Is motor-driven insertion of orthodontic miniscrews more advantageous than manual insertion? A micro-CT evaluation of bone miniscrew contact surface area and cortical microcracks in rabbits.

AIM: This in vitro study aimed to evaluate and compare the bone-miniscrew contact surface area (BMC) and the cortical bone microcracks (CM) resulting from manual (hand-driven) and automated (motor-driven) orthodontic miniscrew (OM) insertion methods. METHODS: Thirty-three OM were inserted in the femurs of nine New Zealand rabbits using manual (n = 16) and automated (n = 17) insertions. After euthanizing the rabbits, bone blocks, each including one OM, were sawed. Micro-CT scanning was performed, and data analysis included reconstruction, binarization and quantification of morphometric parameters of BMC and the number and length of CM. Means and standard deviations for complete BMC, complete BMC proportion, cortical BMC, cortical BMC proportion, and length and number of CM were calculated. Mixed model analysis was used to adjust for more than one sample/CM per animal. A paired t-test was used to compare the number of CM between the two groups. RESULTS: Compared to the automated insertion, manually inserted miniscrews had significantly lower complete BMC (7.54 ± 1.80 mm2 vs. 11.99 ± 3.64 mm2), cortical BMC (5.91 ± 1.48 mm2 vs. 8.48 ± 1.90 mm2) and cortical BMC proportion (79.44 ± 5.84% vs. 87.94 ± 3.66%). However, it was not statistically significant in complete BMC proportion (p = .052). The automated insertion also resulted in a significantly lower mean number of CM than the manual method (p = .012). However, the length of the cracks was shorter in the manual group but with no significant difference (p = 0.256). CONCLUSION: Motor-driven OM insertion results in superior BMC and reduction in the number of CM, which may lead to better miniscrew stability.

Effect of the Sauvé-Kapandji method on the wrist contact surface for distal radial ulnar joint disorders.

BACKGROUND: The Sauvé-Kapandji (S-K) method is a surgical procedure performed for chronic deformities of the distal radial ulnar joint (DRUJ). Changes to the joint contact surface from pre- to postoperatively under physiological in vivo conditions have not yet been determined for this useful treatment. The aim of the present study was therefore to compare the articular contact area of the wrist joint between before and after the S-K method for DRUJ disorders. METHODS: The SK method was performed for 15 patients with DRUJ osteoarthritis and ulnar impaction syndrome. We calculated the Mayo Wrist Score as the patient's clinical findings and created 3-dimensional bone models of cases in which the S-K method was performed and calculated the contact area and shift in the center of the contact area using customized software. RESULTS: The Mean modified Mayo Wrist Score improved significantly from 60.3 preoperatively to 80.3 postoperatively (P < 0.01). Scaphoid contact area to the radius increased significantly from 112.6 ± 37.0 mm2 preoperatively to 127.5 ± 27.8 mm2 postoperatively (P = 0.03). Lunate contact area to radius-ulna was 121.3 ± 43.3 mm2 preoperatively and 112.5 ± 37.6 mm2 postoperatively, but this decrease was not significant (P = 0.38). Contact area ratio of scaphoid to lunate increased significantly from 1.01 ± 0.4 preoperatively to 1.20 ± 0.3 postoperatively (P = 0.02). Postoperative translations of the center of the scaphoid and lunate contact areas were decomposed into ulnar and proximal directions. Ulnar and proximal translation distances of the scaphoid contact area were 0.8 ± 1.7 mm and 0.4 ± 0.6 mm, respectively, and those of the lunate contact area were 1.1 ± 1.7 mm and 0.4 ± 1.1 mm, respectively. This study revealed changes in wrist contact area and center of the contact area before and after the S-K method. CONCLUSION: These results may accurately indicate changes in wrist joint contact area from pre- to postoperatively using the S-K method for patients with DRUJ disorder. Evaluation of changes in contact area due to bone surface modeling of the wrist joint using 3DCT images may be useful in considering surgical methods.

Evaluation of bone contact area and intercondylar distance changes in orthognathic surgery - a comparison between BSSO and HSSO technique depending on mandibular displacement extent.

OBJECTIVES: The present study aims to assess the impact of bilateral and high oblique sagittal split osteotomy (BSSO/HSSO), as well as displacement distances and directions on the expected and achievable bone contact area (BCA) and changes in the intercondylar distance (ICD). The primary question addressed is whether mandibular splitting through BSSO results in a greater BCA and/or ICD when compared to splitting through HSSO. MATERIALS AND METHODS: Totally 80 mandibular displacements were performed on 20 fresh cadavers, for each subject, four splints were produces to facilitate mandibular advancement as well as setbacks of 4 and 8 mm. Pre- and postoperative CBCT scans were performed to plan the surgical procedures and to analyze the expected and achieved BCA and ICD. RESULTS: Regarding the maximum mandibular displacement, the expected BCA for HSSO/BSSO were 352.58 ± 96.55mm2 and 1164.00 ± 295.50mm2, respectively, after advancement and 349.11 ± 98.42mm2 and 1344.70 ± 287.23mm2, respectively, after setback. The achieved BCA for HSSO/BSSO were 229.37 ± 75.90mm2 and 391.38 ± 189.01mm2, respectively, after advancement and 278.03 ± 97.65mm2 and 413.52 ± 169.52 mm2, respectively after setback. The expected ICD for HSSO/BSSO were 4.51 ± 0.73 mm and 3.25 ± 1.17 mm after advancement and - 5.76 ± 1.07 mm and - 4.28 ± 1.58 mm after setback. The achieved ICD for HSSO/BSSO were 2.07 ± 2.9 mm and 1.7 ± 0.60 mm after advancement and - 2.57 ± 2.78 mm and - 1.28 ± 0.84 mm after setback. Significant differences between the BCA after HSSO and BSSO were at each displacement (p < 0.001), except for the achieved BCA after 8-mm setback and advancement (p ≥ 0.266). No significant differences were observed regarding ICD, except for the expected ICD after 8-mm setback and advancement (p ≤ 0.037). CONCLUSIONS: Compared to the virtual planning, the predictability regarding BCA and ICD was limited. ICD showed smaller clinical changes, BCA decreased significantly in the BSSO group. CLINICAL RELEVANCE: BCA and ICD might have been less important in choosing the suitable split technique. in orthognathic surgery.

Orthodontic maxillary molar movement-induced zygomatic pillar remodeling and its consequences on occlusal characteristics and stress distribution.

OBJECTIVE: We aimed to evaluate changes in the zygomatic pillar during orthodontic treatment involving premolar extraction, analyze the effects of maxillary first molar movement on zygomatic pillar remodeling, and examine occlusal characteristics and stress distribution after remodeling. METHODS: Twenty-five patients who underwent premolar extraction were included in the study. The zygomatic pillar measurement range was defined, and cross-sectional areas, surface landmark coordinates, alveolar and cortical bone thicknesses, and density changes were assessed using Mimics software based on the cone-beam computed tomography scans taken before (T0) and after the treatment (T1). Multiple linear regression analysis was performed to determine the correlation between changes in the zygomatic pillar and maxillary first molar three-dimensional (3D) movement and rotation. Additionally, the correlation between pillar remodeling and occlusal characteristics was analyzed by Teetester. Pre- and post-reconstruction 3D finite element models were constructed and loaded with an average occlusal force of two periods. RESULTS: The morphological and structural remodeling of the zygomatic pillar after orthodontic treatment involving premolar extraction showed a decreased cross-sectional area of the lower segment of the zygomatic pillar. The zygomatic process point moved inward and backward, whereas the zygomatico-maxillary suture point moved backward. The thicknesses of the zygomatic pillar alveolar and cortical bones were thinner, and reduced alveolar bone density was observed. Simultaneously, the movement and angle change of the maxillary first molar could predict zygomatic pillar reconstruction to a certain extent. With decreasing the total occlusal force and the occlusal force of the first molar, occlusal force distribution was more uniform. With zygomatic pillar remodeling, occlusal stress distribution in the zygomatic alveolar ridge decreased, and occlusal stress was concentrated at the junction of the vertical and horizontal parts of the zygomatic bone and the posterior part of the zygomatic arch. CONCLUSIONS: Orthodontic treatment involving premolar extraction led to zygomatic pillar remodeling, making it more fragile than before and reducing the occlusal force of the maxillary first molar and the entire dentition with stress concentrated in weak areas. CLINICAL RELEVANCE: No other study has focused on the effects of orthodontics on pillar structures. The present study indicates that the mesial movement of the maxillary first molar weakened the zygomatic pillar and reduced occlusal function, thereby providing insights for inserting anchorage screws and facial esthetics.

In vivo evaluation of T-Scan in quantifying occlusal contact.

BACKGROUND: The T-scan system has been used previously to analyse occlusion, but the quantitative analysis of occlusal contact by T-Scan system has yet to be reported. OBJECTIVES: To evaluate the reliability and validity of T-Scan system for quantitatively measuring occlusal contact area and occlusal contact number. METHODS: Twenty-two individuals with normal occlusion, 11 men and 11 women, were recruited for the study. Two occlusal analysis methods, including silicone transmission analysis method (STA) and T-Scan occlusion analysis method (TSO), were used to make quantitative analysis to measure occlusal contact area (OCA) and occlusal contact number (OCN). A test-retest check was performed with an interval of 2 weeks. The values of intraclass correlation coefficients (ICC) between test-retest of each method were calculated for reliability evaluation. Pearson correlations analysis, paired t-tests, regression analysis and Bland-Altman analysis were performed for validity evaluation. RESULTS: The ICC values of STA were greater than those of TSO for OCA while for OCN, ICC values of TSO were greater than STA. The higher OCA and OCN values were found in TSO compared with STA. Pearson's correlation coefficient indicated strong relations between TSO and STA (0.730-0.812) for OCA, while good relations between then (0.569-0.583) for OCN. Paired t-test showed a significant difference between the OCA and OCN values between TSO and STA. Bland-Altman analysis showed good agreement between OCA and OCN values of TSO and STA both in men and women. Regression analysis identified a linear correlation between OCA values obtained from these two methods. CONCLUSIONS: T-Scan method showed strong reliability for measuring OCA and OCN quantitatively. Strong correlations were found between OCA values from TSO and STA method, but the validity of TSO for measuring OCN needs to be promoted. CLINICAL SIGNIFICANCE: T-Scan system demonstrates good potential in quantitative analysis of occlusion, which will expand its clinical application.

Quantitative evaluation of the proximal contact area gap change characterization under intercuspal occlusion by intraoral 3D scanning: Food impaction with tight proximal contact.

OBJECTIVE: This study aimed to present three indicators that represent the proximal contact area gap change under intercuspal occlusion and to see if and how these indicators influence food impaction with tight proximal contact. MATERIALS AND METHODS: Ninety volunteers were recruited for bite force measurement and intraoral scanning. Three-dimensional surface data and buccal bite data were obtained for 60 impacted and 60 non-impacted teeth. The scanning data were imported into the Geomagic Studio 2013 to measure three indicators, which included the gap change maximum (Δdm, µm), the buccolingual position of Δdm (P), and the gap expanded buccolingual range (S, mm). The difference between two groups of three indicators and their relationship with food impaction with tight proximal contact were analyzed by the t test, the Pearson chi-squared test, the nonparametric Mann-Whitney U test, and the binary logistic regression analysis (a = 0.05). RESULTS: All indicators (Δdm, P, and S) were statistically different (p < 0.001, p = 0.002, and p < 0.001) in the impacted and non-impacted groups. Food impaction with tight proximal contact was affected by Δdm and S (p < 0.001, p = 0.039), but not by P (p = 0.409). CONCLUSION: The excessive increase of the gap change maximum and the gap expanded buccolingual range under bite force promoted the occurrence of food impaction with tight proximal contact. CLINICAL SIGNIFICANCE: The use of intraoral scanning to measure the characteristics of the proximal contact area gap change under bite force may help to deepen our understanding of the pathogenesis of food impaction with tight proximal contact. Importantly it can provide a reference basis for individualizing and quantifying occlusal adjustment treatment.

Numerical simulations of the effect of lateral malleolus fracture malunion on ankle biomechanics: Different offset directions and offsets.

INTRODUCTION: Ankle fractures account for approximately 10 % of all fractures. Approximately 5-68 % of patients with ankle fractures may suffer from malunion. Besides, suboptimal reduction of fracture fragments can affect the biomechanics of the ankle joint, ultimately leading to damage to the ankle joint. However, there are certain controversies over the conclusion of previous cadaveric studies. METHODS: In this study, a three-dimensional model of the ankle joint was established based on CT image data. In addition, the effects of backward offset (1-2 mm) and outward offset (0.5-1 mm) of the fracture fragment on the contact area, contact pressure, and ligament force of the ankle joint were investigated via the finite element method. Moreover, lateral malleolus fracture malunion in five ankle positions (neutral, 10° dorsiflexion, 10° plantarflexion, 20° dorsiflexion, and 20° plantarflexion) was investigated. RESULTS: This model predicted an overall increased contact area in the ankle joint in patients with lateral malleolus fracture malunion compared with the normal ankle joint. The results demonstrated that the outward offset had a more significant effect than the backward one. The larger the dorsiflexion-plantarflexion angle, the more pronounced the effect of malunion. Further, an outward offset can cause the fibula to lose its function. CONCLUSION: Post-traumatic osteoarthritis occurs under the action of unaccustomed cartilage forces due to altered tibial talar joint contact patterns, rather than increased contact pressure reported in previous studies. Malunion leads to an increase or decrease in force on the affected ligament, while the cause of malunion can be envisioned based on a decrease in the force on the ligaments.

Contact area and pressure changes of patellofemoral joint during stair ascent and stair descent.

PURPOSE: To investigate the differences of patellofemoral joint pressure and contact area between the process of stair ascent and stair descent. METHODS: The finite element models of 9 volunteers without disorders of knee (9 males) to estimate patellar cartilage pressure during the stair ascent and the stair descent. Simulations took into account cartilage morphology from magnetic resonance imaging, joint posture from weight-bearing magnetic resonance imaging, and ligament model. The three-dimension models of the patella, femur and tibia were developed with the medical image processing software, Mimics 11.1. The ligament was established by truss element of the non-linear FE solver. The equivalent gravity direction (-z direction) load was applied to the whole end of femur (femoral head) according to the body weight of the volunteers, and the force of patella was observed. A paired-samples t-test or Wilcoxon rank sum test to make comparisons between stair ascent and stair descent. Statistical analyses were performed using SPSS 22.0 using a P value of 0.05 to indicate significance. RESULTS: During the stair descent (knee flexion at 30°), the contact pressure of the patella was 2.59 ± 0.06Mpa. The contact pressure of femoral trochlea cartilage was 2.57 ± 0.06Mpa. During the stair ascent (knee flexion at 60°), the contact pressure with patellar cartilage was 2.82 ± 0.08Mpa. The contact pressure of the femoral trochlea cartilage was 3.03 ± 0.11Mpa. The contact area between patellar cartilage and femoral trochlea cartilage was 249.27 ± 1.35mm2 during the stair descent, which was less than 434.32 ± 1.70mm2 during the stair ascent. The area of high pressure was located in the lateral area of patella during stair descent and the area of high pressure was scattered during stair ascent. CONCLUSION: There are small change in the cartilage contact pressure between stair ascent and stair descent, indicating that the joint adjusts the contact pressure by increasing the contact area.

The influence of varus and valgus deviation on the contact area of patellofemoral joint in healthy knees.

OBJECT: Varus-valgus lower alignment is a risk factor for patellofemoral osteoarthritis, but malalignment alone affect not only the tibiofemoral joint but also the patellofemoral joint. The aim of the present study was to analyse the contact area of patellofemoral joint in varus alignment and valgus alignment of healthy subjects using magnetic resonance imaging. METHODS: Twenty-six healthy subjects with valgus lower limb alignment (Group I, n = 26) and twenty-six volunteers with varus lower limb alignment (Group II, n = 26) was performed. An MRI scan was used to capture and measure the patellofemoral joint articular cartilage contact area at different degrees of knee flexion (20°, 40°,60°) in passive movement. All subjects were categorized on the basis of the global limb alignment and mechanical alignment of the femur and tibia. Varus alignment is hip-knee-ankle angle ≥ 3°; and valgus alignment is hip-knee-ankle angle ≥ - 3°. To obtain medial facet contact area and lateral facet contact area for each slice, the length of each respective line of contact was multiplied by the 5 mm slice thickness. RESULTS: The overall joint contact area increased from 168.0 ± 20.5 mm2 at 20° knee flexion to 334.4 ± 30.5 mm2 at 60° knee flexion in group (I) The overall joint contact area increased from 178.0 ± 18.9 mm2 at 20° knee flexion to 328.9 ± 27.2 mm2 at 60° knee flexion in group (II) There was a significant difference in lateral facet contact area between group I and group II at 40° of knee flexion. There was significantly different in medial facet contact area between group I and group II at 20° and 40° of knee flexion. CONCLUSIONS: Throughout the knee movement, the contact area on the lateral facet of the patellofemoral joint was greater in the valgus group. In the early phase of knee flexion, the contact area of the medial patellofemoral joint was larger in the varus group. Lower alignment is an important factor in patellofemoral joint degeneration.

Biocompatibility of fiber-reinforced composite (FRC) and woven-coated FRC: an in vivo study.

OBJECTIVES: To investigate biocompatibility and bone contact area of FRC and woven-coated FRC (FRC-C) in rats. MATERIALS AND METHODS: Sixty rats were allocated to three groups: FRC (n=20), FRC-C (n=20), and control group (n=20). Subgroups were determined as 4th (n=10) and 12th weeks (n=10). The specimens were placed in the femur of rats. In the control group, the bone defects were left empty and sutured. Four and 12 weeks after implantation, the rats were sacrificed. Histopathological examinations were performed in a semi-quantitative manner. Twenty rats (n=20) were used for scanning electron microscopy (SEM) examination. Bone contact surfaces were calculated in SEM analysis. A chi-square test was performed to analyze the data. RESULTS: No statistical difference was detected between the 4th and 12th weeks in the quality of bone union. Quality of bone union was lower in FRC compared to the control group in the 4th week (p=0.012) and the 12th week (p=0.017). The periosteal reaction at the 12th week was lower in FRC than in the control group (p=0.021). Bone contact of FRC and FRC-C was 85.5% and 86.3%, respectively. CONCLUSIONS: FRC and FRC-C were biocompatible and showed no inflammation. The woven coating did not increase the quality of bone union and bone contact area, while not reducing biocompatibility. CLINICAL RELEVANCE: The biocompatibility and good bone response of the woven glass fiber net were demonstrated to have the potential as a scaffold for the augmentation of alveolar bone deficiencies and the reconstruction of maxillofacial defects.

Changes in masticatory performance during the retention period following 4-premolar extraction and non-extraction orthodontic treatment.

OBJECTIVES: To evaluate changes in masticatory performance (MP) during the retention period after extraction and non-extraction treatment and compare it with MP in individuals with normal occlusion. MATERIALS AND METHODS: Adult patients who had completed orthodontic fixed appliance treatment comprised the extraction and non-extraction treatment groups, and those with normal occlusion comprised the control group. Their mixing ability (MA), maximum bite force (MBF), and occlusal contact area (OCA) were recorded immediately after the fixed appliance was removed and at 1 month, 6 months, and 1 year post-treatment. The MA was measured via the two-color chewing gum MA test using ViewGum software, and the MBF and OCA were measured using Dental Prescale II system. RESULTS: MA immediately after orthodontic treatment was lower than that in the normal group but showed a time-dependent gradual increase during a 1-year retention period (P < 0.01). The MA at 1 month post-treatment was not significantly different between the three groups (P > 0.05). The MA revealed a significant correlation with the MBF and OCA (P < 0.01). CONCLUSIONS: The MP immediately after orthodontic treatment was lower than that in the normal group but increased gradually, with levels comparable to those of the normal occlusion group at 1 month post-treatment. Further, extraction did not affect the recovery of the MP after orthodontic treatment. CLINICAL RELEVANCE: No other study has evaluated the changes in MP during the retention period after orthodontic treatment. The findings show that compared with MBF and OCA, the patients' MP improved faster to levels found in normal occlusion.

Flexible and Robust Triboelectric Nanogenerators with Chemically Prepared Metal Electrodes and a Plastic Contact Interface Based on Low-Cost Pressure-Sensitive Adhesive.

Triboelectric nanogenerators (TENGs) are devices that can harvest energy from mechanical motions; such devices can be used to power wearable sensors and various low-power electronics. To increase the lifetime of the device, scientists mainly use the method of making TENG in a hard skeleton to simplify the complex possible relative movements between two triboelectric parts. However, the hard skeletons cannot be embedded in soft and lightweight clothing. To make matters worse, the materials used in the garments must be able to withstand high mechanical forces when worn, such as the pressure of more than 100 KPa exerted by body pressure or everyday knocks. Notably, the TENGs are usually made of fragile materials, such as vacuum-evaporated metal electrodes and nano-sized coatings, on the contact interface; these electrodes and coatings often chip or wear off under the action of external loads. In this work, we succeeded in creating a thin, light-weight, but extremely robust garment-integrated triboelectric nanogenerator (G-TENG) that can be embedded in clothing and pass the water wash test. First, we chemically deposited a durable electrode with flexible properties for G-TENG using a novel technique called polymer-assisted metal deposition (PAMD). The as-formed metal electrodes are firmly bonded to the plastic substrate by a sub-10 nm adhesive polymer brush and can withstand a pressure of 22.5 MPa and a tear force of 0.7 MPa. We then removed the traditionally used fragile nanoparticle materials and the non-durable poly-dimethylsiloxane (PDMS) layer at the triboelectric interface, and then used a cost-effective, durable and slightly flowable pressure-sensitive adhesive to form a plastic contact interface. Such a soft plastic interface can ensure full contact of the triboelectric materials, which is excellent in complex environments and ultimately improves the power generation efficiency of the devices. The as-formed low-cost energy harvesting device could become an industry standard for future smart clothing.

High-Precision Tribometer for Studies of Adhesive Contacts.

Herein, we describe the design of a laboratory setup operating as a high-precision tribometer. The whole design procedure is presented, starting with a concept, followed by the creation of an exact 3D model and final assembly of all functional parts. The functional idea of the setup is based on a previously designed device that was used to perform more simple tasks. A series of experiments revealed certain disadvantages of the initial setup, for which pertinent solutions were found and implemented. Processing and correction of the data obtained from the device are demonstrated with an example involving backlash and signal drift errors. Correction of both linear and non-linear signal drift errors is considered. We also show that, depending on the research interests, the developed equipment can be further modified by alternating its peripheral parts without changing the main frame of the device.

Occlusal function and electromyographic activity of masticatory muscles in skeletal Class III patients with different patterns of mandibular asymmetry.

BACKGROUND: Although jaw asymmetry is commonly seen in skeletal Class III patients, its correlation with occlusal function and masticatory muscle activity has not been fully elucidated. OBJECTIVES: The purpose of this study was to investigate the occlusal function and masticatory muscle activity in skeletal Class III patients with various patterns of mandibular asymmetry. METHODS: Forty-two patients and 10 normal participants were examined. The patients were categorised into three groups. Groups 1 and 2 exhibited menton and ramus deviation to the same side. Menton deviation was larger than ramus deviation in Group 1, whereas Group 2 showed the inverse relation. Group 3 patients showed menton and ramus deviation in opposite directions. Occlusal contact area (OCA), relative bite force (RBF), and temporalis anterior (TA) and masseter muscle (MM) activity at maximum clenching were measured using T-Scan Novus system and Bio-EMG-III. Statistical analysis was performed using the t-test, one-way analysis of variance with Bonferroni correction and Spearman correlation (α = .05). RESULTS: Compared with normal participants, the patients had smaller OCA and greater asymmetry in the distribution of masticatory muscle activity. Greater ramus deviation was associated with smaller OCA in Group 1 but with larger OCA in Group 3. In Group 1, greater menton deviation was related to stronger TA activity on the non-deviation side. In Group 2, greater ramus deviation was related to stronger MM activity on the deviation side. CONCLUSION: Deviation of the menton and ramus was individually related to OCA and masticatory muscle activity, and this relationship varied according to the pattern of mandibular asymmetry.

Effect of different occlusal forces on the accuracy of interocclusal records of loose teeth.

BACKGROUND: This study aimed at investigating the effect of loose teeth on the accuracy of occlusal records by comparing the differences in the number of occlusal contact points, occlusal contact area and the centre of the occlusal contact region under different occlusal forces in patients with periodontitis. OBJECTIVE: The effects of different occlusal forces on the occlusal contact point (OCP), occlusal contact area (OCA) and the centre of occlusal contact region (OCC) of loose teeth. METHODS: Occlusal training was performed on the 30 patients who completed periodontal serial treatment. One doctor took the occlusal records with silicone rubber and the T-scan system; the patients were digitally scanned intraorally by a technician. The data of the healthy teeth were recorded as the control group, and the data of the loose teeth were recorded as the experimental group. Then, we used Image J to measure the numbers of OCP and OCA and Auto CAD to calculate the coordinates of OCC. A paired t test was used to analyse whether the differences in OCP, OCA and OCC were statistically significant when the occlusal forces were different. RESULTS: The OCA of all three experimental methods increased under heavy occlusal force (p < .01), and the silicone rubber OCA increased the most. The OCC of all three experimental methods was shifted in the buccal and mesial (p < .01). And the occlusal records obtained by the T-scan system showed a low correlation between the differences of OCA and OCC. CONCLUSION: Whether the teeth were loose or not, the OCA increased under heavy occlusal forces. For patients with loose teeth, the OCC was shifted towards the buccal under heavy occlusal force.

Comparison of iridolenticular contact area under different light brightness between post primary acute angle closure and cataract eyes.

BACKGROUND: To study the iridolenticular contact area (ILCA) under different light conditions in acute primary angle closure (APAC). METHODS: This cross-sectional, observational study involved 22 unilateral APAC patients and 59 cataract patients (59 eyes). Images of the APAC eyes, fellow eyes and cataract eyes were collected by anterior segment optical coherence tomography (ASOCT) under different light conditions respectively. The ILCA, anterior chamber width (ACW), anterior chamber area (ACA), lens vault (LV), angle opening distance at 750 µm (AOD750), trabecular iris space area at 750 µm (TISA750) and iris area at 750 µm (IA750) were measured using Image J software. RESULTS: The ILCA of cataract eyes were significantly larger than APAC eyes (4.424 ± 1.208 vs 4.049 ± 2.725mm2, P = 0.034) and fellow eyes (4.424 ± 1.208 vs 3.651 ± 1.629 mm2, P = 0.008) under dark condition. Under dark condition, ILCA of APAC eyes was negatively correlated with AOD750 (r = -0.444, P = 0.038), TISA750 (r = -0.498, P = 0.018). The ILCA of cataract eyes under dark condition was significantly greater than under bright condition (4.424 ± 1.208 vs 2.526 ± 0.992 mm2, P < 0.001). CONCLUSIONS: This study showed that ILCA in both APAC eye and fellow eye were smaller than cataract eye. Future study should focus on both the contact area and force at the interface of lens and iris with larger sample size.

Factors affecting masticatory performance during the mixed dentition period.

BACKGROUND: During the mixed dentition period, masticatory performance may temporarily decline as deciduous teeth are replaced by permanent teeth. This may lead to an insufficient intake of chewy foods. OBJECTIVES: This study aimed to clarify the characteristics of factors that affect masticatory performance during the dentition exchange period. METHODS: The participants were 229 students in grades 4-6 who were in the lateral dentition exchange period. Shearing performance (SP) was evaluated using gummy jelly, and mixing performance (MP) was evaluated using colour-changing gum. The chewing rate, occlusal force and area, number of teeth, Hellman's tooth age, Rohrer index, grip strength and walking speed were also evaluated. The χ2 test, Mann-Whitney test, Spearman's rank correlation coefficient and a generalised linear model were used for statistical analysis. RESULTS: SP/MP showed a significant positive correlation with occlusal force, occlusal contact area and chewing rate for gummy jelly and gum but there was a difference in the strength of the correlation between boys and girls. Chewing rate for gummy jelly and gum showed a significant relationship with both SP and MP, suggesting that masticatory performance is higher with slower chewing. Maximum occlusal force was selected as a significant independent variable for SP, and Rohrer index was selected as a significant independent variable for MP. When the occlusal force was higher and the Rohrer index was lower, the masticatory performance tended to be higher. CONCLUSIONS: Our results suggest that masticatory performance during the dentition exchange period is higher with slower chewing and a stronger occlusal force, which may be related to obesity.

[Finite element analysis method and optimization of flexible ginger moxibustion based on Abaqus and Taguchi method].

Ginger moxibustion has the effect of regulating zang-fu organs and activating qi and blood circulation. When used, ginger paste is required to be close to human skin. Currently, the ginger box used clinically in the hospital can't meet the requirement of large area fitting human skin, and the efficacy of ginger moxibustion is significantly reduced. In this study, a flexible ginger paste box was proposed, which was composed of flexible components polydimethylsiloxane (PDMS), spring and wire netting. The large flexibility of the structure made it fit well with human skin. Finite element method was used to study the fitting degree between ginger paste box and waist soft tissue. Finite element models of flexible ginger paste box and waist soft tissue were established based on Hypermesh and Abaqus software. The equivalent contact area between the flexible ginger paste box and waist was obtained by numerical simulation under different PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness. The four parameters were taken as the influencing factors, and the equivalent contact area was taken as the optimization objective. The typical value analysis and variance analysis of S/N were performed by Taguchi method, and the results showed that among the four influencing factors, the wire netting diameter had the largest influence on equivalent contact area and its contribution rate reached 41.98%. The contribution rates of PDMS unilateral thickness, spring wire diameter and ginger paste layer thickness reached 36.48%, 13.97% and 6.50%, respectively. The optimized PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness were 1.5, 0.4, 0.15, 35 mm, respectively, and the equivalent contact area was 95.60 cm 2. The optimized flexible ginger paste box with great fitting performance can improve the effect of ginger moxibustion.

Modeling and Experimental Validation of Microbial Transfer via Surface Touch.

Surface touch spreads disease-causing microbes, but the measured rates of microbial transfer vary significantly. Additionally, the mechanisms underlying microbial transfer via surface touch are unknown. In this study, a new physical model was proposed to accurately evaluate the microbial transfer rate in a finger-surface touch, based on the mechanistic effects of important physical factors, including surface roughness, surface wetness, touch force, and microbial transfer direction. Four surface-touch modes were distinguished, namely, a single touch, sequential touches (by different recipients), repeated touches (by the same recipient), and a touch with rubbing. The tested transfer rates collated from 26 prior studies were compared with the model predictions based on their experimental parameters, and studies in which the transfer rates were more consistent with our model predictions were identified. New validation experiments were performed by accurately controlling the parameters involved in the model. Four types of microbes were used to transfer between the naked finger and metal surface with the assistance of a purpose-made touch machine. The measured microbial transfer rate data in our new experiments had a smaller standard deviation than those reported from prior studies and were closer to the model prediction. Our novel predictive model sheds light on possible future studies.

Fracture asperity evolution during the transition from stick slip to stable sliding.

Fracture asperities interlock or break during stick slip and ride over each other during stable sliding. The evolution of fracture asperities during the transition between stick slip and stable sliding has attracted less attention, but is important to predict fracture behaviour. Here, we conduct a series of direct shear experiments on simulated fractures in homogeneous polycarbonate to examine the evolution of fracture asperities in the transition stage. Our results show that the transition stage occurs between the stick slip and stable sliding stages during the progressive reduction in normal stress on the smooth and rough fractures. Both the fractures exhibit the alternative occurrence of small and large shear stress drops followed by the deterministic chaos in the transition stage. Our data indicate that the asperity radius of curvature correlates linearly with the dimensionless contact area under a given normal stress. For the rough fracture, a bifurcation of acoustic energy release appears when the dimensionless contact area decreases in the transition stage. The evolution of fracture asperities is stress-dependent and velocity-dependent. This article is part of the theme issue 'Fracture dynamics of solid materials: from particles to the globe'.