Tuesday, 29 May 2012

Sex, teeth and syphilis...

Perusing through the British Dental Journal (BDJ) this morning, I noticed an article about syphilis (one of the more exciting sexually transmitted diseases) which I thought might be worth reading. From an osteological point of view, syphilis is one of the most interesting conditions to find in an individual because, left without treatment, it manifests in a number of horrible ways in the skeleton. The disease, caused by the Treponema pallidum organism eventually leads to skeletal lesions such as 'caries sicca', the pitting and whole-scale destruction of the skull through necrosis of the bone, amongst other things.

Figure 1: Caries sicca, the destruction of the frontal bone of the skull.
Image courtesy of the Cambridge Encyclopaedia of Palaeoanthropology, pp 161.

Syphilis can also be transmitted from mother to fetus, leading to a congenital form of the disease. Although it can cause a variety of developmental problems, from an osteological and dental point of view, it is the manifestation of 'Hutchinson's teeth' that are most diagnostic. The front teeth of such individuals are deformed and notched in a peculiar way - the result of particular kinds of bacteria called spirochetes inhibiting bone formation in the developing child.

So, why did the article in the BDJ inspire this blog? Mostly because it's a bit on the scary side. The cases of syphilis in the UK increased by 951% between 1999 and 2008. Although initially curable, the disease only presents a brief lesion at first (the chancre, which can appear at the point of infection), followed by a rash and sometimes - up to 50 years later - the bone changes mentioned above. Ignoring the initial appearance of the disease is probably a bad thing to do, then.

Jones et al (2012) discuss three case studies of the disease, pointing out that the initial presentation of the disease may occur in the oral cavity, in the form of a painful ulcer or lesion. Although the appearance will vary from one individual to the next, it can look a bit like this:

Figure 2: A syphilitic chancre on the tongue.
(Reprinted from the New England Journal of Medicine
without permission.  Ahem.)

The article states that the 'significant increase of syphilis and its high infectivity require the dental profession to increase their awareness of sexually infectious diseases and the appropriate dental management' (Jones et al 2012: 477), a useful recommendation, considering the rise in the number of cases in recent years.

However, I would like to increase everyone's awareness of the really horrible things that can happen if you're not careful with your sexy times. Because as fun as things might seem at the time, having your bone become infected and rot away, sending you slowing insane, probably isn't worth it in the end. So remember:

Figure 3: Yep, all of them. Including that one a few rows
back on the right. Especially him.

Jones et al 2012. Three cases of oral syphilis – an overview. 
Available at: http://www.nature.com/bdj/journal/v212/n10/full/sj.bdj.2012.420.html#f2

Thursday, 10 May 2012

By tooth or by beak...

Researchers at the University of Sheffield and King's College London have discovered that the pufferfish, a highly poisonous but silly looking tropical fish, may hold the key to how and why humans do not replace their teeth in adulthood - which may in turn lead to advances in dental treatments.

Certain adult pufferfish have a parrot like 'beak' with a distinct cutting edge. This beak is formed by bands of dentine which continually grow to replace those lost through feeding.  In young pufferfish, the beak is not present, instead 'first-generation' teeth develop, only to be replaced by four teeth at the front of the jaw which subsequently make-up the beak structure.

 Figure 1: A, the freshwater pufferfish, Monotrete abei. B, side-view 
showing the large lips covering the beak. C & D, views of the beak itself. 
Photo courtesy of Fraser et al (2012: 2)

According to Dr Gareth Fraser, who led the project, investigating the manner and mechanisms of tooth replacement is of  "great interest for science... to understand the genes that govern the continued supply of teeth and mechanisms of dental stem cell maintenance."

Humans only replace their teeth once, in childhood.  Unlike a shark with its many rows of teeth, or a rat with it's continually erupting ones, humans cannot replace teeth naturally. The much increased longevity of modern human populations is therefore at odds with the single set of trauma-and-disease-prone adult teeth they have. Dr Fraser believes that the knowledge could eventually be used to "facilitate advances in dental therapies" with this in mind. 

Fraser, GJ, Britz, A, Johanson, Z and Smith, M. 2012. Replacing the first-generation dentition in pufferfish with a unique beak. PNAS. 
Available at: http://www.pnas.org/content/early/2012/05/04/1119635109.full.pdf+html
University of Sheffield press release. 
Available at: http://sheffield.ac.uk/mediacentre/2012/pufferfish-gareth-fraser-natural-history-museum-evolution-denistry.html