Chemical composition and morphology study of bovine enamel submitted to different sterilization methods

OBJECTIVES

The morphology and chemical composition of enamel submitted to different sterilization methods was studied.

METHODS

X-ray photoelectron spectroscopy (XPS), field emission gun scanning electron microscopy (FEG-SEM), and energy-dispersive X-ray spectroscopy (EDS) were performed to evaluate 50 bovine enamel specimens sterilized using four methods: microwaving (MI), gamma irradiation (GI), ethylene oxide (EO), and steam autoclave (SA). Non-sterilized specimens were used as control.

RESULTS

XPS indicated that the concentration of P (phosphorus), CO₃ (carbonate), and CO₃/P was not changed in all groups. GI produced no significant change on elemental composition. SA produced the major decrease in calcium (Ca), Ca/P ratio, and increase in N (nitrogen). MI was found to decrease Ca, Ca/P ratio and O (oxygen), and increase in C (carbon) and N. EO produced decrease in Ca and O with increased C concentration. FEG-SEM revealed surface and in-depth morphological changes on SA specimens. Minor surface alterations were observed for EO and for MI groups, and no alteration was observed on GI group. EDS indicated no difference on elemental composition of enamel bulk among groups.

CONCLUSIONS

SA produced mineral loss and morphological alterations on surface and in depth. MI and EO sterilization caused mineral loss showing only slight alteration on enamel surface. GI sterilization preserves the morphological characteristics of enamel. The sterilization methods could be classified from lower to high damage as GI < MI < EO < SA.

CLINICAL RELEVANCE

This is a comprehensive comparative study where different methods for enamel sterilization were investigated in terms of chemical changes. The results presented here may help researchers to choose the most appropriate method for their research setting and purpose.

FREQUENCY OF THE MDR1 GENE POLYMORPHISM RS1045642 (C3435T) IN HCV-HIV CO-INFECTED PATIENTS

Background

Due to the high prevalence of co-infection by hepatitis C virus (HCV) and human immunodeficiency virus (HIV) and the severity of these infections, the understanding of the biological mechanisms involved in these processes, including viral behavior and host genetic profile, is of great importance for patient treatment and for public health policies.Some single nucleotide polymorphisms (SNPs) in the human genome, such as the SNP rs1045642 (C3435T) in the MDR1 gene, have been reported to be associated to the sustained virological response (SVR) to HCV treatment in HCV-HIV co-infected patients.

Objective

The present study analyzes the MDR1 gene C3435T polymorphism in HCV-HIV co-infected patients.

Methods

A total of 99 HCV-HIV patients were included in the study. The DNA was extracted from blood samples, and the SNP rs1045642 was assessed by Real Time PCR (qPCR). Risk factors for acquiring the virus and the SVR after HCV treatment with pegylated interferon-alpha and ribavirin were also analyzed.

Results

Among the patients, 54 (54.5%) were male and 45 (45.5%) were female. The average age was 46.1±9.8 years. The SVR after HCV treatment was 40%. The frequencies of MDR1 genotypes CC, CT and TT were 28.3%, 47.5% and 24.2%, respectively. Allele frequencies were 52% for the C allele and 48% for the T allele. No association was found for SNP rs1045642 (C3435T) regarding response to treatment (P=0.308).

Conclusion

- In this study, the C3435T polymorphism in the MDR1 gene appears not to be associated with SVR in HCV-HIV co-infected individuals.

Clinical evaluation of abutment teeth of removable partial denture by means of the Periotest method

Prosthodontics should be one of the means of establishing conditions for the maintenance of periodontal health. The forces applied to the abutment teeth and their effects are very important considerations in the design and construction of the removable partial dentures. This 6-month follow-up clinical study evaluated the degree of mobility of abutment teeth of distal extension and tooth supported removable partial dentures by using Periotest. Two types of clasp design were selected for evaluation. In cases with unilateral and bilateral distal-extension, a clasp design including a T clasp of Roach retentive arm, a rigid reciprocal arm and a mesial rest were used. For the abutments of tooth-supported removable partial dentures, a second clasp design with a cast circumferential buccal retentive arm, a rigid reciprocal clasp arm and a rest adjacent to the edentulous ridges was selected. A total of 68 abutment teeth was analysed. Periotest values were made at the time of denture placement (control) and at 1, 3 and 6 months after the denture placement. The statistical analysis was performed using Friedman test. All analysis was performed at a 0.05 level of significance. The results revelled that no significant changes in tooth mobility were observed during the 6-months follow-up (P > 0.05). In conclusion, our findings suggest that adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments play an important role in preventing changes in abutment tooth mobility caused by removable partial denture placement.

Development and application of methods for determination of residual monomer in dental acrylic resins using high performance liquid chromatography

Two high-performance liquid chromatographic methods for determination of residual monomer in dental acrylic resins are described. Monomers were detected by their UV absorbance at 230 nm, on a Nucleosil C18 (5 microm particle size, 100 A pore size, 15 x 0.46 cm i.d.) column. The separation was performed using acetonitrile-water (55:45 v/v) containing 0.01% triethylamine (TEA) for methyl methacrylate and butyl methacrylate, and acetonitrile-water (60:40 v/v) containing 0.01% TEA for isobutyl methacrylate and 1,6-hexanediol dimethacrylate as mobile phases, at a flow rate of 0.8 mL/min. Good linear relationships were obtained in the concentration range 5.0-80.0 microg/mL for methyl methacrylate, 10.0-160.0 microg/mL for butyl methacrylate, 50.0-500.0 microg/mL for isobutyl methacrylate and 2.5-180.0 microg/mL for 1,6-hexanediol dimethacrylate. Adequate assay for intra- and inter-day precision and accuracy was observed during the validation process. An extraction procedure to remove residual monomer from the acrylic resins was also established. Residual monomer was obtained from broken specimens of acrylic disks using methanol as extraction solvent for 2 h in an ice-bath. The developed methods and the extraction procedure were applied to dental acrylic resins, tested with or without post-polymerization treatments, and proved to be accurate and precise for the determination of residual monomer content of the materials evaluated.

Effects of chemical disinfectants on the transverse strength of denture base acrylic resins

The disinfection of dental prostheses by immersion in a chemical solution should be capable of rapid inactivation of pathogenic microorganisms, without causing any adverse effect on the denture base resins. This study evaluated the effect of disinfection immersion on the transverse strength of two heat-cured resins. The denture base resins (Lucitone 550 and QC 20) were polymerized according to the manufacturers' instructions. After polymerization, the specimens were polished, and then stored in water at 37 degrees C for 50 +/- 2 h prior immersion in one of the following solutions for 10 min: 4% chlorhexidine, 1% sodium hypochlorite and 3.78% sodium perborate. The specimens were submitted to disinfection twice, simulating when dentures come from the patient and before being returned to the patient. Ten specimens were made for each group. The transverse strength was evaluated by a 3-point bend test. The flexural strength of the two denture base acrylic resins evaluated remained unaffected after immersion in the three solutions evaluated. In general, the QC 20 resin specimens exhibited lower transverse strength than the Lucitone 550 resin specimens, regardless of immersion solutions.

The effect of disinfectant solutions on the hardness of acrylic resin denture teeth

This investigation studied the effects of disinfectant solutions on the hardness of acrylic resin denture teeth. The occlusal surfaces of 64 resin denture teeth were ground flat with abrasives up to 400-grit silicon carbide paper. Measurements were made after polishing and after the specimens were stored in water at 37 degrees C for 48 h. The specimens were then divided into four groups and immersed in chemical disinfectants (4% chlorhexidine; 1% sodium hypochlorite and sodium perborate) for 10 min. The disinfection methods were performed twice to simulate clinical conditions and hardness measurements were made. Specimens tested as controls were immersed in water during the same disinfection time. Eight specimens were produced for each group. After desinfection procedures, testing of hardness was also performed after the samples were stored at 37 degrees C for 7, 30, 60, 90 and 120 days. Data were analysed using two-way analysis of variance (anova) and Tukey's test at 95% confidence level. According to the results, no significant differences were found between materials and immersion solutions (P > 0.05). However, a continuous decrease in hardness was noticed after ageing (P < 0.05). It was conclude that the surfaces of both acrylic resin denture teeth softened upon immersion in water regardless the disinfecting solution.

An infection control protocol: effectiveness of immersion solutions to reduce the microbial growth on dental prostheses

This investigation evaluated the effectiveness of an infection control protocol for cleansing and disinfecting removable dental prostheses. Sixty-four dentures were rubbed with sterile cotton swab immediately after they had been taken from patients' mouths. Samples were individually placed in the culture medium and immediately incubated at 37 +/- 2 degrees C. The dentures were scrubbed for 1 min with 4% chlorhexidine, rinsed for 1 min in sterile water and placed for 10 min in one of the following immersion solutions: 4% chlorhexidine gluconate, 1% sodium hypochlorite, Biocide (iodophors) and Amosan (alkaline peroxide). After the disinfection procedures, the dentures were immersed in sterile water for 3 min, reswabbed and the samples were incubated. All samples obtained in the initial culture were contaminated with micro-organisms. All the lower dentures immersed in Biocide showed positive growth, and the upper dentures were positive for growth in six of eight dentures. The 4% chlorhexidine gluconate, 1% sodium hypochlorite and Amosan solutions have been proved effective to reduce the growth of the micro-organisms in the 10 min immersion period. The protocol evaluated in this study seems to be a viable method to prevent cross-contamination between dental personnel and patients.

Bonding strength between a hard chairside reline resin and a denture base material as influenced by surface treatment

Direct relining of dentures made with hard chairside reline resins is faster than laboratory-processed reline systems and the patient is not without the prosthesis for the time necessary to perform the laboratory procedures. However, a weak bond between the autopolymerizing acrylic reline resins and the denture base material has been observed. This study evaluated the effect of six different surface treatments on the bond strength between a hard chairside reline acrylic resin and a heat-cured acrylic resin. Specimens of the heat-cured acrylic resin were divided into seven groups. One of these groups remained intact. In the other groups, a 10-mm square section was removed from the centre of each specimen. The bonding surfaces were then treated with (i) methyl methacrylate monomer, (ii) isobutyl methacrylate monomer, (iii) chloroform, (iv) acetone, (v) experimental adhesive and (vi) no surface treatment -- control group. Kooliner acrylic resin was packed into the square sections and polymerized. The bonding strength was evaluated by a three-point loading test. The results were submitted to one-way analysis of variance (ANOVA) followed by a Tukey multiple range test at a 5% level of significance. No significant difference was found between the surface treatment with Lucitone 550 monomer or chloroform, but both were stronger than the majority of the other groups. The bond strength provided by all the surface treatments was lower than that of the intact heat-cured resin.

Overlay removable partial dentures for a patient with ectodermal dysplasia: a clinical report

The orofacial characteristics of ectodermal dysplasia include anodontia or hypodontia, hypoplastic conical teeth, underdevelopment of the alveolar ridges, frontal bossing, a depressed nasal bridge, protuberant lips, and hypotrichosis. Patients with this disease often need complex prosthetic treatment. The options for a definitive treatment plan may include fixed, removable, or implant-supported prostheses, singly or in combination. However, financial constraints and other priorities can prevent patients from choosing the most desirable treatment. This clinical report describes the diagnosis and treatment of ectodermal dysplasia in an 18-year-old man. The treatment included interim removable partial dentures fabricated to establish an acceptable therapeutic occlusal vertical dimension, followed by definitive overlay removable partial dentures and composite restorations.

Effect of surface treatments on the bond strength between composite resin and acrylic resin denture teeth

PURPOSE

This investigation studied the effects of 3 surface treatments on the shear bond strength of a light-activated composite resin bonded to acrylic resin denture teeth.

MATERIALS AND METHODS

The occlusal surfaces of 30 acrylic resin denture teeth were ground flat with up to 400-grit silicon carbide paper. Three different surface treatments were evaluated: (1) the flat ground surfaces were primed with methyl methacrylate (MMA) monomer for 180 seconds; (2) light-cured adhesive resin was applied and light polymerized according to the manufacturer's instructions; and (3) treatment 1 followed by treatment 2. The composite resin was packed on the prepared surfaces using a split mold. The interface between tooth and composite was loaded at a cross-head speed of 0.5 mm/min until failure.

RESULTS

Analysis of variance indicated significant differences between the surface treatments. Results of mean comparisons using Tukey's test showed that significantly higher shear bond strengths were developed by bonding composite resin to the surfaces that were previously treated with MMA and then with the bonding agent when compared to the other treatments.

CONCLUSION

Combined surface treatment of MMA monomer followed by application of light-cured adhesive resin provided the highest shear bond strength between composite resin and acrylic resin denture teeth.

[Social representations in nursing: commentaries on theses and dissertations]

The starting point of this work consists on a revision of thesis and dissertations developed by nurses aiming to check how the social representation was used as a theoretical referential on these researches. Through a systematic reading of these works some points were dettached, as thematic, main result as and reflections proposed in order to atain professional practice nursing. It was ascertained from the analysed work that this theoretical referential is used by nurses, and that some studies developed introduce significative results from these professionals.

Heterogeneity of mitochondrial DNA haplotypes in Pre-Columbian Natives of the Amazon region

We report the first study of mitochondrial DNA (mtDNA) sequencing from ancestral Amerindian populations of the South American continent. Sequencing of the D-loop region of mtDNA was carried out for bone fragments from 18 skeletons of Pre-Columbian Amerinidians. The skeletons were excavated in different archeological sites of the Brazilian Amazon region, with dating estimated at 500-4,000 years before the present. The sequencing of at least 354 bases permitted the identification of 13 haplotypes defined by variation of 26 nucleotide positions. Two haplotypes were shared by more than one sample, while 11 haplotypes were observed for a single sample. Seven haplotypes observed in 11 individuals (61% of the sample) belong to the four haplogroups described by Horai et al. (1993). Three samples that shared the transition C-->T in positions 16,223 and 16,278 formed a fifth haplogroup, which has been previously described in present-day Indian populations. Finally, four samples formed a heterogeneous group but each haplotype had at least one mutation typically detected in Asian or Mongoloid populations. Thus, although only haplotypes shared by Asian populations were detected, a wide haplotype variability was observed. If our sample is representative of Pre-Columbian South America, the percentage of haplotypes (39%) not belonging to the four haplogroups described by Horai is much greater than in contemporary indigenous populations. This permits us to suggest that, in addition to the postulated bottleneck effect during the migration from Asia to the Americas, the depopulation effect started by European colonization in the 16th century contributed to the reduction in genetic variability of Amerindians.

Selective distal splenorenal shunts. Technique and results

Selective distal splenorenal shunt was successfully performed in 20 patients from October 1974 to August 1978. All of them had had gastrointestinal hemorrhage from gastroesophageal varices, diagnosed by barium swallow roentgenography or esophagogastroscopy. Only one patient underwent emergency surgery. Portal hypertension was due to hepatic schistosomiasis in 16 patients, and all underwent rectal biopsy and examination of stools to confirm the clinical diagnosis. A small group of patients had ascites, jaundice and hemorrhage. Hepatic encephalopathy has not been a problem, although the follow-up study is short.

Effects of haemoperfusion through charcoal or XAD-2 resin on an animal model of fulminant liver failure

In a group of dogs in whom fulminant liver failure had been induced, perfusion of blood through activated charcoal resulted in a significantly longer survival than that of a similar group of dogs whose blood was not so treated. An otherwise progressive rise in blood ammonia concentration was halted in the treatment group. In another group of dogs with fulminant liver failure perfusion of blood through the resin Amberlite XAD-2 was associated with a fall in the serum bilirubin concentration and complete clearance from the blood of (14)C-labelled sodium glycocholate. Survival in this group of animals was not significantly prolonged. This was due at least in part to the occurrence of haemorrhage due to thrombocytopenia. Platelets adhere to the resin but do not adhere to the same degree to charcoal coated with a thin layer of polymer.

Percutaneous transhepatic cholangiography

The author reports his experiences with a technique which is extremely helpful not only in distinguishing between intra- and extrahepatic cholestasis but also in establishing preoperatively the aetiology of the jaundice, in this way helping the surgeon to choose the best surgical procedure.

The technique employed, the criteria of selection of the patients, the complications, and the results obtained in 53 patients are described.

To date, 53 patients have undergone percutaneous transhepatic cholangiography, and a total of 56 examinations have been performed in the radiography department under local anaesthesia.

In 1 patient a severe bile leakage occurred with signs and symptoms of biliary peritonitis and peralytic lesions.

The biliary tree was outlined in 41 patients out of 47 (87.2 per cent) with obstructive jaundice. In 6 patients the method failed (12.8 per cent).