The effects of increasing occlusal vertical dimension on the deep masseter of rat at different ages.

OBJECTIVE: To investigate the influence of increasing the occlusal vertical dimension (iOVD) on the fibre-type distribution and ultrastructure of deep masseter of rat at different ages. DESIGN: A total of forty-eight male Wistar rats were divided into two groups according to age: 'teenage' group (n=24, 1.5 months) and 'young adult' group (n=24, 8 months). Both the teenage and the young adult rats were then randomly divided into the control group (n=12) and the experimental group (n=12). The occlusal vertical dimensions of the rats in the experimental groups were increased by placing composite resin on all maxillary molars. The fibre-type distribution and ultrastructure of the deep masseter were subsequently observed on day 7 and day 14 after iOVD. RESULTS: In the teenage experimental group, the proportion of type IIa fibres increased, while the proportion of type IIb and type IIx fibres decreased by day 7 after iOVD (P<0.05). However, no significant fibre phenotype transformation was observed in the young adult experimental group until day 14 after iOVD. In addition, the proportion of type IIa in the teenage experimental group was higher than that of the young adult experimental group on day 7 and 14 (P<0.05). Under the transmission electron microscope, muscle fibre reconstruction and the compensatory increase in the number and volume of mitochondria appeared earlier in the teenage experimental group. The cellular traumatic reaction was less than that in the young adult experimental group. CONCLUSION: The teenage rat alters masseter muscle structure to a slower phenotype earlier and to a greater degree than that of the young adult rat when increasing the occlusal vertical dimension.

Effects of a mandibular advancement device on genioglossus in obstructive sleep apnoea hypopnea syndrome.

OBJECTIVE: To investigate effects of mandibular advancement device (MAD) therapy for obstructive sleep apnoea hypopnea syndrome (OSAHS) on the genioglossus contractile properties and fibre-type distribution. MATERIALS AND METHODS: Thirty 6-month old male New Zealand white rabbits were randomised into three groups: OSAHS, MAD, and controls. Rabbits in Group OSAHS and Group MAD were established as OSAHS models by injection, at a dose of 2 ml hydrophilic polyacrylamide gel, via the submucous muscular layer of soft palate. Spiral computed tomography (CT) showed a significant reduced retropalatal upper airway, and apnoeas happened with an increase of Apnea Hypopnea Index (AHI) and a decrease of blood oxygen saturation during polysomnography (PSG), which indicated the OSAHS model developed successfully. OSAHS rabbits in Group MAD were fitted with a MAD made from self-curing composite resin, at 30 degrees to the upper incisors, and the mandible was guided forward 3 to 4mm. Further, spiral CT and PSG suggested MAD was effective. Rabbits in 3 groups were induced to sleep for 4-6 hours per day for 8 weeks, after which the genioglossus was removed, mounted in a tissue bath, and stimulated through platinum electrodes; maximal twitch tension, contraction time, half-relaxation time, force-frequency relationship, and fatigability were recorded. The percentage of Type I and Type II fibres was quantified. RESULTS: The fatigability and percentage of Type II fibres of genioglossus increased in Group OSAHS compared with controls; this abnormality was corrected by MAD. CONCLUSION: MAD therapy for OSAHS could prevent genioglossus fatigue and abnormal fibre-type distribution of genioglossus in OSAHS.

[Establishment of the craniofacial three-dimensional finite element models with the sutures defined alone].

OBJECTIVE: To develop a child craniofacial three-dimensional (3D) finite element model (FEM) with sutures defined alone. METHODS: The CT data for this study was developed from sequential computed tomography scan images taken at 0.625 mm intervals of an 8 years children skull. Data set was imported into Mimics 10.0 and processed with Geomagic 9.0, and exported as initial graphics exchange specification(IGES) files. The IGES files were then imported into Ansys 13.0 to set up two FEM with or without the median palatine suture being opened. The FEM contained nine craniofacial sutures and eight teeth which were defined alone.For simulating orthopedic maxillary protraction, three forces (F1-F2) were loaded on FEM.F1(1 N) was loaded at 1 cm above the geison. F2(1 N) was loaded at articular fossa of temporal bone. F3(2 N) was directed anteriorly and paralleled with occlusal plane near the canine. The stress distribution and the values distributed in each point gained in the two models were compared. RESULTS: Two craniofacial 3D FEM of the child were developed with the median palatine suture opened or not .With median palatine suture being opened or not, the two models showed the similar von Mises stresses (VMS). The distribution of the VMS was in the bridge of the nose and dextro-ala nasi.When the median palatine suture was opened, the max VMS value was 18916.00×10(-4) MPa which appeared in the nose point and the min VMS value was 1.61×10(-4) MPa which appeared in the maxillary central incisor point. At the same time, the max stress value at the direction Y was -3985.30×10(-4) MPa and appeared in the frontomaxillary suture point, and the min Y value was 0.08×10(-4) MPa which appeared in the maxillary central incisor point. When the median palatine suture was not opened, the max VMS value was 19 244.00×10(-4) MPa and appeared in the nose point. The min VMS value was 1.62×10(-4) MPa and appeared in the maxillary central incisor point. At the same time, the max stress value at the direction Y was -4258.20×10(-4) MPa and appeared in the frontomaxillary suture point, and the min Y value was 0.08×10(-4) MPa which appeared in the maxillary central incisor point. CONCLUSIONS: To define the sutures as entities alone contributed to develop child craniofacial 3D FEM which consist nine sutures. There was tiny difference in stress distribution in both the VMS and in Y direction with the median palatine suture being opened or not.

[Effect of maxillary protraction with or without rapid palatal expansion in treating early skeletal Class III malocclusion].

OBJECTIVE: To evaluate the effectiveness of treatment with maxillary protraction with or without rapid palatal expansion (RPE) for skeletal Class III malocclusion in mixed dentition. METHODS: A total of 31 children with Class III malocclusion in mixed dentition were selected, and 15 (group A) received maxillary protraction treatment with RPE, the other 16 (group B) received maxillary protraction without RPE. Cephalometric films were taken before and after treatment, and traditional and Pancherz analysis were used. RESULTS: The average duration of treatment was 10.14 months in group A and 9.77 months in group B respectively (P>0.05). According to Pancherz analysis, maxillary basal bone moved forwards by 2.99 mm in group A and 3.33 mm in group B respectively (P>0.05), mandibular basal bone moved backwards by 0.07 mm in group A, while forwards by 0.80 mm in group B (P>0.05), the overjet increased by 4.51 mm in group A and 6.37 mm in group B respectively (P<0.05), and the molar relationship improved by 4.97 mm in group A and 4.73 mm in group B respectively (P>0.05). The effects were clinically satisfactory in the both groups. Lower molar moved forwards by 1.18 mm in basal bone in group A, while backwards by 1.20 mm in group B (P<0.05). Traditional cephalometric analysis showed no statistic differences between the two groups except that upper incisior showed greater procline in group B than in group A (P<0.05). CONCLUSION: The study shows that maxillary protraction treatment, with or without RPE, is clinically satisfactory to correct early skeletal Class III malocclusion.

[Fluorescence quenching assay of ultratrace horseradish peroxidase using rhodamine dye].

In acetate buffer solution, the reaction of H2O2 with KI was catalyzed by horseradish peroxidase (HRP) to form I3-. The I3- combined respectively with rhodamine S(RhS), rhodamine 6G(Rh6G), rhodamine B(RhB) and butyl-rhodamine B(b-RhB) to form RhS-I3, Rh6G-I3, RhB-I3 and b-RhB-I3 association particles, resulting in the fluorescence quenching at 580, 580, 554 and 554 nm, respectively. The effect of pH value, rhodamine dye concentration, KI concentration, H2O2 concentration, reaction temperature and time on the fluorescence quenching intensity (deltaF) of the four catalytic systems was considered respectively. For the RhS, Rh6G, RhB and b-RhB catalytic systems, pH 4.6-3.2 x 10(-5) mol x L(-1) RhS-4 x 10(-3) mol x L(-1) KI-1.30 x 10(-5) mol x L(-1) H2O2-25 degrees C-20 min, 4.8-2.4 x 10(-5) mol x L(-1) Rh6G-4 x 10(-3) mol x L(-1) KI-2.59 x 10(-5) mol x L(-1) H2O2-25 degrees C-20 min, 4.6-1.6 x 10(-5) mol x L(-1) RhB-4 x 10(-3) mol x L(-1) KI-2.16 x 10(-5) mol x L(-1) H2O2-25 degrees C-20 min, and 4.6-1.6 x 10(-5) mol x L(-1) b-RhB-4 X 10(-3) mol x L(-1) KI-3.02 x 10(-5) mol x L(-1) H2O2-25 degrees C-20 min were chosen for use respectively. Under the optimal conditions, the HRP linear range was 8-6 400 pg x mL(-1) for the RhS catalytic system, 40-4 000 pg x mL(-1) for the Rh6G catalytic system, 32-3 200 pg x mL(-1) for the RhB catalytic system and 40-6 400 pg x mL(-1) for the b-RhB catalytic system, with a detection limit of 3.2, 3.0, 2.4 and 3.7 pg x mL(-1) HRP, respectively. The regress equation of the four catalytic systems was deltaF = 0.061 1c+39.6, deltaF = 0.047 2c+50.4, deltaF = 0.138 6c+34.2 and deltaF = 0.026 25c+36.72, with a correlation coefficient of 0.997 9, 0.999 0, 0.997 3 and 0.996 9, respectively. The RhS catalytic system was most sensitive, and was chosen for the determination of HRP. The influence of foreign substance on the RhS assay of 3.5 ng x mL(-1) HRP was examined, with a relative error of +/- 10%. A 3000-times L-glutamic acid, L-lysine, Ca2+, Mg2+, Cu2+, Fe3+, Zn2+ and vitamin B6, 1000-times HAS etc did not interfere with the assay. This showed that the assay has good selectivity. The RhS fluorescence quenching assay was applied to the determination of HRP in the solution of hepatitis B surface antibody labeling HRP, with satisfactory results.

[Immune resonance scattering spectral analysis of fenvalerate].

In the pH 7.2 Na2HPO4-NaH2PO4 buffer solutions and in the presence of PEG-6000, fenvalerate (Fen) antisera was combined with Fen specifically, and aggregated to form immune complex particles that exhibited five resonance scattering peaks at 350, 390, 420, 440 and 480 nm respectively. The peak at 390 nm was the strongest and was chosen for use. Fen concentration (c) in the range of 0.20 to 6.40 microg x mL(-1) was proportional to the resonance scattering intensity at 390 nm. Its regression equation was DeltaIRS 23.05c-1.39, the correlation coefficient was 0.9978, and the detection limit was 0.07 microg x mL(-1). Effects of buffer solution type, pH value, buffer solution volume, fenvalerate antisera concentration, PEG-6000 concentration, incubation temperature and time on the resonance scattering intensity were considered in detail. With pH (5.8-8.0) increasing, the IRS and Ib all decreased. When the pH value was at 7.2, the DeltaIRS was bigger. Three buffer solutions of pH 7.2, including Na2HPO4-citric acid, Na2HPO4-KH2PO4 and Na2HPO4-NaH2PO4, were examined. The pH 7.2 Na2HPO4-NaH2PO4 buffer solution gives the biggest DeltaIRS value. PEG-6000 could enhance the DeltaIRS value. When the concentration of PEG-6000 was 50.0 mg x mL(-1), the DeltaIRS was achieved at max. Fen was a stable chemical. The IRS increased within 20 min,while the DeltaIRS remained constant when incubation time was in the range of 20-40 min. The condition of a pH 7.2 Na2HPO4-NaH2PO4 buffer solution-50.0 mg x mL(-1) PEG-6000-6.67 microg x mL(-1) Fen antisera-30 degrees C-incubation time 20 min was chosen. According to the procedure, the influence of foreign substances on the determination of 1.60 microg x mL(-1) Fen was examined, within a relative error of +/- 5%. Results showed that the following coexistent substances had no impact on the RS assay: 96 microg x mL(-1) ametryne, 96 microg x mL(-1) m-aminotoluene, 48 microg x mL(-1) simetryne, 48 microg x mL(-1) p-aminotoluene,80 microg x mL(-1) BSA, 80 microg x mL(-1) HSA, 80 microg x mL(-1) Fe3+, 80 microg x mL(-1) Mg2+, 160 microg x mL(-1) Ca2+, and 160 microg x mL(-1) glucose. The results indicated that this RSS assay has good selectivity. This immune resonance scattering spectral assay was applied to the determination of Fen in waste water samples with satisfactory results. The recovery was in the range of 92.91%-101.25%, and the relative standard deviation was in the range of 1.71%-4.80%.

[Rapid canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance].

OBJECTIVE: To investigate the effect of rapid canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance. METHODS: Twenty canines in 11 patients who needed first premolar extractions were involved. A tooth-borne, custom-made distractor was bonded right after the first premolar extraction and the interseptal bone resistance reduction. Three days post-operatively, the distractor was activated 0.1 mm three times a day. Orthodontic models, panoramic radiographs, periapical radiographs, electrical vitality test were assessed pre- and post distraction procedure and 3 months after the completion of the procedure. RESULTS: The distraction procedure was completed in 18 to 35 days [mean (25.6 +/- 4.7) days], with the distal displacement of the canines ranging from 3.53 to 8.29 mm [mean (5.56 +/- 1.32) mm]. The canines showed a mean of 12.20 degrees distal tipping and 18.53 degrees rotation. The anchorage teeth showed an average of (0.76 +/- 0.75) mm mesial movement. The mesial contact point of incisors showed a mean of (0.67 +/- 0.55) mm lingual movement. There was no significant root resorption or long-time change on pulp vitality after distraction. CONCLUSIONS: The canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance was an effective approach to move canines rapidly.

[Study on effect of snore guard to upper airway structure of normal occlusion people by magnetic resonance imaging].

OBJECTIVE: To investigate the imagery changes of the upper airway and the surrounding soft tissues of local adults with non-apnea who used snore guard and to provide experimental data for the clinical diagnosis and treatment of obstructive sleep apnea syndrome (OSAS). METHODS: Thirty students with non-apnea from Hebei medical university were chosen, and magnetic resonance imaging (MRI) was used to measure the changes of the upper airway and the surrounding soft tissues after snore guards were used. SPSS 105 software was used to analyze statistically. RESULTS: After the snore guard was put into oral cavity, the change of the average section and volume of the nasopharynx, the palatopharynx, the hypopharynx and the glossopharynx were statistically significant. The average sagittal size, the average horizontal size of the nasopharynx, the palatopharynx, the hypopharynx and the glossopharynx were increased statistically. The ratio of sagittal size, the horizontal sizand the in the hypopharynx and the glossopharynx changed statistically important. There was a decrease of the soft palate, the shape, the height, and the length of the tongue, the difference was statistically significant. The results demonstrated that snore guard affected the upper airway mainly by changing the volume and the shape of the upper airway, there was an obvious increase of the pharynx. The results also showed that snore guard could increase the width (both sagittal and horizontal) of the upper airway and could change the shape of the surrounding soft tissues, which caused air way more smooth. Snore guard could make the indexes of soft palate and tongue change decreasingly, resulted in the straight stand up of the tongue and the forwardness of the soft palate. CONCLUSION: Snore guard is an effective and convenient instrument for treating the patients with OSAS.

[Effect of early treatment with the Twin-block appliance].

OBJECTIVE: To evaluate the effectiveness of early treatment with the Twin-block appliance for the developing Class II division 1 malocclusion. METHODS: A Total of 30 children with Class II division 1 malocclusion, 18 (8 male, 10 female) out of which received treatment with the Twin-block appliance, the other 12 cases (6 male, 6 female) without treatment served as control group. Cephalometric data were collected at the start and the end of the study and statistical analysis were applied. RESULTS: Except the factor of growth, treatment with the Twin-block appliance resulted in reduction of ANB (1.55 degrees), overjet (5.46 mm) and correction of molar relationship (4.07 mm). These changes were due to the change of Pg/OLp, Co/OLp and mandibular length. The change of A/OLp was not significant. The skeletal effect contributing to the change on overjet and molar relation were 58% and 78% respectively. CONCLUSION: Early treatment with the Twin-block appliance was effective in reducing ANB angle, overjet and correction of molar relationship. The changes were mainly profit from the favorable skeletal change of mandible, especially from its length, while the effect on maxillary was not significant.