Periodontal pathogen Aggregatibacter actinomycetemcomitans JP2 correlates with colonic leukocytes decrease and gut microbiome imbalance in mice.

AIM: Evidence suggests that translocation of oral pathogens through the oral-gut axis may induce intestinal dysbiosis. This study aimed to evaluate the impact of a highly leukotoxic Aggregatibacter actinomycetemcomitans (Aa) strain on the gut microbiota, intestinal mucosal integrity and immune system in healthy mice. METHODS: Eight-week-old male C57BL6 mice were divided into control (n = 16) and JP2 groups (n = 19), which received intragastric gavage with PBS and with a suspension of Aa JP2 (HK921), respectively, twice a week for 4 weeks. Colonic lamina propria, fecal material, serum, gingival tissues, and mandibles were obtained for analyses of leukocyte populations, inflammatory mediators, mucosal integrity, alveolar bone loss, and gut microbiota. Differences between groups for these parameters were examined by non-parametric tests. RESULTS: The gut microbial richness and the number of colonic macrophages, neutrophils, and monocytes were significantly lower in Aa JP2-infected mice than in controls (p < .05). In contrast, infected animals showed higher abundance of Clostridiaceae, Lactobacillus taiwanensis, Helicobacter rodentium, higher levels of IL-6 expression in colonic tissues, and higher splenic MPO activity than controls (p < .05). No differences in tight junction expression, serum endotoxin levels, and colonic inflammatory cytokines were observed between groups. Infected animals presented also slightly more alveolar bone loss and gingival IL-6 levels than controls (p < .05). CONCLUSION: Based on this model, intragastric administration of Aa JP2 is associated with changes in the gut ecosystem of healthy hosts, characterized by less live/recruited myeloid cells, enrichment of the gut microbiota with pathobionts and decrease in commensals. Negligible levels of colonic pro-inflammatory cytokines, and no signs of mucosal barrier disruption were related to these changes.

Chronic alcohol and nicotine consumption as catalyst for systemic inflammatory storm and bone destruction in apical periodontitis.

AIM: To assess the periapical alveolar bone pattern and the serum levels of proinflammatory cytokines, biochemical markers and metabolites in rats subjected to chronic alcohol and nicotine consumption and induced apical periodontitis. METHODOLOGY: Twenty-eight male Wistar rats were divided into four groups: Control, Alcohol, Nicotine and Alcohol+Nicotine. The alcohol groups were exposed to self-administration of a 25% alcohol solution, while the other groups were given only filtered water. The nicotine groups received daily intraperitoneal injections of a nicotine solution (0.19 µL of nicotine/mL), whereas the other groups received saline solution. Periapical lesions were induced by exposing the pulps of the left mandibular first molars for 28 days. After euthanasia, the mandibles were removed and the percentage bone volume, bone mineral density, trabecular thickness, trabecular separation and trabecular number of the periapical bone were measured using micro-computed tomography images. Serum samples were collected for analysis of proinflammatory cytokines (IL-1ß, IL-4, IL-6 and TNF-α), biochemical and metabolomic analysis. Statistical analysis was performed with a significance level of 5%. Nonparametric data were analysed using the Kruskal-Wallis test followed by Dunn's test, while one-way anova followed by Tukey's test was performed for parametric data. RESULTS: The groups exposed to alcohol or nicotine consumption exhibited an altered bone pattern indicating lower bone density and higher levels of IL-1ß, IL-6 and TNF-α compared to the Control group (p < .05). Significant differences were observed among the groups in the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase, cholesterol, triglycerides, urea, creatinine, albumin, uric acid, bilirubin and calcium. Metabolomic analysis revealed significant differences in glycine, phosphocholine, lysine, lactate, valine, pyruvate and lipids (CH2 CH2 CO), n(CH2 ) and n(CH3 ). Most of these parameters were even more altered in the simultaneous consumption of both substances compared to single consumption. CONCLUSION: Alcohol and nicotine chronic consumption altered several metabolic markers, impaired liver and kidney function, increased the production of systemic proinflammatory mediators and harmed the periapical bone microarchitecture in the presence of apical periodontitis. The simultaneous consumption of alcohol and nicotine intensified these detrimental effects.

Stress distribution on teeth restored with veneers using various incisal preparation designs: A 3D finite element analysis study.

STATEMENT OF PROBLEM: The type of veneer preparation is often chosen according to the patient's tooth structure and occlusion. Taking biomechanics into account in this decision-making process provides the clinician with more technical information on how to improve the clinical longevity of restorations. However, biomechanical analyses of veneer preparation designs are sparse. PURPOSE: The purpose of this 3-dimensional (3D) finite element analysis with microcomputed tomography (µCT) data obtained from realistic models was to assess the influence of different preparations for ceramic and composite resin veneers on restoration and resin layer stress distribution. MATERIAL AND METHODS: Four replicas of a central incisor were printed and prepared for laminate veneers with 4 different incisal edge designs: shoulder (SH), palatal chamfer (PC), palatal chamfer and oblique fracture involving the distal angle (OF-PC), and palatal chamfer involving horizontal incisal fracture (IF-PC). After fabrication and cementation of the veneers, the restored replicas were assessed with µCT, and 3D finite element models were built. A 100-N load was applied on the palatal surface at 60 and 125 degrees relative to the longitudinal axis. Maximum principal stress and stress distribution on the veneers, cement layer, and tooth structure were calculated and analyzed. RESULTS: The SH preparation exhibited better stress distribution than the PC preparation, and the cement layer and the veneer were subjected to lower stress. The IF-PC preparation had better stress distribution than the OF-PC. The shoulder and IF-PC showed higher stress on laminate veneers, but lower stress on the cement layer. Ceramic veneers exhibited lower stress than composite resin veneers. CONCLUSIONS: The different incisal preparations for laminate veneers influenced stress distribution on restorations and on the resin cement layer. The shoulder type preparation showed better stress distribution and the composite resin veneers showed unfavorable results compared with the ceramic veneers.

Atypical antipsychotics olanzapine and clozapine increase bone loss in female rats with experimental periodontitis.

BACKGROUND AND OBJECTIVES: Periodontitis is a highly prevalent disease in psychiatric patients, including those undergoing symptomatic treatment with second-generation antipsychotics. Some of these drugs, such as clozapine (CLO) and olanzapine (OLA), have prominent metabolic effects such as weight gain, hyperglycemia, and dyslipidemia, which are risk factors for periodontitis. In addition to the metabolic effects, there are reports of changes in salivary flow, gingival bleeding, and caries. In this context, we aimed to evaluate if the metabolic effects of OLA and CLO alter periodontal parameters in an animal model of periodontitis without the environmental and psychosocial biases inherent to human diseases. METHODS: In the first set of experiments, male and female adult Wistar rats received oral administration of CLO, OLA, or vehicle for 45 days. They were evaluated for body mass composition and weight gain, blood glucose parameters (fasting and glucose tolerance and insulin resistance tests), and lipid profile (HDL, total cholesterol, and triglycerides). In a second set of experiments, the same measurements were performed in female rats exposed to the antipsychotics for 45 days and ligature-induced periodontitis on the 30th day of treatment. Macroscopic measurements of exposed roots, microtomography in the furcation region of the first molar, and histological evaluation of the region between the first and second molars were evaluated to assess bone loss. Additionally, gingival measurements of myeloperoxidase activity and pro-inflammatory cytokine TNF-α were made. RESULTS: Only females exposed to OLA had more significant weight gain than controls. They also exhibited differences in glucose metabolism. Ligature-induced periodontitis produced intense bone retraction without changing the density of the remaining structures. The bone loss was even higher in rats with periodontitis treated with OLA or CLO and was accompanied by a local increase in TNF-α caused by CLO. These animals, however, did not exhibit the same metabolic impairments observed for animals without periodontitis. CONCLUSION: The use of clozapine and olanzapine may be a risk factor for periodontal disease, independent of systemic metabolic alterations.

Dentine Mineral Changes Induced by Polyalkenoate Cements after Different Selective Caries Removal Techniques: An in vitro Study.

This study aimed at evaluating the mineral variation induced by polyalkenoate cements in residual dentine after different caries removal methods. Ten extracted sound molars were selected, and five cavities were prepared on the occlusal surface of each specimen. Carious lesions were generated using a microbial protocol, while the caries removal was performed using bur, hand excavator, or two papain-based chemo-mechanical agents. One cavity was left unexcavated in each tooth. Cavities were restored using a zinc polycarboxylate cement (ZPC; n = 25), or a glass ionomer cement (GIC) was used (n = 25). Subsequently, the specimens were stored under simulated pulpal pressure for 45 days. Micro-CT scanning was performed after caries formation, removal, and restoration. Cavity volumes (mm3) and mineral density (MD) changes were calculated. Remineralisation ability was investigated by scanning electron microscopy (SEM) and Fourier-transformed infrared spectroscopy (FTIR). Statistical analysis was performed (5% significance level). Baseline caries, cavity volume, and MD increase after caries removal were similar to all excavation groups (p > 0.05). MD was higher in ZPC compared to GIC (p < 0.05). SEM revealed that the chemo-mechanical techniques produced a smoother dentine surface compared to mechanical methods. FTIR showed silicon-based minerals in GIC-treated dentine, while ZPC-treated presented mineral deposits characterised by amorphous calcium phosphate. In both cases, the presence of carbonates was detected on dentine surfaces. All caries removal techniques performed similarly in terms of carious dentine excavation. ZPC can be used as dentine replacement material after caries removal as it may induce higher MD increase in residual dentine via deposition of calcium phosphates, compared to GIC.

Instrumentation time and effectiveness of hand and rotary files in a prototyped second mandibular primary molar: A micro-CT study.

BACKGROUND: Eccentric instruments have been proposed as more effective and less time-consuming for endodontic instrumentation. AIM: To compare biomechanical outcomes of different instrumentation systems and time undertaken for instrumentation in resin prototypes. DESIGN: Sixty standardized prototypes of mandibular second primary molars were instrumented according to the following systems: K-files, ProTaper Next (PTN), XP-endo Shaper (XPS), XP-endo Finisher (XPF), XP-Clean (XPC), and Sequence Baby File (SBF; n = 10/each). Irrigation was performed with saline with simultaneous aspiration, and time spent was recorded. The prototypes were micro-CT-scanned before and after the instrumentation, and image sets were reconstructed and registered. Non-instrumented areas, accumulated debris, removed root material volume, and canal transportation were quantified. Data were analyzed through ANOVA, the Kruskal-Wallis test, and the Wilcoxon signed-rank test (α = 5%). RESULTS: K-files and SBF resulted in more instrumentation time (p < .05). SBF, XPC and PTN removed less root dentine (p < .05), but PTN left more untouched areas (p < .05). Accumulated debris were lower for XPC and SBF (p < .05). Canal transportation was similar among the groups. CONCLUSION: Rotary systems reduced instrumentation time, whereas SBF and XPC resulted in more conservative instrumentation, with less debris accumulation and non-instrumented areas. A dedicated paediatric endodontic system (SBF) outperformed eccentric instruments in terms of effectiveness.

Influence of conservative endodontic access cavities on instrumentation of oval-shaped straight root canals.

AIM: To evaluate the influence of the design of endodontic access cavities on the percentage of unprepared areas of canal walls and flexural fatigue of instruments activated by reciprocating movement in oval-shaped straight root canals of extracted teeth. METHODOLOGY: Forty-two mandibular incisors with oval canals were scanned by a microcomputed tomography (micro-CT) device for homogeneous selection and distribution of the samples. Then, the teeth were divided into two groups (n = 21) according to the design of access cavity being tested: ultraconservative endodontic access cavity (UltraAC) and traditional access cavity. The canals were accessed with the aid of a surgical microscope, instrumented with the WaveOne Gold Medium system and irrigated with 2.5% NaOCl and 17% EDTA. The unprepared areas of the canal wall were analysed by overlaying images before and after instrumentation and expressed as percentages. micro-CT data were analysed using t-test, Mann-Whitney and Wilcoxon tests. The endodontic instruments used during instrumentation were subjected to static flexural fatigue testing using an artificial stainless steel canal with a 60° angle of curvature and a radius of 5 mm, located 5 mm from the tip of the instrument. The instruments were activated until fracture occurred, and the time in seconds for the fracture was recorded using a digital timer. The number of cycles to fracture was calculated and analysed statistically. For flexural fatigue data, an anova test complemented by a Tukey range test was used. The significance level of 5% was used for all analyses. RESULTS: There was no significant difference between the groups related to unprepared areas by the instrument during canal preparation (p > .05). The difference in flexural fatigue resistance between the groups was not significant. CONCLUSION: The use of UltraAC did not interfere with the canal instrumentation of extracted mandibular incisors with straight and oval canals. There was no difference in the flexural fatigue resistance of the instruments in relation to access cavity design.

A Comparative Study of Multidetector Computed Tomography, Cone Beam Computed Tomography, and Computed Microtomography on Trabecular Bone Structures in the Human Mandible: An Ex Vivo Study.

OBJECTIVE: The aim of this study was to evaluate the accuracy of multislice computed tomography (MSCT) and cone beam computed tomography (CBCT) scanners in the assessment of trabecular bone microarchitecture by radiomorphometric analysis. METHODS: Eight dry human hemimandibles were selected and scanned by 4- and 128-MSCT, CBCT with different voxel sizes, and a computed microtomography (micro-CT). The images were spatially aligned, the axial slices were segmented using CTAn software (Skyscan, Konitch, Belgium), and 10 bone morphometric parameters were quantified. The micro-CT images were the criterion standard. RESULTS: The results show the superiority of CBCT images with 0.2-mm voxel size and 128-MSCT. CONCLUSIONS: We can conclude that the CBCT scanner with 0.2-mm voxel size and 128-MSCT had better performance on reproducibility of the distribution and organization of trabecular bone and marrow spaces evaluated in this study.

Periodontal status, vascular reactivity, and platelet aggregation changes in rats submitted to hypercholesterolemic diet and periodontitis.

BACKGROUND AND OBJECTIVES: Periodontitis can corroborate with development and progression of atherosclerosis and a possible bidirectional interaction between both pathologies has been hypothesized. The aim of this work was to study the interactions between diet-induced hypercholesterolemia and ligature-induced periodontitis in Wistar rats submitted to both conditions. MATERIAL AND METHODS: Animals were divided into four experimental groups: C (control: standard diet without periodontitis), Perio (periodontitis plus standard diet), HC (high cholesterol diet without periodontitis), and HC + Perio (high cholesterol diet plus periodontitis). The diets were offered for 45 days and a silk ligature was applied in the lower first molars of Perio and HC-Perio animals on day 34 and maintained for 11 days until euthanasia. The mandibles were excised, and alveolar bone loss was determined by macroscopic and micro-tomographic (µ-CT) imaging. Blood samples were obtained, and platelet aggregation was induced in plasma rich in platelets by adenosine diphosphate (ADP) and collagen. Endothelium-dependent vascular reactivity and protein expression of endothelial (eNOS), phosphorylated endothelial (peNOS), and inducible (iNOS) nitric oxide synthases were evaluated in aorta samples. RESULTS: The HC diet combined with periodontitis (HC + Perio group) was associated with an increased alveolar bone loss, when compared to the other groups. Both in Perio and HC groups, platelet aggregation induced by ADP or collagen was increased, while maximum aortic relaxation induced by acetylcholine was decreased. Periodontitis or HC diet alone decreased the expression of peNOS and HC diet increased the expression of iNOS. In contrast, no additive or synergistic effects were found in vascular reactivity or in platelet aggregation when the two conditions were associated (HC + Perio group). CONCLUSION: Hypercholesterolemia accelerated the process of bone loss induced by periodontitis while a high cholesterol diet or periodontitis individually increased platelet aggregation and vascular reactivity in rats without additive or synergistic effects, when associated.

Root canal obturation materials and filling techniques for primary teeth: In vitro evaluation in polymer-based prototyped incisors.

BACKGROUND: Achieving a void-free root canal filling is a challenge in current clinical pulpectomy practice. AIM: To compare filling effectiveness and internal voids of root filling materials and obturation techniques in resin-prototyped primary incisors by micro-CT. DESIGN: Fifty prototypes were instrumented and randomly divided (n = 10) according to the filling materials (Vitapex® , ZOE, Calcicur® , Feapex, and Calen® -ZO) and obturation technique: lentulo or pressure syringe (n = 5). The specimens were micro-CT scanned (pixel size = 7.83 µm) and reconstructed, and the total volume of filled canal (%FC) and internal voids (%IV) of the bulk filling material was calculated. Kruskal-Wallis and Mann-Whitney tests were used to detect differences and interactions among groups. RESULTS: Calen® -ZO, Vitapex® , and ZOE showed similar %FC. Calcicur® showed lower %FC compared with Calen® -ZO, Vitapex® , and ZOE (P < .05) but similar to Feapex. No statistically significant differences in %FC between lentulo or pressure syringe were disclosed. Regarding %IV, Vitapex® , and Calen® -ZO performed better with syringe, although Calcicur® was better with lentulo. The number of voids in the obturation bulk was similar among materials, but always lower (P < .05) in syringe filled specimens. CONCLUSION: Vitapex® , Calen® -ZO, and ZOE outperformed Calcicur® and Feapex in %FC and if the syringe technique is used, %IV of the obturation bulk and presence of defects was lower.

Mineral density changes in bovine carious dentin after treatment with bioactive dental cements: a comparative micro-CT study.

OBJECTIVES: To evaluate the potential of conventional glass ionomer cement (GIC), Biodentine™, MTA, and Portland cement to induce mineral density changes in carious dentin compared to zinc oxide eugenol control cement (ZOE). MATERIALS AND METHODS: Fifty blocks of bovine root dentin were prepared and a biofilm model using ATCC strains of S.mutans, S.sobrinus, and L.casei was used to promote artificial dentin lesions. After demineralization, the blocks were randomly divided into the five cement groups. Half of the surface of each specimen received the tested material and the other half was covered with wax (control). Samples were stored in phosphate buffered saline solution for 30 days and after that were scanned in a micro-CT with standardized parameters. Dentin mineral density changes were calculated using differences in plot profiles of the exposed and control carious dentin. Friedman's test, followed by Wilcoxon signed-rank test was used with 5% significance. RESULTS: Mean ΔZ values for the cements were 48.63 ± 19.09 for the control (ZOE), 63.31 ± 32.59 for Biodentine™, 114.63 ± 72.92 for GIC, 109.56 ± 66.28 for MTA, and 106.88 ± 66.02 for Portland cement. All cements showed a statistically significant increase in ΔZ values compared to the control, but Biodentine™ values were statistically significantly lower compared to GIC and the other calcium silicate cements. CONCLUSIONS: Tested materials present potential to induce mineral density changes in carious bovine dentin. MTA, Portland, and GIC showed higher bioactivity potential than Biodentine™. CLINICAL RELEVANCE: Based on minimally invasive concept, materials with remineralization potential can be used to preserve diseased but still repairable dental tissue.

Micro-CT evaluation of different final irrigation protocols on the removal of hard-tissue debris from isthmus-containing mesial root of mandibular molars.

OBJECTIVES: This study aimed to compare four final irrigation protocols (passive ultrasonic irrigation [PUI], EndoVac, Self-Adjusting File [SAF] and EasyClean) on the removal of accumulated hard-tissue debris (AHTD) from mesial canals of mandibular molars through microcomputed tomographic (micro-CT) analysis. MATERIALS AND METHODS: Forty mesial roots of mandibular molars presenting isthmuses type I or III were scanned in a micro-CT device and instrumented up to Reciproc R40 instrument. After the completion of canal preparations, root canals of each group were submitted to a final rinse using 20 mL of solution (16 mL of 5.25% NaOCl and 4 mL of 17% EDTA) in a total time of 5 min according to one of the four final irrigation protocols (n = 10): PUI, EndoVac, SAF and EasyClean operated at reciprocating motion. The sample was scanned again after canal preparation and after the use of the final irrigation protocols, and the registered data sets were examined to evaluate the percentage of AHTD. Data were statistically compared using the Tukey test with a significance level set at 5%. RESULTS: All groups presented a decrease on the accumulation of hard-tissue debris after the use of the final irrigation protocols (P < 0.05). No significant differences in the removal of AHTD were observed among the final irrigation protocols (P > 0.05). CONCLUSIONS: All final irrigation protocols showed the same effectiveness in the removal of AHTD. None of them was able to render mesial canals of mandibular molars completely free from packed debris. CLINICAL RELEVANCE: This study highlighted that all final irrigation protocols (PUI, EndoVac, SAF, and EasyClean) promoted a similar removal of AHTD. However, none of the final irrigation protocols was able to render mesial canals of mandibular molars completely free from packed debris.

Micro-CT comparison of XP-endo Finisher and passive ultrasonic irrigation as final irrigation protocols on the removal of accumulated hard-tissue debris from oval shaped-canals.

OBJECTIVE: To compare the effectiveness of the XP-endo Finisher instrument and passive ultrasonic irrigation (PUI) as final irrigation protocols on the removal of accumulated hard-tissue debris (AHTD) from oval-shaped canals using micro-computed tomographic (micro-CT) analysis. METHODS: Twenty mandibular incisors were anatomically pair-matched based on similar morphological dimensions (length, volume, aspect ratio, and configuration) through micro-CT analysis, prepared with Reciproc R25 instrument, scanned again, and assigned to one of the two experimental groups (n = 10), according to the final irrigation protocol: XP-endo Finisher and PUI. After the final irrigation protocols, the specimens were rescanned and the registered datasets were examined to quantify the amount of AHTD. Data were statistically analyzed using Student's t test with a significance level of 5%. RESULTS: The final irrigation protocols were highly similar in terms of volumetric percentage reduction of AHTD (P = 1.000). CONCLUSIONS: XP-endo Finisher and PUI showed the same effectiveness on the removal of AHTD. None of the tested final irrigation protocols completely removed the AHTD from oval-shaped root canals. CLINICAL RELEVANCE: AHTD may be considered clinically relevant because it could harbor bacterial contents away from the disinfection procedures. Both final irrigation protocols were effective on the removal of AHTD.

Reciprocating instrumentation in a maxillary primary central incisor: A protocol tested in a 3D printed prototype.

BACKGROUND: Efficient endodontic instrumentation of primary teeth is a challenge for paediatric dentists. AIM: To evaluate biomechanical outcomes of endodontic instrumentation with a reciprocating system in a polymer-prototyped primary maxillary central incisor. DESIGN: The specimen was systematically instrumented and micro-CT scanned before and after each file. The amount of debris, percentage of non-instrumented areas, removed dentin volume, and lower dentin thickness at specific points along the root canal were analyzed. RESULTS: A 10% increase in removed dentin volume was observed when R40 was compared to R25 (14.5% vs 4.2%). When comparing R50 with R40, this increase was only 3.4% (17.9% vs 14.5%). In the root cervical third, there was substantial reduction in dentin thickness with R50 (48.8%), followed by R40 (39.5%) and R25 (18.6%). There was no difference between R25 and R40 in the removal of dentin at the apical third (15.8%), while R50 resulted in 39.8% reduction in dentin thickness. Percentage of non-instrumented areas were the same for all files. Accumulated debris with R40 and R50 was the same (0.19 mm³) while for R25 was 0.11 mm³. CONCLUSIONS: The Reciproc® system was effective for instrumentation of a prototyped primary maxillary central incisor. The most suitable file for apical preparation was R40.

Influence of bone architecture on the primary stability of different mini-implant designs.

INTRODUCTION: Mechanical interlocking between a mini-implant (MI) and the bone substrate reflects directly on the primary stability achieved. The purposes of this study were to evaluate MI design performance in distinct bone substrates and correlate geometric characteristics with insertion site quality. METHODS: Two types of self-drilling MIs (1.6 × 8 mm) were allocated to 2 groups according to their geometric designs: Tomas system (Dentaurum, Ispringen, Germany) and Dual-Top (Rocky Mountain Orthodontics, Denver, Colo). Forty sections (8 × 10 mm) were taken from bovine pelvic ilium and pubic bone. Geometric design characteristics were evaluated using scanning electron microscope imaging and Image-Pro Insight software (Media Cybernetics, Rockville, Md). Bone quality parameters were assessed with a microcomputed tomography system, and primary stability was evaluated by insertion torque and pull-out strength. Intergroup comparisons were performed with analysis of variance and Tukey tests, and the Pearson correlation test was carried out (P <0.05). RESULTS: No significant difference was observed in the comparisons of the groups (Tomas: insertion torque, 12.87 N·cm; pull-out strength, 181 N; and Dual-Top: insertion torque, 9.95 N·cm; pull-out strength, 172.5 N) in the ilium. However, the Tomas group had a marked increase in insertion torque (25.08 N·cm; P <0.05) in the pubic bone. CONCLUSIONS: MI mechanical performance differed according to bone quality parameters, indicating that certain geometric parameters may be set depending on the insertion substrate.

Root canal dentin wear during final irrigation in endodontic retreatment with passive ultrasonic irrigation and easy clean instruments.

Context: Complementary procedures have been proposed to improve the endodontic retreatments. Aim: The aim of this study was to evaluate, by microcomputed tomography (micro-CT), the dentin wear caused by passive ultrasonic irrigation (PUI) and easy clean (EC) instruments, when used for the final removal of filling material during endodontic retreatment. Methods: Thirty-six mesial roots of the lower first molars were divided into four groups (n = 9), according to the final irrigation and sealer: PUI/AH Plus, EC/AH Plus, PUI/Total Fill (TF), and EC/TF. Canal volume was evaluated, both before and after the final irrigation, by micro-CT analysis. The Kruskal-Wallis test was used to compare the volumes among groups and the paired Wilcoxon test was used to compare the volume values before and after the final irrigation within each group. Results: Both complementary cleaning procedures promoted dentin wear that was observed only when the volume was analyzed for each third of the root canal. In the apical third, both instruments showed significant wear, where the use of the EC instrument resulted in greater wear than the PUI, in teeth filled with both AH Plus and TF BC Sealers (P < 0.05). Conclusion: Both complementary cleaning procedures promoted dentin wear and must be used cautiously.

Assessing peri-implant bone microarchitecture: conventional vs. osseodensification drilling - ex vivo analysis.

The aim was to evaluate primary implant stability and bone microarchitecture in two drilling situations, by comparing the conventional technique (CT) and osseodensification (OD) (Versah Burs - Jackson - Mississippi - USA). The implant insertion torque (IT), implant stability quotient (ISQ), and the peri-implant trabecular microstructure were assessed on bone fragments obtained from pig's tibia (n=12), divided between CT (n=6) and OD (n=6). After the drilling procedure, the implants were installed (3.5x8.5 mm, Epikut - SIN - São Paulo - Brazil). The IT and ISQ were measured using a digital torque wrench and resonance frequency analysis. Then, the bone fragments containing the implants were removed with a trephine and analyzed by Microtomography (µCT, 8.0 µm). The comparison between groups was performed using the unpaired t-test (α=0.05). The results revealed that OD promotes a higher insertion torque (CT: 7.67±2.44 Ncm; OD: 19.78±5.26 Ncm) (p=0.0005), although ISQ was not different (CT: 61.33±4.66; OD: 63.25±4.58) (p=0.48). There was a significant increase in peri-implant bone volume (CT: 23.17±3.39 mm3; OD: 32.01±5.75 mm3) (p=0.008), and trabecular parameters: separation (CT: 0.4357±0.03 mm; OD: 0.3865±0.04 mm) (p=0.0449), number (CT: 1.626±0.18 1/mm; OD: 1.946±0.13 1/mm) (p=0.007), and thickness (CT: 0.1130±0.009 mm; OD: 0.1328±0.015 mm) (p=0.02). Structure model index (SMI) data demonstrate no significant differences between groups (CT: 1.7±0.2; OD: 1.4±0.4) (p=0.12). In conclusion, OD increases the insertion torque values and promotes beneficial changes regarding bone microarchitecture compared with CT, revealing more peri-implant bone volume with consequent higher primary stability.

The impact of long-term storage conditions on the development of experimental dentinal microcracks.

This study evaluated the impact of long-term storage conditions (medium and time) on the development of experimental dentinal microcracks through micro-computed tomography. Sixty freshly extracted premolars were stored in formalin, water, or dry conditions (n = 20) and scanned after 72 h, 30 days, 6 months and 3 years of extraction. The effect of the storage medium and time on the occurrence of dentinal defects was statistically evaluated. A total of 211 000 images were screened revealing the existence of 11 519 slices with dentinal defects. Dry conditions significantly contributed to the development of new defects in all time points. During the 3-year follow-up period, no new defects were detected in the teeth that were stored in water and, in a single tooth, in the formalin group, after 6 months of storage.

Effects of increasing instrument size and taper on the disinfection and shaping of mandibular incisors.

This study assessed canal preparation effects on disinfection and dentin preservation. Thirty mandibular incisors were paired into two experimental groups (n = 10). Following contamination, the initial microbial sample was collected. Instruments 30/0.03 (Group 1) and 30/0.05 (Group 2) were employed and a second sample was obtained. Canals were enlarged using instruments 40/0.03 and 40/0.05, respectively, and a third sample was collected. Final irrigation was performed, and sample S4 obtained. A final scan evaluated volume, surface area, unprepared areas, removed dentin and dentin thickness. Data were analysed using Student t-test, Mann-Whitney, Kruskal-Wallis and Dunn tests. A significant difference was observed between S1 and other time points (p < 0.05). Comparison between groups showed no differences in bacterial loads and in the percentage of microbial reduction (p > 0.05). Group 2 exhibited greater reduction in dentin thickness than group 1 in the mesial aspect of the root (p < 0.05). Instrument 30/0.03 might provide effective disinfection and safety during mandibular incisors canal preparation.

Analysis of the penetration of NaOCl 5.25% into dentinal tubules using different irrigation protocols: An ex vivo study.

The objective of the study was to investigate the 5.25% sodium hypochlorite (NaOCl) penetration into the dentinal tubules after different irrigation methods. Seventy canines were stained with 1% crystal violet and divided into groups (n = 20): GEC-EasyClean; GPUI-E1 Irrisonic ultrasonic insert; GXP-XP-Endo finisher; GPC-conventional irrigation and GNC-stained tooth without irrigation. Axial sections (16×) were assessed and irrigant penetration was quantified as a bleaching halo on the surface of the apical, middle and coronal third. In the apical third, GPUI promoted greater NaOCl penetration (p < 0.05). GXP was better than GEC (p < 0.05), as was GPC (p > 0.05). The GPUI and GXP groups were similar in the middle and coronal third (p > 0.05). GPUI and GXP showed better results than GEC (p < 0.05). GPUI was more effective in the apical third and like GXP in the cervical and middle third.