Assessment of bruxism in the clinic

Bruxism is a much-discussed clinical issue in dentistry. Although bruxism is not a life-threatening disorder, it can influence the quality of human life, especially through dental problems, such as tooth wear, frequent fractures of dental restorations and pain in the oro-facial region. Therefore, various clinical methods have been devised to assess bruxism over the last 70 years. This paper reviews the assessment of bruxism, provides information on various assessment methods which are available in clinical situations and discusses their effectiveness and usefulness. Currently, there is no definitive method for assessing bruxism clinically that has reasonable diagnostic and technical validity, affects therapeutic decisions and is cost effective. One future direction is to refine questionnaire items and clinical examination because they are the easiest to apply in everyday practice. Another possible direction is to establish a method that can measure actual bruxism activity directly using a device that can be applied to patients routinely. More clinical studies should examine the clinical impact of bruxism on oral structures, treatment success and the factors influencing the decision-making process in dental treatment.

The effect of oral splint devices on sleep bruxism: a 6-week observation with an ambulatory electromyographic recording device

This study investigated the effect of stabilization splint (SS) and palatal splint (PS), which had the same design as SS except for the elimination of the occlusal coverage, on sleep bruxism (SB) using a portable electromyographic (EMG) recording system. Sixteen bruxers participated in this study. The EMG activities of the right masseter muscle during sleep were recorded for three nights each in the following five recording periods: before, immediately after, and 2, 4 and 6 weeks after the insertion of the splint. The crossover design, in which each splint was applied to each subject for 6 weeks with an interval of 2 months for a washout period, was employed in this randomized-controlled study. The number of SB events, duration and total activities of SB were analysed. The number of SB events before the insertion of splints (baseline) was 2.98 +/- 1.61 times h(-1). Both splints significantly reduced SB immediately after the insertion of devices (P < 0.05, one-way repeated-measures anova followed by Dunnett); however, no reduction was observed in 2, 4 or 6 weeks (P > 0.05). There was no statistical difference in the effect on SB between the SS and PS (P > 0.05, two-way repeated-measures anova). Both splints reduced the masseter EMG activities associated with SB; however, the effect was transient.

Melting and heating of two-dimensional Coulomb clusters in dusty plasmas

The heating and melting of two-dimensional dust clusters with one additional particle in the lower layer has been investigated experimentally in a gas discharge. The full dynamical properties of the system during the entire phase transition were determined in terms of the spectral power densities of the crystal modes. A two-step melting transition is identified when the gas pressure in the discharge is reduced: first, a sudden increase of the dust temperature takes place due to an instability of the lower-layer particle resulting in a hot crystalline state of the cluster, and second, the actual transition into a fluid state is observed at a decisively lower gas pressure.

Mutational analysis of the synapsin III gene on chromosome 22q12-q13 in schizophrenia

Synapsins are a family of neuron-specific, synaptic vesicle-associated phosphoproteins that have been implicated in the modulation of neurotransmitter release. Synapsins are coded by three distinct genes for synapsin I. II, and III. The synapsin III gene is located on human chromosome 22q12-q13, where a possible schizophrenia susceptibility locus is located. Using the single strand conformation polymorphism method, we searched for variants in 13 exons and the 5'-flanking region of the synapsin III gene in schizophrenia. Three polymorphisms, -631C/G, -271T/C, and E525Q, and one rare variant, -669C >A, were identified. Case-control comparisons of these polymorphisms revealed no significant differences in the allelic and genotypic distributions between schizophrenic and control subjects. The present study did not provide evidence for an association between the synapsin III gene and schizophrenia.

Effect of occlusal splint on masticatory movement in healthy individuals

To investigate the effects of wearing an occlusal splint on masticatory movements in healthy individuals, twelve healthy individuals were examined. A full maxillary stabilization splint made of heat-cured acrylic resin was fabricated for, and worn by, each individual for 24 hours. Masticatory movement was measured before and after the 24-hour period using a 3-D mandibular movement analyzing system. While the duration of a masticatory cycle+ did not change, the occlusal time significantly decreased after use of the splint. The lateral displacement of the opening phase to the balancing-side area also decreased after use of the splint, showing a vertical pattern of the opening path. Measurement in more healthy individuals and patients should help clarify the therapeutic mechanism of the splint in the treatment of temporomandibular disorders.