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The hypothesis is rejected. Both maxillary incisor labiolingual inclination and AP position play an essential role in the esthetics of the smiling profile. However, when formulating treatment plans, dentists should never underestimate the labiolingual inclination's influence on the smiling profile.

Hertwig's epithelial root sheath (HERS) cells participate in cementum formation through epithelial-mesenchymal transition (EMT). Previous studies have shown that transforming growth factor beta 1 (TGF-β1) and fibroblast growth factor 2 (FGF2) are involved in inducing EMT. However, their involvement in HERS cell transition remains elusive. In this study, we confirmed that HERS cells underwent EMT during the formation of acellular cementum. We found that both TGF-β1 and FGF2 stimulated the EMT of HERS cells. The TGF-β1 regulated the differentiation of HERS cells into periodontal ligament fibroblast-like cells, and FGF2 directed the differentiation of HERS cells into cementoblast-like cells. Treatment with TGF-β1 or FGF2 inhibitor could effectively suppress HERS cells differential transition. Combined stimulation with both TGF-β1 and FGF-2 did not synergistically accelerate the EMT of HERS. Moreover, TGF-β1/FGF2-mediated EMT of HERS cells was reversed by the MEK1/2 inhibitor U0126. These results suggest that TGF-β1 and FGF2 induce the EMT of HERS through a MAPK/ERK-dependent signaling pathway. They also exert their different tendency of cellular differentiation during tooth root formation. This study further expands our knowledge of tooth root morphogenesis and provides more evidence for the use of alternative cell sources in clinical treatment of periodontal diseases.

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Introduction: A protocol was introduced to achieve accurate bracket placement in vivo, which consisted of operative procedures for precise control, and a computer-aided design and computer-aided manufacturing-guided bonding device. To evaluate the accuracy of this protocol, a 3-dimensional assessment was performed. Methods: Ten consecutive patients were enrolled. Strictly following the protocol, from December 2017 to March 2018, brackets were placed on the teeth of each patient using the device. To evaluate the accuracy, deviations of positions and orientations for bracket placement were measured. Each patient was followed up after 3 months regarding bracket failures. Results: The guided bonding device was used in all cases, and a total of 205 brackets were successfully bonded and evaluated. Except for 15.12% brackets with torque deviation over 2 , the deviations in mesiodistal, buccolingual, vertical, rotation, and angulation were below the clinical acceptable range (0.5 mm in translation or 2 in orientation) for all brackets. In the 3-month follow-up, there was no bracket failure in any patient. Conclusion: This protocol transferred the planned bracket position from the digital setup to patient's dentition with generally high positional accuracy. (Am J Orthod Dentofacial Orthop 2020;157:269-77)

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has attracted worldwide concerns because of its high person-to-person infectivity and lethality, and it was labeled as a pandemic as the rapid increase in the number of confirmed patients in most areas around the world became evident. The SARS-CoV-2 is mainly transmitted through respiratory droplets and close contact. There is also evidence of transmission through aerosols and digestive tracts. Because orthodontic treatment involves a large population who need routine return-visits, it was significantly affected and suspended because of the COVID-19 pandemic and the shutdown of the dental clinics and hospitals. Although the spread of COVID-19 has been effectively controlled in China, and many areas have gradually resumed work and classes, orthodontic participants are still under high risks of SARS-CoV-2 infection. This is due to the fact that the asymptomatic carriers of SARS-CoV-2 or patients in the incubation period may cause the cross-infection between orthodontic practitioners and patients. The close proximity between the practitioners and the patients, and the generation of droplets and aerosols that contain saliva and blood during treatment further increase the risks of transmission. In this article, we summarized the preventive strategies for control of SARS-CoV-2 transmission to protect both staff and patients during the orthodontic practice.

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