Journal of Dental Biomaterials
Volume:2 Issue: 4, 2015

Statement of Problem: The pH of the human abscess has been measured as low as 5.0. This low pH could potentially inhibit setting reactions, affect adhesion, or increase the solubility of root end filling materials hence affect the compressive strength. Moreover, root end filling materials might expose or even mix with lidocaine HCL during periapical surgery. The aim of this in vitro study was to evaluate the effect of acidic pH and lidocaine on the compressive strength of calcium-enriched mixture (CEM). CEM was mixed according to the manufacturer’s instructions or with lidocaine (L), and condensed into 6×4 mm split moulds. The samples were exposed to phosphate buffered saline (PBS) at pH 5 or 7.4 for 7 or 28 days. Cylindrical blocks of CEM (total number = 120 and 15 for each group) were subjected to compressive strength test using a universal testing machine. Data were analysed using three-factor analysis of variance (ANOVA). Regardless of pH and time, significant differences were not found between lidocaine groups and the groups that were mixed according to the manufacturer’s instruction (p = 0.083). For both mixing agents, regardless of time, there were no significant differences between the two pH levels (p = 0.157). Regardless of the material and pH, there was a significant increase in the compressive strength from days 7 to 28 (p 0.001). Mixtures with lidocaine and exposure to an acidic environment had no adverse effects on the compressive strength of CEM Cement.

Statement of Problem: Mechanical strength and durability of dental composites are the main topics studied in this field of science today. This study examined fumed silica-based composite as a strong and durable restorative material through flexural and cycling test methods. The purpose of this study was to evaluate the effect of silanization, ageing, cycling and hybridizing on mechanical properties of fumed silica-based resin composite. Composites were made of light-cured copolymer based on Bisphenol A glycolmethacrylate (Bis-GMA) and Triethylene glycoldimethacrylate (TEGDMA) at proportion of 50:50 which reinforced by fumed silica filler. For each composite sample, 5 specimen bars were made using Teflon mould (2 x 2 x 25 mm3). The samples with 12 wt% fumed silica (FS) were considered as a base line group. The samples were exposed to cyclic cold water (FS-CCW) and hot water (FS-CHW). The effect of silanization and adding more filler was studied together with samples containing 12 wt% (FS-S (12), 16 wt% (FS-S (16) and 20 wt% (FS-S (20) fumed silica filler. The filler was silanized with (γ-MPS). The degree of conversion was assessed with Fourier Transform Infra-Red spectroscopy. Flexural properties were evaluated with the Three-Point Bending test. Flexural data were analyzed with Excel software. Hardness was measured with an Atomic Force Microscope (AFM). The degree of conversion of the resin reached 74% within 24 hrs. Salinization allowed more filler to be wetted by resin. Addition of silanized particles from sample FS-S (12) to sample FS-S (20) improved the mechanical strength. Hybridizing fumed silica with nano-silica (FS-N) had no significant effect on the strength, but nano-hardness improved greatly. Ageing and cycling had adverse effects on the strength of the sample FS. The flexural strength of FS-CHW was 72% less than FS sample. Sample FS-N with low diluent and filler percentage complied with the requirements of flexural strength was established by ISO 4049/2009 and may be cost benefit to be used as a dental composite for clinical application.

Statement of Problem: Bleaching systems with different concentrations and applications are widely used to improve the visual appearance of the teeth, but one of the complications of these materials is reduction of bond strength for immediately bonding to the bleached enamel. The aim of this study was to evaluate the influence of using different modified hydrogen peroxide bleaching agents on the shear bond strength of composite resin bonded to the bleached enamel. Forty-eight sound extracted premolar teeth were collected, sectioned 1 mm below the CEJ to detach the root. The proximal surfaces of the teeth were flattened using diamond disks and silicon carbide papers to achieve flat homogeneous enamel surfaces without exposure to the dentin. The teeth were randomly divided into four groups as follows (n = 12): group 1: bleaching with 35% hydrogen peroxide gel; group 2: bleaching with 35% hydrogen peroxide gel contained (casein phosphopeptide-amorphous calcium phosphate (CPP-ACP); group 3: bleaching with 35% hydrogen peroxide gel combined with fluoride; and group 4: bleaching with 35% hydrogen peroxide applying one week before resin restoration placement. Composite resin, Clearfil AP-X (Kuraray, Tokyo, Japan), was bonded on each tooth in the mould (4 mm diameter × 3 mm height) using Clearfil SE Bond (Kuraray, Tokyo, Japan). After 24 hours of storage and 1000 cycles of thermocycling, the shear bond strength of the specimens at a cross-head speed of 0.5 mm/min was measured in MPa. Data were analyzed using ANOVA and Tukey’s post-hoc test. The minimum and maximum mean shear bond strength values were observed in groups 2 (15.82 ± 4.41) and 4 (21.00 ± 3.90), respectively. Multiple comparisons of groups revealed no significant differences among the groups except between group 4 and all the other groups. The most common type of failure was adhesive. Using modified bleaching agents decreased the bond strength of the composite resin to the enamel when it was used immediately after bleaching.

Statement of Problem: There is no enough published data about the shear bond strength of resin modified glass ionomer adhesives on caries-affected primary tooth dentin excavated using minimally invasive systems. To evaluate the shear bond strength of 2 different adhesives (one resin modified glass ionomer and one resin) using two caries removal techniques on healthy and caries-affected primary dentin. Two caries removal methods including mechanical (handpiece) and chemomechanical (Carisolv) techniques and two types of adhesives including one resin adhesive (Clearfil SE Bond; CSEB, Kuraray) and one resin-modified glass ionomer adhesive (Riva Bond LC; RBLC, SDI) were used in this study. Ten extracted healthy primary teeth were used for the control group. The teeth were sectioned bucco-lingually and mesio-distally in order to obtain four specimens from each tooth. Thirty suitable specimens were selected as the “control” and randomly divided into two groups of “sound dentin” based on the type of the adhesive used. Sixty extracted caries affected teeth were used for the carious group; sectioned as mentioned above and sixty suitable specimens were selected as the “treatment”. Then the specimens were arbitrarily divided into four groupsbased on caries removal techniques and the type of adhesive used (n =15). After bonding with either CSEB or RBLC, the specimenswere restored with a resin composite by means of PVC tubes and subjected to the shear bond strength test. The data was analyzed using ANOVA and Tukey’s test. The specimens in Carisolv group bonded with CSEB (11.68 3.1) showed a statistically significant higher mean bond strength followed by those in handpiece group bonded with CSEB (9.4 2.7), which exhibited higher mean values than those groups with RBLC (p < 0.05). Shear bond strength values for Clearfil SE Bond was not significantly higher than Riva Bond LC when used in sound dentin. The lowest shear bond strengths for both adhesives were observed on caries-free dentin.

Statement of Problem: The viscosity of orthodontics adhesive primers is crucial for stability and correct brackets ‘position during bond up. An excessive adhesive flow during brackets seating could change the brackets’ position. The main purpose of this study was to investigate the viscosity of four orthodontic adhesive primers in two different temperatures. Four orthodontic adhesive primers were used in this study. They include Transbond self-etching primer (SEP; 3M Unitek, USA), Transbond XT(3M Unitek, USA), Transbond moisture insensitive primer (MIP; 3M Unitek, USA), and Unite adhesive primer (3M Unitek, USA). A controlled stress rheometer (Carri-Med MKII, UK) with truncated cone and plate were used to investigate the viscosity of each orthodontic adhesive primer in two different temperatures. The orthodontic adhesive primers were tested at 25°C and 35°C for five times to calculate the means for each material during ascent and descent of the controlled stress rheometer. Statistical analysis was done with one-way ANOVA and two-sample t-test. In this study, a statistically significant difference was found among viscosity of different orthodontic adhesive primers (p = 0.005). At 25°C, the Transbond XT (192.20 ± 1.21 MPa·s) was the most viscous primer and Transbond MIP (21.74 ± 1.50 MPa·s) the least viscous one. Unite adhesive primer (143.40 ± 2.17MPa·s) was the second most viscous primer followed by Transbond SEP (44.28 ± 3.09 MPa·s). The difference of the viscosity of orthodontic adhesive primers was also statistically significant when compared in two different temperatures. This study showed that there was a statistically significant difference among the viscosity of the four orthodontic adhesive primers. Moreover, the viscosity of orthodontic adhesive primers also changed with temperatures. This might affect the orthodontic bond up procedure during summer and winter.

Statement of the Problem: Dental prosthesis is usually made indirectly; therefore dimensional stability of the impression material is very important. Every few years, new impression materials with different manufacturers’ claims regarding their better properties are introduced to the dental markets which require more research to evaluate their true dimensional changes. The aim of this study was to evaluate dimensional stability of additional silicone impression material (Panasil® and Affinis®) in different time intervals. In this experimental study, using two additional silicones (Panasil® and Affinis®), we made sixty impressions of standard die in similar conditions of 23 °C and 59% relative humidity by a special tray. The die included three horizontal and two vertical lines that were parallel. The vertical line crossed the horizontal ones at a point that served as reference for measurement.All impressions were poured with high strength dental stone. The dimensions were measured by stereo-microscope by two examiners in three interval storage times (1, 24 and 168 hours). The data were statistically analyzed using t-test and ANOVA. All of the stone casts were larger than the standard die. Dimensional changes of Panasil and Affinis were 0.07%, 0.24%, 0.27% and 0.02%, 0.07%, 0.16% after 1, 24 and 168 hours, respectively. Dimensional change for two impression materials wasn’t significant in the interval time, expect for Panasil after one week (p = 0.004). According to the limitations of this study, Affinis impressions were dimensionally more stable than Panasil ones, but it was not significant. Dimensional change of Panasil impression showed a statistically significant difference after one week. Dimensional changes of both impression materials were based on ADA standard limitation in all time intervals (< 0.5%); therefore, dimensional stability of this impression was accepted at least until one week.