Influence of CO2 Laser Irradiation and CPP-ACP Paste Application on Demineralized Enamel Microhardness

Introduction: It has been suggested that the application of casein phosphopeptide-amorphous calcium phosphate paste (CPP-ACP) and CO2 laser irradiation on enamel could increase the resistance of enamel to caries and acid attacks. The aim of the current study was to compare the influence of CPP-ACP paste application and irradiation of CO2 laser on microhardness of demineralized enamel.Methods: Thirty sound maxillary extracted premolars were selected. The crowns were cut at the cervical line and were split into facial and palatal halves. Specimens were mounted in self-cure acrylic blocks in such way that the enamel surface was exposed to 4×4 mm. After a pH cycling of the specimens, they were randomly divided into 4 groups (n = 15), as follows: CG: Control group, LAS: CO2 laser, CP: CPP-ACP and LASCP: laser combined CPP-ACP treatment. The Vickers microhardness of the specimens was measured (500 g load, 5 seconds, 3 points). Data were analyzed using one-way ANOVA and post hoc Tukey tests (α = 0.05).Results: The lowest mean Vickers microhardness value was observed in CG group (192.57±50.87 kg/mm2) and the highest in LASCP group (361.86±22.22 kg/mm2). There were significant differences between groups (P < 0.001). The pairwise comparison of the groups revealed that there were significant differences between these groups: CG versus LAS, CP, LASCP (P < 0.05) and LASCP versus LAS and CP (P < 0.05). No significant difference between LAS group versus CP group (P > 0.05) was observed.Conclusion: The results of the current study revealed that CO2 laser and CCP-ACP were effective for improvement of enamel hardness value after demineralization. Incorporation of CO2 laser irradiation and CCP-ACP paste application provides additional remineralizing potential for demineralized enamel

Biochemical Pathway and Protein-Network Analysis of Dental Caries Based on Systems Biology Approaches

Background: Tooth decay (TD) is a multifactorial disorder, and several factors are involved in its etiology. Objective: The present study aimed to unravel the main genes and molecular mechanisms underlying TD. Methods: The dataset GSE1629 in the Gene Expression Omnibus (GEO) database was analyzed to uncover differentially expressed genes (DEGs) in patients with TD compared to patients with sound teeth. A protein-protein interaction network was built, and the most important clusters, hub genes, transcription factors (TFs), and protein kinases involved in the regulation of TFs were disclosed. Signaling pathways and Gene Ontology terms dysregulated in TD were also identified. Results: A total of 196 DEGs were determined (false discovery rate1). PTPRC, ITGB2, TYROBP, MMP9, CXCL8, CD44, CCL2, C1QB, C3, and SPP1 were considered hub genes. Further, BPTF and MAPK1 were demonstrated to be the highest TFs and protein kinases likely involved in the pathogenesis of TD, respectively. Conclusion: PTPRC, ITGB2, TYROBP, MMP9, CXCL8, CD44, CCL2, C1QB, C3, SPP1, BPTF, and MAPK1 may be regarded as potential markers for the therapeutic purposes of TD

Effect of Tubular Orientation on the Microtensile Bond Strength of Composite-dentin using Universal Bonding Agents

The aim of this study was to evaluate the effect of dentinal tubules orientation on the composite-dentin microtensile bond strength using universal adhesives. A total of 36 caries-free third molars were selected. The teeth were allocated to (axial, wall) and (occlusal, floor) groups and each group was divided into three subgroups based on the type of bonding used. The specimens were then sectioned to obtain dentin-composite sticks with a binding area of approximately 1 mm2. Then sticks were mounted in the universal testing machine (UTM) at a crosshead speed of 0.5mm/min. Data collection was carried out using two-way ANOVA and T-test. Then, the failure mode of the specimens was observed using a stereomicroscope, and one specimen from each group was evaluated under a scanning electron microscope (SEM). The results of two-way ANOVA showed that the highest and lowest mean microtensile bond strength (μTBS) were observed in the group of Adper Single Bond 2 adhesive (axial, wall) (28.92±8.75) and Single Bond Universal adhesive (occlusal, floor) (12.83±7.90), respectively. On the other hand, there was no significant difference between the three adhesives in the mean of μTBS in the (occlusal, floor)orientation, but the mean μTBS of Adper Single Bond 2 adhisive was significantly higher than that of G-premio and Single Bond Universal adhesives in the (axial, wall) orientation (P=0.05). There was no significant difference in two universal adhesives (P= 0.994). The stereomicroscopic analysis showed that the highest adhesive failure was related to Adper Single Bond 2 in (axial, wall) orientation. However, the failure mode results were nearly identical in both adhesives in the (axial, wall) orientation. The failure mode results were also similar in all three adhesives in the (occlusal, floor) orientation. The dentinal tubules orientation showed no significant effect on the microtensile bond strength of the Gpremio, Single Bond Universal adhesives. Adper Single Bond 2 had a significantly higher μTBS rate in the (axial, wall) orientation, but its μTBS was similar to that of the universal adhesives in the (occlusal, floor) orientation, which was not statistically significant

Effect of cyclic loading on bond strength of fiber posts to root canal dentin.

The aim of this study was to evaluate the effect of cyclic loading on the bond strength of quartz fiber posts to root canal dentin after different surface treatments of different regions of root canal dentin.Forty-eight single-rooted human teeth were selected. Post spaces were prepared and then the teeth were divided into four groups: G1: no treatment (control); G2: irrigation with a chemical solvent; G3: etching with 37% phosphoric acid; G4: treatment with ultrasonic file. The fiber posts were cemented using dual-cured resin cement. Half of the specimens were load-cycled (10000 cycles, 3 cycles/s) and the others did not undergo any load cycling. From each root, two slides measuring 1 mm in thickness were obtained from the apical and cervical regions. The push-out bond strength test was performed for each slice. Data were analyzed by using 3-way ANOVA and Tukey HSD tests. The fracture modes were evaluated under a stereomicroscope at ×20.The effect of load cycling and surface treatment as the main factors and the interaction of main factors were not significant (P=0.734, P=0.180, and P=0.539, respectively). The most frequent failure mode under the stereomicroscope was adhesive.It appears that load cycling and surface treatment methods had no effect on the bond strength of fiber posts to root canal dentin, but it depended on the region of the root canal dentin

Effect of Proanthocyanidin, Fluoride and Casein Phosphopeptide Amorphous Calcium Phosphate Remineralizing Agents on Microhardness of Demineralized Dentin

Objectives: The aim of this study was to evaluate the effect of dentin remineralization using proanthocyanidin (PA), fluoride varnish and casein phosphopeptide amorphous calcium phosphate (CPP-ACP) paste and their various combinations on microhardness of demineralized root dentin. Materials and Methods: One-hundred and twenty freshly extracted sound human premolars were selected and randomly divided into eight groups for dentin treatment as follows. C: Deionized water (control); PA: 6.5% PA solution; F: fluoride varnish (5% NaF, 22600 ppm fluoride); CP: CCP-ACP; PAF: 6.5% PA + fluoride varnish; PACP: 6.5% PA + CCP-ACP; FCP: fluoride varnish + CCP-ACP and PAFCP: 6.5% PA + fluoride varnish + CCP-ACP. All specimens were subjected to Vickers microhardness test (500 g, 10 seconds, 3 points). Data were analyzed using one-way ANOVA and Tukey’s post hoc test. The significance level was set at 0.05. Results: The mean and standard deviation (SD) values of Vickers hardness number (VHN) in groups C, PA, F, CP, PAF, PACP, FCP and PAFCP were 37.39±4.97, 38.68±4.62, 48.28±2.68 ,41.91±3.32, 48.59±2.55, 53.34±2.57, 48.413±4.00 and 55.20±1.82, respectively. Pairwise comparisons of the groups revealed that there was no significant difference between groups C and PA, PA and CP, F and PAF, F and FCP, PAF and FCP, and PACP and FPACP (P>0.05); but significant differences were observed between other groups (P<0.05). Conclusions: The results of this study showed that the tested dentin treatments increased the microhardness of demineralized root dentin except for PA application

In-Vitro Evaluation of the Effect of Sage on Shear Bond Strength of Composite Resin to Bleached Enamel

Background and Aim : There is a reduction in bond strength of composite resin to bleached enamel. The aim of the present study was to evaluate the effect of sage (Salvia officinalis) on the shear bond strength of composite resin to bleached enamel .   Materials and Methods : In this in vitro study, 60 labial surfaces of maxillary incisors were randomly divided into 4 groups as follows: G1: bleaching G2: bleaching and application of sodium ascorbate-containing solution G3: bleaching and application of Salvia officinalis-containing solution G4: control (no bleaching). A composite resin ( Z100 3M ESPE, Dental products, St Paul, MN, USA) cylinder was bonded on each specimen after acid etching and application of a fifth generation bonding agent ( Single Bond 3M ESPE, Dental products, St Paul, MN, USA ). After thermocycling, the shear bond strengths of the samples were measured in MPa. Data were analyzed using one-way ANOVA and Tukey’s HSD test (α=0.05) .   Results : Minimum and maximum mean values of shear bond strengths were observed in G1 (12.31±2.44) and G3 (25. 04 ± 3.52), respectively . No statistically significant differences were found in bond strength between the bleached and non-bleached groups after the antioxidant treatment (P>0.05 ).   Conclusion: There is a considerable decrease in bond strength of composite resin to enamel immediately after bleaching. Application of sodium ascorbate and Salvia officinalis solution can increase the bond strength of composite resin to bleached enamel

In-Vitro Evaluation of the Effect of Herbal Antioxidants on Shear Bond Strength of Composite Resin to Bleached Enamel

Objectives: A reduction in bond strength of composite to bleached enamel has been reported immediately after bleaching treatment. Application of some antioxidant agents may decrease the adverse effects of whitening agents on bond strength and enhance composite bond to enamel. This study aimed to assess the effect of green tea, sodium ascorbate, sage and grape seed extract on bond strength of composite to bleached enamel. Materials and Methods: In this in-vitro study, 90 human enamel surfaces were randomly divided into six groups as follows (n=15): G1, no bleaching; G2, bleaching with 40% hydrogen peroxide (HP); G3, HP+1000 μmol epigallocatechin gallate (EGCG) for 10 minutes; G4, HP+10% sodium ascorbate for 10 minutes; G5, HP+10% sage for 10 minutes and G6, HP+5% grape seed extract for 10 minutes. The specimens were bonded to composite in all groups. The shear bond strength of specimens was measured in Megapascals (MPa). Data were analyzed using one-way ANOVA and Tukey’s HSD test (α=0.05). Results: The highest and the lowest mean shear bond strength values were observed in group 1 (22.61±3.29MPa) and group 2 (5.87±1.80MPa), respectively. The reduction in bond strength in group 2 was greater than that in other groups (P0.05).  Conclusions: All the herbal antioxidants used in this study equally compensated for the reduced bond strength of composite to bleached enamel.

Microtensile bond strength of quartz fiber posts to different composite cores

The aim of this in vitro study was to assess the microtensile bond strength of quartz fiber posts to different composites, and to composite combinations used as core materials. Thirty fiber posts were treated with a 24% hydrogen peroxide solution and silanized. The posts were divided into 5 groups according to the resin composite used as follows (n = 6): G1 - Ælite Flow (Bisco, Inc), G2 - Filtek Z250 (3M ESPE), G3 - Biscore (Bisco, Inc), G4 - Ælite Flow + Filtek Z250, G5 - Ælite Flow + Biscore. The resin composites were placed around the posts to produce cylindrical specimens. Two 1-mm² thick sticks containing the post in the center and composite cores on both ends were provided from each cylinder and tested for microtensile strength with a crosshead speed of 0.5 mm/min. One-way ANOVA and Tukey HSD tests were used for statistical analysis. Fractured surfaces were observed using a stereomicroscope with 20× magnification. Scanning electron microscopy (SEM) was used to evaluate the interface of the fractured sticks. The results showed that G2 had the highest bond strength values, and the lowest values were seen with G3. There were significant differences between groups 1, 2, 4 and groups 3, 5 (p < 0.05). Under the stereomicroscope, most of the failures were adhesive between the post and core material. Under SEM, Ælite and Z250 had smoother surfaces than Biscore, containing less porosities and voids

Educational Objectives Achieved by Department of Operative Dentistry: Viewpoints of General Dentists Graduated from Hamedan Dental School (2004-2009)

Introduction: Evaluation of educational objectives achievement is one of the most important jobs by medical universities. Therefore the aim of this study is to evaluate educational goal achievements of operative dentistry department from the viewpoints of general dentists graduated from dental school of Hamadan University of Medical Sciences during 2004-2009 years. Also their viewpoints about preclinical and clinical courses were surveyed. Methods: In this descriptive cross-sectional study, a questionnaire was sent to all dentists graduated during the years 2004 to 2009 from dental school of Hamadan University of Medical Sciences. This researcher made questionnaire encompassed multiple choice questions to evaluate theoretical knowledge of graduates and opinion poll about preclinical and clinical courses. Data was analyzed using Fisher's exact test. Results: Achievement of general goals was desirable in 16.3%, almost desirable in 83%, and poor in 0.7% of dentists. The impact of preclinical courses on operative skills of dentists was considered desirable by 16.72%, and almost desirable by 83.2 percent. The effect of clinical courses on operative skills of dentistry was considered desirable by 21.94% of graduates, almost desirable by 61.87%, and poor in 16.18% of them. Achievement of educational objectives of operative dentistry showed a significant correlation with sex, age, admission allotment, marital status, interest, and graduation year (p<.05). Conclusion: This study showed that the educational objective achievement of operative dentistry department of dental school of Hamedan University of Medical Sciences enjoys a good status

Synthesis of Boron Nanocomposites Doped on the Hydroxyapatite-Chitosan Surface and Its Effect on the Microhardness of Demineralized Tooth Enamel

Background and Objective: Noninvasive treatments are preferred for tooth enamel remineralization, and metal nanocomposites could be used for this purpose. The present study investigated the effect of boron nanocomposites doped on the hydroxyapatite-chitosan surface on the microhardness of demineralized tooth enamel. Materials and Methods: In this laboratory study, boron nanocomposites doped on the hydroxyapatite-chitosan surface were made by the sol-gel method. A total of 45 healthy human teeth were selected and divided into buccal and lingual halves. The demineralization cycle of the samples was performed for 14 days to demineralize the tooth enamel surface. The samples were randomly divided into three equal groups based on the use of remineralizing materials, G1:hydroxyapatite-chitosan nanocomposites; G2:boron nanocomposites doped on the hydroxyapatite-chitosan surface, and G3:control group without nanocomposite. Nanocomposites were applied on the surface of the teeth for 28 days (twice a day). The microhardness of the samples was performed by the Vickers test at three points. The SPSS software (version 19), one-way analysis of variance, and Tukey's test were used for statistical analysis of the data (α=0.05). The surface morphology of the groups was examined by SEM[A1] . Results: There was a statistically significant difference between the three studied groups (P<0.001). The highest mean was first observed in the G2(368.12) and then in the G1(342.62). Moreover, the lowest mean was related to the control group(267.53). Pair-by-pair comparison of groups showed that there was a significant statistical difference between groups 1 and 2, 1 and 3 as well as 2 and 3 (P<0.05). Conclusion: Both HApC and B@HApC compounds improve remineralization and increase the microhardness of tooth enamel; however, this increase was greater in the presence of a boron-containing compound.  [A1]Please expand