Effect of stimulus parameters and contraction level on inhibitory responses in human jaw-closing muscles: Implications for contingent stimulation

Objective

Examine the effect of stimulus duration, intensity and level of muscle contraction on the inhibitory responses evoked by electrical stimuli in human jaw-closing muscles applied to the right mental nerve.

Design

The inhibitory jaw-reflexes, short-latency (ES1) and long-latency (ES2), were recorded in the surface electromyogram (EMG) of masseter and temporalis muscles in 16 healthy subjects. Three stimulus durations (1 ms single square-wave pulse, 10 and 450 ms square-wave pulse train), two stimulus intensities adjusted to perceived intensity of 3 (non-painful) and 7 (distinct painful) on a 0–10 verbal rating scale were applied to the right mental nerve while the subject was biting at 25% and 50% of the maximal voluntary contraction (MVC).

Results

The magnitude of suppression in the ES2 evoked by 1 and 10 ms stimuli was dependent on stimulus intensity (P < 0.002 and P < 0.001, respectively) but not contraction level. However, ES1 could not be observed in most of the recordings. There were significant decreases evoked by the 450 ms stimuli in RMS–EMG values in the 400–500 ms compared with the pre-stimulus interval (P < 0.001) which was dependent on contraction level (P < 0.01) but not on stimulus intensity (P = 0.486).

Conclusions

The present results suggest that the ES2 reflex response is associated with the duration of the electrical stimuli, the intensity level but not the contraction level. In contrast, the inhibitory effects of ultra-long stimuli (450 ms) are not specifically related to the intensity level suggesting that this is a non-nociceptive response.     

The influence of zero-value subtraction on the performance of two laser fluorescence devices for detecting occlusal caries in vitro

BACKGROUND: The aim of this study was to evaluate the influence of zero-value subtraction on the performance of two laser fluorescence (LF) devices developed to detect occlusal caries. METHODS: The authors selected 119 permanent molars. Two examiners assessed three areas (cuspal, middle and cervical) of both mesial and distal portions of the buccal surface and one occlusal site using an LF device and an LF pen. For each tooth, the authors subtracted the value measured in the cuspal, middle and cervical areas in the buccal surface from the value measured in the respective occlusal site. RESULTS: The authors observed differences among the readings for both devices in the cuspal, middle and cervical areas in the buccal surface as well as differences for both devices with and without the zero-value subtraction in the occlusal surface. When the authors did not perform the zero-value subtraction, they found statistically significant differences for sensitivity and accuracy for the LF device. When this was done with the LF pen, specificity increased and sensitivity decreased significantly. CONCLUSIONS: For the LF device, the zero-value subtraction decreased the sensitivity. For this reason, the authors concluded that clinicians can obtain measures with the LF device effectively without using zero-value subtraction. For the LF pen, however, the absence of the zero-value subtraction changed both the sensitivity and specificity, and so the authors concluded that clinicians should not eliminate this step from the procedure. CLINICAL IMPLICATIONS: When using the LF device, clinicians might not need to perform the zero-value subtraction; however, for the LF pen, clinicians should do so.     

Differentialindikation zum operativen Vorgehen beim progenen Formenkreis

Zusammenfassung In Abhängigkeit der Fehlbildung des progenen Formenkreises müssen die operativen Verfahren am Ort der Ursache angreifen, um ästhetisch und funktionell befriedigende Ergebnisse zu erzielen. Die Möglichkeiten der Alveolarfortsatzchirurgie für den dentoalveolären Bereich und die gesamtkieferverschiebenden Operationen für den gnathischen Bereich werden dargestellt. Mit den modernen Methoden der Kieferchirurgie ist es möglich, entsprechend der vorangegangenen Diagnostik, in Kooperation mit dem Kieferorthopäden eine am Ort des Krankheitsbildes angreifende Therapie durchzuführen.

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Summary Due to there being different types of class-III malocclusions, the treatment methods have to vary in order to achieve a satisfactory esthetic and functional result. The different operations would therefore be. 1. The movement of the alveolar process to correct the dentoalveolar class III. 2. The movement of the whole body of the mandible for the true class III. Using the new methods available in maxillo-facial surgery, it is possible after a joint diagnosis with the orthodontist, to correct the class III malformation.

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Résumé Le traitement chirurgical des différentes formes de prognathie mandibulaire doit s'efforcer d'intervenir au lieu même de l'anomalie; à cette condition, les résultats seront satisfaisants, tant du point de vue esthétique que fonctionnel. Les différentes possibilités du traitement chirurgical sont exposées, à savoir les ostéotomies alvéolaires pour les anomalies siégeant au niveau dento-alvéolaire et les ostéotomies permettant la mobilisation d'un maxillaire in toto pour les anomalies squélettiques basales. Grâce aux techniques chirurgicales modernes et à l'étude diagnostique précise effectuée en étroite collaboration avec l'orthodontiste, il est possible d'intervenir sélectivement au siège même de l'anomalie.

     

Cephalometric Analysis in Patients with Obstructive Sleep Apnea Part II: Prognostic Value in Treatment with a Mandibular Advancement Device

Background: The mandibular advancement device (MAD) is accepted as an additional treatment option for snoring and mild obstructive sleep disorders. Its therapeutic efficacy can only be verified through nocturnal polysomnography with the appliance in situ. The relevance of the craniofacial skeletal and soft-tissue structures as an etiological cofactor is controversial. While the lateral cephalogram of the facial skeleton is of no direct diagnostic relevance, it remains unclear to what extent cephalometric assessment can provide prognostic information to better ensure treatment success with an MAD. Methods and Results: This study is based on the evaluation of 57 patients diagnosed polysomnographically with obstructive sleep apnea (OSA). The patients were treated primarily with a modified activator; after 6-12 weeks, control polysomnography was carried out in the sleep laboratory. The cephalometric variables were analyzed using a multivariate regression procedure with the response variable of treatment outcome. In addition to a horizontal craniofacial morphology, the downward and forward posture of the hyoid is a prognostic variable for effective therapy with an MAD. Zusammenfassung Hintergrund: Intraorale Protrusionsgeräte (IPG) gelten als eine Therapiemodalität bei Schnarchen und leichten obstruktiven Schlafstörungen. Der therapeutische Effekt dieser Therapieform kann zurzeit ausschließlich in einer nächtlichen Polysomnogrphie mit dem Gerät in situ beurteilt werden. Die Bedeutung der skelettalen und weichteiligen Strukturen des Gesichtsschädels als ätiologischer Kofaktor von nächtlichen obstruktiven Atemregulationsstörungen ist umstritten. Während die Fernröntgenseitenaufnahme des Gesichtsschädels der Forderung nach einer unmittelbaren diagnostischen Relevanz nicht gerecht wird, ist es gegenwärtig ungeklärt, inwiefern mit der Kephalometrie eine prognostische Aussage zum Therapieeffekt bei der Behandlung mit einem IPG getroffen werden kann. Methoden und Ergebnisse: Die Studie basiert auf der Untersuchung von 57 Patienten mit der polysomnographisch gestellten Diagnose einer obstruktiven Schlafapnoe (OSA). Die Patienten wurden mit einem modifizierten Aktivator primär therapiert. Nach 6-12 Wochen wurde eine Kontrollpolysomnographie im Schlaflabor durchgeführt. Die kephalometrischen Parameter wurden in einer multivarianten Regressionsanalyse zur Kriteriumsvariablen des erzielten therapeutischen Erfolges untersucht. Neben einem horizontalen Gesichtsschädelaufbau ist eine kaudoventraele Position des Hyoids ein prognostisch positiver Parameter für eine erfolgreiche Therapie mit einem IPG.