by Colin Dawes
I started in Dental School at Manchester in 1953. After the 2nd MB, BDS exams, in which I shared the Sydney Renshaw prize in Physiology, I had the opportunity to be the first dental student to take a one-year intercalated B.Sc. in Physiology (Pip Thomas was the second!), thanks to a Nuffield Foundation scholarship. Although the Physiology Department wanted me to stay on for an M.Sc., Dean Horace Radden, strongly advised me to finish my dental degree first, which was good advice.
In my final dental year (December 1958), I was fortunate to be the one chosen to spend September at Newcastle Dental School. I was assigned to a different department each day of the week, where I found they often did clinical procedures differently from how we were taught at Manchester.
It was in Newcastle that I had my first experience of a patient having an attack of epilepsy, removed a broken down upper molar which had defeated the best efforts of two Newcastle students, assisted Prof. Fred Hopper (a future Dean at Leeds Dental School) with patients requiring specialistoral surgery and generally felt that my career was influenced by this albeit short stay in a different dental school! However, my life changing experience there was to spend four days in the laboratory of Prof. Neil Jenkins, the leading oral biologist in Britain at the time.
This encouraged me, after graduation and a house surgeon appointment, to work for three years with Prof. Jenkins for a Ph.D. in oral physiology. For someone contemplating an academic career, the most important decision they must make is selection of the best possible supervisor, no matter where they are located. My research initially focused on the inorganic composition of dental plaque and one study involved a comparison of the fluoride concentration in plaque from children from North Shields (0 ppm F in the water) and West Hartlepool (2 ppm F in the water).
I had never seen so many caries-free children as in those from West Hartlepool and I became a great believer in the value of water fluoridation as a protection against dental caries. I also did studies on some of the many factors influencing the flow rate and composition of saliva. While a student I was told virtually nothing about saliva but I am sure that has now changed.
When I began writing my thesis, I found the literature on dental plaque and the other integuments of the teeth to be very confusing and, together with Profs. Jenkins and Tonge, I came up with a recommended nomenclature, which is still commonly used today. I finished my Ph.D. in 1962 but there were no academic positions available in oral biology in the UK, where the only four positions available in the whole country were all held by relatively young men.
However, Prof. Jenkins had a stream of visitors from around the world, one being Finn Brudevold, of fluoride fame, from Boston. He did not have a post-doctoral position available but he put me in touch with Prof. Jim Shaw at the Harvard School of Dental Medicine (HSDM) in Boston. Jim Shaw was a biochemist and a leading authority on the effect of diet on dental caries in rats, so I was set to work in a laboratory which had recently been occupied by Phil Holloway, before he left for a position in Children’s Dentistry in Manchester.
After spending two years in Boston where I did studies on both rat caries and on the proteins in human saliva, I applied for a faculty position at the virtually new Dental School at the Univ. of Manitoba in Winnipeg, Canada where in 1964, I was appointed an Associate Professor and promoted to Full Professor in 1972. The Dept. Head in Biochemistry (Iz Kleinberg) had taken his Ph.D. with Neil Jenkins and the Head of Physiology (Charles Dowse) had done a postdoc with Neil Jenkins. Despite having these research interests in common, however, I never worked on research with them except for one project with Charles Dowse.
We found Winnipeg to be an attractive city. Summers are quite pleasant, although we do see the occasional mosquito, in winter temperatures can reach -30°C but, as we like to say, it is a dry cold! My academic duties were to teach general and oral physiology, as well as contribute to some graduate courses, such as the Ph.D. programme in Oral Biology, which was the first in the world with that name. I did not take the clinical licensure examination until 1976 but then, for 25 years, I practised clinical dentistry, one day per week, on two Indian reservations. Dental students subsequently seemed more attentive when they realised that I also treated patients!
My research for about 20 years was on identifying the normal physiological variables which can influence salivary flow rate and composition, such as the duration of stimulation, the nature of the stimulus, circadian rhythms and exercise, funded mainly by the Canadian Medical Research Council, on which I spent six years as a dental representative.
In 1970 I took a six-month sabbatical, the first three months of which I spent in the Physiology Department in Manchester with David Ferguson. That Department had expertise in rhythm research and they had a separate suite outside Manchester in which I lived by myself for two weeks with no time clues. My various circadian rhythms, such as temperature and salivary flow rate, “free-ran” with a period of 25.5 hours, instead of the normal 24 hours.
The other three months I spent in Minneapolis with Prof. Franz Halberg, who coined the term ‘circadian’ and was an expert on the statistical analysis of rhythms. Incidentally, peak unstimulated salivary flow rate occurs at about 5 p.m.
I regularly attended the yearly IADR and ORCA meetings and soon grew to know many internationally recognised dental researchers. This led to my appointment from 1983-93 as Editor of the Journal of Dental Research, the main dental research journal in the world. This was a very time-consuming position, there being no internet, during which time I edited 3,500 manuscripts for publication. Three of my research papers have been particularly well cited.
The first was a new model of salivary clearance which likens the process to the operation of an incomplete syphon. Clearance of sugar from the mouth depends not only on the salivary flow rate but also on how much saliva is in the mouth before swallowing is elicited and how much is left in the mouth afterwards. The second paper showed that the sensation of dry mouth occurs when the flow of saliva drops, not to zero, but to 40 – 50% of normal.
The third one presented the new concept that saliva is present in the mouth as a thin film, less than 0.1 mm in thickness and we showed that its velocity varies markedly in different oral sites. This strongly influences acid diffusion from plaque.
I officially retired in 2004 but I still carry on with academic matters. I am a member of an international group chosen by the World Workshop on Oral Medicine VI, and we have produced five publications related to salivary dysfunction in the last two years. Over my career I have been fortunate to be invited to give 221 lectures on my research in 27 different countries. I have also served in the army in three different countries – England, America and Canada. I refer, of course, to the Salivation Army!