Chain Features and Their Influence on the Thermal Stability of Poly(propylene‐co‐1‐nonene) Copolymers

The thermal stability of several isotactic polypropylenes and propylene‐co‐1‐nonene copolymers is assessed under nitrogen by means of thermogravimetric analysis (TGA). The samples involve wide ranges of molecular weight, isotactic average length, and 1‐nonene content, in order to perform a comprehensive analysis of the effect that chain features exert on the apparent activation energy (E_a), in the initial stages of the molten state degradation. The degradation process correlates with chain mobility and, accordingly, with chain features that are linked to. Thus, microstructure and chain size are found to play a key role. In fact, isotactic average length of propylene sequences and molecular weight are driving factors in the E_a required for main chain thermal scission.     

The acceptability and effectiveness of a questionnaire for the identification of risk factors for HIV and hepatitis B and C: An observational study in general practice

Background: Many people in Europe remain undiagnosed for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV).

Objectives: To evaluate acceptability and effectiveness of a questionnaire designed to facilitate identification of risk factors for these viruses.

Methods: We performed an observational study, in a prospectively enrolled cohort of patients in Paris (France) seen in 2014. Eighteen GPs administered a questionnaire to the first 50 patients, collecting information about risk factors. GPs were randomized into two groups: A (self-administered questionnaire) and B (GP-administered questionnaire). We used the overall response rate to assess the acceptability of the questionnaire. We used the rate of newly identified risk factors and compared the number of tests performed one year before and immediately after the intervention to assess the effectiveness of the questionnaire.

Results: 842 patients were randomized: 349 (41.5%) in group A and 493 (58.5%) in group B. Acceptability was 88.5% (95%CI: 86.3–90.6); 93.1% (95%CI: 90.5–95.8) in-group A and 85.2% (95%CI: 82.1–88.3) in group B (P?=?0.0004). Prevalence of risk factors was 51.8% (95%CI: 48.2–54.4) and 58.3% were newly identified (95%CI: 52.9–63.7). The number of HIV tests performed during the four weeks after intervention increased by 27% compared to the same period one year before (P?=?0.22). It increased by 113% (P?=?0.005) and 135% (P?=?0.005) for HBV and HCV, respectively.

Conclusion: The questionnaire proved acceptable and effective in identifying risk factors for HIV, HBV and HCV in general practice.     

Prospective evaluation of implants connected to teeth

PURPOSE: This prospective clinical trial examined the effect on teeth and implants when rigidly or non-rigidly connected in a cross-arch model. MATERIALS AND METHODS: Thirty patients received 2 implants, 1 on each side of the mandible, and were restored with 3-unit fixed partial dentures connected either rigidly or non-rigidly to an abutment tooth. Patients were followed for at least 5 years post-restoration. RESULTS: Repeated-measures analysis revealed no significant difference in crestal bone loss at implants (rigid versus non-rigid methods). An overall significant difference (P < .001) was found comparing methods for teeth. Paired t tests revealed no significant differences in crestal bone levels for implants or teeth at the 5-year recall. Kaplan-Meier methods and the Cox proportional hazards model showed no differences between attachment methods with regard to success based on survival and bone loss criteria. During the 5-year recall period, 1 implant (rigid side) was removed. Four implants developed bone loss greater than 2 mm during the course of this trial. One tooth on the rigid side and 2 teeth on the non-rigid side had greater than 2 mm of crestal bone loss and were removed secondary to fractures. In all, 5 abutment teeth were removed, all of which had been treated with root canal therapy and fractured at the interface of the post within the tooth. There was no clear relationship of tooth fracture to attachment. Repeated-measures analysis of mobility values revealed no significant changes over the time course of this study, and paired t tests revealed no statistically significant differences between implants for mobility. Repeated-measures analysis and paired t tests for probing depth revealed no significant changes over the time course of this study. There were no significant differences in soft tissue indices for either attachment method. The percentage of patients who had measurable intrusion was 66% for the non-rigid group, and 44% for the rigid group; 25% of the non-rigid teeth had greater than 0.5 mm intrusion, compared with 12.5% for the rigid group. For the 2 time periods evaluated, there was no significant increase in intrusion over time. The non-rigid-side implant required more nonscheduled visits to treat problems than the rigid implant and the teeth. Discussion: Most patients were treated successfully with rigid or non-rigid attachment of implants to teeth. CONCLUSION: The high incidence of intrusion and non-scheduled patient visits suggest that alternative treatments without connecting implants to teeth may be indicated.     

Shaping of curved root canals instrumented with stainless steel and nickel titanium files

The cleaning efficiency and the quality of the surgical preparation is mainly conditioned by root canal anatomy, the instruments and the technique employed. The purpose of the present study was to evaluate the extent of straightening of curved root canals and the changes in endodontic anatomy caused by the use of Flex-R, Onyx-R and Nitiflex files with the balanced forces technique. Sixty mandibular molars were selected for evaluation of angulation and transportation. Pre and post instrumentation radiographs were taken of the mesiodistal and buccolingual aspects of each tooth. The radiographs were projected on a transparent sheet, the contours of each tooth and file were outlined and the canal curvature was measured. Pre and post instrumentation tracings were overlaid and the extent of transportation was measured with a micrometric caliper. Statistical analysis of the data was performed employing Student's "t" test, Analysis of Variance and Bonferroni's test. The results showed that all the instruments reduced canal curvature significantly. Transportation in the mesiodistal direction did not reach statistical significance whereas transportation in the buccolingual direction was statistically significant.     

Outcomes of root canal treatment and restoration, implant-supported single crowns, fixed partial dentures, and extraction without replacement: a systematic review

STATEMENT OF PROBLEM: Dentists and patients are regularly confronted by a difficult treatment question: should a tooth be saved through root canal treatment and restoration (RCT), be extracted without any tooth replacement, be replaced with a fixed partial denture (FPD) or an implant-supported single crown (ISC)? PURPOSE: The purpose of this systematic review was to compare the outcomes, benefits, and harms of endodontic care and restoration compared to extraction and placement of ISCs, FPDs, or extraction without tooth replacement. MATERIAL AND METHODS: Searches performed in MEDLINE, Cochrane, and EMBASE databases were enriched by hand searches, citation mining, and expert recommendation. Evidence tables were developed following quality and inclusion criteria assessment. Pooled and weighted mean success and survival rates, with associated confidence intervals, were calculated for single implant crowns, fixed partial dentures, and initial nonsurgical root canal treatments. Data related to extraction without tooth replacement and psychosocial outcomes were evaluated by a narrative review due to literature limitations. RESULTS: The 143 selected studies varied considerably in design, success definition, assessment methods, operator type, and sample size. Direct comparison of treatment types was extremely rare. Limited psychosocial data revealed the traumatic effect of loss of visible teeth. Economic data were largely absent. Success rates for ISCs were higher than for RCTs and FPDs, respectively; however, success criteria differed greatly among treatment types, rendering direct comparison of success rates futile. Long-term survival rates for ISCs and RCTs were similar and superior to those for FPDs. CONCLUSIONS: Lack of comparative studies with similar outcomes criteria with comparable time intervals limited comparison of these treatments. ISC and RCT treatments resulted in superior long-term survival, compared to FPDs. Limited data suggested that extraction without replacement resulted in inferior psychosocial outcomes compared to alternatives. Long-term, prospective clinical trials with large sample sizes and clearly defined outcomes criteria are needed.