Dentin Removal Research Articles

Comparative evaluation of microhardness of residual dentin in primary molars following caries removal with chemomechanical agent (BRIX 3000) and polymer burs (ss white)

Aim: To evaluate and compare microhardness of residual dentin in primary molars following caries removal with chemomechanical agent (BRIX 3000) and polymer burs (SS white). Materials and Method: Extracted maxillary or mandibular primary molars with proximal carious lesion, were selected with active carious cavities extending in to 2/3rd of dentin. The selected teeth were preserved in phosphate buffer saline solution no longer than 30 days. The selected teeth were separated into two experimental groups: group A- chemomechanical method – Brix3000 and Group B- slow speed polymer bur. After caries excavation the microhardness test was carried out on treated dentin using a Knoop indenter. Results: The results suggest a significant difference between among the groups Brix 3000â showed superior results compared to group B (Polymer burs) i.e., The results showed that the microhardness of the remaining dentine after caries excavation with Brix 3000 was found to be greater than the microhardness of the remaining dentine after caries excavation with Polymer bur. Conclusion: In conclusion of the current study, it can be stated that Brix 3000 may be utilized as a successful agent in minimally invasive caries excavation since Polymer burs showed partial removal of carious dentine.

Evaluation of Remaining Dentin Thickness of the Distal Portion of the Mesial Root of Mandibular Molar with Protaper Gold, Neoendo and Stainless Steel (SS) Hand K Files Using Cone Beam Computed Tomography for Analysis.

Aim: To evaluate the remaining dentin thickness of the distal portion of the mesial root of mandibular molar with stainless steel (SS) hand K files, ProTaper Gold and NeoEndo using cone beam computed tomography for analysis.
 Materials and Methods: Forty-five extracted human mandibular molars were collected. Teeth were randomly assigned to three groups (n=15). Samples were stabilized on blocks of wax. The working length for each sample was determined at 1 mm short from the apical foramen by using a ISO size #15 K file. Preparation was carried out according to the manufacturer’s instructions and canals were instrumented upto apically for each group. After each instrumentation, root canals were irrigated with 5.25% sodium hypochlorite solution followed by 17% EDTA solution. Final irrigation was done with normal saline. Post cleaning and shaping, cone beam computed tomography scans of all samples in the three groups were collected.
 Result: Protaper Gold and NeoEndo removed more dentin than SS hand file. As the mean remaining dentin thickness for SS K file, Neoendo and Protaper was 1.30, 1.05 and 0.80mm respectively
 
 Conclusion: Protaper Gold, NeoEndo and SS Hand files showed statistically significant difference in remaining dentin thickness of root canal length. Therefore, it was concluded that Protaper Gold file system showed a greater amount of removal of dentin as compared to NeoEndo file system & SS Hand K files.

Ageing-related effects of dye penetration in the apical 5 mm mesiobuccal and mesial roots of molars.

This study examined how the tubular permeability in the apical 5 mm of mesial roots was affected by age, direction, distance from root apex, canal shape and canal number. Twenty mesiobuccal/mesial roots of maxillary/mandibular molars from three age groups (<30, 30-60, >60 years) were prepared. Maximal dye penetration in buccal, lingual, mesial and distal directions was measured at 1-mm segment depth and analysed statistically. The <30 years group, when comparing to the >60 years group, had significantly deeper dye penetration in buccal and lingual directions. The permeability in proximal directions was not affected by either age or canal number. In the >60 years group, neither direction, segment depth nor canal number significantly impacted the permeability. However, these parameters significantly impacted samples younger than 60 years. Effective removal of infected root canal dentine would depend on age and its related preferred direction, distance from root apex and canal number.

Effectiveness of an actuator-driven pulsed water jet for removal of softened carious dentin.

The aim of this study was to assess the utility of an actuator-driven pulsed water jet (ADPJ) as a hardness-dependent carious dentin removal device by using different outputs. Thirty-six plane surface dental caries samples were treated with the ADPJ at 150, 200, and 250 voltage (12 teeth each). The Knoop hardness number (KHN) and Ca/P mass ratio were measured at 70 μm from the deepest point of the removing groove. Furthermore, three other teeth samples were manually treated with the ADPJ at the three above mentioned voltages (one tooth each) for 1 min. The KHN and Ca/P mass ratio were measured at 70 μm from the surface of the residual dentin part. In both the KHN and Ca/P mass ratio, higher residual dentin depended on the applied voltage of ADPJ. The ADPJ enabled the removal of softened carious dentin in an applied voltage-dependent manner.

Shaping outcome of ProTaper NEXT for root canal preparation in mandibular incisors: a micro-CT study

BackgroundRelatively high incidence of single canals with oval or round shape were observed in human mandibular incisors. In order to investigate the influence of the root canal morphology on root canal preparation, the shaping outcome of ProTaper NEXT in oval and round canals of mandibular incisors were evaluated by using micro-computed tomography (micro-CT) analysis.MethodsThis experiment was approved by the School Medical Ethics Committee. The sample size calculation was conducted using G*Power software. Intact mandibular incisors with a single canal were selected. Oval canals (2 < aspect ratio (AR) ≤ 4) and round canals (AR ≤ 2) were pair-matched according to canal length, and assigned to two experimental groups (13 per group). ProTaper NEXT was used for root canal preparation for both groups. Untouched canal wall (UCW), root canal morphological parameters and three-dimensional (3D) dentin thickness were evaluated in the entire root canal and each canal third after micro-CT scanning. Statistical analysis: Data were collected and analyzed with Mann–Whitney test and Friedman test using SPSS statistics software 25 (P < 0.05). Additionally, correlations of UCW area with canal morphological parameters were also investigated.ResultsAfter root canal preparation, no significant difference was observed in all analyzed parameters in the apical third between oval and round canal groups (P > 0.05). In the coronal two thirds of the canal, the post-operative structure model index (SMI), form factor and roundness were significantly increased, while the AR was significantly decreased in both groups (P < 0.05). In addition, in the coronal two thirds, significantly more UCW and higher UCWΔ% was observed in oval canal group (P < 0.05). Furthermore, UCW correlated very strongly to canal major diameter (0.924) and initial volume (0.938), and strongly to canal form factor (− 0.724), minor diameter (0.799) and canal area (0.882). Proximal dentin wall was associated with significantly thinner pre-operative dentin thickness and higher amount of dentin removal after root canal preparation in both oval and round canal groups.Conclusions(1) Both types of canals were more conical after root canal preparation, but oval root canals tend to leave more UCW area than round canals in the coronal two thirds of mandibular incisors, which contributes to the challenge for endodontic infection control. (2) Root canal preparation usually results in excessive dentin removal in the proximal dentin wall comparing with buccal and lingual walls in both types of canals of mandibular incisors.

Evaluation of Caries Removal Efficacy Using BRIX 3000 and Atraumatic Restorative Treatment in Primary Molars: A Clinical Comparative Study

The aim of the present study was to compare and evaluate the efficacy of two minimally invasive methods in the removal of infected carious dentin in primary molars. Eighty primary molars with class I occlusal caries involving dentin were selected and allocated to either of the two groups using convenient sampling. Group A (n = 40) caries were excavated using BRIX 3000 and in Group B (n = 40) atraumatic restorative treatment (ART) caries were excavated using hand instruments only. In both groups, caries removal efficacy was evaluated clinically using caries detection dye (Sable and Sleek), and the patient's discomfort level was noted using the Wong-Baker faces pain rating scale (WBFPS). The results indicated that BRIX 3000 was effective in the removal of caries from primary molars with a significant difference. While there was no statistically significant difference seen in pain perception on caries excavation using both the methods. Although, a mild discomfort was noted in Group B. Comparing the two minimally invasive techniques, the new chemomechanical solution (BRIX 3000) was an effective method for the removal of caries from primary molars. So, it can be considered an alternative to the conventional caries removal method in treating pediatric dental patients. BRIX 3000 gel is effective in the removal of caries in children who are anxious and apprehensive as it is a noninvasive method of treatment in the pediatric age group.

Efficacy of adding dexmedetomidine to lidocaine to enhance inferior alveolar nerve block in patients with asymptomatic irreversible pulpitis: double-blind randomized clinical trial.

This randomized, double-blind study was to determine whether dexmedetomidine (DEX) helped to improve the inferior alveolar nerve block's (IANB) success in patients with asymptomatic irreversible pulpitis (AIP). We hypothesized that adding DEX to lidocaine enhances the anesthetic effect of lidocaine to a satisfactory level by localizing anesthesia in a safer way. Fifty adult volunteers with AIP in a first or second mandibular molar were randomly assigned to two groups to either receive 1.4ml 2% plain lidocaine or 1.4ml 2% lidocaine + 0.4ml (40μg) DEX, for standard IANB injection. Access cavity preparation initiated 10-15min postinjection when the patient reported lower lip numbness and had two negative electric pulp tests (EPTs) with 5-min intervals. Heft-Parker visual analog scale (VAS) was used to report pain in three steps: during caries and dentin removal, access cavity preparation, and canal working-length determinations; EPT and VAS were analyzed by Friedman test; and success rates were analyzed by Mann-Whitney and Fisher's exact test using SPSS software version 20. Successful anesthesia (defined as no or mild pain during any of steps and no need for additional injection) is obtained in 12% of patients in the lidocaine group, while DEX-lidocaine group increased the success rate of IANB to 72% (p-value = 0.0001). DEX significantly increases the anesthetic effect of lidocaine in IANB injection in patients with AIP. DEX would be a safe adjunct to lidocaine to increase the success rate in IANB and could be a suitable alternative for conventional vasoconstrictors in sensitive groups.

Computed Tomographic Assessment of Remaining Dentin and Risk of Perforation after Kedo-S and Mtwo Rotary Instrumentation in Root Canals of Primary Teeth: An In Vitro Study.

BackgroundRoot canal cleaning is a key step in the endodontic treatment of the primary molars. An innovative generation of endodontic instruments has been devised with the aim of emerging better procedures. The objective of the study is to assess the preparation of time, the risk of lateral perforation, and the removal of dentin from Kedo-S and Mtwo rotary instruments on primary teeth.Study designThis is an in vitro experimental study comparing the two groups.Materials and methodsA total of 50 extracted mandibular primary first molars are collected, divided randomly into two groups of 25 teeth each. Group I: Kedo-S Pediatric rotary file, Group II: Mtwo rotary file. Distal canal is standardized for evaluation and teeth are sectioned at the CEJ. The teeth were instrumented according to manufacturer's guideline. Both the groups are scanned before and after instrumentation of the canal using cone-beam computed tomography (CBCT) and values are evaluated.ResultsCompared with Mtwo files, Kedo-S files need less instrumentation time and limited lateral perforation. No statistical differences were reported between the instrumentation of Kedo-S and Mtwo with regard to the amount of dentin removed.ConclusionIn pediatric endodontics, Kedo-S pediatric rotary file can be considered an effective alternative to traditional rotary files because it requires less instrumentation time and preserves dentin thickness.How to cite this articleSwaminathan K, Rakkesh KM, Haridoss S. Computed Tomographic Assessment of Remaining Dentin and Risk of Perforation after Kedo-S and Mtwo Rotary Instrumentation in Root Canals of Primary Teeth: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(S-1):S87-S91.

Present status and future directions: Management of curved and calcified root canals.

Root canal curvature and calcification introduce factors that increase the risk of procedural accidents during root canal treatment. The inability to achieve patency to the apical third, asymmetrical dentine removal leading to transportation, perforation, and instrument fracture inside the curved trajectories are some of the procedural problems that might jeopardize the management of intraradicular infection and result in poor treatment outcomes. In fact, curved and constricted canals introduce such complexity that total instrumentation concepts and specially designed instruments have been developed to deal with the challenge. This narrative review seeks to provide and consolidate the principles necessary for understanding the dynamics of curved and constricted canal management and to improve the understanding for future developments in this field.

The Impact of TruNatomy and ProTaper Gold Instruments on the Preservation of the Periradicular Dentin and on the Enlargement of the Apical Canal of Mandibular Molars

IntroductionThis study aimed to evaluate the preservation of periradicular dentin and the enlargement of the apical canal of mandibular molars with TruNatomy (Dentsply Sirona, Ballaigues, Switzerland) and ProTaper Gold (Dentsply Sirona) instruments. MethodsTwenty mandibular molars were scanned in a micro–computed tomographic device, anatomically paired, and distributed into 2 groups (n = 10). In the ProTaper Gold group, mesial and distal canals were prepared up to F2 (25/.08v) and F3 (30/.09v) instruments, whereas in the TruNatomy group, mesial and distal canals were enlarged up to the prime (26/.04v) and medium (36/.03v) instruments, respectively. After a new scan, the surface area, volume, unprepared areas, transportation, percentage of dentin removal, and dentin thickness parameters were calculated. Data were compared between groups using the Mann-Whitney test, the Student t test, and the nonmetric multidimensional scaling test with alpha set at 5%. ResultsNo difference was found between groups regarding unprepared canal areas and the reduction of dentin thickness (P > .05). Transportation was lower than 0.1 mm in all groups, and statistical differences were observed only at the apical third of the mesiobuccal canal with lower values in the TruNatomy group. ProTaper Gold removed more dentin than TruNatomy at the coronal level of mesial roots (1.8% and 1.0%, respectively) (P < .05). ConclusionsTruNatomy and ProTaper Gold were efficient for performing canal preparation in mandibular molars. The tested systems were similar in terms of untouched canal walls and remaining dentin thickness and slightly different in the apical transportation of mesial canals and the percentage of dentin removal at the coronal third but without clinically significant errors.

Ultrasound device as a minimally invasive approach for caries dentin removal.

The aim of this study was to evaluate the efficacy of an ultrasound device and the dentin surface morphology after removal of the caries dentin lesions by removal rate and scanning electron microscopy (SEM). The Knoop hardness test on the bovine dentin blocks (n = 20, 4x4x2mm) was performed to standardize the samples and only those with 38 ± 2 KHN were included. The dentin blocks were submitted to induction of artificial caries lesions, using the bacterial model. Strains of Streptococcus mutans and Lactobacillus acidophilus were used for 7 days. The caries dentin lesion was removed for 1 min, according to two methods: G1 - carbide bur under low-speed rotation (control group) and G2 - ultrasound device under refrigeration. For the removal rate, the samples were weighed 3 times: T0 (before induction), T1 (after induction) and T2 (after removal). Morphology evaluation of the residual dentin surface was performed by SEM. Data normality was verified by Shapiro-Wilk test (p ≥ 0.240). T-test for independent samples was applied to evaluate the removal rate. A significance level of 5% was adopted. G2 provided lower removal rate than G1 (G1: 3.68 mg and G2 = 2.26 mg). SEM images showed different morphological characteristics between the groups. G2 showed absent of smear layer, while G1 showed a visible smear layer over the surface. We concluded that ultrasound device provides minimally invasive removal with residual dentin exhibiting open dentin tubules and no smear layer formation and no bacteria, which infer the removal of the infected tissue.

Evaluation of rotary file system (Kedo-S-Square) in root canal preparation of primary anterior teeth using cone beam computed tomography (CBCT)-in vitro study

BackgroundIn recent years, pediatric endodontics has witnessed various advances including use of rotary files in pulpectomy. This study aimed to comparatively evaluate taper, amount of dentin removal and instrumentation time of the pediatric rotary Kedo-S Square file, hand K-files and H-files in primary canines using cone beam computed tomography (CBCT).Methods60 primary canines were randomly assigned into three groups; A1 Kedo-S-Square rotary file (group I), hand stainless steel K file (group II) and hand stainless steel H file (group III). Teeth were mounted in vinyl poly siloxane impression material templates to be scanned before and after instrumentation by CBCT scans using Ondemand 3D software. Shaping ability of the files were evaluated in terms of taper of the canal and amount of dentin remaining of each group. Instrumentation time was recorded using a digital stopwatch.ResultsKedo-S Square removed a significantly less amount of dentin in both apical (P < 0.002) and coronal thirds (P < 0.014). Taper of the preparations showed significant differences as Kedo-S Square file showed good taper in maximum number of root canals, while maual K- and H-files showed poor taper in maximum number of root canals (P < 0.0001). Rotary Kedo-S Square files required less instrumentation time (P < 0.0001).ConclusionThe use of rotary Kedo-S Square files resulted in better conservation of tooth structure, superior tapering ability and least instrumentation time compared to hand K- and H-files.

Microtomographic Evaluation of Canal Centralization and Dentine Removal after Canal Preparation with Two Rotary Systems: HyFlex EDM and ProTaper Next.

Objective This study compared the ProTaper Next (PTN; Dentsply Sirona, Tulsa, Oklahoma, United States) and HyFlex EDM (HEDM; Coltene/Whaledent AG, Alstätten, Switzerland) systems using micro–computed tomography (CT). Materials and Methods Twenty-one mesial roots classified as Vertucci's type IV from extracted mandibular first molars with curvatures between 20 and 40 degrees were selected. The teeth were scanned using a micro-CT before and after root canal preparation by both systems, applied to the same root, in alternating canals. The following parameters were analyzed: canal centering, apical transportation, root canal diameter/root diameter. Results No statistically significant differences between both systems were observed for any of the assessed morphological parameters ( p > 0.05). All canals presented diameter enlargement of more than 40% in relation to root diameter in the cervical and middle segments. No statistically significant difference was noted between the HEDM and PTN groups. The wear percentage for the HEDM group in the cervical and middle thirds were 49.66 ± 8.65 and 46.48 ± 14.29, respectively, and 51.02 ± 11.81 and 45.48 ± 10.79 for the PTN group, respectively. Conclusion Both systems displayed similar mandibular molar mesial canals preparation, with no differences noted for any of the assessed parameters. Both groups showed increased canal diameter in the cervical and middle thirds by more than 40%.

Comparative Analysis of Root Canal Dentin Removal Capacity of Two NiTi Endodontic Reciprocating Systems for the Root Canal Treatment of Primary Molar Teeth. An In Vitro Study.

The objective of the present study was to evaluate and compare the dentin removal capacity of Endogal Kids and Reciproc Blue NiTi alloy endodontic reciprocating systems for root canal treatments in primary second molar teeth via a micro-computed tomography (micro-CT) scan. Materials and Methods: Sixty root canal systems in fifteen primary second molar teeth were chosen and classified into one of the following study groups: A: EK3 Endogal Kids (n = 30) (EDG) and B. R25 Reciproc Blue (n = 30) (RB). Preoperative and postoperative micro-CT scans were uploaded into image processing software to analyze the changes in the volume of root canal dentin using a mathematical algorithm that enabled progressive differentiation between neighboring pixels after defining and segmenting the root canal systems in both micro-CT scans. Volumetric variations in the root canal system and the root canal third were calculated using a t-test for independent samples or a nonparametric Mann–Whitney–Wilcoxon test. Results: Statistically significant differences (p = 0.0066) in dentin removal capacity were found between the EDG (2.89 ± 1.26 mm3) and RB (1.22 ± 0.58 mm3) study groups for the coronal root canal third; however, no statistically significant differences were found for the middle (p = 0.4864) and apical (p = 0.6276) root canal thirds. Conclusions: Endogal and Reciproc Blue NiTi endodontic reciprocating systems showed similar capacity for the removal of root canal dentin, except for the coronal root canal third, in which the Reciproc Blue NiTi endodontic reciprocating system preserved more root canal dentin tissue.

Comparative Analysis of Ease of Removal of Fractured NiTi Endodontic Rotary Files from the Root Canal System-An In Vitro Study.

This study aimed at analyzing and comparing the ease of removal of fractured nickel–titanium (NiTi) endodontic rotary files from the root canal system between the ultrasonic tips and the Endo Rescue appliance removal systems, as well as comparing the volume of dentin removed between ultrasonic tips and the Endo Rescue appliance using a micro-computed tomography (micro-CT) scan. Material and Methods: Forty NiTi endodontic rotary files were intentionally fractured in 40 root canal systems of 20 lower first molar teeth and distributed into the following study groups: A: Ultrasonic tips (n = 20) (US) and B: Endo Rescue device (n = 20) (ER). Preoperative and postoperative micro-CT scans were uploaded into image processing software to analyze the volumetric variations of dentin using an algorithm that enables progressive differentiation between neighboring pixels after defining and segmenting the fractured NiTi endodontic rotary files and the root canal systems in both micro-CT scans. A non-parametric Mann–Whitney–Wilcoxon test or t-test for independent samples was used to analyze the results. Results: The US and ES study groups saw 8 (1 mesiobuccal and 7 distal root canal system) and 3 (distal root canal system) fractured NiTi endodontic rotary files removed, respectively. No statistically significant differences were found in the amount of dentin removed between the US and ER study groups at the mesiobuccal (p = 0.9109) and distal root canal system (p = 0.8669). Conclusions: Ultrasonic tips enable greater ease of removal of NiTi endodontic rotary files from the root canal system, with similar amounts of dentin removal between the two methods.

Retrieval of Separated Endodontic Ni-Ti Rotary File with the Aid of Hypodermic Needle and K-File: A Case Report

One of the most prevalent operational errors that can occur during endodontic therapy is instrument separation. A fractured instrument may cause a blockage in the root canal, impeding the cleaning and shaping process. There are numerous recommended ways for retrieving a separated instrument, some of which are challenging to implement in clinical practice. Some of these procedures may need removal of substantial root dentin, which may weaken the tooth structure. This case report describes an alternate method for removing a fractured endodontic instrument from the root canal using a hypodermic needle and a K-file. A 31-year-old female patient came to the Department of Conservative Dentistry and Endodontics with the chief complaint of pain in the upper left front tooth region since two weeks. The clinical and radiographic examination indicated the existence of a broken Nickel-Titanium (Ni-Ti) rotary file along the coronal third of the root canal till apex. Under magnification, the fragment was initially exposed by creating a 2 mm trough around the fractured instrument using ultrasonics. In order to fix the fragment, a hypodermic needle was introduced into the root canal and the K-file was fitted in the needle lumen. Together, the fragment was removed without any complications. This technique can be used as a safe, easy, and low-cost approach of fractured instrument retrieval from the root canal.

Loss of dental tissue after restoration or sealing of occlusal carious lesions: 3-4-year results of randomized clinical trials.

Although preservation of the tooth structure is quoted as the main advantage of sealing of carious lesions, there are no long-term studies comparing the maintenance of dental tissue after restoration or after caries sealing. To measure the radiographically visible loss of dental tissue after conventional restoration and sealing of carious lesions. This study was a secondary analysis of two randomized controlled clinical trials, one conducted in Brazil and another in Belgium, which evaluated two different therapies for the treatment of occlusal carious lesions in permanent teeth: sealant (SE) without previous carious tissue removal or restoration (RE) with total removal of carious dentin. The greater depth and width of sealed carious lesions and restorations were compared. The independent t-test was used to compare therapies at different time points, while the paired t-test was used to compare the same therapy over time. Carious lesions in the RE and SE groups showed similar measurements at baseline (P > 0.05). Over time, significantly greater loss of tooth structure was observed in the RE group than in the SE group. No increase in lesion depth or width was observed in the SE group, suggesting no progression of sealed lesions. Sealing of carious lesions resulted in greater preservation of dental tissue.

Validity of the dental operating microscope and selective dentin removal with ultrasonic tips for locating the second mesiobuccal canal (MB2) in maxillary first molars: An in vivo study.

BackgroundSeveral investigations have determined whether the use of a dental operating microscope (DOM) in combination with selective dentine removal with ultrasonic tips increases the percentage of location of the Mesiobuccal 2 (MB2) root canal in maxillary first molars (MFM). However, these studies did not report the performance of in vivo measurements with the comparison with a gold standard. The aim of this study was to determine the validity of the DOM and selective dentin removal with ultrasonic tips to locate the MB2 root canal in MFM using Cone Beam Computed Tomography (CBCT) as the gold standard. Material and MethodsThe initial sample size was 91 patients, but 7 were excluded, so the sample size was 84 patients who signed the informed consent. Inclusion criteria: MFM indicated for root canal treatment. An expert blinded observer identified the MB2 in the CBCT. Two standardized examiners (Kappa=91%) performed the clinical assessment in three stages: Stage 1, canal location with an endodontic explorer and a mirror; Stage 2, use of DOM and Stage 3, use of DOM plus selective dentine removal with ultrasonic tips. The validity of each stage was calculated. ResultsThe prevalence of MB2 using CBCT was 79%, by clinical location was 68%. Sensitivity was 79%, 82%, 86% for stage 1, 2 and 3, respectively. Specificity and Positive Predictive Values were 100% for all methods. Negative Predictive Value was 56%, 60%, 67%, respectively. Positive Likelihood Ratio tends to infinity for all methods, Negative Likelihood Ratio= 0.21, 0.18 and 0.14 and Accuracy= 83%, 86% and 89%, respectively. ConclusionsThe use of DOM with selective dentine removal with ultrasonic tips is the most valid method for locating MB2 canal in MFM. There was an increase in the location of the MB2 root canal with the DOM and ultrasonic tips, which definitely help the clinician. Key words:Cone beam computed tomography, microscopy, second mesiobuccal canal, sensitivity and specificity, validity.

Impact of several NiTi-thermally treated instrumentation systems on biomechanical preparation of curved root canals in extracted mandibular molars.

To evaluate the shaping ability of several heat-treated nickel-titanium systems used to prepare root canals with moderate and severe curvature, in extracted mandibular molars, by micro-computed tomography, considering their variation in kinematics and design. Curved-mesial roots of mandibular molars were randomly selected and assigned into 4 balanced experimental groups (n=10), established by determining homogeneous 3D parameters of volume and surface area: R-Motion (RM) size 30, 0.04 taper (RM; FKG Dentaire), Reciproc Blue (RCB) size 25, 0.08 taper (RCB; VDW GmbH), HyFlex CM (HFX) size 30, 0.04 taper (HFX; Coltène Whaledent) and XP-endo Shaper size (XPS) 30, 0.01 taper (XPS; FKG Dentaire). The volume of irrigation was established at 10ml of 2.5% NaOCl. Throughout the entire root canal preparation procedures, the samples were fixed in a vice submerged in a container with water monitored at 37°C. Dimensional cross-sectional measures of area, perimeter, roundness, major/minor diameters and 3-dimensional (volume, surface area, structure model index - SMI) parameters as well as the smallest dentine thickness along the cervical and middle root thirds were evaluated by micro-CT. Data were analysed using analysis of variance and post hoc Tukey tests (α=5%). Reciproc Blue and XPS had significantly greater mean increases in cross-sectional area measurements, only in the middle third, when compared with RM and HFX (p<.05). RM, RCB and XPS had a similar increase in measurements of length and width of perimeter (p>.05), and HFX had significantly lower mean increases in perimeter values only when compared with XPS (p<.05). RCB and XPS had significantly greater mean increases in volume when compared with RM and HFX (p<.05). RM had a significantly lower difference in SMI after preparation, compared with RCB, HFX and XPS (p<.05). The smallest dentine thickness was observed after the use of RCB (p<.05), in the danger and safety zones. XP-endo Shaper and RM had a shaping ability similar to that of instruments with larger tapers, achieved with less dentine removal in danger and safe zones in curved-mesial canals of extracted molar teeth treated on a laboratory benchtop.

Effect of rotary systems and root canal preparation and dentin crack formation

Evidence indicates that root canal preparation is a critical step upon which the prognosis of the endodontic treatment depends. Vertical root fractures can furtherly develop as propagations from the previously formed dentin cracks. Therefore, root canal preparation should be carefully approached with the minimal crack formation and careful dentin removal. Different modalities have been proposed in the literature and rotary systems are most commonly used nowadays. Although the reported efficacy of these modalities is high, evidence shows that they are usually associated with a considerable risk of crack formation. In the present literature review, we have discussed the effects of rotary instrumentation and root canal preparation on dentinal crack formation based on evidence from the different studies in the literature. Our evidence showed that all of the investigated approaches to prepare root canals adequately can result in crack formation. The different rotary instrumentations also showed variable frequencies of developing dentinal cracks, and evidence from some comparative investigations shows that ProTaper modalities are associated with the least frequencies of the events. However, to make a solid conclusion for clinical practice, further research is still needed to validate our current evidence.