Surgical repair of external cervical resorption - Prognosis and prognostic factors

Background/purpose

External cervical resorption (ECR) is an aggressive form of root resorption, which etiology is unclear and its prognosis remains unpredictable. The purpose of this study was to investigate the prognosis and potential prognostic factors of ECR-affected teeth after surgical intervention for external repair with/without root canal treatment.

Materials and methods

Treated ECR cases from 2009 to 2019 were collected retrospectively. The survival of the teeth and the status of root resorption were assessed during the follow-up period. Potential prognostic factors were analyzed with log-rank test and Kaplan-Meier statistics.

Results

A total of 42 treated ECR-affected teeth were enrolled. The two-year survival rate was 71.20% [54.16%, 93.59%]. Persistent root resorption was the main complication after treatment. Patients with multiple ECR-affected teeth had greater recurrent potential than patients with solitary ECR-affected teeth. Prolonged calcium hydroxide dressing may contribute to a more favorable clinical outcome. Gender, age, tooth position and the need for root canal treatment did not show statistically significant effect on the prognosis.

Conclusion

The current surgical method was able to arrest ECR in most cases. However, the case type (the number of ECR-affected teeth per patient) could highly affect the prognosis of the teeth. Clinicians should consider long-term calcium hydroxide dressing in case of pulp involvement to achieve better results.

The effect of immersion in water on deformation with the variety of denture base materials and manufacturing techniques

PURPOSE

To evaluate the effect of immersion in water on deformation of maxillary denture bases created by computer-aided design and computer-aided manufactured (CAD-CAM), and heat-polymerized resin fabrication techniques under loading condition.

MATERIALS AND METHODS

Two-millimeter thick denture bases were fabricated using four techniques: CAD-CAM milling (CCM) (Polywax; Yamahachi), 3D printing (3DP) (BV0005; NextDent), compression molding (CM) (Luciton 199), and injection molding (IM) (Ivobase) (n = 5 per group). Three static 49 N loads were applied perpendicular to each denture base, and the mean strain value (MSV) was recorded by strain gauges attached to the denture surface. The denture bases were stored at 37°C in distilled water for 14 and 28 days, and the MSVs under the same static load were recorded.

RESULTS

The highest MSVs were observed at the posterior palatal seal, tuberosity, and labial notches of the dentures. The lowest MSVs were recorded for the CCM group, then the CM and IM. The highest MSVs were recorded for the 3DP group. No significant differences in regional MSVs (P > .05) were observed among the CCM, CM, and IM after 14 and 28 days in water. Large deviations in MSVs were recorded for the 3DP group across the measurement sites after water exposure (P < .05).

CONCLUSIONS

CCM had the lowest denture deformation under static loading. After immersion in water, the deformation changes under static loading were stable for CCM, CM, and IM. However, variations among the materials used in 3DP group influenced the mechanical performance and presented larger deformations. Int J Prosthodont. 10.11607/ijp.8332.

The multi-factor analysis of computer-based test scores in objective structured clinical examination of clerkship in school of dentistry, National Taiwan University

Background/purpose

The objective structured clinical examination (OSCE) is a test designed to test technical, clinical, and practical competency in medicine teaching. This study tried to evaluate the influencing factors of the computer-based tests (CBT) results for dental students.

Materials and methods

The 32 5th-year dental students of the dental school of National Taiwan University (NTU) joined preclinical CBT. The contents of CBT included clinical knowledge and practical skills of nine dental specialties. Twenty single-choice questions were played with the PowerPoint 2016 on a desktop, and the playing time for each question was 30 s. Several factors including the gender, age, and dental student admission ways (with or without the skill tests) were evaluated. Also, the comparison between the clerk's grade and CBT scores of nine dental specialties was performed. The students also filled the feedback questionnaire about the examination questions and suggestions for the CBT.

Results

There were no significant differences in the mean CBT scores between male and female dental students, between two groups of dental students with or without the skill tests in the admission process, and among three different age groups of dental students. The clerk's scores were not directly related to the CBT scores.

Conclusion

The CBT has been well-intentioned in dental education since 2022 in Taiwan. The CBT results revealed that the conjunction of knowledge from the textbook and clinical observation should be enhanced. The guideline should be established to integrate CBT into preclinical education and promote the performance of clinical work of dental students.

[The analysis of related factors on the unilateral aldosterone secretion in the functional diagnosis of primary aldosteronism and establishment of a predictive model]

Objective: To explore related factors associated with unilateral aldosterone secretion of patients with primary aldosteronism (PA) and construct a predictive model. Methods: The clinical data of patients who were diagnosed as PA in West China Hospital from April 2016 to September 2020 was analyzed retrospectively. According to the results of the adrenal enhancement CT, patients were divided into 3 groups, namely non-nodular group with no bilateral adrenal glands lesions, only with unilateral adrenal hyperplasia or bilateral adrenal hyperplasia, unilateral nodule group with unilateral adrenal nodules and the contralateral adrenal glands with hyperplasia or not, and bilateral nodules group with nodules in both adrenal glands. Regarding the related factors of dominant side of aldosterone secretion, univariate analysis and binary logistic regression were used. Receiver operating characteristic curve and nomogram were used to evaluate the diagnostic performance of regression models. Results: A total of 237 patients with PA were included, of which, 118 males and 119 females, the median age was 39 years, and the body mass index (BMI) was (25.2±3.5) kg/m². There were 157 (66.2%) of 237 patients with typical imaging findings. There were 32 cases in no-nodular group, 183 cases in unilateral nodule group, and 22 cases in bilateral nodules group. Multivariate analysis showed that age (OR=0.876, P<0.001), blood potassium concentration (OR=0.430, P=0.004), and typical imaging findings (OR=2.202, P=0.035) were associated with unilateral aldosterone secretion. As for unilateral nodule group, multivariate analysis showed that age (OR=0.900, P<0.001), plasma aldosteronism concentration (PAC) (OR=1.050, P=0.018), and typical imaging findings (OR=2.637, P=0.025) were associated with unilateral aldosterone secretion. The agreement rate between the dominant side of the adrenal CT and AVS was only 50.2%. Multivariate analysis showed that age (OR=0.954, P=0.001), BMI (OR=0.893, P=0.024) and PAC (OR=1.043, P=0.011) were independently associated with concordance between AVS and CT. The cut-off value of the ROC curve was 0.43; the model sensitivity was 56.3%; the specificity was 86.7% and the area under the ROC curve was 0.742. Conclusions: Age is an important predictor in the diagnosis of PA subtypes. It is recommended to refer to subgroup based on imaging results for clinical decision. For patients with no obvious lesions or bilateral lesions on CT, AVS should be performed as far as possible to confirm the subtypes in diagnosis of PA.

Effect of butyrate, a bacterial by-product, on the viability and ICAM-1 expression/production of human vascular endothelial cells: Role in infectious pulpal/periapical diseases

AIM

To 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.

METHODOLOGY

Endothelial 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.

RESULTS

Butyrate (>4 mM) inhibited cell viability and induced cellular apoptosis and necrosis. It inhibited cyclin B1 but stimulated p21 and p27 expression. Butyrate stimulated ROS production and hemeoxygenase-1 (HO-1) expression as well as activated the Ac-H3, p-ATM, p-ATR, p-Chk1, p-Chk2, p-p38 and p-Akt expression of endothelial cells. Butyrate stimulated ICAM-1 mRNA/protein expression and significant sICAM-1 production (p < .05). Superoxide dismutase, 5z-7oxozeaenol, SB203580 and compound C (p <  .05), but not ZnPP, CGK733, AZD7762 or LY294002, attenuated butyrate cytotoxicity to endothelial cells. Notably, little effect on butyrate-stimulated sICAM-1 secretion was found. Valproic acid, phenylbutyrate and trichostatin (three histone deacetylase inhibitors) significantly induced sICAM-1 production (p < .05).

CONCLUSION

Butyric acid inhibited proliferation, induced apoptosis, stimulated ROS and HO-1 production and increased ICAM-1 mRNA expression and protein synthesis in endothelial cells. Cell viability affected by BA was diminished by some inhibitors; however, the increased sICAM-1 secretion by BA was not affected by any of the tested inhibitors. These results facilitate understanding of the pathogenesis, prevention and treatment of pulpal/periapical diseases.

Effects of low-dose rhBMP-2 on peri-implant ridge augmentation in a canine model

AIMS

The aim of this study was to investigate the potential of low-dose rhBMP-2 combined with Hydroxyapatite (HAp)/β-tricalcium phosphate (TCP)/ Collagen (Col) composite in repairing the peri-implant critical size defect and to determine the optimal rhBMP-2 concentration.

MATERIALS AND METHODS

Fifty saddle-type alveolar defects (10 mm mesiodistally and 4 mm apicocoronally) were surgically prepared on edentulous ridges in ten beagle dogs. Following implant placement, the defects with vertically exposed implant fixtures either received (a) no graft, (b) HAp/TCP/Col composite, (c) HAp/TCP/Col +0.02 mg/ml rhBMP-2, (d) HAp/TCP/Col +0.08 mg/ml rhBMP-2 or (e) HAp/TCP/Col +0.2 mg/ml rhBMP-2. After healing for 4 or 8 weeks, bone regeneration and mineralization were assessed through radiography, micro-CT, fluorescence labelling and histologic analyses. Implant stability was measured through resonance frequency analysis.

RESULTS

It was evident HAp/TCP/Col with 0.2 mg/ml rhBMP-2 manifested strong osteogenic potential in this large animal model, as significantly more and faster new bone formation with better implant stability was identified compared to the HAp/TCP/Col-alone control group (adjusted p < .05).

CONCLUSIONS

Our results highlight the constructs of HAp/TCP/Col +0.2 mg/ml rhBMP-2 without barrier membranes as a promising tool for peri-implant ridge augmentation.

IL-1β-induced ICAM-1 and IL-8 expression/secretion of dental pulp cells is differentially regulated by IRAK and p38

BACKGROUND/PURPOSE

Interleukin 1 beta (IL-1β) is a pro-inflammatory cytokine involved in the acute and chronic inflammatory processes of dental pulp. Intercellular adhesion molecule-1 (ICAM-1) and IL-8 are two major inflammatory mediators. However, the role of interleukin-1 receptor-associated kinases (IRAKs) signaling pathways in responsible for the inflammatory effects of IL-1β on dental pulp cells is not clear.

METHODS

Cultured human dental pulp cells were exposed to IL-1β with/without pretreatment and co-incubation with IRAK1/4 inhibitor or SB203580 (p38 inhibitor). IRAK-1 phosphorylation was evaluated by immunno fluorescent staining. The protein expression of ICAM-1 and IL-8 were tested by western blotting. The secretion of soluble ICAM-1 (sICAM-1) and IL-8 was measured by enzyme-linked immunosorbant assay (ELISA).

RESULTS

IL-1β stimulated IRAK-1 phosphorylation of pulp cells within 120 min of exposure. IRAK1/4 inhibitor attenuated the IL-1β-induced ICAM-1, but not IL-8 protein expression. IRAK1/4 inhibitor also prevented the IL-1β-induced sICAM-1, but not IL-8 secretion. SB203580 showed little effect on IL-1β-induced sICAM-1 secretion, but effectively inhibited its induction of IL-8 secretion in pulp cells.

CONCLUSION

The Results reveal the important role of IL-1β in pulpal inflammatory responses via stimulation of IL-8 and ICAM-1 expression and secretion. Moreover, IL-1β-induced effects on IL-8 and ICAM-1 are differentially regulated by IRAK1/4 and p38 signaling in dental pulp cells. Blocking of IRAKs and p38 signaling may have potential to control inflammation of dental pulp in the future.

Lysophosphatidylcholine induces cytotoxicity/apoptosis and IL-8 production of human endothelial cells: Related mechanisms

Increased levels of oxidized low-density lipoprotein oxLDL) are shown to elevate the risk of cardiovascular diseases such as atherosclerosis, thrombosis, stroke, and myocardial infarction. This is possibly due to the toxic effects of oxLDLs on vascular cells. Various oxLDLs including lysophosphatidylcholine (LPC) and 7-ketocholesterol injure vascular endothelial cells and stimulate inflammatory reaction. However the toxicity of LPC on endothelial cells is not clear. In this study, human endothelial cells were exposed to LPC. Cytotoxicity was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Propidium iodide (PI) staining or PI/Annexin V dual staining flow cytometry were used to determine cell cycle progression and apoptosis. Reactive oxygen species (ROS) level was analyzed by DCFH-DA labeling flow cytometry. RNA and protein expression of endothelial cells was studied by reverse transcriptase-polymerase chain reaction and western blotting. IL-8 secretion was measured by enzyme-linked immunosorbant assay. LPC showed cytotoxicity to endothelial cells (>50 µg/ml). LPC induced cell cycle arrest and apoptosis with concomitant inhibition of cdc2 and cyclin B1 expression. LPC stimulated intracellular ROS production and ATM/Chk2, ATR/Chk1 and Akt activation. IL-8 expression and secretion in endothelial cells were induced by LPC. LPC-induced apoptosis, and IL-8 expression/secretion was attenuated by LY294002, a PI3K/Akt inhibitor. These results reveal that LPC is involved in the pathogenesis of atherosclerosis and vascular diseases by stimulation of inflammation and injury to endothelial cells. These events are related to ROS, ATM/Chk2, ATR/Chk2 and PI3K/Akt signaling. Understanding the toxic mechanisms of LPC is useful for future prevention and treatment atherosclerosis.

Influence of Implant Number and Location on Strain Around an Implant Combined with Force Transferred to the Palate in Maxillary Overdentures

This study evaluated the effect of implant number and location on strain around the implant and force transferred to the palate in maxillary implant overdentures (IODs), including two locators attached bilaterally in the canine region (IOD 2), four locators attached bilaterally in the canine and premolar regions (IOD 4CP), four locators attached bilaterally in the canine and molar regions (IOD 4CM), and six locators attached bilaterally in the canine, premolar, and molar regions (IOD 6). As the implant number increased, strain around the implant regions increased, whereas force transferred to the palate decreased under loading. However, the differences were small between IOD 4CM and IOD 6, suggesting identical biomechanical effectiveness.

Increased Expression of Glutaminase in Osteoblasts Promotes Macrophage Recruitment in Periapical Lesions

INTRODUCTION

Recently, we have shown that tissue hypoxia stimulates the progression of periapical lesions by up-regulating glycolysis-dependent apoptosis of osteoblasts. Other facets of hypoxia-induced metabolic reprogramming in disease pathogenesis require further investigation. In this study, we examined the connection between hypoxia-augmented glutamine catabolism in osteoblasts and the development of periapical lesions.

METHODS

Primary human osteoblasts were cultured under hypoxia. The expression of glutaminase 1 (GLS1) was examined using Western blot analysis. The production of glutamate was measured by colorimetric assay. Knockdown of GLS1 was performed with small interfering RNA technology. C-C motif chemokine ligand 2 (CCL2) secretion and chemotaxis of J774 macrophages were examined by enzyme-linked immunosorbent assay and transwell migration assay, respectively. In a rat model of induced periapical lesions, the relations between disease progression and osteoblastic expression of GLS1 or macrophage recruitment were studied.

RESULTS

Hypoxia enhanced GLS1 expression and subsequent glutamate production in osteoblasts. Glutamate induced chemoattraction of macrophages by osteoblasts through up-regulation of CCL2 synthesis. Hypoxia promoted CCL2 secretion and macrophage recruitment through augmentation of glutaminolysis. Knockdown of GLS1 abolished hypoxia-induced effects. In rat periapical lesions, progressive bone resorption was significantly related to elevated GLS1 expression in osteoblasts and increased macrophage recruitment.

CONCLUSIONS

In addition to the rise in glycolytic activity, the progression of periapical lesions is also associated with enhanced glutamine catabolism in osteoblasts. GLS1 may be a potential therapeutic target in the management of periapical lesions.

Prostaglandin E2 Stimulates EP2, Adenylate Cyclase, Phospholipase C, and Intracellular Calcium Release to Mediate Cyclic Adenosine Monophosphate Production in Dental Pulp Cells

INTRODUCTION

Prostaglandin E2 (PGE2) plays a crucial role in pulpal inflammation and repair. However, its induction of signal transduction pathways is not clear but is crucial for future control of pulpal inflammation.

METHODS

Primary dental pulp cells were exposed to PGE2 and 19R-OH PGE2 (EP2 agonist) or sulprostone (EP1/EP3 agonist) for 5 to 40 minutes. Cellular cyclic adenosine monophosphate (cAMP) levels were measured using the enzyme-linked immunosorbent assay. In some experiments, cells were pretreated with SQ22536 (adenylate cyclase inhibitor), H89 (protein kinase A inhibitor), dorsomorphin (adenosine monophosphate-activated protein kinase inhibitor), U73122 (phospholipase C inhibitor), thapsigargin (inhibitor of intracellular calcium release), W7 (calmodulin antagonist), verapamil (L-type calcium channel blocker), and EGTA (extracellular calcium chelator) for 20 minutes before the addition of PGE2.

RESULTS

PGE2 and 19R-OH PGE2 (EP2 agonist) stimulated cAMP production, whereas sulprostone (EP1/EP3 agonist) shows little effect. PGE2-induced cAMP production was attenuated by SQ22536 and U73122 but not H89 and dorsomorphin. Intriguingly, thapsigargin and W7 prevented PGE2-induced cAMP production, but verapamil and EGTA showed little effect.

CONCLUSIONS

These results indicate that PGE2-induced cAMP production is associated with EP2 receptor and adenylate cyclase activation. These events are mediated by phospholipase C, intracellular calcium release, and calcium-calmodulin signaling. These results are helpful for understanding the role of PGE2 in pulpal inflammation and repair and possible future drug intervention.

The effect of implant design and bone quality on insertion torque, resonance frequency analysis, and insertion energy during implant placement in low or low- to medium-density bone

PURPOSE

This study investigated the effect of implant design and bone quality on insertion torque (IT), implant stability quotient (ISQ), and insertion energy (IE) by monitoring the continuous change in IT and ISQ while implants were inserted in artificial bone blocks that simulate bone of poor or poor-to-medium quality.

MATERIALS AND METHODS

Polyurethane foam blocks (Sawbones) of 0.16 g/cm³ and 0.32 g/cm³ were respectively used to simulate low density and low- to medium-density cancellous bone. In addition, some test blocks were laminated with a 1-mm 0.80 g/cm³ polyurethane layer to simulate cancellous bone with a thin cortical layer. Four different implants (Nobel Biocare Mk III-3.75, Mk III-4.0, Mk IV-4.0, and NobelActive-4.3) were placed into the different test blocks in accordance with the manufacturer's instructions. The IT and ISQ were recorded at every 0.5-mm of inserted length during implant insertion, and IE was calculated from the torque curve. The peak IT (PIT), final IT (FIT), IE, and final ISQ values were statistically analyzed.

RESULTS

All implants showed increasing ISQ values when the implant was inserted more deeply. In contrast to the ISQ, implants with different designs showed dissimilar IT curve patterns during the insertion. All implants showed a significant increase in the PIT, FIT, IE, and ISQ when the test-block density increased or when the 1-mm laminated layer was present. Tapered implants showed FIT or PIT values of more than 40 Ncm for all of the laminated test blocks and for the nonlaminated test blocks of low to medium density. Parallel-wall implants did not exhibit PIT or FIT values of more than 40 Ncm for all of the test blocks. NobelActive-4.3 showed a significantly higher FIT, but a significantly lower IE, than Mk IV-4.0.

CONCLUSIONS

While the existence of cortical bone or implant designs significantly affects the dynamic IT profiles during implant insertion, it does not affect the ISQ to a similar extent. Certain implant designs are more suitable than others if high IT is required in bone of poor quality. The manner in which IT, IE, and ISQ represent the implant primary stability requires further study.

Using acrylic resin tooth veneers in patients with an abnormal jaw relationship: a case report

This case report describes and evaluates a method of arranging artificial teeth in patients with an abnormal jaw relationship in which a wider maxillary arch opposes a narrower mandibular arch. First, the fossa of mandibular posterior teeth was positioned on the crest of the mandibular edentulous ridge. The maxillary posterior teeth were then placed palatally to maximize occlusal contacts with the opposing mandibular teeth. Finally, acrylic resin tooth veneers were attached on the buccal surface of posterior maxillary teeth to improve the arch discrepancy. This method addresses functional considerations with the inner aspect of teeth and esthetic considerations with acrylic resin tooth veneers.

Low pressure radio-frequency oxygen plasma induced oxidation of titanium--surface characteristics and biological effects

OBJECTIVE

This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time.

MATERIALS AND METHODS

CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples.

RESULTS

The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti(°), Ti(2+), and Ti(3+) of the samples' surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped.

CONCLUSIONS

Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples' surface. The CP-Ti/Ti6Al4V treated with 5 min OPT displayed the roughest surface, sharpest surface profile and best biocompatibility.

Growth and differentiation factor-5 regulates the growth and differentiation of human dental pulp cells

INTRODUCTION

Growth and differentiation factor-5 (GDF-5) is a multifunctional protein that regulates the development and repair in many tissues. The purpose of this study was to investigate whether GDF-5 may influence the proliferation, differentiation, and collagen turnover of human dental pulp cells.

METHODS

Human dental pulp cells were treated with different concentrations of GDF-5 (0-500 ng/mL). Morphology of pulp cells was observed under a microscope. Cell proliferation was evaluated by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Immunofluorescent assay was used to observe the percentages of cell mitosis. Collagen content was measured by Sircol collagen assay. Tissue inhibitor of metalloproteinase-1 level in the culture medium was measured with enzyme-linked immunosorbent assay and Western blotting. Cell differentiation was evaluated by alkaline phosphatase (ALP) staining and ALP enzyme activity assay.

RESULTS

After exposure of dental pulp cells to various concentrations of GDF-5, cell number was up-regulated significantly in dose-dependent manner. GDF-5 also stimulated mitosis of dental pulp cells as indicated by an increased percentage of binucleated cells from 28% to 35%-45%. GDF-5 did not affect the collagen content and tissue inhibitor of metalloproteinase-1 level of pulp cells. GDF-5 decreased the ALP activity of pulp cells as analyzed by ALP staining and enzyme activity assay, with 14%-44% of inhibition.

CONCLUSIONS

GDF-5 revealed mitogenic and proliferative activity to dental pulp cells. GDF-5 showed inhibitory effect on ALP activity but little effect on the collagen turnover. These events are crucial in specific stages of dental pulp repair and regeneration. GDF-5 may be potentially used for tissue engineering of pulp-dentin complex.

Simvastatin inhibits cysteine-rich protein 61 expression in rheumatoid arthritis synovial fibroblasts through the regulation of sirtuin-1/FoxO3a signaling

OBJECTIVE

To examine the role of sirtuin-1 (SIRT-1)/FoxO3a in the expression of cysteine-rich protein 61 (CYR-61) in rheumatoid arthritis synovial fibroblasts (RASFs) and the influence of simvastatin on this pathway, and to determine the relationship between disease progression and FoxO3a/CYR-61 signaling in synovial fibroblasts in vivo using a rat model of collagen-induced arthritis (CIA).

METHODS

In RASFs, the expression of CYR-61 and SIRT-1, the localization of FoxO3a in the nucleus/cytoplasm, and the phosphorylation/acetylation of FoxO3a were examined by Western blotting. Secretion of CCL20 was assessed by enzyme-linked immunosorbent assay. Promoter activity of the Cyr61 gene was evaluated by luciferase assay, with or without forced expression of FoxO3a and SIRT-1 by lentiviral transduction. FoxO3a-Cyr61 promoter interaction was examined by chromatin immunoprecipitation. In rats with CIA, the expression of CYR-61 and phosphorylated FoxO3a in synovial fibroblasts was examined by immunohistochemistry.

RESULTS

In RASFs, simvastatin suppressed the tumor necrosis factor α (TNFα)-induced production of CYR-61 and CCL20. Nuclear levels of FoxO3a were decreased after TNFα stimulation of RASFs, and forced expression of FoxO3a reversed the inductive effects of TNFα on CYR-61. Simvastatin inhibited the nuclear export, phosphorylation, and acetylation of FoxO3a and maintained its binding to the Cyr61 promoter. Forced expression of SIRT-1 in RASFs led to decreased levels of CYR-61 and deacetylation of FoxO3a. Following treatment with simvastatin, the expression of SIRT-1 was up-regulated and SIRT-1/FoxO3a binding was enhanced in RASFs. In rats with CIA, intraarticular injection of simvastatin alleviated arthritis and suppressed CYR-61 expression and FoxO3a phosphorylation in synovial fibroblasts.

CONCLUSION

CYR-61 is important in the pathogenesis of RA, and SIRT-1/FoxO3a signaling is crucial to induction of CYR-61 in RASFs. Simvastatin plays a beneficial role in inflammatory arthritis through its up-regulation of SIRT-1/FoxO3a signaling in synovial fibroblasts. Continued study of the pathways linking sirtuins, FoxO proteins, and the inflammatory responses of RASFs may provide new insights into the pathophysiology of RA.

Simvastatin suppresses osteoblastic expression of Cyr61 and progression of apical periodontitis through enhancement of the transcription factor Forkhead/winged helix box protein O3a

INTRODUCTION

In this study, the role of transcription factor Forkhead/winged helix box protein O3a (FoxO3a) in Cyr61 expression and its modulation by simvastatin were investigated in cultured murine osteoblasts and a rat model of induced apical periodontitis. We also examined the effects of simvastatin on the synthesis of chemokine CCL2 and chemotaxis of macrophages in vitro.

METHODS

We assessed tumor necrosis factor (TNF)-α-stimulated expression of Cyr61 and phosphorylated inactive FoxO3a (p-FoxO3a) in MC3T3-E1 murine osteoblasts by Western analysis. Forced expression of FoxO3a by lentiviral-based gene transduction was performed, and its effect on Cyr61 expression was evaluated. The modulation of CCL2 secretion and macrophage chemotaxis by simvastatin were examined by enzyme-linked immunosorbent assay and transwell migration assay, respectively. In a rat model of induced apical periodontitis, the relation between disease progression and osteoblastic expression of Cyr61, p-FoxO3a, and CCL2 and macrophage recruitment were studied by radiographic and immunohistochemistry analyses.

RESULTS

Western blot analysis showed enhanced expression of Cyr61 and p-FoxO3a after TNF-α treatment in a time-dependent manner. Simvastatin significantly counteracted the actions of TNF-α. Forced expression of FoxO3a reduced TNF-α-stimulated Cyr61 synthesis. Simvastatin and FoxO3a diminished TNF-α-induced CCL2 secretion and macrophage recruitment, whereas Cyr61 partially restored the stimulating action. In rat periapical lesions, simvastatin significantly attenuated bone resorption, reduced osteoblastic expressions of Cyr61, p-FoxO3a, and CCL2, and suppressed macrophage recruitment.

CONCLUSIONS

Simvastatin may alleviate periapical lesions by enhancing FoxO3a activity to suppress the synthesis of Cyr61 in osteoblasts. Moreover, the downstream effector mechanism of Cyr61 may involve CCL2 production and macrophage recruitment.

Cloning, expression and characterization of CCL21 and CCL25 chemokines in zebrafish

Chemokines are a large group of proteins implicated in migration, activation, and differentiation of leukocytes. They are well-surveyed in mammals, but less is known in lower vertebrates about their spatiotemporal expressions and functions. From an evolutionary point of view, comparative analyses may provide some fundamental insights into these molecules. In mammals, CCL21 and CCL25 are crucial for thymocyte homing. Herein, we identified and cloned the zebrafish orthologues of CCL21 and CCL25, and analyzed their expression in embryos and adult fish by in situ hybridization. We found that CCL21 was expressed in the craniofacial region, pharynx, and blood vessels in embryos. In adult fish, CCL21 transcripts were located in the kidney, spinal cord, and blood cells. In contrast, expression of CCL25 was only detected in the thymus primordia in embryos. In adult fish, transcripts of CCL25 were maintained in the thymus, and they were also found in the brain and oocytes. Furthermore, we performed an antisense oligonucleotide experiment to evaluate the biological function of CCL25. Results showed that the recruitment of thymocytes was impeded by morpholino-mediated knockdown of CCL25, suggesting that CCL25 is essential for colonization of T-cells in the thymus in early development. Together, our results demonstrate the basic profiles of two CCL chemokines in zebrafish. The tissue-specific expression patterns may pave the way for further genetic dissection in this model organism.

Translucent titanium coating facilitates observation of osteoblast migration behavior on a titanium surface

PURPOSE

The appropriate surface composition and topography are crucial for osseointegration of titanium dental implants, and surface properties are known to enhance cell adhesion and promote expression of specific osteoblastic genes. In this study, a translucent titanium coating on glass coverslip (TiGlass) was introduced as a potential tool for direct observation of cell behavior on a titanium surface.

MATERIALS AND METHODS

Scanning electron microscopy, energy-dispersive x-ray analysis, and atomic force microscopy were performed on TiGlass to provide information about its physical properties. Random migration, osteoblastic gene expression, and immunofluorescence cell staining on TiGlass were also examined and analyzed.

RESULTS

The translucent titanium surface offered excellent optical characteristics that facilitated transmitted light observations under an optical microscope, transforming the opaque metal into an observable titanium matrix. Random migration analysis of the primary osteoblasts on TiGlass revealed that the titanium coating enhanced the migration speed of the osteoblasts and significantly shortened the time lag for the initial migration behavior. Further study of osteoblastic gene expression on this smooth titanium surface revealed no significant changes. Co-localization of actin filament and vinculin was found on TiGlass under epifluorescent microscopy.

CONCLUSION

The application of a translucent titanium-coated coverslip in vitro altered the migration pattern of osteoblasts. Collectively, the results suggest that titanium promotes initial adhesion and accelerates osteoblast migration.

Comparative cytotoxicity of five current dentin bonding agents: role of cell cycle deregulation

To compare the cytotoxicity of three nano-dentin bonding agents (nano-DBAs) and two non-nano-DBAs using Chinese hamster ovary (CHO-K1) cells. We found that nano fillers were not the major contributing factor in DBA cytotoxicity, as analyzed by colony forming assay and 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Exposure of CHO-K1 cells to all three tested total-etching DBAs led to G(0)/G(1) cell cycle arrest, whereas exposure to higher concentrations of two tested nano-DBAs induced G(2)/M arrest. All five DBAs further induced apoptosis at the highest concentration, as analyzed by propidium iodide staining flow cytometry. The toxicity of all DBAs (1:4000v/v or higher) is related to increased reactive oxygen species (ROS) production, as analyzed by single cell DCF fluorescence flow cytometry. These results indicate that clinical application of DBAs may be potentially toxic to dental pulp tissues. Cytotoxicity of DBAs is associated with ROS production, cell cycle deregulation and apoptosis. Presence of methacrylate monomers such as PENTA and UDMA is possibly the major cytotoxic factor for DBAs. Further studies on other toxicological endpoints of nano-DBAs are necessary to highlight their safe use.

Removal torque of miniscrews used for orthodontic anchorage--a preliminary report

PURPOSE

Implant anchors such as miniscrews and miniplates have been loaded immediately for anchorage during orthodontic treatment. The purpose of this study was to measure the removal torque of immediately loaded miniscrews after clinical usage and to determine the possible factors associated with this value.

MATERIALS AND METHODS

From 29 patients with malocclusions, 46 miniscrews were removed, and removal torque was measured with a torque gauge. Removal torque values were subjected to statistical analysis for possible association of different clinical characteristics.

RESULTS

The mean removal torque value was 1.10 kg x cm, and removal torques for 50% of the implants were greater than 0.89 kg x cm (8.7 N x cm). Removal torque values were significantly higher in the mandible than in the maxilla. The removal torques of 15-mm and 17-mm miniscrews were significantly higher than those of 13-mm miniscrews. Therefore, the site of implantation and miniscrew length were important factors associated with removal torque. However, there was no significant correlation between the removal torque value and age, gender, healing time, or time in function.

DISCUSSION

When miniscrews are used as anchorage for uprighting tipped molars, excessive torque in a counterclockwise direction may loosen them. From the measurements obtained in this investigation, miniscrews can sufficiently sustain an uprighting moment.

CONCLUSION

The removal torque values of the majority of miniscrews in this study population when loaded immediately as orthodontic anchorage were greater than 0.89 kg x cm, and this was sufficient for these implants to fulfill their purpose as anchors in 3-dimensional tooth movements.

Intrusion and reversal of a free-standing natural tooth bounded by two implant-supported prostheses: a clinical report

Although intrusion of natural tooth abutments in tooth-implant connected fixed prostheses has been reported, it can also occur to a free-standing natural tooth bounded by implant prostheses. For the patient described in this article, intrusion was noted with a natural tooth bounded by 2 implant-supported prostheses 5 months after insertion of the prostheses. The intrusion was reversed completely after 5 months with appropriate management. The course of treatment and possible mechanisms of intrusion are provided.

The role of lipopolysaccharide in infectious bone resorption of periapical lesion

BACKGROUND

The role of lipopolysaccharide (LPS) in periapical lesion-induced bone resorption was investigated. Polymyxin B (PMB), a specific 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-1alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF-alpha) in a time-dependent manner.

RESULTS

Combination of LPS further enhanced the stimulation. PMB inhibited these effects significantly. LPS also stimulated matrix metalloproteinase-1 (MMP-1) gene expression in J774, whereas anti-IL-1 alpha and anti-TNF-alpha 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-1 alpha and TNF-alpha from macrophages. These pro-inflammatory cytokines up-regulate the production of MMP-1 by macrophages to promote periapical bone resorption.

The effects of masseter muscle pain on biting performance

The present study applied a standardized test food of known hardness to evaluate the biting performance of 20 female patients who had pain mainly in the masseter muscle during palpation. Another 20 women of a similar age group who were pain-free during examination served as controls. Electromyograms (EMG) of the masseter and sternocleidomastoid (SCM) muscles and the jaw position were recorded and measured when the subjects were biting through two types of test foods with known hardness (hard type, 20 kg hardness and extra-hard type, 60 kg hardness). Pressure-pain-threshold (PPT) values of both the patients and the normal subjects were obtained with an algometer. It was found that the PPT of the patients with pain was significantly lower and that the extra-hard food took more masseter muscle activity and more working side jaw movement in both the pain and the normal groups. During both hard and extra-hard food biting, a significantly longer duration of masseter muscle activity was found in pain patients while the total muscle activity was not significantly stronger. Strong correlation existed between SCM and masseter muscle activity during both hard and extra-hard food biting in the patient group, while such correlation was very weak in the normal group. In conclusion, painful masseter muscles required longer masseter and SCM muscle contraction time for breaking through a hard food of 20 kg and more, and co-activation of SCM and masseter muscles existed and was more evident when the food was harder or the pain was more severe.

Effects of prosthesis materials and prosthesis splinting on peri-implant bone stress around implants in poor-quality bone: a numeric analysis

PURPOSE

A 3-dimensional finite element model consisting of a bone block and 2 simulated premolar crowns supported by 2 adjacent cylindric implants without immediately surrounding cortical bone was generated and used to investigate the effects of prosthesis materials and prosthesis splinting on the peri-implant bone stress under static loads.

MATERIALS AND METHODS

The peri-implant maximum equivalent bone stress (von Mises [VM] stress) was evaluated when a vertical or a horizontal load of 1 N was applied to the center of a single resin, gold alloy, or porcelain crown, nonsplinted or splinted to the adjacent crown.

RESULTS

The numeric results indicated that: (1) in a single crown, no significant difference could be found in the maximum VM stress between different materials for both vertical and horizontal loading; (2) splinting the crowns reduced the maximum VM stress induced by the horizontal load, and the maximum VM stress increased about 14% for the horizontal loading when the restorative material was changed from gold alloy or porcelain to resin.

DISCUSSION

Under the condition of this study's analysis, prosthesis materials of a single crown have insignificant effects on the peri-implant bone stress. Splinting the crowns reduced the peri-implant bone stress under horizontal load, and gold alloy and porcelain each demonstrated less peri-implant bone stress than resin in the splinted crown situation under static horizontal load.

CONCLUSION

Splinting the crowns of adjacent implants with relatively stiff restorative materials is recommended for implants surrounded by poor-quality bone.

Effects on non-human primate mastication of reversible inactivation by cooling of the face primary somatosensory cortex

Rhythmical jaw movements can be evoked by intracortical microstimulation within four physiologically defined 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 affected 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, 37 degree C), cool (2-4 degrees C), and postcool (37 degrees C) 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 modified 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 significant increase in anterior digastric muscle duration, a significant delay in the onset of masseter EMG activity, and a significant 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.

An electromyographic analysis of orofacial motor activities during trained tongue-protrusion and biting tasks in monkeys

This study sought to characterise the electromyographic (EMG) activity patterns of orofacial-muscles during trained tongue-protrusion and biting tasks in two awake monkeys (Macaca fascicularis). 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 (OOI) 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 OOI (and also the OOS 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 OOI 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.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional properties of single neurons in the primate face primary somatosensory cortex. I. Relations with trained orofacial motor behaviors

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 mechanosensitive afferent inputs from the upper lip, lower lip, or both; 72 "tongue RF" neurons that received mechanosensitive afferent inputs from the tongue; 11 "periodontium RF" neurons receiving periodontal inputs; and 8 neurons that received inputs from other orofacial regions. 3. Nearly all (249/253) of the face SI neurons responded to light tactile stimuli, and most of them received contralateral inputs (78%) and showed a rapidly adapting (RA) response to tactile stimulation (82%). There was no significant difference in the ratio of slowly adapting (SA) to RA neurons in areas 3b and 1. 4. For 193 neurons studied in one or both of the orofacial tasks, 113 were found, on the basis of histological reconstruction, to be distributed in area 1, 61 in area 3b, and 19 in area 2. 5. The firing rate of most tongue RF (79% of 56) neurons and lip RF (60% of 93) neurons tested was significantly altered during the tongue-protrusion task. Only some (14% of 36 tongue RF neurons and 34% of the 92 lip RF neurons tested) showed a significant change in firing rate during the biting task. Three of 7 periodontium RF neurons studied in the tongue-protrusion task altered their firing rate and 5 of 10 altered their firing rate during the biting task. 6. Most of the 116 face SI neurons studied during both tasks exhibited a preferential relation to the tongue-protrusion task as distinct from the biting task, and none showed task-related activity during the biting task only.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional properties of single neurons in the primate face primary somatosensory cortex. II. Relations with different directions of trained tongue protrusion

1. In previous papers we have presented evidence suggesting an important role for the face primary somatosensory cortex (SI) in the fine control of tongue movements. These findings, plus our earlier evidence that many neurons in face motor cortex (MI) may exhibit firing rates related to the direction of tongue protrusion, led us to test the hypothesis that variations in the direction of a tongue-protrusion movement would be associated with variations in the activity of different face SI neurons. 2. Two monkeys were trained to perform a tongue-protrusion task in each of three directions: the task transducer was positioned at 0 degrees, 30 degrees to the left, or 30 degrees to the right from the midsagittal plane. The latter two positions were termed asymmetrical tongue-protrusion task positions. Single-neuron activity was recorded from face SI during trials of the tongue-protrusion task at each of two or three of the above positions. In addition, the mechanoreceptive field (RF) was delineated for each neuron. 3. Directional relations were found in 25 (58%) of the 43 neurons studied; this included 20 neurons showing a significant direction-by-time interaction in firing rate, i.e., the change of firing rate from the pretrial period to the task period was significantly different between different directions, and 5 showing no direction-by-time interaction but a significant difference in firing rate between different directions of the tongue-protrusion task. 4. Of the 43 neurons investigated, 21 and 20 had a RF on the tongue and lips, respectively ("tongue RF" and "lip RF" neurons), and the remaining 2 received mechanosensitive afferent inputs from other orofacial regions. There was no significant difference in the incidence of directional sensitivity between the neurons with a tongue RF and those with a lip RF (12/21 and 11/20, respectively). 5. Eight of the 25 "directional" neurons were located in area 3b and 17 in area 1. There was no significant difference in the proportion of directional neurons between areas 3b and 1. 6. The increase in discharge frequency at the preferred direction was, on the average for the 25 directional neurons, 39% over the mean discharge frequency observed during the task period for all directions of the tongue-protrusion task. Eight directional neurons showed a significant increase in firing rate during the tongue-protrusion task up to 130 ms before the onset of genioglossus electromyographic activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional properties of single neurons in the primate face primary somatosensory cortex. III. Modulation of responses to peripheral stimuli during trained orofacial motor behaviors

1. In previous papers we have demonstrated that most single neurons in the face primary somatosensory cortex (SI) alter their firing rate during a trained tongue-protrusion task and some also during a trained biting task. Although the data suggest that some of the task-related activity in face SI might conceivably come from reafferent inputs from moving orofacial structures, it is possible that orofacial inputs are modulated during the trained orofacial movements. This study was initiated to investigate the possible modulation of evoked orofacial somatosensory responses of face SI neurons during trained tongue-protrusion and biting tasks. 2. Two monkeys were trained to perform a tongue-protrusion and a biting task and to accept stimulation applied to the facial skin or the lingual nerve during the tasks. For SI neurons with a tongue mechanoreceptive field (RF), electrical stimulation was applied to the lingual nerve to elicit neuronal activity; for SI neurons with a RF at the other locations, electrical or mechanical stimulation was applied to the RF to elicit neuronal activity. Modulation of neuronal activity evoked by low-threshold stimulation of the RF was tested, during the tongue-protrusion and/or biting tasks, in 44 face SI neurons and an additional 3 forelimb SI neurons with a palm RF (palm RF neurons). The 44 face SI neurons included 13 with a tongue RF (tongue RF neurons), 29 with a lip RF (lip RF neurons), and 2 with a lateral face RF (face RF neurons). 3. For face SI neurons tested during both force dynamic and holding phases of the task period, the evoked activity (i.e., the number of evoked spikes in 50 ms after the onset of stimulation) was decreased in at least one of the two phases for the majority (90%) of 31 neurons studied during the tongue-protrusion task and 61% of 23 studied during the biting task. The proportion of neurons modulated during the tongue-protrusion task was significantly higher than that during the biting task. For the 18 face SI tested during both tasks, a decrease in evoked activity occurred in 10 lip RF neurons for both tasks and in the remaining 5 lip RF and 3 tongue RF neurons for the tongue-protrusion task only. No neurons tested showed a clear facilitation of evoked activity during the task period of either task.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of bilateral cold block of the primate face primary somatosensory cortex on the performance of trained tongue-protrusion task and biting tasks

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 the tasks. 3. During bilateral cooling of face SI, there was a statistically significant reduction in the success rates for the performance of the tongue-protrusion task in comparison with control series of trials while the thermodes used to cool face SI were kept at 37 degrees C. Detailed analyses of force and EMG activity showed that the principal deficit was the inability of the monkeys to maintain a steady tongue-protrusive force in the force holding period during each trial and to exert a consistent tongue-protrusion force between different trials. The task performance returned to control protocol levels at 4 min after commencement of rewarming. 4. Identical cooling conditions did not significantly affect the success rates for the performance of the biting task. Although the extent of the deficit was not severe enough to cause a significant reduction in successful rates for the biting task, cooling did significantly affect the ability of the monkeys to maintain a steady force in the holding period during each trial and to exert a consistent force between different trials. In one monkey the success rate of the biting task was also not affected by bilaterally cooling of face SI with a pair of larger thermodes placed on the dura over most of the face SI, face primary motor cortex (face MI), and adjacent cortical regions.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of reversible inactivation by cooling of the primate face motor cortex on the performance of a trained tongue-protrusion task and a trained biting task

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)