Comparison of the micro-tensile bond strengths of four different universal adhesives to caries-affected dentin after ER:YAG laser irradiation.

The micro-tensile bond strengths (micro-TBSs) of four universal adhesive systems, applied in two different bonding techniques, to carries-affected dentin after Er:YAG laser irradiation were investigated. Twenty-four extracted human molars were divided into four groups, according to the adhesive systems used. Each group was subdivided into two subgroups, depending on the bonding method used: the etch-and-rinse procedure or self-etch procedure. The carious lesions were irradiated using an Er:YAG laser. Resin composites were used to restore the adhesive-treated dentin surfaces. After 2,500 thermal cycles, the vertical composite resin-dentin sticks obtained were subjected to micro-TBS tests. One tooth in each group was examined using scanning electron microscopy (SEM). There were statistically significant differences (p<0.001) in micro-TBS values between universal adhesives. The results of this study suggested that universal adhesives applied both with self and total etch technique can be used for adhesive restorations to caries-affected dentin after Er:YAG laser irradiation. If lasers are preferred as a caries removal method, choosing a dentin bonding agent containing MDP may be recommended in clinical practice due to the property of increasing the bonding strength.

Comparison of Smear Layer Removal Ability of QMix with Different Activation Techniques.

INTRODUCTION: To evaluate the effectiveness of QMix solution (Dentsply Tulsa Dental Specialties, Tulsa, OK) on the smear layer using the following irrigation activation techniques: the EndoActivator (EA) system (Dentsply Tulsa Dental Specialties), photon-initiated photoacoustic streaming (PIPS), and an Er:YAG laser with an endodontic fiber tip. METHODS: Sixty-four extracted single-rooted human teeth were decoronated and the canals instrumented with ProTaper (Denstply Maillefer, Ballagues, Switzerland) up to size F4. The canals were irrigated with 5.25% sodium hypochlorite and a saline solution for 1 minute each. The specimens were then divided randomly into 4 experimental and 4 control groups (n = 8) according to the final irrigation activation technique. These groups included group 1, 2.5 mL QMix; group 2, QMix + EA; group 3, QMix + PIPS; and group 4: QMix + Er:YAG. Laser activated distilled water was used as control groups 5, 6, 7, and 8. Teeth were split longitudinally, and specimens were observed under a scanning electron microscope. Images were taken at the coronal, middle, and apical thirds of the teeth at a magnification of 1000× and were scored in the presence of the smear layer. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests. RESULTS: The highest scores were found in the apical third of all groups (P < .05). The QMix + Er:YAG group removed the smear layer more effectively than the nonactivated QMix group in the apical third (P < .05). The QMix + EA group removed the smear layer significantly in all thirds of the teeth when compared with the nonactivated QMix group (P < .05). The QMix + PIPS group showed a significantly better effect than the QMix group in the coronal third (P < .05). CONCLUSIONS: The EA and Er:YAG laser enhanced the smear layer removal ability of QMix in the apical thirds of the canals. QMix removed more smear layer in the coronal thirds when activated with the PIPS technique.

Efficacy of Laser-Activated Irrigants in Calcium Hydroxide Removal from the Artificial Grooves in Root Canals: An Ex Vivo Study.

OBJECTIVE: The aim of this study was to investigate the efficacy of an erbium chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser with different irrigation solutions [sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), QMix 2in1, and peracetic acid] in removing calcium hydroxide (CH) from artificial grooves created in root canals. BACKGROUND DATA: CH has to be removed totally before the root canal filling. Any CH residue on the dentin walls may affect the dentinal bond strength and the penetration of sealers into the dentin tubules, and may increase apical leakage. In addition, such a remnant could react chemically with sealers and, possibly, influence physical properties. Therefore, complete removal of CH placed inside the root canals is recommended, using various products and techniques. METHODS: The root canals of 160 extracted single-rooted mandibular premolars were prepared with ProTaper Universal rotary instruments up to size F4. The roots were split longitudinally along the length of the instrumented canals, and a standardized groove was prepared in the apical part of one segment. CH powder mixed with distilled water was placed into the grooves, and the root halves were then reassembled. The roots were randomly divided into two main groups according to the selected irrigation techniques (needle and laser activation) and then each main group was divided into four subgroups according to the final irrigation (NaOCl, EDTA, QMix 2in1, and peracetic acid) protocols used. After irrigation, the roots were disassembled and digital images were taken using a stereomicroscope. Measurements of residual CH were performed as percentages of the overall groove surface area with image analysis software. The data obtained were analyzed using one way analysis of variance and Tukey's honest significant difference tests. Statistical significance was set at p < 0.05. RESULTS: Significantly less residual CH was obtained in the laser-activated groups than in the needle-irrigated groups (p < 0.05). According to both main groups' data, NaOCl left significantly more CH than the other groups (p < 0.05). However, there was no significant difference among the EDTA, QMix 2in1, and peracetic acid groups. CONCLUSIONS: None of the techniques removed the CH dressing completely. Laser-activated irrigation was significantly more effective than needle irrigation.

Pulp tissue dissolution capacity of QMix 2in1 irrigation solution.

OBJECTIVE: The aim of this study was to evaluate the tissue dissolution efficacy of four root canal irrigation solutions (sodium hypochlorite [NaOCl], chlorhexidine gluconate [CHX], Octenidine [OCT], and QMix 2in1) on bovine pulp tissue. MATERIALS AND METHODS: Fifty bovine pulp tissue samples, each weighing 6.55 mg, were prepared and randomly divided into four experimental groups and one control group (n = 10) according to the dissolution irrigants used: (1) 5.25% NaOCl group; (2) 2% CHX group; (3) OCT group; (4) QMix 2in1 group; and (5) control group (saline solution). These samples were then placed into special bovine dentin reservoir models and immersed for 1 h with each test solution (0.1 mL of each) at room temperature. The pulp samples were then blotted dry and weighed again. The percentage of weight loss was calculated. Statistically analyzed with one-way analysis of variance and post-hoc Tukey tests (P = 0.05). RESULTS: Saline solution did not dissolve the bovine pulp tissue. All groups, except OCT, dissolved pulp samples more effectively than the control group (P < 0.05). The highest tissue dissolution was observed in 5.25% NaOCl group (P < 0.05). No statistically significant difference was found between the tissue-dissolving effect between QMix 2in1 and those of 2% CHX. CONCLUSIONS: Within the limitations of this in vitro study, NaOCl exhibited the best tissue-dissolving effect out of all solutions tested. CHX and QMix 2in1 were able to dissolve pulp tissue but less than NaOCl. OCT and saline solutions could not exhibit significantly tissue-dissolving effectiveness. This study shown that QMix 2in1 has little capacity to dissolve pulp tissue therefore used alone is not sufficient for this purpose.

Three different adhesive systems; three different bond strength test methods.

OBJECTIVE: The aim of this study was to evaluate the efficacy of the microtensile, microshear and shear bond strength test methods to assess the bond strength of two self-etch adhesives and one etch&rinse adhesive on dentin. MATERIALS AND METHODS: Seventy-five extracted human molars were ground to expose their flat dentin surfaces and randomly assigned to one of three groups according to the type of test method (15 for microtensile, 15 for microshear, 45 for shear). Each of these groups was then assigned to three sub-groups according to the bonding systems (Clearfil SE Bond, Kuraray; G Bond, GC; Prime&Bond NT, Dentsply) used. Then, 15 specimens were prepared for each sub-group according to the test method employed (n = 15). After being stored in distilled water at 37°C for 24 h, the specimens were placed in a universal testing machine for three test methods and stressed at a crosshead speed of 0.5 mm/min. Mean bond strengths were analyzed using Kruskall-Wallis and Mann-Whitney U-tests at a significance level of p < 0.05. RESULTS: The microtensile test had the highest bond strength (p = 0.046). Clearfil SE Bond and Prime&Bond NT produced significantly higher values than the G Bond in the microtensile bond test (p < 0.05), whereas no significant differences were found among the adhesives in the microshear bond test (p > 0.05). For the shear test, Clearfil SE Bond showed higher bond strength than Prime&Bond NT and G Bond (p < 0.05). CONCLUSION: Bond strength to dentin depends on the material and the test method used.

Fracture resistance of retreated roots using different retreatment systems.

OBJECTIVES: This study was designed to evaluate the fracture resistance of retreated roots using different rotary retreatment systems. METHODS: Forty eight freshly extracted human canine teeth with single straight root canals were instrumented sequentially increasing from size 30 to a size 55 using K-files whit a stepback technique. The teeth were randomly divided into three experimental and one control groups of 12 specimens each. The root canals were filled using cold lateral compaction of gutta-percha and AH Plus (Dentsply Detrey, Konstanz, Germany) sealer in experimental groups. Removal of gutta-percha was performed with the following devices and techniques: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), R-Endo (Micro-Mega, Besançon, France), and Mtwo (Sweden & Martina, Padova, Italy) rotary retreatment systems. Control group specimens were only instrumented, not filled or retreated. The specimens were then mounted in copper rings, were filled with a self-curing polymethylmethacrylate resin, and the force required to cause vertical root fracture was measured using a universal testing device. The force of fracture of the roots was recorded and the results in the various groups were compared. Statistical analysis was accomplished by one-way ANOVA and a post hoc Tukey tests. RESULTS: There were statistically significant differences between the control and experimental groups (P<.05). However, there were no significant differences among the experimental groups. CONCLUSIONS: Based on the results, all rotary retreatment techniques used in this in vitro study produced similar root weakness.

Shear Bond Strength of Orthodontic Brackets Cured with Different Light Sources under Thermocycling.

OBJECTIVES: The aim of this study was to compare the shear bond strength (SBS) of two different light sources under different thermal cycle frequencies. METHODS: Ninety human premolar teeth were divided into six groups, in which three groups consisted of halogen groups - Group I was cured with halogen without thermocycle, Group II cured with halogen with 500 thermocycles, and Group III cured with halogen with 10,000 thermocycles. The other three groups consisted of Plasma arc (PAC) group - Group IV was cured with PAC without thermocycle, Group V cured with PAC thermocycled 500 cycles, and Group VI cured with PAC thermocycled 10,000 cycles. Two way ANOVA was used to compare the SBS between the groups, and chi square-test was used to compare the bond failure of ARI scores among the groups. RESULTS: A significant difference was found for curing lights (P<.001) and thermocycling (P<.01). However, there was no interaction between light curing and thermocycling (P=.177). The halogen groups demonstrated higher mean SBS than the PAC groups. Both groups showed a significant reduction between no cycles and 10,000 cycles (P<.05). CONCLUSIONS: Both light sources showed favorable SBS performance without the thermocycle procedure. Thermocycling significantly decreased the SBS values of both groups.

Shear bond strength comparison of a conventional and a self-etching fluoride-releasing adhesive following thermocycling.

AIM: To compare the effect of thermocycling on the shear bond strength of brackets bonded using different primers. METHODS: One hundred twenty extracted defect-free premolars were randomly divided into three groups. In all three, Transbond XT was the bonding adhesive of choice. In the control group (I), the standard Transbond primer was used, in group II a fluoride-releasing primer (Reliance fluoride containing light cure bond), and in group III an antimicrobial fluoride-releasing self-etching primer (Clearfil Protect Bond). These three groups were divided into two subgroups of 20 teeth each. In the first subgroups, the teeth were stored in only distilled water for 24 hours, whereas in the second subgroups, they were thermocycled 500 times between 5 degrees C and 55 degrees C. The shear bond strength was determined with a universal testing machine. After bracket failure, the Adhesive Remnant Index (ARI) score was verified. The data were analyzed using two-way analysis of variance, Bonferroni, and chi-square tests. RESULTS: The group with the antimicrobial fluoride-releasing self-etching primer had a significantly lower shear bond strength than all other groups (P<.05). Thermocycling reduced the shear bond strength in all groups considerably. CONCLUSION: The antimicrobial fluoride-releasing self-etching primer performed comparably worse regardless of thermocycling. Brackets attached with self-etching primers demonstrated a shear bond strength after thermocycling approaching the border of acceptable adhesion. Thermocycling changed the ARI scores of the self-etching primer groups from the bracket-adhesive to the enamel-adhesive interface.

Cytotoxicity analysis of strontium ranelate on cultured human periodontal ligament fibroblasts: a preliminary report.

BACKGROUND/PURPOSE: The aim of this study was to analyze the cytotoxicity of strontium ranelate (SR) on human periodontal ligament fibroblasts (PDL cells) in vitro. METHODS: PDL cells were obtained from healthy human third molars and cultured in Dulbeccos Modified Eagles Medium. The experimental groups were: G1, cultures treated with fresh medium (control); and G2, G3, G4 and G5: treated with SR at 20, 10, 5 and 2.5 mg/mL, respectively. The experimental times were 1, 6, 12 and 24 hours (short-term) for viability, and 2, 4, 6 and 8 days (long-term) for cell survival. The cells were counted using a hemocytometer. Data were then analyzed by one-way ANOVA and Tukey's tests (p < 0.05). RESULTS: Cultures treated with the highest SR concentrations (G2 and G3) had significantly lower cell viability and cell numbers (p < 0.05) than those in G1, G4 and G5. SR at 2.5 mg/mL was non-cytotoxic to PDL cells. CONCLUSION: SR was non-toxic at appropriate concentrations. Preclinical tests are needed to further assess its safety and effectiveness for tooth resorption prior to clinical use.

Comparison of the sealing of different dentin bonding adhesives in root-end cavities: a bacterial leakage study.

OBJECTIVE: To compare the root-end sealing of the different dentin-bonding adhesives (DBAs) in root-end cavities using a bacterial leakage system. STUDY DESIGN: One hundred extracted single-rooted teeth were instrumented, and root-ends were resected and ultrasonically prepared. All teeth were then randomly assigned to 6 experimental groups (n = 15) and 2 control groups (positive and negative control; n = 5) for root-end filling with iBond (Heraeus Kulzer, Hanau, Germany), G-bond (GC Co., Tokyo, Japan), Xeno III Bond (Dentsply/Caulk, Milford, DE), AdheSe Bond (Ivoclar Vivadent, Schaa, Liechenstein), Clearfil Protect Bond (Kuraray, Osaka, Japan), or Clearfil Tri-S Bond (Kuraray). All preparations were further restored with a hybrid resin composite (Renew; Bisco, Schaumburg, IL). Nail varnish was applied to all external root surfaces to the level of the resected root-ends to prevent lateral microleakage. Samples were sterilized in an ethylene oxide sterilizer for 12 h. The apical 3-4 mm of the roots were immersed in brain-heart infusion culture medium with phenol red indicator within culture chambers. The coronal access of each specimen was inoculated every 48 h with a suspension of Enterococcus faecalis. Bacterial leakage was monitored every 24 h for 4 weeks. The data obtained were analyzed using a chi-squared test, with alpha = .05 as the level for statistical significance. RESULTS: All positive controls leaked within 24 h; none of the negative controls leaked. Under the conditions of the study, despite some variations, there were no statistically significant differences in rate of bacterial leakage among the experimental test materials at 1-4 weeks (P > .05). CONCLUSIONS: The type of DBA had no influence in the bacterial leakage of the root-end fillings.

Apical extrusion of intracanal debris using two engine driven and step-back instrumentation techniques: an in-vitro study.

OBJECTIVES: The purpose of this study was to compare in-vitro the amount of debris extruded apically from extracted teeth, using K3, Protaper rotary instruments and manual step-back technique. METHODS: Forty five human single-rooted mandibular premolar teeth were randomly divided into 3 groups. The teeth in 3 groups were instrumented until reaching the working length with K3, Protaper rotary instruments and K-type stainless steel instruments with manual step-back technique, respectively. Debris extruded from the apical foramen was collected into centrifuge tubes and the amount was determined. The data obtained were analyzed using Kruskal-Wallis one-way analysis of variance and Mann-Whitney U tests, with P=.05 as the level for statistical significance. RESULTS: Statistically significant difference was observed between K3, Protaper and step-back groups in terms of debris extrusion (P<.05). Step-back group had the highest mean debris weight, which was significantly different from the K3 and Protaper groups (P<.05). The lowest mean debris weight was related to K3 group, which was significantly different from the Protaper group (P<.05). CONCLUSIONS: Based on the results, all instrumentation techniques produced debris extrusion. The engine-driven Ni-Ti systems extruded significantly less apical debris than step-back technique. However, Protaper rotary instruments extruded significantly more debris than K3 rotary instruments.

Bond strength of adhesives to dentin involving total and self-etch adhesives.

OBJECTIVE: Currently, the trend in dentin adhesion seems to be shifting from moist bonding systems to self-etching systems and from several application steps to single steps. However, recent studies have indicated that the performance of single-step adhesives was lower than the 2-step self-etch or total etch systems. In the present study, microtensile bond strength of a total etch, 2-step self-etch and single-step self-etch adhesives was comparatively evaluated. METHOD AND MATERIALS: The superficial occlusal dentin of 12 noncarious extracted human molars was exposed, finished with wet 600-grit silicon carbide paper, and a block of resin composite bonded with adhesives according to the manufacturers' instructions. The teeth were kept in tap water for 24 hours at 37 degrees C and sectioned to produce beams, with adhesive areas of +/- 0.9 mm2 (4 beams per tooth were obtained). The specimens were stressed at a crosshead speed of 1 mm per minute until the bonds ruptured. RESULTS: The mean bond strengths were calculated as MPa and compared by performing analysis of variance and Tukey tests to identify significant differences between the materials (P = 0.05). The mean bond strength of Clearfil SE Bond was significantly higher than that of OptiBond Solo Plus and iBond (P <.05). OptiBond Solo Plus gave significantly higher bond strengths than iBond (P <.05). CONCLUSIONS: The self-etching adhesive system Clearfil SE Bond (2 step) had higher bond strength than the 1-bottle self-etching adhesive iBond (single application) and the 2-step single-bottle system OptiBond Solo Plus (total etch). However, the 1-bottle adhesive system OptiBond Solo Plus (total etch system) had higher bond strength than the 1-bottle self-etching adhesive system iBond.

Fracture resistance of endodontically treated premolars restored with ormocer and packable composite.

In this study, mesiodistocclusal (MOD) cavity preparations of endodontically treated maxillary premolars that were enlarged to size #50 were restored using three restorative materials (one ormocer, one packable composite, and one high-copper amalgam) and two application techniques (with or without coronal radicular technique). Copper rings were filled with self-curing polymethylmethacrylate resin and the teeth were placed into resin up to the level of the CEJ. The teeth were grouped according to the restorative material and technique, mounted in a Universal Testing Machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. The group restored with packable composite without radicular extension showed the highest resistance to fracture (p < 0.05). Both groups restored with amalgam were significantly weaker than all the other groups (p < 0.05).