This in vitro study was performed to evaluate antibacterial effect and thermal expansion of commercial available poly-methyl methacrylate (PMMA) incorporated by nano graphene oxide (GO) in different concentration. Method: Nano graphene oxide in five concentrations 0 %, 0.05 %, 0.1 %, 0.15 % and 1 % by weight was incorporated to PMMA to form groups I-V respectively. To evaluate the antibacterial effect against Streptococcus Mutans, minimal inhibitory concentration (MIC) for GO dispersion was done and agar well diffusion test for groups I-IV was done. Thermal expansion was assessed through measuring the linear coefficient of thermal expansion. Results: For antibacterial effect, all concentrations tested for MIC showed inhibition zone varied from 0.5 to 2mm in diameter. All tested groups evaluated by agar well diffusion method showed no inhibition zones except for group II. Significant reduction in coefficient of thermal expansion was showed by increasing GO concentration. Conclusions: Incorporation of GO in to PMMA at concentration of 0.5 % can inhibit the growth of Streptococcus Mutans. There is an inverse relation between the concentrations of GO and the coefficient of thermal expansion.
Purpose:The purpose of the present study was to assess the influence of repeated piezoelectric ultrasonic strokes on the marginal leakage of different ceramic cemented crowns.
Materials and Methods:Forty human maxillary first premolars received full coverage standardized preparation 1mm above the cemento-enamel junction (CEJ). All teeth were classified into 2 groups (n=20) related to the type of the examined ceramic material; high translucent zirconia (HTZ) and hybrid resin ceramic (HRC). After all the fabricated crowns cementation with selfadhesive resin cement, each group was later partitioned into 4 subgroups (n=5). This was based on the amount of exposed ultrasonic scaler strokes. Microleakage assessment of buccolingual sectioned samples was performed, after their immersion in 2% methylene blue (MB) dye. Stereomicroscope was used for dye penetration measurement.
Results:The highest leakage percentage was recorded for HTZ, while the lowest mean value was achieved with HRC. The difference between the two groups was statistically significant (P= 0.022 <.05) as reported by one-way ANOVA. 7 years of scaler strokes for HTZ showed the highest microleakage mean with statistical significant difference p=0.008 between the subgroups. All the subgroups for HRC showed statistical insignificant difference with p=0.728.
Root canal preparation is one of the most important steps in endodontic treatment (1,2) . An old endodontist saying, "What is removed from the root canal may be more important than what is placed inside it" (3) .
Although many advancements have been madein endodontics in the last years, the complicated root canal anatomy still adversely affects root canal preparation (4) . The apical third is the most difficult to be cleaned and shaped because of the ever-increasing complexity of the anatomy (5) .
Background: Stability of implant bone interface is a critical determinant for long term success of implant supported prostheses. This is of paramount importance in edentulous patients undergoing haememandibulectomy due to small remaining bony foundation area combined with increased level of stresses. Fatigue life of bone is affected by amount of stress transmitted which may exceed physiological tolerance of bone with subsequent resorption. Implant abutment connection system (IACS) is an influential factor affecting stress distribution. Objective: The purpose of the study is to compare the effect of different type of implant abutment connection system (external hexagonal, internal hexagonal and internal conical) of used implants under the overdenture in fatigue life of remaining bone of hemimandible. Materials & methods: A threedimensional finite element study model was constructed and duplicated three times. The model was composed of hemimandible screwed with reconstructive plate and restored by overdenture. The overdenture was retained by three implants of the same type of (IACS) at three positions. The only difference between the three models was the type of IACS used. Model (A) had implants of external hexagonal connection system, Model (B) had implants of internal hexagonal connection and model (C) had internal conical connection. Results: bone of internal hexagonal connection model showed largest number of fatigue life cycles, whereas external hexagonal connection showed smallest one and the values of internal conical connection model was intermediate. Conclusion: under the limitations of the current study, it may be concluded that using internal hexagonal IACS in implant supported mandibular overdenture rehabilitating hemimandible may be the most suitable type
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