Abdulkadir Sengun

Effect of artificial aging regimens on the performance of self-etching adhesives.

This in vitro study was performed to compare the microtensile bond strengths (MTBS) of current self-etching adhesives to dentin and to evaluate the effects of artificial aging [(thermocycling (TC) and/or mechanic loading (ML)] on MTBS and on nanoleakage of self-etching adhesives. Two-step (AdheSE Bond, Clearfil Protect Bond, Clearfil SE Bond, Optibond Self-Etch) and one-step (Hybrid Bond, G-bond, Clearfil Tri-S Bond, and Adper Prompt L-Pop) self-etching adhesives were tested. Resin composite build-ups were created, and the specimens were subjected to 10(4) TC, 10(5) ML, and 10(4)/10(5) TC/ML. Non-aged specimens served as controls. In the control group, no significant differences were found among the MTBS of the one-step self-etching adhesives and among those of three two-step self-etching adhesives (AdheSE Bond, Clearfil Protect Bond, and Clearfil SE Bond) (p > 0.05). The MTBS of AdheSE Bond and Clearfil Protect Bond were higher than were those of all one-step self-etching adhesives and than those of Optibond Self-Etch. The MTBS of Clearfil SE Bond was higher than were those of two one-step self-etching adhesives (Adper Prompt L-Pop, G-bond) (p < 0.05). Compared with the non-aged controls, TC did not decrease (p > 0.05), but ML and TC/ML significantly decreased the MTBS of the adhesives tested (p < 0.05). Two-step self-etching adhesives tended to fail more cohesively in dentin. Transmission electron microscopy revealed different nanoleakage patterns in the adhesive and hybrid layers of all adhesives examined, and signs of additional silver-filled water channels were more readily detectable after TC/ML.

Effect of a new restoration technique on fracture resistance of endodontically treated teeth

The aim of the study was to investigate the effect of a new fiber-reinforced composite restoration technique on fracture resistance in endodontically treated premolars. Eighty sound extracted human mandibular premolars were assigned to four groups (n = 20). Group 1 did not receive any treatment. In groups 2, 3 and 4, the teeth received root canal treatment and a mesio-occluso-distal cavity preparation. Group 2 was kept unrestored. Group 3 was restored with a dentin bonding system and composite resin. In group 4, a piece of polyethylene ribbon fiber was inserted into the groove in a buccal to lingual direction during the restoration of teeth with dentin bonding system and composite resin. After finishing and polishing, the specimens were stored in 100% humidity at 37 degrees C for 24 h and placed at an angle of 45 degrees to the long axis of the tooth and subjected to compressive loading in a universal testing machine at a crosshead speed of 0.5 mm min(-1). The load necessary to fracture the samples was recorded in Newton (N) and submitted to Kruskal-Wallis anova and Mann-Whitney U-test. The fracture strength of the teeth reinforced with a combination of polyethylene fiber and composite resin were not significantly different than those that were restored with only composite resin (P > 0.05). However, most of the failure modes of the reinforced teeth were limited to the level of the enamel, while the other three groups showed fractures generally at the level of the dentin, cemento-enamel junction or more below (P < 0.05). Therefore, polyethylene ribbon fiber-reinforced composite resin restorations seemed a more reliable restorative technique than traditional composite restorations for extensive cavities.

Effects of Chlorhexidine and Povidone-Iodine Mouth Rinses on the Bond Strength of an Orthodontic Composite

The purpose of this study was to determine whether the application of two antibacterial mouth rinses to etched and unetched enamel affects the shear bond strength (SBS) of an orthodontic composite resin. Eighty-five lower human incisors were divided into five groups, ie, group 1: control group, no mouth rinse was used; groups 2 and 3: mouth rinses were applied to the intact enamel surface before etching; groups 4 and 5: mouth rinses were applied to the etched enamel. A bonding agent and a composite resin were applied to the teeth surface. For shear bond testing, the specimens were mounted in a universal testing machine, and an apparatus attached to a compression load cell was applied to each specimen until failure occurred. The data were analyzed using analysis of variance and Tukey honestly significance tests. Fracture modes were analyzed by Mann-Whitney U-test. There was no statistically significant difference between the SBS values of group 1 (31.64 +/- 3.62 MPa) and group 4-five experimental applications (P > or = .05). However, the SBS value of group 3 (36.56 +/- 5.95 MPa) was significantly larger than those of group 4 (30.00 +/- 4.97 MPa) and group 5 (30.26 +/- 7.30 MPa). In addition, no significant differences were observed between group 1 and groups 2 (34.33 +/- 7.26 MPa) and 3 (36.56 +/- 5.95 MPa) (P > or = .05). Because the application of chlorhexidine and povidone-iodine before acid etching did not cause any decrease in bond strength, it is advisable for use under the orthodontic resin composite to obtain an antibacterial effect or to prevent the risk of bacteremia.

Cytotoxic effects of resin-modified orthodontic band adhesives. Are they safe?

OBJECTIVE To evaluate the cytotoxic effects of three different resin-modified orthodontic band adhesives. MATERIALS AND METHODS Three resin-modified orthodontic band adhesives (Bisco Ortho Band Paste LC, Multi-Cure Glass Ionomer Band Cement, and Transbond Plus Light Cure Band Adhesive) were prepared and the samples were extracted in 3 mL of Basal Medium Eagle with 10% newborn calf serum for 24 hours. The L929 cells were plated (25,000 cells/mL) in wells of 96-well dishes and maintained in a humidified incubator for 24 hours at 37 degrees C, 5% CO(2), and 95% air. After 24-hour incubation of the cells, the incubation medium was replaced by the immersed medium in which the samples were stored. Then L929 cells were incubated in contact with eluates for 24 hours. The cell mitochondrial activity was evaluated by the methyltetrazolium test. Twelve wells were used for each specimen, and methyltetrazolium tests were applied two times. The data were statistically analyzed using one-way analysis of variance and Tukey Honestly Significantly Different tests. RESULTS Results with L929 fibroblasts demonstrated that all freshly prepared resin-modified orthodontic band adhesive materials reduced vital cell numbers (P > .05), in comparison to the control group. Our data demonstrate that all materials showed significant cytotoxicity compared to the control group. CONCLUSIONS The results indicate that all materials showed significant cytotoxicity compared to the control group, and further studies using different test methods are needed for all resin-modified orthodontic band adhesives.

Evaluation of cytotoxicity of six different flowable composites with the methyl tetrazolium test method

Background: The aim of this study was to investigate the cytotoxicity of six different flowable composites with the methyl tetrazolium test (MTT). Materials and Methods: For MTT, six different flowable composites (Bisco Aelite, Bisco Inc., USA; Esthet X Flow, Dentsply, USA; Filtek™ Supreme XT Flowable Restorative, 3M Espe, USA; Gradia ® Direct Flo, GC, USA; Estelite ® Flow Quick, Tokuyama Dental Corporation, Japan; and Clearfil Majesty Flow, Kuraray Medical Inc., Japan) were prepared according to the manufacturers instructions in standard Teflon disks (2 mm × 5 mm) and the samples were extracted in 7 ml of Basal Medium Eagle with 10% new born calf serum and 5% penicillin streptomycin gentamisin for 24 h. In the experiments: The L929 cells were plated (25.000 cells/ml) in wells of 96 well-dishes and maintained in a humidified incubator for 24 h at 37°C, 5% CO 2 , and 95% of air. After 24 h incubation of the cells, the incubation medium was replaced by the immersed medium in which the samples were stored. Then L929 cells were incubated in contact with evaluates for 24 h. The cell mitochondrial activity was evaluated by the MTT. 12 well used for each specimen and MTT tests applied 2 times. The data were submitted to the statistically analyzed by one-way ANOVA and Tukeys honestly significant difference (HSD) tests. Results: According to the results of MTT test with L-929 fibroblasts demonstrated that all freshly prepared flowable composites did not reduce vital cell numbers ( P >0.05) in comparison to control group. Conclusion: This study revealed important information for clinical applications of flowable composites in dentistry.

Reliability of electronically detection of fissure caries (by using a prototype device): An alternative diagnostic electronic caries monitor device

Objective: The purpose of this in vitro study was to investigate the reliability of a prototype electronic caries monitor (ECM) for diagnosis of the dental caries on the occlusal surfaces of posterior teeth and to compare using histological examination as gold standard. Materials and Methods: Data were obtained from 93 occlusal sites of 33 extracted human molars. Electrical resistance to alternative currency of 21 Hz and 24 Vpp of the teeth was measured with the ECM, which produced in Selcuk University. After obtaining electrical conductance values, each tooth was then sectioned into two pieces mesiodistally and examined histologically for occlusal caries under the stereomicroscope. Statistical evaluations were made using Pearson correlation test. Results: A statistically significant negative correlation was found between electrical resistance of the teeth and occlusal caries presence ( P < 0.05). Conclusion: As a result, it is suggested that ECM is a nondestructive and suitable method at detection of occlusal caries.

Effect of endodontic irrigants on microtensile bond strength of a self-etching adhesive system

Aim: The aim of this in vitro study was to evaluate the effect of two different irrigation solutions, alone or in combination, with different application times on the dentin bond strength of a self-etching adhesive. Materials and Methods: Twenty-eight extracted non-carious human third molars were randomly distributed into seven groups according to the irrigant. The crowns of the molars were sectioned vertically through bucco-lingual direction. Solutions of 5% sodium-hypochlorite (NaOCl), 3% hydrogen-peroxide (H 2 O 2 ), and a combination of NaOCl and H 2 O 2 were applied to the dentin surface for various lengths of time. The adhesive system (Clearfil SE Bond; Kuraray, Japan) was applied according to the manufacturers′ directions and then the dentin surfaces were built up with a hybrid composite resin (Clearfil AP-X Kuraray, Japan). Specimens were sectioned into 15 sticks; each of them had a 0.65 mm 2 bonding area. Microtensile bond strength was determined (MPa), and the results were statistically analyzed using one-way ANOVA and Tukey′s HSD test. Results: Irrigation with NaOCl alone showed similar micro-tensile bond strength values with the control group (P > 0.05). In comparison to control group, irrigation with H 2 O 2 alone for 5 min and 30 min and the irrigation with H 2 O 2 /NaOCl combination each for 15 min decreased the microtensile bond strength. Conclusion: The use of H 2 O 2 significantly reduced the bond strengths of the self-etching adhesive when applied alone or in combination with NaOCl for a long time.

Effects of five different resin-based sealers on L929 and Saos-2 cell viability

The aim of this study was to evaluate the cytotoxic effects of five different resin-based root canal sealers: EndoREZ, Epiphany SE, EZ-Fill, MMSeal and AHPlus. Set materials were extracted in culture medium and cytotoxicity was determined in two cell lines, human osteosarcoma cell line (Saos-2) and mouse skin fibroblast cells (L929). The cells were incubated in contact with elutes for 24 h. The cell mitochondrial activity was evaluated by the methylthiazole tetrazolium assay. Results with demonstrated that all sealers showed a reduced vital cell number in comparison with the control group (P < 0.05). For L929 cells, the ranking of the most to the least toxic material was: EZ-Fill (12.0%) = EndoREZ (12.1%) = AHPlus (12.4%) > MMSeal (44%) = Epiphany SE (46.2 %). For Saos-2 cells revealed that cell survival with extracts of EndoREZ, Epiphany SE, EZ-Fill, MMSeal and AHPlus was 33.9%, 32.9 %, 33.1%, 35.3% and 34.6%, respectively, all tested sealers showed moderate cytotoxicity. Based on the results obtained from the present study, all tested resin-based sealers appear to show toxicity potential to both cells in spite of different toxicity degrees. Therefore, better sealers need to be developed with acceptable biological properties for root canal filling.