RESUMO
OBJECTIVE: Polymeric framework represent an innovative approach for implant-supported dental prostheses. However, the mechanical response of ultra-high performance polymers as frameworks for full-arch prostheses under the "all-on-four concept" remains unclear. The present study applied finite element analysis to examine the behavior of polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) prosthetic frameworks. MATERIALS AND METHODS: A three-dimensional maxillary model received four axially positioned morse-taper implants, over which a polymeric bar was simulated. The full-arch prosthesis was created from a previously reported database model, and the imported geometries were divided into a mesh composed of nodes and tetrahedral elements in the analysis software. The materials were assumed as isotropic, elastic, and homogeneous, and all contacts were considered bonded. A normal load (500 N magnitude) was applied at the occlusal surface of the first left molar after the model was fixed at the base of the cortical bone. The microstrain and von-Mises stress were selected as criteria for analysis. RESULTS: Similarities in the mechanical response were observed in both framework for the peri-implant tissue, as well as for stress generated in the implants (263-264 MPa) and abutments (274-273 MPa). The prosthetic screw and prosthetic base concentrated more stress with PEEK (211 and 58 MPa, respectively) than with PEKK (192 and 49 MPa), while the prosthetic framework showed the opposite behavior (59 MPa for PEEK and 67 MPa for PEKK). CONCLUSION: The main differences related to the mechanical behavior of PEKK and PEEK frameworks for full-arch prostheses under the "all-on-four concept" were reflected in the prosthetic screw and the acrylic base. The superior shock absorbance of PEKK resulted in a lower stress concentration on the prosthetic screw and prosthetic base. This would clinically represent a lower fracture risk on the acrylic base and screw loosening. Conversely, lower stress concentration was observed on PEEK frameworks.
RESUMO
OBJECTIVES: To examine the prognostic significance of pretreatment C-reactive protein (CRP), N-terminal pro-brain natriuretic peptide (NT-proBNP), and cardiac troponin T (cTnT) levels on all-cause mortality 3 years after head and neck squamous cell carcinoma (HNSCC) diagnosis. SUBJECTS AND METHODS: Data from 118 consecutive HNSCC patients, treated between 2012 and 2015, were evaluated prospectively. The impact of CRP, high-sensitive (hs)-cTnT, and NT-proBNP levels on the 3-year overall survival was estimated using the Kaplan-Meier method and Cox proportional hazard models. RESULTS: During the 36-month follow-up, 37 patients (31.35%) died. Multivariate analysis revealed that elevated CRP (Hazard ratio: 3.71, 95% CI: 1.44-9.53, p = .007) and NT-proBNP levels (Hazard ratio: 5.04, 95% CI: 2.02-12.55, p = .001) were associated with negative prognosis, independent on age, sex, smoking and alcohol status, TNM classification, tumor site, body mass index (BMI), systolic blood pressure (SBP), and treatment modality (except for radiotherapy). hs-cTnT had no influence over the prognosis, but it was correlated with TNM classification and SBP. CRP was significantly correlated with BMI and TNM classification, and NT-proBNP with SBP and hs-cTnT. CONCLUSIONS: Pretreatment CRP and NT-proBNP levels were identified as independent prognostic markers for poor clinical outcome 3 years after HNSCC diagnosis.
