Amir Reza Rokn, DDS, MSc
Mohammad-Sadegh Ahmad-Akhoundi, DDS, MSc.
Shahroo Etemad-Moghadam, DDS, MSc.
Abbas Mirzaei, PhD
Vol 16, No 1 (2019)
Objectives: The purpose was to determine the antibacterial properties of propolis and to evaluate its use as an antibacterial mouthwash with minimal complications
Materials and Methods: In this experimental laboratorial study, the alcoholic extract of Propolis was first prepared. Then the Minimum Inhibitory Consentration(MIC) was calculated for four bacterial species of staphylococcus aureus, Streptococcus mutans, Lactobacillus acidophilus and Enterococcus faecalis using the agar dilution test. Using the MIC, the Propolis antibacterial mouthwas was produced and compared to water, chlorhexidine and Listerine in laboratory rats for clinical examination. Salivary specimens of rats were collected 12 hours, 1 week and 2 weeks after using the mouthwash and examined by the real time PCR. Data were analyzed by SPSS using one-way ANOVA and the independent t-test (α=0.05).
Results: The results of agar dilution test showed the lowest MIC for Staphylococcus aureus and the highest for Lactobacillus acidophilus. On the other hand, the results of this study showed that water alone had no effect on the level of oral bacteria. In the case of Streptococcus mutans, Enterococcus faecalis, and Lactobacillus Acidophilus mouthwash, the Propolis mouthwash showed a significant difference with chlorhexidine and listerine (P <0.05), while chlorhexidine and listerine had lower effect in comparison. As for Staphylococcus aureus, there was no significant difference between chlorhexidine and Propolis bacteria (P >0.05), but Listerine had the lower effect than either (P <0.05).
Conclusions: According to the results, propolis mouthwash was more efficient against the studied oral bacteria compared to CHX and Listerine.
Objectives: Nickel-chromium (Ni-Cr) base dental alloys with desirable properties have been employed in prosthodontics for years. Corrosion behavior of a Ni-Cr base alloy in artificial saliva with different pH values is determined in this work.
Materials and Methods: Corrosion behavior of Ni-Cr alloy was studied using weight loss described by corrosion rate (CR) in mils per year (mpy) and potentiodynamic polarization described by corrosion potential (CP) in mV and current density (CD) in mA/cm2 in artificial saliva with different pH. Surface morphology was studied using scanning electron microscopy (SEM). Statistical difference was assessed using one-way ANOVA and post-hoc Tukey's honestly significant difference (HSD) test with a difference significance of 95%.
Results: In weight loss method, CR was 71.95±3.40, 17.26±1.03, 8.92±0.35, and 6.93±0.54 mpy at pH values of 2.5, 5, 7, and 9, respectively. CR obtained at pH of 2.5 was significantly different than that in other groups, but those obtained at pH of 5, 7, and 9 were not significantly different. In the polarization method, CP values were significantly different. CD measured at pH of 2.5 and 5 was significantly different than the rest of pH values (P<0.05). CRs at pH of 7 and 9 were not significantly different. SEM exhibited the formation of preferential sites of corrosion attacks influenced by pH.
Conclusions: Both techniques revealed consistent results. Corrosion resistance increases as pH increases towards less acidic conditions. In more acidic saliva, .....
Objectives: Pit and fissure sealants are recognized as an effective preventive approach in pediatric dentistry. Composite resin is the most commonly used sealant material. Adding nanoparticles to composite resin could result in production of flowable composite with higher mechanical properties and better flowability than previous sealants. This study aimed to compare the microleakage of a flowable nanocomposite and materials conventionally used as pit and fissure sealants.
Materials and Methods: A total of 185 extracted mandibular third molar teeth were selected and randomly divided into 5 groups (n=36): flowable nanocomposite, flowable composite, filled sealants, nano-filled sealants, and unfilled sealants. Five teeth were reserved for examination under a scanning electron microscope (SEM). The samples were thermocycled (5-55°C, 1-minute dwell time) for 1000 cycles and immersed in 0.2% fuchsine solution for 24 hours. Teeth were sectioned buccolingually. Microleakage was assessed qualitatively and quantitatively by means of dye penetration and SEM. Data were analyzed using chi-square, Kruskal-Wallis, and Bonferroni-corrected Mann-Whitney U tests.
Results: Qualitative microleakage assessment showed that flowable composite and nanofilled flowable composite had almost no microleakage (P<0.001). Regarding quantitative scores, the nanofilled flowable composite and unfilled fissure sealant showed the lowest and the highest rate of microleakage, respectively. No statistically significant difference was found between the two flowable composites (P=0.317). Filled resin-based sealant had significantly lower microleakage than unfilled resin-based sealant (P<0.001).
Conclusion: Use of flowable and nanofilled flowable composites (but not unfilled resin-based fissure sealant) is recommended for sealing of pits and fissures of molars
Objectives: This study aimed to assess the microleakage of Pedo Jacket crowns compared to stainless steel crowns (SSCs) cemented with different cements.
Materials and Methods: In this in vitro experimental study, 80 primary molars were randomly divided into four groups of 20. Groups 1 and 2 were subjected to standard tooth preparation for SSC. Crowns in group 1 were cemented with glass ionomer (GI) and crowns in group 2 were cemented with resin modified glass ionomer (RMGI) cement. In groups 3 and 4, minimal tooth preparation was performed for Pedo Jacket crowns, and the crowns were cemented with RMGI and Panavia resin cement, respectively. Microleakage was measured in mesial and distal surfaces in micrometers, and the mean value for each tooth was calculated. One-way ANOVA was applied to compare the microleakage of the four groups.
Results: Group 3 (Pedo Jacket cemented with RMGI) showed the highest microleakage (1523.83±250.32 µm) with significant differences with the remaining three groups (P<0.001). Microleakage in group 4 (Pedo Jacket cemented with Panavia) was significantly lower than that in the other three groups (301.25±219.53 µm, P<0.001). Groups 1 (SSCs cemented with GI) and 2 (SSCs cemented with RMGI) were not significantly different in terms of microleakage (P=0.49), although group 1 showed slightly higher microleakage than group 2 (598.43±260.85 µm versus 500.25±124.74 µm).
Conclusion: Pedo Jacket crowns can serve as an acceptable esthetic alternative to SSCs if cemented with resin cements.
Objectives: The purpose was to compare shear bond strength (SBS), pulp temperature, and adhesive remnant index (ARI) in debonding of stainless steel brackets from enamel surface using neodymium-doped yttrium aluminum garnet (Nd:YAG) laser versus the conventional debonding method.
Materials and Methods: Forty-eight extracted premolars were bonded to stainless steel brackets. The samples were divided into three experimental groups and one control group. In the first three groups, Nd:YAG laser was used for debonding with the power of 1, 1.5, and 2 W, respectively, for 10 seconds. The SBS and ARI of the samples were assessed. Pulp temperature was recorded before and after irradiation. Two samples from each group were used for determining enamel morphology after debonding using scanning electron microscopy (SEM).
Results: The mean SBS in the groups was 33.05, 28.69, 24.37, and 31.53 MPa, respectively, with no statistically significant differences (P=0.205). Significant differences in post-irradiation temperature were noted among the lased groups (P=0.000). Debonding mainly occurred at the adhesive-enamel interface in the 1-W laser and control groups and at the bracket-adhesive interface in the 1.5-W and 2-W laser groups. Enamel structure was amorphous and irregular following laser irradiation.
Conclusions: Based on the results of this study, the use of Nd:YAG laser could not significantly affect the SBS. Therefore, this laser would not be suitable for debonding of metal brackets. The use of a 2-W laser could significantly raise the pulpal temperature. Nd:YAG laser renders a more heterogeneous enamel morphology compared to conventional debonding methods.
Objectives: In this study, chitosan was introduced and used as a substitute for pulpectomy obturation against conventional materials: zinc oxide eugenol (ZOE) and iodoform-calcium hydroxide (Ca(OH)2) compounds. Also, efficacies of rotary versus manual instrumentations were compared.
Materials and Methods: This preliminary in-vitro study was performed on 152 intact non-resorbed root canals of primary molars divided into rotary (n=78) versus hand-instrumentation (n=74) and also into ZOE (n=53), iodoform-Ca(OH)2 (n=50), and 3% nano-chitosan (n=49). Canals were cleaned/shaped using hand or rotary files. Canal spaces were measured using spiral computed tomography (CT). Canals were then obturated using the three materials. The percentages of obturation volume (POV) were estimated. Rotary and manual instrumentations were compared in terms of canal spaces before and after obturation. Three obturation materials were compared in terms of canal spaces after obturation (α=0.05).
Results: Average POVs of materials were 96.54% (ZOE), 97.87% (Metapex), and 74.74% (nano-chitosan; P=0.000). POV of chitosan differed from the other two (P=0.000) but the other two were similar (P=0.896). Average POVs were 91.46% (manual) and 88.51% (rotary); the difference was not significant (P=0.322). Pre-obturation spaces of canals for different methods were 3.89 mm3 (manual) and 3.26 mm3 (rotary); the difference was significant (P=0.013). Two-way ANCOVA showed a significant effect of materials (P=0.000) but not root length (P=0.585) or shaping methods (P=0.362) on POVs.
Conclusions: Nano-chitosan showed a considerable success rate but it still needs reformulation as it was weaker than the extremely successful commercial competitors.....
Objectives: This study aimed to evaluate the effect of toothbrushing after application of 15% carbamide peroxide (CP) on the surface roughness of three types of composite resins.
Materials and Methods: Twenty samples, measuring 4 mm in height and diameter, were fabricated of three composite resins namely microfilled (MF) Heliomolar HB, nanohybrid (NH) IPS Empress Direct and microhybrid (MH) Tetric Ceram HB. After polishing, the initial surface roughness was measured with a profilometer. The tray technique was used to apply 15% CP gel for 6 hours. Then, cleaning was carried out with an Oral-B electric toothbrush for 3 minutes in a tank containing a freshly mixed toothpaste. These procedures were repeated for 21 days. Then, the surface roughness was measured again and compared with the initial values. A mixed-design ANOVA model was used for the analysis of data (P<0.05).
Results: The baseline roughness was significantly lower in MF compared to the NH and MH composites (P<0.001). Roughness increased in all study groups during the intervention period; however, this increase was not significant in the MH group (P=0.17). Furthermore, the increase in roughness in MF was smaller than that in NH (P<0.001) and MH (P=0.02) groups.
Conclusions: The effect of intervention was more pronounced on NH and MH groups. Surface roughness changes were minor in MF composite resin.
Objectives: This study aimed to compare the shear bond strength (SBS) of self-adhesive and conventional flowable composites and resin-modified glass-ionomer cement (RMGIC) to primary dentin.
Materials and Methods: In this in vitro, experimental study, the buccal surface of 48 primary canine and first molar teeth was longitudinally sectioned to expose dentin. The teeth were randomly divided into three groups (n=16) of 37.5% phosphoric acid+ OptiBond+ Premise Flow composite (group 1), Vertise Flow composite (group 2) and RMGIC (group 3). A plastic cylindrical mold was placed on the exposed dentin and filled with restorative materials. The samples were then immersed in distilled water at 37°C for 24 hours, subjected to 1000 thermal cycles between 5-55°C and underwent SBS test. The mode of failure was determined under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s test.
Results: A significant difference was noted in SBS of the groups (P<0.05). The SBS of conventional flowable composite was significantly higher that of RMGIC and self-adhesive flowable composite (P<0.05). The difference in SBS of RMGIC and self-adhesive flowable composite was not significant (P>0.05). Failure at the dentin-restoration interface (adhesive failure) had the highest frequency in groups 1 and 2. The frequency of adhesive failure was 100% in group 3.
Conclusions: Within the limitations of this study, the conventional flowable composite yielded the highest SBS to primary dentin. Self-adhesive flowable composite and RMGIC showed the lowest SBS with no significant difference with each other.
Objectives: This study aimed to compare the fracture resistance of a bulk-fill and a conventional composite and a combination of both for coronal restoration of severely damaged primary anterior teeth.
Materials and Methods: In this in vitro experimental study, 45 primary anterior teeth were randomly divided into three groups. After root canal preparation, the canals were filled with Metapex paste such that after the application of 1 mm of light-cure liner, 3 mm of the coronal third of the canal remained empty for composite post fabrication. Filtek Z250 conventional composite was used in group 1, Sonic-Fill bulk-fill composite was used in group 2 and Sonic-Fill with one layer of Filtek Z250 as the veneering were used in group 3. Adper Single Bond 2 was used in all groups. The teeth were thermocycled, and fracture resistance was measured by a universal testing machine. The mode of fracture was categorized as repairable or irreparable. Data were analyzed using one-way ANOVA.
Results: The mean fracture resistance was 307.00±74.72, 323.31±84.28 and 333.30±63.96 N in groups 1 to 3, respectively (P=0.55). The mean fracture strength was 14.53±2.98, 15.08±2.82 and 15.26±3.02 MPa in groups 1 to 3, respectively (P=0.77). The frequency of repairable mode of failure was 80% for the conventional, 73.6% for the bulk-fill and 80% for the bulk-fill plus conventional group, with no significant difference (P>0.05).
Conclusions: Bulk-fill composites can be used for coronal reconstruction of severely damaged primary anterior teeth similar to conventional composites to decrease the treatment time in pediatric patients.
Objectives: Despite the increasing popularity of pediatric dental treatments under general anesthesia, information is scarce regarding occlusal changes in patients that receive stainless steel crowns (SSCs) under general anesthesia. This study sought to compare canine overlap before and after general anesthesia in children who received SSCs under general anesthesia. In case of change, the possibility of return to the preoperative state and time required for this process were also evaluated.
Materials and Methods: This interventional before and after study was performed on 60 children between 2 to 7 years requiring dental treatment under general anesthesia. The contact point of the most prominent area of the maxillary primary canine and mandibular primary canine was marked before and immediately after general anesthesia and one and two weeks later. The change in canine overlap was analyzed using repeated measures ANOVA and linear regression test.
Results: Canine overlap significantly decreased immediately after general anesthesia (P<0.05). The mean magnitude of bite opening was 0.51±0.22 mm at the site of right canine and 0.50±0.185 mm at the site of left canine. These values returned to their normal preoperative state after one week (P<0.05). Repeated measures ANOVA showed significant differences in this respect between time points (P=0.002).
Conclusions: The occlusion and vertical dimension of pediatric patients may change following dental treatment under general anesthesia; the magnitude of change in canine overlap may vary depending on the class of occlusion and number of SSCs placed. These changes are temporary and often resolve within a week.
Amir Reza Rokn, DDS, MSc
Mohammad-Sadegh Ahmad-Akhoundi, DDS, MSc.
Shahroo Etemad-Moghadam, DDS, MSc.
Abbas Mirzaei, PhD
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