Activation of Prefrontal Cortex in Process of Oral and Finger Shape Discrimination: fNIRS Study.

BACKGROUND: The differences in the brain activities of the insular and the visual association cortices have been reported between oral and manual stereognosis. However, these results were not conclusive because of the inherent differences in the task performance-related motor sequence conditions. We hypothesized that the involvement of the prefrontal cortex may be different between finger and oral shape discrimination. This study was conducted to clarify temporal changes in prefrontal activities occurring in the processes of oral and finger tactual shape discrimination using prefrontal functional near-infrared spectroscopy (fNIRS). METHODS: Six healthy right-handed males [aged 30.8 ± 8.2 years (mean ± SD)] were enrolled. Measurements of prefrontal activities were performed using a 22-channel fNIRS device (ETG-100, Hitachi Medical Co., Chiba, Japan) during experimental blocks that included resting state (REST), nonsense shape discrimination (SHAM), and shape discrimination (SHAPE). RESULTS: No significant difference was presented with regard to the number of correct answers during trials between oral and finger SHAPE discrimination. Additionally, a statistical difference for the prefrontal fNIRS activity between oral and finger shape discrimination was noted in CH 1. Finger SHAPE, as compared with SHAM, presented a temporally shifting onset and burst in the prefrontal activities from the frontopolar area (FPA) to the orbitofrontal cortex (OFC). In contrast, oral SHAPE as compared with SHAM was shown to be temporally overlapped in the onset and burst of the prefrontal activities in the dorsolateral prefrontal cortex (DLPFC)/FPA/OFC. CONCLUSION: The prefrontal activities temporally shifting from the FPA to the OFC during SHAPE as compared with SHAM may suggest the segregated serial prefrontal processing from the manipulation of a target image to the decision making during the process of finger shape discrimination. In contrast, the temporally overlapped prefrontal activities of the DLPFC/FPA/OFC in the oral SHAPE block may suggest the parallel procession of the repetitive involvement of generation, manipulation, and decision making in order to form a reliable representation of target objects.

Quantitative and qualitative assessment of sensory changes induced by local anesthetics block of two different trigeminal nerve branches.

OBJECTIVES: The aims were to use different techniques to assess the degree of sensory changes and magnitude of perceived size changes in the facial region induced by nerve blocks of two different trigeminal nerve branches in healthy participants. MATERIALS AND METHODS: This placebo-controlled study included 30 healthy volunteers. The participants underwent quantitative and qualitative sensory testing (QST and QualST) thrice: before, 10 min, and 2 h after mental (n = 15) and infraorbital (n = 15) nerve blocks and during control (saline) sessions. Perceived numbness, temperature changes, and perceptual distortion were also measured at all time points during the nerve block and control sessions. Differences in outcome parameters between the sessions and time points were analyzed using analyses of variance and McNemar's tests. RESULTS: There was a significant degree of sensory loss to most QST and all QualST parameters, with significant numbness and increased perceived size at the injection site 10 min and 2 h after the nerve blocks compared with saline (P < 0.030) and the baseline (P < 0.042). Two hours after the nerve blocks, the sensitivity was significantly closer to baseline than after 10 min to most of the QST parameters (P < 0.011). CONCLUSIONS: QST and QualST revealed that the nerve blocks in the orofacial region resulted in complete or partial blockade of afferent nerve fibers mediating thermal and mechanical function for more than 2 h with significant numbness and perceptual distortion. CLINICAL RELEVANCE: Both QST and QualST can provide information on the degree of blockade of afferent nerve fibers after nerve blocks in the orofacial region.

Characteristics of middle-aged and older patients with temporomandibular disorders and burning mouth syndrome.

The aim of this study was to evaluate the relationship between pain intensities and psychosocial characteristics in middle-aged and older patients with temporomandibular disorders (TMDs) and burning mouth syndrome (BMS). Subjects were selected according to the Research Diagnostic Criteria for TMD (n = 705) and International Association for the Study of Pain criteria for BMS (n = 175). Patients were then divided into two age groups: 45-64 years (middle-aged, Group A) and 65-84 years (older, Group B). Pain intensity and depression and somatization scores were evaluated in both groups. In BMS patients, present and worst pain intensities were significantly higher in Group B than in Group A {4.6 [95% confidence interval (CI) = 4.0-5.2] vs. 3.5 [95% CI = 3.1-3.9] and 5.9 [95% CI = 5.2-6.4] vs. 5.0 [95% CI = 4.5-5.6], respectively; P < 0.05}, with no difference observed in TMD patients. The depression and somatization scores were significantly higher in Group A than in Group B among BMS patients [0.57 (95% CI = 0.45-0.69) vs. 0.46 (95% CI = 0.34-0.59) and 0.537 (95% CI = 0.45-0.63) vs. 0.45 (95% CI = 0.34-0.55); P < 0.05], with no difference observed in TMD patients. The results of the present study indicate that pain intensities and psychosocial characteristics in BMS appear to differ between middle-aged and older patients.

Micromolar sodium fluoride mediates anti-osteoclastogenesis in Porphyromonas gingivalis-induced alveolar bone loss.

Osteoclasts are bone-specific multinucleated cells generated by the differentiation of monocyte/macrophage lineage precursors. Regulation of osteoclast differentiation is considered an effective therapeutic approach to the treatment of bone-lytic diseases. Periodontitis is an inflammatory disease characterized by extensive bone resorption. In this study, we investigated the effects of sodium fluoride (NaF) on osteoclastogenesis induced by Porphyromonas gingivalis, an important colonizer of the oral cavity that has been implicated in periodontitis. NaF strongly inhibited the P. gingivalis-induced alveolar bone loss. That effect was accompanied by decreased levels of cathepsin K, interleukin (IL)-1ß, matrix metalloproteinase 9 (MMP9), and tartrate-resistant acid phosphatase, which were up-regulated during P. gingivalis-induced osteoclastogenesis. Consistent with the in vivo anti-osteoclastogenic effect, NaF inhibited osteoclast formation caused by the differentiation factor RANKL (receptor activator of nuclear factor κB ligand) and macrophage colony-stimulating factor (M-CSF). The RANKL-stimulated induction of the transcription factor nuclear factor of activated T cells (NFAT) c1 was also abrogated by NaF. Taken together, our data demonstrate that NaF inhibits RANKL-induced osteoclastogenesis by reducing the induction of NFATc1, ultimately leading to the suppressed expression of cathepsin K and MMP9. The in vivo effect of NaF on the inhibition of P. gingivalis-induced osteoclastogenesis strengthens the potential usefulness of NaF for treating periodontal diseases.

Age-related associations between psychological characteristics and pain intensity among Japanese patients with temporomandibular disorder.

We investigated the relationship between pain intensity and psychosocial characteristics in patients with temporomandibular disorder (TMD). Participants with painful TMD, according to the Research Diagnostic Criteria for TMD (RDC/TMD), were recruited from our clinic and classified into six age groups: 15 to 24, 25 to 34, 35 to 44, 45 to 54, 55 to 64, and 65 to 85 years (Groups A through F, respectively). Self-reported present pain intensity and worst pain intensity during the past 6 months were ascertained using a numeric rating scale (0 to 10). Depression and somatization scores were evaluated using the RDC/TMD axis II questionnaire. Among women, worst pain intensity was significantly lower in Groups E and F than in Groups B and C (P < 0.05). In Groups A, C, and D, depression scores were significantly higher in women than in men (P < 0.05). Among women, depression score was significantly lower in Group F than in Groups A through C (P < 0.05). In Groups A through D, somatization scores were significantly higher for women than for men (P < 0.05). Depression score and TMD symptom severity appear to decrease with age in women.

Pain intensity and psychosocial characteristics of patients with burning mouth syndrome and trigeminal neuralgia.

This study compared pain intensity and psychosocial characteristics between patients with burning mouth syndrome (BMS) and those with trigeminal neuralgia (TN). Data from 282 patients with BMS and 83 patients with TN were analyzed. Patients reported duration of illness: duration ≤ 6 months was defined as acute illness and > 6 months as chronic illness. Present pain intensity and worst pain intensity during the past 6 months were reported using a 0-10 numeric rating scale (NRS). In addition, depression and somatization scores were evaluated on questionnaires. Patients with chronic BMS reported significantly higher pain intensity and had worse psychosocial characteristics than did those with acute BMS. Pain intensity was higher in TN patients than in BMS patients, although neither pain intensity nor psychosocial characteristics significantly differed between patients with acute and chronic illness. Logistic regression analysis of BMS and TN patients revealed that the odds ratio for worst pain was significantly lower for BMS patients than for TN patients and that the odds ratio for somatization score was 3.8 times higher in BMS patients. These findings suggest that BMS patients may require pain control targeting the central nervous system or psychosocial characteristics.