‘the science that deals with the morphological, functional and behavioural aspects of thegosis and the treatment of its related physical, emotional and social pathologies.’ Every 1972
GREEK thego, to whet, sharpen; also metaphorically, to excite, provoke. Every 1972
Some background and comments:
In 1958 at a Dental Conference in Christchurch, New Zealand, Dr R.G. Every, a Christchurch dentist, presented an argument that tooth grinding in human beings was in fact tooth sharpening. The biological and clinical significance of this discovery was published in The Lancet: “The Significance of Extreme Mandibular Movements” [Every 1960) and “The Teeth as Weapons” [Every 1965].
Homer first recorded the phenomenon of a specific tooth-sharpening behaviour when he described specific dental weapon sharpening in the wild boar.
In 1967 at a London symposium of vertebrate palaeontology and comparative anatomy he introduced the word thegosis to define the instinctive tooth sharpening behaviour he had discovered [Every 1970]
It is appropriate, in view of Homer’s observation, that a term to describe the innate tooth sharpening behaviour should be derived from the Greek word thego – to whet and to sharpen; also, metaphorically, to excite and provoke [Every 1972].
Just as when hounds, and young men in their bloom, press round a boar, and he comes forth from his deep lair whetting his white tusks between crooked jaws, and round him they rush: and in the midst of all this is heard the noise (from the whetting) of his teeth, and straightway they await his assault, dread as he is – even so then round Odysseys dear to Zeus, rushed the Trojans.
– Homer the Iliad, 700 BC,
While early dental writers understood that our teeth cut with blades and crush and pierce with cusps, they were lead to the mistaken interpretation that tooth grinding and abrasion destroyed the tooth’s morphological or primary sharpness [Balkwill 1867].
In contrast, Every demonstrated that the usual abrasive wearing due to incision, mastication, and other processes was complemented by an innate, genetically programmed behaviour – thegosis. This innate behaviour refreshed the tooth surface, refined, and redefined the abraded morphologically sharp features of the teeth in human and many other mammals. The evidence for this behaviour is the presence of thegosis-facets. Thegosis-facets are the biological equivalents of the honed back of a chisel, adze, or sickle .
It is clear that thegosis is a universal phenomenon. It is found in many animals, both vertebrates and invertebrates, and in each it affords the same biological advantage: the honing of teeth and tooth-like structures for efficient function as tools and/or weapons [Tunnicliffe 1973, Scally 1973, Scally Tunnicliffe et.al. 1974].
This view that tooth grinding is a normal innate behaviour is completely contrary to orthodox teaching that facets are evidence of bruxism and that this behaviour is pathological.
Since 1958 Every’s hypothesis has been exhaustively tested and his original views have found increasing independent support [Craddock & Johnston 1961, Simpson 1972, Scally 1973, Tunnicliffe 1973, Scally 1979, Scally 1980, Wells, et al 1982, Von Vierhaus 1983]. In spite of this there has been little or no acceptance of the phenomenon, or recognition of its clinical significance and general applicability.
During the 60s and early 70s there was some independent discussion of thegosis in two disciplines, vertebrate palaeontology and physical anthropology; with cautious acknowledgment of Every’s discovery [Simpson 1972]. However, in recent literature, all discussion or citation of thegosis and its significance has ceased in these disciplines. In addition, other authors, while familiar with the concepts have either ignored, or in some instances, misinterpreted Every’s ideas and misquoted his arguments [Teaford & Walker 1983].
As a consequence, almost the entire literature on tooth-wear, including studies of the human dentition, and the dietary and behavioural conclusions derived from them is fundamentally flawed [Scally 1991a].
Kevin B Scally November 1998