Oxytocin-Dependent Regulation of TRPs Expression in Trigeminal Ganglion Neurons Attenuates Orofacial Neuropathic Pain Following Infraorbital Nerve Injury in Rats.

We evaluated the mechanisms underlying the oxytocin (OXT)-induced analgesic effect on orofacial neuropathic pain following infraorbital nerve injury (IONI). IONI was established through tight ligation of one-third of the infraorbital nerve thickness. Subsequently, the head withdrawal threshold for mechanical stimulation (MHWT) of the whisker pad skin was measured using a von Frey filament. Trigeminal ganglion (TG) neurons innervating the whisker pad skin were identified using a retrograde labeling technique. OXT receptor-immunoreactive (IR), transient receptor potential vanilloid 1 (TRPV1)-IR, and TRPV4-IR TG neurons innervating the whisker pad skin were examined on post-IONI day 5. The MHWT remarkably decreased from post-IONI day 1 onward. OXT application to the nerve-injured site attenuated the decrease in MHWT from day 5 onward. TRPV1 or TRPV4 antagonism significantly suppressed the decrement of MHWT following IONI. OXT receptors were expressed in the uninjured and Fluoro-Gold (FG)-labeled TG neurons. Furthermore, there was an increase in the number of FG-labeled TRPV1-IR and TRPV4-IR TG neurons, which was inhibited by administering OXT. This inhibition was suppressed by co-administration with an OXT receptor antagonist. These findings suggest that OXT application inhibits the increase in TRPV1-IR and TRPV4-IR TG neurons innervating the whisker pad skin, which attenuates post-IONI orofacial mechanical allodynia.

Verification of the reliability of current perception threshold and pain threshold testing by application of an electrical current stimulus to mandibular mucosa in young adults.

BACKGROUND: There is little evidence regarding the reliability of CPT and PT measurements to gauge mandibular perception. Thus, this study aimed to evaluate the test-retest reliability of CPT and PT values obtained from the mandibular oral mucosa and to test the bilateral differences in CPT and PT values obtained from the mental foramen region and buccal shelf region by a single operator. METHODS: CPT and PT values were obtained from the mental foramen and buccal shelf regions of 20 volunteers (10 males and 10 females; average age: 26.4 ± 2.6 years) by using the Neurometer CPT/C® device to deliver electrical stimulation. RESULTS: Relative and absolute reliabilities were confirmed over two measurements of CPT and PT over a 7- to 10-day measurement interval. Intra-class correlation coefficients (ICCs) for CPT and PT table obtained from the mental foramen region were >0.8, while most ICC for the buccal shelf region were <0.8. Standard error of measurement, minimal detectable change and Bland-Altman analyses showed that the CPT and PT measurements had no systematic error and could serve as useful methods. At all frequencies, the bilateral difference in CPT and PT values at the mental foramen and buccal shelf region was not significant. CONCLUSION: CPT and PT measurements using a custom-made device that applied an electrical current to the mental foramen region have appropriate reliability to assess intra-oral sensitivity to electrical stimulation in young adults.

Comparison of masticatory muscle myofascial pain in patients with and without a chief complaint of headache.

OBJECTIVES: Headaches are a common complaint in temporomandibular disorder (TMD) patients. However, few studies have compared the symptom characteristics between TMD patients with and without a complaint of headache. The aim of this study was to compare subjective symptoms and treatment outcomes between myofascial TMD patients who had a chief complaint of headache and those who did not. METHODS: One hundred sixty one patients underwent comprehensive examinations and scored their pre- and post-treatment symptoms on a form (4 items assessing pain intensity and 1 assessing sleeping difficulty). On the basis of the primary diagnosis, patients were divided into two groups: myofascial pain with and without a chief complaint of headache (MPH and MP). RESULTS: Before treatment, patients in the MPH group scored significantly higher with respect to pain intensity and level of sleeping difficulty than did patients in the MP group (jaw/face pain, P = 0.015; headache, P < 0.001; neck pain, P < 0.001, and difficulty in sleeping, P = 0.005; Mann-Whitney U-test). Patients in the two groups demonstrated similar treatment outcomes, except for neck pain. CONCLUSION: Significant differences in symptom characteristics and outcomes were observed between primarily myofascial TMD patients with and without a chief complaint of headache.

Association between central sensitivity syndrome and psychophysical factors in patients with masticatory myofascial pain.

PURPOSE: This study explored the relationship between central sensitization symptoms, assessed using the Central Sensitization Inventory (CSI), and psychophysical factors in patients with chronic masticatory myofascial pain (MMP) transitioning from the acute to chronic stages. METHODS: In this study, 23 patients with MMP and 22 healthy volunteers were assessed using psychophysical tests, including measurements of pressure pain threshold (PPT) and temporal summation of pain (TSP). Additionally, CSI scores were recorded to evaluate central sensitization symptoms. RESULTS: Patients with chronic MMP showed significantly lower PPT in all masticatory muscles and extratrigeminal areas compared with controls. However, there was no significant correlation between CSI scores and psychophysical test results in patients with MMP. CONCLUSION: The significant enhancement of TSP in patients with subchronic MMP suggests a potential role in the onset of myofascial pain. The main finding suggests that sub-chronic symptom patients show higher CSI scores despite no sensory testing changes, indicating that central sensitization possibly precedes observable symptoms.

Coordinated features in jaw and neck muscle activities induced by chewing of soft and hard gum in healthy subjects.

BACKGROUNDS: Jaw and neck muscles may be activated by chewing load using a hard food. However, it remains unclear how effects the gum hardness to the coordinated features in jaw and neck muscle activities during chewing performance. OBJECTIVES: This study was conducted to quantitatively elucidate the effects of the hardness of the gum on coordinated features in jaw and neck muscle activities using intermuscular EMG-EMG transfer function and EMG-EMG coherence function analyses in 18 healthy subjects. METHODS: Jaw and neck muscle activities were aggregated into the first peak frequency of the power spectrum, and power, gain, phase, and coherence parameters between jaw and neck muscle activities were examined in the first peak frequencies during soft and hard gum chewing. RESULTS: The first peak frequency was not significantly different between soft and hard gum chewing. In contrast, power values of the jaw and neck muscles were significantly increased by chewing of hard gum as compared with soft gum, whereas gain, phase, and coherence were not significantly changed by gum hardness. CONCLUSIONS: The chewing rhythm, the quantitative and temporal coordination, and the functional coordination in jaw and neck muscle activities were not changed during soft and hard gum chewing, as well as increased jaw and neck muscles activities. It is therefore concluded that the chewing rhythmicity and jaw and neck muscles coordination accompanied with the increased jaw and neck muscle activities are maintained under the condition of the chewing load using gum hardness in the healthy individuals.

The effects of silicone-based resilient denture liners on pain: A randomized controlled trial.

PURPOSE: This randomized controlled trial aimed to study the effects of lining mandibular complete dentures with silicone-based resilient denture liners, especially with respect to sensation. METHODS: The trial included completely edentulous patients who were willing to fabricate new set of complete denture. A random permuted block method (block size: 4) was used to assign participants to one of the following groups: mandibular conventional denture (CD) group or mandibular denture with resilient denture liner (RD) group. The outcomes were evaluated using both, objective measures (current perception threshold (CPT) and pain threshold (PT)) for external stimuli measured using the Neurometer CPT® and subjective measures (physical pain and psychological discomfort measured using the Japanese version of Oral Health Impact Profile for Edentulous patients-OHIP-EDENT-J). The outcomes were measured twice, at immediately after completion of denture adjustments (first measurement), and 3 months after the completion of denture adjustments (second measurement). All outcomes were analyzed using the Student t-test. A p-value of <0.05 was considered statistically significant. RESULTS: CPT was significantly higher with RD than CD only at second measurement with frequency level of 2000 Hz and 5 Hz. The pain thresholds were significantly higher in the RD group than the CD group. The physical pain and psychological discomfort scores were significantly lower in the RD group than in the CD group. CONCLUSION: This study concludes that edentulous patients wearing mandibular complete dentures with silicone-based resilient denture liners dull perception mandibular ridge mucosa and felt less pain than those without the liners.

Receptivity of the mandible versus the maxilla to external stimuli in patients with complete dentures.

PURPOSE: This study aimed to investigate whether the mandible is more receptive to external stimuli than the maxilla in patients with complete dentures by comparing regional current perception thresholds (CPTs) and pain threshold (PTs). METHODS: A single operator obtained measurements from maxillae at the incisor foramen and the left side of the greater palatine foramen region and the mandible at the left side of the mental foramen region, using the Neurometer CPT/C device, CPT and PT values from the oral mucosa of 20 edentulous individuals wearing complete dentures were analyzed. Participant characteristics such as mucosal thickness, occlusal force, age, and sex. Mucosal thickness over target regions and occlusal force were measured by the same operator using Krupp SDM and Occlusal Force-Meter GM10s devices. Differences in CPT and PT among the three measurement regions were tested with an analysis of covariance, and post hoc t-tests with the Bonferroni correction. RESULTS: There were no significant differences between the mental foramen, incisor papilla, and greater palatine regions CPT values. PTs obtained at all current frequencies (2000Hz, 250Hz, and 5Hz) were lowest in the mental foramen region and highest in the greater palatine region. Covariates including sex, mucosal thickness, and occlusal force had no significant influence on CPT or PT values at all frequencies. CONCLUSIONS: The mandible exhibits higher receptivity to external pain stimuli than the maxilla.

Prefrontal Consolidation and Compensation as a Function of Wearing Denture in Partially Edentulous Elderly Patients.

BACKGROUND: The cognitive effects of wearing a denture are not well understood. This study was conducted to clarify the effects of denture use on prefrontal and chewing muscle activities, occlusal state, and subjective chewing ability in partially edentulous elderly individuals. METHODS: A total of 16 partially edentulous patients were enrolled. Chewing-related prefrontal cortex and jaw muscle activities were simultaneously examined using a functional near-infrared spectroscopy (fNIRS) device and electromyography, under the conditions of unwearing, and wearing a denture. Occlusal state and masticatory score were also determined under both conditions. Using multiple linear regression analysis, associations between prefrontal and chewing activities with wearing were examined using change rates. RESULTS: Chewing rhythmicity was maintained under both conditions. As compared with unwearing, the wearing condition was associated with improved prefrontal cortex and chewing muscle activities, occlusal state in regard to force and area, and masticatory score. Also, prefrontal activities were positively associated with burst duration and peak amplitude in masseter (Mm) and temporal muscle activities, as well as masticatory scores. In contrast, prefrontal activities were negatively associated with occlusal force. CONCLUSION: Wearing a denture induced a positive association between burst duration and peak amplitude in Mm and temporal muscle activities and prefrontal activity, which may indicate a parallel consolidation of prefrontal cortex and rhythmical chewing activities, as well as masticatory scores. On the other hand, denture use induced a negative association of occlusal force with prefrontal activities, which might suggest that prefrontal compensative associations for the physiocognitive acquisition depended on biomechanical efficacy gained by wearing a denture.

Measurement reliability of current perception threshold and pain threshold in parallel with blood sampling.

The irritation and pain associated with oral blood sampling necessary to monitor glycemic control can alter oral sensation, but no studies have measured the reliability of oral sensation testing when performed concurrently with blood sampling. The primary and secondary aims of this study were to verify the measurement reliability of current perception threshold (CPT) and pain threshold (PT) tests performed before and after blood sampling and to investigate the differences in CPTs/PTs obtained from the oral cavity, hand, and foot, respectively. CPT/PT measurements were obtained from the oral mucosa and the tips of fingers and toes of 18 volunteers (10 males and 8 females, average age = 26.3 years) using electrical stimulation at frequencies of 5, 250, and 2,000 Hz. Participants also provided blood samples by pricking their own index fingers with a small needle. All subjects completed the following 3 conditions at once-weekly intervals as follows: (a) sensory measurements followed by blood sampling (SB block); (b) blood sampling followed by sensory measurements (BS block); (c) sensory measurements without blood sampling (CO control block). Cronbach's α coefficients were over 0.78 for the SB, BS, and CO blocks, and are considered to be acceptable for assuring measurement reliability. The oral cavity had significantly lower CPT/PTs than both hands and feet, such that the threshold increased in the order oral cavity < hand < foot. CPT and PT measurements performed concurrently with blood sampling are both reliable and region specific, and for which the oral cavity is the most sensitive testing region.

[Case report of partial denture using Dimple-bar telescopic system].

PATIENT: A 49-year-old female patient presented to Prosthodontic Clinic at Nihon University School of Dentistry at Matsudo with the chief complaints of chewing difficulty and poor appearance. She was diagnosed moderate to severe periodontitis and partially edentulous dentition on both maxilla and mandible. Occlusal reconstruction was conducted with crown restorations and removable partial dentures (RPD). From the esthetic request of patient, Dimple-bar telescopic (DBT) system was applied to the mandible with bilateral distal coping abutments. DISCUSSION: DBT system has been functioning well for more than 5 years without abutment tooth loss. It was thought that bilateral distal coping abutments can help to resolve problem with bilateral distal extension RPD dilemma. CONCLUSION: It is suggested that DBT system has great potential to resolving weak points of clasps, such as low retentive forces and/or esthetic problem. Furthermore, author got a new understanding of the importance of maintenances.

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.

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.

Comparing student-generated learning needs with faculty objectives in PBL cases in dental education.

The purpose of this study was to compare learning need reports generated by students during their investigation of a problem-based learning (PBL) case with the faculty-identified learning objectives established for it. Four PBL cases facilitated by four group tutors were selected for comparison. The student-generated learning needs were collected for each and were compared to the faculty-specified learning outcomes. The results were analyzed by individual case and compared among the four student groups. Over 96 percent of the faculty-specified objectives across all four cases and across all four groups of students were covered by the student-generated learning need reports. Only one of the four cases demonstrated a statistically significant difference between small groups with regard to percent coverage of the stated case objectives. Our data agree with previous research findings. Although there was some variability in the learning objectives investigated by student small groups studying the same case, the faculty-specified case objectives were included in the student-generated learning needs. First-trimester dental students were capable of generating learning needs that produced an excellent match with the faculty objectives for the cases studied.