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Background: This study aims to compare design, phase transformation behavior, and torsional resistance of the ProGlider (PG) and ProTaper ultimate slider (PUS) and to compare the performance of two files in the glide-path preparation of a double-curved artificial canal. Methods: Scanning electron microscopy, micro-computed tomography, and differential scanning calorimetry were used to characterize the samples. A torsional resistance test was performed to obtain ultimate strength and distortion angle. Simulated glide-path preparation was conducted with a double-curved resin canal, and both PG and PUS were operated on by 300 and 400 rpms. Maximum screw-in force, torque generated during canal shaping, number of pecking strokes to reach the apex were compared between groups. After canal shaping centering ratio and alteration of files were assessed. Statistical analyses were performed using the Mann-Whitney U test, and the Kruskal-Wallis test with Bonferroni correction. A p value less than 0.05 was considered significant. Results: While the PG had a square cross-section, the PUS had variable square and rhomboid cross-sections and alternating cutting-edge. PG and PUS have austenitic transformation starting and finishing temperatures of 24–25℃, and 57–59℃, respectively. Ultimate strength of PUS are superior to that of PG, whereas the distortion angle of PG is greater than that of PUS (p < 0.05). The maximum screw-in force and clockwise torque generated during glide-path preparation were highest in the PUS group rotated at 300 rpm (p < 0.05). Shaping with the PG at 300 rpm and shaping with the PUS at 400 rpm exhibited comparable maximum screw-in forces. There were no significant differences in the number of pecking strokes to reach the apex and centering ability among groups shaped with PG and PUS at both rotation speeds. PG shaped at 400 rpm demonstrated severe alteration on its surface, while PUS shaped at 300 and 400 rpms exhibited comparable surface alterations. Conclusions: PG has a constant square cross-section, while PUS has a variable cross-section and alternating cutting-edge. Using PUS at recommended speed of 400 rpm ensures safe use with minimal screw-in force and surface alteration. At recommended speeds, both PG and PUS perform comparably and are safe for double-curved canals. [ABSTRACT FROM AUTHOR]

Background: Increasing demand for durable and aesthetically pleasing dental restorations, including laminates, inlays, onlays, and crowns, has led to advancements in all-ceramic systems, particularly with the development of advanced lithium disilicate materials. However, limited data on the fit accuracy and fracture resistance of these materials restricts their wider application in clinical restorative practices. Aim of the study: This in vitro study aims to compare the marginal and internal fit, assess the fracture resistance, and evaluate the failure modes of crowns fabricated from advanced and conventional lithium disilicate materials. Materials and methods: Thirty two (n = 32) crowns were fabricated and categorized into two groups based on the material used: Group (CT), where crowns were milled from CEREC Tessera (n = 16), and Group (EM), where crowns were milled from IPS e.max CAD (n = 16) using a CAD/CAM system. The marginal and internal fit were assessed digitally via a triple scan protocol. All samples were subjected to a fracture resistance test with a universal testing machine, followed by an analysis of failure modes under a stereomicroscope. Results: In the evaluation of marginal, internal and total gaps, CEREC Tessera (CT) showed slightly better fit with lower gap values compared to e.max CAD (EM). However, an independent samples t-test indicated no statistically significant differences between the two groups (p = 0.141, p = 0.471). For fracture resistance (N), the CT group demonstrated higher values than the EM group; however, the independent samples t-test indicated no statistically significant difference (p = 0.053). Additionally, the Chi-squared test with Monte Carlo correction revealed no statistically significant differences in the modes of fracture between the two groups (p = 0.484). Conclusion: Considering the limitations of this study, advanced lithium disilicate crowns demonstrated better results in terms of marginal fit, internal adaptation, and fracture resistance compared to traditional lithium disilicate crowns; however, the differences were not statistically significant. Both materials exhibited comparable fracture patterns. [ABSTRACT FROM AUTHOR]

Background: Clear aligner treatment (CAT) has emerged as an effective alternative to conventional multibracket systems in orthodontics. The trimline design and extension of aligners may significantly influence their biomechanical performance and tooth movement efficacy. Aim: To systematically review the biomechanical effects of different aligner trimline designs and extensions on orthodontic tooth movement. Methods: A systematic search was conducted across PubMed, Scopus, Embase, ProQuest Dissertations & Theses Global, and Google Scholar for studies published between January 2000 and August 2024. The review included any types of empirical research focusing on the influence of trimline of orthodontic aligners on tooth movement efficacy conducted between January 2000 and August 2024. The Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool was used for quality assessment. Results: Twelve studies met the inclusion criteria, all assessed as having low to moderate risk of bias. Aligner trimline design significantly influenced orthodontic tooth movement efficacy through two primary mechanisms: enhanced force delivery and increased aligner retention. Aligners with straight and extended margins generally exerted higher forces and moments compared to scalloped or shorter designs. This resulted in greater tooth displacement for certain movements, particularly intrusion, translation, tipping, and root torquing. Extended trimlines also demonstrated superior retention. However, the effects varied depending on the type of tooth movement. Conclusion: Aligner trimline designs and extensions can significantly influence biomechanical performance and tooth movement efficacy in CAT. Straight extended trimlines generally demonstrate superior force delivery and retention, leading to more predictable clinical outcomes. This could reduce the need for revisions, thereby decreasing overall treatment time and increasing patient satisfaction. However, further research is needed to investigate the interactions between aligner trimline designs and other factors to develop evidence-based guidelines for their optimal combination in various clinical scenarios. [ABSTRACT FROM AUTHOR]

Background: Nickel titanium (NiTi) rotary files have drastically altered the treatment protocol in endodontics, allowing for faster and easier preparation and more thorough irrigation of the root canal system. Despite the advantages of the NiTi files, instrument separation still remains a major concern. The aim of this study was to compare the cyclic fatigue resistance of three different single-file NiTi systems after clinical use: WaveOne Gold (WOG, Dentsply Maillefer, Ballaigues, Switzerland), One Curve (OC, Micro Mega, Besancon, France), and Reciproc Blue (RPC Blue, VDW, Munich, Germany). Methods: A total of 120 patients requiring endodontic treatment to first or second mandibular molars, were randomly divided into three groups (patient n = 40) and root canals were prepared with WOG, OC or RPC Blue. Each group consists of 2 subgroups: first use (file n = 10, patient n = 10) and third use of file (file n = 10, patient n = 30). In control group, files were subjected to cyclic fatigue test without use (file n = 10). Cyclic fatigue resistance of files was assessed by groove method. The data was evaluated by two-way ANOVA, Games & Howell post hoc and Weibull reliability analyses (p <.05). Results: RPC Blue files showed the highest failure time value in all groups. In third use group, OC and RPC Blue files showed significantly higher failure time values compared to WOG files (p <.05). In general, RPC Blue files show the highest values in terms of number of cycles to fracture (NCF) in all groups, while OC and WOG files follow RPC Blue files respectively. There was statistically significant difference among groups considering the fragment length (p <.05). Conclusions: Within the limitations of this study, RPC Blue files exhibited highest cyclic fatigue resistance after clinical use. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effect of the universal and rapid autoclave cycles on the mechanical properties and surface roughness of nickel-titanium archwires following clinical use. Material and methods: Thirty-six NiTi archwires (0.016 × 0.022 inch) were equally divided into a control group (Group A) and 2 experimental groups (Group B & C). Wires in group A were tested in the "as-received" form. Wires in the two other groups were installed in patients mouth for 4 weeks, and then autoclaved using the rapid-cycle (Group B) or the universal-cycle (Group C). All wires were subjected to 3-point bending test to calculate the elastic limit, modulus of elasticity, spring-back, yield strength, resilience and toughness. Atomic force microscopy (AFM) was used for surface roughness qualitative and quantitative analysis. Results: Group B showed significantly higher values of elastic limit, modulus of elasticity, resilience, yield strength and toughness than the other two groups. No significant differences were detected between groups A and C (P > 0.05). Group B showed significantly lower average surface roughness than the other two groups, but no significant differences were detected between groups A and C (P > 0.05). Conclusions: The mechanical properties and surface roughness of clinically used NiTi wires were less affected by the universal-cycle than the rapid-cycle autoclaving. However, the difference between the effect of both autoclave cycles was diminutive. Clinical relevance: The mechanical properties and surface roughness of the tested NiTi wires were not notably altered by clinical use and autoclaving. [ABSTRACT FROM AUTHOR]

Objective: A hybrid manufacturing technique that combines selective laser melting (SLM) and computer numerical control (CNC) has been developed for the fabrication of implant-platform/framework interfaces (PFIs) for mandibular and maxillary full-arch implant-supported titanium frameworks. The aim of this study was to compare the discrepancies in specimens fabricated using the hybrid technique (termed SLM/m hereafter) with those in specimens fabricated by conventional CNC milling. Materials and methods: Based on a mandibular four-PFI CAD model and a maxillary six-PFI CAD model, four groups of titanium frameworks (eight per group, totaling 32) were fabricated according to the fabrication technique (SLM/m or milling) and number of PFIs (four or six). The frameworks were scanned by a structured light scanner and aligned with the CAD model in Geomagic Control X. Discrepancy was defined as the difference between the PFIs of the scanned framework and those of the CAD model. Discrepancies were measured and evaluated by multilevel analysis using a mixed-effects model (α = 0.05), followed by independent samples t-tests (α = 0.0125). Furthermore, the manufacturing times and raw-material costs were recorded and compared. Results: The maximum discrepancy values for the four-PFI and six-PFI hybrid frameworks were 52.2 and 64.3 μm, respectively. Multilevel analysis revealed that the fabrication technique and the number of PFIs had no significant effect on the discrepancy value. However, a significant interaction between the two factors was observed (P = 0.020). The discrepancies for the four-PFI hybrid frameworks were significantly lower than those for the four-PFI milled frameworks (P = 0.001). No significant difference in discrepancies between the six-PFI hybrid frameworks and six-PFI milled frameworks was observed (P = 0.697). Furthermore, the hybrid frameworks required only 11% of the raw materials and 25% of the milling time required for the conventionally milled frameworks. Conclusion: SLM/m hybrid frameworks are viable, accurate alternatives to CNC-milled frameworks, with the added benefit of substantial cost reduction. [ABSTRACT FROM AUTHOR]

Background: Occlusal veneer had been evaluated for mechanical properties using lithium disillicate. However, studies evaluating the mechanical properties of occlusal veneer with different preparation designs and ceramic materials are lacking. So, this in vitro study aimed to evaluate the fracture resistance of occlusal veneers with two designs fabricated from two different ceramic materials. Material and methods: Fourty mandibular third molars were distributed to 2 groups (n = 20) according to preparation design: group (O) anatomical occlusal reduction and group (OA) anatomical occlusal and 1 mm axial reduction. Each group was additionally subdivided into two subgroups (n = 10) according to ceramic materials; in subgroup X, lithium disilicate (e.max CAD, Ivoclar AG, Schaan, Liechtenstein) was used, and in subgroup S, zirconia-reinforced lithium silicate (ZLS) (Vita Suprinity, VitaZahnfabrik, Bad Säckingen, Germany) was used. All specimens were cemented with a light-cure resin cement (Choice 2, Bisco, Schaumburg, USA). 5000 thermocycles were applied to all specimens with both temperatures of 5 °C and 55 °C in two water baths; the dwell time was 30s at each bath, and the transfer time was 10s. Then all specimens were subjected to a fatigue simulation under dynamic loading of 200 N for 250,000 cycles. A universal testing machine (5500R/1123, Instron, Norwood, USA) was used to evaluate the fracture strength with a crosshead speed of 1 mm/min. All data were analyzed statistically by using a two-way ANOVA, and for some violations of assumptions, these results were compared with those obtained by the nonparametric test (Scheirer Ray Hare) (α = 0.05). Results: A statistically significantly higher fracture resistance in the 'OA' (3389 N) compared to the 'O' (2787 N) group regardless of the ceramic material (P <.001) and a statistically significantly higher fracture resistance in the 'X' (3295 N) compared to the 'S' (2881 N) regardless of the preparation design (P =.015). Conclusions: For occlusal veneers, all preparation designs and materials (such as Vita Suprinity and e.max CAD) had clinically acceptable fracture resistance values that were greater than the maximal biting forces. On the other hand, the e.max CAD with occlusal veneer, including axial reduction design, demonstrated the maximum fracture resistance value. Finally, no relationship between fracture strength and mode of failure was found. Clinical implications: Proper preparation design and the use of dental materials with high fracture resistance are key factors in extending the life of occlusal veneer restorations. The highest fracture resistance was demonstrated by lithium disilicate glass-ceramic occlusal veneers with axial preparation, which may increase the clinical longevity of teeth restored with occlusal veneers. [ABSTRACT FROM AUTHOR]

Background: The fit of a metal-ceramic restoration is essential to its long-term durability. Regarding marginal and internal fit, there is not enough information about the technologies used in the production of metal-ceramic restorations. The aim of this in vitro study is to compare, both before and after porcelain firing, the marginal, axial, axio-occlusal, and occlusal fit of metal-ceramic restorations manufactured using casting, additive or subtractive computer-aided design, and computer-aided manufacturing techniques (CAD/CAM). Methods: CAD/CAM were used to create 50 prepared maxillary first molar-shaped Co-Cr die models, which were randomly divided into 5 groups (n = 10). Cobalt-chrome copings were produced by casting (C), hard metal milling (HM), soft metal milling (SM), selective laser melting (SLM), and selective laser sintering (SLS) techniques. Before and after porcelain firing, discrepancies of the copings were measured using the silicone replica technique. The data obtained by measurements with a stereomicroscope at x80 magnification were analyzed statistically in the SPSS program. The ROBUST three-way analysis of variance (ANOVA) method was used to compare the discrepancy values. Results: There were statistically significant differences among fabrication methods (P <.001). The HM method showed the highest discrepancy (90.1 μm), and the C (63 μm) method showed the lowest discrepancy in terms of the die model- crown fit. The C, SLS, and SM methods (63 μm; 61.6 μm; 67.7 μm) were statistically similar (P >.001). The highest discrepancy was observed on the occlusal area (87.1 μm), and the lowest discrepancy was observed on the axial area (47.7 μm) of the coping. Porcelain firing had a decrease in the discrepancy values (P =.001). Conclusion: All CAD/CAM techniques are appropriate for clinical use; selective laser sintering and soft milling can be the more recommended methods for the compatibility of metal-porcelain restorations, as they have lower discrepancy values than the SLM and HM methods. [ABSTRACT FROM AUTHOR]

Nanotechnology has contributed important innovations to medicine and dentistry, and has also offered various applications to the field of orthodontics. Intraoral appliances must function in a complex environment that includes digestive enzymes, a diverse microbiome, mechanical stress, and fluctuations of pH and temperature. Nanotechnology can improve the performance of orthodontic brackets and archwires by reducing friction, inhibiting bacterial growth and biofilm formation, optimizing tooth remineralization, improving corrosion resistance and biocompatibility of metal substrates, and accelerating or decelerating orthodontic tooth movement through the application of novel nanocoatings, nanoelectromechanical systems, and nanorobots. This comprehensive review systematically explores the orthodontic applications of nanotechnology, particularly its impacts on tooth movement, antibacterial activity, friction reduction, and corrosion resistance. A search across PubMed, the Web of Science Core Collection, and Google Scholar yielded 261 papers, of which 28 met our inclusion criteria. These selected studies highlight the significant benefits of nanotechnology in orthodontic devices. Recent clinical trials demonstrate that advancements brought by nanotechnology may facilitate the future delivery of more effective and comfortable orthodontic care. [ABSTRACT FROM AUTHOR]

Objective: One of the most imprortant factors in achieving ideal teeth positions is the precision of the slot dimensions of orthodontic brackets into the archwires are inserted.This study aimed to assess the accuracy of the dimensions of orthodontic bracket slots and molar buccal tube apertures and to compare them with the specifications provided by the manufacturers. Method: A total of sixty brackets and ten molar buccal tubes with varying slot heights were examined using a scanning electron microscope from the mesial side. The dimensions and morphology of these bracket slots and buccal tubes apertures were assessed using the AutoCAD Software. A one-sample t-test was conducted to compare the measurements with the values provided by the manufacturer. Results: The findings of the present study indicated that the height of the measured bracket slots and buccal tube apertures dimensions were significantly larger than the actual dimensions and exhibiting divergent walls. On the other hand, the depth of the brackets slots showed significantly smaller values than the actual one. Conclusion: A need for careful consideration when selecting a commercially accessible brand for everyday use is essential as certain materials may not meet acceptable standards. [ABSTRACT FROM AUTHOR]

Background: The aim of this study is to conduct a comparative evaluation of different designs of clear aligners and examine the disparities between clear aligners and fixed appliances. Methods: 3D digital models were created, consisting of a maxillary dentition without first premolars, maxilla, periodontal ligaments, attachments, micro-implant, 3D printed lingual retractor, brackets, archwire and clear aligner. The study involved the creation of five design models for clear aligner maxillary anterior internal retraction and one design model for fixed appliance maxillary anterior internal retraction, which were subsequently subjected to finite element analysis. These design models included: (1) Model C0 Control, (2) Model C1 Posterior Micro-implant, (3) Model C2 Anterior Micro-implant, (4) Model C3 Palatal Plate, (5) Model C4 Lingual Retractor, and (6) Model F0 Fixed Appliance. Results: In the clear aligner models, a consistent pattern of tooth movement was observed. Notably, among all tested models, the modified clear aligner Model C3 exhibited the smallest differences in sagittal displacement of the crown-root of the central incisor, vertical displacement of the central incisor, sagittal displacement of the second premolar and second molar, as well as vertical displacement of posterior teeth. However, distinct variations in tooth movement trends were observed between the clear aligner models and the fixed appliance model. Furthermore, compared to the fixed appliance model, significant increases in tooth displacement were achieved with the use of clear aligner models. Conclusions: In the clear aligner models, the movement trend of the teeth remained consistent, but there were variations in the amount of tooth displacement. Overall, the Model C3 exhibited better torque control and provided greater protection for posterior anchorage teeth compared to the other four clear aligner models. On the other hand, the fixed appliance model provides superior anterior torque control and better protection of the posterior anchorage teeth compared to clear aligner models. The clear aligner approach and the fixed appliance approach still exhibit a disparity; nevertheless, this study offers a developmental direction and establishes a theoretical foundation for future non-invasive, aesthetically pleasing, comfortable, and efficient modalities of clear aligner treatment. [ABSTRACT FROM AUTHOR]

Background: The objective of this study was to evaluate the antibacterial effect of titanium dioxide nanoparticles incorporated into the acrylic baseplates of the maxillary part of twin block appliances in orthodontic patients during the treatment period. Materials and methods: Twenty-six patients were selected randomly and divided into two groups(n = 13). Test group patients used orthodontic functional appliances containing 1% titanium dioxide nanoparticles in acrylic baseplates. Control group patients used orthodontic functional appliances without titanium dioxide nanoparticles in acrylic baseplates. Swap samples were taken from the palatal gingiva facing the fitting surface of the acrylic component of the maxillary part of a twin block appliance for each patient at five-time intervals (baseline sample, after one, two, four, and six months) and then cultured in blood agar plates to calculate bacterial colony count. The Mann‒Whitney U test and the Friedman test were used to compare data. Bonferroni correction (p value ≤ 0.05) was applied to detect significant differences. The results: showed a decrease in the bacterial colony count in the test group compared to the control group. Pairwise comparisons revealed a statistically significant difference in samples after four- and six-month groups (p values = 0.002 and 0.011, respectively) vs. the one-month test group. A higher statistically significant difference was observed in the six-month group (p-value = 0.037) vs. the baseline group in the control group. Conclusion: The addition of 1% titanium dioxide nanoparticles to acrylic baseplates of orthodontic functional appliances significantly reduced the bacterial colony count under the base plate after at least four months of application. [ABSTRACT FROM AUTHOR]

Background: Orthodontic treatment is associated with numerous adverse side effects, such as enamel discoloration, demineralization or even caries. The presence of microleakage between the enamel and the adhesive and between the adhesive and the base of the orthodontic bracket allows penetration of the bacteria, molecules, and liquids into the enamel and can lead to unpleasant "white spot lesions" or secondary caries beneath and around the brackets. The aim of this in vitro study was to evaluate microleakage in five adhesive systems commonly used in orthodontic practice for bonding brackets. Methods: One hundred extracted premolars were divided into five groups of twenty teeth. Stainless steel Legend medium metal brackets were bonded to teeth using five adhesive systems: resin-reinforced glass ionomer cement GC Fuji Ortho LC (GCF) and composite materials Light Bond (LB), Transbond XT (TB), Trulock™ Light Activated Adhesive (TL), and GC Ortho Connect (GCO). The specimens were subjected to thermal cycling, stained with 2% methylene blue, sectioned with low–speed diamond saw Isomet and evaluated under a digital microscope. Microleakage was detected at the enamel-adhesive and adhesive-bracket interfaces from occlusal and gingival margins. Statistical analysis was performed using generalized linear mixed models with beta error distribution. Results: Microleakage was observed in all materials, with GCF showing the highest amount of microleakage. Composite materials GCO, TB, and LB exhibited the lowest amount of microleakage with no statistical difference between them, while TL showed a statistically significantly higher amount of microleakage (p < 0.001). The enamel–adhesive interface had more microleakage in all composite materials (GCO, LB, TB, and TL) than the adhesive bracket–interface (p < 0.001). The highest amount of microleakage occurred in the gingival region in all materials. Conclusion: Composite materials showed better adhesive properties than a resin-reinforced glass ionomer cement. The presence of microleakage at the enamel-adhesive interface facilitates the penetration of various substances into enamel surfaces, causing enamel demineralization and the development of dental caries. [ABSTRACT FROM AUTHOR]

Introduction: To assess the accuracy, repeatability and reproducibility of a measurement digital technique to quantify the wear of the bracket slot walls of the fixed multibracket appliance after orthodontic treatment with the previous measurement traditional technique (scanning electronic microscope (SEM)). Methods: A total of 100 fixed multibracket appliances were cemented during the 15 months orthodontic treatment and subsequently removed. The fixed multibracket appliances were submitted preoperatively and postoperatively to a micro-computed tomography (micro-CT) scan to obtain accurate standard tessellation language (STL) digital files of the fixed multibracket appliances and to a preoperatively and postoperatively SEM analysis. Afterwards, pre-operatively and postoperatively STL digital files of each fixed multibracket appliances were aligned using morphometric software with the best fit algorithm. Subsequently, area and volume wear of fixed multibracket appliances was identified, isolated and measured. Results: The repeatability and reproducibility of the digital measurement method for the area (mm2) and volume (mm3) were analyzed by Gage R&R statistical analysis. The area wear of the bracket slot walls of the fixed multibracket appliance after orthodontic treatment showed a repeatability of 3.7% and a reproducibility of 0%. The volume of the bracket slot walls of the fixed multibracket appliance after orthodontic treatment showed a repeatability of 0.9% and a reproducibility of 5.6%. However, the traditional measurement technique showed a repeatability of 0.58% and a reproducibility of 33.01%; hence, it was repeatable but not reproducible. Conclusions: The digital measurement technique is a reproducible, repeatable, and accurate method for quantifying the wear of the bracket slot walls of the fixed multibracket appliance after orthodontic treatment. [ABSTRACT FROM AUTHOR]

Background: The effects of topical fluoride applications on the release of monomer ingredients from resin-based dental materials by immersion in various extraction solutions are unclear. The aim of this study was to determine the effect of topical fluorides (APF and NaF) on the elution of residual monomers (Bis-GMA, TEGDMA, UDMA, and HEMA) from resin-based materials. Methods: Ninety specimens were prepared, 30 bulk-fill composite resin, 30 nanohybrid universal composite resin, and 30 polyacid-modified composite resin (compomer). These were randomly divided into three groups based on fluoride application procedures. Each specimen was kept in 75% ethanol solution, and residual monomers released from materials were analyzed using high-performance liquid chromatography (HPLC) after 10 min, 1 h, 24 h, and 30 days. The groups were compared using the Mann Whitney U and Kruskal Wallis tests. Measurements were analyzed using the Friedman and Wilcoxon signed-rank tests. Results: Fluoride applications generally had no considerable effect on the amount of residual monomer released from resin-based restorative materials. The amount of monomer release after topical APF application was similar to the release in the control group and was lower than the release in the NaF group. The release of monomers from the resin-based material used in the study did not approach toxic levels at the applied time intervals. The compomer released lower amounts of monomer than other resin-based materials. Conclusions: Fluoride applications do not increase monomer release from resin-based restorative materials. However, compomers should be employed by clinicians due to their lower monomer release compared to other resin restorative materials. The release of monomers from all the resin-based materials did not approach toxic levels at the applied time intervals. [ABSTRACT FROM AUTHOR]

Background: To evaluate the effect of pecking motions with faster upward speed on the dynamic cyclic fatigue resistance of nickel-titanium rotary instruments with different metallurgy. Methods: Forty each of ProTaper Universal F3 (PTU) and ProTaper Gold F3 (PTG) instruments (size #30/.09) were equally divided into four groups. The test was performed using an 18-mm-long stainless steel artificial canal with a 5-mm radius of curvature, a 45° canal curvature and a 2-mm canal diameter. A downward speed of 100 mm/min was employed, while the upward speed was set at 100, 150, 200 or 300 mm/min. Time to failure (Tf), number of cycles to failure (Nf) and number of pecking motions to failure (Np) were recorded. Statistical analysis was performed using Kruskal Wallis and Mann–Whitney U tests for Tf, Nf, and Np (α = 0.05). Results: The 100/300 mm/min group showed significantly higher Np values than the 100/100 mm/min group (p < 0.05), whereas there were no significant differences in Tf and Nf among the tested speed groups (p < 0.05) in either PTU or PTG. PTG exhibited significantly higher Tf, Nf, and Np than PTU (p < 0.05). Conclusions: Under the tested conditions, the fastest upward speed group showed significantly higher cyclic fatigue resistance, as demonstrated by larger Np, than the same speed group. PTG had significantly higher cyclic fatigue resistance than PTU in all groups. [ABSTRACT FROM AUTHOR]

Background: To compare the solution on the cyclic fatigue resistance of EdgeTaper Platinum (ETP) instruments with that of ProTaper Gold (PTG) in the presence of ethylenediaminetetraacetic acid (EDTA) or sodium hypochlorite (NaOCl) irrigating solutions. Methods: Sixty PTG and 60 ETP instruments with the same size (#25) and taper (8%) were tested under 17% EDTA, 5.25% NaOCl, or distilled water (n = 20 each). Cyclic fatigue was tested using artificial canals that were milled in stainless steel blocks using a laser micromachining technique. The canals had a curvature angle of 60 and a curvature radius of 5 mm. The center of maximum curvature was set at 5 mm from the instrument tip. The block of artificial canals was stabilized inside a container that was filled with one of the tested solutions. The temperature was fixed at 37 °C with a tolerance limit of 1 °C. The number of cycles to fracture (NCF) was calculated and the fractured surfaces were examined using a scanning electron microscope. All statistical analyses were performed using SPSS software Version 20 (IBM-SPSS Inc., Chicago, IL) at a confidence level of 95%. Results: ETP showed higher NCF than PTG in any of the tested solutions (P < 0.05). Within each group, NaOCl drastically decreased the NCF compared to water and EDTA (P < 0.05) and changing the solution from distilled water to EDTA did not affect the fatigue resistance (P > 0.05). Conclusions: ETP showed improved cyclic fatigue performance compared to PTG in all tested irrigating solutions. EDTA can be used in combination with NiTi instruments during canal instrumentation without compromising the cyclic fatigue resistance of PTG and ETP instruments. However, NaOCl drastically decreased the NCF. [ABSTRACT FROM AUTHOR]

Background/purpose: How long do lithium disilicate restorations last before they fail? The aim of this study was to assess the success rate of four different types of restorations made from lithium disilicate. Materials and methods: A total of 87,203 ceramic restorations, classified into four different types (inlay or onlay, veneers (Vs), single crowns (SCs), and fixed partial dentures (FPDs)), were used. All were made of lithium disilicate (IPS e.Max CAD) with Cerec Inlab CAD/CAM system (Sirona Dental Systems, Bensheim, Germany). They were reported by dentists and entered in the database of the private B&R Dental Center between March 2015 and June 2020 and assessed retrospectively up to a period of 5 years based on the following parameters: failure rate and cause of failures (ceramic fracture, debonding, marginal adaptation, color match, endodontic intervention, periodontal disease, and secondary caries). Failure distribution according to gender, arch, and teeth type was also evaluated. The time-dependent time-to-failure/complication and their differences were calculated in months according to the Kaplan Meier and log-rank tests. The Chi-squared test (p 0.05) was used to assess the variations in causes of failure rates between different restorations. Results: Kaplan Meier test showed overall cumulative survival probability of lithium disilicate restorations for up to years was 85.08%. Inlay/onlay and Vs ceramic restorations showed highest cumulative survival probability (99.4%, 98.6, respectively). FPDs had the least cumulative survival probability (52.9%) which was significantly (P < 0.00001) higher than for other ceramic restorations using the log-rank test. Moreover, overall time-dependent time-to-failure/complication occurred after 52.373 months according to Kaplan–Meier (CI: lower bound: 51.875 months; upper bound: 52.871 months). Ceramic fracture in both FPDs and SCs (27.6% and 26.6%, respectively) and debonding in Vs (12.7%) were significant as the main reasons for failure (P = 0.000). The failure rate was significantly higher for the maxillary arch than the mandibular arch (P = 0.021). Fracture and marginal discrepancy were more frequent in the molar region (77.5% and 14.75%, respectively) and significantly higher here than in the anterior and premolar regions (P = 0.000). Conclusion: The medium-term performance of lithium disilicate is ideal. Ceramic fracture was the most common cause of failure in SCs and FPDs. FPDs presented with the highest failure rate based on evaluation for up to 5 years. [ABSTRACT FROM AUTHOR]

Background: The transformation temperatures were important values, influencing the mechanical properties and clinical performance of nickel-titanium instruments. The aim of this study was to determine the transformation temperatures of three rotary nickel-titanium (NiTi) instruments: Reciproc, HyFlex CM Pro, and Neoniti before and after simulated clinical uses. Methods: Ninety new NiTi instruments of three single-file instruments: Reciproc, HyFlex CM Pro, and Neoniti were divided into three groups. Thirty instruments of each group were divided into 3 subgroups (10 instruments for each subgroup): new, one-time simulated clinical used and sterilised, and three times simulated clinical used and sterilized subgroups. The instruments were in the as-received condition for the new subgroups, one time used in the plastic endo-training blocks and sterilised for the one-time subgroups, and three times used in the plastic endo-training blocks and sterilised for the three times subgroups. Each instrument in subgroups was cut into four small segments of 4–5 mm. All segments of instruments were analysed using Differential Scanning Calorimetry (DSC). Data was collected and analysed using SPSS version 20.0 with ANOVA test or Kruskal–Wallis test at the significant level of 0.05. Results: There was not significant difference between before and after simulated clinical use with sterilised procedure in three NiTi instrument systems. The austenite-finish (Af) temperatures of three instrument systems were higher than that of the human body (37 °C), of these, the Af temperature of Neoniti was highest and that of HyFlex CM Pro was lowest. Conclusions: The austenite-finish (Af) temperatures of three NiTi instruments were higher than that of human body temperature, therefore, material was in the phase transformation from martensite to austenite, gives the instruments more flexibility when used in the clinical situation. [ABSTRACT FROM AUTHOR]

Background: Bond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare bond strength of light-cure orthodontic composites by measuring debonding forces and evaluating locations of bond failure. Investigations on chemical compositions clarified adhesive behaviors and abilities, exploring effects of ageing processes in this junction materials. Methods: Twelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT™ 3 M UNITEK, USA, Light-Cure Orthodontic Paste, LEONE, Italy and Bisco Ortho Bracket Paste LC, BISCO, Illinois) and underwent to Shear Bond Strength test. Metallic brackets were bonded to twenty-seven human premolar, with one of the adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces. Raman Spectroscopy analysis was performed on eight discs of each composites to investigate on chemical compositions, before and after accelerated aging procedures in human saliva and sugary drink. Results: Orthodontic adhesive systems showed similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone at adhesive-bracket interface. Accelerated in vitro aging demonstrated good physical–chemical stability for all composites, Bisco only, was weakly contaminated with respect to the other materials. Conclusion: A similar, clinically adequate and acceptable bond strength to enamel for debonding maneuvers was recorded in all orthodontic adhesive systems under examination. No significant chemical alterations are recorded, even in highly critical situations, not altering the initial mechanical properties of materials. [ABSTRACT FROM AUTHOR]

Background: The purpose of the in vitro study is to investigate and compare the morphological features and the chemical stability in weight of two different polyurethane-based blends, Smart Track (LD30) and Exceed30 (EX30), used for orthodontic aligners manufacture before and after the oral usage. Methods: Twenty orthodontic aligners were randomly selected: 10 LD30 and 10 EX30, each group was divided in two subgroups, never used and intra-orally aged. By the employment of a Stereomicroscope, a section of 5 × 5 mm was cut from the buccal surface of the incisal region of each aligner. All samples were subjected to Scanning Electron Microscopy and Ageing tests in different solutions to simulate the hostility of the oral environment. The statistical method used was t-test. Results: At SEM images, LD30 appears more homogeneous in texture respect to EX30. However, after clinical usage, both materials show significant structural alterations: findings have been supported by higher magnifications at SEM, by which it is clearly to observe many superficial cracks cross through the polymer structures of LD30U, absent in never used samples. LD30U surface becomes also smoother due to the disappearance of most of the conglomerates, but at the same time also rougher while EX30U shows a greater irregularity and porosity in which large and deep cracks are also highlighted. Although these changes occur persistently, in the aging tests no significant weight loss from both materials has been found, confirming the initial hypothesis of a good chemical stability and safety of both polyurethane mixtures even in conditions of severe hostility. Conclusion: LD30 is the expression of the technological evolution of EX30, this is made evident above all by its morphological architecture, more homogeneous and defined but also by the chemical stability that can be appreciated even in evident critic situations. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was the assessment of shear bond strength (SBS), adhesive remnant characteristics, integrity of the enamel, integrity of Discovery Pearl as well as the integrity of Fascination 2 ceramic brackets following SBS testing. Methods: Sixty maxillary first premolars were randomly assigned into two groups. These groups were bonded with their respective brackets. The samples underwent thermocycling (1000 cycles), SBS testing and assessment of the residual adhesive. The statistical analyses used were the independent samples t-test, the Weibull analysis and the chi-square test. Results: The independent samples t-test for the comparison of the mean SBS resulted in significant differences between Fascination 2 (10.50 ± 2.61 MPa) and Pearl (13.01 ± 2.50 MPa) brackets (p = 0.0003). The results of the chi-square test for ARI demonstrated a significant difference (p = 0.000) between the groups. A higher frequency of ARI scores of 2 and 3 for Pearl brackets existed. Enamel damage and bracket fracturing was not observed. Conclusions: The mean bond strength value, the adhesive remnant characteristics, the integrity of the enamel and the ceramic brackets as well as the Weibull analyses outcomes were highly encouraging during this in vitro screening. The way is paved for an in vivo investigation with the Pearl ceramic bracket. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to evaluate orthodontic debonding methods by comparing the surface roughness and enamel morphology of teeth after applying two different debonding methods and three different polishing techniques. Methods: Forty eight human maxillary premolars, extracted for orthodontic reasons, were randomly divided into three groups. Brackets were bonded to teeth with RMGIC (Fuji Ortho LC, GC, Tokyo, Japan) (two groups, n =1 8 each) after acid etching (30s), light cured for 40 s, exposed to thermocycling, then underwent 2 different bracket debonding methods: debonding pliers (Shinye, Hangzhou, China) or enamel chisel (Jinzhong, Shanghai, China); the third group (n = 12) comprised of untreated controls, with normal enamel surface roughness. In each debonded group, three cleanup techniques (n = 6 each) were tested, including (I) diamond bur (TC11EF, MANI, Tochigi, Japan) and One-Gloss (Midi, Shofu, Kyoto, Japan), (II) a Super-Snap disk (Shofu, Kyoto, Japan), and (III) One-Gloss polisher. The debonding methods were compared using the modified adhesive remnant index (ARI, 1-5). Cleanup efficiencies were assessed by recording operating times. Enamel surfaces were qualitatively and quantitatively evaluated with scanning electron microscopy (SEM) and surface roughness tester, respectively. Two surface roughness variables were evaluated: Ra (average roughness) and Rz (10-point height of irregularities). Results: The ARI scores of debonded teeth were similar with debonding pliers and enamel chisel (Chi-square = 2.19, P > 0.05). There were significant differences between mean operating time in each group (F = 52.615, P <0.01). The diamond bur + One-Gloss took the shortest operating time (37.92 ± 3.82 s), followed by the Super-Snap disk (56.67 ± 7.52 s), and the One-Gloss polisher (63.50 ± 6.99 s). SEM appearance provided by the One-Gloss polisher was the closest to the intact enamel surface, and surface roughness (Ra: 0.082 ± 0.046 µm; Rz: 0.499 ± 0.200 µm) was closest to the original enamel (Ra: 0.073 ± 0.048 µm; Rz: 0.438 ± 0.213 µm); the next best was the Super-Snap disk (Ra: 0.141 ± 0.073 µm; Rz: 1.156 ± 0.755 µm); then, the diamond bur + One-Gloss (Ra: 0.443 ± 0.172 µm; Rz: 2.202 ± 0.791 µm). Conclusions: Debonding pliers were safer than enamel chisels for removing brackets. Cleanup with One-Gloss polisher provided enamel surfaces closest to the intact enamel, but took more time, and Super-Snap disks provided acceptable enamel surfaces and efficiencies. The diamond bur was not suitable for removing adhesive remnant. [ABSTRACT FROM AUTHOR]

Background: This study was carried out as a prospective clinical field study with the aim of evaluating the clinical performance of Equia Fil® with a nanofilled resin coating and the conventional Fuji IX GP® fast with an LC coating according to the World Dental Federation (FDI) restoration material evaluation criteria.Methods: The clinical performance of Equia Fil® and Fuji IX GP® fast was evaluated on permanent posterior teeth of 643 adult patients aged between 20 to 80 years old in randomly selected clinics across Germany. Occlusal cavities in posterior permanent teeth were restored with Equia Fil® with a nanofilled, light-cured resin coating (n = 515) and Fuji IX GP® fast with an LC coating (n = 486). Direct clinical assessment as well as photographic assessment and assessment of stone casts of the restorations were made at 1 year, 2 years, 3 years, and 4 years.Results: In 4 years, a total of 1001 fillings from both materials were placed by 111 dentists in 643 patients. Random slope models showed that the Equia filling system had overall lower odds of obtaining a delta event (material needs replacement) in comparison to Fuji IX GP® fast with an LC coating within all models. In both materials, filling size/surface was the most important component affecting the clinical performance of the materials. When measuring the odds of obtaining a delta event (material needs replacement), the odds ratios jumped to approximately 43 and 296 times for class II (two surfaces) and class II mesial-occlusal-distal (three surfaces) respectively in comparison to class I fillings.Conclusion: Both materials showed similar good overall performance in class I cavities; however, when including numbers from both class I and II fillings, the Equia system with a nanofilled resin coating showed better overall performance with fewer failures in all the follow-up intervals. Nonetheless, the percentage of unsatisfactory to poor fillings according to the FDI criteria was relatively high in two-surface class II fillings and higher in three-surface class II fillings for both materials.Trial Registration: Deutsches Register Klinischer Studien (German Clinical Trials Register): DRKS00004220. ( www.germanctr.de ). Registration date: 6 Sept 2012. [ABSTRACT FROM AUTHOR]

Background: The present study aimed at 3D analysis of adhesive remnants and enamel loss following the debonding of orthodontic molar tubes and orthodontic clean-up to assess the effectiveness and safety of One-Step Finisher and Polisher and Adhesive Residue Remover in comparison to tungsten carbide bur. Materials and methods: Thirty human molars were bonded with chemical-cure orthodontic adhesive (Unite, 3M, USA), stored 24 h in 0.9 % saline solution, debonded and cleaned using three methods (Three groups often): tungsten carbide bur (Dentaurum, Pforzheim, Germany), one-step finisher and polisher (One gloss, Shofu Dental, Kyoto, Japan) and Adhesive Residue Remover (Dentaurum, Pforzheim, Germany). Direct 3D scanning in blue-light technology to the nearest 2 urn was performed before etching and after adhesive removal. Adhesive remnant height and volume as well as enamel loss depth and volume were calculated. An index of effectiveness and safety was proposed and calculated for every tool; adhesive remnant volume and duplicated enamel lost volume were divided by a sum of multiplicands. Comparisons using parametric ANOVA or nonparametric ANOVA rank Kruskal-Wallis tests were used to compare between tools for adhesive remnant height and volume, enamel loss depth and volume as well as for the proposed index. Results: No statistically significant differences in the volume (p = 0.35) or mean height (p = 0.24) of adhesive remnants were found (ANOVA rank Kruskal-Wallis test) between the groups of teeth cleaned using different tools. Mean volume of enamel loss was 2.159 mm³ for tungsten carbide bur, 1.366 mm³ for Shofu One Gloss and 0.659 mm³ for Adhesive Residue Remover - (F= 2.816, p = 0.0078). A comparison of the proposed new index between tools revealed highly statistically significant differences (p = 0.0081), supporting the best value for Adhesive Residue Remover and the worst - for tungsten carbide bur. Conclusions: The evaluated tools were all characterized by similar effectiveness. The most destructive tool with regards to enamel was the tungsten carbide bur, and the least was Adhesive Residue Removal. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to compare the apical and coronal extrusions by using two reciprocating and two rotary instrumentation systems. Methods: Eighty extracted human single-rooted anterior teeth were randomly assigned to four groups. Four different root canal instrumentation systems were used according to the manufacturers instructions, including two reciprocating single-file systems, Reciproc and WaveOne, and two full-sequence rotary BLX and ProTaper instruments. Debris collected from the coronal by the instruments and apical extrusions were quantified respectively. After drying the collections, the mean weight of debris collected from apical and coronal extrusions was assessed using an electronic balance and analyzed using the Kruskal--Wallis H and Mann-Whitney U tests. Results: Statistically significant differences in the apical extrusion were observed among the four groups. Reciproc and WaveOne instruments produced significantly less debris than BLX and ProTaper instruments (P < 0.05). Conclusions: All of the systems produced apical extrusion of debris. However, reciprocating single-file systems produced less apical extrusion than full-sequence rotary systems. No relationship was observed between apical and coronal extrusions. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of the present study was to investigate and compare early biofilm formation on biomaterials, which are being used in contemporary fixed orthodontic treatment. Methods: This study comprised 10 healthy volunteers (5 females and 5 males) with a mean age of 27.3 +–3.7 years. Three slabs of different orthodontic materials (stainless steel, gold and ceramic) were placed in randomized order on a splint in the mandibular molar region. Splints were inserted intraorally for 48 h. Then the slabs were removed from the splints and the biofilms were stained with a two color fluorescence assay for bacterial viability (LIVE/DEAD BacLight–Bacterial Viability Kit 7012, Invitrogen, Mount Waverley, Australia). The quantitative biofilm formation was analyzed by using confocal laser scanning microscopy (CLSM). Results: The biofilm coverage was 32.7 ± 37.7% on stainless steel surfaces, 59.5 ± 40.0% on gold surfaces and 56.8 ± 43.6% on ceramic surfaces. Statistical analysis showed significant differences in biofilm coverage between the tested materials (p=0.033). The Wilcoxon test demonstrated significantly lower biofilm coverage on steel compared to gold (p=0.011). Biofilm height on stainless steel surfaces was 4.0 ± 7.3 μm, on gold surfaces 6.0 ± 6.6 μm and on ceramic 6.5 ± 6.0 μm. The Friedman test revealed no significant differences between the tested materials (p=0.150). Pairwise comparison demonstrated significant differences between stainless steel and gold (p=0.047). Conclusion: Our results indicate that initial biofilm formation seemed to be less on stainless steel surfaces compared with other traditional materials in a short-term observation. Future studies should examine whether there is a difference in long-term biofilm accumulation between stainless steel, gold and ceramic brackets. [ABSTRACT FROM AUTHOR]

Background Mercury vapor poses a known health risk with no clearly established safe level of exposure. Consequently there is debate over whether the level of prolonged exposure to mercury vapor from dental amalgam fillings, combining approximately 50% mercury with other metals, is sufficiently high to represent a risk to health. The objective of our study is to determine if mercury exposure from amalgam fillings is associated with risk of adverse health effects. Methods In a large longitudinal non-blind sample of participants from a preventative health program in Calgary, Canada we compared number of amalgam fillings, urine mercury measures and changes in 14 self-reported health symptoms, proposed to be mercury dependent sub-clinical measures of mental and physical health. The likelihood of change over one year in a sample of persons who had their fillings removed was compared to a sample of persons who had not had their fillings removed. We use non-parametric statistical tests to determine if differences in urine mercury were statistically significant between sample groups. Logistic regression models were used to estimate the likelihood of observing symptom improvement or worsening in the sample groups. Results At baseline, individuals with dental amalgam fillings have double the measured urine mercury compared to a control group of persons who have never had amalgam fillings. Removal of amalgam fillings decreases measured urine mercury to levels in persons without amalgam fillings. Although urine mercury levels in our sample are considered by Health Canada to be too low to pose health risks, removal of amalgam fillings reduced the likelihood of self-reported symptom deterioration and increased the likelihood of symptom improvement in comparison to people who retained their amalgam fillings. Conclusions Our findings suggest that mercury exposure from amalgam fillings adversely impact health and therefore are a health risk. The use of safer alternative materials for dental fillings should be encouraged to avoid the increased risk of health deterioration associated with unnecessary exposure to mercury. [ABSTRACT FROM AUTHOR]

Background: Finite element simulation has been used in last years for analysing the biomechanical performance of post-core restorations in endodontics, but results of these simulations have been interpreted in most of the works using von Mises stress criterion. However, the validity of this failure criterion for brittle materials, which are present in these restorations, is questionable. The objective of the paper is to analyse how finite element results for brittle materials of endodontic restorations should be interpreted to obtain correct conclusions about the possible failure in the restoration. Methods: Different failure criteria (Von Mises, Rankine, Coulomb-Mohr, Modified Mohr and Christensen) and material strength data (diametral tensile strength and flexural strength) were considered in the study. Three finite element models (FEM) were developed to simulate an endodontic restoration and two typical material tests: diametral tensile test and flexural test. Results: Results showed that the Christensen criterion predicts similar results as the Von Mises criterion for ductile components, while it predicts similar results to all other criteria for brittle components. The different criteria predict different failure points for the diametral tensile test, all of them under multi-axial stress states. All criteria except Von Mises predict failure for flexural test at the same point of the specimen, with this point under uniaxial tensile stress. Conclusions: From the results it is concluded that the Christensen criterion is recommended for FEM result interpretation in endodontic restorations and that the flexural test is recommended to estimate tensile strength instead of the diametral tensile test. [ABSTRACT FROM AUTHOR]

Background: To investigate the complications associated with the use of nickel titanium rotary instruments (NiTi-RIs) for root canal treatments (RCTs), in Saudi Arabia dental practice, and to explore the influencing factors. Methods: After obtaining an ethical approval, two pilot studies were conducted to formulate the final questionnaire. The sample size was measured taking into consideration 60% expected response rates and confidence level of 99.9%. The questionnaire was emailed to 600 general dentists (GDs) randomly selected from the dental register and all of the endodontists (175). The email's introduction clarified objectives of the study and guaranteed that all of the collected information would remain confidential. A reminder was sent after 10 weeks. The data were collected and analyzed using the chi-squared test at a 0.05 significance level. Results: With a 51% overall response rate, 71.9% off the respondents used NiTi-RIs. The majority (83.1%) experienced complications while using NiTi-RIs; with the instruments' fracture being significantly the most common complication (52.7%) (p < 0.001). The majority (87.7%) experienced NiTi-RIs' fractureat least once; with more endodontists (94.3%) than GDs (83.3%) (p < 0.001). The greater the number of weekly performed RCTs and participants' experiences, the more NiTi-RIs fractures and the greater the number of fracture incidents (p < 0.001). While 60% of those who performed 1–3 RCTs per week experienced NiTi-RIs fractures, 100% of those who performed more than 12 RCTs per week did so. The highest percentage of those who experienced more than 10 fractured NiTi-RIs (60%) was within the group who performed more than 12 RCTs per week. Although fracture incidents decreased with a smaller number of reuses, there was no significant correlation between the number of fractured instruments and NiTi-RIs discard strategy (p ≥ 0.05). Conclusion: Fracture incidence was the most common complication while using NiTi-RIs, regardless of the clinicians' experiences and skills. While the single use may reduce NiTi-RIs fractures, to some extent, the greater number of RCTs performed per week was the most influential factor. [ABSTRACT FROM AUTHOR]

Background: The introduction of the new generation of particle-filled and high strength ceramics, hybrid composites and technopolymers in the last decade has offered an extensive palette of dental materials broadening the clinical indications in fixed prosthodontics, in the light of minimally invasive dentistry dictates. Moreover, last years have seen a dramatic increase in the patients' demand for non-metallic materials, sometimes induced by metal-phobia or alleged allergies. Therefore, the attention of scientific research has been progressively focusing on such materials, particularly on lithium disilicate and zirconia, in order to shed light on properties, indications and limitations of the new protagonists of the prosthetic scene. Methods: This article is aimed at providing a narrative review regarding the state-of-the-art in the field of these popular ceramic materials, as to their physical-chemical, mechanical and optical properties, as well as to the proper dental applications, by means of scientific literature analysis and with reference to the authors' clinical experience. Results: A huge amount of data, sometimes conflicting, is available today. Both in vitro and in vivo studies pointed out the outstanding peculiarities of lithium disilicate and zirconia: unparalleled optical and esthetic properties, together with high biocompatibility, high mechanical resistance, reduced thickness and favorable wear behavior have been increasingly orientating the clinicians' choice toward such ceramics. Conclusions: The noticeable properties and versatility make lithium disilicate and zirconia materials of choice for modern prosthetic dentistry, requiring high esthetic and mechanical performances combined with a minimal invasive approach, so that the utilization of such metal-free ceramics has become more and more widespread over time. [ABSTRACT FROM AUTHOR]

Background: To establish the extent of using nickel titanium rotary instruments (NiTi-RIs), to identify reasons for using / not using NiTi-RIs, to explore usage modalities and to identify factors and measures that can increase implementation of NiTi-RIs in general dental practice. Methods: Two pilot questionnaires were conducted on academic staff members at College of Dentistry, Taibah University, general dentists (GDs) and endodontists to finalise the questionnaire. A sample size was calculated considering the expected and minimum accepted response rates (60 and 48%, respectively) and a 99.9% Confidence Level. The online-questionnaire was sent to 600 GDs and all endodontists (175) working in Saudi Arabia. A reminder was emailed after 10 weeks to encourage non-respondents to complete the questionnaire. Responses, were collected and converted into numerical data which were analysed using the Chi-square test (p = 0.05). Results: Significantly most respondents (71.9%) used NiTi-RIs (p < 0.001); with more endodontists (96.9%) than GDs (60%). Most users (62.5%) had been using NiTi-RIs for More than 3 years (p < 0001). The trend of using NiTi-RIs increased as participants' experience and the number of root-canal treatments performed per week increased (p = 0.021). While most respondents (45.3%) used NiTi-RIs because of faster root-canal preparation, the majority of non-users (85.3%) didn't do so because of high cost. The highest proportion (43.3%) reported better undergraduate education as the most important factor that can significantly increase NiTi-RIs usage. The majority (91.8%) prepared glide-path before using NiTi-RIs; especially with stainless steel hand-files (63.3%). Conclusions: NiTi-RIs are relatively well adopted in Saudi dental practice. However, better education, especially during undergraduate training and lower cost can increase their usage. Overall, clinicians showed good awareness of NiTi-RIs usage aspects which reflected on usage modalities. [ABSTRACT FROM AUTHOR]