Butyric acid modulates periodontal nociception in Porphyromonas gingivalis-induced periodontitis.

PURPOSE: Periodontitis progresses with chronic inflammation, without periodontal pain. However, the underlying mechanisms are not well known. Here, the involvement of butyric acid (BA) in periodontal pain sensitivity in Porphyromonas gingivalis (P. gingivalis)-induced periodontitis was examined. METHODS: P. gingivalis was inoculated into the ligature which was tied around the molar (P. gingivalis-L) and the gingival mechanical head withdrawal threshold (MHWT) was measured. Following P. gingivalis-L, the expressions of orphan G protein-coupled receptor 41 (GPR41) in trigeminal ganglion (TG) neurons were examined. The amount of gingival BA was analyzed following the P. gingivalis-L and the changes in the MHWT in complete Freund's adjuvant (CFA)-injected gingival tissue by gingival BA were examined. The changes in the MHWT following P. gingivalis-L by gingival GPR41 antagonist (HA) were examined. RESULTS: No change in the MHWT was observed, GPR41-immunoreactive TG neurons were increased following P. gingivalis-L. The gingival BA amount increased following P. gingivalis-L, and the gingival BA suppressed the decrease in MHWT following CFA. HA decreased MHWT following P. gingivalis-L. CONCLUSION: Gingival BA modulates periodontal mechanical nociception via GPR41 signaling in P. gingivalis-L-induced periodontitis.

Age dependence of the maturation of the midpalatal suture in the stability of orthodontic anchoring screws.

INTRODUCTION: Orthodontic anchoring screws (OASs) have been placed around midpalatal sutures in patients of various ages. Our previous study found that OAS placement more than 1.5 mm from midpalatal suture was more successful than placement directly at the suture. This study aimed to investigate the relationship between age and midpalatal suture maturation, considering factors affecting the failure of OASs using cone-beam computed tomography. METHODS: In total, 150 patients who underwent cone-beam computed tomography were selected. The total depth and sutured depth of the midpalatal suture corresponding area to anterior (interpremolar zone) and posterior region (mesial and distal borders of the first molar) were measured, and the ratio of sutured depth to total depth (sutured ratio) was calculated. RESULTS: The mean sutured ratios at interpremolar zone and mesial and distal borders of the first molar according to age were 40%, 60%, and 63% in the younger group (≤17 years), 46%, 76%, and 76% in the middle group (18-25 years), and 47%, 74%, and 76% in the older group (≥26 years), respectively. The sutured ratio of the anterior region was significantly lower than that of the posterior region (P <0.01). Each mean sutured ratio of the middle and older group was significantly higher than that of the younger group on both sides (P <0.01). According to the cervical vertebral maturation, the mean sutured ratio of cervical vertebral stages 5-6 was significantly higher than cervical vertebral stages 1-3 on the distal side (P <0.05). CONCLUSIONS: Incomplete closure of the midpalatal suture was observed frequently, even in the older group. This might be caused by insufficient calcification of the midpalatal suture, including in elder patients. To prevent OAS placement to the unsutured area, the midpalatal suture should be avoided regardless of age.

Periodontal acidification contributes to tooth pain hypersensitivity during orthodontic tooth movement.

Tooth movements associated with orthodontic treatment often cause tooth pain. However, the detailed mechanism remains unclear. Here, we examined the involvement of periodontal acidification caused by tooth movement in mechanical tooth pain hypersensitivity. Elastics were inserted between the first and second molars to move the teeth in Sprague-Dawley rats. Mechanical head-withdrawal reflex threshold to first molar stimulation and the pH of the gingival sulcus around the tooth were measured. The expression of acid-sensing ion channel 3 (ASIC3) in trigeminal ganglion neurons and phosphorylation of ASIC3 in the periodontal tissue were analyzed. The mechanical head-withdrawal reflex threshold to first molar stimulation and pH in the gingival sulcus decreased on day 1 after the elastic insertion. These decreases recovered to the sham level by buffering periodontal acidification. Periodontal inhibition of ASIC3 channel activity reversed the decreased mechanical head-withdrawal reflex threshold to first molar stimulation. On day 1 after elastic insertion, the tooth movement did not change the number of ASIC3 immunoreactive trigeminal ganglion neurons innervating the periodontal tissue but increased phosphorylated-ASIC3 levels in the periodontal tissue. Periodontal acidification induced by tooth movement causes phosphorylation of ASIC3, resulting in mechanical pain hypersensitivity in mechanically forced tooth.

Influence of pre-drilling diameter on the stability of orthodontic anchoring screws in the mid-palatal area.

PURPOSE: The aim of this study was to investigate the stability of orthodontic anchor screws (OASs) in the mid-palatal area according to pre-drilling diameter. METHODS: The success rate of 161 OASs (83 patients, φ2.0 mm, 6.0 mm in length) placed in a corresponding area to the mesial and distal borders of the first molar (mesial zone and distal zone) was assessed according to placement location and pre-drilling diameter (1.2 and 1.5 mm). Placement torque values from 73 OASs with a pre-drilling diameter of 1.2 mm were compared between success and failure groups. RESULTS: The success rates of OASs pre-drilled with φ1.2 and 1.5 mm were 94.5% and 83.0%, respectively (P < 0.05); corresponding rates in the mesial zone were 100.0% and 77.3% (P < 0.005), and those in the distal zone were 89.2% and 88.6%, respectively. Placement torques of OASs predrilled with φ1.2 mm in the success and failure groups were 25.9 and 19.2 N·cm, respectively (P < 0.05). CONCLUSION: A smaller pre-drilling diameter was associated with a higher success rate of OASs in the mid-palatal area, especially in the mesial zone. When pre-drilling diameter of 1.2 mm was used for φ2.0 mm OAS, greater placement torque was indicative of greater OAS stability.

Evaluation of torque moment in esthetic brackets from bendable alloy wires.

OBJECTIVES: To examine the torque moment that occurs between esthetic brackets and bendable alloy (stainless steel [SS], titanium-molybdenum [Ti-Mo], and titanium-niobium [Ti-Nb]) wires. MATERIALS AND METHODS: This study examined ceramic (CR), zirconium oxide (ZC), polycarbonate (PC), and conventional metallic brackets (MT) (upper, 0.018-inch and 0.022-inch slots) combined with SS, Ti-Mo, and Ti-Nb wires using elastic module ligation. The torque moments delivered by various wire and bracket combinations were measured using a torque gauge apparatus. The wire torque angles at 5-40° were examined. RESULTS: The torque value increased in the order of CR, ZC, MT, and PC brackets for both 0.018-inch and 0.022-inch slots. The fracture points of the CR and ZC brackets combined with SS and Ti-Mo wires were approximately more than 30° and 35°, respectively. No fracture points were detected in the combination of ZC brackets and Ti-Nb wires. CONCLUSIONS: The current study identified the material characteristics of CR, ZR, and PC brackets during torque tooth movements. The present results demonstrate a characteristic combined effect between different esthetic brackets and bendable alloy wires.

Suppression of Superficial Microglial Activation by Spinal Cord Stimulation Attenuates Neuropathic Pain Following Sciatic Nerve Injury in Rats.

We evaluated the mechanisms underlying the spinal cord stimulation (SCS)-induced analgesic effect on neuropathic pain following spared nerve injury (SNI). On day 3 after SNI, SCS was performed for 6 h by using electrodes paraspinally placed on the L4-S1 spinal cord. The effects of SCS and intraperitoneal minocycline administration on plantar mechanical sensitivity, microglial activation, and neuronal excitability in the L4 dorsal horn were assessed on day 3 after SNI. The somatosensory cortical responses to electrical stimulation of the hind paw on day 3 following SNI were examined by using in vivo optical imaging with a voltage-sensitive dye. On day 3 after SNI, plantar mechanical hypersensitivity and enhanced microglial activation were suppressed by minocycline or SCS, and L4 dorsal horn nociceptive neuronal hyperexcitability was suppressed by SCS. In vivo optical imaging also revealed that electrical stimulation of the hind paw-activated areas in the somatosensory cortex was decreased by SCS. The present findings suggest that SCS could suppress plantar SNI-induced neuropathic pain via inhibition of microglial activation in the L4 dorsal horn, which is involved in spinal neuronal hyperexcitability. SCS is likely to be a potential alternative and complementary medicine therapy to alleviate neuropathic pain following nerve injury.

Changes in thoracic and lumbar spinal motions during running in a female with scoliosis.

[Purpose] The aim of this study was to analyze changes in thoracic and lumbar spinal motions during running in a female athlete with scoliosis. [Participant and Methods] A female with scoliosis who was a member of a college track team was recruited for this study. On 1.5-T magnetic resonance imaging, angles between bodies of adjacent vertebrae in the frontal plane were calculated. We measured real-time spine movement while running using a three-dimensional motion analysis system, wherein the running speed was altered (6, 9, and 12 km/h). [Results] We observed a Cobb angle of 29.0° and the right convex curvature of the thoracolumbar spine on magnetic resonance imaging. As the running speed increased, during the right stance phase, the participant increased the lateral bending angle of the thoracic spine to the left and the lumbar spine to the right. However, during the left stance phase, the runner bent the thoracic spine to the right and the lumbar spine to the left, indicating a decreased convex curvature of the spine. [Conclusion] As the running speed increased, the convex curvature of the spine was corrected during the left stance phase but was uncorrected during the right stance phase.

Changes in hip and spine movement with increasing running speed.

[Purpose] We aimed to clarify and compare the changes in thoracic and lumbar spine motion and to elucidate the relationship between hip and lumbar spine motion during running. [Participants and Methods] Seven healthy females were recruited in this study. Hip and spine movement were measured using a 3D motion analysis system when running at 6, 9, and 12 km/h. One-way analysis of variance was used to compare the changes in hip joint and spine angles during running. Correlation coefficient analysis was used to determine the relationship between the hip and lumbar spine angles at right and left toe-offs. [Results] As the running speed increased, the rotation angles of the thoracic and lumbar spine and the extension angles of the lumbar spine and hip joint significantly increased in the late stance phase. Significant positive relationships were observed between hip flexion and lumbar spine extension angles at toe-off when running at 6 and 9 km/h but not when running at 12 km/h. [Conclusion] To increase the running speed, participants increased the rotation angle of spine and the extension angles of the hip joint and lumbar spine during the stance phase. Participants extended the lumbar spine to compensate for the restricted hip motion at toe-off, which could cause stress to the lumbar spine.