Effects of different intrusion patterns during anterior teeth retraction using clear aligners in extraction cases: an iterative finite element analysis.

Background: Overtreatment design of clear aligner treatment (CAT) in extraction cases is currently primarily based on the clinical experience of orthodontists and is not supported by robust evidence on the underlying biomechanics. This study aimed to investigate the biomechanical effects of overtreatment strategies involving different maxillary anterior teeth intrusion patterns during anterior teeth retraction by CAT in extraction cases. Materials and methods: A finite element model of the maxillary dentition with the first premolar extracted was constructed. A loading method of clear aligners (CAs) based on the initial state field was proposed. The iterative method was used to simulate the long-term orthodontic tooth movement under the mechanical load exerted by the CAs. Three groups of CAs were utilized for anterior teeth retraction (G0: control group; G1: incisors intrusion group; G2: anterior teeth intrusion group). Tooth displacement and occlusal plane rotation tendency were analyzed. Results: In G0, CAT caused lingual tipping and extrusion of the incisors, distal tipping and extrusion of the canines, mesial tipping, and intrusion of the posterior teeth. In G1, the incisors showed minimal extrusion, whereas the canines showed increased extrusion and distal tipping tendency. G2 showed the smallest degree of posterior occlusal plane angle rotation, while the inclination tendency of the canines and second premolars decreased. Conclusion: 1. In CAT, tooth displacement tendency may change with increased wear time. 2. During anterior teeth retraction, the incisor intrusion pattern can provide effective vertical control for the lateral incisors but has little effect on the central incisors. Anterior teeth intrusion patterns can alleviate the inclination of canines and second premolars, resulting in partial relief of the roller-coaster effect.

Comparison of mandibular buccal shelf morphology between adolescents and adults with different vertical patterns using CBCT.

OBJECTIVE: This retrospective study aimed to analyze the anatomical structure of the mandibular buccal shelf (MBS) in adolescents and adults with different vertical patterns to determine the optimal location for miniscrew insertion in orthodontic treatment. METHODS: Cone-beam computed tomography (CBCT) scans of 230 patients were utilized for measurements. The morphology and thickness of alveolar bone at the MBS were measured. Two-way ANOVA and regression analysis were conducted to analyze the influencing factors on alveolar bone and cortical bone thickness. RESULTS: Age had a significant effect on alveolar bone thickness (level I: F = 62.449, level II: F = 18.86, p < 0.001), cortical bone thickness (level II: F = 18.86, p < 0.001), alveolar bone tilt (F = 6.267, p = 0.013), and second molar tilt (F = 6.693, p = 0.01). Different vertical patterns also influenced alveolar bone thickness (level I: F = 20.950, level II: F = 28.470, p < 0.001), cortical bone thickness (level I: F = 23.911, level II: F = 23.370, p < 0.001), and alveolar bone tilt (F = 27.046, p < 0.001). As age increased, the alveolar bone thickness at level I decreased by 0.096 mm and at level II decreased by 0.073 mm. Conversely, the thickness of alveolar bone at level I and level II increased by 0.06 mm and 0.075 mm, respectively. The cortical bone thickness at level I and level II increased by 0.024 mm and 0.29 mm, respectively. However, the alveolar bone thickness decreased by 0.931 mm and 1.545 mm at level I and level II, and the cortical bone thickness decreased by 0.542 mm and 0.640 mm at level I and level II, respectively. CONCLUSION: Age, different vertical patterns, alveolar bone inclination, and different shapes of MBS significantly affected the thickness of alveolar bone and cortical bone in the MBS area. Notably, only alveolar bone thickness and cortical bone thickness at level II were affected by age and different vertical patterns simultaneously. These findings can provide valuable insights for orthodontic practitioners in selecting the most suitable location for miniscrew insertion during treatment planning.

Geochemical Analysis of Dolomite in the Fourth Member of the Upper Sinian Dengying Formation, Northern Sichuan Basin, China.

The fourth member of the Sinian Dengying Formation in northern Sichuan was reformed by multistage diagenetic fluids. It is beneficial to systematically analyze the diagenetic evolution of the area to clarify the sedimentary evolution of the dolomite in the fourth member of the Dengying Formation and the fluid characteristics at different diagenetic stages. In this study, the petrological characteristics, vertical sedimentary evolution, diagenetic fluid stages, and diagenetic environment of Dengsi dolomite were analyzed by using carbon-oxygen strontium isotopes, rare-earth elements, major and trace elements, combined with the supporting thin section identification and cathodoluminescence techniques, and the source and properties of diagenetic fluid of Dengsi dolomite in different diagenetic environments were determined. The results show that (1) during the deposition period of the fourth member of the Dengying Formation, the water body showed a trend from shallow to deep and then steadily to shallow, which was in a shallow freshwater reducing environment and had a warm and humid paleoclimate environment; (2) the dolomite of the fourth member of Dengying Formation in northern Sichuan is less affected by terrigenous materials. The C and O isotopes of dolomite are generally negative at the top of the fourth member of the Dengying Formation, and the top of the formation is obviously transformed into rock by atmospheric fresh water; rare-earth elements show that dolomitized fluid is dominated by primitive seawater, and the marine fluid from or flowing through the carbonaceous shale formation rich in feldspar minerals in the Qiongzhusi formation during burial period makes the rare earth elements show obvious positive EU anomalies. The high 87Sr/86Sr ratio of the surrounding rock and cement is caused by the 87Sr-rich marine fluid coming from the fault communication or along the unconformity zone; (3) since the deposition of the dolomite of the fourth member of Dengshan formation in northern Sichuan, it has experienced multistage diagenesis. The multistage cement and fillings in the pores have recorded at least seven stages of fluid activity history: during the quasi-contemporaneous period, fresh water was transformed to increase pores, and seawater was cemented to damage pores. During the supergene period, the pore size of atmospheric freshwater increased generally; during the middle deep burial period, the acid fluid was reformed to increase the porosity, the 87Sr-rich hydrocarbon-bearing fluid was used to fill the damaged pores, and the Eu2+-rich marine source fluid was used to fill the damaged pores. In the deep burial period, siliceous hydrothermal fluid filled the damaged hole.

A novel directional-oriented method for predicting shear wave velocity through empirical rock physics relationship using geostatistics analysis.

This study attempts to design a novel direction-oriented approach for estimating shear wave velocity (VS) through geostatistical methods (GM) using density employing geophysical log data. The research area involves three hydrocarbon wells drilled in carbonate reservoirs that are comprised of oil and water. Firstly, VS was estimated using the four selected empirical rock physics relationships (ERR) in well A (target well), and then all results were evaluated by ten statistical benchmarks. All results show that the best ERR is Greenberg and Castagna, with R2 = 0.8104 and Correlation = 0.90, while Gardner's equation obtained the poorest results with R2 = 0.6766 and correlation = 0.82. Next, Gardner's method was improved through GM by employing Ordinary Kriging (OKr) in two directions in well A, and then Cross-Validation and Jack-knife methods (JKm and CVm, respectively) were used to assess OKr's performance and efficiency. Initially, CVm and JKm were employed to estimate Vs using the available density and its relationship with shear wave velocity, where the performance of CVm was better with R2 = 0.8865 and correlation = 0.94. In this step, some points from the original VS were used to train the data. Finally, Vs was estimated through JKm and using the relationship between the shear wave velocity of two wells near the target well, including wells B and C; however, in this step, the original shear wave velocity of the target well was completely ignored. Reading the results, JKm could show excellent performance with R2 = 0.8503 and Corr = 0.922. In contrast to previous studies that used only Correlation and R-squared (R2), this study further provides accurate results by employing a wide range of statistical benchmarks to investigate all results. In contrast to traditional empirical rock physics relationships, the developed direction-oriented technique demonstrated improved predicted accuracy and robustness in the investigated carbonate field. This work demonstrates that GM can effectively estimate Vs and has a significant potential to enhance VS estimation using density.

The short- and long-term changes of upper airway and alar in nongrowing patients treated with Mini-Implant Assisted Rapid Palatal Expansion (MARPE): a systematic review and meta-analysis.

OBJECTIVE: This study aims to assess the short- and long-term changes in the upper airway and alar width after mini-implant -assisted rapid palatal expansion (MARPE) in nongrowing patients. METHODS: Five electronic databases (PubMed, Scopus, Embase, Web of Science, and Cochrane Library) were searched up to 2 August, 2023 based on the PICOS principles. The main outcomes were classified into three groups: 1) nasal cavity changes, 2) upper airway changes and 3) alar changes. The mean difference (MD) and 95% confidence intervals (CI) were used to assess these changes. Heterogeneity tests, subgroup analyses, sensitivity analyses, and publication bias were also analyzed. RESULT: Overall, 22 articles were included for data analysis. Nasal cavity width (WMD: 2.05 mm; 95% CI: 1.10, 3.00) and nasal floor width (WMD: 2.13 mm; 95% CI: 1.16, 3.11) increased significantly. While palatopharyngeal volume (WMD: 0.29 cm3, 95% CI: -0.44, 1.01), glossopharyngeal volume (WMD: 0.30 cm3, 95% CI: -0.29, 0.89) and hypopharyngeal volume (WMD: -0.90 cm3; 95% CI: -1.86, 0.06) remained unchanged, nasal cavity volume (WMD: 1.24 cm3, 95% CI: 0.68, 1.81), nasopharyngeal volume (MD: 0.75 cm3, 95% CI: 0.44, 1.06), oropharyngeal volume (WMD: 0.61 cm3, 95% CI: 0.35, 0.87), and total volume of the upper airway (WMD: 1.67 cm3, 95% CI: 0.68, 2.66) increased significantly. Alar width (WMD: 1.47 mm; 95% CI: 0.40, 2.55) and alar base width (WMD: 1.54 mm; 95% CI: 1.21, 1.87) also increased. CONCLUSION: MARPE can increase nasal cavity width, nasal cavity volume, nasopharyngeal volume and oropharyngeal volume for nongrowing patients, but has no significant effect on hypopharyngeal volume. In addition, the alar width also increased. However, the studies included in this meta-analysis were mainly retrospective, nonrandomized and small in number, so the findings should be interpreted with caution and high-quality RCTs need to be studied.

Case report: Condylar metastasis from hepatocellular carcinoma: An uncommon case report and literature review.

Background: Patients with hepatocellular carcinoma are often affected by metastases, but condylar metastasis is particularly rare. Case presentation: A 51-year-old man with a history of hepatocellular carcinoma requested treatment for facial pain. Computed tomography indicated that the condylar bone has been destroyed and fractured. Pathology confirmed condylar metastasis from hepatocellular carcinoma. Complete metastasectomy and condylar reconstruction were performed to preserve his facial appearance. No local recurrence or distant metastasis was found at 8 months of follow-up. Conclusion: The condyle can be a metastatic site of hepatocellular carcinoma, regardless of its rarity. Long-term comprehensive surveillance and follow-up are needed for patients with hepatocellular carcinoma. The presence of solitary mass does exclude the possibility of metastatic cancer for these patients, and postoperative imaging and pathological diagnosis are important to determine its origin. If patients' physical condition permits, the mass can be completely excised, and the physiological function can be restored and reconstructed.

Comparison of the efficacy of different periodic periodontal scaling protocols for oral hygiene in adolescents with fixed orthodontic appliances: A prospective cohort study.

INTRODUCTION: The purpose of this reseach was to compare the effects of different periodic periodontal scaling protocols on the periodontal health of adolescents with fixed orthodontic appliances by assessing the aspartate aminotransferase (AST) and alkaline phosphatase (ALP) levels in gingival crevicular fluid and periodontal clinical indexes in a prospective cohort study. METHODS: Forty-eight adolescents were divided into 3 groups according to the interval of periodontal scaling (group A: once a month; group B: once every 3 months; group C: once every 6 months). The AST and ALP levels in the gingival crevicular fluid were measured before orthodontic treatment (T0) and at 1 (T1), 3 (T2), 6 (T3), and 9 (T4) months during orthodontic treatment. Periodontal clinical indexes (plaque index [PI], gingival index [GI], and probing depth) were also assessed. RESULTS: At T2, significantly lower AST and ALP levels were observed in group A than in groups B and C (P <0.05). At T3 and T4, lower AST and ALP levels were detected in groups A and B than in group C (P <0.05), and there was no significant difference between the A and B groups at T4 (P >0.05). At T2, the PI and GI were increased in groups B and C compared with group A, and at T3 and T4, significantly lower PI and GI values were observed in groups A and B than in group C (P <0.05). CONCLUSIONS: Periodontal scaling promotes the oral hygiene of adolescents undergoing fixed orthodontic treatment, and periodontal scaling protocols administered monthly and once every 3 months are better for controlling periodontal health than treatments administered once every 6 months.

Relationship between dental calcification of mandibular teeth and cervical vertebrae maturity in patients with unilateral complete cleft lip and palate.

OBJECTIVE: The purpose of this study was to investigate the relationship between the dental calcification stage (DCS) of the mandibular teeth and the cervical vertebral maturation stage (CVMS) in patients with unilateral complete cleft lip and palate (UCLP). METHODS: One hundred sixty-two UCLP patients (100 males and 62 females) between 8-16 years old were included in this study. The DCS was estimated by the Demirjian method and was converted to the dental age (DA). The CVMS was evaluated by the Baccetti method. The DA of mandibular teeth on two sides of the cleft were analyzed using a t-test. Spearman correlation was used to study the association between CVMS and DCS. The correlation coefficient between the two sides of the cleft was then compared. RESULTS: The total DA was significantly smaller on the cleft side than on the noncleft side in males (p = 0.022). The Spearman rank correlation coefficient revealed a significant correlation between the DCS of each examined tooth and the CVMS (r = 0.627-0.793 in males and r = 0.806-0.899 in females). Additionally, the correlation of the two sides was not significantly different (p > 0.05). The DCS of the first premolar showed the strongest correlation with the CVMS. CONCLUSION: The results confirm the utility of the DCS on both sides of the mandible in male UCLP patients as a simple first-level diagnostic test to evaluate growth and development. The findings also indicate that both the DCS and the CVMS should be assessed if the maturity stage of a growing UCLP patient is relevant to clinical practice.

[The symmetry of nasal maxillary complex of patients with unilateral complete cleft lip and palate at the stage of mixed dentition-A cone beam CT study].

PURPOSE: To investigate the symmetry of nasal maxillary complex in the three-dimensional directions of patients with unilateral complete cleft lip and palate(UCLP) at the stage of mixed dentition. METHODS: Craniofacial cone-beam CT(CBCT) images of 20 UCLP patients at the stage of mixed dentition were selected. Three-dimensional reconstruction of bone tissue was carried out by Mimics software, nasal root point and 32 markers with the same name of the healthy side and the cleft side of the nasal maxillary complex were traced, three-dimensional reference planes were set up, then the distances between the points to the three-dimensional planes were measured respectively. SPSS 22.0 software package was used to analyze the data. RESULTS: In the horizontal direction, compared with the non-cleft side, the width of the cleft side of the maxilla at INM and SPC was smaller, the width of maxilla at LPA and SPr was larger, the differences were statistically significant (P<0.05). In the sagittal direction, compared with the non-cleft side, the depth of LPA, Maz and SPr at the cleft side was larger, the depth of SPM and SPC was smaller, the differences were statistically significant (P<0.05).In the vertical direction, the positions of LPA, INM and Maz at the cleft side was lower than the non-cleft side, SPC and SPr were higher, the differences were statistically significant(P<0.05). The remaining points had no significant difference (P>0.05). CONCLUSIONS: The nasal maxillary complex of UCLP patients at the stage of mixed dentition is asymmetric in three directions. The asymmetric locations were mainly located in the nasal cavity and alveolar bone. No obvious asymmetry is found in the orbital region and the maxillary region far from the cleft.

Interleukin-8/ß-catenin mediates epithelial-mesenchymal transition in ameloblastoma.

OBJECTIVE: Epithelial-mesenchymal transition (EMT) is important in the tooth development and tumor invasion. We investigated the effect of interleukin-8 (IL-8) on the EMT process in primary-cultured ameloblastoma tumor cells (AM-P) and ameloblastoma immortalized tumor cells (AM-L) and its underlying mechanism. METHODS: IL-8 levels in ameloblastomas were detected by immunofluorescence staining and ELISA. AM-P cells and AM-L cells were stimulated with IL-8, and EMT transcription factors, total ß-catenin and phosphorylated-ß-catenin (p-ß-catenin) levels were determined by Western blot analysis and immunofluorescence staining. ß-catenin siRNA was used to knockdown ß-catenin expression in AM-P cells and AM-L cells stimulated with IL-8. RESULTS: IL-8 was highly expressed in the solid ameloblastomas. IL-8 promoted the EMT process in ameloblastoma tumor cells in vitro, as evidenced by decreased E-cadherin and increased vimentin, twist and zeb1 levels. IL-8 also increased total ß-catenin and p-ß-catenin expression in ameloblastoma tumor cells, and ß-catenin knockdown partially inhibited the EMT process in tumor cells, as evidenced by increased E-cadherin, and decreased vimentin and zeb1 levels. CONCLUSIONS: IL-8 could promote EMT in ameloblastoma tumor cells by activating ß-catenin and its downstream transcription factor zeb1.

[Association between cervical vertebral maturation stages and dental calcification stages in patients with unilateral complete cleft lip and palate].

OBJECTIVE: The purpose of the study is to investigate the relationship between dental calcification stages (DCS) and cervical vertebral maturation stages (CVMS) in patients with unilateral complete cleft lips and palates (UCLP) and to provide a theoretical basis for the treatment time selection of cleft lip and palate (CLP) patients. METHODS: A total of 123 UCLP patients and 215 non-CLP subjects were selected. The DCS of the left mandibular canine, premolar, and second molar in non-CLP subjects and on both cleft sides of UCLP patients were assessed utilizing the Demirjian method. CVMS was observed utilizing the Baccetti method. The results were analyzed by Spearman rank correlation, and the correlation coefficients were compared. RESULTS: There was a correlation between the CVMS and the DCS of the left mandibular canine, the first premolar, the second premolar, and the second molar in the non-CLP subjects and on both cleft sides of the UCLP patients (r=0.762-0.864, P<0.05; r=0.809-0.914, P<0.05, respectively). The correlation between the CVMS and the DCS of the mandibular first premolar was highest among the UCLP patients. Except for the first and the second premolars of UCLP females, the correlation between the DCS and the CVMS of the other teeth did not differ among the non-CLP subjects (P>0.05). CONCLUSIONS: DCS can be utilized as a biological index to determine the growth development statuses. The correlation between the CVMS and the DCS of the mandibular first premolar was the highest.

Stretching magnitude-dependent inactivation of AKT by ROS led to enhanced p53 mitochondrial translocation and myoblast apoptosis.

Previously, we had shown that high magnitude stretch (HMS), rather than low magnitude stretch (LMS), induced significant apoptosis of skeletal muscle C2C12 myoblasts. However, the molecular mechanism remains obscure. In this study, we found that p53 protein accumulated in the nucleus of LMS-loaded cells, whereas it translocated into mitochondria of HMS-loaded cells. Knocking down endogenous p53 by shRNA abrogated HMS-induced apoptosis. Furthermore, we demonstrated that overaccumulation of reactive oxygen species (ROS) during HMS-inactivated AKT that was activated in LMS-treated cells, which accounted for the distinct p53 subcellular localizations under HMS and LMS. Blocking ROS generation by N-acetylcysteine (NAC) or overexpressing constitutively active AKT vector (CA-AKT) inhibited HMS-incurred p53 mitochondrial translocation and promoted its nuclear targeting. Moreover, both NAC and CA-AKT significantly attenuated HMS-induced C2C12 apoptosis. Finally, we found that Ser389 phosphorylation of p53 was a downstream event of ROS-inactivated AKT pathway, which was critical to p53 mitochondrial trafficking during HMS stimuli. Transfecting p53-shRNA C2C12s with the mutant p53 (S389A) that was unable to target p53 to mitochondria underwent significantly lower apoptosis than transfection with wild-type p53. Altogether, our study uncovered that mitochondrial localization of p53, resulting from p53 Ser389 phosphorylation through ROS-inactivated AKT pathway, prompted C2C12 myoblast apoptosis during HMS stimulation.

Intermittent Stretching and Osteogenic Differentiation of Bone Marrow Derived Mesenchymal Stem Cells via the p38MAPK-Osterix Signaling Pathway.

AIMS: The relationship between the p38MAPK signaling pathway and osterix in osteogenic differentiation of BMMSCs subjected to intermittent stretching was investigated. METHODS: BMMSCs derived from C57BL/6J mice were divided into the following groups: 1) control, 2) stretch, and 3) SB203580+stretch (SB203580 is a p38MAPK signal pathway inhibitor). BMMSCs were exposed to an intermittent mechanical strain of 0.8% (8000µ strain) at 0.5 Hz, twice a day for 30 min each application. BMMSCs were harvested on days 1, 3, and 5 post-treatment. The expression of ALP, COL I, OCN, and osterix mRNA was assessed utilizing RT-PCR while the expression of P-p38MAPK and osterix protein was assessed by Western blot analysis. The osterix gene in mouse BMMSCs was knocked down using RNAi technology and its protein expression was also assessed by Western blot. RT-PCR was used to detect ALP, COL I, and OCN mRNA expression. RESULTS: Intermittent stretching was found to promote expression of ALP, COL I, OCN, and osterix mRNA. Silencing the osterix gene was found to reduce levels of ALP, COL I, and OCN mRNA. Western blot analysis demonstrated that the levels of osterix and P-p38MAPK proteins in the stretch group were significantly higher than in the control group (P<0.05). There was less expression of ALP, COL I, OCN, and osterix mRNA in the SB203580+stretch group than in the control and stretch groups. CONCLUSIONS: Data demonstrate that intermittent stretching promotes osteogenic differentiation of BMMSCs, and the p38MAPK-osterix pathway has an important role in the control of osteogenesis-related gene expression.

[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.

[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.

[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.

[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.

Genetically modified cotton and farmers' health in China.

This study provides the first evidence of a direct link between the adoption of a genetically modified (GM) crop and improvements in human health. Estimation of the impact of Bacillus thuringiensis (Bt) cotton adoption on pesticide use from data from a survey of cotton farmers in northern China, 1999-2001, showed that Bt cotton adoption reduced pesticide use. Assessment of a health-production function showed that predicted pesticide use had a positive impact on poisoning incidence. Taken together, these results indicate that the adoption of Bt cotton can substantially reduce the risk and the incidence of poisonings.

[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.