Emma Muriel Strode Cosh was born on 27 December 1907 in Newcastle-upon-Tyne, eldest child of Arthur Strode Cosh, pharmacist. Her mother was born on St Helena, Ellen (Nell) Janisch, whose father Bertram, son of the then Governor of the island, had been the colonial medical officer. On Bertram's death at an untimely age his widow Emma, with two young daughters and pregnant with a third, returned to live with her siblings in Newcastle-upon-Tyne.

Arthur and Nell Cosh and their small daughter Muriel moved to Bristol in 1910, where Arthur had acquired a chemist's shop and over the years built up a flourishing chain of shops. Muriel's younger brother John, born in 1915, became a distinguished rheumatology consultant, and the youngest child is a historical and architectural writer.

Muriel attended Colston Girls' School in Bristol and then took a degree in dentistry at Bristol University, graduating BDS in 1930 in a profession then unusual for women. After a short spell as assistant in a private practice she embarked on her life's career in children's dental service, first with Bristol County Council, in charge of East Bristol clinic, the largest area in the city, expanding in 1937 to peripheral clinics in south Gloucestershire. This also involved visiting country schools, carrying in her car all the necessary equipment, including a cumbersome foot drill. For this job she was well qualified, not only for efficiency but getting on well with her young patients.

Early in 1949 Muriel transferred to London County Council and the clinic at Acton, living at Notting Hill Gate. Here she continued in charge until her retirement in 1967.

A keen traveller, holidaying in most European countries, Muriel was also an avid reader, notably of detective stories, in which she was a connoisseur. She was also an accomplished gardener, and for many years one of her greatest pleasures was creating and maintaining a fine flower and kitchen garden out of the mud patch of a run-down cottage which she bought and restored near Newbury in Berkshire. Here she happily entertained friends and relatives at weekends.

In her last years Muriel lived a retired life, victim to arthritis and impaired hearing, and died peacefully in hospital on 17 October 2007, after a serious fall at home. Sadly missed by devoted friends and family, had she lived a mere ten weeks longer she and they would have been celebrating her hundredth birthday.