STATEMENT OF PROBLEM: Injuries along with discomfort may result on the oral mucosa when non-rigid material is used as the major connector in construction of RPD, since nonrigid major connectors transmit unstable forces throughout the appliance. Titanium which recently draws attention as a substitute of Co-Cr had a difficulty in fabricating due to high melting temperature, but the development of casting technique makes it possible to apply to the clinical case. PURPOSE: The purpose of this study was to investigate the rigidity and the castability of titanium upper major connector by design and make a comparison with Co-Cr major connectors which are widely used in clinical cases now. MATERIAL AND METHODS: Casting was done using CP-Ti(Grage 2)(Kobe still Co., Japan) for the experimental groups, and 4 various designs namely palatal strap, U-shaped bar, A-P strap, and complete palatal plate were casted and 5 of each designs were included in each group. For the experimental group, Universal testing machine (Model 4502;Instron, Canton, Mass) was used to apply vertical torsional force vertically to the horizontal plane of major connector. In the second experiment, Vertical compressive force was applied to the horizontal plane of major connector. As a comparative group, Co-Cr major connector was equally manufactured and underwent the same experimental procedures. Strain rate was measured after constant loading for one minute duration, and statistical analysis was done with SPSS ver.10.0 for WIN(SPSS. Inc. USA). From the one-way ANOVA and variance analysis (P=0.05), Scheffe's multiple comparison test implemented. RESULTS: 1. Least amount of strain was observed with complete palatal plate followed by A-P bar, palatal bar, and the U-shaped bar having most amount of strain. 2. In all designs of titanium major connector, less strain rate was observed under compressive loading than under torsional loading showing more resistance to lateral force. 3. For titanium major connector, less strain rate was observed when the force is applied to the first premolar area rather than to the second molar area indicating more strength with shorter length of lever. 4. In comparison of Co-Cr major connector with titanium major connector, palatal strap and U-shaped bar designs showed higher strength under torsional force that is statically significant, and under compressive force, no significant difference was observed expert for U-shaped bar. 5. In titanium major connector, complete palatal plate showed lowest success rate in casting when compared with the Co-Cr major connector. CONCLUSION: Above results prove that when using titanium for major connector, only with designs capable of generating rigidity can the major connector have almost equal amount of rigidity as Co-Cr major connector and show lower success rate in casting when compared with the Co-Cr major connector.
Bicuspid ; Freezing ; Molar ; Mouth Mucosa ; Titanium* ; Torsion, Mechanical

system may include bending force in first and second orders and a torsional force in third order. Analytical and experimental studies on bending force have been introduced, but information about torsion is still lack. The purpose of this study was to estimate the torsional moment in the force system of rectangular arch wires through theoretical and experimental studies. Wires most frequently used for third order control were selected as study materials. Cross sections of 0.016X17.022, 0.0174.025, 0.0194.025 inch rectangular wires in four different materials such as stainless steel (O mco), TMA (Ormco), NiTi (Ormco), and braided stainless steel (DentaFlex, Dentaurum) were used. The torque/twist rate of each test material was calculated using the torsion fotiuula Torque/twist rate, yield torsional moment, and ultimate torsional moment were measured with a torque gauge. The torsion formula assesses that the torque,/twist rate (T/theta) is proportional to the characteristics of material(G) and cross section (J), and is inversely proportional to the length of wire (L). Most experimental results conesponded with the formula. The relative stiffness was calculated for reference to a logical sequence of wire changes.
Logic ; Orthodontic Wires* ; Stainless Steel ; Torque ; Torsion, Mechanical

OBJECTIVE: The purpose of this study was to estimate the fracture resistance of commercially available ceramic brackets to torsional force exerted from arch wires and to evaluate the characteristics of bracket fracture. METHODS: Lingual root torque was applied to maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x0.027-inch stainless steel arch wire. A custom designed apparatus that attached to an Instron was used to test seven types of ceramic brackets (n = 15). The torque value and torque angle at fracture were measured. In order to evaluate the characteristics of failure, fracture sites and the failure patterns of brackets were examined with a Scanning Electron Microscope. RESULTS: Crystal structure and manufacturing process of ceramic brackets had a significant effect on fracture resistance. Monocrystalline alumina (Inspire) brackets showed significantly greater resistance to torsional force than polycrystalline alumina brackets except InVu. There was no significant difference in fracture resistance during arch wire torsional force between ceramic brackets with metal slots and those without metal slots (p > 0.05). All Clarity brackets partially fractured only at the incisal slot base and the others broke at various locations. CONCLUSION: The fracture resistance of all the ceramic brackets during arch wire torsion appears to be adequate for clinical use.
Aluminum Oxide ; Ceramics* ; Incisor ; Stainless Steel ; Torque ; Torsion, Mechanical*

PURPOSE: To assess union and complication rates associated with the use of 2 small diameter headless compression screws and volar wedge bone grafting for the treatment of scaphoid fracture waist nonunions with collapse. METHODS: A total of 12 patients (11 male and 1 female) at an average age of 32.5 years were treated with open reduction and internal fixation with 2 small diameter headless compression screws for scaphoid nonunions with a mean follow-up of 11 months. Tricortical wedge shaped autograft were harvested from the iliac crest and placed into the nonunion site to restore length and alignment in all patients. Union was determined by radiographs and computed tomography, and scapholunate and radiolunate angles, and height-to-length ratio were calculated on final radiographs and follow-up computed tomography. RESULTS: All 12 scaphoids united with a mean time for 2.8 months. The mean postoperative scapholunate angle was significantly reduced from 73° preoperatively to 56° postoperatively. The mean radiolunate angle was significantly improved from 21° from neutral preoperatively to 12° postoperatively. The height-to-length ratio was also demonstrated significant improvement from 0.73 preoperatively to 0.60 postoperatively. No hardware problems were identified and no revision procedures have been necessary. CONCLUSION: Our results indicate that the use of 2 small diameter headless compression screws with volar structural bone graft stabilizes the fracture for predictable union, while reducing the deformity reliably from a collapsed scaphoid nonunion. The presented technique is safe and effective, and may provide superior biomechanical stability, especially against the torsional force.
Autografts ; Bone Transplantation ; Congenital Abnormalities ; Follow-Up Studies ; Humans ; Male ; Torsion, Mechanical ; Transplants

OBJECTIVETo study biomechanical changes of newly formed bones 24 weeks after repairing large defects of long bones of goats using heterogeneous deproteinated bone (DPB) prepared by modified methods as an engineering scaffold.

METHODSAccording to a fully randomized design, 18 goats were evenly divided into three groups: normal bone control group (Group A), autologous bone group (Group B) and experimental group (Group C). Each goat in Groups B and C were subjected to the periosteum and bone defect at middle-lower part of the right tibia (20% of the whole tibia in length), followed by autologous bone or DPB plus autologous MSCs + rhBMP2 implantation, respectively and semi-ring slot fixation; while goats in Group A did not perform osteotomy. At 24 weeks after surgery, biomechanical tests were carried out on the tibias.

RESULTSAt 24 weeks after surgery, the results of anti-compression test on tibias in three groups were recorded by a functional recorder presented as linear pressure-deformation curve. The shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values were 10.74 MPa+/-1.23 MPa, 10.11 MPa+/-1.35 MPa and 10.22 MPa+/-1.32 MPa and fracture compression rates were 26.82%+/-0.87%, 27.17%+/-0.75% and 28.22%+/-1.12% in Groups A, B and C, respectively. Comparisons of anti-compression ultimate pressures and fracture compression rates among three groups demonstrated no significant difference (P(AB) equal to 0.415, P(BC) equal to 0.494). Three-point anti-bend test on tibias was recorded as load-deformation curves, and the shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values of the anti-bend test were 481.52 N+/-12.45 N, 478.34 N+/-14.68 N and 475.62 N+/-13.41 N and the fracture bend rates were 2.62 mm+/-0.12 mm, 2.61 mm+/-0.15 mm and 2.81 mm+/-0.13 mm in Groups A, B and C, respectively. There was no significant difference between groups (P(AB) equal to 0.7, P(BC) equal to 0.448). The ultimate anti-torsion torque values were 6.55 Nm+/-0.25 Nm, 6.34 Nm+/-0.18 Nm and 6.42 Nm+/-0.21 Nm and fracture torsion rates were 29.51 degree+/-1.64degree, 28.88 degree+/-1.46 degree and 28.81 degree+/-1.33 degree in Groups A, B and C, respectively. There was no significant difference between groups (P(AB) equal to 0.123, P(BC) equal to 0.346).

CONCLUSIONSThe biomechanical characteristics of newly formed bones from heterogeneous DPB for repairing large segmental long bone defect are comparable to those of normal bones and autologous bones. DPB has the potential for clinical usage as bone graft material.

Animals ; Biomechanical Phenomena ; Female ; Goats ; Male ; Proteins ; Tibia ; physiology ; surgery ; Tissue Engineering ; Torsion, Mechanical

OBJECTIVETo prepare andrographolide composite particles, and evaluate their particle structure and dissolution.

METHODThe mechanical crushing method was adopted to prepare andrographolide and polyethylene glycol (PEG) 6000 composite particles. The structures were characterized by the scanning electron microscope (SEM) and the differential scanning calorimeter (DSC). The contact angles were determined by the contact angle analyzer. The in vitro dissolution curve was detected.

RESULTAndrographolide and PEG 6000 gave rise to coated composite particle structures, with the decrease in the crystallinity of andrographolide. The in vitro dissolution rate of composite particles was significantly obvious than that of its raw materials, ultrafine powder and their physical mixtures.

CONCLUSIONAndrographolide composite particles based on the mechanical crushing method could notably enhance the in vitro dissolution of andrographolide.

Calorimetry, Differential Scanning ; Chemistry, Pharmaceutical ; methods ; Diterpenes ; chemistry ; Drugs, Chinese Herbal ; chemistry ; Particle Size ; Solubility ; Torsion, Mechanical

OBJECTIVEIn pedicle screw fixation, the heads of monoaxial screws need to be directed in the same straight line to accommodate the rod placement by backing out during operation, which decreases the insertional torque and internal fixation strength. While polyaxial screws facilitate the assembly of the connecting rod, but its ball-in-cup locking mechanism reduces the static compressive bending yield strength as compared with monoaxial screws. Our study aimed to assess the mechanical performance of a modified pedicle screw.

METHODSIn this study, the tail of the screw body of the modified pedicle screw was designed to be a cylinder-shaped structure that well matched the inner wall of the screw head and the screw head only rotated around the cyclinder. Monoaxial screws, modified screws and polyaxial screws were respectively assembled into 3 groups of vertebrectomy models simulated by ultra high molecular weight polyethylene (UHMWPE) blocks. This model was developed according to a standard for destructive mechanical testing published by the American Society for Testing Materials (ASTM F1717-04). Each screw design had 6 subgroups, including 3 for static tension, load compression and torsion tests, and the rest for dynamic compression tests. In dynamic tests, the cyclic loads were 25%, 50%, and 75% of the compressive bending ultimate loads respectively. Yield load, yield ultimate load, yield stiffness, torsional stiffness, cycles to failure and modes of failure for the 3 types of screws were recorded. The results of modified screws were compared with those of monoaxial and polyaxial screws.

RESULTSIn static tests, results of bending stiffness, yield load, yield torque and torsional stiffness indicated no significant differences between the modified and monoaxial screws (P > 0.05), but both differed significantly from those of polyaxial screws (P < 0.05). In dynamic compression tests, both modified and monoaxial screws showed failures that occurred at the insertion point of screw body into the UHMWPE block, while the polyaxial screw group showed screw body swung up and down the screw head because of loosening of the ball-in-cup mechanism.

CONCLUSIONSThe modified screw is well-designed and biomechanically improved. And it can provide sufficient stability for segment fixation as monoaxial screws.

Bone Screws ; Compressive Strength ; Equipment Design ; Humans ; In Vitro Techniques ; Internal Fixators ; Materials Testing ; Models, Structural ; Spine ; surgery ; Tensile Strength ; Torsion, Mechanical

OBJECTIVETo investigate the relationship between pathological abnormalities of placenta and small-for-gestational-age neonates.

METHODSOne hundred placentas of small-for-gestational-age (SGA group) and 200 appropriate-for-gestational-age (AGA group) with single living birth in third trimester were investigated by gross and microscopic examination. The AGA placentas were collected from 2 cases following every SGA placenta. All cases were collected from Shanghai Changning District Maternity and Infant Health Hospital from January 2010 to December 2011.

RESULTSThe gestational week, neonatal birth weight, full-term neonatal birth weight, the preterm birth rate and vaginal spontaneous delivery rate were significantly lower in SGA group than that in AGA group (P < 0.002). Full-term placental volume, placental weight and fetal placental weight ratio were lower in SGA group than that in AGA group (P < 0.05). Unusual insertion and torsion of umbilical cord were more common in SGA group (P < 0.05). Syncytial knots increase, avascular villi and villous infarcts were significantly higher in SGA group (P < 0.005), but there were no significant difference between SGA group and AGA group in intervillous thrombi, chronic villitis and chorangiosis (P > 0.05). Gestational hypertension disease and abnormality of fetal monitoring were more common in SGA group (P < 0.05).

CONCLUSIONSGestational hypertension disease is the main clinical cause of SGA. Some placental abnormality can affect the growth and development of intrauterine fetus.

Birth Weight ; Female ; Gestational Age ; Humans ; Hypertension, Pregnancy-Induced ; Infant, Newborn ; Infant, Small for Gestational Age ; Placenta ; pathology ; Pregnancy ; Torsion, Mechanical ; Umbilical Cord ; pathology