Resin Blocks Research Articles

Influence of endodontic motors on the behaviour of root canal shaping instruments: an in vitro comparative study

AimsThe endodontic literature reports a lot of comparative study on endodontic instruments, concerning as well their geometry, instrumental dynamics, material, mechanical behavior or heat treatment. However, to our knowledge, no study has focused on the influence of endodontic motors on the shaping abilities of endodontic instruments. Thus, the aim of this study was to analyze the influence of the endodontic motors on root canal shaping instruments.MethodDual Move (MICRO-MEGA, Besançon, France), Canal Pro CL2i (COLTENE, Alstätten, Suisse), Canal Pro Jeni Motor (COLTENE, Alstätten, Suisse), Ai Motor (WOODPECKER, Guilin, China), Wave One motor (VDW, Postfach, Munich) and Smart A (WOODPECKER, Guilin, China) were pre-clinically compared in continuous rotation and reciprocating motion on a traction/compression bench using resin blocks. Canal shaping in continuous rotation and reciprocating motion were performed with One Curve and One RECI instruments (MICRO-MEGA, Besançon, France), respectively. The penetration/removal forces, making it possible to objectify the cutting effect and screwing effect of the instruments during root canal shaping, were analyzed.ResultsThe results showed (i) that endodontic motors influence the mechanical behavior of endodontic instruments, (ii) that the influence of the motors is essentially felt during reciprocating motion and (iii) that the reciprocating angles influence the mechanical behavior of endodontic instruments.ConclusionOnly endodontic instruments are widely studied in literature while endodontic motors have a direct influence on root canal treatment. This study analyzes the influence of the endodontic motors on root canal shaping instruments. This study tends to demonstrate that Jeni Motor could optimize the mechanical behavior of endodontic instruments.

Novel CAD–CAM fabrication of a custom-made ball attachment retentive housing: an in-vitro study

PurposeThis study aims to evaluate the digitally designed ball attachment housing in its initial retentive force and after 2 years of simulated clinical use and to compare it with the regular nylon ball attachment housing.Materials and methodsTwenty implants with their corresponding ball abutments (diameter 4.5 × 4.0 mm) were inserted in resin blocks. They were divided into two groups. In Group I, ten ball abutments each received their corresponding conventional attachment with nylon rings. In Group II, ten ball abutments received the novel CAD–CAM polyetheretherketone ball attachment housing. A universal testing machine was used to measure the retention force. The achieved maximum values of retention force were recorded at the beginning of the study (initial retention) and after 2 years of artificial ageing (2000 cycles of insertion and removal). Results were statistically analyzed using an independent sample T test.ResultsThe PEEK attachment housing showed high retention forces (25.12 ± 0.99 N) compared to the conventional attachment with a nylon ring (15.76 ± 0.93 N) in the initial dislodgement test. There was a statistically significant difference in mean retention at the initial retention test and after 2 years of stimulated usage between the two studied groups, p = 0.000.ConclusionsWithin the limitations of this study, the novel CAD–CAM–PEEK attachment showed high retention characteristics compared to the conventional attachment with nylon rings, initially and after simulated long-term use.

Influence of two kinematics on canal transportation and centering ability of WaveOne Gold and One Curve files.

This research examines canal transportation and centering ability of single-file systems when operated in continuous rotation or reciprocation. Sixty J-shaped resin blocks were used. The specimens were divided into two main groups (n = 30). Then, based on the motion used to operate the instruments, each group was subdivided into two subgroups (n = 15). Group A1: One Curve/rotation, Group A2: One Curve/clockwise reciprocation, Group B1: WaveOne Gold/Reciprocation, Group B2: WaveOne Gold/counter-clockwise rotation. Pre- and post-instrumentation images were obtained using digital microscope. Canal transportation was measured at five levels. A non-significant difference (p > 0.05) resulted between two motions at all levels. However, group A1 showed significantly less transportation at levels 3 and 4 (p ≤ 0.05), also more centered preparation at level 4 (p ≤ 0.05) than group B1. Within the limitations of this study, the apical transportation and centering ability of single-file systems are unaffected by different kinematics.

Precision-milled simulated curved root canals in bovine dentine for the assessment of chemo-mechanical root canal preparation.

The aim was to develop a standardized curved root canal model in bovine dentine and to assess whether that natural substrate would behave differently from the resin in standard plastic training blocks when prepared chemo-mechanically. The impact of substrate microhardness on simulated canal transportation was considered. High-precision computer numerical control (CNC) milling was used to recreate a simulated root canal from a resin training block (Endo Training Bloc J-Shape, size 15) in longitudinally sectioned, dis- and re-assembled bovine incisor roots. Optical overlays obtained from 10 resin blocks were used to identify an average canal and program the CNC milling apparatus accordingly. Resin and dentine microhardness were measured. Simulated root canals in resin training blocks and their bovine counterparts were then instrumented at 37°C using Reciproc R25 instruments (VDW) with water or 17% EDTA (n = 10). Open-access image processing software was used to superimpose and analyse pre- and postoperative images obtained with a digital microscope. Centering ratios were averaged to indicate canal transportation. The effects of substrate and irrigant on canal transportation were assessed by two-way anova. Superimposed images showed that resin blocks under investigation varied considerably in terms of simulated canal length and curvature, whilst the milled canals were highly similar. The microhardness of dentine was more than three times higher than that of the resin. Conversely, canal transportation was considerably greater in dentine compared to resin, and in dentine had a tendency to be increased by EDTA. There was a strong effect of substrate on canal transportation (p < .001), no overall effect of irrigant, and a marginally significant interaction between irrigant and substrate (p = .077). CNC milling allows to create standardized simulated curved root canals in bovine dentine. These models may be useful to test and compare materials and concepts of chemo-mechanical root canal instrumentation. Microhardness is a bulk feature that does not predict the response to chemo-mechanical instrumentation of a composite material such as dentine.

Comparison of trueness and margin quality of additively and subtractively manufactured definitive resin-based laminate veneers

Currently available 3-dimensional (3D) additively manufactured (AM) resins used for definitive restorations have different chemical compositions and viscosities. The fabrication trueness and margin quality of laminate veneers additively manufactured with different resins have not been extensively studied. The purpose of this in vitro study was to evaluate the fabrication trueness and margin quality of AM and subtractively manufactured (SM) definitive resin-based laminate veneers. A laminate veneer restoration for a maxillary right central incisor with a 25-µm cement space was designed to generate a reference laminate veneer standard tessellation language (STL) file (RLV-STL). This RLV-STL was used to fabricate resin-based laminate veneers (N=60) for definitive use, either using AM (a low-viscosity, urethane acrylate-based resin (C&B Permanent, AM-LV), a high-viscosity, urethane acrylate-based resin (Tera Harz TC-80DP, AM-HV), and a glass-reinforced composite resin (Crowntec, AM-S) or SM (glass-filler reinforced composite resin blocks (Tetric CAD, SM) technologies. All laminate veneers were digitized with an intraoral scanner (CEREC Primescan SW 5.2) to generate their test STL files (TLV-STLs). RLV-STL and TLV-STLs were transferred into a 3D analysis software program (Geomagic Control X), and a trueness (external, intaglio, and marginal surface) analysis was performed by using the root mean square (RMS) method. The margin quality of laminate veneers was examined visually under a stereomicroscope and graded. The Kruskal-Wallis and Dunn tests were performed to analyze the data (α=.05). External, intaglio, and marginal RMS values showed statistically significant differences among test groups (P<.001). The SM group had the highest RMS values for the external surface (P<.001), whereas the AM-LV group had the lowest RMS values. The AM-HV group had the highest RMS values for the intaglio surface (P<.001). No significant difference was found between the SM and AM-HV groups for marginal RMS values, which were higher than for the other groups (P=.830). All average values for the axial mesial, axial distal, and incisal edge margin quality of laminate veneers were found to be similar and Grade 3 (smooth edge) in all groups. Regardless of the evaluated surface, the fabrication technique affected the trueness of laminate veneers. The low-viscosity AM laminate veneers and AM laminate veneers reinforced with glass fillers had higher trueness than the SM laminate veneers at all surfaces. The low-viscosity AM laminate veneers had the highest trueness on external and marginal surfaces among the test groups and had higher trueness than the high-viscosity AM laminate veneers.

Effect of Er,Cr:YSGG and Nd:YAG Lasers on Microleakage of Composite Resin Restorations Using Universal Adhesives

Background: Clinical long-term success of bonded restorations is depended to reduce marginal microleakage and the laser application with combination of new bonding systems may play positive role. The aim of this study was comparative evaluation of Er,Cr:YSGG and Nd:YAG lasers effect on microleakage of class V composite resin restorations using several universal adhesives. Methods: In this in vitro study, standard class V cavities were prepared on both lingual and buccal surfaces of 72 intact premolar teeth. For evaluation of microleakage, the cavities were divided into 9 groups according to conditioning method (n=15): G1: G-Premio Bond [GP]; G2: Scotchbond Universal Adhesive [SU]; G3: All-Bond Universal [AB]; G4: GP+Nd:YAG Laser; G5: SU+Nd:YAG Laser; G6: AB+Nd:YAG Laser; G7: GP+Er,Cr:YSGG Laser; G8: SU+Er,Cr:YSGG Laser; and G9: AB+Er,Cr:YSGG Laser. The cavities were filled with composite resin and then subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco­lingual direction. The microleakage in occlusal and gingival margins was defined as linear penetration of methylene blue and determined with a stereomicroscope to assign microleakage scores using a four­point scale. Data were analyzed by using SPSS software and Kruskal-wallis and Mann-Whitney U tests. Results: Microleakage scores had statistically significant different before and after laser irradiation in dependent to the adhesive used (P&lt;0.05) but there were no significant different between Nd:YAG and ER,Cr:YSGG laser, also between different universal adhesives (GP, SU, AB). The results showed that total microleakage scores of occlusal margins had significant statistical different in comparison with gingival margins (P&lt;0.001). Conclusion: The results indicate that Nd:YAG and Er,Cr:YSGG lasers irradiation, after using the investigated universal adhesives, had a positive effect on reducing the microleakage of composite Class V restorations. The microleakage rate was shown to be independent of adhesives and lasers type used in this study.

Effects of cyclic loading on loss of abutment screw torque of angled screw channel single implant crowns on narrow diameter implants

Statement of problemScrew access channels that emerge on the facial aspect of anterior screw-retained implant crowns can compromise esthetics. Recently, angled screw channels (ASCs) have been developed that can alter screw access channel angulations to improve esthetics. While ASCs can be used on narrow-diameter implants, information is limited on the loss of abutment screw torque on narrow-diameter implants with ASCs. PurposeThe purpose of this in vitro study was to compare the loss of abutment screw torque after thermocycling and the cyclic loading of ASCs from 3 different companies connected to narrow-diameter implants. Material and methodsA total of 40 narrow-diameter implants (NobelReplace Conical Connection 3.5×11.5 mm) were mounted individually in acrylic resin blocks and divided equally into 4 groups. The first group, NB-0 (Control), consisted of screw-retained zirconia crowns fabricated on ASCs at 0-degree angulation (n=10). The other 3 groups consisted of a total of 30 screw-retained zirconia crowns fabricated on ASCs at 20-degree angulation: NB-20 (Angulated Screw Channel Solutions), ATL-20 (Atlantis Custom Base Solution with angulated screw access), and DA-20 (Dynamic TiBase). Each crown was secured on the mounted implant with its corresponding titanium base insert and screw and then tightened to the manufacturer’s recommended torque with a digital torque gauge. The initial reverse torque value (RTVI) was obtained and recorded at baseline. Subsequently, a new set of screws were tightened to recommended values, and each specimen underwent thermocycling and then cyclic loading at 0 to 100 N at 10 Hz for 1 million cycles to simulate 1year of functional loading. After cyclic loading, the final reverse torque values (RTVF) were recorded and compared with the RTVI to evaluate the percentage torque loss (PTLF). Statistical analysis was performed using the Kruskal-Wallis analysis, Rank base analysis of covariance (ANCOVA), and the Tukey HSD post hoc comparisons (α=.05). ResultsSignificant differences were found for the PTLF among all groups after cyclic loading (P<.001). The PTLF in ATL-20 (51.4%) was significantly higher than in NB-0 (22.2%) (P<.001) and NB-20 (29.2%) (P=.010). No significant difference was found in the PTLF among other groups (P>.05). ConclusionsThe abutment screw torque loss after cyclic loading of the ASCs on narrow diameter implants among the 4 groups did not perform comparably. The largest percentage torque loss was recorded for the ATL-20 group. The NB-20 group demonstrated the lowest percentage torque loss. DA-20 showed percentage torque loss less than ATL-20; however, its RTVF was the lowest.

Long-term salt spray corrosion behaviors of HVOF-sprayed WC-Cr3C2-Ni coatings before and after vacuum sealing with silicone resin

The application of thermal sprayed WC based cermet coatings is restricted by their structure defects including pores and cracks during thermal spraying. This article fabricated a corrosion-resistant WC-Cr3C2-Ni coating by high velocity oxy-fuel (HVOF) spraying and vacuum sealing with silicone resin. Experiment outcomes show that silicone resin fills into the defects of the WC-Cr3C2-Ni coating. Benefiting from the block of silicone resin in pores and cracks, the sealed coating shows less corrosion pits than the unsealed coating after long-term salt spray corrosion. The sealed coating shows surface without grooves, corrosion pits with smaller size and cracks with decreased amount in comparison with the as-sprayed coating. The vacuum sealing with silicone resin is a strategy with high potential for expanding the application range of thermal sprayed coatings.

Influence of varying titanium base abutment heights on retention of zirconia restorations: An in vitro study

Implant manufacturers have introduced titanium base (Ti-Base) abutments with increased abutment heights, ostensibly, to increase the retention of the bonded restoration and to improve overall strength. However, evidence regarding the effects of increasing Ti-Base height on improving retention is lacking. The purpose of this in vitro study was to evaluate the effect of different Ti-Base abutment heights on the retention of zirconia implant-supported crowns. Thirty Ti-Base abutments of the same diameter and heights of 3.5mm (n=10), 4.5mm (n=10), and 5.5mm (n=10), were used for testing. Zirconia restorations were cemented onto the Ti-Base abutments with a resin cement after treatment with a 10-methacryloyloxydecyl dihydrogen phosphate primer by a single operator using a positioning device. The zirconia-Ti-Base restorations were tightened to an implant analog embedded in an autopolymerizing resin block. The specimens were placed and tested in a universal testing machine for pull-out testing. Retention was measured by recording the force at load drop. Statistical analysis was performed using 1-way analysis of variance with the Tukey method for pairwise comparisons. The abutment height had a significant effect on retention (P=.010). Ti-Base abutments of 4.5 and 5.5mm had significantly greater retention than Ti-Base abutments of 3.5mm (P=.020, P=.040, respectively). However, Ti-Base abutments of 4.5 and 5.5mm in height were statistically similar (P=.890). An increase in the height of Ti-Base abutments above the standard 3.5mm height significantly improved the retention of the overlying restoration.

Comparative Evaluation of Different Irrigant Agitating Devices for Debris Removal from the Mesial Roots of Mandibular Molars: An In Vitro Study.

To evaluate the efficiency of debris removal from the mesial root canals and isthmus of mesial roots of mandibular molars after final irrigant agitation with XP-endo Shaper, EndoVac (EV), plastic finishing file, and conventional needle irrigation. Forty extracted human mandibular first molar teeth with the isthmus between the mesial roots were selected, access cavities were prepared and distal roots were decoronated. All the mesial root specimens were mounted in acrylic, sectioned at the coronal, middle, and apical thirds, along with the resin block, and examined for debris in the canals and isthmus before the start of the procedure using a stereomicroscope and were mounted back in a custom-made jig. After determination of the working length, they were allocated to the following four different irrigant activation groups (n = 10): Group I-XP-endo Finisher; group II-EndoVac; group III-plastic finishing file; and group IV-standard needle irrigation. After biomechanical preparation (BMP) till F3, final agitation was done for debris removal with the respective agitating devices, and all the samples were examined under a stereomicroscope for the amount of debris in the canal after final agitation. Of all the irrigation devices used, the XP-endo Finisher and EV showed more debris removal when compared to other groups (p < 0.05). The plastic finishing file in continuous rotation was more efficient in cleaning debris compared with conventional needle irrigation (p < 0.05). The XP-endo Finisher and EV showed a significant difference in cleaning efficacy than the plastic finishing files. So, these can be used as adjunctive for agitating the final irrigant. The irrigant agitation devices promote the penetration of irrigants into the intricate root canal anatomy and increase their antibacterial and tissue-dissolving effectiveness thereby improving the success rate and treatment outcome.

Clinical Applications and Mechanical Properties of CAD-CAM Materials in Restorative and Prosthetic Dentistry: A Systematic Review.

Clinical outcomes of dental restorations depend primarily on the choice of materials used, and nowadays, dental CAD-CAM (Computer-Aided Design Computer-Aided Manufacturing) materials have strongly changed daily clinical practice. The aim of this systematic review is to analyze CAD-CAM dental materials according to their mechanical properties and in relation to their clinical applications. A literature review was performed on PubMed, Scopus, Web of Knowledge, and the Cochrane Library. Articles addressing at least one of the following topics regarding dental materials for CAD-CAM systems: manufacturers, mechanical features, materials' composition, optical properties, clinical indications, and/or outcomes were included in the review. A flowchart was performed as described in the PRISMA guidelines. Among the 564 articles found, 63 were analyzed and evaluated. Within the limitations of this systematic review, it can be concluded that CAD-CAM materials present a wide range of clinical applications due to their improved mechanical properties. Specifically, in addition to materials that have been in use for a long time (such as feldspathic ceramics), resin block composites can also be used for permanent restorations.

Quasi-3D dynamic photoelastic analysis of stress distribution during preparation of simulated canals with 13 mechanical preparation systems.

The aim of this study is to compare the stress produced on the internal walls of simulated canals by nine rotary and four reciprocating systems. Sixty-five isotropic transparent blocks containing a 60° curved and tapered simulated canal were selected and distributed into 13 groups (n = 5) according to the preparation system: BioRace, HyFlex EDM, iRaCe, Mtwo, One RECI, ProTaper Next, RaCe EVO, Reciproc, Reciproc Blue, R-Motion, VDW.ROTATE, XP-Endo Rise Shaper, and XP-Endo Shaper. Each resin block was mounted in a vice and a digital camera recorded the entire sequence of each preparation system through a circular polariscope set for dark field analysis. The video frames when each instrument reached the end of the coronal, middle, and apical thirds of the canal were extracted from the recordings and analysed by two independent observers regarding the stress generated on the canal walls using a semi-quantitative evaluation on a 0-5 scale. Intra- and inter-observer agreement were subjected to the Cohen's Kappa coefficient test, whilst the experimental results were compared using Kruskal-Wallis test post hoc pairwise comparisons with Bonferroni correction (α = 5%). The inter- and intra-observer agreement were 0.98 and 1, respectively. Most instruments demonstrated acceptable performance (scores ≤ 2) in all thirds. Other instruments, such as the HyFlex EDM 25.12 (coronal and middle thirds), Reciproc Blue R25 and Reciproc R25 (coronal and apical thirds), R-Motion 30.04 (apical third), and VDW.ROTATE 20.05 (apical third) showed scores higher than 3. Statistical analysis revealed a significant difference amongst the tested systems at the coronal, middle, and apical thirds (p < .05). None of the canal instrumentation protocols were stress-free, showing varying levels of stress concentrations. Various factors seemed to influence the magnitude of stress and its distribution pattern on the canal walls. Overall, instruments characterized by a larger taper, lower speed, reciprocating motion, and made of heat-treated NiTi alloy exhibited higher patterns of stress distribution.

High ablation-resistant silicone rubber composites via nanoscale phenolic resin dispersion

High ablation-resistant silicone rubber composites exhibit significant potential for solid rocket engine ablation coating applications. However, the low char yield of silicone rubber restricts its real-world usage. Herein, silicone rubber with nanoscale dispersed Novolac-type phenolic resin particles (novolac-silicone rubber, NSR) is synthesized. The introduction of dynamic urethane bonds is crucial for achieving nanoscale dispersion of the phenolic resin, as it leads to both improved mechanical strength and enhanced char yield. In addition, the NSR-based composite materials demonstrate linear and mass ablation rates of 0.1440 mm/s and 0.0466 g/s, respectively, representing reductions of 44.19 % and 17.81 % compared with their conventional silicone rubber counterparts. Moreover, unlike the traditional physical blending approach, the nanoscale dispersion in this work is achieved by introducing a dihydroxypropyl-terminated silicone oil-novolac phenolic resin block copolymer to the silicone rubber matrix. The enhanced structural compatibility is proven to be pivotal for the improved performance of NSR. This work provides new routes for the synergistic improvement of the ablation resistance and mechanical properties of silicone rubber composites.

Evaluation of shaping performance and surface changes of two different minimally invasive shaping file systems used in resin blocks

Aims: This study aimed to compare the shaping ability of T-endo MIS and TruNatomy (TRN) file systems in J-shaped resin root canals and to investigate the deformation of the files after two acrylic block preparation and two sterilization cycles.&#x0D; Methods: Forty acrylic blocks were numbered, then four file groups (n=10) were established: T-endo MIS glider (15.04) + T-endo MIS Finisher (25.04) (first and second usage) and TRN Glider (17.02) + TRN Prime (26.04) (first and second usage). Preoperative and postoperative images after the root canal preparation of simulated acrylic blocks were taken for each sample, and superimposed. The amount of resin removed from both the inner and outer walls of the canal to the level of 3, 5, and 7 mm from the apical point was measured, and the amount of transportation was calculated. Additionally, the deformation of the files was examined under a scanning electron microscope before and after usage and sterilization process.&#x0D; Results: Tip deformation of TRN files increased with the number of uses (p=0.007). With the second use, the surface deformation of the MIS files increased (p=0.015). There was no difference in cutting-edge deformation in either file type according to the number of uses (p&gt;0.05). There was no difference in transportation values between the MIS and TRN file systems at any level (p&gt;0.05). The file systems did not show a significant difference in the amount of transportation between first and second use (p&gt;0.05).&#x0D; Conclusion: When TRN (26.04) and MIS (25.04) NiTi rotary files were used twice on acrylic blocks, the amount of deformation did not differ. Both file types were similar in terms of transportation values.

Impact of sodium fluoride and nano silver fluoride-based varnishes on remineralisation of enamel caries: an in-vitro study

Background: The aim of this study was to perform a comparative evaluation of 5% Sodium fluoride varnish, neutral nano silver fluoride (NSF) varnish and acidulated nano silver fluoride varnish in remineralising artificially induced enamel caries of primary teeth. Methods: 39 primary anterior teeth were sectioned 2mm below the cemento-enamel junction (CEJ) and mounted in acrylic resin blocks. Incipient enamel caries were induced on the samples artificially and primary Vicker’s surface microhardness (SMH) was assessed. Samples were divided equally and applied varnishes; Group 1: 5% Sodium fluoride varnish; Group 2: Neutral NSF varnish, and Group 3: Acidulated NSF varnish. A pH cycling protocol of 7 days was followed, and second Surface microhardness (SMH) testing was carried out. One sample from each group was observed for Scanning electron microscopy and Energy Dispersive Spectroscopy (SEM EDS). Statistical analysis was conducted using HSD Tukey and one way ANOVA tests. Results: There was a statistically significant difference between the pre-treatment and post-treatment values of all three groups. The difference in SMH after applying 5% Sodium fluoride varnish and acidulated NSF varnish was statistically significant (p&lt;0.01). Similarly, neutral NSF varnish and acidulated NSF varnish also showed statistical significance (p&lt;0.01). However, SMH after application of 5% Sodium fluoride varnish and neutral NSF varnish was statistically not significant. The SEM EDS analysis revealed the presence of an even fine granular layer of minerals on the surface of treated enamel in the acidulated NSF group whereas other groups showed uneven deposits of minerals. EDS showed fluoride and silver in groups containing NSF. Conclusions: Acidulated NSF varnish has the highest efficacy followed by neutral NSF varnish and 5% Sodium fluoride in remineralisation of enamel caries in primary teeth.

Combined use of stannous fluoride-containing mouth rinse and toothpaste prevents enamel erosion in vitro

ObjectiveTo compare the protective effect of commercial stannous-containing mouth rinses on enamel erosion in a simulated 5-day in vitro cycling model.Materials and methods81 human enamel specimens were embedded in resin blocks and divided into nine groups as follows; group 1: stannous fluoride (1000SnF2) toothpaste; groups 2,3, and 4 were the same as group 1 plus Elmex®, PerioMed™, and Meridol®, respectively, group 5: stannous fluoride (1450SnF2) toothpaste, groups 6, 7, and 8 were the same as group 5 plus Elmex®, PerioMed™, and Meridol®, respectively, group 9: negative control. An erosive challenge was induced with a 1 min hydrochloric acid (0.01 M, pH 2.2) treatment 3 times per day. Each cycle included immersing in the toothpaste slurry twice for two minutes and a one-minute rinse. The enamel slabs were immersed in artificial saliva between each erosive cycle and incubated overnight at 37 °C. Surface hardness loss and enamel loss were determined by Knoop surface hardness and non-contact profilometry, respectively. Finally, enamel surfaces were analyzed by scanning electron microscopy and X-ray energy dispersive spectroscopy (SEM/EDS).ResultsAll three mouth rinses had similar protective effects against erosion when using adjunct with 1000 SnF2 toothpaste (p > 0.05). With 1450 SnF2 toothpaste, Elmex® presented significantly lower surface hardness loss than Meridol® (p < 0.05). The combined use of Elmex® or PerioMed™ with toothpaste provided significantly better erosion protection than toothpaste alone, either 1000 or 1450 SnF2. In addition, 1000SnF2 toothpaste adjunct with mouth rinse is comparable to 1450 SnF2 toothpaste alone in preventing enamel erosion.ConclusionAll three mouth rinses reduced enamel erosion. The additional use of a high concentration stannous containing mouth rinse with 1450 SnF2 toothpaste increases the protective effect against enamel erosion in vitro.Clinical significanceTo date, no standard protocol for preventing dental erosion is available. There are three stannous-containing mouth rinses on the market; however, no study compared their efficacy or indicated whether using adjuncts with anti-erosion toothpaste provides additional benefits. This study found that adding stannous mouth rinse to twice-daily toothpaste increases erosion protection.

Assessment of the Push-Out Bond Strength for Glass Fiber Posts After Different Surface Treatments: An In Vitro Study.

The goal of the study was to assessthe push-out bond strength of the glass fibre post after different surface treatments. For the purpose of the investigation, 40 mandibular premolars were chosen. After gaining access, the biomechanical preparation was completed using the step-back approach up to a size 40K file, and the canals were sealed using gutta-percha cones and the lateral condensation procedure with AH Plus sealer (epoxide-amine resin pulp canal sealer). Peeso reamers were used to remove the canal fillings, leaving 5mm of gutta-percha apically. Drills included in the package were used to prepare the post spaces so that the posts would fit in their respective post slots. These were attached to self-curing acrylic resin blocks. Fibre posts were split into four groupings of n = 10 each for surface treatment, i.e., control, hydrogen fluoride, sandblasting, and hydrogen peroxide. The cementation of posts was done by utilising dual-cure resin cement. Two millimetres of the anatomical crown were removed from each sample. Each sample's 1-mm cervical segment was taken utilising the isotope from the remaining coronal area. To perform a push-out test, at the rate of 0.5mm/min of the crosshead, every sample was inserted into a universal testing device. Each post's dislodge force from the pre-set post spacing was measured. Statistics were utilised to analyse the data. Strongest bonds were made by silanization, followed by sandblasting (p value=0.002). The weakest bonds were made by the control group. The ultimate deduction was that when glass fibre posts underwent various types of surface treatments followed by silanization, it had a significant impact on increasing their strength.

The Effect of Biomimetic Remineralization of Calcium Phosphate Ion Clusters-Treated Enamel Surfaces on Bracket Shear Bond Strength.

To evaluate the remineralization effect of calcium phosphate ion clusters (CPICs) on demineralized enamel surfaces and their effects on bracket shear bond strength. Extracted premolars were prepared in resin blocks. The samples in the form of resin blocks were divided into five experimental groups: control group, demineralized group, and groups of CPIC solution treatment for 30, 60, and 90s. The specimens were examined using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), microhardness testing, micro-computed tomography (micro-CT) assessment, shear bond strength (SBS) test, and adhesive remnant index (ARI) score. The SEM images revealed epitaxial growth of enamel and a decrease in the thickness of the demineralized enamel layer when treated with CPIC solution. The EDX analysis revealed an increase in the Ca/P ratio in the CPIC-treated groups. The microhardness value significantly increased when treated with CPICs; however, it showed a lower value than that of the sound enamel groups. As a result of the micro-CT test, radiolucency decreased gradually as the CPIC treatment time increased. The SBS test and ARI score results showed an improvement in bonding stability after treatment with CPICs. We demonstrated an enamel biomodification approach using CPIC solution treatment, which is a promising strategy for enamel remineralization. Specifically, remineralization of demineralized enamel improves the orthodontic bracket SBS.

Impact of sodium fluoride and nano silver fluoride-based varnishes on remineralisation of enamel caries: an in-vitro study

Background: The aim of this study was to perform a comparative evaluation of 5% Sodium fluoride varnish, neutral nano silver fluoride (NSF) varnish and acidulated nano silver fluoride varnish in remineralising artificially induced enamel caries of primary teeth. Methods: 39 primary anterior teeth were sectioned 2mm below the cemento-enamel junction (CEJ) and mounted in acrylic resin blocks. Incipient enamel caries were induced on the samples artificially and primary Vicker’s surface microhardness (SMH) was assessed. Samples were divided equally and applied varnishes; Group 1: 5% Sodium fluoride varnish; Group 2: Neutral NSF varnish, and Group 3: Acidulated NSF varnish. A pH cycling protocol of 7 days was followed, and second Surface microhardness (SMH) testing was carried out. One sample from each group was observed for Scanning electron microscopy and Energy Dispersive Spectroscopy (SEM EDS). Statistical analysis was conducted using HSD Tukey and one way ANOVA tests. Results: There was a statistically significant difference between the pre-treatment and post-treatment values of all three groups. The difference in SMH after applying 5% Sodium fluoride varnish and acidulated NSF varnish was statistically significant (p&lt;0.01). Similarly, neutral NSF varnish and acidulated NSF varnish also showed statistical significance (p&lt;0.01). However, SMH after application of 5% Sodium fluoride varnish and neutral NSF varnish was statistically not significant. The SEM EDS analysis revealed the presence of an even fine granular layer of minerals on the surface of treated enamel in the acidulated NSF group whereas other groups showed uneven deposits of minerals. EDS showed fluoride and silver in groups containing NSF. Conclusions: Acidulated NSF varnish has the highest efficacy followed by neutral NSF varnish and 5% Sodium fluoride in remineralisation of enamel caries in primary teeth.

The effect of different ferrule heights and crown-to-root ratios on fracture resistance of endodontically-treated mandibular premolars restored with fiber post or cast metal post system: an in vitro study

BackgroundThis study aimed to investigate the effects of different ferrule heights and crown-to-root ratios on the fracture resistance of endodontically-treated premolars restored with fiber post or cast metal post system.MethodsEighty extracted human mandibular first premolars with single root canal were treated endodontically and cut from 2.0 mm above the buccal cemento-enamel junction, to create horizontal residual roots. The roots were randomly divided into two groups. The roots in group FP were restored with a fiber post-and-core system, while the roots in group MP were restored with a cast metal post-and-core system. Each group was divided into five subgroups with different ferrule heights (0: no ferrule; 1: 1.0 mm ferrule; 2: 2.0 mm ferrule; 3: 3.0 mm ferrule; 4: 4.0 mm ferrule). All specimens were subsequently restored with metal crowns and embedded in acrylic resin blocks. The crown-to-root ratios of the specimens were controlled at approximately 0.6, 0.8, 0.9, 1.1, and 1.3 of the five subgroups, respectively. Fracture strengths and fracture patterns of the specimens were tested and recorded by a universal mechanical machine.ResultsMean fracture strengths (mean ± standard deviation (kN)) of FP/0 to FP/4 and MP/0 to MP/4 were: 0.54 ± 0.09, 1.03 ± 0.11, 1.06 ± 0.17, 0.85 ± 0.11; 0.57 ± 0.10, 0.55 ± 0.09, 0.88 ± 0.13, 1.08 ± 0.17, 1.05 ± 0.18 and 0.49 ± 0.09, respectively. Two-way ANOVA revealed significant effects of different ferrule heights and crown-to-root ratios on the fracture resistance (P < 0.001), but no difference in fracture resistance between two post-and-core systems (P = 0.973). The highest fracture strengths of the specimen were found with the ferrule length of 1.92 mm in group FP and 2.07 mm in group MP, the crown-to-root ratio of which in 0.90 and 0.92 respectively., there is a significant difference in fracture patterns among the groups(P < 0.05).ConclusionsWhen a certain height of ferrule is prepared and a cast metal or fiber post-and-core system is restored for the residual root, the clinical crown-to-root ratio of the tooth after restoration should be kept within 0.90 to 0.92, so as to improve the fracture resistance of endodontically-treated mandibular first premolars.