JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2020 | Volume:32 | Issue:1-2|Papers Count:6

Background and Aim: Dislodgment of prosthetic crowns is a common occurrence. In such cases, recementation is a suitable treatment option. The aim of this study was to compare the retention in cementation and recementation using different resin cements. Materials and Methods: In this in vitro, experimental study, 40 premolars were selected (n=10). They were standardized relative to some properties and then the wax patterns were prepared and cast. After 24 h, all specimens were decemented using Instron universal testing machine. The castings were then re-cemented and stored under the same conditions. After 24 h, the cemented copings were dislodged, and the separation load was recorded. Results: The highest and the lowest mean retention values belonged to Panavia F2 and Maxcem cements in both initial cementation and recementation groups, respectively. Paired sample t-test showed a significant difference in the retention of G-CEM group between initial cementation and recementation (P=0. 009). The two-factorial repeated measures ANOVA showed the significant effect of cement type on retention (P=0. 009), and there was a significant difference in retention between initial cementation and recementation (P=0. 006). The Tukey’ s HSD test revealed a significant difference in retentive strength between the Maxcem and Panavia F2 (P=0. 011). The lowest mean difference was observed between Bifix SE and Maxcem groups (-16. 75 kgf, P=0. 89). Conclusion: The maximum and minimum mean retention values belonged to Panavia F2 cement and Maxcem in both initial cementation and recementation groups, respectively. There was a significant difference between the initial cementation and recementation in G-CEM group.

Background and Aim: Er, Cr: YSGG laser irradiation has been suggested as an effective method of cavity preparation and surface treatment to enhance the bond strength. The aim of this study was to assess the microshear bond strength of Fuji II LC glass ionomer (GI) cement to primary dentin following bur preparation and Er, Cr: YSGG irradiation. Materials and Methods: This in vitro, experimental study was conducted on 20 extracted primary canine teeth. After debris removal, the teeth were sectioned buccolingually and divided into two groups. In group 1, the exposed dentin surface was prepared by fissure bur; while in group 2, the dentin surface was subjected to Er, Cr: YSGG laser irradiation with 2 W power and 80% air and 50% water. Fuji II LC GI cement was applied. After 24 h of storage, the samples were subjected to microshear bond strength test in a microtensile tester. The bond strength values in the two groups were compared using Student t-test. Results: The mean (± standard deviation) microshear bond strength of GI to dentin was 15. 36± 2. 98 MPa in the laser and 4. 86± 1. 36 MPa in the bur group. The mean microshear bond strength in the laser group was significantly higher than that in the bur group (P<0. 0001). Conclusion: Irradiation of Er, Cr: YSGG laser with 2 W power increases the microshear bond strength of Fuji II LC GI to primary dentin, and is superior to bur preparation for this purpose.

Background and Aim: High chipping rates of the veneering porcelain in zirconia ceramic restorations have been reported in many clinical studies. However, information on the bonding behavior of veneering porcelain to zirconia and lithium disilicate frameworks is limited. The purpose of this study was to evaluate the bonding strength of porcelain veneering to zirconia, lithium disilicate, nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys. Materials and Methods: In this in vitro experimental study, core specimens were fabricated with 12 mm height and 11 mm diameter, and veneering specimens were fabricated with 7 mm height and 5 mm diameter according to the manufacturer’ s instructions in four groups (n=12) as follows: Group I: Ni-Cr alloy, group II: Co-Cr alloy, group III: lithium disilicate, and group IV: zirconia. The shear bond strength (SBS) test was performed in all samples with a universal testing machine with a crosshead speed of 0. 5 mm/min. The fractured samples were examined under a stereomicroscope (×10) to determine the mode of failure. The results were analyzed by one-way ANOVA (P<0. 05). Results: Maximum SBS was recorded in group IV (zirconia; 34. 6 MPa) followed by groups II (Co-Cr; 30. 66 MPa), I (Ni-Cr; 30. 58 MPa), and III (lithium disilicate; 20. 05 MPa). One-way ANOVA revealed no significant difference between the study groups (P=0. 174). Conclusion: The SBS of porcelain veneering to zirconia, lithium disilicate, Ni-Cr, and Co-Cr alloys was not significantly different.

Background and Aim: The conventional procedure for removal of porcelain laminate veneers (PLVs) is time-consuming and inconvenient. The purpose of this study was to evaluate the efficacy of Er: YAG laser for debonding of PLVs. Materials and Methods: Forty-eight intact extracted human maxillary anterior teeth received discoid PLVs (24 feldspathic and 24 e-max ceramic). The PLVs had 0. 7 mm thickness and 4 mm diameter. After cementation of all PLVs with a light-cure cement, samples were stored at 37º C distilled water for 48 h. Samples of each ceramic were randomly divided into 3 groups of 8 samples. Then, laser was irradiated on the cemented PLVs as follows: (I) feldspathic PLVs without laser irradiation (control group), (II) feldspathic PLVs with laser irradiation (6 s, 10 Hz, 200 mJ, 2 W), (III) feldspathic PLVs with laser irradiation (6 s, 10 Hz, 300 mJ, 3 W), (IV) e-max PLVs without laser irradiation (control group), (V) e-max PLVs with laser radiation (6 s, 10 Hz, 200 mJ, 2 W), (VI) e-max PLVs with laser irradiation (6 s, 10 Hz, 300 mJ, 3 W). The shear bond strength of all samples was measured using a universal testing machine. We used Mann-Whitney and Kruskal-Wallis tests for data analysis (P<0. 05). Results: Laser irradiation decreased the shear bond strength of both ceramics. But this decrease was only significant for the e-max group (P<0. 05). No significant difference was found between different laser irradiation powers in the two ceramic groups. Conclusion: Er: YAG laser is effective for debonding of e-max PLVs.

Background and Aim: Saliva, as an easy diagnostic tool, has various defense mechanisms such as immunological, enzymatic and antioxidant defense systems. Salivary peroxidase is one of the most important salivary antioxidants. Human immunodeficiency virus (HIV) positive and acquired immunodeficiency syndrome (AIDS) patients have decreased antioxidant and increased oxidative stress levels. Therefore, the aim of this study was to compare the level of salivary peroxidase in HIV positive patients and healthy controls. Materials and Methods: In this case-control study, 49 HIV positive patients and 49 healthy controls were selected as the case and control group, respectively. Demographic, clinical, and paraclinical information was recorded in a checklist. Next, 5 mL of unstimulated whole saliva was collected during 5 min in sterile Falcon tubes. Peroxidase activity of the saliva was measured by the Gelycol method. Data were analyzed by SPSS 11 via t-test and Chi-square test. Results: The salivary peroxidase level was slightly higher in the case group in comparison with the healthy control group, but this difference was not statistically significant (P=0. 157). Dental status of the case group was significantly different from the control group (P=0. 029). The mean age of the case group was also significantly higher than the control group (P=0. 005). In the case group, females had a higher frequency than males. Conclusion: The results showed slightly, but not significantly, higher level of peroxidase in the study group than the healthy controls. Minimal change in salivary peroxidase in HIV positive patients may be related to the early stage of their disease and good function of the immune system.

Background and Aim: Local anesthetic injection is among the most anxiety-provoking procedures in children. Some scales are currently available to quantify the level of pain experienced based on the child’ s behavior. The purpose of this study was to compare two commonly used pain scales. Materials and Methods: This split-mouth study was conducted on 49 healthy children aged 3. 5 to 9 years who needed dental treatment of bilateral primary molars under local anesthesia. The patients were randomly assigned to two groups. The level of anxiety was recorded at baseline and during local anesthetic injection according to the face-legs-activity-cry-consolability (FLACC) and the sound-eyesmotor (SEM) scales in the two groups. Then, the level of pain experienced by the child was determined according to the visual analog scale (VAS). Data were analyzed by SPSS version 20 using Mann-Whitney and Wilcoxon tests at 0. 05 level of significance. Results: There was no statistically significant difference in pain score based on VAS after local anesthetic injection in the first and second sessions between the SEM (P=0. 877) and FLACC (P=1. 00) groups. Conclusion: This study showed that there was no difference between the SEM and FLACC scales regarding pain perception during local anesthetic injection in children, and some parameters of the two scales that were measured in the children’ s face area were behaviors that the children exhibited during local anesthetic injection.