Control of Orthodontic Tooth Movement by Nitric Oxide Releasing Nanoparticles in Sprague-Dawley Rats.

Orthodontic treatment commonly requires the need to prevent movement of some teeth while maximizing movement of other teeth. This study aimed to investigate the influence of locally injected nitric oxide (NO) releasing nanoparticles on orthodontic tooth movement in rats. Materials and Methods: Experimental tooth movement was achieved with nickel-titanium alloy springs ligated between the maxillary first molar and ipsilateral incisor. 2.2 mg/kg of silica nanoparticles containing S-nitrosothiol groups were injected into the mucosa just mesial to 1st molar teeth immediately prior to orthodontic appliance activation. NO release from nanoparticles was measured in vitro by chemiluminescence. Tooth movement was measured using polyvinyl siloxane impressions. Bones were analyzed by microcomputed tomography. Local tissue was assessed by histomorphometry. Results: Nanoparticles released a burst of NO within the first hours at approximately 10 ppb/mg particles that diminished by 10 × to approximately 1 ppb/mg particles over the next 1-4 days, and then diminished again by tenfold from day 4 to day 7, at which point it was no longer measurable. Molar but not incisor tooth movement was inhibited over 50% by injection of the NO releasing nanoparticles. Inhibition of molar tooth movement occurred only during active NO release from nanoparticles, which lasted for approximately 1 week. Molar tooth movement returned to control levels of tooth movement after end of NO release. Alveolar and long bones were not impacted by injection of the NO releasing nanoparticles, and serum cyclic guanosine monophosphate (cGMP) levels were not increased in animals that received the NO releasing nanoparticles. Root resorption was decreased and periodontal blood vessel numbers were increased in animals with appliances that were injected with the NO releasing nanoparticles as compared to animals with appliances that did not receive injections with the nanoparticles. Conclusion: Nitric oxide (NO) release from S-nitrosothiol containing nanoparticles inhibits movement of teeth adjacent to the site of nanoparticle injection for 1 week. Additional studies are needed to establish biologic mechanisms, optimize efficacy and increase longevity of this orthodontic anchorage effect.

Program and candidate experience with virtual interviews for the 2020 Complex General Surgical Oncology interview season during the COVID pandemic.

BACKGROUND: The COVID crisis hit during the interview season for the Complex General Surgical Oncology (CGSO) fellowship. With minimal time to adapt, all programs transitioned to virtual interviews. Here we describe the experience of both program directors (PDs) and candidates with virtual interviews, and provide guidelines for implementation based on the results. METHODS: Surveys regarding interview day specifics and perceptions were created for CGSO fellowship PDs and candidates. They were distributed at the conclusion of the season, prior to match. RESULTS: Thirty (94%) PDs and 64 (79%) candidates responded. Eighty-three% of PDs and 79% of candidates agreed or strongly agreed that they felt comfortable creating a rank list. If given the choice, 60% of PDs and 45% of candidates would choose virtual interviews over in-person interviews. The majority of candidates found PD overviews, fellows only sessions and pre-interview materials helpful. CONCLUSION: Overall, the majority of PDs and candidates felt comfortable creating a rank list; however, more PDs preferred virtual interviews for the future. Our results also confirm key components of a virtual interview day.

Inactivation of Fam20B in the dental epithelium of mice leads to supernumerary incisors.

Tooth formation is tightly regulated by epithelial-mesenchymal interactions via hierarchic cascades of signaling molecules. The glycosaminoglycan (GAG) chains covalently attached to the core protein of proteoglycans (PGs) provide docking sites for signaling molecules and their receptors during the morphogenesis of tissues and organs. Although PGs are believed to play important roles in tooth formation, little is known about their exact functions in this developmental process and the relevant molecular basis. Family with sequence similarity member 20-B (FAM20B) is a newly identified kinase that phosphorylates the xylose in the common linkage region connecting the GAG with the protein core of PGs. The phosphorylation of xylose is essential for elongation of the common linkage region and the subsequent GAG assembly. In this study, we generated a Fam20B-floxed allele in mice and found that inactivating Fam20B in the dental epithelium leads to supernumerary maxillary and mandibular incisors. This finding highlights the pivotal role of PGs in tooth morphogenesis and opens a new window for understanding the regulatory mechanism of PG-mediated signaling cascades during tooth formation.