The modification of meteorological factors on the relationship between air pollution and periodontal diseases: an exploration based on different interaction strategies.

We aimed to characterize the association between air pollutants exposure and periodontal diseases outpatient visits and to explore the interactions between ambient air pollutants and meteorological factors. The outpatient visits data of several large stomatological and general hospitals in Hefei during 2015-2020 were collected to explore the relationship between daily air pollutants exposure and periodontal diseases by combining Poisson's generalized linear model (GLMs) and distributed lag nonlinear model (DLNMs). Subgroup analysis was performed to identify the vulnerability of different populations to air pollutants exposure. The interaction between air pollutants and meteorological factors was verified in both multiplicative and additive interaction models. An interquartile range (IQR) increased in nitrogen dioxide (NO2) concentration was associated with the greatest lag-specific relative risk (RR) of gingivitis at lag 3 days (RR = 1.087, 95% CI 1.008-1.173). Fine particulate matter (PM2.5) exposure also increased the risk of periodontitis at the day of exposure (RR = 1.049, 95% CI 1.004-1.096). Elderly patients with gingivitis and periodontitis were both vulnerable to PM2.5 exposure. The interaction analyses showed that exposure to high levels of NO2 at low temperatures was related to an increased risk of gingivitis, while exposure to high levels of NO2 and PM2.5 may also increase the risk of gingivitis and periodontitis in the high-humidity environment, respectively. This study supported that NO2 and PM2.5 exposure increased the risk of gingivitis and periodontitis outpatient visits, respectively. Besides, the adverse effects of air pollutants exposure on periodontal diseases may vary depending on ambient temperature and humidity.

[Dynamic changes in PD-1, TLR3, and TLR4 surface expression on peripheral blood mononuclear cells in chronic hepatitis C patients undergoing peg-IFNalpha-2a plus ribavirin combination therapy].

OBJECTIVE: To investigate the dynamic changes in expression of programmed death (PD)-1, Toll-like receptor (TLR)3, and TLR4 on the surface of peripheral blood mononuclear cells (PBMCs) in patients with chronic hepatitis C (CHC) that occur in response to pegylated-interferon alpha-2a (peg-IFNalpha-2a) plus ribavirin (RBV) combination therapy, and to analyze the relation to achievement of sustained virological response (SVR). METHODS Twenty-three CHC patients and 10 healthy controls were enrolled in the study. All CHC patients underwent 48 weeks of combination therapy with peg-IFNalpha-2a (180 microg, subcutaneous injection, once weekly) plus RBV (15 microg/kg, oral, once daily). Total PBMCs were isolated from both groups (CHC patients at treatment week 0, 12, 24, and 48 and post-treatment week 24; controls at enrollment) and subjected to flow cytometric analysis of PD-1, TLR3, and TLR4 surface expression. In addition, serum levels of alanine aminotransferase (ALT) and hepatitis C virus (HCV) RNA levels were analyzed by enzymatic assay and the AmpliPrep/COBAS (Roche) nucleic acid amplification test, respectively. SVR was defined as undetectable levels of HCV RNA at post-treatment week 24. Intergroup differences were assessed by one-way ANOVA. RESULTS: The expression ratios of PD-1, TLR4 and PD-1: TLR4 on PBMCs were significantly higher in CHC patients before therapy than in the healthy controls (45.20 +/- 7.12% vs. 16.82 +/- 4.13%, 58.45 +/- 15.13% vs. 21.09 +/- 2.89%, and 35.54 +/- 7.69% vs. 14.12 +/- 2.89%; all P < 0.05). In contrast, the expression ratios of TLR3 and PD-1:TLR3 were slightly, but not significantly, higher in CHC patients before therapy than in the healthy controls (P > 0.05). During the course of peg-IFNalpha-2a plus RBV combination therapy, the expression ratios of PD-1 and TLR4 on PBMCs showed a decreasing trend, while TLR3 expression showed an increasing trend. Furthermore, CHB patients who achieved SVR at post-treatment week 24 had a significantly different expression ratio of PD-1 and TLR3 than those who did not achieve SVR (P < 0.05). CONCLUSION: Surface expression of PD-1, TLR4, and PD-1:TLR4 is up-regulated in the total PBMCs of CHC patients. Peg-IFNalpha-2a plus RBV treatment-induced suppression of HCV replication results in a significant reduction in PD-1 and TLR4 expression on the surface of PBMCs, but a remarkably elevated level of TLR3 expression. The dynamic change in PD-1 and TLR3 expression on PBMCs that occurs during antiviral therapy may be related to achievement of SVR.

Efficacy of invisible advancement correction for mandibular retraction in adolescents based on Pancherz analysis.

BACKGROUND: Mandibular retraction is the main etiological mechanism of class II malocclusion in China and the subsequent distal molar relationship can cause functional discomfort in mastication, breathing and the temporomandibular joint. The use of mandibular advancement (MA) devices has recently emerged as an adolescent mandibular retraction treatment; however, current studies regarding the effect thereof are relatively few, and there is lack of sufficient clinical support. AIM: To investigate the clinical effect of invisalign MA on the treatment of mandibular retraction in adolescents. METHODS: This study included 30 adolescent patients who underwent treatment with the MA appliances from December 2017 to June 2021. The lateral cephalometric data before and after treatment were collected and imported into Dolphin Imaging software. The changes were measured by linear measurement superimposed with lateral cephalometric trajectory based on the Pancherz technology. RESULTS: There was no significant difference in the length and position of maxilla before and after the treatment. The position of the mandible moved 3.13 mm, the length increased 4.14 mm, the mandibular ramus length increased 4.09 mm, the body length increased 4.25 mm, and the position of the condyle moved 1.03 mm forward after treatment. Additionally, changes in the incisor sagittal position and labial inclination were observed. The position of the upper incisor point moved back 1.33 mm, without statistical difference, the inclination and tooth angle decreased by 3.44° and 4.06°, respectively; the position of the lower incisor point was moved 2.98 mm, and the inclination and tooth angle increased by 2.62° and 1.23°, respectively. Furthermore, changes in the incisor overjet and molar relationship were seen. Overjet decreased by 4.31 mm, of which 1.78 mm was due to dental factors, accounting for 41.3% of the effect as opposed to 58.7% due to skeletal factors. Molar relationship improved 3.87 mm, with 1.34 mm due to dental factors, and dental and skeletal factors were accounted for 34.6% and 65.4% of the effect, respectively. CONCLUSION: For adolescent patients with mandible retraction, invisalign MA can effectively promote the mandible growth, and it was proven to be mainly due to skeletal effects.

Recent Advances in Cell and Functional Biomaterial Treatment for Spinal Cord Injury.

Spinal cord injury (SCI) is a devastating central nervous system disease caused by accidental events, resulting in loss of sensory and motor function. Considering the multiple effects of primary and secondary injuries after spinal cord injury, including oxidative stress, tissue apoptosis, inflammatory response, and neuronal autophagy, it is crucial to understand the underlying pathophysiological mechanisms, local microenvironment changes, and neural tissue functional recovery for preparing novel treatment strategies. Treatment based on cell transplantation has become the forefront of spinal cord injury therapy. The transplanted cells provide physical and nutritional support for the damaged tissue. At the same time, the implantation of biomaterials with specific biological functions at the site of the SCI has also been proved to improve the local inhibitory microenvironment and promote axonal regeneration, etc. The combined transplantation of cells and functional biomaterials for SCI treatment can result in greater neuroprotective and regenerative effects by regulating cell differentiation, enhancing cell survival, and providing physical and directional support for axon regeneration and neural circuit remodeling. This article reviews the pathophysiology of the spinal cord, changes in the microenvironment after injury, and the mechanisms and strategies for spinal cord regeneration and repair. The article will focus on summarizing and discussing the latest intervention models based on cell and functional biomaterial transplantation and the latest progress in combinational therapies in SCI repair. Finally, we propose the future prospects and challenges of current treatment regimens for SCI repair, to provide references for scientists and clinicians to seek better SCI repair strategies in the future.

[Expression and significance of chemokines CCL21, E-selectins and Hsp90 in periodontal tissues of rats with experimental periodontitis].

PURPOSE: To investigate the expression and significance of chemokines CCL21, E-selectins and heat shock protein 90 (Hsp90) in periodontal tissues of rats with experimental periodontitis. METHODS: Forty 10-week-old male Wistar rats were significantly randomly divided into 4 groups with 10 rats in each group. Periodontitis models were established in groups A, B and C, and the rest were 10 blank control groups. Rats in group A, B and C were sacrificed at 4, 8 and 12 weeks after basic periodontal treatment, and the periodontal tissues of the first and second molars were taken for CCL21, E-selectins and Hsp90 protein expression detection. SPSS 25.0 software package was used to analyze the data. RESULTS: The levels of periodontal attachment in group A, B and C were higher than those in the control group(P<0.05). The levels of periodontal attachment, CCL21, E-selectins, Hsp90 mRNA and protein expression in periodontal tissues increased first and then decreased(P<0.05). The levels of periodontal attachment, CCL21, E-selectins, Hsp90 mRNA and protein expression in group B and C were significantly higher than those in group A(P<0.05). The levels of periodontal attachment, CCL21, E-selectins, Hsp90 and relative protein expression in periodontal tissues of group C were significantly lower than those of group B(P<0.05). CONCLUSIONS: The expression of CCL21, E-selectins and Hsp90 is up-regulated in periodontitis tissues. With local periodontal treatment, the expression level of CCL21, E-selectins and Hsp90 gradually decreases.

Effect of fluoride treatment on gene expression in tea plant (Camellia sinensis).

Tea plant is a typical fluorine (F) accumulator. F concentration in mature tea leaves is several hundred times higher than that in normal field crops. Long-term consumption of teas with high level F will increase the risks of dental and skeletal fluorosis. The mechanism of F accumulation in tea stands unclear. RNA-Seq and digital gene expression (DGE) techniques were used to investigate the effect of F on the differential expressions of transcriptome in tea plant. The results showed that F content in mature tea leaves was increased with increase in F concentration of cultural solution and duration of F treatment time. Based on comparison with data of GO, COG, KEGG and Nr databases, 144 differentially expressed unigenes with definite annotation were identified. Real-time reverse transcription PCR (qRT-PCR) was used to validate the effect of F on expression of 5 unigenes screened from the 144 unigenes. F treatment induced the expression of defense genes such as receptor-like kinases (RLKs) and U-box domain-containing protein. Based on the present study, F uptake is considered to be related to calcium-transporting ATPase, especially autoinhibited Ca2+ ATPase (ACAs) which was activated by the RLKs and worked as a carrier in uptake of F by tea plant.

[Synthesis and crystal structure of a porous coordination polymer [Nd2 (C6H8O4)3 (H2O)2]n x n (4,4'-bpy)].

A novel porous coordination polymer [Nd2 (C6H8O4)3 (H2O)2]n x n (4,4'-bpy) was synthesized by hydrothermal synthesis reaction of hexyl acid, 4,4'-bpy with NdCl3 x XH2O. The structure was characterized by elemental analysis, thermal gravimetric analysis, IR spectroscopy, and X-ray single crystal analysis. The crystal data are of an orthorhombic crystal system, Pbcn space group. Crystallographic data are: a = 2.201 2 nm(6), b = 0.777 8 nm(2), c = 1.972 4 nm(5), alpha = beta = gamma = 90 degrees, V = 337.70 nm(15)3, Z = 4, D(c) = 1.796 g x cm(-3), mu = 3.108 mm(-1), F(000) = 1 800, R = 0.043 0 and wR2 = 0.056 0. X-ray analysis reveals that three-dimensional porous nets were formed between Nd3+ and Nd3+ by carboxyl of hexyl acid.

[A Meta-analysis on Acupuncture Treatment of Attention Deficit/Hyperactivity Disorder].

OBJECTIVE: To assess the efficacy and safety of acupuncture in treating attention-deficit/hyperactivity disorder (ADHD) children. METHODS: A literature search was conducted to retrieve randomized cotrolled clinical trials of acupuncture in treating ADHD covering the period of the years of establishment of the databases to January 2014 from database of CBM, CNKI, PubMed, Cochrane Library by using key words "attention deficit hyperactivity disorder" "hyperactivity""minimal brain dysfunction" "acupuncture". Two independent researchers extracted data from located articles in a pre-defined structured way, and consulted the third researcher if necessary. RESULTS: Thirteen original trials including 1 304 cases of children with ADHD were obtained in this study according to our included criteria and excluded criteria. In these trials, acupuncture intervention alone, or acupuncture plus pharmacotherapy (methylphenidate, haloperidol) or acupuncture plus behavioral therapy were compared with simple pharmacotherapy or behavioral therapy alone. Results of Meta-analysis indicated that the total effective rate and Conners' index of hyperactivity (CIH) score-reduction rate in the acupuncture group were significantly superior to those of the other treatment groups [OR = 2.22, 95% CI (1.65, 3.00), Z = 5.22, P < 0.00001] [SMD = -0.94, 95% CI (-1.41, -0.47), Z = 3.89, P < 0.0001]. Acupuncture treatment is more effective than haloperidol in reducing the score of Conners' Rating Scale for ADHD [SMD = -7.28, 95% CI (-8.32, -6.23), Z = 13.62, P < 0.00001]. Acupuncture is similarly effective as Methylphenidate (Ritalin) in improving the Chinese medicine syndrome (liver-kidney yin hypoactivity) of children with ADHD [SMD = -1.14, 95% CI (-2.53, 0.25), Z = 1.60, P = 0.11]. Less severe adverse effects were reported with acupuncture therapy than the pharmacotherapy (poor appetite, dry mouth, nausea and constipation). These effects were not likely due to publication bias (approximately symmetry funnel plot, Egger's test P > 0.1). CONCLUSION: Acupuncture is an effective and safe therapy in treating ADHD, combined administration of acupuncture and pharmacotherapy or behavioral therapy is more effective than the pharmacotherapy or behavioral therapy alone. However, more rigorously designed and high-quality RCTs are needed to confirm the above conclusion.

[Solitary median maxillary central incisor syndrome:a case of report].

Solitary median maxillary central incisor (SMMCI) is a rare dental anomaly characterized by a symmetric central incisor of normal size, developed and erupted precisely in the midline of the maxilla in both primary and permanent dentitions. SMMCI may occur alone or be associated with other midline structures defects of the body or other systemic disorders. The best known association is holoprosencephaly (HPE). This paper reported a case of SMMCI that companied with other midline structures defects of the body.

[Effect of different orthodontic interproximal reduction methods on the enamel].

PURPOSE: To find a suitable interproximal enamel (IER) reduction method for clinical use by pH cycles in vitro. METHODS: 50 human premolars extracted for orthodontic reasons were collected for the experiment. After removal of the roots, the crowns were split vertically into two halves with wafer-thin wheel blade. Then the 100 samples were randomly divided into 5 groups, 20 samples for each group. The enamel in each group was reduced with different IER methods: group I, stripping strip; group II, stripping disk; group III, stripping strip with polishing system and 35% orthophosphoric acid; group IV, stripping disk with polishing system and 35% orthophosphoric acid; group V, no treatment control group. All the samples were treated with pH cycles in vitro for 30 days. The microhardness of enamel surface of all samples was detected by microhardness testing machine. The enamel surface morphology of microstructure was examined by scanning electron microscopy(SEM).The data was analyzed with SPSS13.0 software package. RESULTS: 1.ANOVA detected statistically significant differences between groups. The post SNK-q test showed that there was no significant difference between group I and group II, between group III and group IV(P>0.05); But there was significant difference between group I and group III, group I and group IV, group II and group III, group II and group IV(P<0.01). And there was significant difference between group I and group V, group II and group V, group III and group V, group IV and group V(P<0.05). 2.From naked eye and SEM, there was no distinct difference between the two chemical polishing groups, but better than the others. CONCLUSIONS: 1.There is no significant difference between strip and disk after IER. 2.Chemical polishing group is better than the others after IER. 3.The scratches of the enamel surface caused by IER are hardly repaired even after remineralization.

[Comparative study on the apical root resorption between self-ligating and conventional brackets in extraction patients].

PURPOSE: To explore whether orthodontic light force with self-ligating brackets can reduce the amount of external apical root resorption (EARR). METHODS: Thirty patients with Class I or II crowding malocclusion were selected. Four first premolars of all patients were extracted in orthodontic treatment. 15 patients were treated with self-ligating brackets (Damon 3MX) and 15 patients with conventional ligation brackets, respectively. Patients in two groups were comparable in gender, age, crowded degree and malocclusion classification at the commencement of treatment. EARR of the maxillary and mandible incisors was evaluated on panoramic radiographs and models taken before and after treatment, and measured in millimeters. Student's t test was performed using SPSS19.0 software package. RESULTS: Overall, no difference was found in the amount of EARR between the two groups. The amount of EARR in maxillary central incisor was (2.05±1.51) mm in Damon group and (2.08±1.21) mm in conventional group(P=0.973>0.05); (1.77±1.01) mm in maxillary lateral incisor in Damon group and (1.91±1.59) mm in conventional group(P=0.848>0.05); (2.06±1.62) mm in mandibular central incisor in Damon group and (1.98±1.50) mm in conventional group(P=0.926>0.05); (1.94±1.45) mm in mandibular lateral incisor in Damon group and (1.84±1.17) mm in conventional group(P=0.888>0.05). CONCLUSION: No difference should be expected for root resorption between self-ligating and conventional brackets in orthodontic extraction treatment.

Adsorption behavior of the catechins and caffeine onto polyvinylpolypyrrolidone.

Adsorbent is one of the most important factors for separation efficiency in fixed-bed purification techniques. The adsorption behavior of catechins and caffeine onto polyvinylpolypyrrolidone (PVPP) was investigated by static adsorption tests. The results showed that catechins rather than caffeine were preferred to adsorb onto PVPP since the adsorption selectivity coefficient of total catechins vs caffeine was around 22.5, and that adsorption of catechins could be described by the pseudo-second-order model. Adsorption amount of caffeine onto PVPP in green tea extracts solution was much higher than that in purified caffeine solution although the initial concentration of caffeine was similar in the two solutions, indicating the caffeine might be attached with catechins which were adsorbed by PVPP instead of being adsorbed by PVPP directly. The results also showed that the adsorption capacity of catechins and caffeine decreased with an increase in temperature, and that Freundlich and Langmuir models were both suitable for describing the isothermal adsorption of catechins, but not suitable for caffeine. The predicted maximum monolayer adsorption capacity of total catechins by PVPP was 671.77 mg g(-1) at 20 °C, which was significantly higher than that by other reported adsorbents. The thermodynamics analyses indicated that the adsorption of catechins onto PVPP was a spontaneous and exothermic physisorption process, revealing lower temperature was favorable for the adsorption of catechins. Elution tests showed that the desorption rates of catechins and caffeine were higher than 91% and 99% after two elution stages; in detail, almost all of the caffeine could be washed down at the water eluting stage, while catechins could be recovered at the dimethyl sulfoxide/ethanol solution eluting stage. Thus, the PVPP could be used as an excellent alternative adsorbent candidate for separating catechins from crude tea extracts, although some investigations, such as exploring the new eluants with low boiling point and high desorption efficiency, should be conducted furthermore.

Preparation of tea catechins using polyamide.

An adsorption separation method using Polyamide-6 (PA) as an adsorbent was developed to separate catechins from green tea extract. The adsorption capacity of total catechins for PA was 193.128 mg g⁻¹ with an adsorption selectivity coefficient K(A)(B) of total catechins over caffeine 21.717, which was better than macroporous resin model HPD 600. The Langmuir model and the pseudo-second order mode were primely fitted to describe its equilibrium data and adsorption kinetics, respectively. PA column separation by two-step elution using water and 80% (v/v) aqueous ethanol was established to prepare catechins complex which contained 670.808 mg g⁻¹ total catechins and 1.828 mg g⁻¹ caffeine. It is considered that PA was a promising adsorbent for selective isolation of catechins.

[Color changes induced by fluoride on nickel-titanium orthodontic wires].

OBJECTIVE: To observe the color changes of nickel-titanium (Ni-Ti) orthodontic wires induced by fluoride. METHODS: Each 40 samples of 4 kinds of nickel-titanium orthodontic wires (IMD, SL, TP, YY) were put into artificial saliva with sodium fluoride at different F concentrations (0.05%, 0.10%, 0.15%) and artificial saliva, separately. Dislodged the species and immersed them into artificial saliva with sodium fluoride for 3 minutes, then washed them with deionized water, and put back to artificial saliva, this course should be repeated 3 times per day. The whole immersion test lasted for 28 days. The color and micro-morphous changing were observed. RESULTS: The color changes came to be more serious as the F- concentration growing (P < 0.05). At the same F- concentration, the color changes of IMD and YY were higher than SL and YP (P < 0.01), while there were no significant difference between IMD and YY, SL and TP (P > 0.05). CONCLUSION: Fluoride can change the color of Ni-Ti wire. Different Ni-Ti wires get different changes at the same F- concentration.

[Changes in mastication efficiency before and after orthodontic treatment of adult skeletal angle III malocclusion].

PURPOSE: To evaluate the changes of mastication efficiency pre- and post-treatment in adult skeletal Angle III malocclusion, and to analyze the effect of malocclusion on mastication efficiency. METHODS: Masticatory efficiency was analyzed in 60 patients with adult skeletal Angle III malocclusion pre- or post-orthodontic treatment and 30 adults with normal occlusion as controls. Masticatory efficiency was measured by means of a spectrophotometer using Gelatin. SPSS 10.0 software package was used for Student's t test and step-wise regression. RESULTS: (1) Significant difference of masticatory efficiency was found among the three groups (P < 0.001). Multiple comparision showed significant difference among pre-treatment group, post-treatment group and normal controls (P < 0.05). (2) Step-wise regression results suggest that overjet and mandibular prognathism were closely related to masticatory efficiency in both pre- and post-treatment group. CONCLUSION: Orthodontic therapy can improve masticatory function in patients with malocclusion.

[Correlation analysis on the malocclusion and articulation of skeletal angle III malocclusion in mixed dentition].

OBJECTIVE: To investigate the effects of skeletal Class III malocclusion in mixed dentition on speech articulation and to look for which factors lead to the speech errors. METHODS: Thirty-eight children with skeletal Angle Ill malocclusion in mixed dentition were selected as a sample group and 40 children with normal occlusion in mixed dentition as a control group. Two phoneticians evaluated their articulations and wrote down error phonemes respectively. The correlation analysis was undertaken between the number of errors and the measurements of patients' cephalometry. RESULTS: The number of errors were correlated significantly with overbite, UI-LI, OBJ (OB+OJ) and TD-PW. CONCLUSION: There is articulatory malfunction in the majority of skeletal Angle III malocclusion patients in mixed dentition. Articulatory malfunction is related to the position of incisors and the tongue.

[Effect of bonding materials and methods on microleakage around the edge of stainless-steel brackets: an in vitro study].

PURPOSE: To observe and compare the effect of different types of adhesive materials and different types of etching methods on microleakage around bonded metal brackets. METHODS: 36 healthy premolars extracted for orthodontic reason were selected in the study. The samples were divided into three groups, 12 in each. Group A was etched with 37% phosphate and bonded with Jingjin adhesive; Group B was with 37% phosphate+3M Transbond; Group C was self-etching primer+3M Transbond. All samples were thermalcycled for 500 times, then put into 1% methylenum solution for 24 hours. Microleakage of samples was observed under stereomicroscope. Multiple comparison and Student t test were used for the comparison of data samples(alpha=0.05). RESULTS: (1) Significant difference of microleakage was found among three groups (F=22.462, P<0.01); Multiple comparison showed no significant difference between Group A and Group B (P>0.05), significant differences of microleakage were found between group A and C (P<0.05), group B and C (P<0.05), respectively. (2) Significant differences between occlusal microleakage and gingival microleakage were found in group A (P<0.05), group B (P<0.01) and group C (P<0.01), respectively. CONCLUSIONS: (1) The type of adhesive had no effect on microleakage. (2)Different etching methods are relevant to microleakage, the microleakage of self-etching groups is much more than that of phosphate-etching groups. (3) Gingival microleakage is significantly larger than occlusal microleakage.

[Influence of different porcelain surface treatment method on the bonding of metal brackets to porcelain].

OBJECTIVE: To investigate the influence of different porcelain surface treatment methods on the shear bond strength of metal brackets bonded to porcelain. METHODS: 80 porcelain facets were divided randomly into two groups according to different adhesive material that was used to bond metal brackets. Adhesive material were Jing-Jin enamel adhesive and light-cured composite resin. Each group was further divided into 4 subgroups according to different surface treatment methods, which were acid etching with 37% phosphoric acid (H3PO4), acid etching with 9.6% hydrofluoric acid (HF), deglazing by grinding and silanating the porcelain surface. All specimens were stored in 37 degrees C water for 24 hours and then the shear bond strength and the porcelain fracture after debonding was determined. The porcelain surfaces after HF etching, H3PO4 etching and deglazing by grinding were examined by scanning electron microscopy respectively. RESULTS: The shear bond strengths in the HF etching groups, the deglazing groups and the silanating groups were much greater than that in the phosphoric etching groups (P < 0.01). Adequate orthodontic bonding strength was achieved both when bonded with light-cured composite resin after deglazing by grinding and when bonded with either of these adhesives after HF etching or surface silanating. There were no differences in the rates of porcelain fractures among groups (P > 0.05). CONCLUSION: HF etching, deglazing by grinding and silanating can all increase the shear bond strength between metal bracket and porcelain. Surface silanating of porcelain is a better surface treatment when metal brackets bonded to porcelain.

[A statistic analysis on absence of third molar germs in orthodontic patients].

OBJECTIVE: To examine the absence of the third molar germs in orthodontic patients and to evaluate the relationship between third molar germs and malocclusion. METHODS: The subjects comprised 234 patients (male 92, female 142) from the orthodontic clinic whose ages were 14-18. The assessments of the third molar germs were made from panoramic radiographs, and the assessments of ANB angle were made from lateral cephalograms. All the data were analyzed by statistic chi2 test. RESULTS: The percentage of male who missed one or more third molar gems (37.0%) was higher than that of female (24.6%). There was no significant difference between the absent frequencies of third molar germs on left and right sides in either maxilla or mandible. The absent percentage of third molar germs in skeletal III subjects was higher than those in both skeletal class I and II subjects. The absent difference of third molar germs was in upper arches (P < 0.05), but not in lower arches (P > 0.05). There was no significant difference in absent percentage of third molar germs between skeletal class I and II subjects. CONCLUSION: Male patients have higher absent frequencies of third molar germs than female ones. Skeletal class III patients have higher absence of third molar germs in upper jaws than skeletal class I and II patients.

Toward understanding the different function of two types of parenchyma cells in bamboo culms.

The bamboo, woody monocot, has two types of parenchyma cells in the ground tissues of its culm, in contrast to a single type of parenchyma cell in rice, maize and other major crop species. The distribution of cell wall components, including lignin, (1-->3), (1-->4)-beta-D-glucans (MGs), the highly-substituted glucuronoarabinoxylans (hsGAXs) and low-branched xylans (lbXs) in ground parenchyma tissue of Phyllostachys heterocycla var. pubescens culms was studied at various developmental stages using light microscopy (LM), UV-microscopy, transmission electron microscopy (TEM) and immunolabeling techniques. The short parenchyma cell walls were lignified in 2-month-old bamboo culms just as the long parenchyma cell walls were. The lignified regions were confined to the portions in contact with the long parenchyma cell walls, while the walls at the cell corner region never lignified, even in 7-year-old culms. Significant differences were also found in the hemicellulose distribution between the short and long parenchyma cell walls. In bamboo parenchyma tissue, MGs were localized in short parenchyma cell walls and few were found in long parenchyma cell walls in both young and 7-year-old culms. The distribution of hsGAXs was similar to that of MGs in young culms, but they only appeared in the cell corner region of short parenchyma cells in old culms. Low-branched xylans were distributed in the lignified, but not in unlignified parenchyma cell walls. Based on this evidence, the differences of function in both short and long parenchyma cells in a bamboo culm are discussed.