Ultrasonic Inserts Research Articles

Fibre post removal using ultrasonic tips: A comparative invitro study using different protocols.

This study evaluated the glass fibre post (GFP) removal using three different protocols with ultrasonic tips. Thirty-six extracted single-rooted teeth were endodontically treated and cemented with a 10-mm GFP. Three protocols were used for GFP removal: 20 s activated with cooling, 20 s activated without cooling and 40 s activated without cooling. The removal time and temperature increase on the external root surface were recorded. The amount of residual material and the volume of dentin loss were assessed using micro-computed tomography. Data were analysed using ANOVA with a 5% significance level. The removal time and the amount of residual material were not affected by the protocol. There was no difference in temperature increase between the 20-s groups. The 40s activated without cooling produced the highest temperatures, especially in the apical region, and greater dentin loss. It is not advisable to use the ultrasonic insert continuously for more than 20 s.

Analysis of the penetration of NaOCl 5.25% into dentinal tubules using different irrigation protocols: An exvivo study.

The objective of the study was to investigate the 5.25% sodium hypochlorite (NaOCl) penetration into the dentinal tubules after different irrigation methods. Seventy canines were stained with 1% crystal violet and divided into groups (n = 20): GEC-EasyClean; GPUI-E1 Irrisonic ultrasonic insert; GXP-XP-Endo finisher; GPC-conventional irrigation and GNC-stained tooth without irrigation. Axial sections (16×) were assessed and irrigant penetration was quantified as a bleaching halo on the surface of the apical, middle and coronal third. In the apical third, GPUI promoted greater NaOCl penetration (p < 0.05). GXP was better than GEC (p < 0.05), as was GPC (p > 0.05). The GPUI and GXP groups were similar in the middle and coronal third (p > 0.05). GPUI and GXP showed better results than GEC (p < 0.05). GPUI was more effective in the apical third and like GXP in the cervical and middle third.

A laboratory pilot study on voids in flowable bulk-fill composite restorations in bovine Class-II and endodontic access cavities after sonic vibration

This pilot study investigated whether sonic-powered application of a bulk-fill resin-based composite (RBC) in Class-II or endodontic access cavities reduces void formation. The crowns and roots of 60 bovine teeth with Class-II cavities (C) and endodontic access cavities (E) respectively, were assigned to ten groups (C1–C5, E1–E5). Cavities were filled with RBC (SDR flow + , one increment) using different application techniques: no adaptation (C1 + E1), spreading of RBC on the cavity surfaces with a dental explorer tip (C2 + E2), low (C3 + E3) or high frequency (C4 + E4) direct activation by inserting a sonic-powered tip into RBC and high frequency indirect activation with an ultrasonic insertion tip (C5 + E5). The restorations were light-cured and investigated for voids using microtomography. The number of voids and percentage of voids related to the volume were statistically analysed (α < 0.05). While most voids in Class-II restorations were observed in C4 (p ≤ 0.0031), no significant differences were found between the other groups (p > 0.05). The percentage of voids showed no differences in E1-E5 (p > 0.05). C4 showed a significantly higher percentage of voids compared to C2 (p < 0.001). There is no benefit in applying sonic vibration when filling Class-II or endodontic access cavities.

Effectiveness of different supplementary protocols for remaining filling material removal in endodontic reintervention: an integrative review.

The aim of this study was to perform an integrative review to identify the most effective supplementary protocols used after filling material (FM) removal and root canal reinstrumentation, during endodontic reintervention. The literature search was performed on the electronic databases PubMed and Latin American and Caribbean Health Sciences Literature (LILACS), using a combination of specific scientific descriptors. Selection criteria accepted articles published in English, Spanish and Portuguese languages, up to August 2021, involving in vitro and ex vivo studies. After applying the eligibility criteria, 46 articles were included for qualitative analysis. The tool for qualitative analysis of quasi-experimental studies of the Joanna Briggs Institute was used to determine the risk of bias of the included articles. The selected articles provided important data regarding the following supplementary protocols: sonic and ultrasonic activation of the irrigating solution; the use of ultrasonic inserts, XP-endo system instruments, and photon-induced photoacoustic streaming for mechanical debridement; and new devices as GentleWave system, and the self-adjusting file. Overall, all supplementary protocols demonstrated efficacy in removing the remaining FM. The implementation of various supplementary protocols can effectively remove the remaining FM from the root canal walls, although complete removal is not always achieved. However, it was not possible to determine the most effective protocol. Conversely, their association can enhance remaining FM removal. Remaining FM attached to root canal walls hinders proper chemical-mechanical preparation during endodontic reintervention. Supplementary protocols optimize the remaining FM removal, enhancing cleaning and disinfection of root canal.

Disinfection and Shaping of Vertucci Class II Root Canals after Preparation with Two Instrument Systems and Supplementary Ultrasonic Activation of Sodium Hypochlorite

IntroductionThis study compared disinfection and shaping after root canal preparation with either XP-endo Shaper or TruNatomy instrument systems, supplemented by ultrasonic activation of sodium hypochlorite (NaOCl) with either stainless-steel (SS) or nickel-titanium (NiTi) inserts. MethodsMesial roots from mandibular molars with Vertucci class II configuration were divided into 2 groups (n = 24) based on anatomically paired micro-computed tomography (micro-CT) analyses. Pre and postpreparation micro-CT scans were obtained to evaluate the shaping performance. The canals were contaminated with a mixed bacterial culture for 30 days and then subjected to preparation with either XP-endo Shaper or TruNatomy instruments using NaOCl irrigation. Supplementary ultrasonic activation of NaOCl was conducted using either an SS (TruNatomy group) or NiTi (XP-endo Shaper group) insert. Bacteriological samples were taken from the canals before preparation (S1), after preparation (S2), and after the supplementary approach (S3). Bacterial reduction was evaluated using a quantitative real-time polymerase chain reaction. ResultsPreparation with both instrument systems significantly reduced bacterial counts (P < .01). After preparation, 36% (TruNatomy) and 35% (XP-endo Shaper) were negative for bacteria. These values increased to 59% and 65% after ultrasonic activation with the SS and NiTi inserts, respectively. The quantitative data in S2 showed that XP-endo Shaper promoted a significantly higher bacterial reduction than TruNatomy (P < .05). No significant intragroup differences were observed after ultrasonic activation (P > .05), probably because the SS insert promoted a significantly higher S2-to-S3 reduction than the NiTi insert (P < .01). Micro-CT analysis revealed no significant differences in the unprepared areas between the groups (P > .05). ConclusionsThe XP-endo Shaper caused a significantly higher bacterial reduction than TruNatomy in Vertucci class II canals. Better antibacterial results after ultrasonic activation were observed for the SS ultrasonic inserts than for the NiTi inserts.

Endodontic treatment of teeth that undertook calcic pulp metamorphosis

The pulp-dentin complex is primarily responsible for the color of teeth. Increasing the thickness of the dentin and decreasing or eliminating the pulp tissue implies changing the tooth color. Calcific Metamorphosis of the Pulp, partial or total calcification of the root canal, replaced by sclerotic dentin is often perceived by darkening of the tooth followed by aseptic pulp necrosis. Endodontic treatment in these cases becomes very difficult due to atresia or even total calcification of the pulp space, requiring the use of specific techniques, knowledge and mastery of internal dental anatomy. In this article we present a clinical case in which we performed the root canal of a tooth that suffered Calcific Pulp Metamorphosis, employing an ultrasonic insert in the modeling of the canal.

Diamond-coated ultrasonic tip decreases debris and uninstrumented surface after preparation of curved canals with isthmus.

The aim of this study was to evaluate root canal preparation with nickel titanium rotary instruments and complementary preparation with ultrasonic tip in curved canals of mandibular molars with isthmus. Twenty-eight mesial roots of mandibular molars with curvature between 20° and 40° and presence of isthmus throughout the entire extension of the root canals were prepared using ProDesign Logic CM (PDL) up to size 40.05, or HyFlex EDM (HFEDM) up to size 40.04. Complementary preparation was performed in the isthmus region using the ultrasonic insert E18D (Helse, Istmo Diamantada). The root canals were scanned using micro-CT (SkyScan 1176) at 9 µm voxel size before and after each preparation step. Transportation, percentage of increase in volume, debris and uninstrumented surface (UNS) were evaluated. Mann Whitney, Wilcoxon, paired and non-paired t-tests were used for statistical analysis (α = 0.05). The canals prepared with PDL and HFEDM obtained similar results for all the variables assessed before using E18D (p > 0.05). E18D significantly decreased the percentage of debris and UNS values in both Groups (p < 0.05). The complementary preparations with E18D caused a smaller quantity of debris in the isthmus of the canals previously prepared with PDL in comparison with HFEDM (p < 0.05). PDL and HFEDM provided similar root canal preparation. PDL promoted a smaller quantity of Debris in the isthmus than HFEDM after using E18D. E18D significantly improved cleaning, and reduced Debris and UNS.

Does the ultrasonic activation of calcium silicate-based sealers affect their physicochemical properties?

This study aimed to evaluate the influence of ultrasonic activation (UA) on the physicochemical properties of hydraulic calcium silicate-based sealers. Nine experimental conditions were created based on the hydraulic calcium silicate-based sealers (Bio-C Sealer, Sealer Plus BC and Bio Root RCS) and the ultrasonic activation (no activation [NA], 10 seconds, and 20 seconds). Then the experimental groups were BC-NA, BC-10, BC-20, SPBC-NA, SPBC-10, SPBC-20, BR-NA, BR-10, and BR-20. Activation was performed with an ultrasonic insert 20/.01. The mold for the physicochemical analysis was filled and evaluated according to the ANSI/ADA specification nº. 57: initial and final setting time, flow, radiopacity and solubility. Tests were also performed to evaluate pH and calcium ion release with experimental periods of 1, 24, 72, and 168 hours with a pH meter and colorimetric spectrophotometer. Data were analyzed by one-way analysis of variance and post-hoc Tukey tests. The significance level was set at 5%. The time of UA progressively delayed the initial setting time for all hydraulic calcium silicate-based sealers (p < 0.05). Twenty seconds of UA increased the mean flow values of Sealer Plus BC and Bio-C Sealer compared to NA (p < 0.05). UA did not influence the radiopacity and solubility of the tested sealers (p > 0.05). UA for 20 seconds enhanced the pH levels and the calcium ion release of Sealer Plus BC and Bio-C Sealer at 168h (p < 0.05). UA for twenty seconds interferes with some physicochemical properties of hydraulic calcium silicate-based sealers.

Design optimization of block horn for ultrasonic joining application using RSM–FEA–GA integration approach

This study investigates the design optimization of block horn used in ultrasonic insertion application. Ultrasonic insertion is the process of joining a metal insert with thermoplastic component. As the performance of ultrasonically produced joint depends upon the uniformity of amplitude of vibration generated by horn, the uniformity of displacement amplitude can be improved by optimizing the block horn design. The horn is computationally designed and acoustically analysed by integrating finite element analysis (FEA) with response surface methodology (RSM). The polynomial model for displacement amplitude is developed using RSM. Further, the design of horn is optimized to improve the displacement amplitude by coupling the developed polynomial model with genetic algorithm (GA) as fitness function. The optimized design is acoustically analysed, the results show that the optimal design yields maximum displacement amplitude of 29.57 µm, and the maximum stress induced in the optimal design is 16.3 MPa, which is much lower than fatigue strength of horn material. As the heat developed at joint is quality indicator, the temperature obtained at joint is measured using data acquisition system (DAQ). The measured temperature is 138°C, which correlates well with displacement amplitude developed by optimal design of block horn. The results of this study revealed that the proposed RSM–FEA–GA integration approach managed to find the optimal combination of design variables, which yields maximum displacement amplitude and results good joint performance.

Main clinical considerations of bioceramic cement in endodontic treatment: a brief systematic review

Introduction: Endodontic treatment is usually indicated when periapical lesions are found, deep caries reach the pulp chamber, or in specific cases of prosthetic rehabilitation. The repair of periapical tissues depends on the total obturation of the root canal system and its hermetic sealing employing physically and biologically compatible materials. Objective: A brief systematic review was carried out to list the main clinical studies on the use of bioceramic cement in endodontic treatments and endodontic surgery. Methods: The rules of the Systematic Review-PRISMA Platform (Transparent reporting of systematic reviews and meta-analysis-HTTP://www.prisma-statement.org/) were followed. The research was carried out from May 2022 to June 2022 and developed based on Scopus, PubMed, Science Direct, Scielo, and Google Scholar. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: Current endodontic surgery has achieved high success rates, through the use of modern techniques such as operative microscopy, ultrasonic inserts, and the choice of good materials to fill the retro filling cavity. MTA was the first bioceramic cement developed and has provided much better results than previously used materials, such as amalgam and Super Eba. This is mainly due to its better sealing properties and its low cytotoxicity. MTA is still the standard material of choice for most endodontists who opt for Endodontic Surgery. However, new bioceramic types of cement are being developed rapidly, trying to improve biological responses, accelerate tissue regeneration, and decrease the rate of residual microorganisms.

Promoting of metallurgical bonding by ultrasonic insert process in steel–aluminum bimetallic castings

Abstract It is challenging to efficiently prepare bimetallic composites with excellent metallurgical bonding. Here, we present a strategy, the ultrasonic insert casting (UIC) process, to solve this problem. The ultrasound cavitation effectively destroys the oxide film and promotes diffusion in the UIC-prepared steel/aluminum bimetallic castings, resulting in a uniform reaction layer between steel and aluminum. The reaction layer contains FeAl3, Al8Fe2Si, and Al4.5FeSi, and has a higher microhardness than the steel/aluminum matrix, with an average thickness of 8 μm. Moreover, the thickness of the reaction layer increases with the improvement of pouring temperature but the thicker reaction layer (approximately 12 μm) does not bring higher strength. The highest shear strength, about 70 MPa, is approximately three times higher than that without ultrasonic treatment. These results indicate a useful strategy for the low cost and high-efficiency preparation of metallurgical boding bimetallic casting.

Impact of the removal of filling material from the post space with ultrasonic insert and magnification with a surgical microscope on the bond strength and adhesive interface of multifilament fiberglass posts onto flat-oval root canals

• Higher BS was found for MFPs compared to conventional fiberglass posts. • Ultrasonic tip filling removal results in higher BS and better adaptation of MFPs. • Highest BS was found for the use of ultrasonic tip with surgical microscopy.

Aerosols generated by high-speed handpiece and ultrasonic unit during endodontic coronal access alluding to the COVID-19 pandemic

To investigate the dispersion and contamination of aerosols generated during coronal access performed by high-speed handpiece and ultrasonic device. To measure the aerosol dispersion, a red dye or an Enterococcus faecalis culture broth inside the bottle of the water system of the dental and ultrasonic unit were used. Bovine extracted teeth were allocated in six groups according to the coronal access: G1: diamond bur in high-speed handpiece (HS) with aspiration (A); G2: ultrasonic (US) inserts with aspiration; G3: combined coronal access with HS and US with aspiration; and G4, G5, and G6 were performed without aspiration (WA). The distance reached by the aerosol with the dye was measured in centimeters, and for environment contamination, agar-plates were arranged at standardized distances for counting colony-forming units (CFU/mL). The ANOVA followed by the Tukey tests were applied (α = 0.05). The coronal access with HS generated higher aerosol dispersion and contamination, even with simultaneous A (P < 0.05), while US generated less aerosol even WA (P < 0.05). The aspiration did not reduce the aerosol statistically. HS is a great source of aerosols in dental clinic during the coronal access and the use of US device should be encouraged.

A Comparative Analysis of the Piezoelectric Ultrasonic Appliance and Trephine Bur for Apical Location: An In Vitro Study.

To compare and contrast the accuracy of piezoelectric ultrasonic insert (PUI) and trephine bur (TB) osteotomy site preparation techniques for apical location. (1) Material and methods: A total of 138 osteotomy site preparations were randomly distributed into one of two study groups. Group A: TB technique (n = 69) and B: PUI technique (n = 69). A preoperative cone-beam computed tomography scan and an intraoral scan were performed and uploaded to implant-planning software to plan the virtual osteotomy site preparations for apical location. Subsequently, the osteotomy site preparations were performed in the experimental models with both osteotomy site preparation techniques and a postoperative CBCT scan was performed and uploaded into the implant-planning software and matched with the virtually planned osteotomy site preparations to measure the deviation angle and horizontal deviation as captured at the coronal entry point and apical end-point between osteotomy site preparations using Student’s t-test statistical analysis. (2) Results: The paired t-test found statistically significant differences at the coronal entry-point deviations (p = 0.0104) and apical end-point deviations (p = 0.0104) between the TB and PUI study groups; however, no statistically significant differences were found in the angular deviations (p = 0.309) between the trephine bur and piezoelectric ultrasonic insert study groups. (3) Conclusions: The results showed that the TB is more accurate than the PUI for apical location.

Comparing Techniques for Removing Fiber Endodontic Posts: A Systematic Review

This systematic review aimed to establish the available techniques for fiber post removal, pointing out where each method stands out evaluating its advantages, and where they fall short indicating the possible harmful effects. This systematic review was registered in PROSPERO (CRD42020193799). A broad search of the electronic databases PubMed, Web of Science, Scopus, and Virtual Health Library was carried out before April 27, 2020, for in vitro studies about techniques for removing fiber posts luted with resin cements of endodontically treated teeth. The methodological quality of included studies was evaluated based on the critical assessment tool for in vitro studies. Thirteen articles were selected and included after applying the inclusion and exclusion criteria. All included studies received an assessment of methodological quality between high and moderate. Most studies used ultrasonic inserts as a strategy to remove fiber posts, manufactured removal kits and drills were also widely used, only one study evaluated the removal capacity of the Er:YAG laser. Ultrasonic inserts seem to lead to a greater working time for removal of the fiber post, tend to generate significant volume changes in the root structure and increase the temperature on the root canal and clean the root canal walls further. Although the results tend to show greater agility in removing fiber posts with manufactured removal kits and the ultrasonic inserts seem to work better in removing fiber remains and luting agent, there is still no consensus in the literature as to which technique is the best. In some cases, clinicians may be faced with the need to remove fiber posts in order to regain access to the root canal due to the need for endodontic retreatment which directly implies the search for the most appropriate removal technique. How to cite this article: Purger LO, Tavares SJO, Martinez RLCH, et al. Comparing Techniques for Removing Fiber Endodontic Posts: A Systematic Review. J Contemp Dent Pract 2021;22(5):587-595.

A novel three-dimensionally printed model to assess biofilm removal by ultrasonically activated irrigation.

To apply an innovative three-dimensionally printed tooth model to investigate the efficacy of three ultrasonically activated irrigation (UAI) systems in removing multispecies biofilms from dentine samples. Three-dimensionally printed teeth with a curved root canal were fabricated with a standardized slot in the apical third of the root to achieve precision fit of human root dentine specimens. Multispecies biofilms including Enterococcus faecalis, Streptococcus mitis and Campylobacter rectus were developed in the root canal for 21days. The canals were allocated to be irrigated with 1% sodium hypochlorite (NaOCl) using a syringe and needle or ultrasonically activated NaOCl with a stainless-steel file (Irrisafe), a conventional nickel-titanium (Ni-Ti) file (CK) or a blue heat-treated Ni-Ti file (Endosonic Blue). Infected root canals irrigated with distilled water served as controls. Bacterial reduction was determined by colony-forming unit (CFU) counting (n=20), whilst biofilms were analysed using confocal laser scanning microscopy (n=7) and field emission scanning electron microscopy. For CFU counting, the independent two-sample t-test (Welch's t-test) was examined to compare overall bacterial reduction amongst groups. For CLSM analysis, the data were analysed using one-way analysis of variance (ANOVA), followed by the Scheffé post hoc test. The p-values <.05 were considered to indicate statistical significance. All groups in which NaOCl was ultrasonically activated had significantly lower CFU values than the syringe-and-needle irrigation and control groups (p<.05). Ultrasonic activation with the stainless-steel file and blue heat-treated Ni-Ti file significantly reduced the biofilm volume compared with other groups (p<.05). Overall, UAI with the blue heat-treated file resulted in the highest antibacterial and biofilm removal efficacy. UAI with different inserts had differential antibiofilm effects. The blue heat-treated Ni-Ti ultrasonic insert resulted in the greatest antibacterial and biofilm removal from dentine in this standardized root canal model.

In Vitro Comparison of Root Surface Treatment Effect between Root Scaling with Ultrasonic Inserts and Gracey Curette and Polishing with Different Cleaning Pastes

The aim of this study was the morphological evaluation of root surfaces subjected to manual (curette) and ultrasonic (conventional and diamond tips) scaling. The surface was then polished with a rubber cup and three medium-sized pastes. Ninety teeth were randomly divided into three groups of 30 and subjected to three different root instrumentation: (1) manual instrumentation with a Gracey® curette; (2) ultrasonic instrumentation with a standard steel tip (Universal Perio S-SERIES: USU, Hu-Friedy, Chicago, IL, USA) at a power equal to 50%; and (3) with a diamond tip (Punta Piezo Serie E Scaling, Hu-Friedy, Chicago, IL, USA) at a power of 20%. Each group of the instrumented teeth was then divided in three subgroups of 10 and subjected to 30 s of rubber polishing with three different polishing pastes with medium grain sizes in single-dose cups: (1) Ultrapro Tx cool mint medium®; (2) Stomyprox media®; and (3) Nupro medium orange®. Polyether root surface replicas were then taken from all 90 samples and analyzed by SEM to evaluate surface morphology after scaling and polishing procedures. All scaling techniques caused an alteration of the root surface without statistically significant difference, whereas polishing resulted in maintenance or improvement of the surface texture.

Removal of fractured endodontic NiTi file in the apical third of the root canal using an alternative approach. A case report

This case report presents an alternative approach for the removal of a fractured endodontic instrument from the apical third of the root canal. A 52-years-old female patient was referred for specialized endodontic treatment of the maxillary left first molar due to the presence of a periapical lesion and root canal calcification. After clinical and radiographic examination, the calcification was confirmed. During biomechanical preparation, the fracture of a size 25/.06 NiTi reciprocating file (ProDesign R) occurred in the apical third of the palatine canal. The patient was informed about the complication and agreed with the attempt to remove the fragment. Firstly, a slight wear of the dentinal walls around the fragment was made using ultrasonic inserts under magnification. Then, a customized extractor was made using a hypodermic needle and a handling file whose mechanism is similar to the removal method previously described by Masserann. For this, the hypodermic needle was inserted in the root canal and the handling file was adapted in the needle lumen, with the function of fixing the fragment and removing it from the canal through the opposite movement performed by the fractured file. After associating the technique with a hypodermic needle and using ultrasound and an operating microscope to perform the procedure, the fragment was successfully removed. The association of techniques to remove fragments using only items already present in the endodontic arsenal can eliminate the need for surgical treatment and improve the prognosis of endodontic treatment through a safe, simple and cost-effective method that can be performed in the endodontic clinical routine.

Evaluation of pain after endodontic retreatment using reciprocating files or ultrasonic inserts for the desobturation of root canals: a randomized clinical study

This randomized clinical trial aimed to evaluate the endodontic retreatment techniques influence using reciprocating files and ultrasonic inserts in relation to the incidence, intensity, and postoperative pain duration. Forty-six patients were randomly assigned into two groups: Reciprocant files (RC group); or the Clearsonic Ultrasonic Insert (CL group;). Participants were asked to report the incidence, duration, and postoperative pain intensity using a visual analog scale (VAS) at 24, 48 and 72 h after retreatment. Fisher’s exact test was used to compare the two methods used regarding postoperative pain. The Mann-Whitney test was used to compare pain intensity, and Friedman’s test was used to assess the time effect on pain intensity. Finally, ordinal logistic regression analysis was used to assess the odds ratio for pain occurrence at a significance level of 5%. The postoperative pain incidence was significantly lower in the CL group in all experimental periods. Comparing the two techniques, pain intensity was significantly lower in the CL group after 24 and 48 h. For the RC group, pain intensity was significantly greater at 24 h compared with the other periods. The technique used in endodontic retreatment can influence postoperative pain.

Studies on dynamic characteristic of stepped horn utilized in ultrasonic insertion process using finite element analysis and experimental methods

In this study, dynamic characteristic of stepped horn profile is investigated theoretically and experimentally in terms of natural frequency, displacement amplitude, stress induced and heat developed at joint interface for improving the performance of ultrasonically fastened joints. The profile of stepped horn is computationally modelled and temperature obtained at the joint interface is predicted using Finite Element Analysis (FEA). Computationally modelled stepped horn is fabricated with Aluminium Alloy (AA 6351) based on the FEA results and temperature at the joint interface is measured using Data Acquisition System (DAQ). Pullout strength of ultrasonically fastened joints utilizing stepped horn is measured using computerized tensile testing machine. Measured temperature is correlated with pullout strength of joint and the design of stepped horn is validated.