Dimensional changes of complete dentures fabricated by milled and printed techniques: An in vitro study.

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.

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.

Resolution of Excessive Interocclusal Restoration Space Post-Mandibulectomy Using a Two-Layer Retrievable Fixed Implant-Supported Prosthesis: A Case Report.

Patients treated with segmental mandibulectomy often require complicated rehabilitation. Maintenance of mandibular continuity and provision of adequate soft and hard tissue volumes are two key factors required for good clinical outcomes. Moreover, excessive interocclusal restoration space is a common problem in these patients. This case report describes the process of prosthetic rehabilitation from extensive surgical excision to final rehabilitation by using a creative two-layer fixed implant prosthesis in a 70-year-old patient with oral squamous cell carcinoma.

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)/ß-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.

Preliminary evaluation of BMP-2-derived peptide in repairing a peri-implant critical size defect: A canine model.

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)/ß-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.

Effects of fabrication techniques on denture base adaptation: An in vitro study.

STATEMENT OF PROBLEM: Information about the accuracy of maxillary and mandibular denture bases made with different fabrication techniques under uniform test conditions is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the denture base adaptation of computer-aided design and computer-aided manufactured (CAD-CAM) milled, 3D printed, and conventional heat-polymerized resin fabrication techniques. MATERIAL AND METHODS: Maxillary and mandibular edentulous models fabricated from cobalt-chromium alloy were scanned, and 2-mm-thick denture bases were designed and fabricated by using 4 fabrication techniques and materials: CAD-CAM milled (CCM), 3D printed (3DP), injection molded (IM), and compression molded (CM). Denture base adaptation was assessed by measuring the thickness of silicone between the denture base and model under a 49-N load at 8 sites. A digital superimposition method was used to compare different groups, and adaptation was assessed by superimposing the scanning data from denture bases and models. The pairwise Wilcoxon signed rank test and Kruskal-Wallis analysis of variance were used for statistical analyses (α=.05). RESULTS: According to the silicone thickness method, the lowest values (0.127-0.567 mm) were present at the bilateral maxillary tuberosities, and the highest values (0.529-2.211 mm) occurred at the postpalatal seal area in all groups. The CCM group had the lowest silicone thickness (P<.05). The 3DP group recorded greater thickness than the IM and CM groups (P<.05). In the mandible, the 3DP group recorded the lowest silicone thickness, followed by the CCM group. The overall results for digital superimposition revealed no significant difference (P>.05) in the trueness of the intaglio surfaces among CCM, IM, and CM. The 3DP group recorded the lowest trueness significantly among all the groups. CONCLUSIONS: CCM, IM, and CM exhibited superior denture adaptation, especially CCM, to both maxillary and mandibular arches compared with 3DP.

Antiplatelet, antioxidative, and anti-inflammatory effects of hydroquinone.

Platelets play crucial roles in thrombosis and hemostasis through platelet activation and aggregation that are crucial in cardiovascular diseases. Hydroquinone (HQ) and its derivatives are present in many dermatological creams, paints, motor fuels, air, microorganisms, and plant products like wheat bread, fruit, coffee, and red wine. The effect of HQ on humans is not clear. In this study, we found that HQ (>25 µM) inhibited arachidonic acid (AA)-induced platelet aggregation. HQ suppressed AA-induced thromboxane B2 production of platelets. HQ (>10 µM) also attenuated ex vivo platelet-rich plasma aggregation. HQ prevented the interleukin (IL)-1ß-induced 8-isoprostane, and PGE2 production, but not IL-8 production of pulp cells. These results indicate that HQ may have an antiplatelet effect via inhibition of thromboxane production. HQ has antioxidative and anti-inflammatory effects, and possible inhibition of COX. Exposure and consumption of HQ-containing products, food or drugs may have antiplatelet, antioxidative, and anti-inflammatory effects.

IL-1ß-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-1ß) 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-1ß on dental pulp cells is not clear. METHODS: Cultured human dental pulp cells were exposed to IL-1ß 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-1ß stimulated IRAK-1 phosphorylation of pulp cells within 120 min of exposure. IRAK1/4 inhibitor attenuated the IL-1ß-induced ICAM-1, but not IL-8 protein expression. IRAK1/4 inhibitor also prevented the IL-1ß-induced sICAM-1, but not IL-8 secretion. SB203580 showed little effect on IL-1ß-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-1ß in pulpal inflammatory responses via stimulation of IL-8 and ICAM-1 expression and secretion. Moreover, IL-1ß-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.

IL-1ß induced IL-8 and uPA expression/production of dental pulp cells: Role of TAK1 and MEK/ERK signaling.

BACKGROUND/PURPOSE: Interleukin 1 beta (IL-1ß) is a pro-inflammatory cytokine involved in the inflammatory processes of dental pulp. IL-8 and urokinase plasminogen activator (uPA) are two inflammatory mediators. However, the role of transforming growth factor beta-activated kinase-1 (TAK1) and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways in responsible for the effects of IL-1ß on IL-8 and uPA expression/secretion of dental pulp cells are not clear. METHODS: Human dental pulp cells were exposed to IL-1ß with/without pretreatment with 5z-7-oxozeaneaeol (a TAK1 inhibitor) or U0126 (a MEK/ERK inhibitor). TAK1 activation was determined by immunofluorescent staining. The protein expression of IL-8 was tested by western blot. The expression of IL-8 and uPA mRNA was studied by reverse transcriptase-polymerase chain reaction (RT-PCR). The secretion of IL-8 and uPA was measured by enzyme-linked immunosorbent assay. RESULTS: Exposure of dental pulp cells to IL-1ß (0.1-10 ng/ml) stimulated IL-8 and uPA expression. IL-1ß also induced IL-8 and uPA secretion of dental pulp cells. IL-1ß stimulated p-TAK1 activation of pulp cells. Pretreatment and co-incubation of pulp cells by 5z-7oxozeaenol (1 and 2.5 µM) and U0126 (10 and 20 µM) prevented the IL-1ß-induced IL-8 and uPA expression. 5z-7oxozeaenol and U0126 also attenuated the IL-1ß-induced IL-8 and uPA secretion. CONCLUSION: IL-1ß is important in the pathogenesis of pulpal inflammatory diseases and repair via stimulation of IL-8 and uPA expression and secretion. These events are associated with TAK1 and MEK/ERK signaling. Blocking of TAK1 and MEK/ERK signaling has potential to control inflammation of dental pulp.

Effect of interleukin-1ß on ICAM-1 expression of dental pulp cells: role of PI3K/Akt, MEK/ERK, and cyclooxygenase.

OBJECTIVE: Interleukin-1ß (IL-1ß) is an important inflammatory mediator of the dental pulp. IL-1ß stimulates cyclooxygenase-2 (COX-2) expression and prostanoid production of pulp cells and affects the inflammatory and healing processes of the dental pulp. There are two interleukin-1 (IL-1) receptors, IL-1RI and IL-1RII, with opposing effect after activation. However, the expression of IL-1Rs, the effects of IL-1ß on intercellular adhesion molecule-1 (ICAM-1) of dental pulp cells, and its relation to protein kinase B (Akt) signaling and COX activation are not clear. METHOD: Human dental pulp cells were treated with IL-1ß with/without pretreatment and co-incubation by LY294002 (a PI3K/Akt inhibitor), U0126 [a mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) inhibitor], aspirin (a COX inhibitor), or eugenol (a COX inhibitor) for different time periods. The expression of ICAM-1, IL-1RI, and IL-1RII messenger RNA (mRNA) was evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). ICAM-1 protein expression was examined by western blotting. Soluble ICAM-1 (sICAM-1) level in the culture medium was determined by enzyme-linked immunosorbent assay (ELISA). Activation of Akt and ERK by IL-1ß was measured by Pathscan p-Akt ELISA or western blot. Viable cell number was evaluated by 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. RESULTS: Dental pulp cells expressed IL-1RI, but little IL-1RII. IL-1ß stimulated COX-2 and ICAM-1 mRNA and protein expression as well as sICAM-1 production of pulp cells. Aspirin and eugenol enhanced the IL-1ß-induced sICAM-1 production and ICAM-1 expression. IL-1ß rapidly activated Akt and ERK. LY294002 and U0126 attenuated IL-1ß-induced ICAM-1 expression and sICAM-1 production. CONCLUSIONS: These results reveal that IL-1ß may be involved in the pulpal inflammatory processes by stimulating ICAM-1 expression and secretion. These events are associated with IL-1RI expression and differential activation of PI3K/Akt and MEK/ERK and COX. CLINICAL RELEVANCE: Pharmacological inhibition of IL-1ß, IL-1RI, COX-2, ICAM-1, and related signaling pathways (MEK/ERK and PI3K/Akt) may be useful for the control of pulpal inflammation.

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.

Needlestick and sharps injuries among dental healthcare workers at a university hospital.

BACKGROUND/PURPOSE: Needlestick/sharps injuries (NSI) are a major occupational hazard among healthcare workers. Since needles and sharps are commonly used during dental procedures, workers in the dental profession are especially prone to sharps-related injuries. In this study, NSI among workers in the dental department of National Taiwan University Hospital (NTUH) were analyzed to find out the risk factors associated with NSI. METHODS: NSI cases reported by the Department of Dentistry to NTUH from 2009 to 2011 were collected. Correlations between NSI and parameters related to the events were analyzed. RESULTS: A total of 56 NSI events including 31 occurring during surgical treatment and 25 occurring during cleanup procedure were reported. The annual incidence of NSI was 8.19% among all dental workers. NSI incidences per person-year were 21.28% for interns, 7.50% for residents, 6.77% for nursing staffs, 3.33% for clerks, and 0.85% for attending doctors (P < 0.001, chi-square test). NSI events occurred more frequently in the 3-month period from July to September (20 cases), on Wednesday (18 cases) or Friday (14 cases), and at the hours from 11:00 to 14:00 and after 16:00 (39 cases). Dental injection needle (19 cases) was the most common instrument involved in NSI and 9 of these 19 needle injuries occurred during need removal. CONCLUSION: NSI events tend to occur in dental personnel (interns) with lesser clinical skill and experience, in the period (from July to September) when new interns and residents join the clinic, on the working days in the middle (Wednesday) and end (Friday) of the week, and at the hours close to lunch break (11:00 to 14:00) and getting off duty (after 16:00). In addition, establishment of standard operating procedure for injection needle removal is necessary, because one-third of NSI are needle-related.

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.

Areca nut-induced buccal mucosa fibroblast contraction and its signaling: a potential role in oral submucous fibrosis--a precancer condition.

Betel quid (BQ) chewing is an oral habit that increases the risk of oral cancer and oral submucous fibrosis (OSF), a precancerous condition showing epithelial atrophy and tissue fibrosis. Persistent fibroblast contraction may induce the fibrotic contracture of tissue. In this study, we found that areca nut extract (ANE) (200-1200 µg/ml) stimulated buccal mucosa fibroblast (OMF)-populated collagen gel contraction. Arecoline but not arecaidine-two areca alkaloids, slightly induced the OMF contraction. Exogenous addition of carboxylesterase (2U/ml) prevented the arecoline- but not ANE-induced OMF contraction. OMF expressed inositol triphosphate (IP3) receptors. ANE-induced OMF (800 µg/ml) contraction was inhibited by U73122 [phospholipase C (PLC) inhibitor] and 2-aminoethoxydiphenyl borate (IP3 receptor antagonist), respectively. Ethylene glycol tetraacetic acid and verapamil, two calcium mobilization modulators, also suppressed the ANE-induced OMF contraction. ANE induced calcium/calmodulin kinase II and myosin light chain (MLC) phosphorylation in OMF. Moreover, W7 (a Ca(2+)/calmodulin inhibitor), HA1077 (Rho kinase inhibitor), ML-7 (MLC kinase inhibitor) and cytochalasin B (actin filament polymerization inhibitor) inhibited the ANE-induced OMF contraction. Although ANE elevated reactive oxygen species (ROS) level in OMF, catalase, superoxide dismutase and N-acetyl-L-cysteine showed no obvious effect on ANE-elicited OMF contraction. These results indicate that BQ chewing may affect the wound healing and fibrotic processes in OSF via inducing OMF contraction by ANE and areca alkaloids. AN components-induced OMF contraction was related to PLC/IP3/Ca(2+)/calmodulin and Rho signaling pathway as well as actin filament polymerization, but not solely due to ROS production.

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 and feedback from the performance of pre-clinical operation skills tests for clerkship in School of Dentistry, National Taiwan University in 2022.

Background/purpose: The simulated pre-clinical operation skill test (PCOST) is part of the objective structured clinical examination (OSCE) and designed for clinical practice using manikins, physical typodonts, and instruments in the laboratory. This study tried to evaluate the influencing factors of the PCOST results for dental students. Materials and methods: The 32 5th-year dental students of the dental school of National Taiwan University (NTU) joined the PCOST. The contents of PCOST included two specialties: operative dentistry (OD) and prosthodontics (PS). The examination content of OD was tooth 36 mesio-occluso-distal (MOD) cavity preparation, and that of PS was crown preparation and temporary crown fabrication of tooth 11. Several factors including the gender, age, and dental student admission ways (with or without the skill tests) were evaluated. Each scoring item was calculated. The students also filled the feedback questionnaire about the examination questions and suggestions for the PCOST. Results: For both OD and PS, there were no significant differences in the mean PCOST 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. According to the feedback questionnaire from the participated dental students, they were satisfied with the PCOST. Conclusion: The PCOST is a good simulated examination in clinical practice. However, we still need to collect more PCOST data and feedback to revise the guideline of the PCOST, and to promote the performance of clinical works of dental students.

Evaluation of sawbones training protocol in bone quality classification using tactile sensation.

Background/purpose: Bone quality may affect the implantation protocol. This study aimed to assess whether training protocols could improve novice dental practitioners' abilities in judging bone densities with tactile sensation. Materials and methods: Twenty-five operators were recruited to evaluate the density of artificial polyurethane bone blocks by a 2-mm twist-drill drilling and reported the bone quality perceived in a 100-mm VAS line. Five blocks (densities: 0.08-0.48 g/cm3) were used to simulate cancellous bone with extremely low to medium-high densities. Five tests were performed on three days, separated by one week and one month. A training session was arranged on the first day and the third day. In each test, the operator drilled a 0.8 g/cm3 block as the reference (VAS = 100) and then the five test blocks in a randomized sequence. Each training session included a 0.8 g/cm3 followed by five 0.16 and 0.32 g/cm3 alternative block-drillings. VAS values and number of density-sequencing errors were analyzed with GLM repeated measures and Friedman test. Results: While mean VAS values were significantly different among the five test blocks, it was not noticed in blocks of the same density between test sessions. Significant linear correlations were observed between VAS values and block densities. Training did not influence the VAS evaluation and hardness sequencing in general but training significantly reduced the sequencing errors in operators with inferior initial performance. Conclusion: The proposed training protocol can improve the bone-quality perception among less experience dentists with poorer initial performance in bone density evaluation.