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Purpose: The aim of this study was to compare the integrity of zirconia, lithium disilicate, and zirconia-reinforced lithium silicate CAD-CAM crowns after being subjected to cyclic loading and then subjected to static loading until fracture., Material and Methods: Zirconia (Zirkonzahn), lithium disilicate (LDS, Ivoclar Vivadent AG), and zirconia-reinforced lithium silicate glass ceramic (ZLS) (Vita Suprinity, Vita Zahnfabrik) monolithic crowns were milled (n = 6). The crowns were bonded using composite resin cements and subjected to cyclic loading under wet conditions. Three specimens from each group were loaded for 10 000 cycles, and the other three specimens were loaded for 50 000 cycles with 250 N. Specimens were subjected to loading until fracture. Load-to-fracture values were analyzed with 2-way (ANOVA) and Tukey-Kramer post hoc test (α = 0.05). Specimens from each group were examined using an SEM., Results: Mean load-to-fracture values among materials were significantly different from each other (P < 0.05). No significant effect of the number of cycles was found on the load-to-fracture values of crowns (P > 0.05)., Conclusion: Load-to-fracture values of zirconia were higher than those of LDS, which were higher than those of ZLS. The number of fatigue loading cycles did not affect the load-to-fracture of the tested crowns for a given material., Clinical Significance: More research needs to be conducted before considering the routine use of ZLS for molars in patients with high risk of parafunctional habits., (© 2019 Wiley Periodicals, Inc.)

In this study, wear and inhibition of enamel demineralization by resin-based coating materials were investigated. Seven commercially available coating materials, with and without fillers, were used. A mechanical wear test was performed, and the specimens were then examined with a scanning electron microscope. Hardness and elastic modulus measurements for each material were obtained by nanoindentation testing. Thin layers of each material were applied on human enamel surfaces, which were subjected to alternating immersion in demineralizing and remineralizing solutions. The inhibition ability of enamel demineralization adjacent to the coating was estimated with depth-dependent mechanical properties using the nanoindentation test. The non-filled coating material showed significantly lower hardness, lower elastic modulus, and higher weight loss. There were no significant differences in weight loss among the six filled coating materials. After the alternating immersion protocol, the enamel specimens having application of coating materials with ion-releasing ability were harder than those in the other groups in some locations 1-11 μm from the enamel surface and within 300 μm from the edge of the coating materials. In conclusion, clinical use of the resin-based coating materials with ion-releasing ability may prevent demineralization of exposed enamel adjacent to the coating during treatment., (© 2017 Eur J Oral Sci.)

Objective: Measure and compare the mechanical properties, translucency, and fluoride-releasing capabilities of EQUIA Forte HT against Fuji IX GP and ChemFil Rock., Materials and Methods: Ten specimens of each material were fabricated for compressive strength (CS), flexural strength (FS), and surface hardness analysis at 24 h and 7 days. The L*a*b* values were measured against a black-and-white background using a spectrophotometer to analyze the translucency parameter (TP). Fluoride release was recorded after 2 months of immersion in distilled water. The mean data was analyzed by 1- and 2-way ANOVA (α = 0.5)., Results: EQUIA Forte HT showed higher CS, surface hardness, and FS values (p < 0.05) compared with Fuji IX GIC, while no significant difference was found in FS values between EQUIA Forte HT and Chemfil Rock (p > 0.05). The EQUIA Forte HT exhibited significantly higher translucency in comparison to both ChemFil Rock (p < 0.001) and Fuji IX GICs (p < 0.05). An increase (p > 0.05) of fluoride release was observed for EQUIA Forte HT., Conclusion: The EQUIA Forte HT Glass-ionomer cements (GIC) offers enhanced translucency, improved strength, and enhanced fluoride-releasing properties compared to the traditionally used Fuji IX GIC and ChemFil Rock GICs. This material might have a wide range of clinical applications due to its improved strength and optical properties., Clinical Significance: Glass-ionomer dental restorative materials possess unique advantageous characteristics. However, its poor mechanical and optical properties have typically limited its clinical applications. Efforts to improve these properties have resulted in enhanced GICs. EQUIA Forte HT GIC offers enhanced mechanical and optical properties with potential applications in posterior and anterior restorative procedures., (© 2023 Wiley Periodicals LLC.)

Purpose: The purpose of this study was to assess the effect of different high-palladium alloys on the resulting color of opaque porcelain. Three Pd-Cu-Ga alloys, Spartan Plus (S; Williams Dental Co/Division of Ivoclar North America, Amhest, NY), Liberty (B; J.F. Jelenko & Co, Armonk, NY), and Freedom Plus (F; J.F. Jelenko & Co); 4 Pd-Ga alloys, Legacy (L; J.F. Jelenko & Co), IS 85 (I; Williams Dental Co), Protocol (P; Williams Dental Co), and Legacy XT (X; J.F. Jelenko & Co); and a Pd-Ag alloy, Super Star (T; J.F. Jelenko & Co), were examined. The Au-Pd alloy Olympia (O; J.F. Jelenko & Co) served as the control., Materials and Methods: Three cast 16-mm discs, 1-mm thick, were prepared from each of the alloys. After metallurgically polishing and air-abrading, the specimens were oxidized following the manufacturer's recommendations. Shade B1 opaque porcelain (Vita-Omega; Vident, Baldwin Park, CA) was applied at a final thickness of 0.1 mm using a mold. After 2 opaque porcelain firing cycles, the surfaces were air-abraded. The colors of the specimens were measured using a colorimeter and expressed in Commission International de l'Eclairage (CIE) L*a*b* coordinates. Color differences (delta E) were determined between the control and each experimental group. Analysis of Variance and Tukey-Kramer tests were performed on the delta E data., Results: The 3 Pd-Cu-Ga alloys showed significantly greater (p < .01) delta E values (S = 2.8 +/- 1.1, B = 3.0 +/- 0.6, and F = 2.1 +/- 0.2) than the remaining 5 experimental groups (L = 0.7 +/- 0.5, I = 0.7 +/- 0.4, P = 0.7 +/- 0.2, X = 0.7 +/- 0.4, and T = 0.7 +/- 0.5). The directions of the significant color changes were relatively equally distributed along the L*, a*, and b* axes, and all delta L*, delta a*, and delta b* values were negative (lower value, more green and blue relative to control O)., Conclusions: This work suggests that a 0.1-mm-thick layer of opaque porcelain in the Pd-Cu-Ga alloys studied, did not reliably reproduce the color of porcelain.

Purpose: This study compared denture base resin shear bond strengths to silicoated Au-Pd, Au-Pd-Ag, Au-Ag-Pd-Cu, high-Pd, and Ni-Cr-Be alloys used to fabricate frameworks for hybrid implant prostheses. Microleakage between alloy and resin was also compared among groups after specimen fracture., Materials and Methods: Twelve cylindrical specimens were cast for each alloy. Each specimen was made from a ring-shaped pattern (diameter [d] = 12 mm and height = 4 mm) and machined to achieve uniform hollow centers (d = 6.5 mm). Castings were abraded with 250-micron aluminum oxide and ultrasonically cleaned in distilled water before silicoating. Denture base resin was processed to the internal surfaces of the silicoated specimens. All specimens were thermocycled (1,000 cycles) between 4 degrees C and 50 degrees C, and placed in basic fuchsin dye for a week. A punch (d = 3.8 mm) driven at a cross-head speed of 0.5 mm/min was used to push out the resin specimens. The force required to cause failure was converted to the nominal shear bond strength for each specimen, and mean shear bond strengths for the 5 groups of specimens (N = 12) were compared using one-way analysis of variance and the Tukey-Kramer HSD multiple range test (alpha = 0.05). Six of the 12 debonded resin samples for each alloy were selected at random and evaluated for dye penetration. Using an 80-square grid, the percentage of dye penetration was evaluated with an optical microscope (x25) to determine the percentage of grid area penetrated by the dye. One-way analysis of variance was used to compare the degree of microleakage among groups., Results: The mean resin-alloy shear bond strengths for the Au-Pd (9.6 +/- 3.7 MPa) and Au-Ag-Pd-Cu (9.2 +/- 1.5 MPa) alloys were significantly greater than mean resin-alloy shear bond strength for the Au-Pd-Ag alloy (5.6 +/- 1.9 MPa). No other significant differences in resin-alloy shear bond strengths were noted among the alloy groups. No significant differences were noted for dye penetration into the resin specimens bonded to any of the 5 alloys. The mean grid area penetrated by the dye was 25% when results for the alloys were pooled., Conclusions: Alloy type influences the shear bond strength of a denture base resin to silicoated alloys, but no difference in bond strength was found between Au-Pd, Au-Ag-Pd-Cu, high-Pd, and Ni-Cr-Be alloys. In addition, under the conditions of this study, all groups showed a similar degree of microleakage, which penetrated approximately 25% of the bonded specimen surface area.

Electrochemical impedance spectroscopy (EIS) has been used to obtain insight into corrosion processes for three Pd–Ag alloys, and compare their behavior with an Au–Pd alloy. Five specimens of each alloy received clinically‐appropriate simulated porcelain‐firing heat treatment. EIS testing was performed at ambient temperature, using 0.09% NaCl, 0.9% NaCl and Fusayama solutions. EIS data are presented as Bode plots. At the open‐circuit potential (OCP), the data fit a modified Randles equivalent electrical circuit with a constant phase element (CPE), and the charge‐transfer resistance (RCT) and the two CPE parameters (CPE‐T and CPE‐P) were determined. The area‐normalized capacitance of the double layer (Cdl) was also calculated. The EIS data at two relevant elevated potentials in the passive range were also found to fit well a modified Randles equivalent circuit with different values for the charge transfer resistance and CPE parameters. At the OCP no significant effect on RCT was found for the alloys and electrolytes, and both alloy and electrolyte significantly affected CPE‐P. In vitro corrosion was controlled by charge transfer and charge accumulation processes, and the behavior differed at the elevated potentials compared to the OCP. Significant effects were found for alloy, electrolyte, and alloy/electrolyte interaction on Cdl at the OCP. The EIS parameters at elevated potentials indicate that the Pd–Ag alloys should have satisfactory clinical corrosion resistance. The EIS analyses yielded information about in vitro corrosion of these alloys that cannot be obtained from potentiodynamic polarization testing. [ABSTRACT FROM AUTHOR]

Purpose: This investigation compared the Vickers hardness and microstructures of four recently marketed, palladium-based alloys for metal-ceramic restorations., Materials and Methods: Wax patterns simulating copings for maxillary central incisors were invested in a fine-grained, carbon-free, phosphate-bonded investment. Following burnout, the palladium alloys were fused with a gas-oxygen torch, centrifugally cast, and bench-cooled. Representative castings were embedded in transparent metallographic resin and sectioned to yield two mirror-image specimens. The specimens were evaluated in either the as-cast condition or following heat treatment simulating the firing cycles for Vita VMK porcelain. Vickers hardness measurements (n = 50) were made using a 1-kg load, and photomicrographs of polished and etched specimens were obtained with a scanning electron microscope., Results: The measured values of microhardness for the as-cast alloys were in excellent agreement with values reported by the manufacturer. The hardness in the as-cast condition was significantly greater for the Pd-Cu-Ga-In alloy, compared with the other three alloys, which did not contain copper. For the three high-palladium (> or = 75 wt%) alloys, there were small (4%-8%) decreases in hardness following heat treatment, whereas a larger decrease (13%) in hardness occurred for the Pd-Ag-In-Sn alloy after heat treatment. The porcelain firing cycles caused microstructural homogenization for all four alloys, and the relatively thick near-surface oxidation region in the Pd-Cu-Ga-In and Pd-Ag-In-Sn alloys was not observed in the two heat-treated Pd-Ga-Ag-In-Au alloys., Conclusions: The multiphasic microstructures of these alloys may have some significance for the in vitro and clinical corrosion behavior and the metal-ceramic bond strength. The hardness for the three high-palladium alloys may be controlled by submicroscopic precipitates that remain unaltered by heat treatment. The significantly greater hardness for the Pd-Cu-Ga-In alloy may cause greater difficulty for finishing castings in the dental laboratory compared with the other three alloys studied. The strengthening mechanism for the Pd-Ag-In-Sn alloy has significant temperature dependence, which might be exploited to achieve optimum mechanical properties.

Purpose: A three-dimensional mathematical model of the maxilla was developed that was used to analyze the stresses and strains produced by an abutment system capable of three abutment angulations., Materials and Methods: Computed tomography was used to derive the geometry and density values used for the maxillary model. A 3.8 x 10-mm cylindrical implant was embedded in the right central incisor position at a 35 degrees angle to the horizontal plane and parallel to the angulation of the bone site. All geometric and elastic properties for the fixture and the surrounding bone were included in the model. A simulated occlusal load of 178 N was applied along the long axis of 0 degrees, 15 degrees, and 20 degrees abutments. The mathematical models were solved by the Cray Y/MP Ohio Supercomputer (Cray, Eagan, MN) using the ABAQUS software program (Hibbitt, Karlsson, and Sorenson, Providence, RI)., Results: Numerical and graphic results were generated for the maximum (tensile) and minimum (compressive) stresses and strains. Principal stresses occurred predominantly in the cortical bone layers, whereas strains occurred mostly in the cancellous bone., Conclusions: In general, there was an increase in the magnitude of stress and strain as the abutment angulation increased. Reported stresses and strains for all three angles were within or slightly above the physiological zone derived from animal studies. A need to investigate the response of human bone to stress and strain was indicated.

Purpose: This investigation compared the mechanical properties of three base metal casting alloys (Vitallium2, Neoloy N [Regular], and Regalloy T) for removable partial denture (RPD) frameworks with those for two base metal RPD alloys (Vitallium, Jelenko LG) whose mechanical properties had been previously reported., Materials and Methods: Plastic patterns with dimensions meeting ADA specification no. 14 requirements were used with appropriate casting investments to cast tensile test bars of the five alloys. Nine specimens of each alloy were loaded to failure, and the mechanical properties of modulus of elasticity, 0.1% yield strength, 0.2% yield strength, and tensile strength were obtained from five well-behaved load-elongation plots. Values of percentage elongation were also determined, along with Vickers hardness of the work-hardened alloys from polished cross-sections of fractured tensile specimens. The fracture surfaces for representative specimens of each alloy were examined with a scanning electron microscope., Results: Although the measured values of mechanical properties generally agreed with those reported by the manufacturers, differences found for Vitallium and Jelenko LG with previous investigations suggest that there may have been some changes in alloy compositions and processing by the manufacturers. The investment burnout procedure adopted for the plastic patterns and the present casting conditions may also have affected the mechanical properties of some alloys. Two alloys, Jelenko LG and Regalloy T, had mean values of percentage elongation exceeding 10%, but caution is recommended for clinicians and dental laboratories when performing clasp adjustments with all five alloys because of the substantial work hardening that can occur., Conclusions: In general, all of the alloys met the requirements in ADA specification no. 14 for base metal RPD alloys. Further research will be necessary to determine the relationships between the mechanical properties, particularly yield strength, rate of work hardening and percentage elongation, and the clinical requirements for these alloys.

Purpose: To evaluate the effect of material type on dimensional stability, occlusal surface wear, fracture resistance, and failure behavior of resin-based onlay restorations., Material and Methods: A mandibular right first molar typodont was prepared and digitized using an intraoral scanner to virtually design an onlay restoration with the minimum occlusal thickness of 1.5 mm. Resin-based onlay restorations (n = 15 per group) were fabricated either additively from 2 different resins indicated either for definitive or interim use or subtractively with a composite resin. After cementing onlays to corresponding dies, each of them was digitized before and after thermomechanical aging (B-STL and A-STL), and then subjected to load-to-failure test to evaluate fracture resistance. The B-STL and A-STL of each onlay were also compared to assess the dimensional stability and occlusal surface wear. One-way analysis of variance and Tukey honestly significant difference tests were used to evaluate dimensional stability, occlusal surface wear, and fracture resistance. The chi-square test was used to evaluate the Weibull modulus and characteristic strength among the groups (α = 0.05)., Results: Material type affected investigated outcomes (p < 0.001). The additively manufactured resin indicated for definitive use led to the highest external surface deviations and the additively manufactured resin indicated for interim use led to the highest mesiodistal width deviations (p ≤ 0.033). The onlays fabricated from the additively manufactured resin indicated for definitive use had the highest occlusal surface wear, while those in composite resin had the lowest (p ≤ 0.006). The composite resin onlays had the highest fracture resistance values and reliability (p ≤ 0.035)., Conclusions: Tested subtractively manufactured composite resin had the lowest occlusal surface wear with the highest fracture resistance and reliability. Additively manufactured resins had lower dimensional stability, while tested resin for additively manufactured definitive restorations had the highest occlusal surface wear., (© 2024 by the American College of Prosthodontists.)

Purpose: To evaluate the fit of metal-ceramic three-unit fixed dental prostheses (FDPs) fabricated using selective laser melting (SLM) and 3D-printed casting pattern (CP) and to compare the effect of tooth type and ceramic veneering on marginal and internal gaps., Materials and Methods: Patients requiring posterior three-unit FDPs were selected. For each subject, two FDPs were fabricated using SLM and CP. Silicon replica was used to measure the internal and marginal fit of frameworks before and after ceramic veneering. For each replica, 36 measurements were performed using a stereomicroscope: 4 marginal and 32 internal (4 deep chamfers, 12 axial, 4 axio-occlusal, and 12 occlusal). Statistical analysis was performed using two-way ANOVA and paired t-test., Results: A total of 44 metal-ceramic FDPs were fabricated in 22 patients. The results showed that the fabrication method had no significant effect on the marginal, deep chamfer, or occlusal gaps. However, the method significantly affected the axial, axio-occlusal, and total internal fit, and the SLM had larger gaps than the CP. For the effect of ceramic veneering, measurements were significantly higher in the CP group at all gaps, except for the premolar axial and molar occlusal gaps. The SLM fit was less affected by ceramic veneering. Only premolar gaps significantly increased at the marginal, deep chamfer, and axial and axio-occlusal positions., Conclusion: Metal-ceramic FDPs fabricated using SLM and CP techniques provided a similar marginal fit. Premolars had smaller discrepancies compared to molars. The ceramic veneering process increased the gap of the prostheses, with SLM being less affected by ceramic veneering., (© 2024 by the American College of Prosthodontists.)

Little information is available about enamel wear caused by zirconia brackets, an inadvertent side effect of orthodontic treatment. The purpose of this study was to examine potential enamel damage induced by contact with zirconia brackets. Sliding and impact wear simulations were performed using bovine enamel specimens positioned at a 25° slant to a zirconium ball to determine wear behaviour. Different chewing patterns, tapping and grinding, were simulated. Specimens were profiled using confocal laser scanning microscopy, and the mean maximum depth and surface roughness were measured. Scanning electron microscopy was also performed. The mean maximum depth of wear values differed according to the number of mastication cycles, with a higher number of cycles producing higher depths of wear. The facet wear depth was significantly greater with the tapping pattern than with the grinding pattern. Scanning electron microscopic observation of the wear facets revealed that surface textures at the edges were rougher than those at the centre of all facets. The results of this study indicated that enamel wear was induced by contact with zirconia brackets during the early period of mastication, and that the patterns and number of cycles of mastication affected the wear progression of enamel., (© 2022 Scandinavian Division of the International Association for Dental Research. Published by John Wiley & Sons Ltd.)

Purpose: To evaluate how build orientation affects the fabrication trueness of additively manufactured implant-supported complete arch prostheses by comparing them to subtractively manufactured high-impact polymer-based prostheses., Materials and Methods: An edentulous maxillary model with four implants at canine and first molar regions bilaterally was digitized (ATOS Core 80 5MP) to design a reference implant-supported complete arch prosthesis standard tessellation language file (RF-STL). The STL file was used to manufacture prostheses additively in five different orientations according to the build platform (AM-0, 0-degree; AM-15, 15-degree; AM-30, 30-degree; AM-45, 45-degree; AM-90, 90-degree) or subtractively (SM-HIP, control) (n = 10). The prostheses were digitized with an intraoral scanner (Trios 3) to generate their STLs (TF-STL). After superimposing TF-STLs over the RF-STL with a metrology-grade analysis software program (Geomagic Control X), surface deviations at four regions (overall, occlusal, overall without occlusal, and abutments), linear deviations at each abutment site, and interimplant distance deviations (canine-to-molar, canine-to-canine, and molar-to-molar) were calculated. One-way analysis of variance and Tukey HSD tests were used for the statistical analyses (α = 0.05)., Results: AM-90 mostly had the highest surface deviations, while AM-0 had the lowest overall, and lowest overall without occlusal region deviations (p ≤ 0.022). SM-HIP had the lowest occlusal region deviations (p < 0.001). AM-90 had the highest linear deviations (p < 0.001). AM-15 had higher canine-to-molar deviations than SM-HIP (p = 0.042). SM-HIP had the highest canine-to-canine deviations, while AM-90 had higher deviations than AM-0 and AM-30 (p ≤ 0.026). AM-45 and AM-90 had the highest and AM-0 had the lowest molar-to-molar deviations (p ≤ 0.013)., Conclusions: AM-0 mostly had higher trueness and AM-90 mostly had lower trueness within tested outcomes. Additively manufactured prostheses mostly had lower canine-to-molar distances and higher molar-to-molar distances, whereas SM-HIP prostheses consistently had higher distances than the design file., (© 2024 The Author(s). Journal of Prosthodontics published by Wiley Periodicals LLC on behalf of American College of Prosthodontists.)

Background: This study investigated endodontic clinical preferences, adoption of newer technologies and information sources among dentists and endodontists. Methods: Dental and endodontic society members in Australia and New Zealand were surveyed online regarding their endodontic treatment preferences, armamentarium, information sources and continuing professional education (CPE) attendance. Results: Complete responses were received from 71 endodontic specialists or postgraduates (Group E) and 139 general dentists (Group D). Most of Group E used dental operating microscopes (95.8%), endodontic cone‐beam computed tomography (CBCT; 98.6%) and calcium silicate‐based materials (CSBMs; 97.2%), significantly more (P < 0.001) than Group D (86.3% used loupes, <32% used CBCT for endodontics or CSBMs). Most respondents used dental dam always for endodontics (94.3%), electronic apex locators (EAL; 81.0%) and engine‐driven nickel‐titanium (NiTi) instruments (91.4%); Group E had more experience with engine‐driven NiTi (P < 0.001). Endodontic CPE attendance was highest at dental association programs (P < 0.001) while hands‐on NiTi training attendance was highest via commercial companies (P < 0.05). Online information sources were commonly used (38.8% of Group D, 59.2% of Group E). Conclusion: Dental dam, EAL and engine‐driven NiTi were almost universally used. The endodontic group reported high adoption of newer endodontic technologies. Endodontic CPE and information sources should be further surveyed as online engagement evolves. © 2023 Australian Dental Association. [ABSTRACT FROM AUTHOR]

Background: Rotary nickel–titanium (NiTi) instruments are made to exacting standards and are costly to manufacture, and quality control is paramount. Consequently, unauthorized factories make counterfeit instruments that are less expensive and may therefore be attractive to dentists. Little information exists about the metallurgy and manufacturing quality of such instruments. There is the potential for counterfeit instruments to be at higher risk of fracture during treatment, thereby compromising clinical outcomes. The aim of this study was to evaluate physical and manufacturing properties of genuine and counterfeit ProTaper Next™ and Mtwo® rotary NiTi instruments. Methods: This study investigated the metallurgical properties, manufacturing quality, microhardness and number of cycles to failure of two commonly used rotary NiTi systems and compared them with counterfeit products purporting to be genuine articles. Results: Counterfeit instruments were found to be inferior in manufacturing standards and were less resistant to cyclic fatigue when compared to genuine instruments. Conclusions: Counterfeit rotary NiTi instruments may be less efficient at preparing root canals and may be at higher risk of fracture during endodontic treatment. Dentists must be aware that, although less expensive, counterfeit instruments may be of dubious manufacturing quality and at higher risk of fracture if used in patients. © 2023 Australian Dental Association. [ABSTRACT FROM AUTHOR]

Objectives: Three‐dimensional (3D) printing technology is a promising manufacturing technique for fabricating ceramic brackets. The aim of this research was to assess fundamental mechanical properties of in‐office, 3D printed ceramic brackets. Materials and Methods: 3D‐printed zirconia brackets, commercially available polycrystalline alumina ceramic brackets (Clarity, 3 M St. Paul, MN) and 3D‐printed customized polycrystalline alumina ceramic ones (LightForce™, Burlington, Massachusetts) were included in this study. Seven 3D printed zirconia brackets and equal number of ceramic ones from each manufacturer underwent metallographic grinding and polishing followed by Vickers indentation testing. Hardness (HV) and fracture toughness (K1c) were estimated by measuring impression average diagonal length and crack length, respectively. After descriptive statistics calculation, group differences were analysed with 1 Way ANOVA and Holm Sidak post hoc multiple comparison test at significance level α =.05. Results: Statistically significant differences were found among the materials tested with respect to hardness and fracture toughness. The 3D‐printed zirconia proved to be less hard (1261 ± 39 vs 2000 ± 49 vs 1840 ± 38) but more resistant to crack propagation (K1c = 6.62 ± 0.61 vs 5.30 ± 0.48 vs 4.44 ± 0.30 MPa m1/2) than the alumina brackets (Clarity and Light Force respectivelty). Significant differences were observed between the 3D printed and the commercially available polycrystalline alumina ceramic brackets but to a lesser extent. Conclusions: Under the limitations of this study, the 3D printed zirconia bracket tested is characterized by mechanical properties associated with advantageous orthodontic fixed appliances traits regarding clinically relevant parameters. [ABSTRACT FROM AUTHOR]

Key Clinical Message: Illustrating F‐quad helix with extension arms that simultaneously expand maxillary arch and rotate its central incisor adjacent to the alveolar cleft while aligning palatally ectopic canines. Incisor rotation occurred before alveolar grafting, while canine traction was performed after alveolar grafting. The construction of this appliance is shown in detail. [ABSTRACT FROM AUTHOR]

The introduction of nickel‐titanium (NiTi) mechanical instruments dramatically changed clinical endodontics over the last few decades. Before NiTi, it was necessary to use more instruments to create an ideal root canal shape, and many approaches, sequences and techniques were developed over the years. Recently, NiTi endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments to improve their root canal preparation outcomes and reduce associated canal preparation risks during root canal treatment. Heat treatment is one of the most fundamental approaches to improving the fatigue resistance and flexibility of NiTi endodontic instruments. In addition, new kinematics have been developed to offer greater safety and efficiency. This narrative review describes the general properties and manufacturing of NiTi instruments, and the mechanical system evolution of NiTi instruments. [ABSTRACT FROM AUTHOR]

The study's main objective is to limit bacterial biofilm formation on fixed orthodontic appliances. Bacterial biofilm formation on such devices (e.g., brackets) causes enamel demineralization, referred to as white spot lesions (WSL). WSL is significant health, social and economic problem. We provide a nanotechnology‐based solution utilizing a nanocomposite of gold nanoparticles embedded in a polyoxoborate matrix (BOA: B—boron, O—oxygen, A—gold, Latin aurum). The nanocomposite is fully inorganic, and the coating protocol is straightforward, effective, and ecologically friendly (low waste and water‐based). Prepared coatings are mechanically stable against brushing with a toothbrush (up to 100 min of brushing). Bacteria adhesion and antibacterial properties are tested against Streptococcus mutans—common bacteria in the oral cavity. BOA reduces the adhesion of bacteria by around 78%, that is, from around 7.99 × 105 ± 1.33 × 105 CFU per bracket to 1.69 × 105 ± 3.07 × 104 CFU per bracket of S. mutans detached from unmodified and modified brackets, respectively. Modified fixed orthodontic brackets remain safe for eukaryotic cells and meet ISO 10993‐5:2009 requirements for medical devices. The gathered data show that BOA deposited on orthodontic appliances provides a viable preventive measure against bacteria colonization, which presents frequent and significant complications of orthodontic treatment. [ABSTRACT FROM AUTHOR]

Objectives: This study compared, retrospectively, the incidence of clinical errors and effects on treatment outcomes, when students were exposed to two different instrumentation techniques: a hybrid rotary technique (HYB), consisting of both hand instrumentation with hand stainless steel and Ni-Ti files plus the use of a rotary system (Vortex Blue, Dentsply Sirona), versus a full reciprocation instrumentation technique (WaveOne Gold [WOG], Dentsply Sirona)., Methods: A total of 368 endodontic cases (n = 184) in anterior and premolar teeth, completed by dental students at the University of Michigan School of Dentistry from 2013 to 2022, were used for the study. The groups were evaluated by two calibrated clinicians, observing the incidence of clinical errors: file separations, over-instrumentation, ledges and transportations. Treatment outcomes were also observed. Data were analyzed statistically by Fisher's exact test and Mann-Whitney U test (p < 0.05)., Results: No significant difference in file separations, ledges, and transportation was observed between the two groups. However, the WOG Group experienced significantly more over-instrumentation than HYB group, although this did not significantly affect tooth survival or periapical index (PAI). Cases with PAI scores of 5 were found to have significantly less tooth survival compared to the other PAI scores., Conclusions: It can be concluded that both techniques in our study are well suited to advancing the endodontic dental education of students and novice operators, anticipating relatively successful outcomes of tooth survival, as long as the cases selected are less severe in progression preoperatively., (© 2024 The Authors. Journal of Dental Education published by Wiley Periodicals LLC on behalf of American Dental Education Association.)

Purpose: Bilayered restorations have both the strength of the substructure material and the esthetics of the veneer material; however, they should have appropriate bonding between the two materials. This study aimed to evaluate the shear bond strength (SBS) according to the substructure material and veneering technique used in bilayered restorations., Materials and Methods: The experimental group was divided into four groups (n = 15 per group) based on the substructure materials (cobalt-chromium [Co-Cr] alloy and 3 mol% yttrium-stabilized tetragonal zirconia polycrystal [3Y-TZP]) and veneering techniques (pressing and layering). Veneering was performed with disk shape (diameter: 5 mm, height: 2 mm) on a substructure using each veneering technique. Shear stress was applied to the interface of the substructure and the veneering ceramic using a universal testing machine. The shear bond strength, according to the substructure and veneering technique, was analyzed using a two-way analysis of variance with a post-hoc Tukey's honestly significant difference test. The failure mode was observed, and the surface was analyzed using a scanning electron microscope and energy-dispersive spectroscopy., Results: The shSBS of the Co-Cr alloy and 3Y-TZP substructure was not different (p > 0.05); however, the pressing technique showed a higher SBS than the layering technique (p < 0.05). The SBS did not differ depending on the veneering technique in the Co-Cr alloys (p > 0.05), whereas the SBS in the pressing technique was higher than that in the layering technique for 3Y-TZP (p < 0.05). In the layering technique, the Co-Cr alloy showed a higher SBS than 3Y-TZP (p < 0.05). In the failure mode, mixed failure occurred most frequently in all groups. Extensive elemental interdiffusion was observed through the opaque layer in the Co-Cr alloy, regardless of the veneering technique. In 3Y-TZP, a wider range of elemental interdiffusion was observed in the pressing technique than in the layering technique., Conclusions: In bilayered restorations with a 3Y-TZP substructure, the pressing technique yielded higher bonding strength than layering. Using the layering technique, 3Y-TZP showed a lower SBS than the Co-Cr alloy. In bilayered restorations using 3Y-TZP as a substructure, the veneering technique and thermal compatibility of the materials must be considered., (© 2024 The Author(s). Journal of Prosthodontics published by Wiley Periodicals LLC on behalf of American College of Prosthodontists.)

This study investigated the accuracy of two electronic apex locators (DentaPort and Bingo) using heat‐treated nickel‐titanium files. The true root canal length of 30 single‐rooted teeth was determined using K files. Next, the electronically measured length was determined using two nickel‐titanium files (ProGlider and HyFlex EDM Glide Path File) with two electronic apex locators at the 'APEX' marks. The accuracy of the electronic apex locator was evaluated by comparing the true root canal length and electronically measured length for each measurement. There was no significant difference between the measurements with two nickel‐titanium files, and all differences between true root canal length and electronically measured length were within ±0.5 mm regardless of the type of nickel‐titanium files or electronic apex locators. Based on the results, the heat treatment of the nickel‐titanium files showed no adverse effects on the working length determination using electronic apex locators. [ABSTRACT FROM AUTHOR]

Sports mouthguards are proven devices that reduce both the probability of and damage to orofacial tissues. While commonly used, clinicians may be unaware of the different sports mouthguard materials, proposed fabrication techniques, design recommendations, and newer digital fabrication methods. An overview of existing sports mouthguard standards is presented. It identifies that identify that the present requirements, while historically chosen in good faith, appear to be arbitrarily selected and not from clinical evidence‐based derived data. In addition, identified sports mouthguard heterogeneous testing and data acquisition methods distinguishes that little possibility is afforded for the correlation of results. Furthermore, updated evidence with concussion prevention and/or alleviation is presented with evidence provided by sports mouthguard imbedded technology. The need for continued research is stressed to provide evidence‐based data for concussion alleviation/prevention, digital fabrication methods and materials, and clinically based information for the revision of existing standards. [ABSTRACT FROM AUTHOR]

To investigate whether flash‐free adhesive ceramic brackets (FFA) have a better clinical performance than conventional adhesive ceramic brackets (CVA) in patients undergoing multi‐bracket orthodontic treatment. PubMed, CENTRAL, Web of Science, Scopus, Embase, CNKI and Grey‐literature were searched without restrictions up to January 2022. Both randomized controlled trials (RCTs) and controlled clinical trials (CCTs) were included. Risk of bias assessment was performed using the RoB 2.0 and ROBINS‐I cochrane risk of bias tools. Eight articles, for seven studies, were included in this systematic review, and four split‐mouth trials (SMT) were included in the meta‐analysis. A random‐effects meta‐analysis found a statistically significant faster bonding time with FFA (mean difference [MD] = −93.85 seconds/quadrant, P =.002, 2 SMT), and no statistically significant difference regarding bracket failure rate at 6 months (risk ratio [RR] = 1.05; P =.93, 3 SMT), adhesive removal time (MD = −18.26 seconds/quadrant, P =.50, 2 SMT), and amount of remnant adhesive (MD = −0.13/bracket, P =.72, 2 SMT) between FFA and CVA. No difference (P >.05, 3 SMT) was found in enamel demineralization and periodontal measurements. CVA showed a statistically significant higher debonding pain score (P =.004, 1 SMT). Both flash‐free and conventional adhesive ceramic brackets had a similar clinical performance, except for the faster bonding with FFA. Further, well‐designed clinical trials are still required. [ABSTRACT FROM AUTHOR]

Purpose: The effect of annealing and firing cycle on the adaptation of cobalt‐chromium (CoCr) restorations fabricated by additive manufacturing has been poorly documented. This study compared the marginal and internal fit of CoCr three‐unit fixed dental prostheses before and after firing cycles. Material and methods: The first right maxillary premolar (MP) and molar (MM) on a typodont model, were prepared with a circumferential 1.2 mm chamfer, 2 mm occlusal reduction, and total taper of 8 degrees, to receive 3‐unit fixed dental prostheses (FDP). After the framework design, 20 framework specimens were fabricated using CoCr metal powder by selective laser melting. The replica technique was used for marginal and internal fit measurements in mesiodistal and buccolingual planes. The specimens were submitted to an annealing process, and to ceramic firing protocol. Measurements were repeated after each firing cycle. The data were compared by using Levene test, t‐test, and analysis of variance (ANOVA) (α = 0.05). Results: A significant difference was found in the total intaglio surface discrepancy between the 3 treatments. The annealing treatment induced a statistical difference in the discrepancy value compared to the as printed state (p = 0.028). A significant difference was detected between the initial manufacturing phase and the ceramic layering firing cycle (p = 0.003). Conclusions: Firing cycles induced an alteration of the frameworks adaptation. [ABSTRACT FROM AUTHOR]

The primary objective of this work was to investigate the effect of material selection and tooth position on orthodontic aligner biomechanics. Additionally, material property changes with thermoforming were studied to elucidate its role in material performance in‐vitro. An orthodontic simulator (OSIM) was used to evaluate forces and moments at 0.20 mm of lingual displacement for central incisor, canine and second premolar using Polyethylene terephthalate (PET), Polyurethane (PU) and Glycol‐modified polyethylene terephthalate (PET‐G) materials. The OSIM was scanned to generate a model used to fabricate aligners using manufacturer‐specified thermoforming procedures. Repeated measures of MANOVA was used to analyze the effect of teeth and material on forces/moments. The role of thermoforming was evaluated by flexural modulus estimated by 3‐point bend tests. Pre‐thermoformed and post‐thermoformed samples were prepared using as‐received sheets and those thermoformed over a simplified arch using rectangular geometry, respectively. Groups were compared using Two‐way ANOVA. The PET, PU, and PET‐G materials exerted maximum buccal force and corresponding moments on the canine. PU exerted more buccal force than PET‐G on the canine and second premolar, and more than PET on the second premolar. The impact of thermoforming varied according to the specific polymer: PET‐G remained stable, there was a slight change for PET, and a significant increase was noted for PU from pre‐thermoformed to post‐thermoforming. The results of this study elucidate the influence of material and arch position on the exerted forces and moments. Further, the mechanical properties of thermoplastic materials should be evaluated after thermoforming to characterize their properties for clinical application. [ABSTRACT FROM AUTHOR]

This research aimed to examine the impact of NaOCl and Irritrol solutions with/without autoclave sterilisation on the cyclic fatigue resistance of ProTaper, WaveOne Gold and Reciproc NiTi files. Seventy files in every group were separated into seven subgroups (n = 10) according to irrigation solutions and sterilisation procedures. The mean and standard deviations of the time to fracture was calculated for each group, and the data statistical analysis was performed (P ≤ 0.05). Significantly higher cyclic fatigue resistance was found in Reciproc files than the other types of files. The differences between the control and other subgroups were found to be statistically insignificant (P > 0.05), except for subgroups 5 and 7 (P ≤ 0.05). Immersing NiTi files in NaOCl or Irritrol with sterilisation for three times considerably reduced the cyclic fatigue resistance of these files. Reciproc files exhibited the highest cyclic fatigue resistance in comparison with ProTaper and WaveOne Gold files. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to develop and evaluate a simple, non-destructive method for assessing the misfit and passivity of implant-retained prostheses frameworks., Materials and Methods: To simulate the rehabilitation of a mandible posterior partially edentulous area using 3-unit screw-retained frameworks supported by two implants were fabricated and divided into the following five groups (n = 10 in each group): OP = one-piece framework cast in Co-Cr with the conventional method (control-group); Co-Cr frameworks sectioned and welded by laser (=LAS) or tungsten inert gas (=TIG); Co-Cr CAD-CAM = milled Co-Cr framework; Zir CAD-CAM = milled zirconia framework. The horizontal |X| and vertical |Y| misfits were measured using confocal laser scanning microscopy with one or both screws tightened. Data were analyzed by a two-way ANOVA with repeated measures and Bonferroni correction (α = 0.05)., Results: The greatest |X| misfit was observed in the OP group with both screws tightened (290 µm) and one screw tightened (388 and 340 µm). The conventional casting groups sectioned and welded by laser or TIG had lower mean values (235.35 µm, both screws tightened; and 275 µm, one screw tightened) than the OP framework. However, these values still exceeded those of the milled Co-Cr and zirconia frameworks (190 and 216 µm with both screws tightened). Across all reading conditions, every framework subjected to testing consistently maintained vertical |Y| misfit levels below the threshold of 53 µm; however, the milled frameworks exhibited higher vertical misfits than the frameworks obtained by the conventional cast method., Conclusions: The frameworks, whether cast and sectioned with laser welding or milled from Co-Cr, exhibit improved marginal misfit and enhanced passive fit when compared to other fabrication methods. Additionally, the use of confocal laser scanning microscopy is highly effective for passivity and misfit analysis., (© 2024 by the American College of Prosthodontists.)

Titanium alloys provide excellent corrosion resistance and favorable mechanical properties well suited for a variety of biomaterial applications. The native oxide surface on titanium alloys has been shown to be less than ideal and surface modification is often needed. Previously, an optimized anodization process was shown to form a porous phosphorus‐enhanced anatase oxide layer on commercially pure Ti grade 4. The anodized layer was shown to improve osseointegration and to reduce bacteria attachment when photocatalytically activated with UVA preillumination. The primary objective of the present study was to create a similar phosphorus‐enhanced anatase oxide layer on series of titanium alloys including commercially pure Ti grade 4, Ti‐6Al‐7Nb, Ti‐6Al‐4V ELI, alpha + beta Ti‐15Mo, beta Ti‐15Mo, and Ti‐35Nb‐7Zr‐5Ta. Phosphorus‐enhanced anatase oxide layers were formed on each titanium substrate. Anatase formation was shown to generally increase with oxide thickness, except on substrate alloys containing niobium. Phosphorus uptake was shown to be dependent on the titanium alloy chemistry or microstructure. Anodized layers formed on beta‐structured titanium alloys revealed the lowest phosphorus uptake and the most nanosized surface porosity. A methylene blue degradation assay showed anodized layers on commercially pure Ti and both Ti‐15Mo alloys to exhibit the highest levels of photocatalytic activity. Given the range of mechanical properties available with the commercially pure Ti and Ti‐15Mo alloys, the results of this study indicate the benefits of phosphorus‐enhanced anatase oxide coatings may be applicable to a wide variety of biomaterial applications. [ABSTRACT FROM AUTHOR]

Objectives: To assess and evaluate the collum angle (CA) of the anterior teeth of the permanent dentition. Methods: A search in seven databases for articles that had measured the CA in sagittal malocclusions was conducted until November 30, 2021. The risk of bias was assessed using the Modified Newcastle Ottawa scale. CA measurements using Cone Beam Computed Tomography or lateral cephalograms were included. The CA data were summarized by random‐effects inverse generic meta‐analyses. Results: Qualitative analysis of the 17 selected articles revealed that four were rated as "very good," 12 as "good" and 1 as "satisfactory." CA was 4.7° (95% CI of 3.1 to 6.4) and 2.0° (95% CI of 0.1 to 3.9) greater in Class II division 2 and Class III malocclusions respectively, than in Class I malocclusion cases. Conclusion: Majority of the studies were rated as good or very good. Most studies evaluated the CA of the maxillary central incisors in Class II division 2 malocclusion. Studies assessing other maxillary anterior and mandibular anterior teeth are required. Clinical Significance: Practice of esthetic dentistry for teeth with increased CA is of clinical importance since the angle would determine the longevity and esthetic/cosmetic success of the rehabilitation. Placement of dental implants in areas of missing teeth with increased collum angle leads to excessive stress between the fixture and abutment leading to gingival recession. Thus, knowledge about the collum angle of anterior teeth and its variations in sagittal malocclusions would enable precise treatment planning in the field of esthetic dentistry. [ABSTRACT FROM AUTHOR]

Aim To evaluate the effect of repeated dry heat sterilization on surface characteristics and microstructure of Mani nickel–titanium rotary instruments. Methodology Thirty-three new Mani NRT instruments, size 30, taper 0.04 and 25 mm in length were examined. Twenty-seven instruments were divided into three groups for surface characterization by scanning electron microscopy (SEM). In the first group ( n = 3), instruments were examined in the ‘as-received’ condition and after they had been subjected to 11 sterilization cycles. In the second and third subgroups ( n = 12), 12 instruments were prepared for cross-section and a further 12 for longitudinal sectional analysis and evaluated in subgroups of three, after 0, 1, 6 and 11 sterilization cycles. The remaining six instruments were analysed with differential scanning calorimetry (DSC), three in the ‘as-received’ condition and three after being subjected to 11 cycles of sterilization. Results Scanning electron microscopy observations indicated the presence of debris, pitting and deep milling marks in both new and sterilized files. After 11 sterilization cycles, debris remained and surface roughness was increased significantly ( P = 0.05). DSC analyses showed that the specimens in the ‘as-received’ condition and after 11 sterilization cycles were in the austenite phase or a mixture of austenite and R-phase at 37 °C. Conclusions The machining defects and structural imperfections of new Mani instruments are indicative of the difficulty in manufacturing nickel–titanium endodontic instruments. DSC measurements suggest that Mani instruments are capable of superelastic behaviour under clinical conditions. [ABSTRACT FROM AUTHOR]

This study intended to help practitioners selecting the appropriate motion according to their level of expertise for glide path and complete root canal preparation of curved canals in terms of instrument fracture and preparation time. A total of 160 curved root canals (angle >30°, radius <6 mm) were allocated randomly to 4 groups: A/B for expert operators and C/D for nonexpert operators. A/C were shaped with rotary and B/D with reciprocating instruments. Preparation time was registered and compared with Kruskal–Wallis non‐parametric test and Dunn's post hoc test. Instrument separation was also registered and compared with chi‐square test. A fractographic analysis was performed with scanning electron microscopy. The use of reciprocation motions allowed nonexpert operators to avoid instrument breakage during glide path and to prepare root canals faster. Experts were equally effective in rotary/reciprocating root canal shaping and faster with rotary motions than nonexpert operators, who also fractured significantly more rotary instruments. [ABSTRACT FROM AUTHOR]

To compare used and unused Reciproc Blue and Reciproc after retreatment, the instruments were used in the mesiobuccal canals of maxillary molars with curvature. The torsional resistances were tested and then unused instruments were subjected to XRD, DSC and microhardness tests. Student's t, ANOVA and Tukey's tests were performed (α‐level 0.05). The torsional strength of used Reciproc Blue was not significantly different than unused ones (P >.05), while torsional strength of Reciproc decreased significantly (P <.05). DSC and XRD indicated that Reciproc Blue exhibited prominent transformation peaks corresponding austenite to R‐phase. Microhardness of Reciproc was significantly higher (P <.05). A second reuse of Reciproc Blue for retreatment could be considered safe in terms of torsional strength. Blue treatment also decreased surface microhardness of the instrument and changed phase composition by increasing the R‐phase. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate three‐dimensional external gap progression after chewing simulation of high translucency zirconia (HTZ) and zirconia‐reinforced lithium silicate (ZLS) applied on endodontically treated teeth with different preparation designs. Materials and Method: Endodontically treated molars were prepared with low‐retentive (adhesive overlay) and high‐retentive (full crown) designs above cementum‐enamel junction and restored with HTZ and ZLS. Micro‐computed tomography analysis was assessed before and after chewing simulation to evaluate three‐dimensionally the external gap progression. Results were statistically analyzed with two‐way ANOVA and post‐hoc Tukey test. Results: High‐retentive preparation design had a significantly inferior gap progression compared to the overlay preparation (p < 0.01); ZLS exhibited a significant inferior gap progression compared to HTZ (p < 0.01). Conclusions: High‐retentive preparations restored with ZLS seem to better perform in maintaining the sealing of the external margin after cyclic fatigue. Clinical significance: The clinician should pay attention to the proper combination of preparation designs and ceramic material selection for an endodontically treated molar restoration. HTZ seems to perform worse than lithium silicate in terms of marginal sealing, still showing lacks in resistance to cyclic fatigue when adhesive preparations are performed. [ABSTRACT FROM AUTHOR]

Fluoride has been shown to be an effective agent in the prevention of caries during orthodontic treatment. Resin‐modified glass‐ionomer cements possess therapeutic anticariogenic properties acting as a fluoride reservoir and releasing fluoride into the environment, particularly at low pH where there is a threat of enamel demineralisation and white spot lesions (WSL's). Patient compliance to instructions in standard oral hygiene measures limits the success of caries prevention and the routine use of glass‐ionomer cements can mitigate the lack of compliance, although RMGIC's are not a panacea against WSL's. The adhesion of GIC's to the enamel surface is a physicochemical bond rather than a mechanical bond which reduces the risk of iatrogenic damage to the enamel when bonding and debonding attachments. RMGIC's can be recommended as a bonding adhesive for all attachments but one needs to be selective when bonding molar attachments to avoid occlusal interferences as masticatory forces can be high in these areas. [ABSTRACT FROM AUTHOR]

This study aimed to compare the shaping ability of ProTaper Next (PTN), HyFlex EDM (HEDM) and One Curve (OC) systems manufactured via different thermal treatment methods in simulated S‐shaped canals. Sixty S‐shaped canals in clear resin blocks were enlarged to a final apical size of 25 using PTN, HEDM and OC instruments (n = 20 canals/group). Composite images were obtained by superimposing pre‐ and post‐preparation images. The amount of removed resin was measured perpendicularly to the canal surface in 22 points. Prepared canal width and canal transportation at different levels were determined. Canal aberrations were also recorded. Data were statistically analysed using analysis of variance, the Kruskal–Wallis and the chi‐square tests at a 0.05 significance level. OC produced the most conservative enlargement and better maintained particularly the apical curvature of the S‐shaped canals than HEDM and PTN. OC and HEDM better maintained the canal terminus and coronal curvature than PTN. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effect of thickness, cement shade, and coffee thermocycling (CTC) on the optical properties of zirconia reinforced lithium silicate (ZLS) paired with different shades of a resin cement. Materials and Methods: Thirty ZLS specimens were prepared in two different thicknesses (0.8 and 1.5 mm) and three different resin cement shades (Tr, A2, and A3) were applied (n = 5). Color determinations were done before and after 5000 CTC by using a noncontact spectroradiometer. Color change due to CTC and relative translucency parameter (RTP) before and after CTC were calculated by using CIEDE2000. Data were analyzed using ANOVA and Bonferroni‐corrected t‐tests(α = 0.05). Results: Material thickness and resin cement shade (P < 0.001) affected baseline color. Material thickness affected color difference (P = 0.025). Thickness, resin cement shade, and CTC (P ≤ 0.0001) affected RTP. The difference between the color changes of the 0.8‐ and 1.5‐mm specimens combined with A2 shade cement after CTC was significant (P = 0.01). RTPs of all pairs decreased after CTC (P < 0.001). Conclusions: Cement shade and material thickness affected the baseline color. The thickness of ZLS affected the color change after CTC only with A2 resin cement and the color change was less when the ZLS was thicker. CTC reduced the translucency of all pairs. Clinical Significance: Clinicians and patients should be aware of a potential color change after long‐term coffee consumption when zirconia reinforced lithium silicate is used particularly for laminate veneers with A2 shade of the tested resin cement. [ABSTRACT FROM AUTHOR]

Objective: Resin composite (RC) layering is increasingly popular in restorative dentistry. However, little is known regarding the color interaction between RC layers. The objective of this article is to review the current literature on color interaction between RC layers and its effect on the overall appearance of the double‐layer restoration. Overview: A literature review was conducted on theoretical and experimental in vitro studies that tested layered RC systems using different thicknesses. This article discusses specimen design, color measurement methods and devices, parameters defined as outcomes, and RC shades and systems used in the studies of double‐layered RC that were reviewed here. Relevant clinical findings and gaps that still exist in the literature were also highlighted. Conclusions: Various methods to test layered RC were found in the literature. Each study had a unique design and provided valuable information on color interaction between the enamel and dentin layers that could be applied to clinical use. For more predictable esthetic outcomes, manufacturers could provide tailored recommendations specific for their RC systems, stating the recommended thickness and shade for each layer used in the RC layering technique. Clinical Significance: With increased variability in RC shades and manufacturers, it is often difficult to predict the final overall color of restoration with multiple layers. Advancing research on RC layering will help clinicians deliver the best customized restorative treatment tailored to the needs and expectations of their patients. Future research along these lines can enhance the efficiency of chair time and will increase the satisfaction of both clinicians and patients. [ABSTRACT FROM AUTHOR]

Finite element analysis has been a valuable research tool for rotary nickel‐titanium endodontic files over the last two decades. This review aims to summarise and critique the methodology as used in currently available endodontic literature for finite element analysis of rotary nickel‐titanium instruments. An electronic literature research in PubMed and Scopus databases was performed using the appropriate search terms, and the titles and abstracts were screened for relevance. The review revealed an inconsistent approach to the finite element method, particularly with regards to the boundary conditions in which the instruments are tested. Moreover, there is a lack of experimental data to validate in silico findings. A standardised protocol to finite element analysis of rotary endodontic instruments could be considered for future studies. [ABSTRACT FROM AUTHOR]

This systematic review was registered in PROSPERO (CRD42017075917) and aimed to investigate whether the available clinical evidence supports the hypothesis that reciprocating motion results in a lower incidence of nickel‐titanium files fracture compared to continuous rotation. Clinical studies that reported the incidence of fracture of engine‐driven nickel‐titanium files were included. The main exposure was the kinematics, and the primary outcome was the incidence of files fracture. The overall incidence of files fracture was 2.27%, with a trend for higher incidence with rotary motion (2.43%) than with reciprocating (1.0%), though without significant differences. Multiple meta‐regression models revealed that the use of nickel‐titanium files in more than four teeth and less proficient operators were associated with a higher incidence of file fracture. There was no difference in the clinical incidence of fracture of nickel‐titanium instruments between reciprocating and rotary motions; however, other factors were identified. [ABSTRACT FROM AUTHOR]

Background: The fit of implant‐supported prostheses is of prime importance for the long‐term success of implant therapy. Purpose This systematic review aimed to evaluate recent evidence on current techniques for assessing implant‐framework misfit, its associated strain/stress, and whether these misfits are related to mechanical, biological, and clinical consequences. Materials and methods: An electronic search for publications from January 2010 to October 2020 was performed using the Pubmed, Embase, Web of Science, and Cochrane Library databases with combined keywords on implant‐framework misfit assessments and related clinical complications. Inclusion and exclusion criteria were applied. After full‐text analyses, data extraction was implemented on current techniques of misfit assessment and the relationship between the misfit and the induced strain/stress. Results: A total of 3 in vivo and 92 in vitro studies were selected, including 47 studies on quantifying the degree of implant‐framework misfit with dimensional techniques, 24 studies measuring misfit‐induced strain/stress with modeling techniques, and 24 studies using both methods. The technical details, advantages, and limitations of each technique were illustrated. The correlation between the implant‐framework misfit and the induced strain/stress has been revealed in vitro, while that with the biological complications and implant/prostheses failure was weak in clinical studies. Conclusions: Dimensional and modeling techniques are available to measure the implant‐framework misfit. The passivity of implant‐supported fixed prostheses appeared related to the induced strain/stress, but not the clinical complications. Further studies combining three‐dimensional (3D) assessments using dimensional and modeling techniques was needed. [ABSTRACT FROM AUTHOR]

Objective: To investigate the color difference using both ΔE*ab and CIEDE2000 formulas of all combinations of all enamel and dentin shades of three different composite systems with three different shade guides, to compare the coverage error (CE) of the shade guides for each composite and to investigate whether coverage error is affected by enamel shade layer thickness (0.5 vs 1 mm). Materials and Methods: Disk specimens from all enamel and dentin shades of Essentia, Enamel Plus HRi, and IPS Empress Direct composites were fabricated. Color measurements were performed for all enamel‐dentin combinations and for two thicknesses per enamel shade: 0.5 and 1 mm. Color was measured for three shade guides: Vitapan Classical, 3DMaster, and Ivoclar. Minimum color difference between layered composites and shade tabs, closest shade tab match and CE of all shade guides were calculated for all composite shade combinations. Results: In most cases, the closest match was a mismatch. CE of 3DMaster was significantly lower for IPS Empress Direct and Enamel Plus HRi at 0.5 mm enamel thickness. Shade guides exhibited higher lightness values compared to composites and composites lower chroma values compared to shade guides. Conclusions: Shade guides do not match well to the layered composites. 3DMaster performed better than the other two shade guides, in most cases. [ABSTRACT FROM AUTHOR]

Surface alterations of instruments were investigated after single and multiple uses in the root canals. XP‐endo Shaper (n = 5) and WaveOne GOLD (n = 5) files were used until the separation of the instruments occurred. The apical 3‐mm and separated fragments were analysed by SEM to determine the changes in the instruments and the cross‐sections of the separated fragments. Each group was divided into five subgroups: control, first, second, third and fourth molar. The results were reported descriptively for each group. In the XP‐endo Shaper group, microcracks started to appear after the second use, and pitting and galvanic corrosion occurred after the third use. During the fourth use, microcracks propagated, resulting in ductile fracture while it happened after the third use in the second group. The single use of XP‐endo Shaper and WaveOne GOLD was safe without any major changes on their surfaces. Reciprocating motion was not necessarily superior to full rotation motion. [ABSTRACT FROM AUTHOR]

A novel antimicrobial dental self‐cured glass‐ionomer cement has been developed and evaluated. Alumina filler particles were covalently coated with an antibacterial polymer and blended into a self‐cured glass‐ionomer cement formulation. Surface hardness and bacterial viability were used to evaluate the modified cements. Results showed that the modified cements exhibited a significantly enhanced antibacterial activity along with improved surface hardness. Effects of antibacterial moiety content, alumina particle size and loading, and total filler content were investigated. It was found that increasing antibacterial moiety content, particle size and loading, and total filler content generally increased surface hardness. Increasing antibacterial moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size showed a negative impact on antibacterial activity. The leaching tests indicate no cytotoxicity produced from the modified cements to both bacteria and 3T3 mouse fibroblast cells. [ABSTRACT FROM AUTHOR]

The Sr 3d X‐ray photoelectron spectroscopy (XPS) spectrum of Sr‐containing hydroxyapatite (SHAp) overlaps completely with the P 2p spectrum. Thus, the chemical state identification of Sr in SHAp is a challenging task. In this work, the Sr 3d spectrum was isolated from the overlapping spectra for analyzing the chemical state of Sr using a generic peak‐fitting method. The SHAp layers containing various Sr concentrations were produced on a Ti substrate using a chemical treatment process with a calcium phosphate slurry that included Sr (NO3)2. The distribution of the constituent elements changed according to the Sr concentration, implying that the chemical state of Sr varied with concentration. The isolation of the Sr 3d XPS spectrum was conducted via spectral deconvolution using the P 2p spectrum corresponding to HAp. The isolated Sr 3d spectrum revealed that the chemical state of Sr was in SrO and Sr‐substituted HAp states, and their ratio varied with the Sr concentration in the layer. The SrO to Sr‐substituted HAp ratios affected the Sr ion releasing behavior from the SHAp layer, supporting the validity of the obtained analytical results. [ABSTRACT FROM AUTHOR]

Background/aims: The appropriate heating temperature for the fabrication of mouthguards using ethylene vinyl acetate sheets is reported to be 80-120°C. However, the measurement side of the heating temperature has not been determined. The aim of this study was to investigate the influence of the measurement side of the heating temperature when fabricating mouthguards.Materials and Methods: Mouthguard sheets of 3.8 mm ethylene vinyl acetate were vacuum-formed on working models until the sheet was heated to 120°C. The sheet temperature was measured at the upper side and the lower side. The thickness of the mouthguard was measured at the labial surface of the central incisor, and the buccal and occlusal surfaces of the first molar. The fit of the mouthguard was examined at the central incisor and the first molar by measuring the distance between the mouthguard and the cervical margin of the working model. Differences in the thickness and fit of the mouthguards were analyzed by two-way analysis of variance.Results: Mouthguard thickness varied among the measured regions of the central incisors and first molars (P < .01). The thicknesses at the labial surface of the central incisor and buccal surface of the first molar were larger when the sheet temperature measured at the lower side was 120°C compared to when the sheet temperature measured at the upper side was 120°C (P < .01). The fit of the mouthguard was better when the sheet temperature measured at the lower side was 120°C (P < .05).Conclusions: The sheet temperature should be measured at the lower side of the sheet and it should be 120°C for fabricating mouthguards. [ABSTRACT FROM AUTHOR]

Background/aims: The appropriate heating conditions for polyolefin sheets have not yet been determined and polyolefin sheets are usually formed in the same manner as ethylene vinyl acetate sheets. The aim of this study was to examine the appropriate heating conditions for polyolefin sheets when fabricating vacuum-formed mouthguards.Materials and Methods: Mouthguard sheets of 3.0 mm polyolefin were vacuum formed on working models at three heating temperatures: 90°C, 105°C, and 120°C. The thickness of the mouthguard was measured at the labial surface of the central incisor, and the buccal and occlusal surfaces of the first molar. The fit of the mouthguard was examined at the central incisor and the first molar by measuring the distance between the mouthguard and the cervical margin of the working model. Differences in the thickness and fit of the mouthguards according to the heating conditions and the measured regions were analyzed by two-way analysis of variance.Results: Mouthguard thickness varied among the measured regions of the central incisors and first molars (P < .01). The smallest thickness was found at the labial surface of the central incisor in mouthguards fabricated at 90°C (P < .01). The smallest thickness was found at the buccal and occlusal surface of the first molar in mouthguards fabricated at 120°C (P < .01). The worst fit was obtained with the heating temperature of 90°C (P < .01).Conclusions: The appropriate heating temperature for polyolefin sheets was 105°C to maintain mouthguard thickness and to obtain proper fit. [ABSTRACT FROM AUTHOR]

Background/aim: The effectiveness of mouthguards used in field hockey is unknown. The aim of this study was to compare the maximum impact heights between currently used mouthguards in field hockey to prevent dental injury.Methods: Four boil-and-bite mouthguards (Dita, Shock Doctor, SISU, and Stag) and one custom-made mouthguard (Elysee) were tested for maximum impact height. A hockey ball was released in a tube from increasing heights onto plaster and polymethylmethacrylate (PMMA) dental models. Models were tested without mouthguard as a control. The experiment was repeated 10 times per mouthguard and for the control on each dental model. The maximum impact height for when the dental model broke was used to calculate the speed. The mouthguards and controls were compared.Results: The maximum impact heights (median [25%-75%] in meters) onto plaster dental models were as follows: control 0.23 (0.15-0.25), Dita 0.35 (0.30-0.35), Elysee 0.45 (0.34-0.50), Shock Doctor 0.68 (0.60-0.74), SISU 0.23 (0.20-0.26), and Stag 0.35 (0.35-0.46). The maximum impact height for Shock Doctor was significantly higher than all other mouthguards and the control (all P < .05). The maximum impact heights onto PMMA dental models were as follows: control 2.00 (1.30-2.50), Dita 3.80 (2.65-6.95), Elysee 3.30 (2.30-4.20), Shock Doctor 6.20 (2.80-8.10), SISU 2.60 (1.90-3.15), and Stag 3.90 (1.25-5.15). The maximum impact height for Shock Doctor was significantly higher than for SISU, Stag, and the control (all P < .05), but did not differ significantly from Dita (P = .43) and Elysee (P = .12).Conclusion: Shock Doctor had the highest maximum impact height compared to the other mouthguards and appears to be the most effective mouthguard tested in this study. [ABSTRACT FROM AUTHOR]

The incorporation of antibiotics in glass ionomer cements (GICs) for the treatment of periodontal diseases has been considered as an effective therapeutic strategy. In this research, metronidazole was added to silanized glass fiber‐reinforced GICs. The fiber‐reinforced cements containing antibiotic were made by adding 6.0 w% silanized E‐glass fibers and 3.0 w% metronidazole to the GIC powder. The GIC reinforced with 6.0 w% silanized fibers showed maximum values of 57 MPa, 2.1 GPa, and 1.3 MPa‧m0.5 for the flexural strength, flexural modulus, and fracture toughness, respectively. The release of metronidazole showed a two‐step release in which about 65% of total amount was released in the first 24 hours. Antibacterial test exhibited no bacteria number (CFU/mL) in the presence of GIC containing metronidazole. In addition, gene expression of Streptococcus mutans was performed by real‐time PCR method. Based on PCR results, metronidazole significantly reduced the gtfB and gtfC genes expression, related to adherence and biofilm formation, up to 98% after 7 days in comparison to the control one (P <.001). According to the obtained results, GICs reinforced with silanized fibers containing metronidazole are effective in inhibiting bacteria associated with caries and also acceptable mechanical properties for the development of the next generation of restoration dental materials. [ABSTRACT FROM AUTHOR]