The effect of nanohydroxyapatite and silver nanoparticles on the microhardness and surface roughness of composite resin.

The aim of this study was to evaluate the effect of nanohydroxyapatite (nanoHAP) and silver nanoparticles (AgNPs) on the microhardness and surface roughness of composite resin. Fifty disc-shaped composite resin specimens (10 mm in diameter and 1.5 mm in height) were prepared in 5 groups (n = 10) as follows: group 1, composite resin (negative control); group 2, hand-spatulated composite resin (positive control); group 3, composite resin and nanoHAP (2 wt%); group 4, composite resin and AgNPs (1 wt%); group 5, composite resin, nanoHAP (2 wt%), and AgNPs (1 wt%). The microhardness and surface roughness of the specimens were measured using a Vickers microhardness tester and surface profilometer. Data analysis was performed using 1-way analysis of variance and a Tukey test (P < 0.05). The incorporation of 2 wt% nanoHAP or 2 wt% nanoHAP plus 1 wt% AgNPs did not affect the microhardness of the composite resin (P > 0.05). However, the incorporation of 1 wt% AgNPs alone had a statistically significant negative effect on the microhardness (P < 0.05). A significant increase in surface roughness was found for the composite resin containing 2 wt% nanoHAP (P < 0.05). However, the incorporation of 1 wt% AgNPs or 2 wt% nanoHAP plus 1 wt% AgNPs into the composite resin did not affect surface roughness (P > 0.05). The incorporation of nanoHAP and AgNPs (group 5) into the composite resin did not have a negative effect on the surface roughness and microhardness of the composite resin. The highest surface roughness was observed in specimens in group 3 (composite resin and nanoHAP) and the lowest microhardness was observed in group 4 (composite resin and AgNPs).

Influence of Cavity Pretreatments on the Fracture Resistance of Premolars with Self-adhesive Cemented Composite Inlay.

AIM: The aim of this study is to investigate whether different cavity pretreatment approaches affect the strength of premolars restored with self-adhesive (SA) resin cemented-composite resin inlays after mechanical and water aging. MATERIALS AND METHODS: A total of 120 intact maxillary premolars were divided into 10 groups (n = 12). Mesio-occluso-distal (MOD) cavities were prepared in the teeth of nine groups, except group I in which the teeth remained intact. In group II, cavities were unrestored. Following fabrication of composite resin inlays for groups III-X, in group III, the inlays were cemented using the etch-and-rinse (E and R) adhesive/conventional resin cement. In other groups, cementation was performed using a SA cement with or without cavity pretreatments as follows: group IV: SA cement alone, group V: acid etching of enamel and dentin, group VI: acid etching of enamel, group VII: universal adhesive in the selective enamel-etching mode, group VIII: universal adhesive in the E and R mode, group IX: ethylenediaminetetraacetic acid (EDTA) conditioning, and group X: 20% polyacrylic acid conditioning. After aging processes, static fracture resistance was tested. Data were analyzed using one-way ANOVA and Dunn tests (α = 0.05). RESULTS: Fracture resistance of the 10 groups yielded a significant difference (p < 0.001). The median fracture resistances in Newton were the following: Gr I = 1025A, Gr II = 311BC, Gr III = 785A, Gr IV = 500B, Gr V = 435B, Gr VI = 775A, Gr VII = 805A, Gr VIII = 411BC, Gr IX = 397BC, and Gr X = 312C. CONCLUSION: Unlike the conventional method, SA cementation could not restore the strength of inlay-cemented premolars. Selective enamel acid etching with or without universal adhesive significantly increased the fracture resistance. CLINICAL SIGNIFICANCE: Selective enamel acid etching is recommended for increasing the fracture resistance of the SA cemented composite inlay to the level of intact teeth.

Effect of Silver Nanoparticles, Zinc Oxide Nanoparticles and Titanium Dioxide Nanoparticles on Microshear Bond Strength to Enamel and Dentin.

AIM: This study was aimed to evaluate whether antibacterial pretreatment of enamel and dentin with silver nanoparticles (SNPs), zinc oxide nanoparticles (ZNPs) and titanium dioxide nanoparticles (TNPs) has any effect on the microshear bond strength of an etch-and-rinse adhesive system. MATERIALS AND METHODS: Eighty human third molars were randomly assigned to eight subgroups (n = 10). Enamel groups included no pretreatment (E), pretreatments with SNPs (ESNP), ZNPs (EZNP) and TNPs (ETNP) before acid etching and adhesive application. Dentinal groups included no pretreat-ment (D), pretreatments with SNPs (DSNP), ZNPs (DZNP) and TNPs (DTNP). The specimens were bonded by Adper Single Bond and polyvinyl chloride microtubes and were restored with Z250 composite. The bonded surfaces underwent microshear bond strength (uSBS) test. Data in megapascal (MPa) were analyzed with the Kruskal-Wallis test and the Mann-Whitney test (p = 0.05). RESULTS: There was not a significant difference among the groups in enamel (p > 0.05). There was no significant difference between the application of three nanoparticles and the control group in dentin. However, DSNPs had a higher uSBS (25.60 ± 14.61) than that of the DZNPs and DTNPs groups (p = 0.03 and p = 0.001, respectively). Also, the mean uSBS value was lower in dentin groups compared to the respective enamel groups (p < 0.05) except for groups DSNPs and ESNPs in which no significant difference was found (p > 0.05). CONCLUSION: Pretreatment with SNPs, TNPs, and ZNPs can be suggested to achieve potent antibacterial activities without compromising the bond strength. The best result was obtained for pretreatment with SNPs compared to pretreatment with TNPs or ZNPs in dentin and enamel, albeit the differences were not significant in the enamel groups. CLINICAL SIGNIFICANCE: Effective antibacterial treatment prior to adhesive bonding application is desirable to provide successful restoration if it would not adversely affect the bond strength of the adhesive system. Nanoparticles can be applied to meet this goal.

Comparison of Cytotoxicity of New Nanohybrid Composite, Giomer, Glass Ionomer and Silver Reinforced Glass Ionomer using Human Gingival Fibroblast Cell Line.

AIM: The objective of this study was to investigate the cytotoxic effects of new nanohybrid composite, giomer, conventional and resin modified and silver reinforced glass ionomer cements and compare the biocompatibility of these dental materials in cell culture. STUDY DESIGN: Five cylindrical specimens were made of each material, using a mold (2mm. thick and 5 mm in diameter). For HGF, cells were cultured in RPMI-1640 medium. After attaining 80% confluence, cells were treated with different doses of five tested materials for 24h. Then cell cytotoxicity was assessed using MTT assay. The data were analyzed using Kruskal-Wallis and Dunn test. RESULTS: The materials evaluated on HGF cells, showed significantly more cytotoxicity in silver reinforced glass ionomer but nanohybrid composite shows mild cytotoxic effect. However, giomer shows no significant cytotoxicity and conventional and resin modified glass ionomer enhance cell proliferation. CONCLUSIONS: Silver reinforced glass ionomer induced a significant high cytotoxic effect over a wide range of concentration. Therefore, higher attention should be focused on this restorative dental material, which should be chosen for further investigations.

Role of TiF4 in Microleakage of Silorane and Methacrylate-based Composite Resins in Class V Cavities.

AIM: This study investigated the effect of TiF4 solution pretreat-ment on microleakage of silorane and nanofilled methacrylate-based composites in class V cavities. MATERIALS AND METHODS: Forty-eight intact premolar teeth were randomly allocated to four groups of 12 teeth. Restorative techniques after standard class V tooth preparations were as follows: Group 1, Filtek P90 composite; group 2, Filtek Z350 XT; group 3, TiF4 solution pretreatment and Filtek P90 composite; group 4, TiF4 solution pretreatment and Filtek Z350 XT. After storing the specimens in distilled water at 37°C for 24 hours and followed by immersion of the specimens in a 0.5% basic-fuchsin solution for 24 hours, they were sectioned buccolingually to obtain four surfaces for each specimen for analysis of microleakage using a stereomicroscope. Data analysis was performed using Kruskal-Wallis test to compare the four groups and the Mann-Whitney test for paired comparisons with Statistical Package for the Social Sciences (SPSS) version 17 software. RESULTS: At the enamel margins, microleakage score of the Filtek Z350 XT group was lower than those of the Filtek P90 with and without the application of the TiF4 (p = 0.009 and p = 0.031 respectively). At the dentin margins, groups 3 and 4 (TiF4+Filtek P90 and TiF4+Filtek z350 XT respectively) showed significantly lower microleakage than group 1 (Filtek P90). However, there was no significant difference between other groups (p > 0.05). CONCLUSION: At the enamel margins, microleakage score of the silorane-based composite was more than that of the nanofilled composite. No significant differences were observed between the other groups. At the dentin margins, for the silorane-based composite restorations, TiF4 solution pretreatment resulted in significantly lower microleakage. However, the similar result was not observed for Filtek Z350 XT. Also, no significant difference was observed between microleakage scores of Filtek P90 and Filtek Z350 XT with or without TiF4 pretreatment. CLINICAL SIGNIFICANCE: In spite of better mechanical and physical properties of modern composites than earlier methacrylate-based composites, polymerization shrinkage has been remaining as one of the main shortcomings of them. Different methods, such as using new low shrinkage resin composites and different dentin pretreatments, have been suggested to overcome this problem. This study evaluated the effect of TiF4 as pretreatment on microleakage of class V tooth preparations restored with a nanocomposite and a silorane-based resin composite.

Frequency of KIT Mutation in Gastrointestinal Stromal Tumors According to Histologic and Immunohistochemical Findings, the First Report from Iran.

BACKGROUND: Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. They are believed to originate from the interstitial cells of Cajal. Most of these tumors contain activating mutations in the KIT receptor tyrosine kinase. This is the first study in Iran to evaluate GISTs at the molecular level. METHODS: In the present study, during 5 years (2007-2012), we found 50 cases of GISTs (recurrent or treated cases have been omitted) from the affiliated hospitals of Shiraz University of Medical Sciences. Demographic findings and gross characteristics have been extracted from the clinical charts and pathology reports, respectively. In addition, immunohistochemistry for c-KIT and DOG-1 were performed and reviewed by two pathologists. Molecular study for two common exons of KIT (9,11)  were performed by PCR and bidirectional DNA sequencing. RESULTS: Among 50 cases of GIST, 17 cases showed wild type KIT and 33 cases (66%) with mutation either in exon 9 or in exon 11. The mutation of exon 9 was detected in 11 (22%) cases, while 29 (58%) cases had mutation of exon 11. In seven cases, both exon 11 and exon 9 mutations were detected at the same time (14%). CONCLUSION: There is significant variation in the frequency of KIT mutation in exon 9 and 11 from the previous reports. Part of this variation in the previous and current studies is due to methodological differences; however, it seems that ethnic differences should not be underestimated. There are very few studies from the geographic region of Iran; however, the reported cases from the countries such as Turkey are very similar to our findings.

Effects of different concentrations of bromelain and papain enzymes on shear bond strength of composite resin to deep dentin using an etch-and-rinse adhesive system.

BACKGROUND: The dentin substrate can be modified by proteolytic agents, which may affect the bonding strength of adhesive systems to the treated dentin surface. Papain, a cysteine protease enzyme with antibacterial and anti-inflammatory properties, can be used for deproteinization of dentin. An alternative deproteinizing enzyme is bromelain. OBJECTIVES: This study aimed to evaluate the impact of deproteinization on the shear bond strength (SBS) of composite resin to deep dentin using different concentrations of bromelain and papain. MATERIAL AND METHODS: Sixty upper premolars were extracted and randomly divided into 5 groups (n = 12 per group). In all groups, the dentin surface was etched with 37% phosphoric acid. Group 1 did not receive any enzyme treatment, group 2 was treated with a 10% papain solution, group 3 was treated with a 15% papain solution, group 4 was treated with a 6% bromelain solution, and group 5 was treated with a 10% bromelain solution. After applying an etch-and-rinse adhesive system, the specimens were restored with composite resin and the SBS was measured. RESULTS: Statistically significant differences were found between groups 2 and 3 (10% papain and 15% papain, p = 0.004), groups 2 and 4 (10% papain and 6% bromelain, p = 0.017), groups 4 and 5 (6% bromelain and 10% bromelain, p = 0.021), and groups 3 and 5 (15% papain and 10% bromelain, p = 0.005). CONCLUSIONS: Deproteinization with papain and bromelain at different concentrations after acid etching did not affect the SBS of composite resin to deep dentin when using an etch-and-rinse adhesive system. However, the group deproteinized with 15% papain demonstrated a higher SBS than the group deproteinized with 10% papain, and the group deproteinized with 6% bromelain showed a higher SBS compared to the group deproteinized with 10% bromelain.

Assessing the Impact of Nano-Graphene Oxide Addition on Surface Microhardness and Roughness of Glass Ionomer Cements: A Laboratory Study.

Background: Nanomaterials, including nano-graphene oxide (nGO), have emerged as promising modifiers for dental materials. Therefore, this study investigated the effect of incorporating nGO into conventional glass ionomer cement (CGIC) and resin-modified glass ionomer cement (RMGIC) on surface roughness and hardness. Methods: Sixty disk-shaped specimens (2 × 6 mm) were divided into six groups: CGIC, RMGIC, CGIC with 1 wt.% nGO, CGIC with 2 wt.% nGO, RMGIC with 1 wt.% nGO, and RMGIC with 2 wt.% nGO. Surface roughness (Ra) and Vickers microhardness (VHN) were measured using a surface profilometer and Vickers microhardness tester, respectively. Statistical analysis employed the Kruskal-Wallis and Mann-Whitney tests (p <0.05). Results: The microhardness of RMGICs significantly increased with 1% and 2% nGO (p=0.017, P=0.001, respectively), while CGICs showed a significant decrease in VHN with nGO incorporation (p=0.001). VHN values of all CGIC groups were significantly higher than those of all RMGIC groups (p=0.001). Mean surface roughness values for all CGICs were significantly higher than those of RMGIC groups (p=0.001). Within the RMGIC groups, mean Ra values of RMGIC + 1 wt.% nGO and RMGIC + 2 wt.% nGO groups decreased significantly compared to the RMGIC control group (p=0.001, p=0.001, respectively). Among CGIC groups, mean Ra values of 1 wt.% and 2 wt.% nGO/CGIC groups were significantly higher than the CGIC control group (p=0.016, p=0.001). Conclusion: Incorporating nGO into RMGICs increased surface microhardness while reducing surface roughness, offering potential advantages for clinical applications. Conversely, adding nGO to CGICs increased surface roughness and decreased surface hardness. These findings emphasize the potential benefits of utilizing nGO in RMGICs and their implications in clinical practice.

Synthesis and characterization of mesoporous zinc oxide nanoparticles and evaluation of their biocompatibility in L929 fibroblasts.

OBJECTIVES: This study aimed to synthesize and characterize mesoporous zinc oxide nanoparticles (ZnO NPs) and also to evaluate the cytotoxicity of mesoporous ZnO NPs on L929 mouse fibroblast cell lines using 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. MATERIALS AND METHODS: The synthesized mesoporous ZnO NPs were extensively characterized using X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectra (EDAX), Fourier-transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The cytotoxicity of mesoporous ZnO NPs was assessed by MTT assay. The study groups for cytotoxicity assay were normal saline, 0.1% calcined mesoporous ZnO NP solution, 1% calcined mesoporous ZnO NP solution, 0.1% noncalcined mesoporous ZnO NP solution, 1% noncalcined mesoporous ZnO NP solution, 0.1% ZnO NP solution, 1% ZnO NP solution, 2% chlorhexidine, and phosphate-buffered saline (PBS). The percentages of mean ± standard deviation of viable cells were analyzed. RESULTS: Characterization of mesoporous ZnO NPs revealed that all the particles were in a more or less spherical shape with a wide particle size distribution of 70-100 nm. TEM image showed the uniformed and aggregated ZnO NPs with a typical size of 10-15 nm. BET analysis showed a mesoporous structure for the prepared mesoporous ZnO NPs. According to the MTT assay, chlorhexidine had the lowest cell viability percentage. Cell viability percentages of 0.1% mesoporous ZnO NP solutions (calcined and noncalcined) were statistically, significantly higher than 0.1% ZnO NP solution (p < .05). Cell viability percentages of 0.1% calcined and noncalcined mesoporous ZnO NP solutions and 0.1% ZnO NP solution were statistically, significantly higher than the 1% solutions (p < .05). CONCLUSION: Mesoporous ZnO NPs exhibited less cytotoxicity against L929 mouse fibroblast cell lines compared to CHX and ZnO NPs, hence are safe to use.

Evaluation of the relationship between bruxism and premature occlusal contacts.

AIM: This study evaluates the relationship between occlusal interferences and premature contacts and bruxism by determining the relationship between unassisted and assisted nonworking interferences. MATERIALS AND METHODS: In this study, 60 subjects (14 males and 46 females) that consisted of 30 bruxers (7 males, 23 females) and 30 nonbruxers (7 males, 23 females) were selected after completion of a questionnaire based on the exclusion criteria. Occlusal interferences in the centric relation and eccentric movements in the two groups were evaluated and recorded. Data were analyzed by SPSS software (version 16) using the Chi-square and paired t-tests. RESULTS: The results showed a statistically significant relationship between bruxism and nonworking interferences (p < 0.05). There was no statistically significant relationship in the centric relation and other eccentric movements (p > 0.05). The number of assisted nonworking occlusal contacts was more than unassisted nonworking occlusal contacts. CONCLUSION: According to the results of this study, there is a relationship between certain types of occlusal interferences (nonworking interferences) and bruxism. Hence, it would be useful to examine occlusal contacts in bruxing patients to eliminate probable causative or contributing occlusal factors. Both assisted and unassisted nonworking occlusal contacts should be evaluated. CLINICAL IMPLICATION: Bruxism is an oral habit that consists of involuntary rhythmic or spasmodic nonfunctional gnashing, grinding or teeth clenching, other than chewing movements by the mandible. Bruxism may lead to occlusal trauma, tooth wear, fracture of the teeth and fillings, and hypertrophy of the masticatory muscles. Treatment of bruxism needs a correct diagnosis. Therefore, it is useful to determine the relationship between occlusal interferences and bruxism in order to prevent its development by adjusting for these interferences.

Evaluation of the Effects of Different Types of Resin Cement Systems on the Push-Out Bond Strength of the Fiber Post to Intracanal Dentin in Anterior Primary Teeth.

Background: This study aimed to evaluate the effects of using three different resin cements on push-out bond strength (PBS) of fiber posts to root canal dentin of primary teeth. Methods: Fifty primary canines were randomly divided into five experimental groups according to the type of the luting agent used for fiber post cementation after endodontic treatment and post space preparation as the following: Group 1: glass ionomer cement (GIC), Group 2: flowable resin composite, Group 3: etch and rinse (E&R) resin cement, Group 4: self-etch (SE) resin cement, Group 5: self-adhesive (SA) resin cement. The PBS values of the cemented fiber posts to root canals were measured. The data were statistically analyzed using a one-way analysis of variance, followed by Tukey's post hoc test. Results: The highest mean PBS value was observed in Group 4 (SE resin cement), followed by Group 3 (E&R resin cement), and the lowest PBS value belonged to Group 1 (GIC), followed by Group 5 (p-values < 0.05). The mean PBS of Group 3 (E&R resin cement) was significantly higher than those of Groups 1 (GIC), 2 (flowable resin composite), and 5 (SA resin cement) (p-values < 0.05). However, no significant difference was found between the mean PBS of GIC and SA resin cement (p-value >0/05). Conclusion: Using SE resin cement for fiber post cementation in primary anterior teeth showed the best results, followed by E&R resin cement. The lowest PBS was observed for GIC, followed by SA resin cement.

Stress, Sleep Quality, and Academic Performance among Dental Students in Shiraz, Iran.

Background: Quality of sleep and stress level can affect the health, capacity of learning, and academic performance of the students. This study aimed to investigate the association between stress and sleep quality with academic performance among undergraduate clinical dental students in Shiraz, Iran. Methods: This cross-sectional study was conducted during the second semester of the academic year 2020-2021 among clinical dental students at Shiraz Dental School, Iran. A total of 138 students completed Pittsburgh Sleep Quality Index (PSQI) and dental environment stress (DES) questionnaire. The grade point averages (GPAs) of the previous terms of the participants were also collected. Data analysis was performed using Kolmogorov-Smirnov test, the one-way ANOVA, post hoc Duncan's test, nonparametric Kruskal-Wallis H test, Wilcoxon-Mann-Whitney test, and the chi-squared test. The p values of less than 0.05 were considered statistically significant. Results: Clinical dental students participated in this study experienced moderate levels of stress and poor sleep quality. Mean total DES and PSGI scores did not differ by sex, year of study, marital status, and place of residence (p values >0.05). Most of the students (52.9%) had moderate GPAs. A significant relationship was observed between sex and GPA as well as between place of residence and GPA (p values <0.05). No significant differences were found between DES total score or PSQI score and GPA categories (p values >0.05). A significant direct relationship between DES total score and PSQI score was observed (p < 0.05). Conclusion: Dental undergraduates in Shiraz, Iran, experienced moderate levels of stress and poor sleep quality. The results showed no significant difference between sleep quality or DES and academic achievement. However, a significant direct correlation was observed between sleep quality and dental environment stress.

Is the Presence of Helicobacter Pylori in the Colonic Mucosa, Provocative of Activity in Ulcerative Colitis?

Background: Epidemiologic studies have shown world-wide increasing incidence of ulcerative colitis (UC) as an autoimmune disease of intestine. In the meantime, gastrointestinal H. Pylori infection is being decreased. Objectives: There are very few studies about comparing the presence of H. Pylori in the colon and the disease activity of UC. There is no study form Iran. In this study, we tried to investigate the presence of H. Pylori in the mucosa of colon by molecular and microbiological as well as pathological methods to find any association between the presence of this organism in the colon and the presence and activity of UC. Patients and Methods: In 100 patients who referred to colonoscopy clinic, colonoscopy was performed. Fifty-seven patients with the new diagnosis of UC were considered as cases and 43 patients with normal screening colonoscopy for polyps were considered as controls. Colon biopsies were evaluated according to histopathology, clinical findings, and laboratory results to confirm the diagnosis and the degree of activity in the cases of UC. Molecular studies were also performed to evaluate the presence of H. Pylori genome in the colon biopsies. A sample of colon was also cultured for H. Pylori. ELISA test was performed in a sample of blood to evaluate the level of IL-10 and IL-17 as regulatory cytokines of inflammation. Results: Cases with the diagnosis of UC showed significantly higher number of positive colonic H. Pylori comparing to normal colonic mucosa. Also, the presence of H. Pylori genome in the colon was associated with higher activity in the cases with UC and higher levels of inflammatory mediators especially IL17 and lower levels of inhibitory mediators such as IL-10. Conclusion: Colonic colonization of H. Pylori was higher in the patients with UC and higher activity of this disease comparing with normal control colonic mucosa.

The effect of proanthocyanidin and casein phosphopeptide-amorphous calcium phosphate on the bond strength durability to caries-affected dentin.

OBJECTIVES: The aim of this study was to evaluate the effect of proanthocyanidin (PA) and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste on the micro-shear bond strength (µSBS) durability of an etch-and-rinse adhesive to caries-affected dentin (CAD). MATERIALS AND METHODS: The occlusal surfaces of 80 human molars with occlusal caries were ground to expose flat dentin surfaces with CAD. Then, they were randomly divided into four groups (n = 20) according to the CAD pretreatment. The study groups included no pretreatment, pretreatment with CPP-ACP for 3 min, pretreatment with PA for 1 min, and pretreatment with PA for 1 min followed by CPP-ACP for 3 min before adhesive application. After restoring the specimens with composite resin, µSBS testing was performed for half of the bonded surfaces in each group after 24 h and the other half was tested after 6 months of water storage and failure mode analysis was performed. RESULTS: The PA group was associated with a higher µSBS than the control and CPP-ACP groups after 24 hours (p < 0.05). No significant difference was observed regarding the µSBS of the control and the other groups after 24 h (p > 0.05). No significant difference was observed regarding the µSBS of the PA and PA + CPP-ACP groups (p > 0.05). The µSBS of the 6-month specimens was significantly lower than those of the 24-h specimens for all the groups (p < 0.05) except for the PA group which did not exhibit a significant difference between the two times (p > 0.05). The most common type of failure was mixed failure. CONCLUSION: PA pretreatment could stabilize the CAD-resin interface and protect degradation over time. The same effect was not observed for CPP-ACP or PA + CPP-ACP.

Evaluation of the Effects of Bromelain and Papain Enzymes on Shear Bond Strength of Composite Resin to Enamel.

AIM: This study aimed to evaluate the effects of 6% bromelain and 10% papain enzymes on shear bond strength (SBS) of composite resin to enamel compared to conventional 37% phosphoric acid etching. MATERIALS AND METHODS: 50 human maxillary premolar teeth were randomly divided into 5 groups (G1-G5/n = 10). In G1 and G2, after etching enamel with 37% phosphoric acid for 15 seconds and washing the surface, 10% papain and 6% bromelain enzymes were used, respectively. In G3 and G4, 6% bromelain or 10% papain enzymes were applied on enamel. In G5, the enamel surface was etched with 37% phosphoric acid for 15 seconds. A two-step etch-and-rinse adhesive system (Adper Single Bond 2) was applied. A nanohybrid composite (Z350) was placed using Teflon molds. All the samples were then subjected to the SBS test using a universal testing machine. Data analysis was performed using a one-way ANOVA test followed by the Tukey test. p values less than 0.05 were considered significant. RESULTS: Comparison of the mean SBS between G1, G2, and G5 shows no significant differences (p > 0.05); however, they had higher mean SBS compared with G3 and G4 (p < 0.0001). CONCLUSIONS: The shear bond strength of composite to enamel was not affected significantly using either 6% bromelain or 10% papain enzymes after 37% phosphoric acid application. Moreover, 6% bromelain and 10% papain enzymes were not as effective as 37% phosphoric acid alone.

Comparison between the effect of adding microhydroxyapatite and chitosan on surface roughness and Microhardness of resin modified and conventional glass ionomer cements.

BACKGROUND: This study aimed to compare the effect of chitosan (CH) and hydroxyapatite (HP) on the surface roughness and microhardness of a conventional glass ionomer cement (CGIC) and a resin modified glass ionomer cement (RMGIC). MATERIAL AND METHODS: 60 disk-shaped specimens (2mm x 6mm) were prepared in 6 groups; group I: CGIC, group II: RMGIC, group III: CGIC + 15% volume CH solution in liquid, group IV: CGIC +10% weight micro-HP in powder, group V: RMGIC + 15% volume CH, group VI: RMGIC + 10% weight micro-HP. After storage in deionized water at room temperature for 24 hours, the surface roughness and microhardness of the specimens were measured using a surface profilometer and Vickers microhardness (VHN) tester, respectively. Data were analyzed using two-way ANOVA, Tukey HSD test and paired t-test (P<0.05). RESULTS: The microhardness values of RMGIC and CGIC decreased significantly with the addition of micro-HP (P<0.001). None of the CH-containing GICs showed significant changes in microhardness (P = 0.552). The VHN values of CGIC were higher than RMGIC, regardless of the added substance (P<0.001). The surface roughness (Ra) values (µm) of both RMGIC and CGIC decreased significantly with the addition of CH (P = 0.004). The incorporation of micro-HP into GICs did not have a significant effect on surface roughness values (P = 0.700). The RMGIC showed less Ra values compared to the CGIC regardless of the added substance (P<0.001). The lowest and highest Ra values were observed in RMGIC + CH and CGIC + micro-HP groups, respectively. CONCLUSIONS: The addition of CH to GIC and RMGIC reduced the surface roughness and did not have an adverse effect on the microhardness. Mixing GIC and RMGIC with micro-HP resulted in microhardness reduction and did not affect the surface roughness. Key words:Glass ionomer, hydroxyapatite, chitosan, hardness, surface roughness.

Microshear Bond Strength of Nanoparticle-Incorporated Conventional and Resin-Modified Glass Ionomer to Caries-Affected Dentin.

The purpose of this study was to assess the influence of three different types of nanoparticles (silver (SNPs), titanium dioxide (TNPs), and zinc oxide (ZNPs)) on the microshear bond strength of conventional glass ionomer cement (CGIC) and resin-modified glass ionomer cement based on whether CGIC or RMGIC is used with four subgroups (based on the incorporation of SNPs, ZNPs, and TNPs in addition to a control subgroup) (n = 12) as follows: CGIC, CGIC + TNP, CGIC + ZNP, CGIC + SNP, RMGIC, RMGIC + TNP, RMGIC + ZNP, and RMGIC + SNP. After 24 hours, the µSBS of specimens was tested and the obtained data were analyzed using two-way ANOVA and Tukey's HSD test. The obtained results showed that the incorporation of TNPs in two glass ionomers was not statistically significant compared with the control subgroups (p > 0.05). In the first group, the highest and lowest mean µSBS were, respectively, observed in the CGIC + SNP subgroup and CGIC + ZNP subgroup. In the second group, RMGIC + ZNP and RMGIC + SNP, respectively, showed the highest and lowest mean µSBS compared to the other subgroups. According to the results, it can be concluded that TNPs can be incorporated into both CGIC and RMGIC without compromising the bond strength of glass ionomers. SNPs and ZNPs can be, respectively, added to CGICs and RMGICs to improve the bond strength of the restoration.

The Effects of Various Restorative Techniques on the Fracture Resistance of Pulpotomized Permanent Premolars.

AIM: This study aimed to evaluate the effects of various restorative techniques on the fracture resistance of pulpotomized premolars with mesioocclusodistal (MOD) cavities treated with mineral trioxide aggregate (MTA) or calcium enriched mixture (CEM) cement. MATERIALS AND METHODS: One hundred and eight sound extracted maxillary premolars were randomly assigned to nine experimental groups (n = 12). The teeth in group 1 did not receive any preparation. Class II MOD cavities were prepared in the other experimental groups. In groups 2, 4, 6, and 8, tooth-colored MTA was used for pulpotomy. In groups 3, 5, 7, and 9, CEM cement was used for pulpotomy. Groups 2 and 3 were left unrestored. Groups 4 and 5 were restored with amalgam. Groups 6 and 7 were restored with a conventional composite resin, and groups 8 and 9 were restored with bulk-fill giomers. Fracture resistance was measured, the fracture pattern of each specimen was assessed, and the results were statistically analyzed. RESULTS: The fracture resistance of group 1 was significantly higher than those of the other groups (p < 0.05). The fracture resistance of group 2 (MTA + amalgam) was statistically lower than those of all experimental groups (p values < 0.05) except groups 3, 4, and 5 (p values > 0.05). No statistically significant differences were found between the groups restored with amalgam, conventional composite resin, and bulk-fill giomer (groups 4, 5, 6, 7, 8, and 9) (p values < 0.05). The highest rate of mode 1 fracture (restorable fracture) was observed in group 1 followed by groups 8 and 9. CONCLUSION: No significant differences were found among the fracture resistances of the restored teeth using various restorative techniques. Bulk-fill giomers followed by conventional composite resin were better able to prevent unfavorable fractures compared to amalgam. Therefore, they seem to be more reliable for the restoration of pulpotomized teeth with MOD cavities.

The influence of the operator's experience on the microleakage of two universal adhesives.

OBJECTIVES: This study aimed to investigate the influence of the operator's experience on the microleakage of two universal adhesives applied in self-etch (SE) and etch-and-rinse (E&R) modes. MATERIALS AND METHODS: Two class V cavities were prepared on the buccal and lingual surfaces of 112 caries-free extracted human molars and were divided into eight groups based on the combination of the factors "adhesive system" (Tetric N-Bond Universal Adhesive [TNU]; Scotchbond Universal Adhesive [SBU]), "adhesive strategy" (SE or E&R), and "the operators performing the procedures" (specialists in operative dentistry or intern students). After 24 h of water storage and thermocycling, the marginal microleakage was evaluated using the dye penetration technique and the data were analyzed. RESULTS: In the SE mode, microleakage at the enamel margin for both adhesives was higher in the student group than in the specialist group (p values < 0.05). The operator's skill did not affect the microleakage scores of both adhesives applied in the E&R mode at the dentin and enamel margins or in the SE mode at the dentin margins (p > 0.05). The microleakage score was significantly higher at the dentin margins than the enamel margins for both universal adhesives applied in the E&R mode (p values <0.05). CONCLUSION: The microleakage values of the universal adhesives applied in the SE mode at the enamel margins were affected by the operator's skill. However, the operator's experience did not affect the microleakage scores of the two universal adhesives applied in the E&R mode at the enamel and dentin margins or in the SE mode at the dentin margins.

Microsatellite Instability and Colorectal Cancer, Immunohistochemical and Molecular Evaluation by Using DNA Sequencing: A Single Center Experience.

BACKGROUND & OBJECTIVE: Microsatellite instability is common in familial colorectal cancers. It can be tested by the molecular and immunohistochemical methods. There are very few studies which address comparing the clinicopathological characteristics of microsatellite stable (MSS) and microsatellite unstable (MSI) colorectal cancers from Iran. In this study, we aimed to evaluate the clinicopathological and immuno-histochemical findings of MSS and MSI colorectal cancers in our Center as the largest Center of gastrointestinal surgery and oncology in the South of Iran. We also compared the immunohistochemical method vs. molecular study using DNA sequencing. METHODS: For 5 years (2015-2019), 34 patients who underwent operation in the affiliated Hospitals of Shiraz University of Medical Sciences were clinically suspected to microsatellite instability (MSI). The molecular diagnostic tests with DNA sequencing were performed. Clinicopathological and immunohistochemical findings of MSI colorectal cancers were compared with those who were stable. RESULTS: In the South of Iran, MSI colorectal cancers were more common in males. These tumors were more common in the right side with more tendencies to produce mucin with lymphocytic infiltration. CONCLUSION: Immunohistochemistry would be a specific method for diagnosis of MSI colorectal cancers but may be associated with high rate of false negative results and of low sensitivity. Therefore, we recommend performing molecular studies by DNA sequencing in those colon cancers with clinical suspicion for MSI and negative immunohistochemical findings.