Effect of preparation size on the removal of accumulated hard-tissue debris from the mesial root canal system of mandibular molars using SWEEPS technology.

OBJECTIVES: This study assessed the influence of preparation size on the efficacy of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and conventional irrigation (CI) on removal of accumulated hard tissue debris (AHTD) from isthmus-containing mandibular molars using micro-computed tomographic analysis. MATERIALS AND METHODS: Sixty extracted mandibular molars with two mesial canals connected by an isthmus were selected. Canals were shaped with Mtwo instruments (VDW, Munich, Germany) up to sizes 25/.06, 40/.04 or 40/.06 (n = 20), and specimens were distributed into 2 final irrigation groups (n = 10): SWEEPS and CI. Roots were scanned at a resolution of 10.5 µm before and after preparation and final irrigation. Data sets were co-registered, and the percentage reduction of AHTD calculated for each specimen was statistically compared using analysis of variance with a of 5% significance level. RESULTS: The preparation size did not significantly influence the percentage reduction of AHTD (p < 0.05), whereas the final irrigation technique had a significant effect on debris removal (p < 0.05). A significant reduction of AHTD was achieved after final irrigation in all groups (p < 0.05); however, SWEEPS was associated with a significantly greater percentage reduction of debris than CI (p < 0.05). None of the specimens presented a completely clean isthmus. CONCLUSIONS: Removal of AHTD was not significantly affected by the preparation size. SWEEPS was associated with significantly less debris than CI. CLINICAL RELEVANCE: SWEEPS performed significantly better than CI regarding the removal of AHTD from isthmus-containing mandibular molars irrespective of the preparation size.

Micro-CT evaluation of frozen and embalmed human cadavers on the effect of root canal preparation on microcrack formation in old dentin.

The aim of this study was to evaluate the existence of preoperative dentinal defects among differently preserved dentoalveolar bone-blocks (frozen vs. embalmed) and to investigate the effect of varying apical forces (low: <4 N, high: 4-8 N) during root canal preparation on microcrack formation using micro-computed tomography (micro-CT). Thirteen embalmed and seven frozen bone-blocks containing 1-3 single rooted teeth were collected. The teeth were evenly divided into three groups (n = 10): FLow (frozen, <4 N), ELow (embalmed, <4 N), EHigh (embalmed, 4-8 N). After working length determination all specimens were scanned preoperatively. Root canal preparation was performed using nickel-titanium instruments sizes 25/.06 and 40/.06 (F6 SkyTaper; Komet, Lemgo, Germany). A postoperative scan was performed and image stacks were co-registered. All cross-sectional images were screened to identify the presence of dentinal defects. The results were expressed as the percentage of teeth/slices presenting dentinal defects. The statistical analyses were performed with Kruskal-Wallis-Test and Mann-Whitney-U-Test (α = 5%). Embalmed specimens presented a significantly higher percentage of slices with preoperative microcracks (p<0.05) than frozen specimens. No significant difference between groups was observed regarding the induction of microcracks (p>0.05). Root canal preparation does not induce microcracks in dentoalveolar bone-blocks from donors of old age, irrespective of the preservation method and the apically directed forces.

Effectiveness of root canal irrigation and dressing for the treatment of apical periodontitis: A systematic review and meta-analysis of clinical trials.

BACKGROUND: Sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) and/or calcium hydroxide (Ca(OH)2 ) are commonly used during root canal treatment. Evaluation of their effectiveness regarding clinical and patient-related outcomes requires further understanding. OBJECTIVES: To assess the effectiveness of root canal irrigation and dressing for the treatment of teeth with apical periodontitis (AP). METHODS: A search was conducted in the PubMed-MEDLINE, Scopus, EMBASE, Google scholar databases and available repositories, followed by hand searches, until July 2021. Eligibility criteria followed the a priori formulated Population, Intervention, Comparator, Outcomes, Timing, and Study design (PICOTS) framework. Clinical studies restricted to English language were included. The revised Cochrane risk-of-bias tool for randomised trials (RoB 2) was used to assess the quality of included studies. Meta-analyses were performed using the fixed-effect model to obtain Risk Ratio (RR) and 95% Confidence Interval (CI), with sensitivity analysis. Overall quality of evidence of meta-analyses was assessed through the Grading of Recommendations Assessment, Development, and Evaluation tool. RESULTS: The search identified 1357 records of which six fulfilled the inclusion criteria, providing data for 'irrigation' from 212 teeth and for 'dressings' from 438 teeth. Two studies reported no significant difference regarding the outcome 'pain at 7 days' using 2% chlorhexidine vs. 5.25% NaOCl and EDTA or after using different concentrations of NaOCl (1% vs. 5%). No significant difference was detected between different NaOCl concentrations regarding the reduction of AP. A meta-analysis was possible for the comparison of single-visit (SV) versus multiple-visits including the use of Ca(OH)2 demonstrating a significant effect in favour of SV (RR: 1.10; 95% CI: 1.03-1.19; p = .007; I2  = 0). RoB of included studies was moderate to low. DISCUSSION: The use of Ca(OH)2 for the treatment of AP may not be beneficial. There is scarce or no evidence fulfilling the proposed PICOTS regarding irrigants and dressings. CONCLUSIONS: There is moderate certainty that SV treatment is associated with better radiographic evidence of normal periodontal ligament space (strict criteria) compared with the use of Ca(OH)2. Reduction of AP is comparable after irrigation with 1% and 5% NaOCl, whereas postoperative pain at 7 days for the irrigants assessed is similar. REGISTRATION: PROSPERO database CRD42021260271.

Clinical performance of CAD-CAM partial-coverage restorations: Experienced versus less-experienced operators.

STATEMENT OF PROBLEM: Less-experienced operators have been shown to require additional training to achieve results similar to those of experienced operators. However, clinical data comparing the survival and success of ceramic restorations by experienced and less-experienced operators by using the computer-aided design and computer-aided manufacturing (CAD-CAM) technology are lacking. PURPOSE: The purpose of this retrospective clinical study was to analyze and compare the clinical performance of CAD-CAM lithium disilicate restorations fabricated by less-experienced (predoctoral dental students) and experienced (dentists) operators. MATERIAL AND METHODS: Patients who received an adhesively luted CAD-CAM lithium disilicate restoration between 2011 and 2019 were included in the study. Clinical performance was assessed by calibrated examiners by using World Dental Federation (FDI) criteria. Success and survival were calculated by the Kaplan-Meier method and statistically compared by log-rank tests and univariate Cox regression analyses. FDI criteria were compared by using Mann-Whitney-U tests (α=.05). RESULTS: Ninety-two restorations (students: n=65, dentists: n=27) were assessed (mean ±standard deviation time from insertion: 4.04 ±1.55 years). The survival rates after 2 years (students: 93.8%, mean annual failure rate [mAFR]: 3.1%; dentist: 96.3%, mAFR: 1.9%) and after 4 years (students: 87.3%, mAFR: 3.3%; dentists: 88.3%, mAFR: 3.1%) were not significantly different (P=.525). Also, success rates after 2 (students: 90.8%, mAFR: 4.7%; dentists: 92.6%, mAFR: 3.8%) and 4 years (students: 82.4%, mAFR: 4.7%; dentists: 76.1%, mAFR: 6.6%) were not significantly different (P=.778). FDI criteria were also not significantly different between less-experienced and experienced operators (P≥.110). CONCLUSIONS: Operator experience did not affect the short-term clinical performance of CAD-CAM lithium disilicate restorations.

Influence of moisture content of frozen and embalmed human cadavers for identification of dentinal microcracks using micro-computed tomography.

The aim of this study was to investigate the influence of moisture content in frozen and embalmed human cadavers on the detection of dentinal microcracks using micro-computed tomography (micro-CT). The group of embalmed specimens included three mandibular and two maxillary segments each containing one tooth. The group of frozen cadavers consisted of two frozen mandibular bone-blocks with two teeth and one mandibular segment containing one tooth. The final number of teeth for each preservation method was n = 5. All specimens were scanned with eight different moisture conditions: 48 h wet, 2 h dry, 48 h wet, 24 h dry, 48 h wet, 1 wk dry, 48 h wet, 1 wk dry. Micro-CT images were screened for the presence of dentinal microcracks. Statistical analysis was performed by nonparametric analysis of variance (α = 5%). Only few microcracks were observed in wet and in 2 h dried bone-blocks with no significant differences (p = 0.63 and p = 0.23, respectively). There was a significant and steady increase of microcracks within the groups of dried specimens as follows: 2 h dry < 24 h dry < first wk dry < second wk dry (all p < 0.008). Preservation method had no significant influence on the visibility of microcracks (p = 0.98). Identification of dentinal microcracks on micro-CT images is influenced by moisture content of cadaveric bone-blocks irrespective of the preservation method.

Comparison of the Bleaching Efficacy of Different Agents Used for Internal Bleaching: A Systematic Review and Meta-Analysis.

INTRODUCTION: The aim of this study was to analyze and compare the efficacy of different bleaching agents typically used for internal bleaching of endodontically treated discolored teeth. METHODS: Electronic databases (PubMed, Web of Science, and Cochrane Library) were searched by 2 reviewers for clinical trials in which the color of endodontically treated discolored teeth before and after internal bleaching was examined using shade guide units (ΔSGU) or a spectrophotometer/colorimeter (ΔE). The efficacies of the bleaching agents were compared using subgroup analyses. Statistical heterogeneity was assessed with the Cochran Q test and I2 statistic. Publication bias was evaluated using funnel plots. RESULTS: Eight studies were included in the systematic review, 6 of which could be included in the meta-analyses. Internal bleaching led to a significant change in tooth shade (ΔSGU: 6.27 [95% confidence interval, 5.36-7.17], ΔE: 12.83 [95% confidence interval, 9.46-16.20]). With regard to ΔSGU, the use of carbamide peroxide (35% or 37%), hydrogen peroxide (35%), and the combination of sodium perborate and hydrogen peroxide (3% or 30%) led to a better bleaching effect than sodium perborate (adjusted P value ≤ .026). Regarding ΔE, there were no significant differences between carbamide peroxide (37%), hydrogen peroxide (35%), and sodium perborate mixed with hydrogen peroxide (P = .051). The risk of bias of the included studies was classified as moderate to high. CONCLUSIONS: Carbamide peroxide, hydrogen peroxide, and sodium perborate have a significant bleaching effect on discolored, root canal-treated teeth. For a valid assessment of shade stability and a comparison of bleaching agents and their concentrations, further studies with long-term recalls are necessary.

Effectiveness of different fiber post removal techniques and their influence on dentinal microcrack formation.

OBJECTIVES: The aim of this study was to evaluate the effectiveness of different fiber post removal techniques and to correlate dentinal loss with microcrack formation. MATERIALS AND METHODS: Forty-five extracted single-rooted teeth were root canal treated and fiber posts were adhesively luted. Specimens were divided into three groups (n = 15) according to the removal technique: long-shaft round bur (EndoTracer #08, Komet, Lemgo, Germany), SonicFlex Endo (KaVo, Biberach, Germany), DT Post Removal Kit (VDW, Munich, Germany). Roots were scanned before post cementation and after post removal using micro-computed tomography. Dentin loss, residual luting material, working time, and the induction of microcracks were assessed. Statistical analysis was performed by using multiple contrast tests (max-t tests, α = 0.05). Correlations between parameters dentin loss/new microcracks and dentin loss/residual material were calculated using Kendall's tau. RESULTS: Post removal with SonicFlex Endo resulted in the highest amount of removed dentin with significant differences to the round bur and the DT Post Removal Kit. No technique was found to completely remove the post and luting material. All techniques induced microcracks with the DT Post Removal Kit presenting the highest number of new defects. No correlation between dentin loss and new microcracks was observed. Deviations from the original root canal occurred in all groups, but no perforation was observed. CONCLUSIONS: All techniques resulted in dentin loss, residual luting material, and the formation of microcracks. However, no correlation between dentin loss and the induction of microcracks was observed. CLINICAL RELEVANCE: As all techniques resulted in microcrack formation and dentin loss, this study emphasizes the risk of iatrogenic damage due to post removal procedures.

COVID-19 Pandemic: Effect of Different Face Masks on Self-Perceived Dry Mouth and Halitosis.

Due to the COVID-19 pandemic, the use of face masks has increased, resulting in potential health-related side-effects. Therefore, the study aimed to analyse the effect of wearing face masks on self-perceived dry mouth and halitosis. A questionnaire addressing the daily wearing time of different face masks (community masks, surgical/medical masks and KN95-/N95-/FFP2-masks) and self-perceived dry mouth and halitosis was given to adults attending or working at a university hospital. Statistical analysis was performed using Wilcoxon signed-rank test and multiple linear regression analysis (p < 0.05). 3750 participants (age: 50.4 ± 15.5 years; 60.0% female) were included. During the pandemic, face masks were used for 4.7 ± 3.8 h per day: community masks: 0.9 ± 2.0 h, medical/surgical masks: 1.9 ± 2.8 h and KN95-/N95-/FFP2-masks: 1.9 ± 2.5 h per day. The use of face masks significantly increased self-perceived dry mouth and halitosis (both p < 0.001). Self-perceived dry mouth and halitosis increased with increasing wearing time (community masks: dry mouth: p < 0.001, halitosis: p = 0.014; medical/surgical masks: both: p < 0.001; KN95-/N95-/FFP2-masks: dry mouth: p < 0.001, halitosis: p = 0.011). The perception of dry mouth and halitosis was increased in females compared to males (both: p < 0.001). Participants used to wearing face masks prior to the pandemic perceived dry mouth to a higher extent (p = 0.043). Self-perceived halitosis was lower in older than in younger participants (p < 0.001). Due to the increased perception of dry mouth and halitosis, people might abstain from wearing face masks. Further studies need to analyse measurable changes in dry mouth or halitosis.

Dental Care of Patients With Dementia: A Survey on Practice Equipment, Training, and Dental Treatment.

For patients with dementia, dental care can pose a considerable challenge due to cognitive impairment, behavioral, and psychological symptoms, and (often subsequently) limited autonomous oral care. In this study, we aimed to assess the proficiency of dentists in general practice in the outpatient dental care of these patients. A total of 119 dentists from private practices in Lower Saxony, Germany, participated in this study. Concerning treatment of patients with dementia, they provided details about (1) practice equipment/consultation, (2) training/expertise, and (3) special circumstances of dental treatment. Participating dentists predominantly reported to use medical aids (e.g., positioning cushions) to improve the treatment situation for patients with dementia. Over two thirds (68.6%) offered consultations in nursing homes, and at the patients' homes (47.0%). The training rate was remarkably low in the field of gerodontology for dentists and their practice staff (<10%), however, 54.5% expressed interest in such training. The majority of dentists reportedly adapted their treatment strategy to the needs of patients with dementia (e.g., communication, inclusion of caregivers, time management). Furthermore, most participants adapted dental treatment adequately (e.g., strict indication for tooth extraction, simple design of dental prostheses). In summary, even though training in the field of gerodontology must be considered insufficient, most dentists in this study showed an adequate adaptation of their treatment strategy as well as consideration of dental characteristics in patients with dementia, along with interest in trainings. We conclude that dementia-specific training should be expanded in the field of dentistry, preferably already at university level.

Incidence of microcracks after preparation of straight and curved root canals with three different NiTi instrumentation techniques assessed by micro-CT.

This study evaluated the effect of three different NiTi instrumentation techniques on the incidence of microcracks after the preparation of straight and curved root canals using micro-CT. Roots from mandibular premolars and maxillary molars (n = 66) with the same mean canal curvatures were assigned to three groups of straight and three groups of curved roots (n = 11). After preoperative micro-CT scans, root canals were prepared with Reciproc, OneShape and ProTaper Next to size 25. Specimens were scanned again, and pre- and post-operative cross-sectional images (n = 75 263) were screened to identify the presence of dentinal microcracks. Overall, microcracks were detected in 2.97% (n = 2236) of the cross-sectional images. No new dentinal microcracks were observed after root canal instrumentation of straight and curved canals with the tested NiTi systems. Instrumentation with Reciproc, OneShape and ProTaper Next did not induce the formation of dentinal microcracks irrespective of canal curvature.

Efficacy of Different Irrigation Techniques in Removing Ledermix Paste from Simulated Root Canal Irregularities.

Introduction: Root discoloration is reported after using Ledermix paste for prevention of external inflammatory root resorption in traumatically injured teeth. Therefore, it seems necessary to remove Ledermix completely from the root canal prior to root canal filling. The aim of this study was to evaluate the efficacy of sodium hypochlorite or alcohol with or without passive ultrasonic irrigation in removing Ledermix from standardized grooves in coronal and apical root canal thirds. Methods and Materials: Root canals of ten extracted single-rooted teeth were prepared to size 35 and split longitudinally. Standardized grooves were cut in the coronal and apical part of the root canal and filled with Ledermix paste. The reassembled specimens were irrigated with 1% NaOCl or 80% alcohol delivered with a size 30 syringe or with an ultrasonic device. The amount of remaining Ledermix paste was evaluated by three calibrated observers under 30× magnification using a four-grade scoring system. The data was analysed with a nonparametric ANOVA-type method for longitudinal data in factorial experiments. Pairwise comparisons were adjusted by using the Bonferroni corrections (P=0.05). Results: For the coronal groove, no statistical difference between passive ultrasonic irrigation with NaOCl or alcohol was found (P=0.089). Irrigation with ultrasonically activated alcohol was significantly more effective than manual irrigation irrespective of the irrigant (P=0.0118). Ultrasonic activation of alcohol removed Ledermix paste significantly better from the apical groove than the other irrigation procedures (P<0.05). Conclusion: This in vitro study showed that ultrasonic activation of alcohol was the most effective irrigation technique for removal of Ledermix paste, especially in the apical third of the root canal.

Diameter and Taper Variability of Single-file Instrumentation Systems and Their Corresponding Gutta-percha Cones.

INTRODUCTION: Manufacturers offer single-file instrumentation systems with matching gutta-percha (GP) cones to simplify root canal preparation and obturation. The purpose of this study was to determine whether file diameters and tapers match with corresponding cone diameters and tapers (precision) as well as industry standards (accuracy). METHODS: Twenty files and corresponding GP cones from each size of F360 (#25, #35, #45, #55 with .04 taper) and Reciproc (#25, #40, #50 with variable tapers) instruments were examined by using optical microscopy (×32) to determine their diameter and taper. Precision was evaluated by using one-way analysis of variance (α = 0.05) with Scheffé post hoc tests and t tests with Bonferroni correction. Accuracy was calculated by subtracting the nominal values from the measured values of all files and GP cones, and mean diameter and taper differences were compared by using one-way analysis of variance (α = 0.05) and Scheffé post hoc test for pairwise comparison. RESULTS: For F360, the majority of file and cone diameters were within the tolerance levels, but most of the file diameters were significantly larger than GP cone diameters (P < .05), but the majority of all measured values were within the tolerance levels. For Reciproc, file and cone diameters at D1 and D3 mostly approached the nominal values. At the coronal end, file diameters #25 and #50 were significantly smaller than cone diameters (P < .05). For both instrumentation systems, almost all file and cone tapers matched with the preset tolerance ranges. For Reciproc, significant differences between file and GP cone demonstrated either smaller cone or smaller file diameters and tapers, depending on the size. Most of the measured values were within the acceptable range, but diameters at the coronal end exhibited the highest percent difference from the nominal values. CONCLUSIONS: Despite the call for standardization, variability in diameter and taper dimensions between single-file instrumentation systems and their corresponding GP cones can be expected.

Comparison of the antibacterial efficacy of sonic- and two ultrasonic-activated irrigation techniques in reducing intracanal Enterococcus faecalis populations.

OBJECTIVE: This in-vitro study evaluated the antibacterial efficacy of sonic and ultrasonic irrigation with either intermittent or continuous flush in root canals infected with Enterococcus faecalis. METHOD AND MATERIALS: Seventy single-rooted, extracted teeth with straight root canals were prepared with FlexMaster NiTi-instruments, sterilized, inoculated with E faecalis and incubated for 72 hours. Sixty roots were randomly divided into four experimental groups as well as into infection and sterile controls (n = 10 each). The remaining teeth were used for SEM analysis of smear layer removal (n = 5) and infection with E faecalis (n = 5). Irrigation in the experimental groups was performed with 1% NaOCl and syringe irrigation, sonic activation of the irrigant with EndoActivator, ultrasonic activation with intermittent flush, or ultrasonic activation with continuous flush. Microbial sampling was performed by collecting dentin shavings from the root canal walls. Colony-forming units were counted and statistical analysis was performed using nonparametric rank-based ANOVA-type tests for longitudinal data (P < .05). RESULTS: A significant reduction of E faecalis of 3 log10 steps compared to the infection control was achieved by all irrigation techniques (P < .0001). There were no significant differences in antibacterial efficacy between syringe irrigation, sonically, or ultrasonically activated irrigation (P > .45). CONCLUSION: Activation of 1% NaOCl with either sonic or ultrasonic devices did not increase the antimicrobial efficacy against E faecalis compared to conventional syringe irrigation in straight root canals.

Removable thermoplastic appliances modified by incisal cuts show altered biomechanical properties during tipping of a maxillary central incisor.

BACKGROUND: The present study aimed to evaluate the force delivery of removable thermoplastic appliances (RTAs), modified by different sized incisal cuts, during tipping of a maxillary central incisor in palatal and vestibular direction. METHODS: Forty-five RTAs from three different materials (Biolon®, Erkodur®, Ideal Clear®) of the same thickness (1 mm) were used. Analysis was performed on a separated maxillary central incisor which was part of a resin model with a complete dentition. In 15 RTAs, of different material, a cut was inserted at the incisal edge of tooth 11. In 15 other appliances, the cut was extended to teeth 12 and 21. Fifteen aligners remained uncut. The experimental tooth was tipped starting from the zero position in 0.05° steps to a maximal deflection of ± 0.42° of the incisal edge in vestibular and palatal direction, after positioning the RTA onto the model. RESULTS: The horizontal (Fx) and the vertical (Fz) force components were decreased by approximately half with increasing cut size. Fz values changed during palatal tipping from a weak intrusive force, for aligners without cut, to an extrusive force with increasing cut size. Compared to both other materials used (Erkodur® and Ideal Clear®), the Biolon® aligners showed significantly higher Fx and Fz values (p < 0.0001, respectively). CONCLUSIONS: RTAs modified by different sized incisal cuts show altered biomechanical properties and an inversion of the vertical force component, during tipping of a maxillary central incisor.

Attitudes, practice, and experience of German dentists regarding repair restorations.

OBJECTIVES: The aim of the present study was to perform a representative survey among German dentists about attitudes, practice, and experience regarding single-tooth repair restorations. MATERIALS AND METHODS: An anonymous questionnaire was designed and mailed to all registered dentists in Lower Saxony (n = 6600). Twenty-eight percent were returned (n = 1852), and n = 1805 could be analyzed. Statistical analyses were done by Wilcoxon signed-rank tests, Kruskal-Wallis tests, and ordered logistic regressions (p < 0.05). RESULTS: Only 2.2 % of the dentists declared to never perform repair restorations. Composite restorations were repaired significantly more often than all other materials. Frequency of performing repair restorations was partially associated to dentist-related factors. The decision for repairing a restoration was dependent on several tooth- and restoration-associated variables. The main indications for repair were the partial loss of restoration or adjacent tooth structure as well as chipping and endodontic access cavities of crowns. Repair restorations were mostly done with composite using various different preconditioning techniques. Overall patients' acceptance was reported to be high. Most of the dentists considered repair restorations as permanent restoration with a moderate to high longevity. Estimated success of repair restorations depended significantly on the dentists' experiences (frequency and techniques of repair restorations). CONCLUSIONS: Repair restorations were often performed and were well accepted by dentists and patients, but indications for repair restorations as well as applied materials and techniques varied distinctly. CLINICAL RELEVANCE: Repairs of single-tooth restorations are well accepted and frequently performed, but indications, techniques, and materials require further research.

Effect of fiber insertion depth on antibacterial efficacy of photodynamic therapy against Enterococcus faecalis in rootcanals.

OBJECTIVES: This in vitro study evaluated the effect of fiber insertion depth on antimicrobial efficacy of antimicrobial photodynamic therapy (aPDT) using a photosensitizer (PS; toluidine blue) and a red light-emitting diode (LED) in root canals infected with Enterococcus faecalis. MATERIALS AND METHODS: Single-rooted extracted teeth were prepared with nickel-titanium-instruments, sterilized, contaminated with E. faecalis, and incubated for 72 h. Roots were randomly divided into four experimental groups: PS only, LED only, aPDT with LED in the apical third, aPDT with LED in the coronal third, as well as into infection and sterile controls (each n = 10). Samples were taken by collecting standardized dentine shavings from the root canal walls. After serial dilution and culturing on blood agar, colony-forming units (CFU) were counted. RESULTS: Both aPDT groups showed a CFU reduction of 1-2 log10 steps compared with the infection control, whereas the effect of fiber insertion depth was negligible (<0.5 log10 steps). CFU reduction of approximately 0.5 log10 steps for PS alone was detected compared with the infection control, but PS alone was less effective than both aPDT groups. No antibacterial effect was detected for LED alone. CONCLUSIONS: aPDT reduced E. faecalis within the root canal, whereas fiber insertion depth had a negligible influence on antimicrobial effectiveness of aPDT. CLINICAL RELEVANCE: The insertion depth of the light-emitting diode may not influence the antibacterial efficacy of photodynamic therapy against E. faecalis in straight root canals.

Comparison of ultrasonic irrigation and RinsEndo for the removal of calcium hydroxide and Ledermix paste from root canals.

AIM: To compare the efficacy of ultrasonic irrigation and RinsEndo in removing calcium hydroxide and Ledermix paste from simulated root canal irregularities. METHODOLOGY: The root canals of sixty extracted single-rooted teeth were prepared using FlexMaster rotary instruments to size 60, 0.02 taper. The roots were split longitudinally, and a standardized groove was prepared in the apical part of one segment. The teeth were randomly allocated into two groups (n = 30), according to the intracanal dressing. In the first group, grooves were filled with calcium hydroxide paste (Calxyl), whereas the grooves in the second group were filled with Ledermix paste. After reassembly, the root canals were completely filled with the respective medicament using a lentulo. The removal of medicament dressing was performed after 7 days with either passive ultrasonic irrigation or RinsEndo and 1% sodium hypochlorite for 3 min. The amount of remaining medicament was evaluated under a microscope with 30 × magnification using a four-grade scoring system. A regression analysis with P ≤ 0.05 was performed. RESULTS: Ledermix paste removal was significantly more effective than the removal of calcium hydroxide (P < 0.0001), whereas irrigation technique was not a significant factor (P = 0.3712). The percentages of complete removal of calcium hydroxide and Ledermix paste were 11.7% and 51.7%, respectively. CONCLUSIONS: None of the irrigation techniques was able to completely remove the intracanal medicaments from the apical part of the root canal. Irrespective of the irrigation technique, significantly less Ledermix paste was detected compared with calcium hydroxide.

The influence of occlusal forces on force delivery properties of aligners during rotation of an upper central incisor.

OBJECTIVE: To determine the forces and moments delivered to a maxillary central incisor during rotation with aligners when a simulated occlusal force generated during swallowing acts on the appliance. MATERIALS AND METHODS: Five identical appliances were manufactured from four different starting materials (Erkodur 0.8 mm and 1.0 mm; Biolon 0.75 mm and 1.0 mm). An upper central incisor fixed in a measuring device was rotated around its central axis in 0.5-degree steps up to ±10 degrees with the appliance fixed in place. An occlusal force of 30 N generated during swallowing was simulated with a weight positioned on the appliance. For statistical analysis, the moments Tz (rotation) and forces Fz (intrusion) at a deflection of ±0.34 mm to the incisor edge (±5 degrees rotation) were tested. Means and standard deviations for Tz and median and 25% and 75% quartiles for Fz were calculated. An analysis of variance was performed. RESULTS: The simulated occlusal force increased the measured intrusive force Fz (maximum with a weight, -3.7 N [-3.7, -2.4]; minimum without a weight, -1.3 N [-1.4, -1.1]) and the rotary moment Tz (maximum with a weight, -50.8 Nmm [±0.8]; minimum without a weight, 18.2 Nmm [±0.9]) significantly in all cases (P < .01). This was found for all materials measured and for both directions of rotation. CONCLUSION: During rotation with aligners, a simulated occlusal force increases the intrusive force and the rotary moment. The biological adverse side effects of these phenomena remain unclear, especially in patients with periods of bruxism.

Effectiveness of different irrigant agitation techniques on debris and smear layer removal in curved root canals: a scanning electron microscopy study.

INTRODUCTION: The aim of this study was to evaluate the cleaning efficacy of different irrigant agitation techniques on debris and smear layer removal in curved root canals. METHODS: Mesiobuccal root canals of 108 mandibular molars were shaped with nickel-titanium instruments, and a final rinse of NaOCl and ethylenediaminetetraacetic acid was performed. Specimens were assigned to 4 groups (n = 20) and submitted to the following irrigation agitation techniques: no agitation (control), ultrasonic, EndoActivator, and CanalBrush. Root canals were split longitudinally and subjected to scanning electron microscopy. The presence of debris and smear layer at coronal and apical levels was evaluated by using a 5-grade scoring system with 200× and 1000× magnification, respectively. RESULTS: Concerning debris removal, no significant differences among groups were detected. In the coronal region, agitation of the irrigants resulted in significantly more smear layer removal than the control. EndoActivator was significantly more effective than ultrasonic agitation and CanalBrush. CONCLUSIONS: In curved root canals, activation of NaOCl and ethylenediaminetetraacetic acid did not enhance debris removal but resulted in significantly more effective smear layer removal at coronal levels.

Effects of different luting agents on bond strengths of fiber-reinforced composite posts to root canal dentin.

PURPOSE: To evaluate the bond strength between two fiber posts (FRC Postec and DT Light Post) and different composite resins following different surface treatments of the posts. MATERIALS AND METHODS: One hundred sixty extracted teeth were divided into sixteen groups (n = 10). After pretreatment of the post surface with (1) no treatment, (2) silanization, (3) sandblasting + silanization or (4) tribochemical coating, the posts were either luted with the resin cements provided by the manufacturers of the post system or with a core buildup material. Push-out tests were performed in a universal testing machine until the post segment was dislodged from the root section. Data were analyzed using ANOVA. Multiple comparisons were performed using Tukey's test. RESULTS: FRC Postec achieved significantly higher bond strengths than DT Light Post (p < 0.0001). Cementation with the core buildup material showed significantly higher bond strengths than the resin cement provided by the post manufacturers (p < 0.0001). CONCLUSION: Post type, type of surface treatment and type of resin cement were significant factors for bond strength. Luting with a core buildup material significantly increased the bond strengths.