Should statistical analysis of bond-strength data include or exclude cohesive failures?

Objectives The aim was to investigate shear bond strengths and failure modes of four self-etch bonding agents to bovine dentin and enamel and to compare evaluation of data sets with or without exclusion of cohesive failure specimens. Methods Composite-cylinders were bonded perpendicularly to bovine dentin and enamel surfaces. Shear-strengths were measured 24 h post-bonding of: Scotchbond Universal® (SBU, 3 M), OptiBond™ XTR (OBXTR, Kerr), OptiBond™ universal (OBU, KaVo-Kerr) and Prime & Bond active® (PBA, Dentsply-Sirona). Analysis of overall data was made via a linear mixed-model. This was repeated after exclusion of specimens associated with cohesive failures. Results When both adhesive and cohesive failures were considered, OBU and OBXTR showed comparable dentin and enamel bond strengths, whereas lower strengths were found on enamel for SBU (p < 0.001) and PBA (p = 0.015). For OBXTR higher shear strengths were measured for specimens associated with cohesive failures. When cohesive failures were excluded, the majority of shear bond strengths of adhesive failure specimens were only slightly different from overall results. However, uniquely with OBXTR dramatically lower shear bond strengths were found for dentin substrate. Significance After exclusion of cases with cohesive failures OBXTR adhesive fell behind other materials in the sequence of average shear strengths. This did not reflect the actual performance of the material. Therefore, in statistical analysis we do not recommend exclusion of data based on a specific fracture mode

Alternatives to amalgam: Is pretreatment necessary for effective bonding to dentin?

Objective The aim of this study was to determine whether pretreatment of the dentin surface is beneficial or not by analysis of the bond strengths of four self-adhesive restoratives and four restoration materials where pretreatment of dentin was necessary. Methods Bovine incisors (n = 160) were ground flat on the labial surfaces to expose dentin using a grinder and silicon carbide (SiC) abrasive papers under running water. Between preparation and bonding procedures, the crowns were stored in Chloramine-T solution at 4 °C. Eight different restorative materials were studied: Activa BioActive (ABA), Cention Forte (CNF), Ceram.x Spectra ST (CXS), Riva self-cure (RSC), Equia Forte (EQF), Fuji II LC (FJI), Ketac Molar (KTM), Surefil one (SFO). Four materials required pretreatment of the dental hard tissue before placement, whereas the other four were self-adhesive (no pretreatment). The specimens were mounted vertically in plaster. A preload of 5 N was applied and the subsequent cross-head speed was 0.8 mm/min. Shear bond strengths (MPa) were calculated as the failure load divided by the bonding area. Failure modes were recorded as adhesive, cohesive or pretest. Data were statistically analyzed via ordinal regression for inference and Tukey’s method to adjust for multiple comparisons. All computations were done using R version 4.1.2 (R Core Team 2021). Results Smax (failure stress in MPa) of the combined groups with pretreatment were significantly higher than the self-adhesive materials. The highest frequency of pretest-failure was seen with FJI. Glass-ionomer cements without pretreatment were the only restoratives with pretest failures. Amongst materials without pretreatment, SFO had the highest bond strengths. Significance The further reduction of the placement steps for materials used as an amalgam alternative, namely the omission of pretreatment of the dentin, results in these self-adhesive materials having lower bond strengths than materials that require pretreatment of the dentin

Results of an international phosphorus digestibility ring test with broiler chickens

The objective of this ring test was to investigate the prececal phosphorus (P) digestibility of soybean meal (SBM) in broiler chickens using the trial protocol proposed by the World's Poultry Science Association. It was hypothesized that prececal P digestibility of SBM determined in the collaborating stations is similar. Three diets with different inclusion levels of SBM were mixed in a feed mill specialized in experimental diets and transported to 17 collaborating stations. Broiler chicks were raised on commercial starter diets according to station-specific management routine. Then they were fed the experimental diets for a minimum of 5 d before content of the posterior half of the ileum was collected. A minimum of 6 experimental replicates per diet was used in each station. All diets and digesta samples were analyzed in the same laboratory. Diet, station, and their interaction significantly affected (P &lt; 0.05) the prececal digestibility values of P and calcium of the diets. The prececal P digestibility of SBM was determined by linear regression and varied among stations from 19 to 51%, with significant differences among stations. In a subset of 4 stations, the prececal disappearance of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate)-P; InsP6-P) also was studied. The prececal InsP6-P disappearance correlated well with the prececal P digestibility. We hypothesized that factors influencing InsP6 hydrolysis were main contributors to the variation in prececal P digestibility among stations. These factors were probably related to the feeding and housing conditions (floor pens or cages) of the birds in the pre-experimental phase. Therefore, we suggest that the World's Poultry Science Association protocol for the determination of digestible P be should extended to the standardization of the pre-experimental period. We also suggest that comparisons of P digestibility measurements among studies are made only with great caution until the protocol is more refined

Comparison of three methods to enumerate gut microbiota of weanling piglets fed insoluble dietary fibre differing in lignin content

SUMMARYThe aim of the current study was to compare three methods for determining the influence of different feeding strategies on the gut microbiota of piglets. Forty-eight weanling piglets were fed four different diets enriched with insoluble dietary fibre (wheat bran and pollen fromPinus massoniana). Starting from ileal and colonic samples, the total microbial DNA was isolated and bacterial parameters (lactobacilli, bifidobacteria,Bacteroides vulgatusand total bacterial counts) were quantified using real-time polymerase chain reaction (PCR). The results for lactobacilli, bifidobacteria and total bacterial counts were compared with those obtained by fluorescencein situhybridization (FISH) and cultivation method. No significant differences could be observed between dietary treatments with real-time PCR and FISH for all investigated parameters. Comparing the applied three methods no consistent results were achieved, whereas FISH usually showed lower values. It was shown that real-time PCR can be regarded as an alternative to conventional techniques and also as a complement to results obtained from conventional culture method.</jats:p

Separation of ethoxylated bisphenol A dimethacrilates in dental composite after derivatisation to ionisable amines by capillary zone electrophoresis

Bisphenol A ethoxylate dimethacrylates (Bis-EMA) are transformed into ionisable amines by derivatisation in order to make the analytes applicable to capillary electrophoresis. For this goal, piperidine was added onto the C=C double bond of the alpha,beta-unsaturated ester group forming a tertiary amine with pKa values between 9 and 10. Formation of the derivatives was confirmed by electrospray ionisation MS. Commercial Bis-EMA is a mixture of homologues with different number of ethoxy groups; it is characterised by the average number of the ethoxy groups in the chains. These homologues were resolved by capillary zone electrophoresis at pH 4. It is shown for the product with an average of four ethoxy groups per Bis-EMA molecule that about seven homologues can be baseline separated when differing by only one ethoxy group. For Bis-EMA with 30 ethoxy groups in average, about 23 homologues could be differentiated. The high resolution power of capillary zone electrophoresis enables characterisation of commercial dental composite material concerning the Bis-EMA constituents

An overview of the current status of national reporting systems for adverse reactions to dental materials

OBJECTIVES: Since all dental materials pose a potential risk to patients and members of the dental team, the post-market monitoring of adverse reactions caused by dental materials should be considered essential. This article reviews the current status of post-market monitoring of adverse reactions to dental materials and highlights some of the issues that arise in trying to establish an evidence base on the characteristics of adverse reactions to dental materials. METHODS: Norway, Sweden and more recently the UK have sought to monitor adverse reactions to dental materials systematically and proactively in an effort to add to the evidence base on the safety of dental materials. Their experiences in undertaking post-market surveillance have been combined in preparing this article. RESULTS: To date the Norwegian, Swedish and the UK projects has received 1268 reports over 11 years, 848 reports over 5.5 years and 1117 reports over 3 years, respectively, relating to adverse reactions seen or experienced by dental personnel and patients. Presently, there are no harmonized criteria for what can be classified as an adverse reaction related to dental materials. Under reporting is a recognised problem and lack of awareness and lack of clarity as to what constitutes an adverse reaction may be contributory factors. A pro-active reporting system takes a considerable time to become established, but can generate a lot of potentially useful information. CONCLUSIONS: There is a need to raise the awareness among dental professionals of the potential for adverse reactions due to dental materials and to develop an internationally accepted system of data gathering that can produce the evidence that reflect the extent, severity and incidence of adverse reactions to dental materials.</p