Outcome of root canal retreatment filled with gutta-percha techniques: A systematic review and meta-analysis

OBJECTIVE

The present systematic review and meta-analysis aimed to evaluate the success rate of root canal retreatment filled with gutta-percha and the variables related to retreatment success.

DATA

The PRISMA guidelines were followed for the present review. The study protocol was registered in the International Prospective Database of Systematic Reviews (PROSPERO CRD42021283134). Risk assessment was performed using the Newcastle-Ottawa scale. Funnel plots were used to detect publication bias and asymmetry was assessed using Egger's tests.

SOURCES

PubMed, Scopus, ScienceDirect, Cochrane, and additional sources were searched.

STUDY SELECTION

Studies published until 10 December 2022. Clinical studies evaluating the success of root canal retreatment filled with gutta-percha with at least a 1-year follow-up were selected.

RESULTS

Ten studies and one unpublished study fulfilled the inclusion criteria for quantitative analysis. The success rate of non-surgical root canal retreatment was 71% (95% CI: 66%-76%) with strict criteria and 87% (79% - 93%) with loose criteria for 1-3 years of follow-up, and 77% (66% - 86%) with strict criteria for a 4-5 years of follow-up. Endodontically retreated teeth with periapical lesions had a lower success rate under strict criteria. The tooth type, dental arch, initial periapical index (PAI) score, and the number of visits also affected the treatment success rate under strict criteria. For the loose criteria, teeth with larger periapical lesions and higher initial PAI scores had a lower success rate.

CONCLUSIONS

According to the present systematic review and meta-analysis, non-surgical root canal retreatment results in favourable outcomes. The presence of a periapical radiolucency, periapical lesions >5mm, a higher initial PAI score, multiple-visit retreatments, and mandibular and molar teeth resulted in a lower success rate.

CLINICAL SIGNIFICANCE

Non-surgical root canal retreatment filled with gutta-percha techniques is a relatively predictable procedure with a high success rate. Several variables can affect retreatment success, mainly the presence and size of a periapical lesion and the type of tooth.

Microcomputed tomographic evaluation of 6 NiTi files on the pericervical dentin and the smallest dentin thickness zones in mesial root canals of mandibular molars: an in vitro study

OBJECTIVE

The aim of this study was to evaluate six files on the pericervical dentin (PCD) and the smallest dentin thickness zones (SDTZ) in mesial root canals of mandibular molars.

MATERIALS AND METHODS

Sixty mandibular molars with two mesial canals and Vertucci configuration were aleatory allocated in 6 experimental groups of 10 molars and 20 root canals. Specimens were scanned before instrumentation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WaveOne Gold (WG), group 2 with Reciproc Blue (RB), group 3 with TRUShape (TS), group 4 with XP-endo Shaper (XP), group 5 with iRace (IR), and group 6 with TruNatomy (TN). After instrumentation, the molars were scanned again and the images recorded were reconstructed with the NRecon v.1.7 (Bruker micro-CT) and analyzed with CTAn v.1.20.8 software (Bruker micro-CT) quantifying the changes produced in the surface, volume, structure thickness, SMI, and centroids at the Pericervical Dentin area of the root canals (PCD) located from the root canal orifices at the floor of the pulp chamber to 4 mm in the apical direction, and the changes in the Smallest Dentin Thickness Zones (SDTZ) located (from the furcation to 4 mm and 7 mm in the apical direction. The data obtained were compared using Wilcoxon and ANOVA with a 5% significance level.

RESULTS

XP and TN were similar in all the parameters (P >.05) at the PCD, but TN showed significant differences from WG, RB, TS, and IR (P <.05), while XP showed significant differences from WG (P <.05) in volume, surface, and structure thickness. Regarding the changes in the SDTZ, the amount of dentin removed was similar between the groups in both canals at the middle 1/3, at the cervical 1/3 for MB canals, and in ML canals for RB, TS, XP, IR, and TN (P>.05). The action of WG was significantly different from that of XP and TN in the cervical 1/3 of the ML canal (P <.05).

CONCLUSIONS

XP and TN rotatory files with small taper and volume maintained better with minor changes at the PCD and SDTZ, while WG reciprocation file produced the largest change. All the files were maintained centered at the PCD, and their performances were safe with a minimal thickness higher 0.5 mm at the SDTZ, and without risk of perforation.

TRIAL REGISTRATION

No clinical trials were indicated in this study.

CLINICAL RELEVANCE

The choice of endodontic files is a relevant factor in the conservative performance of root canal treatments.

Calcium hydroxide-loaded nanoparticles dispersed in thermosensitive gel as a novel intracanal medicament

AIM

Design, produce and assess the viability of a novel nanotechnological antibacterial thermo-sensible intracanal medicament This involves encapsulating calcium hydroxide (Ca(OH)2 ) within polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) and dispersing them in a thermosensitive gel (Ca(OH)2 -NPs-gel). In addition, perform in vitro and ex vivo assessments to evaluate tissue irritation and penetration capacity into dentinal tubules in comparison to free Ca(OH)2 .

METHODOLOGY

Reproducibility of Ca(OH)₂-NPs was confirmed by obtaining the average size of the NPs, their polydispersity index, zeta potential and entrapment efficiency. Moreover, rheological studies of Ca(OH)2 -NPs-gel were carried out with a rheometer, studying the oscillatory stress sweep, the mean viscosity value, frequency and temperature sweeps. Tolerance was assessed using the membrane of an embryonated chicken egg. In vitro Ca(OH)2 release was studied by direct dialysis in an aqueous media monitoring the amount of Ca(OH)2 released. Six extracted human teeth were used to study the depth of penetration of fluorescently labelled Ca(OH)2 -NPs-gel into the dentinal tubules and significant differences against free Ca(OH)2 were calculated using one-way anova.

RESULTS

Ca(OH)2 -NPs-gel demonstrated to be highly reproducible with an average size below 200 nm, a homogeneous NPs population, negative surface charge and high entrapment efficiency. The analysis of the thermosensitive gel allowed us to determine its rheological characteristics, showing that at 10°C gels owned a fluid-like behaviour meanwhile at 37°C they owned an elastic-like behaviour. Ca(OH)2 -NPs-gel showed a prolonged drug release and the depth of penetration inside the dentinal tubules increased in the most apical areas. In addition, it was found that this drug did not produce irritation when applied to tissues such as eggs' chorialantoidonic membrane.

CONCLUSION

Calcium hydroxide-loaded PLGA NPs dispersed in a thermosensitive gel may constitute a suitable alternative as an intracanal antibacterial medicament.

Novel strategies enhancing endodontic disinfection: Antibacterial biodegradable calcium hydroxide nanoparticles in an ex vivo model

Due to the high failure rates associated to endodontic disinfection, this study aimed to investigate the antibacterial properties of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with Ca(OH)2 for endodontic disinfection procedures. Ca(OH)2 NPs production and physicochemical characterization were carried out as well as multiple antibacterial tests using three bacterial strains and an ex vivo model of endodontic infection with extracted human teeth. Agar diffusion test and broth dilution determined the inhibition growth zones (n = 5) and the minimal inhibitory concentration (MIC, n = 5), respectively. Cell viability was assessed using Live/Dead staining with confocal microscopy (n = 5). Data was analysed using ANOVA followed by post-hoc analysis. After 24 h of incubation, Ca(OH)₂ NPs demonstrated a MIC of 10 µg/mL for Porphyromonas gingivalis (p < 0.001) and Enterococcus faecalis and 5 µg/mL for Fusobacterium nucleatum (p < 0.001). Although the agar diffusion test did not exhibit any inhibition area for Ca(OH)2 nor for Ca(OH)₂ NPs, this was probably due to the buffering effect of the agar medium. However, the antibacterial capacity was confirmed in an ex vivo model, where instrumentalized teeth were infected with Enterococcus Faecalis and treated after 28 days of culture. A significant reduction in bacterial metabolic activity was confirmed for Ca(OH)2 NPs (40 % reduction with a single dose) and confirmed by Live/Dead staining. In conclusion, Ca(OH)₂-loaded PLGA NPs present promising antibacterial efficacy for endodontic disinfection procedures.

Outcome of non-surgical root canal retreatment procedures obturated with warm gutta-percha techniques: A longitudinal clinical study

OBJECTIVE

To evaluate the success rate of non-surgical root canal retreatment at the 2- to 3-year follow-up and identify the possible prognostic factors.

METHODS

Patients who underwent root canal retreatment at a university dental clinic were contacted for clinical and radiographic follow-up. The retreatment outcomes in these cases were based on clinical signs, symptoms, and radiographic criteria. Inter- and intra-examiner concordance were calculated using Cohen's kappa coefficient. The retreatment outcome was dichotomized into success or failure according to strict and loose criteria. The radiographic success criteria consisted of complete resolution or absence of a periapical lesion (strict criteria) or a reduction in the size of an existing periapical lesion at recall (loose criteria). χ² tests were used to evaluate possible variables associated with retreatment outcomes (age, sex, tooth type, location, contact points, periapical status, quality of previous and final root canal filling, previous and final restoration, number of visits, and complications).

RESULTS

Overall, 129 teeth (113 patients) were included in the final evaluation. The success rate was 80.6% under strict criteria and 93% under loose criteria. Molars, teeth with an initially higher periapical index (PAI) score, and teeth with > 5 mm periapical radiolucency had a lower success rate according to the strict criteria model (p < 0.05). When the loose success criteria were used, teeth with larger (> 5 mm) periapical lesions and those that had been perforated during retreatment showed a lower success rate (p < 0.05).

CONCLUSIONS

The present study demonstrated that non-surgical root canal retreatment is a highly successful procedure after an observation period of 2-3 years. Treatment success is primarily affected by the presence of periapical lesions.

Nanoparticles in Endodontics Disinfection: State of the Art

Endodontic-related diseases constitute the fourth most expensive pathologies in industrialized countries. Specifically, endodontics is the part of dentistry focused on treating disorders of the dental pulp and its consequences. In order to treat these problems, especially endodontic infections, dental barriers and complex root canal anatomy should be overcome. This constitutes an unmet medical need since the rate of successful disinfection with the currently marketed drugs is around 85%. Therefore, nanoparticles constitute a suitable alternative in order to deliver active compounds effectively to the target site, increasing their therapeutic efficacy. Therefore, in the present review, an overview of dental anatomy and the barriers that should be overcome for effective disinfection will be summarized. In addition, the versatility of nanoparticles for drug delivery and their specific uses in dentistry are comprehensively discussed. Finally, the latest findings, potential applications and state of the art nanoparticles with special emphasis on biodegradable nanoparticles used for endodontic disinfection are also reviewed.

Calcium hydroxide-loaded PLGA biodegradable nanoparticles as an intracanal medicament

AIM

To develop a formulation in which calcium hydroxide (Ca(OH)₂) was successfully loaded into poly(lactic-co-glycolic acid) (PLGA) biodegradable nanoparticles (NPs) to be used in the field of endodontics as an intracanal medicament, including NP optimization and characterization, plus drug release profile of the NPs compared with free Ca(OH)₂. Additionally, the depth and area of penetration of the NPs inside the dentinal tubules of extracted teeth were compared with those of the free Ca(OH)₂.

METHODOLOGY

Ca(OH)₂ NPs were prepared using the solvent displacement method. NPs was optimized with a central composite design to obtain a final optimized formulation. The morphology of the NPs was examined under transmission electron microscopy (TEM), and characterization was carried out using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). The drug release profile of the Ca(OH)₂ NPs and free Ca(OH)₂ was evaluated up to 48 h. Finally, the depth and area of penetration inside the dentinal tubules of extracted teeth were examined for both the Ca(OH)₂ NPs and free Ca(OH)₂ using the Mann-Whitney U test to determine any significant differences.

RESULTS

Utilizing the optimized formulation, the Ca(OH)₂ NPs had an average size below 200 nm and polydispersity index lower than 0.2, along with a highly negative zeta potential and suitable entrapment efficiency percentage. The spherical morphology of the Ca(OH)₂ NPs was confirmed using TEM. The results of the XRD, FTIR and DSC revealed no interactions and confirmed that the drug was encapsulated inside the NPs. The drug release profile of the Ca(OH)₂ NPs exhibited a prolonged steady release that remained stable up to 48 h with higher concentrations than the free Ca(OH)₂. After examination by confocal laser scanning microscopy, Ca(OH)₂ NPs had a significantly greater depth and area of penetration inside dentinal tubules compared with the free drug.

CONCLUSIONS

Ca(OH)₂-loaded PLGA NPs were successfully optimized and characterized. The NPs exhibited a prolonged drug release profile and superior penetration inside dentinal tubules of extracted teeth when compared to Ca(OH)₂ .

Cone-beam Computed Tomographic Analysis to Detect the Association between Primary and Secondary Endodontic Infections and Mucosal Thickness of Maxillary Sinus

INTRODUCTION

This retrospective study used cone-beam computed tomographic (CBCT) imaging to evaluate the differences in the mucosal thickness of the Schneiderian membrane in primary and secondary endodontic lesions.

METHODS

A total of 121 CBCT scans were analyzed. Clinical features such as sex, age, size and volume of the periapical lesion, dimension of the bone, morphology, and relationship between the roots and the mucosal thickness were recorded and analyzed in primary and secondary endodontic lesions in CBCT sagittal and coronal planes. Data were analyzed using the chi-square test, the Mann-Whitney U test, and multiple logistic regression (P < .05).

RESULTS

Statistical analysis revealed no significant differences in membrane thickness between the primary and secondary lesions in the sagittal and coronal planes (P = .08 and .06). Differences between age groups were statistically significant in both groups (P < .05). The volume of the periapical lesions of the secondary endodontic lesions were statistically greater than that of the primary lesions (P < .05). Mucosal thickness prevalence increased when the volume of the lesion was greater, and the bone dimension was narrower in maxillary second premolars and first and second molars. Teeth with 2 or more affected roots were directly related to increased sinus mucosa thickening.

CONCLUSIONS

CBCT images showed no differences in mucosal thickening between primary and secondary endodontic lesions.

Safety concerns of Piezoelectric Units in Implantable Cardioverter Defibrillator

PURPOSE

Evidence-based research appears to conflict on the potential risk of electromagnetic interference (EMI) between piezoelectric units (Pzs) and implantable cardioverters and defibrillators (ICDs). The purpose of this study was to observe whether the EMI produced by Pzs is hazardous for ICDs.

MATERIALS AND METHODS

A cross-sectional study of 6 Pzs was conducted in vitro for EMI using an ICD system. To simulate the human body's electrical resistance, electrographic recordings were made of the ICD and lead that were immersed in a bath of saline solution. The variables investigated were the presence of EMI, the distance between the ICD and the Pz, and signal intensity, damage, and type of damage to the ICD and lead. Each series of tests was repeated 3 times, beginning with a 15-second baseline recording (control), until all recording conditions had been covered. Each Pz was recorded under the following conditions: less than 2 cm from the tip of the ICD lead; less than 2 cm from the ICD; less than 2 cm from the lead body and coils; and 15 cm from the lead or the ICD (R4).

RESULTS

In the positive control (direct contact between the lead or the ICD with the Pz switched on), the ICD detected electrical activity as false heart activity. However, after covering all test conditions, no EMI was produced by the Pzs.

CONCLUSION

No EMI or permanent changes in the functioning of the ICD were detected in vitro.

Comparison of postoperative pain after root canal treatment using reciprocating instruments based on operator's experience: A prospective clinical study

Background

The aim of the present study was to compare clinically the incidence of postoperative pain after endodontic treatment using the Reciproc System, taking into account the operator’s experience.

Material and Methods

One hundred patients scheduled for routine endodontic treatment were enrolled in this study. Endodontic treatment was carried out in a single visit by undergraduate and postgraduate students. The chemomechanical preparation of root canals was performed with Reciproc instruments. Pretreatment and postoperative pain was recorded using a visual analogue scale (VAS). Postoperative pain and the need for analgesic consumption were assessed at 4, 8, 16, 24, 48 and 72 hours post-treatment. The data were analyzed using the Mann–Whitney U and Chi-Square test, and the significance was set at P<0.05.

Results

The mean value of pain after root canal treatment was 1.13±1.94 and 1.91±2.07 on a VAS between 0 and 10 in treatments performed by undergraduate and postgraduate students, respectively. There was a significant difference in the incidence of postoperative pain between the two groups (P<0.05).

Conclusions

The prevalence of postoperative pain was high in the treatments performed by postgraduate students in comparison with undergraduate students. This suggests that operator experience has an influence on the prevalence of postoperative pain after root canal treatment.

Key words:Post-endodontic pain, root canal treatment, reciprocating systems, Expert operators Inexperienced operators.

Influence of academic training in endodontics and implantology on decision-making in undergraduate students

PURPOSE

To evaluate the effect of academic training on decision-making in a group of undergraduates who have undergone training in endodontics and implantology.

BASIC PROCEDURES

A single group of undergraduate dentistry students (n = 65) was given a survey consisting of 15 endodontic cases. Each case included periapical radiographs and clinical photographs. Students were asked to select one of the eight proposed treatments. In their 4th year, the students first responded to the survey after completing endodontics. One year later, after completing their studies in implantology, the same students completed the same survey again.

MAIN FINDINGS

Under the conditions of this study, differences in undergraduate training significantly affected treatment decisions.

PRINCIPAL CONCLUSIONS

Undergraduate decision-making was affected by academic training.

Development of Periapical Lesions in Endodontically Treated Teeth with and without Periodontal Involvement: A Retrospective Cohort Study

INTRODUCTION

The purpose of this study was to investigate the incidence of apical periodontitis (AP) in endodontically treated teeth with and without periodontal involvement.

METHODS

The records of 602 patients with 775 root canal-treated teeth were initially examined. Only teeth with adequate root canal filling, adequate coronal restoration, and no AP (periapical index = 1) were selected for further investigation. A total of 194 teeth were included in this cohort study. Age, sex, history of diabetes mellitus, smoking, hypertension, and immunodeficiency disorders were recorded. Two groups were made according to the periodontal status of the patients. The control group included periodontally healthy patients and the periodontal group patients with periodontal disease receiving nonsurgical periodontal treatment. After an observation period of at least 2 years, the incidence of AP was scored using the periapical index. The relationship between patients' variables and AP was conducted using the Cohen kappa test, the chi-square test, odds ratio (OR), and logistic regression analysis.

RESULTS

Newly emerged AP was found in 14% of periodontally involved teeth and in 3% of nonperiodontal involved teeth (P < .05, OR = 5.19, 95% confidence interval). The periodontal condition and hypertension were the only significant factors associated with the presence of AP in the follow-up after univariate logistic regression. Adjusting for hypertension, multivariate logistic regressions showed that periodontal status remained significant (OR = 5.25, 95% CI, P < .05).

CONCLUSIONS

The risk of developing AP in endodontically treated teeth is 5.19 times higher for patients with periodontal disease compared with patients without periodontal disease.

In vivo and in vitro spectrophotometric evaluation of upper central incisors before and after extraction

OBJECTIVES

This in vivo and in vitro study investigated the influence of pulpal vitality on the optical properties of teeth over a 1-month period.

MATERIALS AND METHODS

We monitored two specific areas (2-mm-thick pure enamel and 3-mm-thick enamel-dentine complex) in 10 teeth against two backgrounds (white and black) using a calibrated reflectance spectrophotometer at the following time points: before extraction (T0); immediately after extraction (T1); at 1-day post-extraction (T2); at 1-week post-extraction (T3); and 1-month post-extraction (T4). We recorded tooth colour based on the Commission Internationale d'Eclairage L*a*b* model and translucency and analysed these characteristics over time using analysis of variance.

RESULTS

The 2-mm-thick pure enamel area showed significant changes (p > 0.05) in L*, a* and b* values between before and 1 month after extraction (T0-T4). Translucency was detectable between (T0-T3) and (T0-T4). The 3-mm-thick enamel-dentine complex also exhibited significant differences (p > 0.05) in L*, a* and b* values within (T0-T4). Translucency value changes significantly (p > 0.05) within the first day (T0-T2) and (T0-T3). CIEDE 2000 DE values revealed no statistically significant differences (p < 0.05) in colour between the T0 L*a*b* measures and all the subsequent measures at times T1, T2, T3 and T4.

CONCLUSIONS

Within the limitations of this study, we conclude that the optical characteristics (i.e. colour and translucency) of teeth change after extraction.

CLINICAL RELEVANCE

The results help understanding the precise moment when the colour of extracted tooth changes to identify optimum time to use a tooth for scientific investigation and determine whether it is necessary to extract pulp tissue beforehand.

Effect of manual dynamic activation with citric acid solutions in smear layer removal: A scanning electron microscopic evaluation

Background/purpose

Chelating agents have been used for the removal of the smear layer on teeth. However, due to inadequate volume and/or penetration of the solutions during irrigation, smear layer removal is less effective in the apical third. The purpose of this study was to compare the efficacy of three chelating solutions with and without manual dynamic irrigation in smear layer removal.

Materials and methods

Sixty-six single-root canal teeth were decoronated, instrumented, and divided into six experimental groups (n = 10) and two control groups (n = 3). The groups received a final rinse with 1 mL of 17% EDTA and 5% or 10% citric acid (CA) for 1 minute, with or without manual dynamic activation, followed by a final 3-mL rinse with 4.2% NaOCl (5 minutes). The teeth were then longitudinally split and prepared for environmental scanning electron microscopy analysis. Digital images (500×) were taken for smear layer removal evaluation at 2 mm, 6 mm, and 10 mm from the working length.

Results

The most effective smear layer removal occurred with 5% and 10% CA combined with manual dynamic activation (Groups 7 and 8), where significant differences were observed when compared with the EDTA groups (Groups 2 and 6; P < 0.05). We found no significant differences between manual dynamic activation with 5% and 10% CA (Groups 7 and 8) in smear layer or debris removal (P > 0.05).

Conclusion

Manual dynamic activation of CA improves smear layer removal, and a reduction in CA concentration to 5% does not compromise smear layer removal in comparison with higher concentrations.

Efficacy of Reciproc(®) and Profile(®) Instruments in the Removal of Gutta-Percha from Straight and Curved Root Canals ex Vivo

Objectives

To compare the efficacy of Reciproc^® (VDW GmbH) and ProFile^® (Dentsply Maillefer) instruments at removing gutta-percha from straight and curved root canals ex vivo filled using the cold lateral condensation and GuttaMaster^® (VDW GmbH) techniques.

Material and Methods

Forty mesial roots of mandibular molars with two curved canals and 80 single-rooted teeth with straight root canals, a total of 160 root canals, were randomly assigned to eight groups (canals per group = 20) according to filling technique, retreatment instrument and root canal curvature as follows: Group I, cold lateral condensation/ProFile^®/straight; Group II, cold lateral condensation/ProFile^®/curved; Group III, cold lateral condensation/Reciproc^®/straight; Group IV, cold lateral condensation/Reciproc^®/curved; Group V, GuttaMaster^®/ProFile^®/straight; Group VI, GuttaMaster^®/ProFile^®/curved; Group VII, GuttaMaster^®/Reciproc^®/straight; and Group VIII, GuttaMaster^®/Reciproc^®/curved. The following data were recorded: procedural errors, retreatment duration and canal wall cleanliness. Means and standard deviations were calculated and analysed using the Kruskal-Wallis test, one-way analysis of variance and Tukey’s test (P < 0.05).

Results

Reciproc^® instruments were significantly faster than ProFile^® instruments at removing GuttaMaster^® from both straight (P = 0.0001) and curved (P = 0.0003) root canals. Reciproc^® were statistically more effective than ProFile^® instruments in removing GuttaMaster^® from straight root canals (P = 0.021). Regardless of filling technique or retreatment instrument, gutta-percha was removed more rapidly from curved than from straight root canals (P = 0.0001).

Conclusions

Neither system completely removed filling material from the root canals. Compared with ProFile^® instruments, Reciproc^® instruments removed GuttaMaster^® filling material from straight and curved root canals more rapidly.

Root canal morphology of Chalcolithic and early bronze age human populations of El Mirador Cave (Sierra de Atapuerca, Spain)

This study provides a morphological characterization of the inner anatomy of the root canals of permanent first and second molars in Chalcolithic and early Bronze Age human fossils using cone-beam computed tomography. The general evolutionary trend in present-day human dentition is related to morphological simplification. As little is known about when this trend appeared in Homo sapiens populations, the aim of this work is to test the presence of modern radicular morphology 4,400 years ago. Fifty-four permanent first and second maxillary and mandibular molars of 17 individuals were included in the study. All maxillary first and second molars showed three separate roots. Almost all the lower molars analyzed (100% of first molars and 75% of second molars) had two separate roots. More differences in the canal system configuration were documented in the maxillary mesiobuccal roots than in the palatal or distobuccal roots. The most variable tooth in root and canal configuration is the maxillary second molar. It should be pointed out that 12.5% of the teeth analyzed showed a C-shaped root configuration.

Evaluation of Dentaport ZX and Raypex 6 electronic apex locators: an in vivo study

INTRODUCTION

Raypex 6 is an electronic apex locator (EAL) that has not yet been tested in vivo. The purpose of this in vivo study was to compare the accuracy of two EALs: the Dentaport ZX and the Raypex 6.

METHODS

The study involved 36 straight single-rooted teeth. A 10-K file was advanced until the EAL detected the major foramen. The file was fixed in a replaceable pattern of light-cured composite. The apical part of each canal was trimmed to expose the file tip. The distances from the file tips to the major foramen were measured.

RESULTS

Wilcoxon's signed Rank test found no significant differences between the Dentaport ZX and Raypex 6 in terms of their abilities to detect the major foramen (P = .52) The Dentaport ZX was accurate 82.35% of the time to ± 0.5 mm and 97.05% of the time to ± 1 mm, whereas the Raypex 6 was accurate 88.22% of the time to ± 0.5 mm and 100% of the time to ± 1 mm.

CONCLUSIONS

No statistically significant differences were observed between the performance of the Dentaport ZX and Raypex 6 EALs under the in vivo clinical conditions used in this study.

Effects of piezoelectric units on pacemaker function: an in vitro study

INTRODUCTION

The use of piezoelectric units on patients with pacemakers is generally discouraged, although there is no empirical evidence of the effects of current piezoelectric units on pacemaker activity in vitro.

METHODS

Four piezoelectric units (Piezosurgery3, Piezotome, Piezotome2, and Variosurg) and 2 magnetostriction units (Piezotome and Piezotome2) were tested for electromagnetic interference (EMI) with the SENSIA SESR01 pacemaker from Medtronic. The pacemaker, with a single electrode, was immersed in a saline-solution bath and adjusted between 400 and 800 ohms to simulate the electrical resistance of the human body and to register and to produce electrographic recordings. The pacemaker was tested with each ultrasonic device to analyze the presence of EMI at different distances, with the ultrasound switched on, switched off, and during operation. If any of the devices produced interference, the characteristics of the interference were categorized.

RESULTS

In the positive control (direct contact between either the electrode or the generator and the ultrasound device when this was switched on), the pacemaker detected electrical activity as false heart activity. When all the scenarios and distances had been covered, no EMI was produced by the ultrasound units.

CONCLUSIONS

No EMI was detected during the testing of the piezoelectric or magnetostriction units in this in vitro model of pacemaker use.

In vivo evaluation of the iPex and Root ZX electronic apex locators using various irrigants

AIM

To evaluate in vivo the performance of the iPex and Root ZX electronic apex locators (EALs) in the presence of several irrigant solutions: 2.5% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX).

METHODOLOGY

Thirty-two single-rooted human teeth that were scheduled for extraction were selected. Teeth with metallic restorations, fractures, root resorption, pulp necrosis or open apices were not included The working length (WL) was determined electronically for the root canals with the iPex and Root ZX EALs in the presence of two different irrigant solutions, 2.5% NaOCl and 2% CHX. After the teeth had been extracted, a size 10 K-file was used to determine the reference working length (RWL), which was established at 0.5 mm short of the major foramen. In each case, the RWL was subtracted from the electronic measurements. Positive values indicated electronic measurements that exceeded the RWL (long measurements), whereas negative values indicated measurements that were short of the RWL. The values obtained with the different irrigants and EALs were compared using the paired t-test. Significance was set at P < 0.05.

RESULTS

The accuracy of the iPex nor Root ZX EAL was not affected by 2.5% NaOCl or 2% CHX (P > 0.05). However, significant differences were observed between the readings of the iPex and Root ZX, irrespective of whether 2.5% NaOCl or 2% CHX was used as the irrigant (P < 0.05). The iPex was less accurate than the Root ZX in determining the RWL.

CONCLUSIONS

The accuracy of neither the iPex nor Root ZX EAL was affected by the irrigant used. However, the iPex was less accurate than the Root ZX in determining the RWL both for 2.5% NaOCl and for 2% CHX.

Influence of light and oxygen on the color stability of five calcium silicate-based materials

INTRODUCTION

Difficult handling, long setting time, and potential discoloration are important drawbacks of white mineral trioxide aggregate (WMTA). The development of Biodentine, a recently developed calcium silicate-based material (CSM), has overcome some of these shortcomings; however, there are no available data on its color stability. A previous study showed that WMTA discolors under light irradiation in an oxygen-free environment. The present study evaluated the influence of light irradiation and oxygen on the color stability of 5 CSMs.

METHODS

Fifteen samples of 5 CSMs (ProRoot WMTA, Angelus WMTA, White Portland Cement [PC], PC with bismuth oxide, and Biodentine) were divided into 5 groups. Each group was exposed to different oxygen and light conditions. A spectrophotometer was used to determine the color of each specimen at 0, 120 seconds, and 5 days. Data were analyzed by using analysis of variance and Tukey honestly significant difference test.

RESULTS

The materials PC with bismuth oxide, Angelus WMTA, and ProRoot WMTA showed dark discoloration after light irradiation in an oxygen-free environment, which was statistically significantly different from Biodentine and PC. In groups that were exposed to no light irradiation or to an oxygen atmosphere, all materials showed color stability over time, and no significant differences were observed among them. PC and Biodentine maintained color stability in all conditions over time and showed no significant differences.

CONCLUSIONS

The combination of light and anaerobic conditions (similar to those in clinical situations) results in differences in color of the tested CSMs during a period of 5 days, of which Biodentine and PC demonstrated color stability.

The effects of six electronic apex locators on pacemaker function: an in vitro study

AIM

To assess the effects of six electronic apex locators (EALs) on pacemaker function in vitro.

METHODOLOGY

Six EALs (Mini Apex Locator®, Dentaport ZX®, Novapex®, Raypex5®, Root ZX mini®, and Justy II®) were tested for electromagnetic interference (EMI) with one pacemaker (Saint Jude Medical). The pacemaker, with a single electrode, was immersed in a saline solution bath adjusted to 400-800 hms to simulate the electrical resistance of the human body and to register the activity by the system. The pacemaker was tested with each of the EALs to analyse the presence of EMI with the EAL switched on, the EAL switched off and during EAL operation. Each series of tests began with a 15-second baseline recording (R0) and continued until all the recording conditions had been covered. The conditions were as follows: R1: recording with the lead of the EAL <2 cm from the tip of the electrode; R2: recording with the lead of the EAL <2 cm from the generator; R3: recording with the lead of the EAL <2 cm from the sensing arc; and R4: recording with the lead of the EAL 15 cm from the sensing arc. If any of the EALs produced interference, its characteristics were categorized.

RESULTS

When the lead of the EAL was <2 cm from the tip of the electrode, the majority of the EALs tested produced only background noise. Only one (the Mini Apex Locator) resulted in EMI that was detected as false heart activity. When the EAL was <2 cm from the generator, just one EAL detected background noise (the Mini Apex Locator). When the EAL was <2 cm from the sensing arc or 15 cm from the sensing arc, the recordings were not affected by any of the EALs. There were no significant differences amongst the EALs analysed with respect to the production of EMI.

CONCLUSIONS

EMI occurred when the EALs were placed close to the tip of the electrode and occasionally when close to the pacemaker; however, no EMI was detected when the EALs were placed near to or 15 cm from the sensing arc in this laboratory experimental model.

Failure of ProTaper rotary Ni-Ti instruments used by undergraduate students

Objective: To evaluate the effect of number of uses, angle and radius of curvature and type of instrument on the fracture of ProTaper rotary instruments when used by undergraduate students. Study Design: Three hundred and seventy-six molars, with a total of 1114 root canals, extracted were instrumented by undergraduate students using ProTaper instruments according to the manufacturer´s recommendations. When fracture occurred, data were collected concerning the number of uses, type of instrument, level of fracture, angle and radius of curvature. ANOVA test were used to determine the influence of type of instrument in the incidence of instrument fracture. Logistic regression model was used to determine the influence of number of uses, angle and radius of curvature in the incidence of instrument fracture. Significance was set at p< 0.05. Results: A total of 37 Ni-Ti rotary instruments fractured during the treatment. Fracture occurred in 9.84% (37/376) of the teeth treated and 3.32% of the canals prepared with Ni-Ti rotary instruments (37/1114). A decrease in the radius of curvature of the canal significantly increased the likelihood of fracture (p=0.0001). Instrument fracture significantly increased as the number of uses increased (p=0.0037). No significant differences were found between the 6 types of ProTaper instruments (p=0.8). A reduction in the angle of curvature did not produce a significant decrease in the incidence of instrument separation (p=0.08). Conclusions: The results of this study imply that instrument fracture is linked to radius of curvature and number of uses.

Key words:Fracture, ProTaper ®, root canal preparation, undergraduate students.

A comparison of apical transportation between FlexMaster and Twisted Files rotary instruments

INTRODUCTION

The aim of this study was to evaluate apical transportation in root canals after the use of Twisted Files (TF; SybronEndo, Orange, CA) and FlexMaster (VDW, Munich, Germany) #40/04 rotary files.

METHODS

A double-digital radiographic technique was used to compare apical transportation between the TF and FlexMaster systems. Each rotary system was used to instrument mesial canals from 80 extracted mandibular molars. The central axes of the file imaged before instrumentation (#15 K-file) and the master apical rotary file (#40/04) were superimposed digitally. AutoCAD 2008 (Autodesk Inc, San Rafael, CA) was used to measure apical transportation at 0.5 mm from the working length (WL). The data were analyzed using the Student's t test, and significance was set at P < .05.

RESULTS

The mean amount of apical transportation at 0.5 mm from the WL was 0.17 ± 0.09 mm for the FlexMaster group and 0.19 ± 0.12 mm for the TF group. No statistically significant differences in apical transportation were found between the 2 groups.

CONCLUSIONS

Under the conditions of the study, no statistically significant differences in apical transportation were observed between FlexMaster and TF rotary files.

Managing severe curvature of radix entomolaris: three-dimensional analysis with cone beam computed tomography

AIM

To present a case of a mandibular first molar with an additional distolingual root [radix entomolaris (RE)] and to discuss the use of cone beam computed tomography (CBCT) for its identification and management during root canal treatment.

SUMMARY

A 52-year-old Caucasian woman was referred for root canal treatment of the right mandibular first molar (tooth 46). After clinical and radiographic examination, a symptomatic irreversible pulpitis was diagnosed. Three periapical radiographs with different horizontal angulations revealed the presence of an additional distolingual root. This extra root, termed RE, has an incidence of <5% in the Caucasian population. A CBCT examination was also taken, which revealed a severe root canal curvature, especially in the middle third, of this supernumerary root. CBCT provided more accurate information in terms of RE inclination and root canal curvature before commencing root canal treatment. The conventional access opening was modified into a more trapezoidal cavity, and five root canals were found. All canals were instrumented with new nickel-titanium (NiTi) files to reduce the risk of fractured instruments. After preparation, the root canals were filled using thermoplastified techniques. The 1-year follow-up periapical radiographs and CBCT images revealed a continuous periodontal space with no signs of apical periodontitis.

KEY LEARNING POINTS

• Cone beam computed tomography imaging is useful in identifying the root canal system and the surrounding structures. • An accurate detection of supernumerary roots, such as RE, can avoid complications during and after root canal treatment. • The analysis of root canal curvature is important because instrument fracture has been linked to angle and radius of curvature. • The use of new instruments can reduce the incidence of instrument fracture.