Effects of a Two-Step Silver Diamine Fluoride Varnish on Shear Bond Strength of Restorations, Dentin and Enamel Hardness, and Biofilm Formation.

INTRODUCTION: Dental caries are a limiting factor in maintaining dental and medical readiness in the military. Untreated dental caries can lead to dire health consequences. Consistent and comprehensive access to dental care is often limited due to the intensive operational demands on our nation's warfighters. The standard of care for dental caries is a surgical model where diseased tooth tissue is surgically removed and restored with appropriate restorative materials. While effective, it is not practical in the military operational environment, especially under time constraints. Dental restoratives offer military personnel a simple and preventive treatment of dental caries and are suitable as self-applied first aids. The purpose of this study was to measure the shear bond strengths of two dental restorative materials to human teeth paired with two different fluoride treatments and the hardness and biofilm formation on teeth after applying the fluoride varnishes. MATERIALS AND METHODS: Specimens were made of human molar teeth treated with each of the following four materials: glass ionomer cement GC Fuji II LC Capsules, Filtek Z250, Riva Star steps 1 and 2, or Mark3 NaF varnish. Step 1 of Riva Star consists of silver diamine fluoride and step 2 contains potassium iodide. On human molar slabs, 10 circular specimens of 5 cm in diameter were prepared with restoratives according to manufacturer procedures. Etch-Rite and a proprietary aluminum chloride-based cavity conditioner were used as etchants on tooth surfaces for the Filtek Z250 and glass ionomer cement, respectively. After at least 24 hours underwater, each assembly was removed, and the shear bond strength of the adhesive was measured according to International Organization for Standardization (ISO) 29022.The hardness was measured according to ISO 14233. Hardness measurements were performed before varnish application, then after storage in an incubator at 37 °C for 4 hours in a demineralization solution (pH = 4.5), and after 1 day in a mineralization solution (pH = 7). A crystal violet staining assay was used to measure biofilm formation of Streptococcus mutans bacteria on human molar teeth after the application of fluoride varnish. RESULTS: We report a 16% increase in shear bond strength of the Filtek Z250/Riva Star coupled treatment compared to the Filtek Z250/Mark3 NaF coupled treatment. We also demonstrate a significant 84% decrease in bond strength with a GC Fuji II LC/Mark3 NaF treatment compared to control (P = .0002), while Riva Star remains statistically unchanged. Enamel and dentinal hardness are significantly improved when Riva Star is applied compared to NaF varnish. A 25%-35% (P < .0001) decrease in oral biofilm formation was observed on samples where a Riva Star or NaF varnish was applied. CONCLUSIONS: Mechanical and antimicrobial testing indicated Riva Star, compared favorably with and in some cases, performed better in the laboratory than a Mark3 NaF varnish. Hardness measurements indicated Riva Star is more effective in dentin tubule occlusion compared to NaF varnish. Our findings help provide practical suggestions to dental treatment, particularly to the unique dental environments seen in the military. Riva Star may be used as an adjunctive treatment prior to placing a final restoration. This study supports the use of Riva Star in conjunction with GC Fuji II LC or Filtek Z250 restorative materials, making it a promising treatment in military dental applications.

Measurement of select physical and mechanical properties of 3 machinable ceramic materials.

OBJECTIVE: To measure select physical and mechanical properties of 3 machinable ceramic materials (IPS Empress CAD, Ivoclar Vivadent; Vitablocs Mark II, Vident; Paradigm C, 3M ESPE). METHOD AND MATERIALS: The physical and mechanical properties tested were hardness (using Vickers hardness), flexural strength and modulus (with 3-point bending), fracture toughness (with Vickers hardness indentation), and coefficient of thermal expansion (using a thermomechanical analyzer). For each of the materials, 25 specimens were fabricated to test each property, except for coefficient of thermal expansion, where n = 5. For each tested property, data were analyzed using 1-way analysis of variance and Tukey Studentized range test (significance level = .05), when required for post hoc testing. RESULTS: Mean Vickers hardness ranged from 511.3 (SD 8.6) for Paradigm C to 569.3 (SD 10.2) for Vitablocs Mark II. Flexural strength was greatest for IPS Empress CAD at 137.51 (SD 23.34) MPa and least for Vitablocs Mark II at 94.08 (SD 14.21) MPa. Flexural modulus ranged from 8.65 (SD 2.24) GPa (Vitablocs Mark II) to 16.10 (SD 5.94) GPa (IPS Empress CAD). IPS Empress CAD had the highest fracture toughness at 2.18 (SD 0.30) MPa.m(1/2), while Vitablocs Mark II had the lowest at 1.37 (SD 0.22) MPa.m(1/2). Paradigm C exhibited the highest thermal expansion coefficient at 16.87 (SD 4.37) 3 10(-6)/degrees C, and Vitablocs Mark II had the lowest at 8.60 (SD 1.47) 3 10(-6)/degrees C. CONCLUSIONS: The 3 ceramic materials significantly differed in all of the properties measured. Vitablocs Mark II was the hardest of the 3 materials, and IPS Empress CAD had the greatest flexure strength, flexural modulus, and fracture toughness.

Development and testing of a novel forward-deployable dental dressing.

The purpose of this study was to measure select properties of four temporary filling materials suitable for use in treating minor dental emergencies in the field. Specimens were made of each of the following four materials: intermediate restorative material, Fuji IX GP Fast, Ketac-Molar Quick, and the forward-deployable dental dressing recently developed by the Naval Institute for Dental and Biomedical Research. Twenty-fours hours after specimen fabrication, five properties (hardness, compressive strength, diametral tensile strength, flexural strength, and flexural modulus) were measured for each of the materials and compared using analysis of variance and Tukey-Kramer tests to determine whether significant differences existed among the materials (alpha = 0.05). Data analysis revealed that significant differences existed among the products for all of the properties tested. The forward-deployable dental dressing's properties compared favorable with and, in many cases exceeded those of intermediate restorative material, Fuji IX GP Fast, and Ketac-Molar Aplicap Quick.

Volumetric polymerization shrinkage of resin composites under simulated intraoral temperature and humidity conditions.

This study measured the volumetric shrinkage of resin composites polymerized under temperature and humidity conditions simulating the oral cavity and compared them to those occurring under ambient room conditions. Small, semispherical specimens of a microhybrid (Z100), microfill (Filtek A110) and flowable microhybrid (4 Seasons Flow) resin composite were manually formed and light activated for 40 seconds using a halogen light-curing unit (Spectrum Curing Light). The volumetric polymerization shrinkage of 10 specimens of each brand of resin composite was measured using a drop shape analysis unit (Drop Shape Analysis System, model DSA10 Mk2) under each of two temperature/relative humidity conditions: room conditions (22 +/- 2 degrees C and 60 +/- 5%) and those simulating intraoral conditions (35 degrees C and 92 +/- 5%). Mean volumetric shrinkage values were calculated for each resin composite and the data were analyzed using two-way analysis of variance and t-test (a=0.05) to determine if significant differences existed between the amount of volumetric polymerization shrinkage that occurred under ambient room conditions and that which occurred under simulated intraoral conditions. Mean volumetric shrinkage values measured for the resin composites were: 2.26 +/- 0.04% (ambient) and 2.61 +/- 0.04% (intraoral) for Z100; 1.96 +/- 0.04% (ambient) and 2.28 +/- 0.04% (intraoral) for Filtek A110 and 4.53 +/- 0.06% (ambient) and 5.34 +/- 0.05% (intraoral) for 4 Seasons Flow. For each resin composite, statistical analysis indicated that the amount of volumetric shrinkage measured under simulated intraoral conditions was significantly greater than what was measured under ambient room conditions (p<0.0001).

Comparison of two video-imaging instruments for measuring volumetric shrinkage of dental resin composites.

OBJECTIVES: The purpose of this study was to measure the polymerization shrinkage of three dental resin composites using two commercially available video-imaging devices to determine if the devices produced equivalent results. METHODS: Small, semi-spherical specimens of a microhybrid (Venus), microfill (Filtek A110), and flowable (Esthet*X Flow) resin composite were manually formed and light activated for 40s using a light-curing unit. The volumetric polymerization shrinkage of fifteen specimens of each brand of resin composite was measured using the AcuVol and the Drop Shape Analysis System model DSA10 Mk2 (DSAS) video-imaging devices. Mean volumetric shrinkage values were calculated for each resin composite and equivalence was evaluated using the two one-sided tests approach. Differences between the means that were less than approximately 5% of the observed shrinkage were considered indicative of clinical equivalence. RESULTS: Mean volumetric shrinkage values measured for the resin composites were: Venus (AcuVol, 3.07+/-0.07%; DSAS, 2.90+/-0.07%); Filtek A110 (AcuVol, 2.26+/-0.10%; DSAS, 2.25+/-0.09%); and Esthet*X Flow (AcuVol, 5.01+/-0.17%; DSAS, 5.14+/-0.11%). Statistical analysis revealed that the two imaging devices produced equivalent results for Filtek A110 and Esthet*X Flow but not for Venus. CONCLUSIONS: Video-imaging systems provide an easy method for measuring volumetric shrinkage of resin composites. As with other methods for measuring volumetric shrinkage, however, they are best used to comparatively measure different materials within the same laboratory.

Thermal emission and curing efficiency of LED and halogen curing lights.

The purpose of this study was to compare the thermal emission and curing efficiency of LED (LEDemetron 1, SDS/Kerr) and QTH (VIP, BISCO) curing lights at maximum output and similar power, power density and energy density using the same light guide. Also, another LED curing light (Allegro, Den-Mat) and the QTH light at reduced power density were tested for comparison. Increase in temperature from the tips of the light guides was measured at 0 and 5 mm in air (23 degrees C) using a temperature probe (Fluke Corp). Pulpal temperature increase was measured using a digital thermometer (Omega Co) and a K-type thermocouple placed on the central pulpal roof of human molars with a Class I occlusal preparation. Measurements were made over 90 seconds with an initial light activation of 40 seconds. To test curing efficiency, resin composites (Z100, A110, 3M/ESPE) were placed in a 2-mm deep and 8-mm wide plastic mold and cured with the LED and QTH curing lights at 1- and 5-mm curing distances. Knoop Hardness Numbers (KHN) were determiped on the top and bottom surfaces (Leco). Bottom hardness values were expressed as a percentage of maximum top hardness. No significant differences were found in maximum thermal emission or KHN ratios between the LED (LEDemetron 1) and the QTH (VIP) at maximum output and similar energy densities (ANOVA/Tukey's; alpha=0.05).