The Effect of a Constant Electrical Field on Osseointegration after Immediate Implantation in Dog Mandibles: A Preliminary Study

PURPOSE: The long time span between insertion of implants and functional rehabilitation often inconveniences patients. Accelerating bone growth around dental implants can shorten this time span. This in vivo study evaluated the effect of a constant electrical field on bone growth around dental implants. MATERIALS AND METHODS: Four mongrel dogs were used in this study. Sixteen dental implants were placed immediately after extraction of the first premolar and molar teeth. A constant electrical field (CEF) generator was placed in the mucoperiostal pouch created from the subperiostral dissection under the inferior border of the dog's mandible and connected to the experiment side fixtures. CEF provided 3 V of electrical potential during osseointegration. Histologic sections were stained with hematoxylin-eosin and observed under light microscopy. The sections were analyzed histomorphometrically to calculate the amount of newly formed bone. Statistical analysis was performed with SPSS 11.0 computer software (alpha= 0.05). RESULTS: At the end of the first stage of the osseointegration (90 days) CEF group sections showed enhanced growth of the trabeculae compared with the control group. Statistical analysis revealed significant differences between experimental and control groups. Bone contact ratio was statistically significant in the experimental group (p= 0.001). An increase in the local bone formation and bone contact ratio was observed with direct electrical stimulation of the implant and the bone area around the implant. CONCLUSION: Minimal direct electrical current, which can produce an electrical field around the implant, can increase the amount of bone formation and decrease the time of osseointegration.     

Haversian cortical bone model with many radial microcracks: an elastic analytic solution

In this study, the fracture micromechanics of Haversian cortical bone has been considered. To this effect, a two-dimensional micromechanical fibre-ceramic matrix composite tissue materials model has been presented. The interstitial tissue was modeled as a matrix and the osteon was modeled as a fibre, followed by the application of linear elastic fracture mechanics theory. The solution for edge dislocations, in terms of Green's functions, was adopted to formulate a system of singular integral equations for the radial microcracks in the matrix in vicinity of the osteon. The problem was solved for various configurations and the corresponding stress intensity factors were computed. The results of this study indicated that the interaction between microcracks and an osteon was limited to vicinity of the osteon. Furthermore, the effect of microstructure morphology and heterogeneity on the fracture behavior has been established. The interactions between microcracks were also analyzed for various configurations. These selected configurations exhibited the effects of stress amplification and stress shielding.     

Innovative restriction site created PCR-RFLP for detection of benzimidazole resistance in Teladorsagia circumcincta

Benzimidazole compounds, especially albendazole, are the most commonly used anthelmintics for deworming of small ruminants in Iran. It is believed that the therapeutic effects of the benzimidazoles (BZs) come through their binding capacity to the β-tubulin isotype 1. Substitution of phenylalanine to tyrosine at position 200 of this polypeptide confers resistance to BZs. Several investigators developed different biological- and molecular-based techniques to demonstrate the occurrence of resistance in helminthes against BZs. To address the determination of resistance at position 200 of β-tubulin isotype 1, we developed an innovative restriction site created polymerase chain reaction-restriction fragment length polymorphism, in which nucleotide A at the position of 637 upstream flanked by the first two coding sequences of the phenylalanine (TT) triplet was substituted through the nucleotide G. The introduced modification in forward primer (UTvet MF-primer) leads to the creation of restriction site (AACGTT) for PSP1. Therefore, in the case of normal allele only, PSP1 can cut the corresponding PCR product. In the first step, the genomic DNA was isolated from each single Teladorsagia circumcincta collected either from the abomasa of untreated (n = 35) or of 5 mg/kg BW 2.5% albendazole suspension-treated (n = 40) sheep. It was amplified with the primer pair, creating PCR product of 403 bp in length. In the second step, the PCR product was extracted from agarose gel and amplified with the modified forward primer (UTvet MF-primer) and the same reverse primer as in step 1, creating a PCR product of 222 bp. The PCR product was then cut with PSP1 to obtain in the case of normal allele two DNA products (183 and 39 bp). Eight of the 35 worms collected from the untreated sheep were BZ^SS homozygotes, and the rest (27) were BZ^RS heterozygotes. In our preliminary experiment, we could not find a BZ^RR homozygote form within the examined samples. Five out of 40 worms collected from the albendazole-treated sheep were BZ^RR homozygotes, whereas the rest (35) were BZ^RS heterozygotes. No BZ^SS homozygote form was detected within this group.     

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus

Purpose

To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosaand Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines.

Methods

Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer''s minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated.

Results

All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosaand S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosaand S. aureuswere acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount.

Conclusions

Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosaand S. aureus, their efficacy may be insufficient against clinical isolates of these organisms.     

Alteration in Matrix Metalloproteinases (MMPS) Activity in Fibroblast Cell Line by Dexamethasone: A Possible Mechanism in Corticosteroid-Induced Glaucoma

Corticosteroids are often used as anti-inflammatory agents in a variety of inflammatory diseases. It is well established that long-term administration of corticosteroids predisposed the patients to develop glaucoma. Although the exact pathophysiology of steroid-induced glaucoma is unknown, it is assumed that Matrix metalloproteinases (MMPs) have a role in its pathogenesis. To study and estimate the pathophysiological effects of MMPs in glaucoma, we established an in vitro cell culture model. We also employed a precise proliferation assay to analyze cytotoxic effect of dexamethasone. The influence of dexamethasone on MMPs production was investigated using an in vitro gelatin Zymography. Cytotoxcity analysis of Dexamethasone revealed no significant cell death in low concentration. However, it caused 50% and 70% cell death at 80 and 100 mg/mL respectively. It also revealed an inhibitory effect on MMPs by dexamethasone in a dose dependent fashion. It may be concluded that an alteration in the level of MMPs expression by dexamethasone interferes with ocular fluid drainage and may contribute to the pathogenesis of glaucoma.     

Determination of occlusal vertical dimension: a literature review

The vertical dimension of occlusion refers to the length of the face as determined by the amount of separation of the jaws. Its determination is important for fabrication of all restorations. Many techniques have been used for measurement of the vertical dimension of occlusion in dentulous and edentulous patients. These range from using preextraction records to the use of swallowing, functionally acquired jaw positions associated with phonetics, and cephalometric radiographs and evaluation of radiopaque paste in the vestibular fornix. There is no universally accepted or completely accurate method of determining the vertical dimension of occlusion in edentulous patients. There seem to be no significant advantages of one technique other than those of cost, time, and equipment requirements. It is the end result that matters. It should be satisfactory to the dentist and the patient from an esthetic point of view and not induce degenerative changes from a functional standpoint. Regardless of the technique, the vertical dimension of occlusion must be determined carefully by the dentist for a successful prosthesis.     

Inhibition of intraocular fibrin formation after infusion of low-molecular-weight heparin during combined phacoemulsification-trabeculectomy surgery

PURPOSE: To evaluate the effect of intraocular infusion of dalteparin, a low-molecular-weight heparin (LMWH) administered in the infusion fluid to prevent early postoperative fibrin formation in combined phacoemulsification-trabeculectomy surgery (phacotrabeculectomy). SETTING: Farabi Eye Hospital, Tehran, Iran. METHODS: Standard combined phacotrabeculectomy was performed prospectively in a masked fashion in 60 eyes; 35 eyes received 5 IU/mL LMWH in the infusate and 25 eyes served as controls. Masked postoperative examinations assessed visual acuity, intraocular pressure (IOP), anterior chamber cell and flare, and fibrin formation with slitlamp examinations 1, 3, 7, 30, and 90 days after surgery. RESULTS: The rate of intraocular fibrin/membrane formation was significantly lower in the LMWH group than in the control group at each follow-up (P<.001, Student t test) . The amount of IOP was lower in LMWH group at each follow up (P<.01, Student t test). Final visual acuity was better in LMWH group (P = .03, Student t test). The frequency of synechia formation was lower in the LMWH group on day 90 (P = .002, chi-square test). CONCLUSIONS: Infusion of dalteparin, a LMWH, may be an effective inhibitor of postoperative fibrin formation in phacotrabeculectomy surgery. It may reduce the frequency of synechia formation and improve visual acuity. It may not be associated with increased risk for intraoperative or postoperative complications at the tested dose. This drug may be a useful adjunct in combined surgery.     

T2* magnetic resonance imaging of the liver in thalassemic patients in Iran

AIM: To investigate the accuracy of T2*-weighted magnetic resonance imaging (MRI T2*) in the evaluation of iron overload in beta-thalassemia major patients. METHODS: In this cross-sectional study, 210 patients with beta-thalassemia major having regular blood transfusions were consecutively enrolled. Serum ferritin levels were measured, and all patients underwent MRI T2* of the liver. Liver biopsy was performed in 53 patients at an interval of no longer than 3 mo after the MRIT2* in each patient. The amount ...