The effect of filler on the mechanical properties of a novel resin-based calcium phosphate cement

Indiana University-Purdue University Indianapolis (IUPUI)Several studies have found that resin-based amorphous calcium phosphate (ACP) composites can function well for applications that do not require high mechanical demand. Milled tricalcium phosphate (TCP), a new calcium-phosphate-releasing material, is crystalline in nature, suggesting it to be strong. In the present study, we investigated the use of a TCP-filled composite resin as a possible tooth restorative-material. An experimental TCP-based composite was prepared using monomer with a mixture of 34.3 percent by mass of EBPADMA, 34.2 percent by mass of HmDMA, and 30.5 percent by mass of HEMA. TCP fillers were added to the monomer mixture at different levels (30 percent, 40 percent, 50 percent, and 60 percent by weight). A universal testing machine (Sintech Renew 1121; Instron Engineering Corp., Canton, MA) was used to measure the compressive strength and modulus. FTIR was used to measure the degree of conversion. The depth of cure was determined according to the ISO standards for dental resin 4049 using the scrapping technique. Knoop hardness numbers were obtained by a microhardness tester (M-400; Leco Co., St. Joseph, MI). The viscosities of the experimental resin were determined in a viscometer (DV-II+ Viscometer; Brookfield, Middleboro, MA). The data were analyzed using a one-way analysis of variance (ANOVA). A 5-percent significance level was used for all the tests. Resin composites with 30-percent TCP filler showed the highest compressive strength and hardness values. Also, this group showed the lowest degree of conversion. Resin composites with 60-percent TCP filler showed the highest degree of conversion. However, this group showed the lowest compressive strength, depth of cure, and hardness. Resin composites with 50-percent filler showed the highest compressive modulus. Resin composites with 40-percent filler showed higher viscosity values than resin composites with 30-percent filler. In conclusion, increasing the filler level significantly reduced the compressive strength, hardness, and depth of cure, but increased the degree of conversion. Also, resin composites with the lowest filler level (30 percent) had the highest compressive strength, depth of cure, and hardness. From these results, it can be concluded that the experimental TCP-filled resin used in this study cannot be used as restorative material

Investigations of the anti-caries potential of fluoride varnishes

Indiana University-Purdue University Indianapolis (IUPUI)The majority of currently marketed fluoride varnishes (FV) have not been evaluated for their effectiveness in preventing dental caries. Fundamental research on FVs and how different formulations affect adherence to teeth, fluoride release into saliva and uptake by teeth is virtually non-existent. The objective of this work was to investigate the anti-caries potential, measured as fluoride release into saliva, change in surface microhardness of early enamel caries lesions, and enamel fluoride uptake, of multiple commercially available FVs. We have found that FVs differed in their release characteristics, rehardening capability, and ability to deliver fluoride to demineralized lesions. In addition to our in vitro work, we have conducted a clinical study that aimed to compare saliva and plaque fluid fluoride concentrations following the application of three commercially available FV treatments at predetermined post application time points. We also investigated the change in fluoride concentration in saliva and plaque fluid fluoride from baseline to each post application predetermined time point. We found that FVs varied in their release of fluoride into saliva and plaque fluid but shared common trends in release characteristics. The outcomes of our in vitro and in vivo investigations demonstrate a great variation in anti-caries potential of FVs. This may be attributed to different compositions and physical properties of the tested FVs

THE EFFECT OF NANO-FILLED RESIN COATING ON FLUORIDE RELEASE IN A NEW CONVENTIONAL GLASS IONOMER CEMENT

poster abstractThe objective of this study was to evaluate fluoride release amounts and patterns from high strength tooth filling material (EQUIA™) which is a con-ventional Glass Ionomer Cement, and investigate whether the application of nano-filled resin-based coating with different thicknesses has any effect on fluoride release from this new material. A total of 120 disc shaped specimens (10 x 2 mm) of EQUIA™ were fabricated according to manufacturer’s in-structions. Samples were subsequently divided into three groups: no resin coating; coated with nano-filled resin-based coat; coated with nano-filled resin-based coat then subjected to abrasion using a mechanical tooth brush-ing machine. Each specimen was soaked individually into a polyethylene container with 20 ml of distilled water and stored at 37ºC. Samples from each group were soaked for four time points; 1 day, 7 days, 14 days and 21 days. Fluoride content was then measured using a fluoride-specific ion elec-trode (Model 9609BNWP, Orion Research, Boston MA, USA). The effects of time and coating on fluoride release were analyzed using two-way analysis of variance (ANOVA), with multiple comparisons performed using the Sidak method at an overall 5% significance level. The distribution of the fluoride release measurements was examined and a natural logarithm transformation of the data was necessary to satisfy the ANOVA assumptions. The time-by-coating interaction was significant (p<0.0001). We can conclude that fluo-ride level significantly increased with time for non-coated and coated then abraded samples only. Application of resin coat significantly reduced fluoride release. Also, subjecting coated samples to tooth brush abrasion increased the fluoride release when compared to coated specimens but was still signifi-cantly less than uncoated samples

An In-Vitro Study to Determine Anti-Caries Efficacy of Fluoride Varnishes

poster abstractFundamental research on fluoride varnishes (FV) and how different formulations affect adherence to teeth, fluoride release into saliva and uptake by teeth is virtually non-existent. The objective of this in vitro study was to investigate the anti-caries efficacy of five commercially available FV: Enamel Pro® Varnish Clear, Flor-Opal® Varnish White, MI Varnish™, PreviDent® and Vanish™. Ninety bovine enamel specimens (4x4mm) were prepared and assigned to five groups (n=18). Early caries lesions were created in the specimens and characterized using Vickers microhardness (VHN). FV was applied to each group of specimens. Immediately afterwards, 7.5ml of artificial saliva (AS) were pipetted over each group, collected and renewed every 15min for 6h. AS samples were analyzed for fluoride using a ion-specific electrode and meter. FV was removed using chloroform and part of the specimens protected to determine enamel fluoride uptake (EFU) using the acid etch technique. Each group was then subjected to pH cycling consisting of a 4h/day acid challenge and two, one-minute treatments with Crest Cavity Protection. Post-pH cycling microhardness was measured and compared to baseline values to determine the ability of the FV to enhance remineralization/prevent demineralization. One-way ANOVA was used for data analysis (p Enamel Pro® (217μg/ml) > Flor-Opal® (153μg/ml) > PreviDent® (84μg/ml) > Vanish(28μg/ml). In conclusion, anti-caries efficacy (measured through EFU, fluoride release and VHN) differs among FV products and this difference may be attributed to different composition, fluoride source and other active ingredients

Fluoride concentration in saliva and biofilm fluid following the application of three fluoride varnishes

Objective Most of the commercially available fluoride varnishes (FV) have not been evaluated for their cariostatic properties. Consequently, the aim of this in vivo study was to investigate intra-oral fluoride retention and clearance patterns from three different FV. Methods Eighteen subjects (7–11 years) participated in a laboratory analyst-blinded, randomized, crossover study comparing the ability of 5% sodium fluoride varnishes (CavityShield-CS, Enamel Pro-EP, Vanish-V) to enhance fluoride concentrations in biofilm fluid, centrifuged and whole saliva over a period of 48 h after a single FV application. Results Similar fluoride concentration × time patterns were noted for all investigated FV and studied variables, with the highest fluoride concentrations observed for the first biological sample collected after FV application (30 min). Mean ± SE (area under fluoride clearance curve) values were (μg F/g or ml × min): biofilm fluid − CS (472 ± 191), EP (423 ± 75), V (1264 ± 279); centrifuged saliva − CS (42 ± 7), EP (19 ± 3), V (41 ± 8); whole saliva − CS (68 ± 11), EP (64 ± 10), V (60 ± 7). V delivered more fluoride to biofilm fluid than CS (p = 0.0116) and EP (p = 0.0065), which did not differ (p = 0.27). For centrifuged saliva, CS and V were not significantly different (p = 0.86), but resulted in higher fluoride retention than EP (p < 0.0008). No significant differences among FV were observed for whole saliva (p = 0.79). Conclusion The present study has shown that FV vary in their ability to deliver fluoride intra-orally potentially related to formulation differences. To what extent the present findings relate to clinical efficacy remains, however, to be determined. Clinical significance Clinical research that investigates fluoride release patterns into saliva and biofilm fluid from different FV products is insufficient. More research is needed to investigate different FV formulations for their efficacy in order to help clinicians make better evidence based treatment choices

Enhancing predicted fluoride varnish efficacy and post-treatment compliance by means of calcium-containing gummy bears

Objectives This study determined whether consumption of calcium-containing gummies prior to fluoride varnish application enhances plaque fluoride retention and compliance with post-varnish application instructions. Methods The present study followed a multi-center, parallel, randomized, and laboratory analyst-blind design. Following IRB approval, parent consent and child assent, 44 subjects (7–12 years), were randomized to either gummy or no-gummy study groups. A baseline plaque sample was obtained after a wash-out period. Fluoride varnish (5% NaF) was applied; subjects in the gummy group received two calcium-containing gummies prior to varnish application. Subjects were given two questionnaires to complete (subject and parent) to investigate adherence to post-treatment instructions. Three days later, a second plaque sample was obtained. Plaque was analyzed for plaque fluid and solid fluoride concentrations. Fluoride data were analyzed using Wilcoxon Rank Sum tests, questionnaire data using Pearson chi-square tests. Results Plaque fluid fluoride did not change pre- to post-treatment in the gummy group (mean ± sd: 8.8 ± 5.7 μmol/l vs. 10.0 ± 6.3 μmol/l; p = 0.265) or in the no-gummy group (8.1 ± 4.4 μmol/l vs. 16.1 ± 20.0 μmol/l; p = 0.058). Groups were not different for plaque fluid fluoride pre-treatment (p = 1.000), post-treatment (p = 0.904), or change (p = 0.904). Plaque solid fluoride did not change pre- to post-treatment in the gummy group (0.89 ± 1.10 μmol/g vs. 1.37 ± 1.77 μmol/g; p = 0.073) or in the no-gummy group (0.68 ± 0.77 μmol/g vs. 2.01 ± 5.00 μmol/g; p = 0.190). Groups were not different for plaque solid fluoride pre-treatment (p = 1.000), post-treatment (p = 0.466), or change (p = 0.874). No significant differences were found between groups for questionnaire responses. Conclusion This study failed to demonstrate an effect of calcium-containing gummies in enhancing plaque fluoride retention

Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

Objectives To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al2O3) particles at different pressures. Materials and Methods Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ2 tests (α = 0.05). Results The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used

Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

OBJECTIVES To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al2O3) particles at different pressures. MATERIALS AND METHODS Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ2 tests (α = 0.05). RESULTS The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. CONCLUSIONS CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used