NA. Laryngoscope, 127:E392-E398, 2017.

Three-dimensional (3D) printing is an emerging technology in the field of dentistry. It uses a layer-by-layer manufacturing technique to create scaffolds that can be used for dental tissue engineering applications. While several 3D printing methodologies exist, such as selective laser sintering or fused deposition modeling, this paper will review the applications of 3D printing for craniofacial tissue engineering; in particular for the periodontal complex, dental pulp, alveolar bone, and cartilage. For the periodontal complex, a 3D printed scaffold was attempted to treat a periodontal defect; for dental pulp, hydrogels were created that can support an odontoblastic cell line; for bone and cartilage, a polycaprolactone scaffold with microspheres induced the formation of multiphase fibrocartilaginous tissues. While the current research highlights the development and potential of 3D printing, more research is required to fully understand this technology and for its incorporation into the dental field.

Restructuring of monodisperse soot aggregates due to coatings of secondary organic aerosol (SOA) derived from hydroxyl radical-initiated oxidation of toluene, p-xylene, ethylbenzene, and benzene was investigated in a series of photo-oxidation (smog) chamber experiments. Soot aggregates were generated by combustion of ethylene using a McKenna burner, treated by denuding, size-selected by a differential mobility analyzer, and injected into a smog chamber, where they were exposed to low vapor pressure products of aromatic hydrocarbon oxidation, which formed SOA coatings. Aggregate restructuring began once a threshold coating mass was reached, and the degree of the subsequent restructuring increased with mass growth factor. Although significantly compacted, fully processed aggregates were not spherical, with a mass-mobility exponent of 2.78, so additional SOA was required to fill indentations between collapsed branches of the restructured aggregates before the dynamic shape factor of coated particles approached 1. Trends in diameter growth factor, effective density, and dynamic shape factor with increasing mass growth factor indicate distinct stages in soot aggregate processing by SOA coatings. The final degree and coating mass dependence of soot restructuring were found to be the same for SOA coatings from all four aromatic precursors, indicating that the surface tensions of the SOA coatings are similar.

Absence of large amounts of orofacial tissues caused by cancerous resections, congenital defects or trauma result in sequelae such as dysphagia and noticeable scars. Oral-neck tissue regeneration was studied in the axolotl (regenerative amphibian) following a 2.5mm punch biopsy that simultaneously removed skin, connective tissue, muscle, and cartilage in the tongue and intermandibular region. The untreated wound was studied macroscopically and histologically at 17 different time points ranging from 0-180d (N= 120 axolotls). At 12h the wound's surface was smoothened and within 1mm, internal lingual muscular modifications occurred; at the same distance, between days 4-7 lingual muscle degradation was complete. Immunofluorescence indicates complete keratinocytes migration by 48h. These cells with epidermal Leydig cells, appearing yellow, lead the chin's deep tissue outgrowth until its closure on the 14 th day. Regeneration speeds varied and peaked in time for each tissue, 1) deep Immunofluorescence toCol IV showed basement membrane reconnected between days 30-45 coinciding with the chin's dermal tissue's surface area recovery. New muscle appeared at 21d and was always preceded by the formation of a collagen bed. Both chin tissues regain all surface area and practically all components while the lingual structure lacks some content but is generally similar to the original.The methodology and high-resolution observations described here are the first of its kind for this animal model and could serve as a basis for future studies in oral and facial regenerative research.3

For salivary gland (SG) tissue engineering, we cultured acinar NS-SV-AC cell line or primary SG fibroblasts for 14 days in avian egg yolk plasma (EYP). Media or egg white (EW) supplemented the cultures as they grew in 3D-Cryo histology well inserts. In the second half of this manuscript, we measured EYP’s freeze-thaw gelation and freeze-thaw induced gelled EYP (GEYP), and designed and tested further GEYP tissue engineering applications. With a 3D-Cryo well insert, we tested GEYP as a structural support for 3D cell culture or as a bio-ink for 3D-Bioprinting fluorescent cells. In non-printed EYP + EW or GEYP + EW cultures, sagittal sections of the cultures showed cells remaining above the well’s base. Ki-67 expression was lacking for fibroblasts, contrasting NS-SV-AC’s constant expression. Rheological viscoelastic measurements of GEYP at 37 °C on seven different freezing periods showed constant increase from 0 in mean storage and loss moduli, to 320 Pa and 120 Pa, respectively, after 30 days. We successfully 3D-printed GEYP with controlled geometries. We manually extruded GEYP bio-ink with fluorescence cells into a 3D-Cryo well insert and showed cell positioning. The 3D-Cryo well inserts reveal information on cells in EYP and we demonstrated GEYP cell culture and 3D-printing applications.