Freeze-drying is an effective means to control scaffold pore size and preserve its composition. The purpose of the present study was to determine the applicability of lyophilized Platelet-rich fibrin (LPRF) as a scaffold for craniofacial tissue regeneration and to compare its biological effects with commonly used fresh Platelet-rich fibrin (PRF). LPRF caused a 4.8-fold ± 0.4-fold elevation in Runt-related transcription factor 2 (Runx2) expression in alveolar bone cells, compared to a 3.6-fold ± 0.2-fold increase when using fresh PRF, and a more than 10-fold rise of alkaline phosphatase levels and mineralization markers. LPRF-induced Runx2 expression only occurred in alveolar bone and not in periodontal or dental follicle cells. LPRF also caused a 1.6-fold increase in osteoblast proliferation (p < 0.001) when compared to fresh PRF. When applied in a rat craniofacial defect model for six weeks, LPRF resulted in 97% bony coverage of the defect, compared to 84% for fresh PRF, 64% for fibrin, and 16% without scaffold. Moreover, LPRF thickened the trabecular diameter by 25% when compared to fresh PRF and fibrin, and only LPRF and fresh PRF resulted in the formation of interconnected trabeculae across the defect. Together, these studies support the application of lyophilized PRF as a biomimetic scaffold for craniofacial bone regeneration and mineralized tissue engineering.

Chewing kinematics reflects interactions between centrally generated motor signals and peripheral sensory feedback from the constantly changing oral environment. Chewing is a strongly modulated behavior that responds to differences in material properties among different type of foods and to changes in the external physical properties of the food as the bolus gets processed. Feeding, as any complex biological behavior, presents variation at multiple hierarchical levels, from among species or higher-order levels to variation among chewing cycles within a single feeding sequence. Thus, to understand the mechanics and evolution of feeding systems requires estimation of how this variation is distributed across each of these hierarchical levels, which in turn requires large sample sizes. The development of affordable, high-resolution, three-dimensional kinematic recording systems has increased our ability to collect large amounts of data on complete or near-complete feeding sequences that can be used to shed light on the mechanisms of control in vertebrate feeding. In this study, we present data on the nature and sources of variation (from species to chewing cycle levels) in kinematics of chewing in two species of primates, Cebus and Macaca, while they feed on foods of known material properties. Variation in chewing kinematics was not evenly distributed among hierarchical levels. Most of the variation was observed among chewing cycles, most likely in response to changes in the external properties of the food bolus throughout the feeding sequence. Species differences were found in duration and vertical displacement during slow-close phase suggesting that each species exhibits different power stroke dynamics. Cebus exhibited more variable gape cycles than did Macaca, in particular when eating low-toughness foods. This increased ability to temporally and spatially modulate the gape cycle may reflect increased efficiency in processing food because Cebus monkeys use fewer, but longer cycles, than does Macaca when feeding on low-toughness foods. This is due to an increase in duration of the jaw-opening phases of the gape cycle, when the tongue repositions the food bolus in the oral cavity.

The functional effects of bone and suture stiffness were considered here using finite element models representing three different theoretical phenotypes of an Alligator mississippiensis mandible. The models were loaded using force estimates derived from muscle architecture in dissected specimens, constrained at the 18th and 19th teeth in the upper jaw and 19th tooth of the lower jaw, as well as at the quadrate-articular joint. Stiffness was varied systematically in each theoretical phenotype. The three theoretical phenotypes included: (i) linear elastic isotropic bone of varying stiffness and no sutures; (ii) linear elastic orthotropic bone of varying stiffness with no sutures; and (iii) linear elastic isotropic bone of a constant stiffness with varying suture stiffness. Variation in the isotropic material properties of bone primarily resulted in changes in the magnitude of principal strain. By comparison, variation in the orthotropic material properties of bone and isotropic material properties of sutures resulted in: a greater number of bricks becoming either more compressive or more tensile, changing between being either dominantly compressive or tensile, and having larger changes in the orientation of maximum principal strain. These data indicate that variation in these model properties resulted in changes to the strain regime of the model, highlighting the importance of using biologically verified material properties when modeling vertebrate bones. When bones were compared within each set, the response of each to changing material properties varied. In two of the 12 bones in the mandible, varied material properties within sutures resulted in a decrease in the magnitude of principal strain in bricks adjacent to the bone/suture interface and decreases in stored elastic energy. The varied response of the mandibular bones to changes in suture stiffness highlights the importance of defining the appropriate functional unit when addressing relationships of performance and morphology.