Coronal Levels Research Articles

Accuracy of Computer-Aided Dynamic Navigation Compared to Computer-Aided Static Navigation for Dental Implant Placement: An In Vitro Study.

Aim: To analyze the accuracy capability of two computer-aided navigation procedures for dental implant placement. Materials and Methods: A total of 40 dental implants were selected, which were randomly distributed into two study groups, namely, group A, consisting of those implants that were placed using a computer-aided static navigation system (n = 20) (guided implant (GI)) and group B, consisting of those implants that were placed using a computer-aided dynamic navigation system (n = 20) (navigation implant (NI)). The placement of the implants from group A was performed using surgical templates that were designed using 3D implant-planning software based on preoperative cone-beam computed tomography (CBCT) and a 3D extraoral surface scan, and the placement of group B implants was planned and performed using the dynamic navigation system. After placing the dental implants, a second CBCT was performed and the degree of accuracy of the planning and placement of the implants was analyzed using therapeutic planning software and Student’s t-test. Results: The paired t-test revealed no statistically significant differences between GI and NI at the coronal (p = 0.6535) and apical (p = 0.9081) levels; however, statistically significant differences were observed between the angular deviations of GI and NI (p = 0.0272). Conclusion: Both computer-aided static and dynamic navigation procedures allow accurate implant placement.

Hippocampal morphometry in sudden and unexpected death in epilepsy.

To determine hippocampal morphometric measures, including granule cell dispersion and features of malrotation, as potential biomarkers for sudden unexpected death in epilepsy (SUDEP) from an archival postmortem series. In a retrospective study of 187 archival postmortems from 3 groups, SUDEP (68; 14 with hippocampal sclerosis [HS]), non-SUDEP epilepsy controls (EP-C = 66; 25 with HS), and nonepilepsy controls (NEC = 53), Nissl/hematoxylin & eosin-stained sections from left and right hippocampus from 5 coronal levels were digitized. Image analysis was carried out for granule cell layer (GCL) thickness and measurements of hippocampal dimensions (HD) for shape (width [HD1], height [HD2]) and medial hippocampal positioning in relation to the parahippocampal gyrus (PHG) length (HD3). A qualitative evaluation of hippocampal malrotational (HMAL) features, dentate gyrus invaginations (DGI), and subicular/CA1 folds (SCF) was also made. GCL thickness was increased in HS more than those without (p < 0.001). In non-HS cases, increased GCL thickness was noted in EP-C compared to NEC (p < 0.05) but not between SUDEP and NEC. There was no difference in the frequency of DGI, SCF, measurements of hippocampal shape (HD1, HD2, or ratio), or medial positioning among SUDEP, EP-C, and NEC groups, when factoring in HS, coronal level, and age at death. Comparison between left and right sides within cases showed greater PHG lengths (HD3) on the right side in the SUDEP group only (p = 0.018). No hippocampal morphometric features were identified in support of either excessive granule cell dispersion or features of HMAL as definitive biomarkers for SUDEP. Asymmetries in PHG measurements in SUDEP warrant further investigation as they may indicate abnormal central autonomic networks.

Effectiveness of Chitosan as Final Irrigating Solution on Bond Strength of Resin Based Sealer to Radicular Dentin

This study was designed to assess the impact of Chitosan-acetate as final root canal irrigant on bond strength of resin-based sealer to radicular dentin.Materials and Methods: Forty extracted human lower premolars with single roots and canals were prepared with ProTaper Universal rotary files till size F4. The samples were dispensed into 3 experimental groups according to the final rinse used and control group (10 samples each); Group I: irrigated with 0.2% chitosan acetate, Group II:17% EDTA, Group III: distilled water and control group (IV): saline. The samples were obturated by cold lateral compaction technique using AH plus sealer. Samples were sectioned into three sections (each 2 mm-thickness) from coronal, middle and apical thirds of each sample. The push out bond strength test was performed using universal testing machine. Three sections from each group were split longitudinally in buccolingual direction where the sealer/dentin interface and the sealer penetration inside the dentinal tubules was evaluated using scanning electron microscope (SEM). Results: Regarding the coronal and middle levels, there was no statistical significant difference among the tested groups. However, at the apical level, there was a statistical significant difference among the tested groups. SEM observation revealed minimal sealer penetration in group I at the apical level, while in group II, there was minimal sealer penetration at the coronal and middle levels. Regarding group III, there was minimal sealer penetration at middle level, while in control group (IV), there was no sealer penetration. Conclusion: The effect of 0.2% Chitosan acetate on the push out bond strength of AH Plus sealer was comparable to that of 17% EDTA when used as a final rinse. AH Plus sealer showed better adhesion to the dentin in the presence of smear layer especially at the apical third.

Evaluation of Chelating Potential of Chitosan Citrate and Chitosan Acetate on Intraradicular Dentin

Purpose: This study was designed to evaluate the chelating potential of chitosan citrate and chitosan acetate on intraradicular dentin using (ESEM) and quantity calcium content of intraradicular dentin using (EDX). Materials and Methods: sixty freshly extracted human single rooted lower premolars with single canal were instrumented with Revo-S files till size AS 35. The samples were divided into 5 experimental groups according to the final rinse used and control group (10 samples each); Group I: irrigated with 0.2% chitosan acetate, Group II: irrigated with 0.2% chitosan citrate, Group III: irrigated with 1% acetic acid, Group IV: irrigated with 1% citric acid, Group V: irrigated with 17% EDTA and control group which was divided into;(VIa) :5 samples irrigated with sterile saline and (VIb): 5 samples were neither prepared nor received any treatment. The cleanliness of the root canals and smear layer were evaluated at three root levels using ESEM. The calcium content of five samples from each experimental group (I,II,III,IV,V) and the samples of control group was measured using EDX. Results: At the coronal, middle and apical root levels; there was a statistical significant difference among the tested groups and the control . Regarding calcium content, the highest mean calcium content was recorded in samples treated with saline followed by samples that did not receive any irrigation Conclusion: The chelating potential of 0.2% chitosan acetate and 0.2% chitosan citrate is comparable to that of 17% EDTA when used as final rinse without much altering the calcium content.

Micro-CT evaluation of ProTaper Next and WaveOne Gold shaping in maxillary first molars curved canals: an in vitro study

Introduction: The aim of this micro-CT study was to analyze the geometrical shaping outcomes after instrumentation with rotary and reciprocating glide path and shaping systems. Materials and Methods: The mesio-buccal canals of thirty extracted maxillary first permanent molars were randomized into two groups (n=15): rotary system ProGlider and ProTaper Next X1, X2 (PG-PTN) was compared with reciprocating system WaveOne Gold Glider and WaveOne Gold Primary (WOGGWOG). Irrigation was performed with EDTA 10% and NaOCl 5%. Specimens were micro-CT scanned before instrumentation and after glide path and shaping. The measured parameters were the increase in canal volume and surface area, the centroid shift and the canal geometry variation through RDR and RA. These parameters were measured in the apical and coronal levels and at the point of maximum curvature. One-way ANOVA and post hoc Turkey- Kramer tests were used to describe the impact of the instrumentation on the selected parameters (P<0.05). Results: Post glide path analysis revealed that increase in canal surface area was slightly greater in WOGG group (P=0.051). Centroid shift was not significant even if the trend seemed more favorable to PG group, except for the apical third. Centroid shift reported no significant differences. Conclusions: Both rotary and reciprocating systems seemed to create a homogeneous and well-centered glide path and shaping.

Anatomical danger zone reconsidered: a micro-CT study on dentine thickness in mandibular molars.

To investigate the smallest dentine thickness in mesial canals of mandibular molars along the cervical and middle thirds of the root by means of a micro-computed tomographic (micro-CT) technology and digital image analysis. Fifty mesial roots of mandibular molars having two independent canals (mesiobuccal and mesiolingual), in the coronal and middle levels, were selected and scanned in a micro-CT device. After reconstruction procedures, approximately 468 slices per root covering the 7mm below the furcation area of the mesial root were analysed to measure the smallest dentine thickness (danger zone [DZ]) in each slice from both distal and mesial regions of the mesial canals by an automatic segmentation process. The DZ values in the mesiobuccal canals varied from 0.67 to 1.93mm, with an average of 1.13±0.21mm. For the mesiolingual canals, the DZ varied from 0.77 to 1.89mm with an average of 1.10±0.21mm. There was no correspondence in the DZ between the mesiobuccal and mesiolingual canals at the same cross-sectional level in 71% of the specimens. Moreover, the smallest dentine thickness was towards the mesial region of the roots in 22% and 18% of the mesiolingual and mesiobuccal canals, respectively. (Figs 1 and 2 CONCLUSIONS: The smallest dentine thickness was on the mesial plane of the roots in about 40% of the canals. The vertical location of the DZ in relation to the furcation area was in the middle third of the root.

Insert conformity variation affects kinematics and wear performance of total knee replacements

BackgroundThe insert conformity is a critical factor for successful total knee replacement which must be considered in design of the implant. However, the effects of conformity on knee kinematics and wear under physiological environment are often neglected in previous studies. The present study involved evaluating the biomechanics and wear performance with regard to different insert conformity in total knee replacement. MethodsDifferent tibial inserts with different sagittal and coronal conformity levels were created and analyzed using a previously developed wear prediction framework, coupling a patient-specific musculoskeletal multibody dynamics simulation, finite element and wear analysis. The contact mechanics, kinematics, and wear performance were compared during 10 million cycles of wear simulation. FindingsThe findings revealed that the knee kinematics was affected by sagittal conformity design variables, which further influenced the wear of insert bearing surface. Additionally, kinematics and wear of artificial knee joint were much more sensitive to sagittal than coronal conformity of tibial insert. The lower sagittal conformity designs had lower wear rates, worn area and contact area. In turn, the wear of insert bearing surface also changed insert conformity, and further impacted on knee kinematics. InterpretationThe present study indicated that the sagittal conformity design of insert surface played a crucial role to improve contact mechanics and kinematics performance and minimize wear of total knee replacement. The optimization of insert conformity should be considered carefully in implant design and surgical procedures.

Three-dimensional modeling and measurements of root canal anatomy in second primary mandibular molars: a case series micro CT study.

This study aimed at establishing a comprehensive specification of the root canal anatomy of second primary mandibular molars using micro computed tomography (CT). 10s primary molars from Caucasian young patients were selected for this purpose. Micro CT imaging with a high resolution of 20 microns was performed to observe the roots and canals according to specific criteria. The Vertucci canal configuration, the presence of lateral canals and their location, the presence of an isthmus and its location, were first observed. Then, the length of the canals, their diameter in the mesio-distal and vestibulo-lingual direction, the dentinal thickness and the direction of the minimal dentinal thickness were measured. The mean working length was not significantly different between the canals (p = 0.710). The bucco-lingual diameter was significantly higher when the tooth had a single distal canal at the coronal (p < 0.001), middle (p < 0.001) and apical (p = 0.012) levels. The root dentin thickness on the distal wall of the mesial root and the mesial wall of the distal roots were reduced, respectively, from the coronal to the apical thirds. The results obtained in this case series report clearly show a complex, sometimes unpredictable, anatomy with dangerous areas where dentin is extremely thin. The plethoric presence of anastomoses, large bands of isthmus, lateral canals at all levels induces the need for the development of instruments specific to pulpectomies on primary teeth.

The Penetration Ability of Calcium Silicate Root Canal Sealers into Dentinal Tubules Compared to Conventional Resin-Based Sealer: A Confocal Laser Scanning Microscopy Study.

The purpose of this study was to compare the penetration ability of calcium silicate root canal sealers and conventional resin-based sealer using confocal laser scanning microscopy (CLSM). A total of 60 recently extracted single-rooted human premolars were used in this study. The root canals were prepared to a size 40/0.06 taper with ProFile rotary instruments and irrigated with NaOCl and EDTA. After drying all canals, the specimens were randomly divided into three experimental groups (n = 20): Group 1, gutta-percha (GP)/AH Plus with continuous wave compaction; group 2, GP/BioRoot RCS with a single-cone technique; and group 3, GP/Endoseal MTA with a single-cone technique. All experimental samples were sectioned perpendicular to their long axis using a low-speed diamond wheel at the apical, middle, and coronal third levels. The penetration abilities of all samples were evaluated using CLSM. A Kruskal–Wallis analysis and a series of Mann–Whitney U post hoc tests were performed. A higher intensity level was found in the coronal area and a lower intensity level in the apical area in all the experimental groups. The AH Plus group showed higher sum fluorescence intensity in the apical and coronal thirds compared with the BioRoot RCS and Endoseal MTA groups, whereas the BioRoot RCS group showed a higher intensity level in the middle third, similar to the AH Plus group. The maximum sealer penetration depth was low in the apical area and high in the coronal area in the AH Plus and Endoseal MTA groups. In the BioRoot RCS group, maximum sealer penetration was observed in the middle third. In conclusion, there were significant differences in sealer penetration pattern and distance according to the root level and sealer type.

Comparison of Canal Transportation and Centric Ability of Two Nickel-Titanium Rotary Systems Using Cone Beam Computed Tomography: An In Vitro Study

Abstract Aim The aim of this study was to compare the canal transportation and canal centric ability of One Shape (Micro Mega, Besançon, France) and Mani Silk (Mani Utsunomiya, Tochigi, Japan) nickel-titanium (NiTi) rotary files in curved canals with the help of cone beam computed tomography (CBCT). Materials and Methods Total 40 mesiobuccal canals of maxillary molars with an angle of curvature ranging between 25 and 45 degrees were divided according to the instrument used in canal preparation into two groups 20 samples each: One Shape (group 1) and Mani Silk (group 2). Pre- and post-instrumentation scans were performed using CBCT (Carestream CS 9300 scanner) to evaluate the transportation and centric ability at apical, middle, and coronal levels using unpaired Student's t-test. Results Mani Silk file showed significantly less canal transportation and better canal centric ability compared to One Shape system. Conclusion Mani Silk file maintained original canal curvature better than One Shape NiTi rotary file.

Effect of different irrigation solutions and techniques on push-out bond strength of resin-based sealer

Aim To evaluate the effect of irrigation solutions [sodium hypochlorite (NaOCl), chlorhexidine (CHX), and normal physiological saline] and different irrigation techniques (conventional needle, EndoVac, and CanalBrush) on push-out bond strength of AH Plus resin-based sealer. Materials and methods Ninety mandibular freshly extracted premolars were selected and divided into three groups according to the irrigation solutions; group I: 5.25% NaOCl, group II: 2% CHX, group III: normal physiological saline solution. Then each group was subdivided into three subgroups according to the irrigation techniques; subgroup A: 27 G side beveled needle, subgroup B: EndoVac irrigating system, subgroup C: medium-sized CanalBrush (30/0.04). Root canals of all groups were prepared using ProTaper Universal Ni-Ti rotary system up to file F4 (40/0.06) and filled by single cone technique using AH Plus sealer. 2 mm thick horizontal sections from the coronal, middle and apical thirds of each root were sliced for the push-out bond strength measurement and tested using universal testing machine. Data were analyzed using one-way analysis of variance in a level of significance (P ≤ 0.05). Results The highest mean push-out bond strength values were recorded for EndoVac system followed by CanalBrush and Needle in all groups and at all root canal levels. In comparison of irrigation solutions in needle subgroup; the highest values were recorded for CHX and least for NaOCl at coronal and middle root levels. While in the apical section, the highest and least mean push-out bond strength values were recorded for CHX and saline respectively. Regarding EndoVac and CanalBrush; the highest push-out bond strength values were recorded for CHX followed by saline and NaOCl at all root canal levels. Conclusions Whenever root canal obturation using AH Plus sealer, it is preferred to use 2% CHX solution throughout and after instrumentation via EndoVac system for improved bond strength. The coronal sections showed higher bond strength than middle and apical sections.

Comparative Evaluation of Cleaning Efficacy of Self-adjusting File and WaveOne File: An in vitro Scanning Electron Microscopic Study.

Aim:This study aims to compare the cleaning efficacy of root canal walls using two rotary single file systems: self-adjusting file (SAF) and WaveOne (WO).Materials and Methods:Forty extracted human premolars with similar range of canal curvature were selected, decoronated, working length determined and roots were divided into two groups of 20 samples each: Group I - SAF and Group II - WO. All root canals were irrigated with 3% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA). The roots were sectioned longitudinally and subjected to scanning electron microscopic examination. The amount of debris and smear layer was evaluated using five score index at coronal, middle and apical third levels. Statistical analysis was performed using the Chi-square test and significance was set at a P < 0.05.Results:Statistically significant difference was observed between the groups in cleaning the apical third. Group I (SAF) showed better canal cleanliness compared to Group II (WO) in the apical third.Conclusion:Within the limitations of this study, SAF in combination with 3% NaOCl and 17% EDTA irrigating solution had significantly better cleaning efficacy in the apical third of root canals when compared to WO rotary file system.

Root Canal Shaping Using Nickel Titanium, M-Wire, and Gold Wire: A Micro–computed Tomographic Comparative Study of One Shape, ProTaper Next, and WaveOne Gold Instruments in Maxillary First Molars

IntroductionThe aim of this study was to evaluate the root canal shaping effect of instruments manufactured from nickel titanium, M-Wire, and Gold wire with different glide path preparation techniques. MethodsOne hundred thirty-five mesiobuccal canals of extracted human maxillary molars were randomly divided into 3 equal groups (N = 45) for glide path preparation with K-files (KF) (Dentsply Sirona, Ballaigues, Switzerland), One G (OG) files (Micro-Mega, Besançon, France), and ProGlider (PG) files (Dentsply Sirona). Specimens of each glide path group were further divided equally into 3 groups for instrumentation with ProTaper Next (PTN, Dentsply Sirona), One Shape (OS, Micro-Mega), and WaveOne Gold (WOG, Dentsply Sirona) systems (n = 15). Micro–computed tomographic imaging was used to scan teeth before instrumentation and after shaping to compare centering ratio and canal transportation values at the apical, midroot, and coronal levels and the overall changes in canal volume. Data sets were statistically analyzed (analysis of variance and Kruskal-Wallis H tests). ResultsThe centering ratios for all groups were statistically similar at all levels. Apical canal transportation was significantly high for K/OS and K/PTN (P = .003). Midroot canal transportation was significantly high for K/PTN, K/OS, and OG/OS (P = .0003). Coronal canal transportation was significantly high for K/PTN and K/OS (P = .011). The highest change in canal volume was observed with all PTN groups and the lowest with PG/WOG (P = .06). ConclusionsWOG manufactured from Gold wire combined with PG showed better root canal shaping ability and removed less dentin from the canal walls. The nickel-titanium (OS) and M-Wire (PTN) instruments used in combination with KF significantly transported more canals. PTN removed the most dentin from the canal walls regardless of the GPP technique.

Root Reinforcement after Obturation with Calcium Silicate–based Sealer and Modified Gutta-percha Cone

IntroductionA root canal obturated with a calcium silicate–based sealer (bioceramic sealer [BCS]) and a modified gutta-percha cone (bioceramic cone [BCC]) might improve the fracture resistance of the root. The objective of this study was to evaluate root reinforcement of a bioceramic cone/sealer (TotalFill; FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) by investigating the fracture resistance, push-out bond strength, sealer penetration, and modulus of elasticity (MOE) in comparison with gutta-percha/AH Plus (Dentsply Maillefer, Tulsa, OK) (GP/AH). MethodsEighty-four roots from bilateral mandibular premolars were prepared. For fracture resistance, 40 teeth were randomly divided into 4 groups (n = 10 each): intact roots (negative control), prepared roots (positive control), and the roots obturated with either BCC/BCS or GP/AH. Root canals were obturated with the matched single-cone technique and vertically loaded with a spreaderlike tip until fracture. For push-out bond strength (n = 10 each), coronal, middle, and apical root slices of BCC/BCS and GP/AH were loaded with a cylindrical plunger, and failure modes were determined. Sealer penetration of BCC/BCS and GP/AH (n = 12 each) was evaluated for the maximum depth and the circumferential and total area of penetration at the coronal, middle, and apical levels using confocal laser scanning microscopy. The MOE was investigated according to ISO 4049:2000. ResultsThe fracture load of BCC/BCS, GP/AH, and the intact roots was not significantly different but significantly higher than the prepared, nonobturated roots. BCC/BCS provided a higher bond strength, maximum depth, and circumferential penetration at the apical root level as well as a greater sealer penetration area at all levels compared with GP/AH. The MOE of all materials was much lower than dentin. ConclusionsBCC/BCS and GP/AH bonded and reinforced the prepared roots; their fracture resistances were similar to the intact roots.

Effect of Different Concentrations of Chitosan as Final Irrigating Solution on Smear Layer Removal and Calcium Ions Concentration

Purpose: This study was designed to evaluate the effect of different concentrations of chitosan as final rinse on removing smear layer using scanning electron microscope (SEM) and to quantify the calcium content using energy dispersive X-ray microanalyzer (EDX). Materials and Methods: Fifty extracted human single rooted premolars were selected and instrumented with Revo-S Ni-Ti rotary files. Samples were divided into 4 experimental groups according to the final rinse used and control group (10 samples each) where group I,II,II,IV were irrigated with 0.2%,1%,2%chitosan and EDTA respectively ,Group V (Control group): Va (5 samples) irrigated with sterile saline. Vb (5 samples) not prepared or received any treatment. Samples were grooved and spilt longitudinally and smear layer were evaluated using (SEM) at (coronal, middle and apical) levels and calcium content of intraradicular dentin was measured using (EDX) at middle level. Results: Regarding smear layer removal, at the coronal level, there was a statistically significant difference among the tested groups and the control group in the mean scores of smear layer, however, there was no statistical significant difference among the tested groups in the mean scores of smear layer .At the middle and apical thirds, the lowest mean score of smear layer was recorded in specimens treated with 2% chitosan with a statistical significant difference from specimens treated with 0.2% chitosan. However, there was no statistical significant difference in the mean smear layer scores among 1% chitosan, 2% chitosan and 17% EDTA. Concerning calcium ion concentration there was no statistical significant difference among the tested groups. Conclusions: Chitosan was capable of adequately removing smear layer from intraradicular dentin when used as final rinse. The concentration of chitosan is influential in smear layer removal from intraradicular dentin, being more effective when used in 1% and 2% concentrations. Different concentrations of chitosan did not affect the calcium content of intraradicular dentin.

Efficacy of Chitosan as Root Canal Irrigant in Removing Smear Layer in Curved Root Canals Using Endovac Irrigation System (SEM Study)

Purpose: This study aimed to evaluate the efficacy of Chitosan as root canal irrigant with Endovac irrigation system in removing smear layer of curved root canal walls using Scanning Electron Microscope (SEM). Materials and Methods: Fifty extracted human first mandibular molars were selected with curved mesiobuccal root (20o-35o). Samples were instrumented with Universal ProTaper rotary files till size F4 then divided into 2 main experimental groups according to the final rinse used; Group I: irrigated with 17 % EDTA Group II: irrigated with 0.2% chitosan acetate and control group, irrigated with sterile saline (10 samples). Each group was further subdivided into 2 subgroups according to the irrigating technique used; Subgroup A: using conventional needle irrigation and Subgroup B: using Endovac irrigation system. Samples were grooved longitudinally and smear layer was evaluated using SEM at the coronal, middle and apical root canal levels. The significance level was set at P≤ 0.05. Results: There was a statistically significant difference among the tested groups and the control group in the mean scores of smear layer at all root canal levels and no significant difference between irrigants used. Concerning the irrigating devices, there was no statistical significant difference between conventional irrigation and Endovac system at the coronal and apical root canal levels while at the middle level, 0.2% chitosan showed statistical significant difference with Endovac system subgroup than conventional irrigation(P ≤ 0.05). Conclusion Endovac irrigation system was effective in smear layer removal from curved root canals using either 0.2% Chitosan acetate or 17 % EDTA as finalrinse.

Effect of several laser systems on removal of smear layer with a variety of irrigation solutions.

To evaluate which laser system is more effective on smear layer removal when distilled water or combination of sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) are used as irrigants. Ninety-six human mandibular premolar teeth were used. Standard access cavities were prepared and the root canals were enlarged using ProTaper system to size F4 and divided into two equal groups according to final irrigation solution. In Group 1, distilled water was used, whilst 2.5% NaOCI and 17% EDTA solutions were used in Group 2. Each group was divided into four equal subgroups according to the activation procedure. In Subgroups 1A (Control) and 2A, no activation protocol was applied. In other subgroups, Er:YAG laser using photon-induced photoacoustic streaming (PIPS; 1B and 2B), Nd:YAG laser (1C and 2C) and Er,Cr:YSGG laser (1D and 2D) were applied for the activation. Teeth were split longitudinally and subjected to scanning electron microscopy evaluation. Smear layer was scored at 1000× magnification in all thirds. The data were analysed statistically using Kruskal-Wallis and Mann-Whitney U test post hoc comparisons. The samples irrigated with distilled water had greater smear layer scores when compared with the combination of NaOCl and EDTA (p < .05). The efficacy of smear layer removal increased when using laser systems (p < .05). Smear layer was removed more effectively in the coronal and middle levels compared to the apical level (p < .05). The sequential use of NaOCl and EDTA is significantly more effective than distilled water in smear layer removal. Regardless of the type of irrigant, laser activated irrigation enhances smear layer removal. RESEARCH HIGHLIGHTS: The use of laser systems for activation of NaOCl and EDTA is the most effective method in terms of smear layer removal. Photon-induced photoacoustic streaming technique with Er:YAG laser was the most efficient smear layer removal method regardless of the solution used.

Internal adaptation of cobalt-chromium posts fabricated by selective laser melting technology

Statement of problemSelective laser melting (SLM) has become popular in prosthetic dentistry. However, only limited information is available for the internal adaptation of cobalt-chromium (Co-Cr) posts fabricated by SLM. PurposeThe purpose of this in vitro study was to investigate the internal adaptation of Co-Cr metal posts fabricated by SLM technique. Material and methodsThirty-six Co-Cr metal posts were fabricated by conventional casting, subtractive computer-aided design and computer-aided manufacturing (CAD-CAM), and additive CAD-CAM, by making an impression from a standardized model of a tooth with a single root canal. Posts and the dies were bonded with cement. Specimens were then sectioned horizontally by using a grinding and polishing machine, and 3 different cross-sections of each post were chosen to represent the apical, middle, and coronal regions. The areas of cement were photographed by using a stereomicroscope at an original magnification of ×32 and measured using image-measuring software. From each group, 1 specimen was randomly selected and observed by using scanning electron microscopy. One-way ANOVA and Tukey honestly significant difference test were performed to identify differences among groups with regard to internal adaptation (α=.05). ResultThe internal adaptation of the SLM group did not differ from that of the CAD-CAM milling group at 3 cross-section levels (P>.05). At the apical and coronal cross-section levels, the cement area of SLM group was smaller than that of the cast group (P<.05). However, at the middle cross-section level, the cement area of the cast group was significantly smaller than that of the SLM group (P<.05). Use of scanning electron microscopy showed both the SLM group and the CAD-CAM milling group exhibited homogeneous microstructures. However, the cast group showed a typical discontinuous dendritic solidification microstructure. ConclusionsThe internal adaptation of SLM was not inferior to that of the CAD-CAM milling group or the cast group. The SLM technique seems a promising choice for fabricating dental posts.

Magnetic activity evolution on Sun-like stars

Context. Characterising the time evolution of magnetic activity on Sun-like stars is important not only for stellar physics but also for determining the environment in which planets evolve. Aims. In recent decades, many surveys of open clusters have produced extensive rotation periods measurements on Sun-like stars of different ages. The present study uses this information with the aim to improve the description of their magnetic activity evolution. Methods. I present a method that infers the long-term evolution of Ca II chromospheric (R′HK) and X-ray coronal (LX) emission on solar mass stars by combining a best fit parametric model of their rotation evolution with empirical rotation-activity relationships. Results. The inferred scenario reproduces the high chromospheric and coronal emission levels around R′HK ≈ 10−4 and LX ≈ 1030 erg s−1 that are observed on pre-main sequence (PMS) stars. At the end of the PMS contraction phase around the age of ~30 Myr, the slowest rotating stars experience a rapid transition of their magnetic activity to more moderate levels around R′HK ≈ 4 × 10−5 and L5 ≈ 1029 erg s−1. This transition occurs later on more rapidly rotating stars, up to an age of ~600 Myr for the fastest rotators. After this brief episode of large magnetic activity decay, the average chromospheric and coronal emission levels of solar-mass stars decrease steadily converging towards similar values (R′HK ≈ 10−5 and LX ≈ 1027 erg s−1) by the age of the Sun. Conclusion. The study suggests that solar mass stars in open clusters with ages between ~30 and ~600 Myr exhibit bimodal distributions of their R′HK chromospheric activity indices and coronal X-ray to bolometric luminosity ratios that can be traced back to their rotation evolution. This conclusion is consistent with available measurements of activity indices from Sun-like stars in nearby open clusters.

Effect of Calcium Hydroxide Dressing on the Dentinal Tubule Penetration of 2 Different Root Canal Sealers: A Confocal Laser Scanning Microscopic Study

IntroductionThe purpose of this study was to evaluate the effect of calcium hydroxide (Ca[OH]2) dressing on the dentinal tubule penetration of epoxy resin–based sealer (AH 26; Dentsply Maillefer, Ballaigues, Switzerland) and tricalcium silicate–based sealer (BioRoot RCS; Septodont, Saint Maurdes Fosses, France). MethodsFifty-two single-rooted mandibular premolars were used. Four samples were assigned as the positive control. Twenty-four samples received Ca(OH)2 labeled with rhodamine B, whereas the rest did not. Ca(OH)2 was removed with passive ultrasonic activation and copious irrigation 2 weeks later. Samples were further subdivided into 2 groups, and root canal fillings were performed with a single ProTaper F4 gutta-percha cone (Dentsply Maillefer) combined with 1 of the tested sealers labeled with fluorescein green. After 2 weeks, samples were transversely sectioned at the apical, middle, and coronal levels. The penetration depth and percentage were evaluated via imaging software. Statistical analysis was performed using Kruskal-Wallis, Siegel Castellan post hoc, and Mann-Whitney U tests at P = .05. ResultsThe mean dentinal tubule penetration depth and percentage values were lowest in the apical third for both sealers. BioRoot RCS showed higher penetrability in all thirds compared with AH 26 (P < .05) despite Ca(OH)2 dressing remnants (P < .05). Ca(OH)2 placement resulted in a shorter dentinal tubule penetration depth with BioRoot RCS statistically in the middle and coronal thirds (P < .05), whereas it did not affect the percentage (P > .05). ConclusionsPassive ultrasonic activation and copious irrigation were insufficient in removing Ca(OH)2 from root canals. BioRoot RCS presented higher dentinal tubule penetration than AH 26 even in the presence of Ca(OH)2 residues. Ca(OH)2 remnants decreased both dentinal tubule penetration depth and the percentage of the tested sealers; however, a more drastic effect was observed for AH 26.