In Vitro Inflammatory Cell-Induced Corrosion Using a Lymphocyte and Macrophage Coculture.

BACKGROUND: Cobalt-chromium-molybdenum (CoCrMo) and titanium alloys have been used for orthopaedic implants for decades. However, recent evidence has shown that inflammatory cell-induced corrosion (ICIC) can damage these metal alloys. This study aimed to investigate the mechanisms of ICIC by coculturing macrophages with lymphocytes. We hypothesized that macrophages would be able to alter the surface oxide layer of CoCrMo and titanium alloy (Ti6Al4V) disks, with greater oxide layer damage occurring in groups with a coculture compared to a macrophage monoculture and in groups with inflammatory activators compared to nonactivated groups. METHODS: Murine macrophages were cultured on American Society for Testing and Materials F1537 CoCrMo and F136 Ti6Al4V disks for 30 days and activated with interferon gamma and lipopolysaccharide. Interferon gamma and lipopolysaccharide were added to the culture medium to simulate local inflammation. Macrophages were either cultured alone or in a coculture with T helper lymphocytes. After the 30-day experiment, scanning electron microscopy was used to examine the disk surfaces, and oxide levels were found using energy dispersive x-ray spectroscopy. RESULTS: Pitting features consistent with previous reports of ICIC were found on disks cultured with cells. Both CoCrMo and Ti6Al4V disks had significantly lower oxide levels in all groups with cells compared to control groups with no cells (P < .01). Additionally, CoCrMo disks had significantly lower oxide levels when cultured with activated macrophages and lymphocytes compared to nonactivated macrophages alone (P < .001), activated macrophages alone (P < .01), and nonactivated macrophages and lymphocytes (P < .05). No differences in the oxide levels were found among the Ti6Al4V groups. CONCLUSIONS: This study demonstrates the ability of macrophages to alter the surface chemistry of commonly used orthopaedic alloys. We found that the addition of lymphocytes and a simulated local inflammatory response may contribute to the ICIC of CoCrMo implants.

Working viscosity and non-Newtonian behavior of silicone denture liners.

PURPOSE: To evaluate flow profile and non-Newtonian behavior of 10 different silicone lining materials. METHODS: Ten commercially available silicone lining materials were selected for evaluation. The flow profile and non-Newtonian behavior of each material was measured using a shark fin testing method. Fin height and resultant base thickness were measured with a digital caliper and compared with one-way ANOVA and Student-Newman-Keuls post hoc test and fin base by Kruskal-Wallis one-way ANOVA on ranks with Dunn post hoc test with significance at P< 0.05 for both. RESULTS: Shark fin heights ranged from 9.62 ± 0.86 mm [Reline II (Soft)] to 25.54 ± 0.43 mm [Sofreliner (Medium)]. Shark fin bases ranged from 2.57 ± 0.51 mm [Sofreliner (Medium)] to 10.31 ± 0.57 mm [Reline II (Soft)]. Statistically significant differences were found between certain samples' shark fin heights as well as resultant bases (P< 0.05) indicating different rheological properties. CLINICAL SIGNIFICANCE: Silicone liner materials differ significantly with respect to flow profile and non-Newtonian behavior. While a high flow profile (low viscosity) of an elastomeric impression material improves accuracy, it may be a detriment to a denture lining material that must achieve a critical minimum thickness to provide resilience. Likewise, a low flow profile (high viscosity) material may also pose a disadvantage, requiring excessive compression and possible tissue distortion to achieve the same critical thickness. The results of this study should be considered when selecting the appropriate material for clinical application. Additional studies are indicated to further quantify rheological properties as well as correlate them to physical properties after the complete cure of the material.

Antibacterial effect of Softsoap used to disinfect dentures.

PURPOSE: To evaluate the in vitro antibacterial effect of Softsoap and Efferdent used as solutions to disinfect Lucitone 199 poly(methyl methacrylate) (PMMA) resin used for dentures. METHODS: S. mutans and plaque bacteria were grown for 24 hours, and suspended to a concentration of 1x106 cells/ml. Bacterial suspensions (0.2 mL) were added to the decontaminated PMMA discs placed in a 48-well culture plate and incubated for 3 days at 37°C. The discs were rinsed to remove the unbound bacterial cells and then incubated for 60 minutes with 5% and 1% dilutions (triplicates) of each of the detergent solutions (0.3 ml). Discs were rinsed and then MTT reagent (0.2 ml) was added and incubated for 2 hours, then overnight with a solubilizing agent. An aliquot from each well (0.1 ml) was transferred to a 96-well flat bottom plate and absorbance was measured to OD @ 595 nm (MTT) of four samples for each data point. Normalized data was compared and statistically analyzed using a three-way ANOVA with Student-Newman-Keuls on Rank data with P< 0.05 for significance. Additionally, data were double-checked with the Holm-Sidak test. RESULTS: There was no statistically significant difference between testing media for C. albicans and mixed plaque (P= 0.078) or testing duration in time at 24 hours and 21 days (P= 0.07). Statistically significant differences were found between all treatment solutions group combinations (P< 0.001) except for 30% Softsoap versus Efferdent (P= 0.056). CLINICAL SIGNIFICANCE: There was no statistically significant difference between testing media for C. albicans and mixed plaque (P= 0.078) or testing duration at 24 hours and 21 days (P= 0.07). Statistically significant differences were noted between all treatment solutions group combinations (P< 0.001), However, there was no difference between 30% Softsoap and Efferdent (P= 0.056).

Mechanical properties of conventional versus microwave-polymerized denture base acrylic resins.

STATEMENT OF PROBLEM: New denture base acrylic resins have been introduced that are specifically formulated for microwave polymerization. Microwave polymerization is a time-efficient procedure, but few studies have evaluated how these new acrylic resin formulations compare with conventionally processed acrylic resins. PURPOSE: The purpose of this in vitro study was to compare the stiffness and strength of denture base acrylic resins formulated for microwave polymerization with conventionally processed acrylic resin. MATERIAL AND METHODS: Rectangular beams were fabricated from 2 microwave-polymerized denture base acrylic resins, microwave-specific resin (Nature-Cryl MC), resin with the option of microwave polymerization (Diamond D), and a conventionally processed resin as a control (Lucitone 199). Specimens (n=10) were stored in water for 1 week and subjected to a 3-point bend test to determine the flexural modulus (stiffness) and flexural strength before (initial properties) or after 120 000 load cycles. The load cycles, conducted between 5 and 25 N at 2 Hz, simulated 6 months of mastication. Data were analyzed by using 2-way ANOVA, followed by pairwise comparisons (α=.05). RESULTS: The initial flexural modulus (mean ±standard deviation) was conventionally processed resin, 2.65 ±0.33 GPa; microwave-specific resin, 3.01 ±0.20 GPa; and microwave-option resin, 2.63 ±0.04 GPa. After load cycling, the mean flexural modulus was conventionally processed resin, 2.34 ±0.32 GPa; microwave-specific resin, 2.69 ±0.20 GPa; and microwave-option resin, 1.96 ±0.11 GPa. The initial flexural strength was conventionally processed resin, 77.6 ±11.0 MPa; microwave-specific resin, 83.6 ±3.5 MPa; and microwave-option resin, 78.9 ±2.6 MPa. After load cycling, the mean flexural strength was conventionally processed resin, 68.7 ±9.0 MPa; microwave-specific resin, 73.3 ±3.3 MPa; and microwave-option resin, 65.5 ±3.5 MPa. Resin and loading state significantly affected the stiffness and strength (P<.01); the interaction resin×state was not significant (P≥.558). CONCLUSIONS: Microwave-polymerized denture base acrylic resins were comparable in stiffness and strength with conventionally processed acrylic resin. All acrylic resins decreased in stiffness and strength after load cycling. The microwave-specific resin was significantly stiffer and stronger than the other denture base acrylic resins, initially and after 120 000 load cycles.

Comparative evaluation of subgingival scaling and polishing techniques on dental material surface roughness.

PURPOSE: To evaluate and compare the effects of different scaling and polishing techniques on the surface roughness of four different restorative materials. METHODS: 72 specimens were prepared, molded to a size of 8.0 by 2.0 mm, and cured according to the manufacturers' instructions. The specimens were stored at 37°C for 24 hours and then thermocycled for 5,000 cycles (from 55°C to 5°C) to simulate 6 months of clinical use. Surface roughness (Ra/average and Rz/max-overall heights) was calculated using a stylus profilometer by subtracting the simulated treatments of hand scaling, ultrasonic scaling, and air polishing from the baseline measurements. The difference in Ra and Rz data were compared independently for each measurement using a two-way ANOVA on Ranks and the Holm-Sidak test, with α< 0.05 used to determine significance. RESULTS: Irrespective of the scaling or polishing technique employed, flowable bulk fill demonstrated the lowest Ra and Rz values. Hand scaling exhibited the highest roughness and variability among the other techniques, regardless of the materials tested (P< 0.001). Air polishing with glycine resulted in the lowest roughness values across all tested materials, with the exception of the tested bioactive restorative material group. CLINICAL SIGNIFICANCE: Regarding surface roughness, air polishing with glycine may be an effective and safe intervention for periodontal maintenance of subgingival restorations compared to the other tested scaling methods.

Microhardness of different thicknesses of bulk fill composites.

PURPOSE: To compare the microhardness values and bottom/top hardness ratios of different composites after being cured in 2 or 4 mm increments. METHODS: Two bulk fill composites, methacrylate-based and ormocer-based, and one conventional composite were tested. 36 cylindrical discs were prepared (n=12/composite, with six for 2 mm, and six for 4 mm thickness) by pressing each composite into a mold between two glass slides covered by Mylar strips. The top and bottom surfaces of each sample were evaluated using a Buehler hardness tester for Knoop microhardness, with a 50 g static load applied for 10 seconds at three different locations of the central part of each sample. The bottom/top hardness ratio was calculated for each sample. The Knoop microhardness data and bottom/top ratio percentages were analyzed using two-way repeated measures ANOVA and Holm-Sidak post hoc test, with significance at P< 0.05. RESULTS: The tested methacrylate-based bulk fill had the highest overall microhardness among the three tested composites. All three composite types showed a significant difference in microhardness between the top and bottom of the 4 mm discs. The bottom/top ratio percentages differed significantly for both tested bulk fill composites across different thicknesses. Both tested bulk fill materials had a bottom/top ratio of ≥ 80% at the deepest level of a 4 mm increment. CLINICAL SIGNIFICANCE: The type of material significantly affected both the bottom and top microhardness values under the experimental conditions used. While both tested bulk fill composites showed a decline in microhardness at the bottom of the 4 mm depth, they had clinically acceptable microhardness ratios at greater depths.

In-Vitro Cell-Induced Corrosion by Macrophages on Cobalt-Chromium-Molybdenum Alloy.

BACKGROUND: Patients have received cobalt-chromium-molybdenum (CoCrMo) implants for their joint replacement for decades. There have been reports of inflammatory cell-induced corrosion (ICIC) of these implants from retrieval studies. The goal of this study is to see if we could recreate ICIC in vitro and whether electrocautery damage to alloy surfaces may hasten this process. METHODS: Murine macrophages were cultured on CoCr disks with and without damage from a monopolar electrocautery. Culture medium was replaced every 12 hours and supernatant was collected every 4 days. After 30 days, cells were removed, counted, and digested. The metal concentrations in the supernatant and within cells were assessed using inductively coupled plasma spectrometry for comparison. RESULTS: The Co supernatant concentration was higher in the undamaged disks with activated macrophages. Higher concentrations of Co and Mo were found in the supernatant of the undamaged disks vs the electrocautery (EC) corrosion damaged disks. There was a significantly higher intracellular Co and Mo concentration with activated cells on CoCrMo disks vs the control group and no difference compared to EC damaged disk group. Scanning electron microscopy displayed microscopic pitting on the surfaces exposed to macrophages without EC damage. CONCLUSION: We found that macrophages could reproduce findings of ICIC pits on the surface of CoCrMo alloy and that the addition of EC damage to the surface did not increase the process. The clinical significance of these findings should be further investigated to determine if this could explain a small number of poor total knee arthroplasty reported outcomes.

Effect of whitening dentifrices on toothbrush abrasion on composites.

PURPOSE: To evaluate the laboratory long-term effect of various whitening dentifrices on the surface roughness of two brands of resin composite (TPH ST, Filtek Bulk Fill One) using a mechanical toothbrushing simulation. METHODS: Thirty-two samples each of Filtek and TPH were fabricated in ring molds 10 x 1 mm. Samples were randomly grouped (n=8; four groups), according to dentifrice used; Crest 3D, Optic White, Hello (charcoal), and Aim as control. Samples were brushed in mixed solutions containing deionized water and dentifrice at 150 gf for 10,000x with rotation to ensure uniform brushing. Surface roughness was measured both before (baseline) and after the mechanical toothbrushing simulation using a stylus profilometer. Data collected was compared independently for each treatment using two-way ANOVA and SNK with α< 0.05 for significance. RESULTS: The data showed that TPH was more susceptible to the abrasive nature of three of the whitening dentifrices tested [Crest 3D, Optic White, and Hello (charcoal) ]. Filtek also exhibited significant susceptibility to the abrasive nature of Hello. Aim showed the least or minimal amount of abrasion. CLINICAL SIGNIFICANCE: TPH ST composite was more susceptible to the abrasive nature of the three whitening dentifrices tested [Crest 3D, Optic White, and Hello (charcoal)]. Filtek also exhibited significant susceptibility to the abrasive nature of Hello. Aside from the data supporting the clinical efficacy of TPH compared to Filtek, clinicians should inform patients of the abrasive capacity of all whitening dentifrices, especially those that are charcoal based.

Effects of NanoAg-ACP Microparticles as Bioactive Fillers on the Mechanical and Remineralization Properties of Dental Resin Cement.

PURPOSE: To investigate the potential of adding silver-nanoparticle-containing amorphous calcium phosphate microparticles as bioactive fillers into commercially available nonbioactive dental resin cement. MATERIALS AND METHODS: Experimental cement was formulated by adding 7.5% silver-nanoparticle-containing amorphous calcium phosphate microparticles to Multilink Automix resin cement (Ivoclar Vivadent). The experimental cement was evaluated for shear bond strength (N = 11 per group) and demineralization/remineralization (N = 16 per group), with BioCem® Universal BioActive cement (NuSmile) as the positive control and Multilink Automix cement as the negative control. One-way analysis of variance and post hoc tests were used to assess the significance of differences among or between the groups RESULTS: The addition of silver-nanoparticle-containing amorphous calcium phosphate microparticles at the level of 7.5% by weight into Multilink Automix did not have a statistically significant effect on the shear bond strength (p > 0.05), but statistically significantly increased the depth of remineralization on both dentin and enamel (p = 0.01 and p < 0.001, respectively) when compared to Multilink Automix alone. The experimental cement prepared in the present study was comparable to BioCem® on the depths of remineralization on both dentin and enamel (p = 0.59 and p = 0.99, respectively). CONCLUSION: When incorporated into nonbioactive commercial dental resin cements as bioactive fillers at the level of 7.5% by weight, silver-nanoparticle-containing amorphous calcium phosphate microparticles could provide remineralization potential without affecting the shear bond strength.

Electrocautery Induced Damage of Total Knee Implants.

BACKGROUND: Pitting damage on implants has been reported and attributed to the use of electrocautery. This study aimed to determine how different total knee arthroplasty bearing surfaces are susceptible to this type of damage and whether surgeons are aware that this damage can occur. METHODS: A survey was sent to Hip and Knee Society members to determine what percentage of adult reconstructive surgeons use electrocautery after implantation of components. Three bearing surfaces for total knee arthroplasty were selected: cobalt chromium, Oxinium, and zirconium nitride to be damaged by electrocautery with a monopolar (MP) and bipolar (BP) electrocautery with 3 different energy settings. A comparison of surface damage using scanning electron microscopy and elemental differences using energy dispersion spectroscopy was performed. Average roughness (Ra), maximal peak-to-valley height (Rz), kurtosis (Rk), and skewness (Rsk) were recorded for comparison using a profilometer was performed. RESULTS: Median Rz and Ra measurements were larger for BP damaged areas compared to MP for all bearing surfaces. The Oxinium surface had the greatest increase in roughness parameters. Survey results indicate that a significant percentage of adult reconstructive surgeons use the electrocautery after implants are in place and are not aware of this type of damage. Backscatter scanning electron microscopy analysis found significant changes for BP damage compared to MP. CONCLUSION: Surface damage caused by electrocautery can have significant effects on the bearing surfaces of implants but further study needs to be performed to determine if this is a clinical issue. Our survey determined that many arthroplasty experts are unaware that this damage can occur.

Evaluation of a novel instrument for placement of dental sealants.

PURPOSE: To evaluate marginal seal, adaptation, surface texture, and bubble presence of pit and fissure sealants when using a novel instrument (C-Shape It) or the manufacturers' supplied applicators for sealant placement into occlusal fissures. METHODS: Extracted molars with occlusal fissures were cleaned with pumice slurry and divided into six groups (n= 10/gp); three treatment and three control. Sealant materials placed included Ultraseal, Delton, and Helioseal. Excess water was removed per manufacturers' instructions. Sealants were applied with each applicator and with the C-Shape It to each group from cusp to cusp without covering marginal ridges, and the polymerization guidelines for photocuring were followed for all the groups. Samples were thermocycled at 500x between 5° and 55°C. Teeth were sectioned in a buccolingual direction with a minimum of four sections per tooth and examined under a light microscope at 50x and scored. RESULTS: Marginal seal, adaptation, penetration ability, surface texture, bubble formation and location of the sealants were analyzed using two-way ANOVA on ranks with a 95% confidence interval. The C-Shape It instrument showed consistently smoother surface texture (P< 0.001), which was statistically significant versus all manufacturers' applicators for all materials. Bubble presence was statistically significantly less with the instrument C-Shape It versus the manufacturers' applicators for all materials (P< 0.001). Results also revealed significant differences in marginal sealant adaptation. CLINICAL SIGNIFICANCE: C-Shape It demonstrated consistent ability to reduce bubbles and improve surface texture and adaptation in occlusal fissures for all pit and fissure products tested.

A quantitative and visual examination of sealed restorative specimens following exposure to artificial aging.

Low-viscosity polymer resins, or surface sealants (SSs), have been utilized as a means of finalizing the polishing step following the placement of composite resin restorations. The aim of this study was to measure the surface roughness (Ra) of composite resins treated with different SSs before and after exposure to an accelerated artificial aging protocol. The study included 5 experimental groups of composite resin discs (TPH Spectra ST) treated with different SSs (PermaSeal, Embrace WetBond Seal-n-Shine, OptiGuard, BisCover LV, and DuraFinish) and a control group consisting of untreated discs (n = 6 per group). The discs were prepared by inserting composite resin in 10 × 1-mm rings, covering the ring and material with a transparent strip, compressing the assembly between glass slides, and polymerizing through the slides on each side for 40 seconds with an LED curing light. Each disc except for the control specimens received a coating of the selected SS followed by application of a transparent matrix strip and then light polymerization for 20 seconds using an LED light source. Surface roughness measurements were obtained with a digital contact profilometer at baseline (immediately after polymerization) and following exposure to a thermocycling regimen to simulate aging. The data were analyzed using 2-way analysis of variance and post hoc Student-Newman-Keuls test with significance set at P < 0.05. There were no statistically significant differences among the groups at baseline. There were no statistically significant differences between the baseline and post-thermocycling Ra measurements except among the DuraFinish specimens, which were significantly rougher than all other groups after accelerated artificial aging. The use of SSs for the initial insertion and possibly for the long-term maintenance of composite resins could be minimally beneficial for restoration maintenance if a transparent covering medium is utilized during polymerization. However, due to the effects caused by formation of an oxygen-inhibited layer of unpolymerized monomers if a covering medium is not used, the results suggest the benefits do not offset the costs considering both gloss and Ra surface-testing parameters.

Antibacterial properties of silver-loaded gelatin sponges prepared with silver diamine fluoride.

PURPOSE: To evaluate the antibacterial efficiency of silver-loaded gelatin sponges prepared from gelatin and silver diamine fluoride, Ag(NH3)2F. METHODS: A series of novel silver-loaded gelatin sponges were prepared from gelatin and silver diamine fluoride. They were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The antibacterial activities against one oral bacteria model S. mutans were evaluated using the agar disk diffusion method and biofilm-grown bacteria assay. For the purpose of comparison, a second series of silver-loaded sponges were prepared using silver nitrate (AgNO3) as the silver source. RESULTS: FT-IR, SEM and EDX results confirmed the successful preparation of silver-loaded gelatin sponges from both silver diamine fluoride and silver nitrate. Agar disk diffusion assays revealed that the antibacterial activity of silver-loaded sponges was strongly correlated with the silver content, and also depending on the silver source used in the preparation of sponges. Sustained inhibition of S. mutans in agar plates was observed for silver-loaded gelatin sponges containing about 5 wt% Ag or more. Biofilm assays showed different viabilities when treated with different formulations, with the viability of 11.4±3.1% for the sponges containing 5.30±1.18 wt% Ag prepared from silver diamine fluoride, and the viability of 15.4±3.1% for the sponges containing 29.13±10.34 wt% Ag prepared from silver nitrate. CLINICAL SIGNIFICANCE: The silver loading contents had a significant effect on the antibacterial activities of silver-loaded gelatin sponges prepared with silver diamine fluoride. In addition, silver diamine fluoride was a superior silver source to prepare antibacterial silver-loaded gelatin sponges when compared with silver nitrate.

Effect of Ferrule Location with Varying Heights on Fracture Resistance and Failure Mode of Restored Endodontically Treated Maxillary Incisors.

PURPOSE: To investigate the effect of the location of a partial ferrule on 2 walls and the influence of ferrule height variations on remaining walls, fracture resistance, and failure mode of maxillary incisors endodontically treated and restored with fiber posts. MATERIALS AND METHODS: Sixty intact human maxillary central incisors were divided into 6 groups (n = 10): no ferrule (NF), 2-mm ferrule (CF2), absence of lingual wall and 1 proximal wall with remaining walls' height, 1 mm (IF1), 2 mm (IF2), 3 mm (IF3), and 4 mm (IF4). They were restored with a fiberglass post and composite resin core. Complete metal crowns were then cemented on all specimens. Completed specimens were subjected to thermal cycling (6000 cycles, 5°C/55°C) followed by the immediate testing of fracture resistance. After failure, the specimens were sectioned buccolingually and evaluated to identify the mode of failure. The data were analyzed with an ANOVA and the Student-Newman-Keuls multiple comparison tests (α = 0.05). RESULTS: An incomplete ferrule (IF2) with the lingual wall missing and 1 proximal wall had a fracture resistance of 494 ± 137 N, which was significantly less that of a complete ferrule (CF2) (707 ± 162 N, p = 0.002). An increase of 3 to 4 mm in height of the remaining walls had negligible influence on the fracture resistance: 514 ± 117 N (IF3), 557 ± 177 N (IF4). Partial decementation was observed in all specimens of IF3 and IF4, in 9 of IF1 and IF2, in 6 in NF, and in 3 in CF2. Root fractures occurred in 7 specimens, 4 in CF2, 1 in IF1, 1 in IF2, and 1 in IF4. Cracks under the cemento-enamel junction occurred in 4 specimens (NF and IF1), in 5 (IF2 and IF3), and in 6 (CF2 and IF4) and were considered catastrophic failures. CONCLUSIONS: Specimens with a complete ferrule of 2 mm height were more resistant to fracture than specimens with 2 mm height and absence of the lingual wall and 1 proximal wall. A 3 or 4 mm wall height increase was associated with an insignificant increase in fracture resistance and cannot compensate for the absence of the lingual wall and 1 proximal wall.

The effect of artificial ultraviolet light on the gloss of composite resin surface sealants.

This study evaluated how exposure to ultraviolet (UV) light affected the gloss of composite resins following application of resin-based surface sealants (SSs). Thirty composite resin discs were fabricated using cylindrical molds and randomly assigned to 1 of 5 SS groups (n = 6 each). Both sides of each disc received a polyester film clear matrix surface finish, and then rotary finishing and polishing procedures were performed on 1 side only. Six baseline measurements for each disc surface were performed using a 60-degree-angle gloss meter. The finished and polished side then received an SS application and was polymerized with an LED light through a polyester film matrix. Gloss measurements were then obtained. All specimens were then exposed to an artificial UV light source for a total of 382 hours, after which final gloss measurements were made. A 2-way repeated-measures analysis of variance and Student-Newman-Keuls pairwise multiple comparison tests revealed statistically significant differences between the SS materials and surface treatments (P < 0.05). No statistically significant (P > 0.05) differences were found between the surfaces that were mechanically finished and polished and those that only received a polyester film finish. However, all specimens exhibited significantly (P < 0.0001) higher gloss readings after SS application. Following UV exposure, all SS specimens exhibited significantly (P < 0.0001) lower gloss readings. The study results suggest that application of SSs to composite resin discs increases the gloss on a short-term basis; however, long-term exposure of SSs to an artificial UV light source might have a negative effect on the surface properties. Thus, dentists need to periodically evaluate composite resin restorations.

A novel antimicrobial and remineralizing toothpaste containing CaCl2/chitosan microspheres.

PURPOSE: To investigate the feasibility of exploiting amorphous calcium phosphate (ACP) formed in situ from chitosan calcium microspheres and phosphate ions in water during brushing for caries control. METHODS: A prototype toothpaste, namely Chi-ACP paste, was specially formulated containing CaCl2/chitosan microspheres. The efficiency of Chi-ACP paste for remineralization on human tooth enamel was evaluated via an in vitro pH cycling approach. After 15 demineralization/remineralization cycles, the treated teeth were analyzed using scanning electron microscope (SEM) /energy dispersive X-ray spectroscopy (EDX), and polarized light microscope (PLM). RESULTS: EDX analysis showed the treated enamel in the Chi-ACP paste group had statistically significantly higher calcium content and Ca/P weight ratios than those in the negative control group, while the MI plus group had a slightly higher Ca content and a slightly higher Ca/P weight ratio. PLM analysis revealed that the Chi-ACP paste group had a larger remineralization band in treated enamel than the negative control group, although there was no statistically significant difference on the demineralization depths in the enamel among the three groups. CLINICAL SIGNIFICANCE: Antibacterial chitosan could be used to encapsulate CaCl2 and then formulated into toothpaste for caries control through in-situ formed amorphous calcium phosphate (ACP) during brushing.

Influence of remaining coronal tooth structure on fracture resistance and failure mode of restored endodontically treated maxillary incisors.

STATEMENT OF PROBLEM: Limited information is available on the effect of an incomplete ferrule because of the varying residual axial wall heights and the volume of residual tooth structure on the fracture resistance of endodontically treated and restored maxillary incisors. PURPOSE: The purpose of this in vitro investigation was to examine the effect of varying residual axial wall heights, residual coronal tooth structure, and the absence of 1 proximal axial wall on the fracture resistance and failure mode of endodontically treated teeth restored with metal posts. MATERIAL AND METHODS: Sixty intact human maxillary central incisors were divided into 6 groups (n=10): no ferrule (NF), 2-mm complete ferrule (CF2), 2-mm (IF2), 3-mm (IF3), and 4-mm (IF4) incomplete ferrules missing a single interproximal wall, and a control group that had a 6-mm incomplete ferrule (IF6). Cast metal post-and-cores were placed in all experimental specimens except for controls. Control specimens received 1 interproximal cavity preparation extending to the root canal access and a composite resin restoration. Complete metal crowns were then cemented on all specimens. Completed specimens were subjected to thermocycling (6000 cycles, 5°C/55°C) followed by the immediate testing of fracture resistance. Failed specimens were sectioned buccolingually and evaluated to identify the failure mode. The data were analyzed with an analysis of variance (ANOVA) and the Student-Newman-Keuls multiple comparison test (α=.05). RESULTS: An incomplete ferrule (IF2) with 1 interproximal wall missing had significantly reduced fracture resistance (697 N) compared with a complete ferrule (932 N). An increase of 3 to 4 mm of remaining wall height improved fracture resistance, from 844 N (IF3) to 853 N (IF4). Partial decementation was noticed in 8 NF and 5 IF2 specimens. IF3 and IF4 had no decementations. Radicular fractures and cracks (catastrophic failure) were observed in all IF2, IF3, and IF4, 9 CF2, and 6 NF specimens. In 7 specimens without posts (IF6, control), composite resin foundation and/or coronal dentin fracture were observed and the failure was considered repairable. CONCLUSIONS: The results of this in vitro study indicated that specimens with a 2-mm ferrule of uniform height were more resistant to fracture than specimens with a 2-mm ferrule and 1 missing interproximal wall. An increased wall height of 3 or 4 mm was associated with a significant increase in fracture resistance and can compensate for the missing interproximal wall.

A Profilometry-Based Dentifrice Abrasion Method for V8 Brushing Machines Part III: Multi-Laboratory Validation Testing of RDA-PE.

OBJECTIVES: We have previously reported on progress toward the refinement of profilometry-based abrasivity testing of dentifrices using a V8 brushing machine and tactile or optical measurement of dentin wear. The general application of this technique may be advanced by demonstration of successful inter-laboratory confirmation of the method. The objective of this study was to explore the capability of different laboratories in the assessment of dentifrice abrasivity using a profilometry-based evaluation technique developed in our Mason laboratories. In addition, we wanted to assess the interchangeability of human and bovine specimens. METHODS: Participating laboratories were instructed in methods associated with Radioactive Dentin Abrasivity-Profilometry Equivalent (RDA-PE) evaluation, including site visits to discuss critical elements of specimen preparation, masking, profilometry scanning, and procedures. Laboratories were likewise instructed on the requirement for demonstration of proportional linearity as a key condition for validation of the technique. Laboratories were provided with four test dentifrices, blinded for testing, with a broad range of abrasivity. In each laboratory, a calibration curve was developed for varying V8 brushing strokes (0, 4,000, and 10,000 strokes) with the ISO abrasive standard. Proportional linearity was determined as the ratio of standard abrasion mean depths created with 4,000 and 10,000 strokes (2.5 fold differences). Criteria for successful calibration within the method (established in our Mason laboratory) was set at proportional linearity = 2.5 ± 0.3. RDA-PE was compared to Radiotracer RDA for the four test dentifrices, with the latter obtained by averages from three independent Radiotracer RDA sites. Individual laboratories and their results were compared by 1) proportional linearity and 2) acquired RDA-PE values for test pastes. RESULTS: Five sites participated in the study. One site did not pass proportional linearity objectives. Data for this site are not reported at the request of the researchers. Three of the remaining four sites reported herein tested human dentin and all three met proportional linearity objectives for human dentin. Three of four sites participated in testing bovine dentin and all three met the proportional linearity objectives for bovine dentin. RDA-PE values for test dentifrices were similar between sites. All four sites that met proportional linearity requirement successfully identified the dentifrice formulated above the industry standard 250 RDA (as RDA-PE). The profilometry method showed at least as good reproducibility and differentiation as Radiotracer assessments. It was demonstrated that human and bovine specimens could be used interchangeably. CONCLUSIONS: The standardized RDA-PE method was reproduced in multiple laboratories in this inter-laboratory study. Evidence supports that this method is a suitable technique for ISO method 11609 Annex B.

Flexural strength and flexural fatigue properties of resin-modified glass ionomers.

OBJECTIVE: To determine the physical properties of several resin-modified glass ionomers (RMGIs) by means of flexural strength and flexural fatigue testing, and to compare them to conventional glass ionomer cements (GICs) and flowable composite resins. METHODS: RMGI samples were fabricated according to ISO 4049 standard. Rectangular specimens were produced using a polytetrafluoroethylene (PTFE) mold with dimensions of 2 x 2 x 25 mm. Flexural strength and flexural fatigue were measured by means of the 3-point bending tests using an Instron universal testing machine at 0.75 mm/min and 0.03 Hz for 100 cycles, respectively. Flexural stress, load, and displacement were recorded for all tests. Data were statistically compared (ANOVA, SNK, p < 0.05). Statistical data analysis for flexural fatigue was achieved through the least frequent events method (failures versus non-failures). The following RMGIs, flowable composites, and GICs were tested: 1) Activa Bioactive-Restorative; 2) Activa Bioactive-Base/Liner; 3) Tetric EvoFlow; 4) Beautifil Flow Plus; 5) Geristore; 6) Fuji Filling LC; 7) Fuji Lining LC; 8) Ketac Nano; 9) Fuji Triage; 10) Ketac Nano; and 11) Vitrebond Plus. RESULTS: The flexural strength of Activa-enhanced RMGIs was statistically significantly greater than all other RMGIs and GICs (p < 0.001). The flexural fatigue of Activa-enhanced RMGIs and flowable composites was significantly greater than all other materials (p < 0.00 1). The flexural fatigue of the Activa-enhanced RMGIs was comparable to the two flowable composites tested. CONCLUSION: The Activa-enhanced RMGIs demonstrated comparable flexural strength and flexural fatigue to flowable composites. Activa-enhanced RMGIs and flowable composites demonstrated flexural strength and flexural fatigue significantly greater than all other tested materials.

Microleakage of Silver-Modified Atraumatic Restorative Technique (SMART) Restorations Using Silver Diammine Fluoride and High-Viscosity Glass Ionomer.

Purpose: The purpose of this study was to investigate the microleakage of atraumatic glass ionomer restorations with and without silver diammine fluoride (SDF) application. Restorations with SDF are termed silver-modified atraumatic restorations (SMART). Methods: Sixty carious extracted permanent teeth were randomly allocated to two SMART groups and two control groups (n equals 15 per group) for a total of four groups. After selective caries removal, test specimens were treated with 38 percent SDF and polyacrylic acid conditioner was applied and rinsed; teeth were restored with Fuji IX GP® glass ionomer (n equals 15) or with SMART Advantage™ glass ionomer (SAGI; n equals 15). For control groups, specimens were restored with their respective GI material after selective caries removal, both without SDF. Restored teeth were placed in Dulbecco's Phosphate-Buffered Saline solution at 37 degrees Celsius for 24 hours. Teeth were thermocycled between five and 55 degrees Celsius for 1,000 cycles, stained with two percent basic fuchsin, sectioned, and visually inspected for microleakage utilizing stereomicroscopy on a four-point scale. Data were statistically analyzed using Kruskal-Wallis one-way analysis of variance on ranks using Dunn's method (P<0.05). Results: Microleakage between the two SMART restoration groups was insignificant. SAGI alone demonstrated significantly more microleakage than all other groups. There was no statistical significance between the Fuji IX GP® control group and the two SMART restoration groups. Conclusions: This in vitro study indicated that silver diammine fluoride placed before glass ionomer restoration does not increase microleakage. Polyacrylic acid may be used after SDF placement without increasing microleakage.