In this study, the depth of cure of composite resins cured within simulated root canals by means of light-transmitting plastic posts was compared to that achieved by the conventional light-curing method. Six sizes of posts with diameters of 1.05 mm, 1.20 mm, 1.35 mm, 1.50 mm, 1.65 mm, and 1.80 mm were investigated. In general, the larger the post diameter, the greater was the depth of cure. There were significant differences in the depth of cure between the control and all sizes of posts investigated. There were also significant differences between the various post diameters except for the 1.35 mm and 1.50 mm diameter posts. It was possible to achieve a depth of cure exceeding 11 mm using these light-transmitting posts.
This study (1) compared the curing-light intensity with various barrier infection-control methods used to prevent cross contamination, (2) compared the Knoop hardness value of cured composite resin when various barrier control methods were used, and (3) correlated the hardness of the composite resin with the light-intensity output when different infection-control methods were used. The light-cure unit tips were covered with barriers, such as cellophane wrap, plastic gloves, Steri-shields, and finger cots. The control group had no barrier. Composite resins were then cured for each of the five groups, and their Knoop hardness values recorded. The results showed that there was significant statistical difference in the light-intensity output among the five groups. However, there was no significant statistical difference in the Knoop hardness values among any of the groups. There was also no correlation between the Knoop hardness value of the composite resin with the light-intensity output and the different infection-control methods. Therefore, any of the five infection-control methods could be used as barriers for preventing cross-contamination of the light-cure unit tip, for the light-intensity output for all five groups exceeded the recommended value of 300 W/m2. However, to allow a greater margin of error in clinical situations, the authors recommend that the plastic glove or the cellophane wrap be used to wrap the light-cure tip, since these barriers allowed the highest light-intensity output.
This study investigated the effects of environmental pH on the flexural properties of ion-releasing restorative materials (IRMs), including giomer (Beautifil-Bulk Restorative - BB), alkasite (Cention N - CN), bioactive composite (Activa - AB) and resin-modified glass ionomer (Riva Light Cure -RV) restoratives. A bio-inert resin-based composite (Filtek Bulk-fill Posterior - FB) served as the control. Stainless steel molds were used to fabricate 40 beam-shaped specimens (12mm × 2mm × 2mm) for each material. The specimens were finished, measured, and randomly distributed into four groups (n=10) and immersed in aqueous solutions of pH 3.0, pH 5.0, pH 6.8, and pH 10.0 at 37°C for 28 days. Specimens were then subjected to a uniaxial three-point bending flexural test with a load cell of 5 KN and a fixed deformation rate of 0.5 mm/min until fracture occurred. Flexural modulus and strength were statistically analyzed using analysis of variance/Dunnet T3's test (p=0.05). Mean flexural modulus varied from (2.40±0.41 to 9.65±1.21 GPa), while mean flexural strength ranged from (21.56±2.78 to 163.86±13.13 MPa). Significant differences in flexural properties were observed among the various pH values and materials. All materials immersed in artificial saliva (pH 6.8) presented the highest flexural properties, except AB. The flexural strength of AB was significantly better when exposed to acidic environments. FB had better flexural properties than IRMs after exposure to a range of environmental pH values.
This study examined the influence of cariogenic environments on the surface roughness of ion-releasing restorative materials (IRMs). Custom-made stainless steel molds with holes of 5 mm × 2mm were used to fabricate 60 disc-shaped specimens of each of the following materials: Activa Bioactive (AV), Beautifil Bulk Restorative (BB), Cention N (Bulk-fill) (CN), and Filtek Z350XT (FZ) (Control). Baseline surface roughness (Ra) measurements were obtained using an optical 3D measurement machine (Alicona Imaging GmbH, Graz, Austria). The specimens were then randomly divided into five subgroups (n=12) and exposed to 10 ml of the following mediums at 37°C: distilled water (DW), demineralization solution (DM), remineralization solution (RM), pH cycling (PC) and air (AR) (control). Ra measurements were again recorded after one week and one month, followed by statistical evaluations with two-way analysis of variance (ANOVA) to determine interactions between materials and mediums. One-way ANOVA and post hoc Games Howell tests were performed for intergroup comparisons at a significance level of 0.05. Mean Ra values ranged from 0.085 ± 0.004 (µm) to 0.198 ± 0.001 µm for the various material-medium combinations. All IRMs showed significant differences in Ra values after exposure to the aqueous mediums. The smoothest surfaces were observed in the AR for all materials. When comparing materials, AV presented the roughest surfaces for all mediums. All IRM materials showed increased surface roughness over time in all cariogenic environments but were below the threshold value for bacterial adhesion, except for AV 1-month post immersion with pH cycling. Therefore, besides AV, the surface roughness of IRMs did not deteriorate to an extent that it is clinically relevant.