Influence of water sorption on mechanical properties of injection-molded thermoplastic denture base resins

Objective. This study investigated the influence of water sorption on certain mechanical properties of injection-molded thermoplastic denture base resins. Materials and methods. Six thermoplastic resins (two polyamides, two polyesters, one polycarbonate, one polymethylmethacrylate) and a polymethylmethacrylate (PMMA) conventional heat-polymerized denture-based polymer, selected as a control, were tested. Specimens of each denture base material were fabricated according to ISO 1567 specifications and were either dry or water-immersed for 30 days (n = 10). The ultimate flexural strength, the flexural strength at the proportional limit and the elastic modulus of the denture base materials were calculated. Results. Water sorption significantly decreased the ultimate flexural strength, the flexural strength at the proportional limit and the elastic modulus of one of the polyamides and the PMMAs. It also significantly increased the ultimate flexural strength of the polycarbonate. Conclusion. The mechanical properties of some injection-molded thermoplastic denture base resins changed after water sorption.     

Osteoporotic fractures of the proximal humerus in elderly Finnish persons: Sharp increase in 1970-1998 and alarming projections for the new millennium

We determined the current trends in the number and incidence of osteoporotic fractures of the proximal humerus in Finland by collecting from the National Hospital Discharge Register all patients 60 years of age or more who were admitted to Finnish hospitals in 1970-1998 for primary treatment of such fractures. The fracture was defined osteoporotic if it was caused by a low-energy trauma only, i.e., a fall from standing height or less. The number and incidence (per 10 5 persons) of fractures increased sharply from 208 (number) and 32 (incidence) in 1970 to 1,105 and 110 in 1998. Even after the age-adjustment, the incidence of fractures showed a clear increase: in women from 50 in 1970 to 133 in 1998, and in men from 14 in 1970 to 49 in 1998. If this trend continues, there will be three times more osteoporotic fractures of the proximal humerus in Finland in the year 2030 than there were in 1998.     

Centenarian hip fracture patients: a nationwide population-based cohort study of 507 patients

Background and purpose — Several studies suggest a global increase of centenarians during the 21st century. We describe temporal trends of hip fracture incidence and mortality in this group and compare these patients with a group of younger hip fracture patients with regards to comorbidities and mortality.

Patients and methods — The full study population included all hip fractures that occurred in Denmark (n = 154,047) between 1996 and 2012. Patients aged 100 or above were identified (n = 507) and hip fracture patients between the ages of 70 to 99 years (n = 124,007) were used for comparison. Data were accessed from national registries. Trends in incidence over time were analyzed using a log-linear regression model, mortality was analyzed using the Kaplan–Meier estimator and trends in mortality over time were analyzed using a log-binomial regression model to obtain relative risk estimates.

Results and interpretation — The centenarian patients had fewer comorbidities than the younger comparison group, but mortality was higher at all timepoints. There was no statistically significant change in mortality over time but the incidence of hip fracture among centenarians decreased during the same time period. Our findings describe the characteristics of an emerging group of hip fracture patients and could be of use in the planning of healthcare in the years to come.     

Decreased cancer risk in patients who have been operated on with total hip and knee arthroplasty for primary osteoarthrosis

3 Nordic cohorts of total hip (THA) and total knee arthroplasty (TKA) in patients operated on for primary osteoarthrosis during 1967–1995 were partly adapted and combined for meta-analysis. THA was performed in 49,000 patients and TKA in 24,000 totaling 497,000 person years. The mean and maximum follow-up times were 6.8 and 30 years, respectively. Standardized incidence ratios (SIRs) with 95% confidence intervals (95% CI) were calculated for the observed and expected number of cancers. The expected numbers were based on national incidence rates. The overall SIRs as well as the site-specific ones were similar in the THA and TKA patients. The observed number of cancers at all sites was 7,639 and the expected one was 8,202 (SIR 0.93,95% CI 0.91–0.95).

The SIRs for lung cancer (0.69, 0.64–0.75) and laryngeal cancer (0.64, 0.44–0.92) were reduced. The incidence was also low for cancers of the stomach (SIR 0.76, 0.67–0.84), colon (SIR 0.86, 0.79–0.93) and rectum (SIR 0.89, 0.80–0.98).

Among TKA patients, the only increases in SIRs were seen in cancers of the endometrium (SIR 1.36, 1.05–1.74), prostate (SIR 1.19, 1.02–1.38) and, among both THA and TKA patients, in skin melanoma (combined SIR 1.21,1.03–1.41).