Journal of Dental School
Volume:30 Issue: 4, 2013

In recent years, composite scaffolds made ofpolymers and bioactive ceramics have foundnumerous applications in bone tissue engineering dueto their superior properties. Among various polymers, chitosan (Cs) and gelatin (Gel) gained more attention because of their desirable properties. In this study, by using these two polymers and hydroxyapatite (HA) which resembles inorganic phase of human bone, three-dimensional composite scaffolds were preparedby freeze-drying method andbehavior of osteoblast cells on them was evaluated.Thisstudy aimed at preparing an appropriate bioactive scaffold for bone tissue engineering.

In order to evaluatethe effect ofgelatin concentration onbiological propertiesof scaffolds, three different concentrations of gelatin (0,10, and 20%) were added to composite scaffolds.Forassessment of thebiological properties of scaffolds, osteoblast cells were cultured on the composite scaffolds and their behavior was monitored.Scanning electron microscopy (SEM)analysis and alkaline phosphatase activity (ALP)testwerecarried out to assess the mentioned factors.

SEM analysis showed high cell attachment and proliferation on the scaffolds. Alkaline phosphatase activity of osteoblast cells indicated the suitability of composite scaffolds containing a higher concentration of gelatincompared to otherconcentrationsas well as overallhigh activity of osteoblast cells on all scaffolds.

Cs/Gel/HA bioactive composite scaffold is recommended for bone tissue regeneration purposes as a suitable scaffold.

Tooth-colored non-metal posts are adhered to the canal walls with the use of resin cements and dentin adhesives. Degree of conversion of these cements is especially important to ensure the durability of the restoration. The present study aimed at evaluating the degree of conversion (DC%) of self-cure and dual-cure resin cements at different depths and time points when using a DT. Light Post.

In this experimental study, metal molds with 5 and 10 mm heights and internal diameter of 0.8 mm were used. Posts were vertically placed in the center of molds. Spectrum of absorption of the dual cure cement was measured before curing using Fourier transform infrared spectroscopy device. The uncured samples were then removed from the device and placed beneath the molds. After light irradiation, samples were transferred again to the FTIR device and their spectrum of absorption was measured. DC% was calculated using the relevant formula. For self-cure cements, spectrum of absorption was measured at 0, 2, 5, 10 and 15 minutes by the FTIR. Results were statistically analyzed using SPSS software.

Self-cure cement had a DC of 5% at 0, 2, 5 and 10 minutes and a DC of 20% at 15 minutes. DC of the dual-cure cement was 44%, 15% and 8% at 0, 5 and 10 mm depths, respectively. Two-way ANOVA and Tukey’s Post Hoc test (HSD) revealed that in the dual-cure cement the DC at 5 and 10 mm depths was significantly different (P<0.05). DC was 20% at 15 minutes which was the highest.

DC% of the dual-cure cement was higher than that of the self-cure cement which is attributed to the optimal characteristics of the dual-cure cement and also the ability of fiber post to pass light.

Nano-sized hydroxyapatite nano particles (nHA) have optimal biological properties and by incorporating them into the restorative materials, we can benefit from these properties. The present study sought to assess the effect of incorporation of various amounts of nHA on the mechanical properties (compressive and flexural strengths) of a resin modified glass ionomer.

In this experimental study, a total of 252Fuji II LC improved GI samples were divided into 6 groups including a control group (0%) and the nHA groups (1%, 2%, 5%, 7% and 10% based on mass percent). Of the samples, 108 were fabricated for the flexural strength testing using a two-piece aluminum mold (2x2x25 mm) according to ISO standard 4049. In each group, a total of 18 samples in 3 subgroups (6 samples each) were fabricated. All samples were removed from the mold after 80 seconds of light irradiation. A total of 144 samples made for compressive strength testing using a two-piece brass mold (4x6 mm) according to ISO standard 9917. Thus, in each group, a total of 24 samples in three subgroups (8 samples each) were fabricated and removed from the mold after 80 seconds of light irradiation. After removal from the mold, all samples were stored in an incubator at 37˚C and 100% moisture and underwent flexural and compressive strength testing with the primary load of 2 N and crosshead speed of 0.5 mm/min-1in a Zwick testing machine after one day, one week and one month. Data were analyzed using normal statistical tests of one-way ANOVA and Tukey’s HSD (Post Hoc). In order to assess the correlation of time (in groups with various mass percentages of HAP) with understudy outcomes, one way ANOVA was employed and P<0.05 was considered statistically significant.

Study results showed that incorporation of 5% nHA resulted in a significant increase in flexural strength after 30 days (17.4 MPa increase)(P<0.05). Also, if the nHA weight percent exceeded 5%, flexural strength suffered a dramatic drop after one month(28.9 MPa reduction). This study also showed that addition of 5% NHAP significantly increased flexural elastic modulus after one month (2.2 GPa increase). Addition of NHAP to resin modified glass ionomer caused a small increase in compressive strength and compressive elastic modulus which was not statistically significant (about 1MPa increase).

Addition of nHA to resin modified glass ionomers (Fuji II LC improved) not only does not reduce compressive strength, but also can increase flexural strength which would be the greatest if nHA is added in an amount of 5%.

Discovery, purification and synthesis of Bone Morphogenetic Proteins (BMP) were an important turning point in understanding of bone physiology for repair of bone defects. The present study aimed at eliminating the limitations caused by the application of bone auto-grafts and finding a proper substitute for bone grafts. This study was the first to evaluate the effect of BMP7 and nanosilver particles on the permeability of muscle cells for ectopic bone formation in Rat gluteofemoral muscle. This experimental double blind study was conducted on 42 rats divided into 6 groups of 7 each. The first 3 groups received an injection of 200 ng BMP7 with 0.1 mg nanosilver particles and the remaining 3 groups received 200 ng BMP7 in 0.4 mg normal saline. Rats were euthanized 7, 14 and 21 days post-operation and evaluated in terms of presence of tissue changes like necrosis, inflammation, and formation of fibrous or calcified tissue under a light microscope with X40, X100, and X400 magnification. The obtained results were analyzed with Hosmer-Lemeshow, chi square and Wilcoxon tests. Results of the 2 groups were analyzed and compared using Mann Whitney U and Kruskal-Wallis tests. No statistically significant differences were detected between the subgroups of our 2 main understudy groups in terms of bone formation, distribution of inflammation (P=0.439), the amount of inflammation (P=0.743) and presence or absence of foreign body (P=0.381) over time. However, the two groups of BMP7 + nanosilver and BMP7 alone showed significant differences over time. Rats do not have sufficient number of efficient receptors for BMP7 in muscle tissue. Even by using nanosilver particles for increasing the permeability of cells, BMP7 was not able to induce muscle cell differentiation to initiate calcification process.

Despite the high success rate, implant-supported prostheses fail in some cases. Control of the applied forces is an important factor determining the success or failure of implants. Complete understanding of the biomechanical principles in implant-supported prostheses is necessary for offering an appropriate custom-made treatment plan for each patient and reducing the risk of functional complications. Finite element analysis is a quantitative method for the assessment of force distribution in complex structures. This study sought to compare the effect of different framework materials on stress distribution in bone supporting implants using three-dimensional finite element analysis. In this in-vitro study, a three-dimensional model of bone was obtained using Cone Beam Computerized Tomography (CBCT). Using CATIA V5R20 (Dassault Systemes, France) software, a NobelReplace tapered implant (Nobelpharma Co., Gothenburg, Sweden) measuring 13 mm in height and 4.3 mm in diameter was virtually inserted in the anterior maxilla. A titanium abutment, ZOE cement and superstructure with different frameworks (Ag-Pd, Ni-Cr, and fiber-reinforced composite) were designed. Force was applied in an amount of 178 N at three angulations of zero, 30 and 45° relative to the implant axis and the maximum von-Mises stress and maximum strain were calculated for cortical and trabecular bone. Changing the framework material caused a small change in level of stress and strain and their distribution pattern. By increasing the angulation of the applied force, amount of stress and strain in the implant-supporting bone increased. Maximum stress and strain were applied at 45° angulation. At zero degree angulation, maximum stress in the cortical bone was 17.326 MPa with Ni-Cr framework, 17.383 MPa with Ag-Pd and 17.321 MPa with fiber-reinforced composite. In loading at 30° angulation, maximum stress in the cortical bone was 136.95 MPa with Ni-Cr framework, 136.03 MPa with Ag-Pd framework and 136.18 MPa with fiber-reinforced composite framework. In loading at 45° angulation, maximum stress in the cortical bone was 161.37 MPa with Ni-Cr, 161.21 MPA with Ag-Pd and 160.4 MPawith fiber-reinforced frameworks. The difference between framework materials with higher and lower strengths in amount and pattern of cortical stress and strain distribution was insignificant

Oral and dental injuries commonly occur during oral and nasal intubation and comprise one third of lawsuits against anesthesiologists. This study sought to assess dental traumas(especially minor injuries like cracks) due to oral and nasal intubation and related risk factors. This observational prospective study was conducted on 60 patients (30 patients in the oral and 30 in the nasal intubation groups) during 2010-2011 in Taleghani Hospital in Tehran. Patients were examined using a disposable sterile clinical examination kit, a periodontal probe and a light curing unit. Maxillary central incisors had the highest incidence of new cracks (60% and 63.3% in the oral and nasal intubation groups, respectively). Gender, BMI, ASA class, Angle’s classification, and experience of the operator who inserted the tube had no significant association with higher frequency of cracks in the two groups. Incidence of visible dental injuries following nasal and oral intubation was 1.7% and 10%, respectively. Invisible dental injuries due to intubation are highly prevalent. These injuries are mostly disregarded by the anesthesiologists since they are not visible and do not cause any complication or problem during anesthesia. Enhancing the knowledge of anesthesiologists about dental anatomy, physiology and pathology and use of teeth-guard are necessary measures to prevent such injuries.

Programming for a successful operation and accurate prediction of the outcome of orthognathic surgery result in correction of occlusal and skeletal relations and improve the facial esthetics and function of patients. This retrospective study sought to assess the soft tissue changes following subcondylar and bilateral sagittal split osteotomy (BSSO) to retrude mandible in patients with mandibular prognathism. This retrospective experimental study evaluated 35 patients with mandibular prognathism and a mean age of 25.5 years (range 18.8 to 30.9 yrs). Cephalometric variables were measured on lateral cephalograms of patients before and after surgery and recorded. A total of 12 patients had undergone BSSO while 23 subjects had received subcondylar surgery. Cephalometric variables were analyzed using paired t- and independent t-tests. The study results demonstrated that the mean changes in cephalometric soft tissue variables of Ls-Pr (P<0.05), Li-Id (P<0.01) and G-Sn/Sn-Me (P<0.05) after BSSO were significantly higher that the rates in Subcondylar surgery group. However, the mean changes in soft tissue variables of SLs-A (P<0.05), a2 facial angle (P<0.05) and LFH (P<0.001) in subcondylar surgery group were significantly higher than the rates in BSSO group. In patients that had undergone subcondylar surgery, the lower facial height and the mentocervical angle had increased which is indicative of a shift towards a straight facial profile after this type of surgery. This study showed that a greater improvement in profile is achieved after BSSO compared to subcondylar surgery according to the current esthetic parameters.

Rhino-orbito-cerebral mucormycosis is a rare invasive fungal disease, which often has a fulminant and characteristic clinical course. The patients are usually immune-compromised, with diabetic ketoacidosis. The underlying disease is an important factor determining the prognosis of infection and response to treatment. Case: The authors report a case of fulminant rhino-orbito-cerebral mucormycosis with no apparent underlying disease. Therapy included surgical intervention and systemic administration of amphotericin B. However, due to the aggressive behavior of disease and occult underlying systemic condition the treatment was unsuccessful and the patient died after debridement and medical therapy.

Only a few cases of Rhino-orbito-cerebral Mucormycosis have been reported in the literature with no identified predisposing factor. In our case, no specific predisposing factors were found accompanying the fulminant progression of rhino-orbito-cerebral mucomycosis.