal skulls contain air spaces inside the bones surrounding the nasal chamber including the frontal, maxilla, ethmoid, and sphenoid, all of which are called paranasal sinuses. Within the Carnivora, frontal sinuses are usually present, but vary widely in size and shape. The causes of this variation are unclear, although there are some functional associations, such as a correlation between expanded frontal sinuses and a durophagous diet in some species (e.g., hyenas) or between absent sinuses and semiaquatic lifestyle (e.g., pinnipeds). To better understand disparity in frontal sinus morphology within Carnivora, we quantified frontal sinus size in relationship to skull size and shape in 23 species within Arctoidea, a clade that is ecologically diverse including three independent invasions of aquatic habitats, by bears, otters, and pinnipeds, respectively. Our sampled species range in behavior from terrestrial (rarely or never forage in water), to semiterrestrial (forage in water and on land), to semiaquatic (forage only in water). Results show that sinuses are either lost or reduced in both semiterrestrial and semiaquatic species, and that sinus size is related to skull size and shape. Among terrestrial species, frontal sinus size was positively allometric overall, but several terrestrial species completely lacked sinuses, including two fossorial badgers, the kinkajou (a nocturnal, arboreal frugivore), and several species with small body size, indicating that factors other than aquatic habits, such as space limitations due to constraints on skull size and shape, can limit sinus size and presence.

A comparative study of dog models for osteotome sinus floor elevation and dental implants in posterior maxilla subjacent to the maxillary sinus

OBJECTIVE

The objective of this study was to investigate the suitability of beagles and Labrador retrievers as animal models for osteotome sinus floor elevation (OSFE) and dental implants in posterior maxilla subjacent to sinus.

STUDY DESIGN

Ten beagles and 8 Labrador retrievers were included. Their posterior maxillas subjacent to the sinus were studied by a gross survey, CT scan, and histologic analysis.

RESULTS

In the posterior maxilla subjacent to sinus, the bone height was significantly higher for Labrador retrievers than for beagles (P < .05). There was no significant difference in sinus size from the coronal section and its location from the sagittal section (P > .05) between Labrador retrievers and beagles.

CONCLUSIONS

As an animal model, the Labrador is more suitable for OSFE and dental implants in posterior maxilla subjacent to sinus. The midpoint of the maxillary fourth premolar is an ideal site for implantation.

Microanatomical variation of the nasal capsular cartilage in newborn primates

The breakdown of nasal capsule cartilage precedes secondary pneumatic expansion of the paranasal sinuses. Recent work indicates the nasal capsule of monkeys undergoes different ontogenetic transformations regionally (i.e., ossification, persistence as cartilage, or resorption). This study assesses nasal capsule morphology at the perinatal age in a taxonomically broad sample of non-human primates. Using traditional histochemical methods, osteopontin immunohistochemistry and tartrate-resistant acid phosphatase procedure, the cartilage of the lateral nasal wall (LNC) was studied. At birth, matrix properties differ between portions of the LNC that ultimately form elements of the ethmoid bone and regions of the LNC that have no postnatal (descendant) structure. The extent of cartilage that remains in the paranasal parts of the LNC varies among species. It is fragmented in species with the greatest extent of maxillary and/or frontal pneumatic expansion. Conversely, greater continuity of the LNC is noted in newborns of species that lack maxillary and/or frontal sinuses as adults. Chondroclasts occur adjacent to elements of the ethmoid bone, along the margin of the nasal tectum, and/or along islands of cartilage that bear no signs of ossification. Chondroclasts are prevalent along remnants of the paranasal LNC in tamarin species (Leontopithecus, Saguinus), which have extensive frontal and maxillary bone pneumatization. Taken together, the morphological observations indicate that the localized loss of cartilage might be considered a critical event at the onset of secondary pneumatization, facilitated by rapid recruitment of chondro-/osteoclasts, possibly occurring simultaneously in cartilage and bone.

Anatomic and histological analysis in a goat model used for maxillary sinus floor augmentation with simultaneous implant placement

OBJECTIVES

The aim of the present study was to carry out an anatomic survey on the goat maxillary sinus in order to provide accurate and definite anatomic parameters for the design of sinus floor elevation and dental implantation studies in this valuable preclinic animal model.

MATERIAL AND METHODS

The anatomic topographic structure of the maxillary sinuses was studied bilaterally in 10 adult goats by a gross survey as well as a histological analysis with parasagittal or coronal sections. Then following parameters were defined and measured: (1) maxillary alveolar height (MAH): vertical height from the alveolar crest to the sinus floor; (2) sinus lateral floor width (SLFW): horizontal distance from the lateral border of the anteroposterior bone crest to the sinus lateral wall; (3) infraorbital canal diameter (ICD); and (4) maxillary sinus volume (MSV): the volume occupied by water injected into the sinus. The data were presented with mean + or - SD on both sides.

RESULTS

The goat has a maxillary sinus similar to humans, with a slender pyramidal shape that pneumatizes the entire maxilla, and a sinus wall covered with a mucosal lining. From the maxillary sinus floor, there is an anteroposterior bone crest protruding with the infraorbital canal enveloped. It divides the maxillary sinus floor into two parts. The SLFW of the lateral part of the maxillary sinus floor becomes broader, about 5.905 + or - 1.475 mm in the third premolar site, and the MAH increases towards the posterior area, where the maxillary sinus floor is close to the related teeth roots. According to original metrical data, we also proposed a possible operation procedure for sinus floor augmentation.

CONCLUSIONS

There is enough space in the lateral floor of the maxillary sinus for dental implantation, and the third premolar area might be a suitable position suggested for maxillary sinus augmentation with simultaneous implant placement in a goat model.

The phylogenetic significance of anthropoid paranasal sinuses

In this study, the phylogenetic significance of anthropoid paranasal sinus anatomy is explored. New information reported in recent years has precipitated new hypotheses of sinus homology and more than doubled the number of anthropoid genera for which confident assessments of sinus identity can be made. As a result, it is likely that the phylogenetic meaning of commonly cited characters such as the ethmoid and frontal sinuses will change. The traditional method of "character mapping" is employed to test hypotheses of sinus homology and to reconstruct the ancestral states for sinus characters in major anthropoid clades. Results show that most sinuses appear to be primitive retentions in anthropoids, with their absences in various genera representing losses. Accordingly, many of these sinuses are potential anthropoid synapomorphies.

Relationship of Premaxillary Bone and Its Sutures to Deciduous Dentition in Nonhuman Primates

Objective:

The relationship of the human premaxillary bone (Pmx) to neighboring craniofacial structures is clouded by its embryonic union with the maxillary bone proper. Only humans among all primates have such early fusion of the premaxillomaxillary suture (PS). This study surveyed the relationship of the PS to the upper deciduous dentition in nonhuman primates, and describes the distribution of bone cells along the osseous margins of the Pmx.

Method:

Twenty-eight subadult primates were studied using gross, CT, and histologic observations. Location of the anterior deciduous dentition relative to the PS was assessed. In sections of selected specimens, observations of bone cells on the osseous boundaries of the Pmx were made. Osteopontin (OPN) immunohistochemistry was used to isolate osteoclastic binding sites along the Pmx boundaries.

Results:

The PS was consistently found between deciduous incisor and canine in strepsirrhines of all ages, whereas the suture passed variably closer to the incisor or canine in haplorhines. In all species, the anterior part of the Pmx was nonarticulating and mostly osteoblastic, except for osteoclastic margins adjacent to dentition and the nasal fossa. Superolaterally, the osteogenic fronts of the PS were osteoblastic, while more inferiorly, at the level of the deciduous canine, the PS was often osteoclastic. Results from OPN immunohistochemistry support the findings on bone cell distribution.

Conclusion:

Bone cell distribution patterns in perinatal nonhuman primates resemble those described for the prenatal human Pmx, suggesting that differences among species relate to magnitude rather than the pattern of osteogenesis.

Morphology, constraints, and scaling of frontal sinuses in the hartebeest,Alcelaphus buselaphus (Mammalia: Artiodactyla, Bovidae)

The frontal sinuses of bovid mammals display a great deal of diversity, which has been attributed to both phylogenetic and functional influences. In-depth study of the hartebeest (Alcelaphus buselaphus), a large African antelope, reveals a number of previously undescribed details of frontal sinus morphology. In A. buselaphus, the frontal sinuses conform closely to the shape of the frontal bone, filling nearly the entire element. However, the horncores are never extensively pneumatized, contrasting with the condition seen in many other bovids. This evidence is inconsistent with the hypothesis that sinuses are opportunistic pneumatizing agents, suggesting that phylogenetic factors also play a role in determining sinus size. Both cranial sutures and neurovasculature appear to constrain the growth of sinuses in part. In turn, the sinus also affects the growth of the parietal; apparently this element is not truly pneumatized by the sinus in most cases, but the bone's shape changes under the influence of the sinus. Furthermore, the sinuses present relatively few struts when compared with the sinuses of some other bovids, such as Ovis. By adapting methods previously developed for measuring structural parameters of trabecular bone, it is possible to quantify certain aspects of sinus morphology. These include the number of bony struts within the sinus, the spacing of these struts, and the size of individual cavities within the sinus. Some differences in the number of struts are evident between subspecies. Similarly, significant differences occur in the relative number of struts between male and female A. buselaphus, which may be related to behavior. The volume of the sinus is strongly correlated with the size of the frontal, but less so with overall cranial size. This finding illustrates the importance of choosing variables carefully when comparing sinus sizes and growth between species.