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.

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.