The upper limb of Homo naledi.

The evolutionary transition from an ape-like to human-like upper extremity occurred in the context of a behavioral shift from an upper limb predominantly involved in locomotion to one adapted for manipulation. Selection for overarm throwing and endurance running is thought to have further shaped modern human shoulder girdle morphology and its position about the thorax. Homo naledi (Dinaledi Chamber, Rising Star Cave, Cradle of Humankind, South Africa) combines an australopith-like cranial capacity with dental characteristics akin to early Homo. Although the hand, foot, and lower limb display many derived morphologies, the upper limb retains many primitive traits. Here, we describe the H. naledi upper extremity (excluding the hand) in detail and in a comparative context to evaluate the diversity of clavicular, scapular, humeral, radial, and ulnar morphology among early hominins and later Homo. Homo naledi had a scapula with a markedly cranially-oriented glenoid, a humerus with extremely low torsion, and an australopith-like clavicle. These traits indicate that the H. naledi scapula was situated superiorly and laterally on the thorax. This shoulder girdle configuration is more similar to that of Australopithecus and distinct from that of modern humans, whose scapulae are positioned low and dorsally about the thorax. Although early Homo erectus maintains many primitive clavicular and humeral features, its derived scapular morphology suggests a loss of climbing adaptations. In contrast, the H. naledi upper limb is markedly primitive, retaining morphology conducive to climbing while lacking many of the derived features related to effective throwing or running purported to characterize other members of early Homo.

Dental development in Homo naledi.

Humans' prolonged somatic development and life history are unique among primates, yet their evolutionary origins remain unclear. Dental development has been used as a proxy to reconstruct life history evolution in the hominin clade and indicates a recent emergence of the human developmental pattern. Here, we analyse tooth formation and eruption in two developing dentitions of Homo naledi, a late-surviving, morphologically mosaic hominin species. Deciduous dental development is more similar to humans than to chimpanzees, probably reflecting hominin symplesiomorphy rather than bearing life history significance. The later stages of permanent tooth development present a mix of human- and chimpanzee-like patterns. Surprisingly, the M2 of H. naledi emerges late in the eruption sequence, a pattern previously unknown in fossil hominins and common in modern humans. This pattern has been argued to reflect a slow life history and is unexpected in a small-brained hominin. The geological age of H. naledi (approx. 300 kya), coupled with its small brain size and the dental development data presented here, raise questions about the relationship between dental development and other variables associated with life history.

Evaluation of healing at molar extraction sites with ridge preservation using a non-resorbable dense polytetrafluoroethylene membrane: A four-arm cohort prospective study.

OBJECTIVES: To examine ridge dimensional changes and histologic parameters of healing when ridge preservation (RP) was performed at molar sites using dense polytetrafluoroethylene (dPTFE) membrane alone, without a bone graft. MATERIAL AND METHODS: Eighteen patients had molar extraction and RP using dPTFE membrane alone. Ridge dimensions were measured using two standardized cone beam computerized tomography (CBCT) scans taken within 72 h and 3 months following extraction. Following a 3-month healing period, an implant osteotomy was prepared using a trephine drill and bone cores were collected for histological analysis. Four-arm analyses were performed using data from three previously published study arms of the same research group. RESULTS: There was a significant change in the buccal ridge height between the four groups at all aspects of the socket. Alveolar ridge width reduction at 3 mm from crest for all aspects (mesial, midpoint, distal) of the socket showed statistically significant difference for dPTFE alone group compared to the other three groups. Percentage of vital bone formation (62.10%) was significantly greater in dPTFE alone group compared to the other groups. CONCLUSIONS: RP using dPTFE membrane alone in molar sites with intact socket walls showed successful outcomes in maintaining ridge dimensions and in histologic wound healing.

Evaluating bony predictors of bite force across the order Carnivora.

In carnivorans, bite force is a critical and ecologically informative variable that has been correlated with multiple morphological, behavioral, and environmental attributes. Whereas in vivo measures of biting performance are difficult to obtain in many taxa-and impossible in extinct species-numerous osteological proxies exist for estimating masticatory muscle size and force. These proxies include both volumetric approximations of muscle dimensions and direct measurements of muscular attachment sites. In this study, we compare three cranial osteological techniques for estimating muscle size (including 2D-photographic and 3D-surface data approaches) against dissection-derived muscle weights and physiological cross-sectional area (PCSA) within the jaw adductor musculature of 40 carnivoran taxa spanning eight families, four orders of magnitude in body size, and the full dietary spectrum of the order. Our results indicate that 3D-approaches provide more accurate estimates of muscle size than do surfaces measured from 2D-lateral photographs. However, estimates of a muscle's maximum cross-sectional area are more closely correlated with muscle mass and PCSA than any estimates derived from muscle attachment areas. These findings highlight the importance of accounting for muscle thickness in osteological estimations of the masticatory musculature; as muscles become volumetrically larger, their larger cross-sectional area does not appear to be associated with a proportional increase in the attachment site area. Though volumetric approaches approximate muscle dimensions well across the order as a whole, caution should be exercised when applying any single method as a predictor across diverse phylogenies.

Evaluation of healing at molar extraction sites with and without ridge preservation: A three-arm histologic analysis.

BACKGROUND: Little evidence is available regarding the benefit of ridge preservation (RP) at molar sites. The primary objective of this three-arm cohort study was to histologically compare the healing outcome between natural healing after molar tooth extraction and two different techniques of RP using freeze-dried bone allograft (FDBA) and a nonresorbable dense polytetrafluoroethylene (dPTFE) membrane, or an absorbable collagen sponge as a barrier. METHODS: Seventy-nine patients requiring extraction and delayed implant placement were placed into three groups: extraction alone (control); ridge preserved using FDBA; and either dPTFE (Test1) or collagen sponge (Test2). Bone cores were harvested from implant osteotomies at ≈3 months after extraction for histomorphometric analysis to determine the percentage of vital bone, residual graft, and connective or other tissue. Ridge dimension changes were also evaluated radiographically (cone-beam computed tomography). RESULTS: The percentage of vital bone was significantly greater in control group compared with Test1 but was not statistically different among other groups. Test2 showed significantly less connective or other tissue than control and Test1. The percentage of residual graft was significantly lower in Test1 compared with Test2. There was no significant correlation between the percentage of vital bone or residual graft and the following parameters: healing time, patient age, gender, buccal plate thickness, or radiographic changes in ridge dimensions. CONCLUSION: RP at molar sites using FDBA and an absorbable collagen sponge may be a sufficient and economic way to preserve the ridge dimension without interfering with the amount of new bone formation.

Evaluation of Healing at Molar Extraction Sites With and Without Ridge Preservation: A Randomized Controlled Clinical Trial.

BACKGROUND: To date, limited evidence is available specifically evaluating ridge preservation (RP) and implant placement in molar sites. The primary aim of this study is to radiographically compare alveolar ridge changes with and without RP with cone-beam computed tomography (CBCT). METHODS: This parallel, two-arm randomized clinical trial included 40 patients evenly distributed between two treatment groups. After molar extraction, sites were allowed to heal naturally or received RP with freeze-dried bone allograft covered by a non-resorbable dense polytetrafluoroethylene membrane. CBCT scans were taken immediately and 3 months postextraction, and then a dental implant was placed. Width and height measurements were made radiographically. RESULTS: Significantly greater loss in alveolar ridge height was found in molar sites allowed to heal without RP on the buccal aspect of the socket (RP: -1.12 ± 1.60 mm versus no RP: -2.60 ± 2.06 mm, P = 0.01). No significant difference in ridge width loss was found between groups. Two-thirds ridge width reduction was experienced on the buccal aspect in sites without RP, but width loss was evenly distributed between buccal and lingual aspects when RP was performed. Bone grafting at time of placement was required in 25% of implants in the group without RP versus 10% of implants in the RP group. CONCLUSIONS: In molar extraction sites without RP, significantly more reduction in ridge height occurred, and the majority of ridge width loss was localized to the buccal aspect. When RP was performed, ridge width loss was not significantly decreased, but the loss was evenly distributed between facial and lingual aspects of the extraction site.

Patient dosimetry and a novel approach to establishing Diagnostic Reference Levels in dental radiology.

Diagnostic Reference Levels provide a method of ensuring that patient doses in medical procedures are kept at acceptable levels. Their application in dentistry can provide an indication of current dose levels and can assist in potentially significant dose reduction in Ireland given the number of patients screened annually. This study involved retrospective analyses of entrance surface dose and dose-width-product measurements obtained in Irish Dental Practices for both Intra-Oral and Panoramic units respectively, followed by comparisons with Monte-Carlo generated computer models of these procedures. Analysis was performed on data from 33 Intra-Oral units for an Adult Mandibular Molar entrance surface dose, 198 readings for a proposed mGy/mAs reference level and 50 Panoramic machines for a dose-width product investigation. The third quartile value of the entrance surface dose for a standard Adult Mandibular Molar Intra-Oral radiograph is (2.40 ± 0.92)mGy, compared to a computer-modelled value of 2.60 mGy. The third quartile mGy/mAs value for Intra-Oral procedures is (1.03 ± 0.38)mGy/mAs, compared to a computer-modelled value of 0.75 mGy/mAs. The third quartile dose width product for an Adult Panoramic radiograph is (59.89 ± 20.97)mGymm, compared to a computer-modeled value of 62.40 mGymm. It is proposed to introduce Diagnostic Reference Levels of 2.4 mGy for an Adult Mandibular Molar Intra-Oral radiograph and 60 mGymm for an Adult Panoramic radiograph. The use of a new reference quantity in Intra-Oral radiology is also suggested. This has a value of 1 mGy/mAs and may be introduced alongside established procedures. These levels can be taken as guides to acceptable doses, but it should be noted that further reductions are practical under ALARA principles.

Microfluidic vias enable nested bioarrays and autoregulatory devices in Newtonian fluids.

We report on a fundamental technological advance for multilayer polydimethylsiloxane (PDMS) microfluidics. Vertical passages (vias), connecting channels located in different layers, are fabricated monolithically, in parallel, by simple and easy means. The resulting 3D connectivity greatly expands the potential complexity of microfluidic architecture. We apply the vias to printing nested bioarrays and building autoregulatory devices. A current source is demonstrated, while a diode and a rectifier are derived; all are building blocks for analog circuitry in Newtonian fluids. We also describe microfluidic septa and their applications. Vias lay the foundation for a new generation of microfluidic devices.