Fracture Strength of Roots Instrumented with Self-Adjusting File and the ProTaper Rotary Systems

Introduction

The purpose of this study was to evaluate the fracture strength of roots instrumented with the Self-Adjusting File (SAF; ReDent-Nova, Ra’anana, Israel) and the ProTaper system (Dentsply Maillefer, Ballaigues, Switzerland) and filled with the cold lateral compaction technique.

Methods

In total, 50 mandibular premolar teeth were sectioned at or below the cementoenamel junction to obtain roots 13 mm in length. The roots were balanced with respect to buccolingual-mesiodistal diameters and weight. They were distributed into 4 experimental groups and 1 control group (n = 10): no instrumentation (control group), instrumentation with ProTaper rotary files but no filling (PT), instrumentation with ProTaper rotary files and filling with cold lateral compaction (PT filling), instrumentation with SAF but no filling (SAF), and instrumentation with SAF and filling with cold lateral compaction (SAF filling). AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) was used along with gutta-percha points. One week later, a vertical load was applied to the specimen’s canal until fracture occurred. Data were statistically analyzed using 1-way analysis of variance (P = .05).

Results

The mean fracture load was 244 ± 51 N for the control group, 226 ± 21 N for the PT, 242 ± 45 N for PT filling, 233 ± 14 N for the SAF, and 271 ± 44 N for SAF filling. However, the differences were not statistically significant (P > .05).

Conclusions

Instrumentation with the SAF or the ProTaper rotary system did not change the fracture strength of standardized roots with respect to cross-sectional diameter and weight.     

What do I do? Developing a competency inventory for postgraduate (residency) program directors

Background: Few new Residency Program Directors (PD) are formally trained for the demands and responsibilities of the leadership aspect of their role. Currently, there are no comprehensive frameworks that describe specific leadership competencies that can inform PD self-reflection or faculty development.

Methods: The authors developed a Postgraduate Program Director Competency Inventory (PPDCI) in order to frame the performance of PDs for a multisource feedback (MSF) program. The development of the PPDCI occurred in five phases which involved: development of an initial inventory, implementation of a key informant survey of national opinion leaders, execution of a validity survey with postgraduate education leaders and committee members and implementation of a further refined inventory with 17 PD and 147 raters as part of a pilot MSF program.

Outcomes: Five distinct domains of leadership competence were identified which included: Communication and relationship management, leadership, professionalism and self-management, environmental engagement, and management skills and knowledge. The content validity of the PPDCI was endorsed by 85% of the key informants. The validity survey indicated strong endorsement of the PPDCI domains and recognition of its utility for both orientation of new PD as well as a frame for self-assessment. The pilot MSF program yielded a further refined and reduced inventory of 26 items of competence as well as recommendations for its utility.

Conclusions: Use of this leadership inventory has the potential to ensure effective leadership of postgraduate programs.     

Nonsynaptic localization of the excitatory amino acid transporter 4 in photoreceptors

Excitatory amino acid transporters (EAATs) are involved in regulating extracellular glutamate levels at synaptic regions in the CNS. EAAT1, 2, 3, and 5 have been found in the mammalian retina, but the presence of EAAT4 has remained controversial. Recently, we found a high level of EAAT4 mRNA in the human retina, and this observation lead us to examine whether EAAT4 was expressed in the mammalian retina. Immunoblotting studies showed the presence of EAAT4-immunoreactive proteins in human and mouse retinas, corresponding to EAAT4 monomers and dimers. Immunohistochemistry revealed that EAAT4 was localized in rod and cone photoreceptor outer segments in the human retina, and in the outer and inner segments of mouse and ground squirrel retinas. In no case was EAAT4 found in the outer plexiform layer or in any other layer in the retina. EAAT4 expression by photoreceptors was confirmed by immunoblotting a purified rod outer segment preparation, which showed the presence of a 50-kDa EAAT4-immunoreactive protein. In addition, the EAAT4-associated protein, GTRAP41, was found in the human, mouse, and squirrel retinas as well as in the rod outer segment preparation. Further immunocytochemical and co-immunoprecipitation experiments demonstrated that GTRAP41 was colocalized and interacted in vivo with EAAT4. Importantly, glutamate uptake and drug inhibition experiments showed that an EAAT4-like glutamate uptake system is present in the rod outer segments. Finally, we examined whether glutamate signaling mediated by EAAT4 can modulate rod outer segment phagocytosis by the retinal pigment epithelium. Results of the present study show that EAAT4 is present in the outer segments, a nonsynaptic region of photoreceptors, where it might provide a feedback mechanism for sensing extracellular glutamate or serve as an outer barrier to prevent glutamate from escaping from the retina.     

Effect of vitamin D receptor (VDR) genotypes on the risk for osteoporosis in type 1 Gaucher disease

The almost universal finding of osteopenia in Gaucher disease and the unpredictable advent of avascular necrosis and/or pathological fractures are clinically relevant issues that are not necessarily reversed by specific enzyme replacement therapy (ERT). However, genetic/epigenetic factors may explain variance for bone mineral density (BMD) in the normal population. Among the candidate genes, vitamin D receptor (VDR) polymorphisms have been correlated with BMD at the lumbar spine (LS) and femoral neck (FN) and/or fracture risk in various populations. Helsinki Committee approval was received. DNA samples from 15 healthy individuals and 83 non-neuronopathic adult patients with recent BMD data at LS and FN were tested for VDR polymorphisms FokI, ApaI, TaqI, and BsmI. Chi-square, Fisher’s exact, analysis of variance (ANOVA), Scheffe post hoc, and non-parametric Kruskal-Wallis ANOVA were applied as appropriate. P values <0.05 was considered statistically significant. There were no significant differences between patients and controls in frequency of any of polymorphic genotypes. The ApaI and BsmI genotypes were correlated with the N370S/N370S Gaucher genotype (p = 0.029, and p = 0.061, respectively). There was a correlation between the BsmI genotype and skeletal involvement (p = 0.018) and a trend to significance with Z scores at LS (p = 0.084). There was a statistically significant correlation between the Taq1 variants and BMD at the FN (p = 0.030) with the TT variant associated with lower BMD. As in other populations, VDR polymorphic genotype may be an independently sorting modifier in the prediction of BMD and bone involvement in Gaucher disease.     

Platelet responses and coagulation activation on polylactide and heparin-polycaprolactone-L-lactide-coated polylactide stent struts

Despite modern stent technology and effective antiplatelet therapy, metallic stents carry the risk of (sub)acute thrombosis. Our aim was to examine short-term differences in platelet deposition and coagulation activation between biodegradable polylactide (PLA), heparin-polycaprolactone-L-lactide-coated polylactide (hepa-P(CL95/L-LA5)-PLA), and stainless steel (SS) stent struts. Gel-filtered platelets (GFP) and platelet-rich plasma (PRP) were labeled with 10 nM (3)H-serotonin. Platelet deposition was measured after incubation of the stent struts in human serum albumin-coated wells at 37 degrees C in either GFP or PRP. Platelet morphology was studied by scanning electron microscopy (SEM). For coagulation activation, the stent struts were incubated in either PRP or platelet-poor plasma (PPP), anticoagulated with D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK), followed by measurement of fibrinogen, thrombin time (TT), prothrombin fragment 1+2 (F1+2), and thrombin-antithrombin complex (TAT). SS showed adherence of larger amounts of GFPs than did PLA at a platelet density of 300 x 10(6)/mL (p < 0.05). Furthermore, representative SEM studies showed more platelet spreading on SS than on PLA stent struts. Between PLA and SS, coagulation activity did not differ at any assessment. Based on prolonged TT values in plasma, the heparin coating strongly inhibited coagulation (p < 0.05). The values of soluble TAT and F1+2 for PLA were similar to those of controls, i.e., to incubated suspensions without a stent strut. In conclusion, when compared with stainless steel, both PLA and hepa-P(CL95/L-LA5)-PLA appear hemocompatible as intravascular stent materials.