Creation of a dental X-ray unit with a contactless exposure control switch.

OBJECTIVE: A new dental radiographic unit (DXRU) with a contactless switch for adjusting exposure conditions and a foot-pedal exposure switch was developed to prevent bacterial or viral contamination from patients and was compared with a conventional DXRU with a panel push-button switch with respect to user friendliness. METHODS: 45 fourth-year dental school students carried out intraoral radiography using both types of DXRU. Errors regarding dose shortages of X-rays were compared and a questionnaire completed. RESULTS: 22 (49%) of the 45 students failed to provide the correct radiographic exposure and the number of errors was 32 for the conventional DXRU, and 4 (9%) students failed to provide the correct radiographic exposure and the number of errors was 4 for our new DXRU, at the first stage (p < 0.001). At the second stage, the number of students who failed to provide the correct radiographic exposure and the number of errors decreased to 12 and 16, respectively, for the conventional DXRU (p < 0.05). 37 (82%) of the 45 students preferred our DXRU because of its contactless switch and the push-pedal exposure switch. CONCLUSIONS: These data suggested that our new contactless mechanism should be used for other DXRUs for contamination control.

Influence of menopause on mandibular bone quantity and quality in Japanese women receiving dental implants.

SUMMARY: The purpose of this study was to evaluate the effect of menopause on bone mineral density and bone width of the mandible. Results indicate that menopause affects the bone quality and quantity of the partially edentulous molar region of the mandible, which should be considered in dental implant treatment for postmenopausal women. INTRODUCTION: The recovery of oral function with dental implant is clinically effective and highly predictable. Bone quantity and quality at the implant installation site affect its prognosis; however, the effects of menopause on jaw bone have not been well documented. The purpose of this study was to evaluate the effect of menopause on bone mineral density (BMD) and bone width of the mandible. METHODS: The subjects were 72 female patients with a partially edentulous molar region of the mandible: 30 premenopausal and 42 postmenopausal women aged 30 to 70 years. Trabecular BMD was measured with quantitative computed tomography. Trabecular region width (TW) and cortical width (CW) were measured with CT. The BMD, TW, and CW of the two groups were compared. RESULTS: The trabecular BMD of postmenopausal women was lower than that of the premenopausal women. The TW of postmenopausal women was greater than that of premenopausal women, whereas the CW of postmenopausal women was significantly smaller than that of premenopausal women. In all these women, BMD correlated negatively with TW and positively with CW. In the premenopausal women, BMD negatively correlated with TW, but it did not correlate with CW. In the postmenopausal women, there was no correlation between BMD and bone width. CONCLUSION: These results indicate that menopause affects the bone quality and quantity of the partially edentulous molar region of the mandible, which should be considered in dental implant treatment for postmenopausal women.

Application of MRI movie for observation of articulatory movement during a fricative /s/ and a plosive /t/.

OBJECTIVE: To use an accurate method of tooth visualization in magnetic resonance imaging (MRI) movie for the observation of spatio-temporal relationships among articulators. MATERIALS AND METHODS: The subjects were two volunteers. Each subject repeated a vowel-consonant-vowel syllable (ie, /asa/; /ata/), and the run was measured using a gradient echo sequence. A custom-made clear retainer filled with the jelly form of ferric ammonium citrate was then fit onto the dental arch, and a T1-weighted turbo-spin-echo sequence was taken. Landmarks were used for superimposition of the incisor boundary onto sequential images of MRI movie. Tracings were conducted to observe the spatio-temporal relationships among articulators. RESULTS: The incisor boundary was clearly visible in the magnetic resonance images. After superimposition, the contact distance of the tongue to palate/incisor was found to be longer during /t/-articulation than during /s/-articulation. There were prominent differences in images with and without tooth superimposition in the front oral cavity. CONCLUSIONS: The method could distinctly extract a tooth boundary in MRI. Detailed configurational relationships between the tongue and tooth were observed during the production of a fricative and a plosive in MRI movie using this method.

Modulation transfer function evaluation of cone beam computed tomography for dental use with the oversampling method.

OBJECTIVES: The aim was to investigate the possibility of evaluating the modulation transfer function (MTF) of cone beam CT (CBCT) for dental use using the oversampling method. METHODS: The CBCT apparatus (3D Accuitomo) with an image intensifier was used with a 100 mum tungsten wire placed inside the scanner at a slight angle to the plane perpendicular to the plane of interest and scanned. 200 contiguous reconstructed images were used to obtain the oversampling line-spread function (LSF). The MTF curve was obtained by computing the Fourier transformation from the oversampled LSF. Line pair tests were also performed using Catphan(R). RESULTS: The oversampling method provided smooth and reproducible MTF curves. The MTF curves revealed that the spatial resolution in the z-axis direction was significantly higher than that in the axial direction. This result was also confirmed by the line pair test. CONCLUSIONS: MTF analysis was performed successfully using the oversampling method. In addition, this study clarified that the 3D Accuitomo had high spatial resolution, especially in the z-axis direction.

Hanging protocol and viewers for a dental full picture [corrected] archiving and communication system (PACS) [corrected].

OBJECTIVES: Study objectives were: to develop a hanging protocol for displaying digital transmission radiographic images of oral and maxillofacial regions using a dental DICOM (digital imaging and communication in medicine) viewer and a dental Web viewer; and to give information on a system that allows patients and health professionals to share image information. METHODS: For the hanging protocol, alphanumeric tags were defined and used in a DICOM modality worklist. These tags consisted of layout information to display images on monitors by the type of projection method and assignment information to display images of template for intraoral full-mouth survey that were numbered and slotted according to tooth position. Tooth code and algorithm for assignment of images for intraoral full-mouth survey were determined. Expanded correspondence for viewers was used for modalities without tags. Images could be edited by quality control system. An electronic medical record (EMR) system, a radiological information system (RIS) and a picture archiving and communication system (PACS) with servers, terminals and viewers were set up in a patient-centred hospital environment. RESULTS: Using the hanging protocol, the viewers displayed digital transmission radiographic images automatically on display areas on one or multiple monitors showing intraoral, panoramic and extraoral views produced during various examinations. The images were also displayed using the coupling function of EMR and RIS. Users can compare the images taken at various times more efficiently. CONCLUSION: The new system using a dental DICOM viewer and a dental Web viewer is the most advanced for examining oral and maxillofacial regions compared with medical viewers. Our local but clinically operational hanging protocol should be a good model for DICOM Working Group 22.

Galanin inhibits neural activity in the subfornical organ in rat slice preparation.

The activation of the subfornical organ (SFO), a circumventricular organ, induces water intake and vasopressin release. Since central administrations of galanin (GAL) suppress water intake and vasopressin release, GAL may inhibit the neural activity of SFO neurons. In the present study, we investigated effects of GAL on the SFO using molecular biological, electrophysiological and anatomical techniques. Reverse transcription-polymerase chain reaction analysis demonstrated the presence in the SFO of rats of the mRNAs for each of the three known GAL receptor subtypes (GalR1, GalR2 and GalR3). In extracellular recordings in SFO slice preparations, GAL dose-dependently inhibited the neural activity of cells from a number of recording sites. Many GAL-sensitive SFO neurons showed excitatory responses to angiotensin II (ANGII). The GalR1 agonist M617 inhibited the activity of SFO neurons, whereas the GalR2 and GalR3 agonist GAL(2-11) had almost no effect. In patch-clamp recordings, GAL induced an outward current in SFO neurons without influencing synaptic currents. An immunoelectron microscopic study revealed the existence of GAL-containing synaptic vesicles in the SFO. These results suggest that the SFO has neural inputs involving GAL. The response to GAL is inhibitory, mediated at least in part by GalR1 and provides a plausible explanation for the opposite effects of ANGII and GAL seen in vivo on water intake and vasopressin release.

Application of magnetic resonance imaging movie to assess articulatory movement.

OBJECTIVE: To introduce the technique of magnetic resonance imaging (MRI) movie and to propose its feasibility for investigating articulatory movement. SUBJECTS: Five healthy adult females participated in the study. METHODS: Dynamic changes in oropharyngeal structures were assessed with MRI movie during the articulation of a bilabial consonant. RESULTS: Movements of the velum and tongue at a time resolution of 30 ms were complex at the tip of the tongue and the anterior part of the velum. These movements that were seen with a time resolution of 30 ms could not be interpolated or in any way derived from the results obtained with a time resolution of 120 ms. CONCLUSION: The results suggest that MRI movie may be useful in the evaluation of articulation. It is important to reduce the time resolution to 30 ms to obtain images of articulators.

Pilocarpine-induced salivation and thirst in conscious rats.

The muscarinic receptor agonist pilocarpine is widely used as a sialogogue. It has been well-established that it also induces water intake in animals. However, the mechanisms underlying the relationships between these events are unknown. To address this problem, we examined water intake and parotid salivary secretion in conscious rats. Intraperitoneally injected pilocarpine increased both water intake and salivary secretion. Intracerebroventricularly injected pilocarpine also induced water intake, but not salivary secretion. Intracerebroventricularly applied atropine, a muscarinic receptor antagonist, suppressed the water intake produced by pilocarpine applied intraperitoneally and intracerebroventricularly. However, it did not affect the salivary secretion induced by pilocarpine applied peripherally. We conclude that peripherally applied pilocarpine affects the parotid glands and the thirst center in the central nervous system, while it may induce salivary secretion mainly via peripheral responses, but water intake mainly via the central nervous system.

Chewing-side preference is involved in differential cortical activation patterns during tongue movements after bilateral gum-chewing: a functional magnetic resonance imaging study.

Contralateral dominance in the activation of the primary sensorimotor cortex (S1/M1) during tongue movements (TMs) has been shown to be associated with a chewing-side preference (CSP). However, little is known about its interaction with chewing-related cortical activation. Functional magnetic resonance imaging was performed before and after gum-chewing in six subjects who exhibited a left CSP to determine the relationship between the CSP and activation patterns in the S1/M1 during TMs. Before the subjects chewed the gum, activation foci were found in the bilateral S1/M1. In the left hemisphere, both signal intensity and the area of activation significantly increased during TMs within 10 min after subjects chewed gum. Moreover, this augmented activation significantly decreased within 20 min during tongue protrusion and leftward movement. In the right hemisphere, there were no marked changes during TMs. These results suggest that bilateral gum-chewing enhances activation of the S1/M1 ipsilateral to the CSP during TMs.

DAMGO suppresses both excitatory and inhibitory synaptic transmission in supraoptic neurones of mouse hypothalamic slice preparations.

Opioid effects on synaptic transmission in the mouse supraoptic nucleus (SON) were investigated using whole-cell, patch-clamp techniques. The mu-opioid receptor agonist, [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO) decreased the amplitude of both evoked excitatory postsynaptic currents (eEPSCs) and inhibitory postsynaptic currents (eIPSCs), and also decreased the frequency of both miniature EPSCs and IPSCs without effect on the amplitude. The selective mu-opioid receptor antagonist, D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2), and the nonselective antagonist naloxone, antagonized these inhibitory effects. The application of DAMGO suppressed the amplitude of both the first and second evoked postsynaptic currents with a paired-pulse stimulus protocol, but increased the paired-pulse ratios (second ePSC/first ePSC). DAMGO induced neither inward nor outward currents, and had no significant changes in either glutamate- or GABA-induced currents. When compared with the relatively selective kappa- and delta-opioid receptor agonists dynorphin and [D-Pen(2), D-Pen(5)]-enkephalin, DAMGO showed the most potent inhibitory effects on evoked and miniature postsynaptic currents. Taken together, these results imply that DAMGO strongly suppresses the release of glutamate and GABA via mu-opioid receptors in the mouse SON, and support the involvement of presynaptic regulation by opioids in the control of magnocellular neurosecretory neurones.

Activation of muscarinic receptors in rat subfornical organ neurones.

Cholinergic muscarinic inputs to subfornical organ (SFO) neurones in rats were studied using histochemical, molecular-biological and electrophysiological techniques. Neurones in the medial septum and the diagonal band (MS-DBB) were retrogradely labelled by a tracer wheat germ agglutinin-conjugated horseradish peroxidase-colloidal gold complex injected into the SFO. Some in the MS-DBB were double-labelled by choline acetyltransferase (ChAT) antibody. Many ChAT-immunoreactive fibres were observed in the SFO. M3 muscarinic receptor subtype-like immunoreactivity, detected using a polyclonal antiserum, was observed in the SFO. In slice preparations, muscarine induced inward currents in a dose-related manner. The inward currents were suppressed by the relatively M3 muscarinic receptor selective antagonist 4-diphenylacetoxy-N-methylpiredine methiodide. In the whole-cell current mode, muscarine depolarized the membrane with increased frequency of action potentials. Reverse transcriptase-polymerase chain reaction showed the presence of M2-M5 receptor mRNA in the SFO tissues. These results suggest that the SFO receives cholinergic muscarinic synaptic inputs from the MS-DBB. Acetylcholine postsynaptically activates and depolarizes neurones in the SFO partly through specific muscarinic receptors, including M3 receptor subtypes.

Artifacts from dental casting alloys in magnetic resonance imaging.

The potential advantage of magnetic resonance imaging (MRI) has been limited by artifacts due to the presence of metallic materials. For quantitative evaluation of the magnitude of artifacts from dental casting alloys and implant materials in MR imaging, 11 dental casting or implant materials were imaged by means of 1.5 T MRI apparatus with three different sequences. Mean and standard deviation of water signal intensity (SI) around the sample in the region of interest (1200 mm(2)) were determined, and the coefficient of variation was compared for evaluation of the homogeneity of the SI. A variety of artifacts with different magnitudes was observed. Only one of the samples, composed mainly of Pd, In, and Sb, showed no artifacts in all imaging sequences. We concluded that selection of specific dental casting alloys according to their elemental compositions could minimize the metal artifacts in MRI; however, titanium alloys currently pose a problem with respect to causing MRI artifacts.

Accuracy of panoramic radiography in assessing the dimensions of radiolucent jaw lesions with distinct or indistinct borders.

OBJECTIVES: To evaluate the accuracy of panoramic radiography (PR) in assessing the dimensions of mandibular lesions. METHODS: One hundred and fifteen cases exhibiting radiolucent lesions in the mandibular premolar, molar or ramus area were selected retrospectively. They were divided into four types: cyst with sclerotic margin (Type I); cyst without sclerotic margin (Type II); ameloblastoma (Type III); or squamous cell carcinoma (Type IV). Maximum mesiodistal length and superoinferior height were measured on PR (Lpmax and Hpmax, respectively) and on CT (Lcmax and Hcmax, respectively) and the results were compared. RESULTS: Correlation coefficients between Lpmax and Lcmax and between Hpmax and Hcmax were high for Type I, II and III lesions but were significantly lower for Type IV lesions. Regression coefficients between Lpmax and Lcmax and between Hpmax and Hcmax were indistinguishable from 1.0 for all types of lesions. The mean relative difference between Lpmax and Lcmax varied from 1.2% to 8.2%. The difference was only -0.3% for larger lesions of combined Types I and II. The mean relative difference between Hpmax and Hcmax varied from--3.5% to 1.1% depending on the type of lesions. CONCLUSION: PR is accurate for assessing the dimensions of radiolucent lesions in the posterior mandible when the margins are well defined.

Hemispheric dominance of tongue control depends on the chewing-side preference.

Blood-oxygenation-level-dependent (BOLD)-functional magnetic resonance imaging (fMRI) is known to be a non-invasive technique for studying human brain function. The purpose of this study was to apply BOLD-fMRI to identify brain areas responsible for producing tongue movements and their relation to chewing-side preference in 15 normal right-handed volunteers. A marked increase in BOLD signals was detected in primary sensorimotor cortices upon protrusion and in rightward and leftward tongue movements compared with at rest. In 10 subjects with an evident chewing-side preference, the BOLD signal change in the primary sensorimotor cortex was significantly greater on the side contralateral to the preferred chewing side. The results suggest that there is a relationship between hemispheric dominance and chewing-side preference in primary sensorimotor cortices responsible for tongue movements.

Salivary glands and lesions: evaluation of apparent diffusion coefficients with split-echo diffusion-weighted MR imaging--initial results.

The authors investigated the feasibility of performing diffusion-weighted (DW) magnetic resonance (MR) imaging with split acquisition of fast spin-echo signals (hereafter, split echo) for the assessment of salivary glands and salivary lesions. Eighteen patients without salivary disease and 10 patients with Sjögren syndrome, chronic parotitis, or focal salivary masses underwent split-echo and echo-planar DW MR imaging. DW MR images and apparent diffusion coefficient maps of the salivary gland had higher quality with split-echo rather than with echo-planar DW MR imaging.

Fractal dimension analysis of static stabilometry in Parkinson's disease and spinocerebellar ataxia.

The static stabilometry patterns associated with Parkinson's disease (PD, n = 15) and spinocerebellar ataxia (SCA, n = 15) were compared with those of normal control (n = 15) by measuring the fractal dimensions. Fractal dimensions were estimated using the modified pixel dilation (mPD) method. The fractal dimensions with closed eyes showed a significant correlation with Environmental area for SCA group (p < 0.05). The fractal dimension for SCA group was significantly higher with closed eyes than that with open eyes (p < 0.05). The fractal dimension with closed eyes was significantly higher in PD and SCA groups than that in normal group (p < 0.05). The fractal dimension with closed eyes was higher when the clinical stage was more severe with PD and SCA group while Environmental and Longitude/Environmental areas were not. These findings suggest that the fractal dimension is more sensitive than traditional stabilometric analysis in an evaluation of postural instability in PD and SCA.

Spontaneously active GABAergic interneurons in the subfornical organ of rat slice preparations.

Inhibitory postsynaptic currents (IPSCs) were recorded from subfornical organ (SFO) neurons in slice preparations of rats, using whole-cell voltage clamp techniques. Some SFO neurons showed bimodal distributions in amplitude with the large and small IPSCs. The large IPSCs vanished in the tetrodotoxin perfusion medium, but the small did not. Both sizes of the IPSCs were completely abolished by application of bicuculline and picrotoxin. Further subpopulation of SFO neurons with the bimodal distributions showed intermittent bursts of the large IPSCs. Immunohistochemical approach revealed existence of gamma-aminobutyric acid (GABA)-immunoreactive neurons and axons in the SFO. These suggest that spontaneously-active and intermittently-burst-firing GABA interneurons affect other SFO neurons in slice preparations of rats.

Angiotensin II induces inward currents in subfornical organ neurones of rats.

The action of angiotensin II on subfornical organ (SFO) neurones was studied using whole-cell current and voltage-clamp recordings in rat slice preparations. In the current-clamp mode, membrane depolarization in response to angiotensin II was accompanied by an increased frequency of action potentials and an increased membrane conductance. In the voltage-clamp mode, angiotensin II elicited inward currents in a dose-dependent manner. The net angiotensin II-induced inward currents were voltage-independent, with a mean reversal potential of -29.8 +/- 6.2 mV. Amplitudes of the angiotensin II-induced inward currents were decreased during perfusion with a low sodium medium. The angiotensin II-induced inward currents were blocked by the AT1 antagonist losartan, and were partially blocked by the AT2 antagonist PD-123319. Neurones which were sensitive to angiotensin II were found in the peripheral region of the SFO, whereas neurones in the central region were less sensitive to angiotensin II. These results suggest that angiotensin II induces inward currents, with opening of nonselective cation channels through mainly AT1 receptors in a subpopulation of SFO neurones of rats.

Muscarinic modulation of GABAergic transmission to neurons in the rat subfornical organ.

Cholinergic actions on subfornical organ (SFO) neurons in rat slice preparations were studied by using whole cell voltage- and current-clamp recordings. In the voltage-clamp recordings, carbachol and muscarine decreased the frequency of GABAergic inhibitory postsynaptic currents (IPSCs) in a dose-dependent manner, with no effect on the amplitudes or the time constants of miniature IPSCs. Meanwhile, carbachol did not influence the amplitude of the outward currents induced by GABA. Furthermore, carbachol and muscarine also elicited inward currents in a TTX-containing solution. From the current-voltage relationship, the reversal potential was estimated to be -7.1 mV. These carbachol-induced responses were antagonized by atropine. In the current-clamp recordings, carbachol depolarized the membrane with increased frequency of action potentials. These observations suggest that acetylcholine suppresses GABA release through muscarinic receptors located on the presynaptic terminals. Acetylcholine also directly affects the postsynaptic membrane through muscarinic receptors, by opening nonselective cation channels. A combination of these presynaptic and postsynaptic actions may enhance activation of SFO neurons by acetylcholine.