Cyclic Fatigue of Different Reciprocating Endodontic Instruments Using Matching Artificial Root Canals at Body Temperature In Vitro.

Reciprocating motion expands the lifetime of endodontic instruments during the preparation of severely curved root canals. This study aimed to investigate the time to fracture (TTF) and number of cycles to failure (NCF) of different reciprocating instruments (n = 20 in each group) at body temperature using a dynamic testing model (amplitude = 3 mm). Reciproc Blue (RPB), size 25/.08, WaveOne Gold (WOG) 25/.07, Procodile (Proc) 25/.06, R-Motion (RM_06) 25/.06 and R-Motion (RM_04) 30/.04 instruments were tested in their specific reciprocating motion in artificial matching root canals (size of the instrument ± 0.02 mm; angle of curvature 60°, radius 5.0 mm, and centre of curvature 5.0 mm from apical endpoint). The number of fractured instruments, TTF, NCF, the and lengths of the fractured instruments were recorded and statistically analysed using the Chi-Square or Kruskal-Wallis test. Both TTF (median 720, 643, 562, 406, 254 s) and the NCF (3600, 3215, 2810, 2032, 1482 cycles) decreased in the following order RM_06 > RPB > RM_04 > Proc > WOG with partially significant differences. During testing, only six RM_06 instruments fractured, whereas 16/20 (RPB), 18/20 (Proc), and 20/20 (RM_04, WOG) fractures were recorded (p < 0.05). Within the limitations of the present study, blue-coloured RPB and RM instruments exhibited a significantly superior cyclic fatigue resistance compared to SE-NiTi and Gold-wire instruments. Heat treatment, cross-sectional design and core mass significantly influenced the longevity of reciprocating instruments in cyclic dynamic testing.

Comparative Analysis of Irrigation Techniques for Cleaning Efficiency in Isthmus Structures.

INTRODUCTION: This study aimed to evaluate the removal of a biofilm-mimicking hydrogel from isthmus structures in a simulated complex root canal system consisting of 2 curved root canals by Laser-activated irrigation (LAI, AdvErl Evo, Morita) and mechanical activation techniques. METHODS: A 3D-printed root canal model with 2 parallel root canals (60°-curvature, radius 5 mm, dimension 25/.06) with a total length of 20 mm connected via isthmuses (2.5 × 0.4 × 0.2 mm) at 5 mm and 8 mm from the apical endpoint and with lateral canals (diameter 0.2 mm) in all directions at 2, 5, and 8 mm from the apex was filled with a colored biofilm-mimicking hydrogel. Irrigation protocols under continuous irrigation with distilled water (3 × 20s per root canal; 3 ml/20s; n = 20) included conventional needle irrigation (=NI); manual agitation (=MA, gutta-percha point 25/.06); EndoActivator (=SAI-EA, 25/.04); EDDY (=SAI-E, 25/.04); ultrasonically-activated irrigation (=UAI) and LAI (Er:YAG-laser; P400FL tip at canal entrance; 25pps, 50 mJ, 300µs). Removal of the hydrogel was determined as a percentage via standardized photos through a microscope. Statistical analysis was performed using Kruskal-Wallis and Conover tests (P = .05). RESULTS: Laser-activated irrigation (LAI) was associated with the greatest removal of hydrogel from the entire root canal system (P < .05), followed by SAI-E. No significant differences were reported for the coronal isthmus between LAI, SAI-E, NI, and MA (P > .05), but inferior results for SAI-EA and UAI (P < .05). In the apical isthmus, all techniques outperformed UAI (P < .05), with LAI, SAI-E, and NI showing the best results (P < .05). CONCLUSIONS: Laser-activated irrigation (LAI) was superior to other irrigation techniques in the entire root canal system. SAI-E and NI performed comparable to LAI in the isthmuses.

Influence of pulse energy, tip design and insertion depth during Er:YAG-activated irrigation on cleaning efficacy in simulated severely curved complex root canal systems in vitro.

AIM: To investigate the influence of pulse energy, tip geometry and tip position in simulated 3D-printed root canals with multiple side canals at different levels in all directions on the cleaning performance of laser-activated irrigation (LAI) compared to sonic activation (EDDY) and conventional needle irrigation (NI). METHODOLOGY: 3D-printed root canal models (25/.06, length 20 mm, curvature 60°, radius 5 mm) with side canals (diameter 0.2 mm) at 2, 5 and 8 mm from the apex were filled with coloured biofilm-mimicking hydrogel. LAI (Morita AdvErL Evo, Kyoto, Japan) was performed with six settings (n = 20; pulse-energy, pulses per second [PPS], tip position): LAI1 (50 mJ, 25 PPS, P400FL, canal entrance [CE]), LAI2 (same as LAI1, but insertion depth 9 mm before the apical endpoint [AE] [corresponding to 1 mm above the first lateral canals]), LAI3 (80 mJ, 25 PPS, P400FL, 9 mm before AE), LAI4 (same as LAI 3, but at CE) for 3 × 20 s each, LAI5 (50 mJ, 25 PPS, P400FL 2 × 20 s, CE & R200T (30 mJ, 25 PPS, 1 × 20 s, 9 mm before AE), LAI6 (30 mJ, 25 PPS, R200T, 9 mm before AE, 3 × 20 s). A continuous irrigation (3 mL/20 s) using distilled water accompanied the irrigation cycles. NI and EDDY (3 × 20 s each; 3 mL/20 s irrigation, insertion AE minus 1 mm, amplitude 4 mm) served as control groups. Biofilm-mimicking hydrogel removal (ImageJ, NIH) was assessed for the entire system, the central canal and the lateral canals using standardized photographs with a microscope (Expert DN, Müller-Optronic) and statistically analysed was performed using Kruskal-Wallis and Dunn tests (p = .05). Irrigant extrusion beyond the foramina was also recorded. RESULTS: LAI2 (99.08%; interquartile range [IQR]: 96.85-100.00) and LAI3 (97.50%; 96.24-100.00) achieved the significantly best and LAI6 (80.08%; 73.41-84.69) the significantly worst removal of hydrogel from the entire root canal system amongst all LAI configurations (p < .05). There were no significant differences between LAI6, EDDY (72.89%; 67.49-76.22) and manual irrigation (54.39%; 51.01-56.94) (p > .05). R200T laser tip caused significantly more often irrigant extrusion than all other techniques (p < .05). CONCLUSION: Tip design, energy settings, and the positioning of the laser tip below the canal entrance caused an improvement in cleaning performance of the LAI. However, the small R200T tip created significantly more procedural errors (irrigant extrusion) due to higher concentrated energy.

Guided endodontics versus conventional access cavity preparation: an ex vivo comparative study of substance loss.

BACKGROUND: To compare the outcomes of conventional access cavity preparation (CONV) versus guided endodontics (GE) for access cavity preparation in anterior teeth with pulp canal calcification (PCC) regarding root canal detection, substance loss, procedural time, and need for additional radiographs. METHODS: Extracted, sound human teeth with PCC (n = 108) were matched in pairs, divided into two groups and used to produce 18 models. An independent endodontist and a general dentist performed access cavity preparation under simulated clinical conditions on nine models each (54 teeth). The endodontist used the conventional technique and the general dentist GE. Time needed to access the root canals and the number of additional radiographs were recorded. Pre- and postoperative cone-beam computed tomography scans were obtained to measure substance loss. Statistical significance was tested by examining the overlap of 95% confidence intervals (CIs) between the groups. RESULTS: All root canals were successfully accessed by both methods. There were no significant differences in substance loss (CI: CONV 15.9-29.6 mm3 vs. GE 17.6-27.5mm3) or procedural time (CI: CONV 163.3-248.5 s vs. GE 231.9-326.8 s). However, 31 additional radiographs were required for GE compared to none for CONV. CONCLUSIONS: For access cavity preparation in teeth with PCC, both CONV by a specialist and GE by a general dentist produce good results in terms of substance loss and time requirements.

Cleaning Efficiency of Different Irrigation Techniques in Simulated Severely Curved Complex Root Canal Systems.

INTRODUCTION: To compare the biofilm-mimicking hydrogel removal efficiency of laser-activated irrigation (LAI) with five other irrigation techniques in simulated curved root canals with lateral canals. METHODS: Three-dimensional-printed root canal models (60°-curvature, radius 5 mm; dimension 25/.06) with a total length of 20 mm and lateral canals in all directions at 2, 5, and 8 mm (diameter 0.2 mm) from the apex were filled with a colored biofilm-mimicking hydrogel. The following protocols (each 3 × 20 seconds continuous irrigation with distilled water 3 ml/20 seconds; n = 20) were carried out: conventional needle irrigation; manual agitation ([MA], gutta-percha point 25/.06); EndoActivator (=sonically-activated irrigation EndoActivator, 25/.04); EDDY (=sonically-activated irrigation EDDY [SAI-E]; 25/.04); ultrasonically-activated irrigation and LAI (Erbium-doped Yttrium Aluminum Garnet laser; P400FL tip at canal entrance; 25 pps, 50 mJ, 300 µs). Standardized photos were taken with a microscope and the removal of the hydrogel was determined as a percentage for the entire system, the main canal and the lateral canals. Statistical analysis was performed using analysis of variance and Scheffé test (P = .05). RESULTS: LAI (89.3% ± 5.9%) showed the greatest hydrogel removal followed by SAI-E (65.5% ± 3.3%) and ultrasonically-activated irrigation (59.1% ± 4.7%), with significant differences between these groups (P < .05). Needle irrigation, MA, and sonically-activated irrigation EndoActivator performed equally (P > .05) and obtained the significantly lowest values (P < .05). LAI and SAI-E showed the significantly best hydrogel removal from the main canal (P < .05). At all three levels, LAI removed significantly more hydrogel from the lateral canals than all other techniques (P < .05). CONCLUSIONS: LAI was superior to other techniques in both the entire system and the lateral canals in removing the hydrogel. SAI-E achieved comparable results in the main canal.

Assessment of the Prevalence of Radix Entomolaris and Distolingual Canal in Mandibular First Molars in 15 Countries: A Multinational Cross-sectional Study with Meta-analysis.

AIM: The aim of this study was two-folded: i) to assess the prevalence of Distolingual Canal (DLC) and Radix Entomolaris (RE) in Mandibular First Molars (M1Ms), using Cone Beam Computed Tomography (CBCT) images and ii) to assess the impact of sociodemographic factors on the prevalence of these conditions worldwide. METHODS: CBCT images were scanned retrospectively and the ones including bilateral M1Ms were included in the study. The evaluation was performed by 1 researcher in each country, trained with CBCT technology. A written and video instruction program explaining the protocol to be followed step-by-step was provided to all observers to calibrate them. The CBCT imaging screening procedure consisted of evaluating axial sections from coronal to apical. The presence of DLC and RE in M1Ms (yes/no) was identified and recorded. RESULTS: Six thousand three hundred four CBCTs, representing 12,608 M1Ms, were evaluated. A significant difference was found between countries regarding the prevalence of both RE and DLC (P < .05). The prevalence of DLC ranged from 3% to 50%, and the overall prevalence was 22% (95% CI: 15%-29%). RE prevalence ranged from 0% to 12%, and the overall prevalence was 3% (95% CI: 2%-5%). There were no significant differences between left and right M1Ms or between genders for either DLC or RE (P > .05). CONCLUSION: The overall prevalence of RE and DLC in M1Ms was 3% and 22%. Additionally, both RE and DLC showed substantial bilaterally. These variations should be considered by endodontic clinicians during endodontic procedures in order to avoid potential complications.

Parallel endodontic education via social media: An exploratory survey study.

There is insufficient research to evaluate social media's influence on endodontic education. Therefore, this study assessed the percentage of students utilising Facebook in their education and the factors influencing their engagement. A survey was conducted on dental students, interns and dentists undertaking specialist programmes. Categorical data were analysed using Fisher's Exact test and multiple pairwise comparisons. The significance level was set at p < 0.05. Responses were received from 801 participants, with 98.4% using Facebook for endodontic knowledge. Although most students knew that scientific evidence is not always provided, they still deemed such information valuable as it was a practical demonstration of clinical cases. Most students turn to Facebook for endodontic education to compensate for the gap between their academic education and clinical practice. The utilisation of social media for education can be a concerning phenomenon and should not be ignored by academic institutes.

Effectiveness of root canal instrumentation for the treatment of apical periodontitis: A systematic review and meta-analysis.

BACKGROUND: The development of endodontic instruments has rapidly advanced, but their impact on endodontic outcome parameters remains unclear. OBJECTIVES: This systematic review aimed to answer the following PICOT questions: In patients with apical periodontitis (P) what is the effectiveness of root canal instrumentation ([Q1] performed with contemporary techniques [I] in comparison with 'traditional' techniques [C]] and ([Q2] performed with contemporary engine-driven NiTi instruments [I] compared with other types of contemporary engine-driven NiTi instruments [with different design and/or technology] [C]) in terms of clinical and patient-related outcomes (O)? METHODS: After PROSPERO protocol registration, a literature search was conducted using Clarivate Analytics' Web of Science, Scopus, PubMed and Cochrane Central Register of Controlled Trials. Grey literature and major journal contents were examined. Two independent reviewers performed the study selection, data extraction and appraisal of included studies. A quantitative meta-analysis was considered, and statistical heterogeneity and overall quality of evidence were assessed. RESULTS: Nine studies were identified showing substantial methodological differences. Five studies addressed PICOT 1 and three PICOT 2, whereas one study aimed both. A random-effects meta-analysis model was considered for the outcome 'radiographic evidence of normal periodontal ligament space or reduction of apical lesion size' (PICOT 1) based on three studies with 332 evaluable participants and showed that contemporary instrumentation was associated with a more favourable outcome (p = .005) compared with root canal preparation with stainless steel instruments (odds ratio = 2.07 [95%-confidence interval = 1.25-3.44]) with no evidence of statistical heterogeneity (I2  = 0%) but low quality of evidence. DISCUSSION: Albeit a few studies fulfilled eligible criteria, no study had a low risk of bias. Compelling evidence indicating significantly different outcome rates using different endodontic instruments when treating teeth with apical periodontitis is lacking. CONCLUSIONS: In terms of healing, the results of the meta-analysis determined the higher effectiveness of root canal instrumentation performed with contemporary techniques in comparison with conventional stainless steel instruments in patients with apical periodontitis followed for a minimum of 1 year with low quality of evidence. No differences could be demonstrated between preparations with traditional stainless steel and contemporary NiTi instruments for other clinical and patient-related outcomes. REGISTRATION: PROSPERO (CRD42021274642).

Short and Long-Term Solubility, Alkalizing Effect, and Thermal Persistence of Premixed Calcium Silicate-Based Sealers: AH Plus Bioceramic Sealer vs. Total Fill BC Sealer.

This study aimed to investigate the short- and long-term solubility, alkalizing potential, and suitability for warm-vertical compaction of AH Plus Bioceramic Sealer (AHBC), and Total Fill BC Sealer (TFBC) compared to the epoxy-resin sealer AH Plus (AHP). A solubility test was performed according to ISO specification 6876 and further similar to ISO requirements over a period of 1 month in distilled water (AD) and 4 months in phosphate-buffered saline (PBS). The pH of the immersion solution was determined weekly. Sealers were exposed to thermal treatment at 37, 57, 67, and 97 °C for 30 s. Furthermore, heat treatment at 97 °C was performed for 180 s to simulate inappropriate implementation of warm vertical filling techniques. Physical properties (setting time, flow, film thickness according to ISO 6876) and chemical properties (Fourier transformed infrared spectroscopy) were assessed. AHBC and TFBC were associated with significantly higher solubility than AHP over 1 month in AD and 4 months in PBS (p < 0.05). AHBC and TFBC both reached high initial alkaline pH, while TFBC was associated with a longer-lasting alkaline potential than AHBC. Initial pH of AHBC and TFBC was higher in AD than in PBS. None of the sealers were compromised by thermal treatment.

A critical analysis of research methods and experimental models to study the physical properties of NiTi instruments and their fracture characteristics.

The aim of this review is to provide a critical overview of the physical properties (surface hardness, cutting efficiency, bending properties, flexibility and cyclic fatigue resistance) of NiTi instruments. Frequently used experimental models regarding these aspects will be presented and discussed with regard to their strengths and weaknesses. For all these aspects, a plethora of experimental models have been described. Based on a critical appraisal and especially taking the appropriate translation of experimental findings to clinical endodontics into account, suggestions for future research based on clearly defined and valid experimental methodologies will be provided. Up to now, very few attempts have been made to assess which particular physical properties of NiTi instruments exert an impact on the clinical outcome of root canal treatment. Departure from merely focusing on physical properties and fracture characteristics towards more biological aspects in terms of treatment outcome is essential.

Effect of Core Mass and Alloy on Cyclic Fatigue Resistance of Different Nickel-Titanium Endodontic Instruments in Matching Artificial Canals.

Instrument failure during root canal preparation is still a concern among endodontists. However, it remains unclear whether the use of more martensitic alloys or the cross-sectional design parameters (i.e., core mass) significantly improve fracture resistance. The aim of the study was to evaluate the impact of core mass and alloy on dynamic cyclic fatigue resistance of nickel-titanium endodontic instruments in matching artificial canals at body temperature. Two groups were tested. (A) taper 0.04: F360 (Komet, Lemgo, Germany), Twisted file (Sybron Endo, Glendora, CA, USA) (=TF), JIZAI (Mani, Tochigi, Japan) (=J_04) (all size #25) and the variable tapered TruNatomy (Dentsply, Ballaigues, Switzerland) (size #26) (=TN). (B) size #25; taper 0.06: (Mtwo (VDW, Munich, Germany), JIZAI (Mani) (=J_06), and variable tapered Hyflex EDM OneFile (Coltene Whaledent, Altstätten, Switzerland) (=HF). Time, number of cycles to fracture (NCF), and number and length of fractured fragments were recorded and statistically analysed using ANOVA Student-Newman-Keuls, Kruskal-Wallis or Chi-square test (significance level = 0.05). (A) TN showed the significantly shortest time until fracture, followed by TF, F360 and J_04 which also differed significantly, while NCF showed the following order: F360 < TN < TF < J_04 (p < 0.05). Only one J_04 but all instruments of the other groups fractured within the test-limit of 10 min. (B) Mtwo was significantly inferior concerning time until fracture and NCF, compared to J_06 and HF (p < 0.05), which did not differ significantly (p > 0.05). While all Mtwo instruments fractured, only four instruments failed in the other groups (p < 0.05). Within the limitations of this study, alloy and cross-sectional design (i.e., core mass) were critical factors regarding instrument failure, but none of these factors could be determined as a main parameter for increased or decreased time, and cycles to fracture. Rather, it seemed to be the interaction of multiple factors (e.g., longitudinal and cross-sectional design, alloy, and rotational speed) that was responsible for differences in the time and cycles to fracture. Nonetheless, all instruments had lifetimes that allow safe clinical use. However, the superiority or inferiority of an instrument with regard to cyclic fatigue based on laboratory results-even when identical trajectories are guaranteed-may be considered questionable, as the characteristics and design parameters of the instruments vary considerably, and the experimental setups lack additional clinical parameters and thus clinical relevance.

Minimal Dentinal Tubule Penetration of Endodontic Sealers in Warm Vertical Compaction by Direct Detection via SEM Analysis.

Sealer staining using rhodamine B dye to investigate the penetration depth of endodontic sealers was proven unsuitable for this purpose. This study aimed to investigate the sealer penetration depth into dentinal tubules by scanning electron microscopy (SEM). Root canals of 52 human upper central incisors were instrumented using the ProTaper Gold NiTi system (Dentsply Sirona, York, PA, USA) up to size F3. After irrigation with sodium hypochlorite and citric acid combined with ultrasonic activation, the root canals were either filled using the epoxy resin sealer AH Plus (Dentsply Sirona) or the calcium silicate-based sealer Total Fill BC Sealer HiFlow (TFHF, FKG Dentaire, La Chaux-de-Fonds, Switzerland) by warm vertical compaction. Root slices of 1 mm thickness were obtained at 2 to 3, 5 to 6 and 8 to 9 mm from the apex. The root slices were investigated for sealer penetration into the dentinal tubules using SEM according to four root quadrants (buccal, mesial, oral, distal). Statistical analysis was performed by the Kruskal-Wallis test (p = 0.05) as data were not normally distributed according to the Shapiro-Wilk test. AH Plus penetrated significantly deeper into the dentinal tubules compared to TFHF at each root level (p < 0.05). Dentinal sealer penetration was deeper in the bucco-oral direction compared to the mesio-distal direction. AH Plus penetrated deeper into dentinal tubules than TFHF. Warm vertical compaction exerting high pressure on the root canal filling material is not able to press sealers deep into dentinal tubules as penetration depth values did not exceed a mean of 110 µm in SEM.

Debunking the Concept of Dentinal Tubule Penetration of Endodontic Sealers: Sealer Staining with Rhodamine B Fluorescent Dye Is an Inadequate Method.

The aim of this study was to investigate the suitability of rhodamine B dye staining of an epoxy resin sealer (AH Plus) and calcium-silicate-based sealers (Total Fill BC Sealer, BioRoot RCS) to represent the penetration depth of the sealers into dentinal tubules after root canal obturation. In a three-step process, (1) leaching of rhodamine B from sealers into a buffer solution, (2) passive penetration of leached rhodamine B into dentinal tubules, and (3) conformity of rhodamine B penetration assessed by confocal laser scanning microscopy (CLSM), and sealer penetration assessed by scanning electron microscopy (SEM), in root-canal-filled teeth, were evaluated. Rhodamine B dye massively leached out of Total Fill BC Sealer and BioRoot RCS into the phosphate-buffered saline (PBS). A pinkish coloration of AH Plus was found after contact with PBS. Leached rhodamine B dye passively penetrated dentinal tubules from all three sealers when placed on root dentin. No correlation was observed between sealer penetration in SEM and rhodamine B penetration in CLSM. Staining of sealers using rhodamine B is an inadequate method with which to evaluate sealer penetration depth into dentinal tubules, as it overestimates the penetration of sealers into root dentin tubules.

Shaping Ability and Debris Extrusion of New Rotary Nickel-Titanium Root Canal Instruments.

The aim was to evaluate the canal straightening and the amount of apically extruded debris associated with five rotary nickel-titanium when preparing curved root canals. A total of 100 root canals in extracted human teeth (angles of curvatures 20°-30°; radii 5.9-13.5 mm) were divided into five groups (n = 20/group). The groups were balanced with respect to the angle and the radius of canal curvature. The root canals were prepared using conventional austenite 55-NiTi alloy instruments F360, F6 SkyTaper (both Komet, Lemgo, Germany), and the heat-treated NiTi Jizai, Silk-Complex and Silk-Standard instruments (all Mani, Tochigi, Japan) to an apical size 25. The amount of extruded debris was assessed with a micro balance. Statistical analysis was performed using Kruskal-Wallis test with Bonferroni correction at a significance level of p < 0.05. During canal preparation, neither instrument fractures nor procedural preparation errors were noticed. Regarding canal straightening, the use of Jizai instruments resulted in the significantly lowest straightening (p < 0.05), while no significant differences were obtained between all other groups (p > 0.05). Regarding the amount of apically extruded debris, no significant differences between all groups were obtained (p > 0.05). Within the limitations of this study, all instruments performed well, and especially the Jizai instruments showed an excellent shaping ability.

Physico-Chemical Investigation of Endodontic Sealers Exposed to Simulated Intracanal Heat Application: Hydraulic Calcium Silicate-Based Sealers.

The aim of this study was to gain information about the effect of thermal treatment of calcium silicate-based sealers. BioRoot RCS (BR), Total Fill BC Sealer (TFBC), and Total Fill BC Sealer HiFlow (TFHF) were exposed to thermal treatment at 37 °C, 47 °C, 57 °C, 67 °C, 77 °C, 87 °C and 97 °C for 30 s. Heat treatment at 97 °C was performed for 60 and 180 s to simulate inappropriate application of warm obturation techniques. Thereafter, specimens were cooled to 37 °C and physical properties (setting time/flow/film thickness according to ISO 6876) were evaluated. Chemical properties (Fourier-transform infrared spectroscopy) were assessed after incubation of the specimens in an incubator at 37 °C and 100% humidity for 8 weeks. Statistical analysis of physical properties was performed using the Kruskal-Wallis-Test (P = 0.05). The setting time, flow, and film thickness of TFBC and TFHF were not relevantly influenced by thermal treatment. Setting time of BR decreased slightly when temperature of heat application increased from 37 °C to 77 °C (P < 0.05). Further heat treatment of BR above 77 °C led to an immediate setting. FT-IR spectroscopy did not reveal any chemical changes for either sealers. Thermal treatment did not lead to any substantial chemical changes at all temperature levels, while physical properties of BR were compromised by heating. TFBC and TFHF can be considered suitable for warm obturation techniques.

Recognizing and differentiating dental anxiety from dental phobia in adults: a systematic review based on the German guideline "Dental anxiety in adults".

Objectives: The prevalence of "dental anxiety" (DA) is often underestimated and numerous diagnostic methods are available for dental practitioners. It is difficult to differentiate between a dental phobia requiring an interdisciplinary approach and DA, which can be managed by dental practitioners alone. The appropriate use of diagnostic tools is key for the successful management of highly anxious and/or phobic patients. The aim was to provide a guideline to recognize dental fear and to differentiate DA from patients who are highly anxious or even have a phobia. Data sources: In total, 8,929 articles that were selected for the development of the German guidelines for "Dental anxiety in adults" in PubMed, Web of Science, Embase, and MedPilot were filtered for diagnosis of DA disorder. The focus for this review was on the use of scales to measure DA levels. The methods and tools used in the 51 reviewed articles to assess DA levels were evaluated in terms of their practicability and suitability in daily practice to differentiate between phobia (ie, DA disorder) and nonpathologic anxiety. In addition, the internal consistency (Cronbach alpha) of the questionnaires/tools was determined. Conclusion: All identified DA questionnaires validated in the German language had an acceptable to excellent internal consistency (0.7 to 0.986). The only validated questionnaire-free method was galvanic skin reaction measurement. For the assessment of DA and diagnosis of a DA disorder in adults, the survey by means of any suitable questionnaire or even several questionnaires in combination with a behavioral observation of the patient is currently the method of choice.

Real-time intracanal temperature measurement comparing mechanically and laser-activated irrigation to syringe irrigation.

Antibacterial activity and tissue dilution of sodium hypochlorite (NaOCl) are improved by moderately heating the irrigant. Temperature can be risen by preheating or intracanal activation. To assess intracanal temperature development of NaOCl during irrigation activation and syringe activation (SI) in a closed system at 37°C, Type-K thermocouples were inserted close to the root canal of one human single-rooted maxillary canine at the apex and 5 and 10 mm from the apical foramen via drilled holes. The root was positioned in a plastic vial filled with alginate simulating surrounding biological structures. Experiments were performed in a closed environment at 37°C (n = 14): EA: EndoActivator (Dentsply Sirona), EDDY: EDDY (VDW), PUI: passive ultrasonic irrigation, PIPS: Photon-induced photoacoustic streaming (Fotona), S60: SI of 60°C-NaOCl, S45: SI of 45°C-NaOCl, and S20: SI of 20°C-NaOCl. S45, PUI and EDDY lead to minor intracanal temperature increases. EA and PIPS did not influence the intracanal temperature. SI with 60°C-NaOCl resulted in higher intracanal temperatures than activation systems. Temperature dissipation into simulated tissues buffered intracanal temperature changes.

Tube Technique with Light-curing Composite for Removing Fractured Root Canal Instruments: Influence of Polymerization Cycles and Mechanical Exposure.

INTRODUCTION: The purpose of this study was to investigate the influence of both polymerization cycles and mechanical exposure procedures on the adhesion of instrument fragments using a modified tube technique with a light-curing composite. METHODS: Eighty Mtwo instruments (size 15.05; VDW, Munich, Germany) were cut at a diameter of 35/100 mm and clamped in a vice with an overlap of 2 mm. Matching cannulas were filled with SDR composite (Dentsply, York, PA) and placed over the instruments. Prime & Bond Active (Dentsply Sirona, Bensheim, Germany) was used as the bonding material. Glass fiber was inserted from the opposite side into the cannula, and 1, 2, 4, or 6 polymerization cycles of 30 seconds were applied (800 mW/mm2) (n = 20/group). Sixty further identical instruments (n = 20/group) were divided into the following groups: group 1, cut at 10 mm and left unprepared (taper = 5%); group 2, parallelized using diamond instruments (taper = 0%); and group 3, prepared in a way that an inverted conical taper resulted (taper = 2%). Polymerization was performed for 2 minutes. The failure load and mode of failure were determined using a tensile testing device (2 mm/min). Data were statistically analyzed using the Kruskal-Wallis or chi-square test. RESULTS: The failure load increased significantly with the number of polymerization cycles (P < .0001). More than 4 polymerization cycles had no further benefit (P > .05). The failure load in the inverted conical group was significantly lower (P < .0001) compared with the parallel and the unprepared groups. Adhesive failure was significantly more frequent in groups 2 and 3 (20/20) than in group 1 (16/20) (P < .05). CONCLUSIONS: Both the number of polymerization cycles and the mechanical exposure procedures had a significant impact on the adhesive force when using the tube technique.

Imaging of root canal treatment using ultra high field 9.4T UTE-MRI - a preliminary study.

OBJECTIVES: To investigate the potential of 9.4T ultrashort echo time (UTE) technology visualizing tooth anatomy and root canal treatment in vitro. In particular, it was evaluated whether the currently achievable resolution is suited presenting all anatomical structures and whether the root canal filling materials are distinguishable in UTE-MRI. METHODS: Four extracted human teeth were examined using 9.4T UTE-MRI prior endodontic treatment (native teeth), after preparation and after obturation procedure. Root canal obturation was performed using warm vertical compaction (Schilder technique) with an epoxy-resin-based sealer. A single gutta-percha cone measured by MRI served as intensity-reference. MRI results were validated with corresponding histologic sections of the teeth. In addition, all teeth were examined at the different stages with CBCT and conventional X-ray. RESULTS: 9.4T UTE-MRI enabled a precise visualization of root canal anatomy of all teeth at a resolution of 66 µm. After obturation, dentin, sealer and gutta-percha cones showed distinct MRI signal changes that allowed clear differentiation of the obturation materials from surrounding tooth structure. The filling materials, isthmal root canal connections and even dentin-cracks that were identified in the MR-images could be verified in histological sections. CONCLUSIONS: 9.4T UTE-MRI is suitable for visualization of root canal anatomy, the evaluation of root canal preparation and obturation with a high spatial resolution and may provide a versatile tool for dental material research in endodontics.