JOURNAL OF DENTAL BIOMATERIALS
Year:2017 | Volume:4 | Issue:1|Papers Count:5

Statement of Problem: Patients’ demand for tooth-colored restoratives in the posterior region is increasing. Clinicians use universal nanohybrid resin composites for both anterior and posterior regions. There are few published reports comparing fracture toughness of nonohybrids and that of hybrid composite stored wet and dry.Objectives: To investigate the fracture toughness of three nanohybrids compared to that of a hybrid resin composite stored dry or wet up to 60 days, using four-point bending test.Materials and Methods: Four resin composites were used: three nanohybrids; Filtek Supreme (3M), Ice (SDI), TPH3 (Dentsply) and one hybrid Filtek P60 (3M). For each material, 40 rectangular notched beam specimens were prepared with dimensions of 30 mm ´ 5mm ´ 2mm. The specimens were randomly divided into 4 groups (n=10) and stored at 37oC either in distilled water or dry for 1 and 60 days. The specimens were placed on the four-point test jig and subjected to force (N) using universal testing machine loaded at a crosshead speed of 0.5mm/min and maximum load at specimen failure was recorded and KIc was calculated.Results: Three-way ANOVA showed a significant interaction between all the factors (all p<.0001). Except for TPH3, all tested materials showed significantly higher KIc when stored dry than stored wet (p<0.05). After 1 day of dry storage, Ice showed the highest KIc (2.04 ± 0.32) followed by Filtek P60 and the lowest was for Filtek Supreme (1.39 ± 0.13). The effect of time on fracture toughness was material dependent.Conclusions: Wet storage adversely affected the fracture toughness of almost all materials. Keeping the restoration dry in the mouth may increase their fracture toughness. Therefore, using a coating agent on the surface of restoration may protect them from early water uptake and increase their strength during a time period.

Statement of Problem: Acid producing bacteria including Streptococcus mutans and lactobacilli cause tooth demineralization and lead to tooth decay. Also, oral colonization of the species of Candida has been reported in many studies that are resistant to antifungal agents.Objectives: In this study, antibacterial and antifungal effects of nano-CuO were studied against some oral bacteria and yeast fungi.Materials and Methods: The minimum inhibitory concentrations (MICs) of copper oxide nanoparticles (CuO NPs) for oral bacterial and fungal test strains were determined in 96-well microtiter plate technique. The agar diffusion test (ADT) was employed to assess the antifungal properties of nystatin.Results: The MIC50 value of CuO NPs was determined at the range of 1-10 mg/ml for S. mutans, <1 mg/ml for L. acidophilus, and 10 mg/ml for L. casei. Higher concentrations of CuO NPs (100-1000 mg/ml) were effective on the bacterial cell growth, resulting in 100% reduction in the optical density in TSB medium. The cells of Candida albicans, C. krusei and C. glabrata were treated with CuO NPs and the results showed a decrease in fungal growth at a concentration of 1-1000 mg/ml in TSB medium. The MIC50 value of CuO NPs was determined 1000 mg/ml for three species of Candida. The diameter of growth inhibition zones of 1100 mg/ml nystatin was obtained 15-21 mm for clinical isolates of three species of Candida.Conclusions: With respect to the potential bactericidal activity of CuO NPs on various cariogenic bacteria examined in this study, these NPs could be introduce as a candidate control agent for preventing dental caries or dental infections. In our study, on the other hand, Nano copper oxide had a weak effect on the candida species.

Statement of Problem: Fixed orthodontic appliances in the oral cavity make tooth cleaning procedures more complicated.Objectives: This study aimed to compare the efficacy of computerized oral hygiene instruction with verbal technique among fixed orthodontic patients referred to the evening clinic of Orthodontics of Shiraz Dental School.Materials and Methods: A single-blind study was performed in Orthodontic Department of Shiraz, Islamic Republic of Iran, from January to May 2015 following the demonstrated exclusion and inclusion criteria. The sample size was considered 60 patients with 30 subjects in each group. Bleeding on probing and plaque indices and dental knowledge were assessed in the subjects to determine pre-intervention status. A questionnaire was designed for dental knowledge evaluation. The patients were randomly assigned into the computerized and verbal groups. Three weeks after the oral hygiene instruction, indices of bleeding on probing and plaque index and the dental knowledge were evaluated to investigate post-intervention outcome. The two groups were compared by chi-square and student t tests. The pre- and post-intervention scores in each group were compared using paired t -test.Results: In the computerized group, the mean score for plaque index and bleeding on probing index was significantly decreased while dental health knowledge was significantly increased after oral hygiene instruction, in contrast to the verbal group.Conclusions: Within the limitations of the current study, computerized oral hygiene instruction is proposed to be more effective in providing optimal oral health status compared to the conventional method in fixed orthodontic patients.

Statement of Problem: The casein phospho peptide-amorphous calcium phosphate with or without fluoride (CPP-ACPF and CPP-ACP respectively) are of considerably new materials which are highly recommended for prevention of dental caries. However, there is a shortage in literature on how they affect the ion concentration of saliva or dental plaque.Objectives: The aim of this study was to evaluate the concentration of calcium, phosphate and fluoride in the plaque and saliva of children with Early Childhood Caries (ECC) after applying the CPP-ACP paste in comparison with the use of CPP-ACPF paste.Materials and Methods: One ml of un-stimulated saliva of 25 preschool children was collected and then 1 mg of the plaque sample was collected from the buccal surfaces of the two first primary molars on the upper jaw. CPP-ACP as well as CPP-ACPF pastes were applied on the tooth surfaces in two separate steps. In steps, plaque and saliva sampling was performed after 60 minutes. The amount of calcium ions was measured by Atomic Absorption Device and the amount of phosphate and fluoride ions was measured by Ion Chromatography instrument. Data were analyzed using Repeated Measurements ANOVA at a p<0.05 level of significance.Results: Application of both CPP-ACPF and CPP-ACP significantly increased the concentration of calcium, phosphate, and fluoride in both saliva and dental plaque. Moreover, significantly higher salivary fluoride concentration was seen after application of CPP-ACPF compared to CPP-ACP. No other significant difference was observed between these two materials.Conclusions: CPP-ACPF can be more useful than CPP-ACP in protecting the primary teeth against caries process, especially when there is poor hygiene.

Statement of Problem: Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures.Objectives: The purpose of this study was to compare the shear bond strength (SBS) of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core.Materials and Methods: Two groups were selected: porcelain fused to metal (PFM) and porcelain fused to Zirconia (PFZ) (n=30).In the PFM group, a wax model (10´10´10mm) was used to cast metal base (Ni_Cr alloy). In the PFZ group, an acrylic cubic model (10´10´10mm) was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness (2.5´2.5´2 mm). All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55°C and 5ºC alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test.Results: Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength (p=0.455).Conclusions: There was no significant difference between the two groups of PFM and PFZ in the item SBS.