Effect of Passive Ultrasonic Irrigation, Er,Cr:YSGG Laser, and Photon-Induced Photoacoustic Streaming against Enterococcus faecalis Biofilms in the Apical Third of Root Canals.

PURPOSE: This study aimed to compare the antibacterial effectiveness of passive ultrasonic irrigation (PUI), Er,Cr:YSGG laser (WTL), and photon-induced photoacoustic streaming (PIPS) using an Er:YAG laser against Enterococcus faecalis biofilms in the apical third of root canals. METHODS: Root canals of 70 single-rooted human teeth were instrumented and infected with E. faecalis for 3 weeks to form biofilms. The samples were randomly divided into five groups as follows: (i) PUI + 3% NaOCl (n = 16); (ii) Er,Cr:YSGG laser (n = 16); (iii) PIPS + 3% NaOCl (n = 16); (iv) positive control group (n = 10); and (v) negative control group (n = 10). The bacterial content in the root canal was sampled using (a) the paper-point sampling method before (S1) and after (S2) treatment and (b) pulverising the apical 5 mm of the root. The number of bacteria recovered from each group was counted as colony-forming units (CFUs). The amount of reduction between the groups was compared with the Kruskal-Wallis test and post-test Dunn's multiple comparisons tests. The significance level was set at 5% (p < 0.05). RESULTS: The samples from the paper-point sampling method showed that the amount of bacteria before (S1) and after treatment (S2) was significantly different between PIPS and WTL, as well as between the PUI and WTL groups. In contrast, no significant difference was found between the PIPS and PUI groups. From the pulverised samples, the results indicated no significant difference among all experimental groups in the amount of bacterial reduction in the apical 5 mm of the root. CONCLUSIONS: PUI and PIPS showed a significantly greater reduction in bacterial content within the main root canal compared with the WTL. There was no difference among all experimental groups in the apical third of the root.

Transition metals and Enterococcus faecalis: Homeostasis, virulence and perspectives.

Enterococcus faecalis, a Gram-positive bacterium, is known to be a key player in several chronic infections as well as nosocomial, heart valve, urinary tract, surgical wound, and dental root canal infections. The capability to sense different transition metal levels and tune its response accordingly endows it with the potential to thrive and cause infections in several host niches. Over the past decade, our knowledge of how transition metals play a critical role in maintaining homeostasis of E. faecalis has improved significantly. The aim of this review is to elucidate the roles of metals such as iron, manganese, zinc, and copper in the physiology, metabolism, and pathogenicity of E. faecalis. These essential micronutrients contribute to energy production, redox stress response, expression of virulence determinants, and cooperation in polymicrobial communities. The review also highlights metal homeostasis systems in E. faecalis, which respond to fluctuations in extracellular metal levels, and regulate the intracellular metal content. Regulation of intracellular metallome secures the tolerance of E. faecalis to oxidative stress and host-mediated metal sequestration strategies. Therapeutic interventions which deprive E. faecalis of its essential metal requirements or disrupt its homeostatic control have been proposed to combat E. faecalis infections.

Debris extrusion during root canal preparation with nickel-titanium instruments using liquid and gel formulations of sodium hypochlorite in vitro.

This study compared the amount of apically extruded debris during root canal preparation with three single-file systems using liquid and gel-based formulations of sodium hypochlorite (NaOCl) or distilled water. Seventy-two single-canalled roots were divided into three groups: HyFlex EDM (Coltene-Whaledent); Reciproc Blue (VDW); and F-One Blue (Shanghai Fanta) and then divided into three subgroups: NaOCl liquid (Imicrly), NaOCl gel (Cerkamed Medical) and distilled water. The amount of extruded debris was calculated by determining the dry weight of the debris collected. Data were analysed using Kruskal-Wallis test with Bonferroni correction. Debris extrusion occurred in all subgroups. Both the instrument and the irrigant had an impact. The F-One Blue tended to extrude the least debris, though no significant difference was observed in the pairwise comparisons between instruments. NaOCl liquid resulted in significantly more extruded debris than NaOCl gel or distilled water. The results lead us to conclude that the NaOCl gel reduced debris extrusion compared to NaOCl liquid.

Ex vivo shaping ability of reciprocating instruments operated by new users: Reciproc versus WaveOne.

OBJECTIVES: To compare two reciprocating NiTi systems operated by novices for use in curved root canals. METHODS: Fifty mesial roots of extracted mandibular first molars, with 2-2 canal configuration, were scanned with micro-CT and divided into 2 groups according to canal length and curvature: Reciproc and WaveOne. Each system was used to prepare one of the two canals by fourth-year dental students, who were new to reciprocating files and were blinded to the system being used. After another scanning, the pre- and post-instrumentation images were compared 3-dimensionally in software. RESULTS: Some 43 to 46% of the canal wall area remained un-instrumented. Significantly higher proportions of canals were transported towards the isthmus or furcation aspect than the mesial or external aspect. Mean transported distance was the greatest in the coronal one-third. Remaining dentine wall was the thinnest at the furcal aspect near the middle root region. No significant difference was noted between the two brands in the parameters examined. CONCLUSIONS: Both brands of reciprocating file left similar amounts of un-instrumented canal wall, and resulted in similar extent of canal transportation. CLINICAL RELEVANCE: NiTi reciprocating files can safely be used by new users to prepare curved root canals into a predictable shape.

Spatial Cleaning Action of Ultrasonic Irrigation on Enterococcus faecalis Biofilm.

This study aimed to examine the spatial cleaning effect of ultrasonic irrigation in simulated root canal with oblong cross section in the absence of antimicrobial agent. A 7-day E. faecalis biofilm was cultivated in a rectangular, simulated canal model and subjected to passive ultrasonic irrigation (PUI) with sterile saline for 5 minutes. After that, the biofilm was examined by confocal microscopy after bacterial viability staining at 58 sites around and beyond the endosonic file. Results showed that, at the vicinity of the file, the amount of viable bacteria ranged from 13.1% (2.75 mm from the tip) to 40.5% (4.5 mm level). Lesser amounts of live bacteria were observed within 1 mm from the vibrating file, which amount increased for sites farther away. At 3 mm distance, the amount of bacteria (35.5 to 64.4%) was significantly greater than areas situated close to the vibrating file (P < 0.01). Sites next to the anti-nodes of file had less bacteria remaining than sites near the nodes (P = 0.050). Apically (0.5 mm or more), the amount of bacteria was significantly greater than that at the file tip (16.4%) (P < 0.05). It was concluded that PUI is able to dislodge a single-species biofilm, provided that they are situated in close vicinity to the vibrating file.

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind.

The prediction of a supersonic solar wind1 was first confirmed by spacecraft near Earth2,3 and later by spacecraft at heliocentric distances as small as 62 solar radii4. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5-7. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9-11, well within the distance at which stream interactions become important. We find that Alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second-considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12-14.

Effectiveness of irrigation strategies on the removal of the smear layer from root canal dentin.

The aim of this study was to evaluate the removal of the smear layer by some commonly used (needle-and-syringe irrigation, sonic activation, ultrasonically activated irrigation) and new root canal irrigation strategies (negative pressure irrigation and polymer rotary file) using a novel approach by comparing pre- and post-experimental images. Prepared root canals (n = 50) were subjected to a split tooth model and divided into 5 groups (n = 10): (1) needle-and-syringe irrigation (control); (2) sonic activation (SA); (3) negative pressure irrigation with continuous warm activated irrigation and evacuation (CWA); (4) polymer finishing file (FF); (5) ultrasonically activated irrigation (UAI). Smear layer scores and percentage of open dentinal tubules (%ODT) were evaluated by 2 examiners before and after irrigation procedures, from the middle and apical thirds of the root canal, on scanning electron microscopic images. Data were analysed using Kruskal-Wallis and post hoc tests at P = 0.05. Needle-and-syringe irrigation (control) showed no significant difference (both smear score and %ODT) compared to the pre-experimental value (P > 0.05). All other groups showed lower smear scores and higher %ODT, compared to the control (P < 0.05). The lowest smear score and highest %ODT were observed in the CWA group, which was significantly different from all other groups (P < 0.05). SA group showed significantly higher smear scores and lower %ODT than FF or UAI (P < 0.05). CWA showed superior removal of smear layer in the middle and apical thirds of the root canal compared to the other irrigation strategies.

Low-cost, flexible, disinfectant-free and regular-array three-dimensional nanopyramid antibacterial films for clinical applications.

In this work, a low-cost, scalable and highly repeatable approach was developed to prepare polystyrene films with three-dimensional nanopyramids on the surface. The nanopyramids have a tunable aspect ratio and more importantly, their anti-bacterial performance has been systematically studied. The effectiveness of the nanopyramids on E. coli growth inhibition and the role of the nanostructure aspect ratio were carefully studied through scanning electron microscopy and confocal laser scanning microscopy. The results showed an excellent antibacterial performance with more than 90% reduction in the E. coli population in all nanopyramid samples after a 168 h prolonged incubation time. The nanopyramid film developed here can be used for clinical and commercial applications to prevent the growth of pathogenic bacteria on various surfaces.

Periodontal Blood Flow Protects the Alveolar Bone from Thermal Injury during Thermoplasticized Obturation: A Finite Element Analysis Study.

INTRODUCTION: The purpose of this study was to investigate the heat transfer during thermoplastic obturation and the cooling capacity of blood flow in the periodontal ligament (PDL) using finite element analysis (FEA). METHODS: A 3-dimensional digital tooth model was constructed based on micro-computed tomographic scanning of a mandibular first molar after chemomechanical preparation in vitro. A layer of PDL with or without simulated blood flow was built on the root portion of the tooth in software. Two heat-assisted obturation techniques (ie, the single-wave condensation technique and the warm vertical compaction technique followed by backfilling with injectable gutta-percha) were examined using an FEA package. RESULTS: In the model without blood flow, the highest temperature at the alveolar bony aspect of the PDL was 50.0°C along the distal canal and 52.5°C for the mesiolingual canal when the single-wave technique was used. With the warm vertical compaction technique, the highest temperature was 47.3°C for the distal canal and 47.8°C for the mesiolingual canal. In the model with simulated periodontal blood flow, a notable drop in the peak temperatures at the root surface and at the adjoining alveolar bone was observed for both the distal and mesiolingual canals; all peak temperatures at the PDL fell below 47°C regardless of the obturation techniques used. The greatest rise in temperature was situated at the furcation aspect of the middle third of both roots. CONCLUSIONS: The cooling capacity of blood flow in the PDL is a factor that must be considered in the investigation of heat transfer during thermoplastic obturation.

Hybrid Simulations of Positively and Negatively Charged Pickup Ions and Cyclotron Wave Generation at Europa.

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K+, O 2+, Na+, and Cl+, indicating the localized pickup of these species. Additional evidence for the presence of chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarized transverse wave power near the Cl+ gyrofrequency, thought to be due to the pickup of both Cl+ and the easily formed chlorine anion, Cl-. To test this hypothesis, we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negative pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in nongyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localized regions at Europa.

Treatment Outcome of Repaired Root Perforation: A Systematic Review and Meta-analysis.

INTRODUCTION: This study aimed to review systematically the reported treatment outcome of repaired root perforation and to identify any preoperative factors that may influence the outcome of such repair. METHODS: A comprehensive search was conducted by using 4 electronic databases, as well as manual search of cited references, to identify reports related to root perforation. Clinical studies published from 1950 to mid-2014 that evaluated the outcome of repaired root perforations were identified. Studies were further screened for similar characteristics for pooling of data for meta-analysis. RESULTS: Seventeen studies were included for systematic review and 12 suitable for meta-analysis. An overall pooled success rate of 72.5% (confidence interval, 61.9%-81.0%) was estimated for nonsurgical repair of root perforations. The use of mineral trioxide aggregate appeared to enhance the success rate to 80.9% (confidence interval, 67.1%-89.8%), but the difference was not statistically significant. The presence of pre-existing radiolucency adjacent to the perforation site fared a lower chance of success after repair (P < .05). Maxillary teeth demonstrated a significantly higher success rate compared with their mandibular counterpart (P < .05). CONCLUSIONS: Within the limitations of this study, it may be concluded that nonsurgical repair of root perforation results in a success rate of more than 70%. Teeth in the maxillary arch and absence of preoperative radiolucency adjacent to the perforation are favorable preoperative factors for healing after perforation repair. In view of the relatively high rate of clinical success, nonsurgical repair may be considered as the preferred treatment to handle this complication that arises during root canal therapy.

Enterococcus faecalis promotes osteoclastogenesis and semaphorin 4D expression.

Enterococcus faecalis is considered a major bacterial pathogen implicated in endodontic infections and contributes considerably to periapical periodontitis. This study aimed to investigate the potential mechanisms by which E. faecalis accounts for the bone destruction in periapical periodontitis in vitro. Osteoclast precursor RAW264.7 cells were treated with E. faecalis ATCC 29212 and a wild strain of E. faecalis derived clinically from an infected root canal. The results showed that, to some extent, E. faecalis induced the RAW264.7 cells to form tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclast-like cells. This pathogen markedly stimulated RAW264.7 cells to express semaphorin 4D (Sema4D), which inhibits bone formation. Once RAW264.7 cells were primed by low-dose receptor activator of nuclear factor-kappa B ligand (RANKL), E. faecalis could significantly increase the production of TRAP-positive multinucleated cells and up-regulate the expression of osteoclast-specific markers, including NFATc1, TRAP and cathepsin K. Both p38 and ERK1/2 MAPK signaling pathways were activated by E. faecalis in RANKL-primed RAW264.7 cells, and meanwhile the expression of Sema4D was highly increased. In conclusion, E. faecalis may greatly contribute to the bone resorption in periapical periodontitis by promoting RANKL-dependent osteoclastogenesis and expression of Sema4D through activation of p38 and ERK1/2 MAPK signaling pathways.

Effect of root canal dimensions, injection rate, and needle design on the apical extrusion of an irrigant: an in vitro study.

AIM: The purpose of this study was to determine the effect of root canal dimensions, type of needle, and injection rate on the apical extrusion of an irrigant in a simulated root canal. METHODS: Ten students used two types of 28-gauge needles, to deliver 3 mL irrigant solution into artificial canals prepared in acrylic blocks to a standard size of ISO 25, 30, or 40 (0.06 taper; n = 10). Each block was preweighed to the nearest microgram before and after irrigation once the canal was dried with paper points. This was repeated with a syringe pump at a flow rate of 50, 100, 200 or 300 µL/s with the needle inserted to a standard depth. RESULTS: Significant differences were observed between the side-vented and notched-end needles when the rate of irrigation was higher than 100 µL/s, and when the apical size was below ISO 40 (P < 0.001). The amount of extrusion was more variable and significantly higher when irrigation was performed manually, compared with the syringe pump groups. CONCLUSIONS: Injection rates above 100 µL/s increased the risk of extrusion, whereas increasing the apical canal size to ISO 40 reduced the amount of extrusion in all groups. The use of a side-vented needle negates the injection-rate effects.

Extension of bactericidal effect of sodium hypochlorite into dentinal tubules.

INTRODUCTION: The aim of this study was to determine the extent of disinfection mediated by 2 concentrations of sodium hypochlorite for bacteria-laden dentin wall of a root canal. METHODS: A dual-species film, Enterococcus faecalis and Porphyromonas gingivalis, was cultivated on root canal dentin for 7 days. The canal wall was irrigated with 0.5% or 3% sodium hypochlorite (n = 8 each), with a control group (n = 2) irrigated with sterile saline. The roots were then split horizontally at 5-, 7-, and 9-mm levels from root apex and examined under confocal laser scanning microscope and then scanning electron microscope. The proportions of viable cells situated on different depths into root canal dentin were compared at a significance level of P = .05. RESULTS: Both concentrations of sodium hypochlorite significantly reduced the amount of live bacteria in the most superficial layer (first 0.1 mm) of root canal dentin, compared with the control; however, the difference was not significant between the 2 concentrations. For the next 2 layers (0.1-0.3 mm into dentinal tubules), irrigation with 3% hypochlorite resulted in significantly lower amounts of viable bacteria than 0.5% hypochlorite or saline. No significant difference between 0.5% or 3% sodium hypochlorite and the positive control was observed in deeper (>0.3 mm) regions into the root canal wall. CONCLUSIONS: Increasing the concentration of sodium hypochlorite improves the penetration depth of its antibacterial action into dentinal tubules, but that seemed unable to completely eradicate bacteria residing there. Total elimination of bacteria from dentinal tubules cannot be achieved by irrigation with sodium hypochlorite alone.

Comparison of the antibacterial effect and smear layer removal using photon-initiated photoacoustic streaming aided irrigation versus a conventional irrigation in single-rooted canals: an in vitro study.

OBJECTIVE: The Er:YAG laser with photon-induced photoacoustic streaming (PIPS) technique was reported to be effective in root canal disinfection. This study attempted to further investigate the antibacterial efficacy and smear layer removal ability of PIPS in comparison with conventional syringe irrigation in vitro. METHODS: For antibacterial analysis, 48 single-rooted human teeth were prepared and inoculated with Enterococcus faecalis, and then divided into six groups of eight roots each. The colony-forming units (CFUs) per milliliter were determined after infection as the baseline. Then, the teeth were subjected to either PIPS plus 3% sodium hypochlorite (PIPS+NaOCl) or conventional syringe irrigation with 0.9% saline, 3% NaOCl, 17% ethylenediaminetetraacetic acid (EDTA), 0.2% chlorhexidine gluconate (CHX), or 3% NaOCl alternating with 17% EDTA. The reduction of CFUs in the individual group was determined. Additionally, scanning electron microscopy (SEM) examination of the canal walls for E. faecalis colonization was performed. For comparing the smear removal efficacy, another 48 single-rooted teeth, assigned to different groups as mentioned, were irrigated after mechanical instrumentation. The presence of a smear layer at different levels of the root canal was scored by SEM examination. RESULTS: No significant differences were found in CFU reduction. No bacteria could be observed by SEM in the NaOCl, NaOCl+EDTA, and PIPS+NaOCl groups. The scores of smear layer of the NaOCl+EDTA and PIPS+NaOCl groups were significantly lower than those of the other groups in the coronal and middle third of the root canal. None of the methods can effectively remove smear layer in the apical third. CONCLUSIONS: PIPS system supplied with NaOCl and conventional syringe irrigation with NaOCl+EDTA are comparable in their ability to remove E. faecalis and smear layer in single-rooted canals.

Suitability of time estimates for survival analysis of endodontic treatment.

INTRODUCTION: This study aimed to determine the most suitable estimates of the event date for Kaplan-Meier (K-M) survival analysis for the assessment of endodontic treatment outcomes. Survival probability computed using the Weibull accelerated failure time (WAFT) models based on interval-censored data was used for comparison. METHODS: A sample of root canal-treated teeth was included for survival analysis using the K-M and WAFT models. Treatment outcomes were categorized for the presence or absence of periapical healing and tooth survival. For the K-M analysis, the following time estimates between a visit when failure was diagnosed and the preceding visit were tested: the one-quarter point (T1), the half-way point (T2), the three-quarter point (T3), the date of diagnosis (T4), and the geometric mean (T5). RESULTS: The survival curve plotted from T2 consistently showed the least discrepancies in trend when compared against the WAFT curve. Those curves generated from T1 to T5 were significantly different from each other for periapical healing but not for tooth survival. CONCLUSIONS: T2 is the most reliable date for K-M analysis for measuring endodontic outcomes, especially when periapical healing is concerned. T4 would be a reasonable estimate for assessing tooth survival. Further research aiming at appropriate statistical exercise with simulations followed by proper goodness of fit tests should be considered.

Storage media enhance osteoclastogenic potential of human periodontal ligament cells via RANKL-independent signaling.

BACKGROUND: Hank's balanced salt solution (HBSS) and milk have gained wide acceptance as storage media for avulsed tooth. However, the effect of the media and storage time on the periodontal ligament (PDL) cells involvement in the development of root resorption is still unclear. The purpose of this study was to evaluate whether precultured PDL cells in HBSS, milk, or modified Eagle's medium alpha (α-MEM) would affect osteoclastogenesis. MATERIALS AND METHODS: PDL cells were precultured in HBSS, milk, or α-MEM for 1 h or 6 h before being co-cultured with RAW 264.7 cells for an additional 3 days for mRNA analysis and 11 days for osteoclastogenesis assay. RESULTS: Cyclooxygenase-2 (COX-2) mRNA was detected immediately in PDL cells precultured in the three storage media. The expression was up-regulated markedly in all co-cultures when compared with RAW cells alone. As a result of the co-culture, interleukin-1ß (IL-1ß) expression was detectable in both PDL and RAW cells. TRAP+ multinucleated, osteoclast-like cells developed in all co-cultures; the number of TRAP+ cells was highest (P < 0.05) in the co-cultures that PDL cells precultured in milk for 6 h. The mRNA level of receptor activator of nuclear factor-kappa B ligand (RANKL) was not detected in PDL cells. Osteoprotegerin (OPG) mRNA expression reduced with increased preculture time, but the difference was not significant (P > 0.05). CONCLUSIONS: PDL cells kept in the three storage media led to TRAP+ multinucleated, osteoclast-like cells formation via RANKL-independent signaling. The ability to induce osteoclastogenesis may be considered as one of the factors to evaluate the ability of storage medium to maintain PDL viability after tooth avulsion.

Cyclic fatigue resistance tests of Nickel-Titanium rotary files using simulated canal and weight loading conditions

OBJECTIVES: This study compared the cyclic fatigue resistance of nickel-titanium (NiTi) files obtained in a conventional test using a simulated canal with a newly developed method that allows the application of constant fatigue load conditions. MATERIALS AND METHODS: ProFile and K3 files of #25/.06, #30/.06, and #40/.04 were selected. Two types of testing devices were built to test their fatigue performance. The first (conventional) device prescribed curvature inside a simulated canal (C-test), the second new device exerted a constant load (L-test) whilst allowing any resulting curvature. Ten new instruments of each size and brand were tested with each device. The files were rotated until fracture and the number of cycles to failure (NCF) was determined. The NCF were subjected to one-way ANOVA and Duncan's post-hoc test for each method. Spearman's rank correlation coefficient was computed to examine any association between methods. RESULTS: Spearman's rank correlation coefficient (rho = -0.905) showed a significant negative correlation between methods. Groups with significant difference after the L-test divided into 4 clusters, whilst the C-test gave just 2 clusters. From the L-test, considering the negative correlation of NCF, K3 gave a significantly lower fatigue resistance than ProFile as in the C-test. K3 #30/.06 showed a lower fatigue resistance than K3 #25/.06, which was not found by the C-test. Variation in fatigue test methodology resulted in different cyclic fatigue resistance rankings for various NiTi files. CONCLUSIONS: The new methodology standardized the load during fatigue testing, allowing determination fatigue behavior under constant load conditions.

Transplantation of dental pulp stem cells and platelet-rich plasma for pulp regeneration.

INTRODUCTION: The loss of dental pulp may weaken teeth, rendering them susceptible to reinfection, fracture, and subsequent tooth loss. Therefore, regeneration of pulp is considered an ideal treatment to preserve teeth. The aim of this study was to explore the capacity of dental pulp stem cells (DPSCs) and platelet-rich plasma (PRP) to regenerate dental pulp in canine mature permanent teeth. METHODS: Pulpectomy with apical foramen enlarged to a #80 file was performed in 16 upper premolars of 4 beagle dogs. Four experimental groups were randomly established: (1) the blood clot group, (2) the autologous DPSCs group, (3) the PRP group, and (4) the DP + PRP group (a mixture of DPSCs and PRP). Four lower premolars without any further treatment after pulpectomy were used as the control group. All teeth were sealed with mineral trioxide aggregate and composite. Twelve weeks after transplantation, the teeth were subjected to radiographic and histologic examination. RESULTS: Twenty-four of 32 experimental root canals gained newly formed tissues. All canals with an introduction of a blood clot showed histologic evidence of vital tissue formation. Cementum-like and periodontal ligament-like tissues along the internal root canal walls were typical structures in most cases. There is no significant difference between groups with or without autologous DPSC transplantation (exact chi-square test, P < .05). CONCLUSIONS: New vital tissues can be regenerated in permanent canine teeth after pulpectomy and enlargement of the apical foramen. Histologically, transplantation of DPSCs and/or PRP into root canals showed no enhancement in new tissue formation compared with inducement of a blood clot into the root canals alone.

Evaluation of fiber post-supported restorations under simulated occlusal loading.

STATEMENT OF PROBLEM: There is a lack of information comparing the effect of a rigid versus flexible post on the marginal seal of post-and-core supported crowns subjected to long-term repeated loading. PURPOSE: The purpose of this study was to examine the leakage pattern of complete coverage restorations retained with either a metal or fiber-reinforced resin post under simulated occlusal loads. MATERIAL AND METHODS: Thirty-six maxillary central incisors were endodontically treated and provided with a post-and-core supported crown. One group was restored with a fiber-post (EasyPost Lux) and another was restored with a metal post (Parapost) (n=12). Both groups were loaded for 120,000 cycles to 70 N while immersed in a dye solution. A control group (n=12), similarly restored with a fiber post but not loaded, was also included. All teeth were transversely sectioned serially from the tooth-core interface towards the apex. Digital photographs were made to determine the extent of leakage on the buccal, mesial, palatal, and distal aspects along the depth of the post. A nonparametric Kruskal-Wallis test was used to determine any difference between groups (α=.05). RESULTS: Dye penetration occurred in all stress-cycled specimens and was more extensive on the palatal than other aspects. The fiber-post group cyclically stressed to 70 N showed a significantly greater amount of leakage than the control or the Parapost group (P<.05). CONCLUSIONS: In in vitro testing, the rigidity of the post influenced the seal of post-and-core-supported crowns at the palatal margin.