Kevin B. Scally and Donald A. Beaven

The articles, “Management of Facial Pain and Headache: Psychiatric Approach” (1) by Charlotte Feinmann and “The Clinical Presentation of Functional Facial Pain Syndromes”(2) by David Wray in the College Journal accurately described the difficulties in diagnosing and managing orofacial and cranial aches and pains.

However, within the plethora of signs, symptoms and diagnoses there is a discrete class of etiological factors that does account for many of these symptoms and signs, and we think that in the future these may provide the basis of a therapeutic model that assigns tooth-sharpening behavior (thegosis) as the major explanation for the symptomatology of these conditions. A brief outline follows.

The discovery by Dr Every that tooth grinding in mammals is a discrete innate behaviour to sharpen and sometimes shape the teeth has shed significant light on tooth-to-tooth contact wear in humans and its biological significance (3,4,5,6,7,8,9,10 ). Many of the jaw movements, currently considered as pathological in humans, do in fact have a function: to hone the teeth. These movements and the attendant tooth-grinding wear are currently considered pathological: parafunction and bruxism. A number of clinical treatments are prescribed to correct the “damage” caused by bruxism , (for example, see 11). In hominids, the tooth- sharpening direction is oblique to incision and diametrically opposite to mastication. The principle muscle responsible for this movement is the lower body of the external pterygoid muscle, the orientation of which is in the direction of the thegotic stroke (5).

During sharpening the teeth are sometimes clenched together with extreme forcefulness. The mandible slides laterally about 5 mm. to sharpen the posterior teeth. To sharpen the canine and incisor blade complex the mandible continues to move laterally about 10 mm or more (this is three times or more than the distance currently thought to be the normal and ‘functional’ range of lateral movements). This can be confirmed by thegosis-facet matching and thegosis striation directions studies (5,8,&9).

Through this range of movement many structures can be traumatized, depending on individual anatomy, frequency of the movement, and the intensity of the sharpening action.

Applying a Darwinian evolutionary model such a behavior should not usually cause injury; but, we suggests that, in the contemporary dentition “modern” food produces little abrasive wear and tooth sharpening excursions are often irregular. Cusps that would normally be abraded interfere with a smooth thegotic excursion. In addition, the lack of between-tooth wear prohibits the forward movement of third molars as is usually seen in most hunter-gather societies. In this sense, contemporary Western dentitions often have “culturally acquired anatomical abnormalities”. Such abnormalities are a potent etiological factor in thegotically induced trauma. For example, during a thegotic stroke the third molar becomes a space occupying abnormality. The thegotic excursion is often frustrated and characteristic trauma to the ascending ramus of the mandible can result (10 and 12, and Figure 1a). In addition, we think when there are impediments to a smooth thegotic pathway the mandible can violently slip beyond the normal ligamentous limit of the excursion with the consequence of acute joint ligament tearing. There is emerging evidence suggesting that other deeper structures can be traumatized (9, see also 3,4).

It is possible using a CAT Scan, to plot the coronoid process position (an anatomical feature of varying height) in relation to the zygomatic arch when the mandible is moved to the limit of its tooth sharpening (and facet-matching) position. Contused interposed tissues, zygomatic arch tenderness, and facial swelling in this area can be explained by the relationship described above (Figure 2).

This can be briefly illustrated by two case histories:

Case One. This patient complained of right unilateral facial pain, arthromyalgia, and headache. Inter- oral examination revealed a haematoma over the right ascending ramus of the mandible, similar to the injury in Figure 1a. Psychological investigation revealed a current relationship crisis. Treatment included counseling, analgesics, physiotherapy, and wisdom tooth removal.

Case Two. This patient complained of bilateral facial pain over the zygomatic arches. Facet matching of the anterior teeth demonstrated that the mandible moved to positions that were beyond the conscious range of movement. Intraoral palpation on the distal aspects of the zygomatic process of the maxillae revealed extreme tenderness and exacerbate the orofacial symptoms. These relationships are illustrated in (Figure 2).. Psychological investigation revealed childhood abuse.

Neither patient has conscious awareness of these extreme movements.

These two cases graphically illustrate injury that explains some of the symptoms of facial pain and headache and suggest the relationship between the soma and the psyche (9). Many other traumatic pathologies, too numerous to document here, have been listed and hypothesized by Every (3,4) .

A central part of Every’s thegotic theory is that the evolving human dentition changed from a slashing maxillary canine weapon to a segmentive biting weapon. In his view our teeth are still our primary biological weapon (4&5). Consequently, stresses of current life events that provoke a “fight or flight” response will provoke thegotic activity.

The thegotic model suggests that symptoms of nocturnal trauma could sometimes worsen during counseling and psychotherapy since this may provoke tooth sharpening activity and the associated nocturnal trauma. This can be minimized if the anatomical abnormalities are addressed, for example, removal of wisdom teeth . Trauma can also be reduce by fitting a nocturnal bite “splint” that contrives a supported and atraumatic thegotic pathway. Removal of the maxillary third molars will often allow a full anterior tooth honing thereby minimising trauma to the ascending ramus of the mandible and allowing full thegotic servicing of the dental weapon.

The thegotic model also explains much of the confusing personality/stress findings discussed in literature and in Feinmann’s and Wray’s papers (1, 2, and see table 1 &2).

The thegotic model argues that there will be a basal level of thegotic activity as a normal physiological mechanism to maintain teeth in optimum function. In a patient who has an anatomical abnormality nocturnal thegotic trauma can occur independently of any psychological pathology. However, a patient with psychological pathology who has high levels of thegotic activity is especially at risk of significant dental, orofacial, and cranial symptomatology. (Table 1 & 2).

In this short comment it is not possible to cover in detail of the full clinical significance of thegosis, but we urge readers to study this normal but previously misunderstood phenomenon as a potent etiological factor in cranio-mandibular, and associated disorders.

We contend that failure to recognise the protean manifestations of Thegotic behaviour, normal and abnormal, at present impairs diagnosis in this difficult and complex area, and exposes many patients to well intentioned, but misconceived and inappropriate treatment.


We would like to thank the following people for their suggestions and advise in preparing this letter: Drs Peter Cook, Ian Easson, Ellis Webb, Don Anderson and Dale Every for their editorial comment and Dr Dale Every for permission to use the photographs in Figure 1.

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