Temporomandibular disorders (TMD) comprise the most common cause of chronic facial pain conditions, and they are often associated with somatic and psychological complaints including fatigue, sleep disturbances, anxiety, and depression. For many health professionals, the subjectivity of pain experience is frequently neglected even when the clinic does not find any plausible biologic explanation for the pain. This strictly biomedical vision of pain cannot be justified scientifically. The purpose of this study is to demonstrate, by original articles from the literature and recent studies conducted in our own laboratory, the biological processes by which psychological stress can be translated into the sensation of pain and contribute to the development of TMD. The role of the hypothalamic-pituitary-adrenal axis, the serotoninergic and opioid systems in the pathogenesis of facial pain is exposed, including possible future therapeutic approaches. It is hoped that knowledge from apparently disparate fields of dentistry, integrated into a multidisciplinary clinical approach to TMD, will improve diagnosis and treatment for this condition through a clinical practice supported by scientific knowledge.

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Objective: To systematically review the relationship between malocclusions and masticatory performance. In addition, we will perform a qualitative analysis of the methodological soundness of the studies. Materials and Methods: A literature survey was done by applying the Medline database (www. ncbi.nim.nih.gov) in the period from January 1965 to June 2009, using the ''Medical Subject Headings'' term malocclusion crossed with various combinations of the following terms: masticatory performance, masticatory efficiency, and chewing efficiency. The articles were separated into two main topics: (1) the influence of malocclusion treatment (orthognathic surgery) and (2) the influence of malocclusion type and severity. Results: The search strategy used identified 78 articles. After selection according to the inclusion/ exclusion criteria, 12 articles qualified for the final analysis. The research quality and methodological soundness were high in one study, medium in 10 studies, and low in one study. The most serious shortcomings comprised the clinical trials and controlled clinical trials designs with small sample sizes and inadequate description of selection criteria. Lack of method error analysis and the absence of blinding in measurements were other examples of shortcomings. Conclusions: Malocclusions cause decreased masticatory performance, especially as it relates to reduced occlusal contacts area. The influence of malocclusion treatment (orthognathic surgery) on masticatory performance is only measurable 5 years after treatment. (Angle Orthod. 2010;80:981-987.)

Objective: To assess, by systematically reviewing the literature, the functional changes of the masticatory muscles associated with posterior crossbite in the primary and mixed dentition. Materials and Methods: A literature survey from the Medline database covering the period from January 1965 to February 2008 was performed. Randomized controlled trials, controlled clinical trials, and clinical trials that evaluated bite force, surface electromyography, and signs and symptoms of temporomandibular disorders (TMD) were included. Two reviewers extracted the data independently and assessed the quality of the studies. Results:The search strategy resulted in 494 articles, of which 8 met the inclusion criteria. Children with posterior crossbite can have reduced bite force and asymmetrical muscle function during chewing or clenching, in which the anterior temporalis is more active and the masseter less active on the crossbite side than the noncrossbite side. Moreover, there is a significant association between posterior crossbite and TMD symptomatology. Conclusion:The consequences of the functional changes for the growth and development of the stomatognathic system deserves further investigation. (Angle Orthod. 2008;79:380-386.)

The aim of this pilot study was to illustrate the feasibility of a new digital procedure to fabricate metallic orthodontic appliances. Hyrax appliances for rapid palatal expansion were produced for 3 patients using a CAD/CAM procedure without physical impressions or printed models. The work flow consisted of intraoral scanning, digital design with incorporation of a scanned prefabricated expansion screw, direct 3-dimensional metal printing via laser melting, welding of an expansion screw, insertion, and finally activation in the patients' mouths. Finite element analyses of the actual hyrax appliances were performed to ensure that the printable material used in combination with the chosen design would withstand the stress generated during activation. The results of these analyses were positive. The clinical results showed that this procedure is an efficient and viable digital way for constructing metallic orthodontic appliances. The flexibility of the digital appliance design, together with the biocompatibility and strength of the chosen material, offers a huge potential for more advanced appliance design.