Root curvature localizations as indicators of post length in various tooth groups

— The straight line length available for post preparations in pulps of 957 human teeth was evaluated. Analysis of radiographs in both buccolingual and mesiodistal directions showed that only 2.7% of the teeth studied were straight to the apex in both views. Average straight line lengths were calculated for the different types of teeth and used to offer guidelines for the length of post preparation. Buccal roots of maxillary molars and the mesial roots of the mandibular molars frequently showed straight line lengths insufficient for post preparations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72918/1/j.1600-9657.1986.tb00125.x.pd

Various heat-treated nickel–titanium rotary instruments evaluated in S-shaped simulated resin canals

AbstractBackground/purposeHeat treatment of nickel–titanium (NiTi) alloy produces a better arrangement of the crystal structure, thereby leading to increased flexibility and improved fatigue resistance or plastic behavior. This study aimed to assess the performance of various heat-treated NiTi rotary instruments in S-shaped resin canals.Materials and methodsForty S-shaped resin canals were instrumented (10/group) with either Twisted Files (R-phase), WaveOne (M-wire), Hyflex CM, or V Taper 2H (CM-wire) with the same apical size and taper (25/0.08). Each S-shaped resin canal was scanned both before and after instrumentation with microcomputed tomography. Changes in canal volume and transportation were evaluated at regular intervals (0.5 mm). Differences between instruments at the apical curve, coronal curve, and straight portion of the canals were analyzed statistically.ResultsAll tested instruments caused more transportation at the coronal rather than apical curvatures, with the exception of Twisted Files for which apical transportation was the highest for any instrument or location (P<0.05). The transportation was mostly influenced by the alloy type rather than their cross-sectional characteristics (P<0.05). The volumetric increase after instrumentation was similar for all tested instruments at the apical curve (P>0.05), whereas Hyflex CM created the most conservative preparations at the coronal curve (P<0.05). At the straight portion, volumetric changes were largest for Twisted Files and smallest for V Taper 2H (P<0.05).ConclusionAmongst heat-treated NiTi instruments, the CM-wire based instruments created the most favorable preparations in S-shaped resin canals

Trauma and Anxiety: The Narratives of Syrian Youth Resettled as Refugees

Background Civilian war trauma and forced migration are among the most traumatic life experiences. There are approximately 36.4 million refugees worldwide; 40% are children. There is a paucity of mixed methods approaches that quantify properties of trauma narratives of refugee youth. This approach could assist in identifying individuals who could benefit from early clinical care. Methods Participants were 68 youth resettled as refugees of Syria in Southeast Michigan ages 7-17 (31F, Mage = 12.85), originally recruited from clinics during health screenings within one month of arrival in the United States. Those enrolled in this study consented to additional data collection and were assessed 1-2 years post-migration. Linguistic Inquiry and Word Count tools analyzed the narratives of youth’s experiences. Participants were asked to recall the overall most hurtful or terrifying event they had ever experienced, and then under their current living situation. Mixed methods approaches were employed to derive thematic elements from trauma narratives. Results Pre-migration narratives consisted of violence and loss from experiences in both Syria and Jordan. The top three most frequent word categories were social references, perception, and spatial language. Post-migration narratives consisted of discrimination and bullying, namely at school and in communities. The top three most frequent word categories were social references, perception, and cognition. Conclusion Most social interactions children have are at school or school-related functions. Schools have a unique opportunity to mitigate traumatic social experiences. Further funds and teaching are needed to positively shape the social experiences of young people, especially youth resettled as refugees

Influence of irrigant needle depth in removing bioluminescent bacteria inoculated into instrumented root canals using real-time imaging in vitro

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73506/1/j.1365-2591.2004.00906.x.pd

Computed micro-tomographic evaluation of glide pathwith nickel-titanium rotary pathFile in maxillary firstmolars curved canals

Introduction: X-ray computed micro-tomography scanning allows high-resolution 3-dimensional imaging of small objects. In this study, micro-CT scanning was used to compare the ability of manual and mechanical glide path to maintain the original root canal anatomy. Methods: Eight extracted upper first permanent molars were scanned at the TOMOLAB station at ELETTRA Synchrotron Light Laboratory in Trieste, Italy, with a microfocus cone-beam geometry system. A total of 2,400 projections on 360 degrees have been acquired at 100 kV and 80 mu A, with a focal spot size of 8 mu m. Buccal root canals of each specimen (n = 16) were randomly assigned to Path File (P) or stainless-steel K-file (K) to perform glide path at the full working length. Specimens were then microscanned at the apical level (A) and at the point of the maximum curvature level (C) for post-treatment analyses. Curvatures of root canals were classified as moderate (<= 35 degrees) or severe (>= 40 degrees). The ratio of diameter ratios (RDRs) and the ratio of cross-sectional areas (RAs) were assessed. For each level of analysis (A and C), 2 balanced 2-way factorial analyses of variance (P < .05) were performed to evaluate the significance of the instrument factor and of canal curvature factor as well as the interactions of the factors both with RDRs and RAs. Results: Specimens in the K group had a mean curvature of 35.4 degrees +/- 11.5 degrees; those in the P group had a curvature of 38 degrees +/- 9.9 degrees. The instrument factor (P and K) was extremely significant (P < .001) for both the RDR and RA parameters, regardless of the point of analysis. Conclusions: Micro-CT scanning confirmed that NiTi rotary Path File instruments preserve the original canal anatomy and cause less canal aberrations. (J Endod 2012;38:389-393

Penetration of Sodium Hypochlorite Modified with Surfactants into Root Canal Dentin

Abstract The aim of this study was to evaluate the effect of concentration, exposure time and temperature of sodium hypochlorite (NaOCl) added with surfactants on its penetration into dentinal tubules. Sixty-five extracted human permanent maxillary anterior teeth with single canals were prepared by ProTaper SX hand-operated instruments. The teeth were then sectioned perpendicular to the long axis. The crowns and apical thirds of all the teeth were removed. The remaining roots were processed into 4-mm-long blocks and stained overnight in crystal violet. One hundred and thirty stained blocks were further split into halves and treated by nine different types of NaOCl-based solutions. Three solutions were added with surfactants (Hypoclean, H6, Chlor-Xtra) and the others were regular hypochlorites at increasing concentrations (1%, 2%, 4%, 5.25%, <6%, 6% NaOCl) from different brands. The dentin blocks were exposed to the solutions for 2, 5, and 20 min at 20 °C, 37 °C and 45 °C, respectively. The depth of NaOCl penetration was determined by bleaching of the stain and measured by light microscopy at 20&#61472;&#61620; and 40&#61620;. Statistical comparisons were made by using a generalized linear model with Bonferroni's post-hoc correction. The shortest penetration (81±6.6 &#956;m) was obtained after incubation in 1% NaOCl for 2 min at 20 °C; the highest penetration (376.3±3.8 &#956;m) was obtained with Chlor-Xtra for 20 min at 45 °C. Varying NaOCl concentration produced a minimal effect while temperature and exposure time had a significant direct relationship with NaOCl penetration into dentinal tubules, especially those with lowered surface tension. The exposure time and temperature of sodium hypochlorite as well as the addition of surfactants may influence the penetration depth of irrigants into dentinal tubules

Association between intra-radicular posts and periapical lesions in endodontically treated teeth

Introduction: A significant number of endodontically treated teeth restored with posts have associated periapical lesions, and several authors have discussed the probable causes of the development of these. Attention has been focused on restorative procedures performed after endodontic treatment and their association with the prognosis of endodontic therapy because a number of root-filled teeth will require post- and core-retained restorations. Purpose: The purpose of this study was to evaluate, by examination of periapical radiographs, whether the placement of intra-radicular posts in endodontically treated teeth may act as a risk factor for development of periapical lesions. Material and Methods: This case-control study analyzed periapical radiographs of 72 endodontically treated teeth with coronal restorations. All radiographs were obtained from a single private practice. Specimens were assigned to 2 groups: Group 1 (control) was composed of teeth without periapical lesions and Group 2 (case) was composed of teeth with periapical lesions. The number of teeth with and without posts in each group was recorded. Three calibrated examiners analyzed the radiographs visually under X4 magnification. Results: In Group 1, 28 (65.1%) out of 43 teeth were restored with posts. In Group 2, 24 (82.8%) out of 29 teeth had intra-radicular posts. The interpretation of chi-square test showed that these percentages were not significantly different (x²=2.687; p=0.101). Odds ratio was 2.571 (0.815-8.118), which indicates that there was no statistically significant association between periapical lesions and posts. Conclusion: Intra-radicular posts placed in endodontically treated teeth were not a significant risk factor for development of periapical lesions in the practice where the cohort of patients was treated

QMix® irrigant reduces lipopolysacharide (LPS) levels in an in vitro model

AbstractThe presence of endotoxin inside the root canal has been associated with periapical inflammation, bone resorption and symptomatic conditions.Objectives To determine, in vitro, the effect of QMix® and other three root canal irrigants in reducing the endotoxin content in root canals.Material and Methods Root canals of single-rooted teeth were prepared. Samples were detoxified with Co-60 irradiation and inoculated with E. coli LPS (24 h, at 37°C). After that period, samples were divided into 4 groups, according to the irrigation solution tested: QMix®, 17% EDTA, 2% chlorhexidine solution (CHX), and 3% sodium hypochlorite (NaOCl). LPS quantification was determined by Limulus Amebocyte Lysate (LAL) assay. The initial counting of endotoxins for all samples, and the determination of LPS levels in non-contaminated teeth and in contaminated teeth exposed only to non-pyrogenic water, were used as controls.Results QMix® reduced LPS levels, with a median value of 1.11 endotoxins units (EU)/mL (p<0.001). NaOCl (25.50 EU/mL), chlorhexidine (44.10 EU/mL) and positive control group (26.80 EU/mL) samples had similar results. Higher levels were found with EDTA (176.00 EU/mL) when compared to positive control (p<0.001). There was no significant difference among EDTA, NaOCl and CHX groups. Negative control group (0.005 EU/mL) had statistically significant lower levels of endotoxins when compared to all test groups (p<0.001).Conclusion QMix® decreased LPS levels when compared to the other groups (p<0.001). 3% NaOCl, 2% CHX and 17% EDTA were not able to significantly reduce the root canal endotoxins load

The effectiveness of enzymic irrigation in removing a nutrient‐stressed endodontic multispecies biofilm

Aim: To establish a nutrient‐stressed multispecies model biofilm and investigate the dynamics of biofilm killing and disruption by 1% trypsin and 1% proteinase K with or without ultrasonic activation. Methodology: Nutrient‐stressed biofilms (Propionibacterium acnes, Staphylococcus epidermidis, Actinomyces radicidentis, Streptococcus mitis and Enterococcus faecalis OMGS 3202) were grown on hydroxyapatite discs and in prepared root canals of single‐rooted teeth in modified fluid universal medium. The treatment groups included trypsin, proteinase K, 0.2% chlorhexidine gluconate and 1% sodium hypochlorite (NaOCl) (with and without ultrasonics). NaOCl and chlorhexidine were the positive controls and untreated group, and sterile saline was the negative control. The biofilms were investigated using confocal laser scanning microscopy (CLSM) with live/dead staining and quantitative microbial culture. Results: Nutrient stress in the multispecies biofilm was apparent as the medium pH became alkaline, glucose was absent, and serum proteins were degraded in the supernatant. The CLSM showed the percentage reduction in viable bacteria at the biofilm surface level due to nutrient starvation. On the disc model, trypsin and proteinase K were effective in killing bacteria; their aerobic viable counts were significantly lower (P < 0.01) than the negative control and chlorhexidine. NaOCl was the most effective agent (P < 0.001). In the tooth model, when compared to saline, trypsin with ultrasonics caused significant killing both aerobically and anaerobically (P < 0.05). Chlorhexidine (1.46 ± 0.42), trypsin (3.56 ± 1.18) and proteinase K (4.2 ± 1.01) with ultrasonics were significantly effective (P < 0.05) in reducing the substratum coverage as compared to saline with ultrasonics (12% ± 4.9). Conclusion: Trypsin with ultrasonic activation has a biofilm killing and disrupting potential