Effect of Three Light Curing Protocols and Load Cycling on Microleakage of Class V Composite Restorations

Objective: Different methods have been suggested to overcome the polymerization shrinkage of composite restorations. Changing the light curing protocol to improve polymerization by using new light curing units is among these methods. The new devices are more efficient, portable and durable and produce less heat. This study aimed to assess the marginal microleakage of class V composite restorations subjected to three different light curing protocols and mechanical cycles.Methods: This was an in-vitro experimental study. Class V cavities measuring 2x3x1.5 mm were prepared on the buccal and lingual surfaces of 90 extracted human premolar teeth 1.5 mm above and below the cement enamel junction (CEJ). The samples were selected using convenience sampling and divided into 9 experimental groups of 10 each by using the Table of Random Numbers to  control for the bias. The cavities were restored with packable composite resin along with Tetric-N- Bond and cured using three light curing protocols of conventional (680 mW/cm2 for 30s), soft-start (380 mW/cm2 for 10s followed by 680 mW/cm2 for 20s) and pulse (680 mW/cm2 for 30s,1s interval and 1s of lighting). The teeth were then subjected to mechanical cycles of 0, 500,000 and 1,000,000 and immersed in 2% Fuchsin for 24h. The teeth were then sectioned in half from the middle of the restoration buccolingually and the degree of microleakage was evaluated under a stereomicroscope (Zeiss, Germany) with 40X magnification. Data were analyzed using the Kruskal Wallis and the Mann-Whitney tests.Results: Despite the structural differences between the enamel and dentin margins, no significant difference was found in the degree of microleakage between the enamel (occlusal wall, p>0.05) and dentin (gingival wall, p>0.05) margins among the understudy groups.Conclusion: The degree of marginal microleakage in soft-start (SS) polymerization was not significantly different from that in conventional and pulse polymerizations of class V composite restoration

Efficacy of Different Root Canal Irrigants on Smear Layer Removal after Post Space Preparation: A Scanning Electron Microscopy Evaluation

Introduction: Effective durable adhesion between post material and dentine using resin cements is essential for longevity of restoration. The aim of this in vitro study was to compare the effect of different irrigants on smear layer removal after post space preparation. Methods and Materials: A total of 75 extracted anterior human teeth were selected. The canals were instrumented by rotary system and then were filled. After preparing the post space, teeth were divided into 5 groups according to irrigants: 17% EDTA; 17% EDTA+2% CHX; 5.25% NaOCl; 17% EDTA+5.25% NaOCl; and saline. The canals were irrigated with 5 cc of each irrigants for 1 min. Specimens were examined with scanning electron microscopy (SEM). Hulsmann’s score was used for marking of smear layer removal at coronal, middle and apical thirds of post space. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: The results revealed that subsequent use of 17% EDTA+5.25% NaOCl was more effective than the other groups in smear layer removal. No statistical difference was found among different levels of root canal within each group. Conclusion: It can be concluded that 17% EDTA+5.25% NaOCl could be an effective irrigant for smear layer removal after post space preparation.Keywords: Post Space; Root Canal Irrigant; Scanning Electron Microscopy; Smear Laye

Effect of Various Finishing and Polishing Systems on Surface Roughness of Nanohybrid and Microhybrid Composites

Objectives Finishing and polishing systems may affect the surface properties of composite resins. In this in vitro study, we evaluated the surface roughness of two composite resins after polishing with three different polishing systems. Methods Thirty-six specimens (8 mm diameter × 2 mm thickness) were fabricated from Kalore nanohybrid and Gradia Direct microhybrid composite in a Teflon mold and divided into four groups according to the polishing protocol (n=9): control group, Sof-Lex, Super Snap, and Jiffy. The mean surface roughness (Ra) values were determined using a profilometer and the surface of two samples in each group was observed under a scanning electron microscope (SEM). Data were analyzed using one-way and two-way ANOVA. The significance level was set at 5%. Results Profilometric evaluation showed that in both composite resins, the smoothest surfaces were obtained with Mylar strip; also Jiffy showed significantly higher Ra values than other polishing systems. Type of composite and polishing technique had significant effects on surface roughness (P=0.0001). SEM observations also showed that surface roughness of Jiffy was more than that of three other groups. Conclusion After the use of finishing and polishing systems, the surface roughness of Gradia was higher than Kalore in all polishing systems. Sof-Lex and Super Snap were effective on Gradia, and jiffy created the roughest surface

Ability of dental students in detection of proximal caries

Objective: Tooth decay is one of the most common chronic diseases in the world. After pit and fissures, enamel of proximal surface is the second region prone to rot. Bitewing images are one of  the most important diagnostic tools for the detection of caries. Given the importance of accurate and timely detection of decay, the current study was aimed to evaluate the ability and skill of the final- year dental students to identify the presence and depth of proximal caries in dental bitewing radiography.Methods: In this descriptive cross-sectional study 208 inter proximal surfaces among the 13 dental bitewing radiographs were selected randomly. The radiographs were evaluated by two experienced dental specialists (a radiologist and a restorative specialist) to detect inter proximal decay between teeth. These diagnoses were considered as the gold standard. The radiographs were further assessed by fourteen final-year dental students. Finally, the collected data were analyzed by SPSS-17  software using Kappa coefficient of agreement and ICC. The sensitivity and specificity values were also determined.Results: The value of Kappa correlation coefficient to assess the similarity between students' responses and gold standards was obtained as 0.28 (p<0.001). The Kappa correlation coefficient for evaluation of the precision of the data was 0.71. The sensitivity in the whole population was 0.43, while the specificity was 0.84.Conclusion: According to the results obtained in this study, the performance of final year dental students to identify the presence and depth of proximal caries from bitewing radiographs was not satisfactory. Moreover, the ability to detect normal surfaces was unacceptable

Microleakage of cervical cavities prepared by an Er:YAG laser or a high-speed handpiece, after restoration using resin composite

Objectives The purpose of this in vitro study was to evaluate the microleakage of cervical cavities prepared by Er:YAG laser or high-speed hand piece and bur.Methods This in vitro experimental study was performed on 40 sound permanent third molar teeth randomly assigned into two equal groups (n = 20). In the first group, high-speed hand piece and bur and in the second group Er:YAG laser was used to prepare class V cavities on the buccal or lingual surfaces. Filtek Z250 composite resin was used as the restorative material. The teeth were thermocycled for 1000 cycles, placed in 2% methylene blue solution for 24 hours, sectioned at the center of restoration and evaluated under a stereomicroscope at x40 magnification for microleakage. Data were analyzed using Mann-Whitney U test at 0.05 level of significance.Results There was no significant difference between the occlusal or gingival margin microleakage of cavities prepared with Er:YAG laser and high-speed hand piece (P = 0.445 and P = 0.758, respectively). However, the difference in the occlusal and gingival margins was significant within the high-speed hand piece (P = 0.042) and Er:YAG laser (P = 0.002) groups.Conclusion Cavity preparation by Er:YAG laser and high speed hand piece and bur is not significantly different in terms of microleakage

Evaluation of Shear Bond Strength and Antimicrobial Effects of Resin-Modified Glass Ionomer Containing Titanium Oxide and Silver Nanoparticles

Objectives Streptococcus mutans, as one of the most important cariogenic bacteria, is responsible for dental caries. To prevent and control dental caries, it is reasonable to use new materials and techniques for eradicating cariogenic bacteria. The present study aimed to evaluate and compare the antimicrobial effects of resin-modified glass ionomer (RMGI) containing silver and titanium oxide nanoparticles, on Streptococcus mutans (S. mutans) and to assess and compare the shear bond strength between coronal and radicular dentins. Methods This study investigated the antibacterial properties of 16 RMGI discs, containing 3 weight percent (wt.%) of silver and titanium nanoparticles prepared for each group. Also, the shear bond strength of RMGI discs containing nanoparticles between the coronal and radicular dentins were compared. Kolmogorov-Smirnov test was used to evaluate the normal distribution of data. Normally distributed data were analyzed and compared between the groups, using two-way ANOVA test; otherwise, Kruskal-Wallis test was performed to analyze the data. The level of statistical significance was set at 0.05. Results The mean colony count of S. mutans significantly reduced in both silver and titanium nanoparticle groups after 15 days compared to one-hour and 24-hour intervals (P<0.0001). The shear bond strength test revealed no significant differences between the two experimental groups (P>0.05). Conclusion Incorporation of silver and titanium oxide nanoparticles at a concentration of 3 wt.% yielded optimal antibacterial characteristics, without causing any significant changes in the shear bond strength. Comparison between nanoparticle containing RMGI and RMGI showed that over time it has more ability to create antibacterial properties against S. mutans bacteria

Comparison of Microleakage between Old and New Comp osite with Two Bonding Agent Systems: An In-vitro Study

Composite restorations usually have so many complications and imperfections and it is possible to eliminate impaired region without complete replacement of the composite. Repair ability of the resin composites is a desirable property. In time of need to repair part of the restoration, the composition of preexisting composite is unknown. The aim of this study was to evaluate the microleakage between old and fresh composite with two bonding agents systems. 144 specimens of P90 (3M, Germany) and Z250xt (3M, Germany) resin composite were aged and after surface roughening with diamond bur, they were placed randomly in 8 groups. All of the specimens were covered with nail varnish except on repair surfaces. Specimens were immersed in methylene blue and after that they were sectioned. Microleakage was measured using Adobe Photoshop portable software and stereomicroscope. Data were analyzed with ANOVA test (p=0.05). G8 group (p90+single bond 2+z250XT) revealed maximum of microleakage (1.131mm) and G7 group (p90+etching+p90 bonding+ p90)showed minimum (0.325mm) (P-value=0.0001). Using acid etching and p90 primer had no effect on microleakage. Comparison of groups which were repaired with the same resin composite as preexisting composite revealed no significant difference. Some groups were detected with valuable results (P-value=0.0001). Using acid etching and p90 primer for surface treatment has no effect on microleakage. Bonding materials were used in this study has shown no difference in results. Repairing old composite restoration with composite based on different resin is not recommended

Evaluation of shear bond strength of bioactive glass ionomer containing titanium and conventional glass ionomer particles to dentin treated with Er-YAG laser and conventional methods

Background and Aims: Recently, the addition of nanoparticles into the restorative materials and tooth preparation by laser for improving the bond strength have been concidered by researchers. The aim of this study was to investigate the shear bond strength of the bioactive glass ionomer containing titanium particles and a conventional glass ionomer with two surface treatments by Er-YAG laser and conventional methods. Materials and Methods: In this in-vitro study, 64 sound extracted premolars were collected. For conventional method, the specimens were prepared in such a way that dentin surfaces with a depth of 0.5 millimeter created at distance of 2 mm from the joint of CEJ at the root or crown.  In the laser group, after preparing the teeth, the surface area was prepared by Er-YAG laser. Then, in the middle part of the buccal surface, a cylindrical mold with dimensions of 3.5 mm in diameter and 4 mm in height was placed and for each group was filled with its own glass ionomers. The  specimens  were divided into 8 groups by simple random sampling (n=8): A (laser, conventional glass ionomer, coronal dentin)/ B (laser, glass ionomer containing titanium nanoparticle, coronal dentin)/C (conventional, conventional glass ionomer, coronal dentin)/ D (conventional, glass ionomer containing titanium nanoparticle, coronal dentin)/ E (laser, conventional glass ionomer, root dentin)/ F (laser, glass ionomer containing titanium nanoparticle, root dentin)/ G (conventional, conventional glass ionomer, root dentin)/ H (conventional, glass ionomer containing titanium nanoparticle, coronal dentin). Finally, the shear bong strength by a universal testing machine was measured at a cross-head speed of 1 mm/min. For data analysis, Two-way ANOVA test was used to evaluate the effect of each variable and their interaction on the shear bond strength and Tukey test was used to compare the two groups. Results: There was significant difference only between groups B with C (P=0.002), E (P=0.007), G (P=0.001) and H (P=0.01). The highest bond strength was found for group B (laser, glass ionomer containing titanium nanoparticle, coronal dentin) and the lowest bond strength for group G (conventional, conventional glass ionomer, root dentin). Conclusion: All three factors of Er-YAG laser, glass ionomer containing titanium nanoparticle and coronal dentin had a positive effect on the improvement of the bond strength

Shear Bond Strength of an Etch-and-rinse Adhesive to Er:YAG Laser- and/or Phosphoric Acid-treated Dentin

Background and aims. Er:YAG laser irradiation has been claimed to improve the adhesive properties of dentin; therefore, it has been proposed as an alternative to acid etching. The aim of this in vitro study was to investigate the shear bond strength of an etch-and-rinse adhesive system to dentin surfaces following Er:YAG laser and/or phosphoric acid etching. Materials and methods. The roots of 75 sound maxillary premolars were sectioned below the CEJ and the crowns were embedded in auto-polymerizing acrylic resin with the buccal surfaces facing up. The buccal surfaces were ground using a diamond bur and polished until the dentin was exposed; the samples were randomly divided into five groups (n=15) according to the surface treatment: (1) acid etching; (2) laser etching; (3) laser etching followed by acid etching; (4) acid etching followed by laser etching and (5) no acid etching and no laser etching (control group). Composite resin rods (Point 4, Kerr Co) were bonded to treated dentin surfaces with an etch-and-rise adhesive system (Optibond FL, Kerr Co) and light-cured. After storage for two weeks at 37°C and 100% humidity and then thermocycling, bond strength was measured with a Zwick Universal Testing Machine at a crosshead speed of 1 mm/min. Data was analyzed using parametric and non-parametric tests (P<0.05). Results. Mean shear bond strength for acid etching (20.1±1.8 MPa) and acid+laser (15.6±3.5 MPa) groups were significantly higher than those for laser+acid (15.6±3.5 MPa), laser etching (14.1±3.4 MPa) and control (8.1±2.1 MPa) groups. However, there were no significant differences between acid etching and acid+laser groups, and between laser+acid and laser groups. Conclusion. When the cavity is prepared by bur, it is not necessary to etch the dentin surface by Er:YAG laser following acid etching and acid etching after laser etching

Evaluation of the effect of nanohydroxyapatite-containing toothpaste and mouthwash on remineralization of early enamel caries and occluding of dentinal tubules

Background and Aims: Different factors play a role in causing tooth decay. Modern dentistry is looking for a way to prevent tooth decay and suggests different ways to increase remineralization. The aim of this study was to evaluate the effect of nanohydroxyapatite toothpaste and mouthwash on remineralization of primary enamel lesions and obstruction of tubules. Materials and Methods: In this study, 90 human extracted central teeth were used. Artificial decay was induced by placing the specimens for 72 hrs in a demineralization solution in an incubator at 37 °C. Hardness of the specimens was determined by a microhardness test before any surface treatment. The specimens were then divided randomly into 6 groups of 15. For 1-6 groups, the specimens were subjected to a pH cycling for 14 days, which included 3 hrs of demineralization and 21 hrs of remineralization. At the same time, 1-3 groups were in contact with diluted toothpaste in a ratio of 1:3 with deionized water at a rate of 5 ml twice a day for two min. Eac specimen of 4-6 groups was exposed to 5 ml of three types of mouthwashes for one min. Then, the specimens were cut in the buccolingual direction in order to simultaneously evaluate the dentinal tubules and Vickers microhardness test was performed again and the before and after microhardness values were compared. Then, the percentage of deposition on the surface and tubule obstruction were analyzed using SEM (Scanning electron microscope) (P=0.006). Data were analyzed using SPSS24 software bu the descriptive statistics, ANOVA analysis of variance, and multiple Tukey comparisons. Results: The results of analysis of variance test showed that there was a statistically significant difference in the microhardness changes between study groups (P=0.006). Also, in-group analysis of microhardness changes, there was a significant difference (P<0.0001). Besides, only in the group containing 0.5% nanohydroxyapatite toothpaste, more than 50% tubule deposition and obstraction was observed (P<0.05). Conclusion: According to the present study, nanohydroxyapatite can be one of the treatment strategies to repair incipient lesions of teeth and the addition of nanohydroxyapatite, preferably to toothpaste, increases the dental microhardness