Background SARS-CoV-2 IgG antibody measurements can be used to estimate the proportion of a population exposed or infected and may be informative about the risk of future infection. Previous estimates of the duration of antibody responses vary. Methods We present 6 months of data from a longitudinal seroprevalence study of 3276 UK healthcare workers (HCWs). Serial measurements of SARS-CoV-2 anti-nucleocapsid and anti-spike IgG were obtained. Interval censored survival analysis was used to investigate the duration of detectable responses. Additionally, Bayesian mixed linear models were used to investigate anti-nucleocapsid waning. Results Anti-spike IgG levels remained stably detected after a positive result, e.g., in 94% (95% credibility interval, CrI, 91-96%) of HCWs at 180 days. Anti-nucleocapsid IgG levels rose to a peak at 24 (95% credibility interval, CrI 19-31) days post first PCR-positive test, before beginning to fall. Considering 452 anti-nucleocapsid seropositive HCWs over a median of 121 days from their maximum positive IgG titre, the mean estimated antibody half-life was 85 (95%CrI, 81-90) days. Higher maximum observed anti-nucleocapsid titres were associated with longer estimated antibody half-lives. Increasing age, Asian ethnicity and prior self-reported symptoms were independently associated with higher maximum anti-nucleocapsid levels and increasing age and a positive PCR test undertaken for symptoms with longer anti-nucleocapsid half-lives. Conclusion SARS-CoV-2 anti-nucleocapsid antibodies wane within months, and faster in younger adults and those without symptoms. However, anti-spike IgG remains stably detected. Ongoing longitudinal studies are required to track the long-term duration of antibody levels and their association with immunity to SARS-CoV-2 reinfection.

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This review article presents an overview of craniofacial malformations and the role of the orthodontist in their management. The first part of this article focuses on cleft lip and palate, followed by more complex deformities including craniosynostosis and craniofacial microsomia. The main features of these anomalies are discussed as well as the clinical problems seen in this group of patients. The emphasis is on the role of the orthodontist in the multi-disciplinary management of these cases.

The transmission of torquing forces between three types of pre-adjusted bracket was investigated. 0·022-inch Roth prescription ‘A’-Company® (stain less steel), Silkon® (reinforced polycarbonate), and Allure III® (polycrystalline ceramic) brackets were used. A selection of stainless steel archwires were chosen, 0·018 × 0·025, 0·019 × 0·025, and 0·021 × 0·025 inch. The brackets were torqued with respect to the archwire and force v. angular deflection was recorded on an Instron machine. The dimension of angular change was in part dependent on the ability of the bracket to elastically or plastically deform. There were no significant differences between bracket types with the 0·018 × 0·025-inch archwire. ‘A’-Company® brackets demonstrated a significantly lower resistance to loading compared to Silkon® brackets in the 0·019 × 0·025-inch group. The greatest amount of distortion was seen in Silkon® brackets with an 0·021 × 0·025-inch archwire. Allure III® brackets demonstrated the greatest resistance to loading in all groups. As no apparent distortion under loading is seen in Allure III® brackets, it is assumed that the load is largely transmitted to the tooth. Full thickness stainless steel rectangular wires should be avoided with these brackets, in order to prevent overloading.