Frontiers in Dentistry
Volume:16 Issue: 1, Jan-Feb 2019

This study aimed to determine the antibacterial properties of Propolis in a laboratory environment and to use it to produce antibacterial mouthwash with minimal complications. 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).

Corrosion of Ni-Cr base dental alloys in saliva influences their application in prostheses. Corrosion behaviour of the NiCr alloy was studied using two techniques including weight lossdescribed by corrosion rate (CR) per mil per year (mpy)and potentiodynamic polarizationdescribed by corrosion potential (CP) in mV and current density (CD) in mA/cm2in 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-HSD tests with a difference significance of 95%. In weight loss method,CRwas 71.95±3.40, 17.26±1.03, 8.92±0.35 and 6.93±0.54mpy in pH values of 2.5, 5, 7 and 9, respectively. CR obtained in pH of 2.5 was significantly different with that in other groups, but those obtained in pH of 5, 7 and 9 were not significantly different. In polarization method, CPwere significantly different. CD measured in pH of 2.5 and 5 was significantly different with the rest of pH values. Corrosion rates in pH of 7 and 9 were not significantly different. The results obtained by both techniques are consistent. Corrosion resistance decreases as pH increases. In more acidic saliva, corrosion rate is greater likely due to the higher dissolution rate of Ni through weak passivation. However, the less acidic saliva leads to formation of more stable passive film on Ni and therefore the dissolution of Ni decreases leading to lower corrosion rates.

Pit and fissure sealant is recognized as an effective preventive approach in pediatric dentistry. The most commonly used sealant material is resin composite. Adding nanoparticles to resin composites could result in production of flowable material with both higher mechanical properties and better flow characteristics than previous sealants. This study aimed to compare the microleakage of a flowable nanocomposite and conventional materials used in the treatment of pit and fissure sealants. A total of 185 extracted mandibular third molar teeth were selected and randomly divided into 5 groups of 36 according to material used as pit and fissure sealant, and the microleakage of flowable nanocomposite, flowable composite, filled sealants, nano-filled sealants and unfilled sealants were compared. Five teeth were reserved for examination under the scanning electron microscope. The samples were thermocycled (5 - 55 degrees C, 1-minute dwell time) at 1000 cycles and immersed in 0.2% fuchsine solution for 24h. teeth were sectioned buccolingually . Microleakage was assessed by means of dye penetration and scanning electron microscope. Data were analyzes using Kruskal-Wallis non- parametric test (p<0.05), Mann-Whitney test p <0.005, and SPSS ver.16.  The nanofilled flowable composite and unfilled fissure sealant showed the lowest and highest rates of microleakage, respectively. No statistically significant difference was found between two flowable composite (P=0.317). Filled resin-based sealant had significantly lower microleakage than unfilled resin-based sealant (P<0.001).   Concerning the microleakage data, use of a flowable nanocomposite is more effective in sealing mechanically prepared occlusal fissures in comparison to the unfilled sealant.

This study aimed to assess the microleakage of Pedo Jacket crowns compared to stainless steel crowns (SSCs) cemented with different cements. 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. 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). Pedo Jacket crowns can serve as an acceptable esthetic alternative to SSCs if cemented with resin cement.

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.

Currently, cytotoxic materials are used for pulpectomy obturation in primary teeth (mostly ZOE or iodoform-Ca(OH)2 compounds). This study compared the volumetric quality of a new biocompatible/antimicrobial agent (nano-chitosan) against conventional obturation materials. It also compared rotary and manual systems. 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), an 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 CT. Canals were then obturated using the three materials. The percentages of obturation volume (POV) were estimated for the materials. Canal spaces both before obturation and after it were compared statistically between two filing systems, and between 3 obturation materials (α=0.05). Average POVs of materials were 96.54% (ZOE), 97.87% (Metapex), and 74.74% (nano-chitosan, ANOVA P=0.000). POV of chitosan differed from the other two (Tukey P=0.000), but the other two were similar (P=0.896). Average POVs were 91.46% (manual) and 88.51% (rotary, t-test P=0.322). Pre-obturation spaces of canals for different methods were 3.89 mm3 (manual) and 3.26 mm3 (rotary, t-test 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. The nano-chitosan showed a considerable success, but it still needs reformulation as it was weaker than the extremely successful commercial competitors. Rotary instrumentation can provide results similar to hand-filing in terms of POV, although they might yield smaller canals.

To evaluate the effect of brushing after application of 15% carbamide peroxide (CP) on the surface roughness of three types of composite resins. Twenty samples measuring 4 mm in height and diameter were prepared from each of three composite resin types including microfilled; Heliomolar HB (MF), nanohybrid; IPS Empress Direct (NH) and microhybrid; Tetric Ceram HB (MH). 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, the cleaning step was carried out with an electric toothbrush (Oral-B, Vitality Precision Model) for 3 minutes within 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. The mixed ANOVA model was used for the analysis of data (P<0.05). At baseline roughness was significantly lower in MF compared to the NH and MH (p<0.001). Roughness increased within all study groups over the intervention period; however, it was not statistically significant in the MH (p>0.05). Furthermore, there was a smaller increase of roughness in MF than in NH (p < 0.001) and MH (p = 0.02). The effect of intervention was more pronounced in NH and MH groups. Surface roughness changes were minor in MF composite resin.

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. 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. Mode of failure was determined under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s test. 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. Conventional flowable composite yielded the highest SBS. Considering the advantages of self-adhesive flowable composite such as decreased chair time, easy clinical application and comparable SBS to that of RMGIC, it can serve as an alternative to RMGIC for restoration of primary teeth in uncooperative children.

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. 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. 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). 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.

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.   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. 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). 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.