Reliability of mixed dentition space analysis using a digital model obtained from an optical impression: a preliminary study.

OBJECTIVE: While mixed dentition space analysis is a common practice in pediatric dentistry, digital models created using an intraoral scanner are not as widely used in clinical settings. This preliminary study used a very small sample size with one reference model and aimed to (1) compare the accuracy of mixed dentition space analysis using a digital model obtained from an optical impression with that of conventional plaster model-based analysis and (2) assess inter-examiner differences. RESULTS: The space required for the mandibular permanent canine and premolars and arch length discrepancy were calculated using each model. The largest significant difference between plaster- and digital model-based analyses was identified when the right arch length discrepancy was considered (-0.49 mm; 95% confidence interval: -0.95-0.03); however, the value was considered clinically insignificant. Significant inter-examiner differences were observed for six items of the plaster model; however, no such differences were observed when using the digital model. In conclusion, digital model space analysis may have the same level of accuracy as conventional plaster model analysis and likely results in smaller inter-examiner differences than plaster model analysis.

Effect of aromatherapy with peppermint essential oil on the gag reflex: a randomized, placebo-controlled, single-blind, crossover study.

BACKGROUND: Sensitive gag reflexes prevent dental patients from receiving appropriate treatment. Aromatherapy helps patients relax during dental procedures. However, the effect of aromatherapy on the gag reflex caused by the stimulation of the oral cavity is unknown. This study aimed to evaluate whether aromatherapy reduces gag reflexes during oral stimulation. METHODS: In this randomized, placebo-controlled, single-blind, crossover study, the gag reflexes of 24 healthy individuals (12 females and 12 males; mean age: 34.3 ± 9.5 years) were quantified. A standard saliva ejector was slowly guided down the participant's throat to determine the maximum tolerance of the gag reflex, and the insertion distance was measured to quantify the gag reflex. All individuals participated in an aromatherapy session with peppermint essential oil and a placebo session with distilled water. The gag reflex was quantified before (baseline) and after each session. Another measurement was performed using nitrous oxide/oxygen inhalation as a positive control. RESULTS: Gag reflex values significantly increased after aromatherapy with both peppermint essential oil and placebo compared to baseline values (paired t-test, P < 0.001 and P = 0.014, respectively). The gag reflex value also increased significantly during nitrous oxide/oxygen inhalation (paired t-test, P < 0.001). There was no significant difference in the increase rate of gag reflex values between the positive control and aromatherapy interventions, but it was significantly lower after the placebo intervention (repeated measures analysis of variance, P = 0.003; post-hoc test, P = 0.83 and P = 0.02). CONCLUSION: Aromatherapy with peppermint essential oil has the potential for reducing gag reflex during dental procedures. TRIAL REGISTRATION: The study was registered in the University hospital Medical Information Network Clinical Trials Registry under the code UMIN000050616 (approved 17/03/2023).

Syntheses and Redox Properties of Carboxylate-Ligated Hexanuclear Ce(IV) Clusters and Their Photoinduced Homolysis of the Ce(IV)-Ligand Covalent Bond.

Oxo- and hydroxo-bridged hexanuclear Ce(IV) clusters surrounded by 12 carboxylate ligands, Ce6O4(OH)4(O2CR)12(L)n (R = 2,6-Me2-4-MeOC6H2 (1a), 2,6-Me2-4-tBuC6H2 (1b), 2,4,6-Me3C6H2 (1c), 2,6-Me2C6H3 (1d), 2,6-Me2-4-FC6H2 (1e), 2,6-Me2-4-ClC6H2 (1f), 9-anthracenyl (1g), and CH2tBu (1h), L = H2O or RCO2H), were synthesized by treating Ce(OtBu)4 with the corresponding carboxylic acids (2-3 equiv.) in acetone or toluene, and the molecular structures of 1d and 1g were clarified by X-ray diffraction studies. UV-vis analyses of the clusters showed broad absorption corresponding to the ligand-to-metal charge transfer (LMCT) in the ultraviolet A (315-400 nm) to blue light region; density functional theory (DFT) studies of the simplified Ce(IV) and related Zr(IV) clusters, M6O4(OH)4(O2CR)12 (M = Ce, Zr, R = Ph, Me), revealed that the low-lying vacant 4f-orbitals of the Ce(IV) were responsible for absorption in the ultraviolet A to blue light region. Irradiation of blue LED light to 1a-f under an argon atmosphere resulted in the formation of 7-methylisobenzofuran-1(3H)-one (2a-f), which involved the following four steps: photoinduced homolysis of the Ce(IV)-OCOR bond, intramolecular hydrogen atom transfer to generate the corresponding benzyl radical, oxidation to the benzyl cation, and intramolecular cyclization. Cyclic voltammetry of cerium clusters 1a-f having 2,6-dimethyl-4-substituted arylcarboxylate ligands showed electrochemically irreversible redox waves in the range of -0.79 to -0.38 V (vs [Cp2Fe]+/Cp2Fe for E1/2). The one-electron-reduced Ce(III)Ce(IV)5 clusters 3a-h were isolated by reducing 1a-h with Cp*2Co to give [Cp*2Co][Ce6O4(OH)4(O2CR)12(thf)n] (3a-h); cluster 3d was the first structurally determined hexanuclear cerium cluster containing a [Ce6O4(OH)4]11+ core.

Ultrafast capture of electrons ejected by photoionization leading to the formation of a charge-separated state at a high energy level.

Electron transfer reactions driven by two-photon ionization in the higher excited state were investigated via transient absorption spectroscopy, with the aim to develop a method for creating the charge-separated (CS) state with a large formation rate, high energy level, and long lifetime. In the proof-in-principle experiments using pyrene and biphenyl as a model system, femtosecond transient absorption spectroscopy revealed that intense irradiation of an ultraviolet laser pulse at 355 nm efficiently pumps up pyrene into a higher excited state via a stepwise two-photon absorption, and then an ionization process takes place. An electron ejected from pyrene is directly captured by biphenyl with a time constant of 200 fs without the diffusion process of the electron in solution. The energy level of the CS state (Py+-Bp-) thus formed was estimated to be higher than that of the S1 state of pyrene by 0.53 eV. In addition, the subsequent ionic dissociation without a remarkable geminate recombination in the sub-nanosecond to nanosecond time region effectively avoids the quantity loss of the CS state. By applying the two-photon excitation method, we experimentally achieved ultrafast formation of the long-lived CS state at a high energy beyond the traditional framework of electron transfer reactions.

Cyclophosphamide-Induced Morphological Changes in Dental Root Development of ICR Mice.

BACKGROUND: Survivors of childhood cancer are at risk of late dental development. Cyclophosphamide is one of the most commonly used chemotherapeutic agents against cancer in children. The aim of this study was to investigate the effects of cyclophosphamide on root formation in the molars of growing mice and to assess the morphological changes in these roots using three-dimensional structural images. METHODS: We treated 16 12-day-old ICR mice with cyclophosphamide (100 mg/kg, i.p.) and 16 control mice with saline. At 16, 20, 24, and 27 days of age, the mandibular left first molars were scanned using soft micro-computed tomography. After scanning, the structural indices were calculated using a three-dimensional image analysis system, and the images were subjected to three-dimensional reconstruction. The length and apical foramen area of all distal roots were assessed. Histological changes in the apical region were then assessed via hematoxylin and eosin staining. RESULTS: The mandibular molars of all experimental mice showed evidence of cytotoxic injury, which appeared in the form of anomalous root shapes. Although all roots developed further after cyclophosphamide injection, the three-dimensional structural images showed that the roots in the experimental group tended to develop more slowly and were shorter than those in the control group. At 27 days of age, the mean root length was shorter in the experimental group than in the control group. Conversely, the apical foramen of the roots in the experimental group tended to close faster than that of roots in the control group. In addition, hematoxylin and eosin staining of the distal roots in the experimental group showed increased dentin thickness in the apical region. CONCLUSION: Our results suggest that cyclophosphamide can result in short root lengths and early apical foramen closure, eventually leading to V-shaped or thin roots.

Prevalence and association of self-reported anxiety, pain, and oral parafunctional habits with temporomandibular disorders in Japanese children and adolescents: a cross-sectional survey.

BACKGROUND: Associations between temporomandibular disorder (TMD) and psychological variables, pain conditions, and daily activities have been reported more commonly in middle-aged individuals than in children. However, to determine factor-specific preventive programs for TMD, it is important to evaluate the associations between multiple factors and TMD symptoms during childhood. The aim of this study was to assess the relationship between TMD symptoms and other orofacial pain conditions, daily activities, and trait anxiety in a population-based cross-sectional survey of Japanese children and adolescents. METHODS: A total of 1,415 subjects (11-15 years old) self-reported their TMD symptoms, headache, neck pain, and toothache, and completed questionnaire scales that assessed 15 daily activities. Trait anxiety was assessed using the State Trait Anxiety Inventory for Children-Trait (STAIC-T) scale. Subjects were dichotomized into a TMD group or control group, based on whether they reported at least 1 TMD symptom: the TMD group (≥1 TMD symptom, n = 182) and the control group (no TMD symptoms, n = 1,233). Data were analyzed using the chi-square test and multivariate logistic regression analysis. RESULTS: The prevalence rates for headache and neck pain were significantly higher in the TMD group than in the control group (44.0% vs. 24.7% and 54.4% vs. 30.0%, respectively; both P < 0.001). The odds ratios for TMD symptoms in subjects with neck pain and frequent diurnal clenching were 2.08 (P < 0.001) and 3.69 (P = 0.011), respectively. Moreover, high STAIC-T scores were weakly associated with TMD symptoms. CONCLUSIONS: In this young Japanese population, TMD symptoms were associated with other orofacial pain conditions, particularly neck pain, although they were only weakly associated with trait anxiety. Diurnal clenching was strongly associated with TMD symptoms. Health professionals should carefully consider these factors when developing appropriate management strategies for TMD in children and adolescents.

Cyclophosphamide inhibits root development of molar teeth in growing mice.

Root development of permanent teeth is disturbed in survivors of childhood cancer. Cyclophosphamide (CY) is a cytostatic drug commonly used for chemotherapy in children with cancer. This study aimed to evaluate the effects of CY on the development of molar teeth until the completion of occlusion in young mice, focusing on Hertwig's epithelial root sheath (HERS). We treated thirty-two 12-day-old ICR mice with CY (100 mg/kg; 100-CY group), and 36 control mice with saline. At 12, 14, 16, 20, 24, 27, 39, 60, and 76 days of age, the mandibular molars were removed. Soft X-ray radiographs were obtained in lateral projection. The root/crown length (R/C) ratio of the first molar was calculated. Serial sagittal sections were prepared and histomorphological hematoxylin and eosin (HE) staining and immunohistochemical (cytokeratin) studies were performed. The R/C ratio of the 100-CY group (0.78) was smaller than that of the control group (1.23) at 76 days (p < 0.05, t test). While all roots developed further after injection, microscopic examination showed that the roots of the first molars that developed in the 100-CY group were shorter than those in the control group. In addition, experimental mice showed apical closure of the roots. By 20 days after injection, the HERS had disappeared from the root surface in the 100-CY group. In conclusion, this study indicates that CY can induce a defect in HERS and cause early loss of HERS. Disruption of the epithelial sheath inhibits normal root formation, and it could cause irreversible short-root development.

Comparison of self-reported pain intensity, sleeping difficulty, and treatment outcomes of patients with myofascial temporomandibular disorders by age group: a prospective outcome study.

BACKGROUND: Subjective symptoms of temporomandibular disorders (TMDs) have rarely been studied by age group. We aimed to compare self-reported pain intensity, sleeping difficulty, and treatment outcomes of patients with myofascial TMDs among three age groups. METHODS: The study population included 179 consecutive patients (151 women and 28 men) who underwent comprehensive clinical examinations at a university-based orofacial pain center. They were classified into myofascial pain subgroups based on the Research Diagnostic Criteria for Temporomandibular Disorders. They were stratified by age group: M1, under 20 years; M2, 20-39 years; and M3, 40 years and older. The patients scored their pretreatment symptoms (first visit) and post-treatment symptoms (last visit) on a form composed of three items that assessed pain intensity and one item that assessed sleeping difficulty. Their treatment options (i.e., pharmacotherapy, physical therapy, and orthopedic appliances) and duration were recorded. All variables were compared between sexes in each group and between the age groups by using the Kruskal-Wallis test, the Mann-Whitney U test, the chi-square test, and analysis of variance (p < 0.05). RESULTS: No significant sex differences were found in any age group. Only sleeping difficulty was significantly different before treatment (p = 0.009). No significant differences were observed in the treatment options or treatment duration. After treatment, the intensity of jaw/face pain and headache and sleeping difficulty was significantly reduced in groups M2 and M3, but only the intensity of jaw/face pain was significantly decreased in group M1. The changes in the scores of pain intensity and sleeping difficulty were not different between the groups. CONCLUSIONS: Pain intensity does not differ by age group, but older patients with myofascial TMDs had greater sleeping difficulties. However, there were no differences between the age groups in the treatment outcomes. Clinicians should carefully consider the age-related characteristics of patients with myofascial TMDs when developing appropriate management strategies.

Comparison of subjective symptoms of temporomandibular disorders in young patients by age and gender.

The authors assessed the subjective symptoms of temporomandibular disorders (TMDs) in 167 young patients using self-reported forms, with five ratings for pain intensity and six ratings for difficulty in activities of daily living (ADL), to compare TMD symptoms according to gender and three age groups: group 1: 6- to 12-year-olds (juvenile); group 2: 13- to 15-year-olds (early adolescent); group 3: 16- to 18-year-olds (late adolescent). No significant gender differences were found in the symptoms among the groups, except for headache and neck pain in group 3. Pain intensity and tightness in the jaw/face, headache, and neck pain, as well as the ADL-related difficulty in prolonged jaw opening, eating soft/hard foods, and sleeping significantly differed among the groups (p < 0.01, Kruskal-Wallis test). Therefore, late adolescent patients with TMDs have higher pain intensity in the orofacial region and greater difficulty in ADL than do early adolescent and juvenile patients with TMDs.

Inter- and intraobserver reliability of the hand-held monitor for measuring salivary alpha-amylase level.

BACKGROUND: Alpha-amylase levels can be used to quantify the psychological stress. A hand-held salivary alpha-amylase (sAA) monitor was recently developed for measuring sAA levels. This study investigated the inter- and intraobserver reliability of this novel instrument. METHODS: Saliva was collected from 32 healthy volunteers. To determine the interobserver reliability, three observers measured the sAA levels in 10 samples. To determine the intraobserver reliability, one observer performed consecutive sAA measurements in 32 samples. The sAA levels in these 32 samples were also measured by a conventional laboratory enzymatic analysis, and these measurements were compared with those obtained using the hand-held monitor. RESULTS: Intraclass correlation coefficients indicated excellent inter- and intraobserver reliability (0.99 and 0.92, respectively). The results from the monitor and the lab assay showed a significant positive correlation (r = 0.96, p < 0.001). CONCLUSIONS: These results suggest that the hand-held monitor is highly reliable for measuring the sAA level.

Combined effect of paste containing casein phosphopeptide-amorphous calcium phosphate and fluoride on enamel lesions: an in vitro pH-cycling study.

PURPOSE: The purpose of this study was to show through enamel remineralization that a combination of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride is better than fluoride alone when the processing time for remineralization is short. METHODS: The bovine enamel slabs (n=28) were subjected to pH cycling for 4 days. Paste containing CPP-ACP and/or fluoride was applied for 30 minutes daily. The sections were observed using a polarizing microscope and microradiographs. RESULTS: In the groups treated solely with sodium fluoride (NaF) solution, tissue loss on the enamel surface was observed. On the other hand, in the groups that had been treated with a mixture of the NaF solution and CPP-ACP, the enamel surface was maintained. CONCLUSIONS: These results show that casein phosphopeptide-amorphous calcium phosphate-containing paste has the ability to maintain the enamel surface; the combined use of CPP-ACP paste and fluoride enhances this ability, thereby reducing demineralization.

Comparison of subjective symptoms among three diagnostic subgroups of adolescents with temporomandibular disorders.

AIM: To compare subjective symptoms among three diagnostic subgroups of young patients with temporomandibular disorders (TMDs). DESIGN: We comprehensively examined 121 patients with TMDs (age ≤20 years; 90 female patients and 31 male patients) who completed self-reported forms for assessing subjective symptoms, which consisted of five items on pain intensity in the orofacial region and six items on the level of difficulty in activities of daily living (ADL) (rating scale, 0-10). They were divided into three diagnostic subgroups: temporomandibular joint (TMJ) problem (JT) group, masticatory muscle pain (MM) group, and the group with a combination of TMJ problems and masticatory muscle pain (JM group). Their symptoms were compared using the Kruskal-Wallis and Mann-Whitney U-tests. RESULTS: The intensity of jaw or face tightness and difficulty in talking and yawning were not significantly different among the groups. However, the MM and JM groups had a significantly higher rating for jaw or face pain, headache, neck pain, tooth pain, and difficulty in eating soft foods (P < 0.01). CONCLUSIONS: Young patients with MM or JM report more intense pain in the orofacial region and have more difficulties in ADL than those with JT problems alone.

Factors affecting the use of protective stabilization in dental patients with cognitive disabilities.

The goal of this study was to investigate the effects of various factors on the use of protective stabilization (PS) in patients with cognitive disabilities during dental treatment. An observational, case-control design was used with a case (protective stabilization group or PS group) and a control (usual management group or UM group) to assess a sample of subjects. Forty-eight dental patients were selected from the two groups. Various factors were compared between the groups. The prevalence of patients with profound cognitive disabilities was higher in the PS group (68.7%) than in the UM group (6.2%) (p<0.0001). The odds ratio of using protective stabilization was 6.18 (95% confidence interval, 1.20-31.72) for patients who were prescribed antipsychotic agents. Our results suggest that patients with profound cognitive disabilities and/or prescriptions for antipsychotic medications have more behavioral disturbances during dental treatments and require protective stabilization.

Cross-cultural comparison of the attitudes of dental students in three countries.

The aim of this study was to identify and compare the attitudes of dental students toward their career choice and dental education in three different countries. Three hundred thirty-six dental students from the University of British Columbia, Canada; Mahidol University and Chiang Mai University, Thailand; and Nippon Dental University, Japan, participated in this study. Information was derived from a questionnaire consisting of career choice items and dental education items. Significant differences in the responses of the participants from each of the three countries were detected for each of the questionnaire items (P<0.001). Regarding factors that may have served as motivations for career choice, the majority of dental students from each country indicated positive reasons such as interpersonal motives, caring for other people, and academic interest. For future career options, the majority of Japanese and Canadian students planned to work as general dentists. Thai students were more likely than Japanese or Canadian to prefer specialization than practicing general dentistry. Nearly three-quarters of the Canadian and Thai students were satisfied with the teaching faculty of their schools, while only a quarter of the Japanese students indicated satisfaction. The findings from this study enhance our understanding of differences and/or similarities among dental students in three nations; this information may help to define strategies to improve the quality of international student exchange programs.

Regulation of prostaglandin E synthases: effects of siRNA-mediated inhibition of microsomal prostaglandin E synthase-1.

Prostaglandin E2 (PGE2) is a key mediator involved in several inflammatory conditions. In this study, we investigated the expression and regulation of the terminal PGE2 synthesizing enzyme prostaglandin E synthases (mPGES-1, mPGES-2 and cPGES) in gingival fibroblasts stimulated with pro-inflammatory cytokines. We used siRNA knockdown of mPGES-1 to elucidate the impact of mPGES-1 inhibition on mPGES-2 and cPGES expression, as well as on PGE2 production. The cytokines TNFalpha and IL-1beta increased protein expression and activity of mPGES-1, accompanied by increased COX-2 expression and PGE2 production. The isoenzymes mPGES-2 and cPGES, constitutively expressed at mRNA and protein levels, were unaffected by the pro-inflammatory cytokines. We show for the first time that treatment with mPGES-1 siRNA down-regulated the cytokine-induced mPGES-1 protein expression and activity. Interestingly, mPGES-1 siRNA did not affect the cytokine-stimulated PGE2 production, whereas PGF(2alpha) levels were enhanced. Neither mPGES-2 nor cPGES expression was affected by siRNA silencing of mPGES-1. Dexamethasone and MK-886 both inhibited the cytokine-induced mPGES-1 expression while mPGES-2 and cPGES expression remained unaffected. In conclusion, mPGES-1 siRNA down-regulates mPGES-1 expression, and neither mPGES-2 nor cPGES substituted for mPGES-1 in a knockdown setting in gingival fibroblasts. Moreover, mPGES-1 siRNA did not affect PGE2 levels, whereas PGF(2alpha) increased, suggesting a compensatory pathway of PGE2 synthesis when mPGES-1 is knocked down.

Signal pathways involved in the regulation of prostaglandin E synthase-1 in human gingival fibroblasts.

Microsomal prostaglandin E synthase-1 (mPGES-1) is the terminal enzyme regulating the synthesis of prostaglandin E2 (PGE2) in inflammatory conditions. In this study we investigated the regulation of mPGES-1 in gingival fibroblasts stimulated with the inflammatory mediators interleukin-1 beta (IL-1beta) and tumour necrosis factor alpha (TNFalpha). The results showed that IL-1beta and TNFalpha induce the expression of mPGES-1 without inducing the expression of early growth response factor-1 (Egr-1). Treatment of the cells with the PLA2 inhibitor 4-bromophenacyl bromide (BPB) decreased the cytokine-induced mPGES-1 expression accompanied by decreased PGE2 production whereas the addition of arachidonic acid (AA) upregulated mPGES-1 expression and PGE2 production. The protein kinase C (PKC) activator PMA did not upregulate the expression of mPGES-1 in contrast to COX-2 expression and PGE2 production. In addition, inhibitors of PKC, tyrosine and p38 MAP kinase markedly decreased the cytokine-induced PGE2 production but not mPGES-1 expression. Moreover, the prostaglandin metabolites PGE2 and PGF2alpha induced mPGES-1 expression as well as upregulated the cytokine-induced mPGES-1 expression indicating positive feedback regulation of mPGES-1 by prostaglandin metabolites. The peroxisome proliferator-activated receptor-gamma (PPARgamma) ligand, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), decreased mPGES-1 expression but not COX-2 expression or PGE2 production. The results indicate that the inflammatory-induced mPGES-1 expression is regulated by PLA2 and 15d-PGJ2 but not by PKC, tyrosine kinase or p38 MAP kinase providing new insights into the regulation of mPGES-1.