This study aimed to elucidate the modulation by nitric oxide (NO) of the apoptosis of macrophages... more This study aimed to elucidate the modulation by nitric oxide (NO) of the apoptosis of macrophages and osteoblasts, the essential cellular components in the development of periapical lesions. Lipopolysaccharide (LPS) induced prominent nitrite synthesis in J774 mouse macrophage cell lines. Exposure to LPS induced obvious apoptosis in J774 cells, whereas transient transfection with murine inducible nitric oxide synthase (iNOS), small interfering RNA (siRNA) diminished this effect. Tumor necrosis factor‐α (TNF‐α) and S‐nitroso‐N‐acetyl‐DL‐penicillamine (SNAP) (a NO donor) triggered apoptosis in UMR‐106 rat osteoblastic cell lines and a synergistic effect was noted when TNF‐α and SNAP were added to the medium together. Administration of siRNAs for c‐Fos and c‐Jun: components of activator protein‐1 (AP‐1) and transforming growth factor‐β1 attenuated the combined effect markedly. Terminal deoxynucleotidyl transferase‐mediated nick end‐labeling (TUNEL) stain in a rat model of induced periapical lesion showed positive apoptotic signals in macrophages and osteoblasts. Administration of NG‐monomethyl‐l‐arginine markedly diminished the extent of bone loss and the amounts of apoptotic macrophages and osteoblasts. In conclusion, NO mediates LPS‐stimulated apoptosis of macrophages. It also induces osteoblast apoptosis and augments the pro‐apoptotic effect of cytokines. Inhibition of NO synthesis in vivo attenuates apoptosis and the size of periapical lesions. Taken together, these results suggest that NO may promote the progression of periapical lesion by inducing the apoptosis of macrophages and osteoblasts.
1. Intracortical microstimulation (ICMS) and surface stimulation studies of primate face motor co... more 1. Intracortical microstimulation (ICMS) and surface stimulation studies of primate face motor cortex have shown an extensive representation within face motor cortex devoted to movements of the tongue and face; only a very small representation for jaw-closing movements has ever been demonstrated. These data suggest that face motor cortex plays a critical role in the generation of tongue and facial movements but is less important in the generation of jaw-closing movements. Our aim was to determine whether disruption of primate face motor cortical function would indeed interfere with the generation of tongue movements but would not interfere with the generation of jaw-closing movements. 2. The face motor cortex was reversibly inactivated with the use of cooling in two monkeys that were trained to perform both a tongue-protrusion task and a biting task. Recording of single neuronal activity in the cortex beneath the thermode confirmed the reversible inactivation of the cortex. Each task involved a series of trials in which the monkey was required to produce a preset force level for a 0.5-s force holding period; the monkey received a fruit-juice reward if it successfully completed a task trial. Cooling of the ICMS-defined face motor cortex was achieved bilaterally or, in one experiment, unilaterally by circulating coolant through thermodes placed either on intact dura overlying face motor cortex in both monkeys or directly on the exposed pia in one of the monkeys;thermode temperature was lowered to 3-5 degrees C during cooling. Electromyographic (EMG) recordings were also made from masseter, genioglossus, and digastric muscles. 3. During bilateral cooling of the thermodes on the dura overlying the face motor cortex, there was a significant reduction in the success rates for the performance of the tongue-protrusion task in comparison with control series of trials (i.e., precool and postcool) in which the thermodes were kept at 37 degrees C. Quantitative analyses of force and EMG activity showed that the principal deficit was an inability of each monkey to exert sufficient force with its tongue for a sufficient length of time onto the tongue-protrusion task transducer; this deficit was paralleled by a reduction in the level of genioglossus and digastric EMG activity. At 4 min after commencement of rewarming, task performance had returned to control, precool levels.(ABSTRACT TRUNCATED AT 400 WORDS)
AimTo investigate the effects of butyric acid (BA), a metabolic product generated by pulp and roo... more AimTo investigate the effects of butyric acid (BA), a metabolic product generated by pulp and root canal pathogens, on the viability and intercellular adhesion molecule‐1 (ICAM‐1) production of endothelial cells, which are crucial to angiogenesis and pulpal/periapical wound healing.MethodologyEndothelial cells were exposed to butyrate with/without inhibitors. Cell viability, apoptosis and reactive oxygen species (ROS) were evaluated using an MTT assay, PI/annexin V and DCF fluorescence flow cytometry respectively. RNA and protein expression was determined using a polymerase chain reaction assay and Western blotting or immunofluorescent staining. Soluble ICAM‐1 (sICAM‐1) was measured using an enzyme‐linked immunosorbent assay. The quantitative results were expressed as mean ± standard error (SE) of the mean. The data were analysed using a paired Student's t‐test where necessary. A p‐value ≤0.05 was considered to indicate a statistically significant difference between groups.Resul...
1. Studies using ablation, intracortical microstimulation (ICMS) and surface stimulation, and sin... more 1. Studies using ablation, intracortical microstimulation (ICMS) and surface stimulation, and single-neuron recordings have suggested that the primate primary somatosensory cortex (SI) may play an important role in movement control. Our aim was to determine whether bilateral inactivation of face SI would indeed interfere with the control of tongue or jaw-closing movements. 2. Effects of reversible inactivation by cooling of face SI was investigated in two monkeys trained to perform both a tongue-protrusion task and a biting task. The cooling experiments were carried out after the orofacial representation within SI was identified by systematically defining the mechanoreceptive field of single neurons recorded in face SI. The deficits in the tongue or jaw-closing movement were evaluated by the success rates for the monkeys' performance of both tasks and by the force and electromyographic (EMG) activity recorded from the masseter, genioglossus, and digastric muscles associated with...
This study sought to characterise the electromyographic (EMG) activity patterns of orofacialmuscl... more This study sought to characterise the electromyographic (EMG) activity patterns of orofacialmuscles during trained tongue-protrusion and biting tasks in two awake monkeys (Macacafascicularis). Chronic or acute EMG electrodes were placed in the anterior digastric (DIG), genioglossus (GG), masseter (MASS), platysma (PLAT), zygomaticus major (ZYGO), orbicularis oris superior (OOS), and orbicularis oris inferior (001) muscles and their EMG activity as well as the force signals of the tongue-protrusion and biting tasks were recorded. A total of 327 tongue-protrusion task trials and a total of 210 biting-task trials were successfully completed in several recording sessions and the EMG patterns were generally consistent between the different sessions. For the tongue task, the mean onset time of increase in GG activity significantly (p < 0.0001) led the mean onset time of increase in the force. The DIG, GG, and 001 (and also the 00s in one of the monkeys) showed a significant (p < 0.0001) increase in mean EMG amplitude during the holding phase, but the GG in both monkeys had the highest mean EMG amplitude ratio (MAR), i.e. the mean EMG amplitude during the holding or dynamic phase divided by the mean EMG amplitude during the pre-trial period. A similar EMG pattern was documented for different directions of the tongue-protrusion task (right, symmetrical, and left) and changes in the levels of EMG activities occurred in GG and 001 as the direction of the tongue-protrusion task changed from left to right, The task at different forces was associated with no apparent change in MAR for the holding phase for each muscle recorded. However, during the dynamic phase, only the GG showed a significant increase in EMG activity as the forces were increased. For the biting task, the mean onset times of the MASS activity and force were not significantly different. The MASS and ZYGO muscles (and the PLAT in one of the monkeys) showed a significant increase in mean EMG amplitude during the holding phase compared with the pre-trial period, and the MASS showed the highest MAR. It was also the only muscle showing a significant increase in the EMG activity when the bite-force level was increased. These findings reveal that certain orofacial muscles are selectively recruited during the two different orofacial tasks. Based on the EMG activity pattern during different directions or force levels of the task, the data suggest that, of the muscles recorded, the principal agonist for the tongue task is the GG and that for the biting task is the MASS; the other muscles that may be active appear to serve as accessories to the task.
Rhythmical jaw movements can be evoked by intracortical microstimulation within four physiologica... more Rhythmical jaw movements can be evoked by intracortical microstimulation within four physiologically de®ned regions, one of which is the primary face somatosensory cortex (face SI). It has been proposed that these regions may be involved in the selection and/or control of masticatory patterns generated at the brainstem level. The aim here was to determine if mastication is aected by reversible, cooling-induced inactivation of the face SI. Two cranial chambers were chronically implanted in two monkeys (Macaca fascicularis) to allow access bilaterally to the face SI. A thermode was placed on the dura or pia overlying each SI that had been shown with micro-electrode recordings to receive intraoral inputs. A hot or cold alcohol±water solution was pumped through the thermodes while the monkey chewed a small piece of apple or a sultana during precool (thermode temperature, 378C), cool (2± 48C), and postcool (378C) conditions. Electromyographic (EMG) activity was recorded intramuscularly from the masseter, genioglossus, and anterior digastric. Cooling of SI impaired rhythmical jaw and tongue movements and EMG activity associated with mastication in one monkey (H5), and modi®ed the pattern of EMG activity in the other (H6). The total masticatory time (i.e., time taken for chewing and manipulation of the bolus before swallowing) was increased. This was due principally to an increase in the oral transport time (i.e., time taken for manipulation of bolus after chewing and before swallowing: monkey H6, control, 2.7 sec; cool, 5.2 sec, p < 0.05); the bolus was manipulated by the tongue during this period before swallowing. Within the chewing time (i.e., time during which chewing occurred), cooling resulted in a signi®cant increase in anterior digastric muscle duration, a signi®cant delay in the onset of masseter EMG activity, and a signi®cant increase in the variance of genioglossus EMG duration. The data support the view that the face SI plays a part in modulating the central pattern generator for mastication.
1. We have demonstrated recently that reversible, cooling-induced inactivation of the face primar... more 1. We have demonstrated recently that reversible, cooling-induced inactivation of the face primary somatosensory cortex (SI) severely impairs the successful performance of a tongue-protrusion task but has relatively minor effects on the performance of a biting task. In an attempt to establish a neuronal correlate for these different behavioral relations, the present study was initiated to document the mechanoreceptive field properties of a population of face SI neurons and their activity during the tongue-protrusion and biting tasks. 2. Within SI, the representation of the face was found immediately lateral to that of the hand, and there was a clear somatotopic pattern of organization within face SI: the periorbital or nose region was located most medially in the face SI, then followed laterally in sequence the representation of the upper lip, lower lip, and intraoral area. A mechanoreceptive field (RF) was identified for 253 neurons, which included 162 “lip RF” neurons receiving me...
Monomers released from resin-containing products may cause various adverse effects. Urethane dime... more Monomers released from resin-containing products may cause various adverse effects. Urethane dimethacrylate (UDMA) is a principal resin monomer and also a major component released from various dental resin materials. Thus the toxic effects and mechanisms should be elucidated for improving of its safety use. Here we investigated the effects of UDMA on the growth, cell cycle progression, reactive oxygen species (ROS) production and glutathione (GSH) alteration in CHO-K1 cells, and the preventive effects by antioxidants (NAC and catalase) were also evaluated. UDMA elicited growth inhibition (>0.025 mM) of CHO-K1 cells in a clearly dose-dependent manner. Cell cycle perturbation and ROS overproduction were also observed. A 0.1 mM UDMA-induced S-phase cell cycle arrest and ROS accumulation. Cell apoptosis and necrosis became significant when UDMA concentration was 0.25 mM. GSH depletion occurred at cells treated with 0.25 mM UDMA, a highly cytotoxic concentration at which point myriad cells were under apoptosis or necrosis. Thus GSH depletion can be crucial for the death of CHO-K1 cells. Furthermore NAC (0.5e10 mM) and catalase (250e1000 U/ml) obviously attenuated the UDMAinduced toxicity by reducing ROS generation and cell cycle disturbance, and the effects were doserelated. These results suggest that UDMA toxicity is associated with ROS production, GSH depletion, cell cycle disturbance and cell apoptosis/necrosis.
STATEMENT OF PROBLEM Information on the dimensional changes in maxillary and mandibular dentures ... more STATEMENT OF PROBLEM Information on the dimensional changes in maxillary and mandibular dentures made by using computer-aided design and computer-aided manufacturing (CAD-CAM) techniques under uniform testing conditions is lacking. PURPOSE The purpose of this in vitro study was to evaluate the dimensional changes and reproducibility of maxillary and mandibular dentures by using CAD-CAM-milled and 3D-printed techniques. MATERIAL AND METHODS Maxillary and mandibular edentulous models with wax occlusal rims were scanned, and dentures were designed by using a CAD software program and fabricated by using 2 techniques and materials: CAD-CAM-milled (CCM) and 3D-printed (3DP). The 3DP fabrications included 4 subgroups: dentures printed with a 90-degree build angle with UV light polymerization on the reference model (3DP 90M), dentures printed with a 90-degree build angle and light polymerization without the reference model (3DP 90), dentures printed with a 45-degree build angle with light polymerization on the reference model (3DP 45M), and dentures printed with a 45-degree build angle and light polymerization without the reference model (3DP 45). The preprocessing and postprocessing scan files of each denture produced by CCM and 3DP were superimposed by using a surface matching software program. Ten points each on maxillary and mandibular dentures were measured for deviations after processing. Additionally, for each denture, the widths were measured between the canines and molars, the anteroposterior plane from cusp tips between the canines and molars, and the vertical plane from the cusp tip of the canines to the marginal gingiva. They were then compared with those in the denture design CAD cast. The Kruskal-Wallis analysis of variance test was used for statistical analyses (α=.05). RESULTS According to digital superimposition, CCM had the smallest values of deviation with no statistical difference (P>.05), indicating more uniform results from measurement points in both maxillary and mandibular dentures, followed by 3DP 90M, 3DP 90, 3DP 45M, and 3DP 45. Regarding the width measurements, CCM had the smallest values of deviation (P<.05). In 3DP, smaller deviation values were observed at the vertical plane from the tip of the canine to the marginal gingiva, and larger values were observed in the intermolar width (P<.05). CONCLUSIONS CCM exhibited smaller dimensional changes and better reproducibility among the tested techniques. In 3DP, the build angle and methods of light postprocessing influenced the dimensional stability. The 90-degree build angle with additional light polymerization on the cast improved the dimensional deviations.
BACKGROUND/PURPOSE A synthetic bone morphogenetic protein (BMP)-2-derived peptide has been discov... more BACKGROUND/PURPOSE A synthetic bone morphogenetic protein (BMP)-2-derived peptide has been discovered to promote bone regeneration. The present study investigated the potential of the BMP-2 peptide combined with hydroxyapatite (HAp)/β-tricalcium phosphate (TCP)/collagen (Col) composite in repairing a peri-implant critical size defect. METHODS Twenty-four saddle-type alveolar defects (10 mm mesiodistally and 4 mm apicocoronally) were surgically prepared in edentulous ridges in four male beagle dogs. Following implant placement, the defects with vertically exposed implant fixtures received (a) HAp/TCP/Col composite, (b) HAp/TCP/Col + 4 mg/mL BMP-2 peptide, (c) HAp/TCP/Col + 20 mg/mL BMP-2 peptide, or (d) HAp/TCP/Col + 0.2 mg/mL recombinant human BMP-2 (rhBMP-2). Bone regeneration and mineralization were assessed using radiography, micro-computed tomography (micro-CT), fluorescence labeling, and histologic analyses after healing for 4 or 8 weeks. Implant stability was measured using resonance frequency analysis. RESULTS The 20 mg/mL BMP-2 peptide groups demonstrated a distinguishable advantage in bone regeneration potential over the control groups, as observed on radiographic imaging and histologic examination, although no significant difference was found in implant stability and histomorphometric analysis of mineralization levels. However, the performance of the 20 mg/mL BMP-2 peptide groups were inferior to that of the 0.2 mg/mL rhBMP-2 groups. CONCLUSION The BMP-2 peptide may accelerate peri-implant bone regeneration. The BMP-2 peptide at 20 mg/mL still cannot complete bone repair of peri-implant critical size defect. The BMP-2 peptide at 20 mg/mL has similar osteoinductive performance to the rhBMP-2 at 0.02 mg/mL.
BACKGROUND: The role of lipopolysaccharide (LPS) in periapical lesion-induced bone resorption was... more BACKGROUND: The role of lipopolysaccharide (LPS) in periapical lesion-induced bone resorption was investigated. Polymyxin B (PMB), a speci®c inhibitor of LPS, was evaluated to treat the apical lesion. METHODS: Lipopolysaccharide isolated from two common endodontic pathogens, Fusobacterium nucleatum and Porphyromonas endodontalis, stimulated mouse macrophage (J774) to release interleukin-1a (IL-1a) and tumor necrosis factor-a (TNF-a) in a time-dependent manner. RESULTS: Combination of LPS further enhanced the stimulation. PMB inhibited these effects signi®cantly. LPS also stimulated matrix metalloproteinase-1 (MMP-1) gene expression in J774, whereas anti-IL-1a and anti-TNF-a antibodies, as well as PMB, diminished this effect. A disease model of periapical lesion was established in Wistar rat. Administration of PMB reduced the extent of lesion-associated bone resorption by 76% to approximately 80%, and simultaneously reduced the numbers of MMP-1-producing macrophages. CONCLUSIONS: It is suggested that LPS released from the infected root canal triggers the synthesis of IL-1a and TNF-a from macrophages. These pro-in¯ammatory cytokines up-regulate the production of MMP-1 by macrophages to promote periapical bone resorption.
Aim To study prostaglandin F 2a (PGF 2a) receptor expression and downstream signalling in culture... more Aim To study prostaglandin F 2a (PGF 2a) receptor expression and downstream signalling in cultured human dental pulp cells and the effect of PGF 2a on the alkaline phosphatase (ALP) activity of dental pulp cells. Methodology Human dental pulp cells were cultured and exposed to PGF 2a. The expression of PGF 2a (FP) receptors was analysed by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. The activation of extracellular regulated kinase (ERK) and cAMP responsive element binding protein/activating transcription factor-1 (CREB/ATF-1) signalling was determined by Western blotting. The expression of ALP in pulp cells after exposure to PGF 2a was evaluated by ALP staining and PCR. Results Dental pulp cells expressed FP receptor mRNA and protein. Exposure to PGF 2a revealed little cytotoxicity to pulp cells. PGF 2a induced both ERK and CREB/ATF-1 phosphorylation in pulp cells. Exposure to PGF 2a (>1 lmol L)1) further decreased the ALP activity and mRNA expression. However, U0126 (an inhibitor of MEK1) showed little preventive effect on the decline of ALP activity in dental pulp cells by PGF 2a. Conclusion PGF 2a may potentially activate FP receptors leading to ERK/CREB-ATF-1 activation during its production in inflamed dental pulp. PGF 2a attenuated the ALP activity of pulp cells possibly via pathways not solely by MEK/ERK activation. PGF 2a is a contributing factor of pulpal inflammation by regulating the activities of pulp cells.
After operative restoration, some monomers released from dentin bonding agents or composite resin... more After operative restoration, some monomers released from dentin bonding agents or composite resin may induce tissue inflammation and affect the vitality of dental pulp. Whether BisGMA, a major monomer of composite resin, may induce prostaglandin release and cytotoxicity to pulp cells and their mechanisms awaits investigation. We found that BisGMA induced cytotoxicity to human dental pulp cells at concentrations higher than 0.075 mM as analyzed by 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. BisGMA (0.1 mM) also stimulated ERK phosphorylation, PGE 2 production, COX-2 mRNA and protein expression as well as ROS production (as indicated by an increase in cellular DCF fluorescence) in dental pulp cells. Catalase (500 and 1000 U/ml) and U0126 (10 and 20 mM, a MEK inhibitor) effectively prevented the BisGMA-induced ERK activation, PGE 2 production and COX-2 expression. Moreover, catalase can protect the pulp cells from BisGMA cytotoxicity, whereas aspirin and U0126 lacked of this protective activity. These results suggest that BisGMA released from composite resin may potentially affect the vitality of dental pulp and induce pulpal inflammation via stimulation of ROS production, MEK/ERK1/2 activation and subsequent COX-2 gene expression and PGE 2 production. Cytotoxicity of BisGMA to dental pulp cells is related to ROS production, but not directly mediated by MEK activation and PGE 2 production.
This study aimed to elucidate the modulation by nitric oxide (NO) of the apoptosis of macrophages... more This study aimed to elucidate the modulation by nitric oxide (NO) of the apoptosis of macrophages and osteoblasts, the essential cellular components in the development of periapical lesions. Lipopolysaccharide (LPS) induced prominent nitrite synthesis in J774 mouse macrophage cell lines. Exposure to LPS induced obvious apoptosis in J774 cells, whereas transient transfection with murine inducible nitric oxide synthase (iNOS), small interfering RNA (siRNA) diminished this effect. Tumor necrosis factor‐α (TNF‐α) and S‐nitroso‐N‐acetyl‐DL‐penicillamine (SNAP) (a NO donor) triggered apoptosis in UMR‐106 rat osteoblastic cell lines and a synergistic effect was noted when TNF‐α and SNAP were added to the medium together. Administration of siRNAs for c‐Fos and c‐Jun: components of activator protein‐1 (AP‐1) and transforming growth factor‐β1 attenuated the combined effect markedly. Terminal deoxynucleotidyl transferase‐mediated nick end‐labeling (TUNEL) stain in a rat model of induced periapical lesion showed positive apoptotic signals in macrophages and osteoblasts. Administration of NG‐monomethyl‐l‐arginine markedly diminished the extent of bone loss and the amounts of apoptotic macrophages and osteoblasts. In conclusion, NO mediates LPS‐stimulated apoptosis of macrophages. It also induces osteoblast apoptosis and augments the pro‐apoptotic effect of cytokines. Inhibition of NO synthesis in vivo attenuates apoptosis and the size of periapical lesions. Taken together, these results suggest that NO may promote the progression of periapical lesion by inducing the apoptosis of macrophages and osteoblasts.
1. Intracortical microstimulation (ICMS) and surface stimulation studies of primate face motor co... more 1. Intracortical microstimulation (ICMS) and surface stimulation studies of primate face motor cortex have shown an extensive representation within face motor cortex devoted to movements of the tongue and face; only a very small representation for jaw-closing movements has ever been demonstrated. These data suggest that face motor cortex plays a critical role in the generation of tongue and facial movements but is less important in the generation of jaw-closing movements. Our aim was to determine whether disruption of primate face motor cortical function would indeed interfere with the generation of tongue movements but would not interfere with the generation of jaw-closing movements. 2. The face motor cortex was reversibly inactivated with the use of cooling in two monkeys that were trained to perform both a tongue-protrusion task and a biting task. Recording of single neuronal activity in the cortex beneath the thermode confirmed the reversible inactivation of the cortex. Each task involved a series of trials in which the monkey was required to produce a preset force level for a 0.5-s force holding period; the monkey received a fruit-juice reward if it successfully completed a task trial. Cooling of the ICMS-defined face motor cortex was achieved bilaterally or, in one experiment, unilaterally by circulating coolant through thermodes placed either on intact dura overlying face motor cortex in both monkeys or directly on the exposed pia in one of the monkeys;thermode temperature was lowered to 3-5 degrees C during cooling. Electromyographic (EMG) recordings were also made from masseter, genioglossus, and digastric muscles. 3. During bilateral cooling of the thermodes on the dura overlying the face motor cortex, there was a significant reduction in the success rates for the performance of the tongue-protrusion task in comparison with control series of trials (i.e., precool and postcool) in which the thermodes were kept at 37 degrees C. Quantitative analyses of force and EMG activity showed that the principal deficit was an inability of each monkey to exert sufficient force with its tongue for a sufficient length of time onto the tongue-protrusion task transducer; this deficit was paralleled by a reduction in the level of genioglossus and digastric EMG activity. At 4 min after commencement of rewarming, task performance had returned to control, precool levels.(ABSTRACT TRUNCATED AT 400 WORDS)
AimTo investigate the effects of butyric acid (BA), a metabolic product generated by pulp and roo... more AimTo investigate the effects of butyric acid (BA), a metabolic product generated by pulp and root canal pathogens, on the viability and intercellular adhesion molecule‐1 (ICAM‐1) production of endothelial cells, which are crucial to angiogenesis and pulpal/periapical wound healing.MethodologyEndothelial cells were exposed to butyrate with/without inhibitors. Cell viability, apoptosis and reactive oxygen species (ROS) were evaluated using an MTT assay, PI/annexin V and DCF fluorescence flow cytometry respectively. RNA and protein expression was determined using a polymerase chain reaction assay and Western blotting or immunofluorescent staining. Soluble ICAM‐1 (sICAM‐1) was measured using an enzyme‐linked immunosorbent assay. The quantitative results were expressed as mean ± standard error (SE) of the mean. The data were analysed using a paired Student's t‐test where necessary. A p‐value ≤0.05 was considered to indicate a statistically significant difference between groups.Resul...
1. Studies using ablation, intracortical microstimulation (ICMS) and surface stimulation, and sin... more 1. Studies using ablation, intracortical microstimulation (ICMS) and surface stimulation, and single-neuron recordings have suggested that the primate primary somatosensory cortex (SI) may play an important role in movement control. Our aim was to determine whether bilateral inactivation of face SI would indeed interfere with the control of tongue or jaw-closing movements. 2. Effects of reversible inactivation by cooling of face SI was investigated in two monkeys trained to perform both a tongue-protrusion task and a biting task. The cooling experiments were carried out after the orofacial representation within SI was identified by systematically defining the mechanoreceptive field of single neurons recorded in face SI. The deficits in the tongue or jaw-closing movement were evaluated by the success rates for the monkeys' performance of both tasks and by the force and electromyographic (EMG) activity recorded from the masseter, genioglossus, and digastric muscles associated with...
This study sought to characterise the electromyographic (EMG) activity patterns of orofacialmuscl... more This study sought to characterise the electromyographic (EMG) activity patterns of orofacialmuscles during trained tongue-protrusion and biting tasks in two awake monkeys (Macacafascicularis). Chronic or acute EMG electrodes were placed in the anterior digastric (DIG), genioglossus (GG), masseter (MASS), platysma (PLAT), zygomaticus major (ZYGO), orbicularis oris superior (OOS), and orbicularis oris inferior (001) muscles and their EMG activity as well as the force signals of the tongue-protrusion and biting tasks were recorded. A total of 327 tongue-protrusion task trials and a total of 210 biting-task trials were successfully completed in several recording sessions and the EMG patterns were generally consistent between the different sessions. For the tongue task, the mean onset time of increase in GG activity significantly (p < 0.0001) led the mean onset time of increase in the force. The DIG, GG, and 001 (and also the 00s in one of the monkeys) showed a significant (p < 0.0001) increase in mean EMG amplitude during the holding phase, but the GG in both monkeys had the highest mean EMG amplitude ratio (MAR), i.e. the mean EMG amplitude during the holding or dynamic phase divided by the mean EMG amplitude during the pre-trial period. A similar EMG pattern was documented for different directions of the tongue-protrusion task (right, symmetrical, and left) and changes in the levels of EMG activities occurred in GG and 001 as the direction of the tongue-protrusion task changed from left to right, The task at different forces was associated with no apparent change in MAR for the holding phase for each muscle recorded. However, during the dynamic phase, only the GG showed a significant increase in EMG activity as the forces were increased. For the biting task, the mean onset times of the MASS activity and force were not significantly different. The MASS and ZYGO muscles (and the PLAT in one of the monkeys) showed a significant increase in mean EMG amplitude during the holding phase compared with the pre-trial period, and the MASS showed the highest MAR. It was also the only muscle showing a significant increase in the EMG activity when the bite-force level was increased. These findings reveal that certain orofacial muscles are selectively recruited during the two different orofacial tasks. Based on the EMG activity pattern during different directions or force levels of the task, the data suggest that, of the muscles recorded, the principal agonist for the tongue task is the GG and that for the biting task is the MASS; the other muscles that may be active appear to serve as accessories to the task.
Rhythmical jaw movements can be evoked by intracortical microstimulation within four physiologica... more Rhythmical jaw movements can be evoked by intracortical microstimulation within four physiologically de®ned regions, one of which is the primary face somatosensory cortex (face SI). It has been proposed that these regions may be involved in the selection and/or control of masticatory patterns generated at the brainstem level. The aim here was to determine if mastication is aected by reversible, cooling-induced inactivation of the face SI. Two cranial chambers were chronically implanted in two monkeys (Macaca fascicularis) to allow access bilaterally to the face SI. A thermode was placed on the dura or pia overlying each SI that had been shown with micro-electrode recordings to receive intraoral inputs. A hot or cold alcohol±water solution was pumped through the thermodes while the monkey chewed a small piece of apple or a sultana during precool (thermode temperature, 378C), cool (2± 48C), and postcool (378C) conditions. Electromyographic (EMG) activity was recorded intramuscularly from the masseter, genioglossus, and anterior digastric. Cooling of SI impaired rhythmical jaw and tongue movements and EMG activity associated with mastication in one monkey (H5), and modi®ed the pattern of EMG activity in the other (H6). The total masticatory time (i.e., time taken for chewing and manipulation of the bolus before swallowing) was increased. This was due principally to an increase in the oral transport time (i.e., time taken for manipulation of bolus after chewing and before swallowing: monkey H6, control, 2.7 sec; cool, 5.2 sec, p < 0.05); the bolus was manipulated by the tongue during this period before swallowing. Within the chewing time (i.e., time during which chewing occurred), cooling resulted in a signi®cant increase in anterior digastric muscle duration, a signi®cant delay in the onset of masseter EMG activity, and a signi®cant increase in the variance of genioglossus EMG duration. The data support the view that the face SI plays a part in modulating the central pattern generator for mastication.
1. We have demonstrated recently that reversible, cooling-induced inactivation of the face primar... more 1. We have demonstrated recently that reversible, cooling-induced inactivation of the face primary somatosensory cortex (SI) severely impairs the successful performance of a tongue-protrusion task but has relatively minor effects on the performance of a biting task. In an attempt to establish a neuronal correlate for these different behavioral relations, the present study was initiated to document the mechanoreceptive field properties of a population of face SI neurons and their activity during the tongue-protrusion and biting tasks. 2. Within SI, the representation of the face was found immediately lateral to that of the hand, and there was a clear somatotopic pattern of organization within face SI: the periorbital or nose region was located most medially in the face SI, then followed laterally in sequence the representation of the upper lip, lower lip, and intraoral area. A mechanoreceptive field (RF) was identified for 253 neurons, which included 162 “lip RF” neurons receiving me...
Monomers released from resin-containing products may cause various adverse effects. Urethane dime... more Monomers released from resin-containing products may cause various adverse effects. Urethane dimethacrylate (UDMA) is a principal resin monomer and also a major component released from various dental resin materials. Thus the toxic effects and mechanisms should be elucidated for improving of its safety use. Here we investigated the effects of UDMA on the growth, cell cycle progression, reactive oxygen species (ROS) production and glutathione (GSH) alteration in CHO-K1 cells, and the preventive effects by antioxidants (NAC and catalase) were also evaluated. UDMA elicited growth inhibition (>0.025 mM) of CHO-K1 cells in a clearly dose-dependent manner. Cell cycle perturbation and ROS overproduction were also observed. A 0.1 mM UDMA-induced S-phase cell cycle arrest and ROS accumulation. Cell apoptosis and necrosis became significant when UDMA concentration was 0.25 mM. GSH depletion occurred at cells treated with 0.25 mM UDMA, a highly cytotoxic concentration at which point myriad cells were under apoptosis or necrosis. Thus GSH depletion can be crucial for the death of CHO-K1 cells. Furthermore NAC (0.5e10 mM) and catalase (250e1000 U/ml) obviously attenuated the UDMAinduced toxicity by reducing ROS generation and cell cycle disturbance, and the effects were doserelated. These results suggest that UDMA toxicity is associated with ROS production, GSH depletion, cell cycle disturbance and cell apoptosis/necrosis.
STATEMENT OF PROBLEM Information on the dimensional changes in maxillary and mandibular dentures ... more STATEMENT OF PROBLEM Information on the dimensional changes in maxillary and mandibular dentures made by using computer-aided design and computer-aided manufacturing (CAD-CAM) techniques under uniform testing conditions is lacking. PURPOSE The purpose of this in vitro study was to evaluate the dimensional changes and reproducibility of maxillary and mandibular dentures by using CAD-CAM-milled and 3D-printed techniques. MATERIAL AND METHODS Maxillary and mandibular edentulous models with wax occlusal rims were scanned, and dentures were designed by using a CAD software program and fabricated by using 2 techniques and materials: CAD-CAM-milled (CCM) and 3D-printed (3DP). The 3DP fabrications included 4 subgroups: dentures printed with a 90-degree build angle with UV light polymerization on the reference model (3DP 90M), dentures printed with a 90-degree build angle and light polymerization without the reference model (3DP 90), dentures printed with a 45-degree build angle with light polymerization on the reference model (3DP 45M), and dentures printed with a 45-degree build angle and light polymerization without the reference model (3DP 45). The preprocessing and postprocessing scan files of each denture produced by CCM and 3DP were superimposed by using a surface matching software program. Ten points each on maxillary and mandibular dentures were measured for deviations after processing. Additionally, for each denture, the widths were measured between the canines and molars, the anteroposterior plane from cusp tips between the canines and molars, and the vertical plane from the cusp tip of the canines to the marginal gingiva. They were then compared with those in the denture design CAD cast. The Kruskal-Wallis analysis of variance test was used for statistical analyses (α=.05). RESULTS According to digital superimposition, CCM had the smallest values of deviation with no statistical difference (P>.05), indicating more uniform results from measurement points in both maxillary and mandibular dentures, followed by 3DP 90M, 3DP 90, 3DP 45M, and 3DP 45. Regarding the width measurements, CCM had the smallest values of deviation (P<.05). In 3DP, smaller deviation values were observed at the vertical plane from the tip of the canine to the marginal gingiva, and larger values were observed in the intermolar width (P<.05). CONCLUSIONS CCM exhibited smaller dimensional changes and better reproducibility among the tested techniques. In 3DP, the build angle and methods of light postprocessing influenced the dimensional stability. The 90-degree build angle with additional light polymerization on the cast improved the dimensional deviations.
BACKGROUND/PURPOSE A synthetic bone morphogenetic protein (BMP)-2-derived peptide has been discov... more BACKGROUND/PURPOSE A synthetic bone morphogenetic protein (BMP)-2-derived peptide has been discovered to promote bone regeneration. The present study investigated the potential of the BMP-2 peptide combined with hydroxyapatite (HAp)/β-tricalcium phosphate (TCP)/collagen (Col) composite in repairing a peri-implant critical size defect. METHODS Twenty-four saddle-type alveolar defects (10 mm mesiodistally and 4 mm apicocoronally) were surgically prepared in edentulous ridges in four male beagle dogs. Following implant placement, the defects with vertically exposed implant fixtures received (a) HAp/TCP/Col composite, (b) HAp/TCP/Col + 4 mg/mL BMP-2 peptide, (c) HAp/TCP/Col + 20 mg/mL BMP-2 peptide, or (d) HAp/TCP/Col + 0.2 mg/mL recombinant human BMP-2 (rhBMP-2). Bone regeneration and mineralization were assessed using radiography, micro-computed tomography (micro-CT), fluorescence labeling, and histologic analyses after healing for 4 or 8 weeks. Implant stability was measured using resonance frequency analysis. RESULTS The 20 mg/mL BMP-2 peptide groups demonstrated a distinguishable advantage in bone regeneration potential over the control groups, as observed on radiographic imaging and histologic examination, although no significant difference was found in implant stability and histomorphometric analysis of mineralization levels. However, the performance of the 20 mg/mL BMP-2 peptide groups were inferior to that of the 0.2 mg/mL rhBMP-2 groups. CONCLUSION The BMP-2 peptide may accelerate peri-implant bone regeneration. The BMP-2 peptide at 20 mg/mL still cannot complete bone repair of peri-implant critical size defect. The BMP-2 peptide at 20 mg/mL has similar osteoinductive performance to the rhBMP-2 at 0.02 mg/mL.
BACKGROUND: The role of lipopolysaccharide (LPS) in periapical lesion-induced bone resorption was... more BACKGROUND: The role of lipopolysaccharide (LPS) in periapical lesion-induced bone resorption was investigated. Polymyxin B (PMB), a speci®c inhibitor of LPS, was evaluated to treat the apical lesion. METHODS: Lipopolysaccharide isolated from two common endodontic pathogens, Fusobacterium nucleatum and Porphyromonas endodontalis, stimulated mouse macrophage (J774) to release interleukin-1a (IL-1a) and tumor necrosis factor-a (TNF-a) in a time-dependent manner. RESULTS: Combination of LPS further enhanced the stimulation. PMB inhibited these effects signi®cantly. LPS also stimulated matrix metalloproteinase-1 (MMP-1) gene expression in J774, whereas anti-IL-1a and anti-TNF-a antibodies, as well as PMB, diminished this effect. A disease model of periapical lesion was established in Wistar rat. Administration of PMB reduced the extent of lesion-associated bone resorption by 76% to approximately 80%, and simultaneously reduced the numbers of MMP-1-producing macrophages. CONCLUSIONS: It is suggested that LPS released from the infected root canal triggers the synthesis of IL-1a and TNF-a from macrophages. These pro-in¯ammatory cytokines up-regulate the production of MMP-1 by macrophages to promote periapical bone resorption.
Aim To study prostaglandin F 2a (PGF 2a) receptor expression and downstream signalling in culture... more Aim To study prostaglandin F 2a (PGF 2a) receptor expression and downstream signalling in cultured human dental pulp cells and the effect of PGF 2a on the alkaline phosphatase (ALP) activity of dental pulp cells. Methodology Human dental pulp cells were cultured and exposed to PGF 2a. The expression of PGF 2a (FP) receptors was analysed by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. The activation of extracellular regulated kinase (ERK) and cAMP responsive element binding protein/activating transcription factor-1 (CREB/ATF-1) signalling was determined by Western blotting. The expression of ALP in pulp cells after exposure to PGF 2a was evaluated by ALP staining and PCR. Results Dental pulp cells expressed FP receptor mRNA and protein. Exposure to PGF 2a revealed little cytotoxicity to pulp cells. PGF 2a induced both ERK and CREB/ATF-1 phosphorylation in pulp cells. Exposure to PGF 2a (>1 lmol L)1) further decreased the ALP activity and mRNA expression. However, U0126 (an inhibitor of MEK1) showed little preventive effect on the decline of ALP activity in dental pulp cells by PGF 2a. Conclusion PGF 2a may potentially activate FP receptors leading to ERK/CREB-ATF-1 activation during its production in inflamed dental pulp. PGF 2a attenuated the ALP activity of pulp cells possibly via pathways not solely by MEK/ERK activation. PGF 2a is a contributing factor of pulpal inflammation by regulating the activities of pulp cells.
After operative restoration, some monomers released from dentin bonding agents or composite resin... more After operative restoration, some monomers released from dentin bonding agents or composite resin may induce tissue inflammation and affect the vitality of dental pulp. Whether BisGMA, a major monomer of composite resin, may induce prostaglandin release and cytotoxicity to pulp cells and their mechanisms awaits investigation. We found that BisGMA induced cytotoxicity to human dental pulp cells at concentrations higher than 0.075 mM as analyzed by 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. BisGMA (0.1 mM) also stimulated ERK phosphorylation, PGE 2 production, COX-2 mRNA and protein expression as well as ROS production (as indicated by an increase in cellular DCF fluorescence) in dental pulp cells. Catalase (500 and 1000 U/ml) and U0126 (10 and 20 mM, a MEK inhibitor) effectively prevented the BisGMA-induced ERK activation, PGE 2 production and COX-2 expression. Moreover, catalase can protect the pulp cells from BisGMA cytotoxicity, whereas aspirin and U0126 lacked of this protective activity. These results suggest that BisGMA released from composite resin may potentially affect the vitality of dental pulp and induce pulpal inflammation via stimulation of ROS production, MEK/ERK1/2 activation and subsequent COX-2 gene expression and PGE 2 production. Cytotoxicity of BisGMA to dental pulp cells is related to ROS production, but not directly mediated by MEK activation and PGE 2 production.
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