Step-down Technique Research Articles

Postoperative pain after endodontic treatment of mandibular molars with two different instrumentation techniques: A randomized clinical trial

Background: This study compared postoperative pain after endodontic treatment of mandibular molars with asymptomatic irreversible pulpitis with the RaCe rotary system and the crown-down versus the step-down technique. Materials and Methods: In this randomized clinical trial, 70 mandibular 1st and 2nd molars with asymptomatic irreversible pulpitis and normal periradicular state were randomly assigned to two groups for single-visit endodontic treatment with RaCe rotary system and the crown-down and the step-down technique (n = 35). Postoperative pain was assessed at 6, 12, 24, 48, 72, and 168 h postoperatively, using a Visual Analog Scale. Data were analyzed using SPSS 17 by repeated measures ANOVA, Chi-square test, independent sample t-test, and lLeast sSignificant Ddifference test. P < 0.05 was considered statistically significant. Results: The two groups were not significantly different regarding the pain scores at any time point (P > 0.05). Within-group comparisons showed a significant reduction in pain score over time, starting from 12 to 168 h, postoperatively (P < 0.05). Conclusion: The crown-down and step-down techniques had no significant difference regarding postoperative pain after endodontic treatment of mandibular molars with asymptomatic irreversible pulpitis with the RaCe rotary system.

The influence of step-down technique on lower extremity mechanics during curb descent

When stepping down from a curb, individuals typically make initial ground contact with either their rearfoot or forefoot. The purpose of this study was to compare vertical ground reaction forces, lower extremity mechanics, and intra-limb work distribution when individuals adopt a rearfoot technique vs. a forefoot technique, during simulated curb descent. Sixteen subjects stepped down from a platform with both a rearfoot and a forefoot technique. Vertical ground reaction forces and sagittal plane joint kinematics and kinetics were examined for the lead limb during the step-down task. Paired t-tests were used for comparison. Subjects demonstrated greater ankle joint power and negative work, and less hip joint power and negative work, with the forefoot technique vs. the rearfoot technique. Total lower extremity negative work was greater for the forefoot technique vs. the rearfoot technique. The percent contribution to the total negative work was greater for the ankle joint, and less for the hip and knee joints, with the forefoot technique vs. the rearfoot technique. The results of this study may provide insight into how curb descent technique can be modified to alter lower extremity loading.

Technical Quality of Root Canal Filling in Preclinical Training at Strasbourg University Using Two Teaching Protocols.

Objectives The aim of this study was to compare two teaching protocols according to the technical quality of root canal therapy (RCT) and the procedural errors occurred in preclinical training. Materials and Methods Two different groups of students were concerned. The first one (G1) performed a crown-down technique to shape the root canal systems and cold lateral condensation technique to fill them. The second one (G2) performed a step-down technique without initial manual scouting to shape the root canal systems, and cold hydraulic condensation technique, to fill them. G2 used clinical operative microscope to check the access cavity preparation. Statistical Analysis The quality of RCTs and procedural errors were recorded and analyzed using chi-squared test and t -test. Results Four hundred sixty-eight root canals from 152 maxillary molars were treated by the G1 students: 46.6% canals were judged as acceptable. Four hundred sixty-nine root canals from 152 mandibular molars were treated by G1: 58.8% canals were judged as acceptable. Five hundred fifteen root canals from 156 maxillary molars were treated by G2 students: 84.1% canals were judged as acceptable. Four hundred ninety-three root canals from 156 mandibular molars were treated by G2: 90.9% canals were judged as acceptable. Among the errors, the incidence of “ledges” and “fractured instruments” was statistically significant in G1 compared with G2, both on maxillary and on mandibular molars. Conclusions The molar RCTs performed by G2, who got benefit from the new teaching protocol, resulted in a better quality of root filling and in fewer procedural errors compared with the molar RCTs performed by G1.

Comparison of Step-Down Versus Step-Back Hand Preparation Technique of Root Canals

Objective: The aim of this study was to compare the frequency of flare-up in terms of post-operative pain and/or swelling, after step down and step back root canal preparation technique.
 Methods: A randomized clinical trial was conducted from 28th October 2011 to 27th April 2012 in de'Montmorency College of Dentistry, Lahore.150 patients with irreversible pulpitis were randomly al- lotted in two equal groups (Group A and B) and root canals were prepared with step-down andstep- back technique respectively. Pain was recorded using visual analogue scale on 1st, 7th and 14th post-operative day. Data was analysed using SPSS version 17.0.
 Results: In Group A, 67 patients had no flare-up and 8 patients had flare-up on 14th postoperative day. In Group B, 57 patients had no flare-up and 18 patients had flare-up on 14th postoperative day. Out of 150 patients 26 (17.33%) showed flare-up and 124 (82.66%) showed no flare-up. The overall flare-up in Group A was 10.6% and in Group B was 24% after 14 days.
 Conclusions: Step-down technique is better for root canal preparation as evaluated by the comparison of flare-up by step-down and step-back techniques.

Root Anatomy of Mandibular Second Premolars in French Subpopulation: A Retrospective Observational Case Series.

Aims:The purpose of this in vivo study is to illustrate endodontic anatomical variants in French subpopulations of human mandibular second premolars to show if the literature matches our findings.Setting and Design:This was an observational retrospective study.Subjects and Methods:This study was performed from September 2016 to September 2017. It was conducted on 56 successive cases of root canal therapies on the mandibular second premolars. All procedures were done in conformity with current state-of-the-art practices in endodontics. These included rigorous clinical and radiographic preaccess analysis, appropriate tooth restoration to insure watertight rubber dam installation, surgical microscopic manipulations for precision, systematic use of ultrasonic endodontic tips to manage cavity access preparation, and step-down technique to shape the root canal systems.Statistical Analysis Used:Fifty-six mandibular second premolars were treated: 76.8% had one canal, and 23.2% had two or more canals.Conclusions:The incidence of two or more canals on mandibular second premolars could be underestimated as our results show. To prevent any missing canals, clinicians must have a perfect knowledge of anatomic variants of the root canal system. Moreover, the systematic use of a surgical microscope, ultrasonic endodontic tips, and a modern step-down technique should facilitate and standardize access cavity preparation, canal localization, and instrumentation.

An In Vivo Study: Location and Instrumentation of the Second Mesiobuccal Canal of the Maxillary Second Molar

The first purpose of this retrospective observational in vivo study was to determine the incidence of the second mesiobuccal canal (MB2) in maxillary second molars. The second purpose was to propose a modern shaping procedure able to transform a difficult canal, like MB2, into a normal canal. This study was led from September 2016 to December 2017, for 15 months. It was conducted on fifty-seven successive cases of root canal therapy on maxillary second molars. All procedures were done in conformity with the current state of the art practices in endodontics. These included rigorous clinical and radiographic pre-access analysis, appropriate tooth restoration to ensure watertight rubber dam installation, surgical microscopic manipulations for precision, the systematic use of ultrasonic endodontic tips to manage the access cavity preparation, and a modern step down technique to shape MB2. Fifty-seven maxillary second molars were treated: 3.5% had one canal, 7.0% two canals, 24.6% three canals; 64.9% four canals (MB2 presence). Weine's method was used to classify mesiobuccal root canal morphology: 27.4% had a type I canal configuration, 35.3% type II, 37.2% type III canal configuration. The perfect knowledge of endodontic anatomy, a painstaking pre-access analysis of the preoperative radiographs, the systematic identification of the CEJ, using a periodontal probe, the use of surgical microscope coupled with the use of specific endodontic ultrasonic tips and the use of a modern step-down technique allows a high accuracy of the access cavity preparation, canal localization and instrumentation. The rate of MB2 localization and instrumentation on maxillary second molars by our surgical protocol is high. The clinician should take the necessary time to locate and negotiate the MB2. The lack of its location can provoke the failure of endodontic treatment.

Effects of different root canal preparation techniques on premolars endodontic interappointment pain

Objective To study the clinical effects of different methods on endodontic inter appointment pain(EIAP) happened to the patients after premolar root canal preparations. Methods 152 teeth from 134 patients with acute or chronic pulpitis or apical periodontitis were randomly divided into T group and K group, used TiLos mixed root canal preparation system with step-down technique and stainless steel K file with step-back technique respectively to prepare root canal.Afterwards, the incidence rates of EIAP were observed and recorded. Results The incidence rates of EIAP in T group and K group were 6.17% and 21.11%, respectively.There was statistically significant difference between the two groups (χ2=7.404, P<0.01). Conclusion TiLos mixed root canal preparation system with step-down technique to prepare root cancal can reduce the incidence rate of EIAP. Key words: Root canal preparation; Toothache; TiLos mixed root canal preparation system; Step-down technique; Step-back technique; Premolar

Error estimation, validity and best practice guidelines for quantifying coalescence frequency during emulsification using the step-down technique.

Coalescence during emulsification has a significant effect on the outcome of the process, especially for the high volume fractions of disperse phase common in food and pharmaceutical processing. Controlling emulsification requires that the extent of coalescence during different conditions can be quantified. The step-down technique is the most commonly used method for measuring coalescence frequency during emulsification. However, the validity of the method has been questioned. No in-depth theoretical validation or best practice guidelines have been provided for the step-down technique, or for any of the suggested alternative methods.This contribution derives error estimates for three non-idealities present in every step-down experiment: i) limited sampling rate, ii) non-instantaneous step-down and iii) residual fragmentation after the step. It is concluded that all three factors give rise to systematic errors in estimating coalescence rate. However, by carefully choosing experimental settings, the errors can be kept small. The method, thus, remains suitable for many conditions. Best practice guidelines for applying the method are given, both generally, and more specifically for stirred tank oil-in-water emulsification.

Survival and periapical health after root canal treatment with carrier-based root fillings: five-year retrospective assessment.

This retrospective study explored survival and periapical healing outcomes in teeth root filled with Thermafil obturators. Root canals of 213 teeth (94 subjects, mean age 48±13years), instrumented with a step-down technique, irrigated with 5% NaOCl and 10% EDTA and filled with Thermafil and AH Plus sealer, were involved in a recall programme. Teeth were retrospectively re-examined after 5±1years in a controlled environment. Clinical and radiographic data that were collected included the following: preoperative Periapical Index (PAI) score and signs/symptoms, treatment type, root filling length and presence/absence of voids, restoration type, follow-up PAI score and signs/symptoms. Teeth were considered 'healthy' (PAI≤2, no signs/symptoms) or 'diseased' (PAI≥3, signs/symptoms present, retreated, extracted for endodontic reasons). Two PAI-calibrated examiners assessed outcomes blinded to preoperative status. Bivariate and multilevel analyses were performed at level of patient and tooth (α=5%). Of 213 teeth treated, 187 (88%) survived and 26 were extracted, six (3%) for persistent endodontic infection (considered 'diseased'), and 20 (9%) for root fracture, periodontal disease or coronal fracture (excluded from analysis). Whilst survival was significantly associated with tooth type (P=0.015), type of treatment (P=0.012) and pulpal/periapical diagnosis (P=0.035), none of these variables were substantiated as survival predictors by the multilevel analysis. A total of 164 of 193 teeth (85%) were assessed as 'healthy', with significantly higher (chi-square; P<0.04) 'healthy' rates for teeth with PAI score ≤2 and root fillings of adequate length. Multilevel analysis identified PAI score ≤2 (P=0.002) as the only predictor of periapical health. In this 5±1year retrospective assessment, survival and healing rates after root canal treatment with Thermafil root fillings were comparable to those previously reported for conventional root filling techniques.

The impact of BTI aging on the reliability of level shifters in nano-scale CMOS technology

On-chip level shifters are the interface between parts of an Integrated Circuit (IC) that operate in different voltage levels. For this reason, they are indispensable blocks in Multi-Vdd System-on-Chips (SoCs). In this paper, we present a comprehensive analysis of the effects of Bias Temperature Instability (BTI) aging on the delay and the power consumption of level shifters. We evaluate the standard High-to-Low/Low-to-High level shifters, as well as several recently proposed level-shifter designs, implemented using a 32nm CMOS technology. Through SPICE simulations, we demonstrate that the delay degradation due to BTI aging varies for each level shifter design: it is 83.3% on average and it exceeds 200% after 5years of operation for the standard Low-to-High and the NDLSs level shifters, which is 10× higher than the BTI-induced delay degradation of standard CMOS logic cells. Similarly, we show that the examined designs can suffer from an average 38.2% additional power consumption after 5years of operation that, however, reaches 180% for the standard level-shifter and exceeds 163% for the NDLSs design. The high susceptibility of these designs to BTI is attributed to their differential signaling structure, combined with the very low supply voltage. Moreover, we show that recently proposed level-up shifter design employing a voltage step-down technique are much more robust to BTI aging degradation. To the best of our knowledge, this is the first work addressing the effects of BTI on the the delay and power consumption of level shifters.

Mutational Analysis of DNAse I Gene in Pakistani SLE Patients

Systemic Lupus Erythematosus (SLE) is one of the classic examples of autoimmune diseases among human beings and is a rare disease in Pakistani population. Clinically, it is a quite diverse and complicated autoimmune disease in a sense that it involves multiple organs of the body and mimics other diseases as well. Mutational analysis of DNAse I gene exon 8 was performed because most of the mutations were reported in these regions with reference to SLE. Genes were amplified by Step-down PCR technique in order to get the bands of our interest. Extracted DNA bands were sequenced to analyze mutations. Thirteen SLE samples showed a missense mutation in DNAse I gene. The codon CAA changed to CGA (+2373 A>G) so the glutamine amino acid was replaced by arginine at position 244 of Deoxyribonuclease I protein.

Costing of commune health station visits for provider payment reform in Vietnam

Expanding effective coverage in Vietnam will require better use of available resources and placing higher priority on primary care. The way providers are currently paid does not give priority to primary care and does not reflect the costs of delivering services. This paper aims to estimate the unit costs of primary care visits at commune health stations (CHS) in selected areas in Vietnam. Seventy-six CHS from two provinces in northern Vietnam were studied. Costs were calculated from the perspective of the CHS using the top-down costing using the step-down cost accounting technique in order to estimate the full cost of delivering services. On average, the cost of one outpatient visit in mountainous, rural and urban CHSs was VND 49,521 (US$2.40), VND 41,375 (US$2.01) and VND 39,794 (US$1.93), respectively. Personnel costs accounted for the highest share of total costs followed by medicines. The share of operating costs was minimal. On average, CHSs recover 18.9% of their total cost for an outpatient visit from social insurance payments or fees that can be charged patients. The results provide valuable information for policy-makers as they revise the provider payment methods to better reflect the costs of services and give greater priority to primary care.

The work and influence of the Raghudeep Eye Clinic, Ahmedabad, India

Interview by Tanya Stezhka, Commissioning EditorDr Abhay R Vasavada completed his FRCS in 1980 from the Royal College of Surgeons, England, and started Raghudeep Eye Clinic, as a cataract speciality clinic in 1984 in Ahmedabad, India. He has been instrumental in positioning cataract management as a subspeciality, and in raising the bar for management outcomes, be it the popularization of intraocular lens (IOLs) or establishing phacoemulsification as a standard of care, in the entire Asia-Pacific region. His expertise extends to managing the most complex and challenging cataracts in adults and children. He has made important contributions to the understanding and practise of cataract surgery like: emphasizing the role of balancing phaco fluidics (step-down technique); innovating a versatile chop technique (step-by-step chop in situ and lateral separation); defining paradigms for challenging cases like dense cataracts, small pupils and subluxated cataracts; devising the ‘inside-out delineation’ technique for posterior polar cataracts; recognizing the entity of ‘cortico-capsular adhesions’; and many more. He firmly believes that quality care should extend to all strata of society. He runs a center in a small town, Dholka, where the highest quality of eye care is provided to lesser privileged sections of society at nominal charges. Research is his passion right from his early days. He set up the Iladevi Cataract & IOL Research Center (ICIRC), a center providing basic research facility in 1991. Today, ICIRC is a Government of India recognized research laboratory dedicated to basic research and translational research pertaining to commonly prevalent eye conditions. He is a distinguished member of different ophthalmic bodies, including the International Council of Ophthalmology (ICO), American Academy of Ophthalmology (AAO), American Society of Cataract and Refractive Surgery (ASCRS), European Society of Cataract and Refractive Surgeons (ESCRS), Academia Ophthalmologica Internationalis (AOI), Asia Pacific Academy of Ophthalmology (APAO), Asia-Pacific Association of Cataract & Refractive Surgeons (APACRS) and others.His contribution to ophthalmology has been recognized worldwide. Some of the most prestigious awards he has received include the Binkhorst Medal lecture by the ASCRS.

Endodontic mishaps among undergraduate dental students attending King Saud University and Riyadh Colleges of Dentistry and Pharmacy

Aim: The purpose of this study was to investigate procedural errors occurring during conventional root canal treatment performed by undergraduate students attending two dental schools in Riyadh, Saudi Arabia. Materials and Methods: A cross-sectional survey was distributed to 600 undergraduate dental students from the Riyadh Colleges of Dentistry and Pharmacy (RCsDP) and the College of Dentistry at King Saud University (KSU) in Riyadh, Saudi Arabia. Participants were senior male and female dental students from the 4 th to 6 th years at RCsDP and the 4 th to 5 th years at KSU. Participants were asked to record their endodontic mishaps; these data were analyzed using IBM SPSS software. Chi-square (X2 ) tests were carried out to compare pairs of groups; significance was established at 5% (p < 0.05). Results: The percentage of endodontic mishaps was 68%. The majority of students who made endodontic mishaps were male (73.6%) (X2 =8.74, =0.002). Most mishaps occurred in the posterior area (63.96%) and those with curved roots (39.46%). Conclusion: The frequency of endodontic mishaps occurring at both schools was found to be higher in 4 th year students from KSU, but this dramatically decreased in the 5 th year. Variable results were obtained from the RCsDP 4 th year students, but they did not improve in the 5 th and 6 th year. We believe that the use of step-down techniques utilizing flexible nickel titanium files and more training in the lab will cause potentially fewer procedural complications at both schools.

A Step-Down Technique to Calibrate AC Current Down to 10 μA Using a Precision 10 mA Current Shunt

This paper describes a calibration procedure for AC current measurements at 1 mA, 100 µA and 10 μA using a NIST-calibrated 10 mA current shunt as a reference standard. The procedure involves a step-down technique using the reference transfer standards (RTS) as a precision current divider. The RTS is used at values of 370 Ω, 3.3 and 30 kΩ to provide the intended currents. Uncertainty calculations are estimated for calibrating the AC current of 10 mA, 1 mA, 100 μA and 10 μA at 55 Hz and 1 kHz. The expanded uncertainties are around the values of 37 nA and 1 nA for the ranges of 1 mA–10 μA respectively.

BREAST ULTRASOUND IMAGE SEGMENTATION BASED ON PARTICLE SWARM OPTIMIZATION AND THE CHARACTERISTICS OF BREAST TISSUE

Breast cancer occurs in over 8% of women during their lifetime, and is the leading cause of death among women. Sonography is superior to mammography because it has the ability to detect focal abnormalities in the dense breasts and has no side-effect. In this paper, we propose a novel automatic segmentation algorithm based on the characteristics of breast tissue and eliminating particle swarm optimization (EPSO) clustering analysis. The characteristics of mammary gland in breast ultrasound (BUS) images are analyzed and utilized, and a method based on step-down threshold technique is employed to locate the mammary gland area. The EPSO clustering algorithm utilizes the idea of "survival of the superior and weeding out the inferior". The experimental results demonstrate that the proposed approach can segment BUS image with high accuracy and low computational time. The EPSO clustering method reduces the computational time by 32.75% compared with the standard PSO clustering algorithm. The proposed approach would find wide applications in automatic lesion classification and computer aided diagnosis (CAD) systems of breast cancer.

Comparative study of shaping efficiency in C-shaped canals of mandibular second molars

To investigate the shaping efficiency of three instrumentation techniques in the C-shaped canals. Sixty extracted mandibular second molars with C-shaped canals were selected and cross-sectioned at 2, 5, 8 mm from the apex by using a muffle system as described by Bramante. The teeth containing C-shaped canals were randomly divided into three groups, respectively instrumented using stainless steel K-files in step-back and step-down techniques, and ProTaper series in crown-down technique. The digital images of canal cross-sections pre- and post-instrumentation were photographed to evaluate the proportion and position of uninstrumented area Working length loss and perforation were recorded. Data were analyzed using ANOVA. Step-down technique gained smaller uninstrumented area in the coronal third of the canals, while step-beck technique gained the same results in the apical third (P < 0.05). Uninstrumented proportion in apical part was significantly higher than in the middle and the coronal (P < 0.05). Instrumenting type I canal as 2 or 3 separated canals was likely to reduce the miss. There were three perforations in manual stainless steel K-file groups. Early opening the coronal part of C-shaped canal, shaping C-shaped canal as two or three separated canals and instrumenting the apical part with step-back technique, seemed to be the effective methods to avoid miss.

Metformin Usage in PCOS Patients Undergoing IVF Does Not Improve Outcome When Utilizing a Dual Suppression Stimulation Protocol

OCP/ GnRH-agonist dual suppression combined with low-dose gonadotropin therapy has been shown to safely and effectively induce ovulation for IVF in PCOS patients. There is increasing data demonstrating the role of metformin for ovarian stimulation. The objective of this study was to review our IVF outcome during treatment with the dual suppression low-dose gonadotropin protocol in PCOS patients comparing those treated with or without metformin. Retrospective review of PCOS patients undergoing IVF evaluating the efficacy of Metformin when added to the dual suppression protocol. We studied patients with PCOS undergoing IVF-embryo transfer with the dual suppression protocol consisting of OCP pretreatment prior to GnRH-agonist suppression and low dose gonadotropin stimulation (no more than 3 ampules) during a four year period (1999-2003). Standard step-down techniques were utilized. A clinical pregnancy was defined as the presence of fetal cardiac activity. An ongoing pregnancy was defined as a pregnancy greater than 20 weeks of gestation. Statistical analysis included Chi-square analysis and non-parametric testing as appropriate. A total of 247 IVF cycles utilizing the OCP- GnRH-agonist- low dose gonadotropin protocol were started. The mean age of patients was 32.7±3.8 years, and the mean body mass index was 24.9±5.3. Of those that were cancelled prior to retrieval(13/247, 5.3%), 6 (46.2%) were cancelled due to poor response, and 7 (53.8%) were cancelled due to drop in serum E2 level. 221 patients underwent a transfer. Of the cycles that did not proceed with ET, 2 cycles (15.4%) were aborted due to hyperstimulation risk, and embryos were cryopreserved. The mean implantation rate was 37.9%. Overall the positive pregnancy rate , clinical pregnancy rate, and ongoing pregnancy rate per ET were 75.6%, 68.3% and 59.3%, respectively. In 43 cycles (17.4%), patients were treated with metformin. These patients had a higher mean BMI (p<.001) than those not treated with metformin. Cycles in which patients were treated with metformin did not differ significantly from those in which patients were not treated with metformin in terms of outcomes such as maximum E2, number of oocytes retrieved, number of fertilized embryos and number of embryos transferred. Cycles in which patients were treated with Metformin required more ampules of gonadotropins than those in which patients were not treated with Metformin (23.9±8.1 vs. 21.2±8.0, p<.05). However, when corrected for BMI, there was no difference in number of ampules required. Tabled 1 We have demonstrated a successful ovulation induction protocol of PCOS women undergoing IVF. The addition of Metformin did not appear to improve outcome parameters. Further work is required to elucidate the value of Metformin in IVF stimulation utilizing the OCP- GnRH-agonist- low dose gonadotropin protocol.

IVF Outcome in Women 45 Years and Older Utilizing Autologous Oocytes: Success is Limited to Women at 45 years of Age With a Good Response

IVF Outcome in Women 45 Years and Older Utilizing Autologous Oocytes: Success is Limited to Women at 45 years of Age With a Good Response

The Effect of Passive Ultrasonic Activation of 2% Chlorhexidine or 5.25% Sodium Hypochlorite Irrigant on Residual Antimicrobial Activity in Root Canals

Ninety-four single-canal roots were prepared using the step-down technique. Forty-two canals were irrigated with 2% chlorhexidine, 42 canals with 5.25% sodium hypochlorite (NaOCl), and 10 control canals with phosphate-buffered saline (PBS). The chlorhexidine and NaOCl groups were each then equally divided into a final irrigation group and a 1-min passive ultrasonic irrigation group. Canals were enlarged with a Parapost drill. The apical 3-5 mm was covered with nail polish. Canals were rinsed with PBS, dried, refilled with PBS, and stored. At 6 h, 20 microl of fluid was pipetted from each canal and placed into wells on agar plates, which were inoculated with Streptococcus sanguinis. The plates were incubated, and zones of inhibition were measured. Sampling was repeated at 24, 48, 72, 96, 120, 144, and 168 h. Residual antimicrobial activity with 2% chlorhexidine was statistically significantly superior to 5.25% NaOCl with irrigation alone and with final passive ultrasonic activation (p < 0.001). Chlorhexidine experimental groups demonstrated residual antimicrobial activity for as long as 168 h.