Academic journal article American Academy of Gnathologic Orthopedics Journal

Cranial Strains and Malocclusion

Academic journal article American Academy of Gnathologic Orthopedics Journal

Cranial Strains and Malocclusion

Article excerpt

In our introductory article (1) we outlined a working hypothesis, the first part of which was regarding cranial movement and the significance of cranial strains in understanding malocclusion. The cranial concept comes from the osteopathic profession. (2) With this concept, they approach cranial and facial anatomy from a different perspective than our dental training provides. Osteopathic research (3,4) has shown that the way a skull is configured has a bearing on all parts of the craniofacial structures, including the position, relative placement and shape of the dental arches. This means that skull morphology has a significant influence on the position and function of the patient's occlusion. We have to consider the parts in relation to the whole. It means accepting that cranial morphology is influential at every step we make, from our first view of the patient, throughout orthodontic treatment and in the final retentive phase.

How can we make the transition from traditional diagnostics to seeing the distortions within the craniofacial complex, not just mal-positioned dental units? The first step as a clinician is to observe the characteristics of the face and head and to become familiar with common variations of these. Rather than trying to categorize the patient immediately by slotting him or her into a cranial strain pattern, it is best to just start looking at faces and recording what you see. One eye may be lower than the other. The lateral occlusal plane may be horizontal, parallel to the ocular plane or divergent from it. One ear may be more flared, lower or more forward than the other, with the mandible usually displaced towards the more flared side. The malar processes may differ one side from the other. In profile view, the relationship of the forehead, maxilla and mandible to each other is significant. By looking at the patient in this way from both a full face and profile view, you begin to recognize frequently occurring patterns and common correlations. Eventually, you can tell from the visible landmarks of the face what the cranial base orientation might be, i.e. the relationship of the sphenoid, the occiput and the temporal bones. It takes time and practice to develop this ability to recognize the cranial strain patterns, but the effort is hugely rewarding.

Our articles provide a foundation on which to build this new way of thinking. Not every patient will fit neatly into an exact strain category, but by using this approach you can gain an understanding of what is the general configuration of a specific face. While each patient is unique, patterns can be detected. The cranial strain concept offers a logical explanation of what you see and it takes into account characteristics, which are simply dismissed or ignored at present. It also offers a broader more comprehensive view of the head and neck than is currently used. We give two examples of how cranial strains may influence the diagnostic process in orthodontic evaluation.

AIRWAY FACTORS AND CRANIAL STRAINS:

Distortions brought about by cranial strains can cause anatomical encroachment on the airway. Two strains are of particular importance. In both hyperextension (5) and an inferior vertical strain (6) there is lateral constriction and elevation of the maxillae. There is constriction within the nares themselves resulting in obstruction through the nose. There is also obstruction in the post-nasal area of the pharynx. In the case of the inferior vertical strain, the distal position of the mandible also encroaches on the lower pharynx. To meet the demand of the airway, there is considerable functional adaptation both in terms of the tongue and lips and also head and neck position. This functional adaptation has been well documented elsewhere. (7,8,9,10) An appreciation of the cranial strains helps in understanding the structural characteristics which predispose to airway obstruction. Treatment can be designed accordingly to deal with this concern. …

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