Diamond Bur Research Articles

The effect of water spray on the release of composite nano-dust.

To evaluate the collection efficiency of water spray on the release of airborne composite particles during grinding of composite materials. Composite sticks (L:35 mm × W:5.4 mm × H:1.6 mm) of seven commercial dental composites were ground with a rough diamond bur (grain size 100 μm, speed 200,000 rpm). All experiments were performed in an enclosed 1-m3 chamber with low particulate background (< 1,000 #/cm3), and airborne particles were evaluated based on their electrical mobility. The number size distribution was determined by scanning mobility particle sizer (SMPS). Particles were collected by an electrostatic precipitator (ESP), and were ultramorphologically and chemically analyzed by a transmission electron microscope equipped with energy-dispersive X-ray spectroscopy (TEM-EDS). SMPS measurements confirmed that both dry and wet grinding generated high concentrations of nanoparticles particles with the highest concentration recorded during the last minute of grinding (1.80 × 106 - 3.29 × 106#/cm3), after which a gradual decline in particle concentration took place. Nevertheless, grinding with water spray resulted in a significant reduction of the number of released particles (5.6 × 105 - 1.37 × 106#/cm3). The smallest particle diameter was recorded during the last minute of grinding followed by a continuous growth for every next measurement. TEM of composite dust revealed a high concentration of particles varying in both size and shape. Regardless of whether the water cooling spray system was used during bur manipulation of composite materials, predominately nanoparticles were released. However, the particle concentrations were significantly decreased with water spray. Since water spray might not be sufficient in nanoparticle collection, special care should be taken to prevent inhalation of composite dust.

A Comparative Evaluation of Shear Bond Strength of Orthodontic Brackets Bonded to Porcelain Fused Metal Crowns Treated with Different Surface Conditioning Techniques―An Invitro Study

With the increase in adult orthodontic treatment comes the need to find a reliable method for bonding orthodontic brackets onto metal or ceramic crowns and fixed partial dentures. In this study, shear bond strength and surface roughness tests by scanning electron microscope study were used to examine the effect of 5 different surface conditioning methods: 37% phosphoric acid gel, 9% Hydrofluoric acid, sandblasting + 9% Hydrofluoric acid, Sandblasting + Silane, Fine diamond bur roughening + silane for bonding metal brackets to ceramic surfaces of feldspathic porcelain. A total of 60 human maxillary premolar teeth extracted for therapeutic purposes from patients seeking orthodontic treatment were collected, and 50 ceramic crowns were fabricated onto the premolar teeth following crown preparation. 10 natural teeth were used as controls, they were acid etched in conventional manner using 37% phosphoric acid. Metal brackets were bonded using a light-curing composite. The samples were stored in distilled water at physiological temperature (37oC) for 1 day, and thermocycled 500 times between 5°C and 55°C. Shear bond tests were performed with a universal testing device, and the results were statistically analysed. Ceramic surfaces conditioned with sand blasting followed by application of Silane produced maximum bond strength of 12.34 ± 0.95 MPa comparable or even better than the control group 11.03 ± 1.63 MPa followed by 9% Hydrofluoric acid 11.48 ± 0.98 MPa & Fine Diamond Bur roughening + Silane 9.28 ± 1.11 MPa. Ceramic surfaces conditioned with 37% Ortho Phosphoric acid produced least SBS of 5.51 ± 0.88 MPa and hence not suitable for bonding Orthodontic brackets in a clinical scenario. Statistical tests showed significant difference between and within the groups in shear bond strength and P value also was highly significant, i.e. ***p<0.001. The SEM photomicrographs of all the six different surface preparations revealed different surface morphologies & were corroborative of SBS values. Even though 9% Hydrofluoric acid and Fine diamond bur roughening produced clinically acceptable SBS values, because of their technique sensitivity and side effects, they have to be used with great care and caution. sand blasting followed by the application of Silane coupling agent was found to be the best porcelain surface conditioning method.

Effects of Finishing and Polishing Methods on the Surface Roughness and Surface Free Energy of Bulk-fill Resin Composites.

The purpose of this study was to determine the influence of finishing and polishing methods on surface properties of bulk-fill resin composites through surface roughness (Ra) and surface free energy (SFE) measurements, and scanning electron microscopy (SEM) observations. Three bulk-fill resin composites, Tetric EvoCeram Bulk Fill (TB), Filtek Bulk Fill (FB), and Filtek Bulk Fill Flowable Restorative (FF), and two conventional resin composites, Clearfil AP-X (AP) and Estelite ∑ Quick (EQ) were used. Seventy cured specimens of each resin composite were prepared and divided into seven groups of 10 specimens. Ra, SFE measurements, and SEM observations were conducted after finishing and polishing procedures. Three groups of specimens were finished with a fine grit diamond bur (FDB), and three with a tungsten carbide bur (CBB). After finishing, one group from each type of finishing was polished with aluminum oxide flexible disks (SSD) and one group from each type of finishing was polished with diamond particles embedded in a silicone point (CMP). A baseline group of samples that were neither finished nor polished after removing the translucent strips from the surface was examined. Although the baseline group showed significantly lower Ra values than the other groups, most resin composites showed lower Ra values with CBB+SSD than with the other finishing and polishing groups. Among the tested resin composites, EQ showed significantly lower Ra values than the other resin composites, regardless of the finishing and polishing methods. On the other hand, AP showed significantly higher Ra values than the other resin composites in all finishing and polishing groups, apart from FB with FDB. For the finished specimens, most resin composites showed higher SFE values with CBB than with FDB. For the polished specimens, all the tested resin composites with CMP showed lower γS values than those with SSD, regardless of the finishing method. The baseline groups of TB and FB showed significantly lower SFE values than the other finished and polished groups. In the SEM observations, all the examined resin composites showed rougher surfaces after finishing with FDB than with CBB. However, when comparing the different polishing methods (CMP and SSD), surface smoothness appeared to be material dependent.

Influence of the Arabic-Coffee on the Overall Color of Glazed or Polished Porcelain Veneers – In vitro Study

Background:Sometimes, porcelain restorations experience some degree of colour change in oral environment, which could be related to the quality of diet and surface roughness of these restorations.Objective:The aim of thisin-vitrostudy was to evaluate the influence of Arabic-Coffee on the overall color of glazed or polished porcelain veneers fabricated from four different porcelain materials and two different thicknesses.Materials and Methods:A total of 160 porcelain disc of tested specimens were fabricated to a standardized thickness of 1.00 mm and 0.6mm using the following materials: Feldspathic porcelain, Zircon, E-max Press, and E-max CAD; (80 discs for each thickness and 20 specimens of each material used). Veneer specimens from each material were randomly divided into two subgroups (n = 10): 10 specimens were kept as glazed, were the other 10 tested specimens were adjusted with diamond burs, and then polished with Ivoclar Vivadent ceramic polishing kits using the recommended protocol for polishing provided by the company. A color of all tested specimens was measured using Vita Easy Shade Spectrophotometer. Then, all specimens were immersed in Arabic coffee (Al Mosafer Coffee, Saudi Arabia) and theromcycled for 1 week, and the colors of all tested specimens were then recorded again.Results:It was shown that there is a significant difference in the average color changes before and after immersing in Arabic-Coffee for all materials and thicknesses used in the current study. In-addition, significant differences in color changes were noticed between glazed and polished specimens. Moreover, colour change caused by the coffee was not significantly related to the thickness of the specimens used.Conclusion:Color stability of porcelain materials could be affected by surface treatment whether glazing or polishing. All aesthetic restorations should be deglazed whenever any adjustments have been done to maintain the color match and stability in an oral environment. Also, Arabic-Coffee is considered as a staining drink to a limited extend where patient should be assured to maintain their oral health to maintain the colour stability of their restorations.

Surface roughness of monolithic zirconia ceramic submitted to different polishing systems

Aim: The objective was to evaluate, quantitative and qualitative, the abrasive effect of three polishing systems on the monolithic zirconia ceramic. Methods: Thirty disk-shaped samples of Yttria Tetragonal Zirconia Polycrystal (Y-TZP) were randomly distributed in three groups (n = 10) according to polishing system: G1- Komet system (KO); G2 - CeraGloss system (CG); G3 - Eve Diacera system (EV). The surface roughness (Ra) was obtained with Rugosimeter in four different moments: a) initial - glaze sample (Ra0); b) after occlusal adjustment with diamond burs (Ra1); c) after polishing with the abrasive systems (Ra2); d) after polishing with felt disc and diamond paste (Ra3). Four additional samples were observed in scanning electron microscopy (SEM). Results: According to the Generalized Estimating Equation followed by the Bonferroni test (α = 0.05), the CG provided the lowest Ra2 (0.63 μm), not differing significantly from the KO (0.78 μm). The highest Ra2 was obtained with the EV (0.97 μm), which did not differ significantly from the KO. There was no statistical difference in Ra between the polishing with the abrasive systems (Ra2) and the final polishing with diamond paste (Ra3). SEM images showed that the polishing systems did not completely remove the grooves caused by the diamond burs during the occlusal adjustment. Conclusion: It was concluded that CG promoted smoother surface of the monolithic zirconia ceramic compared to EV, and intermediate smoothness was obtained with KO.

Grinding, polishing and glazing of the occlusal surface do not affect the load-bearing capacity under fatigue and survival rates of bonded monolithic fully-stabilized zirconia simplified restorations

This study aims to evaluate the effect of distinct surface treatments (grinding, polishing and glaze) of the occlusal surface of fully-stabilized zirconia (FSZ) simplified restorations bonded onto epoxy resin on the fatigue behavior of the restorations. Disc shaped specimens of FSZ (IPS e.max Zircad MT Multi) were produced (Ø = 10 mm and 0.8 mm in thickness) and randomly allocated into 5 groups, considering the factor ‘surface treatment’ of the occlusal surface: Ctrl – as-sintered; Gr – ground with coarse diamond bur; Gr + Pol– grinding + polishing with two-step polishing system; Gr + Gl – grinding + glaze application; Gr + Pol + Gl – grinding + polishing + glaze application. Next, the FSZ intaglio surface was air-abraded with 45 μm aluminum oxide powder for 10 s at 15 mm of distance under 2 bar pressure and the discs were adhesively cemented (Multilink Automix) onto its dentin analogue pair (Ø = 10 mm; thickness = 2.7 mm). Finally, the step-stress fatigue test was executed (load ranging from 200 to 1300 N; step-size of 100N; 10,000 cycles per step, 20 Hz). In addition, surface topography, roughness, phase transformation and fractography analyses were performed. Grinding altered the topographical pattern introducing defects into the material surface and increasing roughness. Polishing and glaze application led to a smoothening effect, reducing surface defects and statistically decreasing roughness. However, the effect on roughness of polishing and glaze was statistically similar. No phase transformation was observed, thus only cubic and tetragonal phases were detected. No surface treatment had a deleterious effect regarding the fatigue failure load, number of cycles for failure and survival rates. All failures (cracks) started on the bonding surface. Thus, polishing and glaze are indicated to reduce surface roughness, despite not leading to differences in terms of fatigue performance.

Variable Smear Layer and Adhesive Application: The Pursuit of Clinical Relevance in Bond Strength Testing.

The removal or modification of smear layers that cover the dentin is critical to allow the penetration of adhesive molecules and to ensure a strong bond between resin and dentin. Aiming to establish a model for clinically-relevant dentin-bond testing, we evaluated the effects of smear layers created by abrasives having similar coarseness (180-grit SiC paper; fine-grit diamond bur) and application modes (single application; double application) on the microtensile bond strengths (µTBS) of two currently available universal adhesives (G-Premio Bond; Scotchbond Universal Adhesive) and a two-step self-etch adhesive (Clearfil Megabond 2). Sixty extracted human third molars were used for the μTBS test. Data were analyzed by three-way ANOVA and Tukey’s test (α = 0.05). Fracture modes were determined using stereomicroscopy. An additional 24 third molars were prepared for observation of the resin–dentin interface by TEM and adhesive-smear layer interaction by SEM. μTBS was significantly affected by the adhesives and their application modes (p < 0.001), implying that the double application of universal adhesives should be recommended to improve their performance. The effect of smear layers was not significant (p > 0.05), indicating that 180-grit SiC papers could be used to prepare dentin as a substitute for fine-grit diamond burs for dentin-bond testing in laboratory settings.

Evaluating and comparing the morphological and histopathological changes induced by erbium:yttrium-aluminum-garnet laser and diamond bur on enamel, dentin and pulp tissue.

Lasers are used for different types of dental treatments. Using the erbium:yttrium-aluminum-garnet (Er:YAG) laser to remove dental hard tissue is simple, advantageous and influences the type of cavity preparation, whether conventional or conservative in nature. The aim of the present study was to evaluate and compare the morphological and histopathological changes in the enamel, dentin and pulp tissue of the teeth treated by Er:YAG laser and conventional burs. A conventional class I cavity was prepared in orthodontic patients by laser and bur. The teeth were extracted and analyzed for morphological changes using a scanning electron microscope, ground sections and histopathological changes under a light microscope. The time with laser was longer than the conventional methods. The lased cavity showed irregular appearance with absence of smear layer which is suitable for the resin restoration. The ground section and the histopathological study showed no differences between the groups. The Er:YAG laser is effective in the removal of dental hard tissue without damaging the pulp when coupled with ideal energy output. It is widely used in different dental fields. It needs time to be accepted by dentist and patients and further studies are required to explore its advantages.

Temperature variations in pulp chamber: an in-vitro comparison between ultrasonic and rotating instruments in tooth preparation. Part 1.

The purpose of this study was to analyze pulpal temperature increase generated by prosthodontic margin repositioning and finishing with ultrasonic and rotating instruments. The temperature changes recorded were also correlated with the residual dentin thickness. A sample of 32 human extracted molars was selected. The teeth were endodontically treated and prepared with prosthetic round chamfer preparation. Then, they were inserted in plaster cubes up to the cement-enamel junction, leaving the apical portion pervious for inserting the thermocouple probe. The conventional technique, which involves the use of a high-speed contra-angle handpiece, was compared with an ultrasonic method (Crown Prep, Mectron, Carasco, Italy). For margin repositioning and finishing, two walls were randomly selected for each tooth: one was included in the test group and cut with the piezoelectric instrument (Multipiezo Touch TipHolder DB2, Mectron, Carasco, Genoa, Italy), the other one was inserted in the control group and cut with the high speed contra-angle handpiece (Kavo, Biberach, Germany). To standardize the operator-dependent parameters, it was used a mechanical arm controlled by a computer. These parameters were the pressure exerted on the dental wall, the cutting length and the time required for margin repositioning and finishing. For both test and control group, test phase consisted in a first stage of margin repositioning using an ultrasound tip or a diamond bur with a greater granulometry (120 µm for the ultrasound tip and 125 µm for the diamond bur), followed by a second finishing step conducted by an ultrasound tip or a diamond bur with smaller granulometry (60 µm for the ultrasound tip and 30 µm for the diamond bur). During these stages the intrapulpal temperature was recorded thanks to a thermocouple. Before and after these steps, the thickness of the remaining dental walls was measured with a caliber. The average pulpal temperature increase was 5.03±0.98 °C for the ultrasonic preparation (test group) and 3.55±0.95 °C for the conventional technique (control group). The difference was statistically significant (P value <0.001). However, neither of the instruments reached the critical level of 5.5 °C reported in the literature. The mean initial dentin thicknesses was 1.82±0.47 mm for the control group and 1.59±0.54 mm for the test group but the analysis of the residual dentin thicknesses revealed a greater reduction of the walls worked up with high speed contra-angle handpiece (mean 0.9±0.5 mm), which was therefore more aggressive than the ultrasonic instrument (mean 1.1±0.5 mm). A very weak negative correlation was present between the thickness of the wall at baseline and the increment of temperature. Within limitations of this study, temperature increasing of ultrasonic instruments shows a statistical difference related to rotary ones. But, as literature shows, the ultrasonic advantages are margin precision, preservation of soft tissues and reduction of operating times. Furthermore, in relation with results of this study, they could be considered safe for pulp vitality because the increase in pulpal temperature is similar to traditional instruments and it does not exceed the critical level of 5.5 °C.

Machinability: Zirconia-reinforced lithium silicate glass ceramic versus lithium disilicate glass ceramic

Diamond grinding used in dental adjustment of high-strength zirconia-reinforced lithium silicate glass ceramic (ZLS) and lithium disilicate glass ceramic (LDGC) is challenging in restorative dentistry. This study aimed to compare the machinability of ZLS and LDGC in diamond grinding in terms of machining forces and energy, debris, surface and edge chipping damage. Grinding experiments in simulation of dental adjustment were conducted using a computer-assisted high-speed dental handpiece and coarse diamond burs. A piezoelectric force dynamometer and a high-speed data acquisition system were used for on-processing monitoring for assessment of grinding forces and energy. Grinding debris and grinding-induced surface and edge chipping damage were examined using scanning electron microscopy. The results show that grinding of ZLS required higher tangential and normal forces and energy than LDGC (p < 0.05). ZLS was ranked the most difficult to machine among dental glass ceramics based on a machinability index associated with the material mechanical properties. The higher machinability indices of ZLS and LDGC pose a challenge for clinicians to conduct high-efficient material removal for dental adjustment and repair. Both ZLS and LDGC debris were micro fractured particles but the former were smaller than the latter due to the finer microstructure of ZLS. Ground ZLS surfaces contained more irregular microchipping and microfracture in comparison with LDGC surfaces with intergranular fracture or grain dislodgement. Grinding-induced edge chipping damage remained a serious issue for both ZLS and LDGC, which depths ranged approximately 20–100 μm and significantly increased with the material removal rate (p < 0.01). As the zirconia-reinforcement in ZLS only slightly reduced edge chipping damage (p > 0.05), continued efforts are required to explore new reinforcement technologies for optimized LDGC.

Effect of different surface treatments on the repair bond strength of resin composites with titanium

The purpose of this study was to evaluate the effect of different surface treatment combinations on the bonding of composite resins to NiCr and titanium alloys after thermal cycling. Square-shaped specimens (10 mm x 10 mm x 2 mm) were made from NiCr and titanium alloys. The specimens were divided into 6 pretreatment groups (n = 11): (1) machined titanium (control, no treatment); (2) CoJet sand application; (3) grinding with a diamond bur; (4) metal primer application; (5) CoJet sand + metal primer application; and (6) grinding with a diamond bur + metal primer application. The surface roughness of the mechanically treated specimens (control, grinding, CoJet sand) was evaluated. The surface morphology of both metals and elemental composition were examined with SEM and EDS. The composite resin was applied to the specimens. Shear bond strength (SBS) was tested after thermal cycling (5000 cycles, 5 °C to 55 °C). Failure modes were determined. The data were analyzed using the Shapiro-Wilk test, two-way ANOVA and post hoc Fisher’s LSD test (p = .05). For titanium specimens, the grinding + metal primer exhibited higher values than the other groups, and all groups showed higher SBS values than the control group. Combined use of CoJet sand, grinding with a diamond bur, and metal primer application would be useful for enhancing the bond strength of composite resin to titanium. The grinding of the NiCr surface with a diamond bur is the only method that could improve the bond strength of a composite resin compared to the other methods.

Low-fusing porcelain glaze application does not damage the fatigue strength of Y-TZP

This study evaluated and compared the effects of two glaze application methods (brush and spray) on the fatigue strength and surface characteristics (topography and roughness) of a translucent yttrium stabilized partially tetragonal zirconia polycrystal ceramic (Y-TZP) prior to and after grinding. Disc-shaped specimens of translucent Y-TZP (Vita YZ-HT; Vita-Zahnfabrik) were processed (ISO 6872–2015) and randomly allocated into 6 groups, according to the surface treatments performed on the tensile surface: Ctrl – as-sintered (no treatment); Gr – grinding with a diamond bur (181 μm-grit; #3101G); Br – glaze obtained from a powder–liquid mix and applied by brush (Vita Akzent; Vita Zahnfabrik); Sp – glaze application via spray (Vita Akzent Plus; Vita Zahnfabrik); Gr + Br and Gr + Sp – association of grinding + respective glaze method. Analyses of surface roughness (Ra and Rz), fatigue strength (staircase method), surface topography and fractography were carried out. The as-sintered condition had the smoothest surface, while grinding led to the rougher and more heterogeneous topography. Both glaze application methods showed a potential for topography evenness (smoothening effect), while the glaze spray method led to thinner layers of material, showing a limitation in reducing the roughness compared to the brush method. No deleterious effect on fatigue strength of the Y-TZP could be observed, as the glaze-spray application on the as-sintered surface showed the highest values. Fractography depicted two distinct fracture origin regions: from defects in the surface/sub-surface region for the Ctrl and Gr groups; and at the zirconia-glaze layer interface for Br, Sp, Gr + Br and Gr + Sp. The clinical relevance of this work is that the tested glaze application methods did not damage the fatigue strength of the tested Y-TZP.

Influence of different laser-assisted retrograde cavity preparation techniques on bond strength of bioceramic-based material to root dentine.

The purposes of the study were to evaluate the bond strength of bioceramic TotalFill root repair material (RRM) in retrograde cavities prepared using Er:YAG and Er,Cr:YSGG laser and steel bur, and to analyze failure modes. The root canals of 30 single-rooted teeth were endodontically treated, their root-ends were resected using a diamond bur, and the teeth were randomly divided into three groups (N= 10) according to the retrograde cavity preparation technique: (1) Er:YAG laser, (2) Er,Cr:YSGG laser, and (3) steel bur. All retrograde cavities were filled with the TotalFill RRM which was prepared according to the manufacturers' instructions. Push-out test was performed using universal testing machine, and failure mode was analyzed using a scanning electron microscope. The data were analyzed using one-way ANOVA, post hoc analysis with Bonferroni correction, and Fisher-Freeman-Halton exact test (p< 0.05). In the Er:YAG-, Er,Cr:YSGG-, and steel bur-prepared cavities, mean bond strengths (MPa) were 12.76, 8.44, and 6.01, respectively. The bond strength of the TotalFill RRM to dentin was significantly higher in the Er:YAG laser compared with the steel bur-prepared cavities (p= 0.004). The bond strength was not significantly different between the Er:YAG and Er,Cr:YSGG cavities (p= 0.074) and between the Er,Cr:YSGG and bur cavities (p= 0.648). In the cavities prepared by the Er,Cr:YSGG laser and bur, the failure mode of the TotalFill RRM was predominantly mixed, then adhesive and cohesive. In the Er:YAG laser-prepared cavities, the most common failure mode was adhesive, followed by mixed type and no cohesive failure. The bond strength of the TotalFill RRM to dentin was highest in the group of retrograde cavities prepared by the Er:YAG laser.

Histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis of tissue response to sealing materials after furcation perforation.

To evaluate in vivo tissue responses after sealing furcation perforations in dog's teeth with either Biodentine™, mineral trioxide aggregate (MTA) or gutta-percha, by means of histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis. After root canal treatment, perforations were created in the central region of the pulp chamber floor using a round diamond bur and filled with one or other of the materials. The animals were euthanized after 120days, and the teeth (n=30) were processed for histopathological analysis of new mineralized tissue formation and collagen fibre reinsertion, immunohistochemical analysis of osteopontin (OPN) and alkaline phosphatase (ALP) and immunofluorescence analysis for bone morphogenetic protein (BMP-2), cementum attachment protein (CAP), bone sialoprotein (BSP), osteocalcin (OCN) and cementum protein1 (CEMP1). Histoenzymology was performed for TRAP activity and osteoclast count. Data were analysed statistically (α=0.05) using chi-square and Kruskal-Wallis tests. Gutta-percha did not induce mineralized tissue formation. MTA and BiodentineTM formed mineralized tissue in 88% and 92% of specimens, respectively, with no significant difference (P>0.05). Gutta-percha was associated with scattered collagen fibres parallel to the perforations. Groups treated with MTA or BiodentineTM had partial fibre reinsertion perpendicular to the newly formed mineralized tissue. All materials induced OPN and ALP expression, weakest for gutta-percha and strongest for MTA (P<0.05). Only MTA induced BMP-2, BSP, OCN, CAP and CEMP1 expression. Osteoclast counts were similar in all groups (P=0.97). Mineral trioxide aggregate and BiodentineTM were biocompatible, with formation of mineralized tissue and partial reinsertion of collagen fibres. In addition, the participation of several molecules by which calcium silicate-based materials induce the formation of mineralized tissue were noted, with expression of ALP and OPN mineralization markers, without interference in the number of osteoclasts. Only MTA stimulated the expression of proteins associated with the formation of a cementum-like mineralized tissue.

Shear Bond Strength of Orthodontic Brackets to Composite Restorations Using Universal Adhesive

Statement of the Problem: The dental adhesives may have the potential to increase the bond strength of orthodontic brackets to composite resin and it would be highly desirable if adequate bracket-composite bond strength could be yielded by using these adhesives without the need for surface roughening. Purpose:The purpose of this study was to measure the shear bond strength (SBS) of metal brackets to composite restorations by use of a universal adhesive compared with a conventional adhesive. Materials and Method: In this in vitro, experimental study, 45 composite discs measuring 6 mm in diameter and 4 mm in thickness were fabricated and assigned to three groups (n=15). In the group 1, discs were etched with 37% phosphoric acid for 15 seconds and Scotchbond Universal was then applied. Discs were roughened by diamond bur in the group 2 and were subjected to the application of Scotchbond Universal. In the group 3, conventional adhesive (Single Bond 2) was applied after roughening the discs by diamond bur. Metal brackets were then bonded to discs and after thermocycling, the SBS was measured by an Instron machine. The mode of failure and adhesive remnant index (ARI) score were determined using stereomicroscope. Data were analyzed by SPSS version 18, one-way ANOVA, and the Kruskal Wallis test. Results: The surface roughening plus universal adhesive group showed the highest SBS (11.90 MPa) but according to one-way ANOVA, the difference in this regard among the three groups was not statistically significant (p= 0.94). Most samples showed ARI score of 4. Conclusion:Universal adhesive can provide sufficient bond strength as high as that provided by conventional adhesives for orthodontic bracket bonding to composite restorations even in absence of surface roughening by bur.

Effect of sodium hypochlorite and chlorhexidine irrigating solutions and their inactivating agents on the push-out bond strength of mineral trioxide aggregate.

The objective of this study was to evaluate the effect of sodium hypochlorite and chlorhexidine solutions and their inactivating agents on the push-out bond strength of mineral trioxide aggregate (MTA). One hundred fifty root slices were prepared and their root canal spaces were enlarged using diamond burs. MTA was prepared and compacted to root canal spaces. The samples were randomly separated to 4 groups that would be immersed into the selected solutions (5.25% sodium hypochlorite (NaOCl), 5.25% NaOCl and sodium thiosulfate, 2% chlorhexidine (CHX), 2% CHX and a mixture of Tween 80 and 0.3% L-alfa-lecithin) and a control group (n =30). Push-out bond strength of each specimen was tested with universal testing machine. The data was analyzed by one-way analysis of variance and Tukey tests. There were no significant differences between the push-out bond strength values of the irrigation groups and the control group. A significant difference was found between the push-out bond strength values of NaOCl-Sodium thiosulfate and CHX-L-alpha-lecithin groups. Contact with NaOCl and its neutralizing agent with MTA after 10 minutes of setting period increased the push-out bond strength of MTA. On the other hand, any contact with CHX alone or with subsequent application using L-alfa-lecithin should be avoided since that might decrease the push-out bond strength of freshly mixed MTA.

Comparison of laser- and bur-prepared class I cavities restored with two different low-shrinkage composite resins: a randomized, controlled 60-month clinical trial.

The aim of this study was to compare the clinical performances of two low-shrinkage composite resins (silorane-based and methacrylate-based) in class I cavities prepared by Er,Cr:YSGG laser or conventional diamond bur over 60months. Eighteen patients with four similar-sized occlusal lesions in molar teeth were included to the study. A total of 72 class I cavities were prepared either by Er,Cr:YSGG laser or conventional diamond bur. Cavities were restored with Filtek Silorane (3M-ESPE) (silorane-based) or Kalore (GC) (methacrylate-based) according to the manufacturers' instructions. All restorative procedures were performed by one operator, and the restorations were examined by two evaluators according to the FDI criteria at baseline and at 6, 12, 24, 36, 48, and 60months. Patients' satisfaction about the preparation methods was also evaluated with a questionnaire. Pearson chi-square test was used for statistical analysis (p = 0.05). The 60-month recall rate was 88.8% and the retention rates for experimental groups were 100%. After 60months, no significant differences were detected among groups, regarding marginal adaptation, marginal staining, surface staining, color match, and translucency. None of the restorations exhibited postoperative sensitivity or recurrence of caries. Different preparation techniques had no effect on the longevity of restorations. The two low-shrinkage composite systems tested were both clinically acceptable after 60months. Low-shrinkage composites showed similar clinical performance in class I cavities prepared with a laser or conventional bur after a 60-month observation period.

The shear bond strength of repaired high-viscosity bulk-fill resin composites with different adhesive systems and resin composite types

This study compared the effect of different adhesive systems and composite resins on the shear bond strength (SBS) of repaired high-viscosity bulk-fill composites(Tetric EvoCeram Bulk Fill) and investigated failure modes. One hundred twenty cylindrical bulk-fill composite blocks (diameter 5 mm) were fabricated and thermocycled for 5000 cycles (5–55 °C). Specimens were roughened by diamond bur and divided into 8 groups (n = 15). Bulk-fill blocks were repaired with the same material or nanohybrid composite resin(Tetric EvoCeram Nanohybrid) (diameter 3 mm) using different adhesive systems:Tetric N-Bond Universal (TSE);37% phosphoric acid etching + Tetric N-Bond Universal (TER); Clearfil SE Bond (CSE); 37% phosphoric acid etching + AdperTMSingle Bond 2(SB). After repair procedures, all specimens were thermocycled again. The shear bond strengths were measured for all specimens using a universal test machine (crosshead speed of 1 mm/min). Cohesive strengths of bulk-fill composites were measured and described as control group. Debonded surfaces were observed with a stereomicroscope under 10x magnification to determine mode of failure. The SBS data of all groups was statistically analyzed by two-way ANOVA and Bonferroni correction test (p < 0.05). The specimens repaired with bulk-fill composites showed significantly higher SBS values (25.86 ± 5.74, 27.05 ± 4.93, 24.49 ± 6.95MPa) than those with nanohybrid composites (20.41 ± 3.70, 22.08 ± 6.37, 18.74 ± 6.40 MPa) for TER,CSE,SB, respectively (p < 0.05). There were no significant differences in SBS according to the type of adhesive systems for both repair materials (p > 0.05). The predominant mode of failure was a mixed type in the restorative material except for the ones repaired with nanohybrid composites using AdperTMSingle Bond 2. High-viscosity bulk-fill composites could be successfully repaired with the same materials. SBS of repaired bulk-fill composites reached cohesive strength for all tested groups.

Bonding Strength of Luting Cement to Zirconia-Based Ceramic Under Different Surface Treatments.

Objectives The aim of this study was to evaluate the bonding strength of self-adhesive luting cement to zirconia under different surface treatments. Materials and Methods Thirty-two zirconia samples were randomly divided into eight experimental groups based on the surface treatment employed (Control: no surface treatment; PMM: wear with diamond bur; JAT: blasting with glass beads; PMA: wear with a medium-roughness milling machine; Primer: primer application on the surface without treatment; PMM +Primer: PMM treatment plus primer application; JAT+Primer: JAT treatment plus primer application; and PMA+Primer: PMA treatment plus primer application). Cement cylinders were built on the ceramic surfaces, and the groups were subdivided according to the storage time employed (i.e., 24 hours or 60 days). After storage, the samples were subjected to microshear testing. Statistical Analysis The Kruskal–Wallis test followed by the Dunn test was employed for comparison between the groups ( p < 0.05). Results The PMM group yielded the optimal results and the mean values increased after both storage times following the primer application. The Control, PMA, and JAT groups gave similar results after 24 hours, while the JAT group gave superior results following primer application over this storage time. After 60 days of storage, all groups gave improved results following chemical treatment with a primer. Conclusion It was concluded that mechanical preparation using the diamond bur followed by primer application significantly improved the bond strength between the ceramic and the luting cement.

Investigation of the effects of different chelating solutions on the microhardness and surface roughness of root canal dentin

Introduction: The purpose of this study is to examine the effect of different chelating solutions on microhardness and surface roughness of root canal dentin.&#x0D; Methodology: The crowns of sixty recently extracted maxillary central incisors were separated by diamond burs from the cemento-enamel junction. Roots are divided longitudinally into two pieces with diamond saw. The obtained samples were embedded in autopolymeric-acrylic and the dentin-surfaces of the teeth were grounded. Micro-hardness and surface-roughness measurements were carried out before the chelating processes. First group, the specimens were treated with gel-formed 17% Ethylenediaminetetraacetic acid [EDTA] (JE), second group, specimens were treated with 17% Liquid-formed EDTA (LE), third group, specimens were treated with 20% Citric acid (CA), and the last group specimens were treated with 7% Maleic acid (MA) for 120 seconds. After application of the chelating agents, micro-hardness and surface-roughness measurements of all samples were performed again. The difference between the initial and final measurements was calculated and statistically analyzed. One Way Analysis of Variance ANOVA was used for statistical-analysis and statistically significant difference was observed between the groups (p &lt;0.05).&#x0D; Results: According to the test results, the microhardness of LE was statistically equal to that of JE and caused the least decrease in micro-hardness, SA decreased micro-hardness more than LE and JE, and MA decreased dentin micro-hardness more than all other solutions. And surface-roughness results are: MA increased surface-roughness more than other groups, SA and JE less roughened the dentin surface than MA, and there was no significant difference between the two solutions, LE caused less increase in dentin surface roughness compared to all solutions.&#x0D; Conclusions: Besides the use of EDTA and SA, the clinical use of MA can be considered, and it should also be noted that EDTA differs in terms of surface roughness between liquid and gel forms.&#x0D; &#x0D; How to cite this article: Topbaş C, Adıgüzel Ö, Çölgeçen Ö. Investigation of the effects of different chelating solutions on the microhardness and surface roughness of root canal dentin. Int Dent Res 2019;9(1):22-9.&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.