Taking up challenges at the interface of wear and tear.

oromandibular dystonia represents the segmental movement disorder, "Meige syndrome". Since Marsden's observation, this disorder is also called "Brueghel syndrome". Interestingly, it is still considered possible that the farmer in Brueghel's painting is actually yawning. Brueghel was very knowledgeable about the peasant men and women of his time, including their good and bad qualities. It is therefore not unlikely that the yawning man represents the Capital Sin of Idleness. My personal contribution to this discussion is that this farmer was an obstructive sleep apnea (OSA) patient, and consequently suffered from excessive daytime sleepiness (see below: Sleep Disorders with Dental Implications). For me, this face doesn't lie! Oral movement disorders like bruxism and their purported consequences—viz., tooth wear and temporo-mandibular pain—constitute the area of interest of the Section of Oral Kinesiology in the Department of Oral Function of ACTA. Below, I will describe my personal view on this emerging discipline at the interface of wear and tear, along with brief descriptions of temporomandibular pain, oral movement disorders, bruxism, and other sleep disorders with dental implications. In our clinic for oral kinesiology at ACTA, patients often report with temporomandibular pain (TMP). For this condition, many etiological theories have been proposed and rejected. Currently, the multifactorial, biopsychosocial etiological model is being considered. As a working hypothesis, a disturbance between load and load-bearing capacity is thereby used. Bruxism is frequently put on the load side of the balance. However, even though this is a common clinical feeling of dentists—including myself—solid evidence for a causal relationship between bruxism and TMP is lacking (Lobbezoo and Lavigne, 1997). To prove causality, longitudinal studies are necessary. Such time-consuming studies must meet several criteria, including a sufficient number of observations (i.e., a number that respects the natural fluctuation in both bruxism and TMP), and the use of proper techniques to quantify the conditions under study. For TMP, a standardized clinical examination may be sufficient. Also, a diary may be used to quantify TMP, as long as the investigators remember that self-reported data have their limitations. Daytime clenching may be quantified with a diary as well, but for sleep bruxism, electromyographic or even polysomnographic recordings are required. This obviously limits the feasibility of longitudinal