Diamond Bur Research Articles

Grinding and polishing of the inner surface of monolithic simplified restorations made of zirconia polycrystals and lithium disilicate glass-ceramic: Effects on the load-bearing capacity under fatigue of the bonded restorations

This study evaluated the effect of grinding and polishing the inner surface of monolithic discs made of zirconia polycrystals (ZR) and lithium disilicate glass-ceramic (LD) on the load-bearing capacity under fatigue of the restorations bonded onto a dentin analogue material (epoxy resin). ZR and LD ceramic discs (10 mm in diameter, 1 mm in thickness) were produced and randomly allocated into 10 groups considering the internal adjustment approach: Ctrl – No adjustment; F – Grinding with fine diamond bur (46 μm); F + Pol – Grinding with fine diamond bur followed by polishing with 2 tips (finisher and polisher); FF – Grinding with extrafine diamond bur (30 μm); FF + Pol – Grinding with extrafine diamond bur followed by polishing. In addition, discs (10 mm in diameter, 2.5 mm in thickness) of fiber reinforced epoxy resin were produced. Afterwards, the intaglio surface of the ZR discs were air-abraded with 45 μm alumina particles for 10 s, the LD and resin epoxy discs were etched with hydrofluoric acid (5%/20 s and 10%/60 s, respectively), and the treated discs were primed as recommended. Each ceramic disc was luted onto the epoxy resin disc with resin cement. Then, the samples were tested under a step-stress fatigue test (20 Hz, 10,000 cycles/step, step-size of 100 N starting at 200 N, and proceeding until failure detection). Fractographic, topographic and surface roughness analysis were also performed. The adjustments (grinding with or without polishing) (ZR: 733–880 N; LD: 1040–1106 N) triggered a detrimental effect on the fatigue behavior in both ceramics compared with the absence of treatment (control group; ZR: 973 N; LD: 1406 N). The polishing step had no effect on fatigue findings. Thus, grinding the inner surface of the tested ceramics should be avoided wherever possible to prevent introducing damage and its detrimental effects on the fatigue behavior.

Effect of finishing/polishing techniques and aging on topography, C. albicans adherence, and flexural strength of ultra-translucent zirconia: an in situ study.

To investigate the influence of different finishing/polishing techniques and in situ aging on the flexural strength (σ), surface roughness, and Candida albicans adherence of 5mol% yttria-stabilized zirconia (ultratranslucent zirconia). A total of 120 zirconia bars (Prettau Anterior, Zirkonzahn) with dimensions of 8 × 2 × 0.5mm were divided into 8 groups (n = 15) according to two factors: "in situ aging" (non-aged and aged (A)) and "finishing/polishing" (control (C), diamond rubber polishing (R), coarse grit diamond bur abrasion (B), and coarse grit diamond bur abrasion + diamond rubber polishing (BR)). Half of the samples from each group were subjected to a 60-day in situ aging by fixing the bars into cavities prepared in the posterior region of the base of complete or partial dentures of 15 patients. The samples were then subjected to the mini flexural (σ) test (1mm/min). A total of 40 zirconia blocks (5 × 5 × 2mm) were prepared and subjected to roughness (Ra) analyses and fungal adherence and complementary analyses (X-ray diffraction (XRD) and scanning electron microscopy (SEM)). The data of mean σ (MPa) and roughness Ra (μm) were statistically analyzed by two-way and one-way ANOVA, respectively, and Tukey's test. The Weibull analysis was performed for σ data. The fungal adhesion (Log CFU/mL) data were analyzed by Kruskal-Wallis tests. For flexural resistance, the "finishing/polishing" factor was statistically significant (P = 0.0001); however, the "in situ aging" factor (P = 0.4458) was not significant. The non-aged (507.3 ± 115.7MPa) and aged (487.6 ± 118.4MPa) rubber polishing groups exhibited higher mean σ than the other techniques. The non-aged (260.2 ± 43.3MPa) and aged (270.1 ± 48.8MPa) bur abrasion groups presented lower σ. The coarse-grit diamond bur abrasion group (1.82 ± 0.61µm) presented the highest roughness value (P = 0.001). Cell adhesion was not different among groups (P = 0.053). Group B presented the most irregular surface and the highest roughness Ra of 0.61 m. The finishing of ultratranslucent zirconia might be preferably done with a diamond rubber polisher. Moreover, the protocols used did not interfere with Candida albicans adhesion. Coarse-grit diamond burs might be avoided for finishing ultratranslucent monolithic zirconia, which might be preferably performed with a diamond rubber polisher.

Effect of different surface treatments on surface roughness, phase transformation, and biaxial flexural strength of dental zirconia.

Background. Interfacial failures at the cement‒restoration interface highlights the importance of effective surface treatment with no adverse effect on the zirconia’s mechanical properties. This study aimed to determine the effect of different surface treatments on dental graded zirconia’s surface roughness and certain mechanical properties. Methods. Forty sintered zirconia specimens were randomly divided into four groups (n=10): control (no surface treatment), sandblasting (SA), grinding with diamond bur (GB), and Er,Cr:YSGG laser (LS). Following surface treatment, the surface roughness and surface topography of the specimens were examined. X-ray diffraction (XRD) was conducted. In addition, the biaxial flexural strengths of specimens were evaluated. The data were analyzed using one-way analysis of variance (ANOVA) and post hoc Tukey tests; the Pearson correlation coefficient was calculated between either volumetric percentage of monoclinic phase or roughness and flexural strength of specimens (α=0.05). Results. The GB group exhibited significantly greater surface roughness compared to the other groups (P < 0.005). The LS and control groups exhibited a significantly lower volumetric percentage of the monoclinic phase (P < 0.001) than the GB and SA treatments. The SA group exhibited significantly higher flexural strength than the control (P = 0.02) and GB groups (P < 0.01). Furthermore, the Weibull analysis for the LS showed higher reliability for the flexural strength than other treatments. Conclusion. Er,Cr:YSGG laser treatment, with the lowest extent of phase transformation and reliable flexural strength, can be a promising choice for surface treatment of zirconia.

Influence of surface treatment of resin composite substrate on the load-bearing capacity under fatigue of lithium disilicate monolithic simplified restorations

This study evaluated the influence of surface treatments of resin composite substrate on the fatigue behavior of adhesively cemented lithium disilicate glass-ceramic simplified restorations. CAD/CAM lithium disilicate ceramic blocks were shaped into discs (N = 60, Ø = 10 mm; thickness = 1.0 mm). Resin composite discs (N = 60, Ø = 10 mm, thickness = 2 mm) were allocated into four groups considering the “surface treatment” factor: Ctrl – no surface treatment; Bur – grinding with coarse diamond bur (#3101G, KG Sorensen); PA – etching with 37% phosphoric acid (15 s); AA – air abrasion with alumina particles (45 μm, 10 mm distance, 2.8 bars, 10 s). The surface topography, the roughness, the fractal dimension (estimated by the box-counting method) and the contact angle analyses were performed after the surface treatments. The lithium disilicate discs were etched (5% hydrofluoric acid, 20 s), silanized and adhesively cemented (Multilink N, Ivoclar Vivadent) on the resin composite discs. The samples (bonded restoration set) were subjected to a step-stress fatigue test at 20 Hz, 10,000 cycles/step with a step-size of 100 N applied on the ceramic surface, having ceramic up and resin composite down. Fractographic analysis was performed. The fatigue data (Fatigue Failure Load – FFL; and Cycles for Failure – CFF) were analyzed by Kaplan Meier with Mantel-Cox log-rank post-hoc tests (α = 0.05). No statistical difference for fatigue performance could be found among the groups (FFL means: 820–867 N; CFF means: 53,195–61,090 cycles). The bur group showed higher surface roughness and contact angle values. The PA group has the highest average fractal dimension. Therefore, the resin composite surface treatment induces topographical changes, however, it has no effect on the fatigue behavior of lithium disilicate restorations.

Cytotoxicity and estrogenicity in simulated dental wastewater after grinding of resin-based materials

ObjectiveThis study evaluated the cytotoxic and estrogenic effects of dust and eluates released into simulated wastewater after grinding of dental resin-based materials. MethodsFour materials were used: ceram.x® universal, Filtek™ Supreme XTE, Lava™ Ultimate and Core-X™ flow. From each composite material, samples (5 × 2 mm, n = 50) were prepared according to the manufacturers’ instructions. Lava™ Ultimate was used as blocks. All samples were ground to dust with a diamond bur (106 μm) and suspended in distilled water at 60 mg/mL. After storage for 72 h, the suspensions were separated into a soluble (eluate) and a particulate (dust) fraction. Eluates and dusts were evaluated for inhibition of Vibrio fischeri bioluminescence and cytotoxicity on human A549 lung cells (WST-1-Assay). The estrogenic activity was assessed by YES-Assay using Saccharomyces cerevisiae. Additionally, dental monomers (BisGMA, BisEMA, UDMA, TEGDMA, HEMA) and Bisphenol A were investigated. ResultsAll eluates showed inhibition of V. fischeri bioluminescence at concentrations above 1.1 mg/mL (p < 0.05). The activity of the eluates of ceram.x® universal and Filtek™ Supreme XTE was significantly higher than Lava™ Ultimate and Core-X™ flow (p < 0.05). In the WST-1-Assay, all materials induced cytotoxic effects at concentrations of 0.1 mg/mL (p < 0.05), while no significant differences were detected among them. The tested materials revealed no estrogenic activity. All dental monomers and Bisphenol A showed concentration dependent cytotoxic effects (p < 0.05), whereas only Bisphenol A induced an estrogenic effect (p < 0.01). SignificanceDust and eluates of resin-based dental materials released into wastewater exert bactericidal and cytotoxic effects in vitro. However, they reveal no estrogenic effect.

EFFECT OF VARIOUS STERILIZATION AND DISINFECTION PROTOCOLS OF TOOTH PREPARATION BURS ON THEIR CUTTING EFFICIENCY AND THEIR RELATION TO THE SURFACE ROUGHNESS OF TOOTH PREPARATION – AN INVITRO STUDY

AIM: This study aims to evaluate the effect of sterilization and disinfection of rotary diamond burs on their cutting efciency and their relation to their surface roughness. A total of 12 (n=12) burs and acrylic typodont teeth of (n=36) were taken MATERIALS AND METHODS: which consists of Diamond TF-13 (MANI) (n=6) and Tungsten carbide bur 169L bur (Prima Dental, Prima Classic) (n=6). These burs were divided into 6 groups. Each group consists of Sub Groups A &amp; B. Sub Group A in each Group Contains Diamond TF-13 (n=1) and Sub Group B in each group contains Tungsten carbide bur 169L bur (n=1). Each single Group is subjected to different methods of sterilization and disinfection with Autoclave, Hot air oven, Ultrasonic, Glass bead, Chemical Disinfection (KORSOLEX) after the tooth preparation. Samples of crown preparation were prepared by placing the mounted tooth on a Modied Milling Machine. After each use, these diamonds and burs were sterilized for 3 cycles of tooth preparation simultaneously and the tooth were evaluated for the surface roughness with a surface prolometer and the resultant values were noted and statistically analyzed. The burs were evaluated for the surface quality under Stereomicroscope and scores were given from 0 to 5 according to the grits and wear present on the surface of the burs. Diamond rotary burs CLINICAL SIGNIFICANCE: should be sterilized and disinfected as it has become a mandatory protocol for the dental professionals to prevent cross-contamination and cross infection between the dentist and dental personnel. However, different sterilization and disinfection methods can have undesirable effects on the ability of the burs to effectively reduce the tooth structure. Irrespective of the type of bur and sterilization process used, the cutting efciency decreases after multiple usage of the burs.

Influência de diferentes métodos para a realização de preparos cavitários - alta rotação, laser de Er:YAG e abrasão a ar - sobre a resistência de união de um sistema adesivo à dentina

The aim of this study was evaluated, in vitro, the tensile bond strength to dentin of the Single Bond (3M) adhesive system applied over dentin surfaces treated with hith-speed handpiece, Er.YAG laser or air abrasion. Thity four enclosed molars extracted due to therapeutic indication had been used. The teeth was sectioned on the mesial-distal sense. The dental portions was included in a selfcured acrilic resin and so fourty five samples was randomly divided in three groups. The first group was treated with a diamond bur plus high-speed handpiece (Kavo) for five seconds under water cooling. On the laser group was used the Er:YAG KavoKey laser (Kavo) with enerv of 450 mJ/pulse and 2 Hz under water cooling. In the air abrasion group was used a Mach 5 (Kreativ) device with 27 mm alumina oxide particles powder. After the treatments was applicd the Single Bond (3M) and Z 100 resin composite. The tensile test was realized in a universal testing machine EMIC DL-2000 at cross-head speed of mm / minute. The average results was: high-speed handpiece (17,52 MPa), Er:YAG laser ( 16,65 MPa) and air abrasion ( 15,83). The results was submitted to statistical treatment by ANOVA and Tukey's test (p ) that showed the diffemcc between the tested groups was not significant.

Methods to Clean Residual Resin Cement from Lithium-Disilicate Glass-Ceramic.

To compare the effect of different methods of cleaning residual composite cement from the surface of lithium-disilicate glass-ceramic on its bond strength. Blocks of lithium-silicate glass-ceramic (e.max CAD) were coated with composite cement. Blocks in a positive control (CO+) group received no cement; negative controls (CO-) received composite cement. After water storage (24 h), specimens were cleaned as follows (n = 20/group): BUR: grinding with a fine-grit diamond bur (20 s); ALUM: air abrasion with 50-µm alumina (10 s); GLASS: air abrasion with 50-µm glass beads (10 s); FURN: firing in ceramic furnace and cleaning with ethanol; SULF: immersion in sulfonic acid solution (1 h); HYFL: no additional treatment. All specimens were etched with hydrofluoric acid, aside from the CO- group, and treated with silane. A 1.5-mm diameter cement-filled tube was affixed to the specimens and light polymerized. Specimens were stored in 37°C water for 24 h (n = 10) or 90 days (n = 10). Shear bond strength was tested. Two-way ANOVA and post-hoc Tukey tests were performed. Specimens from each group were examined with SEM. Bond strength significantly differed according to surface cleaning method (p < 0.01) and storage time (p < 0.01), but their interaction was not significant (p = 0.264). Longer storage time decreased the bond strength. BUR, ALUM, GLASS, and FURN did not differ statistically significantly from CO+, but were significantly greater than CO-. SULF and HYFL did not differ statistically significantly from CO- and were significantly lower than CO+. Cleaning composite cement with BUR, ALUM, GLASS, and FURN restored bond strengths to that of the positive control. However, only GLASS and FURN did not roughen the surface of the underlying lithium-silicate glass-ceramic.

Bonding Performance of Self-etching Adhesives to Bur-cut Dentin with Active Application Mode.

This study evaluated whether active application of self-etching adhesives would influence their microtensile bond strength (µTBS) to dentin cut with burs of different grit sizes. Eighty-four human premolars were divided into 12 groups according to 1) two dentin surface preparations with either superfine- or regular-grit diamond burs; 2) three adhesives - Clearfil SE Bond 2 (SE2), Scotchbond Universal (SBU, 3M Oral Care) and G-Premio Bond (GPB, GC); and 3) two application modes of each adhesive (active or passive). Six bonded teeth per group were sectioned into sticks for µTBS testing. Statistical analyses were performed using 3-way ANOVA followed by Duncan's test (p < 0.05). Additional teeth were prepared to observe the interaction between the dentin smear layer obtained from each bur with adhesives under different application modes using transmission electron microscopy (TEM). Active application significantly increased the dentin bond strength of SE2, irrespective of the kind of bur used (p < 0.05). The highest bond strength of SBU was observed when bonded to superfine-grit diamond bur-cut dentin with the active application. There was, however, no influence of the tested factors on GPB group (p > 0.05). TEM observation showed that active application promoted dentin smear layer dissolution in all adhesive groups. Bond strengths of self-etching adhesives to dentin are influenced by bur-cut smear layers and mainly by application mode of adhesive materials. Active application improves µTBS of self-etching adhesives by enhancing smear layer modification and resin penetration into bur-cut dentin.

Effect of Surface Moisture on Bur-cut Dentin on Bonding of HEMA-free and HEMA-containing Universal Adhesives with or without Methacrylamide Monomer.

The effect of surface moisture on bur-cut dentin on the microtensile bond strength (μTBS) of universal adhesives with various contents of 2-hydroxyethyl methacrylate (HEMA) and methacrylamide monomers was evaluated. Flat mid-coronal dentin surfaces of human molars were exposed, and a standardized smear layer was prepared using a fine-grit diamond bur. The surfaces were either left wet or air dried for 10 s before bonding with Clearfil Universal Bond Quick (UBQ), experimental UBQ without an amide monomer (UBQexp), Scotchbond Universal (SBU), Prime&Bond Universal (PBU), or BeautiBond Universal (BBU). The specimens were built up with resin composite, sectioned into sticks and subjected to the μTBS test after 24 h or 10,000 thermal cycles. The μTBS data were analyzed using three-way ANOVA followed by pairwise comparisons with Bonferroni's correction (α = 0.05). The level of dentin moisture did not significantly affect μTBS of UBQ and BBU (p > 0.05). HEMA-containing UBQ, UBQexp, and SBU exhibited higher μTBS to dry dentin, while HEMA-free PBU and BBU showed higher μTBS to wet dentin. Thermocycling significantly decreased the μTBS of UBQexp (p < 0.01) and BBU (p < 0.001) irrespective of dentin moisture level, while SBU was significantly affected only on dry dentin (p < 0.001). Thermocycling had no significant effect on UBQ and PBU containing methacrylamide monomers (p > 0.05). Dry surfaces enabled obtaining optimal bonding for HEMA-containing adhesives to bur-cut dentin, while wet surfaces enabled optimal bonding for HEMA-free adhesives. Methacrylamide monomers could contribute to the improvement of the initial and long-term bonding performance of universal adhesives to bur-cut dentin.

Effect of Sodium Hypochlorite in Ground Fluorotic Enamel: Shear Bond Strength and Surface Analysis

Evaluate the effect on the shear bond strength (SBS) of 5% NaOCl applied after acid etching on ground anterior teeth with fluorosis and analyze the surface with scanning electron microscopy (SEM), also compare fluorotic and healthy ground enamel by atomic force microscopy (AFM) and Vickers microhardness (VM). For the SBS test 30 anterior teeth with moderate and severe fluorosis according Dean index were selected by an examiner previously calibrated with an expert in fluorosis by using the intraclass correlation coefficient (ICC). With the help of a calibrated high speed diamond bur for veneer preparation and a parallel chamfer high speed diamond bur the vestibular face was prepared with a uniform reduction of .3 mm under water cooling. In one half of the vestibular face of the teeth the conventional adhesive procedure was carried out while in the other half was added an additional step with 5% NaOCl applied for 1 minute and washing after acid etchant. A resin post was adhered in each half and load was applied until fracture. The failure mode was evaluated and a SEM analysis was made. Posteriorly 10 samples of fluorotic and healthy ground enamel were used to measure the nanostructural characteristics by AFM (roughness average and absolute depth profile) and the VM in three operative steps (after ground, after etchant and after deproteinization). The Shapiro-Wilks and Brown-Forsythe methods were used to test the distribution of variables. The Paired Student's t-test was used to compare the differences between mean bond strength (MPa) in the two groups for SBS test. Chi-square analyzes were performed to compare the failure modes between groups. One-way ANOVA analysis and Tukey-Kramer post hoc test were used to compare groups for roughness average, absolute depth profile and Vickers microhardness. A greater SBS (32.17±4.20 MPa) and a surface more homogeneous and less contaminated were observed in the deproteinization subgruoup compared to the conventional subgroup (27.74±4.88 MPa). AFM parameters were greater in fluorosis subgroup than in healthy enamel subgroup. VM was lower in the fluorotic enamel in each operative step in comparation with healthy enamel. The use of 5% NaOCl as a deproteinizing agent after acid etchant in ground fluorotic enamel results in better adhesion, which may imply greater success in adhesive treatments. The ground surface of fluorotic enamel shows higher values of roughness and depth and lower values of VM which proves that there is a more irregular and less hard surface.

Cutting Efficiency of Welded Diamond and Vacuum Diffusion Technology Burs and Conventional Electroplated Burs on the Surface Changes of the Teeth - An In vitro Study.

Context:Welded diamond and vacuum diffusion technology (WDVDT) burs in comparison to electroplated burs claim to approach the solution of dental hard tissues by increased cutting efficiency, decreasing the overheating of oral tissues and thus reducing the microcracks on the prepared tooth surface.Aims:This study aimed to evaluate the cutting efficiency of two different rotary diamond burs used for tooth preparation with their repeated usage on the surface changes of the prepared tooth.Settings and Design:This in vitro comparative study evaluated the cutting efficiency and surface changes of the teeth prepared with conventional electroplated burs and WDVDT burs.Subjects and Methods:Thirty freshly extracted, healthy, noncarious human premolars were divided into Group A and Group B with 15 each, and were further subdivided into three subgroups depending on the different usage intervals as first, fifth, and tenth (A1–A3 and B1–B3). The surface of each prepared specimen was evaluated quantitatively using a surface profilometer, and qualitative analysis was done using a scanning electron microscope.Statistical Analysis Used:Two-way ANOVA and Turkey's multiple post hoc tests were used.Results:The mean surface roughness of Groups A1, A2, and A3 was 1.50 ± 0.40, 2.39 ± 0.39, and 2.65 ± 0.65 Ra, respectively. The mean surface roughness of Groups B1, B2, and B3 was 0.76 ± 0.23, 0.92 ± 0.10, and 1.24 ± 0.07 Ra, respectively. The mean surface roughness of the prepared tooth surface was significantly higher in Group A and its subgroups when compared to that of Group B and its subgroups.Conclusions:The study results showed that surface roughness was considerably lesser and also had less wear and increased cutting efficiency of tooth preparations using burs made with WDVDT compared to the preparations using conventional electroplated burs.

Clinical comparison of instrumentation systems for periodontal debridement: A randomized clinical trial.

To compare clinical efficacy, chairside time and post-treatment hypersensitivity of four instruments used for subgingival periodontal debridement. Seventeen patients with stage II and III periodontitis were enrolled in this randomized clinical trial using a split-mouth design. Quadrants were randomly divided into four treatment groups: Group A: Gracey curettes-Hu-Friedy® ; Group B: piezoelectric ultrasonic (Satelec® ) with No.1S insert; Group C: diamond burs 40µm (Intensiv Perioset® ); and Group D: piezosurgery ultrasonic (Mectron® ) with PP1 insert. Clinical outcomes, chairside time and hypersensitivity were assessed at 1, 2, 4 and 8weeks after treatment. The primary outcome variable was improvement in clinical attachment level. At 8weeks post-treatment, Gracey curettes, piezoelectric ultrasonic (Satelec® ) and piezosurgery ultrasonic (Mectron® ) were statistically more effective than diamond burs in increasing attachment level and reducing probing pocket depth. Comparison of piezoelectric ultrasonic (Satelec® ) and piezosurgery ultrasonic (Mectron® ) with the other instruments showed a statistical difference (p<0.001) in chairside time. Regarding post-treatment hypersensitivity, no statistical differences were observed in any of the groups. Gracey curettes, piezoelectric ultrasonic (Satelec® ) and piezosurgery ultrasonic (Mectron® ) were clinically more effective than diamond burs 40µm. The ultrasonic instruments showed a significant reduction in chairside time.

Better Glass-fiber Post Preservation in Teeth with Ferrule When Subjected to Chewing.

To evaluate the influence of ferrule effect and mechanical fatigue aging on glass-fiber post push-out bond strength (PBS) to root-canal dentin at different root thirds of premolars. Thirty-two sound maxillary premolar teeth were collected, and randomly assigned to two experimental groups (n=16): 'Remaining Dentin Ferrule' (RDF) = coronal crown cut 2.0 mm above the cementoenamel junction (CEJ); 'Without Dentin Ferrule' (WDF) = coronal crown cut at the cemento-enamel junction. Teeth were endodontically treated, post spaces were prepared up to 10.0-mm depth from CEJ, and glass-fiber posts were cemented using a dual-cure self-adhesive composite cement. Standardized cores were built using a light-cure composite, upon which tooth cores were prepared using a 1.5-mm taper ogival-end diamond bur. Crowns were handmade using self-cure acrylic resin and cemented using the aforementioned composite cement. Half of the specimens were subjected to 1,200,000 cycles of mechanical fatigue in a chewing simulator (F = 'Fatigue'), while the other half were stored in distilled water at 37°C for 1 week (C = 'Control'). All specimens were horizontally sectioned into 1.0-mm thick slices prior to PBS test; the failure modes were assessed using stereomicroscopy and scanning electron microscopy (SEM). Data were analyzed for each root third using two-way analysis of variance (ANOVA) followed by Tukey HSD post-hoc test; frequency distribution was compared by Chi-square test (α=0.05) and post-hoc comparisons with Bonferroni. The mean PBS in MPa (SD) were = RDF_F = 10.4 (2.9); WDF_F = 6.9 (1.7); RDF_C = 14.5 (2.7); WDF_C = 14.2 (2.9). Similar PBS were found for the root thirds. For all root thirds, significant differences were found for both the factors Dentin Ferrule and Fatigue, and their interaction (p<0.05). The lowest PBS was found for specimens without dentin ferrule subjected to chewing fatigue (p<0.001). Most failures occurred at the composite cement/dentin interface, followed by mixed and composite cement/glass-fiber post interfacial failures. There was a significant increase in mixed failures for the WDF_F group (p<0.001). Absence of 2.0-mm remaining dentin ferrule in premolars resulted in a higher decrease of the glass-fiber posts' PBS to dentin after mechanical fatigue, irrespective of root third.

In Vivo Pulp Temperature Changes During Class V Cavity Preparation and Resin Composite Restoration in Premolars.

This in vivo study evaluated the influence of the sequence of all restorative steps during Class V preparation and restoration in human premolars on pulp temperature (PT). Intact premolars with orthodontic extraction indication of 13 volunteers received infiltrative anesthesia and isolation with rubber dam. An occlusal preparation was made with a high-speed diamond bur under air-water spray until the pulp was minimally exposed, then a thermocouple probe was inserted within the pulp. A deep, 2.0-mm depth Class V preparation was made using a high-speed diamond bur under air-water spray. Three restorative techniques were performed (n=7): Filtek Z250 placed in two increments (10-second exposure, shade:A2, 3M ESPE, St. Paul, MN, USA), Filtek Z350 XT (40-second exposure, shade:A3D, 3M ESPE) and Tetric N Ceram Bulk Fill (10-second exposure, shade:IVA, Ivoclar Vivadent, Schaan, Liechtenstein), both placed in a single layer. Bonding layer and resin composite were exposed to light from the same Polywave LCU (Bluephase 20i, Ivoclar Vivadent). The peak PT and the difference between peak PT and baseline (ΔT) values were subjected to two-way, repeated measures analysis of variance (ANOVA), followed by the Bonferroni post-hoc test (α=0.05). Cavity preparation and etch & rinse procedures decreased the PT values (p<0.001). The 40-second exposure of Filtek Z350 caused the highest peak PT values (38.7±0.8°C) and the highest ΔT values (3.4±0.8°C), while Tetric N Ceram Bulk Fill showed the lowest values (-1.6±1.3°C; p=0.009). None of the evaluated procedures resulted in a PT rise near to values that could offer any risk of thermal damage to the pulp.

Effect of different crown removing procedures on the implant stability quotient and removal torque values of dental implants

Objective: To investigate the effects of different crown-removal methods on the osseointegration of dental implants in implant-retained single crowns. Methods: Two implants were inserted in each tibia of each New Zealand rabbit’s rear legs. After 28 days, resonance frequency analysis was performed on the implants to detect the degree of osseointegration; 24 hours later, the sacrificed tibias were divided into 3 groups according to different crown-removal methods: crown removal with a diamond bur, the use of a spring-loaded crown remover, and the use of a pneumatic crown remover. Following the crown-removal procedures, the implants’ resonance frequency analysis values and removal torque values were measured. Results: No significant difference in implant stability quotient was measured after crown removal for either group of diamond bur or group of pneumatic crown remover (p=0.677 and p=0.918, respectively). However, there was a statistically significant difference in implant stability quotient after crown removal for group of spring-loaded crown remover (p=0.008). Moreover, no significant difference was detected between the groups’ removal torque values (p&amp;gt;0.05). Conclusion: The crown-removal procedure has significantly unfavorable effect on the implant stability quotient values of the implants, whereas removal torque values of the implants was not affected crown-removal procedures.

Effect of universal adhesive on shear bond strength of metal bracket to enamel and dental amalgam

background: the bond strength of bracket to the tooth substrate is a critical matter. The different surface treatments are introduced to achieve an appropriate bond strength. We aimed to investigate the shear bond strength(SBS) of metal brackets to amalgam surfaces with universal adhesive and compared the results with the enamel group. Material and methods: in this in-vitro study, eighty specimens of amalgam in four groups and sixty specimens of the enamel in three groups were prepared. In amalgam groups, the control group was sandblasted and treated with transbond Xt whilst the other three groups prepared in the following order, group 2 sandblasted and treated with All Bond Universal(ABU), group 3 using diamond bur and ABU, and group 4 using self-etch mode of ABU. In enamel groups, control group was acid-etched and using transbond XT as a primer; in other two groups, the ABU was used as a primer in etched and self-etched mode. The specimens thermocycled and prepared for the SBS test. SEM analysis and ARI index were performed. pvalue≤ was considered significantly. Results: SBS of enamel was significantly higher than amalgam. Within enamel groups, etched with ABU showed the highest SBS. In amalgam group, the highest SBS was related to surface treated with ABU only, and the lowest SBS was related to diamond bur group. Conclusion: The etched surface of enamel showed the appropriate bond strength to bracket, and in the amalgam group, using mechanical preparation can decrease the oxide layer and compromise amalgam SBS. Keywords: Dental amalgam, Enamel, shear strength, Adhesive

Bond Strength of Orthodontic Brackets to Temporary Crowns: In Vitro Effects of Surface Treatment.

Background The number of patients seeking orthodontic treatment has been consistently increasing. During orthodontic treatment, it is recommended to place the provisional restoration and to delay the final restoration until completion of orthodontic treatment. Recurrent bracket debonding necessitates orthodontists to prepare the bonding area with special measures. Objective This study aimed to evaluate the effect of different grit sizes of diamond burs and sandblasting surface treatment on the shear bond strength of orthodontic brackets to provisional crowns. Materials and Methods A total of 75 discs were fabricated from a bisacrylic composite and divided into 5 groups (n = 15) according to surface treatment by black, blue, and green diamond burs and sandblasting in addition to a control group. Metal orthodontic brackets were bonded to discs in a standardized conventional manner. All specimens were subjected to thermocycling with 5000 cycles of alternating 5°C and 55°C waterbaths. The shear bond strength test was performed using a universal testing machine. A scanning electron microscope (SEM) was used to analyze the surface treatment effect and features of debonded surfaces. The amount of composite resin left on the specimen surfaces was analyzed and classified with the adhesive remnant index. One-way ANOVA was performed at α = 0.05. Results The shear bond strength of specimens treated with sandblasting was significantly higher than that of the control group under thermal aging conditions (p=0.022), as well as blue burs (p=0.001), while no significant differences were found between different grit diamond burs and the controls (p > 0.05). Conclusion Under thermocycling conditions, sandblasting of provisional crowns increases the bond strength of orthodontic brackets.

Effect of Endodontic Access Preparation on Fracture Load of Translucent versus Conventional Zirconia Crowns with Varying Occlusal Thicknesses.

To evaluate the effect of endodontic access hole preparation on fracture resistance of translucent zirconia (5Y) and conventional zirconia crowns (3Y) with varying occlusal thicknesses. Polymethylmethacrylate (PMMA) dies, representing a prepared tooth, were milled. Zirconia crowns with 1 mm thick axial walls and varying occlusal thicknesses were milled from 3Y (Cercon HT) or 5Y (Cercon XT) zirconia discs and sintered. 160 crowns were divided into 16 groups (n = 10 per group) based on the zirconia type (3Y, 5Y), occlusal thickness (0.5, 1.0, 1.5, 2.0 mm), and access hole preparation (with access hole, control). Crowns were cemented on the PMMA dies with resin-modified glass ionomer cement (Rely X Luting Plus) under constant weight (500 g) and thermocycled for 10,000 cycles. In half of the samples, following 5000 cycles of thermocycling, a uniform endodontic access hole was created using a diamond bur and restored immediately with resin composite (Filtek Supreme Ultra, 3M ESPE). The fracture resistance of the specimens was tested on an Instron 5566 universal testing machine with a stainless steel ball indenter (9.0 mm dia.) and the maximum load before failure was recorded as fracture load (N). Three-way ANOVA testing examined the effect of zirconia type, occlusal thickness, and access hole preparation on fracture loads of the crowns. Statistical tests were two-sided and significance level was set at 95% (α= 0.05). Fracture load was significantly affected by the type of zirconia, occlusal thickness, and access hole preparation (p < 0.001). Pairwise comparisons revealed that access hole preparation significantly reduced the fracture load of 3Y crowns with 0.5 or 1.0 mm of occlusal thickness and 5Y zirconia crowns with 0.5, 1.0, or 1.5 mm of occlusal thickness (p < 0.05). Increasing occlusal thickness reduced the effect of access hole preparation on fracture load. Type of zirconia, occlusal thickness, and access hole preparation had significant effects on the fracture load of zirconia crowns. The effect of endodontic access was significant on the 3Y and 5Y zirconia crowns with ≤1.0 and ≤1.5 mm occlusal thicknesses, respectively.

Effect of different surface treatments on optical, colorimetric, and surface characteristics of a lithium disilicate glass-ceramic.

To evaluate the effect of surface treatments on optical, colorimetric, and surface characteristics of lithium disilicate glass-ceramic. Specimens (n=5, IPS e.max CAD) were randomly allocated to the following treatments: mirror-polished: SiC papers; as-cut: mimicking CAD-CAM milling; ground: 90-120 μm-grit diamond bur; ground polished: ground, finished (46-30 μm-grit diamond bur), polished (diamond cups, brush and diamond paste); ground glazed: ground, glazed; ground polished glazed: association of methods. CIELAB color coordinates were obtained by a spectrophotometer. CIEDE2000 color differences (ΔE00 ) and the translucency parameter (TP00 ) were calculated. Light transmittance was assessed with a colorimeter. Surface characteristics (topography and roughness) were analyzed. Statistical differences for each condition and outcome were detected using one-way ANOVA with Tukey's post-hoc test (α=0.05). TP00 data show statistical reduction after grinding (p < 0.05), which was only restored with polishing (solely or with glazing). ΔE00 shows that grinding results in perceptible variations in color (above 0.81), which were restored after all post-processing protocols (exception to only glaze application in contact with a black background). Light transmittance data corroborated such performance. Polishing and glazing reduced roughness and improved surface topography. Grinding statistically increased roughness, reduced translucency, light transmittance through the ceramic, and resulted on color differences. On contrary, polishing (followed or not by glazing) reduced roughness and enhanced ceramic translucency and light transmittance. Glaze also reduced roughness, but it still presented reduced translucency. The positioning (facing up or down) of the ceramic treated surface influenced the considered outcomes. Grinding with diamond burs results in a deleterious impact to the optical, colorimetric and surface characteristics of lithium disilicate ceramic. Thus, polishing (followed or not by glazing) is recommended for optical and topographical enhancements when lithium disilicate monolithic restorations require occlusal adjustments.