Dentin Removal Research Articles

Comparative evaluation of different endodontic access cavity designs on canal transportation and centering ability using bondent platinum file system on mandibular molar – An in vitro cone-beam computed tomography study

ABSTRACT Aim: This study aimed to compare the effects of different endodontic access cavity designs on canal transportation (CT) and centering ability (CA) using the bondent platinum file system on mandibular molars, utilizing cone-beam computed tomography (CBCT). Methodology: Thirty extracted human permanent mandibular molars which fulfilled the inclusion criteria were divided into three groups, Group 1 (TEC): Traditional endodontic access cavity (control group), Group 2 (CEC): Conservative endodontic access cavity, and Group 3 (TrEC): Truss endodontic access cavity. The teeth were scanned using CBCT initially followed by random allocation into three groups. Root canals were prepared using Bondent platinum file system in mesiobuccal and mesiolingual canals using #25.06 file and in distal canal #30.06 file. Postpreparation, CBCT scans to assess CT and CA at 3 mm, 5 mm, and 7 mm from the apex. Data analysis was performed using a one-way analysis of variance and Tukey’s post hoc test. Results: Significant differences (P < 0.01) in mean CT and CA were observed between Group 1 (TEC) and Groups 2 (CEC) and 3 (TrEC). Dentin removal was highest at 3 mm, followed by 5 mm and 7 mm. The distal canal showed the greatest dentin loss compared to other canals. Conclusion: Minimal access cavity designs (CEC and TrEC) demonstrated less CT and improved CA compared to the traditional access cavity design (TEC). Study limitations acknowledged that conservative access cavity designs result in less deviation (CT) and better centering of the prepared canals compared to the traditional approach (TEC). These results imply the potential benefits of adopting less invasive access cavity designs in endodontic practice to enhance treatment outcomes.

Shaping ability of HyFlex EDM and ProTaper Gold files with or without using glide path files: An in vitro study

Abstract Introduction: The necessity of using a glide path before the canal preparation is inconclusive. Therefore, this study aimed to assess the shaping ability of two rotary systems in the maxillary first molars’ first mesiobuccal canal (MB1), with or without employing the glide path files. Materials and Methods: The MB1 canals of 100 extracted molars were randomly prepared using either HyFlex EDM (HEDM) or ProTaper Gold (PTG) systems (n = 50 each). Half of the samples in each group were prepared using ProGlider (PG) or HyFlex EDM Glide (HEG). The cone-beam computed tomography scanning was conducted before and after the instrumentation. The canal transportation, centering ability, and remaining dentin thickness were evaluated and compared between the groups using the independent sample t-test and Mann–Whitney U-test (α =0.05). Results: Using HEDM compared to PTG led to greater centering ability at the sub-furcation area (P < 0.05), lower canal transportation at 2 mm below furcation (P = 0.025), and more dentin removed at the middle area (P = 0.011). The systems’ centering ability and canal transportation were comparable when path files were used. Utilizing HEG with HEDM decreased dentin removal at 2 mm below furcation (P = 0.045) and middle area (P = 0.008). Canal preparation with HEDM-HEG caused less dentin removal at 2 mm below furcation than PTG-PG (P = 0.007). Conclusions: The HEDM system outperformed PTG regarding centering ability in the sub-furcation areas and canal transportation 2 mm below the furcation. However, HEDM showed more dentin removal in the middle region than PTG, which was resolved when HEG was used. Therefore, using PathFile with the HEDM system might be suggested.

Metallurgical influence of separated endodontic instruments on the retrieval capability of katana-sword-like ultrasonic tip under different lubricants: In vitro study

Abstract Introduction: Ultrasonic retrieval is a time-consuming procedure sacrificing considerable amounts of dentin. This study aimed to assess the retrieval capability of katana tip on different alloys under different lubricants regarding dentin thickness and retrieval time. Materials and Methods: Extracted premolars were used to reach 40 samples. The apical 4 mm of X2 ProTaper Next and A1 Neoniti instruments were fractured, and katana tip was utilized for retrieval, using ethylenediaminetetraacetic acid or olive oil as intracanal lubricants. Dentin thickness was assessed using cone-beam computed tomography, and the time of retrieval was recorded. Results: There was no significant difference in the retrieval capability among the groups. Different alloys and lubricants had no significant effect on dentin thickness. However, olive oil significantly reduced the retrieval time. Conclusion: Katana tip proved to be efficient enough to retrieve apically separated instruments in curved canals, with instrument’s metallurgical makeup presenting minimal effect on its capability. Katana tip and high-viscosity lubricants reduced the retrieval time, which might reduce the dentin removal amount.

Endodontic Microsurgery Using Dynamic Navigation and Trephine Burs

Objectives: The use of the surgical operating microscope, CBCT imagining, biocompatible filling materials and ultrasonic instruments have improved the success and predictability of apical surgery. Despite these advances, more accurate and precise techniques for creating osteotomies and root-resections (apicoectomies) have not been widely adopted. This study highlights how dynamic navigation systems (DNS) can help avoid unnecessary dentin removal and “mitigate iatrogenic errors” such as root perforation. Methods: A total of 56 root-end resections were planned and completed on two sets of identical TrueJaw Endosurg models (DE Labs, Santa Barbra, CA, USA). One set of maxillary and mandibular jaws were used for 28 preparations, performed with a DNS (X-Guide, X-Nav Technologies, Lansdale, PA, USA). A second set of maxillary and mandibular jaws were used for 28 preparations executed freehand (FH), with pre-op measurements taken from a CBCT scan (CS 9600; Carestream, Atlanta, GA, USA). A Mann-Whitney test was used to compare the accuracy of the two groups Results: The average preparation depth was 10.77 mm. For the DNS group the average angular deviation was 2.35 degrees. The average deviation at the terminal end of the preparations was 0.96 mm (global apical deviation). For the freehand group average angular deviation was 13.55 degrees and the average global apical deviation was 2.62 mm. Significant differences were identified between the DNS and FH groups for angular deviation (p<0.05), apical non-depth deviation (p<0.05) and between the Global apical deviation(p<0.05). Conclusion: Dynamic navigation demonstrated superior accuracy and precision over freehand in the context of apical microsurgery preparations. This study provides further proof of concept for the application of DNS in Endodontics. Clinical significance: Apical surgery can be a daunting task for an endodontist. Surgical guides can make the procedure easier, but they take time and money to make. DNS virtual planning can be completed rapidly and may be altered mid-procedure. This inherent flexibility makes same-day guided apical surgeries practical and predictable.

Evaluation of the shaping ability of different rotary file systems in severely and abruptly curved root canals using cone beam computed tomography

BackgroundWhen selecting an instrument for canal preparation, it is important to consider several parameters that influence the shaping efficiency, including instrument design, metallurgy, and operating motion. This study aimed to evaluate the shaping ability of the ProTaper Next (PTN), WaveOne Gold (WOG), and XP-endo Rise Shaper (XPRS) rotary systems in severely and abruptly curved root canals using cone beam computed tomography (CBCT) and ImageJ software. Materials and MethodsForty-eight mesial root canals of the mandibular first molars were assigned equally to three groups: PTN, WOG, and XPRS. Using ImageJ software, CBCT images were acquired pre- and post-instrumentation to assess dentin removal, remaining dentin thickness (RDT), canal transportation, and centering ratio at the coronal, middle, and apical levels. Statistical analyses were conducted on all numerical data. ResultsAll rotary systems removed significantly more distocoronal dentin in the danger zone (DZ), than the mesiocoronal area. PTN removed significantly more dentin and caused less RDT than XPRS (p < 0.05). However, there were no significant differences between PTN-WOG and WOG-XPRS. In the DZ, the highest percentage of specimens with an RDT < 0.5 mm was observed when using PTN (50%), followed by WOG (31.3%), and XPRS (6.3%). Compared with PTN and WOG, XPRS demonstrated less coronal transportation. Among all rotary systems, there was no significant difference in apical transportation or centering ratio. ConclusionsBased on our observations, all rotary instruments exhibited a tendency to remove dentin in the DZ, but to different degrees. XPRS demonstrated better results in terms of coronal transportation and dentin thickness in the DZ. Comparable centering abilities and minimal apical transportation were demonstrated using all rotary instruments.

A Fluorescence-based Method to Reaccess Root Canals in Endodontically Treated Teeth: A Micro–Computed Tomography Tridimensional Assessment

IntroductionThe aim of this study was to evaluate the volume of dentin removal and the volume of remnants of restorative material after the removal of an esthetic restorative coronal set and cervical barrier in endodontically treated mandibular molars with the aid of different magnification methods using 3-dimensional (3D) micro–computed tomographic (micro-CT) morphometric analysis. MethodsA sample of 30 mandibular first molars (N = 30) was used. All teeth were endodontically treated, and the specimens were initially scanned using micro-CT imaging and reconstructed. The molars were filled by a single-cone technique, and immediately the material at the initial 2-mm cervical level was removed. Cervical barriers were confected using ionomer glass cement with fluorescein 0.1%, filling the 2 mm at the cervical level of the canals and an additional 2 mm as the base. The coronal restoration set was performed using esthetic resin composites. A simulated tooth aging process was performed with 20,000 thermocycling cycles. The sample was distributed into the following 3 groups (n = 10) for the removal of the restoration set and cervical barrier with diamond burs based on the magnification aid: no magnification aid (naked eye), operative microscope aid, and REVEAL device (Design for Vision Inc, Bohemia, NY) aid. After removal, the final 3D micro-CT scanning and reconstruction were conducted with the same parameters as the initial scanning, and superposition of the final and initial scanning was performed. Morphometric analysis was conducted using CTAn software (Bruker microCT, Kontich, Belgium) to assess the volume of remnant restorative material (mm³), the volume of dentin removal (mm³), and the direction and site of dentin removal. Data were analyzed using 1-Way analysis of variance (P < .05). ResultsThe REVEAL group showed better results regarding the volume of remnant material (3.17 ± 1.65) and the percentage of dentin removal (2.56 ± 1.34). The microscope group showed no statistical difference compared with the REVEAL group regarding dentin removal (3.30 ± 1.48) and was statistically similar to the naked eye group in the volume of remnant material (9.63 ± 4.33). The naked eye group showed the worst results for the volume of remnant material (7.60 ± 2.68) and the percentage of dentin removal (6.60 ± 3.70). ConclusionsThe use of fluorescence associated with magnification was the method that presented the best results, with lower percentages of dentin removal and smaller volumes of remaining restorative material. This is an innovative technology in endodontics that shows potential to overcome the challenge of reaccessing root canals in the context of endodontic retreatment.

Traditional Versus Advanced Pulp Capping Materials in Primary Teeth.

In situations where pulp degeneration and carious lesions may coexist, pulp therapy is a regularly employed method. Mineral trioxide aggregate, a material that is now utilized for indirect pulp treatment (IPT), is nontoxic and nonmutagenic. There is proof that the restoration margin can be sealed to manage the caries lesion. In terms of the clinical and radiological outcome, it has been demonstrated that IPT is more effective and secure than direct pulp capping and pulpotomy. The pulp capping treatment's goal is to protect the pulp from microorganisms as well as from thermal, electrical, chemical, and physical stimulation. There is evidence that suggests targeted caries clearance and composite restoration may stop caries lesions more effectively than full dentin removal. Various pulp capping materials that are available in the market were highlighted in this review, and the discussion of each material was expanded to demonstrate its clinical efficacy. Articles were specifically selected and discussed for the materials used for the IPT in the primary teeth as very few studies have been done so far in relation to this subject. A literature search in various libraries, including PubMed, Cochrane, ResearchGate, Scopus, ScienceDirect, and other libraries, was done for several available materials that have been used for the IPT procedure in primary dentition in the last 20 years.

Inverted Layering Technique as a Biomimetic Procedure in a Multidisciplinary Resolution of Discolored Teeth: A Case Report.

The objective of this work is to report a restorative approach with composite resin applied in reverse in the aesthetic resolution of darkened anterior teeth. A 27-year-old female patient presented with the main complaint of dissatisfaction with the aesthetics of her smile due to dental darkening, a result of childhood trauma, without painful symptoms, pathological clinical signs or change in care. In the intraoral examination, a darkening of teeth 11 and 21 was observed, which radiographically showed thickening of the periodontal ligament, with disharmonious configuration of the marginal gingiva. From the clinical and radiographic characteristics, we opted for periodontal intervention for recovery and gingival levelling, followed by endodontic intervention and aesthetic restorative restoration. The restorative step was carried out sequentially by internal tooth bleaching, removal of dentin still pigmented after bleaching and enamel preservation. Soon after, it was restored in an alternative way and layered using a technique called reverse, using strips of polyethylene fiber over the dentin resin. The technique preserved the remaining enamel with the maintenance of the original remaining guides, proving to be a viable conservative alternative since of the diagnosis to the restorative conclusion in view of the longitudinal confirmation of the restorative efficacy after 1 year.

Clinical conduct of dentists in the treatment of deep dental carious lesions

Different techniques are employed to contain the carious process: non-invasive, microinvasive, and invasive, and with restorative needs. Thus, it is essential that dentists are duly updated regarding scientific evidence and perform with skill and precision the techniques proposed as treatment, being aware of the consequences and risks, and aiming at the most conservative therapy. Objective: To identify the clinical practices for the treatment of deep carious lesions used by dental surgeons of the Family Health Strategy (FHS) program of a Brazilian city. Material and methods: This was a quantitative and cross-sectional study carried out with 43 dental surgeons from the FHS program in the city of Sobral, State of Ceará, Brazil, using a Google Forms online questionnaire, containing questions related to the clinical criteria used during caries removal, deep dentin caries removal techniques, lining materials, survival rate of some treatments, in addition to sociodemographic data and questions regarding professional qualification. Results: Among those interviewed, 62.8% were aged between 25 and 30 years. Most dentists (58.7%) considered that the cavity floor should be hard at the end of the carious dentin removal, which demonstrates the non[1]adherence to Selective Carious Tissue Removal (SCTR) protocols. Only 25.6% considered SCTR a treatment with a chance of success and a 2-year survival rate greater than 80%. More than half of the interviewees (51.2%) disagreed with the maintenance of carious tissue in the axial/pulp walls of deep cavities to preserve pulp vitality. More invasive treatments were preferred in a greater proportion by dentists who work exclusively in the public sector (66.7%) compared to those who also work in the private sector (17.6%) [p=0.002], with an evident need for cariology education workshops and more studies on the topic. Conclusion: The dentists who participated in the study showed little adherence to less invasive techniques in the treatment of deep carious lesions.

Cone Beam Computed Tomography Analysis of Post Space in Bifurcated Premolars Using ParaPost and Peeso Reamer Drills

Introduction Core buildups are usually maintained by the usage of posts. Even so, in curved and narrow canals, such as bifurcated premolars, excessive dentin removal during post-space preparation can result in a vertical root fracture or perforation. In order to preserve root canal dentin during post-space preparation of bifurcated premolars, this study examined and analyzed the effects of two widely used drills: Peeso Reamer (Dentsply Maillefer, Ballaigues, Switzerland) and ParaPost (Coltene/Whaledent, Inc., Altstätten, Switzerland). We also examined the risks associated with using Cone-beam Computed Tomography (CBCT). Methods Three operators with varying levels of experience treated a total of 72 removed bifurcated premolars, dividing them into equal groups. The rotary ProFile system (Dentsply Sirona, Charlotte, NC) was utilized for root canal treatments, and gutta-percha size #30/0.4 was used for obturation. Peeso Reamer #2 and ParaPost #1 were then used to prepare the palatal canals. CBCT was used to assess the total mean intracanal spaces of 3 mm, 5 mm, and 7 mm that were measured both preoperatively and postoperatively. To compare the mean dentin thickness within the canal area across all groups, we used analysis of variance testing. We detected complications, like deviations or perforations, using mesiodistal periapical radiographs. Results When utilizing the Peeso Reamer, the mean dentin thickness (0.749 mm) was slightly more than when using the ParaPost (0.736 mm) with p=0.16. There was no significant difference in the mean dentin thickness of the canal area between the Peeso Reamer and the ParaPost drills. The Pesso Reamer drill had fewer complications since it matched the canal configuration, while the Parapost drill removed somewhat more dentin in the canal area. Only seven teeth with minimum deviation from the center of the canal during preparation were produced by the Peeso Reamer drill (20% of teeth having deviation), whereas twenty-one teeth had deviations (72.2% of teeth) and eight had furcal perforations generated by the ParaPost. Conclusion Within the limitations of our study, the Pesso Reamer drill caused little more dentin removal than the ParaPost drill. However, the Peeso Reamer had fewer risks and was safer to use in bifurcated premolars. The ParaPost drill is not recommended in bifurcated premolars due to the high risks of deviation and perforation because they have narrow canals. The selection of an appropriate drill for post-space use in bifurcated premolars is essential for successful patient outcomes.

Management of Separated Endodontic Instrument in Mandibular Second Molar with Bypass Technique

One of the most common mishaps in root canal treatment is a separated endodontic instrument. Bypass technique is an effective alternative besides file retrieval while clinical conditions have lack of access and visibility. Other than, this technique gives a more conservative outcome because it prevents more dentin removal. The aim of this case report was to describe management of separated endodontic instruments in the mandibular second molar with bypass technique during endodontic treatment. A 3,5 mm F1 ProTaper Hand Use file was separated in the mesiobuccal canal of the mandibular second molar. Radiograph examination was taken to make sure the level of fragment. Bypass was performed with #10 until #25 K-File to pass the separated instrument through the gap between it and the root canal wall. Obturation has been done with gutta percha and resin-based sealer using cold lateral condensation technique. Direct restoration was chosen as final restoration after 6 days follow up. Bypass technique can be performed as management of separated instrument considering the risks involved fragment extrusion to apical region, secondary separated instrument, and conservative aspect.

The use of the autofluorescence diagnostics device for controlled сaries excavation

The modern standard in dentistry is minimally invasive treatment, as it allows you to preserve the viability of teeth.&#x0D; The purpose of this study was to evaluate the possibility of using an autofluorescence diagnostic device (AFS) to determine the end-points of the carious cavity preparation.&#x0D; Material and methods. The study was conducted on ten third molars extracted for medical reasons. Autofluorescence with AFS device and caries-marker were used to visualize infected carious dentin at different stages of cavity preparation.&#x0D; Results. The method showed effectiveness for differentiating affected and infected dentin. Sound dentin, dense carious dentin, and soft infected dentin was characterized with green, orange, and red fluorescence, respectively. The data obtained from caries markers do not always coincide with the probing indicators and the AFS device. For the FACE method with AFS device sensitivity, specifity, and overall diagnostic accuracy were 81.8%, 88.9%, and 85%, respectively. For the caries-marker sensitivity, specifity, and overall diagnostic accuracy were 90%, 77.8%, and 80%, respectively.&#x0D; Conclusions. The AFS device allows selective removal of infected dentin more carefully compared to caries-marker staining as fluorescence allows us to visualize infected dentin and to preserve demineralized (affected) dentin.

Fracture strength of fiber post with polyetheretherketone post: An In vitro comparative study

Abstract Aim: To assess and compare the fracture strength of polyetheretherketone (PEEK) post materials with fiber posts on endodontically treated maxillary central incisors. Materials and Methods: In this in vitro comparative study, two dental post materials were evaluated: fiber-reinforced post and PEEK post. Simple random sampling was done and 30 specimens were fabricated using extracted, decoronated, and endodontically treated maxillary central incisors (n = 15 for each group). Post-space preparation was done 5 mm short of the apex and restored with prefabricated fiber post (n = 15) and customized PEEK post (n = 15). Samples were mounted in a cold cure acrylic cylindrical block, at 45° angulation for testing the fracture strength using a universal testing machine. The data were analyzed and compared statistically, using an independent t test. Results: Mean fracture strength of the PEEK post was 65.79 kg and the fiber post was 59.32 kg with no statistically significant difference in the fracture strength between the two groups. Conclusion: Within the limitations of the study, it can be concluded that the PEEK post has similar mechanical properties to the fiber post and could be considered as an alternative to the fiber post having the advantages of being custom-made requiring conservative canal preparation with minimal dentin removal.

The Impact of Coronal Flaring Files on Pericervical Dentin Thickness in Mandibular Molars

IntroductionThis study aimed to assess the influence of different coronal flaring files on dentin removal in mandibular teeth using cone-beam computed tomographic (CBCT) images. MethodsCBCT images of 48 mandibular molar teeth were acquired and randomly divided into 2 main groups, with each main group further divided into 3 subgroups. In the first main group, root canal preparation was performed using TruNatomy (Dentsply Sirona, Ballaigues, Switzerland), ProTaper Gold (Dentsply Sirona), and One Curve (Micro-Mega, Besancon, France) files without the use of coronal flaring files. In the second main group, root canal preparation was performed using the same files with the use of coronal flaring files. After the completion of root canal preparation, a second set of CBCT images was obtained. Subsequently, the dentin removal and remaining critical dentin were assessed by measuring at 4 distinct points below the furcation level. Data were compared between groups using the Mann-Whitney U and Kruskal-Wallis tests with alpha set at 5%. ResultsThe ProTaper Gold files demonstrated higher dentin removal compared with the TruNatomy files. In the no-flaring groups, the One Curve files exhibited greater dentin removal than the TruNatomy files at specific levels. The use of coronal flaring files generally did not significantly impact dentin removal, except for certain cases in the TruNatomy and ProTaper Gold groups. ConclusionsThe TruNatomy instrument group was more effective in preserving pericervical dentin compared with the other instrument groups. Coronal flaring files can be confidently used to preserve critical dentin during root canal treatment.

Evaluation of Carisolv in the Chemico-Mechanical Removal of Carious Dentine in Primary Molars (In vivo study)

Caries removal by the Chemo-mechanical technique involves the application of chemical agents, to cause a selective softening of the carious dentine and facilitate removal by gentle excavation. Carisolv is one such new chemical agent used in this minimal invasive technique of carious dentine removal. The aims of this study was to evaluate the efficacy of Carisolv in the chemo-mechanical removal of carious dentine in primary teeth, the time taken for caries removal and to evaluate the restorations radiographically. Forty primary 1st and 2nd molars with dentinal carious lesions were excavated using this technique of caries removal. After isolation of the involved tooth, the Carisolv " new gel" marketed by Mediteam Dental AB (Goteborg, Sweden) was applied then the superficial softened carious dentine was gently excavated and scraped using a spoon excavator, the procedure repeated until the cavity was free from caries and the cavity was checked for remaining caries using an explorer. The time taken for the removal of carious dentine, beginning from the application of the gel until the completion of the procedure was evaluated using a stopwatch. After the placement of the restoration an intra-oral periapical radiograph was taken for immediate evaluation and after a period of six months, the longevity of the restorations and the presence of secondary caries at the restoration- dentine interface were evaluated radiographically. The statistical analysis of the results showed that the soft carious dentine was removed more effectively than the hard carious dentine and the removal of the soft carious dentine required a shorter period of time (4.96±0.99) minutes when compared to the removal of hard carious dentine (6.09±1.04) minutes and on radiographic evaluation of the restoration, none of the treated lesions showed the presence of secondary caries. In conclusion, the chemico-mechanical caries removal technique using Carisolv proved to be an effective atraumatic treatment modality with potential interest for use in clinical pediatric dentistry.

Impact of Access Cavity Design on Fracture Resistance of Endodontically Treated Maxillary First Premolar: In Vitro.

This study was designed to investigate the impact of access cavity designs on fracture resistance of endodontically treated maxillary first premolars. The study sample consisted of 72 intact maxillary first premolars, randomly divided into six groups (n = 12). A standardized proximal cavity preparation was prepared for all samples using standard bur. Groups I: control group with only standard proximal cavity and no endodontic access, group II: Truss access cavity, group III: Separated access to buccal and palatal canals without removal of dentine in between, group IV: Access to buccal and palatal canals with removal of dentine in between, group V: Traditional access cavity, group VI: Mesio-occlusal-distal cavity (MOD). For groups I and VI, only composite restoration was used to restore the proximal cavity, while for groups II- V, the access was prepared and endodontic treatment was performed on all teeth, then composite restoration was placed. The root canals were instrumented using nickel-titanium files, irrigated with sodium hypochlorite, and filled with AH plus sealer and gutta-percha using warm vertical condensation. All samples were then placed in an acrylic mold and underwent thermal aging for 10,000 cycles between 5 and 55°C. The samples were fixed in a universal testing machine with the long axis of the roots positioned at 20° to a load applied at a crosshead speed of 1 mm/min using a stainless steel semi-spherical indenter (Ø = 3 mm) until fracture occurred to determine the fracture resistance force in Newton. The normality test (Shapiro-Wilk) showed that data are normally distributed. Group II exhibited the highest mean fracture resistance, and group VI was the least likely to resist the fracture. No statistically significant differences between tested groups (p-value = 0.237). The MOD group showed a more unfavorable mode of fracture compared to other groups. No significant difference in fracture resistance between conservative and traditional access cavities. The missing marginal ridges, such as in MOD cavities played an important role in decreasing the fracture resistance of endodontically treated teeth.

Glycolic acid and ultrasonic activation: Effects on smear layer removal, dentin penetration, dentin structure and bond strength of the root dentin filling material.

Glycolic acid (GA) has been tested as enamel and dentin etchant, and final irrigant for smear layer removal. This study evaluated the effects of GA and ultrasonic activation (US) on smear layer removal, dentin penetration, dentin structure and bond strength of the root dentin filling material. The root canals of 210 teeth were distributed into four test groups: smear layer removal (N=50), dentin penetration (N=50), dentin structure (N=10) and bond strength (N=100). In all tests, specimens were subdivided into five groups, according to the final irrigation protocols: G1:distilled water(DW)+US; G2:17% EDTA; G3:17% GA; G4:17% EDTA+US; G5:17% GA+US. Scanning electronic microscopy, confocal laser scanning microscopy, transmission electronic microscopy and the push-out test were performed to evaluate smear layer removal, dentin penetration, dentin structure and bond strength, respectively. Statistical analysis was performed for each evaluation (α=5%). Groups 4 (EDTA+US) and 5 (GA+US) were the most effective on smear layer removal, with no statistical differences from each other (p>0.05). The maximum penetration depth into dentinal tubules was observed for group 5(GA+US), being statistically different from all other groups (pp<0.05). Group 5(GA+US) showed the largest collagen dispersion area, being statistically different from groups 1(DW+US), 2(EDTA) and 3(GA) (pp<0.05), and similar to group 4(EDTA+US) (p>0.05). The highest BS values for filling and restorative material were observed for all experimental groups, being statistically different from control group (pp<0.05), with higher predominance of cohesive failure. The association of GA and US promotes better smear layer removal, dentin penetration and collagen dispersion, with no influence on bond strength of the root dentin filling/restorative material. Key words:EDTA, final irrigation, glycolic acid, ultrasonic activation.

Root canal curvature influences uncontrolled removal of dentin and cleaning efficacy after ultrasonic activation.

This study evaluated the correlation between root canal curvature and the effects of ultrasonic irrigation in the following parameters: volume of uncontrolled dentin removal (UDRVol), maximum depth of dentin defects, removal of accumulated hard tissue debris (AHTD), and canal transportation in prepared curved root canals. Twenty-four human permanent mandibular molars were divided into two groups according to root canal curvature: moderate curvature (MC: mean 25°); and severe curvature (SC: mean 48°). The specimens were scanned using an X-ray microcomputed scanner (Skyscan 1172) before and after cleaning and shaping and after the final irrigation protocol with ultrasonic irrigation. There was a moderate correlation between the degree of root canal curvature and the volume of remaining AHTD (p<0.05) and between the degree of root canal curvature and maximum depth of defects due to uncontrolled removal of dentin (p<0.05). The teeth in the SC group had a greater maximum depth of defects on the dentin wall in the apical third than the teeth in the MC group (p <0.05). Both groups had a significant reduction of AHTD in all canal thirds, but the amount of remaining AHTD in the middle and apical thirds and the whole canal was significantly greater in the SC than in the MC group (p <0.05). Canal transportation was not influenced by the canal curvature in all thirds (p >0.05). This study concluded that root canal curvature affects significantly the uncontrolled removal of dentin and remaining AHTD volume after the final irrigation protocol with ultrasonic irrigation.

CBCT Comparison of the Remaining Dentin Thickness Following Biomechanical Teeth Preparation using Edge Endo X7, Hero Gold, and Neo Endo Flex Rotary File Systems: An In-vitro Study

Introduction: Success in endodontics depends on canal preparation, disinfection, and obturation. Cleaning and shaping play a pivotal role in successful endodontic therapy. An important factor in preventing procedural mishaps and further complications is the quantity of dentine removed during instrumentation because the fracture resistance of the root is directly influenced by the amount of dentine that remains after instrumentation. Aim: To evaluate and compare the remaining dentine thickness of the root canal after instrumentation with three different rotary file systems using Cone Beam Computed Tomography (CBCT) imaging. Materials and Methods: Thirty permanent extracted, singlerooted teeth were collected. The samples were decoronated at the level of the Cementoenamel Junction (CEJ). A preinstrumentation CBCT scan was taken. Access opening and working length were determined. The samples were randomly assigned to three groups: Group I - Edge Endo X7, Group II- Hero Gold, Group III - Neo-endo flex files. Biomechanical preparation was carried out using the respective files. To evaluate the remaining dentine thickness, a comparison was made with the pre-instrumentation CBCT scan. Statistical analysis was performed using One-way ANOVA. Results: Upon inter-group comparison of the pre-instrumentation group, no significant difference (p≥0.05) was observed. Postinstrumentation, it was noted that the remaining dentine thickness in Group I (p≤0.05) at the apical third was significantly less than in Group II (p=0.007) and Group III (p=0.042). Maximum preservation of dentine was seen with Hero gold files, whereas the minimum preservation of dentine was seen with Edge Endo X7. Conclusion: Hero gold files exhibited less removal of dentine apically, whereas Edge Endo X7 showed more removal of dentine apically

Shear Bond Strength of Adhesives Placed following Selective Removal of Red-Fluorescing Carious Dentine in vitro

Red-fluorescing dentine indicates bacterial contamination [Caries Res 2002; 36: 315–319]. We investigated effect of removal of red fluorescent dentine caries on shear bond strength and fracture mode of 4 adhesive approaches. Sixty-five carious teeth and 50 noncarious controls were distributed into 4 groups: Clearfil™ self-etch (CSE), OptiBond™ FL total etch (OTE), Scotchbond™ Universal total etch (STE) and self-etch (SSE). Samples were excited at 405 nm and viewed through 530 nm filter. Carious samples were ground flat exposing strongly red-fluorescing (StrongRF) dentine, on which a composite cylinder was placed, using one of 4 adhesives. After 22 h in water, shear bond strength and fracture mode were analysed. StrongRF was removed; composite cylinders were placed on weakly red-fluorescing (WeakRF) dentine and tested as described above. Finally, red-fluorescing dentine was removed, and composite cylinders were placed on non-fluorescing (NonRF) dentine and tested. Composites were placed at 3 corresponding heights in controls. After 22 h in water, shear bond strength testing and fracture mode analysis were performed. Differences were tested using Mann-Whitney or Wilcoxon tests (p ≤0.05). Median (Q1, Q3) shear bond strength on StrongRF was SSE 14.4 (9.2, 18.2) MPa >CSE 10.2 (6.4, 17.3) MPa >STE 9.1 (6.9, 11.2) MPa >OTE 6.8 (4.0, 10.8) MPa. Shear bond strength increased statistically significantly for all adhesives on WeakRF: SSE 19.8 (13.6, 24.3) MPa >STE 19.5 (12.7, 23.1) MPa >CSE 17.5 (12.0, 22.5) MPa >OTE 15.8 (11.9, 20.9) MPa. Only STE 25.6 (22.4, 29.1) MPa and CSE 22.1 (17.6, 24.6) MPa were significantly different on NonRF compared to WeakRF. For controls tested at corresponding depths, superficial shear bond strength was OTE 18.7 (16.0, 22.1) MPa >STE 18.4 (12.0, 25.9) MPa >CSE 18.1 (12.7, 20.7) MPa >SSE 13.0 (9.6, 17.8) MPa. This was significantly higher compared to StrongRF except for SSE. Central shear bond strength was not significantly different to WeakRF, deep shear bond strength was significantly lower for SSE and CSE but higher for OTE compared to carious. Conclusion: StrongRF dentine should be removed for higher shear bond strength, but WeakRF dentine can often be preserved without compromising adhesive bond strength.