Voltammetry and surface analysis of AISI 316 stainless steel in chloride-containing simulated concrete pore environment

The study of passive layers grown on AISI 316 stainless steel in solutions that simulate concrete pore environments contaminated with Cl^? is presented. Model solutions of saturated Ca(OH)₂ and cement extract (CE) with and without the addition of 5 g/L of NaCl are compared. Cyclic voltammetry (CV) shows different electrochemical responses of passive layers grown on samples immersed in these solutions under open circuit potential (ocp). A more resistive passive film was found on the samples exposed to the CE solution. The different voltammetric responses suggest differences in composition of the passive layers formed on each solution. XPS spectra confirm the dissimilarity in atomic composition. Optical microscope images and AFM images of the pits formed on the samples illustrate the differences of AISI 316 surface topography after exposure to model solutions. Because of these differences, it is recommended to use CE solution as a model solution and ocp passivation to simulate concrete environments.     

Histomorphometric analysis of rat alveolar wound healing with hydroxyapatite alone or associated to BMPs

Several materials and techniques have been proposed to improve alveolar wound healing and decrease loss of bone height and thickness that normally follow dental extraction. The objective of this research was the histologic analysis of bone morphogenetic proteins implanted into dental alveoli of rats after extraction. A total of 45 adult male Wistar rats were divided into three groups of 15 animals each: control (no treatment), implanted with pure hydroxyapatite (HA, 3 mg) and implanted with hydroxyapatite plus bone morphogenetic proteins (HA/BMPs, 3 mg). Five animals from each group were sacrificed at 7, 21 and 42 days after extraction for the histometric analyses of the osteoconductive potential of hydroxyapatite associated or not with BMPs. After dissection, fixation, decalcification and serial microtomy of 6-micron thick sections, the samples were stained with hematoxylin-eosin for histologic and histometric analyses. Both HA and HA/BMPs caused a delay in wound healing compared to control animals, evaluated by the percentage of bone tissue in the alveoli. The treatment with HA/BMPs had the greatest delay at 21 days, even though it produced values similar to the control group at 42 days. The materials did not improve alveolar repair in the normal period of wound healing and the association of HA/BMPs did not have osteoconductive properties with granulated hydroxyapatite as the vehicle.     

Rational basis for the use of a new clinical procedure in immediately loaded implant rehabilitations: a case report

This report presents a new clinical protocol that facilitates the diagnostic, surgical, and prosthetic phases of immediately loaded implant rehabilitations. The proposed technique aims to simplify recording of the centric relation, which is usually done immediately after surgery, during the surgical impression phase. This shortens operative time while meeting requirements for an accurate impression and is thus simple and cost effective. The case report of a maxillary full-arch immediately loaded implant rehabilitation in a 45-year-old patient illustrates the clinical steps in the proposed procedure and confirms its repeatability.     

Presence and antibiotic resistance of Porphyromonas gingivalis,Prevotella intermedia,and Prevotella nigrescens in children

BACKGROUND/AIMS: Only limited information exists about the prevalence in children of pathogens associated with periodontitis. The aim of the present study was to determine by culture whether 8-11-year-old children carry Porphyromonas gingivalis, Prevotella intermedia, and/or P. nigrescens in samples from the gingiva and/or the buccal mucosa taken before, and after caries treatment and oral hygiene instruction. A second aim was to assess the proportion of subjects who had gram-negative anaerobes carrying the tet(Q) and erm(F) genes, suggesting antibiotic resistance to tetracycline or erythromycin. METHOD: A total of 150 children provided gingival and buccal swab bacterial samples that were cultured for P. gingivalis, P. intermedia, and P. nigrescens. The species was verified using DNA-DNA hybridization with species-specific probes made from the variable region of the 16S rRNA sequences. Antibiotic-resistant genes, tet(Q) and erm(F), were identified using specific DNA-DNA hybridization with specific DNA probes. RESULTS: A total of 116 isolates of black-pigmented bacteria were cultured from 47 (31%) of 150 children. Five isolates were identified as P. gingivalis, 29 as P. intermedia, 33 as P. nigrescens, and 49 as other species. In general, the bacteria were not culturable at more than one time period. We found that 55% of these 47 children harbored black pigmented bacteria that carried either one or both of the two antibiotic-resistant genes studied (tet(Q), and erm(F)). CONCLUSION: The present study demonstrated that children not exposed to regular dental treatment carry bacteria outside the gingival sulcus that have been associated with periodontitis, and that standard treatment procedures may not clear the presence of the putative pathogens. In addition, antibiotic-resistant genes are common in identifiable gram-negative anaerobes, including putative pathogens.     

A European perspective on fluoride use in seven countries

Abstract -  Objectives: The aim of this study was to collate data on national policies for the use of fluoride in the seven European countries participating in the FLINT project. Methods: Policies on the use of fluoride were obtained for each of the study areas. Data collected included the presence of water fluoridation and regulations governing fluoride toothpaste and fluoride supplements. Results: In Ireland 74% of the population had a fluoridated water supply but in all the other countries fluoride toothpaste was the principal form of delivering fluoride, usually recommended as a dose of a pea-sized amount. Fluoride supplement use varied considerably between countries. The Netherlands had the clearest regulations covering the use of fluoride supplements and definition of at-risk individuals. Most countries, even if they recognized particular caries-risk did not define the term clearly. In Iceland all children were regarded as being at high risk of developing caries. Conclusion: Considerable variation exists between European countries in their policies for fluoride use and no clear definitions of high-caries-risk individuals were found. The results show that there is even a lack of coherent thought and planning within the different countries, let alone between them.     

Evaluation of antibacterial and fluoride-releasing adhesive system on dentin--microtensile bond strength and acid-base challenge

This study evaluated the influence of a fluoride-containing adhesive on microtensile bond strength (microTBS) to dentin, as well as analyzed the dentin-adhesive interface after acid-base challenge. Experimental groups were: G1--Clearfil SE Bond control (SE); G2--Clearfil Protect Bond control (PB); G3--Primer[SE]/Adhesive[PB]; G4--Primer[PB]/Adhesive[SE]. For microTBS evaluation, dentin surfaces were ground, bonded, and composite resin crowns were built up to obtain beams to be tested. For interfacial analysis, adhesive system was applied on dentin surface and a low-viscosity resin was placed between two dentin disks. Then, the specimens were subjected to acid-base challenge, sectioned, and polished to be observed by SEM. microTBS data showed no statistical differences among the groups (GI: 51.3, G2: 47.6, G3: 55.0, G4: 53.9; mean in MPa). Through SEM, it was observed that a thick acid-base resistant zone adjacent to the hybrid layer was created only when the fluoride-releasing adhesive was used. In conclusion, the presence of fluoride in an adhesive contributed significantly to preventing secondary caries, and did not interfere with dentin-adhesive bond strength.     

Maxillary and mandibular overlay removable partial dentures for the restoration of worn teeth

This clinical report describes the fabrication of maxillary and mandibular cast overlay removable partial dentures for the restoration of severely worn teeth with accompanying loss of vertical dimension of occlusion. The frameworks supported porcelain veneers for esthetics and metal occlusal surfaces for strength and durability.     

The effects of systemic alendronate with or without intraalveolar collagen sponges on postextractive bone resorption: a single masked randomized clinical trial

Alendronate is a bisphosphonate frequently used to reduce bone resorption. It has been used for osteoporosis, Paget's disease, and also as adjunctive therapy for periodontal disease. The aim of this study was to evaluate the effect of systemic alendronate with or without endoalveolar collagen sponge on vertical bone resorption after lower wisdom tooth extraction. Forty patients referred for wisdom tooth impaction were selected. Before surgery, patients were randomly assigned to receive one of the following pharmacologic treatments: no medication (group 1), postextractive endoalveolar collagen sponge (group 2), systemic alendronate for 4 months starting the day of surgery (group 3), and group 2 + group 3 (group 4). Standardized orthopantomographic evaluation was obtained during recruitment (T1), immediately after surgery (T2), and 4 months (T3) to evaluate crestal and alveolar socket changes. Results indicate that at T2, crest and socket level did not show significant differences between the four groups. At T3, test sites treated showed less bone resorption compared with controls. In particular, higher vertical bone height levels and a faster intraalveolar healing were achieved in groups 3 and 4. Systemically given alendronate may be used successfully to reduce vertical bone resorption after wisdom tooth extraction.     

Influence of casting methods on marginal and internal discrepancies of complete cast crowns

The relationship between the application of die-spacer prior to wax pattern fabrication and metal removal from the inner surface of the casting on marginal and internal discrepancies of complete cast crowns was evaluated. One hundred and twenty complete crowns were cast with palladium-silver alloy melted by gas-oxygen torch or electrical resistance and cast with a centrifuge casting machine. After casting, the crowns were seated on each type of different marginal configuration dies (90-degree shoulder, 20-degree beveled shoulder, and 45-degree chamfered shoulder) with a static load of 90 N during 1 min. Evaluation of the marginal fit of the specimens was made using a digital micrometer. The crowns were embedded in acrylic resin and longitudinally sectioned to verify the internal discrepancy that occurred in lateral and occlusal interfaces with a digital micrometer. The data were submitted to ANOVA and Tukey's test with a significance level of 5%. The best marginal and inner fits were obtained with the gas-oxygen torch source. The 45-degree chamfered shoulder showed the best marginal and inner fit, and better internal relief was obtained in the crowns abraded with 50 microm Al2O3 particles.