Press-on force during polishing of resin composite restorations.

OBJECTIVE: To measure the press-on force during the polishing of composite restorations carried out by 10 dentists in a clinically simulated procedure. METHODS: Composite restorations (Tetric EvoCeram Bulk Fill) were placed in standardized Class II two-surface cavities in first upper acrylic molars. The surfaces were roughened by sandblasting (50µm, 1bar). The tooth was mounted on a tailor-made device with a 3D force sensor (Kistler, Z21134-300, 10Hz). Ten dentists (7 male, 3 female) polished one Class II restoration each using the one-step polishing system OptraPol together with a dental handpiece and water spray. The dentists were allowed to use all shapes of the polishing system (small flame, large flame, cup, lens). During polishing, the press-on forces measured for up to 2 minutes. Simultaneously, the polishing procedure was recorded with a digital camera to correlate the forces with the polishing shapes and movements. RESULTS: In total, 17,999 force measurements were available for analysis. The mean forces of all operators varied between 0.77(±0.63) N and 2.23(±1.48) N; the difference was statistically significant (ANOVA, post-hoc Tukey B, p<0.05). All dentists exerted maximum forces higher than 3 N (between 3.3N and 18.3N). Force values exceeded 2N during 25% of the polishing time. Female dentists polished with a statistically significant lower force than male dentists (ANOVA, p<0.001). Polishing with the large flame and the cup generated significantly higher forces than polishing with the small flame and the lens (ANOVA, post hoc Tukey B, p<0.01). CONCLUSIONS: The press-on forces applied during polishing varied significantly between dentists and within the same dentist. In about 25% of the polishing time, forces were above the 2N limit, which is recommended by some manufacturers as the maximum polishing force. Test institutes and manufacturers should evaluate the polishing performance of polishing instruments with various press-on forces.

Yersinia pseudotuberculosis Prevalence and Diversity in Wild Boars in Northeast Germany.

In this study, the prevalence of Yersinia pseudotuberculosis in wild boars in northeast Germany was determined. For that purpose, the tonsils of 503 wild boars were sampled. The presence of Y. pseudotuberculosis was studied by diagnostic PCR. Positive samples were analyzed by cultural detection using a modified cold enrichment protocol. Ten Y. pseudotuberculosis isolates were obtained, which were characterized by biotyping, molecular serotyping, and multilocus sequence typing (MLST). In addition, whole-genome sequences and the antimicrobial susceptibility of the isolates were analyzed. Yersinia pseudotuberculosis was isolated from male and female animals, most of which were younger than 1 year. A prevalence of 2% (10/503) was determined by cultural detection, while 6.4% (32/503) of the animals were positive by PCR. The isolates belonged to the biotypes 1 and 2 and serotypes O:1a (n = 7), O:1b (n = 2), and O:4a (n = 1). MLST analysis revealed three sequence types, ST9, ST23, and ST42. Except one isolate, all isolates revealed a strong resistance to colistin. The relationship of the isolates was studied by whole-genome sequencing demonstrating that they belonged to four clades, exhibiting five different pulsed-field gel electrophoresis (PFGE) restriction patterns and a diverse composition of virulence genes. Six isolates harbored the virulence plasmid pYV. Besides two isolates, all isolates contained ail and inv genes and a complete or incomplete high-pathogenicity island (HPI). None of them possessed a gene for the superantigen YPM. The study shows that various Y. pseudotuberculosis strains exist in wild boars in northeast Germany, which may pose a risk to humans.IMPORTANCEYersinia pseudotuberculosis is a foodborne pathogen whose occurrence is poorly understood. One reason for this situation is the difficulty in isolating the species. The methods developed for the isolation of Yersinia enterocolitica are not well suited for Y. pseudotuberculosis We therefore designed a protocol which enabled the isolation of Y. pseudotuberculosis from a relatively high proportion of PCR-positive wild boar tonsils. The study indicates that wild boars in northeast Germany may carry a variety of Y. pseudotuberculosis strains, which differ in terms of their pathogenic potential and other properties. Since wild boars are widely distributed in German forests and even populate cities such as Berlin, they may transmit yersiniae to other animals and crop plants and may thus cause human infections through the consumption of contaminated food. Therefore, the prevalence of Y. pseudotuberculosis should be determined also in other animals and regions to learn more about the natural reservoir of this species.

Complete Genome Sequences of 10 Yersinia pseudotuberculosis Isolates Recovered from Wild Boars in Germany.

We report here the draft genome sequences of 10 Yersinia pseudotuberculosis isolates recovered from tonsils of wild boars hunted between 2015 and 2016 in Germany. Whole-genome sequencing and bioinformatic analyses were performed to assess the diversity of Y. pseudotuberculosis, which may result in human infections caused by the consumption of game meat.