Journal of Craniomandibular Function, 01/2012

The role of occlusal factors in the etiology of temporomandibular disorders (TMD) is currently often estimated to be marginal or non-existent. However, the number of highlevel studies addressing the causal problem of TMD is low and the theoretical basis of the studies is vague. Despite the very large number of published articles discussing evidence-based medicine, the very concept of evidence has remained unclear. The same is true of the concept of causality. The usage of the concepts of evidence and causality appears to be based on mistaken assumptions of their meaning. Therefore, the conclusions drawn from studies on the etiologic role of occlusal factors appear unfounded or premature. Keywords: causality, evidence, occlusion

Masticatory movements are characterized by variability. Although chewing patterns vary depending on the type and position of the food being eaten, individual-specific features can be observed. This study comprised computerassisted tracking and analysis of jaw muscle activity during standardized chewing activity using the Jaw Motion Analyzer (JMA), an ultrasonic measurement system, in conjunction with JawReports software, developed at the University of Greifswald. This study's findings show that temporomandibular dysfunction (TMD) has a significant impact on the variability of chewing patterns. The healthier the masticatory system, the more variable the chewing patterns, and the more impaired the system, the more monotonous and stereotyped the patterns become. The same applies to lateral preference in mastication. Mastication may take place on both sides of the mouth at the same time (simultaneous bilateral), may switch back and forth between the right to the left side of the mouth (alternating bilateral), or may occur preferentially on either the right or the left side of the mouth (unilateral chewing). Alternating bilateral mastication can be classified as "normal," because unilateral mastication is less effective and can be associated with dysfunctions. Lateral preference in mastication is associated with unilateral facial muscle pain, unilateral temporomandibular joint pain, and unilateral clicking sounds. Furthermore, there is a highly significant association between chewing side preference and asymmetrical loss of antagonist contact and specific types of dentures. Regarding relative risk, the odds of having a preferred chewing side were significantly higher in individuals with plastic removable partial dentures (RPDs) with wrought wire clasps and attachment-retained RPDs, than in those with fixed partial dentures, telescopic dentures and full dentures. Any type of monotonous jaw movement is likely to cause repetitive stereotyped movements and detrimental occlusal forces, resulting in increased wear of anatomical structures. Appropriate measures to prevent these problems and to promote the variability of chewing patterns will be discussed in this article. Keywords: chewing movement, dysfunction of stomat-ognathic system, variability of occlusal movements, chewing side preference

To determine the effect of slight differences in pin alignment markings on pin alignment and occlusal contacts, left and right second premolar and first molar occlusal contact areas were compared before and after the height of the incisal pin was increased. One Kavo Protar 3 articulator with an incremental type of calibrated guide pin was used for the study. Ten polyvinylsiloxane right and left posterior interocclusal records of occluded impact resistant resin casts were made at five different pin positions: 0, 50, 150, 250 and 500 µm. The use of a computerized image analysis program provided quantitative measurements of light transmitted through the occlusal records. T-tests were used to statistically determine effects of the initial 50 µm increase in incisal pin alignment. Data of certain areas for other pin heights were incomplete due to an unpredictable increase of material thickness beyond the measuring threshold of this study. Data was gathered from analysis of the second premolar and the first molar areas bilaterally. There were statistically significant differences from a 0 to 50 µm raise of the incisal guide pin (P 0.05). Statistics at other pin heights were not performed because data were incomplete due to an increase in material thickness that could not be predicted based on current literature. Precise alignment of incisal pin is required to assure occlusal precision in restorative dentistry. Keywords: articulator, incisal guide pin, interocclusal recording material, occlusal contacts

Temporomandibular disorders (TMDs) are a frequent finding in cases of facial trauma or dental malpractice, and legal claims for TMD damage have increased over the years. TMD treatment in the medical legal setting is complicated by the peculiarities of these disorders, whose symptoms are heterogeneous, fluctuant, and recognize a multifactorial origin. A systematic Medline search in the National Library of Medicine's Pubmed database pointed out that despite the medical legal aspects of the dental profession gaining a growing attention, there is a paucity of literature dealing with TMD patients' assessment. For these reasons, evidence-based knowledge in the field of TMD treatment was summarized in the present paper, with the aim of providing useful suggestions for a medical legal approach to temporomandibular disorders. Keywords: diagnosis, ethics, forensic medicine, legal medicine, temporomandibular disorders, treatment

The restoration of normal temporomandibular joint function in static and dynamic occlusion can be the key the successful treatment of temporomandibular disorders (TMD), in many cases. An interdisciplinary approach characterized by close cooperation between the dentist, orthopedist and manual therapist is required for the individual patient. The dentist's job is to adjust the occlusion to the changes in jaw relationships that occur in response to functional normalization of the involved muscles, and to improve the patient's head and body posture. The craniomandibular orthopedic positioning appliance (COPA), a removable interocclusal appliance for reversible correction of the occlusion, is designed to eliminate the pathological interferences associated with temporomandibular joint (TMJ) dysfunction. As such, it is predestined for use as a primary therapeutic instrument in these indications. If the position of the temporomandibular joint changes over the course of treatment, further orthodontic and/or prosthodontic treatment may be needed after the completion of interdisciplinary treatment, to ensure the longterm, interference-free stabilization of the occlusion. If the clinical findings indicate that the occlusal splint has successfully eliminated the problems of infraocclusion, and that further treatment is needed, the removable occlusal splint can be transformed into bonded onlay elements in order to transfer the splint position with the highest possible precision, while maintaining the temporomandibular joint position achieved in the first stage of splint therapy. This approach allows the clinician to simulate the planned therapeutic occlusion before irreversible occlusal treatment measures are performed, in order to obtain the most accurate assessment of the effectiveness of the therapeutic occlusion based on the patient's subjective impression, as well as the results of interdisciplinary functional analysis. Keywords: biomechanical wax-up technique according to Polz, bonded occlusal splint, craniomandibular system (CMS), dynamic occlusion, functional treatment, musculoskeletal system (MSS), orthodontics, prosthodontics, removable occlusal splint, static occlusion