Fracture behavior of cantilever fixed dental prostheses fabricated from different zirconia generations.

OBJECTIVE: The aim of this study was to compare the fracture behavior of cantilever fixed dental prostheses (FDPs) fabricated from 3Y-TZP, 4Y-TZP, or 5Y-TZP zirconia. METHOD AND MATERIALS: Posterior cantilever FDPs (three groups, each n = 16) were digitally designed and milled. After sintering, eight specimens/group were stored in demineralized water for 72 hours; eight specimens/group were subjected to accelerated aging using chewing simulation with thermal cycling (1,200,000 × 50 N; 2 × 3,000 × 5°C/55°C; H2O, 2 minutes/cycle) and finally stored in demineralized water for 24 hours. The cantilever FDPs were then statically loaded to failure to determine fracture load. Phase transformation towards the monoclinic phase was controlled with x-ray diffractometry. RESULTS: One failure was identified after accelerated aging in the 5Y-TZP group. Fracture load decreased with increasing yttria content and decreasing bending strength. Accelerated aging using chewing simulation with thermal cycling caused a significant decline in fracture load. All FDPs failed in the area of the prepared tooth and in proximity to the cantilever, where the largest bending moment occurred. The yttria content had no influence on the type of fracture. With increasing yttria content, the relation between deformation and fracture load decreased only slightly. On the surface of FDPs that had been subjected to chewing simulation, no phase transformation towards the monoclinic phase (eg, low temperature degradation) was detected. CONCLUSION: Within the limitations of a laboratory study, the data indicate that 3Y-, 4Y-, and 5Y-TZP may be employed as material for the fabrication of permanent posterior cantilever FDPs. However, more data are necessary to finally advocate the application of 5-Y-TZP. (Quintessence Int 2022;53:414-422; doi: 10.3290/j.qi.b2793243).

Diagnosis of ventricular drainage-related bacterial meningitis by broad-range real-time polymerase chain reaction.

OBJECTIVE: To compare a broad-range real-time polymerase chain reaction (PCR) diagnostic strategy with culture to evaluate additional effects on the etiological diagnosis and the quantification of the bacterial load during the course of ventricular drainage-related bacterial meningitis (VR-BM). METHODS: We applied a PCR that targeted conserved regions of the 16S ribosomal ribonucleic acid gene to cerebrospinal fluid (CSF) samples from patients with external ventricular drainage or a ventriculoperitoneal shunt during the course of VR-BM. We compared the PCR results with CSF cultures. A total of 350 routine CSF samples were consecutively collected from 86 patients. The CSF deoxyribonucleic acid was automatically purified and subjected to PCR. Amplicons from the PCR samples that were positive for VR-BM were subsequently deoxyribonucleic acid sequenced for final identification. Clinical data were extracted from patient files. RESULTS: Sixteen patients had at least one VR-BM-positive sample as diagnosed from culture or PCR. Nineteen episodes were diagnosed with signs of VR-BM (n = 16 patients) or were determined to be contaminated (n = 3 patients). Four episodes of VR-BM were diagnosed via PCR alone and were predominantly caused by gram-negative pathogens, five episodes were diagnosed via culture alone, and seven episodes were diagnosed via both culture and PCR. Five patients had mixed infections. Overall, 71 samples were positive for VR-BM as indicated by either one or both of the methods. Eighteen CSF samples were VR-BM positive as indicated by culture alone, and 21 CSF samples were positive as indicated via PCR alone. CONCLUSIONS: Culture supplemented with broad-range, real-time PCR may increase the number of etiologically diagnosed VR-BM episodes, particularly when these are caused by gram-negative bacteria.

Broad-range real time PCR and DNA sequencing for the diagnosis of bacterial meningitis.

Rapid aetiological diagnosis of bacterial meningitis is crucial for the early targeting of antimicrobial and adjuvant therapy. Broad-range polymerase chain reaction (PCR) targeting the 16S rRNA gene allows aetiological diagnosis of bacterial meningitis when applied to cerebrospinal fluid (CSF). We assessed the additional diagnostic effect of applying a novel broad-range real time PCR and subsequent DNA sequencing to culture, microscopy, and broad-range conventional PCR on CSF in patients with suspected bacterial meningitis. Broad-range conventional PCR and broad-range real time PCR with subsequent DNA sequencing were applied to 206 CSF specimens collected consecutively from 203 patients aged 6 d to 86 y. Patients' charts were reviewed for clinical information. 17 pathogens were identified by PCR and DNA sequencing or culture. Three specimens were negative by culture but positive by broad-range real time PCR. Three specimens were positive by culture but negative by broad-range real time PCR. Compared with culture, the sensitivity of broad-range real time PCR was 86%, and the specificity 98%. Conventional PCR resulted in a sensitivity of 64% and specificity of 98%. Broad-range real time PCR was generally comparable to culture of CSF and may be a useful supplement, particularly when antimicrobial therapy has been administered. Broad-range real time PCR was more sensitive than broad-range conventional PCR and microscopy.