Elimination of an intraradicular biofilm composed of enterococcus faecalis and candida albicans using a negative apical pressure irrigation system / Eliminación de una biopelícula intraradicular compuesta por enterococcus faecalis y candida albicans utilizando un sistema de irrigación de presión apical negativa

Endodontic treatment consists of the cleaning and disinfecting the root canal system, which is achieved using adequate mechanical instru-mentation and chemical irrigation. Endodontic microorganisms are present in root canals in the form of a biofilm, and their elimination ensures the success of endodontic treatment. Irrigation is a key factor contributing to the elimination of this intraconduct biofilm, and different irrigator agents and irrigation techniques, such as irrigation with negative apical pressure, a novel automated irrigation mechanism based on suction intraconduct, have been used. In this study, we evaluated the ability of a negative apical pressure system with different concentrations of sodium hypochlorite and durations to reduce the microbial load. Materials and Methods: An intraradicular biofilm composed of Enterococcus faecalis and Candida albicans was generated during twenty-one days of static culture on one hundred mesio-vestibular roots of upper molars with complex curvatures greater than 30°C, and the roots were classified in six groups with different concentrations and contact times of sodium hypochlorite. Subsequently, the reduction in the microbial load was measured with McFarland scale and the enumeration of colony forming units and was evaluated with scanning electronic microscopy. Results: We observed a significant difference in the reduction of the microbial load prior to instrumentation compared with postinstrumentation between the groups treated with 2.25% and 5.25% NaOCl for 30, 60 and 90 seconds of contact time (p<0.05), but we did not observe differences in the reduction of microbial load between different contact times and concentrations of sodium hypochlorite employed (p>0.05). Conclusion: Negative apical pressure is a good option for irrigation in endodontics, as it allows the passage of the irrigation fluid along the total length of the root canal and produces a better antimicrobial effect.

El tratamiento de endodoncia consiste en la limpieza y desinfección del sistema de conducto radicular, lo que se logra utilizando instrumentación mecánica adecuada y riego químico. Los microorganismos endodónticos están presentes en los conductos radiculares en forma de una biopelícula, y su eliminación asegura el éxito del tratamiento endodóntico. La irrigación es un factor clave que contribuye a la eliminación de esta biopelícula intraconductora, y se han utilizado diferentes agentes irrigadores y técnicas de irrigación, como la irrigación con presión apical negativa, un nuevo mecanismo automatizado de irrigación basado en la intraconducción de succión. En este estudio, evaluamos la capacidad de un sistema de presión apical negativa con diferentes concentraciones de hipoclorito de sodio y duraciones para reducir la carga microbiana. Material y Métodos: Se generó una biopelícula intraradicular compuesta por Enterococcus faecalisy Candida albicans durante veintiún días de cultivo estático en cien raíces mesio-vestibulares de molares superiores con curvaturas complejas superiores a 30°C, y las raíces se clasificaron en seis grupos con diferentes concentraciones y tiempos de contacto de hipoclorito de sodio. Posteriormente, la reducción en la carga microbiana se midió con la escala de McFarland y la enumeración de las unidades formadoras de colonias y se evaluó con microscopía electrónica de barrido. Resultado: Observamos una diferencia significativa en la reducción de la carga microbiana antes de la instrumentación en comparación con la postinstrumentación entre los grupos tratados con NaOCl 2.25% y 5.25% durante 30, 60 y 90 segundos de tiempo de contacto (p<0.05), pero lo hicimos No se observan diferencias en la reducción de la carga microbiana entre los diferentes tiempos de contacto y las concentraciones de hipoclorito de sodio empleado (p>0.05). Conclusión:La presión apical negativa es una buena opción para el riego en endodoncia, ya que permite el paso del líquido de riego a lo largo de todo el conducto radicular y produce un mejor efecto antimicrobiano.

Superfast Set, Strong and Less Degradable Mineral Trioxide Aggregate Cement.

PURPOSE: Despite the good sealing ability and biocompatibility of mineral trioxide aggregate (MTA), its slow setting, high degradation, and weakness limit its use in surgical endodontics and high stress-bearing areas. This study aimed to develop two new liquids to control these drawbacks. They were prepared from calcium chloride, fumed silica, and hydroxyapatite or calcium phosphate and coded "H" and "P," respectively. METHODS: Portland cement, Grey ProRoot® MTA, and white ProRoot MTA were mixed with distilled water (control) or liquid "H" or "P." The pH, setting time, degradation rate, leachant/precipitate' composition, compressive strength, and morphology were assessed. RESULTS: Both liquids maintained MTA's high alkalinity and reduced the setting time by 1-2 orders of magnitude. Both liquids, H in particular, significantly reduced the degradation rate of Grey ProRoot and White ProRoot MTA®. Calcite has been identified as the main phase of the leachant or precipitate formed during the cement's degradation. Calcium hydroxide or hydroxyapatite was also identified with Grey ProRoot MTA mixed with H liquid. These liquids also significantly increased the compressive strength with no statistical differences between them; this was associated with the production of dense, consolidated structures. CONCLUSIONS: The modified MTA could be used in surgical endodontics and high stress-bearing areas.

Effectiveness of an infiltrant on sealing of composite restoration margins with/without artificial caries.

AIM: The aim of this in vitro study was to evaluate the effectiveness of a resin infiltrant (ICON) on marginal sealing ability of class II resin restorations with/without-caries. MATERIALS AND METHODS: Forty-eight noncarious human pre-molar teeth were embedded and MO and DO preparations of standard dimensions were prepared. The left side of dentin margins of the cavities were left nonbonded (UB) while the right side were bonded using total etch-bonding agent and all restored with a Nanohybrid composite. The teeth were thermocycled and half of the specimens in the UB and B groups were subjected to an artificial caries process. ICON was applied to caries and noncaries subgroups following the manufacturer's directions. Impressions were made at each step: after the restorations were completed, thermocycling, artificial caries procedures, and infiltrant application and the silicone tag lengths were measured with a stereomicroscope. The specimens were immersed in 0.5% basic fuchsine at 37° C for 24 hours, sectioned and microleakage was evaluated with a stereomicroscope. Selected samples and their replicas were assessed for marginal quality under a stereomicroscope and SEM. Statistical evaluation of the data were made using Kruskal-Wallis, Mann-Whitney U and Wilcoxon Sign Rank tests. RESULTS: While bonding application did not create a meaningful difference, the thermocycling and artificial caries significantly increased the gap length and microleakage (p < 0.05). ICON application was decreased the microleakage, created gap-free margins and closed the gaps which were previously occurred at the same cavities (p < 0.05). CONCLUSION: A resin infiltrant (ICON) application decreased the microleakage, created gap-free margins and closed the gaps, which previously occurred at the same cavities. CLINICAL SIGNIFICANCE: Approximal application of resin infiltrant may increase the success of the class II composite restorations also reduced the risk of needing more complex restoration therapy.

Wear of two denture teeth materials in vivo-2-year results.

OBJECTIVE: (1) To quantify wear of two different denture tooth materials in vivo with two study designs, (2) to relate tooth variables to vertical loss. METHODS: Two different denture tooth materials had been used (experimental material=test; DCL=control). In study 1 (split-mouth, 6 test centers) 60 subjects received complete dentures, in study 2 (two-arm, 1 test center) 29 subjects. In study 1 the mandibular dentures were supported by implants in 33% of the subjects, in study 2 only in 3% of the subjects. Impressions of the dentures were taken and poured with improved stone at baseline and after 6, 12, 18 and 24 months. Each operator evaluated the wear subjectively. Wear analysis was carried out with a laser scanning device. Maximal vertical loss of the attrition zones was calculated for each tooth cusp and tooth. A mixed linear model was used to statistically analyse the logarithmically transformed wear data. RESULTS: Due to drop-outs and unmatchable casts, only 47 subjects of study 1 and 14 of study 2 completed the 2-year recall. Overall, 75% of all teeth present could be analysed. There was no statistically difference in the overall wear between the test and control material for either study 1 or study 2. The relative increase in wear over time was similar in both study designs. However, a strong subject effect and center effect were observed. The fixed factors included in the model (time, tooth, center, etc.) accounted for 43% of the variability, whereas the random subject effect accounted for another 30% of the variability, leaving about 28% of unexplained variability. More wear was consistently recorded in the maxillary teeth compared to the mandibular teeth and in the first molar teeth compared to the premolar teeth and the second molars. Likewise, the supporting cusps showed more wear than the non-supporting cusps. The amount of wear did not depend on whether or not the lower dentures were supported by implants. The subjective wear was correct in about 67% of the cases if it is postulated that a wear difference of 100µm should be subjectively detectable. SIGNIFICANCE: The clinical wear of denture teeth is highly variable with a strong patient effect. More wear can be expected in maxillary denture teeth compared to mandibular teeth, first molars compared to premolars and supported cusps compared to non-supported cusps. Laboratory data on the wear of denture tooth materials may not be confirmed in well-structured clinical trials probably due to the large inter-individual variability.

Effect of laser preparation on bond strength of a self-adhesive flowable resin.

The aim of this in vitro study was to evaluate the effect of laser treatment on shear bond strength of a self-adhesive flowable resin composite to human dentin. Eighty extracted sound human molar teeth were used for the study. The teeth were sectioned mesiodistally and embedded in acrylic blocks. The dentin surfaces were ground wet with 600-grit silicon carbide (SiC) paper. They were randomly divided into two preparation groups: laser (Er:YAG laser, with 12 Hz, 350 mJ energy) and control (SiC). Each group was then divided into two subgroups according to the flowable resin composite type (n = 20). A self-adhesive flowable (Vertise Flow) and a conventional flowable resin (Premise Flow) were used. Flowable resin composites were applied according to the manufacturer's recommendations using the Ultradent shear bond Teflon mold system. The bonded specimens were stored in water at 37 °C for 24 h. Shear bond strength was tested at 1 mm/min. The data were logarithmically transformed and analyzed using two-way analysis of variance and Student-Newman-Keul's test at a significance level of 0.05. The self-adhesive flowable resin showed significantly higher bond strength values to laser-prepared surfaces than to SiC-prepared surfaces (p < 0.001). The conventional flowable resin did not show such differences (p = 0.224). While there was a significant difference between the two flowable resin composites in SiC-prepared surfaces (p < 0.001), no significant difference was detected in laser-prepared surfaces (p = 0.053). The bond strength of a self-adhesive flowable resin composite differs according to the type of dentin surface preparation. Laser treatment increased the dentin bonding values of the self-adhesive flowable resin.

Influence of abutment height and surface roughness on in vitro retention of three luting agents.

PURPOSE: This study evaluated the effects of abutment height, airborne-particle abrasion, and type of cement on the tensile resistance to dislodgement of cement-retained implant restorations. MATERIALS AND METHODS: Three groups of 12 standardized abutments each were prepared with different heights (4 mm, 5 mm, and 6 mm) using a milling machine. Crowns were cast in cobalt-chrome using the lost-wax technique, airborne particle-abraded using 50-Μm aluminum oxide, and cleaned with acetone. Restorations were cemented using a noneugenol acrylic urethane cement, a resin-modified glass ionomer, or a zinc oxide-noneugenol cement. A 5-kg load was applied for 10 minutes. Samples were kept at 37°C and 100% humidity overnight. A tensile force was applied to the crown using a testing machine at a crosshead speed of 5 mm/minute until failure occurred. Next, the abutments were airborne particle-abraded with 50-Μm aluminum oxide, and the cementation and testing procedures were repeated. The effects of cement, abutment height, and surface treatment were evaluated statistically. RESULTS: There were significant differences among the cements. The resin-modified glass ionomer provided the greatest retention in all the tested conditions, while the zinc oxide-noneugenol cement produced the lowest retention values. Significant differences were also detected between 4-mm and 6-mm abutments, with the 6-mm abutments being more retentive. No differences were found between 4-mm and 5-mm abutments or between 5-mm and 6-mm abutments. The effect of airborne-particle abrasion was also found to be significant. A maximum increase of 90 N in retention force was observed after airborne-particle abrasion for the 5-mm abutments cemented with the acrylic urethane cement. CONCLUSIONS: Cement, airborne-particle abrasion, and abutment height can significantly influence retention of implant-supported crowns. Different parameters, including those specific to the patient, should be considered in the selection of a luting agent.

Laboratory methods for evaluating the wear of denture teeth and their correlation with clinical results.

OBJECTIVE: To correlate different laboratory wear simulation protocols for three denture tooth materials with clinical wear results of the same materials. METHODS: Three denture tooth materials were evaluated for which clinical wear data of posterior denture teeth were available: DCL (double cross-linked PMMA with organic fillers; Ivoclar Vivadent), experimental material EM (double cross-linked PMMA with organic fillers; Ivoclar Vivadent), and NFC (PMMA with inorganic nanofillers, Candulor). The clinical data on the three denture tooth materials (10 subjects for each material) came from clinical studies conducted at three different locations. The investigators sent the impressions to one center where they were analyzed with the same methodology and by the same operator. Four different wear simulation protocols were evaluated in a chewing simulator (Willytec) with integrated thermocycling (5 °C/55 °C) and 8 specimens for each group: (A) molar denture tooth against premolar denture tooth with 1 mm sliding, lifting, 5 kg load; (B) standardized conical ceramic stylus (Ø2.3 mm); (C) standardized ball-shaped ceramic stylus (Ø6 mm); (D) standardized conical stylus (Ø2.3 mm) cut with a special bur from the denture tooth material to be tested. For the protocols B, C and D, the stylus slid under a load of 3 kg for 3 mm on the flat specimen without lifting. All the tests were run for 100,000 chewing cycles. The maximum vertical wear of the material and stylus was quantified on replicas of improved white stone with the etkon es1 scanner and the match 3-D software. RESULTS: The ranking of the materials according to mean clinical vertical wear after 1 year was as follows: DCL=EM>NFC. The ranking of the materials according to the mean vertical wear was as follows (ANOVA post hoc Tukey B, p<0.05): group A: NFC>DCL=EM; group B: NFC>DCL>EM; group C: NFC>DCL=EM; group D: DCL=EM>NFC. SIGNIFICANCE: Only the results of the experimental setup with standardized antagonists of the same denture tooth material against flat specimens were similar to the clinical wear results with a comparable relative difference in mean vertical wear between the materials. When evaluating denture teeth for wear in the laboratory, a protocol should be applied that matches the clinical wear results.

The art of scientific writing: how to get your research published!

The purpose of this article is to provide potential authors with a contemporary guide to scientific writing. It is in essence a handbook that covers the planning for a scientific publication from inception of the project or study to manuscript preparation and, ultimately, acceptance by a journal. Major topics such as manuscript formatting, data analysis, use of charts, graphs and images, reference formats, and manuscript submission are presented.

Effects of a chemical disinfectant on the physical properties of dental stones.

PURPOSE: This study compared the effects of an antimicrobial agent (Asepto-Sol) on the physical properties of types III, IV, and V gypsum casts made from two types of impression materials. MATERIALS AND METHODS: Selected physical properties of five gypsum-based dental stones (Prima-Rock, Ortho Stone, New Fujirock, Die-Keen, Microstone) and two resin-based dental stones (Resin-Rock, Instone) were evaluated using an addition silicone impression material (Reprosil) and an irreversible hydrocolloid (Jeltrate Plus). In group 1, Asepto-Sol solution replaced water as the gauging liquid for the seven dental stones. The mixed gypsum was poured directly onto impressions of two master dies using two impression materials. In group 2, impressions made with both impression materials were sprayed with the Asepto-Sol solution, left for 10 minutes, rinsed for 30 seconds with tap water, and poured with each dental stone mixed with deionized water. In group 3 (control), the gypsums were mixed with deionized water and the mixed stone was poured directly into impressions, with no exposure to Asepto-Sol. The physical properties evaluated for the gypsum specimens were linear dimensional change, detail reproduction, Knoop hardness, and transverse strength. RESULTS: The linear dimensional stability, detail reproduction, and transverse strength tests were relatively unaffected by the use of Asepto-Sol, with few exceptions. Detail reproduction appeared to be least affected by Asepto-Sol, and changes in Knoop hardness were noted but results differed among the seven dental stones. However, New Fujirock was not ideally matched with Jeltrate Plus, and no stone specimens could be produced. CONCLUSION: Whether mixed with the gypsum powder or sprayed on impressions, Asepto-Sol solution did not adversely affect the physical properties of the dental stones tested.

A review of the clinical management of mobile teeth.

The clinical management of mobile teeth can be a perplexing problem, especially if the underlying causes for that mobility have not been properly diagnosed. In some cases, mobile teeth are retained because patients decline multidisciplinary treatment that might otherwise include strategic extractions. This article discusses the relationship between occlusion and tooth mobility with an emphasis on identifying differences between increased mobility and increasing mobility. The indications, contraindications, and basic principles of tooth splinting are also reviewed. Provisional and definitive splints are defined and described with their respective occlusal considerations. Some mobile teeth can be treated through occlusal equilibration alone (primary occlusal trauma). Whereas mobile teeth with a compromised periodontium can be stabilized with the aid of provisional and/or definitive splinting (secondary occlusal trauma). It is important to consider splint therapy, because it may not only improve the prognosis of teeth, but may actually enhance the stability of the final prosthodontic treatment. The ultimate goal of successful management of mobile teeth is to restore function and comfort by establishing a stable occlusion that promotes tooth retention and the maintenance of periodontal health.

Reducing bacterial counts in dental unit waterlines: distilled water vs. antimicrobial agents.

BACKGROUND: This study evaluated five chemical disinfectants to compare their abilities to improve dental unit waterline quality and assess their effects, if any, on the biofilm layer. METHODS: Sixty new dental units, with a closed-circuit water system, were used to compare microbial levels in DUWLs treated with five antimicrobials: Listerine, Bio 2000, Rembrandt, Dentosept, and sodium fluoride to a control group of sterile distilled water alone over a six-week period. For all units, the waterlines were filled with solution, left overnight, and then flushed for 30 seconds with sterile distilled water the following morning prior to patient treatment. Waterlines were examined for biofilm buildup using scanning electron microscopy and colony-forming-unit counts. RESULTS: The sodium fluoride and the four chemical antimicrobials reduced the microbial count to 200 cfu/ml or less. Only samples taken from dental units receiving the control treatment (distilled water with no added antimicrobial) failed to meet ADA's stated goal. Examination of the SEMs revealed an apparent decrease in the biofilm mass but not elimination, despite repeated treatment with the four antimicrobial materials. CONCLUSIONS: Even in a closed-circuit water system, distilled water alone cannot reduce microbial contamination of dental treatment water from dental unit waterlines to the 200 cfu/ml ADA stated goal. However, water treated with Listerine mouthrinse, Rembrandt mouthrinse, Bio 2000, 0.5 percent sodium fluoride and Dentosept, did meet the microbial reduction goal. The biofilm apparently was reduced in volume, but not entirely eliminated. CLINICAL SIGNIFICANCE: The ADA goal of a maximum of 200 cfu/ml was achieved using any of five chemical antimicrobials and distilled water in a closed-water system. Despite the successful reduction in microbial contamination of the dental treatment water, the biofilm was not completely eliminated. Biofilm elimination and prevention would be needed through some other means.

Reducing bacterial counts in dental unit waterlines: tap water versus distilled water.

BACKGROUND: The maximum recommended level of microbial contamination of water from dental unit waterlines (DUWL) is 200 colony-forming units per milliliter (CFU/mL). This article addresses the importance of water selection in achieving that standard. METHODS: Microbial contamination in water samples from 75 new dental units, with a closed-circuit water system, were compared using combinations of tap water and sterile distilled water with and without two chemical disinfectants (bleach and 0.12% chlorhexidine gluconate, Bio2000) over a six-week period. Baseline tap water samples were collected and tested initially. RESULTS: The microbial plate counts of seven tap water specimens (controls) ranged from 4 to 95 CFU/mL. These results were well below both the 500 CFU/mL standard for public drinking water and the 200 CFU/mL goal for dental treatment water. However, when passed through dental units, no significant bacterial reduction was achieved for samples of tap water (Group 1), tap water treated with bleach (Group 2), or tap water treated with Bio2000 (Group 4). Only water samples from dental units using Bio2000 alone (Group 3) or a combination of sterile, distilled water with Bio2000 (Group 5) met or exceeded the 200 CFU/mL standard. CONCLUSIONS: Using tap water alone or tap water with bleach did not improve water quality. However, the American Dental Association (ADA) standard for reduced microbial contamination of dental unit waterlines was met using Bio2000 and distilled water treated with Bio2000. CLINICAL SIGNIFICANCE: The ADA standard of 200 CFU/mL was achieved using a closed water system and distilled water treated with Bio2000. Using 100% Bio2000 is also effective, but more costly.