Filiz Yalcin Cakir

Effect of surface conditioning on the retentive bond strengths of fiberreinforced composite posts

STATEMENT OF PROBLEM Debonding is a common cause of failure encountered with fiber-reinforced composite (FRC) posts, and usually occurs along the post space-dentin adhesive interface. Surface conditioning of posts is expected to increase the chemical and mechanical bond between the luting composite resin and the post, but the best method has not been definitively determined. PURPOSE The purpose of this in vitro study was to compare the effects of 3 surface-conditioning methods on the retentive bond strengths of FRC posts using 5 composite resin materials, and compare results to those of unconditioned FRC posts as well. MATERIAL AND METHODS Post space preparations (DentinPost ER root post system, length of 12 mm) were performed on 200 human anterior teeth. Groups of 50 FRC posts (ISO size 90) each were treated using 1 of the following conditioning methods: silanization, etching with 5% hydrofluoric acid, tribochemical coating (CoJet system), or were left untreated (control group). FRC posts (n=10) in each group were placed using 1 of 5 composite resin materials (Calibra or RelyX Unicem resin cements or Build-It, MultiCore Flow, or Rebilda DC foundation composite resins). Following water storage (37 degrees C, 24 hours) and thermal cycling (5000 cycles, 5 degrees -55 degrees C, 30-second dwell time), tensile strength testing was performed. Fracture modes were assessed using a light microscope. Data were analyzed statistically (1-way and 2-way ANOVA, Bonferroni-Dunn correction, alpha=.05). RESULTS Retentive bond strengths of FRC posts luted with MultiCore Flow in combination with the CoJet system, and of posts inserted with Rebilda DC in combination with hydrofluoric acid (HF) etching as well as with the CoJet system, were significantly higher than those of the corresponding unconditioned FRC posts (P<.001). No significant differences were noted between the bond strength values of RelyX Unicem with CoJet, MultiCore Flow with CoJet, and Rebilda DC with either CoJet or HF etching (P>.05). Retentive bond strengths were significantly lower for HF etching (Calibra, RelyX Unicem, Build-It), and for the treatment with the CoJet system in combination with Build-It compared to the corresponding control groups (P<.001). Fracture modes were primarily adhesive at the post surface or cohesive within the composite resin layer or within the FRC post. CONCLUSIONS The retentive bond strengths differed significantly with respect to the tested combinations of conditioning method and luting composite resin.

Chemical Analysis of Enamel and Dentin Following the Application of Three Different At-home Bleaching Systems

PURPOSE To determine the change in the chemical composition of enamel and dentin as well as to evaluate the differences in surface texture of the same dental hard tissues following three at-home bleaching systems in vitro. METHODS Sixty extracted intact human anterior teeth were used in this study. Thirty teeth were used as samples for enamel, and the buccal surfaces of the remaining 30 teeth were abraded and used as dentin samples. Prior to bleaching treatments, calcium (Ca), phosphorus (P), potassium (K), sodium (Na), magnesium (Mg), fluoride (F), and oxygen (O) levels of each sample were measured using an energy dispersive spectrometer. The teeth were then randomly allocated into three groups according to the bleaching system used, as follows: GI, 10% carbamide peroxide (CP); GII, 20% CP; GIII, and 35% CP. Following the bleaching treatments, Ca, P, K, Na, Mg, F, and O measurements were repeated. The surface configurations were examined using scanning electron microscopy (SEM). The data were analyzed using Wilcoxon signed rank and Kruskal-Wallis tests followed by the Dunn test. RESULTS All three bleaching systems tested caused similar changes in the chemical composition of enamel and dentin. Bleaching systems decreased Ca and K, while F and O levels increased in enamel. In dentin, Ca, P, and K levels decreased; however, Na, F, and O levels increased. SEM observations revealed no deleterious effect on enamel and dentin. CONCLUSION The use of home bleaching agents could affect the chemical composition of dental hard tissues, whereas the change in the chemical composition of enamel and dentin was not affected by the CP concentration of the bleaching systems used.

Effect of different adhesive systems and laser treatment on the shear bond strength of bleached enamel

PURPOSE This study determined the shear bond strength of a nanohybrid composite resin to bleached enamel immediately or 15 days later using different adhesive systems and laser application. METHODS One hundred and forty enamel specimens were prepared from human molar teeth and bleached either with 16% carbamide peroxide (CP) or 30% CP according to the manufacturers (Vivastyle/Vivadent) recommendations. After bleaching treatments specimens were divided into two groups according to the treatment time of the adhesive procedures: immediately or 15 days after the bleaching treatments. The four groups were then divided into five subgroups due to the surface treatments: using a two-step self-etching adhesive (AdheSe, Ivoclar Vivadent G, Schaan, Liechtenstein) or a two-step etch and rinse adhesive (Excite, Ivoclar Vivadent G, Schaan, Liechtenstein) and application of laser prior to adhesive procedures or not. After adhesive procedures nanohybrid composite resin cylinders of 4 mm x 2 mm (Tetric Evo Ceram/Vivadent) were bonded to the enamel surfaces. All specimens were subjected to shear bond strength test after thermocycling and 24h of storage in water. Data were analyzed statistically. RESULTS Mann-Whitney U-test analysis showed no significant difference in the mean bond strength values of enamel bleached with either 16% CP or 30% CP (p>0.05). There was no difference between the groups bonded immediately or 15 days after bleaching (p>0.05). Application of the etch and rinse adhesive after 15 days showed the highest bond strength values, whereas self-etching adhesive and laser application showed the lowest values in both bleaching treatments. CONCLUSIONS The results suggested that following the bleaching treatments, the use of etch and rinse adhesive system may provide higher bond strengths than self-etching adhesive and laser application.

Shear bond strength of composite bonded to Er,Cr:YSGG laser-prepared dentin.

OBJECTIVE The purpose of this in vitro study was to evaluate dentin bond strength to resin composite following high-speed rotary or Er,Cr:YSGG laser preparation using two different adhesive systems. MATERIALS AND METHODS One hundred and forty dentin specimens were prepared from human molars. Seventy specimens were prepared with a high-speed diamond bur and 70 of the specimens were prepared with an Er,Cr:YSGG laser. Each group was subdivided into 7 groups of 10 teeth and etched with either 37% H3PO4, laser etched at two different power levels (1.25 W and 3 W), or not etched. Nano-hybrid composite resin cylinders 4 x 2 mm in size (Tetric EvoCeram, Vivadent) were bonded to the dentin surfaces with the application of an etch-and-rinse adhesive (Exite/Vivadent), or a self-etching adhesive (AdheSe/Vivadent). After storage in distilled water and thermocycling, a shear bond strength test was performed on all specimens and the data were statistically analyzed. RESULTS ANOVA detected significant differences between the tested groups (p < 0.001). Duncans multiple comparison test showed that Excite-applied specimens that were prepared with laser and laser etched (1.25 W or 3 W) had higher mean bond strengths. Both AdheSe- and Excite-applied specimens prepared with the diamond bur and laser etched (1.25 W) showed the lowest mean bond strength values (p < 0.05). CONCLUSION The results suggest that dentin surfaces prepared with the Er,Cr:YSGG laser and etched with the laser (at either 1.25 or 3 W) may provide comparable or increased composite resin bond strengths, depending on the adhesive used.

Four-year Randomized Clinical Trial to Evaluate the Clinical Performance of a Glass Ionomer Restorative System

OBJECTIVE The aim of this study was to evaluate the clinical performance of a glass ionomer restorative system compared with a microfilled hybrid posterior composite in a four-year randomized clinical trial. METHODS A total of 140 (80 Class 1 and 60 Class 2) lesions in 59 patients were either restored with a glass ionomer restorative system (Equia, GC, Tokyo, Japan), which was a combination of a packable glass ionomer (Equia Fil, GC) and a self-adhesive nanofilled coating (Equia Coat, GC), or with a microfilled hybrid composite (Gradia Direct Posterior, GC) in combination with a self-etch adhesive (G-Bond, GC) by two experienced operators according to the manufacturers instructions. Two independent examiners evaluated the restorations at baseline and at one, two, three, and four years postrestoration according to the modified US Public Health Service criteria. Polyvinyl siloxane impression negative replicas at each recall were observed under scanning electron microscopy (SEM) to evaluate surface characteristics. The statistical analyses were carried out with McNemar, Pearson Chi-square, and Cochran Q-tests (p<0.05). RESULTS After four years, 126 (76 Class 1 and 50 Class 2) restorations were evaluated in 52 patients, with a recall rate of 88.1%. None of the restorations showed trends to downgrade in anatomical form, secondary caries, surface texture, postoperative sensitivity, and color match (p>0.05). Significant differences in marginal adaptation and discoloration were found at four years compared to baseline for both restorative materials for Class 1 and Class 2 restorations (p<0.05). Only one Class 2 Equia restoration was missing at three years (3.9%), and another one was missing at four years (7.7%) (p>0.05). SEM evaluations were in accordance with the clinical findings. CONCLUSIONS The use of both materials for the restoration of posterior teeth exhibited a similar and clinically successful performance after four years.

The Effect of Different Preparation and Etching Procedures on the Microleakage of Direct Composite Veneer Restorations

OBJECTIVES The aim of this in vitro study was to compare the microleakage of direct composite veneer restorations prepared by a conventional dental bur or Er,Cr:YSGG (erbium, chromium doped yttrium scandium gallium garnet) laser and etched with different procedures. METHODS Fifty maxillary incisor teeth prepared for direct veneers with gingival margins in dentin and incisal margins in enamel were randomly divided into five groups (n = 10): group 1 (control), prepared with diamond bur and etched with phosphoric acid; group 2, prepared with diamond bur and etched with Er,Cr:YSGG laser (Waterlase MD/Biolase); group 3, prepared with laser and not etched; group 4, prepared with laser and etched with phosphoric acid; and group 5, prepared and etched with laser. After the application of the etch and rinse adhesive system (Prime & Bond NT/Dentsply), teeth were restored with the nano ceramic restorative material (Ceram X Duo/Dentsply), subjected to thermocycling and immersed in 0.5% basic fuchsin dye for 24 h. The teeth were sectioned longitudinally and dye penetration was evaluated by a binocular stereomicroscope equipped with a measuring device. Data were analyzed by Kruskal-Wallis and Wilcoxon signed ranks tests. The level of significance was set at p = 0.05. RESULTS Significant differences were observed in enamel of the five groups (p < 0.05). Minimal microleakage was observed in groups 1 and 3. The highest microleakage was evaluated in group 5 (p < 0.05). No significant differences were found among the five groups in dentin (p > 0.05). No differences were recorded between the microleakage values in enamel and dentin within each group and this was valid for all groups (p > 0.05). CONCLUSIONS The results confirmed that enamel and dentin surfaces prepared with Er,Cr:YSGG laser for direct composite veneer restorations may provide comparable sealing.

Effect of bleaching on mercury release from amalgam fillings and antioxidant enzyme activities: a pilot study.

OBJECTIVE The aim of this pilot clinical study was to determine the mercury release from amalgam fillings and antioxidant enzyme activities (Superoxide Dismutase [SOD] and Catalase[CAT] ) in body fluids after exposure to two different vital tooth bleaching systems. MATERIAL AND METHODS Twenty eight subjects with an average age of 25.6 years (18-41) having at least two but not more than four Class II amalgam fillings on each quadrant arch in the mouth participated in the study. Baseline concentrations of mercury levels in whole blood, urine, and saliva were measured by a Vapor Generation Accessory connected to an Atomic Absorption Spectrometer. Erythrocyte enzymes, SOD, and CAT activities in blood were determined kinetically. Subjects were randomly assigned to two groups of 14 volunteers. Group 1 was treated with an at-home bleaching system (Opalescence PF 35% Carbamide Peroxide, Ultradent), and Group 2 was treated with a chemically activated office bleaching system (Opalescence Xtra Boost 38% Hydrogen Peroxide, Ultradent) according to the manufacturers recommendations. Twenty-four hours after bleaching treatments, concentrations of mercury and enzymes were remeasured. RESULTS There were no significant differences on mercury levels in blood, urine, and saliva before and after bleaching treatments (p > 0.05). No differences were also found in the level of antioxidant enzyme activities (SOD and CAT) before and after treatments (p > 0.05). Mercury release did not affect the enzyme activities (p > 0.05). CONCLUSION Bleaching treatments either office or home did not affect the amount of mercury released from amalgam fillings in blood, urine, and saliva and the antioxidant-enzyme activities in blood. CLINICAL SIGNIFICANCE Bleaching treatments with the systems tested in this pilot study have no deleterious effect on the mercury release from amalgam fillings and antioxidant enzymes in body fluids.

Comparison of two different methods of detecting residual caries

Objectives The aim of this study was to investigate the ability of the fluorescence-aided caries excavation (FACE) device to detect residual caries by comparing conventional methods in vivo. Materials and Methods A total of 301 females and 202 males with carious teeth participated in this study. The cavity preparations were done by grade 4 (Group 1, 154 teeth), grade 5 (Group 2, 176 teeth), and postgraduate (Group 3, 173 teeth) students. After caries excavation using a handpiece and hand instruments, the presence of residual caries was evaluated by 2 investigators who were previously calibrated for visual-tactile assessment with and without magnifying glasses and trained in the use of a FACE device. The tooth number, cavity type, and presence or absence of residual caries were recorded. The data were analyzed using the Chi-square test, the Fishers Exact test, or the McNemar test as appropriate. Kappa statistics was used for calibration. In all tests, the level of significance was set at p = 0.05. Results Almost half of the cavities prepared were Class II (Class I, 20.9%; Class II, 48.9%; Class III, 20.1%; Class IV, 3.4%; Class V, 6.8%). Higher numbers of cavities left with caries were observed in Groups 1 and 2 than in Group 3 for all examination methods. Significant differences were found between visual inspection with or without magnifying glasses and inspection with a FACE device for all groups (p < 0.001). More residual caries were detected through inspection with a FACE device (46.5%) than through either visual inspection (31.8%) or inspection with a magnifying glass (37.6%). Conclusions Within the limitations of this study, the FACE device may be an effective method for the detection of residual caries.